JP2004251785A - Light tracking type laser interferometer by oscillating optical lever using spherical surface motor, and coordinate measuring method using this device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser interferometer having an oscillating optical lever driven with a spherical surface motor. <P>SOLUTION: The light tracking type laser interferometer using an oscillating optical lever in a mechanism for varying irradiation direction of an object light in the interference metering optical system, is provided with an oscillating mechanism 3 to widen irradiation angle range by driving the mechanism 3 with the spherical surface motor 1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ray-tracking laser interferometer that measures the coordinates of a retro-reflector while tracking the retro-reflector moving in a three-dimensional space.
[0002]
[Prior art]
As a conventional ray-tracking type laser interferometer for measuring the coordinates of a retro-reflector while tracking the retro-reflector moving in a three-dimensional space, there is, for example, an apparatus as shown in FIG. This tracking type laser interferometer is configured such that the reflection mirror 610 at the last stage can rotate around the X axis and the Y axis via rotating bodies 614 and 616, respectively. Thereby, the retroreflector provided on the moving body can be irradiated with the laser beam. That is, the rotating body 614 supporting the reflection mirror 610 is rotatably supported around the X axis via the bearings 612 and 612 with respect to the rotating body 616, and the rotating body 616 is supported by the bearing 620 with respect to the fixed base 618. , 620 so as to be rotatable around the Y axis.
[0003]
A laser beam oscillated from a laser light source (not shown) is split by a polarizing beam splitter 622, and one of the laser beams is incident on a corner cube 624, and the reflected light is transmitted to a detection unit 626 via the beam splitter 622. Incident. On the other hand, the other split laser beam is bent coaxially with the Y axis by the prism 628, and then bent coaxially with the X axis via the prisms 630 and 632 supported by the rotating body 616. 610. Therefore, the laser beam emitted from the reflection mirror 610 rotates when the rotating body 616 rotates around the Y axis, and moves in the vertical direction when the rotating body 614 rotates around the X axis. The laser beam can be emitted toward the retroreflector provided on the moving body by controlling the rotation of the moving body 616 and the rotating body 616, respectively. The reflected light from the retroreflector provided on the moving body passes through the reflection mirror 610, the prisms 632, 630, and 628 in this order as measurement light, and is incident on the detection unit 626 via the polarization beam splitter 622. You. The detection unit 626 measures the movement of the moving body based on the interference between the reference light reflected by the corner cube 624 and the measurement light reflected from the retroreflector.
[0004]
However, recently, there has been an increasing demand for higher resolution of the device, and with this device, it has been difficult to maintain the currently required eccentricity of the measurement origin at an accuracy of 1 μm or less. The reason for this will be described with reference to FIG. 7 which schematically shows FIG. 6. One is a virtual axis of a cylinder having a certain cross-sectional area where the laser optical axis 601 of the laser beam emitted from the reflection mirror 610. Therefore, mechanical contact is impossible, and the other is that it is difficult to match the XY gimbal rotation center line 602 with the laser optical axis 601 in three axes.
[0005]
As an improvement over this, there is a "beam tracking laser interferometer using a swinging light lever disclosed in Patent Document 1. This device has a swinging light lever mechanism in the optical path, and has a swing movement. A laser beam is made incident on the center of the reflecting surface of the light lever so that the reflected light beam can be changed in an arbitrary direction. As shown in FIG. The eccentricity of the surface is suppressed to about 0.1 to 0.25 μm so that the required eccentricity of the measurement origin can be maintained at 1 μm or less. The hemisphere 202 is brought into contact with the V-shaped surface of the V-plate 205 fixed to the upper surface, and the hemisphere 202 is made up of three steel balls 241 of a three-sphere spherical seat by the tension of two right and left tension springs 207 inclined from the vertical direction. And the spherical contact 204 is the same as the V-shaped surface. It is structured to sometimes come into pressure contact.
