U.S. patent application number 13/053989 was filed with the patent office on 2011-09-22 for drive device, lens barrel, image pickup apparatus, lens drive method and method of producing shape memory alloy.
This patent application is currently assigned to Konica Minolta Opto, Inc.. Invention is credited to Saori HIRATA, Chie Nemoto, Katsumi Ohtsuka, Kenpo Tsuchiya.
Application Number | 20110226392 13/053989 |
Document ID | / |
Family ID | 37727273 |
Filed Date | 2011-09-22 |
United States Patent
Application |
20110226392 |
Kind Code |
A1 |
HIRATA; Saori ; et
al. |
September 22, 2011 |
Drive device, lens barrel, image pickup apparatus, lens drive
method and method of producing shape memory alloy
Abstract
A lens barrel, an image pickup apparatus, a lens drive method
and a method of producing a shape memory alloy used for the drive
device are disclosed. A drive device includes: a lens group for
guiding light from a subject; a shape memory alloy adopted to be
deformed by an electricity supplied to the shape memory alloy, for
moving the lens group in a direction of an optical axis; and
electricity-supply controlling means for controlling an amount of
the electricity supplied to the shape memory alloy; and a detecting
means for detecting whether a movement of the lens group starts or
not. In the drive device, a movement amount of the lens group in
the direction of the optical axis is controlled based on the amount
of electricity supplied when the detecting means detects the
movement of the lens group.
Inventors: |
HIRATA; Saori; (Tokyo,
JP) ; Ohtsuka; Katsumi; (Tokyo, JP) ; Nemoto;
Chie; (Tokyo, JP) ; Tsuchiya; Kenpo; (Tokyo,
JP) |
Assignee: |
Konica Minolta Opto, Inc.
Tokyo
JP
|
Family ID: |
37727273 |
Appl. No.: |
13/053989 |
Filed: |
March 22, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11990253 |
Feb 7, 2008 |
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PCT/JP2006/315261 |
Aug 2, 2006 |
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13053989 |
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Current U.S.
Class: |
148/566 ;
148/559 |
Current CPC
Class: |
H04N 5/232123 20180801;
G02B 13/001 20130101; F03G 7/065 20130101; G02B 7/023 20130101;
G03B 3/10 20130101; H04N 5/2254 20130101; H04N 5/2257 20130101 |
Class at
Publication: |
148/566 ;
148/559 |
International
Class: |
C21D 1/00 20060101
C21D001/00; C21D 9/00 20060101 C21D009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 11, 2005 |
JP |
2005-232920 |
Aug 22, 2005 |
JP |
2005-239758 |
Sep 13, 2005 |
JP |
2005-265023 |
Claims
1-17. (canceled)
18. A method of producing shape memory alloy for use in a drive
apparatus comprising a driven body, a shape memory alloy in contact
with the driven body, a heating section for heating the shape
memory alloy, a controlling section for controlling a drive of a
driven body by controlling the heating section, the method
comprising: a step of applying an aging treatment to the shape
memory alloy which is in contact with the driven body, after the
drive apparatus has been assembled, the aging treatment repeating a
predetermined number or more of times of heating and no-heating
processes.
19. The method of producing shape memory alloy of claim 18, wherein
the shape memory alloy is heated by applying an electric current to
the shape memory alloy.
20. The method of producing shape memory alloy of claim 18, wherein
the controlling section controls the heating section to heat the
shape memory alloy, for applying the aging treatment to the shape
memory alloy.
Description
RELATED APPLICATIONS
[0001] This is a continuation of application Ser. No. 11/990,253,
filed Feb. 7, 2008 which is a U.S. National Phase Application under
35 USC 371 of International Application PCT/JP2006/315261 filed on
Aug. 2, 2006.
[0002] This application claims the priority of Japanese application
nos. 2005-232920 filed Aug. 11, 2005, 2005-239758 filed Aug. 22,
2005 and 2005-265023 filed Sep. 13, 2005, the entire content of all
of which is hereby incorporated by reference.
TECHNICAL FIELD
[0003] The present invention relates to a drive device constructed
to move a lens group representing a driven body by using expansion
and contraction of a shape memory alloy, a lens barrel, an image
pickup apparatus, a lens drive method and a method of producing a
shape memory alloy used for the drive device.
BACKGROUND ART
[0004] With regard to the shape memory alloy (hereinafter referred
to sometimes as "SMA"), even if it is plastically deformed due to
receiving force in a temperature not higher than martensitic
transformation completion temperature, it recovers its shape when
it is heated to the temperature that is not less than reverse
transformation completion temperature.
[0005] FIG. 23 is a diagram wherein a relation between temperature
and deformation of the shape memory alloy is graphed schematically.
In FIG. 23, the horizontal axis represents temperature (.degree.
C.) and the vertical axis represents deformation (%).
[0006] As shown in FIG. 23, when electricity is supplied between
both ends of the shape memory alloy at a low temperature, the shape
memory alloy is contracted by generated heat to return to its
memorized length. On the other hand, when the electricity supply
stops at the state of this high temperature, the temperature of the
shape memory alloy decreases due to heat radiation, and its length
changes with hysteresis to become the state of elongated again. The
shape memory alloy is possible to use as an actuator by utilizing
this effect of shape memory, and there have been made various
proposals.
[0007] However, actions of a shape memory alloy (SMA) are provided
by heating SMA with Joule heat through supplying electricity for
SMA, and thereby obtaining displacement of a driven member by
utilizing a deformation corresponding to the temperature resulted
from the heating. Therefore, it has been difficult to determine the
unique input condition for SMA to obtain desired displacement,
because of various un-uniformity in the constituted system such as,
for example, errors in a length of SMA, errors in a resistance
value of SMA, errors of mechanical dimensions of constituent
members and the ambient temperature.
[0008] For dissolving the aforesaid problems, therefore, there has
been proposed a position-control drive device that detects a
position of a lens group representing a driven body, and partially
changes the shape memory alloy based on the results of the
detection (for example, see Japanese Patent Publication Open to
Public Inspection No. 10-307628).
[0009] Further, Japanese Patent Publication Open to Public
Inspection (JP-A) No. 11-324896 discloses a drive mechanism that
detects the ambient temperature with a temperature sensor, and
controls a current value and a voltage value to be supplied to a
wire formed by a shape memory alloy, or controls a duty ratio of a
pulse current or of a pulse voltage to be supplied to the wire,
based on the detected result.
[0010] Further, JP-A No. 2002-99019 discloses a drive mechanism
using a string-like shape memory alloy which is formed to be in a
doglegged shape to be in contact with a driven body at the
substantial center position of the string-like shape memory alloy
and to be fixed at both ends of the string-like shape memory
alloy.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0011] The position control drive device in the aforesaid JP-A No.
10-307628 is suitable to drive a lens group with being arranged in
a lens barrel of a device such as a camera. However, when it is
applied to a lens drive device of a small-sized and thin image
pickup apparatus provided to be housed in, for example, a mobile
terminal, there are needed position detecting sensors for acquiring
information about the present position of a driven member to be
arranged on the total area where the driven member moves, resulting
in slight disadvantage for downsizing and cost reduction, which is
a problem.
[0012] In the drive mechanism described in the aforesaid JP-A No.
11-324896, it is suitable to be utilized at the inside of the
apparatus where temperature distribution is relatively uniform such
as a rear cover of a camera. However, when it is applied to a lens
drive device of a small-sized and thin image pickup apparatus
provided to be housed in, for example, a mobile terminal, circuit
parts that operate other functions are arranged densely in the
vicinity of the drive mechanism, whereby, temperature distribution
in the apparatus is not uniform, and detection values vary
depending on a position where a temperature sensor is arranged.
Thus, it is sometimes provide a situation hardly to conduct optimum
control.
[0013] Further, the drive mechanism described in JP-A No.
