U.S. patent application number 15/843785 was filed with the patent office on 2018-06-14 for drive apparatus, drive method, and optical device.
This patent application is currently assigned to NIKON CORPORATION. The applicant listed for this patent is NIKON CORPORATION. Invention is credited to Takatoshi ASHIZAWA, Toshikazu MORIOKE, Shinji NISHIHARA, Kazuyasu OONE.
Application Number | 20180164658 15/843785 |
Document ID | / |
Family ID | 49082800 |
Filed Date | 2018-06-14 |
United States Patent
Application |
20180164658 |
Kind Code |
A1 |
ASHIZAWA; Takatoshi ; et
al. |
June 14, 2018 |
DRIVE APPARATUS, DRIVE METHOD, AND OPTICAL DEVICE
Abstract
Noise produced during phase-difference changes is minimized
without decreasing the responsiveness of a vibration-wave motor. A
lens-side MCU for a lens barrel controls a drive apparatus that
applies a drive voltage to the vibration-wave motor by outputting
an A-phase drive signal and a B-phase drive signal thereto. The
lens-side MCU uses, for example, a drive-voltage setting unit and a
duty-cycle change unit to change the drive voltage. Also, the
lens-side MCU is provided with a phase-difference change unit that
changes the phase difference between the A-phase drive signal and
the B-phase drive signal. When driving the vibration-wave motor,
the lens-side MCU changes the drive voltage to V.sub.reg, and when
the phase-difference change unit is changing the aforementioned
phase difference, the drive voltage is changed to V.sub.1, V.sub.1
being greater than zero and less than V.sub.reg.
Inventors: |
ASHIZAWA; Takatoshi; (Tokyo,
JP) ; OONE; Kazuyasu; (Tokyo, JP) ; NISHIHARA;
Shinji; (Tokyo, JP) ; MORIOKE; Toshikazu;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIKON CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
NIKON CORPORATION
Tokyo
JP
|
Family ID: |
49082800 |
Appl. No.: |
15/843785 |
Filed: |
December 15, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15152001 |
May 11, 2016 |
9869921 |
|
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15843785 |
|
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|
14381063 |
Dec 29, 2014 |
9366940 |
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PCT/JP2013/055522 |
Feb 28, 2013 |
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15152001 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02N 2/142 20130101;
G03B 3/10 20130101; G02B 7/08 20130101; G02B 7/04 20130101; G02B
7/36 20130101; G03B 2205/0084 20130101; H02N 2/163 20130101 |
International
Class: |
G03B 3/10 20060101
G03B003/10; G02B 7/36 20060101 G02B007/36; G02B 7/04 20060101
G02B007/04; G02B 7/08 20060101 G02B007/08; H02N 2/16 20060101
H02N002/16; H02N 2/14 20060101 H02N002/14 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2012 |
JP |
2012-042439 |
Mar 16, 2012 |
JP |
2012-059692 |
Dec 28, 2012 |
JP |
2012-286941 |
Dec 28, 2012 |
JP |
2012-287812 |
Feb 7, 2013 |
JP |
2013-022196 |
Claims
1. An optical device comprising: a vibration actuator that drives a
lens using a drive force generated at a driving face by way of
excitation of an electro-mechanical conversion element; a drive
control unit that provides two drive signals to the vibration
actuator; and a photography setting unit that can select a moving
image photography mode, wherein the drive control unit can change a
speed of the vibration actuator, in a case of the photography
setting unit selecting the moving image photography mode, by
changing a phase difference of the two drive signals, and changing
a frequency of the two drive signals to correspond to the phase
difference thus changed, while maintaining a voltage of the two
drive signals to be constant.
2. The optical device according to claim 1, wherein the drive
control unit can continuously change the phase difference of the
two drive signals between 90.degree., -90.degree. and
0.degree..
3. The optical device according to claim 1, wherein the drive
control unit performs a wobbling operation that is an operation to
cause the lens to move back and forth in small motions to cause a
focal position to follow a subject.
4. The optical device according to claim 3, further comprising a
contrast detection unit that detects contrast of a subject image,
wherein the drive control unit switches the frequency of the two
drive signals in a subsequent one cycle to a predetermined one
cycle so as to cause the focal position of the lens to follow the
subject, based on the contrast of the predetermined one cycle in
the wobbling operation, detected by way of the contrast detection
unit.
5. The optical device according to claim 1, wherein the drive
control unit can switch the phase difference of the two drive
signals between 90.degree. and -90.degree., in a case of the
photography setting unit selecting a still image photography
mode.
6. A drive apparatus comprising: a vibrating part having an
electro-mechanical energy conversion element to which two drive
signals having variable phase difference are inputted; a relative
motion part that relatively moves in relation to the vibrating
part, by way of a drive force generate at the vibrating part by
according to vibration of the electro-mechanical energy conversion
element; and a control unit that inputs the two drive signals to
the electro-mechanical energy conversion element at a startup
frequency that is higher than a drive frequency used in driving,
while maintaining at phase difference at which the relative motion
part is in a stopped state, and when gradually reducing the
frequency of the two drive signals from the startup frequency and
reaching the drive frequency, sets the phase difference to a phase
difference that enables the relative motion part to relatively move
in relation to the vibrating part.
7. The drive apparatus according to claim 6, wherein the startup
frequency is a frequency of at least a resonance frequency of a
next higher-order vibration mode of a vibration mode including the
drive frequency.
8. The drive apparatus according to claim 6, wherein the phase
difference at which the relation motion part maintains a stopped
state is +/-15.degree. from 0.degree. or 180.degree..
9. A method of driving a vibration actuator, wherein the vibration
actuator comprises: a vibrating part having an electro-mechanical
energy conversion element to which two drive signals having
variable phase difference are inputted; and a relative motion part
that relatively moves in relation to the vibrating part, by way of
a drive force generated at the vibrating part according to
vibration of the electro-mechanical energy conversion element, the
method comprising the steps of: during startup of the vibration
actuator, inputting the two drive signals to the electro-mechanical
energy conversion element in a state maintaining a phase difference
therebetween at a phase difference at which the relation motion
part stays in a stopped state, and at a startup frequency that is
higher than the drive frequency used in driving of the vibration
actuator; and setting the phase difference to a phase difference at
which the relation motion part can relatively move in relation to
the vibrating part, upon gradually reducing the frequency of the
two drive signals from the startup frequency and reaching the drive
frequency.
10. An optical device comprising the drive apparatus according to
claim 6.
11. A drive apparatus for controlling driving of a vibration
actuator that generates a drive force, by applying two-phase
alternating signals having different phases to a piezeoelectric
body provided to a vibrating body to cause the vibrating body to
vibrate, the drive apparatus comprising: a speed control unit that
controls a drive speed of the vibration actuator, by causing a
frequency of the two-phase alternating signals applied to the
piezoelectric body to change; a frequency storage unit that stores
a predetermined frequency; and a stop determination unit that
determines whether the vibration actuator is stopped, wherein the
speed control unit causes the frequency of the alternating signals
applied to the piezoelectric body to change to the predetermined
frequency stored in the frequency storage unit, in a case of the
stop determination unit having determined that the vibration
actuator is stopped.
12. A drive apparatus that controls driving of a vibration actuator
that generates a drive force, by applying two-phase alternating
signals having different phases to a piezeoelectric body provided
to a vibrating body, the drive apparatus comprising: a speed
control unit that controls a drive speed of the vibration actuator,
by causing a frequency of the two-phase alternating signals applied
to the piezoelectric body to change; and a stop determination unit
that determines whether the vibration actuator is stopped, wherein
the speed control unit causes the frequency of the alternating
signals applied to the piezoelectric body to change so as to
approach an electrical resonance frequency, in a case of the stop
determination unit having determined that the vibration actuator is
stopped.
13. The drive apparatus according to claim 12, wherein the speed
control unit causes the frequency of the alternating signals
applied to the piezoelectric body to change to a rising direction,
in a case of the stop determination unit having determined that the
vibration actuator is stopped.
14. The drive apparatus according to claim 12, wherein the speed
control unit causes the frequency of the alternating signals
applied to the piezoelectric body to change to a frequency at which
the vibration actuator begins driving from a stopped state, in a
case of the stop determination unit having determined that the
vibration actuator is stopped.
15. The drive apparatus according to claim 12, wherein the speed
control unit causes the frequency of the alternating signal applied
to the piezoelectric body to change to the electrical resonance
frequency, in a case of the stop determination unit having
determined that the vibration actuator is stopped.
16. The drive apparatus according to claim 12, wherein the
electrical resonance frequency is a resonance frequency of a
capacitance of the piezoelectric body and an inductance of a drive
circuit applying the alternating signal to the piezoelectric
body.
17. The drive apparatus according to claim 11, further comprising a
speed detection unit that detects a drive speed of the vibration
actuator, wherein the speed control unit controls the drive speed
of the vibration actuator by causing a phase difference of the
two-phase alternating signals applied to the piezoelectric body to
change, and wherein the stop determination unit determines whether
the vibration actuator stopped, based on a state of the phase
difference of the two-phase alternating signals applied to the
piezoelectric body, and information of the drive speed detected by
way of the speed detection unit.
18. An optical device comprising: the drive apparatus for a
vibration actuator according to claim 11; a vibration actuator that
is driven by way of the drive apparatus for a vibration actuator;
and an optical member that is driven by way of the vibration
actuator.
19. An optical device comprising: an electro-mechanical energy
conversion element to which a drive signal is applied from a drive
circuit; a vibrating body that generates a drive force by way of
the electro-mechanical energy conversion element; a moving body
that is driven by the drive force of the vibrating body; and a
control unit that performs first control to control so that the
drive signal becomes a first frequency when causing the moving body
to drive, and performs second control to control so that the drive
signal becomes a second frequency when the moving body is stopped,
wherein the drive circuit has a smaller amount of power consumption
when the drive signal is the second drive signal than when the
drive signal is the first drive signal.
Description
[0001] This application is a Divisional of application Ser. No.
15/152,001 filed May 11, 2016 which is a Divisional of application
Ser. No. 14/381,063 filed Dec. 29, 2014, which is a National Stage
of PCT/JP2013/055522, filed Feb. 28, 2013, and claims the benefit
of priority (priorities) from Japanese Patent Application No.
2013-022196 filed Feb. 7, 2013, Japanese Patent Application No.
2012-287812 filed Dec. 28, 2012, Japanese Patent Application No.
2012-286941 filed Dec. 28, 2012, Japanese Patent Application No.
2012-059692 filed Mar. 16, 2012, and Japanese Patent Application
No. 2012-042439 filed Feb. 28, 2012, the entire contents of the
prior applications being incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a drive apparatus, a drive
method and an optical device.
BACKGROUND ART
[0003] (1) A technique of suppressing the generation of abnormal
noise related to the driving of a vibration wave motor has been
known (for example, refer to Patent Document 1). In Patent Document
1, abnormal noise when stopping the vibration-wave motor is
suppressed by causing the phase difference between an A-phase drive
signal and a B-phase drive signal to gradually vary from 90 deg to
0 deg.
[0004] (2) An imaging device that performs processing such as
auto-focus by driving an optical system by way of a vibration-wave
motor has been known (Patent Document 2).
[0005] (3) A vibration actuator causes a progressive vibration wave
(hereinafter abbreviated as progressive wave) to generate at the
driving face of an elastic body using the expansion and contraction
of a piezoelectric body, causing an elliptic motion to occur at the
driving face by way of this progressive wave, thereby driving a
moving element in pressurized contact with the wave crest of the
elliptic motion (for example, refer to Patent Document 3). Such a
vibration actuator has a characteristic in having high torque even
at low revolutions, and in the case of equipping to a drive
apparatus, it is possible to omit gears in the drive apparatus. For
this reason, it is possible to achieve quieting by elimination gear
noise, and the positioning accuracy also improves. This vibration
actuator has been equipped to some electric cameras. In addition,
some electric cameras can perform photography of a moving image in
addition to photography of still images (refer to Patent Document
4). In the case of performing photography of a moving image,
normally the capturing of sound is also performed.
[0006] (4) Conventionally, two vibration signals having different
phases from each other are applied to a piezoelectric effect
element in order to drive the vibration actuator. The frequency of
the vibration signal inputted starts from a frequency (startup
frequency) between the drive frequency used in order to drive the
vibration actuator and a resonance frequency of a next higher-order
vibration mode to a vibration mode (drive mode) including this
drive frequency, and gradually lowers to the drive frequency (for
example, refer to Patent Document 5).
[0007] (5) Conventionally, the drive apparatus of a vibration
actuator has controlled the operation of the vibration actuator by
causing the phase difference and frequency of alternating signals
input to the vibration actuator to vary (for example, Patent
Document 6).
[0008] [Patent Document 1]: Japanese Unexamined Patent Application,
Publication No. 2002-199749
[0009] [Patent Document 2]: Japanese Unexamined Patent Application,
Publication No. 2009-153286
[0010] [Patent Document 3]: Japanese Patent Publication No.
H01-017354
[0011] [Patent Document 4]: Japanese Unexamined Patent Application,
Publication No. H08-080073
[0012] [Patent Document 5]: Japanese Unexamined Patent Application,
Publication No. H03-022873
[0013] [Patent Document 6]: Japanese Patent Publication No.
4765405
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0014] (1) Upon performing stopping of a vibration-wave motor and
reverse rotation to the driving direction, the phase difference
between the A-phase drive signal and B-phase drive signal has been
made to change. With a method of causing the phase difference to
gradually change, the responsiveness of the vibration-wave motor is
harmed, as in Patent Document 1.
[0015] (2) Upon switching the driving direction of an optical
system by way of a vibration-wave motor, there has been a problem
in that abnormal noise occurs. Upon switching the driving direction
with the invention of Patent Document 2, driving of the optical
system is temporarily stopped by causing the voltage application to
the vibration-wave motor to stop. At this time, abnormal noises
generate accompanying the energy rise inside the drive circuit,
upon performing voltage application to the vibration-wave motor for
driving after switching direction. These abnormal noises are then
recorded during moving image photography, etc. by the imaging
device, for example.
[0016] (3) During moving image photography, when the lens is driven
in auto-focus (hereinafter abbreviated as AF), the sound at the
time of operation start of the vibration actuator is captured along
with the moving image. The sound at the time of operation start of
the vibration actuator is generated from the stator (vibrator) upon
causing the drive voltage to change from 0 V step-wise to a
predetermined voltage during the driving of the vibration
actuator.
[0017] (4) The above-mentioned startup frequency cannot be defined
as such a high frequency because it is limited to a frequency
between the drive frequency and the resonance frequency of the next
higher-order vibration mode of this drive mode. Therefore, due to
not being started from a sufficiently high frequency at the time of
startup, an outbreak sound may generate by the vibrator 20 suddenly
beginning vibration.
[0018] In recent years, there are many cases of a vibration
actuator being used in cameras for moving image photography, and in
these case, this outbreak sound is captured during moving image
photography, etc. In particular, during moving image photography,
the generation of this abnormal noise is further actualized since a
wobbling operation is performed and the power source is frequently
turned ON-OFF.
[0019] (5) The drive apparatus of Patent Document 6 enters a state
in which electricity is always being supplied during control of the
vibration actuator; therefore, there has been a problem in that
electricity consumption rises.
[0020] The object of the present invention is to provide a drive
apparatus, a drive method and an optical device that can suppress
the generation of abnormal noise. Another object of the present
invention is to provide a drive apparatus and optical device that
can reduce the electricity consumption of a vibration actuator
during control.
Means for Solving the Problems
[0021] A first aspect of the present invention provides an optical
device including: a vibration actuator for which a driving
direction changes according to a phase difference between a first
drive signal and a second drive signal; a drive apparatus that
applies a drive voltage to the vibration actuator by outputting the
first drive signal and the second drive signal; a drive voltage
change unit that changes the drive voltage; and a phase difference
change unit that changes the phase difference, wherein the drive
voltage change unit changes the drive voltage to a first voltage in
a case of driving the vibration actuator, and changes the drive
voltage to a second voltage that is greater than 0 and less than
the first voltage in a case of the phase difference change unit
changing the phase difference.
[0022] A second aspect of the present invention provides a drive
apparatus, including: a signal generation unit that generates a
pair of drive signals; an electro-mechanical conversion element to
which the drive signals generated by the signal generation unit are
applied; a vibrating body that generates a drive force by way of
vibration of the electro-mechanical conversion element; a moving
body that is under pressurized contact with the vibrating body and
is driven by way of the drive force; and a control unit that sets a
frequency and phase difference of the drive signals, wherein the
control unit changes the phase difference after setting the
frequency to a holding frequency at which a drive speed of the
moving body becomes substantially zero, when changing a driving
direction of the moving body.
[0023] A third aspect of the present invention provides an optical
device, including: vibration actuator that drive a lens using a
drive force generated at a driving face by way of excitation of an
electro-mechanical conversion element; a drive control unit that
provides two drive signals to the vibration actuator; and a
photography setting unit that can select a moving image photography
mode, wherein the drive control unit can change a speed of the
vibration actuator, in a case of the photography setting unit
selecting the moving image photography mode, by changing a phase
difference of the two drive signals, and changing a frequency of
the two drive signals to correspond to the phase difference thus
changed, while maintaining a voltage of the two drive signals to be
constant.
[0024] A forth aspect of the present invention provides a drive
apparatus, including: a vibrating part having an electro-mechanical
energy conversion element to which two drive signals having
variable phase difference are inputted; a relative motion part that
relatively moves in relation to the vibrating part, by way of a
drive force generate at the vibrating part by according to
vibration of the electro-mechanical energy conversion element; and
a control unit that inputs the two drive signals to the
electro-mechanical energy conversion element at a startup frequency
that is higher than a drive frequency used in driving, while
maintaining at phase difference at which the relative motion part
is in a stopped state, and when gradually reducing the frequency of
the two drive signals from the startup frequency and reaching the
drive frequency, sets the phase difference to a phase difference
that enables the relative motion part to relatively move in
relation to the vibrating part.
[0025] A fifth aspect of the present invention provides a method of
driving a vibration actuator, wherein the vibration actuator
includes: a vibrating part having an electro-mechanical energy
conversion element to which two drive signals having variable phase
difference are inputted; and a relative motion part that relatively
moves in relation to the vibrating part, by way of a drive force
generated at the vibrating part according to vibration of the
electro-mechanical energy conversion element, the method comprising
the steps of: during startup of the vibration actuator, inputting
the two drive signals to the electro-mechanical energy conversion
element in a state maintaining a phase difference therebetween at a
phase difference at which the relation motion part stays in a
stopped state, and at a startup frequency that is higher than the
drive frequency used in driving of the vibration actuator; and
setting the phase difference to a phase difference at which the
relation motion part can relatively move in relation to the
vibrating part, upon gradually reducing the frequency of the two
drive signals from the startup frequency and reaching the drive
frequency.
[0026] A sixth aspect of the present invention provides a drive
apparatus for controlling driving of a vibration actuator that
generates a drive force, by applying two-phase alternating signals
having different phases to a piezeoelectric body provided to a
vibrating body to cause the vibrating body to vibrate, the drive
apparatus comprising: a speed control unit that controls a drive
speed of the vibration actuator, by causing a frequency of the
two-phase alternating signals applied to the piezoelectric body to
change; a frequency storage unit that stores a predetermined
frequency; and a stop determination unit that determines whether
the vibration actuator is stopped, wherein the speed control unit
causes the frequency of the alternating signals applied to the
piezoelectric body to change to the predetermined frequency stored
in the frequency storage unit, in a case of the stop determination
unit having determined that the vibration actuator is stopped.
[0027] A seventh aspect of the present invention provides a drive
apparatus that controls driving of a vibration actuator that
generates a drive force, by applying two-phase alternating signals
having different phases to a piezeoelectric body provided to a
vibrating body, the drive apparatus comprising: a speed control
unit that controls a drive speed of the vibration actuator, by
causing a frequency of the two-phase alternating signals applied to
the piezoelectric body to change; and a stop determination unit
that determines whether the vibration actuator is stopped, wherein
the speed control unit causes the frequency of the alternating
signals applied to the piezoelectric body to change so as to
approach an electrical resonance frequency, in a case of the stop
determination unit having determined that the vibration actuator is
stopped.
[0028] A eighth aspect of the present invention provides an optical
device, including: an electro-mechanical energy conversion element
to which a drive signal is applied from a drive circuit; a
vibrating body that generates a drive force by way of the
electro-mechanical energy conversion element; a moving body that is
driven by the drive force of the vibrating body; and a control unit
that performs first control to control so that the drive signal
becomes a first frequency when causing the moving body to drive,
and performs second control to control so that the drive signal
becomes a second frequency when the moving body is stopped, wherein
the drive circuit has a smaller amount of power consumption when
the drive signal is the second drive signal than when the drive
signal is the first drive signal.
