JP6887644B2 - Calibration device and calibration method - Google Patents

Description

The present invention relates to a calibration device and a calibration method for calibrating a device to be calibrated having a movable portion that can be displaced in a plurality of directions.

Conventionally, it has a drive unit (movable part) that displaces the position and orientation of the touch probe, and by bringing this touch probe into contact with an object to be measured such as a mechanical part, various measurements such as the size and shape of the object to be measured can be performed. A three-dimensional measuring machine (device to be calibrated) is known (see Patent Document 1).

A three-dimensional measuring machine requires regular calibration (inspection) to guarantee the quality of its measurement. Therefore, in the past, calibration was performed by a method using artifacts such as step gauges or block gauges in accordance with the provisions of JIS B7440 series (ISO 10360 series) of Japanese Industrial Standards (JIS) (non-patent documents). 1).

Specifically, the dimensional measurement accuracy of the coordinate measuring machine is evaluated based on the dimensional error which is the difference between the dimension of the artifact and the measurement result of the dimensional measurement by the coordinate measuring machine. In this case, in the JIS B7440 series described above, it is determined that the dimensional measurement at five points is repeated three times in each of the seven calibration directions within the measurement range of the coordinate measuring machine. Of the seven calibration directions, four directions are defined as four diagonal directions within the above measurement range, and the remaining three directions are the moving directions (XYZ axis directions) of the probe of the coordinate measuring machine. .. When the maximum value of the dimensional error is within the maximum permissible error (MPE) of the coordinate measuring machine, the accuracy of the three-dimensional measuring machine is guaranteed.

However, the conventional method using an artifact such as a step gauge has a problem that it is necessary to level the temperature of the artifact for a long time and it is difficult to produce and manage the artifact.

Therefore, Non-Patent Document 1 discloses a method of calibrating (inspecting) a coordinate measuring machine using a pulse interferometer using an optical comb (referred to as an optical frequency comb) as a light source. Specifically, a ball lens is attached to the probe head of the coordinate measuring machine, and the ball lens is emitted from a pulse interferometer or the like arranged on a surface plate (also referred to as a table or stage) of the three-dimensional measuring machine. Target the optical frequency comb (measurement light). Since the optical comb has extremely high frequency stability, a national standard or an international standard is secured for length measurement using the optical comb. Therefore, by evaluating the positioning accuracy of the probe head of the CMM based on the absolute distance guaranteed by the pulse interferometer using the optical comb, the calibration (inspection) of the CMM can be performed with high accuracy and in a short time. Can be done with.

Also in Non-Patent Document 2, it is disclosed that a ball lens is attached to the probe head of the coordinate measuring machine and the three-dimensional measuring machine is calibrated (inspected) by a method of irradiating the ball lens with a laser beam. There is. Further, Non-Patent Document 3 discloses a technique in which a plurality of length measuring units using laser light are arranged in a three-dimensional measuring machine to simultaneously perform high-precision length measuring in a plurality of directions.

Japanese Unexamined Patent Publication No. 2009-010675

"2015-2016 3D Absolute Position Measurement Report by Optical Comlaser, Takamasu Laboratory, Department of Precision Engineering, Graduate School of Engineering, University of Tokyo", [online], [Search on July 20, 2017], Internet <Http://www.nanolab.tu-tokyo.ac.jp/pdffiles/comb-3d2017.pdf> "Etalon Laser Tracer Series Machine Tool & Coordinate Measuring Machine Space Correction System", [online], [Search on July 20, 2017], Internet <http://www.ykt.co.jp/products/etalon/ pdf / metalon_lasertracer_catalog.pdf> "LINECAL-AUTOMATISCHE VOLUMETRISCHE KALIBRIERUNG", [online], [Search on July 20, 2017], Internet <http://www.etalon-ag.com/wp-content/uploads/pdf/Datasheet_LineCAL.pdf>

By the way, according to the JIS B7440 series described above, it is necessary to evaluate the dimensional measurement accuracy (probe positioning accuracy) of the coordinate measuring machine for each calibration direction in a total of 7 directions. Therefore, when calibrating (inspecting) the coordinate measuring machine by the method disclosed in Non-Patent Document 1 and Non-Patent Document 2, the setting (arrangement change) of the pulse interferometer on the surface plate is performed for each calibration direction. ), And each time, so-called "setup change" is required to align the pulse interferometer with the ball lens of the probe head. For this reason, not only man-hours are required, but also the environment (temperature, etc.) changes in each calibration direction due to the time difference in each calibration direction, which causes a problem that calibration under the same conditions becomes difficult.

Further, as in the method disclosed in Non-Patent Document 3, a plurality of length measuring units are arranged in the coordinate measuring machine, and the length is measured by individual length measuring units for each calibration direction. It is possible to evaluate the dimensional measurement accuracy (probe positioning accuracy) of the coordinate measuring machine in seven directions. However, when the coordinate measuring machine is large, if the laser beam is distributed from one light source to each length measuring unit, the amount of laser light emitted from each length measuring unit may become unstable. Therefore, it is difficult to construct a stable proofreading (evaluation) system by the method disclosed in Non-Patent Document 3.

The present invention has been made in view of such circumstances, and regardless of the size of the device to be calibrated, it is possible to omit the setup change in the device to be calibrated, improve the accuracy of calibration, and shorten the time. It is an object of the present invention to provide a calibration device and a calibration method.

A calibrator for achieving the object of the present invention is a calibrator that calibrates a device to be calibrated having a movable portion that can be displaced in a plurality of directions. When a plurality of reflectors are arranged in the device to be calibrated in an arrangement pattern corresponding to a plurality of calibration directions, the first control unit controls the position and orientation of the optical head to align the optical head with respect to the reflector. The optical frequency comb light source that emits an optical comb having a repetition frequency and the optical comb emitted from the optical frequency comb light source are branched into measurement light and reference light, and the measurement light is emitted from the optical head to the reflector. An interference optical system that emits reference light to a reference surface at a predetermined position and outputs an optical interference signal between the measurement light received by the optical head from the reflector and the reference light reflected by the reference surface, and a repetition frequency. When the position having the space interval determined based on the specific position is set as the specific position, the second control unit that drives the movable part and positions the optical head at each specific position along the calibration direction corresponding to the reflector from the reflector. An optical path difference variable unit provided in the interference optical system and changing the optical path difference between the optical path of the measurement light and the optical path of the reference light each time the optical head is positioned at a specific position by the second control unit, and the optical path difference. A signal detection unit that detects the optical interference signal output from the interference optical system while the variable unit changes the optical path difference, and a first control unit, an optical frequency comb light source, and a second control for each reflector. It includes a unit, a variable optical path difference unit, and a third control unit that repeatedly operates a signal detection unit.

According to this calibrator, by providing the optical head in the movable part of the calibrated device, the alignment of the optical head with respect to each of the plurality of reflectors arranged in the calibrated device is executed by driving the movable part. be able to. As a result, it is possible to omit the setup change work for each calibration direction by the operator without providing a plurality of optical heads in the device to be calibrated.

In the calibration device according to another aspect of the present invention, the positioning accuracy for measuring the positioning accuracy of the optical head by the movable portion for each specific position based on the detection result of the signal detection unit and the change in the optical path difference due to the optical path difference variable portion. A measuring unit is provided, and the third control unit repeatedly operates the positioning accuracy measuring unit for each reflector. As a result, the data required for calibration (inspection) of the device to be calibrated, that is, the positioning accuracy of the optical head for each calibration direction can be obtained.

In the calibration apparatus according to another aspect of the present invention, the optical path difference variable unit changes the optical path difference within a certain range centered on a predetermined reference. As a result, the measurement result of the positioning accuracy of the optical head by the movable part of the device to be calibrated can be obtained based on the optical path difference at which the optical interference signal is maximized.

