U.S. patent application number 10/808577 was filed with the patent office on 2004-12-09 for surveying instrument having an optical distance meter and an autofocus system, and a surveying instrument having a detachable autofocus system.
This patent application is currently assigned to PENTAX Precision Co., Ltd.. Invention is credited to Hoshino, Tadahisa, Kaneko, Kenji, Suzuki, Shinichi, Takayama, Homu, Ueno, Masayuki, Yachi, Takanori.
Application Number | 20040246462 10/808577 |
Document ID | / |
Family ID | 26598792 |
Filed Date | 2004-12-09 |
United States Patent
Application |
20040246462 |
Kind Code |
A1 |
Kaneko, Kenji ; et
al. |
December 9, 2004 |
Surveying instrument having an optical distance meter and an
autofocus system, and a surveying instrument having a detachable
autofocus system
Abstract
A surveying instrument includes a sighting telescope optical
system, a distance measuring system which outputs first data, a
phase detection autofocus system which and outputs second data, and
an AF driver which moves a focusing lens of the sighting telescope
optical system to bring the sighting object into focus in
accordance with one of the first data and the second data. A
surveying instrument is also disclosed, which includes a sighting
telescope and an AF drive unit which is provided separately from
the sighting telescope, wherein the AF drive unit can be mounted to
and dismounted from a body of the surveying instrument.
Inventors: |
Kaneko, Kenji; (Tokyo,
JP) ; Suzuki, Shinichi; (Saitama, JP) ;
Takayama, Homu; (Saitama, JP) ; Hoshino,
Tadahisa; (Tokyo, JP) ; Yachi, Takanori;
(Tokyo, JP) ; Ueno, Masayuki; (Saitama,
JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
PENTAX Precision Co., Ltd.
Tokyo
JP
|
Family ID: |
26598792 |
Appl. No.: |
10/808577 |
Filed: |
March 25, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10808577 |
Mar 25, 2004 |
|
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09938663 |
Aug 27, 2001 |
|
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6734410 |
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Current U.S.
Class: |
356/5.1 |
Current CPC
Class: |
G01C 15/002 20130101;
G02B 7/28 20130101; G01S 17/88 20130101; G01S 7/4812 20130101 |
Class at
Publication: |
356/005.1 |
International
Class: |
G01C 003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 30, 2000 |
JP |
2000-261075 |
Sep 11, 2000 |
JP |
2000-274365 |
Claims
What is claimed is:
1. A surveying instrument comprising: a sighting telescope optical
system through which a sighting object can be sighted; a distance
measuring system which measures a distance to said sighting object;
and a phase detection autofocus system which detects a focus state
of an image of said sighting object on a reference focal plane; and
an AF driver which moves a focusing lens of said sighting telescope
optical system to bring said sighting object into focus in
accordance with an output of said phase detection autofocus
system.
2. The surveying instrument according to claim 1, wherein said AF
driver moves said focusing lens to bring said sighting object into
focus in accordance with an output of said phase detection
autofocus system without the use of a reflective device at a point
of said sighting object.
3. The surveying instrument according to claim 1, further
comprising a start button, wherein said distance measuring system
and said AF driver operate consecutively upon a single-push
operation of said start button.
4. The surveying instrument according to claim 1, further
comprising a controller which provides a consecutive autofocus mode
in which said sighting object is brought into focus automatically
consecutively via said AF driver, and a consecutive distance
measurement mode in which said distance to said sighting object is
consecutively measured via said distance measuring system; wherein
said consecutive autofocus mode starts at the same time said
consecutive distance measurement mode is started.
5. The surveying instrument according to claim 1, further
comprising a controller which drives said AF driver to move said
focusing lens to a predetermined position thereof so that an object
at a predetermined distance is in focus when said sighting object
is unable to be brought into focus in the case of a measurement
mode in which a target is set at an arbitrary point.
6. The surveying instrument according to claim 1, wherein said
surveying instrument is a total station.
7. The surveying instrument according to claim 1, wherein said
distance measuring system comprises a distance meter having a
light-emitting element and a light-receiving element.
8. The surveying instrument according to claim 1, wherein said
phase detection autofocus system comprises a pair of line sensors.
Description
[0001] This is a divisional of U.S. application Ser. No.
09/938,663, filed Aug. 27, 2001, the contents of which are hereby
incorporated herein by reference in their entireties.
BACKGROUND OF TEE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a surveying instrument
having an optical distance meter and an autofocus system which
moves the focusing lens of the sighting telescope in accordance
with the location of the sighting object, and also relates to a
surveying instrument having a detachable autofocus system.
[0004] 2. Description of the Related Art
[0005] When a surveyor measures the distance between two points
with a surveying instrument such as a total station, a reflecting
prism such as a corner cube is often used together with the
surveying instrument. After the operator of the surveying
instrument directs the sighting telescope to the reflecting prism
and sights the reflecting prism through the sighting telescope, the
distance measuring system (EDM) incorporated in the surveying
instrument starts operating at the push of a distance measurement
start button provided on the surveying instrument. Upon the
commencement of the operation of the distance measuring system, a
measuring light such as laser beam is projected from the surveying
instrument toward the reflecting prism, and is reflected thereby to
be eventually received by a light-receiving sensor in the surveying
instrument. The distance measuring system calculates the distance
to the reflecting prism via the phase difference between the
projecting light and the received light.
[0006] A surveying instrument such as a total station is generally
provided with a sighting telescope. Conventionally, the focusing
lens of the sighting telescope is manually moved to focus the
sighting telescope on a sighting object such as a reflecting prism.
However, in recent years, surveying instruments equipped with an
autofocus system which automatically moves the focusing lens to an
in-focus position with respect to the sighting object have been
proposed and developed.
[0007] With this type of surveying instrument equipped with an
autofocus system, the sighting object is brought into focus
automatically at the push of an AF start button after the operator
aims the sighting telescope at the sighting object.
[0008] In a surveying instrument equipped with a phase detection
type autofocus system, it is sometimes the case that the sighting
object is unable to be brought into focus if the sighting object is
like a white wall having no contrast, or a reflecting prism such as
a corner cube.
[0009] If the sighting object is unable to be brought into
auto-focus with the use of reflecting prism, the operator can try
to perform the distance measuring operation with the autofocus
system without the use of reflecting prism. However, in the case of
the distance measuring operation being performed with the autofocus
system without the use of reflecting prism, if infrared rays are
used as measuring light that is to be projected toward the sighting
telescope, the point of reflection of the infrared rays at the
point of measurement cannot be visually confirmed, so that the
point of measurement cannot be determined precisely.
[0010] When a distance measurement such as tracking distance
measurement operation (consecutive distance measurement operation)
is performed with a surveying instrument such as a total station
which is equipped with an autofocus system, the distance
measurement operation is performed with the surveying instrument in
a manner such as shown in the flow chart in FIG. 9.
[0011] Firstly, the specified distance and other design data that
are necessary for the tracking distance measurement operation are
input to a controller of the surveying instrument via devices such
as a design value input device and a measured distance (specified
value) input device (step SA1).
[0012] Subsequently, a distance measurement start button is
depressed to start the distance measurement operation. For
instance, the tracking distance measurement mode is set at the push
of the distance measurement start button (step SA2). After the
tracking distance measurement mode is set, the measured distance
value is determined immediately after the measuring light reflected
by the target returns to the surveying instrument, while the
measured distance and the deviation between the input design value
and the measured distance to the target are indicated on an
indicating device.
[0013] Subsequently, when the sighting telescope is not aimed at
the target, a sighting operation is performed (step SA3). In the
sighting operation, the operator manually aims the sighting
telescope at the target so that the optical axis of the sighting
telescope is generally in line with the target while viewing the
target through a collimator (not shown) which is attached to the
sighting telescope. If the sighting telescope is in an in-focus
state on the target, the operator manually operates the sighting
telescope to sight the center of the target via the sighting
telescope.
