JP3800541B2 - Beam tracking type laser interferometric length measuring device by swinging optical lever using spherical motor and coordinate measuring method using the device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a beam tracking laser interference length measuring device that measures the coordinates of a retroreflector while tracking the retroreflector moving in a three-dimensional space.
[0002]
[Prior art]
As a conventional beam tracking laser interferometer for measuring the coordinates of a retroreflector while tracking a retroreflector moving in a three-dimensional space, for example, there is an apparatus as shown in FIG. This tracking laser interferometer is configured so that the last-stage reflection mirror 610 can rotate about the X axis and the Y axis via the rotators 614 and 616, respectively. As a result, the laser beam can be applied to the retroreflector provided on the moving body. That is, the rotating body 614 that supports the reflection mirror 610 is supported by the rotating body 616 so as to be rotatable around the X axis via the bearings 612 and 612, and the rotating body 616 is supported by the bearing 620 with respect to the fixed base 618. , 620, and is supported rotatably around the Y axis.
[0003]
A laser beam oscillated from a laser light source (not shown) is split by the polarization beam splitter 622, and one laser beam is incident on the corner cube 624, and the reflected light is transmitted to the detection unit 626 via the beam splitter 622. Incident. On the other hand, the other divided laser beam is bent on the same axis as the Y axis by the prism 628, and then bent on the same axis as the X axis via the prisms 630 and 632 supported by the rotating body 616. 610 is incident. Therefore, the laser beam emitted from the reflection mirror 610 turns when the rotating body 616 rotates around the Y axis, and moves up and down when the rotating body 614 rotates around the X axis. By controlling the rotation of 616 and 616, the laser beam can be emitted toward the retroreflector provided on the moving body. 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 enters the detection unit 626 via the polarization beam splitter 622. The 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, in recent years, there has been an increasing demand for higher resolution of the apparatus. With this apparatus, it has been difficult to maintain the eccentricity of the measurement origin that is currently required with an accuracy of 1 μm or less. The reason for this will be described with reference to FIG. 7 which is a schematic diagram of FIG. 6. One is a virtual axis of a cylinder in which the laser optical axis 601 of the laser beam emitted from the reflecting mirror 610 has a certain cross-sectional area. Therefore, mechanical contact is impossible, and the other is that it is difficult to match the three axes of the XY gimbal rotation center line 602 with the laser optical axis 601 together.
[0005]
As an improvement of this, there is a “light beam tracking laser interferometer using a swing motion optical lever” disclosed in Patent Document 1. This device is provided with a swing motion optical lever mechanism in the optical path, and the swing motion A laser beam is incident on the center of the reflecting surface of the light lever so that the reflected 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 made up of three steel balls 241 of a three-sphere spherical seat by the tension of the two left and right tension springs 207 inclined from the vertical direction so as to come into contact with the V-shaped surface of the V plate 205 fixed to the upper surface. And the spherical contactor 204 is the same as the V-shaped surface. It has a structure that sometimes makes pressure contact.
[0006]
FIG. 9 is a cross-sectional view of a laser interferometer that uses such a swing motion optical lever. Like the optical axis of the laser beam indicated by a two-dot chain line, the return light from the retroreflector 100 is reflected in the neck. The light is reflected at the center 220 of the upper surface of the hemisphere 202 of the swinging light lever 201, passes through the plane reflecting mirror 104 and the right-angle prism 105, and reaches the beam splitter 106. About 1/2 of the return light is reflected here and enters the quadrant light receiving element 107. The quadrant light receiving element 107 drives the swinging movement light lever 201 by the X moving table 110 and the motor 115, the Y table 111 and the motor so as to accurately irradiate the reflection center point 101 of the retroreflector 100 with the laser beam. In the adjustment method, when the retroreflector 100 is stationary, the electric outputs abcd are all adjusted to be equal, and the movement of the retroreflector 100 is followed to make (a + c) − (b + d) = 0 as a target X The position of the retroreflector 100 can be tracked by performing axial position control and performing Y-axis control with the target of (a + b) − (c + d) = 0.