2002-99019 wherein a string-like shape memory alloy which is formed
to be in a doglegged shape is used, is not so problematic for
mounting in a large equipment such as binocular glasses. However,
it requires any other ideas for applying the drive mechanism to a
small-sized image pickup apparatus to mount it in a mobile
terminal, because fixed sections on both ends are protruded greatly
from both sides of a driven body.
[0014] It is known that the shape memory alloy occurs an initial
creep phenomenon that a deformation amount changes depending on the
number of times of supplying electricity at the initial step where
the frequency of supplying electricity is small. When a drive
device utilizing a shape memory alloy controls a position of a
driven body, the deformation amount changes unwillingly even when
applying the same amount of current, because of the aforesaid
initial creep phenomenon. Therefore, there is also in a problem
that accurate position control is difficult.
[0015] In view of the aforesaid problems, an object of the
invention is to obtain a small-sized and low-cost drive device that
employs a shape memory alloy for an actuator, and can stop a lens
group at a desired position and is suitable to be mounted in a
mobile terminal; a lens barrel; an image pickup apparatus; a lens
drive method; and a method of producing a shape memory alloy used
for the drive device.
Means to Solve the Problems
[0016] The aforesaid problems are solved by the structures listed
below:
1. A drive device comprising: a lens group for guiding light from a
subject; a shape memory alloy adopted to be deformed by an
electricity supplied to the shape memory alloy, for moving the lens
group in a direction of an optical axis; an electricity-supply
controlling means for controlling an amount of the electricity
supplied to the shape memory alloy; and a detecting means for
detecting whether a movement of the lens group starts or not,
[0017] wherein a movement amount of the lens group in the direction
of the optical axis is controlled based on the amount of the
electricity supplied when the detecting means detects the movement
of the lens group.
2. A drive device comprising: a lens group for guiding light from a
subject; a shape memory alloy adopted to be deformed by an
electricity supplied to the shape memory alloy, for moving the lens
group in a direction of an optical axis; an electricity-supply
controlling means for controlling an amount of the electricity
supplied to the shape memory alloy; and a detecting means for
detecting a movement of the lens group at the two predetermined
positions,
[0018] wherein a movement amount of the lens group in the direction
of the optical axis is controlled based on each of amounts of the
electricity supplied when the detecting means detects the movement
of the lens group between two predetermined positions along the
optical axis.
3. The drive apparatus of Item 1 or 2, wherein the detecting means
is an output of an image pickup element. 4. A drive device
comprising: a driven body; a shape memory alloy engaged with the
driven body; a heating section for heating the shape memory alloy;
a controlling section for controlling a drive of the driven body by
controlling the heating section,
[0019] wherein the controlling section applies an aging treatment
to the shape memory alloy when the shape memory alloy is initially
used, the aging treatment controlling the heating section to repeat
a predetermined number or more of times of heating and no-heating
processes.
5. The drive device of Item 4, wherein the heating section heats
the shape memory alloy by applying an electric current to the shape
memory alloy. 6. A drive device comprising: a driven body; a shape
memory alloy engaged with the driven body; a heating section for
heating the shape memory alloy; a controlling section for
controlling a drive of the driven body by controlling the heating
section,
[0020] wherein the shape memory alloy is applied an aging treatment
in advance, the aging treatment repeating a predetermined number or
more of times of heating and no-heating processes.
7. The drive device of Item 6, wherein the shape memory alloy is
heated by applying an electric current to the shape memory alloy.
8. A lens barrel comprising: a lens group for guiding light from a
subject; a lens frame supporting the lens group; and a shape memory
alloy formed in a shape of a string for moving the lens frame in a
predetermined direction,
[0021] wherein a part of the shape memory alloy is arranged in an
optical path of the lens group, and
[0022] the shape memory alloy moves the lens frame by being
contracted due to an electricity supplied to the shape memory
alloy.
9. The lens barrel of Item 8, wherein the shape memory alloy moves
the lens frame in a direction of an optical axis by being
contracted. 10. The lens barrel of Item 9, wherein the shape memory
alloy moves the lens frame close, to the subject by being
contracted. 11. The lens barrel of Item 10, wherein the lens frame
is pressed toward an image-forming surface. 12. An image pickup
apparatus comprising the drive apparatus of any one of Items 1 to
7. 13. An image pickup apparatus comprising the lens barrel of any
one of Items 8 to 11. 14. A lens drive method of driving a lens
group for controlling an amount of a movement of a lens group for
guiding light from a subject in an optical axis, by controlling the
lens group, a shape memory alloy, and an amount of an electricity
supplied to the shape memory alloy, the method comprising:
[0023] a step of gradually changing an electricity supplied to the
shape memory alloy and detecting whether a movement of the lens
group starts or not;
[0024] a step of determining an amount of an electricity to be
supplied to the shape memory alloy which is needed to move the lens
group to a predetermined position based on an amount of an
electricity supplied when the movement of the lens group starts;
and
[0025] a step of supplying the electricity which is determined to
the shape memory alloy.
15. A lens drive method of driving a lens group for controlling an
amount of a movement of a lens group for guiding light from a
subject in an optical axis, by controlling the lens group, a shape
memory alloy, and an amount of an electricity supplied to the shape
memory alloy, the method comprising:
[0026] a step of gradually changing an electricity supplied to the
shape memory alloy and detecting a movement of the lens group at
two predetermined positions along the optical axis;
[0027] a step of determining an amount of an electricity to be
supplied to the shape memory alloy which is needed to move the lens
group to a predetermined position based on each of amounts of the
electricity supplied when the movement of the lens group are
detected at the two predetermined positions; and
[0028] a step of supplying the electricity which is determined to
the shape memory alloy.
16. A method of producing shape memory alloy for use in a drive
apparatus comprising a driven body, a shape memory alloy connected
to the driven body, a heating section for heating the shape memory
alloy, a controlling section for controlling a drive of a driven
body by controlling the heating section, the method comprising: a
step of applying an aging treatment to the shape memory alloy, the
aging treatment repeating a predetermined number or more of times
of heating and no-heating processes. 17. The method of producing
shape memory alloy of Item 16, wherein the shape memory alloy is
heated by applying an electric current to the shape memory
alloy.
Effects of the Invention
[0029] The invention makes it possible to obtain a small-sized and
low cost drive device that has a simple and convenient structure
and can stop a lens group at a desired position accurately, a lens
barrel, an image pickup apparatus, a lens drive method and a method
of producing a shape memory alloy used for the drive device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is an appearance diagram of a cell-phone representing
an example of a mobile terminal equipped with an image pickup
apparatus relating to the present embodiment.
[0031] FIG. 2 is a perspective view of an image pickup apparatus
provided as a unit relating to the present embodiment.
[0032] FIG. 3 is a sectional view showing an internal structure of
the image pickup apparatus.
[0033] FIG. 4 is a perspective view showing the inside of the image
pickup apparatus.
[0034] FIG. 5 is a front view showing arrangement of respective
parts inside the image pickup apparatus.
[0035] FIG. 6 is a schematic diagram showing relationship for
respective parts about which the string-like shape memory alloy is
extended.
[0036] Each of FIGS. 7(a), 7(b), and 7(c) is a diagram showing an
initial state (no-electricity state) of each part of the lens drive
device relating to the first embodiment.
[0037] FIG. 8 is a flow chart showing a lens drive method of an
image pickup apparatus relating to the first embodiment.
[0038] FIG. 9 is a graph showing relationship between an amount of
current for a shape memory alloy and deformation of the shape
memory alloy, which shows a method of determining the amount of
current.
[0039] FIG. 10 is a flow chart showing a lens drive method of an
image pickup apparatus relating to the second embodiment.
[0040] FIG. 11 is a graph showing relationship between an amount of
current for a shape memory alloy and deformation of the shape
memory alloy, which shows a method of obtaining relationship
between an amount of lens movement and an amount of current.