[0014] Subsequently, it is determined whether the AF start button
is depressed (step SA4). The AF start button is depressed if the
operator desires to bring the target into focus after the sighting
operation is performed.
[0015] The autofocus system starts operating immediately after the
AF start button is depressed. After the AF button is depressed, it
is determined whether the target is in focus (step SA5). If it is
determined that the target is in focus, control proceeds to step
SA7.
[0016] If it is determined at step SA5 that the target is not in
focus, control proceeds to step SA6 at which a focusing lens is
automatically moved to a predetermined default position thereof to
bring an object at a predetermined distance, which is stored as a
default distance value in a conventional default-distance setting
device, into focus.
[0017] After the target has been brought into focus, the measured
distance value is determined while the sighting operation is being
performed, and subsequently it is determined whether the measured
distance value has been determined (step SA7). Namely, the measured
distance value is determined immediately after the measuring light
reflected by the target returns to the surveying instrument.
Control proceeds to step SA8 if the measured distance value has
been determined at step SA7. Control proceeds to step SA9 if the
measured distance value has not yet been determined at step
SA7.
[0018] If it is determined at step SA7 that the measured distance
value has been determined, the measured distance and the deviation
between the input design value (specified distance) and the
measured distance to the target are calculated to be indicated on
the indicating device (step SA8). Consequently, the operator can
identify the deviation between the current location of the target
and the staking point by looking at the indicating device. This
makes it possible for the operator of the surveying instrument to
instruct the worker who holds the target to move the target in
accordance with the deviation.
[0019] Thereafter, at the moment the deviation indicated on the
indicating device becomes zero, the stakeout operation, in which
the target is staked out at a staking point, is completed.
Accordingly, after the operation at step SA8, it is determined
whether a distance measurement stop button is depressed (step SA9).
The operator pushes the distance measurement stop button if it is
determined that the stakeout operation, in which the target is
staked out at a staking point, is completed. If the distance
measurement stop button is depressed during the sighting operation,
control proceeds to step SA10 and the tracking distance measurement
operation is terminated. Otherwise, control returns to step SA4
from step SB9 to repeat the operations from step SB4 to step
SB9.
[0020] Accordingly, when a distance measurement such as a tracking
distance measurement (consecutive distance measurement),
consecutive distance stakeout measurement, or lot staking
measurement is performed, the AF start button must be pushed
frequently while the distance measurement is performed
repetitively. However, it is troublesome for the operator to push
the AF start button frequently. Furthermore, having to push the AF
start button frequently hinders the target tracking operation.
[0021] Under such circumstances, it is difficult for the operator
to concentrate on the target tracking operation and to finish the
target tracking operation promptly with a conventional surveying
instrument such as a conventional total station. For instance, if
the line of sight of the sighting telescope deviates from the
target to thereby make it impossible to bring the target into focus
automatically during the stakeout operation, the focusing lens of
the sighting telescope is generally moved to be focused on an
object at a predetermined distance. However, it is often the case
that such a predetermined distance is not at all related to any
points for the stakeout operation, which makes it difficult to
perform the stakeout operation promptly.
[0022] Various types of surveying instruments such as total
stations having a sighting telescope have been developed. In a
typical surveying instrument, the focusing lens of the sighting
telescope is manually moved to adjust the focus of the sighting
telescope. In recent years advanced surveying instruments equipped
with an autofocus system which drives the focusing lens of the
sighting telescope to adjust the focus thereof automatically have
been developed.
[0023] In order to incorporate such an autofocus system into
surveying instrument, it is necessary to provide the surveying
instrument with a sensor (e.g., a multi-segment CCD line sensor)
for gaining information on the focal point of the sighting
telescope, a lens driver having gears and a motor which drives the
focusing lens of the surveying instrument in accordance with the
information on the focal point of the sighting telescope, a
controller for controlling the operation of the lens driver, and a
hand-operated member such as an AF start button to enable
activation of the autofocus system.
[0024] However, the task of incorporating such an autofocus system
into surveying instrument is time-consuming because elements of the
autofocus system need to be connected to associated internal
elements of the surveying instrument mechanically, electrically and
optically. Moreover, the built-in autofocus system generally
complicates the internal structure of the surveying instrument,
which increases the possibility of the surveying instrument
breaking down.
[0025] If the built-in autofocus system breaks down, it is
generally the case that the autofocus system needs to be repaired
with one or more exterior covers of the surveying instrument being
uncovered. Furthermore, one or more exterior covers of the
surveying instrument need to be uncovered even when the autofocus
system is inspected. This is obviously a troublesome task.
[0026] If such a surveying instrument equipped with an autofocus
system and a conventional type surveying instrument equipped with
no autofocus system are manufactured at the same time, these two
types of surveying instruments normally need to be manufactured in
different production lines because the autofocus system cannot be
simply separated from the conventional surveying instrument to
produce the surveying instrument equipped with an autofocus system.
This increases the cost of production.
[0027] In conventional surveying instruments equipped with an
autofocus system, a battery (a main electric power source)
accommodated in the body of the surveying instrument supplies power
to a lens drive motor of the autofocus system. Therefore, if
battery of the surveying instrument runs out, the lens drive motor
is not supplied with power, and consequently the autofocus system
becomes dysfunctional.
SUMMARY OF THE INVENTION
[0028] The present invention has been devised in view of the
problems noted above, and accordingly, an object of the present
invention is to provide a reliable and easy-operable surveying
instrument having an optical distance meter and an autofocus
system, which make it possible to complete the stakeout operation
promptly and to free the operator from the troublesome frequent
operation of the AF start button.
[0029] Another object of the present invention is to provide a
surveying instrument equipped with an autofocus system which has
easy maintainability, and also a unique structure which makes it
easy to produce two types of surveying instruments: one type with
an autofocus system and the other with no autofocus system, at a
low cost of production.
[0030] To achieve the first above-mentioned object, according to an
aspect of the present invention, a surveying instrument is
provided, including a sighting telescope optical system through
which a sighting object can be sighted; a distance measuring system
which measures a distance to the sighting object, and outputs first
data; a phase detection autofocus system which detects a focus
state of an image of the sighting object on a reference focal
plane, and outputs second data; and an AF driver which moves a
focusing lens of the sighting telescope optical system to bring the
sighting object into focus in accordance with one of the first data
and the second data.
[0031] Preferably, the surveying instrument further includes a
start button, wherein the distance measuring system and the AF
driver operate consecutively upon a single-push operation of the
start button.
[0032] In an embodiment, the surveying instrument further includes
a controller which provides a consecutive autofocus mode in which
the sighting object is brought into focus automatically
consecutively via the AF driver, and a consecutive distance
measurement mode in which the distance to the sighting object is
consecutively measured via the distance measuring system. The
consecutive autofocus mode starts at the same time the consecutive
distance measurement mode is started.
[0033] In an embodiment, the surveying instrument according to
claim 1, further including a controller which drives the AF driver
to move the focusing lens to a predetermined position thereof so
that an object at a predetermined distance is in focus when the
sighting object is unable to be brought into focus in the case of a
measurement mode in which a target is set at an arbitrary
point.
[0034] The surveying instrument can be a total station.
[0035] Preferably, the distance measuring system includes a
distance meter having a light-emitting element and a
light-receiving element.
[0036] Preferably, the phase detection autofocus system includes a
pair of line sensors.