[0006]
FIG. 9 is a cross-sectional view of a laser interferometer using such a swinging motion lever, and the return light from the retro-reflector 100 has a neck as shown by the optical axis of the laser light indicated by a two-dot chain line. The light is reflected at the center 220 of the upper surface of the hemisphere 202 of the swinging motion lever 201, passes through the plane reflecting mirror 104 and the right-angle prism 105, and reaches the beam splitter 106. About の of this return light is reflected here and enters the four-divided light receiving element 107. The four-divided light receiving element 107 drives the swinging motion lever 201 by the X moving table 110 and the motor 115 and the Y table 111 and the motor so that the laser beam is accurately irradiated on the reflection center point 101 of the retro-reflector 100. In the adjustment method, when the retroreflector 100 is stationary, the electric outputs abcd are adjusted so as to be all equal, and X is set to the target of (a + c) − (b + d) = 0 following the movement of the retroreflector 100. By performing position control in the axial direction and performing Y-axis control with the target of (a + b)-(c + d) = 0, the position tracking of the retro-reflector 100 becomes possible.
[0007]
On the other hand, in FIG. 9, a portion 108 surrounded by a dashed line is a configuration of the length measuring interferometer, and the optical path length from the center 109 to the center 220 of the upper surface of the swinging light lever 201 is constant. By measuring the optical path length from the center of the retro-reflector 100 to the center 101 of the retro-reflector 100, the value of the moving distance L2-L0 of the retro-reflector 100 between the center 101 of the retro-reflector 100 and the center 220 of the upper surface of the swinging light lever 201 is calculated. Interference measurement can be performed based on the laser wavelength.
[0008]
[Patent Document 1]
JP-A-2002-98510 (paragraph numbers [0004] to [0008] and [0012] to [0018], FIGS. 1, 3, 8, and 9)
[0009]
[Problems to be solved by the invention]
However, in the above-described conventional technology, the spherical contact 204 at the lower end moves upward with the rotation of the hemispherical mirror 202 of the swinging light lever 201. Therefore, the rotation angle of the hemispherical mirror is limited within a range where the contact between the spherical contact 204 and the V plate 205 is maintained, and the beam scanning range of the beam tracking type laser interferometer is narrowed. there were.
[0010]
Therefore, the present invention uses a spherical motor for the driving mechanism of the swinging light lever, so that even when the rotation angle of the hemispherical mirror is increased, the rotation angle of the hemispherical mirror is not restricted, and the ray tracking is performed. It is an object of the present invention to provide a laser tracking type laser interferometer using a swiveling lever using a spherical motor and a coordinate measuring method using the device, which can expand the beam scanning range of the laser interferometer of the type.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is a beam tracking type laser interferometer using a swinging motion lever in a mechanism for changing an irradiation direction of object light in an interferometer optical system, It is characterized by having a swing mechanism for expanding the irradiation angle range by being driven by a spherical motor.
According to the second aspect of the present invention, a beam splitter different from that used for interference measurement is provided in the return optical path of the interference optical system, and a part of the return light is guided to the four-divided light receiving element, which is obtained by the light receiving element. It is characterized by being able to control the attitude by swinging the head by feedback-controlling the rotation angle of the spherical motor using the electrical output as an input to the control device and to automatically track the retro-reflector.
The invention according to claim 3 is characterized in that the spherical motor is configured such that a tilt axis drive is constituted by an arc-shaped linear motor and a twist axis drive is constituted by a rotary motor.
According to a fourth aspect of the present invention, there is provided a light-tracking type laser interferometer using a swinging light lever using the spherical motor according to the first embodiment, and measurement is performed from the laser interferometer. The position of the retro-reflector can be determined from the distance data to the target retro-reflector and the direction data of the retro-reflector viewed from the laser interferometer measured by the angle of the two axes of the spherical motor. And
According to a fifth aspect of the present invention, the position of the retro-reflector to be measured is determined by using four sets of a beam tracking type laser interferometer using a swinging light lever using the spherical motor according to the first aspect. By performing tracking measurement for a predetermined number of times, the relative position of the ray-tracking laser interferometer and the distance between the ray-tracking laser interferometer and the retro-reflector cannot be measured even when the retro-reflector cannot be measured. It is characterized in that the position can be determined.