Effects of the Invention
[0029] According to the present invention, it is possible to
suppress the generation of abnormal noise.
[0030] In addition, it is possible to reduce the electricity
consumption of a vibration actuator during control.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a schematic view of a lens barrel according to a
first embodiment of the present invention;
[0032] FIG. 2 is a schematic view of a vibration-wave motor
provided to a lens barrel according to the first embodiment of the
present invention;
[0033] FIG. 3 is a control block diagram of a lens barrel according
to the first embodiment of the present invention;
[0034] FIG. 4 is a schematic electrical circuit diagram showing an
example of a booster unit;
[0035] FIG. 5 is a graph illustrating the relationship between the
drive voltage and duty cycle;
[0036] FIG. 6 is a graph showing the relationship between the
frequency of drive signals applied to the vibration-wave motor and
the rotational speed of the vibration-wave motor;
[0037] FIG. 7 is a graph showing the relationship between the phase
difference between an A-phase drive signal and B-phase drive signal
applied to the vibration-wave motor, and the rotational speed of
the vibration-wave motor;
[0038] FIG. 8 is a flowchart related to control of a drive
apparatus by a control device of the lens barrel according to the
first embodiment of the present invention;
[0039] FIG. 9 is a timing chart showing an example of control of
the drive apparatus by the control device of the lens barrel
according to the first embodiment of the present invention;
[0040] FIG. 10 is a table showing the relationship of a change rate
of the phase difference between the A-phase drive signal and the
B-phase drive signal and the abnormal noise suppression level
during phase difference change;
[0041] FIG. 11 is a control block diagram of a lens barrel
according to a second embodiment of the present invention;
[0042] FIG. 12 is a flowchart related to control of the drive
apparatus by the control device of the lens barrel according to the
second embodiment of the present invention;
[0043] FIG. 13 is a flowchart related to control of the drive
apparatus by the control device of the lens barrel according to the
second embodiment of the present invention;
[0044] FIG. 14 is a schematic view of a lens barrel according to a
third embodiment of the present invention;
[0045] FIG. 15 is a schematic view of a vibrating body of the
vibration-wave motor;
[0046] FIG. 16 is a graph showing phase difference-rotational speed
characteristic of the vibration-wave motor;
[0047] FIG. 17 is a graph showing a frequency-rotational speed
characteristic of the vibration-wave motor;
[0048] FIG. 18 is a block diagram showing the drive apparatus
according to a third embodiment of the present invention;
[0049] FIG. 19 is a flowchart related to the drive control of the
vibration-wave motor by the drive apparatus according to the third
embodiment of the present invention;
[0050] FIGS. 20A to 20C provide a timing chart example related to
drive control of the vibration-wave motor by the drive apparatus
according to the third embodiment of the present invention;
[0051] FIG. 21 is a graph illustrating a holding frequency;
[0052] FIG. 22 is a flowchart related to setting processing of the
holding frequency;
[0053] FIG. 23 is a diagram illustrating a electric camera of a
fourth embodiment of the present invention;
[0054] FIG. 24 is a diagram illustrating a lens barrel of the
fourth embodiment of the present invention;
[0055] FIG. 25 is a diagram illustrating a vibrator of a
vibration-wave motor according to the fourth embodiment of the
present invention;
[0056] FIG. 26 is a block diagram illustrating a drive apparatus of
the vibration-wave motor;
[0057] FIG. 27A is a graph showing the relationship of the
rotational speed of the vibration-wave motor relative to the phase
difference of the drive signals, and FIG. 27B is a graph showing
the relationship of rotational speed of the vibration-wave motor
relative to the drive frequency;
[0058] FIG. 28 is a timing chart illustrating the operations of a
first operation example of the drive apparatus according to the
fourth embodiment;
[0059] FIG. 29 is a flowchart illustrating the operations of the
first operation example of the drive apparatus according to the
fourth embodiment;
[0060] FIG. 30 is a timing chart illustrating the operations of a
second operation example of the drive apparatus according to the
fourth embodiment of the present invention;
[0061] FIG. 31 is a view illustrating a lens barrel according to a
fifth embodiment of the present invention;
[0062] FIG. 32 is a view illustrating a vibration-wave motor
according to the fifth embodiment;
[0063] FIG. 33 is a view illustrating the operating principle of
the vibration-wave motor according to the fifth embodiment;
[0064] FIG. 34 is a view illustrating a camera including a lens
barrel equipped with a vibration actuator driven by a drive
apparatus according to a sixth embodiment;
[0065] FIG. 35 is a block diagram illustrating a vibration actuator
and a drive apparatus of a vibration-wave actuator according to the
sixth embodiment;
[0066] FIG. 36 is a view illustrating the lens barrel equipped with
the vibration actuator driven by the drive apparatus according to
the sixth embodiment;
[0067] FIG. 37 is a graph showing the relationship between the
phase difference between the A-phase and B-phase and the rotational
speed of a moving element;
[0068] FIG. 38 is a graph showing the relationship between the
frequency of the drive signal and the impedance of the vibration
actuator;
[0069] FIG. 39 is a graph showing an example of lens driving by the
vibration actuator according to the sixth embodiment;
[0070] FIG. 40 is a schematic view illustrating the overall
configuration of a camera 701 according to a seventh
embodiment;
[0071] FIG. 41 is a diagram illustrating the configuration of an
ultrasonic-wave motor 720 according to the seventh embodiment;
[0072] FIG. 42 is a diagram illustrating the configuration of a
drive apparatus 330 connected to the ultrasonic-wave motor 720 of
the seventh embodiment;
[0073] FIGS. 43A and 43B provide graphs showing the characteristics
of the ultrasonic-wave motor 720 according to the seventh
embodiment;
[0074] FIG. 44 is a timing chart illustrating the driving pattern
of the drive apparatus 730 in wobbling operation according to the
seventh embodiment;
[0075] FIG. 45 is a timing chart illustrating the driving pattern
of a drive apparatus in the wobbling operation of a comparative
example; and
[0076] FIG. 46 is a graph comparing between the electricity
consumptions of ultrasonic-wave motors according to the comparative
example and the seventh embodiment.
EXPLANATION OF REFERENCE NUMERALS
[0077] 10, 30: lens barrel, 12: vibration-wave motor, 14: drive
apparatus, 15, 35: lens-side MCU, 17: storage unit, 20: camera
body, 21: body-side MCU, 141: drive pulse generation unit, 142:
booster unit, 151: frequency change unit, 152: drive voltage
setting unit, 153: duty-cycle change unit, 154, 35-4: phase
difference change unit, 35-3: power source voltage change unit,
35-5: change rate setting unit, 50: level table, 201:
vibration-wave motor, 202: lens barrel, 280: drive circuit, 281:
control unit, 282: oscillation part, 283: phase shifting unit,
284a, 284b: amplifier, 290: drive apparatus, 261: vibrating body,
262: moving body, f0: holding frequency, f9, f10: natural
frequency, 301: camera, 310: vibration-wave motor, 313:
piezoelectric body, 320: lens barrel, 339: contrast detection unit,
341: drive control unit, 347: photography setting unit, 350:
vibration-wave motor, 353: piezeoelectric body, L3: third lens
unit, 501: lens barrel, 502: camera, 520: vibrator, 521:
piezoelectric body, 522: elastic body, 522a: driving face, 528:
moving element, 600: vibration actuator, 601: drive apparatus, f1:
startup frequency, f3: resonance frequency, fs: drive frequency,
710: lens barrel, 720: ultrasonic-wave motor, 722: vibrator, 724:
piezoelectric element, 730: drive apparatus, 731: control unit,
731a: speed control part, 731b: stop determination part, 732: drive
circuit, 733: storage unit, 734: speed detection unit.
PREFERRED MODE FOR CARRYING OUT THE INVENTION
First Embodiment
[0078] FIG. 1 is a schematic view showing the configuration of a
lens barrel according to a first embodiment of the present
invention. A lens barrel 10 is a lens barrel for an imaging device
such as a digital camera. The lens barrel 10 includes an outer
fixed cylinder 101, a first inner fixed cylinder 102 and second
inner fixed cylinder 103. The outer fixed cylinder 101 covers an
outer circumferential part of the lens barrel 10. The first inner
fixed cylinder 102 and second inner fixed cylinder 103 are present
more on the inner circumferential side than the outer fixed
cylinder 101, with the first inner fixed cylinder 102 being
positioned on a subject side, and the second inner fixed cylinder
103 being positioned on the image side.
[0079] Between the outer fixed cylinder 101 and first inner fixed
cylinder 102, a vibration-wave motor (vibration actuator) 12, drive
apparatus 14, and gear unit module 104 are provided, and are fixed
to the first inner fixed cylinder 102. The gear unit module 104 has
a reduction gear 105 that reduces and transmits the output of the
vibration-wave motor 12.
[0080] In addition, from the subject side, a first lens unit L1 and
second lens unit L2 are fixed to the first inner fixed cylinder
102. From the subject side, a fourth lens unit L4 is fixed to the
second inner fixed cylinder 103. Between the second lens unit L2
and fourth lens unit L4, the third lens unit L3 is arranged that is
an AF lens for focusing retained in an AF ring 107. In other words,
the first lens unit L1, second lens unit L2, third lens unit L3 and
fourth lens unit L4 are arranged in order in an optical axis
direction from the subject side to an imaging element side.
[0081] Between the AF ring 107 and first inner fixed cylinder 102,
a cam ring 106 is provided to rotate freely about the optical axis
direction. The cam ring 106 rotates by way of the output of the
vibration-wave motor 12 transmitted by way of the reduction gear
105. In addition, on the inner side of the cam ring 106, a key
groove 106a is cut in a spiral shape in the circumferential
direction. In addition, a fixed pin 107a is provided to the outer
circumferential side of the AF ring 107. This fixed pin 107a is
inserted into the key groove 106a of the cam ring 106.
[0082] In addition, the drive apparatus 14 is arranged at a
retention unit 101a that overhangs from an inner circumferential
side of the outer fixed cylinder 101 to inside. The drive apparatus
14 is electrically connected to the vibration-wave motor 12, and
causes the vibration-wave motor 12 to drive.
[0083] The output of the vibration-wave motor 12 causes the cam
ring 106 to rotate through the reduction gear 105, whereby the
fixed pin 107a moves being guided in the key groove 106a, and
causes the AF ring 107 to move in the optical axis direction. In
addition, the output of the vibration-wave motor 12 can cause the
AF ring 107 to stop by causing the cam ring 106 to stop. In other
words, the drive apparatus 14 can cause the third lens unit L3 to
move by driving the AF ring 107 in the optical axis direction by
way of causing the vibration-wave motor 12 to drive, and thus can
cause a subject focused on the imaging element to form an
image.
[0084] FIG. 2 is a schematic view showing the configuration of the
vibration wave motor 12. The vibration-wave motor 12 is a rotating
shaft-type (S-type) vibration-wave motor, and includes a vibrator
121, moving element 124, fixed member 125, bearing 126, output
shaft 127, pressurizing member 128, bearing receiver 129, stopper
130, rubber member 131 and gear member 132.
[0085] The vibrator 121 has an elastic body 122 and piezoelectric
body 123. The elastic body 122 is formed from a metallic material
having a large resonance sharpness. The shape of the elastic body
122 forms an annular shape. The elastic body 122 consists of a
comb-tooth part 122a and a base part 122b. The piezoelectric body
123 is joined at one face of the base part 122b, and the comb-tooth
part 122a is provided to the opposing face of this face. The
comb-tooth part 122a has a tip end face of a projecting portion
thereof that forms a driving face, and pressurized contacts the
moving element 124. At the driving face of the elastic body 122, a
resin film is formed for abrasion resistance securement when driven
at high speed. The material of this resin film, for example, has
polyamideimide as a main component, and PTFE is added thereto. This
resin film has a Young modulus on the order of 4 to 8 GPa, and the
film thickness thereof is no more than 50 .mu.m, for example.
[0086] The piezoelectric body 123 is an electro-mechanical
conversion element such as a piezoelectric element or
electrorestrictive element that converts electrical energy to
mechanical energy. The piezeoelectric body 123 is divided into two
phases (A-phase, B-phase) along the circumferential direction, and
is arranged so that poles are alternatingly arranged every 1/2
wavelength for each phase, and an interval of 1/4 wavelength is
open between the A-phase and B-phase. The phase difference between
the drive signal output to the A-phase of the piezoelectric body
123 and the drive signal output to the B-phase thereof is variable.
When the respective drive signals are applied to the A-phase and
B-phase of the piezoelectric body 123, the piezoelectric body 123
excites. Deflection of the base part 122b of the elastic body 122
due to excitation of the piezoelectric body 123 is magnified by the
comb-tooth part 122a of the elastic body 122, and makes a
progressive wave at the tip end of the driving face of the
comb-tooth part 122.
[0087] The moving element 124 is formed from a light metal such as
aluminum. A sliding face of the moving element 124 that pressurized
contacts the comb-tooth part 122a is subjected to Alumite treatment
for an abrasion resistance improvement.
[0088] The output shaft 127 is joined so as to rotate together with
the moving element 124 via the rubber member 131. The rubber member
131 has a function of joining the moving element 124 and output
shaft 127 with the adhesion by way of rubber, and a function of
absorbing vibrations in order not to transmit vibration from the
moving element 124 to the output shaft 127.
[0089] The pressurizing member 128 is arranged between the gear
member 132 fixed to the output shaft 127 and the bearing receiver
129. The bearing receiver 129 is inserted inside of the bearing
126. The bearing 126 is inserted inside of the fixed member 125.
The gear member 132 is inserted so as to fit in the notched parts
(D cut) (not illustrated) of the output shaft 127. Then, the gear
member 132 is fixed by the stopper 130, and rotates along with the
output shaft 127. It should be noted that a pressure force
adjusting washer (not illustrated) is arranged between the pressure
member 128 and the bearing receiver 129.
[0090] FIG. 3 is a control block diagram of the lens barrel
according to the first embodiment of the present invention. FIG. 3
illustrates a camera body 20 along with the lens barrel 10. In FIG.
3, the lens barrel 10 includes the vibration-wave motor 12, drive
apparatus 14, lens-side MCU (Micro Control Unit) 15, detection unit
16 and storage unit 17.
[0091] The drive apparatus 14 includes a drive pulse generation
unit 141 and booster unit 142, and drives the vibration-wave motor
12 by applying drive voltage to the vibration-wave motor 12. The
lens-side MCU 15 includes a frequency change unit 141, drive
voltage setting unit 152, duty-cycle change unit 153 and phase
difference change unit 154, and controls the drive apparatus
14.
The camera body 20 includes a body-side MCU 21.
[0092] The drive pulse generation unit 141 generates a drive pulse
for the A-phase and a drive pulse for the B-phase, and outputs to
the booster unit 142. The drive pulse generation unit 141 can
change the frequency of the drive pulse for the A-phase and the
drive pulse for the B-phase, duty cycle (value arrived at by
dividing pulse width by pulse period), and phase difference, based
on the control of the lens-side MCU 15.
[0093] The booster unit 142 has a circuit configuration like that
shown in FIG. 4, for example, and outputs the A-phase drive signal
and B-phase drive signal based on the drive pulse for the A-phase
and drive pulse for the B-phase input from the drive pulse
generation unit 141. The booster unit 142 outputs the A-phase drive
signal and B-phase drive signal to the vibration-wave motor 12.
[0094] The vibration wave motor 12 is driven according to the
A-phase drive signal and B-phase drive signal. The drive voltage
driving the vibration-wave motor 12 becomes substantially the
average amplitude of these drive signals, i.e. a value arrived at
by dividing the time integral of the voltage of a predetermined
period by the time. In the case of the drive signal being a square
wave that changes between zero and a predetermined maximum voltage
V.sub.MAX as shown in FIG. 5, the product of the maximum voltage
V.sub.MAX of the drive signal and the duty cycle is an average
amplitude V.sub.AVE, and this average amplitude V.sub.AVE
corresponds to the drive voltage. In the example of FIG. 3, the
maximum output voltage of the booster unit 142 corresponds to the
maximum voltage V.sub.MAX of FIG. 5, and the product with the duty
cycle changed by the duty cycle changed by way of the duty-cycle
change unit 153 becomes the drive voltage.
[0095] In order to change the drive voltage, it is sufficient to
change the amplitude, duty cycle or both thereof. In the first
embodiment, the drive voltage is changed by changing the duty cycle
by way of the duty-cycle change unit 153.
[0096] When the vibration-wave motor 12 is rotating, the drive
voltage is set to V.sub.reg. Then, in the present invention, when
changing the phase difference in order to stop the vibration-wave
motor 12 or perform reversing the driving direction, the drive
voltage is set to V.sub.1, which is smaller than V.sub.reg and not
zero. Since the amplitude of vibration generated at the vibrator
121 is great in a state in which the drive voltage is set to
V.sub.reg, abnormal noise tends to generate in a case of changing
the phase difference with the drive voltage remaining as V.sub.reg
as is conventionally. In the present invention, the generation of
abnormal noise is reduced by setting the drive voltage to V.sub.1
during phase difference changing.
[0097] The frequency change unit 151 of the lens-side MCU 15
changes the setting of the drive pulse generation unit 14 for the
frequency of the drive pulses of the A-phase and B-phase. The
frequency of the drive signal outputted to the vibration-wave motor
12 is changed accompanying change of the frequency of the drive
pulses, whereby the rotational speed of the vibration-wave motor 12
changes. The frequency-rotational speed characteristic of the
vibration-wave motor 12 is as shown in FIG. 6.
[0098] When the frequency of the drive signal becomes the frequency
f.sub.0 shown in FIG. 6, the rotational speed of the vibration-wave
motor 12 becomes N.sub.0 rpm (for example, 0 rpm), and stops. When
the frequency of the drive signal becomes a frequency f.sub.1,
which is smaller than the frequency f.sub.0, the vibration-wave
motor 12 is driven at the rotational speed N.sub.1 rpm. Similarly,
when the frequency of the drive signal becomes a frequency f.sub.2,
which is smaller than the frequency f1, the vibration-wave motor 12
is driven at a rotational speed N.sub.2 rpm, which is faster than
the rotational speed N.sub.1.
[0099] The drive voltage setting unit 152 sets the drive voltage
applied to the vibration-wave motor 12. The duty-cycle change unit
153 changes the setting of the drive pulse generation unit 141 for
the duty cycle of the A-phase drive pulse and the B-phase drive
pulse so that the drive voltage set by the drive voltage setting
unit 152 is applied.
[0100] The phase difference change unit 154 changes the setting of
the drive pulse generation unit 141 for the phase difference
between the drive pulse for the A-phase and the drive pulse for the
B-phase outputted by the drive pulse generation unit 141. The phase
difference-rotational speed characteristic of the vibration-wave
motor 12 is as shown in FIG. 7.
[0101] As shown in FIG. 7, the rotational speed of the
vibration-wave motor 12 reaches a maximum speed of positive
rotation (for example, clockwise rotation) when the phase
difference is +90 deg, and reaches a maximum speed of reverse
rotation (for example, counter-clockwise rotation) when the phase
difference is -90 deg. The setting of the drive pulse generation
unit 141 for the phase difference between the drive pulse for the
A-phase and the drive pulse for the B-pulse is set to +90 deg or
-90 deg.
[0102] The lens-side MCU 15 performs communication with the
body-side MCU 21. The lens-side MCU 15 sends lens information, for
example, to the body-side MCU 21. On the other hand, the body-side
MCU 21 sends drive instructions of the third lens unit L3 according
to the vibration-wave motor 12 to the lens-side MCU 15. A target
position to which to drive the third lens unit L3 is at least
included in the drive instructions of the third lens unit L3.
[0103] The detection unit 16 is configured from an optical-type
encoder, magnetic encoder, etc., detects the position and/or speed
of the third lens unit L3 driven by the driving of the
vibration-wave motor 12, and outputs these detection values to the
lens-side MCU 15 as electrical signals (detection signals). The
storage unit 17 is ROM or the like, and a control program executed
by the lens-side MCU 15 to control the lens barrel 10, lens
information and the like are stored therein.
[0104] FIG. 8 is a flowchart relating to control of the drive
apparatus 14 executed by the lens-side MCU 15. The processing in
FIG. 8 is started when the lens-side MCU 15 received a drive
instruction for the third lens unit L3 from the body-side MCU
21.