[0037] According to another aspect of the present invention, a
surveying instrument is provided, including a sighting telescope
optical system through which a sighting object can be sighted; a
distance measuring system which measures a distance to the sighting
object; and a phase detection autofocus system which detects a
focus state of an image of the sighting object on a reference focal
plane; and an AF driver which moves a focusing lens of the sighting
telescope optical system to bring the sighting object into focus in
accordance with an output of the phase detection autofocus
system.
[0038] In an embodiment, the AF driver can move the focusing lens
to bring the sighting object into focus in accordance with an
output of the phase detection autofocus system without the use of a
reflective device at a point of the sighting object.
[0039] In an embodiment, the surveying instrument includes a start
button, wherein the distance measuring system and the AF driver
operate consecutively upon a single-push operation of the start
button.
[0040] In an embodiment, the surveying instrument further includes
a controller which provides a consecutive autofocus mode in which
the sighting object is brought into focus automatically
consecutively via the AF driver, and a consecutive distance
measurement mode in which the distance to the sighting object is
consecutively measured via the distance measuring system. The
consecutive autofocus mode starts at the same time the consecutive
distance measurement mode is started.
[0041] In an embodiment, the surveying instrument further includes
a controller which drives the AF driver to move the focusing lens
to a predetermined position thereof so that an object at a
predetermined distance is in focus when the sighting object is
unable to be brought into focus in the case of a measurement mode
in which a target is set at an arbitrary point.
[0042] The surveying instrument can be a total station.
[0043] Preferably, the distance measuring system includes a
distance meter having a light-emitting element and a
light-receiving element.
[0044] Preferably, the phase detection autofocus system includes a
pair of line sensors.
[0045] To achieve the second above-mentioned object, according to
an aspect of the present invention, a surveying instrument is
provided, including a sighting telescope through which a sighting
object can be sighted; and an AF drive unit which is provided
separately from the sighting telescope, wherein the AF drive unit
can be mounted to and dismounted from a body of the surveying
instrument. The AF drive unit includes a sensor which receives part
of a light bundle which is passed through an objective lens of the
sighting telescope; a drive mechanism which drives a focusing lens
group of the sighting telescope along an optical axis thereof; a
controller which inputs sensor data output from the sensor to
control the operation of the drive mechanism in accordance with the
input sensor data so as to focus the sighting telescope on the
sighting object; and a driving force transmitting device which
transmits a driving force generated by the drive mechanism to the
focusing lens group in a state where the AF drive unit is mounted
to the body of the surveying instrument.
[0046] Preferably, the surveying instrument further includes a
light guide, provided between the AF drive unit and the body of the
surveying instrument, for guiding the part of the light bundle
which is passed through the objective lens to the sensor.
[0047] In an embodiment, the light guide includes a first aperture
formed on the body of the surveying instrument and a second
aperture formed on a body of the AF drive unit, the first aperture
and the second aperture being aligned so that the part of the light
bundle can travel from inside of the body of the surveying
instrument to the sensor via the first and second apertures.
[0048] Preferably, the AF drive unit includes a focus control
portion which is manually operated to control the operation of the
drive mechanism.
[0049] In an embodiment, the focus control portion includes an AF
start button, the controller performing an autofocus operation upon
the AF start button being depressed.
[0050] In an embodiment, the focus control portion is positioned in
the vicinity of an eyepiece of the sighting telescope.
[0051] In an embodiment, at least one of the drive mechanism and
the AF controller is supplied with power from a battery
accommodated in the AF drive unit.
[0052] In an embodiment, the body of the surveying instrument
includes a manual focus system with which the focusing lens group
can be manually moved to adjust a focal point of the sighting
telescope.
[0053] In an embodiment, the body of the surveying instrument
includes a motorized manual focus system with which the focusing
lens group can be manually moved by operating at least one
hand-operated member to adjust a focal point of the sighting
telescope.
[0054] Preferably, the body of the surveying instrument includes
the sighting telescope.
[0055] The surveying instrument can be a total station.
[0056] Preferably, the driving force transmitting device includes a
first gear provided in the AF drive unit, the first gear partly
projecting out of the AF drive unit; and a second gear provided in
the body of the sighting telescope. The first gear and the second
gear mesh with each other in a state where the AF drive unit is
mounted to the body of the surveying instrument.
[0057] In an embodiment, the second gear partly projects out of the
body of the surveying instrument.
[0058] In an embodiment, the body of the surveying instrument
includes the sighting telescope, the sighting telescope includes an
erecting optical system positioned behind the focusing lens group,
and the light guide includes a beam splitting optical member
attached to a surface of the beam splitting optical member.
[0059] Preferably, the erecting optical system includes a
Porro-prism.
[0060] The present disclosure relates to subject matter contained
in Japanese Patent Applications Nos.2000-261075 (filed on Aug. 30,
2000) and 2000-274365 (filed on Sep. 11, 2000) which are expressly
incorporated herein by reference in their entireties.
BRIEF DESCRIPTION OF THE DRAWINGS
[0061] The present invention will be described below in detail with
reference to the accompanying drawings in which:
[0062] FIG. 1 is a schematic diagram of the first embodiment of a
total station equipped with an autofocus system, according to the
present invention;
[0063] FIG. 2 is a conceptual diagram of a focus detecting device
and a Porro-prism erecting system which are shown in FIG. 1;
[0064] FIG. 3 is a flow chart for a main routine which is performed
at the push of an AF start button;
[0065] FIG. 4 is a flow chart for a subroutine "Autofocus Process"
shown in FIG. 3;
[0066] FIG. 5 is a flow chart for another embodiment of the
subroutine "Autofocus Process" shown in FIG. 3;
[0067] FIG. 6 is a flow chart for another embodiment of the
subroutine "Autofocus Process" shown in FIG. 3;
[0068] FIG. 7 is a schematic diagram of the second embodiment of
the total station equipped with an autofocus system, according to
the present invention;
[0069] FIG. 8 is a flow chart for a stakeout measurement operation
performed on a consecutive basis with the second embodiment of the
total station shown in FIG. 7;
[0070] FIG. 9 is a flow chart for a stakeout measurement operation
performed on a consecutive basis with a conventional total station
equipped with an autofocus system;
[0071] FIG. 10 is a perspective view of the third embodiment of the
total station equipped with an autofocus system, according to the
present invention;
[0072] FIG. 11 is an elevational side view of a fundamental portion
of the total station shown in FIG. 10;
[0073] FIG. 12 is a schematic diagram of a fundamental portion of
the total station shown in FIG. 10, showing a state where an AF
drive unit is mounted to the body of the sighting telescope;
[0074] FIG. 13 is a schematic diagram of fundamental elements of
the AF drive unit and fundamental elements of the sighting
telescope;
[0075] FIG. 14 is a schematic diagram of the internal structure of
the AF drive unit;
[0076] FIG. 15 is a perspective view of a fundamental portion of
the total station shown in FIG. 10, showing a state where the AF
drive unit is dismounted from top of a block which includes the
sighting telescope and a distance measuring system; and
[0077] FIG. 16 is a perspective view of another embodiment of the
fundamental portion shown in FIG. 15, showing a state where the AF
drive unit is dismounted from top of the block which includes the
sighting telescope and the distance measuring system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0078] FIG. 1 shows the first embodiment of a total station (a
surveying instrument) equipped with an autofocus system. The first
embodiment of the total station 1 is provided with an optical
system 2, a distance measuring system (EDM) 3, an angle measuring
system (not shown), an autofocus system 4, and a controller 5. The
optical system 2 includes a sighting telescope optical system.
[0079] The optical system 2 is provided with an objective lens 21,
a focusing lens (focus adjustment lens) 22, a Porro-prism erecting
system 23, a focal-plane plate (reticle plate) 24, and an eyepiece
lens 25, in that order from the object side (i.e., left to right as
shown in FIG. 1). These optical elements 21, 22, 23, 24 and 25 are
fundamental optical elements of the sighting telescope optical
system.