[0012]
According to the laser interferometer of the beam tracking type using the swinging light lever using the spherical motor, the swinging movement light lever converts the motor into a coupling, a feed screw, an X / Y table, a V plate, a spherical contactor or the like. Without the need for the rotation transmitting mechanism, the optical lever connecting rod can be directly fixed to the rotor of the direct-acting circular-arc linear motor and driven to rotate, so that it can move over the entire rotatable range of the spherical motor. Is possible, the beam scanning range of the beam tracking type laser interferometer can be expanded, and the drive error decreases as the mechanism becomes simpler.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a beam tracking type laser interferometer using a swiveling lever using a spherical motor according to an embodiment of the present invention.
FIG. 2 is a cutaway perspective view of the biaxial actuator shown in FIG.
FIG. 3 is a structural explanatory view of the two-axis actuator shown in FIG.
FIG. 4 is a front view of the quadrant light receiving element shown in FIG.
In FIG. 1, FIG. 1 (b) is a side sectional view of a ray tracking type laser interferometer, and FIG. 1 (a) is a top view thereof. In the figure, reference numeral 1 denotes a two-axis actuator constituted by a two-axis composite spherical motor. Reference numeral 2 denotes a mount for the biaxial actuator 1, and reference numeral 4 denotes a hemispherical part of the swinging lever 3, which has a reflecting surface on its upper surface for irradiating a retroreflector with laser light.
[0014]
A connecting rod 5 is connected to the rotating shaft of the biaxial actuator 1. Reference numeral 6 denotes a steel ball having a spherical seat on which the hemispherical portion 4 is set. Reference numeral 7 denotes a mirror for positioning the laser beam. Reference numeral 8 denotes a laser beam for measurement, which is introduced from an external oscillation light source through an optical fiber. Reference numeral 9 denotes a laser interferometer, and reference numeral 10 denotes a laser interferometer mounting base on which the laser interferometer 9 is mounted and installed on the biaxial actuator 1. Reference numeral 11 denotes a beam splitter for separating the laser beam 8 into irradiation light and reference light for measurement. Reference numeral 12 denotes a beam splitter for inputting return light to a four-division light receiving element 13 for direction tracking. Reference numeral 14 denotes an optical fiber for taking an interference signal of the return light and the reference light reflected from the retroreflector into a distance measuring circuit. Reference numeral 15 denotes a center point of the reflecting surface of the hemispherical portion 4. Reference numeral 16 denotes a polarizing plate for measurement.
[0015]
In FIG. 2, reference numeral 21 denotes a tilt shaft (up and down) rotor of a spherical motor, which is constituted by a permanent magnet having teeth. Reference numeral 24 denotes a tilt axis coil that drives the tilt axis rotor 21. The tilt axis rotor 21 and the tilt axis coil 24 constitute an arc-shaped linear motor. Reference numeral 22 denotes a tilt axis origin sensor that detects the origin position of the tilt axis. Reference numeral 25 denotes a twist shaft (horizontal direction) rotor constituted by a rotary motor coaxial with the tilt shaft motor, reference numeral 26 denotes a twist shaft coil of the stator, and reference numeral 23 denotes a twist axis origin sensor for detecting the origin position of the twist axis. The connection shaft 5 of the hemisphere 4 is connected to the rotation shaft of the tilt shaft rotor 21 by a connection jig 27. Reference numeral 28 denotes an upper plate of the biaxial actuator 1, reference numeral 29 denotes a tilt shaft frame portion, reference numeral 30 denotes a twist shaft frame portion, and reference numeral 32 denotes a slip ring having a shaft tube structure for preventing the wiring bundle from being twisted by the rotation of the shaft. . Reference numeral 33 denotes an ambient temperature detecting unit for correcting the temperature of the laser wavelength.
[0016]
Next, the operation will be described.