[0041] FIG. 12 is a diagram showing another example of a detecting
device that detects a movement of a lens group at two predetermined
locations in the optical axis direction.
[0042] FIG. 13 is a conceptual diagram showing relationship between
deformation amount E and temperature T when electricity is supplied
at the first time and the tenth time.
[0043] FIG. 14 is a conceptual diagram showing relationship between
an amount of deformation and the number of times of supplying
electricity.
[0044] FIG. 15 is a diagram showing a control block of a drive
device in the present embodiment.
[0045] FIG. 16 is a diagram showing a control routine of a drive
device in the present embodiment.
[0046] FIG. 17 is a diagram showing an aging control routine.
[0047] FIG. 18 is a front view showing another example of
arrangement of respective parts constituting a lens barrel inside
an image pickup apparatus.
[0048] Each of FIGS. 19(a) and 19(b) is a sectional view of the
lens barrel inside the image pickup apparatus shown in FIG. 18
which is taken on a plane including the shape memory alloy.
[0049] Each of FIGS. 20(a) and 20(b) is an illustration diagram
wherein an optical path is interrupted by the shape memory
alloy.
[0050] FIG. 21 is a top surface diagram of a leaf spring of a
diaphragm type.
[0051] Each of FIGS. 22(a) and 22(b)a sectional view in which a
shape memory alloy is extended.
[0052] FIG. 23 is a diagram wherein relationship between
temperature and deformation of a shape memory alloy is graphed
schematically.
EXPLANATION OF NOTATION
[0053] 11. Lens group [0054] 12. Cover member [0055] 13. Bottom
plate [0056] 15, 16. Guide shaft [0057] 17. First lens frame [0058]
18. Second lens frame [0059] 19. Helical compression spring [0060]
21. Screw [0061] 23. Shape memory alloy [0062] 31. Print board
[0063] 32. Flexible print board [0064] 34. Image pickup element
[0065] 41. Photo-interrupter [0066] 100. Image pickup apparatus
BEST MODE FOR CARRYING OUT THE INVENTION
[0067] The invention will be explained in detail as follows,
referring to the embodiment, to which, however, the invention is
not limited.
[0068] FIG. 1 is an appearance diagram of a mobile phone T which is
an example of a mobile terminal provided with the image pickup
apparatus relating to the present embodiment.
[0069] In the mobile phone T shown in FIG. 1, an upper casing 71 as
a case provided with the display image screens D1 and D2, and the
lower casing 72 provided with operation buttons P, are connected
with each other through a hinge 73. The image pickup apparatus 100
is housed below the display image screen D2 in the upper casing 71,
and the image pickup apparatus 100 is arranged in such a manner
that the light can be taken-in from the outer surface side of the
upper casing 71.
[0070] Hereupon, this image pickup apparatus 100 may also be
arranged above or on the side surface of the display image screen
D2 in the upper casing 71. Further, it is of cause that the mobile
phone is not limited to a folding type.
[0071] FIG. 2 is a perspective view of an image pickup apparatus
relating to the present embodiment in the state provided as a
unit.
[0072] As shown in FIG. 2, an outer surface of the image pickup
apparatus relating to the embodiment is composed of box-shaped
cover member 12 that has an opening so that lens group 11 may take
in light from a subject; bottom plate 13 that fixes thereon the
cover member 12 through screw 14 and holds respective members
arranged inside; print board 31 that is fixed on the bottom surface
of the bottom plate 13, and holds therein image pickup elements
mounted therein; and flexible print board 32 that is connected to
the print board 31. There is further arranged flexible print board
32f for supplying electric power to a shape memory alloy which will
be explained later. Further, the flexible print board 32f is
connected also to photo-interrupter 41 that is fixed on the bottom
plate 13. This flexible print board 32f may either be constructed
integrally with the flexible print board 32 or be constructed
separately from the flexible print board 32.
[0073] Incidentally, on the flexible print board 32, there is
formed contact point section 32t for connecting to another board of
a mobile terminal, and reinforcing plate 33 is pasted on the
reverse side of the flexible print board 32. Now, the symbol O
represents an optical axis of lens group 11. Further, the contact
point section 32t represents an element which has 20 pins or more
such as a power supply, control signals, image signal output and a
terminal for inputting to a shape memory alloy, and it is shown
schematically.
[0074] Next, internal structures of the image pickup apparatus
relating to the present embodiment will be explained as follows,
referring to FIGS. 3, 4 and 5. Incidentally, in the following
figures, the same symbols are given to the same function members
for the explanation.
[0075] FIG. 3 is a sectional view showing the internal structures
of the image pickup apparatus. FIG. 3 shows a section taken on line
F-F in FIG. 2.
[0076] FIG. 4 is a perspective view showing the inside of the image
pickup apparatus. FIG. 4 shows a situation wherein cover member 12,
print board 31 and flexible print board 32 and 32f are removed from
image pickup apparatus 100 shown in FIG. 2.
[0077] FIG. 5 is a front view showing arrangement of respective
parts constituting a lens barrel inside the image pickup apparatus.
FIG. 5 is a diagram wherein the image pickup apparatus shown in
FIG. 4 is viewed from the subject side in the optical axis
direction.
[0078] Inside the image pickup apparatus 100, there are arranged
the first lens frame 17 (hereinafter referred to as lens frame 17)
that houses therein lens group 11 that is composed of a single lens
or of plural lenses, and the second lens frame 8 (hereinafter
referred to as lens frame 18) that holds the lens frame 17 in the
outside of lens frame 17.
[0079] The lens frame 17 is engaged with the lens frame 18 through
screw sections 17n and 18n, and the lens frame 17 can be moved in
the optical axis direction against the lens frame 18 when the lens
frame 17 is rotated on the lens frame 18. Incidentally, the lens
frame 17 and the lens frame 18 may also be arranged so that both of
them may be moved relatively in the optical axis direction through
a helicoid or through other structures.
[0080] The bottom plate 13 is formed to be a quadrangle
substantially when it is viewed in the optical axis direction.
Guide shafts 15 and 16 are located at almost diagonal positions
with in-between optical axis O on the bottom plate. Guide shaft 15
is planted in the bottom plate 13 to be in substantially parallel
with the optical axis, and guide shaft 16 is integrally formed with
the bottom plate as one body. Alternatively, the guide shaft 15 may
also be integrally formed as one body with the bottom plate 13 and
the guide shaft 16 may be planted in the bottom plate 13.
[0081] Cylindrical section 18p through which the guide shaft 15 is
engaged and is penetrated is integrally formed as one body on the
lens frame 18, and U-shaped engaging section 18u that engages with
the guide shaft 16 is formed on the lens frame 18. Owing to this,
the lens frame 18 can move in the optical axis direction along the
guide shafts 15 and 16, and lens frame 17 and lens group 11 can
move together with the lens frame 18 in the optical axis direction.
Further, this cylindrical section 18p is pressed by helical
compression spring 19 representing a pressing member in the axial
direction of the guide shaft 15. In the present example, the
cylindrical section 18p is pressed toward image pickup element 34
arranged in the rear of the lens group 11.
[0082] Further, there is integrally formed light-shielding plate
18s on the cylindrical section 18p of the lens frame 18 as one
body. This light-shielding plate 18s is arranged in the optical
path of light emitted from or received by photo-interrupter 41 that
is fixed on the bottom plate 13 with screw 42. Thus, the
light-shielding plate 18s is moved by a movement of the lens frame
18 in the optical axis direction, to shield the optical path of
light emitted from or received by photo-interrupter 41, or to
retreat from the optical path of light emitted from or received by
photo-interrupter 41.
[0083] Further, there is integrally formed protrusion section 18t
on the side of the lens frame 18 as one body. On the other hand,
boss 20 is formed on the bottom plate 13, and flat-head screw 21 is
screwed in an unillustrated hole of the boss 20. The protrusion
section 18t is in contact with a head portion of this screw 21.