In the calibration apparatus according to another aspect of the present invention, the optical path of the measurement light and the optical path of the reference light pass through a common optical path. This makes it possible to eliminate the difference in the environment between the optical path of the measurement light and the optical path of the reference light, and reduce the error that occurs in the measurement for calibration.

In the calibration apparatus according to another aspect of the present invention, the optical path of the measurement light and the optical path of the reference light are each composed of an optical fiber cable. This makes it possible to form a long common path (common optical path) for the measurement light and the reference light.

A calibration method for achieving the object of the present invention is a calibration method for calibrating a device to be calibrated having movable parts that can be displaced in a plurality of directions, in which a plurality of reflectors are covered with an arrangement pattern corresponding to a plurality of calibration directions. The first step in which the first control unit controls the position and orientation of the optical head to align the optical head with respect to the reflector while the optical head is attached to the movable portion and is arranged in the calibration device. The second step of emitting an optical comb having a repeating frequency from the optical frequency comb light source and the interference optical system branch the optical comb into measurement light and reference light, and emit the measurement light from the optical head to the reflector and refer to it. Based on the third step of emitting light to a reference surface at a predetermined position and outputting an optical interference signal between the measurement light received by the optical head from the reflector and the reference light reflected by the reference surface, and the repetition frequency. When the position having the determined space interval is set as a specific position, the second control unit drives the movable part to position the optical head from the reflector to the specific position along the calibration direction corresponding to the reflector. The fourth step, the fifth step in which the optical path difference variable unit changes the optical path difference between the optical path of the measurement light and the optical path of the reference light each time the optical head is positioned at a specific position, and the signal detection unit While the change of the optical path difference by the optical path difference variable unit is being executed, the sixth step of detecting the optical interference signal output from the interference optical system and the third control unit perform the first step to the first step for each reflector. It has a seventh step of repeatedly executing each step up to the sixth step.

In the calibration method according to another aspect of the present invention, the eighth position in which the positioning accuracy of the optical head by the movable portion is measured for each specific position based on the detection result of the signal detection unit and the change in the optical path difference due to the optical path difference variable portion. The third control unit repeatedly operates the eighth step for each reflector.

The calibration device and the calibration method of the present invention can realize omission of setup change in the device to be calibrated, high accuracy of calibration, and shortening of time regardless of the size of the device to be calibrated.

It is a schematic diagram of a three-dimensional measurement system. It is a perspective view of a probe head. It is the schematic of the calibration apparatus main body. It is explanatory drawing for demonstrating an optical comb in a time domain and an optical comb in a frequency domain. It is explanatory drawing for demonstrating the wiring state of the optical fiber cable between a pulse interferometer and a laser probe. It is sectional drawing of the optical fiber cable shown in FIG. It is a figure which shows an example of the reference light (upper row) and measurement light (lower row) in the time domain. It is a top view of seven ball lenses arranged on the upper surface of a surface plate at the time of calibration of a three-dimensional measuring machine. It is explanatory drawing for demonstrating the calibration direction D1. It is explanatory drawing for demonstrating the calibration direction D2. It is explanatory drawing of the attitude control of a laser head. It is explanatory drawing of the position control of a laser head. It is explanatory drawing for demonstrating the relationship between the position of a laser head, and the intensity of an optical interference signal detected by a photodetector. It is explanatory drawing of the positioning control of a laser head. It is a functional block diagram which shows the function of a computer. It is a flowchart which shows the flow of the calibration process of a three-dimensional measuring machine, more specifically, the measurement process of the positioning accuracy of a laser head. It is a flowchart which shows the flow of the creation process of a calibration program.

[Overall configuration of 3D measurement system]
FIG. 1 is a schematic view of the three-dimensional measurement system 9. As shown in FIG. 1, the coordinate measuring system 9 includes a coordinate measuring machine 10 (CMM: Coordinate Measuring Machine) corresponding to the device under test of the present invention, a drive controller 30, a calibration device main body 40, and a computer 60. And.

[Configuration of 3D measuring machine]
The three-dimensional measuring machine 10 is a coordinate value (coordinate value in the X-axis direction) at a measurement position in an object (workpiece) (not shown) while shifting the position and orientation of the contact type touch probe 25a (see FIG. 2). , A coordinate value in the Y-axis direction, and a coordinate value in the Z-axis direction), and is also referred to as a coordinate measuring machine or a three-dimensional coordinate measuring machine. The X-axis, Y-axis, and Z-axis in FIG. 1 are coordinate systems determined based on the machine coordinate origins unique to the coordinate measuring machine 10.

The coordinate measuring machine 10 includes a gantry 12, a surface plate 14 provided on the gantry 12, a right Y carriage 16R and a left Y carriage 16L erected at both ends of the surface plate 14, a right Y carriage 16R, and a right Y carriage 16R. An X guide 18 for connecting the upper portion of the left Y carriage 16L is provided. The portal frame 19 is composed of the right Y carriage 16R, the left Y carriage 16L, and the X guide 18.

An object to be measured (not shown) is arranged on the upper surface of the surface plate 14. Further, when the three-dimensional measuring machine 10 is calibrated by the calibration device main body 40 described later, seven ball lenses 80A and 80B are arranged in a predetermined arrangement pattern on the upper surface of the surface plate 14.

Sliding surfaces on which the right Y carriage 16R and the left Y carriage 16L slide along the Y-axis direction are formed at both ends of the surface plate 14. Further, the right Y carriage 16R and the left Y carriage 16L are provided with air bearings (not shown) at positions facing the sliding surface of the surface plate 14. As a result, the right Y carriage 16R and the left Y carriage 16L can be moved in the Y-axis direction together with the X guide 18.

An X carriage 20 is attached to the X guide 18. A sliding surface on which the X carriage 20 slides is formed on the X guide 18 along the X-axis direction. Further, the X carriage 20 is provided with an air bearing (not shown) at a position facing the sliding surface of the X guide 18. As a result, the X carriage 20 becomes movable in the X-axis direction.

A Z carriage 22 (also referred to as a Z spindle) is attached to the X carriage 20. Further, the X carriage 20 is provided with an air bearing (not shown) for guiding the Z carriage 22 in the Z axis direction. As a result, the Z carriage 22 is held by the X carriage 20 so as to be movable in the Z axis direction.

A probe head 24 is attached to the lower end of the Z carriage 22. The right Y carriage 16R, the left Y carriage 16L, the X carriage 20, the Z carriage 22, and the second drive unit 36 described later constitute the movable unit of the present invention.

FIG. 2 is a perspective view of the probe head 24. As shown by reference numeral 2A in FIG. 2, the probe head 24 is, for example, a 5-axis simultaneous control probe head provided with a stepless positioning mechanism, and various probes are interchangeably attached. Specifically, when measuring an object to be measured (not shown) by the coordinate measuring machine 10, a touch probe 25a of a contact type touch trigger is attached to the probe head 24. The base end of the stylus 25b is attached to the tip of the touch probe 25a. A contactor 25c is attached to the tip of the stylus 25b. The stylus 25b and the contactor 25c form a stylus for the touch probe 25a.

The probe head 24 includes a first drive unit 35 such as a motor that rotates the touch probe 25a around each of two rotation axes (a rotation axis parallel to the Z axis and a rotation axis perpendicular to the Z axis). Is provided. In FIG. 1, the first drive unit 35 is shown outside the probe head 24 in order to prevent the drawings from becoming complicated. The first drive unit 35 can adjust the rotation angle ψ and the rotation angle θ of the touch probe 25a steplessly, and as a result, the posture of the touch probe 25a can be arbitrarily displaced (rotated). ..