First, for the biaxial actuator 1, as shown in FIG. 3, the connecting rod 5 supporting the hemispherical portion 4 of the swinging light lever 3 is screwed by the rotating shaft 40 of the tilt shaft rotor 21 and the connecting jig 27. Since there is no stop / fixed connection, there is no spherical contact, V plate, X / Y table for transmitting motor output, feed screw, etc. Accurate with no loss.
The tilt shaft rotor 21, which is a permanent magnet type rotor of the linear motor, is driven by a tilt shaft coil 24 which is fastened to the stator 41 and is arranged at a predetermined interval from the tooth row on the rotor side to rotate the arc in the vertical direction. I do.
[0017]
On the other hand, a rotary motor composed of a twist shaft rotor 25 and a stator-side twist shaft coil 26 for driving the same and arranged coaxially with the tilt shaft motor rotates in the horizontal direction. Since the rotary shaft 40 performs a combined motion on the X and Y spherical surfaces by the motor having two degrees of freedom, the hemispherical portion 4 connected thereto can be driven on the spherical surface. The rotation angle in this case depends on the moving range of the tilt shaft rotor 21 of the linear motor.
Further, in this apparatus, as shown in FIG. 3 (b), ventilation holes 42 and 43 are provided near the upper and lower motors, respectively, to cool the heat generated by the motors and to suppress the temperature rise in order to avoid fluctuations due to temperature changes. I have.
[0018]
In order to track the position of an object to be measured by a beam tracking type laser interferometer using a swinging light lever directly rotated by such a two-axis actuator (spherical motor) 1, a measuring laser beam 8 is first reflected by a retro-reflector. Is reflected at the center 15 of the reflecting surface of the hemispherical part 4 of the swinging motion lever 3 and is bent in the X direction by the positioning mirror 7 to enter the beam splitter 12. About half of the return light is reflected and input to the four-divided light receiving element 13. The four-divided light receiving element 13 is formed of four light receiving surfaces ABCD as shown in FIG. 4, and the two-axis actuator 1 is arranged so that the four electric outputs abcd become equal when the retroreflector is stationary. The direction of the swinging motion lever 3 is adjusted by this, and the light is reflected at the center point 15. Based on the state in which the laser light is accurately reflected at the center point of the retroreflector, when the retroreflector moves from this state, the electrical Since the balance of the output abcd is lost, the rotation angle of each motor of the two-axis actuator 1 is, for example, (a + c)-(b + d) = 0 in the X-axis direction and (a + b)-(c + d) in the Y-axis direction. By controlling the position so that = 0, the balance of the electric output abcd can be adjusted and the moving position of the retro-reflector can be accurately tracked.
[0019]
Next, in the distance measurement by the laser interferometer of the beam tracking type laser interferometer, the laser beam 8 was irradiated with the reference laser beam by the beam splitter 11 while tracing the retro-reflector moved as described above. The laser beam is divided into laser beams, and the irradiation laser beam is applied to the center point of the retro reflector through the beam splitter 12, the mirror 7, and the oscillating motion light reflecting surface 15, and the reflected return wave is oscillated motion lever. After passing through the reflecting surface 15 and the mirror 7, the return wave for the position control to the four-divided light receiving element 13 by the beam splitter 12 and for the measurement by the beam splitter 12 interfere with the previous reference wave by the beam splitter 11 for the measurement. The interference wave is counted by a counter of a measuring circuit (not shown), and the distance to the retroreflector is calculated based on the wavelength of the laser light.
[0020]
As described above, the distance of the moved object to be measured to the retroreflector can be calculated. However, if the direction cannot be specified, the three-dimensional position cannot be determined.
Therefore, for example, the distance r from the measured origin (the reflection center 15 of the hemispherical portion 3) to the retroreflector of the measured object, the horizontal angle and the vertical angle of the retroreflector viewed from the origin are tilted. The position of the three-dimensional retro-reflector can be determined from the detection values of the axis origin sensor 22 and the twist axis origin sensor 23 and displayed on a spherical surface having a radius r by polar coordinates.