[0105] In Step S300 in FIG. 8, the lens-side MCU 15 determines the
rotational direction and rotational speed of the vibration-wave
motor 12 based on the drive instruction for the third lens unit L
received from the body-side MCU 21 and the detection signals
detected by the detection unit 16.
[0106] In Step S301, the lens-side MCU 15 judges whether to change
the phase difference between the drive pulse for the A-phase and
the drive pulse for the B-phase. The lens-side MCU 15 positively
judges Step S301 in the case of it being necessary to make the
rotational direction reverse, based on the rotational direction of
the vibration-wave motor 12 at the moment when starting Step S301
and the rotational direction of the vibration-wave motor 12
determined in Step S300. The lens-side MCU 15 advances the
processing to Step S302 in the case of Step S301 being positively
judged, and advances the processing to Step S305 in the case of
Step S301 being negatively judged.
[0107] In Step S302, the lens-side MCU 15 changes the drive voltage
to V.sub.1. For example, the following such processing is performed
using the drive voltage setting unit 152 and the duty-cycle change
unit 153. First, the drive voltage setting unit 152 sets the drive
voltage to V.sub.1. Next, the duty-cycle change unit 153 changes
the setting of the drive pulse generation unit 141 relating to the
duty cycles of the drive pulses of the A-phase and B-phase, so that
the average amplitudes of the A-phase drive signal and B-phase
drive signal become V.sub.1.
[0108] In Step S303, the lens-side MCU 15 changes the phase
difference between the drive pulse of the A-phase and the drive
pulse of the B-phase, based on the rotational direction of the
vibration-wave motor 12 determined in Step S300. For example, the
phase difference change unit 154 of the lens-side MCU 15 changes
the setting of the drive pulse generation unit 141 relating to the
phase difference to a phase difference corresponding to the
rotational direction of the vibration-wave motor 12 determined in
Step S300.
[0109] In Step S304, the lens-side MCU 15 changes the drive voltage
to V.sub.reg. For example, the following such processing is
performed using the drive voltage setting unit 152 and the
duty-cycle change unit 153. First, the drive voltage setting unit
152 sets the drive voltage to V.sub.reg. Next, the duty-cycle
change unit 153 changes the setting of the drive pulse generation
unit 141 relating to the duty cycles of the drive pulses of the
A-phase and B-phase, so that the average amplitudes of the A-phase
drive signal and B-phase drive signal become V.sub.reg.
[0110] In Step S305, the lens-side MCU 15 changes the frequencies
of the drive pulses of the A-phase and B-phase to drive the
vibration-wave motor 12. For example, the frequency change unit 151
of the lens-side MCU 15 changes the setting of the drive pulse
generation unit 141 relating to the frequency of the drive pulses
of the A-phase and B-phase from f.sub.0 to f.sub.1 or f.sub.2.
[0111] In Step S306, the lens-side MCU 15 judges whether the third
lens unit L3 was driven until a target position of the third lens
unit L3 included in the drive instruction. For example, the
lens-side MCU 15 detects the position of the third lens unit L3
based on the detection signals of the detection unit 16, and
compares this position with the target position of the third lens
unit L3 included in the drive instruction. The lens-side MCU 15
returns the processing to Step S305 in the case of Step S306 being
negatively judged, and advances the processing to Step S307 in the
case of Step S306 being positively judged.
[0112] In Step S307, the lens-side MCU 15 changes the frequency of
the drive pulses of the A-phase and B-phase to cause the
vibration-wave motor 12 to stop. For example, the frequency change
unit 151 of the lens-side MCU 15 changes the frequencies of the
drive pulses of the A-phase and B-phase to f.sub.0.
[0113] FIG. 9 is a timing chart relating to drive control of the
vibration-wave motor 12. FIG. 9 illustrates side-by-side the
position of the third lens unit L3, rotational speed of the
vibration-wave motor 12, setting value of frequency in the drive
pulse generation unit 141, setting value of phase difference in the
drive pulse generation unit 141 and timing chart of drive voltage,
respectively.
[0114] In FIG. 9, the lens-side MCU 15 receives from the body-side
MCU 21 the drive instructions for the third lens unit L3 three
times (for example, timing t1, t5, t11). The first time drive
instruction is a drive instruction to cause the third lens unit L3
to drive until a position Wbe on the optical axis. The second time
drive instruction is a drive instruction to cause the third lens
unit L3 to drive until a position Waf on the optical axis. The
third time drive instruction is a drive instruction to cause the
third lens unit L3 to drive until a position W.sub.0 on the optical
axis.
[0115] The lens-side MCU 15 changes the setting value of the
frequency at the timing t2 (Step S305) when receiving the first
time drive instruction at timing t1, since it is no longer
necessary to change the phase difference (NO in Step S301 of FIG.
8). The rotational speed of the vibration-wave motor 12 gradually
becomes faster in proportion as the setting value of the frequency
becomes smaller than f.sub.0. The position of the third lens unit
L3 reaches the target position Wbe at the timing t4 (YES in Step
S306), and subsequently the setting value of the frequency becomes
f.sub.0 and the vibration-wave motor 12 stops (Step S307).
[0116] The lens-side MCU 15 first changes the drive voltage from
V.sub.reg to V.sub.1 (Step S302) when receiving the second time
drive instruction at the timing t5 since it is necessary to change
the phase difference (YES in Step S301 of FIG. 8). Next, the
lens-side MCU 15 changes the phase difference between the drive
pulse of the A-phase and the drive pulse of the B-phase at the
timing t6 from +90 deg to -90 deg (Step S303). While changing the
phase difference, the drive voltage is maintained as is at V.sub.1.
The lens-side MCU 15 changes the drive voltage from V.sub.1 to
V.sub.reg (Step S304) at the timing t7 after changing of the phase
difference finished. Subsequently, the lens-side MCU 15 changes the
setting value of the frequency at the timing t8 (Step S305). At
this time, since the distance that is necessary to drive the third
lens unit L is longer than when at the timing t2, the setting value
of the frequency is set to be lower than at the timing t2. The
position of the third lens unit L3 arrives at the target position
Waf at the timing t10 (YES in Step S306), and subsequently the
setting value of the frequency becomes f.sub.0 and the
vibration-wave motor 12 stops (Step S307).
[0117] The lens-side MCU 15 first changes the drive voltage from
V.sub.reg to V.sub.1 (Step S302) when receiving the third time
drive instruction at the timing t11 since it is necessary to change
the phase difference (YES in Step S301 of FIG. 8). Next, the
lens-side MCU 15 changes the phase difference between the drive
pulse of the A-phase and the drive pulse of the B-phase at the
timing t12 from -90 deg to +90 deg (Step S303). While changing the
phase difference, the drive voltage is maintained as is at V.sub.1.
The lens-side MCU 15 changes the drive voltage from V.sub.1 to
V.sub.reg (Step S304) at the timing t13 after changing of the phase
difference finished. Subsequently, the lens-side MCU 15 changes the
setting value of the frequency at the timing t14 (Step S305). The
position of the third lens unit L3 arrives at the target position
W.sub.0 at the timing t16 (YES in Step S306), and subsequently the
setting value of the frequency becomes f.sub.0, and the
vibration-wave motor 12 stops (Step S307).
[0118] Abnormal noise upon changing the phase difference such as at
the timing t6 and t12 can be suppressed enough to set the value of
V.sub.1 lower relative to the value of V.sub.reg. The effect of
abnormal noise suppression is not limited to only the phase
difference change explained in FIG. 9 and, for example, is
effective also for a phase difference change from 0 deg to +90 deg,
a phase difference change from +90 deg to 0 deg, a phase difference
change from 0 deg to -90 deg, a phase difference change from -90
deg to 0 deg, etc. In addition, lowering the drive voltage to
V.sub.1 contributes also to a reduction in the electricity
consumption of the vibration-wave motor 12.
[0119] The below operating effects are obtained according to the
first embodiment explained above. The lens-side MCU 15 of the lens
barrel 10 controls the drive apparatus 14 that outputs the A-phase
drive signal and B-phase drive signal to the vibration-wave motor
12, and applies drive voltage to the vibration-wave motor 12. The
lens-side MCU 15 includes the drive voltage setting unit 152 and
duty-cycle change unit 153, and changes the drive voltage applied
to the vibration-wave motor 12. In addition, the lens-side MCU 15
includes the phase difference change unit 154, and changes the
phase difference between the A-phase drive signal and B-phase drive
signal by changing the phase difference between the drive pulses of
the A-phase and B-phase. The drive voltage setting unit 152 and
duty-cycle change unit 153 change the drive voltage to V.sub.reg in
the case of rotationally driving the vibration-wave motor 12 (Step
S304 in FIG. 8), and change the drive voltage to V.sub.1 which is
greater than zero and smaller than V.sub.reg in the case of the
phase difference change unit 154 changing the phase difference
(Step S302 in FIG. 8). By configuring in this way, the lens barrel
10 can reduce the abnormal noise during phase difference changing
without harming the responsiveness of the vibration-wave motor
12.
Second Embodiment
[0120] A second embodiment of the present invention will be
explained. In the second embodiment, a reduction in abnormal noise
during phase difference change is achieved by not only lowering the
drive voltage prior to changing the phase difference, but also
setting the change rate of the phase difference to be low
(slowing).
[0121] For the duty cycle of the drive pulse of each phase, the
range of value options thereof is limited by the resolving power of
PWM, etc. For example, the duty cycle of the drive pulse is
assigned to the setting values of 0 to 255, and it is not possible
to set the setting value of the duty cycle to a value between "0"
and "1". The lower limit for the setting value of V.sub.1 is
decided, for example, by the product of the duty cycle d1
corresponding to the setting value "1" and the maximum voltage VMAX
of the drive signal.
[0122] The value of VMAX varies according to the circuit
configuration, ambient temperature, etc. of the drive apparatus of
the vibration-wave motor 12. For example, the value of VMAX becomes
larger as the ambient temperature becomes lower. In the case of the
drive voltage serving as the level at which abnormal noise can be
ignored being defined as Vs, there is a risk of the duty cycle ds
such that V.sub.1.ltoreq.V.sub.8 when the value of V.sub.MAX is
large becoming a value smaller than the duty cycle d1 corresponding
to the setting value "1".
[0123] In the second embodiment, by setting the change rate of the
phase difference to be low in order to solve the problem in the
above-mentioned such design, the generation of abnormal noise is
suitably suppressed even in the case of the lower limit for the
setting value of V.sub.1 being large. FIG. 10 is a table
illustrating the abnormal noise suppression effect by setting the
change rate of the phase difference to be low.
[0124] FIG. 10 is an example of a level table relating to the
suppression level of abnormal noise. In level table 50 exemplified
in FIG. 10, in the cases of the proportion of V.sub.1 relative to
V.sub.reg being 100%, 75%, 50% and 25%, the suppression levels of
abnormal noise are shown for when the change rate of the phase
difference is 90 deg/msec, 30 deg/msec and 5 deg/msec,
respectively. The suppression level of abnormal noise is a value
determined in advance at the design stage of the lens barrel, and
is divided into the three stages of level 1, level 2 and level 3.
When the suppression level is level 1, abnormal noise does not
generate upon phase difference change. When the suppression level
is level 2, abnormal noise upon phase difference change does not
stand out and can be ignored. When the suppression level is level
3, the abnormal noise during phase difference change stands out.
Abnormal noise standing out represents a state in which abnormal
noise is recorded without confusing for other noise, within
recorded sound during moving image capture.
[0125] As is evident from looking at FIG. 10, for the suppression
level of abnormal sound, the level becomes lower as the proportion
of V.sub.1 relative to V.sub.reg is decided smaller. In other
words, abnormal noise can be suppressed more as the proportion of
V.sub.1 relative to V.sub.reg is decided smaller. In addition, for
the suppression level of abnormal noise, the level comes to be
lower as the change rate of the phase difference becomes
slower.
[0126] For example, when deciding the setting value of V.sub.1 so
that the proportion of V.sub.1 relative to V.sub.reg becomes 50% in
the case of the change rate of the phase difference being 90
deg/msec, the suppression level of abnormal noise is level 2. On
the other hand, in the case of slowing the change rate of the phase
difference to 30 deg/msec, the setting value of V.sub.1 can be
decided so that the suppression level of abnormal noise becomes
level 2, even if the proportion of V.sub.1 relative to V.sub.reg is
75%. The lens barrel according to the second embodiment of the
present invention, in the case of the suppression level being the
same, when the proportion of V.sub.1 relative to V.sub.reg is
large, the change rate of the phase difference is set to be lower
than when the proportion of V.sub.1 relative to V.sub.reg is
small.
[0127] The lens barrel according to the second embodiment of the
present invention includes the same configuration as FIG. 1. FIG.
11 is a control block diagram for the lens barrel according to the
second embodiment of the present invention. For the same
configurations as the control block diagram shown in FIG. 3 in the
control block diagram shown in FIG. 11, the same reference numbers
as FIG. 3 are assigned and explanations thereof are omitted. It
should be noted that, in the following explanation, the setting
value relating to the duty cycle of the drive pulse generation unit
141 is explained as being constant at a predetermined value. The
drive voltage applied to the vibration-wave motor 12 is changed
based on the power source voltage of the booster unit 142 (FIG.
4).
[0128] The lens barrel 30 in FIG. 11 includes a lens-side MCU 35 in
place of the lens-side MCU 15. In addition, the lens barrel 30
further includes a temperature detection unit 38 that detects the
ambient temperature. The lens-side MCU 35 includes a power source
voltage change unit 35-3 and phase difference change unit 35-4 in
place of the duty-cycle change unit 153 and phase difference change
unit 154. Furthermore, the lens-side MCU 35 newly includes a change
rate setting unit 35-5.
[0129] The power source voltage change unit 35-3 changes the power
source voltage of the booster unit 142. When the power source
voltage of the booster unit 142 is changed, the amplitudes of the
A-phase drive signal and B-phase drive signal change, and thus the
drive voltage applied to the vibration-wave motor 12 changes.
[0130] The change rate setting unit 35-5 sets the change rate of
the phase difference based on the proportion of V.sub.1 relative to
V.sub.reg decided at the design stage, and the setting value of the
suppression level set in advance. For example, in the case of
V.sub.1 being set to 75% of V.sub.reg, and the suppression level
being set to level 2 in advance, the change rate setting unit 35-5
references the column of the level table 50 in which the proportion
of V.sub.1 relative to V.sub.re, is 75%, and sets the change rate
of the phase difference to a change rate such that the suppression
level is level 2, e.g., 30 deg/msec. It should be noted that the
level table 50 is stored in the storage unit 17 or the like. For
the setting value of the suppression level, it may be configured
for the user to set using an operation member that is not
illustrated, or it may be configured so that the lens-side MCU 35
or body-side MCU 21 automatically sets based on the operation mode
of the imaging device equipped with the lens barrel 30. For
example, it may be configured so that, in the case of performing
photography not accompanied by recording of sound like in still
image photography, the lens-side MCU 35 or the body-side MCU 21
sets the suppression level to level 3, and in the case of
performing photography accompanied by the recording of sound like
in moving image photography, the lens-side MCU 35 or the body-side
MCU 21 sets the suppression level to level 1.
[0131] The phase difference change unit 35-4 changes the setting of
the drive pulse generation unit 141 relating to the phase
difference between the drive pulse for the A-phase and the drive
pulse for the B-phase outputted by the drive pulse generation unit
141. Upon doing so, the phase difference is changed based on the
change rate set by the change rate setting unit 35-5.
[0132] FIG. 12 and FIG. 13 are flowcharts relating to the control
of the drive apparatus 14 performed by the lens-side MCU 35. The
processing of FIG. 12 is initiated when the lens-side MCU 35
receives the drive instruction for the third lens unit L3 from the
body-side MCU 21. For processing that is the same as that shown in
FIG. 8 among the processing shown in FIG. 12 and FIG. 13,
explanations thereof will be omitted.
[0133] In Step S401, the lens-side MCU 35 changes the drive voltage
to V.sub.1. For example, the drive voltage setting unit 152 of the
lens-side MCU 35 sets the drive voltage to V.sub.1. Next, the power
source voltage change unit 35-3 changes the power source voltage of
the booster unit 142 so that the drive voltage becomes V.sub.1.
[0134] In Step S402, the lens-side MCU 35 sets the change rate of
the phase difference. For example, the change rate setting unit
35-5 sets the change rate of the phase difference based on the
proportion of V.sub.1 relative to V.sub.reg, and the suppression
level set in advance. It should be noted that it may be configured
so that the change rate setting unit 35-5 references the level
table 50 based on the proportion of V.sub.1 relative to V.sub.reg
to set the change rate of the phase difference.
[0135] In Step S403, the lens-side MCU 35 changes the phase
difference between the drive pulse of the A-phase and the drive
pulse of the B-phase, based on the change rate set in Step S402 and
the rotational direction of the vibration-wave motor 12 determined
in Step S300.
[0136] In Step S404, the lens-side MCU 35 judges whether the phase
difference of the drive pulse of the A-phase and the drive pulse of
the B-phase changed to a target value. Herein, target value
indicates the phase difference representing the rotational
direction of the vibration-wave motor 12 determined in Step S300 of
FIG. 12. The lens-side MCU 35 returns the processing to Step S403
in the case of Step S403 being negatively judged, and advances the
processing to Step S304 of FIG. 12 in the case of Step S404 being
positively judged. The lens-side MCU 35 changes the drive voltage
to V.sub.reg in Step S304 of FIG. 12, and then advances the
processing to Step S305 of FIG. 13. Since the processing in FIG. 13
is the same processing for Steps S305, S306 and S307 in FIG. 8,
explanations thereof will be omitted.
[0137] The following functional effects are obtained according to
the second embodiment explained above.
[0138] The lens-side MCU 35 of the lens barrel 30 controls the
drive apparatus 14 that outputs the A-phase drive signal and
B-phase drive signal to the vibration-wave motor 12, and applies
drive voltage to the vibration-wave motor 12. The lens-side MCU 35
includes the drive voltage setting unit 152 and power source
voltage change unit 35-3, and changes the drive voltage applied to
the vibration-wave motor 12. The lens-side MCU 35 includes the
phase difference change unit 35-4, and changes the phase difference
between the A-phase drive signal and B-phase drive signal by
changing the phase difference between the drive pulses of the
A-phase and B-phase. The drive voltage setting unit 152 and the
power source voltage change unit 35-3 change the drive voltage to
V.sub.reg (Step S304 in FIG. 12) in the case of causing the
vibration-wave motor 12 to rotationally drive, and change the drive
voltage to V.sub.1, which is larger than zero and smaller than
V.sub.reg (Step S401 in FIG. 12) in the case of the phase
difference change unit 154 changing the phase difference.
[0139] By configuring in this way, the lens barrel 30 can reduce
abnormal noise during phase difference changing, without harming
the responsiveness of the vibration-wave motor. In addition, the
lens-side MCU 35 can reduce the abnormal noise during phase
difference changing, even in a case of not being able to set
V.sub.1 to a sufficiently small value according to the circuit
configuration or ambient temperature of the drive apparatus of the
vibration-wave motor 12, by the speed change setting unit 35-5
setting the change rate of the phase difference suitably.
[0140] The embodiments explained above can be modified and
implemented in the following ways.
Modified Example 1
[0141] In the first embodiment, the lens-side MCU 15 is configured
so that the duty-cycle change unit 153 changes the setting value of
the duty cycle in the drive pulse generation unit 141. However, it
may be configured so that the lens-side MCU 15 includes the power
source voltage change unit 35-3 in place of the duty-cycle change
unit 153. In addition, in the second embodiment, the lens-side MCU
35 is configured so that the power source voltage change unit 35-3
changes the power source voltage of the booster unit 142. However,
it may be configured so that the lens-side MCU 35 includes the
duty-cycle change unit 153 in place of the power source voltage
change unit 35-3.
Modified Example 2
[0142] The vibration-wave motor driven by the drive apparatus 14
controlled by the lens-side MCU 15 and 35 is not limited to only a
rotating shaft-type motor like that shown in FIG. 2. For example,
it may be a ring-type vibration-wave motor. Control by way of the
lens-side MCU 15 and 35 can be performs similarly to the
above-mentioned embodiments even if the vibration-wave motor is of
ring type.
Modified Example 3
[0143] The present invention can be applied to electronic devices
other than digital cameras so long as being electronic devices that
control a drive apparatus by a control device such as an MCU, and
drive a vibration-wave motor with this drive apparatus.
