JP2823112B2 - Rangefinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring instrument, and more particularly to a distance measuring instrument for measuring the distance of a measured object based on the time from when a pulsed light beam oscillates to when it is reflected back by the object. Regarding rangefinder.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional apparatus for irradiating a measurement object at an arbitrary position with a laser beam to measure the displacement and position of the measurement object (US Pat. No. 4,790,651).
. As shown in the figure, this apparatus is configured such that the final-stage reflecting mirror 10 can rotate around the X axis and the Y axis, respectively, whereby a retroreflector (shown in FIG. Laser beam). That is, the rotating body 14 supporting the reflection mirror 10 is
The rotating body 16 is supported rotatably about the X axis via bearings 14, 14, and the rotating body 16 is rotatable about the Y axis via bearings 20, 20 with respect to the fixed base 18. It is supported by.

A laser beam oscillated from a laser light source (not shown) is split by a polarizing beam splitter 22 fixed to a fixed base 18, and one of the split laser beams is incident on a corner cube 24 and reflected therefrom. The light enters the detection unit 26 via the polarization beam splitter 22 as reference light. On the other hand, the other split laser beam is bent coaxially with the Y axis by the prism 28, and then the prism 3 supported by the rotating body 16
It is bent coaxially with the X axis via 0 and 32, and is incident on the reflection mirror 10 at the final stage.

Accordingly, the laser beam emitted from the reflection mirror 10 rotates when the rotating body 16 rotates around the Y axis, and moves vertically when the rotating body 14 rotates around the X axis. By controlling the rotation of the rotating bodies 14 and 16, respectively, a laser beam can be emitted toward the retroreflector provided on the object to be measured. The reflected light from the retroreflector provided on the measurement object enters the detection unit 26 via the reflection mirror 10, the prisms 32, 30, and 28, and the polarization beam splitter 22 as object light.

[0005] In the detector 26, the corner cube 24
The movement of the object is measured based on the interference between the reference light reflected by the object and the object light reflected by the retroreflector provided on the object. That is, when the optical path length of the object light changes with the movement of the measurement object, interference fringes are generated between the object light and the reference light, and the displacement of the measurement object is measured by counting the interference fringes. be able to.

[0006]

Since the above-mentioned apparatus utilizes the interference of the laser beam accompanying the movement of the measurement object, it can measure only the displacement of the measurement object. For example, the distance of the stationary measurement object from the reference point can be measured. Cannot be measured. On the other hand, a pulsed laser beam is oscillated from the laser
By receiving the reflected light from the cube 24 and the reflected light from the retroreflector provided on the measurement object, measuring the time difference between these reflected lights, and multiplying the time difference by the speed of light, or By adding the initial value corresponding to the measurement reference point to the multiplied value, the absolute distance of the measured object can be measured.

[0007] However, the above-mentioned device comprises a bearing 12,
There is a problem in that the accuracy of 20 or the like affects the measurement accuracy and high-precision measurement cannot be performed. That is, when the measurement object is irradiated with the laser beam, the rotating body 14 is rotated via the bearings 12 and 12, and the rotating body 16 is rotated via the bearings 20 and 20. Blurring of the rotation centers of 14, 16 appears as a change in the optical path length to the object to be measured. Also,
The optical path length to the object to be measured also changes due to thermal expansion of the rotators 14 and 16 and the like, which affects measurement accuracy.

The present invention has been made in view of such circumstances, and is configured so that a measurement error does not occur even if the center of rotation of the rotating body is deflected, thereby making it possible to reduce the distance of the measured object at an arbitrary position. An object of the present invention is to provide a distance measuring instrument capable of measuring with high accuracy.

[0009]

According to the present invention, there is provided a first retroreflector disposed at a fixed position, comprising:
A second retroreflector disposed on the object to be measured, a rotating portion rotatable about an X axis and a Y axis orthogonal to the first retroreflector, and fixedly disposed on the rotating portion. A light source that emits a pulsed light beam at the time of distance measurement, means for guiding the light beam emitted from the light source to the rotating unit regardless of the rotation of the rotating unit, and fixedly disposed on the rotating unit. An optical system comprising a plurality of optical components, wherein the optical system receives a pulsed light beam emitted from the light source, divides the light beam, and divides one of the divided light beams into an optical path orthogonal to the X axis. And incident on the first retroreflector via
The other light beam is emitted on the extension of the optical path, and
An optical system for making the light reflected by the first and second retroreflectors, and obtaining the reflected light from the first and second retroreflectors, respectively;
Photoelectric conversion means for respectively receiving the reflected light from the retroreflector and converting the reflected light into an electric signal, based on the electric signal from the photoelectric conversion means, And a calculating unit that measures a time difference between the time point of receiving the reflected light from the second retroreflector and a time point to the object from the measured time difference.