As shown by reference numeral 2B in FIG. 2, when the three-dimensional measuring machine 10 is calibrated by the calibration device main body 40 described later, the laser probe 47 is attached to the probe head 24. The laser probe 47 constitutes a part of the calibration device main body 40, and the optical comb 50 input from the pulse interferometer 44 described later is directed toward the ball lenses 80A and 80B arranged on the surface plate 14. Exit. The probe head 24 to which the laser probe 47 is attached corresponds to the optical head of the present invention, and is hereinafter referred to as a laser head 24L. Further, the type and configuration of the laser head 24L are not particularly limited as long as its posture (light emission direction) can be changed.

The laser head 24L can adjust the rotation angle φ and the rotation angle θ of the laser probe 47 steplessly by the first driving unit 35 described above, and as a result, the posture of the laser head 24L is arbitrarily displaced. Can be (rotated). Therefore, the emission direction of the measurement light 50A (see FIG. 3) emitted from the laser head 24L, which will be described later, can be directed to an arbitrary position within the measurement range of the coordinate measuring machine 10.

Returning to FIG. 1, although not shown, the coordinate measuring machine 10 has a Y-axis drive unit that moves the portal frame 19 in the Y-axis direction and an X-axis drive that moves the X-carriage 20 in the X-axis direction. A second drive unit 36 including a unit and a Z-axis drive unit that moves the Z-carriage 22 in the Z-axis direction is provided. As a result, the probe head 24 (laser head 24L) can be moved in the three-axis directions (XYZ directions) orthogonal to each other. The positions and orientations of the touch probe 25a and the laser probe 47 can be displaced by the first drive unit 35 and the second drive unit 36.

A linear scale (not shown) for detecting the position in the Y-axis direction is provided at the end of the surface plate 14 on the right Y carriage 16R side. Further, the X guide 18 is provided with a linear scale for detecting the position in the X-axis direction (not shown), and the Z carriage 22 is provided with a linear scale for detecting the position in the Z-axis direction (not shown).

On the other hand, the right Y carriage 16R is provided with a Y-axis direction position detection head (not shown) that reads a linear scale for Y-axis direction position detection. Further, the X-carrying 20 includes an X-axis direction position detection head (not shown) and a Z-axis direction position detection head (not shown) that read the X-axis direction position detection linear scale and the Z-axis direction position detection linear scale, respectively. ) And are provided. Further, the probe head 24 is provided with a rotation angle detection unit (not shown) such as a rotary encoder that detects the rotation angles θ and φ of the touch probe 25a and the laser probe 47, respectively. When measuring an object to be measured (not shown) by the coordinate measuring machine 10, the contact 25c of the touch probe 25a is measured based on the detection result of the XYZ axis direction detection head and the detection result of the rotation angle detection unit. It is possible to detect the coordinate value in the XYZ axis direction when it comes into contact with an object.

The coordinate measuring machine 10 controls the first drive unit 35 and the second drive unit 36 to control the movement of the probe head 24, that is, the displacement of the positions and postures of the touch probe 25a and the laser probe 47. It has. Here, the coordinate measuring machine 10 has an automatic mode in which measurement and calibration are automatically performed and a manual mode in which measurement and calibration are manually performed. Therefore, in the automatic mode, the drive controller 30 controls the first drive unit 35 and the second drive unit 36 under the control of the computer 60 described later to displace the positions and postures of the touch probe 25a and the laser probe 47.

Further, the drive controller 30 is provided with a manual operation unit (not shown) for manually operating the positions and orientations of the touch probe 25a and the laser probe 47. Therefore, in the manual mode, the drive controller 30 displaces the positions and postures of the touch probe 25a and the laser probe 47 by controlling the first drive unit 35 and the second drive unit 36 in response to the operation input to the manual operation unit. Let me.

A contact detection sensor (not shown) of the touch probe 25a described above, a XYZ axial direction detection head (not shown) and a rotation angle detection unit (not shown) described above are connected to the drive controller 30. .. Then, the drive controller 30 detects that the contact 25c of the touch probe 25a has come into contact with the measurement position in the object to be measured by the contact detection sensor at the time of measuring the object to be measured (not shown). The detection results of each of the direction detection head and the rotation angle detection unit are acquired, and the coordinate values of the measurement position in the XYZ axis direction are detected. The coordinate values of the measurement position in the XYZ axis direction are output from the drive controller 30 to the computer 60.

Further, the drive controller 30 acquires the detection results of the XYZ axial direction detection head and the rotation angle detection unit at the time of calibration of the coordinate measuring machine 10, and outputs each detection result to the computer 60. As a result, the position and orientation of the laser probe 47 can be acquired in the computer 60.

[Configuration of calibration device]
FIG. 3 is a schematic view of the calibration device main body 40. As shown in FIGS. 1 and 3, the calibration device main body 40 constitutes the calibration device of the present invention together with the computer 60 described later. The calibration device main body 40 positions the probe head 24 (laser head 24L) of the coordinate measuring machine 10 by using seven ball lenses 80A and 80B arranged on the upper surface of the surface plate 14 of the coordinate measuring machine 10. Measure the accuracy (that is, the dimensional measurement accuracy). The calibrator main body 40 includes an optical frequency comb light source 42, an etalon 43, a pulse interferometer 44, a laser probe 47, a photodetector 48, and the like.

The optical frequency comb light source 42 generates an optical comb 50 having a predetermined repetition frequency, and outputs the optical comb 50 to the etalon 43 via the optical fiber cable C1. Since the configuration of the optical frequency comb light source 42 is known, detailed description thereof will be omitted.

FIG. 4 is an explanatory diagram for explaining the optical comb 50 in the time domain and the optical comb 50 in the frequency domain. As shown by reference numeral 4A in FIG. 4, the optical comb 50 appears as a sequence of ultrashort pulses that are very stable in the time domain. Further, as shown by reference numeral 4B in FIG. 4, the optical comb 50 is composed of a large number of lights that are _{accurately separated by a constant frequency (repetition frequency prep) in the frequency domain.} Specifically optical comb 50 is outputted as a stable pulse train having a time interval T _R of the reciprocal of the repetition frequency f _{rep. Note that fceo} in the figure is an offset frequency.

Returning to FIG. 3, as the etalon 43, for example, Fabry Perot etalon having a fixed intersymbol interference distance is used. The etalon 43 generates an optical comb 50 having _{a desired repetition frequency prep} from the optical comb 50 input from the optical frequency comb light source 42 via the optical fiber cable C1, and uses the optical comb 50 to connect the optical fiber cable C2. It is output to the pulse interferometer 44 via. For example the etalon 43 of the present embodiment generates an optical comb 50 having a repetition frequency _{f rep} of 1 GHz. By interposing the etalon 43 in this way, it is possible to generate _{an optical comb 50 having a repetition frequency frep} that matches the measurement purpose, that is, an optical comb 50 in which the pulse interval of the pulse train (the spatial distance _Dr described later) is shortened. it can.

When the optical comb 50 output from the optical frequency comb light source 42 is originally _{generated as the optical comb 50 having a repeating frequency prep} that matches the measurement purpose, the etalon 43 can be omitted.

The pulse interferometer 44 corresponds to the interference optical system of the present invention, and is a so-called common path (common optical path) type. The pulse interferometer 44 includes a fiber circulator 52, a beam splitter 53, an optical path difference variable portion 54, optical fiber cables C3 to C6, and the like.

The fiber circulator 52 outputs the optical comb 50 input from the etalon 43 via the optical fiber cable C2 to the beam splitter 53 via the optical fiber cable C3.

The beam splitter 53 splits (splits) the optical comb 50 input from the fiber circulator 52 via the optical fiber cable C3 into the measurement light 50A and the reference light 50B. Then, the beam splitter 53 outputs the measurement light 50A to the optical fiber cable C4 and outputs the reference light 50B to the optical fiber cable C5.