[0080] The focusing lens 22 is guided in a direction of the optical
axis thereof. The axial position of the focusing lens 22 is
automatically adjusted via a drive mechanism (AF driver) 45 of the
autofocus system 4 in accordance with the distance to a sighting
object 6 to focus the image of the sighting object 6 that is formed
through the objective lens 21 on the front surface (the surface
facing the objective lens 21) of the focal-plane plate 24.
Accordingly, the image of the sighting object 6 can be precisely
focused on the front surface of the focal-plane plate 24 by
automatically adjusting the axial position of the focusing lens 22
in accordance with the distance to the sighting object 6. The
operator sights a magnified image of the sighting object 6, which
is focused on the focal-plane plate 24, via the eyepiece 25.
[0081] The focusing lens 22 is driven either automatically via the
drive mechanism 45 of the autofocus system 4 or manually via a
manual focus (MF) system (not shown) or a motorized power focus
system (i.e., a motorized manual focus system). The drive mechanism
45 is provided therein with a lens drive motor (not shown) for
moving the focusing lens 22.
[0082] The Porro-prism erecting system 23 is of a type which
employs three right angle prisms having four rectangular reflection
surfaces (first through fourth reflection surfaces in that order
from the incident light side). A part of the first reflection
surface is formed as a semitransparent surface (e.g., a
half-silvered surface) which serves as a beam splitting surface,
while a specific surface of a beam splitting prism 42 is entirely
adhered to the semitransparent surface by an adhesive.
[0083] The focal-plane plate 24 is provided thereon with a reticle
(collimation axis) 24A.
[0084] The distance measuring system 3 offers two modes of distance
measurement. In one mode, the operator places a corner cube
(reflective device) (not shown) at an aiming point, and thereafter
the distance measuring system 3 is set to emit measuring light
(e.g., a laser beam) to the corner cube (not shown) and receives
the measuring light reflected by the corner cube to measure the
distance. In the other mode, the distance measuring system 3 is set
to emit the measuring light directly to a sighting object (i.e.
without the use of a corner cube) and receives the measuring light
reflected by the sighting object to measure the distance. These two
modes of distance measurement can be freely selected by the
operator in accordance with the type or characteristics of the
sighting object 6.
[0085] The distance measuring system 3 is provided therein with an
optical distance meter 30. The optical distance meter 30 is
provided, behind the objective lens 21, with a light
transmitting/receiving mirror (reflection member) 31 and a
wavelength selection mirror (wavelength selection filter) 32, which
are arranged in that order from the object side. The optical
distance meter 30 is further provided with a light-emitting element
(e.g., a laser diode) 33 which emits light (measuring light) having
a specific wavelength, a light-receiving optical fiber 34, and a
light-receiving element 35.
[0086] The light transmitting/receiving mirror 31 is made of a
parallel-plate mirror having front and rear parallel surfaces
positioned on the optical axis of the objective lens 21. The front
surface of the parallel-plate mirror which faces the objective lens
21 is formed as a light transmitting mirror 31A, while the rear
surface of the parallel-plate mirror which faces the wavelength
selection mirror 32 is formed as a light receiving mirror 31B.
[0087] The measuring light, emitted from the light-emitting element
33 to be incident on the light transmitting mirror 31A, is
reflected thereby to proceed toward the sighting object 6 along the
optical axis of the objective lens 21. The measuring light which is
reflected by the sighting object 6 to be passed through the
objective lens 21 is reflected back to the light receiving mirror
31B via the wavelength selection mirror 32. The light receiving
mirror 31B reflects the incident measuring light so as to make the
measuring light enter at an incident end surface 34A of the light
receiving optical fiber 34. The measuring light emitted from the
light-emitting element 33 is incident on the light transmitting
mirror 31A via a collimating lens 33A and a fixed mirror 33B.
[0088] A fiber holder 34C supports the incident end of the
light-receiving optical fiber 34 which has the incident end surface
34A. The fiber holder 34C is immovably supported together with the
light transmitting/receiving mirror 31 by a fixing device (not
shown) provided in a space behind the objective lens 21.
[0089] The optical distance meter 30 is provided between the
light-emitting element 33 and the fixed mirror 33B, on a
distance-measuring optical path, with a switching mirror 36 and an
optical attenuator 37. The light (measuring light) emitted by the
light-emitting element 33 is incident on the fixed mirror 33B when
the switching mirror 36 is retracted from the distance-measuring
optical path between the collimating lens 33A and the fixed mirror
33B, and the light (internal reference light) emitted by the
light-emitting element 33 is reflected by the switching mirror 36
to be incident directly on the incident end surface 34A of the
light-receiving optical fiber 34 when the switching mirror 36 is
positioned in the distance-measuring optical path between the
collimating lens 33A and the fixed mirror 33B. The optical
attenuator 37 is used to adjust the amount of light of the
measuring light incident on the sighting object 6.
[0090] The optical distance meter 30 is provided, between an exit
end surface 34B of the light-receiving optical fiber 34 and the
light-receiving element 35, with a condenser lens 35A, an optical
attenuator 38 and a band-pass filter 35B, in that order from the
exit end surface 34B to the light-receiving element 35. The
light-receiving element 35 is connected to a controller 5. The
light-receiving element 35 is connected to the controller 5. The
controller 5 is connected to an actuator 36A which drives the
switching mirror 36, and an indicating device (e.g., an LCD panel)
8 which indicates the calculated distance.
[0091] The light bundles which are respectively passed through two
pupil areas on the objective lens 21 pass through optical paths
which do not interfere with fundamental elements of the optical
distance meter 30 such as the light transmitting/receiving mirror
31, and the light receiving optical fiber 34, the fiber holder 34C,
and supporting and/or fixing members (not shown) for these
elements.
[0092] As known in the art, the optical distance meter 30
establishes two different states: one state wherein the measuring
light emitted by the light-emitting element 33 is supplied to the
fixed mirror 33B, and another state wherein the same light
(internal reference light) is directly supplied to the incident end
surface 34A of the light-receiving optical fiber 34, which are
determined in accordance with the switching state of the switching
mirror 36 driven by the controller 5 via the actuator 36A.
[0093] As described above, the measuring light supplied to the
fixed mirror 33B is projected toward the sighting object 6 via the
light-transmitting mirror 31A and the objective lens 21, and the
measuring light reflected by the sighting object 6 is incident on
the incident end surface 34A via the objective lens 21, the
wavelength selection mirror 32, and the light receiving mirror
31B.
[0094] Thereafter, both the measuring light reflected by the
sighting object 6 to be eventually incident on the incident end
surface 34A, and the internal reference light directly supplied to
the incident end surface 34A via the switching mirror 36 are
received by the light-receiving element 35.
[0095] The light-receiving element 35 which receives the measuring
light and the internal reference light outputs a signal to the
controller 5.
[0096] The controller 5 having received such a signal from the
light-receiving element 35 detects the phase difference between the
projecting light (the measuring light projected outwards) and the
reflected light (the measuring light reflected by the sighting
object 6) and the initial phase of the internal reference light to
calculate the distance (distance data/first data) from the location
of the total station to the sighting object 6. The calculated
distance (distance data/first data) is indicated by the indicating
device 8.
[0097] The beam splitting prism 42, an AF sensor unit 43 which
includes a pair of line sensors (e.g., multi-segment CCD sensors)
43C (see FIG. 2) that receive the light reflected by the
Porro-prism erecting system 23, and the drive mechanism 45 of the
autofocus system 4 are fundamental elements of the autofocus system
4.
[0098] A part of the light which enters the Porro-prism erecting
system 23 enters the beam splitting prism 42 to be reflected
thereby to proceed toward a reference focal plane 44.
[0099] The reference focal plane 44 is formed between the beam
splitting prism 42 and the AF sensor unit 43, and is located at a
position optically equivalent to the position at which the reticle
24A of the focal-plane plate 24 is placed. The AF sensor unit 43
utilizes a phase difference detecting method, and detects the focus
state (e.g., a front focus or a rear focus) on the reference focal
plane 44. FIG. 2 shows a conceptual diagram of the AF sensor unit
43 and the Porro-prism erecting system 23. The AF sensor unit 43
includes a condenser lens 43A, a pair of separator lenses
(image-forming lenses) 43B, a pair of separator masks 43D located
in the close vicinity of the pair of separator lenses 43B, and the
aforementioned pair of line sensors 43C located behind the
respective separator lenses 43B. The hatched areas (see FIG. 1)
conceptually indicate areas (optical paths) which correspond to the
pair of pupil areas determined by a pair of apertures respectively
formed on the pair of separator masks 43D. The pair of separator
lenses 43B are arranged apart from each other by the base length.
The image of the sighting object 6 formed on the reference focal
plane 44 is separated into two images by the pair of separator
lenses 43B to be respectively formed on the pair of line sensors
43C. Each of the pair of line sensors 43C includes an array of
photoelectric converting elements. Each photoelectric converting
element converts the received light of an image into electric
charges which are integrated (accumulated), and outputs as an
integrated electric charge to the controller 5 to constitute AF
sensor data (positional data/second data). The controller 5
calculates an amount of defocus and direction of the focal shift
through a predetermined defocus operation in accordance with a pair
of AF sensor data respectively input from the pair of line sensors
43C.
[0100] As shown in FIG. 1, the autofocus system 4 is provided with
an AF start button 52 connected to the controller 5. The autofocus
system 4 offers two autofocus modes: a one-shot autofocus mode in
which the controller 5 performs an autofocus operation only once,
by which the focusing lens 22 is automatically moved to an in-focus
position with respect to the sighting object 6, and a consecutive
autofocus mode in which the controller 5 performs the autofocus
operation more than one time in series (i.e., a consecutive
autofocus operation). The operator can select either the one-shot
autofocus mode or the consecutive autofocus mode at the push of the
AF start button 52. For instance, the one-shot autofocus mode and
the consecutive autofocus mode are selected when the AF start
button 52 is depressed once, and twice in a row, respectively.
Alternatively, the one-shot autofocus mode and the consecutive
autofocus mode can be selected when the AF start button 52 is
depressed for a short time and a long time, respectively.
[0101] In the one-shot autofocus mode, which can be set, e.g., with
a double-push operation of the AF start button 52, predetermined
arithmetic computations and controls are performed only once in
accordance with the AF sensor data output from the AF sensor unit
43 to move the focusing lens 22 to an in-focus position with
respect to the sighting object 6. At this time, if the sighting
object 6 is in focus, the total station delivers an audible signal
via a sound generator 55 to inform the operator of the in-focus
state. Subsequently, the power of the autofocus system 4 is turned
OFF automatically upon completion of the autofocus operation. The
sound generator 55 is connected to the controller 5.
[0102] On the other hand, in the consecutive autofocus mode, which
can be set, e.g., with a single-push operation of the AF start
button 52, the same predetermined arithmetic computations and
controls are performed more than once in series in accordance with
the AF sensor data output from the AF sensor unit 43 to move the
focusing lens 22 to an in-focus position with respect to the
sighting object 6 each time the predetermined arithmetic
computations and controls are performed. Therefore, in the
consecutive autofocus mode, the sighting object 6 is brought into
focus repetitively even if the sighting object 6 is moving. In this
case, the audible sound is generated each time the sighting object
6 is in focus. Thereafter, the power of the autofocus system 4 is
turned OFF automatically upon completion of the last autofocus
operation.
[0103] The controller 5 uses either a phase difference method using
the aforementioned positional data in which the separation of the
pair of images respectively formed on the pair of line sensors 43C
is phase-detected, or another phase difference method using the
aforementioned distance data generated via the distance measuring
system 3 to bring the sighting object into focus automatically in
accordance with type or characteristics of the sighting object 6.
In the present embodiment, input terminals of the controller 5 are
connected with output terminals of the AF sensor unit 43 and the
light-receiving element 35 of the distance measuring system 3,
while output terminals of the controller 5 are connected with the
actuator 36A for driving the switching mirror 36 and the indicating
device 8.
[0104] Accordingly, the controller 5 operates to move the focusing
lens 22 to an in-focus position via the drive mechanism 45 of the
autofocus system 4 in accordance with the `distance data` generated
by the distance measuring system 3, or calculates an amount of
defocus via a predetermined defocus operation in accordance with a
pair of AF sensor data (`positional data`) respectively input from
the pair of line sensors 43C to drive the focusing lens 22 so as to
bring the sighting object 6 into focus via the drive mechanism 45
in accordance with the calculated amount of defocus. If the
controller 5 determines that both the distance data and the
positional data are reliable, the controller 5 operates to perform
the autofocus operation in accordance with the distance data, which
is generally considered more reliable than the positional data, in
accordance with a data table shown in Table 1 below.
[0105] The total station 1 is further provided with a distance
measurement start button 51, a timer 53 and a default-distance
setting device 54 which are all connected to the controller 5.
1TABLE 1 Data used for Pattern AF Operation Judgement (1)
Positional Data Distance Data Distance Data In-focus OK OK (2)
Positional Data Distance Data Distance Data In-focus FAILED OK (3)
Positional Data Distance Data Positional In-focus OK FAILED Data
(4) Positional Data Distance Data NONE Unable to FAILED FAILED
Focus
[0106] An arbitrary/design distance can be set/stored in the
default-distance setting device 54. If the positional data output
from the AF sensor unit 43 represents an unable-to-focus state
after the aforementioned autofocus operation has been performed,
the controller 5 actuates the lens driver 45 to move the focusing
lens 22 to a predetermined position to bring an object at the
corresponding arbitrary/design distance that is stored in the
default-distance setting device 54 into focus in either autofocus
mode (the one-shot autofocus mode or the consecutive autofocus
mode) before the subsequent autofocus operation is performed.
[0107] The process of bringing the sighting object 6 into focus
will be hereinafter discussed with reference to the flow charts
shown in FIGS. 3 and 4. FIG. 3 is a flow chart of a main routine
which is performed at the push of the AF start button 52 (with a
single-push or a double-push operation of the AF start button 52),
and FIG. 4 is a flow chart for an autofocus process ("Autofocus
Process" shown in FIG. 3) in which the autofocus operation is
performed.
[0108] Control enters the main routine immediately after the AF
start button 52 is depressed one or twice in a row.
[0109] In the main routine, firstly the timer 53 is initialized and
started (step S101). Subsequently, the autofocus process shown in
FIG. 4 is performed (step S102). Subsequently, it is determined
whether the sighting object 6 is in focus (step S103). If the
sighting object is in-focus, the sound generator 55 generates an
audible signal (step S104). If the sighting object is unable to be
brought into focus, the focusing lens 22 is driven to move to a
predetermined position thereof to bring an object at the
corresponding arbitrary/design distance that is stored in the
default-distance setting device 54 into focus (step S105).
[0110] Subsequently, it is determined whether a predetermined
period of time (e.g., one minute) has elapsed since the timer 53
started (step S106). If one minute has not yet elapsed, it is
determined whether the AF start button 52 was depressed twice in a
row, i.e., whether the consecutive autofocus mode has been selected
by the operator (step S107). If the AF start button 52 was
depressed only once, i.e., if the one-shot autofocus mode has been
selected by the operator, the power of the autofocus system 4 is
turned OFF (step S108) and subsequently control ends. If it is
determined at step S106 that one minute has elapsed, control
proceeds to step S109 at which the power of the autofocus system 4
is turned OFF and subsequently control ends.
[0111] If it is determined at step S107 that the AF start button 52
was depressed twice in a row, i.e., that the consecutive autofocus
mode has been selected by the operator, control returns to step
S102 to perform the autofocus process. Accordingly, in the
consecutive autofocus mode, the autofocus process is performed
repeatedly until the timer 53 expires.
[0112] The autofocus process at step S102 in FIG. 3 will be
hereinafter discussed with reference to the flow chart shown in
FIG. 4.
[0113] In the autofocus process, firstly the signal output from the
light-receiving element 35 of the autofocus system 4, and the AF
sensor data (the positional data) output from the pair of line
sensors 43C of the AF sensor unit 43 of the distance measuring
system 4 are input to the controller 5, while the distance data is
calculated from the signal output from the light-receiving element
35 (step S1). Subsequently, it is determined whether the calculated
distance data is reliable (step S2). If the distance data is deem
reliable, i.e., as in the case of patterns (1) or (2) shown in
Table 1, control proceeds to step S3. At step S3, the controller 5
adopts the calculated distance data to perform the autofocus
operation. Thereafter, the controller 5 actuates the lens drive
motor of the drive mechanism 45 to move the focusing lens 22 to a
predetermined position in accordance with the distance data (step
S4).
[0114] As a result, the sighting object 6 is brought into focus via
the focusing lens 22 having been moved to the predetermined
position (step S5). Subsequently, control returns to the main
routine.
[0115] However, if it is determined at step S2 that the calculated
distance data is not reliable, i.e., as in the case of patterns (3)
or (4) shown in Table 1, control proceeds to step S6 at which it is
determined whether the positional data is reliable.
[0116] If it is determined that the positional data is reliable,
i.e., in the case of pattern (3) shown in Table 1, control proceeds
to step S7. At step S7, the controller 5 adopts the positional data
to perform the autofocus operation. Subsequently, the controller 5
actuates the lens drive motor of the drive mechanism 45 to move the
focusing lens 22 to a predetermined position in accordance with the
positional data (step S4). As a result, the sighting object 6 is
brought into focus via the focusing lens 22 having been moved to
the predetermined position (step S5). Subsequently, control returns
to the main routine.
[0117] If it is determined at step S6 that the positional data is
not reliable, i.e., as in the case of pattern (4) shown in Table 1,
control proceeds to step S8 at which it is determined that both the
distance data and the positional data are not available (i.e., the
sighting object is unable to be brought into focus), so that
control returns to the main routine. In this case, at step S105 of
FIG. 3, the focusing lens 22 is driven so as to bring an object at
the corresponding arbitrary/desigh distance that is stored in the
default-distance setting device 54 into focus.
[0118] In the above illustrated embodiment of the autofocus process
shown in FIG. 4, although the distance data and the positional data
are obtained at the same time at step S1, the positional data and
the distance data can be obtained in that order as shown in the
flow chart in FIG. 5, or the distance data and the positional data
can be obtained in that order as shown in the flow chart in FIG. 6
since the reliability of the distance data and the positional data
are not determined at the same time.
[0119] As can be understood from the above descriptions, according
to the process shown in FIGS. 3 and 4, if reliable distance data
calculated via the distance measuring system 3 is obtained, the
autofocus operation can be carried out using the distance data
rather than the positional data since the distance data is
generally more reliable than the positional data. Therefore, the
sighting object 6 can be brought into focus surely and precisely
even if the sighting object 6 is like a white wall having no
contrast. Furthermore, even if the sighting object 6 is positioned
at a location beyond the predetermined measurement range of the
distance measuring system 3, the sighting object 6 can be brought
into focus via the autofocus system 4 with a phase difference
method using the positional data (AF sensor data) output from the
AF sensor unit 43.
[0120] FIG. 7 shows the second embodiment of the total station
equipped with an autofocus system. The structure of the second
embodiment of the total station 1' is similar to that of the first
embodiment of the total station 1 except that the second embodiment
of the total station 1' is further provided with a design value
input device 7A and a measured distance (specified value) input
device 7B which are each connected to the corresponding input
terminal of the controller 5.
[0121] Numerical design values are input to the controller 5 via
the design value input device 7A. For instance, design values are
input via the design value input device 7A in a distance stakeout
measurement mode; a specified distance and the dividing number "n"
for dividing the specified distance into "n" equal parts are input
via the design value input device in a lot staking measurement
mode; specified coordinate data is input via the design value input
device in a coordinate stakeout measurement mode; and a single
distance and width values are input via the design value input
device 7A in width stakeout measurement mode.
[0122] Measured values are input to the controller 5 via the
measured distance (specified value) input device 7B. For instance,
a reference distance is input via the measured distance input
device 7B in a lot staking measurement mode, while a single
distance is input via the measured distance input device 7B in
width stakeout measurement mode.
[0123] Distance stakeout measurement operation performed on a
consecutive basis with the total station 1' shown in FIG. 7 will be
hereinafter discussed with reference to the flow chart shown in
FIG. 8.
[0124] Firstly, the specified distance and other design data that
are necessary for the consecutive distance stakeout measurement
operation are input to the controller 5 via the design value input
device 7A and the measured distance input device 7B (step SB1). It
should be noted that an appropriate measurement mode needs to be
selected by the operator in advance before the operation at step
SB1 when a stakeout operation such as distance stakeout
measurement, coordinate stakeout measurement, lot staking
measurement or width stakeout measurement is performed.
[0125] Subsequently, a tracking distance measurement mode
(consecutive distance measurement mode) is selected at the push of
the distance measurement start button 51 (step SB2). Upon the push
of the distance measurement start button 51, a tracking distance
measurement operation and the consecutive autofocus operation start
at the same time. With these operations, the measured distance
value is determined immediately after the measuring light reflected
by a target returns to the total station 1', while the measured
distance and the deviation between the input design value
(specified distance) and the measured distance to the target are
indicated on the indicating device 8.
[0126] Subsequently, a sighting operation is performed when the
sighting telescope is not aimed at the target. The sighting
operation continues to be performed until the tracking distance
measurement operation or the consecutive autofocus operation stops
(step SB3). In the sighting operation, the operator tracks the
target by manually aiming the sighting telescope at the target (the
sighting object) so that the optical axis of the sighting telescope
is generally in line with the target while viewing the target
through a collimator (not shown) which is attached to the sighting
telescope. Namely, in the present embodiment, the operator sights
the target with the optical axis of the sighting telescope being
generally in line with the target. If the sighting telescope is in
an in-focus state on the target, the operator manually operates the
sighting telescope to sight the center of the target via the
sighting telescope.
[0127] After the operation at step SB2, it is determined whether
the target is in focus (step SB4). This operation at step SB4 is
performed each time the autofocus process, which is performed
repetitively by the autofocus system 4, is performed. If it is
determined that the target is not in focus, control proceeds to
step SB5. If it is determined that the target is in focus, control
proceeds to step SB6.
[0128] At step SB5, the controller 5 actuates the lens driver 45 to
move the focusing lens 22 to a predetermined position in advance to
bring an object at the corresponding design distance that is stored
in the default-distance setting device 54 into focus before the
subsequent autofocus operation is performed.