Namely, the lens frame 18 is pressed toward the image pickup
element side by compression coil spring 19 representing a pressing
member, and a position of the lens frame 18 on the image pickup
element side is determined when the protrusion section 18t touches
the head portion of the screw 21 that is a contact member arranged
on the bottom plate 13.
[0084] Two columnar sections 22 are integrally formed on the bottom
plate 13 as one body. These two columnar sections 22 are formed at
the position to be arranged at both ends of a line connecting
optical axis O of lens group 11 to a center line of the cylindrical
section 18p. Both ends of shape memory alloy 23 which is in a
string shape are fixed on the two columnar sections 22. The
string-like shape memory alloy 23 is extended with being in contact
with a bottom portion of the lens frame 18 closer to image pickup
element 34 between optical axis O of lens group 11 and the
cylindrical section 18p.
[0085] FIG. 6 is a schematic diagram showing relationship for
respective parts about which the shape memory alloy formed in a
string shape is extended.
[0086] As shown in FIG. 6, both ends of shape memory alloy 23
formed in a string shape are fixed on the two columnar sections 22
which are integrally formed on the bottom plate 13 as one body. The
shape memory alloy 23 formed in a string shape is extended in a way
so that it comes in contact with a bottom portion of the lens frame
18 at about the center portion thereof, after angles of the shape
memory alloy 23 formed in a string shape are changed by a part of
the columnar section 22 to be symmetrical from both of the fixed
portions.
[0087] Further, each of the both end portions of the shape memory
alloy 23 formed in a string shape is cut with being held by plate
member 23k, and this plate member 23k is fixed at the upper portion
of the columnar section 22.
[0088] When predetermined current or voltage is applied to the
shape memory alloy 23 thus extended, from flexible print board 32f
(see FIG. 2) through the plate member 23k, the shape memory alloy
23 representing a resistive element generates heat to raise its
temperature, and it changes to shorten its total length, namely, it
is contracted. Due to this, the lens frame 18 can be moved in the
optical axis direction O along guide shafts 15 and 16, resisting
helical compression spring 19 representing a pressing member.
Namely, lens group 11 held by lens frames 18 and 17 can move toward
a subject along optical axis O to adjust a focal position with a
shorter distance.
[0089] The foregoing is the internal structure of the image pickup
apparatus 100 relating to the present embodiment.
[0090] Next, a drive device and a drive method for moving lens
group 11 of image pickup apparatus 100 having the aforesaid
structure housed in cell-phone T will be explained as follows.
First Embodiment
[0091] First, a lens drive device and a lens drive method relating
to the First Embodiment will be explained. In the First Embodiment,
the presence or absence of movement of a lens group is detected by
gradually changing electricity supplied to a shape memory alloy.
Based on an amount of electricity supplied at a point in time when
the movement is detected, an amount of the electricity to move the
lens group by a predetermined amount in the optical axis direction
is determined, and then, drive control for the lens group is
conducted.
[0092] Each of FIGS. 7(a), 7(b) and 7(c) is a diagram showing an
initial state (state of no-electricity) of each part of lens drive
device 100 relating to the First Embodiment. FIG. 7(a) is a diagram
schematically showing positional relationship between
light-shielding plate 18s and photo-interrupter in the initial
state, FIG. 7(b) is a diagram showing output of photo-interrupter
41 and FIG. 7(c) is a diagram showing relationship between lens
frame 18 and shape memory alloy 23.
[0093] First, lens frame 18 of image pickup apparatus 100 is
adjusted so that it may be located at its predetermined position,
and a position of the light-shielding plate 18s is adjusted so that
a part of a light flux emitted from or received by
photo-interrupter 41 may be shielded as shown in FIG. 7(a). This
adjustment is conducted by rotating flat-head screw 21 and by
moving the touching protrusion section 18t in the optical axis
direction (see FIGS. 4 and 5).
[0094] More closely, a position of the lens frame 18 is determined
by flat-head screw 21 so that a position of the light-shielding
plate 18s may agree with a position in a range of illustrated D
representing a transition area between the state of shielding and
the state of retreating caused by light-shielding plate 18s within
an area where light is emitted from or received by
photo-interrupter 41 shown in FIG. 7(b), namely, a position of the
light-shielding plate 18s may agree with a position where the
light-shielding plate 18s shields a part of a light flux emitted
from or received by photo-interrupter 41.
[0095] Next, focal point is adjusted by moving lens frame 17 in the
optical axis direction O by rotating the lens frame 17 on lens
frame 18. A focal point of lens group 11 held by lens frame 17 is
adjusted so that, for example, a subject positioned at a hyperfocal
distance may be focused on an image pickup surface of image pickup
element 34. In this case, the shape memory alloy 23 is in the
tensional state against lens frame 18 as shown in FIG. 7(c). A
component in the optical axis direction of force applied on SMA is
small, thus, the shape memory alloy 23 remains stationary under the
condition that the shape memory alloy 23 is elongated slightly by
pressing force of helical compression spring 19, and that
protrusion section 18t of the lens frame is in contact with a head
of screw 21. Incidentally, SMA may also be in the state having
slight slackness between itself and lens frame 18.
[0096] Namely, the lens drive device 100 relating to the First
Embodiment is adjusted so that a subject positioned at a hyperfocal
distance may be focused under the state of no-electricity.
Incidentally, this focus position is not limited to only to the
hyperfocal distance, and it may also be a position where a subject
positioned at an infinite distance is focused. However, in the
present embodiment, an explanation is given under the condition of
an adjustment where a subject positioned at a hyperfocal distance
is focused.
[0097] FIG. 8 is a flow chart showing a lens drive method of image
pickup apparatus 100 relating to the First Embodiment. The present
embodiment is described with following the flow chart shown in FIG.
8.
[0098] In FIG. 8, it is confirmed whether a photographing mode is
set or not (step S101). When the mode other than the photographing
mode is designated due to certain operations (step S101; No), the
photographing mode is terminated (step S120) and the flow moves to
the other mode which is designated (step S121).
[0099] When the photographing mode is set (step S101; Yes), the
image pickup element is driven to display preview images (which are
also called through images) on a display screen on a real time
basis (step S102). Then, the flow is in a state waiting for an
operation that a button corresponding to a release button among
buttons on a cell-phone is turned on (step S103). When a button
corresponding to a release button is not turned on (step S103; No),
the flow returns to step S101.
[0100] When a button corresponding to a release button is turned on
(step S103; Yes), an image for evaluating focus is taken in (step
S104). It means that the image for evaluating focus taken in at
step S104 is an image on the occasion where a lens group is at a
hyperfocal position.
[0101] Then, a current value set in advance is applied to the shape
memory alloy (step S105), and an output of a photo-interrupter is
judged whether it changes or not (step S106). When the output of
the photo-interrupter does not change (step S106; No), a current
whose value increases from the current value applied previously by
a predetermined increment amount is applied to the shape memory
alloy (step S107). Then, an output of a photo-interrupter is judged
again whether it changes or not (step S108). When the output of the
photo-interrupter does not change (step S108; No), the flow returns
to step S107, a current whose value further increases from the
current value applied previously by a predetermined increment
amount is applied to the shape memory alloy, and judgment whether
the output of the photo-interrupter changes at step S108 or not is
repeated.
[0102] It means that a current value applied to the shape memory
alloy gradually increases until the moment when the output of the
photo-interrupter changes. The current value at which the output of
the photo-interrupter starts changing means that the current value
at which a component in the optical axis direction of force that
acts on the shape memory alloy exceeds pressing force in the
optical axis direction by helical compression spring 19, and
protrusion section 18t of the lens frame leaves a head of screw
21.