Also, a part of the reflected light from the second retroreflector is fixedly disposed on the rotating section, and
Position detecting means for outputting a position signal in accordance with the amount of deviation of the light beam incident on the retroreflector, and X of the rotating portion so that the amount of deviation becomes zero based on the position signal from the position detecting means. Control means for controlling the rotation position about the axis and the Y axis.

[0011]

According to the present invention, the first retroreflector is fixedly disposed at the position where the X axis and the Y axis intersect, and the first retroreflector is centered around the X axis and the Y axis. Each is provided with a rotatable rotating part. An optical system composed of a plurality of optical components is fixed to the rotating unit. The optical system divides a light beam emitted from a light source and transmits one of the divided light beams to an optical path orthogonal to the X axis. And the other light beam is emitted along an extension of the optical path, and is incident on the second retroreflector provided on the measurement object. Then, the distance between the second retroreflector is calculated based on the time difference between the reflected light from the first and second retroreflectors. Even when a relative displacement occurs between the rotating part and the first retroreflector during the distance measurement of the object to be measured, the light beam incident on the first retroreflector and the second retroreflector Since it is collinear with the light beam incident on the body, it does not appear as a measurement error.

Further, the rotating section is provided with position detecting means on which a part of the reflected light from the second retroreflector is incident, and the position detecting means is provided with light incident on the second retroreflector. A position signal is output according to the beam shift amount. Therefore, if the rotation position of the rotating unit about the X-axis and the Y-axis is controlled based on the position signal from the position detecting means so that the displacement amount becomes zero, the light beam is always emitted even if the object moves. Can be applied to the measurement object.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a distance finder according to the present invention; FIG. 1 is a perspective view showing one embodiment of a distance measuring instrument according to the present invention. As shown in the figure, the range finder mainly includes a cat's eye 106 provided on a fixed base 100, a rotating unit 108, a cat's eye 110 provided on an object to be measured, and the cat's eyes 106, 11
An arithmetic unit (not shown) for calculating the distance of the object to be measured based on the time difference of the reflected light from zero, and a tracking control unit including the four-division photodiode 112, the motors MX _{, MY,} and the control device 114 It is configured.

The rotating portion 108 is supported rotatably around the X axis via bearings 122 and 124 provided between the rotating frame 108 and the support frame 120.
Are supported rotatably about the Y axis via a bearing 126 provided between the first and second members. Therefore, the rotating unit 108 is supported on the fixed base 100 so as to be rotatable around the X axis and the Y axis, respectively.

The control unit 114 controls the rotating unit 108 based on the output signal from the four-division photodiode 112 (the details of this signal will be described later) so that the laser beam enters the cat's eye 110 for object light. motor M for rotating the motor M _X and the supporting frame 120 to rotate the
Drive control of _Y. The laser unit 102, the photodiode 205, and various optical members are arranged in the rotating unit 108. The laser diode 102 emits a pulsed laser beam every time an object to be measured is measured,
This laser beam is collimated by the lens 201.

The collimated laser beam enters the polarization beam splitter 154 via the prism 152 and is split into two mutually perpendicular linearly polarized light beams. The laser beam transmitted through the polarizing beam splitter 154 is incident on the cat's eye 106 via the prism 172, the quarter-wave plate 202, and the lens 156. Cat's Eye 10
Reference numeral 6 denotes, for example, a true sphere having a refractive index of 2 and a reflecting mirror formed on a hemispherical surface, and can reflect a laser beam incident in a predetermined incident range in the same direction as the incident direction. When the laser beam is converged by the lens group 156, the refractive index of the cat's eye 106 can be made smaller than 2.

The light reflected by the cat's eye 106 is returned as reference light in the direction opposite to the incident light path. The reflected light changes its polarization direction by 90 ° by reciprocating through the quarter-wave plate 202. Therefore, the laser beam incident on the polarizing prism 154 is reflected by the polarizing prism 154 and detected by the photodiode 207 via the condenser lens 206.

On the other hand, the linearly polarized light reflected by the polarization beam splitter 154 passes through the non-polarization beam splitter 208, the prisms 160 and 162, and the quarter-wave plate 164.
The light is emitted to the cat's eye 110 provided on the measurement object.
The light reflected by the cat's eye 110 is returned as object light in the direction opposite to the incident light path. This reflected light is first split by the non-polarizing beam splitter 208.

The laser beam reflected by the non-polarizing beam splitter 208 is used for tracking control. The reflected laser beam is condensed by the lens 166 and is imaged on the photodiode 112 divided into four. When the laser beam is incident on the spherical center of the cat's eye 110, the reflected light is incident on the center of the light receiving surface of the photodiode 112.