Third Embodiment
[0144] FIG. 14 is a schematic view of a lens barrel according to a
third embodiment of the present invention. The lens barrel 202 in
FIG. 14 is a lens barrel for an imaging device such as a digital
camera. The vibration-wave motor 201 includes a vibrating body 261,
a moving body 262, a dampening support member 263 from a non-woven
fabric or the like, and a pressurized contact means 264. The
vibration-wave motor 201 provides drive power for causing a lens
unit L to drive in the optical axis direction relative to the lens
barrel 202.
[0145] The vibrating body 261 has an elastic body 261a and a
piezoelectric body 261b. The elastic body 261a is formed from a
metallic material having a large resonance sharpness. The shape of
the elastic body 261a forms an annular shape as shown in FIG. 15.
The piezoelectric body 261b is joined to one face of the round
shape of the elastic body 261a, and a comb-teeth part 221 in which
grooves are cut is provided on the opposing face thereof.
[0146] The piezoelectric body 261b is an electro-mechanical
conversion element that converts electrical energy to mechanical
energy. The piezeoelectric body 123 is divided into two phases
(A-phase, B-phase) along the circumferential direction. Poles are
arranged alternatingly arranged every 1/2 wavelength for each phase
of the piezoelectric body 261b. It is arranged so that an interval
of 1/4 wavelength is open between the A-phase and B-phase of the
piezoelectric body 262b. A drive signal is outputted from a drive
circuit 280 to each phase of the piezoelectric body 261b. The phase
difference between the drive signal output to the A-phase and the
drive signals output to the B-phase of the piezoelectric body 261b
is variable. When the respective high-frequency voltages are
applied to the A-phase and B-phase of the piezoelectric body 261b,
the piezoelectric body 261b excites. Deflection of the base part
222 of the elastic body 261a due to excitation of the piezoelectric
body 261b is magnified by the comb-tooth part 221 of the elastic
body 161a, and makes a progressive wave at the driving face 223 at
the tip ends of the comb-tooth part 221. It should be noted that,
in the present embodiment, the piezoelectric body 261b is made to
be an electrode pattern for which a 9-peak progressive wave (9th
order bending vibration wave) tends to generate.
[0147] The moving body 262 is formed from a light metal such as
aluminum. The moving body 262 pressure contacts the driving face
223 by way of the pressure from the pressurized contact means 264
having the pressure plate and pressurizing member. Elliptic motion
occurs at the crests of the wave of the progressive wave generated
by the driving face 223. The moving body 262 under pressurized
contact with the driving face 223 is driven by the friction from
this elliptic motion to rotationally move. The rotational direction
of the moving body 262 changes according to the phase difference
between the drive signals of the A-phase and B-phase of the
piezoelectric body 261b.
[0148] A vibration absorbing member 266 such as of rubber that
absorbs vibration in the optical axis direction of the moving body
262 is arranged in the moving body 262. The vibration absorbing
member 266 pressure contacts an output transfer unit 255 by way of
the pressurized contact means 264. The rotational motion of the
moving body 262 is transferred to the output transfer unit 255.
However, for the output transfer unit 255, the movement in the
optical axis direction and movement in the radial direction are
restricted by a bearing 256 attached in a fixed member 251.
[0149] The output transfer unit 255 has a projecting part 255a.
This projecting part 255a fits together with a fork 254. The
rotational motion of the output transfer unit 255 is transferred to
the fork 254 via the projecting part 255a. Furthermore, the
rotational motion thereof transfers to a cam ring 253. On the inner
side of the cam ring 253, a key groove 253a is cut in a spiral
shape in the circumferential direction. A fixed pin 252a is
provided to the outer circumferential side of an AF ring 252. When
the cam ring 253 rotates, the fixed pin 252a moves being guided in
the key groove 253a, and the AF ring 252 retaining the lens unit L
moves in the optical axis direction.
[0150] In the above-mentioned way, the progressive wave generated
by the vibration-wave motor 201 is transferred to the AF ring 252
via the moving body 262, output transfer unit 255, fork 254 and cam
ring 253, whereby the lens unit L is driven in the optical axis
direction along with the AF ring 252. The lens barrel executes a
wobbling operation, etc. using this driving.
[0151] FIG. 16 is a graph showing the relationship between the
phase difference between the drive signals of the A-phase and
B-phase and the rotational speed of the moving body 262. The
rotational speed of the moving body 262 reaches a maximum speed of
positive rotation (for example, clockwise rotation) when the phase
difference is +90.degree., and reaches a maximum speed of reverse
rotation (for example, counter-clockwise rotation) when the phase
difference is -90.degree..
[0152] FIG. 17 is a graph showing the relationship between the
frequency of drive signals and the rotational speed of the moving
body 262. The rotational speed of the moving body 262 is
substantially zero when the frequency of the drive signal is with a
predetermined range. Herein, substantially zero refers to a state
in which torque for only causing the moving body 262 under
pressurized contact with the vibration absorbing member 266, etc.
to rotate is not generated. For example, within the range shown in
FIG. 17, the rotational speed of the moving body 262 becomes zero
within the range from 28.5 kHz to 30.0 kHz. In addition, even if a
lower frequency than 28.5 kHz or a higher frequency than 30.0 kHz,
a frequency exists at which a torque for only causing the moving
body 262 under pressurized contact with the vibration absorbing
member 266, etc. to rotate is not generated, the cam ring 253, etc.
are not rotated, and the rotational speed of the moving body 262 is
substantially zero. The matter of such a frequency at which the
rotational speed of the moving body 262 becomes substantially zero
is referred to as holding frequency f0.
[0153] In the present invention, upon switching the rotational
driving direction of the moving body 262, the frequency of the
drive signal is changed to the holding frequency f0 without
stopping the voltage application to the vibration-wave motor 201.
It is thereby possible to reduce the abnormal noise generating upon
applying voltage again after stopping voltage application.
[0154] FIG. 18 is a block diagram relating to the drive apparatus
according to the third embodiment of the present invention. A drive
apparatus 290 exemplified in FIG. 18 includes a vibration-wave
motor 201 and drive circuit 280. The drive circuit includes a
control unit 281, oscillation part 282, phase shifting unit 283,
amplifiers 284a and 284b, detection unit 285 and temperature
measurement unit 286.
[0155] The oscillation part 282 oscillates a signal of a frequency
set by the control unit 281. The phase shifting unit 283 generates
the signal of the A-phase and the signal of the B-phase based on an
oscillation signal oscillated by the oscillation part 282. A phase
difference between this signal of the A-phase and signal of the
B-phase is set by the control unit 281.
[0156] The amplifier 284a amplifies (boosts) the voltage amplitude
of the signal of the A-phase generated by the phase shifting unit
283 to a voltage set by the control unit 281. The drive signal of
the A-phase is thereby generated. In addition, the amplifier 284b
amplifies (boosts) the voltage amplitude of the signal of the
B-phase generated by the phase shifting unit 283 to a voltage set
by the control unit 281. The drive signal of the B-phase is thereby
generated.
[0157] The vibrating body 261 is driven based on the drive signal
of the A-phase amplified by the amplifier 284a, and the drive
signal of the B-phase amplified by the amplifier 284b. The
detection unit 285 is configured by an optical encoder, magnetic
encoder or the like, detects the position and/or speed of the lens
unit L driven by the driving of the moving body 262, and outputs
these detection values to the control unit 281 as electrical
signals (detection signals). The control unit 281 acquires
information relating to the position and/or speed of the lens unit
L based on the detection signals from the detection unit 285.
[0158] The temperature measurement unit 286 measures the
temperature of the vibration-wave motor 201. The temperature of the
vibration-wave motor 201 rises from the heat producing from
friction between the vibrating body 261 and the moving body 262. A
temperature rise in the vibration-wave motor 201 adversely affects
the driving ability thereof. The temperature measurement unit 286
outputs the measured temperature signal to the control unit 281.
The control unit 281 estimates the influence on the driving ability
imparted by the temperature of the vibration-wave motor 201, based
on the temperature signal thereof.
[0159] The control unit 281 acquires a drive instruction relating
to the movement direction and movement amount of the lens unit L
from a CPU 203 of the lens barrel 202. The control unit 281
controls the frequency set in relation to the oscillation part 282,
the phase difference set in relation to the phase shifting unit
283, and the voltage amplitude set in relation to the amplifiers
284 and 284b, so that the lens unit L is positioned at the target
position decided based on the drive instruction. It should be noted
that the drive instruction acquired by the control unit 281 is not
limited to only instructions related to combinations of movement
direction and movement amount. For example, it may include the
patterns of movement speed and movement sequence (for example,
number of revolutions of wobbling operations). In addition, the
drive instruction acquired by the control unit 281 may be a
combination of movement direction and movement speed.
[0160] Drive control of the vibration-wave motor 201 of the present
invention will be explained using FIG. 19 and FIGS. 20A to C. FIG.
19 is an example of a flowchart relating to drive control of the
vibration-wave motor 201. FIGS. 20A to C are examples of timing
charts relating to drive control of the vibration-wave motor 201.
FIG. 20A is a timing chart relating to the phase difference between
the drive signals of the A-phase and B-phase. FIG. 20B is a timing
chart relating to the oscillation frequency of the oscillation part
282, i.e. frequency of the drive signal. FIG. 20C is a timing chart
relating to the revolution speed of the vibration-wave motor
201.
[0161] The processing of FIG. 19 starts execution when the control
unit 281 acquires a drive instruction. In Step S100, the control
unit 281 controls so as to set the holding frequency f0 in the
oscillation part 282, and the signal of the holding frequency f0
from the oscillation unit 282 is oscillated.
[0162] In Step S110, the control unit 281 sets the phase difference
of +90.degree. or -90.degree. in the phase shifting unit 283, and
changes the phase difference between the signal of the A-phase and
the signal of the B-phase outputted by the phase shifting unit 283
(timing T0 to T1, and timing T3 to T4 in FIG. 20). When the
frequency oscillated by the oscillation unit 282 is the holding
frequency f0, the revolution speed of the vibration-wave motor 201
is substantially zero. Therefore, driving of the vibration-wave
motor 201 will not become unstable, even if the control unit 281
changes the phase difference in Step S110.
[0163] After changing of the phase difference in Step S110 ends,
the control unit 281 controls the frequency set in the oscillation
part 282 based on the drive instruction, the position and/or speed
of the lens unit L calculated from the detection signals from the
detection unit 285, the temperature of the vibration-wave motor 201
measured by the temperature measurement unit 286, individual
differences in vibration-wave motors 201, etc., and controls so
that the lens unit L is positioned at the target position (timing
T1 to T2 in FIG. 20).
[0164] If the frequency set in the oscillation unit 282 becomes a
lower frequency wave than the holding frequency f0, the revolution
speed of the vibration-wave motor 201 will become greater than
zero. Since the voltage application to the vibration-wave motor 201
is not made to stop when causing the vibration-wave motor 201 to
stop, abnormal noise is not generated even when the vibration-wave
motor 201 starts driving.
[0165] In Step S130, the control unit 281 judges whether the lens
unit L has reached the target position. The control unit 281
advances the processing to Step S120 in the case of Step S130 being
negatively judged, and advances the processing to Step S140 in the
case of Step S130 being positively judged.
[0166] In Step S140, the control unit 281 controls so as to set the
holding frequency f0 in the oscillation part 282, and the signal of
the holding frequency f0 is oscillated from the oscillation unit
282 timing T2 to T3 in FIG. 20).
[0167] In Step S150, the control unit 281 judges whether a
subsequent drive instruction is being acquired. The control unit
281 advances the processing to Step S110 in the case of Step S150
being positively judged, and advances the processing to Step S160
in the case of Step S150 being negatively judged.
[0168] In Step S160, the control unit 281 sets the phase difference
of 0.degree. in the phase shifting unit 283, changes the phase
difference between the signal of the A-phase and the signal of the
B-phase outputted by the phase shifting unit 283, and then ends the
processing of FIG. 19. It is thereby controlled so that the
rotational speed of the vibration-wave motor 201 becomes zero
according to the phase difference as shown in FIG. 16.
[0169] As shown in FIG. 17, the holding frequency f0 has a range of
available values. In Step S140, the effect obtained in the
vibration-wave motor 201 changes according to what value within the
range the control unit 281 sets the holding frequency f0 set in the
oscillation unit 282. The difference in effects thereof will be
explained using FIG. 21.
[0170] FIG. 21 is a graph exemplifying the frequency-vibration
deformation characteristic of the vibrating body 261. FIG. 21
exemplifies the position at which the natural frequency f9 of a
9th-order bending vibration of the vibrating body 262 is 26 kHz,
and exemplifies the position at which the natural frequency f10 of
the 10th-order bending vibration is 32 kHz. Hereinafter, the
natural frequency f9 of the 9th-order bending vibration is
abbreviated simply as natural frequency f9, and the natural
frequency f10 of the 10th-order bending vibration is abbreviated
simply as natural frequency f10.
[0171] When the frequency of the drive signal is in the vicinity of
the natural frequency f9 of the 9th-order bending vibration, a
9-peak progressive wave generates at the driving face 223 of the
vibrating body 261. Then, when the frequency of the drive signal is
in the vicinity of the natural frequency f10 of the 10th-order
bending vibration, a 10-peak progressive wave generates at the
driving face 223 of the vibrating body 261. Among the magnitudes of
vibration of the vibrating body 261, the 9-peak progressive wave
component becomes smaller as the frequency distances from the
natural frequency f9. Similarly, among the magnitudes of vibration
of the vibrating body 261, the 10-peak progressive wave component
becomes smaller as the frequency distances from the natural
frequency f10.
[0172] As mentioned in the foregoing, the piezoelectric body 261b
assumes an electrode pattern that tends to cause a 9-peak
progressive wave to be excited, and the vibration-wave motor 201
has a better drive efficiency when using a 9-peak progressive wave
than when using a 10-peak progressive wave. For this reason, the
magnitude of the vibration of the 9-peak progressive wave in FIG.
21 is greater than the magnitude of the vibration of the 10-peak
progressive wave.
[0173] In the case of the phase difference between the drive
signals of the two phases being the same, the rotational direction
of the 9-peak progressive wave and the 10-peak progressive wave
will be opposite directions from each other. For example, in the
case of the phase difference between the drive signals of the two
phases being +90.degree., when the frequency of the drive signal is
27 kHz, the moving body 262 rotates as positive rotation, and when
the frequency of the drive signal is 33 kHz, the moving body 262
rotates as reverse rotation. When the frequency is between the
natural frequency f9 and the natural frequency f10, the rotation of
the moving body 262 according to 9-peak progressive wave component
and the rotation of the moving body 262 according to the 10-peak
progressive wave component cancel out each other.
[0174] (1) Case of holding frequency f0 being average value of
natural frequency f9 and natural frequency f10. In the case of the
holding frequency f0 being the average value of natural frequency
f9 and natural frequency f10, e.g., a case of the holding frequency
f0 being 29 kHz in the example of FIG. 21, the magnitude of the
vibration of the vibrating body 261 becomes small. This is because,
in the middle between the natural frequency f.sub.9 and the natural
frequency f10, the 9-peak progressive wave component and the
10-peak progressive wave component decrease together. Furthermore,
the rotation of the moving body 262 according to the 9-peak
progressive wave component and the rotation of the moving body 262
according to the 10-peak progressive wave component cancel.
[0175] Therefore, in the case of the holding frequency f0 being the
average value of the natural frequency f9 and natural frequency
f10, since the moving body 262 will not distance from the vibrating
body 261 due to the magnitude of the vibration of the vibrating
body 261 being small, abnormal noise will not generate from
collisions between the moving body 262 and vibrating body 261. In
addition, since the rotation of the moving body 262 according to
the 9-peak progressive wave component and the rotation of the
moving body 262 according to the 10-peak progressive wave component
cancel, the certainty of stopping rotation of the moving body 262
increases.
[0176] (2) Case of holding frequency f0 being higher frequency than
average value of natural frequency f9 and natural frequency f10. In
the case of the holding frequency f0 being higher frequency than
the average value of natural frequency f9 and natural frequency
f10, i.e. a case of being closer to natural frequency f10 than
natural frequency f9, the 10-peak progressive wave component
becomes dominant in the progressive wave generated by the vibrating
body 262. The moving body 262 rotating based on the 9-peak
progressive wave component in Step S120 of FIG. 19 is controlled
based on the 10-peak progressive wave component when the drive
frequency is changed to the holding frequency f0 in Step S140. In
other words, since the rotation according to the 10-peak
progressive wave component has a rotational direction that is an
opposite direction to the rotation according to the 9-peak
progressive wave component, the rotational direction of the moving
body 262 in Step S140 becomes an opposite direction to the
rotational direction during control in the immediately previous
Step S120. However, since the torque generating from the
vibration-wave motor 201 at this time is small, the fork 254, cam
ring 253 and AF ring 252 do not rotate.
[0177] Therefore, in the case of there being a subsequent drive
instruction in Step S150, when deciding to cause the moving body
262 to rotate in the reverse direction in the subsequent drive
instruction, rattling between the projecting part 255a and fork 254
and rattling between the key groove 253a and fixed pin 252a stop.
It is thereby possible to suppress mechanical collision noise when
the moving body 262 actually starts to rotate in the reverse
direction.
[0178] (3) Case of holding frequency f0 being lower frequency than
average value of natural frequency f9 and natural frequency f10. In
the case of the holding frequency f0 being lower frequency than the
average value of natural frequency f9 and natural frequency f10,
i.e. a case of being closer to natural frequency f9 than natural
frequency f10, the 9-peak progressive wave component becomes
dominant in the progressive wave generated by the vibrating body
262.
In this case, the rotational direction of the moving body 262 in
Step S140 is the same direction as the rotational direction during
control in the immediately prior Step S120. Therefore, in the case
of there being a subsequent drive instruction in Step S150, when
deciding to cause the moving body 262 to rotate in the same
direction in the subsequent drive instruction, rattling between the
projecting part 255a and fork 254 and rattling between the key
groove 253a and fixed pin 252a stop. It is thereby possible to
suppress mechanical collision noise when the moving body 262
actually starts to rotate in the same direction.
[0179] In addition, since the holding frequency f0 is closer to
natural frequency f9 when the above (1) and (2), the period of
timing T2 to T3 in FIG. 20 can be shortened when the above (1) and
(2). The processing time in drive control of the moving body 262 is
thereby shortened, and the stop accuracy of the moving body 262
rises.
[0180] As explained in the above (2), when driving in the opposite
direction to the immediately prior drive instruction with the
subsequent drive instruction, it is better to set the holding
frequency f0 to a higher frequency than the average frequency of
natural frequency f9 and natural frequency f10. In addition, as
explained in the above (3), when driving in the same direction as
the immediately prior drive instruction with the subsequent drive
instruction, it is better to set the holding frequency f0 to a
lower frequency than the average frequency of natural frequency f9
and natural frequency f10.
[0181] FIG. 22 is a flowchart relating to the processing of Step
S140 in FIG. 19. In the processing of FIG. 22, the holding
frequency is appropriately set based on the subsequent drive
instruction executed after executing a drive instruction.
[0182] In Step S141, the control unit 281 judges whether to acquire
a subsequent drive instruction. The control unit 281 advances the
processing to Step S142 in the case of Step S141 being positively
judged, and advances the processing to Step S143 in the case of
Step S141 being negatively judged.
[0183] In Step S142, the control unit 281 judges whether the
subsequent drive instruction is an instruction to cause the moving
body 262 to rotate in the same direction as the drive instruction
completed immediately prior. The control unit 281 advances the
processing to Step S145 in the case of Step S142 being positively
judged, and advances the processing to Step S144 in the case of
Step S142 being negatively judged.
[0184] In Step S143, the control unit 281 sets the holding
frequency f0 to the average value of natural frequency f9 and
natural frequency f10. Effects like those explained in the above
(1) are thereby obtained. In Step S144, the control unit 281 sets
the holding frequency f0 to a frequency that is higher frequency
than the average value of natural frequency f9 and natural
frequency f10, and lower frequency than natural frequency f10.
Effects like those explained in the above (2) are thereby obtained.
In Step S145, the control unit 281 sets the holding frequency f0 to
a frequency that is lower frequency than the average value of
natural frequency f9 and natural frequency f10, and higher
frequency than natural frequency f9. Effects like those explained
in the above (3) are thereby obtained.
[0185] In Step S146, the control unit 281 sets the holding
frequency f0 set in Steps S143 to S145 in the oscillation part
282.
