JP6512917B2 - Tracking laser interferometer and return method of tracking laser interferometer - Google Patents

Description

  The present invention relates to a tracking laser interferometer and a return method of the tracking laser interferometer.

  As tracking type laser interferometers for measuring displacement and position of a moving body with high accuracy while tracking the moving body, there are ones described in Patent Documents 1 to 3. Hereinafter, the case where a homodyne-type Michelson-type laser interferometer described in Patent Document 1 is used will be described with reference to FIGS. 1 to 3. FIG. 1 is a perspective view showing the entire configuration of a conventional tracking type laser interferometer, FIG. 2 is a top view of the conventional tracking type laser interferometer, and FIG. 3 is a schematic configuration view of the conventional interferometer portion.

  As shown in FIG. 1, the tracking type laser interferometer of Patent Document 1 includes a light source unit 100, a main body unit 200, a retroreflector 300, a circuit unit 400, and a PC 500.

  The light source unit 100 has a frequency stabilized He—Ne laser light source 101, a lens 102, and an optical fiber 103.

  The main body unit 200 includes a carriage 201, a reference sphere 202, a displacement gauge 203, an interferometer 204, an elevation angle motor 205, an azimuth angle motor 206, and an azimuth rotation unit 207. The two-axis rotation mechanism includes an azimuth rotation mechanism rotating in an azimuth direction about a reference sphere 202 and a supination rotation mechanism rotating in a supination direction. The supine angle rotation mechanism includes a carriage 201 and a supine angle motor 205. The azimuth rotation mechanism includes an azimuth motor 206 and an azimuth rotation unit 207. The interferometer 204 is disposed in the supine-angle rotation mechanism. Further, the measurement unit is configured to include the displacement meter 203 and the interferometer 204. Each component of the biaxial rotating mechanism is fixed on the base, and each component of the measuring unit is fixed on the biaxial rotating mechanism. The reference sphere 202 is fixed to the base, and the center of the reference sphere 202 is the same as the rotation center of the two-axis rotation mechanism.

  The circuit unit 400 includes signal processing circuits 401 to 403 and motor drive circuits 404 and 405.

  As shown in FIG. 2, the tracking type laser interferometer of Patent Document 1 measures the change amount ΔL (ΔL1 + ΔL2) of the distance between the reference sphere 202 and the retroreflector 300 using the interferometer 204 and the displacement meter 203. .

  As shown in FIG. 3, the interferometer 204 includes a collimator lens 222, a polarization beam splitter (PBS) 230, a non-deflection beam splitter (NPBS) 236, an optical position detector 238, a plane mirror 270, and a photodetector. 272, and. The light position detector 238 is, for example, a two-dimensional PSD (Position Sensing Detector) or a four-split PD (QPD).

The operation will be described below with reference to FIGS. 1 to 3.
The laser beam incident on the interferometer 204 is emitted from the frequency stabilized He—Ne laser light source 101, and is incident on the interferometer 204 via the lens 102 and the optical fiber 103. The laser beam incident on the interferometer 204 is split into two by the PBS 230, one of which is used as a reference beam for length measurement, and the other is emitted toward the retroreflector 300. The laser beam 104 emitted toward the retroreflector 300 is reflected by the retroreflector 300 and then enters the interferometer 204 again. The laser beam 104 re-incident on the interferometer 204 is split into two by the NPBS 236, one of which interferes with the reference beam as a measurement beam. The intensity change of the interference light is detected by the light detector 272, processed by the signal processing circuit 401, and the displacement ΔL1 between the retroreflector 300 and the interferometer 204 is measured using the PC 500 (see FIG. 2). ).

  The displacement meter 203 is a capacitive displacement meter or an eddy displacement meter, detects displacement with the reference sphere 202, processes it with the signal processing circuit 402, and uses the PC 500 to detect the reference sphere 202, the displacement gauge 203, and the like. Measure the displacement ΔL2 between (see FIG. 2). By adding ΔL1 and ΔL2 on the PC 500, the displacement ΔL between the retroreflector 300 and the reference sphere 202 can be determined (see FIG. 2).