The optical fiber cable C4 constitutes the measurement optical path OP1 which is the optical path of the measurement light 50A. One end of the optical fiber cable C4 is connected to the beam splitter 53, and the other end is connected to the laser probe 47 of the laser head 24L. As a result, the measurement light 50A output from the beam splitter 53 to the optical fiber cable C4 is input to the laser head 24L (laser probe 47) through the optical fiber cable C4.

The laser probe 47 of the laser head 24L emits the measurement light 50A input from the optical fiber cable C4 toward the ball lenses 80A and 80B at the time of calibrating the coordinate measuring machine 10. As a result, the measurement light 50A reflected by the ball lenses 80A and 80B is incident on the laser probe 47, and is further input from the laser probe 47 to the beam splitter 53 via the optical fiber cable C4.

The optical fiber cable C5 constitutes the reference optical path OP2, which is the optical path of the reference light 50B. One end side of the optical fiber cable C5 is connected to the beam splitter 53, and the reflection coated surface 59 is formed on the other end side. Further, an optical path difference variable portion 54 is provided in the middle of the optical fiber cable C5.

The optical path difference variable unit 54 changes the optical path length of the reference light 50B within a certain range, so that the optical path difference between the optical path of the measurement light 50A and the optical path of the reference light 50B (hereinafter, simply referred to as an optical path difference) is within a certain range. Change with. The optical path difference variable portion 54 includes a first collimator 55A, a reflector 56, a reflector 57, a scanning stage 58, and a second collimator 55B.

The first collimator 55A emits the reference light 50B input from the beam splitter 53 toward the reflector 56 as parallel rays.

The reflector 56 has a first reflecting surface 56A that reflects the reference light 50B input from the first collimator 55A toward the reflector 57, and a reference light 50B that is incident from the reflector 57 through the first reflecting surface 56A as the second collimator 55B. It has a second reflecting surface 56B that reflects toward. The second reflecting surface 56B reflects the reference light 50B input from the second collimator 55B toward the reflector 57. Further, the first reflecting surface 56A reflects the reference light 50B incident from the reflector 57 through the second reflecting surface 56B toward the first collimator 55A.

The reflector 57 is arranged on the optical path of the reference light 50B reflected by the reflector 56. The reflector 57 reflects the reference light 50B incident from one of the first reflecting surface 56A and the second reflecting surface 56B of the reflector 56 to the other of the first reflecting surface 56A and the second reflecting surface 56B.

The scanning stage 58 holds the reflector 57 in a reciprocating manner. The scanning stage 58 scans (reciprocates) the reflector 57 along a direction parallel to the optical path of the reference light 50B between the reflector 56 and the reflector 57 under the control of a computer 60 described later. As a result, the optical path length of the reference light 50B can be changed within a certain range, and as a result, the optical path difference described above can also be changed within a certain range.

The second collimator 55B collects the reference light 50B incident from the reflector 56, and outputs the reference light 50B to the reflection coated surface 59 via the optical fiber cable C5.

The reflective coated surface 59 corresponds to a reference surface at a predetermined position of the present invention. The reflective coated surface 59 reflects the reference light 50B input from the second collimator 55B via the optical fiber cable C5 and returns it to the second collimator 55B. Various mirrors, reflectors, and the like may be arranged on the other end side of the optical fiber cable C5 as a reference surface at a predetermined position of the present invention.

The reference light 50B reflected from the reflection coat surface 59 toward the second collimator 55B passes through the second collimator 55B, the second reflection surface 56B, the reflector 57, the first reflection surface 56A, the first collimator 55A, and the like, and is a beam. It is input to the splitter 53.

The optical fiber cables C4 and C5 have a sufficient length so that the other end side of each of the optical fiber cables C4 and C5 can be displaced together with the laser head 24L according to the displacement of the laser head 24L in the XYZ axis direction.

FIG. 5 is an explanatory diagram for explaining the wiring state of the optical fiber cables C4 and C5 between the pulse interferometer 44 and the laser probe 47. FIG. 6 is a cross-sectional view of the optical fiber cables C4 and C5 shown in FIG.

As shown in FIGS. 5 and 6, the optical fiber cable C4 constituting the measurement optical path OP1 and the optical fiber cable C5 constituting the reference optical path OP2 are integrated. Therefore, the wiring paths of the optical fiber cables C4 and C5 between the pulse interferometer 44 and the laser head 24L can be shared in the facility 500 such as a factory or a laboratory where the coordinate measuring machine 10 is installed. As a result, the measurement optical path OP1 and the reference optical path OP2 become a common path (common optical path).

In the present embodiment, it is necessary to extend the measurement optical path OP1 (optical fiber cable C4) to the laser head 24L of the coordinate measuring machine 10, but at this time, there is a difference in the environment (temperature, etc.) between the measurement optical path OP1 and the reference optical path OP2. If there is, an error may occur in the calibration (measurement of the positioning accuracy of the laser head 24L) described later. Therefore, in the present embodiment, by making the measurement optical path OP1 and the reference optical path OP2 a common path, it is possible to eliminate the difference between the two environments and reduce the error in calibration. As described above, in the present embodiment, since it is necessary to form a long common path, the measurement optical path OP1 is configured by the optical fiber cable C4 and the reference optical path OP2 is configured by the optical fiber cable C5. Further, in an interferometer using a continuous wave, it is difficult to configure the optical path with an optical fiber cable, and it is also difficult to miniaturize the optical path so as to be attached to the tip of the probe head 24 (the tip of the control shaft). In the calibrator main body 40 of the above, a pulse interferometer 44 is adopted.

Returning to FIG. 3, the beam splitter 53 generates an optical interference signal SL between the measurement light 50A input from the optical fiber cable C4 and the reference light 50B input from the optical fiber cable C5, and the optical interference signal SL is generated. The light is output to the fiber circulator 52 via the optical fiber cable C3. Further, the fiber circulator 52 outputs the optical interference signal SL input from the beam splitter 53 to the photodetector 48 via the optical fiber cable C6.

The light detection unit 48 corresponds to the signal detection unit of the present invention. The optical detection unit 48 is various photoelectric conversion sensors that convert the optical interference signal SL input from the fiber circulator 52 via the optical fiber cable C6 into an electric signal, and corresponds to the strength of the incident optical interference signal SL. Outputs an electric signal (voltage signal). This electric signal is output from the photodetector 48 to the computer 60 via an amplifier and a filter (not shown).

FIG. 7 is a diagram showing an example of the reference light 50B (see the upper part of FIG. 7) and the measurement light 50A (see the lower part of FIG. 7) in the time domain. As shown in FIG. 7, the reference light 50B and the measuring light 50A is the same an optical comb 50 outputted from the optical frequency comb source 42, a repetition frequency f _rep and time interval T _R of the pulse train is the same.

Therefore, when the optical path length of the reference beam 50B and the optical path length of the measuring light 50A are the same, or the spatial distance difference in optical path length of the two (the optical path difference described above) correspond to the time interval T _R of the pulse train D _In the case of an integral multiple of r (see FIG. 13), the reference light 50B and the measurement light 50A interfere with each other. That is, in FIG. 7, when the time waveform shift time (ΔT) between the reference light 50B and the measurement light 50A becomes zero, the reference light 50B and the measurement light 50A interfere with each other.

[Calibration method for coordinate measuring machine]
<Arrangement of ball lens and calibration direction>
The calibration of the coordinate measuring machine 10 is performed according to the JIS B 7440 series described above using the calibration device main body 40 described above and the seven ball lenses 80A and 80B arranged on the upper surface of the surface plate 14. Specifically, the positioning accuracy (dimensional measurement accuracy) of the laser head 24L in seven calibration directions within the measurement range of the coordinate measuring machine 10 is measured. The seven calibration directions include four calibration directions D1 along any four diagonal directions within the measurement range, and three calibration directions D2 along the XYZ axes of the coordinate measuring machine 10.