[0186] The following operational effects are obtained according to
the embodiment explained above. The drive apparatus 290 driving the
lens unit L in the lens barrel 202 includes the drive circuit 280
and vibration-wave motor 201. The drive circuit 280 generates the
drive signals of the A-phase and B-phase. The vibration-wave motor
201 includes the vibrating body 261 and moving body 262. The
vibrating body 261 includes the piezoelectric body 261b to which
the drive signals of the A-phase and B-phase generated by the drive
circuit 280 are applied, thereby causing a progressive wave to be
generated at the driving face 223 of the elastic body 261a by the
vibration of this piezoelectric body 261b, and causing a drive
force for driving the moving body 262 under pressurized contact to
generate. The drive circuit 280 has the control unit 281 that sets
the frequency and phase difference of the drive signals of the
A-phase and B-phase, changes the phase difference set in the phase
shifting unit 283 (Step S110 of FIG. 19) after setting the
frequency oscillated by the oscillation part 282 to the holding
frequency f0 when changing the driving direction of the moving body
262. By configuring in this way, it is possible to suppress the
generation of abnormal noise since driving of the moving body 262
is made to stop according to the control of drive frequency, upon
switching the driving direction of the moving body 262 by the drive
apparatus 290.
[0187] When changing the phase difference while the moving body 262
is driving, the rotation of the moving body 262 becomes unstable,
and there is concern over abnormal noise generating by collision
between the moving body 262 and vibrating body 261. However, there
is no concern over such abnormal noise generating so long as
configuring so as to control the phase difference between the drive
signals of the A-phase and B-phase in a state in which driving of
the moving body 262 is stopped, as in the present invention.
[0188] In addition, when changing the phase difference while the
moving body 262 is driving, the moving body 262 may be temporarily
driven at low speed; however, the rotational unevenness of the
moving body 262 increases during low speed driving, and thus there
is concern over no longer being able to ensure stop precision.
However, such an increase in rotational unevenness does not occur,
and thus there is no concern over no longer being able to ensure
stop precision, so long as configuring so as to control the phase
difference between the drive signals of the A-phase and B-phase in
a state in which driving of the moving body 262 is stopped, as in
the present invention.
[0189] The third embodiment explained above can be implemented by
modifying in the following way.
Modified Example 4
[0190] In the above-mentioned embodiment, the piezoelectric body
261b is configured to be in an electrode pattern for which a 9-peak
progressive wave tends to generate, and generates a 9-peak
progressive wave or 10-peak progressive wave at the driving face
223 of the vibrating body 261. However, the progressive wave
generated by the vibrating body 261 is not limited to a 9-peak
progressive wave. The present invention may be configured to cause
an nth-order bending vibration to generate from any n-peak
progressive wave at the driving face 223.
Modified Example 5
[0191] In the above-mentioned embodiment, the phase difference
between drive signals of the A-phase and B-phase is not controlled
while performing drive control of the lens unit L by controlling
the frequency set in the oscillation part 282. However, within a
range in which abnormal noise from collisions between the moving
body 262 and vibrating body 261 and an increase in rotational
unevenness of the moving body 262 can be ignored, the phase
difference of the drive signals of the A-phase and B-phase may be
controlled also while performing drive control of the lens unit L
by controlling the frequency set in the oscillation part 282.
Fourth Embodiment
[0192] Hereinafter an embodiment of a electric camera 301 according
to the present invention will be explained in detail while
referencing the attached drawings. FIG. 23 is a view illustrating a
electric camera 301 of a fourth embodiment of the present
invention. The electric camera 301 is a camera capable of still
image and moving image photography, is configured from a lens
barrel 320, which is an imaging optical system, an imaging element
330, an AFE (Analog Front End) circuit 360, an image processing
unit 370, a voice detection unit 380, an operation member 390, a
CPU 400, buffer memory 410, a recording interface 420, memory 430,
and a monitor 440, and is connectable with a PC 450 of an external
device.
[0193] The lens barrel 320 is configured from a plurality of
optical lens units L, and causes a subject image to focus on a
light receiving surface of the imaging element 330. FIG. 23
illustrates the plurality of optical lens units L by simplifying as
a single lens. Among these optical lens units L, a third lens unit
L3 for AF described later (illustrated in FIG. 23) is driven by a
vibration-wave motor 310.
[0194] The imaging element 330 is configured by a CMOS image sensor
and the like in which light-receiving elements are aligned in
two-dimensions on the light receiving surface. The imaging element
330 generates an analog image signal by photoelectrically
converting the subject image from a beam having passed through the
lens barrel 320.
[0195] The analog image signal is inputted to the AFE circuit 360.
The AFE circuit 360 performs gain adjustment (signal amplification
according to the ISO sensitivity) on the analog image signal. More
specifically, the imaging sensitivity is changed within a
predetermined range according to a sensitivity setting instruction
from the CPU 400. The AFE circuit 360 converts the image signal
after analog processing by a built-in A/D conversion circuit into
digital data. This digital data is inputted to the image processing
unit 370.
[0196] The image processing unit 370 performs various image
processing on digital image data. The buffer memory 410 temporarily
records image data in pre-process or post-process of the image
processing by the image processing unit 370.
[0197] The voice detection unit 380 is configured from a microphone
and a signal amplifier, mainly detects and captures a voice from
the subject direction during moving image photograph, and transmits
this data to the CPU 400.
[0198] The operation member 390 indicates mode dials, the arrow
keys, a select button and a release button, and sends an operation
signal according to the respective operations to the CPU 400. The
setting of still image photography and moving image photograph is
set by way of the operation member 390.
[0199] The CPU 400 unifyingly controls actions performed by the
electric camera 301 by executing a program stored in the ROM that
is not illustrated. For example, AF (autofocus) operation control,
AE (automatic exposure) operation control, and auto white balance
control, etc. are performed.
[0200] The recording interface 420 has a connector that is not
illustrated, a recording medium such as a memory card 421 is
connected to this connector, and performs the writing of data to
the connected recording medium or reading of data from the
recording medium.
[0201] The memory 430 records a sequence of image data subjected to
image processing. Images corresponding to a moving image are
captured in the electric camera 301 of the present embodiment. The
monitor 440 is configured by a liquid crystal panel, and displays
an operation menu, still image, moving image, etc. according to an
instruction from the CPU 400.
[0202] Next, the lens barrel 320 will be explained. FIG. 24 is a
view illustrating the lens barrel 320 according to the fourth
embodiment of the present invention. FIG. 25 is a view illustrating
a vibrator 311 of the vibration-wave motor 310 according to the
fourth embodiment of the present invention. The lens barrel 320
includes an outer fixed cylinder 331 that covers the outer
circumferential part of the lens barrel 320, an inner fixed
cylinder 332 that is positioned more to the inner circumferential
side than the outer fixed cylinder 331, and further includes the
vibration-wave motor 310 between the outer fixed cylinder 331 and
the inner fixed cylinder 332.
[0203] From a subject side, a first lens unit L1, a second lens
unit L2, a third lens unit L3, which is an AF lens retained in an
AF ring 334, and a fourth lens unit L4 are arranged in the inner
fixed cylinder 332. The first lens unit L1, second lens unit L2 and
fourth lens unit L4 are fixed to the inner fixed cylinder 332. The
third lens unit L3 is configured to be moveable relative to the
inner fixed cylinder 332 by way of the AF ring 334 moving.
[0204] As shown in FIG. 24, the vibration-wave motor 310 includes a
vibrator 311, a moving element 315, a pressurizing member 318,
etc., and assumes a form fixing the vibration 311 side thereof and
rotationally driving the moving element 315. The vibrator 311 will
be explained. As shown in FIG. 25, the vibrator 311 is configured
from an electro-mechanical conversion element exemplified as a
piezoelectric element or electrorestrictive element that converts
electrical energy to mechanical energy (hereinafter referred to as
piezoelectric body 313), and an elastic body 312 joined with the
piezoelectric body 313. Although made so that a progressive wave
generates in the vibrator 311, a 9-peak progressive wave is
generated as one example in the present embodiment.
[0205] The elastic body 312 consists of a metal material having a
large resonance sharpness, and the shape thereof is an annular
shape The opposing face of the elastic body 312 to which the
piezoelectric body 313 is joined forms a comb-teeth portion 312 in
which grooves are cut, and the tip end face of the projecting
portions (parts without grooves) are a driving face and are under
pressurized contact with the moving element 315. The vibration-wave
motor 310 drives the third lens unit L3 by driving the moving
element 315 using the drive force generated at the driving face by
way of the excitation of the piezoelectric body 313. The reason for
cutting the grooves is to bring the neutral plane of the
progressive wave as near as possible to the piezoelectric body 313
side, thereby making the amplitude of the progressive wave at the
driving face amplified. The portions not cut with grooves are
called base parts 312b in the present embodiment.
[0206] The piezoelectric body 313 is joined at the opposing face of
the base parts 312b than the comb-teeth part 312a. Lubricity
surface treatment is made on the driving face of the elastic body
312. The piezoelectric body 313 is divided into the two phases
(A-phase, B-phase) along the circumferential direction, and in each
phase, elements for which the poles are alternating every 1/2
wavelength are aligned, and a 1/4 wavelength interval is open
between the A-phase and B-phase.
[0207] The piezoelectric body 313 is generally configured from a
material like lead zirconate titanate, which is called by the
abbreviation PZT; however, due to environmental problems in recent
years, it may also be configured from potassium sodium niobate,
potassium niobate, sodium niobate, barium titanate, bismuth sodium
titanate, bismuth potassium titanate, etc., which are lead-free
materials.
[0208] As shown in FIG. 24, below the piezoelectric body 313, a
non-woven fabric 316, pressure plate 317 and pressurizing member
318 are arranged. The non-woven fabric 316 is exemplified as felt,
is arranged below the piezoelectric body 313, and makes so that
vibration of the vibrator 311 does not convey to the pressure plate
317 or pressurizing member 318.
[0209] The pressure plate 317 is made so as to receive the pressure
of the pressurizing member 318. The pressurizing member 318 is
configured from a disk spring, is arranged below the pressure plate
317, and causes an applied pressure to generate. In the present
embodiment, although the pressurizing member 318 is a disk spring,
it does not need to be a disk spring, and may be a coil spring or a
wave spring. The pressurizing member 318 is retained by a pressing
ring 319 being fixed to a fixed member 314.
[0210] The moving element 315 consists of a light metal such as
aluminum, and surface treatment of a sliding material or the like
for abrasion resistance improvement is done on the surface 315a of
sliding face (refer to FIG. 25).
[0211] In order to absorb vibrations in the longitudinal direction
of the moving element 315, a vibration absorbing member 323 formed
from rubber or the like is arranged on the moving element 315, and
thereon, an output transfer member 324 is arranged.
[0212] The output transfer member 324 is made so as to define the
pressurizing direction and radial direction by way of a bearing 325
provided to the fixed member 314, whereby the pressurizing
direction and radial direction of the moving element 315 are
defined.
[0213] The output transfer member 324 has a projecting part 324a
and, therefrom, a fork 335 connecting to a cam ring 336 fits. The
cam ring 336 is rotated along with the rotation of the output
transfer member 324.
[0214] A key groove 337 is cut obliquely relative to the
circumferential direction in the cam ring 336. In addition, a fixed
pin 338 is provided at the outer circumferential side of the AF
ring 334. The fixed pin 338 fits into the key groove 337, and by
the cam ring 336 rotationally driving, the AF ring 334 is driven in
the optical axis advancing direction, and makes it possible to stop
at a desired position.
[0215] The pressing ring 319 is attached by a spring to the fixed
member 314. By attaching the pressing ring 319 to the fixed member
314, it is possible to configure from the output transfer member
324, moving element 315, vibrator 311 until the pressurizing member
318 as one motor unit.
[0216] Next a drive apparatus 340A will be explained. FIG. 26 is a
block diagram illustrating the drive apparatus 340A of the
vibration-wave motor 310. The drive apparatus 340A is provided to a
substrate 340 (refer to FIG. 24). The drive apparatus 340A is
connected to the vibration-wave motor 310 as shown in FIG. 26, and
receives a revolution speed of the vibration-wave motor 310 from
the rotation detection unit 345 provided to the vibration-wave
motor 310, as well as performing control of the vibration-wave
motor 310.
[0217] The drive apparatus 340A includes a drive control unit 341,
oscillation part 342, phase shifting unit 343, and amplifier 344.
In addition, the rotation detection unit 346 attached to the
vibration-wave motor 310, a contrast detection unit 339 and a
photography setting unit 347 that can select moving image
photography mode or a still image photography mode are connected to
the drive control unit 341 of the drive apparatus 340A.
[0218] The drive control unit 341 controls driving of the
vibration-wave motor 310 based on a drive command from the CPA 340
inside of the lens barrel 320 or the main body of the camera 301.
The oscillation part 342 generates a drive signal of a desired
frequency according to the command of the drive control unit 341.
The drive signal is asymmetrically shaped in the + direction and -
direction based on zero potential. The phase shifting unit 343
divides the drive signal generated by the oscillation part 342 into
two drive signals of different phases. The amplifier 344 boosts the
two drive signals divided by the phase shifting unit 343 to desired
voltages, respectively. The two drive signals from the amplifier
344 are transmitted to the vibration-wave motor 310, whereby a
progressive wave generates at the vibrator 311 by way of the
application of these two drive signals, and the moving element 315
is driven.
[0219] The rotation detection unit 346 is configured from an
optical encoder, magnetic encoder, or the like, detects the
position and/or speed of a driven object driven by the driving of
the moving element 315, and transmits the detection value to the
drive control unit 341 as an electrical signal. The contrast
detection unit 339 detects the contrast of the subject image. The
contrast detection unit 339, for example, determines if the subject
is within a current range of focal positions of the lens, is in the
+ direction, is in the - direction, and being displaced to what
extent. The contrast detected by the contrast detection unit 339 is
transmitted to the drive control unit 341 as an electrical
signal.
[0220] The drive control unit 341 controls the driving of the
vibration-wave motor 310 based on the drive command from the CPU
400 inside of the lens barrel 320 or of the main body of the camera
301. When receiving the detection signal from the rotation
detection unit 346, the drive control unit 341 obtains positional
information and speed information based on this value, and controls
the frequency of the oscillation part 342, phase difference of the
phase shifting unit 343 and voltage of the amplifier 344, so as to
position at the target position.
[0221] In addition, the drive control unit 341 makes so that the
photography information (still image mode/moving image mode, etc.
selected by way of the photography setting unit 347) is transferred
by the lens or camera. The drive control unit 341 smoothly controls
the frequency and phase difference of the drive signals based on
this photography information from the lens or camera. More
specifically, in a case of the photography setting unit 347 having
selected moving image photography mode, the drive control unit 341
switches the phase difference of the two drive signals, as well as
switching the frequency of the two drive signals to correspond to
the switched phase difference, while maintaining the voltages of
the two drive signals to be constant, whereby the speed of the
vibration-wave motor 310 is variable. In addition, the drive
control unit 341 switches the frequencies of the two drive signals
based on the contrast detected by the contrast detection unit
339.
[0222] In order to simplify the explanation in the present
embodiment, a configuration is established in which the information
of the contrast detection unit 339 and information of the
photography setting unit 347 are transmitted directly to the drive
control unit 341; however, it is not to be limited thereto. For
example, it may be configured so that the information of the
contrast detection unit 339 and/or information of the photography
setting unit 347 is temporarily conveyed to the CPU of the camera,
and subsequently conveyed to the drive control unit 341 in the
lens.
[0223] Next, driving and control of the vibration-wave motor 310 by
the drive apparatus 340A will be explained. First, the target
position is transmitted from the CPU 400 inside the lens barrel 320
or the main body of the camera 301 to the drive control unit 341.
The drive signal generates from the oscillation part 342, this
signal is split into two drive signals of 90.degree. different
phase by the phase shifting unit 343, and is amplified to a desired
voltage by the amplifier 344. The drive control unit 341 provides
two drive signals to the vibration-wave motor 310.
[0224] The two drive signals are applied to the piezoelectric body
313 of the vibration-wave motor 310, the piezoelectric body 313 is
excited, and a 9-peak bending vibration generates at the elastic
body 312 according to this excitation. The piezoelectric body 313
is divided into the A-phase and B-phase, and the two drive signals
are respectively applied to the A-phase and B-phase. The 9-peak
bending vibration generating from the A-phase and the 9-peak
bending vibration generating from the B-phase form so as to have a
positional phase shifted by 1/4 wavelength, and the A-phase drive
signal and B-phase drive signal are shifted by 90.degree. phase;
therefore, the two bending vibrations are combined to form a 9-peak
progressive wave. A +90.degree. or -90.degree. value of the phase
difference is an ideal value, and although the shape of the
progressive wave is disturbed at an intermediate value thereof, a
progressive wave is produced. Elliptic motion occurs at the crests
of the wave of the progressive wave. Therefore, the moving element
315 under pressurized contact with the driving face is driven by
the friction from this elliptic motion.
[0225] An optical encoder is arranged at the driven body driven by
the driving of the moving element 315, and from this, an electrical
pulse generates, which is transmitted to the drive control unit
341. The drive control unit 341 becomes able to obtain the current
position and current speed based on this signal, and controls the
drive frequency of the oscillation part 342 based on this
positional information, speed information and target position
information.
[0226] In addition, in the case of driving the AF ring 334 in the
positive direction, the phase difference between the two drive
signals (frequency voltage signals) may be set to a + value, e.g.,
+90.degree., by the phase shifting unit 343, and in the case of
driving the AF ring 334 in the reverse direction, the phase
difference between the two drive signals (frequency voltage
signals) may be set to a - value, e.g., -90.degree., by the phase
shifting unit 343.
[0227] On the other hand, based on the information as to the
current photography mode being the still image mode/moving image
mode, the drive control unit 341 controls the drive frequency of
the oscillation part 342 in the case of being the still image mode,
and controls the drive frequency of the oscillation part 342 and
the phase difference of the phase shifting unit 343 in the case of
being the moving image mode. In particular, in the wobbling
operation causing the third lens unit L3 for AF to move back and
forth in small motions, the phase difference is changed to control
the position and speed. Wobbling operation is an operation causing
the lens for AF to move back and forth in small motions to make the
focal position follow the subject.
[0228] FIG. 27A is a graph showing the relationship of rotational
speed relative to the phase difference of the drive signals of the
vibration-wave motor, and FIG. 27B is a graph showing the
relationship of the rotational speed relative to the drive
frequency of the vibration-wave motor. As shown in FIG. 27A, the
rotational speed reaches a maximum speed of positive rotation at
the phase difference of the two drive signals of +90.degree., and
reaches a maximum speed of reverse rotation at the phase difference
of the two drive signals of -90.degree., and the intermediate phase
differences thereof indicate intermediate speed values. In
addition, as shown in FIG. 27B, when the drive frequency is
decreased, the rotational speed increases, and when increasing the
frequency, the rotational speed declines, and reaches 0. For
example, when setting the phase difference of the two drive signals
to +90.degree., the rotational speed increases with smaller drive
frequency.
First Operation Example
[0229] Next, a first operation example of a fourth embodiment of
the present invention will be explained based on a timing chart for
the driving of the vibration-wave motor 310 by the drive apparatus
340A in the case of the moving image mode being selected. FIG. 28
is a timing chart illustrating operations of the first operation
example of the drive apparatus 340A according to the fourth
embodiment. In the case of the moving image mode being selected in
the present embodiment, the relationships of the drive frequency,
drive voltage, phase difference, and rotational speed of the
vibration-wave motor 310 will be explained in sequential order. In
the present embodiment, in the case of the moving image mode being
selected, the drive frequency is set to f0 (maximum frequency), and
the drive voltage is set to V0 (minimum voltage).
[0230] At t0, the drive apparatus 340A sets the phase difference of
the two drive signals to +90.degree., and turns ON the drive
signal.
[0231] At t1, the drive apparatus 340A causes the drive voltage to
increase.
[0232] At t2, the drive apparatus 340A sets the drive voltage to
V1.
[0233] At t3, the drive apparatus 340A starts sweeping the drive
frequency from the maximum frequency f0.
[0234] At t4' immediately after t4, the drive apparatus 340A starts
driving the vibration-wave motor 310 in the middle of the drive
frequency being swept, and sets the drive frequency to frequency
f1.