[0103] When the output of the photo-interrupter changes (step S108;
Yes), a current amount to be applied to the shape memory alloy for
moving a lens group to a predetermined position (macro position) is
determined based on the current value on that occasion (step S109).
The amount of current thus determined is applied to the shape
memory alloy (step S110). The method of determining an amount of
current in step S109, for example, is described below.
[0104] FIG. 9 is a graph showing relationship between a current
amount for a shape memory alloy and deformation of the shape memory
alloy, and showing a method of determining a current amount. The
horizontal axis represents the current value, and the vertical axis
represents the deformation.
[0105] When a current value I.sub.a1 is obtained at a point of time
when an output of the photo-interrupter is changed, current value
I.sub.a2 which is increased by a prescribed amount from the current
value I.sub.a1 is applied to the shape memory alloy. On the other
hand, when a current value I.sub.b1 is obtained at a point of time
when an output of the photo-interrupter is changed, current value
I.sub.b2 which is increased by a prescribed amount from the current
value I.sub.b1 is applied to the shape memory alloy. By doing this,
it is possible to move lens frame 18 from its initial state by a
predetermined amount. Namely, it is possible to move a lens group
from a position for focusing to hyperfocal distance to a position
for macro photographing.
[0106] By employing the structure, as stated above, determining an
amount of electricity to move the lens group to the position for
macro photographing based on the current value at the point of time
when an output of the photo-interrupter changes, and supplying the
amount of electricity to the shape memory alloy, it is possible to
dissolve microscopic errors in a length of the shape memory alloy,
mounting errors and un-uniformity of an amount of movement of lens
group caused by ambient temperatures, and to obtain an image pickup
apparatus which does not provides individual difference when moving
a lens group to a macro position.
[0107] Incidentally, though a method of determining a current value
in step S109 has been explained by using a graph, it is naturally
possible to employ those using a lookup table and to employ those
determining by calculation.
[0108] Returning to the flow in FIG. 8, the lens group moves to the
macro position in step S110. At this position, an image for
evaluating focus is taken in (step S111). Then, two images taken in
at step S104 and step S111 are evaluated (step S112).
[0109] Then, a lens group is set at the position where the image
having larger high-frequency component between two images in
evaluation in step S112 (step S113). Specifically, when the image
for evaluation obtained in step S104 has larger high-frequency
component, applying current to the shape memory alloy is stopped
and a lens group is positioned in the initial state, namely, the
lens group is located at the position for focusing to the
hyperfocal distance. When the image for evaluation obtained in step
S111 has larger high-frequency component, the current value
determined in step S110 is applied to the shape memory alloy, and
the lens group is located at the macro photographing position.
[0110] Then, photographing and image recording on a recording
material are conducted at the lens group position established in
step S113 (step S114), and the flow returns to step S101.
[0111] As explained above, by detecting whether the movement of the
lens group has started or not while gradually changing an amount of
electricity supplied to the shape memory alloy, then, by
determining an amount of electricity to move the lens group to a
desired position, based on the amount of electricity at the time
when the movement starts, and by applying the amount of electricity
thus determined to the shape memory alloy, it is possible to
dissolve microscopic errors in a length of the shape memory alloy,
mounting errors and un-uniformity of an amount of movement of lens
group caused by ambient temperatures, and to obtain a lens drive
device which does not provide individual difference when moving a
lens group to a macro position, and thereby to obtain a small-sized
and low-cost image pickup apparatus wherein the structure is
simple, and a lens group can be stopped accurately at a desired
position.
[0112] Incidentally, although the explanation has been given about
the position control for two points including a hyperfocal position
and a macro position, in the aforesaid explanation, it is also
possible to provide a structure such that plural current values
each being increased from I.sub.a1 are established stepwise, to be
capable of being stopped at plural steps of lens positions.
Further, though the explanation uses the example wherein a position
for detecting changes of output of a photo-interrupter and a
hyperfocal position of the lens are at the substantially same
position, the present invention is not limited to this. A position
of the lens which is protruded by a prescribed distance from the
hyperfocal position may also be set as a position for detecting
changes of output of a photo-interrupter.
[0113] Further, though the explanation has so far been given
referring to the example of a self-focusing image pickup apparatus,
the invention can also be applied to manual setting as the
followings: when the hyperfocal position is selected, the
electricity does not supplied to the shape memory alloy, while,
when a macro position is selected, a position of a lens group is
set manually by following operations of step S105--step S110 in
FIG. 8.
[0114] Further, in the aforesaid example, a photo-interrupter is
used to detect whether the movement of the lens group has started
or not. However, it is also possible to provide a structure, for
example, to monitor a predetermined area of preview images
continuously, and a point of time when the focusing condition
changes is regarded as the time of starting movement.
Second Embodiment
[0115] In the Second Embodiment, movement of the lens group is
detected at two locations by gradually changing current values to
be supplied to the shape memory alloy. Based on the amounts of
electricity at points of time when movement of lens group were
detected at two predetermined positions, an amount of electricity
necessary for moving the lens group to the desired position is
determined, and then, drive control for the lens group is
conducted.
[0116] Initial state (state of no-electricity) of each section of
lens drive device 100 is the same as one shown in FIGS. 7(a), 7(b),
and 7(c), and it is preferable that light-shielding plate 18s
approaches the very limit of an optical path for emitting light
from or receiving light on a photo-interrupter, and shields neither
emitted light nor received light.
[0117] FIG. 10 is a flow chart showing a lens drive method of image
pickup apparatus 100 relating to the Second Embodiment. An
explanation will be given as follows, referring to the flow chart
shown in FIG. 10.
[0118] In FIG. 10, it is confirmed whether a photographing mode is
set or not (step S201). When the mode other than the photographing
mode is designated due to certain operations (step S201; No), the
photographing mode is terminated (step S220) and the flow moves to
the other mode which is designated (step S221).
[0119] When the photographing mode is set (step S101; Yes), a
current value set in advance is applied to the shape memory alloy
(step S202), and output of a photo-interrupter is judged whether it
is changed or not (step S203). When output of a photo-interrupter
changes (step S203; Yes), the applied current value is stored (step
S204).
[0120] When the output of the photo-interrupter does not change
(step S203; No), a current whose value increases from the current
value applied previously by a predetermined increment amount is
applied to the shape memory alloy (step S205). Then the output of
the photo-interrupter is judged again whether it changes or not
(step S206).
[0121] When the output of the photo-interrupter does not change
(step S206; No), the flow returns to step S205, and a current whose
value further increases from the current value applied previously
by a predetermined increment amount is applied to the shape memory
alloy, and judgment to check whether the output of the
photo-interrupter changes or not (step S206) is repeated.
[0122] When the output of the photo-interrupter changes (step S206;
Yes), the applied current value is stored (step S207). Then, it is
judged whether the number of the stored current values becomes two
(step S208). When it remains to be one (step S208; No), the flow
returns to step S205 and a current whose value further increases
from the current value applied previously by a predetermined
increment amount is applied to the shape memory alloy, to repeat
step S205 and step S206 until the output of the photo-interrupter
changes again. When the number of the stored current value becomes
two (step S208; Yes), the flow moves to step S209, and relationship
between an amount of lens movement and an amount of current is
obtained from two current values obtained. The relationship
obtained in the step S209 is as follows.
[0123] FIG. 11 is a graph showing relationship between an amount of
current and deformation that shows a method of obtaining
relationship between an amount of lens movement and an amount of
current. The horizontal axis represents a current value and the
vertical axis represents deformation.