[0007]
On the other hand, in FIG. 9, a portion 108 surrounded by an alternate long and short dash line is a configuration of a length measuring interferometer, and the optical path length from the center 109 to the upper surface center 220 of the swinging movement light lever 201 is constant. The distance L2-L0 of the retroreflector 100 from the center 101 of the retroreflector 100 to the upper surface center 220 of the swinging optical lever 201 is measured by measuring the optical path length from the center of the retroreflector 100 to the center 101 of the retroreflector 100. Interferometry can be performed based on the laser wavelength.
[0008]
[Patent Document 1]
JP 2002-98510 A (paragraph numbers [0004] to [0008] and [0012] to [0018], FIG. 1, FIG. 3, FIG. 8, FIG. 9)
[0009]
[Problems to be solved by the invention]
However, in the above prior art, the spherical contact 204 at the lower end moves upward as the hemispherical mirror 202 of the swing motion light lever 201 rotates. Therefore, the rotation angle of the hemispherical mirror is limited within a range in which the contact between the spherical contactor 204 and the V plate 205 is maintained, and the beam scanning range of the beam tracking laser interference length measuring device is narrowed. there were.
[0010]
Therefore, the present invention uses a spherical motor for the driving mechanism of the swing motion light lever, and even when the rotation angle of the hemispherical mirror increases, the rotation angle of the hemispherical mirror is not limited, and the beam tracking is performed. It is an object of the present invention to provide a beam tracking laser interference length measuring device using a swinging beam lever using a spherical motor and a coordinate measuring method using the device, which can expand the beam scanning range of the laser interference length measuring device.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 relates to a beam tracking type laser interference length measuring device using a swinging motion light lever using a spherical motor, and the object light irradiation direction in the interference length measuring optical system is determined. A beam tracking type laser interference length measuring device using a swinging motion optical lever using a spherical motor with a swinging mechanism that uses a swinging motion optical lever as the mechanism to change and is driven by a spherical motor to expand the irradiation angle range. The spherical motor is characterized in that the tilt axis drive is an arc-shaped linear motor and the twist axis drive is a rotary motor .
According to a second aspect of the present invention, there is provided a beam tracking type laser interferometric length measuring apparatus using a swinging-motion optical lever using the spherical motor according to the first aspect, wherein the interference optical measurement system is different from that for interference measurement in the return optical path of the interference optical system. A beam splitter is provided, and a part of the return light is guided to the quadrant light-receiving element, and the electrical output obtained by the light-receiving element is used as an input to the control device to feedback control the rotation angle of the spherical motor, thereby swinging motion It is characterized by the ability to control the lever position and automatically track the retro-reflector.
A third aspect of the present invention relates to a coordinate measuring method using the beam tracking type laser interference length measuring apparatus, and a beam tracking type laser interference using a swing motion light lever using the spherical motor according to the first aspect. A retroreflector viewed from the laser interference length measuring device measured by using the distance data from the laser interference length measuring device to the retroreflector to be measured and the angle of the two axes of the spherical motor using one set of length measuring device. The position of the retroreflector can be determined from the direction data .
A fourth aspect of the present invention relates to a coordinate measuring method using the beam tracking type laser interference length measuring apparatus, and a beam tracking type laser interference using a swinging motion optical lever using the spherical motor according to the first aspect. Using four sets of length measuring devices, the position of the retroreflector to be measured is tracked and measured a predetermined number of times, so that the positional relationship between the beam tracking laser interference length measuring devices and the beam tracking laser interference length measurement The position of the retroreflector can be determined even when the distance between the apparatus and the retroredirector cannot be measured .
[0012]
According to the beam tracking type laser interference length measuring device using the swinging optical lever using this spherical motor, the swinging optical lever is moved from the motor to the coupling, feed screw, XY table, V plate, spherical contact, etc. The optical lever connecting rod is directly fixed to the rotor of the linear arc motor and can be driven for rotation without the need for a rotation transmission mechanism. As a result, the beam scanning range of the beam tracking laser interferometer can be expanded, and the driving error is reduced as the mechanism is simplified.
[0013]
DETAILED DESCRIPTION OF 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 laser interferometer using a swinging optical lever using a spherical motor according to an embodiment of the present invention.
2 is a cutaway perspective view of the biaxial actuator shown in FIG.