  On the other hand, the other laser beam 104 split into two by NPBS 236 is the distance between the optical axis of laser beam 104 incident on retroreflector 300 and the center position of retroreflector 300 (hereinafter referred to as tracking error amount ΔTr Incident upon a light position detector 238 that can detect Here, the light position detector 238 can measure ΔTr by dividing it into components in two orthogonal directions. For example, as shown in FIG. 1, with the optical axis of the laser beam 104 emitted from the interferometer 204 as the Z axis, an axis perpendicular to the Z axis and in the horizontal direction is the X axis and an axis orthogonal to the Z axis and the X axis is Y As an axis, the light position detector 238 can detect an X-direction component ΔTrX of ΔTr and a Y-axis direction component ΔTrY. Therefore, signals corresponding to ΔTrX and ΔTrY are taken into PC 500 through signal processing circuit 403, and control signals according to the values of ΔTrX and ΔTrY are applied to motor drive circuits 404 and 405. According to the given control signal, the motor drive circuits 404 and 405 drive the supine angle motor 205 and the azimuth angle motor 206 to rotate the carriage 201 in the supine angle direction and the azimuth angle direction, and the retroreflector 300 is rotated. Control is performed so that the center position and the optical axis of the laser emitted from the interferometer 204 coincide with each other and tracking is performed.

Japanese Patent Application Publication No. 2007-057522 Patent No. 2603429 gazette U.S. Pat. No. 6,147,748

  However, in the conventional homodyne tracking type laser interferometer represented by the invention described in Patent Document 1, when the laser light is blocked due to the presence of an obstacle between the interferometer 204 and the retroreflector 300, etc. When the laser beam is blocked due to other reasons, the position of the retro reflector 300 may not be tracked. In this case, the laser beam 104 can be irradiated to the retroreflector 300 from the position of the main body 200 having the interferometer 204, and the light position detector 238 in the interferometer 204 can detect the reflected light from the retroreflector 300. Thus, it is necessary for the operator to go to the tracking laser interferometer and adjust either the position of the retro reflector 300 or the emission direction of the laser emitted from the laser interferometer 204. In addition, since this work is performed manually, temperature changes due to the movement of the human body at that time, vibrations and the generation of dust, etc. cause changes in the measurement environment, which is inconvenient for high precision measurement. Then, after installing the tracking type laser interferometer, the same problem occurs in order to manually perform the initial adjustment work and start the measurement.

  And such a situation was not peculiar to Patent Document 1, and had the problem of being common to Patent Documents 2 and 3.

  The present invention has been made to solve the above-mentioned conventional problems, and in the tracking type laser interferometer, it is possible to automatically return the tracking when the tracking can not be performed because the laser light is blocked or the like. Alternatively, it is an object of the present invention to provide a tracking type laser interferometer which enables automation of initial adjustment work at the start of measurement and a method of returning the same.

  A tracking type laser interferometer according to an embodiment of the present invention irradiates a laser beam toward a retroreflector which is an object to be measured, and causes interference between the laser beam and a laser beam reflected in the return direction by the retroreflector. In the tracking type laser interferometer, the displacement is detected using the retroreflector, and tracking is performed by the two-axis rotation mechanism using the change in the position of the optical axis of the reflected laser light. And an optical unit capable of emitting a diffused laser beam in which a beam is diffused along a predetermined plane, and capable of rotating one axis of the two-axis rotating mechanism.

  Further, the optical unit may be interlocked with the rotation operation of an axis orthogonal to an axis perpendicular to the predetermined surface in the two-axis rotation mechanism.

  Furthermore, the optical axis of the laser beam may be parallel to the predetermined plane.

  Further, the two-axis rotation mechanism includes an azimuth rotation mechanism capable of rotating in an azimuth direction and an elevation rotation mechanism capable of rotation in a supine direction, and the azimuth rotation mechanism includes an azimuth motor and the azimuth. An azimuth rotation unit rotated by a corner motor, and the optical unit is a position at which the laser beam is incident when it is rotated in a depression angle direction by the elevation rotation mechanism of the azimuth rotation unit. It may be attached to

  Furthermore, the optical unit may include a reflection mirror that reflects the laser beam, and a cylindrical lens that diffuses the laser beam reflected by the reflection mirror and emits the diffused laser light as the diffused laser light.