[0235] In the case of being the moving image mode, wobbling
operation is performed to make the third lens unit L3 for AF to
move back and forth in small motions. In the case of the present
embodiment, it is established at an interval of 20 Hz. At t4 to t5,
the drive apparatus 340A sets the phase difference of the two drive
signals to +90.degree. to cause rotation as positive rotation, and
makes the speed V. At t5 to t6, the drive apparatus 340A sets the
phase difference of the two drive signals to 0.degree., and the
contrast at position Wbe is detected by the contrast detection unit
339. At t6 to t7, the drive apparatus 340A sets the phase
difference of the two drive signals to -90.degree., setting the
frequency to f2, which is smaller than f1, causing to
reverse-rotationally drive at the frequency f2, and the speed is
set to -2V (twice V). The reason for setting the speed during
reverse rotation of the wobbling operation to twice the positive
rotation is that the movement amount of the lens position is
twice.
[0236] At t7 to t8, the drive apparatus 340A sets the phase
difference of the two drive signals to 0.degree., and detects the
contrast at position Waf. At t8 to t9, the drive apparatus 340A
sets the phase difference of the two drive signals to +90.degree.,
causing positive rotational driving at frequency f1, and makes the
speed V. At t9 to t10, the drive apparatus 340A sets the phase
difference of the two drive signals to 0.degree., and detects the
contrast at W.sub.0 position.
[0237] Wobbling operation is performed by repetition hereinafter.
One cycle of the wobbling operation (for example, between t4 and
t10) is an interval of 20 Hz (=approx. 50 msec). Between t9 and
t10, the position of the subject is calculated from the detection
results of contrast of position Wbe, position Waf and position
W.sub.0 to decide the drive frequency of one cycle of the next
wobbling operation. In other words, based on the contrast of a
predetermined one cycle in the wobbling operation detected by the
contrast detection unit 339, the drive control unit 341 switches
the frequency of the two drive signals of a subsequent one cycle to
a predetermined one cycle, so that the focal position of the third
lens unit L3 for AF follows the subject.
[0238] The deciding parameters are the frequency fs between t10 and
t11, the frequency fb between t12 and t13, and the frequency fs2
between t14 and t15. For example, in the results of contrast
detection in one cycle of the wobbling operation between t4 and
t10, in the case of being determined that the subject is between
the wobbling amplitude (+1 to -1), in one cycle of the subsequent
wobbling operation, the wobbling amplitude is set to +1 to -1 and
defines frequency fs=f.sub.1, frequency fb=f2 and frequency
fs2=f.sub.1. It should be noted that the subject detection results
in FIG. 28 are configured so as to indicate better contrast with a
larger value (good contrast=in focus=defined as 1, and indicating a
smaller numerical value as going more out of focus).
[0239] In addition, as another case, in the case of being
determined that the subject is in the + direction from the current
lens position as a result of contrast detection in one cycle of the
wobbling operation between t17 to t22, one cycle of the subsequent
wobbling operation defines the speed at t22 to t23 as 3V, and
performs movement of the lens at three times the wobbling
amplitude. In this case, it defines frequency fs=f3 (frequency even
smaller than f2), frequency fb=f2, and frequency fs2=f1.
[0240] Furthermore, as another case, in the case of being
determined that the subject is greatly in the + direction from the
current lens position as a result of contrast detection in one
cycle of the wobbling operation between t40 and t45, one cycle of
the subsequent wobbling operation performs movement of the lens at
three times the wobbling amplitude, with the speed between t40 and
t41 as 4V. In this case, it defines frequency fs=f4 (frequency even
smaller than f3), frequency fb=f2, and frequency fs2=f1.
[0241] Herein, when trying to drive the lens, there is a
possibility of a problem arising in that a very small sound during
the drive signal ON when starting the drive signal to the
vibration-wave motor is picked up by the microphone that detects
voices during moving image photography. The cause thereof is from
sound of various frequencies generating from the stator (vibrator)
at the moment when the drive signal applied to the vibration-wave
motor changes step-wise from 0V to a certain voltage, and the
audible sound thereof being picked up with the voices. The sound
pressure of this sound depends on the magnitude of voltage, and in
the case of the voltage of the drive signal being small, a trend is
observed of the sound pressure declining.
[0242] In this aspect, the moment when the drive signal is ON, the
voltage value of the drive signal voltage decreases, and a
countermeasure is taken by setting the sound pressure of the sound
generated from the stator (vibrator) to no more than the
sensitivity of the microphone, and after the drive signal is ON,
returning the drive voltage to a normal voltage (rated
voltage).
[0243] However, it is necessary to perform the wobbling operation
to cause the AF lens to move forward and backward during moving
image photography, and between when driving in the positive
direction and when driving in the reverse direction, it temporarily
stops, and the phase difference must change. In this case, in order
to prevent a small noise from generating from the stator
(vibrator), by a conventional control method, the phase difference
between the two drive signals is set to +90.degree., and the drive
voltage is changed from V.sub.0 to V.sub.1 to cause the AF ring 34
to positively rotationally drive. Next, the drive voltage is
changed from V.sub.1 to V.sub.0, and the phase difference between
the two drive signals is set to -90.degree.. Furthermore, the drive
voltage is changed from V.sub.0 to V.sub.1 to cause the AF ring 34
to reverse rotationally drive. Next, the drive voltage is changed
from V.sub.1 to V.sub.0, and the phase difference between the two
drive signals is set to +90.degree.. Since repetition is performed
hereinafter, it becomes a very complicated operation.
[0244] In the present embodiment, it is configured so as to perform
the wobbling operation by switching the phase difference of the two
drive signals between three stages (90.degree., 0.degree.,
-90.degree.), and the setting a frequency according to this phase
difference, while maintaining the voltage to be fixed. It should be
noted that switching of the phase difference of the two drive
signals is ideally continuously switching the phase difference
gradually for very small sound generation prevention.
[0245] By configuring in this way, silent driving becomes possible
without requiring complicated driving as is conventionally.
[0246] It should be noted that, in the case of the still image mode
being selected, the voltage is set to the rated voltage V.sub.1 and
then the drive signal is turned ON to perform sweeping start of the
drive frequency, as is conventionally. In addition, in the case of
the still image mode, positional and/or speed control becomes
control according to the drive frequency or drive voltage due to
not being required to perform wobbling operation.
[0247] It should be noted that the sound during drive signal ON is
small and detected as sound due to the voice microphone being
provided very near the vibration-wave motor; however, it is sound
that can almost not be heard by the operating person.
[0248] Hereinafter, operations of a first operation example of the
drive apparatus 340A according to the fourth embodiment will be
explained based on the flowchart.
[0249] FIG. 29 is a flowchart illustrating operations of the first
operation example of the drive apparatus 340A according to the
fourth embodiment.
[0250] First, driving of the lens is started.
[0251] In S501, the drive apparatus 340A determines whether being
the moving image mode or being the still image mode. In the case of
being the moving image mode, the processing advances to Step S502.
The drive apparatus 340A advances to Step S601 in the case of being
the still image mode, and performs the driving operation during
still image photography without performing the wobbling
operation.
[0252] In Step S502, the drive apparatus 340A sets the voltage to
V0, as well as setting the phase difference of the two drive
signals to +90.degree..
[0253] In Step S503, the drive apparatus 340A turns the drive
signal ON.
[0254] In Step S504, the drive apparatus 340A causes the voltages
of the two drive signals increase.
[0255] In Step S505, the drive apparatus 340A sets the voltages of
the two drive signals to V.sub.1.
[0256] In Step S506, the drive apparatus 340A starts sweeping of
the frequency, and sets the frequency to f1.
[0257] The moving element 315 thereby drives, and the AF ring 334
is driven in the positive direction.
[0258] In Step S507, the drive apparatus 340A sets the phase
difference of the two drive signals to 0.degree.. Driving of the
moving element 315 thereby stops.
[0259] In Step S508, the drive apparatus 340A detects the position
Wbe and contrast.
[0260] In Step S509, the drive apparatus 340A sets the frequency to
f2.
[0261] In Step S510, the drive apparatus 340A sets the phase
difference of the two drive signals to -90.degree..
[0262] The moving element 315 thereby drives, and the AF ring 334
is driven in the reverse direction.
[0263] In Step S511, the drive apparatus 340A sets the phase
difference of the two drive signals to 0.degree.. Driving of the
moving element 315 thereby stops.
[0264] In Step S512, the drive apparatus 340A detects the position
Waf and contrast.
[0265] In Step S513, the drive apparatus 340A sets the frequency to
f1.
[0266] In Step S514, the drive apparatus 340A sets the phase
difference of the two drive signals to 90.degree..
[0267] The moving element 315 thereby drives, and the AF ring 334
is driven in the positive direction.
[0268] In Step S515, the drive apparatus 340A sets the phase
difference of the two drive signals to 0.degree..
Driving of the moving element 315 thereby stops.
[0269] In Step S516, the drive apparatus 340A detects the position
W0 and contrast.
[0270] In Step S517, the drive apparatus 340A calculates the
subject position according to the position Wbe, position Waf,
position W0 and respective contrast information.
[0271] In Step S518, the frequencies fs and fb are calculated.
[0272] In Step S519, the drive apparatus 340A sets the phase
difference of the two drive signals to +90.degree..
[0273] The drive apparatus 340A sets the frequency to fs. For
example, in the results of detecting contrast in one cycle of the
wobbling operation between t17 and t22 in FIG. 28, when determined
that the subject is in the + direction from the current lens
position, one cycle of the subsequent wobbling operation sets f3
(frequency even smaller than f2). The moving element 315 thereby
drives, and the AF ring 334 is driven in the positive
direction.
[0274] In Step S520, the drive apparatus 340A sets the phase
difference of the two drive signals to 0.degree.. Driving of the
moving element 315 thereby stops.
[0275] In Step S521, the drive apparatus 340A detects the position
Wbe and contrast.
[0276] In Step S522, the drive apparatus 340A sets the frequency to
fb. For example, in the contrast detection results in one cycle of
the wobbling operation between t17 and t22 in FIG. 28, the drive
apparatus 340A sets the drive frequency to f2.
[0277] In Step S523, the phase difference of the two drive signals
is set to -90.degree.. The moving element 315 thereby drives, and
the AF ring 334 is driven in the reverse direction.
[0278] In Step S524, the drive apparatus 340A sets the phase
difference of the two drive signals to 0.degree.. Driving of the
moving element 315 thereby stops.
[0279] In Step S525, the drive apparatus 340A detects the position
Waf and contrast.
[0280] In Step S526, the drive apparatus 340A sets the frequency to
fs2 (=f1).
[0281] In Step S527, the drive apparatus 340A sets the phase
difference of the two drive signals to 90.degree.. The moving
element 315 thereby drives, and the AF ring 334 is driven in the
positive direction.
[0282] In Step S528, the drive apparatus 340A sets the phase
difference of the two drive signals to 0.degree.. Driving of the
moving element 315 thereby stops.
[0283] In Step S529, the drive apparatus 340A detects the position
W0 and contrast.
[0284] In Step S530, the drive apparatus 340A detects the subject
position according to the position Wbe, position Waf, position W0
and respective contrast information.
[0285] In Step S531, the drive apparatus 340A determines whether
driving of the AF ring 334 is finished.
[0286] In the case of driving of the AF ring 334 not being
finished, the processing returns to Step S518, and performs the
subsequent wobbling operation. In the case of there being a
photography end command and making stop when driving finishes,
phase difference switching control is finished, and the motion of
the vibration-wave motor is stopped by sweeping the frequency to
the high frequency side to f0. Then, the voltage is gradually
decreased from V1 to V0, and thereafter, the drive signal is turned
OFF.
[0287] In the present embodiment, the subject position is estimated
by detecting the contrast of three places of the lens position in
Steps S519 to S530, and the calculation of the frequencies fs and
fb is done in Step S518 according to this information. By switching
the phase difference between the A-phase and B-phase in three
stages (90.degree., 0.degree., -90.degree.) and setting the three
drive frequencies of frequencies fs, fb and fs2, wobbling operation
of the vibration-wave motor 10 is made possible.
Second Operation Example
[0288] Next, a second operation example according to the fourth
embodiment of the present invention will be explained. In the
second operation example, since the configurations of the lens
barrel, vibration-wave motor and drive apparatus 340A are the same
as the first operation example, explanations thereof will be
omitted. The first operation example and second operation example
differ in the operations within the drive apparatus 340A. The
second operation example is a case of the position of the subject
moving to the + direction of the lens position, and then from
midway, moving in one direction.
[0289] Driving of the vibration-wave motor 310 by the drive
apparatus 340A of the second operation example will be explained
based on the timing chart. FIG. 30 is a timing chart illustrating
operations of the second operation example of the drive apparatus
340A according to the fourth embodiment of the present invention.
The second operation example will be explained in the case of the
moving image mode being selected, in chronological order for the
behavior in the case of the position of the subject moving in the +
direction of the lens position, and from midway, moving in one
direction.
[0290] In the present embodiment, in the case of the moving image
mode being selected, the drive frequency is set to f0 (maximum
frequency), and the drive voltage is set to V0 (minimum
voltage).
[0291] At t0, the drive apparatus 340A sets the phase difference of
the two drive signals to +90.degree., and turns the drive signal
ON.
[0292] At t1, the drive apparatus 340A causes the drive voltages of
the two drive signals to increase.
[0293] At t2, the drive apparatus 340A sets the drive voltages of
the two drive signals to V.sub.1.
[0294] At t3, the drive apparatus 340A starts sweeping of the drive
frequency from the maximum frequency f0.
[0295] At t4' immediately after t4, the drive apparatus 340A starts
driving of the vibration-wave motor 310 in the middle of the drive
frequency being swept, and then sets the drive frequency to
frequency f1.
[0296] In the case of the moving image mode, the wobbling operation
to cause the AF lens to move back and forth in small motions is
performed. In the case of the present embodiment, the interval of
20 Hz is established.
[0297] At t4 to t5, the drive apparatus 340A sets the phase
difference of the two drive signals to +90.degree. to cause to
rotate as positive rotation, and make the speed V.
[0298] At t5 to t6, the drive apparatus 340A sets the phase
difference of the two drive signals to 0.degree., and detects the
contrast at position Wbe.
[0299] At t6 to t7, the drive apparatus 340A sets the phase
difference of the two drive signals to -90.degree. to reverse
rotationally drive at the frequency f2, and make the speed -2V
(twice V). In proportion to increasing speed, the frequency is set
to f2, which is smaller than f1.
[0300] The reason for setting the speed during reverse rotation in
the wobbling operation to twice the positive rotation is that the
movement amount of the lens position is twice.
[0301] At t7 to t8, the drive apparatus 340A sets the phase
difference of the two drive signals to 0.degree., and detects the
contrast at position Waf.
[0302] At t8 to t9, the drive apparatus 340A sets the phase
difference of the two drive signals to +90.degree. to positive
rotationally drive at the frequency f1, and makes the speed V.
[0303] At t9 to t10, the drive apparatus 340A sets the phase
difference of the two drive signals to 0.degree., and detects the
contrast at position W0.
[0304] Wobbling operation is performed by repetition hereinafter.
One cycle of the wobbling operation (for example, between t4 and
t10) is an interval of 20 Hz (=approx. 50 msec)
[0305] Between t9 and t10, the position of the subject is
calculated from the detection results of contrast at position Wbe,
position Waf and position W0 to decide the next wobbling
operation.
[0306] The deciding parameters are the frequency fs between t10 and
t11, the frequency fb between t12 and t13, and the frequency fs2
between t14 to t15.
[0307] For example, in the results of contrast detection in one
cycle of the wobbling operation between t4 and t10, in the case of
being determined that the subject is between the wobbling amplitude
(+1 to -1), in one cycle of the subsequent wobbling operation, the
wobbling amplitude is set as +1 to -1 and defines frequency fs=f1,
frequency fb=f2 and frequency fs2=f1.
[0308] It should be noted that the subject detection results in
FIG. 30 are configured so as to indicate better contrast with a
larger value (good contrast=in focus=defined as 1, and indicating a
smaller numerical value as going more out of focus).
[0309] In addition, in the case of the subject moving to the +
direction of the lens, for example, in the case of being determined
that the subject is in the + direction from the current lens
position as a result of contrast detection in one cycle of the
wobbling operation between t10 and t16, one cycle of the subsequent
wobbling operation defines the speed at t16 to t17 as 3V, and
performs movement of the lens at three times the wobbling
amplitude. In this case, it defines frequency fs=f3 (frequency even
smaller than f2), frequency fb=f2, and frequency fs2=f1.
[0310] Next, in the case of the subject moving from the + direction
to the - direction, if determined that the subject is greatly in
the - direction from the current lens position as a result of
contrast detection in one cycle of the wobbling operation between
t22 and t27, one cycle of the subsequent wobbling operation
performs movement of the lens at four times the wobbling amplitude,
with the speed 4V between t30 and t31. In this case, it defines
frequency fs=f1, frequency fb=f4 (frequency even smaller than f3),
and frequency fs2=f1.
[0311] Basically, it is the same as the explanation for the logic
and the flowchart illustrated in FIG. 28 and FIG. 29, as in the
aforementioned first operation example. In other words, in the
wobbling operation during moving image photography, the subject
position is estimated by detecting the contrast at three places of
the lens position, and the frequencies fs and fb are calculated
according to this information. Then, by switching the phase
difference between the A-phase and B-phase in three stages (approx.
90.degree., 0.degree., -90.degree.) and setting the three drive
frequencies of frequencies fs, fb and fs2, it is possible to handle
both a case of the subject moving in the + direction of the lens
midway, and a case of moving in the -direction.
[0312] In addition, in the case of being determined that the
subject is greatly shifting from the current position, focusing on
the subject is made possible by inserting suitable values for the
frequencies fs and fb (by setting to frequency values far smaller
than f4 in FIG. 28 or FIG. 30)
[0313] The following effects are possessed by the present
embodiment above.
[0314] (1) In a case of the photography setting unit 347 having
selected the moving image photography mode, the phase difference of
the two drive signals is switched, as well as the frequency of the
two drive signals being switched to correspond to the switched
phase difference, while maintaining the voltages of the two drive
signals to be constant, whereby the speed of the vibration-wave
motor 310 can be changed. It is thereby possible to decrease the
operating noise of the vibration-wave motor 310 during moving image
photography, without performing complicated drive control.
[0315] (2) Based on the contrast of a predetermined one cycle in
the wobbling operation, it is configured so as to switch the
frequencies of the two drive signals in the subsequent one cycle to
a predetermined one cycle so as to make the focal position of the
third lens unit L3 for AF to follow the subject. The vibration-wave
motor 310 can thereby cause the third lens unit L3 for AF to move
by following the movement of the subject, and can decrease the
operating noise upon causing the vibration-wave motor 310 to drive
by way of the wobbling operation.
Fifth Embodiment
[0316] Next, a fifth embodiment of the present invention will be
explained. The fifth embodiment has similarly configurations for
the lens barrel and drive apparatus 340A as the aforementioned
embodiment; therefore, explanations thereof will be omitted. In
addition, operations of the drive apparatus 340A during moving
image photography are also similar to the fourth embodiment. The
point by which the fifth embodiment differs from the fourth
embodiment is mainly the configuration of a vibration-wave motor
350.
[0317] The configuration of a lens barrel 320A according to the
fifth embodiment will be explained next. FIG. 31 is a view
illustrating the lens barrel 320A according to the fifth embodiment
of the present invention. FIG. 32 is a view illustrating the
vibration-wave motor 350 according to the fifth embodiment. FIG. 33
is a view illustrating the operating principle of the
vibration-wave motor 350 according to the fifth embodiment.
[0318] As shown in FIG. 31, the lens barrel 320A includes an outer
fixed cylinder 331 that covers the outer circumferential part of
the lens barrel 320A, an inner first fixed cylinder 332A that is
positioned more to the inner circumferential side on the subject
side than the outer fixed cylinder 331, an inner second fixed
cylinder 332B that is positioned on an image side more to the inner
circumferential side than the outer fixed cylinder 331, and further
includes the vibration-wave motor 350 between the outer fixed
cylinder 331 and the inner first fixed cylinder 332A.
[0319] The first lens unit L1 and second lens unit L2 are fixed
from the subject side to the inner first fixed cylinder 332A. In
addition, the fourth lens unit L is fixed to the inner second fixed
cylinder 332B. The third lens unit L3, which is the AF lens
supported by the AF ring 334, is arranged between the second lens
unit L2 and fourth lens unit L4.
[0320] As shown in FIG. 31, the vibration-wave motor 350 includes a
vibrator 351, moving element 355, pressurizing member 357, etc.,
and assumes a form that drives by moving the moving element
355.