[0124] Output of the photo-interrupter changes, at the first time,
at the point of time when light-shielding plate 18s united with
lens frame 18 starts moving to the subject side in the optical axis
direction from the initial state shown in FIG. 7(a). Output of the
photo-interrupter changes, at the second time, at the point of time
when the light-shielding plate 18s retreats from an area for light
emitted from or light received on a photo-interrupter after moving
toward the subject side in the optical axis direction. Namely, with
respect to the stored two current values, the first current value
is one at the point of time when a component in the optical axis
direction of force applied to shape memory alloy exceeds pressing
force in the optical axis direction by helical compression spring
19 and protrusion section 18t of lens frame leaves a head portion
of screw 21; and the second current value is one at the point of
time when lens frame 18 is moved by an amount equivalent to a
thickness in the optical axis direction of light-shielding plate
18s.
[0125] In FIG. 11, a current value I.sub.c1 is obtained at the
point of time when the output of a photo-interrupter changes first
time, and a current vale I.sub.c2 is obtained at the point of time
when the second output of a photo-interrupter changes. When the
current value increases from I.sub.c1 to I.sub.c2, a deformation
factor is changed, which means that lens frame 18 is moved by an
amount equivalent to a thickness in the optical axis direction of
light-shielding plate 18s by changes of illustrated H.
[0126] Namely, when a thickness of light-shielding plate 18s is
represented by A (mm), a current value to move lens frame 18 by B
(mm) in the optical axis direction from the initial state shown in
FIGS. 7(a), 7(b), and 7(c) is expressed by
I.sub.c1+B(I.sub.c2-I.sub.c1)/A.
[0127] Owing to the foregoing, it is possible to obtain a current
value to move lens frame 18, namely, lens group 11 from a position
of the initial state to the position on the subject side in the
optional optical axis direction.
[0128] Returning to the flow in FIG. 10, electricity to the shape
memory alloy is stopped (step S210) after storing relationship
obtained in step S209. Owing to this, lens frame 18 is restored to
the initial state.
[0129] Then, when it is judged again whether a photographing mode
is set or not (step S211) and the photographing mode is not set
(step S211; No), the flow returns to step S201. While, when the
photographing mode is set (step S211; Yes), an image pickup element
is driven, and a preview image (which is also called a through
image) is displayed on a display screen on a real time (step S212).
Then, a button corresponding to a release button among buttons on a
cell-phone is on standby to be turned on (step S213). When the
button corresponding to a release button is not turned on (step
S213; No), the flow returns to step S211.
[0130] When the button corresponding to a release button is turned
on (step S213; Yes), an image for evaluating focusing is taken in
first (step S214). Namely, the image for evaluating focusing which
is taken in at step S214 is an image when a lens group is at a
hyperfocal position.
[0131] Then, relationship between a current amount to be applied to
a shape memory alloy obtained in the foregoing and an amount of
movement of a lens frame is used to obtain a current value to move
the lens group to the desired lens position, and this current value
is applied to the shape memory alloy (step S215). Due to this, the
lens group is moved from its initial position to a desired focusing
position on the short distance side. At this position, an image for
evaluating focusing is taken in (step S216).
[0132] Incidentally, when plural focusing positions on the short
distance side has been set, a current value to move to each lens
position is obtained and step S215 and step S216 are repeated,
thereby, an image for evaluating a focus is taken in at each
position.
[0133] Then, images for evaluation taken in at step S214 and at
step S216 are evaluated (step S217).
[0134] The lens group is set at the position at which evaluation at
step S217 was obtained, for example, at which an image having
larger high frequency component among obtained images for
evaluation was obtained (step S218). Specifically, when an obtained
image for evaluation at step S214 contains larger high frequency
component, applying of a current to the shape memory alloy is
stopped. The lens group is set to the initial state, namely, a lens
group is set at a position where the lens group is focused at a
hyperfocal position. When any of images for evaluation obtained in
step S216 contains larger high frequency component, the lens group
is set to state wherein an amount of current to move the lens group
to the position where the aforesaid image was obtained is applied
to a shape memory alloy.
[0135] Then, photographing and recording of images on a recording
medium are conducted at the position where the lens group was set
in step S218 (step S219), and the flow returns to step S201.
[0136] In other words, the Second Embodiment is one wherein a
current value to move a lens group by an amount determined in
advance is detected, and based on this, an amount of current to
move to the desired position is obtained.
[0137] As explained above, by providing a structure wherein a
movement of a lens group is detected at two predetermined positions
in the optical axis direction while gradually changing electricity
supplied to the shape memory alloy, and an amount of electricity to
move a lens group to the desired position is determined based on
the amount of electricity at each of these two positions, and a
lens group is moved to the desired position by supplying the
determined amount of electricity to the shape memory alloy, it is
possible to dissolve fluctuations of an amount of movement of the
lens group caused by errors in length of the shape memory alloy,
errors in mounting and by ambient temperatures, and to obtain a
lens drive device which does not provides individual difference
when moving a lens group, to obtain a small-sized and low cost
image pickup apparatus that can stop the lens group accurately at
the desired position with a simple structure.
[0138] Further, by detecting the movement at two positions, it is
possible to conduct accurate position control, even when
fluctuations of inclination in characteristic curves caused by
un-uniformity of pressing force of helical compression spring and
by un-uniformity of wire diameter of the shape memory alloy are
generated, which is different from the occasion where detection is
conducted at one position.
[0139] Incidentally, although the explanation has been given
referring to the example of the self-focusing image pickup
apparatus, the invention can be applied also the occasion of manual
setting. In this case, changing the steps S214-S218, when the
hyperfocal position is selected, electricity to the shape memory
alloy is stopped, while, when the focus position on the desired
short distance side is selected, a current value to move the lens
group to the designated lens position is obtained from the relation
acquired in step S209, and it is applied to the shape memory alloy.
Thus, it is possible to conduct manual setting.
[0140] Further, although the explanation has been given referring
to the occasion where the initial setting of the lens group is on
the hyperfocal position, it is also possible to use a position for
focusing on infinity in place of the hyperfocal position, or, it is
further possible to position the lens group on the image pickup
element side.
[0141] In the foregoing, current values at two positions where
photo-interrupter outputs changes were obtained before taking in
images for evaluation, in the structure. However, the invention is
not limited to this, and current values may also be obtained after
the step S213, or it is also possible to obtain current value with
a change of the first photo-interrupter output before step S213 and
to obtain current value with a change of the second
photo-interrupter output after step S213.
[0142] FIG. 12 is a diagram showing another example of a detecting
device that detects a movement of a lens group at prescribed two
positions in the optical axis direction.
[0143] As shown in FIG. 12, sheet member 43 having flexibility is
fixed on lens frame 18. It is preferable that the sheet member 43
is made of a material having light shielding effect.
[0144] An edge portion on one side of the sheet member 43 is
superposed as illustrated on an area of pixels that are not used
for image among light-receiving pixels of the image pickup element
34, to shield a light flux of a subject coming from lens group 11.
If lens frame 18 is moved from this state in the optical axis
direction, the sheet member 43 fixed on the lens frame 18 is moved
in the direction of the illustrated arrow, and pixel output of the
pixel area that is not used as an image is changed.
[0145] Namely, by monitoring pixel output of image pickup element
34 while gradually changing electricity supplied to shape memory
alloy 23, and by detecting the change of pixel output on the pixel
area that is not used for image, a start of movement of the lens
group can be detected. Further, when movement between prescribed
number of pixels is detected by the sheet member 43, movement of a
lens group can be detected at prescribed two positions in the
optical axis direction.
[0146] By providing this structure, it is possible to detect
movement of a lens group without adding a new member such as a
photo-interrupter, and thereby to make an image pickup apparatus to
be lower cost.
[0147] Though the explanations were given in the aforesaid First
and Second Embodiments referring to those wherein a current value
changes when electricity supplied to the shape memory alloy, the
invention is not limited to this. It is naturally possible to
employ the structure wherein voltage is changed or a current value
is fixed with duty ratio being changed. Further, the shape memory
alloy, as described above, provides an initial creep phenomenon
wherein a deformation amount changes with the number of times of
turning electricity on in the initial stage where the frequency of
turning electricity on is small. The initial creep phenomenon is
described as follows.