  A return method of a tracking type laser interferometer according to another aspect of the present invention irradiates a laser beam toward a retroreflector which is an object to be measured, and a laser reflected in the return direction by the laser beam and the retroreflector In a tracking type laser interferometer in which displacement of a retroreflector is detected using interference with light and tracking is performed by a two-axis rotation mechanism using a change in position of an optical axis of the reflected laser light. The light irradiator provided on the two-axis rotation mechanism emits diffused laser light diffused along a plane including the optical axis of the reflected laser light when the tracking control is not performed. A diffusion movement in which the laser beam incident from the optical unit is diffused, wherein the rotational movement is performed about an axis orthogonal to an axis perpendicular to a predetermined plane of the two-axis rotation mechanism. The interferometer emits a laser beam to perform rotational movement about one axis of the two-axis rotational mechanism, and detects the diffused laser beam in an interferometer that detects interference between the laser beam and the reflected laser beam. Thus, a first rotation angle at which tracking can be controlled is determined, and the first rotation angle is moved by rotation about an axis perpendicular to the axis perpendicular to the predetermined plane, and the first rotation is performed. While maintaining the angle, by performing rotational movement with respect to the remaining axes and detecting the reflected laser beam, a second rotation angle that enables tracking control is determined to be centered on the remaining axes. By moving to a second rotation angle by rotation, it is possible to control the tracking.

  Further, the optical unit may perform rotational movement about an axis orthogonal to an axis perpendicular to the predetermined surface in the two-axis rotation mechanism.

  Furthermore, the optical axis of the laser beam may be parallel to the predetermined plane.

  Further, the two-axis rotation mechanism includes an azimuth rotation mechanism capable of rotating in an azimuth direction and an elevation rotation mechanism capable of rotation in a supine direction, and the azimuth rotation mechanism includes an azimuth motor and the azimuth. An azimuth rotation unit rotated by a corner motor, wherein the optical unit is attached to the azimuth rotation unit, and when the tracking control is not performed, the elevation unit rotates in the depression angle direction by the elevation rotation mechanism. The laser beam may be rotated to be incident on the optical unit.

  Furthermore, the optical unit may include a reflection mirror that reflects the laser beam, and a cylindrical lens that diffuses the laser beam reflected by the reflection mirror and emits the diffused laser light as the diffused laser light.

  According to the present invention, it is possible to automatically restore tracking without manual operation when tracking can not be performed because the laser beam is blocked. In addition, it is possible to automatically perform an initial adjustment operation at the start of measurement.

  Therefore, environmental changes due to human intervention can be avoided, and more accurate and stable measurement is possible.

It is a whole structure perspective view of the conventional tracking-type laser interferometer. It is a top view of the conventional tracking-type laser interferometer. It is a schematic block diagram of the conventional interferometer part. FIG. 1 is an overall configuration perspective view of a tracking laser interferometer according to a first embodiment of the present invention. It is a schematic block diagram of the optical unit concerning a 1st embodiment of the present invention.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the attached drawings. However, the present invention is not limited to the following embodiments. Further, in order to clarify the explanation, the following description and the drawings are simplified as appropriate.

Embodiment 1
A first embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is an overall configuration perspective view of a tracking type laser interferometer according to the present embodiment, and FIG. 5 is a schematic configuration view of an optical unit in the present embodiment.

  As shown in FIG. 4, this embodiment is a main component of a conventional homodyne tracking type laser interferometer, a light source unit 100, a main unit 200, a retroreflector 300, a circuit unit 400, and a PC 500. In the above, the optical unit 600, which is a characteristic element of the present embodiment, is added to the main body 200. Hereinafter, although the description of the conventional components is omitted, the functions of the above-described elements and the changes of the conventional components will be described.

  The optical unit 600 is attached to an azimuth angle rotation unit 207 which is a component of the two-axis rotation mechanism, as shown in FIG. The optical unit 600 is disposed at a position on the front side of the interferometer 204 so that the laser beam 104 from the interferometer 204 is incident when the carriage 201 is rotated in the depression angle direction. The optical unit 600 diffuses the incident parallel laser beam 104 along a predetermined plane, and emits the diffused laser beam as the diffused laser beam 700. In this example, the diffused laser beam 700 is a laser beam diffused along a plane parallel to the Z axis. The diffused laser beam 700 is diffused in a predetermined plane, so that the diffused laser beam 700 becomes a laser beam diffused in a substantially fan shape. The optical unit 600 emits the diffused laser beam 700 so that the optical axis of the incident laser beam 104 and the emitted diffused laser beam 700 are located on the same plane.