Here, when the laser beam deviates from the center of the cat's eye 110 and enters the cat's eye 110 with the movement of the object to be measured, the reflected light is reflected on the light receiving surface of the photodiode 112 in accordance with the direction and amount of the deviation. Is incident off the center. The light receiving surface of the four-division photodiode 112 is divided into four parts in the upper, lower, left, and right directions.
The two electrical signals are output to the controller 114. Control device 1
Reference numeral 14 designates a motor M so that the levels of the electric signals corresponding to the upper and lower division planes of the four electric signals to be input are the same.
_X is driven, and the motor _MY is driven so that the levels of electric signals corresponding to the left and right division planes match. As a result, the rotation of the rotation unit 108 is controlled around the X axis and the Y axis.
The outgoing direction is controlled so as to be incident on. still,
In order to track the measured object by the tracking control unit, it is necessary to shorten the measurement period (the laser beam pulse period) of the measured object with respect to the moving speed of the measured object.

On the other hand, the laser beam transmitted through the non-polarizing beam splitter 208 enters the polarizing beam splitter 154. Since the polarization direction of this laser beam has been changed by the 波長 wavelength plate 164, it passes through the polarization beam splitter. Further transmitted laser beam,
The light passes through the polarizing beam splitter 203 and is focused on the condenser lens 20.
6 and is detected by the photodiode 205.

After the above procedure, the photodiodes 205 and 2
The laser beam detected by 07 is photoelectrically converted and then transmitted as an electric signal to an arithmetic unit (not shown). The calculation unit multiplies the time difference between the incident time of the electric signal indicating the reference light and the time of incidence of each electric signal indicating the object light by the speed of light, as is well known, and calculates a known optical path difference and the response of the photodiodes 205 and 207. The distance from the reference point of the measured object is calculated by adding an initial value that takes into account gender differences and the like.

Next, the measurement accuracy of the rangefinder will be described. FIG. 2 is a main part plan view showing the internal configuration of the rotating unit 108 in FIG. As shown in the figure, the laser beam emitted from the laser diode 102 is
1. Polarizing beam splitter 15 through prism 152
4 is incident. The laser beam transmitted through the polarizing beam splitter 154 is applied to the prism 172 and the 波長 wavelength plate 2.
02, the light is incident toward the spherical center of the cat's eye 106 via the condenser lens 156. On the other hand, the laser beam reflected by the polarization beam splitter 154 includes the non-polarization beam splitter 208, the prisms 160, 162, and 1
The light enters the cat's eye 110 provided on the object to be measured via the wavelength plate 164. At this time, the laser beam emitted from the quarter-wave plate 164 to the cat's eye 110 is emitted on the extension of the optical path of the laser beam emitted to the cat's eye 106.

The optical path related to the distance measurement of the object to be measured is the difference in the distance from the position separated by the polarizing beam splitter 154 to each of the cat's eyes 106, 110,
Other optical paths are common. However, according to the rangefinder having the above-described configuration, the rotating unit 108 has the X-axis and the Y-axis centered on the fixedly arranged cat's eye 106 (in FIG. Therefore, even if the center of the cat's eye 106 does not coincide with the intersection of the X-axis and the Y-axis during this rotation, each cat's eye is separated from the position separated by the polarizing beam splitter 154. The difference between the distances to 106 and 110 does not change. That is, according to the ranging finder having the above-described configuration, even if a shake occurs at the rotation center of the rotating unit 108, the shake does not affect the measurement accuracy, and high-precision measurement can be performed. Also,
Even if the rotation unit 108 thermally expands, the polarization beam splitter 1
Each cat's eye 10 from the position separated by 54
The difference in distance to 6,110 does not change and there is no dead path error.

In this embodiment, since a pulsed laser beam is oscillated, each electric signal obtained by photoelectrically converting the reflected light is also pulsed. When comparing the rising points of these electric signals, errors may occur at the stage of waveform shaping. Therefore, in order to perform distance measurement with high accuracy, it is preferable to modulate the pulsed laser beam. Further, the ranging finder of the present embodiment has a tracking control unit for tracking the measured object, but the tracking control unit is not essential for measuring the distance of the measured object.

Although a laser diode is used as a light source in this embodiment, other types of lasers, light emitting diodes, and the like can be used. Further, not limited to the pulsed light beam as in the present embodiment, an intensity-modulated light beam can also be used. However, in this case, the arithmetic unit measures the phase difference between the reflected lights from the cat's eyes 106 and 110, and calculates the distance to the object from the measured phase difference.

Further, in this embodiment, the cat's eye is used as the retroreflector. However, the present invention is not limited to this. For example, a corner cube, a right-angled three-sided mirror, a sphere having a mirror surface, or the like may be used. You may make it. The rotating part is rotatable around the X axis and the Y axis by a gimbal mechanism. However, the present invention is not limited to this. For example, the L-shaped bracket is rotated by a motor and the motor fixed to the L-shaped bracket is used. The rotating unit may be fixed and the rotating unit may be rotated.