[0148] FIG. 13 is a conceptual diagram showing relationship between
deformation amount s and temperature T when the electricity is
supplied at the first time and the tenth time. FIG. 13 shows an
occasion wherein a prescribed load weight is impressed on a
string-like shape memory alloy to change a temperature of the shape
memory alloy in order of T2, T1, and T2 (where T1<T2). A
deformation amount represented by the vertical axis indicates a
rate of an elongated length at each frequency to the string length
at temperature T2 at the start, which is defined as the
standard.
[0149] As shown in FIG. 13, a deformation amount when electricity
is supplied at the tenth time is smaller than that at the first
time. For example, a deformation amount .epsilon.1 is obtained when
electricity is supplied at the tenth time in the occasion of
lowering a temperature from T2 to T1. The deformation amount
.epsilon.1 is smaller than .epsilon.2 that is a deformation amount
when the electricity is supplied at the first time.
[0150] FIG. 14 is a conceptual diagram showing relationship between
a deformation amount and the number of times of supplying
electricity. FIG. 14 shows an occasion wherein a prescribed load
weight is applied to a string-like shape memory alloy, and
prescribed current is applied to the shape memory alloy for the
prescribed length of time to turn the current ON and to the
prescribed length of time to turn the current OFF. A deformation
amount represented by the vertical axis indicates a rate of an
elongated length to the string length when the electricity is
turned on at first time, which is defined as the standard.
[0151] As shown in FIG. 14, a deformation amount during the
electricity is turned ON is greatly changed up to the moment of
about (ten-odd).sup.th electricity supply. These phenomena mean
that accurate position control is difficult, because an amount of
distortion is changed undesirably even when the same current is
applied, until the moment of about (ten-odd).sup.th electricity
supply.
[0152] It is preferable to do as follows for coping with the
initial creep phenomenon described above. FIG. 15 is a diagram
showing a control block of a drive device in the present
embodiment. Control section 50 controls a current to be applied to
shape memory alloy 23 through current supply circuit 52, based on
an amount of lens barrel movement inputted from lens barrel
movement amount input section 51. In the control section 50, there
is provided memory section 501 that is constituted with a
nonvolatile memory such as EEPROM that stores the number of times
of supplying electricity one after another.
[0153] FIG. 16 is a diagram showing a control routine of a drive
device in the present embodiment. Control section 50 judges first
whether an aging action completion flag is set on memory section
501 in control section 50 or not (S1). When the aging action
completion flag is judged to be set (S1; Yes), the control section
50 jumps to ordinary control routine (S3), and controls a current
to be applied to shape memory alloy 23 through current supply
circuit 52, based on an amount of lens barrel movement inputted
from lens barrel movement amount input section 51. On the other
hand, when the aging action completion flag is judged not to be set
(S1; No), the control section 50 jumps to aging control routine
(S2).
[0154] FIG. 17 is a diagram showing an aging control routine.
[0155] First, control section 50 sets electricity-supply frequency
i=0 as an initial setting (S21). Next, the control section 50
applies a prescribed amount of current (for example, 80 mA) to
shape memory alloy 23 through current supply circuit 52 for a
prescribed period of time (for example, 0.5 sec.) (S22). Next, the
control section 50 stops applying current to the shape memory alloy
23 through current supply circuit 52 for a prescribed period of
time (for example, 1.0 sec.) (S23). Next, the control section 50
increments electricity-supply frequency i by one (S24). Next, the
control section 50 judges the electricity-supply frequency i
whether it has arrived at a prescribed frequency or not (S25). When
the electricity-supply frequency i is judged to have arrived at the
prescribed frequency (S25; Yes), the control section 50 sets the
aging action completion flag on memory section 501 (S26) to
terminate the routine. When the electricity-supply frequency i is
judged not to have arrived at the prescribed frequency (S25; No),
the flow returns to S22, and steps S22-S25 are repeated until the
electricity-supply frequency i arrives at the prescribed
frequency.
[0156] Incidentally, the prescribed frequency may be set to the
frequency at which a deformation amount is stabilized, and there is
no upper limit for the prescribed frequency.
[0157] As stated above, by operating the aging treatment by
repeating prescribed number of switching of electricity-supply
between ON and OFF, an amount of deformation for applied current is
stabilized as seen in FIG. 14. It enables, in the control
thereafter, to provide accurate position control by setting an
amount of current to be applied to the shape memory alloy based on
an amount of lens barrel movement.
[0158] Incidentally, though heating and no-heating processes for
the shape memory alloy were repeated by joule heat that is
generated due to current applied to the shape memory alloy, it is
also possible to externally repeat heating and no-heating
processes.
[0159] Though the aging processing was applied to shape memory
alloy 23 after completion of assembly of an image pickup apparatus
unit, the aging processing for the shape memory alloy can be
conducted by external heating process, for example, at any time
before sheet member 23k is fixed on both edge portions, or before
mounting on columnar section 22, or before pressing by helical
compression spring 19. In particular, aging processing can be
conducted either under the state where the shape memory alloy is
stressed, or under the state where the shape memory alloy is not
stressed.
[0160] In the aforesaid embodiment, the explanation was given
referring to the example wherein the string-like shape memory alloy
23 is in contact with a bottom portion of lens frame 18 on the
image pickup element 34 side between optical axis O of lens group
11 and cylindrical section 18p, to be extended, as shown in FIG. 5.
However, the invention is not limited to this, and the following
structure can also be employed.
[0161] FIG. 18 is a front view showing another example of
arrangement of respective parts constituting a lens barrel inside
an image pickup apparatus. FIG. 18 will be partially explained
about only a portion which is different from the image pickup
apparatus shown in FIG. 5.
[0162] In the image pickup apparatus shown in FIG. 18, two columnar
sections 22 are formed to be standing on bottom plate 13, and they
face each other with optical axis P in-between. Both end portions
of shape memory alloy 23 formed to be in a string shape are
interposed and fixed on columnar sections 22 by plate member 23k.
Then, both end portions of the shape memory alloy 23 are connected
to the flexible print board through the plate member 23k.
[0163] A central portion of the shape memory alloy 23 is arranged
to be capable of touching a rear end portion of the second lens
frame 18 on the image pickup element 34 side (image forming surface
side). Therefore, the shape memory alloy 23 is extended under the
condition that the central portion is arranged in the optical path
of lens group 11.
[0164] Each of FIGS. 19(a) and 19(b) is a sectional view of the
lens barrel inside the image pickup apparatus shown in FIG. 18
which is taken on a plane including the shape memory alloy. FIG.
19(a) is a diagram showing a situation wherein no electricity is
supplied to shape memory alloy 23, and FIG. 19(b) is a diagram
showing a situation wherein electricity is supplied to shape memory
alloy 23, and lens group 11 is protruded.
[0165] As shown in FIG. 19(a), a protrusion section on the rear end
of the second lens frame 18 is in contact with a receiving surface
of bottom plate 13. As a result, when no-electricity is supplied to
shape memory alloy 23, lens group 11 is stationary located at a
certain position, and an image of a subject is formed on image
pickup element 34. Therefore, if the focal position of the lens
group 11 is adjusted at a hyperfocal distance, it is possible to
take a photograph that is in focus for the distance covering from
infinity to a half of a hyperfocal distance.
[0166] Under the aforesaid condition, if an electricity is applied
to the shape memory alloy 23 through plate member 23k, the shape
memory alloy 23 representing a resistor generates heat and its
temperature rises, and its total length contracts to be shortened.
Owing to this, the second lens frame 18 is guided by guide shafts
15 and 16 against pressing force of helical compression spring 19,
to be moved to the subject side that is opposite to image pickup
element 34, as shown in FIG. 19(b). Namely, lens group 11 that is
held by the first lens frame 17 through the second lens frame 18 is
moved to the subject side along optical axis O. Therefore, it is
possible to focus an image of a subject that is in a shorter
distance onto image pickup element 34.