  The motor 205 for supine angle is rotated to rotate the carriage 201 in the depression angle direction, and the carriage 201 is maintained at a predetermined supine angle. At this time, the laser beam 104 from the interferometer 204 is incident on the optical unit 600. When the laser beam 104 from the interferometer 204 passes through the optical unit 600, the diffused laser beam 700 is emitted from the optical unit 600.

  Since the optical unit 600 is attached to the azimuth angle rotation unit 207, the rotation of the diffusion laser beam 700 is interlocked with the rotation of the azimuth angle motor 206, that is, interlocked with the rotational movement around the Y axis. Therefore, by rotating the azimuth angle motor 206, it is possible to efficiently rotate and irradiate the diffused laser light 700 in the azimuth angle direction.

  By rotating the diffusion laser beam 700 in the azimuthal direction while maintaining the carriage 201 at a predetermined supine angle, the diffusion laser beam 700 is irradiated to the area in front of the optical unit 600. When a part of the diffused laser light 700 is irradiated to the retroreflector 300 while the diffused laser light 700 is irradiated, a part of the diffused laser light 700 is reflected by the retroreflector 300 and the reflected laser beam As (laser light), the light returns to the optical unit 600 and is incident. For this reason, when the diffused laser beam 700 is rotated in a certain azimuth direction, if the laser beam which is a part of the diffused laser beam 700 is returned to the optical unit 600 and is incident, From the orientation, the approximate orientation in which the retroreflector 300 is present can be easily grasped.

  The optical unit 600 will be described with reference to FIG. In FIG. 5, for the sake of easy understanding, the elements other than the carriage 201, the interferometer 204, the optical unit 600, the diffusion laser beam 700, and the retro reflector 300 are not shown.

  The optical unit 600 includes a reflection mirror 601 and a cylindrical cylindrical lens 602. The optical unit 600 causes the laser beam 104 from the interferometer 204 to be reflected by the reflection mirror 601 and to be incident on the cylindrical lens 602. The cylindrical lens 602 diffuses the laser beam light 104 incident from the cylindrical lens 602 to a predetermined surface and emits it. The reflection mirror 601 and the cylindrical lens 602 are adjusted and disposed so that the optical axis of the laser beam 104 from the interferometer 204 and the diffused laser light 700 are located on the same YZ plane. Thus, the optical unit 600 can be realized with an inexpensive and simple configuration.

  Next, the return procedure in the present embodiment will be described.

  First, when an obstacle or the like is present between the main body 200 and the retroreflector 300 and the laser beam 104 is blocked, the amount of light detected by the light position detector 238 in the interferometer 204 becomes zero. Then, a signal of light amount 0 is sent from the light position detector 238 to the PC 500 via the signal processing circuit 403. Based on the signal, the PC 500 determines that the laser beam 104 from the interferometer 204 has been blocked, and the tracking control of the tracking type laser interferometer by the two-axis rotation mechanism in the motor drive circuits 404 and 405 (control of tracking) Stop. At the same time, the measurement of the displacement by the output of the light detector 272 is stopped.

  Next, the PC 500 causes the motor drive circuit 404 to rotate the supine angle motor 205 to rotate the carriage 201 to the predetermined supine angle, to stop and maintain the carriage 201 at the predetermined supine angle. Then, the PC 500 causes the interferometer 204 to emit the laser beam 104 and causes the laser unit 104 to enter the optical unit 600, and causes the optical unit 600 to emit the diffused laser beam 700.

  Next, the PC 500 sends a signal to the motor drive circuit 405, and causes the azimuth angle motor 206 to rotate the azimuth angle rotation unit 207. In conjunction with the rotation of the azimuth angle rotation unit 207, the diffused laser light 700 emitted from the interferometer 204 also rotates. At the same time, the PC 500 starts measuring the signal sent from the interferometer 204 via the signal processing circuit 401.