[0129] At step SB6, it is checked whether the measured distance
value has been determined. If it is determined at step SB6 that the
measured distance value has not yet been determined, control
proceeds to step SB8. The operation at step SB6 is performed
repeatedly until it is determined at step SB6 that the measured
distance value has been determined unless a distance measurement
stop button (not shown) is depressed, since the measured distance
value is determined immediately after the measuring light reflected
by the target returns to the total station 1' while the sighting
operation is being performed.
[0130] If it is determined at step SB6 that the measured distance
value has been determined, the measured distance and the deviation
between the input design value (specified distance) and the
measured distance to the target are indicated on the indicating
device 8 (step SB7).
[0131] As a result, the operator can identify the deviation between
the current location of the target and a staking point by looking
at the indicating device 8. This makes it possible for the operator
of the total station 1 to guide the person who holds the target to
move the target in accordance with the deviation. Thereafter, at
the moment the deviation indicated on the indicating device 8
becomes zero, the stakeout operation in which the target is staked
out at a staking point is completed. Accordingly, after the
operation at step SB7, it is determined whether the distance
measurement stop button (not shown) is depressed (step SB8). If the
distance measurement stop button is depressed during the sighting
operation, control proceeds to step SB9 and the tracking distance
measurement operation and the consecutive autofocus operation are
terminated. Otherwise, control returns to step SB4 from step SB8 to
repeat the operations from step SB4 to step SB8.
[0132] As can be understood from the foregoing, according to each
of the above described first and second embodiments of the total
stations, the distance data and the positional data (AF sensor
data) are selectively effectively utilized and are supplementary to
each other. Therefore, the sighting object can be brought into
focus reliably and precisely even if the sighting object is like a
white wall having no contrast, to thereby minimize the chances that
the autofocus operation may end in failure. This increases the
reliability of the autofocus system, and consequently makes it
possible to complete the stakeout operation promptly.
[0133] In an conventional total station, when a distance measuring
operation is carried out without a prism, there is a possibility
that the measuring point may not be identified clearly or may be
misidentified. However, according to each of the above described
first and second embodiments of the total station, the measuring
point can be reliably brought into focus without a prism under
various conditions. This increases the reliability of the total
station.
[0134] Furthermore, according to each of the above described first
and second embodiments of the total station, in the case where the
tracking distance measurement mode in which such an operation as
the distance stakeout measurement operation is performed is set,
the consecutive autofocus operation starts at the same time the
distance stakeout measurement operation starts. Therefore, it is no
longer necessary to push an AF start button, which makes it
possible for the operator of the total station to focus his/her
energy on carrying out the sighting operation. Consequently, the
stakeout operation can be completed promptly.
[0135] FIGS. 10 through 15 show the third embodiment of the total
station equipped with an autofocus system. The total station 100,
which is mounted on a tripod (not shown) when used, is provided
with a sighting telescope (a sighting telescope optical system)
102, a distance measuring system (EDM) 103, an angle measuring
system (not shown) and a detachable AF drive unit (an AF system)
104.
[0136] As shown in FIG. 13, the sighting telescope 102 includes an
objective lens 121, a focusing lens (focus adjustment lens) 123, a
Porro-prism erecting system (erecting optical system) 124, a
focal-plane plate (reticle plate) 125, and aneyepiece lens 122,
inthatorder from the object side (i.e., left to right as shown in
FIG. 13).
[0137] The focusing lens 123 is guided in a direction of the
optical axis thereof. The axial position of the focusing lens 123
is automatically adjusted via an AF drive mechanism 142 provided in
the AF drive unit 104 in accordance with the distance to a sighting
object to focus the image of the sighting object that is formed
through the objective lens 121 on the front surface (the surface
facing the objective lens 121) of the focal-plane plate 125.
Accordingly, the image of the sighting object can be precisely
focused on the front surface of the focal-plane plate 125 by
automatically adjusting the axial position of the focusing lens 123
in accordance with the distance to the sighting object. The
operator sights a magnified image of the sighting object, which is
focused on the focal-plane plate 125, via the eyepiece 122. The
focusing lens 123 is moved along the optical axis thereof either
automatically via the AF drive mechanism 142, or manually via a
manual focus (MF) system 105, or a motorized power focus system
(i.e., a motorized manual focus system/PF system) 106. Therefore,
the focusing lens 123 can be driven via the manual focus system 105
or the motorized power focus system 106 even if the AF drive unit
104 is dismounted from top of the sighting telescope 102.
[0138] A beam splitting prism (a beam splitting optical
member/light guide) 126 is adhered to a specific inclined surface
124A of the Porro-prism erecting system 124 so that part of the
light which enters the Porro-prism erecting system 124 enters the
beam splitting prism 126 to be reflected thereby to be incident
upon an AF sensor 141 (see FIG. 13).
[0139] The focal-plane plate 125 is provided thereon with a reticle
(cross hair), which is known in the art.
[0140] As shown in FIG. 15, the AF drive unit 104 is designed so as
to be dismountably mounted to top of a housing 102A of the sighting
telescope 102 via four set screws 146 (only one is shown in FIG.
15). As shown in FIG. 14, the AF drive unit 104 is provided in a
housing 104A thereof with an AF sensor (e.g., a pair of
multi-segment CCD line sensors) 141, an AF drive mechanism 142, an
AF controller 143, and an AF power source 145. In a state where the
AF drive unit 104 is properly mounted to the housing 102A of the
sighting telescope 102, the AF sensor 141 is optically in alignment
with the sighting telescope optical system 102 positioned in the
housing 102A, the AF drive mechanism 142 is mechanically connected
to the focusing lens 123, and the AF controller 143 is electrically
connected to an AF start button 144C of a focus control portion 144
via male and female connectors 144A and 144B.
[0141] The AF sensor 141 receives part of the light which enters
the Porro-prism erecting system 124 from the sighting object to
attain information on the focal point of the sighting telescope
with respect to the sighting object. In the third embodiment of the
sighting telescope, part of the light which enters the Porro-prism
erecting system 124 is led to the photosensitive surface (not
shown) of the AF sensor 141 via the beam splitting prism 126. The
AF sensor 141 detects the focus state (e.g., a front focus or a
rear focus) on a reference focal plane (not shown) which is located
at a position optically equivalent to the position at which the
reticle of the focal-plane plate 125 is placed. The AF controller
143 calculates an amount of defocus and direction of the focal
shift through a predetermined defocus operation in accordance with
AF sensor data (focal-point positional data) output from the AF
sensor 141. With the calculated amount of defocus and direction of
the focal shift, the focusing lens 123 can be moved to an in-focus
position with respect to the sighting object.
[0142] In a state where the AF drive unit 104 is properly mounted
to the housing 102A of the sighting telescope 102, the light bundle
which emerges from an exit surface of the beam splitting prism 126
is incident on a photosensitive surface (not shown) of the AF
sensor 141 via two openings (first aperture) 121A and (second
aperture) 141A which are respectively formed on a top plate of the
housing 102A and a bottom plate of the housing 104A (see FIG. 15).
The openings 121A and 141A are aligned when the AF drive unit 104
is properly mounted to the housing 102A of the sighting telescope
102. The openings 121A and 141A and the beam splitting prism 126
constitute a light guide. Alternatively, the light bundle which
emerges from the exit surface of the beam splitting prism 126 can
be incident on the photosensitive surface of the AF sensor 141 via
a conventional optical coupler (light guide) using detachable
connectors or plugs.
[0143] As shown in FIG. 12, the AF drive mechanism 142 is provided
with an AF motor 142B, a drive gear 142C which is fitted fixedly on
the drive shaft of the AF motor 142B, and a gear train including a
first gear (not shown) and a final gear (first gear) 142D. In FIG.