[0021]
As described above, the three-dimensional position of the retro-reflector can be measured with one set of the laser interferometer, but a method of using three to four sets of laser interferometers for more precise and high-resolution measurement. There is.
As shown in FIG. 5, a measurement unit (laser interferometer) is installed at three locations 01, 02, and 03, and a retroreflector is installed at 100. The distance L11, L12, L13 from each measurement unit to the center 101 of the retro-reflector 100 is measured. Here, if the relative positions of the measuring units 01, 02, and 03 are measured in advance, three-sided surveying (not the conventional triangulation, but the three-sided The coordinates of the center position 101 can be uniquely determined based on the principle of (method of obtaining three-dimensional coordinates from distance).
However, it is very difficult to accurately measure the positional relationship between the measurement units 01, 02, and 03 with an accuracy of 1 μm or less. Furthermore, when an incremental counter is used for the measuring unit, only the movement amount of the retro-reflector can be measured, and a relative measurement by comparison can be performed, but the absolute distance between the measuring unit and the retro-reflector can be measured. Is impossible.
However, according to the self-calibration method described below, the absolute distance can be measured, and thereby the coordinates of the center 101 of the retroreflector 100 can be measured by the principle of trilateration.
[0023]
In the self-calibration method, a fourth measurement unit 04 is used in addition to the measurement units 01, 02, and 03. First, the retroreflector 100 is installed at an arbitrary position, and the four reflectors are used to measure the retroreflector 100 while arbitrarily moving, and the measurement is repeated. That is, if the retroreflector 100 is moved n times, 4 × n measurement values can be obtained.
At this point, the unknowns are first the three-dimensional coordinates of the measurement point 100, which are three unknowns. Since the measurement was performed n times, there will be a total of 3 × n unknowns. In addition, there are six unknowns relating to the positional relationship of the measurement unit and three unknowns relating to the initial position of the retro-reflector. Therefore, the total number of unknowns is 3 × n + 6 + 3.
[0024]
On the other hand, since there are 4 × n distance measurement values by the measurement units 01 to 04, the equation 3 × n + 6 + 3 = 4 × n is solved, and nine points are measured from n = 9 to obtain nine simultaneous equations. , All these unknowns can be mathematically uniquely determined. The principle of the self-calibration method has been described above. With this method, once the positional relationship between the measurement units and the initial distance to the retroreflector can be determined, even if the retroreflector moves to an arbitrary location thereafter, it is applied to each measurement unit. The position of the retroreflector can be determined from the measurements of the equipped laser interferometer by the principle of trilateration. If nine or more measurement points can be used for the calculation for determining the unknown number, the equation is over-constrained and cannot be solved. In this case, the determination may be made using the least squares method.
[0025]
【The invention's effect】
As described above, according to the present invention, a beam tracking type laser interferometer using a swinging motion lever as a mechanism for changing the irradiation direction of object light in an interferometer optical system is driven by a spherical motor. A tilting mechanism that expands the irradiation angle range by guiding a part of the return light to the four-divided light receiving element, and using the electric output obtained by the light receiving element as an input to the control device, and setting the tilt axis to a circular arc By controlling the rotation angle of a spherical motor with a twisted shaft consisting of a rotary motor with a type linear motor, this attitude can be controlled by swinging the head, enabling the retro-reflector to be automatically tracked and a neck using a spherical motor. By using four sets of beam tracking laser interferometers with swinging motion levers, the position of the retroreflector to be measured can be tracked and measured a predetermined number of times. The distance between mutual positional relationship and light tracking type laser interferometer device and retro relay selector of the tracking type laser interferometer system has to be able to determine the position of the retroreflector in the case can not be measured,
There is an effect that the light beam scanning range of the light beam tracking type laser interferometer can be expanded, and the measurement range can be expanded as compared with the related art.
In addition, the degree of freedom in the arrangement of the ray-tracking laser interferometer is increased, and in the case of the self-calibration method using four sets of measurement units, the measurement accuracy is greatly affected by the arrangement. There is an effect that is improved.