  When a part of the diffused laser beam 700 is reflected by the retroreflector 300 while irradiating the diffused laser beam 700 while rotating, the reflected minute laser beam interferes via the optical unit 600. It returns to the total 204 and is incident on the light position detector 238. Since the light quantity of the laser beam incident on the light detector 238 at this time is smaller than that of the laser beam 104, the electronic circuit 403 may have a signal amplification function to increase the signal gain. The light detector 238 can detect not only the light quantity of the laser beam but also the place where the laser beam is incident.

  When the PC 500 satisfies a stop condition exceeding a predetermined threshold value with respect to the light amount detected by the light position detector 238, the PC 500 is positioned at a rotation angle (first rotation angle) satisfying the stop condition. Stop and maintain azimuthal rotation.

  Finally, the PC 500 sends a signal to the motor drive circuit 404, rotates the interferometer 204 in the elevation direction by the motor for supposing and supposing angles 205, and the position of the rotation angle at which the light position detector 238 in the interferometer 204 can detect the light quantity. Stop and maintain at (2nd rotation angle). When the laser beam 104 from the interferometer 204 directly enters the retroreflector 300, the tracking error signal (ΔTrY) output from the light position detector 238 to the signal processing circuit 403 falls within the measurement range. In this state, the laser light from the interferometer 204 is adjusted within the measurement range of the light position detector 238, and the tracking error signals ΔTrX and ΔTrY output from the light position detector 238 are usually measured. It is possible to resume control of tracking of the tracking laser interferometer of

  As described above, since the tracking type laser interferometer can be controlled and returned by each input signal on the PC 500, the laser beam 102 emitted from the main body 200 is blocked as described above. When tracking can not be performed, it is possible to automatically return the tracking laser interferometer without relying on manual operation. Therefore, the initial adjustment work at the start of measurement, which is the same situation, can be automated. Thus, environmental changes due to human intervention can be avoided, and more accurate and stable measurement can be performed.

  The measurement and tracking method of the displacement by the tracking type laser interferometer is the same as that of the conventional example, and thus will not be described.

  Therefore, according to the present embodiment, the displacement measurement function of the conventional homodyne tracking laser interferometer can be obtained according to the present embodiment without requiring significant addition and change of components as compared with the conventional homodyne tracking laser interferometer. In addition, it is possible to automatically realize the return operation of the tracking laser interferometer.

  Furthermore, the optical unit 600 according to the present embodiment can be realized by an inexpensive and simple configuration, and such an optical unit 600 is attached to the azimuth angle rotation unit 207 to interlock the rotation of the diffused laser beam 700 with the rotation in the azimuth direction. By configuring as described above, it is not necessary to newly prepare a mechanism for causing the optical unit 600 itself to rotate independently, and the return operation of the automatic tracking type laser interferometer is realized by an inexpensive and simple configuration. It is possible.

<Other Embodiments>
Further, the arrangement of the optical unit 600 is not limited to the azimuth angle rotation unit 207, and the laser beam 104 from the interferometer 204 can be incident as long as it does not interfere with the tracking control of a normal tracking type laser interferometer. May be placed at any position.

  Further, there are many methods of generating the diffused laser light by the optical unit 600, and the method of generating the diffused laser light is not limited in the present invention. For example, a rod lens may be used instead of the cylindrical lens 602.

  In the above embodiment, the present invention is applied to a tracking type laser interferometer using a reference sphere, but the effect of the present invention can be achieved even if the reference sphere is not used. It is obvious that the present invention is also applicable to the tracking type laser interferometer described in No.3.

  The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the scope of the present invention.

100 light sources,
101 frequency stabilized He-Ne laser light source,
102 lenses,
103 optical fiber,
104 laser beams,
200 body,
201 carriage,
202 reference sphere,
203 displacement gauge,
204 interferometer,
222 collimator lens,
230 polarization beam splitter (PBS),
236 Non-Deflecting Beam Splitter (NPBS),
238 light position detector,
270 flat mirrors,
272 light detectors,
205 Motor for supine angle,
206 azimuth motor,
207 azimuth rotation,
300 retro reflectors,
400 circuit parts,
401 to 403 signal processing circuit,
404-405 motor drive circuit,
500 pcs,
600 optical units,
601 reflection mirror,
602 cylindrical lens,
700 diffused laser light

Claims (10)