12, among all the gears of the gear train, only the final gear 142D
is shown. The first gear of the gear train is engaged with the
drive gear 142C, while the final gear 142D of the gear train is
engaged with a circumferential gear (second gear) 123B formed on a
rotatable lens barrel 123A. The final gear 142D partly projects
downwardly outwards from the bottom plate of the AF drive unit 104
via a rectangular opening 142A formed on the bottom plate of the AF
drive unit 104 (see FIG. 15). The housing 102A of the sighting
telescope 102 is provided on the top plate of the housing 102A with
a corresponding rectangular opening 122A via through which the
circumferential gear 123B of the rotatable lens barrel 123A partly
projects externally upward from the top plate of the housing 102A
to be engaged with the final gear 142D. The final gear 142D and the
circumferential gear 123B constitute a driving force transmitting
device which transmits a driving force generated by the AF drive
mechanism to the focusing lens group.
[0144] As shown in FIGS. 14 and 15, the housing 104A is provided
along the bottom edge with an annular projecting portion 104B to
secure a space between the bottom plate of the housing 104A and the
top plate of the housing 102A so that the final gear 142D and the
circumferential gear 123B can be engaged with each other in this
space. The final gear 142D and the circumferential gear 123B
constitute a mechanical coupler for coupling the AF drive mechanism
142 to the rotatable lens barrel 123A. Upon mounting the AF drive
unit 104 onto the sighting telescope 102, the final gear 142D
meshes with the circumferential gear 123B.
[0145] As shown in FIG. 12, the rotatable lens barrel 123A is
slidably fitted on an inner barrel 150 which surrounds and holds
the focusing lens 123. The inner barrel 150 is guided linearly
along the optical axis of the focusing lens 123 via a conventional
guiding mechanism. The rotatable lens barrel 123A is provided on an
inner peripheral surface thereof with a female helicoidal thread
150A, while the inner barrel 150 is provided on an outer peripheral
surface with a male helicoidal thread 150B which meshes with the
female helicoidal thread 150A. Therefore, rotating the rotatable
lens barrel 123A causes the inner barrel 150 to move along the
optical axis of the focusing lens 123 relative to the rotatable
lens barrel 123A, which makes it possible to adjust the axial
position of the focusing lens 123 so as to bring the sighting
object into focus. Accordingly, the focus lens 123 is driven to
move along the optical axis thereof by rotation of the AF motor
142B.
[0146] Although the circumferential gear 123B of the rotatable lens
barrel 123A partly projects externally upward from the top plate of
the housing 102A in the third embodiment, the sighting telescope
102 can be designed so that the circumferential gear 123B does not
project externally upward from the top plate of the housing 102A.
According to this design, the rectangular opening 122A only has to
be closed by an appropriate simple covering member (not shown) when
the total station 100 is produced as a total station without the AF
drive unit 104.
[0147] The AF controller 143 calculates the amount of defocus in
accordance with the AF sensor data output from the AF sensor 141 to
move the focusing lens 123 to an in-focus position thereof with
respect to the sighting object, and at the same time performs a
distance measuring operation to measure the distance to the
sighting object with the use of the AF sensor data when necessary.
The AF controller 143 performs the autofocus operation at the push
of the AF start button 144C of the focus control portion 144
provided at the rear of the housing 102A of the sighting telescope
102 around the eyepiece lens 122 (see FIG. 15). In the third
embodiment of the sighting telescope, the focus control portion 144
is provided at the rear of the housing 102A, i.e., on a portion of
the body of the total station 100. The focus control portion 144
includes the AF start button 144C, a manual focus adjustment ring
144D and a pair of focus adjustment switches (hand-operated
members) 144E. As shown in FIG. 13, the AF start button 144C is
electrically connected to the AF controller 143 via connecting male
and female connectors 144A and 144B which are provided on the
housings 102A and 104A, respectively. The pair of focus adjustment
switches 144E are connected to the motorized power focus system 106
for driving the focusing lens 123 in the optical axis direction.
The AF controller 143 is positioned in the housing 104A of the AF
drive unit 104, and controls the operation of the AF motor 142B of
the drive mechanism 142. However, the AF controller 143 can be
modified so as to control both the operation of the AF motor 142B
and the operation of the distance measuring system 103. In this
case, the AF controller 143 can be positioned in the housing of the
distance measuring system 103 or in other appropriate space in the
main body of the sighting telescope 100.
[0148] Although the AF start button 144C, which is depressed by the
operator to actuate the AF motor 142B of the AF drive system 104 to
bring the sighting object into focus automatically, is arranged on
the focus control portion 144 together with other control buttons
or switches (e.g., pair of focus adjustment switches 144E) in
consideration of operability, the AF start button 144C can be
arranged on the housing 104A of the AF drive unit 104 in a manner
shown in FIG. 16. FIG. 16 shows another embodiment of a fundamental
portion of the total station 100 wherein an AF start button 144C'
which corresponds to the AF start button 144C is provided on the
housing 104A of the AF drive unit 104. In this embodiment, the
manual focus adjustment ring 144D and the pair of focus adjustment
switches 144E are provided on the housing 102A of the sighting
telescope 102 in consideration of the case where the total station
100 is used without the AF drive unit 104. The pair of focus
adjustment switches 144E are manually operated to move a PF motor
(not shown) provided in the housing 102A forwardly and reversely
via the motorized power focus system 106.
[0149] The AF power source 145 that is provided in the housing 104A
of the AF drive unit 104 includes a battery which is used
exclusively by the AF drive unit 104 (i.e., by the AF motor 142B
and the AF controller 143). Namely, the battery of the AF power
source 145 is independent of another battery (not shown) which is
accommodated in the body of the total station 100 to serve as the
main power source of the total station 100. Accordingly, the AF
drive unit 104 can function even if the battery of the total
station 100 which serves as the main power source thereof goes
dead. The AF power source 145 can be omitted in the AF drive unit
104 if the total station 100 is modified so that the battery
accommodated in the body of the total station 100 supplies power to
the AF drive unit 104. In this case, it is of course necessary to
provide the total station with a power supply line for supplying
power from the battery accommodated in the body of the total
station 100 to the AF drive unit 104 via appropriate connectors or
the like.
[0150] As can be understood from the foregoing, according to the
above described third embodiment of the surveying instrument
equipped with an autofocus system, the AF drive unit 104 is
provided independent of the body of the total station 100, and can
be simply connected electrically, optically and mechanically to the
body of the total station 100 via set screws 146. Therefore, when
one type of surveying instrument equipped with an autofocus system
and another type of surveying instrument equipped with no autofocus
system are manufactured, these two types of surveying instruments
can share the great number of components to thereby reduce the cost
of production. Accordingly, the manufacturer can provided such two
types of surveying instruments at low prices. Furthermore, the AF
drive unit can be removed if necessary when the total station is
carried from one place to another, which facilitates transportation
of the total station.
[0151] Furthermore, the operator can remove the AF drive unit from
the body of the total station as circumstances demand, which
facilitates the versatility of the total station. As can be
understood from the above descriptions, according to the third
embodiment of the surveying instruments equipped with an autofocus
system, a surveying instrument equipped with an autofocus system
which can be checked up or repaired easily promptly with the
autofocus system being removed from the body of the surveying
instrument if necessary according to the circumstances is achieved.
Furthermore, one type of surveying instrument equipped with an
autofocus system and another type of surveying instrument which is
not equipped with an autofocus system can be manufactured easily
with a low cost of production.
[0152] The present invention can be applied to not only a total
station having both a distance measuring system and an angle
measuring system but also an electronic distance meter having a
distance measuring system but having no angle measuring system.
[0153] Obvious changes may be made in the specific embodiments of
the present invention described herein, such modifications being
within the spirit and scope of the invention claimed. It is
indicated that all matter contained herein is illustrative and does
not limit the scope of the present invention.
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