FIG. 3 is an explanatory diagram of the structure of the biaxial 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 beam tracking type laser interferometer, and FIG. 1 (a) is a top view thereof. In the figure, reference numeral 1 denotes a biaxial actuator composed of a biaxial composite spherical motor. Reference numeral 2 denotes a mounting base for the biaxial actuator 1, and 4 denotes a hemispherical portion of a swinging light lever 3, which has a reflecting surface for irradiating the retroreflector with laser light on the upper surface.
[0014]
A connecting rod 5 is connected to the rotation shaft of the biaxial actuator 1. Reference numeral 6 denotes a spherical steel ball on which the hemispherical portion 4 is seated. Reference numeral 7 denotes a mirror for alignment of laser light. 8 is a laser beam for measurement, which is introduced from an external oscillation light source by 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 that separates the laser light 8 into irradiation light and reference light for measurement, and reference numeral 12 denotes a beam splitter that makes the return light incident on the four-track light receiving element 13 for tracking the direction. Reference numeral 14 denotes an optical fiber that takes in the interference signal between the return light and the reference light reflected from the retroreflector into the 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 (upper and lower) rotor of a spherical motor, which is constituted by a permanent magnet having teeth. A tilt axis coil 24 drives the tilt axis rotor 21. The tilt axis rotor 21 and the tilt axis coil 24 constitute an arc-shaped linear motor. A tilt axis origin sensor 22 detects the origin position of the tilt axis. Reference numeral 25 denotes a twist shaft (horizontal direction) rotor composed of a rotary motor coaxial with the tilt shaft motor, 26 denotes a twist shaft coil of the stator, and 23 denotes a twist axis origin sensor for detecting the origin position of the twist axis. The connecting shaft 5 of the hemisphere 4 is connected to the rotating shaft of the tilt shaft rotor 21 by a connecting jig 27. 28 is an upper plate of the biaxial actuator 1, 29 is a tilt shaft frame portion, 30 is a twist shaft frame portion, and 32 is a slip ring having a shaft tube structure for preventing the wire bundle from being twisted by shaft rotation. . Reference numeral 33 denotes an ambient temperature detector 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 that supports 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. Because it is fixed, fixed, and connected, there is no transmission mechanism such as the conventional spherical contactor and V plate, XY table that transmits motor output, and feed screw, so that rotation transmission is direct acting type It is accurate with no loss.
A tilt shaft rotor 21 that is a permanent magnet type rotor of a linear motor is driven by a tilt shaft coil 24 that is clamped by a stator 41 and arranged at a predetermined distance from a tooth row on the rotor side. I do.
[0017]
On the other hand, a rotary motor, which is composed of a twist shaft rotor 25 and a stator-side twist shaft coil 26 that drives the rotor, is arranged coaxially with the tilt shaft motor and rotates in the horizontal direction. Since the rotating shaft 40 performs a combined motion on the X and Y spherical surfaces by the two-degree-of-freedom motor, the hemispherical portion 4 connected to the rotary shaft 40 can be driven on the spherical surface. The rotation angle in this case depends on the movement range of the tilt shaft rotor 21 of the linear motor.
Further, in this apparatus, in order to avoid fluctuation due to temperature change, ventilation holes 42 and 43 are provided in the vicinity of the upper and lower motors, respectively, as shown in FIG. Yes.
[0018]
The position tracking of the measurement target of the beam tracking type laser interference length measuring device using the swing motion light lever that is directly rotated by such a biaxial actuator (spherical motor) 1 is performed by first using the retroreflector for the measurement laser beam 8. Is reflected at the center 15 of the reflection surface of the hemispherical portion 4 of the swinging movement light lever 3, is bent in the X direction by the alignment mirror 7, and enters the beam splitter 12. About half of the return light is reflected and input to the four-divided light receiving element 13. As shown in FIG. 4, the quadrant light receiving element 13 is composed of four light receiving surfaces ABCD. When the retroreflector is stationary, the four electric outputs abcd are equal to each other. If the retroreflector moves from this state with reference to the state where the direction of the swinging movement light lever 3 is adjusted and reflected at the center point 15 and the laser beam is accurately reflected at the center point of the retroreflector, Since the balance of the output abcd is lost, the rotation angle of each motor of the biaxial actuator 1 is, for example, the electrical output is (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 electrical output abcd can be adjusted to accurately track the movement position of the retroreflector.