FIG. 8 is a top view of the seven ball lenses 80A and 80B arranged on the upper surface of the surface plate 14 when the coordinate measuring machine 10 is calibrated. FIG. 9 is an explanatory diagram for explaining the calibration direction D1. FIG. 10 is an explanatory diagram for explaining the calibration direction D2. The coordinates (0,0,0) and the coordinates (1,0,0) in FIGS. 8 to 10 and the like are the coordinates indicating the relative positional relationship on the platen 14.

As shown in FIGS. 8 to 10, four ball lenses 80A are arranged on the upper surface of the surface plate 14, and three ball lenses 80B are arranged on the upper surface of the surface plate 14. The ball lenses 80A and 80B are reflectors of the present invention that reflect the measurement light 50A incident from the laser head 24L toward the laser head 24L. As the reflector of the present invention, various reflectors such as a corner cube reflector may be used, but since the ball lenses 80A and 80B can reflect light incident from any direction, the laser head 24L described later will be used. Alignment is easy.

The four ball lenses 80A are arranged at the coordinates (0,0,0), the coordinates (1,0,0), the coordinates (1,1,0), and the coordinates (0,1,0), respectively. Has been done. Each ball lens 80A is used to measure the positioning accuracy of the laser head 24L in the four calibration directions D1.

The calibration direction D1 is the direction connecting the ball lens 80A at the coordinates (0,0,0) and the coordinates (1,1,1), and the ball lens 80A at the coordinates (1,0,0) and the coordinates (0,1,1). The direction connecting 1), the direction connecting the ball lens 80A with coordinates (1,1,0) and the coordinates (0,0,1), and the direction connecting the ball lens 80A with coordinates (0,1,0) and the coordinates (1). , 0, 1).

The three ball lenses 80B have coordinates (1,1 / 2, 1/2), coordinates (1/2, 1, 1/2), and coordinates (1/2, 1/2, 0). Each is arranged. Each ball lens 80B is used to measure the positioning accuracy of the laser head 24L in the three calibration directions D2.

The calibration direction D2 is the direction connecting the ball lens 80B at the coordinates (1, 1/2, 1/2) and the coordinates (0, 1/2, 1/2), and the coordinates (1/2, 1, 1/2). ) In the direction connecting the ball lens 80B and the coordinates (1/2, 0, 1/2), and the coordinates (1/2, 1/2, 0) between the ball lens 80B and the coordinates (1/2, 1/2). , 1).

<Measurement of probe head positioning accuracy>
The measurement of the positioning accuracy of the laser head 24L is performed individually for each of the calibration directions D1 and D2, that is, for each of the seven directions. First, the alignment of the laser head 24L is performed. The alignment of the laser head 24L includes attitude control of the laser head 24L and position control of the laser head 24L in the XYZ axis direction.

FIG. 11 is an explanatory diagram of attitude control of the laser head 24L. As shown in FIG. 11, in the attitude control of the laser head 24L, the first driving unit 35 described above is driven to adjust the attitude of the laser head 24L to the Nth position in the calibration directions D1 and D2 in the seven directions. N is set in the "Nth calibration direction" which is the direction (natural number of 1 or more and 7 or less). Specifically, the posture of the laser head 24L is made parallel to the "Nth calibration direction".

FIG. 12 is an explanatory diagram of position control of the laser head 24L. As shown in FIG. 12, in the alignment of the laser head 24L, the second drive unit 36 described above is driven to align the laser head 24L with respect to the ball lenses 80A and 80B corresponding to the "Nth calibration direction". Move to P0.

The alignment position P0 is a position where the optical axis (outgoing optical axis) of the measurement light 50A emitted from the laser head 24L coincides with the centers of the ball lenses 80A and 80B corresponding to the "Nth calibration direction". there are a and an integer multiple of a position of the aforementioned spatial distance optical path difference corresponding to the time interval T _R of the pulse train _(see FIG. 7) D _{r (see} FIG. 13). Therefore, when the laser head 24L is moved to the alignment position P0, the intensity of the optical interference signal SL detected by the photodetector 48 becomes the maximum (maximum).

This completes the alignment of the laser head 24L with respect to the ball lenses 80A and 80B corresponding to the "Nth calibration direction". The alignment (attitude control, position control) of the laser head 24L is performed by driving the first drive unit 35 and the second drive unit 36 based on the calibration program 62B (see FIG. 15) described later. The method of creating the calibration program 62B will be described later.

After the alignment of the laser head 24L with the alignment position P0 is completed, the laser head 24L is step-moved in the extension direction (direction away from the ball lenses 80A and 80B) along the "Nth calibration direction".

FIG. 13 is an explanatory diagram for explaining the relationship between the position of the laser head 24L and the intensity of the optical interference signal SL detected by the photodetector 48. The optical comb 50 has a national standard or an international standard, and has very high frequency stability. Therefore, when the laser head 24L is moved from the alignment position P0 along the extension direction described above (here, it is assumed that the scanning stage 58 does not control the scanning of the reflector 57), optical interference as shown in FIG. The signal SL is detected by the photodetector 48.

In this case, each time the optical path difference described above the laser head 24L is positioned an integer multiple a position of the spatial distance D _r corresponding to a time interval T _R of the pulse train, the optical interference signal detected by the photodetector 48 The intensity of SL becomes the maximum (interference peak). In other words, when the intensity of the optical interference signal SL that is detected by the light detector 48 becomes maximum, so that the laser head 24L is controlled from the alignment position P0 to an integral multiple of the position of the spatial distance D _r. Therefore, in the present embodiment, the positioning accuracy (positioning error) of the laser head 24L is measured by using the optical comb 50 as a so-called “light ruler”.

FIG. 14 is an explanatory diagram of positioning control of the laser head 24L. As shown in FIG. 14, the maximum position LM is a position corresponding to a distance of 5 times the space interval L0 from the alignment position P0. Individual spatial interval L0 is a repetition interval that is determined based on the frequency interval of the frequency _{f rep} (time interval _{T R)} of the spatial distance _{D r,} i.e. the optical frequency comb 50 described above.

Specifically space interval L0 is a distance corresponding to an integral multiple of the spatial distance D _r. Incidentally, when considering the wrapping of the measuring beam 50A and the reference light 50B in pulse interferometer 44, the space interval L0 is not limited to an integral multiple of the spatial distance D _r, at least spatial distances D _r 1 / The interval may be an integral multiple of 2. The space spacing L0 is set to a value five times that value (5 × L0), that is, the distance from the alignment position P0 to the maximum position LM is set to be maximum within the movable range of the laser head 24L. Since the spatial distance is known as D _r a movable range of the laser heads 24L, if the alignment position P0 is determined, the maximum position LM (spatial interval L0) can be automatically determined. As a result, specific positions P1 to P5 for each spatial interval L0 along the "Nth calibration direction" from the alignment position P0 to the maximum position LM are defined. The specific positions P1 to P5 for each of the calibration directions D1 and D2 are also defined in advance by the calibration program 62B described later.

After the alignment of the laser head 24L is completed, the second drive unit 36 is driven according to the calibration program 62B, so that the laser head 24L is sequentially positioned from the alignment position P0 to each of the specific positions P1 to P5 (that is, step movement). Will be done.

Then, in the present embodiment, each time the laser head 24L is sequentially positioned at each of the specific positions P1 to P5, the optical comb 50 is emitted from the optical frequency comb light source 42 and the reflector 57 is scanned by the scanning stage 58. Control and perform. The optical comb 50 may be emitted from the optical frequency comb light source 42 at all times. In this case, for example, each time the laser head 24L is positioned at each of the specific positions P1 to P5, the photodetector 48 causes optical interference. The detection of the signal SL may be started.