[0321] The vibrator 351 is pivotally supported in the longitudinal
direction of the vibrator 351 by a support pin 358 provided to a
fixed member 354, and is configured so there is a degree of freedom
in pressurizing direction.
[0322] The pressurizing member 357 is provided between the fixed
member 354 and vibrator 351, and makes the vibrator 351 pressurized
contact the moving element 355.
[0323] The fixed member 354 is attached to the inner first fixed
cylinder 332A. By attaching the fixed member 354 to the inner first
fixed cylinder 332A, it comes to be possible to configure from the
moving element 355, vibrator 351 to the pressurizing member 357 as
one motor unit.
[0324] The moving element 355 consists of a light metal such as
aluminum, and a sliding plating for an abrasion resistance
improvement is provided to the surface of the sliding face. In
addition, the moving element 355 is fixed to a linear guide 361,
and the linear guide 361 is pivotally supported to the inner first
fixed cylinder 332A, whereby the moving element 355 is able to move
in a linear direction relative to the inner first fixed cylinder
332A.
[0325] A fork 362 connected to the AF ring 334 fits to an end part
355A of the moving element 355, and the AF ring 334 is driven
straight ahead by the driving of the moving element 355.
[0326] The AF ring 334 assumes a mobile structure along a linear
rail 363 provided to the inner first fixed cylinder 332A and inner
second fixed cylinder 332B. A guide part 364 provided to the AF
ring 334 fits to the linear rail 363, and accompanying the straight
ahead driving of the moving element 355, is driven in the straight
ahead direction on the optical axis direction, and is configured so
as to be able to stop at the desired position.
[0327] The vibrator 351 is configured from the piezoelectric body
353, the elastic body 352 made of metal, and a projecting part 352A
for output extraction, as shown in FIG. 32 and FIG. 33. The design
of the elastic body 352 makes so that the resonance frequencies of
a vertical first-order vibration and a curved fourth-order
vibration match. When the voltage of this frequency (drive signal)
is applied to the piezoelectric body 353 and the phases of both
vibrations are shifted 900, an elliptic motion is produced from the
combination of the vertical vibration and curved vibration excited
at the projecting part 352A, as shown in FIG. 33. Since the
projecting part 352A is under pressurized contact to the moving
element 355, a drive force is produced from friction. A
wear-resistance material is used on the projecting part 352A, and
suppresses the abrasion from friction.
[0328] The piezoelectric body 353 is generally configured from a
material like lead zirconate titanate, which is called by the
abbreviation PZT; however, due to environmental problems in recent
years, it may also be configured from potassium sodium niobate,
potassium niobate, sodium niobate, barium titanate, bismuth sodium
titanate, bismuth potassium titanate, etc., which are lead-free
materials.
[0329] In the fifth embodiment, the vibration-wave motor 350 is a
linear-type vibration-wave motor. However, speed control is
possible by controlling the frequency, voltage and phase difference
of the two drive signals in the vibration-wave motor 350 according
to the fifth embodiment; therefore, the same effects as the
aforementioned fourth embodiment can be obtained.
[0330] In addition, as in the case of equipping the ring-type
ultrasonic-wave motor according to the fourth embodiment, the
conversion efficiency rises in the fifth embodiment due to there no
longer being loss occurring when converting from rotational motion
to linear motion. For this reason, the efficiency as a drive system
overall can be raised.
Sixth Embodiment
[0331] FIG. 34 is a view illustrating a camera 502 including a lens
barrel 501 equipped with a vibration actuator 600 driven by a drive
apparatus according to a sixth embodiment of the present
invention.
[0332] The lens barrel 501 of the present embodiment is detachable
relative to the main body of the camera 502; however, it is not
limited thereto, and maybe be an undetachable one.
[0333] The camera 502 of the present embodiment includes an imaging
optical system (lens) 503 inside of the lens barrel 501.
[0334] In addition, the inside of the main body of the camera 502
is configured from an imaging element 504, an AFE (Analog Front
End) circuit 505, an image processing unit 506, a voice detection
unit 507, buffer memory 508, a recording interface 509, a monitor
510, an operation member 511, memory 512 and a CPU 513, and is
connectable with a PC 514 of an external device.
[0335] The imaging optical system 503 is configured from a
plurality of optical lenses, and causes an subject image to focus
on a light receiving surface of the imaging element 504. FIG. 34
illustrates the optical lens system with reference number 503 by
simplifying as a single lens.
[0336] In addition, in the optical lens unit, the optical lens for
AF is driven by the driving of the vibration actuator 600.
[0337] The exposure time (shutter speed) to the imaging element 504
is decided according to the operation member 511 and the conditions
of the image.
[0338] The imaging element 504 is configured by a CMOS image sensor
and the like in which light-receiving elements are aligned in
two-dimensions on the light receiving surface. The imaging element
504 generates an analog image signal by photoelectrically
converting the subject image from the beam having passed through
the imaging optical system 503. The analog image signal is input to
the AFE circuit 505.
[0339] The AFE circuit 505 performs gain adjustment (signal
amplification according to ISO sensitivity) on the analog image
signal. More specifically, the imaging sensitivity is changed
within a predetermined range according to the sensitivity setting
instruction from the CPU 513. The AFE circuit 505 further converts
the image signal after analog processing by a built-in A/D
conversion circuit into digital data. This digital data is input to
the image processing unit 506.
[0340] The image processing unit 506 performs various image
processing on the digital image data.
[0341] The memory 512 temporarily records image data in pre-process
or post-process of the image processing according to the image
processing unit 506.
[0342] The voice detection unit 507 is configured from a microphone
and a signal amplifier 605, mainly detects and captures a voice
from the subject direction during moving image photography, and
transmits this data to the CPU 513.
[0343] The recording interface 509 has a connector that is not
illustrated, a recording medium 515 is connected to this connector,
and performs the writing of data to the connected recording medium
515 or reading of data from the recording medium.
[0344] The monitor 510 is configured by a liquid crystal panel, and
displays images, an operation menu, etc. according to an
instruction from the CPU 513.
[0345] The operation member 511 indicates mode dials, the arrow
keys, a select button and a release button, and sends an operation
signal according to respective operations to the CPU 513. The
setting of still image photography and moving image photograph is
set by way of the operation member 511.
[0346] The CPU 513 unifyingly controls actions performed by the
camera 502 by executing a program stored in the ROM that is not
illustrated. For example, AF (autofocus) operation control, AE
(automatic exposure) operation control, and auto white balance
control, etc. are performed.
[0347] The memory 512 records a sequence of image data subjected to
image processing. The present invention captures images
corresponding to a moving image in the camera 502 of such a
configuration.
[0348] FIG. 35 is a block diagram illustrating the vibration
actuator 600 and a drive apparatus 601 of the vibration-wave
actuator according to the sixth embodiment. The drive apparatus 601
includes an oscillation part 602, phase shifting unit 604,
amplifier, detection unit 606 and control unit 603 that controls
these.
[0349] The oscillation part 602 generates a drive signal of a
desired frequency according to the command of the control unit
603.
[0350] The phase shifting unit 604 divides the drive signal
generated by the oscillation part 602 into two drive signals of
different phases desired according to the command of the control
unit 603.
[0351] The amplifier 605 boosts the two drive signals divided by
the phase shifting unit 604 to desired voltages, respectively. The
drive signal from the amplifier 605 is transmitted to the vibration
actuator 600, and by way of the application of this drive signal, a
progressive wave generates at the vibrator 520 described later of
the vibration actuator 600, whereby the moving element 528 is
driven.
[0352] The rotation detection unit 606 is configured from an
optical encoder, magnetic encoder, or the like, detects the
position and/or speed of a driven object driven by the driving of
the moving element 528, and transmits the detection value to the
control unit 603 as an electrical signal.
[0353] The control unit 603 controls the driving of the vibration
actuator 600 and the movement of the vibration-wave actuator based
on the drive command from the CPU 513 inside the lens barrel 501 or
the camera main body. The control unit 603 receives the detection
signal from the rotation detection unit 606, obtains positional
information and speed information based on this value, and controls
the frequency of the oscillation part 602 of the vibration actuator
600, phase difference, etc., so as to position at the target
position.
[0354] FIG. 36 is a view illustrating the lens barrel 501 equipped
with the vibration actuator 600 driven by the drive apparatus
according to the sixth embodiment of the present invention, and is
a view of a state in which a ring-shaped vibration actuator 600 is
incorporated into the lens barrel 501.
[0355] The vibrator 520 is configured from an electro-mechanical
energy conversion element 521 exemplified as a piezoelectric
element or electrorestrictive element that converts electrical
energy to mechanical energy (hereinafter referred to as
piezoelectric body), and an elastic body 522 joined with the
piezoelectric body 521. A 9-peak progressive wave is generated at
the vibrator 520 as one example in the present embodiment.
[0356] The elastic body 522 consists of a metal material having a
large resonance sharpness, and the shape thereof is an annular
shape A groove is cut into the opposing face of the elastic body
522 to which the piezoelectric body 521 is joined, and the tip end
face of the projecting portions (parts without grooves) are the
driving face 522a and are under pressurized contact with the moving
element 528. The reason for cutting the grooves is to bring the
neutral plane of the progressive wave as near as possible to the
piezoelectric body 521 side, thereby making the amplitude of the
progressive wave at the driving face 522a amplified.
[0357] The piezoelectric body 521 is divided into the two phases
(A-phase, B-phase) along the circumferential direction, and in each
phase, elements for which the poles are alternating every 1/2
wavelength are aligned, and al/4 wavelength interval is open
between the A-phase and B-phase.
[0358] Below the piezoelectric body 521, a non-woven fabric 523,
pressure plate 524 and pressurizing member 525 are arranged.
[0359] The non-woven fabric 523 is felt, for example, is arranged
below the piezoelectric body 521, and makes so that vibration of
the vibrator 520 does not convey to the pressure plate 524 or
pressurizing member 525.
[0360] The pressure plate 524 is made so as to receive the pressure
of the pressurizing member 525.
[0361] The pressurizing member 525 is arranged below the pressure
plate 524, and causes an applied pressure to generate.
[0362] In the present embodiment, although the pressurizing member
525 is a disk spring, it does not need to be a disk spring, and may
be a coil spring or a wave spring.
[0363] The pressurizing member 525 is retained by a pressing ring
526, and the pressing ring 526 is fixed to a fixed member 527.
[0364] The moving element 528 consists of a light metal such as
aluminum, and a sliding material for abrasion resistance
improvement is provided on the surface of sliding face.
[0365] In order to absorb vibrations in the longitudinal direction
of the moving element 528, a vibration absorbing member 529 like
rubber is arranged on the moving element 528, and thereon, an
output transfer member 530 is arranged.
[0366] With the output transfer member 530, the pressurizing
direction and radial direction are defined by way of a bearing 531
provided to the fixed member 527, whereby the pressurizing
direction and radial direction of the moving element 528 are
defined.
[0367] The output transfer member 530 has a projecting part 532
and, therefrom, a fork connecting to a cam ring 533 fits, whereby
the cam ring 336 is rotated along with the rotation of the output
transfer member 530.
[0368] In the cam ring 533, a key groove 534 is cut obliquely in
the cam ring 533, and a fixed pin 536 provided to the AF ring 535
fits together with the key groove 534.
[0369] Then, by the cam ring 533 rotationally driving, the AF ring
535 is driven in the straight ahead direction on the optical axis
direction, and is made so as to be able to stop at the desired
position.
[0370] The fixed member 527, the pressing ring 526 is attached by a
spring to the fixed member 314, and by the fixed member 527
attaching this, it is possible to configure from the output
transfer member 530, moving element 528, vibrator 520 until the
pressurizing member 525 as one motor unit.
[0371] The phase shifting unit 604 of FIG. 35 separates the drive
signal generated by the oscillation part 602 into drive signals of
the A-phase and B-phase having different phases from each other.
These drive signals of the A-phase and B-phase are applied at the
respective electrodes of the piezoelectric body 521.
[0372] In the case of the phase difference existing between the
drive signals of the A-phase and B-phase, a wave generating at the
driving face 522a of the elastic body 522 by way of the vibration
excited by the piezoelectric body 521 is a progressive wave,
causing the moving body 528 to rotate.
[0373] FIG. 37 is a graph showing the relationship between the
phase difference of the A-phase and B-phase and the rotational
speed of the moving element 528.
[0374] As illustrated, when the phase difference of the A-phase and
B-phase is +/-90.degree., the rotational speed of the moving
element 528 becomes the fastest. Then, when the phase differences
approaches 0 (or 180.degree.), the wave generating at the driving
face 522a becomes a standing wave rather than a progressive wave,
and the rotation of the moving element 528 stops.
[0375] FIG. 38 is a graph showing the relationship between the
frequency of the drive signal and the impedance of the vibration
actuator 600. The portion shown by fs in the graph is the drive
frequency used upon driving the lens.
[0376] During driving of the vibration actuator 600, since it is
preferable to start the vibration actuator 600 from low speed, it
is common for the frequency of the drive signal applied to the
piezoelectric body 521 to start from a higher frequency than the
drive frequency (hereinafter referred to as startup frequency), and
gradually lower to the drive frequency.
[0377] For ease of explanation of this startup frequency, first, a
comparative embodiment relative to the present embodiment will be
explained. In the comparative embodiment, upon driving the
vibration actuator 600, the phase difference of the drive signals
of the A-phase and B-phase applied to the piezoelectric body 521 is
fixed at 90.degree., for example.
[0378] In this case, the startup frequency starts from a frequency
f1 between the drive frequency fs and a resonance frequency f3 of
the next high-order vibration mode than the vibration mode (drive
mode) in which this drive frequency fs is included, and gradually
lowers to the drive frequency fs.
[0379] The reason for a higher frequency than the resonance
frequency f3 of the next high-order vibration mode than the
vibration mode not using f1 in this way is because control of the
operation is difficult by the impedance of the vibration actuator
600 increasing upon the frequency of the drive signal exceeding the
resonance frequency f3.
[0380] However, in the case of this comparative embodiment, the
A-phase and B-phase of the startup frequency f1 with the phase
difference of 90.degree. are applied to the piezoelectric body 521,
simultaneously with the power source turning ON. The startup
frequency f1 cannot be set to a sufficiently high frequency due to
being smaller than f3, and the vibrator 520 of the vibration
actuator 600 suddenly starts a large vibration, and there is a
possibility of an outbreak sound generating.
[0381] Therefore, in the present embodiment, the electricity
application to the piezoelectric body 521 starts from the frequency
f2, exceeding the resonance frequency f3 of the next higher-order
vibration mode than the drive vibration mode.
[0382] The resonance frequency f3 must be exceeded upon lowering
the frequency down to the drive frequency fs also in the present
embodiment.
[0383] Upon exceeding the resonance frequency f3, if the moving
element 528 drives, there is a possibility of the movement of the
vibration actuator 600 becoming unstable as mentioned above.
[0384] Therefore, in the present embodiment, the phase difference
between the A-phase and B-phase is set to 0 or 180.degree. until
arriving at the drive frequency. However, 0.degree. and 180.degree.
are not strict values and, for example, it is a permissible range
up to on the order of +/-5.degree., so long as a range in which the
moving element 528 will not rotate.
[0385] Then, when the vibration frequency arrives at the drive
frequency fs, the phase difference between the A-phase and B-phase
is set to about 90.degree.. When the phase difference becomes
90.degree., the moving element 528 starts rotation, and lens
driving by way of the vibration actuator 600 becomes possible.
[0386] According to the present embodiment, since not a progressive
wave, but rather a standing wave is produced at the driving face
522a of the vibrator 520 until the vibration frequency arrives at
the drive frequency fs, torque is not transmitted to the moving
element 528. Therefore, since the vibration actuator 600 is
stopped, it does not bring about a malfunction in operation. On the
other hand, vibration of the vibrator 520 is started from a small
vibration; therefore, there is a low possibility of outbreak
sound.
[0387] FIG. 39 is a graph showing an example of lens driving by the
vibration actuator 600 according to the sixth embodiment.
[0388] First, at the time t1 at which voltage supply to the
vibration actuator 600 is started, since the phase difference is 0,
the lens remains stopped. Therefore, outbreak sound does not
generate by the lens suddenly starting driving.
[0389] Then, at t2 at which the frequency of the drive signal is
made to decrease, and exceeds the resonance frequency f3 to reach
the drive frequency fs, a phase difference between the A-phase and
B-phase is produced. In the present embodiment, it is about
90.degree.. It should be noted that, although 90.degree. has good
efficiency, it is not limited thereto.
[0390] Then, the phase difference is set to about 0.degree. at the
time t3 at which the lens 503 arrives at the desired position. The
lens 503 thereby stops.
[0391] A phase difference between the A-phase and B-phase is
produced again at the time t4 at which the necessity for driving of
the lens 503 arises again. On this occasion, in a case of causing
the lens 503 to drive in the reverse direction to the movement from
time t2 to t3, the phase difference is set to -90.degree..
[0392] The following effects are possessed according to the present
embodiment above.
[0393] (1) Conventionally, upon startup of the vibration actuator
600, the power source voltage is slowly input, and starts up at a
slightly higher frequency than the drive frequency. However, the
outbreak sound upon turning ON the power source is still present
with this. During moving image photography, etc., outbreak sound
generates every time turning ON the actuator. In addition, even
with suppressing abnormal noise generation, the frequency upon
startup only widens until before the resonance point of the next
mode.
[0394] However, with the present invention, the frequency upon
startup widens until the next drive mode, and by starting up from a
state in which the vibration is sufficiently small, the generation
of outbreak sound upon startup is decreased.
[0395] (2) By setting the phase difference of drive signals upon
turning the power source ON to 0 or 180.degree., even if the
vibrator 520 starts vibration, there will not be an event of the
moving element 528 starting to move, and thus a malfunction will
not occur upon the vibration frequency of the drive signal
exceeding the resonance frequency.
[0396] The present invention is not to be limited to the
embodiments explained above, and various modifications and changes
like those shown below are possible, and these also are within the
scope of the present invention.
Modified Example 6
[0397] In the present embodiment, the lens barrel 501 is detachable
relative to the main body of the camera 502; however, it is not
limited thereto, and may be undetachable.
Modified Example 7
[0398] In addition, in the present embodiment, the vibration
actuator 600 is explained with an example as ring type equipping
the lens inside; however, it is not limited thereto, and may be
miniature type that rotates about a different axis from the axis
line of the retaining cylinder, outside of the lens retaining
cylinder.
Seventh Embodiment
[0399] Hereinafter, a seventh embodiment of the present invention
will be explained by referencing the drawings, etc.
[0400] FIG. 40 is a schematic view illustrating the overall
configuration of a camera 701 according to the seventh
embodiment.
[0401] FIG. 41 is a diagram illustrating the configuration of an
ultrasonic-wave motor 720 according to the seventh embodiment.
[0402] FIG. 42 is a diagram illustrating the configuration of a
drive apparatus 730 connected to the ultrasonic-wave motor 720
according to the seventh embodiment.
[0403] It should be noted that, in FIG. 40, the front-back
direction of the camera 701 is defined as the X direction, the
left-right direction is defined as the Y direction, and the
vertical direction is defined as the Z direction.
[0404] The camera 701 includes a camera housing 702 having an
imaging element 703, and a lens barrel 710 as shown in FIG. 40, and
is a digital camera that can not only photograph still images of a
subject, but also moving images.
[0405] The lens barrel 710 is an interchangeable lens that is
detachable from the camera housing 702. The lens barrel 710
includes a lens 711 (optical member), a cam cylinder 712, a
position detection unit 713, an ultrasonic-wave motor 720
(vibration actuator), a drive apparatus 730 (drive apparatus of
vibration actuator), etc. It should be noted that the lens barrel
710 may be established as an integral unit with the camera housing
702.
[0406] The lens 711 is supported by the cam cylinder 712, and is a
focus lens that performs focal adjustment by moving in the optical
axis direction (X direction) by way of the drive power of the
ultrasonic-wave motor 720.
[0407] The cam cylinder 712 is connected with a rotational element
721 (described later) of the ultrasonic-wave motor 720, converting
rotational motion of the ultrasonic-wave motor 720 into linear
motion in the optical axis direction (X direction) to make the lens
711 mobile in the optical axis direction (X direction).
[0408] The position detection unit 713 is an encoder that detects
the position of the lens 711, which moves in the optical axis
direction (X direction).
[0409] The ultrasonic-wave motor 720 is an annular progressive
wave-type ultrasonic-wave motor of rotational type, and is
configured from an annular rotational element 721, and a vibrator
722 (vibrating body) that pressurized contacts the rotational
element 721, as shown in FIG. 41.