[0019]
Next, the distance measurement by the laser interferometer of the beam tracking type laser interferometer is performed by tracking the retroreflector moved as described above, and the laser beam 8 is irradiated with the reference laser beam and the irradiation beam by the beam splitter 11. The laser beam is divided into laser beams, the irradiation laser beam is irradiated to the center point of the retroreflector through the beam splitter 12, the mirror 7, the swing motion light and the reflection surface 15, and the reflected return wave is the swing motion light beam. The reflected wave 15 passes through the reflecting surface 15 and the mirror 7, and is divided for measurement by the beam splitter 12 to the four-divided light receiving element 13 and the measurement return wave interferes with the reference wave at the beam splitter 11, The interference wave is counted by a counter of a measurement circuit (not shown), and the distance to the retroreflector is calculated based on the wavelength of the laser beam.
[0020]
Although the distance to the retroreflector of the object to be measured moved as described above can be calculated, the three-dimensional position cannot be determined unless the direction can be specified.
Therefore, for example, the distance r from the measured origin (reflection center 15 of the hemispherical part 3) to the retroreflector of the object to be measured, the horizontal angle of the retroreflector viewed from the origin, and the angle in the vertical direction are tilted. The position of the three-dimensional retroreflector can be determined by obtaining the detection values of the axis origin sensor 22 and the twist axis origin sensor 23 and displaying the polar coordinates on the spherical surface having the radius r.
[0021]
Thus, although one set of laser interferometers can measure the three-dimensional position of the retroreflector, a method of using three to four sets of laser interferometers for precise and high-resolution measurement. There is.
As shown in FIG. 5, measurement units (laser interference length measuring devices) are installed at three locations 01, 02, and 03, and retro reflectors are installed at 100 locations. Distances L11, L12, and L13 from each measurement unit to the center 101 of the retroreflector 100 are measured. If the positional relationship between the measurement units 01, 02, 03 is measured in advance here, three-sided surveying (three-sided survey as seen in the recent paramel mechanism method, not the conventional triangulation method) The coordinates of the center position 101 can be uniquely determined by the principle of the method of obtaining the three-dimensional coordinates from the 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. In addition, when an incremental counter is used for the measurement unit, only the amount of movement of the retroreflector can be measured, and relative measurement by comparison is possible, but measurement of the absolute distance between the measurement unit and the retroreflector is possible. Is impossible.
However, according to the self-calibration method described below, it is possible to measure an absolute distance and thereby measure the coordinates of the center 101 of the retroreflector 100 based on the principle of triangulation.
[0023]
In the self-calibration method, the fourth measurement unit 04 is used in addition to the measurement units 01, 02, 03. First, the retroreflector 100 is installed at an arbitrary position, and the retroreflector 100 is measured with four measurement units while moving arbitrarily, and the measurement is repeated. That is, if the retro reflector 100 is moved n times, 4 × n measurement values can be obtained.
At this point, the unknown is first a three-dimensional coordinate of the measurement point 100, which is three unknowns. Since the measurement was performed n times, a total of 3 × n unknowns exist. Further, there are six unknowns regarding the positional relationship of the measurement units, and three unknowns regarding the initial position of the retroreflector. Therefore, the total 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 determined mathematically and uniquely. The above is the principle of the self-calibration method. Once the positional relationship of the measurement unit and the initial distance to the retroreflector can be determined by this method, even if the retroreflector moves to any place after that, The position of the retroreflector can be determined from the measurement value of the equipped laser interferometer by the principle of triangulation. If 9 or more measurement points can be used for the calculation for determining the unknown, the equation becomes over-constrained and cannot be solved. In that case, the least square method may be used.
[0025]
【The invention's effect】
As described above, according to the present invention, in the beam tracking type laser interference length measuring device using the swing motion light lever as the mechanism for changing the irradiation direction of the object light in the interference length measuring optical system, it is driven by the spherical motor. A tilting mechanism that expands the irradiation angle range by guiding a part of the return light to the quadrant light receiving element, and using the electrical output obtained by the light receiving element as an input to the controller, the tilt axis is circular Controls the posture by swinging the head by controlling the rotation angle of a spherical motor that has a twisted shaft with a rotary motor and a rotary motor. The retroreflector can be automatically tracked, and a neck that uses a spherical motor. By using four sets of beam tracking laser interferometers with a swinging motion lever, the position of the retroreflector that is the object of measurement is 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 beam scanning range of the beam tracking type laser interference length measuring device can be expanded and the measurement range can be expanded as compared with the conventional one.
In addition, the degree of freedom of arrangement of the beam tracking type 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, so that the degree of freedom of arrangement increases. Has the effect of improving.
In addition, since the tilt axis motor is composed of a linear motion linear motor, the intermediate transmission mechanism such as the X, Y table, ball screw, V plate, and spherical contactor is deleted, and the direct connecting rod is fixed to the rotor for driving. Since the apparatus can be simplified, the operation error can be reduced, and the control can be simplified, there is an effect that more accurate measurement is possible.
In addition, when a retro reflector is attached to the end of the work axis of an industrial robot and tracking is performed with a laser interferometer, the robot positioning error can be detected. Program correction work performed at the actual work site is not required, and positioning programming work can be completed by desk-top programming work, so that there is an effect that significant work time can be saved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a beam tracking type laser interference length measuring apparatus using a swinging-motion 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 an explanatory diagram of the structure of the biaxial actuator shown in FIG. 2;
4 is a front view of the quadrant light receiving element of FIG. 1. FIG.
FIG. 5 is a principle diagram of three-side surveying by the laser interference length measuring apparatus shown in FIG. 1;
FIG. 6 is a cross-sectional view of a conventional laser interferometer.
7 is an explanatory diagram of a three-axis intersection of the laser interference length measuring device shown in FIG. 6. FIG.
FIG. 8 is a front view of a swing motion light lever used in a conventional laser interferometer.
FIG. 9 is a cross-sectional view of a conventional beam tracking laser interferometer using a swinging optical lever.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 2 axis | shaft actuator 2 2 axis | shaft actuator mount 3 Swing motion optical lever 4 Hemisphere part 5 Connecting rod 6 Steel ball 7 Alignment mirror 8 Laser beam 9 Laser interferometer 10 Laser interferometer mount 11, 12 Beam splitter 13 4 Divided light receiving element 14 Interference signal 15 Reflection center point 16 Polarizing plate 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 part frame 32 Slip ring 33 Ambient temperature sensor 41 Stator 42, 43 Ventilation hole 100 Retro reflector 101 Retro reflector center

Claims (4)

“Neck using a spherical motor with a swing mechanism that expands the irradiation angle range by using a swinging optical lever as a mechanism to change the irradiation direction of the object light in the interferometric measurement optical system. In the beam tracking type laser interferometer with a swinging motion lever ,
The spherical motor is a beam tracking type laser interference length measuring apparatus using a swinging-motion light lever using a spherical motor, wherein the tilt axis drive is constituted by an arc-shaped linear motor and the twist axis drive is constituted by a rotary motor .   A beam splitter different from that for interference measurement is provided in the return optical path of the interference optical system, a part of the return light is guided to the four-divided light receiving element, and the electrical output obtained by the light receiving element is used as an input to the control device. 2. A beam tracking method using a swinging optical lever using a spherical motor according to claim 1, wherein the posture is controlled by feedback control of the rotation angle of the spherical motor to control this posture and the retroreflector can be automatically tracked. Laser interference length measuring device.   Using one set of a beam tracking type laser interference length measuring device using a swinging motion optical lever using the spherical motor according to claim 1, distance data from the laser interference length measuring device to a retroreflector to be measured; Swing motion light using a spherical motor, wherein the position of the retroreflector can be determined from the direction data of the retroreflector viewed from the laser interference length measuring device measured by the angle of the two axes of the spherical motor Coordinate measurement method using a beam tracking laser interferometer with a lever.   Using four sets of beam tracking type laser interference length measuring devices using a swing motion optical lever using the spherical motor according to claim 1, the position of the retroreflector as a measurement target is tracked and measured a predetermined number of times, thereby The position of the retroreflector can be determined even when the positional relationship between the tracking laser interferometer and the distance between the beam tracking laser interferometer and the retroredirector cannot be measured. A coordinate measuring method using a beam tracking type laser interferometric length measuring device using a swinging optical lever using a spherical motor.

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