In the above-mentioned scanning control, the scanning stage 58 scans the reflector 57 within a certain range centered on an interference reference point which is a predetermined reference. Here, the interference reference point is the position of the reflector 57 at which the intensity of the optical interference signal SL detected by the photodetector 48 is maximum (interference peak) in an ideal state where the positioning error of the laser head 24L is zero. For example, it is a substantially central position of the scanning stage 58.

When the second drive unit 36 is driven to position the laser head 24L at each position of the specific positions P1 to P5 in order, a positioning error of the laser head 24L occurs at each of the specific positions P1 to P5. Therefore, when the scanning stage 58 controls the scanning of the reflector 57 to change the optical path difference described above, the light is emitted at a position where the reflector 57 deviates from the interference reference point according to the direction and magnitude of the positioning error described above. The intensity of the optical interference signal SL detected by the detection unit 48 becomes the maximum (interference peak). Therefore, when the scanning control of the reflector 57 is performed by the scanning stage 58, the position of the reflector 57 at which the intensity of the optical interference signal SL detected by the photodetector 48 is maximized (the direction of deviation from the interference reference point and the amount of deviation). ), The positioning accuracy of the laser head 24L can be measured.

In the JIS B7440 series, the measurement of the positioning accuracy of the laser head 24L for each specific position P1 to P5 described above is repeated three times. This completes the measurement of the positioning accuracy (positioning error) of the laser head 24L corresponding to the "Nth calibration direction". Then, the above-mentioned processing (alignment, positioning for each specific position P1 to P5, scanning control, etc.) is repeatedly executed for each of the calibration directions D1 and D2 in the seven directions. As a result, the data necessary for calibration of the coordinate measuring machine 10 specified in the JIS B 7440 series can be obtained.

[Creation of proofreading program]
The calibration program 62B (see FIG. 15) defines the posture of the laser head 24L for each calibration direction D1 and D2, the alignment position P0, and the specific positions P1 to P5, respectively. This calibration program 62B is created in advance prior to the measurement of the positioning accuracy of the laser head 24L, and then stored in the computer 60.

First, the postures (rotation angle ψ and rotation angle θ) of the laser head 24L (laser probe 47) for each of the calibration directions D1 and D2 are stored in the computer 60 in advance.

When creating the calibration program 62B (see FIG. 15) corresponding to the "Nth calibration direction", the rotation angle ψ and the rotation angle ψ of the laser head 24L corresponding to the "Nth calibration direction" stored in advance in the computer 60 Based on the rotation angle θ, the first drive unit 35 is driven to control the attitude of the laser head 24L. As a result, the posture of the laser head 24L becomes parallel to the "Nth calibration direction".

Next, the second drive unit 36 is driven to move the laser head 24L to the alignment position P0 described above. This moving method is not particularly limited, and may be performed manually or automatically, and when it is performed automatically, a known method can be used.

For example, when the approximate positions of the ball lenses 80A and 80B on the surface plate 14 are known, a temporary alignment position P0 is estimated based on the approximate positions, and the laser head 24L is moved in the XYZ axis direction at the temporary alignment position P0. The optical interference signal SL is detected by the optical detection unit 48 while adjusting the position. Then, the position of the laser head 24L at which the intensity of the optical interference signal SL is maximized is determined as the alignment position P0.

Further, the center coordinates of the ball lenses 80A and 80B may be detected by a known method, and the alignment position P0 may be determined based on the center coordinates and the posture (rotation angle ψ and rotation angle θ) of the laser head 24L.

After completion of the alignment of the laser head 24L alignment position P0, and the orientation of the laser head 24L, the alignment position P0, based on the spatial distance D _r described above, the movable range of the laser heads 24L, "the N-th The maximum position LM and the spatial interval L0 corresponding to the "calibration direction" are determined. Thereby, the specific positions P1 to P5 corresponding to the "Nth calibration direction" can be determined. As a result, the calibration program 62B (FIG. 6) defines the posture (rotation angle ψ and rotation angle θ) of the laser head 24L corresponding to the “Nth calibration direction”, the alignment position P0, and the specific positions P1 to P5. 15) can be created.

Hereinafter, by repeating the above processing for all the calibration directions D1 and D2, the calibration program 62B (which defines the posture of the laser head 24L for each calibration direction D1 and D2, the alignment position P0, and the specific positions P1 to P5, respectively). (See FIG. 15) can be created.

[Computer]
FIG. 15 is a functional block diagram showing the functions of the computer 60. As shown in FIG. 15, the computer 60 is connected to the coordinate measuring machine 10 via the drive controller 30 and is connected to each part of the calibration device main body 40 (optical frequency comb light source 42 and light detection unit 48). .. The computer 60 functions as a measurement control device that controls the measurement of the object to be measured (not shown) by the coordinate measuring machine 10, and also functions as the calibration device of the present invention together with the calibration device main body 40. Since the function of the computer 60 as a measurement control device is a known technique, it is not shown in FIG.

The computer 60 is composed of a CPU (central processing unit), a memory, and the like (not shown). The computer 60 has a general control unit 61, a storage unit 62, a drive control unit 63, a light source control unit 64, a scanning control unit 65, a signal acquisition unit 66, and positioning accuracy when the CPU executes a software program (not shown). It functions as a measuring unit 67.

The integrated control unit 61 controls the operations of the coordinate measuring machine 10 and the calibration device main body 40 by controlling the operations of the other units of the computer 60.

The storage unit 62 stores control information 62A, calibration program 62B, and the like, in addition to a software program (not shown) for controlling the coordinate measuring machine 10 and the calibration device main body 40. Control information 62A is 7 direction of the calibration direction D1, D2 laser head 24L posture corresponding respectively to the (rotation angle ψ and the rotation angle theta), spatial distance Dr (time interval _{T R} and the repetition frequency _{f rep),} and the laser head Includes a movable range of 24 L and the like. With reference to this control information 62A, the overall control unit 61 creates the calibration program 62B described above.

Specifically, the general control unit 61 acquires the postures (rotation angle ψ and rotation angle θ) of the laser head 24L for each of the calibration directions D1 and D2 based on the control information 62A. Further, when the laser head 24L is moved to the alignment position P0 for each of the calibration directions D1 and D2 by the drive of the second drive unit 36, the control control unit 61 sets the alignment position P0 and the above-mentioned spatial distance _Dr. , The maximum position LM and the space interval L0 for each of the calibration directions D1 and D2 are determined based on the posture and the movable range of the laser head 24L. As a result, the integrated control unit 61 creates a calibration program 62B that defines the posture of the laser head 24L for each of the calibration directions D1 and D2, the alignment positions P0, and the specific positions P1 to P5, and stores them in the storage unit 62.

The drive control unit 63 drives the first drive unit 35 and the second drive unit 36, respectively, via the drive controller 30, and controls the posture and position of the laser head 24L. The drive control unit 63 includes a position / attitude control unit 63A and a positioning control unit 63B.

The position / attitude control unit 63A functions as the first control unit of the present invention. At the time of creating the calibration program 62B, the position / attitude control unit 63A drives the first drive unit 35 via the drive controller 30 based on the attitude of the laser head 24L included in the control information 62A, thereby driving the first drive unit 35. The attitude control of the laser head 24L described in 11 is performed. Next, the position / attitude control unit 63A automatically or manually drives the second drive unit 36 to move the laser head 24L to the alignment position P0 with respect to the ball lenses 80A and 80B corresponding to the “Nth calibration direction”. ..

On the other hand, when measuring the positioning accuracy of the laser head 24L, the position / orientation control unit 63A drives the first drive unit 35 and the second drive unit 36 based on the calibration program 62B in the storage unit 62 to drive the laser head 24L. By controlling the posture and position, the laser head 24L is aligned with the ball lenses 80A and 80B corresponding to the "Nth calibration direction". As a result, the posture of the laser head 24L can be paralleled to the "Nth calibration direction". Further, the position of the laser head 24L can be set to the alignment position P0 corresponding to the "Nth calibration direction".

The positioning control unit 63B corresponds to the second control unit of the present invention. The positioning control unit 63B drives the second drive unit 36 based on the calibration program 62B in the storage unit 62 to move the laser head 24L in steps along the “Nth calibration direction”. As a result, as shown in FIG. 14, the laser head 24L is specified at specific positions P1 to P5 (hereinafter collectively specified) for each spatial interval L0 along the "Nth calibration direction" from the alignment position P0. Position PM: M is a natural number of 1 or more and 5 or less) in order.

The light source control unit 64 controls the emission of the optical comb 50 by the optical frequency comb light source 42. Each time the laser head 24L is positioned at any of the specific positions PM, the light source control unit 64 emits the optical comb 50 from the optical frequency comb light source 42 until at least the scanning control of the reflector 57 is completed. As a result, the measurement light 50A is emitted from the laser head 24L toward the ball lenses 80A and 80B corresponding to the "Nth calibration direction", and the measurement light 50A reflected by the ball lenses 80A and 80B is further emitted from the laser head. The light is received by 24L. As a result, the optical interference signal SL is detected by the optical detection unit 48.

The scanning control unit 65 drives the scanning stage 58 to control the scanning of the reflector 57 each time the laser head 24L is positioned at any of the specific positions PM. As a result, the optical path length of the reference light 50B changes, and the optical path difference described above changes with this change. As a result, the photodetector 48 detects the optical interference signal SL and detects the electric signal while the laser head 24L is positioned at any of the specific positions PM and at least the scanning control of the reflector 57 is being executed. Is output continuously.

Further, the scanning control unit 65 sequentially transmits information on the position of the reflector 57 on the scanning stage 58, that is, information on the deviation direction and deviation amount of the position of the reflector 57 from the above-mentioned interference reference point to the positioning accuracy measuring unit 67. Output.

The signal acquisition unit 66 is connected to the light detection unit 48. The optical detection unit 48 continuously detects the optical interference signal SL while at least scanning control of the reflector 57 is being executed, and outputs the electric signal of the optical interference signal SL to the signal acquisition unit 66. Then, the signal acquisition unit 66 outputs the electric signal acquired from the light detection unit 48 to the positioning accuracy measurement unit 67.

The positioning accuracy measuring unit 67 receives information regarding the position of the reflector 57 input from the scanning control unit 65 each time the positioning of the laser head 24L to any of the specific position PMs and the scanning control of the reflector 57 are executed. Based on the electric signal input from the signal acquisition unit 66, the position of the reflector 57 at which the intensity of the optical interference signal SL detected by the photodetector unit 48 is maximum (interference peak) is measured. As a result, the positioning accuracy (positioning error) of the laser head 24L for each specific position PM is measured.

The integrated control unit 61 controls each unit of the computer 60 to repeatedly measure the positioning accuracy of the laser head 24L for each specific position PM three times. Then, the general control unit 61 repeatedly operates each part of the computer 60 to perform the above-mentioned processing (alignment, positioning to a specific position PM, scanning control, and measurement of positioning accuracy) for each of the calibration directions D1 and D2 in the seven directions. Etc.) are repeated. Therefore, the integrated control unit 61 functions as the third control unit of the present invention.

[Action of 3D measurement system]
FIG. 16 is a flowchart showing the flow of the calibration process of the coordinate measuring machine 10 in the coordinate measuring system 9 having the above configuration, more specifically, the measurement process of the positioning accuracy of the laser head 24L (in the calibration method of the present invention). Equivalent).

When the operator calibrates the coordinate measuring machine 10 according to the JIS B7440 series described above, that is, measures the positioning accuracy of the laser head 24L, the operator first attaches the laser probe 47 to the probe head 24 to make the laser head 24L. Further, the operator arranges the seven ball lenses 80A and 80B on the upper surface of the surface plate 14 as shown in FIG. 8 and the like described above (step S1).

Further, the operator operates the keyboard or the like of the computer 60 to store the above-mentioned control information 62A in the storage unit 62. Thus, the posture of the 7 direction of the laser head 24L (rotation angle ψ and the rotation angle theta), spatial distance Dr (time interval _{T R} and the repetition frequency _{f rep),} and movable range or the like of the laser head 24L is, the computer 60 It is memorized (step S2). If the control information 62A input in the past is stored in the storage unit 62, step S2 may be omitted. Next, the process of creating the calibration program 62B is started (step S3).

FIG. 17 is a flowchart showing the flow of the creation process of the calibration program 62B. As shown in FIG. 17, when the operator inputs the creation instruction of the calibration program 62B to the computer 60, the position / orientation control unit 63A of the computer 60 refers to the control information 62A in the storage unit 62 and “first. The posture (rotation angle ψ and rotation angle θ) of the laser head 24L corresponding to the third (N = 1) calibration direction is acquired. Then, the position / attitude control unit 63A drives the first drive unit 35 based on the acquired attitude of the laser head 24L to make the attitude of the laser head 24L parallel to the “first calibration direction” (step S3A). , S3B, S3C).

Next, the position / attitude control unit 63A automatically (known method) or manually drives the second drive unit 36 to move the laser head 24L with respect to the ball lenses 80A and 80B corresponding to the "first calibration direction". It is moved to the alignment position P0 (step S3D).

When the movement of the laser head 24L is completed, the central control unit 61 includes an alignment position P0, based a spatial distance D _r, in the posture and the movable range of the laser heads 24L, maximum position LM and shown in FIG. 14 or the like The space interval L0 is determined (step S3E). As a result, the specific positions P1 to P5 corresponding to the "first calibration direction" are determined by the integrated control unit 61. As a result, the posture of the laser head 24L, the alignment position P0, and the specific position PM corresponding to the "first calibration direction" are determined.

Hereinafter, similarly, with respect to the "second calibration direction" to the "seventh calibration direction", the above-described processes from step S3B to step S3F are repeatedly executed (NO in step S3F, step S3G). As a result, the general control unit 61 creates a calibration program 62B that defines the posture of the laser head 24L, the alignment position P0, and the specific position PM for each of the calibration directions D1 and D2, and stores the calibration program 62B in the storage unit 62. (YES in step S3F, step S3H). This completes the preparation for calibration of the coordinate measuring machine 10.

Returning to FIG. 16, when the operator inputs the measurement start instruction of the positioning accuracy of the laser head 24L to the computer 60, the positioning accuracy of the laser head 24L is first measured in the “first (N = 1) calibration direction”. Is started (step S4 and step S5).

The position / orientation control unit 63A of the computer 60 drives the first drive unit 35 and the second drive unit 36, respectively, to control the attitude and position of the laser head 24L based on the calibration program 62B in the storage unit 62. The laser head 24L is aligned with the ball lenses 80A and 80B corresponding to the "first calibration direction" (steps S6 and S7). As a result, the posture of the laser head 24L becomes parallel to the "first calibration direction", and the position of the laser head 24L is set to the alignment position P0 corresponding to the "first calibration direction". Note that step S7 corresponds to the first step of the present invention.

When the alignment of the laser head 24L is completed, the positioning control unit 63B drives the second drive unit 36 according to the calibration program 62B to position the laser head 24L at the specific position P1 (M = 1) (steps S8 and S9). , Corresponding to the fourth step of the present invention).