In addition, since the tilt axis motor is composed of a direct acting linear motor, the intermediate transmission mechanism such as the X, Y table, ball screw, V plate, and spherical contact is eliminated, and the direct connection rod is fixed to the rotor and driven. The operation can be simplified, the operation error can be reduced, the control can be simplified, and more accurate measurement can be performed.
In addition, when a retro-reflector is attached to the end of the working axis of an industrial robot and tracking is performed with a laser interferometer, it is possible to detect the positioning error of the robot. This eliminates the need for the program correction work performed in the actual work site, and allows the positioning programming work to be completed using the desk-top programming work. This has the effect of greatly reducing the work time.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a beam tracking type laser interferometer using a swinging light lever using a spherical motor according to an embodiment of the present invention.
FIG. 2 is a cutaway perspective view of the biaxial actuator shown in FIG.
FIG. 3 is a structural explanatory view of the two-axis actuator shown in FIG. 2;
FIG. 4 is a front view of the quadrant light receiving element of FIG.
FIG. 5 is a principle diagram of three-side measurement by the laser interferometer shown in FIG. 1;
FIG. 6 is a sectional view of a conventional laser interferometer.
7 is an explanatory diagram of a three-axis intersection of the laser interferometer shown in FIG. 6;
FIG. 8 is a front view of a swinging light lever used in a conventional laser interferometer.
FIG. 9 is a cross-sectional view of a conventional laser interferometer of a light-tracking type using a swinging light lever.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 2-axis actuator 2 2-axis actuator mounting base 3 Swing motion optical lever 4 Hemisphere part 5 Connecting rod 6 Steel ball 7 Alignment mirror 8 Laser light 9 Laser interferometer 10 Laser interferometer mounting base 11, 12 Beam splitter 13 4 Divided light receiving element 14 Interference signal 15 Reflection center point 16 Polarizer 21 Tilt axis rotor 22 Tilt axis origin sensor 23 Twist axis origin sensor 24 Tilt axis coil 25 Twist axis rotor 26 Twist axis coil 27 Connecting jig 28 Upper plate 29 Tilt axis portion Frame 30 Twist shaft frame 32 Slip ring 33 Ambient temperature sensor 41 Stator 42, 43 Ventilation hole 100 Retro reflector 101 Retro reflector center

Claims (5)

In a beam tracking type laser interferometer using a swinging motion lever as a mechanism to change the irradiation direction of the object light in the interferometer optical system,
A beam interfering laser interferometer using a swaying motion lever using a spherical motor, comprising a swaying mechanism that expands an irradiation angle range by being driven by a spherical motor. Provide another beam splitter for interference measurement in the return optical path of the interference optical system, guide a part of the return light to the four-divided light receiving element, and input the electrical output obtained by the light receiving element to the control device, 2. A beam tracking method using a swinging light lever using a spherical motor according to claim 1, wherein the attitude of the swinging motion is controlled by feedback control of the rotation angle of the spherical motor, and the retro-reflector can be automatically tracked. Laser interferometer. 2. The laser according to claim 1, wherein the spherical motor includes a circular-arc linear motor for driving the tilt axis and a rotary motor for driving the twist axis. Interferometer. Using one set of a beam tracking type laser interferometer using a swinging light lever using the spherical motor according to claim 1, distance data from the laser interferometer to the retroreflector to be measured, A head movement light using a spherical motor, wherein the position of the retro-reflector can be determined from directional data of the retro-reflector viewed from the laser interferometer measured by the angles of two axes of the spherical motor. A coordinate measuring method using a laser interferometer with a beam tracking type using a lever. The position of a retroreflector to be measured is tracked and measured a predetermined number of times by using four sets of a laser interferometer of a beam tracking type using a swinging light lever using a spherical motor according to claim 1, whereby the light beam is measured. It is characterized in that the position of the retro-reflector can be determined even when the positional relationship between the tracking laser interferometers and the distance between the ray-tracking laser interferometer and the retroreflector cannot be measured. A coordinate measuring method using a beam tracking type laser interferometer using a swinging light lever using a spherical motor.

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