[0410] The vibrator 722 is configured from an annular elastic body
723, and an annular piezoelectric element 724 (piezoelectric body)
joined to this elastic body 723.
[0411] The elastic body 723 is an elastic member to which
comb-teeth are rovided to a face that pressurized contacts the
rotational element 721.
[0412] The piezoelectric element 724 is joined to a face on the
opposite side to the contact face with the rotational element 721
of the elastic body 723, and has electrode patterns A-phase and
B-phase consisting of two phases. The electrode patterns A-phase
and B-phase are polarized so that the polarity differs
alternatingly for each in the circumferential direction.
[0413] The ultrasonic-wave motor 720 causes a progressive vibration
wave to generate at the vibrator 722 by applying the two-phase
alternating signal having respectively different phases to the
electrode patterns A-phase and B-phase of the piezoelectric element
724, and the rotational element 721 under pressurized contact to
the vibrator 722 is excited by this vibration wave, whereby a drive
force to rotate in the circumferential direction (clockwise
direction G, counter-clockwise direction H) is generated.
[0414] The drive apparatus 730 is a device that controls driving of
the ultrasonic-wave motor 720, as shown in FIG. 42. The drive
apparatus 730 includes a control unit 731, a drive circuit 732, a
storage unit 733 (frequency storage unit), a speed detection unit
734, etc.
[0415] The control unit 731 is a control circuit that unifyingly
controls each part of the drive apparatus 730, and is configured
from a CPU, etc., for example. The control unit 731 realizes
various functions according to the present invention in cooperation
with the aforementioned hardware, by reading various programs
stored in the storage unit 733 and executing as appropriate.
[0416] The control unit 731 is connected to the drive circuit 732,
storage unit 733, speed detection unit 734, etc. The control unit
731 includes a speed control part 731a, a stop determination part
731b, etc.
[0417] The speed control part 731a controls the drive operation of
the ultrasonic-wave motor 720 and rotational speed n via the drive
circuit 732. More specifically, the speed control part 731a causes
the phase difference p and drive frequency f of alternating signals
input to the respective electrode patterns A-phase and B-phase of
the piezoelectric element 724 of the ultrasonic-wave motor 720 to
change so as to control the drive operation and rotational speed n
of the ultrasonic-wave motor 720. Herein, drive operation refers to
an operation of rotational motion (refer to FIG. 41) in the
positive rotational direction G of the rotational element 721 of
the ultrasonic-wave motor 720, rotational motion in the reverse
rotational direction H (refer to FIG. 41), or stopping.
[0418] The stop determination part 731b determines whether or not
the ultrasonic-wave motor 720 has stopped, based on the state of
the phase difference p of the two-phase alternating signals applied
to the piezoelectric element 724, and information of the rotational
speed n of the ultrasonic-wave motor 720 detected by the speed
detection unit 734. More specifically, the stop determination part
731b determines that the ultrasonic-wave motor 720 stopped when
confirming that the phase difference of the alternating signals
applied to the piezoelectric element 724 is p=0, and the rotational
speed detected by the speed detection unit 734 is n=0.
[0419] The drive circuit 732 is connected to the electrodes of the
respective electrode patterns A-phase and B-phase of the
piezoelectric element 724, and is a circuit that generates
alternating signals set to a predetermined phase difference p and
predetermined drive frequency f, based on the drive signal input
from the speed control part 731a.
[0420] The storage unit 733 is a storage device such as
semiconductor memory device for storing programs, information, etc.
required in the operation of the drive apparatus 730. In addition,
the storage unit 733 stores information of the drive frequency of
the alternating signals applied to the ultrasonic-wave motor 720
while stopped as a stop frequency fx (described later).
[0421] The speed detection unit 734 inputs information of a
position W of the lens 711 detected from the position detection
unit 713, and detects the rotational speed n of the rotational
element 721 based on this information of position W.
[0422] The speed detection unit 734 outputs information of the
detected rotational speed n to the control unit 731.
[0423] Next, the characteristics of the ultrasonic-wave motor 720
will be explained.
[0424] FIG. 43 provides graphs showing the characteristics of the
ultrasonic-wave motor 720 according to the seventh embodiment.
[0425] FIG. 43A is a graph showing the relationship between the
drive frequency f of the alternating signals applied to the
ultrasonic-wave motor 720 and the rotational speed n. FIG. 43B is a
graph showing the relationship between the phase difference p of
the alternating signals applied to the ultrasonic-wave motor 720
and the rotational speed n.
[0426] As shown in FIG. 43A, with the ultrasonic-wave motor 720, it
is possible to change the rotational speed n thereof by changing
the drive frequency f between fr and f0. More specifically, the
ultrasonic-wave motor 720 has a characteristic of the rotational
speed n rising when lowering the drive frequency f thereof from f0.
For example, in the case of the drive frequency f=f1, the
rotational speed becomes n=N1, and in the case of f=f2, then
becomes n=N2 (f1>f2, N2>N1).
[0427] Herein, fr in FIG. 43A is the mechanical resonance frequency
of the vibrator 722 of the ultrasonic-wave motor 720. In addition,
f0 is a frequency at which the rotational element 721 of the
ultrasonic-wave motor 720 in a state with no load starts to rotate
from the stopped state. By taking into account the stability, etc.
of control of the ultrasonic-wave motor 720, the relationships
between the drive frequency f, fr, and f0 are generally desired to
be fr<f<f0, and in the control of the ultrasonic-wave motor
720, uses the characteristic of decreasing to the right from fr in
FIG. 43A.
[0428] In addition, based on the inductance L of the secondary
winding of a transformer (not illustrated) provided to the drive
circuit 732 of the drive apparatus 730 and the capacitance C of the
piezoelectric element 724 of the vibrator 722, since making f0
match the electrical resonance frequency fc obtained from the
formula below is desirable from the aspect of an electricity
consumption reduction, f0=fc is established in the seventh
embodiment.
fc=1/{2.pi. (LC)}
[0429] As stated above, f0 is the frequency at which the rotational
element 721 of the ultrasonic-wave motor 720 in a state with no
load starts rotation from the stopped state; whereas, f.alpha. in
FIG. 43A is the frequency at which the rotational element 721 in a
state in which the lens 711, cam cylinder 721, etc. are connected
starts rotation from the stopped state. The rotational element 721
to which the lens 711, etc. are connected cannot begin rotation at
the drive frequency f=f0 due to the weight of the lens 711, etc.,
the frictional resistance of the sliding part, etc., and begins
rotation at the drive frequency f=f.alpha..
[0430] The relationship between f.alpha. and f0 is
f0>f.alpha..
[0431] The stop frequency fx stored in the storage unit 733 is the
drive frequency of the alternating signals applied to the
ultrasonic-wave motor 720 while stopped as described above;
therefore, in order to decrease the electricity consumption
thereof, it is a frequency arbitrarily set between the
aforementioned f0 and f.alpha.. In the seventh embodiment, the stop
frequency fx is set to a frequency in the middle of f0 and
f.alpha., i.e. fx=(f0+f.alpha.)/2.
[0432] In addition, as shown in FIG. 43B, with the ultrasonic-wave
motor 720, it is possible to cause the drive operation to change by
the phase difference p of the alternating signals applied to the
respective electrode patterns A-phase and B-phase of the
piezoelectric element 724 being controlled. In the seventh
embodiment, the ultrasonic-wave motor 720 rotates in the positive
rotational direction G (refer to FIG. 41) when the phase difference
of the alternating signals applied to the respective electrode
pattern A-phase and B-phase is set to p=+90.degree., and rotates in
the reverse rotational direction H when the phase difference is set
to p=-90.degree. (refer to FIG. 41). In addition, it stops when the
phase difference is p=0.degree.. At this time, the lens 711 moves
to the subject side (X1 side) when the ultrasonic-wave motor 720
rotates in the positive rotational direction G, and moves to the
imaging element 703 side (X2 side) when rotating in the reverse
rotational direction H, as shown in FIG. 40.
[0433] Next, the driving of the ultrasonic-wave motor 720 and
operation of the lens 711 moving by way of this driving will be
explained with the wobbling operation as an example.
[0434] FIG. 44 is a timing chart illustrating the driving pattern
of a drive apparatus 730 in the wobbling operation according to the
seventh embodiment. In FIG. 44, the vertical axis shows in order
from the top the drive voltage v, drive frequency f, phase
difference p and rotational speed n of the ultrasonic-wave motor
720 and the position W of the lens 711, and the horizontal axis
shows time (t1 to t29).
[0435] Herein, wobbling operation is one of the focusing means for
focusing on a subject automatically during moving image
photography. In the wobbling operation, the drive apparatus 730
drives the ultrasonic-wave motor 720 based on a command signal
inputted from a control unit of the camera 701 that is not
illustrated, and during moving image photography, repeats a
sequence of operations (t5 to t16) to cause the position of the
lens 11 to move from an initial position W1 to Wbe on the subject
side (X1 side) and then stop, cause to move from Wbe to Waf on the
imaging element 703 side (X2 side) and then stop, and cause to move
from Waf to W0 and then stop, as shown in FIG. 44.
[0436] At t4, when moving image photography of the camera 701 is
started, the speed control part 731a of the drive apparatus 730
applies alternating signals having a drive frequency f=f0 and phase
difference p=+90.degree. to the piezoelectric element 724 of the
ultrasonic motor 720. At this time, the lens 711 is stopped at the
initial position Wi.
[0437] At t5, the speed control part 731a causes the drive
frequency of the ultrasonic-wave motor 720 to change in the
lowering direction from f0 to f1, in order to cause the position W
of the lens 711 to move from Wi to Wbe, accompanying the start of
the wobbling operation.
[0438] At t6, when gradually lowering the drive frequency f from f0
to f1, upon passing f.alpha., the ultrasonic-wave motor 720 starts
rotation in the clockwise direction G, and the rotational speed
reaches n=N1. Along with this, the position W of the lens 711 also
starts movement from Wi to the subject side (X1 side). Then, in
accordance with the position W of the lens 711 arriving at Wbe, the
speed control part 731a changes the phase difference p of the
alternating signals applied to the ultrasonic-wave motor 720 from
+90.degree. to 0.degree. to cause the ultrasonic-wave motor 720 to
stop.
[0439] At t7, the stop determination part 731b of the control unit
731 determines whether the ultrasonic-wave motor 720 has stopped,
based on the phase difference p of the alternating signals, and
information of the rotational speed n output from the speed
detection unit 734. If the stop determination part 731b determines
that the ultrasonic-wave motor 720 has stopped, the speed control
part 731a reads information of a stop frequency fx stored in the
storage unit 733, and changes the drive frequency f in the rising
direction from f1 to fx.
[0440] At t8, the speed control part 731a causes the
ultrasonic-wave motor 720 to stop while the drive frequency is
f=fx.
[0441] At t9, the speed control part 731a causes the drive
frequency f of the ultrasonic-wave motor 720 to change in the
lowering direction from fx to f2 in order to cause the position W
of the lens 711 to move from Wbe to Waf.
[0442] At t10, the speed control part 731a gradually changes the
phase difference p of the alternating signals applied to the
piezoelectric element 724 from 0.degree. to -90.degree..
[0443] The ultrasonic-wave motor 720 thereby rotates in the reverse
rotational direction (H direction) and the position W of the lens
711 moves from Wbe to Waf.
[0444] Then, in accordance with the position W of the lens 711
arriving at Waf, the speed control part 731a changes the phase
difference p of the alternating signals applied to the
piezoelectric element 724 from -90.degree. to 0.degree. to cause
the ultrasonic-wave motor 720 to stop.
[0445] At t11, when the stop determination part 731b determines
that the ultrasonic-wave motor 720 has stopped based on information
of the phase difference p of the alternating signals and of the
rotational speed n output from the speed detection unit 734, the
speed control part 731a reads information of the stop frequency fx
in the storage unit 311, and changes the drive frequency f in the
rising direction from f2 to fx.
[0446] At t12, the speed control part 731a causes the
ultrasonic-wave motor 720 to stop while the drive frequency is
f=fx.
[0447] At t13, the speed control part 731a causes the drive
frequency f of the ultrasonic-wave motor 720 to change from fx to
f1, in order to cause the position W of the lens 711 to move from
Waf to W0.
[0448] At t14, the speed control part 731a gradually changes the
phase difference p of the alternating signals applied to the
ultrasonic-wave motor 720 from 0.degree. to +90.degree..
[0449] The ultrasonic-wave motor 720 thereby rotates in the
positive rotational direction (G direction), and the position W of
the lens 711 moves from Waf to W0.
[0450] Then, in accordance with the position of the lens 711
arriving at W0, the speed control part 731a changes the phase
difference p of the alternating signals applied to the
piezoelectric element 724 from +90.degree. to 0.degree. to cause
the ultrasonic-wave motor 720 to stop.
[0451] At t15, when the stop determination part 731b determines
that the ultrasonic-wave motor 720 has stopped, based on
information of the phase difference p of the alternating signals
and the rotational speed n output form the speed detection unit
734, the speed control part 731a reads information of the stop
frequency fx in the storage unit 733, and changes the drive
frequency f in the rising direction from f1 to fx.
[0452] At t16, the speed control part 731a causes the
ultrasonic-wave motor 720 to stop while the drive frequency is
f=fx.
[0453] The above sequence of the wobbling operation in t5 to t16
comes to an end, and the drive apparatus 730 repeatedly performs
the same operation again from t17.
[0454] Next, the operation pattern of the ultrasonic-wave motor in
the wobbling operation of a comparative example will be explained.
It should be noted that, in the following explanation and in the
drawings, explanations for operations similar to the aforementioned
operation pattern of the ultrasonic-wave motor 720 of the present
invention will be omitted, and only differing operations will be
explained.
[0455] FIG. 45 is a timing chart illustrating the drive pattern of
the drive apparatus in the wobbling operation of a comparative
example. Similarly to FIG. 44, in FIG. 45, the vertical axis shows
in order from the top the drive voltage v, drive frequency f, phase
difference p and rotational speed n of the ultrasonic-wave motor
and the position W of the lens, and the horizontal axis shows time
(t1 to t29).
[0456] As shown in FIG. 45, in the drive pattern of the drive
apparatus in the wobbling operation of the comparative example, if
the position W of the lens moves from Wi to Wbe, at t7, the speed
control unit changes the drive frequency f in the lowering
direction from f1 to f2 in order to move the position W of the lens
in a subsequent operation from Wbe to Waf. Then, the speed control
part maintains the drive frequency at f=f2, while causing the
position W of the lens to move from Wbe to Waf at t10. In contrast,
the drive pattern of the present invention differs from the drive
pattern of the comparative example in the point of, the speed
control part 731a causes the ultrasonic-wave motor 720 to stop with
the drive frequency set at f=fx at t8, as mentioned above. In
addition, this is similar for t11 to t13 and t15 to 17.
[0457] Next, the difference in the amount of power consumption of
the ultrasonic-wave motors between the seventh embodiment and the
comparative example will be explained.
[0458] FIG. 46 is a graph comparing the amount of power consumption
of the ultrasonic-wave motors between the seventh embodiment and
the comparative example. In FIG. 46, the vertical axis shows the
amount of electrical power consumed by the control of the
ultrasonic-wave motor, and the horizontal axis shows the control
time.
[0459] Since the ultrasonic-wave motor 720 has a trend of the
electricity consumption thereof decreasing as the drive frequency f
approaches f0 (=fc), when the ultrasonic-wave motor 720 is stopped,
the drive apparatus 730 of the present invention changes the drive
frequency f thereof to f=fx in the rising direction so as to
approach f0.
[0460] On the other hand, as mentioned above, when the
ultrasonic-wave motor is stopped, in preparation for the subsequent
operation, a conventional drive apparatus changes the drive
frequency f thereof to f1, f2 or the like, which are in a direction
distancing from f0.
[0461] Herein, due to being fx>f1>f2, the electricity
consumption during stopping of the ultrasonic-wave motor 720 is
smaller for the control of the drive apparatus 730 of the present
invention, than the control by the drive apparatus of the
comparative example.
[0462] In FIG. 46, for a case of the stop time of the
ultrasonic-wave motor during control being long (condition 1) and a
case of being short (condition 2), the electricity consumption is
compared according to the drive apparatus 730 of the present
invention and the drive apparatus of the comparative example,
respectively.
[0463] As shown in FIG. 46, in either case, the electricity
consumption was lower for the drive apparatus 730 of the present
invention than for the drive apparatus of the comparative example,
and thus the effect of a reduction in the electricity consumption
by the ultrasonic-wave motor 720 of the drive apparatus 730 of the
present invention could be confirmed. In addition, since the stop
time also lengthens as the control time lengthens, the
aforementioned effect of a reduction in the electricity consumption
of the present invention becomes more remarkable.
[0464] As explained above, there are the following such effects in
the drive apparatus 730 and lens barrel 710 according the seventh
embodiment.
[0465] (1) The drive apparatus 730 can reduce the electricity
consumption while stopping of the ultrasonic-wave motor 720 during
control, due to making the drive frequency f of the alternating
signals applied to the piezoelectric element 724 change to fx in
the rising direction so as to approach the electric resonance
frequency fc, in the case of the ultrasonic-wave motor 720 being
stopped.
[0466] (2) Since the stop determination part 731b determines
whether the ultrasonic-wave motor 720 has stopped based on the
state of the phase difference p of the alternating signals applied
to the piezoelectric element 724 and the rotational speed n of the
rotational element 721, the speed control part 731a causes the
drive frequency f to change prior to the ultrasonic-wave motor 720
completely stopping, and thus can avoid the ultrasonic-wave motor
720 from malfunctioning.
[0467] (3) Since the speed detection unit 734 detects the
rotational speed n of the rotational element 721 of the
ultrasonic-wave motor 720 based on the positional information of
the lens 711, an existing position detection unit 713 provided to
the lens barrel 710 can be used without providing a sensor for
detecting the rotational speed n to the rotational element 721,
whereby a reduction in the size of the lens barrel 710 and a cost
reduction can be achieved.
[0468] (4) Due to using the drive apparatus 730 in driving of the
lens 711 of the lens barrel 710, it is possible to reduce the
electricity consumption of the ultrasonic-wave motor 720
continuously driving, in a focus operation such as the wobbling
operation of the lens 711.
Modified Example 8
[0469] The seventh embodiment shows an example in which the stop
frequency fx stored in the storage unit 733 is set to a frequency
in the middle of f0 and f.alpha., i.e. fx=(f0+f.alpha.)/2; however,
it is not limited thereto.
[0470] As mentioned above, fx can be arbitrarily set so long as
between f0 and f.alpha.; therefore, it is also possible to set the
stop frequency to fx=f.alpha., for example. By configuring as such,
it is possible to reduce the electricity consumption during
stopping of the ultrasonic-wave motor 720, and quicken the response
time from a stopped state of the ultrasonic-wave motor 720 to
rotational motion.
[0471] In addition, due to being f0=fc if setting the stop
frequency to fx=f0, the drive apparatus 730 can cause the
electricity consumption during stopping of the ultrasonic-wave
motor 720 to reduce the most efficiently.
Modified Example 9
[0472] The seventh embodiment shows an example in which the speed
detection unit 734 detects the rotational speed n of the rotational
element 721 based on positional information of the position
detection unit 713; however, it is not limited thereto. For
example, a sensor for detecting the rotational speed n may be
provided to the rotational element 721, and the rotational speed n
of the rotational element 721 may be detected directly.
Modified Example 10
[0473] The seventh embodiment shows an example in which the
ultrasonic-wave motor 720 is an annular progressive wave-type
ultrasonic-wave motor of rotational type; however, it is not
limited thereto. For example, it is also possible to employ a
rod-shaped ultrasonic-wave motor of rotational type.
Modified Example 11
[0474] The seventh embodiment shows an example of using the drive
circuit 732 to which a transformer is provided; however, it is also
possible to employ a drive circuit to which an inductor is
provided, for example.
Modified Example 12
[0475] The seventh embodiment explains an example of a wobbling
operation during moving image photography of the lens barrel 710;
however, it is not limited thereto. It is also possible to employ a
different operation, for example, an auto-focus operation during
still image photography, and similar effects as the present
invention can be obtained thereby.
[0476] The embodiments and modified examples explained above are
merely exemplifications after all, and the present invention is not
limited to these contents so long as the characteristics of the
invention are not impaired. In addition, the embodiments and
modified examples explained above may be realized by combinations
thereof, so long as the characteristics of the invention are not
impaired.
* * * * *