[0028]

As described above, according to the range finder of the present invention, even if the center of rotation of the rotating body is deviated, the distance from the beam splitter to the retroreflector for reference and the reverse distance for measurement are reduced. Since the difference from the distance to the reflector does not change, the distance to the object can be measured with high accuracy.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a distance measuring instrument according to the present invention.

FIG. 2 is a plan view of a main part including an internal configuration of a rotating unit of FIG. 1;

FIG. 3 is a perspective view showing an example of a conventional apparatus for irradiating a measurement object with a laser beam.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 fixed base 102 laser diode 106, 110 cat's eye 108 rotating part 112 four-segment photodiode 114 control device 120 support frame 122, 124, 126 bearing 154, 203 polarizing beam splitter 205, 207 Photodiodes M _X, M _Y … Motor

──────────────────────────────────────────────────続 き Continuing from the front page (72) Koji Toyoda, 1-4-1 Umezono, Tsukuba, Ibaraki Pref., National Institute of Metrology (72) Inventor Yoshihisa Tanimura 1-1-4 Umezono, Tsukuba, Ibaraki, Japan Inside the Metrology Laboratory (72) Inventor Toru Nakamata 9-7-1 Shimorenjaku, Mitaka City, Tokyo Co., Ltd.Tokyo Seimitsu Co., Ltd. (72) Inventor Nozomi Takai 9-7-1, Shimorenjaku, Mitaka-shi, Tokyo Examiner, Tokyo Seimitsu Co., Ltd.Hideo Ariya (56) References JP-A-59-95404 (JP, A) Field (Int.Cl. ⁶ , DB name) G01C 3/00-3/32 G01B 11/00-11/30 G01C 1/02 G01S 7/00-7/66 G01S 17/00-17/95

Claims (4)

(57) [Claims] 1. A first retroreflector disposed at a fixed position, a second retroreflector disposed on an object to be measured, an X axis orthogonal to the first retroreflector, A rotating unit that is rotatable around the Y axis, a light source that is fixed to the rotating unit and emits a pulsed light beam during distance measurement, and a plurality of optical components that are fixed to the rotating unit An optical system consisting of: receiving a pulsed light beam emitted from the light source, splitting the light beam, and passing one of the split light beams through an optical path orthogonal to the X axis. And the other light beam is emitted on the extension of the optical path and made incident on the second retroreflector, and the reflected light from the first and second retroreflectors is reflected by the first and second retroreflectors. An optical system for obtaining each of them, and receiving light reflected from the first and second retroreflectors, respectively, Photoelectric conversion means for converting the reflected light from the first retroreflector to a light reception time of the reflected light from the second retroreflector based on the electric signal from the photoelectric conversion means. A distance measuring instrument comprising: a calculating unit that measures a time difference between the two and calculates a distance to the object from the measured time difference. 2. A light source fixedly disposed on the rotating section and periodically emitting a pulsed light beam, and a light source fixedly disposed on the rotating section and reflected from the second retroreflector. A position detector that outputs a position signal corresponding to the amount of deviation of the light beam incident on the second retroreflector, wherein the amount of deviation becomes zero based on the position signal from the position detector. 2. A distance measuring instrument according to claim 1, further comprising: control means for controlling a rotation position of the rotating section about the X axis and the Y axis. 3. A first retroreflector disposed at a fixed position, a second retroreflector disposed on an object to be measured, an X-axis orthogonal to the first retroreflector as a center, and A rotating unit rotatable around the Y axis, a light source fixedly disposed on the rotating unit and emitting an intensity-modulated light beam, and a plurality of optical components fixedly disposed on the rotating unit. An optical system that receives an intensity-modulated light beam oscillated from the light source, splits the light beam, and splits one of the split light beams via an optical path orthogonal to the X axis into the first light beam.
And the other light beam is emitted on the extension of the optical path and made incident on the second retroreflector, and the reflected light from the first and second retroreflectors is respectively reflected. An optical system to obtain, a phase difference between the reflected light from the first retroreflector and the reflected light from the second retroreflector based on the electric signal from the photoelectric conversion means, and the measured phase difference A calculating unit for calculating a distance from the object to the object to be measured. 4. A part of the light reflected from the second retroreflector, which is fixedly disposed on the rotating section, and corresponds to a shift amount of a light beam incident on the second retroreflector. Position detecting means for outputting a position signal, and control means for controlling a rotational position of the rotating portion about the X-axis and the Y-axis based on the position signal from the position detecting means so that the displacement amount becomes zero. The rangefinder according to claim 3, further comprising: