JP6284771B2 - Parallel mechanism - Google Patents

Description

  The present invention relates to a parallel mechanism, for example, a parallel mechanism having precise position measuring means.

  The parallel mechanism has a plurality of drive mechanisms such as a linear drive mechanism extending from a fixed base plate, a bending drive mechanism, and a slide mechanism (also referred to as a link). By simultaneously operating the plurality of drive mechanisms, it is possible to move the output moving stage relative to the base plate (for example, Patent Documents 1 and 2). The parallel mechanism has long been put into practical use as a driving mechanism for flight simulators, robot systems for assembly, and amusement devices. In recent years, application of parallel mechanisms to machine tools has been reported. With the expansion of the application range of the parallel mechanism, for example, the application of the parallel mechanism to a shape measuring machine has also been reported.

  The parallel mechanism can be driven at a relatively high speed among the drive mechanisms. Therefore, for example, if it is mounted on a measuring machine, the measurement stage can be driven at high speed, so that the measurement time can be shortened. Also, various types of parallel mechanisms are known. For example, a type capable of driving a moving stage with three degrees of freedom in space, a type capable of driving a moving stage with three degrees of freedom in translation, and three XYZ orthogonal to each other. There are types that can be driven with six degrees of freedom in the axial direction and the rotational direction of each axis.

JP 2000-130536 A Japanese Examined Patent Publication No. 04-045310

  However, the inventors have found that the above-described method has the following problems. While the parallel mechanism can operate at high speed, the drive mechanism has a low rigidity and a drive accuracy is inferior. Therefore, for example, it is not suitable for mounting on a measuring instrument for precision measurement.

  A parallel mechanism according to a first aspect of the present invention is provided between a base plate, a moving stage that moves relative to the base plate, and the base plate and the moving stage, and changes a relative position of the moving stage relative to the base plate. A plurality of drive mechanisms that are provided, a reflecting portion that is provided on the moving stage and reflects incident light, a position that is spatially fixed with respect to the base plate, irradiates the reflecting portion with measurement light, and the reflecting portion And a measurement unit that measures the movement distance and movement direction of the moving stage by observing interference between the measurement light reflected by the reference light and the reference light, and a control unit that controls the plurality of drive mechanisms.

  The parallel mechanism according to the second aspect of the present invention is the parallel mechanism described above, wherein the reflecting section is installed on the surface of the moving stage on the base plate side, the measuring section is installed on the base plate, The reflective portion is irradiated with the measurement light.

  A parallel mechanism according to a third aspect of the present invention is the parallel mechanism described above, further comprising a plurality of joints that connect each of the plurality of driving mechanisms, the base plate, and the moving stage, and the measurement. The unit is installed on a line connecting any one of the plurality of joints connecting the plurality of drive mechanisms and the base plate, and a centroid of the surface of the base plate on which the measurement unit is installed, and the reflection unit Is installed on a line connecting any one of the plurality of joints connecting the plurality of driving mechanisms and the moving stage and the centroid of the surface of the moving stage on which the reflecting portion is installed. is there.

  A parallel mechanism according to a fourth aspect of the present invention is the parallel mechanism described above, wherein a plurality of the reflecting portions are provided on the movable stage at a predetermined interval, and each of the plurality of reflecting portions is irradiated with measurement light. A plurality of the measurement units are provided at predetermined intervals on the base plate.

  A parallel mechanism according to a fifth aspect of the present invention is the parallel mechanism described above, wherein two measuring units are provided, two reflecting units are provided, and the two measuring units are surfaces of the base plate. The two reflecting parts are installed at positions symmetrical with respect to the centroid of the surface of the moving stage.

  A parallel mechanism according to a sixth aspect of the present invention is the parallel mechanism described above, wherein three measurement units are provided, three reflection units are provided, and the three measurement units are surfaces of the base plate. The three reflecting parts are installed at equal intervals with reference to the centroid of the surface of the moving stage.

  A parallel mechanism according to a seventh aspect of the present invention is the parallel mechanism described above, wherein the first to sixth drive mechanisms constituting the plurality of drive mechanisms, and the base plate constituting the plurality of joints, The first to sixth joints that connect each of the first to sixth drive mechanisms, and the movable stage that constitutes the plurality of joints and each of the first to sixth drive mechanisms are connected. Seventh to twelfth joints, and the first to twelfth joints are spherical joints.

  A parallel mechanism according to an eighth aspect of the present invention is the parallel mechanism described above, wherein the measurement unit includes a sphere whose relative position is fixed with respect to the base plate, a center of the sphere, and the reflection unit. An interferometer that emits the measurement light having a connecting line as an optical axis and observes interference between the measurement light reflected by the reflecting portion and the reference light, and two rotation axes orthogonal to each other at the center of the sphere And a drive unit for driving the interferometer around.

  A parallel mechanism according to a ninth aspect of the present invention is the parallel mechanism described above, wherein the two rotation shafts are parallel to a surface of the base plate on which the measurement unit is installed. There is something.

  A parallel mechanism according to a tenth aspect of the present invention is the above-described parallel mechanism, wherein the measurement unit emits the measurement light and causes the measurement light reflected by the reflection unit to interfere with the reference light. An interferometer, a base plate-side rotation mechanism that is provided on the base plate and supports the interferometer so as to be rotatable around two rotation axes orthogonal to each other at a first point fixed to the base plate; A telescopic structure comprising a first part fixed to an interferometer and a second part linearly reciprocating relative to the first part; and a second part provided on the moving stage and fixed to the moving stage A movable stage-side rotation mechanism that supports the second portion of the telescopic structure so as to be rotatable around two rotation axes orthogonal to each other at a point, and the reflection section includes the second portion It is intended to be disposed.

  A parallel mechanism according to an eleventh aspect of the present invention is the parallel mechanism described above, wherein the measurement unit includes a sphere whose center coincides with the first point, and the interferometer includes the first point. And the measurement light is emitted with a straight line connecting the second point as an optical axis.

  A parallel mechanism according to a twelfth aspect of the present invention is the parallel mechanism described above, wherein the plurality of drive mechanisms include a linear actuator, and the telescopic structure is a part of the linear actuator. .

  A parallel mechanism according to a thirteenth aspect of the present invention is the parallel mechanism described above, and includes a first optical fiber and a second optical fiber connected to the interferometer, and the interferometer includes the first optical fiber. The measurement light and the reference light are generated from the input light, the measurement light reflected by the reflection unit is interfered with the reference light, and interference light is generated. The interference light is output via an optical fiber.

  According to the present invention, a parallel mechanism capable of observing the position of the moving stage with high accuracy can be realized.

  The above and other objects, features and advantages of the present invention will be more fully understood from the following detailed description and the accompanying drawings. The accompanying drawings are presented for purposes of illustration only and are not intended to limit the present invention.

1 is a perspective view schematically showing a schematic configuration of a parallel mechanism 100 according to a first exemplary embodiment. 2 is a perspective view showing the structure of the parallel mechanism 100 in more detail. FIG. It is a block diagram at the time of observing the linear drive mechanism 1 from the A direction of FIG. FIG. 3 is an overhead view of a base plate 4 of a parallel mechanism 100 when viewed from a direction B in FIG. 2. It is a figure which shows typically an example of a structure of the laser tracker 411. FIG. FIG. 3 is an overhead view of the moving stage 5 of the parallel mechanism 100 when viewed from the direction C in FIG. 2. It is a figure which shows typically the path | route of the incident light and reflected light in a cat's eye. FIG. 6 is a perspective view schematically showing a configuration of a parallel mechanism 200 according to the second exemplary embodiment. FIG. 9 is an overhead view of the base plate 4 of the parallel mechanism 200 when viewed from the direction B of FIG. 8. FIG. 9 is an overhead view of the moving stage 5 of the parallel mechanism 200 when viewed from the direction C in FIG. 8. FIG. 6 is a perspective view schematically showing a configuration of a parallel mechanism 300 according to the third exemplary embodiment. FIG. 12 is an overhead view of the base plate 4 of the parallel mechanism 300 when viewed from the direction B of FIG. 11. FIG. 12 is an overhead view of the moving stage 5 of the parallel mechanism 300 when viewed from the direction C in FIG. 11. FIG. 6 is an optical path diagram of the laser interference length meter 4103 shown in FIG. 5. It is a figure which shows typically the other example of a structure of the laser tracker 411. FIG. FIG. 16 is an optical path diagram of the laser interferometer 4103 shown in FIG. 15. FIG. 6 is a perspective view schematically showing a configuration of a parallel mechanism 400 according to the fourth exemplary embodiment. It is a figure which shows typically the structure of the base plate 4 vicinity part of the universal laser interference length measuring unit 441. FIG. It is a top view of the universal joint 812 with which the universal laser interference length measurement unit 441 is provided. It is a side view of the universal joint 812 with which the universal laser interference length measurement unit 441 is provided. FIG. 10 is a diagram illustrating a configuration of a linear drive mechanism of a parallel mechanism according to a fifth embodiment. FIG. 22 is an optical path diagram of the laser interferometer 4103 shown in FIG. 21.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted as necessary.

Embodiment 1
First, the parallel mechanism 100 according to the first embodiment will be described. FIG. 1 is a perspective view schematically showing a schematic configuration of a parallel mechanism 100 according to the first exemplary embodiment. The parallel mechanism 100 includes linear drive mechanisms 1, 2 and 3, a base plate 4, a moving stage 5, two-degree-of-freedom joints J11 to J13, J21 to J23, a laser tracker 411, and a reflector 511. In the present embodiment, a case where the parallel mechanism 100 is applied to a shape measuring machine will be described. The parallel mechanism 100 is controlled by the control unit 7. The control unit 7 controls the shape measuring machine including the parallel mechanism 100, the driving of the measuring unit (laser tracker 411) mounted on the parallel mechanism 100, and the measurement operation as the shape measuring machine. A probe 6 is provided on the lower surface of the moving stage 5. The stylus 6a of the probe 6 extends in the vertical direction (the direction along the Z axis in FIG. 1). A tip sphere 6b is provided at the lower end of the stylus 6a. In the shape measuring machine, the tip sphere 6b comes into contact with the object to be measured 71 placed on the stage 72, and the shape of the object to be measured 71 can be measured by detecting the amount of displacement of the tip sphere 6b. . In FIG. 1, the linear drive mechanisms 1 to 2 and the two-degree-of-freedom joints J11 to J13 and J21 to J23 are simplified for the sake of simplification of the drawing.

  FIG. 1 shows an example in which the base plate 4 is supported by the pole 8. On the lower surface of the base plate 4, two-degree-of-freedom joints J11 to J13 are arranged on the circumference of a circle C1 having a radius R1 by 120 ° apart from each other. The base plate 4 and the moving stage 5 are formed in a hexagonal shape including three connecting sides to which linear driving mechanisms 1, 2, and 3 to be described later are connected, and straight portions connecting these connecting sides.

  The linear drive mechanisms 1, 2, and 3 are provided between the base plate 4 and the moving stage 5, and have a configuration that can be expanded and contracted between the base plate 4 and the moving stage 5 (expandable in the longitudinal direction or the axial direction). One end of each of the linear drive mechanisms 1, 2 and 3 is connected to the base plate 4 via two-degree-of-freedom joints J11 to J13. As a result, the linear drive mechanisms 1, 2 and 3 each have two declination directions orthogonal to the base plate 4 in a three-dimensional polar coordinate system having the two-degree-of-freedom joints J11 to J13 as support ends (rotation centers). It is possible to exercise.

  On the upper surface of the moving stage 5, two-degree-of-freedom joints J <b> 21 to J <b> 23 are arranged on the circumference of a circle C <b> 2 having a radius R <b> 2 by 120 ° apart from each other. The other ends of the linear drive mechanisms 1, 2 and 3 are connected to the moving stage 5 via two-degree-of-freedom joints J21 to J23, respectively. For simplification of the drawing, the display of the circle C2 is omitted in FIG. 1, and the circle C2 is displayed in FIG.

  The control unit 7 controls the expansion and contraction of the linear drive mechanisms 1, 2 and 3. As each of the linear drive mechanisms 1, 2 and 3 expands and contracts, the relative position of the moving stage 5 with respect to the base plate 4 changes. That is, the linear drive mechanisms 1, 2, and 3 expand and contract as appropriate, so that the moving stage 5 remains parallel to the base plate 4 and is parallel to the main surface of the base plate 4 (the X direction and the Y direction in FIG. 1). ) And a vertical direction (Z direction in FIG. 1).

  FIG. 2 is a perspective view showing the structure of the parallel mechanism 100 in more detail. The linear drive mechanisms 1, 2, and 3 have the same configuration. Below, the linear drive mechanism 1 is demonstrated as a representative. FIG. 3 is a configuration diagram when the linear drive mechanism 1 is observed from the direction A in FIG. 2. The linear drive mechanism 1 includes a telescopic rod 10 and linear motion rods 11 and 12. The linear motion rods 11 and 12 function as a guide when the telescopic rod 10 performs the telescopic motion.

  One end of the telescopic rod 10 is joined to a spherical joint 101 constituting a two-degree-of-freedom joint J11. The other end of the telescopic rod 10 is connected to the moving stage 5 via a spherical joint 15 constituting a two-degree-of-freedom joint J21. The spherical joint 15 is sandwiched and supported by the moving stage 5 from the horizontal direction in FIG.

  One end of the linear motion rod 11 is connected to the two-degree-of-freedom joint J11 by a linear motion bearing 13. The linear motion bearing 13 is inserted into a spherical joint 131 that constitutes a two-degree-of-freedom joint J11. Thereby, the linear motion rod 11 can be expanded and contracted in the radial direction with the two-degree-of-freedom joint J11 as a support end. Further, the linear motion rod 11 can move in two declination directions orthogonal to each other with respect to the two-degree-of-freedom joint J11.

  Fixing members 18 and 19 are provided at both ends of the connecting side of the moving stage 5 to support the spherical joints 16 and 17 with the side surfaces of the connecting side. The other end of the linear motion rod 11 is connected to the connecting side of the moving stage 5 via a spherical joint 16 that constitutes a two-degree-of-freedom joint J12. Thereby, the linear motion rod 11 can perform the motion in two declination directions orthogonal to each other with respect to the two-degree-of-freedom joint J21.

  One end of the linear motion rod 12 is connected to the two-degree-of-freedom joint J11 by the linear motion bearing 14. The linear motion bearing 14 is inserted through a spherical joint 141 that constitutes a two-degree-of-freedom joint J11. Thereby, the linear motion rod 12 can be expanded and contracted in the radial direction using the two-degree-of-freedom joint J12 as a support end. Further, the linear motion rod 12 can move in two declination directions orthogonal to each other with respect to the two-degree-of-freedom joint J11.

  The other end of the linear motion rod 12 is connected to the connection side of the moving stage 5 via a spherical joint 17 constituting a two-degree-of-freedom joint J12. Thereby, the linear motion rod 12 can perform the motion in two declination directions orthogonal to each other with respect to the two-degree-of-freedom joint J21.

  From the above, the telescopic rod 10 and the linear motion rods 11 and 12 of the linear drive mechanism 1 are rotated between the two-degree-of-freedom joint J11 and the two-degree-of-freedom joint J21, Thus, rotational movement about the vertical direction is possible.

  The linear drive mechanism 2 has the same configuration as the linear drive mechanism 1. Further, the two-degree-of-freedom joint J12 and the two-degree-of-freedom joint J22 have the same configuration as the two-degree-of-freedom joint J11 and the two-degree-of-freedom joint J21, respectively. Therefore, the two-degree-of-freedom joint J12 is connected to the telescopic rod 10 and the linear motion rods 11 and 12 in the same manner as the two-degree-of-freedom joint J11. The two-degree-of-freedom joint J22 is connected to the telescopic rod 10 and the linear motion rods 11 and 12 in the same manner as the two-degree-of-freedom joint J21.

  The linear drive mechanism 3 has the same configuration as the linear drive mechanism 1. Further, the two-degree-of-freedom joint J13 and the two-degree-of-freedom joint J23 have the same configuration as the two-degree-of-freedom joint J11 and the two-degree-of-freedom joint J21, respectively. Therefore, the two-degree-of-freedom joint J13 is connected to the telescopic rod 10 and the linear rods 11 and 12 in the same manner as the two-degree-of-freedom joint J11. The two-degree-of-freedom joint J23 is connected to the telescopic rod 10 and the linear rods 11 and 12 in the same manner as the two-degree-of-freedom joint J21.

  Accordingly, the moving stage 5 can translate with respect to the base plate 4. That is, it can be understood that the parallel mechanism 100 constitutes a translational three-degree-of-freedom parallel mechanism.

  Next, the laser tracker 411 and the reflector 511 will be described. The laser tracker 411 is provided on the upper surface of the base plate 4. 4 is an overhead view of the base plate 4 of the parallel mechanism 100 when viewed from the direction B of FIG. At this time, the laser tracker 411 is located at the center of the laser tracker 411 installation surface of the base plate 4 (the centroid of the laser tracker installation surface of the base plate 4, that is, the geometric center of gravity). It is desirable. As shown in FIG. 2, the laser tracker 411 can emit laser light (coherent light) toward the reflector 511 on the moving stage 5 through the opening 611 provided in the base plate 4.

  Here, the configuration of the laser tracker 411 will be described. FIG. 5 is a diagram schematically showing the configuration of the laser tracker 411. The laser tracker 411 includes a base block 4100, a reference sphere 4101, a biaxial rotation drive mechanism 4102 that incorporates a rotation angle detector (for example, a rotary encoder) (not shown) in each axis, a laser interference length meter 4103, and a base 4106. Hereinafter, the laser tracker is also simply referred to as a measurement unit. The reflector is also simply referred to as a reflection part.

  The base block 4100 has a rectangular parallelepiped shape and is placed on the base plate 4. The reference sphere 4101 is supported by a round bar shaft extending from the base block 4100 in parallel with the base block 4100 mounting surface on the base plate 4. Thereby, the relative position of the center of the reference sphere 4101 with respect to the base plate 4 is fixed. The center of the reference sphere 4101 is located on the round bar axis. The base block 4100 is provided with a cylindrical base 4106 coaxially with the round bar shaft. On the base 4106, a biaxial rotation driving mechanism 4102 including a reference sphere 4101 is provided. Accordingly, the center of the reference sphere 4101 is located on the axis of the base 4106. The biaxial rotation drive mechanism 4102 is rotatable about an axis passing through the center of the reference sphere 4101 and orthogonal to the axis of the base 4106 and the axis of the base 4106 and parallel to the installation surface of the laser tracker 411 of the base plate 4. It is said that.

  In the above description, it has been described that it is desirable that the laser light emission port be located at the centroid of the laser tracker 411 installation surface of the base plate 4 (the geometric center of gravity of the laser tracker 411 installation surface). This means that the center of the reference sphere 4101 is arranged at the center of the laser tracker 411 installation surface of the base plate 4 (the centroid of the laser tracker installation surface of the base plate 4, that is, the geometric center of gravity). . Thereby, the position dependency of the measurement due to the installation position of the laser tracker 411 can be minimized and averaged. However, the installation position of the laser tracker 411 is not limited to this example, and can be installed at other positions on the base plate 4.

  Accordingly, the biaxial rotation drive mechanism 4102 can be driven in the direction of the azimuth angle φ and the direction of the elevation angle θ with the center of the reference sphere 4101 as the origin. The azimuth angle φ and the elevation angle θ can be detected by, for example, a rotary encoder (not shown).

  The laser interference length meter 4103 measures the moving distance of the object that has emitted the reflected light by causing the emitted laser light (coherent light) to interfere with the reflected light. The laser interferometer 4103 can be configured using, for example, a Michelson type laser interferometer. The laser interferometer 4103 includes a laser light source (coherent light source) and a light receiving unit. As the laser light source, for example, a He-Ne laser traceable to a length standard whose wavelength is stabilized is used.

  The laser interferometer 4103 emits laser light 4104 from the laser light source. Since the biaxial rotation drive mechanism 4102 rotates with reference to the reference sphere 4101, the laser light is emitted so that the optical axis coincides with a line connecting the reference sphere 4101 and the reflector 511. As a result, even if the positional relationship between the laser interferometer 4103 and the reflector 511 changes, the laser interferometer 4103 can be driven by the biaxial rotation drive mechanism 4102 to irradiate the reflector 511 with laser light.

  The laser beam 4104 is reflected by the reflector 511. In FIG. 5, the reflected light is displayed as reflected light 4105. The laser interferometer 4103 can measure a variation in the distance between the laser interferometer 4103 and the reflector 511 by causing the laser beam 4104 and the reflected beam 4105 to interfere with each other. Further, the distance between the laser interferometer 4103 and the reference sphere 4101 is known. The laser tracker 411 outputs a value obtained by adding the distance between the laser interferometer 4103 and the reflector 511 and the distance between the laser interferometer 4103 and the reference sphere 4101 to the control unit 7 as a length measurement result. .

  The laser tracker 411 can automatically change the emission direction of the laser light following the movement of the reflector 511 under the control of the control unit 7. For example, the light-receiving unit of the laser interferometer 4103 is a two-dimensional light-receiving element that can detect the center of gravity of the beam spot of reflected light. The control unit 7 detects the movement of the center of gravity of the reflected light beam spot so that the center of gravity of the reflected light beam spot falls within a certain range. And drive in the direction of the elevation angle θ (referred to as tracking control).

  Next, the reflector 511 will be described. FIG. 6 is an overhead view of the moving stage 5 of the parallel mechanism 100 when viewed from the direction C in FIG. The reflector 511 is provided on the upper surface of the moving stage 5. At this time, the reflector 511 is preferably provided at the center of the upper surface of the moving stage 5 (the centroid of the reflector installation surface of the moving stage 5, that is, the geometric center of gravity). Thereby, the position dependence of the measurement resulting from the installation position of the reflector 511 can be minimized and averaged. However, the installation position of the reflector 511 is not limited to this example, and the reflector 511 can be installed at another position on the moving stage 5.

  The reflector 511 has a function of faithfully reflecting the laser beam in the direction opposite to the incident direction, regardless of the direction in which the laser beam emitted from the laser tracker 411 is incident. A cube corner can be used as such a reflector. In order to widen the angle range in which laser light can be incident, so-called cat's eyes obtained by processing an optical material having a refractive index of 2 into a true sphere can also be used.

  FIG. 7 is a diagram schematically showing paths of incident light and reflected light in the cat's eye. For example, it is assumed that light is incident on the cat's eye 5102 fixed to the pedestal 5101. Incident light is refracted when entering the cat's eye 5102 and reaches the interface opposite to the incident surface. Incident light is reflected at a reflection angle equal to the incident angle at the interface where it arrives, and becomes reflected light. The reflected light is refracted when it reaches the incident-side interface of the cat's eye 5102. As a result, the optical axis of the reflected light is the same as the optical axis of the incident light.

  The control unit 7 performs the above-described tracking control for controlling the biaxial rotation drive mechanism 4102 of the laser tracker 411 in accordance with the movement of the moving stage 5 so that the laser beam 4104 is always incident on the reflector 511.

  The control unit 7 can calculate the moving distance of the moving stage 5 with high accuracy by monitoring the measurement result output from the laser tracker 411. In the present embodiment, the control unit 7 uses the variation in the laser beam emission direction of the laser tracker 411 (the variation in the azimuth angle φ and the elevation angle θ) and the length information in the radial direction obtained from the length measurement result. The spatial coordinates of the reflector 511 are determined (so-called polar coordinate system).

  In order to perform precise coordinate measurement using a laser tracker and a reflector, a laser tracker may be provided outside the parallel mechanism, and a reflector may be provided on the moving stage. However, when the moving stage moves, the linear drive mechanism may block the laser light from the laser tracker incident from the outside. In addition, in a 6-degree-of-freedom parallel mechanism in which the moving stage can rotate around each axis, the moving stage itself may block the reflector. Therefore, if a laser tracker is provided outside the parallel mechanism, the movable range of the movable stage that can be tracked is limited, and the coordinate position of the parallel mechanism being driven cannot be accurately tracked.

  On the other hand, in the parallel mechanism 100, the laser tracker 411 is provided on the base plate 4, and the reflector 511 is provided on the surface of the moving stage 5 on the base plate 4 side. Therefore, the laser tracker 411 can always overlook the moving stage 5 through the opening 611. Therefore, the laser tracker 411 can always irradiate the reflector 511 with laser light regardless of the driving state of the moving stage 5. As a result, the parallel mechanism 100 can accurately track the coordinate position of the driving parallel mechanism.

Embodiment 2
Next, the parallel mechanism 200 according to the second embodiment will be described. FIG. 8 is a perspective view schematically showing the configuration of the parallel mechanism 200 according to the second exemplary embodiment. The parallel mechanism 200 is a modification of the parallel mechanism 100. The parallel mechanism 200 includes laser trackers 421 and 422 and reflectors 521 and 522 instead of the laser tracker 411 and the reflector 511 of the parallel mechanism 100. The laser trackers 421 and 422 have the same configuration as the laser tracker 411. The reflectors 521 and 522 have the same configuration as that of the reflector 511. Since the other structure of the parallel mechanism 200 is the same as that of the parallel mechanism 100, description thereof is omitted.

  FIG. 9 is an overhead view of the base plate 4 of the parallel mechanism 200 when viewed from the direction B of FIG. The laser tracker 421 is provided on the upper surface of the base plate 4. At this time, the laser tracker 421 is desirably provided in the vicinity of the side portion between the two-degree-of-freedom joint J11 and the two-degree-of-freedom joint J13 on the laser tracker 421 installation surface of the base plate 4. At this time, the center of the reference sphere 4101 of the laser tracker 421 may be located on a perpendicular line extending from the centroid of the upper surface of the base plate 4 to the side between the two-degree-of-freedom joint J11 and the two-degree-of-freedom joint J13. desirable.

  The laser tracker 422 is provided on the upper surface of the base plate 4. At this time, the laser tracker 422 is preferably provided in the vicinity of the two-degree-of-freedom joint J12 on the surface of the base plate 4 where the laser tracker 422 is installed. At this time, the center of the reference sphere 4101 of the laser tracker 422 is preferably arranged at a position symmetrical to the center of the reference sphere 4101 of the laser tracker 421 with respect to the centroid of the upper surface of the base plate 4.

  FIG. 10 is an overhead view of the moving stage 5 of the parallel mechanism 200 when viewed from the direction C of FIG. The reflector 521 is provided on the upper surface of the moving stage 5. At this time, it is desirable that the center of the reflector 521 be located on a perpendicular line extending from the centroid of the upper surface of the moving stage 5 to the side between the two-degree-of-freedom joint J21 and the two-degree-of-freedom joint J23.

  The reflector 522 is provided on the upper surface of the moving stage 5. At this time, the reflector 522 is desirably arranged at a position symmetrical to the reflector 521 with respect to the centroid of the upper surface of the moving stage 5 on the reflector 522 installation surface of the moving stage 5.

  The laser tracker 421 can emit laser light toward the reflector 521 through the opening 621 provided in the base plate 4. The reflector 521 has a function of faithfully reflecting the laser beam in the direction opposite to the incident direction, regardless of the direction in which the laser beam emitted from the laser tracker 421 is incident.

  The laser tracker 422 can emit laser light toward the reflector 522 through the opening 622 provided in the base plate 4. The reflector 522 has a function of accurately reflecting the laser beam in the direction opposite to the incident direction, regardless of the direction in which the laser beam emitted from the laser tracker 422 is incident.

  Thereby, the coordinates of the reflector 521 and the reflector 522 on the moving stage 5 can be specified. It is also possible to detect the rotation of the moving stage 5 in the direction orthogonal to the line connecting the reflector 521 and the reflector 522 (rotation about the direction D in FIG. 10).

  However, the installation positions of the laser trackers 421 and 422 are not limited to this example, and can be installed at other positions on the base plate 4. The installation positions of the reflectors 521 and 522 are not limited to this example, and can be installed at other positions on the moving stage 5.

  The control unit 7 performs tracking control for controlling the biaxial rotation drive mechanism 4102 of the laser tracker 421 in accordance with the movement of the moving stage 5 so that the laser light from the laser tracker 421 is always incident on the reflector 521. In addition, the control unit 7 performs tracking control for controlling the biaxial rotation drive mechanism 4102 of the laser tracker 422 in accordance with the movement of the moving stage 5 so that the laser light is always incident on the reflector 522 from the laser tracker 422.

  Thereby, the control unit 7 can calculate the moving direction and moving distance of the moving stage 5 with high accuracy by monitoring the measurement results output from the laser trackers 421 and 422.

In the present embodiment, the control unit 7 includes accurate position information measured in advance on the base plate 4 of the laser trackers 421 and 422 and the azimuth angles φ ₁ and φ ₂ observed by the laser trackers 421 and 422, respectively. Using the depression angles θ ₁ and θ ₂ and the length information L ₁ and L ₂ in the radial direction obtained from the length measurement results, the respective laser trackers 421 and 422 are moved to different positions on the moving stage 5 (measurement is performed in advance). The spatial coordinates of the two reflectors (reflectors 521 and 522) arranged in (possible) are determined (so-called triangulation method).

  In general, in the case of the polar coordinate system, the coordinates can be determined using the azimuth angle φ, the elevation angle θ, and the radial distance. In this case, the longer the distance in the radial direction, the greater the error in the movement distance due to the error in the azimuth angle φ and elevation angle θ when calculating the movement distance.

  According to this configuration, the moving distance and position of the moving stage 5 can be calculated with higher accuracy from the four angle information and the two length information that are twice as many as those of the parallel mechanism 100 according to the first embodiment. Can do.

Embodiment 3
Next, the parallel mechanism 300 according to the third embodiment will be described. FIG. 11 is a perspective view schematically illustrating the configuration of the parallel mechanism 300 according to the third embodiment. The parallel mechanism 300 is a modification of the parallel mechanism 100. The parallel mechanism 300 includes laser trackers 431, 432 and 433 and reflectors 531, 532 and 533 instead of the laser tracker 411 and the reflector 511 of the parallel mechanism 100. The laser trackers 431, 432, and 433 have the same configuration as the laser tracker 411. The reflectors 531, 532, and 533 have the same configuration as the reflector 511. Since the other structure of the parallel mechanism 300 is the same as that of the parallel mechanism 100, description thereof is omitted.

  FIG. 12 is an overhead view of the base plate 4 of the parallel mechanism 300 when viewed from the direction B of FIG. On the upper surface of the base plate 4, laser trackers 431 to 433 are arranged 120 ° apart from each other on the circumference of a circle C 3 having a radius R 3. That is, in the laser trackers 431 to 433, the centers of the reference spheres 4101 of the laser trackers 431 to 433 are arranged on the circumference of the circle C3. That is, the laser trackers 431 to 433 are arranged at equal intervals with reference to the centroid of the laser tracker installation surface of the base plate 4 (the geometric center of gravity of the laser tracker installation surface of the base plate 4).

  FIG. 13 is an overhead view of the moving stage 5 of the parallel mechanism 300 when viewed from the direction C of FIG. On the upper surface of the moving stage 5, reflectors 531 to 533 are arranged 120 ° apart from each other on the circumference of a circle C4 having a radius R4. That is, the reflectors 531 to 533 are arranged at equal intervals with reference to the centroid of the reflector installation surface of the moving stage 5 (the geometric center of gravity of the reflector installation surface of the movement stage 5).

  The laser tracker 431 can emit laser light toward the reflector 531 through the opening 631 provided in the base plate 4. The reflector 531 has a function of faithfully reflecting the laser beam in the direction opposite to the incident direction regardless of the direction in which the laser beam emitted from the laser tracker 431 is incident.

  The laser tracker 432 can emit laser light toward the reflector 532 through the opening 632 provided in the base plate 4. The reflector 532 has a function of faithfully reflecting the laser beam in the direction opposite to the incident direction, regardless of the direction in which the laser beam emitted from the laser tracker 432 is incident.

  The laser tracker 433 can emit laser light toward the reflector 533 through the opening 633 provided in the base plate 4. The reflector 533 has a function of faithfully reflecting the laser beam in the direction opposite to the incident direction, regardless of the direction in which the laser beam emitted from the laser tracker 433 is incident.

  As described above, the distance between the laser tracker 431 and the reflector 531, the distance between the laser tracker 432 and the reflector 532, and the distance between the laser tracker 433 and the reflector 533 can be measured with high accuracy. The center coordinates of the reflectors 531 to 533 can be easily specified. It is also possible to detect the rotation of the moving stage 5 (rotation about the directions D and E in FIG. 13). Therefore, it is possible to control the position and posture of the moving stage 5 with higher accuracy by feeding back the measurement result to the control unit 7.

  However, the installation positions of the laser trackers 431 to 433 are not limited to this example, and can be installed at other positions of the base plate 4. The installation positions of the reflectors 531 to 533 are not limited to this example, and can be installed at other positions on the moving stage 5.

  The control unit 7 performs tracking control for controlling the biaxial rotation drive mechanism 4102 of the laser tracker 431 in accordance with the movement of the moving stage 5 so that the laser light from the laser tracker 431 is always incident on the reflector 531. Further, the control unit 7 performs tracking control for controlling the biaxial rotation drive mechanism 4102 of the laser tracker 432 in accordance with the movement of the moving stage 5 so that the laser light emitted from the laser tracker 432 is always incident on the reflector 532. Do. Further, the control unit 7 performs tracking control for controlling the biaxial rotation driving mechanism 4102 of the laser tracker 433 in accordance with the movement of the moving stage 5 so that the laser light emitted from the laser tracker 433 is always incident on the reflector 533. Do.

  Thereby, the control part 7 can calculate the moving distance of the moving stage 5 with high precision by monitoring the measurement result output from the laser trackers 431-433.

  In the present embodiment, the control unit 7 determines the spatial coordinates of the reflectors 531 to 533 using so-called three radial length information obtained from the laser trackers 431 to 433 (so-called trilateral survey method). Since the laser trackers 431 to 433 use laser beam interference, the distance in the radial direction can be obtained with high resolution. In the three-side survey method, when determining the spatial coordinates, length information suitable for Abbe's principle from three directions is used without using angle information. Therefore, the coordinate determination accuracy is high compared to the polar coordinate method and the triangulation method described above. Therefore, the parallel mechanism 300 (triangulation method) can calculate the movement distance of the moving stage 5 with higher accuracy than the parallel mechanism 100 (polar coordinate method) and 200 (triangulation method).

  In other words, the angle information of the azimuth angle φ and the elevation angle θ measured by the two-dimensional light receiving element and the rotation angle detector built in the two-axis rotation drive mechanism 4102 is used only for tracking control, and the moving distance of the moving stage 5 Only three pieces of length information in the radial direction obtained from the laser trackers 431 to 433 are used for the calculation. Therefore, unlike the parallel mechanisms 100 and 200, an error does not increase with an increase in the radial distance, and the moving distance of the moving stage 5 can be calculated with high accuracy regardless of the position of the moving stage 5.

  In the first to third embodiments described above, since the laser trackers 411, 421, 422, 431 to 433 include the reference sphere, the distance between the point fixed to the base plate 4 and the reflector provided on the moving stage 5 Can be measured accurately. The reason will be described below.

  Referring to FIG. 14, the center O of the reference sphere 4101 is a point fixed with respect to the base plate 4. The two rotation axes of the biaxial rotation drive mechanism 4102 are orthogonal at the center O. Therefore, even if the biaxial rotation drive mechanism 4102 rotates the laser interferometer 4103, the optical axis of the laser interferometer 4103 always passes through the center O of the reference sphere 4101. The laser interferometer 4103 includes a light source 41 such as a laser diode, a collimator lens 42, a polarizing beam splitter 43, a polarizing plate 44, a photodetector 45, and a quarter wavelength plate (λ / 4 plate) 46. And 47, a non-polarizing beam splitter 48, a position detector (PSD) 49, and a condenser lens 50. Note that a quadrant photodiode (QPD) may be used instead of the position detector 49.

  The light beam emitted from the light source 41 passes through the collimator lens 42 and is divided into two by the polarization beam splitter 43. On the other hand, (S-polarized light) travels straight toward the polarizing plate 44 as reference light. The other (P-polarized light) is reflected by the polarization beam splitter 43 as measurement light and is emitted toward the center O or the surface of the reference sphere 4101 through the λ / 4 plate 46 and the condenser lens 50. Here, the measurement light is converted from P-polarized light to circularly-polarized light by the λ / 4 plate 46. The measurement light reflected by the surface of the reference sphere 12 is irradiated to the reflector 511 through the condenser lens 50, the λ / 4 plate 46, the polarization beam splitter 43, the λ / 4 plate 47, and the unchanged beam splitter 48. . Here, the measurement light is converted from circularly polarized light to S polarized light by the λ / 4 plate 46, and converted from S polarized light to circularly polarized light by the λ / 4 plate 47. The measurement light is emitted with a straight line connecting the center O of the reference sphere 4101 and the reflector 511 as an optical axis.

  The measurement light reflected by the reflector 511 enters the laser interference length meter 4103. The measurement light incident on the laser interferometer 4103 is divided into two by the non-polarizing beam splitter 48. One is reflected by the non-polarizing beam splitter 48 and enters the position detector 49. The other passes through the λ / 4 plate 47, the polarizing beam splitter 43, and the polarizing plate 44, and interferes with the reference light described above to generate interference light. Here, the measurement light is converted from circularly polarized light to P polarized light by the λ / 4 plate 47. The interference light enters the photodetector 45. Since the output of the photodetector 45 changes according to the interference fringes of the interference light, the displacement of the reflector 511 with reference to the center O of the reference sphere 4101 can be measured based on the output of the photodetector 45.

  Since the distance between the surface of the reference sphere 4101 and the center O is constant with high accuracy, even if the laser interferometer 4103 tracks the reflector 511 and rotates around the rotation axis of the biaxial rotation drive mechanism 4102, the light Based on the output of the detector 45, the displacement of the reflector 511 with reference to the center O of the reference sphere 4101 can be measured with high accuracy.

  On the other hand, tracking with respect to the reflector 511 is performed as follows. The measurement light reflected by the reflector 511 enters the position detector 49. Based on the output signal of the position detector 49, the control unit 7 controls the driving of the biaxial rotation drive mechanism 4102 so that the measurement light is incident on a predetermined position on the position detector 49. As a result, the optical axis of the laser interferometer 4103 always passes through the reflector 511.

  FIG. 15 shows another configuration of the laser tracker 411. The laser tracker 411 includes a carriage 4108 that is driven by a biaxial rotation drive mechanism 4102. The laser interferometer 4103 is attached to the carriage 4108. The straight line L411 coincides with the optical axis of the laser interference length meter 4103. Even if the biaxial rotation drive mechanism 4102 rotates the carriage 4108, the straight line L411 always passes through the center O of the reference sphere 4101. Displacement meters 52 and 53 are provided on the carriage 4108. The displacement meters 52 and 53 are arranged on a straight line L411, and a reference sphere 4101 is arranged between the displacement meters 52 and 53. The displacement meters 52 and 53 output signals according to the distance to the reference sphere 4101.

  As the displacement meters 52 and 53, for example, a capacitance displacement meter or an eddy current displacement meter can be used. As the reference sphere 4101, a metal, ceramic, semiconductor, or glass sphere can be used. However, when eddy current displacement meters are used as the displacement meters 52 and 53, it is necessary to use metal balls or balls whose surfaces are coated with metal.

  Referring to FIG. 16, the laser interferometer 4103 shown in FIG. 15 includes a light source 41, a collimator lens 42, a polarization beam splitter 43, a polarizing plate 44, a photodetector 45, and a λ / 4 plate 46. And 47, a non-polarizing beam splitter 48, a position detector 49, and a cube corner 51. The cube corner 51 may be referred to as a corner cube prism.

  The light beam emitted from the light source 41 passes through the collimator lens 42 and is divided into two by the polarization beam splitter 43. On the other hand, (P-polarized light) travels straight toward the polarizing plate 44 as reference light. The other (S-polarized light) is reflected by the polarization beam splitter 43 as measurement light, and irradiates the reflector 511 through the λ / 4 plate 47 and the unchanged beam splitter 48. Here, the measurement light is converted from S-polarized light to circularly-polarized light by the λ / 4 plate 47. The measurement light is emitted with a straight line L411 connecting the center O of the reference sphere 4101 and the reflector 511 as an optical axis.

  The measurement light reflected by the reflector 511 enters the laser interference length meter 4103. The measurement light incident on the laser interferometer 4103 is divided into two by the non-polarizing beam splitter 48. One is reflected by the non-polarizing beam splitter 48 and enters the position detector 49. The other is incident on the cube corner 51 through the λ / 4 plate 47, the polarization beam splitter 43, and the λ / 4 plate 46. Here, the measurement light is converted from circularly polarized light to P-polarized light by the λ / 4 plate 47 and converted from P-polarized light to circularly polarized light by the λ / 4 plate 46. The measurement light reflected by the cube corner 51 passes through the λ / 4 plate 46, the polarizing beam splitter 43, and the polarizing plate 44, and interferes with the above-described reference light to generate interference light. Here, the measurement light is converted from circularly polarized light to S polarized light by the λ / 4 plate 46. The interference light enters the photodetector 45. Since the output of the photodetector 45 changes according to the interference fringes of the interference light, the displacement of the reflector 511 with reference to the center O of the reference sphere 4101 can be measured based on the output of the photodetector 45.

  Since the distance between the surface of the reference sphere 4101 and the center O is constant with high accuracy, even if the laser interferometer 4103 tracks the reflector 511 and rotates around the rotation axis of the biaxial rotation drive mechanism 4102, the light Based on the outputs of the detector 45, the displacement meter 52, and the displacement meter 53, the displacement of the reflector 511 with reference to the center O of the reference sphere 4101 can be measured with high accuracy. Although it is preferable to use both of the displacement meters 52 and 53, only one of the displacement meters 52 and 53 may be used. The tracking with respect to the reflector 511 is the same as in the case of the laser interference length meter 4103 shown in FIG.

Embodiment 4
Next, a parallel mechanism 400 according to the fourth embodiment will be described. The parallel mechanism 400 according to the fourth embodiment solves the following problems. That is, the control unit 7 of the parallel mechanism 100 not only controls the linear drive mechanisms 1 to 3 to move the moving stage 5 but also controls the biaxial rotation drive mechanism 4102 so that the laser tracker 411 tracks the reflector 511. There is a need to. According to the parallel mechanism 100, the position of the movable stage 5 can be observed with high accuracy, but the system configuration of the parallel mechanism 100 is complicated and expensive. Similarly, the system configuration of the parallel mechanisms 200 and 300 is also complicated and expensive.

  FIG. 17 is a perspective view schematically illustrating the configuration of the parallel mechanism 400 according to the fourth embodiment. The parallel mechanism 400 is a modification of the parallel mechanism 300. The parallel mechanism 400 includes universal laser interference length measuring units 441 to 443 instead of the laser trackers 431 to 433 of the parallel mechanism 300. The control unit 7 includes a drive control unit 701 and an arithmetic control unit 702. Since the other structure of the parallel mechanism 400 is the same as that of the parallel mechanism 300, description is abbreviate | omitted.

  The universal laser interference length measuring units 441 to 443 include driven joint mechanisms 81 to 83, respectively. The driven joint mechanism 81 includes a telescopic barrel 811 having a telescopic structure that can be expanded and contracted, and a universal joint 812. The telescopic barrel 811 forms an optical path that can be expanded and contracted. The telescopic barrel 811 includes a first portion 8101 and a second portion 8102 that reciprocates linearly with respect to the first portion 8101. The first portion 8101 and the second portion 8102 may be relatively rotatable around the telescopic axis. For example, the first portion 8101 is connected to the second portion 8102 via a stroke bearing (not shown). FIG. 17 shows the case where the first portion 8101 and the second portion 8102 are respectively an inner tube and an outer tube, but the first portion 8101 and the second portion 8102 may be an outer tube and an inner tube, respectively.

  The drive control unit 701 controls expansion and contraction of the linear drive mechanisms 1 to 3. The drive control unit 701 may control expansion and contraction of the linear drive mechanisms 1 to 3 based on a feedback signal output from the linear encoders of the linear drive mechanisms 1 to 3. The drive control unit 701 may perform power on and initial setting of the universal laser interference length measuring units 441 to 443. The arithmetic processing unit 702 calculates the position and orientation of the moving stage 5 based on the outputs of the universal laser interference length measuring units 441 to 443.

  Referring to FIG. 18, universal laser interference measurement unit 441 includes a universal interferometer unit 451. The universal interferometer unit 451 is basically configured similarly to the laser tracker 411. However, the biaxial rotation drive mechanism 4102 of the universal interferometer unit 451 does not have a function of driving the carriage 4108 and the laser interferometer 4103 and a function of detecting the azimuth angle φ and the elevation angle θ. Hereinafter, the biaxial rotation drive mechanism 4102 having no drive function is referred to as a biaxial rotation mechanism 4102. The biaxial rotation mechanism 4102 is provided on the base plate 4 and supports the laser interferometer 4103 so that it can rotate around two rotation axes orthogonal to each other at a point fixed to the base plate 4. The center O of the reference sphere 4101 coincides with the intersection of the two rotation axes. The first portion 8101 of the telescopic barrel 811 is fixed coaxially to the laser beam exit 4107 of the laser interferometer 4103.

  The laser interferometer 4103 of the universal interferometer unit 451 does not have a function of detecting a deviation of the reflector 531 from the optical axis. For example, the laser interferometer 4103 of the universal interferometer unit 451 is obtained by removing the non-polarizing beam splitter 48 and the position detector 49 from the configuration shown in FIG. The laser interferometer 4103 of the universal interferometer unit 451 may be obtained by removing the non-polarizing beam splitter 48 and the position detector 49 from the configuration shown in FIG. In this case, at least one of the displacement meters 52 and 53 is provided on the carriage 4108.

  Referring to FIGS. 19 and 20, the universal joint 812 is provided on the moving stage 5, and can be rotated around two rotation axes orthogonal to each other at a fixed point with respect to the moving stage 5. 8102 is a rotation mechanism that supports The two rotation axes of the universal joint 812 are parallel to the moving stage 5. The intersection of the two rotation axes of the universal joint 812 coincides with the center of the reflector 531.

  When the moving stage 5 is moved by the linear drive mechanisms 1 to 3 by the mechanism described above, the laser interference length meter 4103 turns following the movement of the moving stage 5. In other words, the universal laser interference length measuring unit 441 always emits the measurement light with the straight line connecting the intersection of the two rotation axes of the two-axis rotation mechanism 4102 and the intersection of the two rotation axes of the universal joint 812 as the optical axis. Can be emitted. Measurement light (laser light 4104) emitted from the laser light emission port 4107 of the laser interference length meter 4103 enters the reflector 531 through the optical path in the telescopic lens barrel 811. The measurement light (reflected light 4105) reflected by the reflector 531 returns to the optical path in the telescopic barrel 811 and enters the laser light emission port 4107.

  Therefore, the universal laser interference length measuring unit 441 can continuously measure the distance between the center of the reference sphere 4101 and the center of the reflector 531. The universal laser interference length measuring units 442 and 443 have the same configuration as the universal laser interference length measuring unit 441. The arithmetic processing unit 702 of the control unit 7 can calculate the position and orientation of the moving stage 5 based on the outputs of the universal laser interference length measuring units 441 to 443.

  According to the present embodiment, the universal laser interference measurement units 441 to 443 can track the reflectors 531 to 533 without performing the tracking control by the control unit 7. The parallel mechanism 400 according to the present embodiment can achieve performance equivalent to that of the parallel mechanism 300 with a simpler and lower-cost system configuration than the parallel mechanism 300.

Embodiment 5
Next, a parallel mechanism 500 according to the fifth embodiment will be described. FIG. 21 shows the vicinity of the linear drive mechanism 1 of the parallel mechanism 500. The parallel mechanism 500 is a modification of the parallel mechanism 400. In the parallel mechanism 500, the functions of the universal laser interference length measuring unit 441 and the reflector 531 are incorporated in the linear drive mechanism 1. The linear drive mechanisms 2 and 3 are configured similarly to the linear drive mechanism 1.

  The telescopic rod 10 of the linear drive mechanism 1 according to the fifth embodiment is a linear motion actuator including a shaft type linear motor having an optical path formed therein. The telescopic rod 10 includes an interferometer support portion 1001 and a telescopic barrel 1002 having a telescopic structure that can be expanded and contracted. A laser interferometer 4103 is disposed on the interferometer support 1001. One end of the interferometer support 1001 is connected to the base plate 4 via the spherical joint 101. An optical fiber 4111 is attached to the spherical joint 101, and an optical fiber 4112 is attached to the interferometer support unit 1001. The optical fiber 4111 may be attached to the interferometer support 1001. The optical fibers 4111 and 4112 are optically connected to the laser interference length meter 4103.

  The center of the spherical joint 101 is fixed with respect to the base plate 4. Therefore, the rotation mechanism formed by the spherical joint 101 is provided on the base plate 4 and supports the laser interferometer 4103 so that it can rotate around two rotation axes that are orthogonal to each other at a fixed point with respect to the base plate 4. .

  The telescopic lens barrel 1002 forms a telescopic optical path. The telescopic lens barrel 1002 includes a first portion 1003 and a second portion 1004 that reciprocates linearly with respect to the first portion 1003. Hereinafter, the first part 1003 and the second part 1004 are referred to as an outer cylinder 1003 and an inner cylinder 1004, respectively. One end of the outer cylinder 1003 is fixed to the other end of the interferometer support 1001. Specifically, one end of the outer cylinder 1003 is fixed coaxially to the laser emission port 4107 of the laser interference length meter 4103. A seal portion 1005 that seals between the outer cylinder 1003 and the inner cylinder 1004 is formed at the other end of the outer cylinder 1003. An electromagnet 1006 is fixed to the other end of the outer cylinder 1003. A gas inlet 1007 is provided in the outer cylinder 1003. Sliding guides 1011 are provided on the upper side (spherical joint 101 side) and the lower side (spherical joint 15 side) of the electromagnet 1006, respectively. The sliding guide 1011 is formed of, for example, a fluorine resin material having a small friction coefficient, and enables relative movement on the same axis while ensuring the coaxiality of the outer cylinder 1003 and the inner cylinder 1004.

  A piston 1008 is fixed to one end of the inner cylinder 1004. The piston 1008 is formed in a hollow disk shape. The piston 1008 is disposed in the outer cylinder 1003. A permanent magnet 1009 is fixed inside the inner cylinder 1004. The permanent magnet 1009 is formed by stacking hollow disk-shaped permanent magnets. Accordingly, an extendable optical path is formed inside the extendable rod 10. The other end of the inner cylinder 1004 is connected to the moving stage 5 via the spherical joint 15. A reflector 541 is disposed at the center of the spherical joint 15. The reflector 541 is, for example, a cube corner.

  The center of the spherical joint 15 is fixed with respect to the moving stage 5. Accordingly, the rotation mechanism formed by the spherical joint 15 is provided on the moving stage 5 and supports the inner cylinder 1004 so as to be rotatable around two rotation axes that are orthogonal to each other at a fixed point with respect to the moving stage 5. .

  The electromagnet 1006 and the permanent magnet 1009 form a linear motor that generates a driving force for expanding and contracting the telescopic rod 10. In addition, compression is performed by setting pressure so as to balance the weight of the driven part from the gas inlet 1007 to the space 1010 surrounded by the inner surface of the outer cylinder 1003, the outer surface of the inner cylinder 1004, the piston 1008, and the seal part 1005 By supplying gas, the load on the linear motor can be reduced.

  The laser interferometer 4103 receives input light through the optical fiber 4111 and generates measurement light and reference light from the input light. The laser beam exit 4107 of the laser interferometer 4103 emits measurement light with a straight line connecting the center of the spherical joint 101 and the center of the spherical joint 15 as the optical axis. The measurement light passes through the telescopic lens barrel 1002 and is applied to the reflector 541. The measurement light reflected by the reflector 541 is incident on the laser light exit 4107 of the laser interference length meter 4103. The laser interference length meter 4103 causes the measurement light reflected by the reflector 541 to interfere with the reference light to generate interference light, and outputs the interference light via the optical fiber 4112. Based on the interference light, the distance between the center of the spherical joint 101 and the center of the spherical joint 15 can be measured.

  According to the present embodiment, the telescopic lens barrel 1002 is a part of the telescopic rod 10. Therefore, the manufacturing cost of the parallel mechanism 500 is reduced, and the driven part driven by the linear drive mechanisms 1 to 3 is reduced in weight. Since the driven part is reduced in weight, the moving stage 5 can be moved at high speed. The telescopic rod 10 may be a linear actuator that includes a ball screw having an optical path formed therein.

  Furthermore, the spherical joint 101 and the interferometer support 1001 are preferably formed of a low thermal expansion material such as super invar (FN-315) or invar (FN-36). Even when the temperature around the parallel mechanism 500 changes, the distance between the center of the spherical joint 101 and the center of the spherical joint 15 can be accurately measured.

  With reference to FIG. 22, the configuration of laser interference length measuring instrument 4103 according to the present embodiment will be described in detail. The laser interferometer 4103 includes a collimator lens 42, a polarizing beam splitter 43, a polarizing plate 44, λ / 4 plates 46 and 47, and a cube corner 51. The laser interference length meter 4103 inputs input light from the light source 41 provided outside the laser interference length meter 4103 via the optical fiber 4111.

  The input light passes through the collimator lens 42 and is then divided into two by the polarization beam splitter 43. On the other hand, (S-polarized light) is reflected by the polarization beam splitter 43 as reference light and travels toward the polarizing plate 44. The other (P-polarized light) travels straight as measurement light and is applied to the reflector 541 through the λ / 4 plate 47. Here, the measurement light is converted from P-polarized light to circularly-polarized light by the λ / 4 plate 47.

  The measurement light reflected by the reflector 541 is incident on the laser interference length meter 4103. The measurement light incident on the laser interferometer 4103 enters the cube corner 51 via the λ / 4 plate 47, the polarization beam splitter 43, and the λ / 4 plate 46. Here, the measurement light is converted from circularly polarized light to S polarized light by the λ / 4 plate 47, and converted from S polarized light to circularly polarized light by the λ / 4 plate 46. The measurement light reflected by the cube corner 51 passes through the λ / 4 plate 46, the polarizing beam splitter 43, and the polarizing plate 44, and interferes with the above-described reference light to generate interference light. Here, the measurement light is converted from circularly polarized light to P-polarized light by the λ / 4 plate 46. The laser interference length meter 4103 outputs the interference light to the photodetector 45 provided outside the laser interference length meter 4103 via the optical fiber 4112.

  According to the present embodiment, by using the optical fibers 4111 and 4112, the light source 41 and the photodetector 45 can be provided outside the laser interference length meter 4103. Therefore, the laser interferometer 4103 is reduced in size, and it becomes easy to incorporate the laser interferometer 4103 into the telescopic rod 10. The optical fibers 4111 and 4112 may also be applied to the laser trackers 411, 421, 422, 431 to 433 and the universal laser interference measurement units 441 to 443.

Other Embodiments The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention. In the first to third embodiments, one or two or more laser trackers are provided on the surface of the base plate opposite to the moving stage side, and the laser tracker is provided on the base plate side of the moving stage through the opening of the base plate. An example in which the laser beam is irradiated has been described. However, the laser tracker may be provided on the surface of the base plate on the moving stage side. In this case, the opening of the base plate can be omitted. However, considering the possibility of interference between the laser tracker and the linear drive mechanism, the laser tracker is preferably provided on the surface of the base plate opposite to the moving stage as in the above-described embodiment.

  In the fourth embodiment, the case where the universal laser interference length measuring units 441 to 443 are used instead of the laser trackers 431 to 433 of the parallel mechanism 300 has been described. However, the universal laser interference length measuring unit 441 can be used instead of the laser tracker 411 of the parallel mechanism 100, and the universal laser interference length measuring units 441 and 442 are used instead of the laser trackers 421 and 422 of the parallel mechanism 200. It is possible. In this case, the laser trackers 421 and 422 output the azimuth angle φ and the elevation angle θ of the biaxial rotation mechanism 4102 to the control unit 7.

  In the above-described embodiment, a three-degree-of-freedom parallel mechanism having three linear drive mechanisms has been described. Needless to say, a laser tracker and a reflector can be applied to other parallel mechanisms.

  A universal laser interference length measurement unit and reflector may be applied to other types of parallel mechanisms, and a laser interference length meter and reflector may be incorporated into a linear drive mechanism of another type of parallel mechanism. A retro reflector can be used as the reflector.

  For example, it has 6 linear drive mechanisms and can be driven in three directions of XYZ orthogonal to each other, in the rotational direction around the X axis, in the rotational direction around the Y axis, and in the rotational direction around the Z axis. It is also possible to use a mechanism. In this configuration, the six linear drive mechanisms and the base plate, and the six linear drive mechanisms and the moving stage are connected by spherical joints (12 in total). In this case, even when the parallelism of the moving stage with respect to the base plate is deviated, the moving stage can be driven in the rotational direction, so that the parallelism can be finely adjusted according to the measurement result by a laser tracker or the like.

  In the above-described embodiment, a so-called Stewart Platform type parallel mechanism has been described, but this is merely an example. For example, other types of parallel mechanisms such as a hexa type or a direct acting fixed type may be used. Furthermore, the drive mechanism that connects the base plate and the moving stage is not limited to the direct drive mechanism, and other drive mechanisms such as a multistage bending drive mechanism or a slide mechanism having a rotation drive mechanism section can also be used.

  The above-described laser tracker can be replaced with an arbitrary measurement unit that emits arbitrary coherent light including laser light and makes the coherent light and reflected light interfere to calculate the moving distance of the moving stage. Further, the reflector is not limited to the cat's eye, and can be replaced with an arbitrary reflecting portion that reflects incident light in the reverse direction.

  In the above-described embodiment, the example in which the parallel mechanism is incorporated in the shape measuring machine has been described, but this is only an example. That is, the parallel mechanism according to the above-described embodiment can be incorporated in an apparatus having a drive mechanism such as another measuring machine, a machine tool, or an operation simulation apparatus.

  When the parallel mechanism according to the above-described embodiment is incorporated into a shape measuring machine such as a coordinate measuring machine (CMM), the output of the laser tracker, the output of the universal laser interferometric length measuring unit, or the laser incorporated into the linear drive mechanism. The output of the interferometer may or may not be fed back to the drive mechanism of the parallel mechanism. Since the position of the moving stage can be observed with high accuracy based on the output, in the case of stationary point measurement, the coordinates of the object to be measured can be obtained accurately without feedback of the output. On the other hand, in the case of scanning measurement, since it is necessary to drive the moving stage with high accuracy, it is preferable that the output is fed back to the driving mechanism of the parallel mechanism. The same applies to the case where the parallel mechanism according to the above-described embodiment is incorporated in a machine tool or an operation simulation apparatus.

1-3 Linear drive mechanism 4 Base plate 5 Moving stage 6 Probe 6a Stylus 6b Tip sphere 7 Control unit 8 Pole 10 Telescopic rods 11, 12 Linear rods 13, 14 Linear bearings 15-17, 101, 131, 141 Spherical joint 18 , 19 Fixing tools 411, 421, 422, 431 to 433 Laser trackers 511, 521, 522, 531 to 533 Reflectors 611, 621, 622, 631 to 633 Opening 71 Measured object 72 Stage 100, 200, 300 Parallel mechanism 4100 Base block 4101 Reference sphere 4102 Two-axis rotation drive mechanism 4103 Laser interferometer 4104 Laser light 4105 Reflected light 4106 Base 5101 Base 5102 Cat's eyes J11-S13, J21-J23 Two-degree-of-freedom joints 81-83 Parallel mechanism 441-443 Universal laser interference measurement unit 451 Universal interferometer unit 541 Reflector 701 Drive control unit 702 Arithmetic processing unit 811, 821, 831, 1002 Telescopic barrel 812 Universal joint 1001 Interferometer support unit 1003 , 8101 First part 1004, 8102 Second part 1005 Sealing part 1006 Electromagnet 1007 Gas inlet 1008 Piston 1009 Permanent magnet 1010 Space 1011 Sliding guide 4107 Laser light exit 4108 Carriage 4111 4112 Optical fiber L411 Straight line O Reference center

Claims (10)

A base plate;
A moving stage that moves relative to the base plate;
A plurality of drive mechanisms provided between the base plate and the moving stage, for changing the relative position of the moving stage with respect to the base plate;
A plurality of joints connecting each of the plurality of driving mechanisms, the base plate and the moving stage;
A plurality of reflectors that are provided at equal intervals on the surface of the moving stage on the base plate side and reflect incident light;
In order to irradiate each of the reflection parts with measurement light, a plurality of equal distances are provided on the base plate , and the interference between the measurement light reflected by the reflection part and the reference light is observed to determine the movement distance of the moving stage and A measuring unit for measuring the moving direction;
A control unit for controlling the plurality of drive mechanisms ,
The measurement unit is disposed on a line connecting any of the plurality of joints connecting the plurality of drive mechanisms and the base plate, and a centroid of the surface of the base plate on which the measurement unit is installed,
The reflecting portion is disposed on a line connecting any one of the plurality of joints connecting the plurality of driving mechanisms and the moving stage and a centroid of the surface of the moving stage on which the reflecting portion is installed. The
Parallel mechanism. Two measuring units are provided,
Two reflection parts are provided,
The two measurement units are installed at positions symmetrical with respect to the centroid of the surface of the base plate,
The two reflecting portions are installed at positions symmetrical with respect to the centroid of the surface of the moving stage.
The parallel mechanism according to claim 1 . Three measurement units are provided,
Three reflection portions are provided,
The three measuring units are installed at equally spaced positions with reference to the centroid of the surface of the base plate,
The three reflecting portions are installed at equally spaced positions with reference to the centroid of the surface of the moving stage.
The parallel mechanism according to claim 1 . First to sixth drive mechanisms constituting the plurality of drive mechanisms;
First to sixth joints connecting the base plate and each of the first to sixth drive mechanisms, which constitute the plurality of joints;
Comprising the seventh to twelfth joints connecting the moving stage and each of the first to sixth drive mechanisms, constituting the plurality of joints;
The first to twelfth joints are spherical joints,
The parallel mechanism according to any one of claims 1 to 3 . The measuring unit is
A sphere whose relative position is fixed with respect to the base plate;
An interferometer that emits the measurement light whose optical axis is a line connecting the center of the sphere and the reflection portion, and observes interference between the measurement light reflected by the reflection portion and the reference light;
A drive unit that drives the interferometer around two rotation axes orthogonal to each other at the center of the sphere,
The parallel mechanism as described in any one of Claims 1 thru | or 4 . The two rotation axes are parallel to a surface of the base plate on which the measurement unit is installed, on which the measurement unit is installed.
The parallel mechanism according to claim 5 . The measuring unit is
An interferometer that emits the measurement light and causes the measurement light reflected by the reflector to interfere with the reference light;
A base plate-side rotation mechanism that is provided on the base plate and supports the interferometer so as to be rotatable around two rotation axes orthogonal to each other at a first point fixed to the base plate;
A telescopic structure comprising a first part fixed to the interferometer and a second part reciprocating linearly with respect to the first part;
Moving stage side rotation that is provided on the moving stage and supports the second part of the telescopic structure so as to be rotatable around two rotation axes orthogonal to each other at a second point fixed to the moving stage. A mechanism,
The reflecting portion is disposed at the second point.
The parallel mechanism as described in any one of Claims 1 thru | or 4 . The measurement unit includes a sphere whose center coincides with the first point;
The interferometer emits the measurement light with a straight line connecting the first point and the second point as an optical axis;
The parallel mechanism according to claim 7 . The plurality of drive mechanisms include a linear actuator,
The telescopic structure is part of the linear actuator;
The parallel mechanism according to claim 7 . A first optical fiber and a second optical fiber connected to the interferometer;
The interferometer inputs input light through the first optical fiber, generates the measurement light and the reference light from the input light, and causes the measurement light reflected by the reflection unit to interfere with the reference light. Generating interference light and outputting the interference light through the second optical fiber,
The parallel mechanism according to any one of claims 7 to 9 .

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