[0167] It is therefore recommended that no-electricity is supplied
to shape memory alloy 23 in the case of long-range photographing
and intermediate-range photographing, and that electricity is
applied to shape memory alloy 23 in the case of close-range
photographing such as photographing flowers.
[0168] Further, in the case where an image pickup apparatus has an
AF function and where manual setting of distance for long-range and
close-range is structured to be possible, electric power to be
supplied to the shape memory alloy can be adjusted in many steps
depending on a photographing distance.
[0169] Since the shape memory alloy 23 is arranged in the condition
to cross optical axis O of lens group 11, and the second lens frame
18 is pressed uniformly, the second lens frame 18 can be moved in
the optical axis direction efficiently. Incidentally, though an
example wherein the shape memory alloy 23 is arranged in the
condition to cross optical axis O of lens group 11 in the
illustration, the shape memory alloy 23 can also be extended to
avoid the optical axis.
[0170] Incidentally, the central portion of the shape memory alloy
23 mentioned above means a portion that is not an edge portion, and
it does not mean the center position that is at equal distance from
both ends.
[0171] Further, in the aforesaid structure, a central portion of
the shape memory alloy 23 is arranged in the optical path of lens
group 11. Therefore, a part of the optical path is interrupted by
the shape memory alloy 23, and it becomes difficult to see an
image, depending on conditions. A way of solving this problem will
be explained based on FIGS. 20(a) and 20(b).
[0172] Each of FIGS. 20(a) and 20(b) is an illustration diagram
wherein an optical path is interrupted by the shape memory alloy.
FIG. 20(a) is a diagram wherein the shape memory alloy 23 is
arranged in the optical path of lens group 11, and FIG. 20(b) is a
diagram wherein the shape memory alloy 23 is viewed in the optical
axis direction.
[0173] First, it is known that, if a size of a subject arranged in
the optical axis of an image pickup lens is 3% or less of an area
of the optical axis crossing the subject, an image of the subject
is difficult to be observed even when the image is formed on an
image pickup element.
[0174] When D represents a diameter of the optical path at a
position where the shape memory alloy 23 is arranged in the optical
path of lens group 11, and d represents a diameter of the shape
memory alloy 23, as shown in FIG. 20(b), an area of the optical
path is .pi.D.sup.2/4, and an area of the shape memory alloy 23 in
the optical path is dD. Therefore, the following conditional
expression (1) is to be satisfied.
dD/(.pi.D.sup.2/4)<0.03 (1)
[0175] This conditional expression (1) can be simplified as
follows.
d/D<0.02 (2)
[0176] Incidentally, for satisfying the conditional expression (2),
it is preferable to arrange the shape memory alloy 23 at the
position where an area of the optical path in the vicinity of a
final surface of lens group 11 is large. However, if an arrangement
is constituted so that an image of the shape memory alloy 23 formed
on image pickup element 34 may be removed by an image processing,
the conditional expression (2) does not always need to be
satisfied.
[0177] According to circumstances, the shape memory alloy may
either be arranged between lenses of an image pickup lens having
plural lenses, or be arranged on the subject side of the image
pickup lens.
[0178] Further, there is a possibility that a cell-phone housing
therein an image pickup apparatus employing the shape memory alloy
of this kind is used under the condition of high temperature.
Therefore, it is preferable to make up the constitution wherein the
shape memory alloy 23 is arranged to be loosened slightly so that
the second lens frame 18 may not be advanced even if the shape
memory alloy 23 shrinks at the temperature of 50-60.degree. C. or
the temperature lower than that, and the shape memory alloy 23
shrinks when the temperature becomes 100.degree. C., for example,
to touch rear end portion 18d and the second lens frame 18 may be
advanced.
[0179] A lens barrel having the structure that is different from
the foregoing will be explained as follows, referring to FIGS. 21,
22(a) and 22(b). FIG. 21 is a top surface diagram of a flat-head
spring of a diaphragm type, and each of FIGS. 22(a) and 22(b) is a
sectional view in which a shape memory alloy is extended. FIG.
22(a) is a diagram showing the situation where an electricity is
not supplied to the shape memory alloy 23, while, FIG. 22(b) is a
diagram showing the situation where electricity is applied to the
shape memory alloy 23 and lens group 11 is protruded. The present
lens barrel is similar to the aforesaid lens barrel on the point
that the shape memory alloy 23 is extended with its central portion
being arranged in the optical path of lens group 11, and both ends
thereof are respectively fixed on columnar section 22. On the other
hand, a different point is one wherein the second lens frame 18 has
no engagement section 18d, guide shafts 15 and 16 are not provided
to stand on bottom plate 13, and helical compression spring 19 is
not provided.
[0180] First, leaf spring 25 of a diaphragm type shown in FIG. 21
is made of phosphor bronze or of stainless steel. Leaf spring 25
have steps in the direction of a center axis on flat portion 25a on
the outer circumferential side and on flat portion 25c on the inner
circumferential side, and flat portion 25a and to flat portion 25c
is connected to each other with inclined portion 25b. Therefore,
leaf spring 25 has a spring function due to deformation of the
inclined portion 25b.
[0181] As shown in FIGS. 22(a) and 22(b), leaf spring 25 is fixed
on the upper reverse side of cover member 12 and on the upper end
portion of the second lens frame 18, and further, the same leaf
spring 26 is fixed on protrusion section on the rear end of the
second lens frame 18 and on bottom surface 13e of bottom plate 13.
Spring pressure of leaf spring 25 is greater than that of leaf
spring 26. Therefore, when no-electricity is supplied to the shape
memory alloy 23, leaf spring 25 presses the second lens frame 18
against leaf spring 26 to cause a reverse side of leaf spring 26 to
touch receiving surface 13b of bottom plate 13, thus, lens group 11
is positioned in the optical axis direction, as shown in FIG.
22(a). Further, when the shape memory alloy 23 is supplied for
close-range photographing, the shape memory alloy 23 contracted,
thereby, the second lens frame 18, namely, lens group 11 is
protruded to the prescribed position against leaf spring 25.
[0182] Though the occasion of using leaf spring 25 of a diaphragm
type is also the same as the occasion of using the aforesaid
helical compression spring 19 in terms of basic function, the
second lens frame 18, the first lens frame 17 and lens group 11 can
be supported without tilting an optical axis, by using two leaf
springs 25 and 26, and thereby, guide shafts 15 and 16 are made
redundant, which makes a lens barrel to be smaller than that in the
aforesaid structure.
[0183] Incidentally, in the aforesaid structure, the shape memory
alloy 23 does not always need to cross optical axis O, but it is
preferable to cross a location that is as close as possible to
optical axis O.
[0184] The orientation for the shape memory alloy to move a lens
group in the optical axis direction is not always limited to that
toward the subject side, and it is also possible to constitute to
move toward the image forming surface side according to
circumstances. For example, a lens group is arranged so that it may
be in the depth of field only for close-range, and the lens group
is moved toward the image forming surface side when photographing
for the long-range including infinity.
[0185] It is also possible to provide a structure so that a lens
may be moved in the direction perpendicular to its optical axis for
a lens movement for correction of shake of an image pickup
apparatus and for a movement of a lens converter. Even in the case
of the structure of this kind, a shape memory alloy is arranged in
an optical path of a lens group. However, what is arranged in an
optical path of a lens group is not always a central portion of the
shape memory alloy, but a part of the shape memory alloy is
arranged in the optical path of the lens group.
[0186] Incidentally, in the aforesaid explanation, there was used
an example wherein the first lens frame 17 and the second lens
frame 18 are provided. However, it is also possible to employ an
example wherein the first lens frame 17 and the second lens frame
18 are integrated.
* * * * *