The laser beam output from the light source is branched into a first laser beam and a second laser beam, and the first laser beam is irradiated toward a retroreflector which is an object to be measured, and the second laser beam And detecting the displacement of the retroreflector using interference of the third laser beam reflected in the return direction by the retroreflector, and using the change in the position of the optical axis of the third laser beam to obtain two axes. In a tracking type laser interferometer in which tracking is performed by a rotation mechanism,
An optical unit capable of diffusing the first laser beam along a predetermined surface and irradiating the retroreflector , and capable of rotating one axis of the two-axis rotating mechanism.
A tracking type laser interferometer characterized by comprising: The optical unit is
It is possible to interlock with the rotational movement of an axis perpendicular to the axis perpendicular to the predetermined plane in the two-axis rotation mechanism,
The tracking laser interferometer according to claim 1, characterized in that The optical axis of the first laser beam before being diffused by the optical unit is parallel to the predetermined plane,
The tracking type laser interferometer according to claim 1 or 2 characterized by things. The two-axis rotation mechanism includes an azimuth rotation mechanism capable of rotating in an azimuth direction and a supination angle rotation mechanism that can rotate in a supination direction.
The azimuth rotation mechanism includes an azimuth motor and an azimuth rotation unit rotated by the azimuth motor.
The optical unit is attached to a position of the azimuth rotation unit where the first laser beam is incident when it is rotated in the depression angle direction by the supine angle rotation mechanism.
The tracking type laser interferometer according to any one of claims 1 to 3, characterized in that: The optical unit is
A reflecting mirror that reflects the first laser beam ;
And a cylindrical lens for illuminating said retroreflector by diffusing the reflected first laser beam by the reflecting mirror,
The tracking type laser interferometer according to any one of claims 1 to 4, comprising: A laser beam is irradiated toward a retroreflector which is an object to be measured, and the displacement of the retroreflector is detected by using the interference between the laser beam and the laser beam reflected in the return direction by the retroreflector, and the reflection In a tracking type laser interferometer in which tracking is performed by a two-axis rotation mechanism using a change in the position of the optical axis of the laser beam,
If the tracking control is not performed,
A light irradiator provided on the two-axis rotation mechanism emits diffused laser light diffused along a plane including the optical axis of the reflected laser light, and a predetermined one of the two-axis rotation mechanisms is emitted. Perform rotational movement about an axis perpendicular to the axis perpendicular to the plane,
The optical unit emits the diffused laser beam obtained by diffusing the incident laser beam, and rotational movement is performed around one axis of the two-axis rotation mechanism,
An interferometer for detecting the interference between the laser beam and the reflected laser beam detects the diffused laser beam, thereby determining a first rotation angle that enables tracking control, and is perpendicular to the predetermined plane. Move to a first rotation angle by rotation around an axis orthogonal to the
While maintaining the first rotation angle, rotational movement is performed on the remaining axes, and the reflected laser light is detected to obtain a second rotation angle that enables tracking control, and the remaining rotation angle is determined. By moving to the second rotation angle by rotating around the axis,
A return method of a tracking type laser interferometer characterized in that control of the tracking is enabled. The optical unit performs rotational movement about an axis orthogonal to an axis perpendicular to the predetermined plane in the two-axis rotation mechanism.
7. The method according to claim 6, wherein the tracking laser interferometer returns. The optical axis of the laser beam is parallel to the predetermined plane,
The return method of the tracking type laser interferometer according to claim 6 or 7, characterized in that The two-axis rotation mechanism includes an azimuth rotation mechanism capable of rotating in an azimuth direction and a supination angle rotation mechanism that can rotate in a supination direction.
The azimuth rotation mechanism is
Azimuth motor,
An azimuth rotation unit rotated by the azimuth motor;
The optical unit is attached to the azimuth rotation unit.
If the tracking control is not performed,
The laser beam is caused to enter the optical unit by being rotated in the depression angle direction by the supination angle rotation mechanism.
The method according to any one of claims 6 to 8, wherein the tracking type laser interferometer is restored. The optical unit is
A reflecting mirror that reflects the laser beam;
A cylindrical lens that diffuses a laser beam reflected by the reflection mirror and emits the diffused laser beam;
The method according to any one of claims 6 to 9, further comprising:

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