When the laser head 24L is positioned at the specific position P1, the light source control unit 64 starts emitting the optical comb 50 by the optical frequency comb light source 42 (step S10, corresponding to the second step of the present invention). As a result, the measurement light 50A is emitted from the laser head 24L to the ball lenses 80A and 80B corresponding to the "first calibration direction", the reflected light of the measurement light 50A is received by the laser head 24L, and the pulse interferometer 44. The output of the optical interference signal SL to the light detection unit 48 and the detection of the optical interference signal SL (output of the electric signal) by the light detection unit 48 are started (corresponding to the third step of the present invention).

On the other hand, when the laser head 24L is positioned at the specific position P1, the scanning control unit 65 drives the scanning stage 58 to scan the reflector 57 within a certain range centered on the interference reference point (scanning control). Step S11, corresponding to the fifth step of the present invention). At this time, the scanning control unit 65 sequentially outputs information regarding the position of the reflector 57 on the scanning stage 58 to the positioning accuracy measuring unit 67.

At the same time, the photodetector 48 continuously detects the optical interference signal SL while at least the scanning control of the reflector 57 is being executed, and outputs the electric signal as the detection result to the signal acquisition unit 66. Then, the signal acquisition unit 66 sequentially outputs the electric signal acquired from the light detection unit 48 to the positioning accuracy measurement unit 67 (step S11, corresponding to the sixth step of the present invention).

When the scanning control of the reflector 57 is completed, the positioning accuracy measuring unit 67 determines the optical interference signal SL based on the information regarding the position of the reflector 57 input from the scanning control unit 65 and the electric signal input from the signal acquisition unit 66. The position of the reflector 57 at which the intensity of the above is maximum (interference peak) is determined. The positioning accuracy measuring unit 67 determines the positioning accuracy (positioning) of the laser head 24L at the specific position P1 in the "first calibration direction" based on the determined position of the reflector 57 (the deviation direction and the deviation amount from the interference reference point). Error) is measured (step S12, corresponding to the eighth step of the present invention).

When the measurement of the positioning accuracy of the laser head 24L at the specific position P1 in the "first calibration direction" is completed, the positioning control unit 63B drives the second drive unit 36 to move the laser head 24L to the specific position P2 ( Positioning to M = 2) (NO in step S13, step S14, and step S9). Then, by repeatedly executing the processes from step S10 to step S12 described above, the positioning accuracy of the laser head 24L at the specific position P2 in the "first calibration direction" is measured.

Hereinafter, similarly, the positioning accuracy of the laser head 24L at the specific positions P3 to P5 in the “first calibration direction” is measured. Although not shown, the measurement of the positioning accuracy of the laser head 24L at the specific positions P1 to P5 is repeatedly executed three times.

When the third measurement of the positioning accuracy of the laser head 24L at the specific position P5 is completed, the measurement of the positioning accuracy of the laser head 24L in the "second (N = 2) calibration direction" is started (step S13). Yes, step S15 is NO, step S16, corresponding to the seventh step of the present invention). By simply controlling the first drive unit 35 and the second drive unit 36 to change the posture and position of the laser head 24L in this way, the measurement of the positioning accuracy of the laser head 24L in the "second calibration direction" is started. Therefore, it is possible to omit the setup change by the operator. Then, by repeatedly executing the processes from step S5 to step S15 described above, the positioning accuracy of the laser head 24L is measured at the specific positions P1 to P5 in the "second calibration direction".

Similarly, the positioning accuracy of the laser head 24L at the specific positions P1 to P5 is measured for each of the "third calibration direction" to the "seventh calibration direction" (YES in step S15, the present invention). Corresponds to the 7th step of).

With the above, the measurement data necessary for calibrating the coordinate measuring machine 10 in accordance with the JIS B 7440 series regulations can be obtained. The operator calibrates the coordinate measuring machine 10 as necessary based on the obtained measurement data. Since the specific calibration method is a known technique, a specific description will be omitted here.

[Effect of this embodiment]
In the present embodiment, seven ball lenses arranged on the surface plate 14 are provided by providing the laser head 24L provided on the movable portion (Z carriage 22) of the coordinate measuring machine 10 that can move in the XYZ axis direction. Alignment of the laser head 24L with respect to each of 80A and 80B can be performed by driving the first drive unit 35 and the second drive unit 36.

Therefore, in the conventional technique of arranging the pulse interferometer 44 on the surface plate 14 and attaching the ball lenses 80A and 80B to the laser head 24L, the operator arranges the pulse interferometer 44 and the like on the surface plate 14 in each calibration direction. It is necessary to perform a so-called "setup change" in which an alignment is performed each time a change is made, but in the present embodiment, the setup change can be omitted. As a result, the time required for calibration (measurement) in each of the calibration directions D1 and D2 is shortened. Therefore, the positioning accuracy of the laser head 24L for each of the calibration directions D1 and D2 can be performed under substantially the same conditions (same environment). In addition, the occurrence of an error caused by changing the arrangement of the pulse interferometer 44 or the like can be suppressed.

Further, in the present embodiment, unlike the non-patent document 3, it is not necessary to provide a plurality of laser heads 24L, so that the light amount of the measurement light 50A is not dispersed and the signal intensity of the optical interference signal SL is secured. As a result, stable measurement becomes possible, and a stable system can be constructed regardless of the size of the coordinate measuring machine 10.

Further, in the present embodiment, by using the pulse interferometer 44 using the optical comb 50 as the light source, the positioning accuracy can be measured with high accuracy. Further, the optical fiber kale can be used as an optical path for the measurement light 50A and the reference light 50B, and the laser head 24L can be miniaturized to a size that can be attached to the movable portion (control shaft) of the coordinate measuring machine 10.

As described above, in the present embodiment, regardless of the size of the coordinate measuring machine 10, it is possible to omit the setup change, improve the accuracy of calibration, and shorten the time.

Furthermore, in the present embodiment, by driving the first drive unit 35 and the second drive unit 36 according to the calibration program 62B, a series of calibration operations (laser in seven directions) after step S4 shown in FIG. 16 described above. The measurement of the positioning accuracy of the head 24L) can be performed automatically and continuously, that is, fully automatically. As a result, the time required for calibration is further reduced.

[Other]
In the above embodiment, an example of the pulse interferometer 44 is shown in FIG. 4, but the configuration of the pulse interferometer 44 may be changed as appropriate. Further, instead of the pulse interferometer 44, a broad spectrum interferometer using an optical comb 50 may be used as the interference optical system of the present invention.

The optical path difference variable unit 54 of the above embodiment changes the optical path difference described above by changing the optical path length of the reference light 50B by scanning control of the reflector 57 by the scanning stage 58, but the optical path length of the reference light 50B. If it is possible to change the optical path difference, the configuration of the optical path difference variable unit 54 may be changed as appropriate. Further, instead of changing the optical path length of the reference light 50B, the optical path difference described above may be changed by changing the optical path length of the measurement light 50A.

In the above embodiment, the computer 60 is provided separately from the coordinate measuring machine 10, but the computer 60 may be provided integrally with the coordinate measuring machine 10. Further, each part of the coordinate measurement system 9 does not have to be provided in the same place. For example, the optical frequency comb light source 42, the etalon 43, the pulse interferometer 44, etc. (or only the optical frequency comb light source 42) are tertiary. It may be provided in a place different from the original measuring machine 10. As a result, the calibration device main body 40 and the laser head 24L of the coordinate measuring machine 10 arranged in a factory or the like located at another place (for example, a position several km away) are connected by optical communication to form a three-dimensional structure in the factory. The present invention can also be applied when calibrating the measuring machine 10. By extending the optical fiber cables C4 and C5 over several kilometers, it is possible to calibrate the coordinate measuring machine 10 existing in different places and buildings.

In the above embodiment, the coordinate measuring machine 10 has been described as an example of the device to be calibrated, but the device is not limited to the coordinate measuring machine 10, and various measuring machines (coordinate measuring machines), machine tools, etc. The present invention can be applied to the calibration of a device to be calibrated having various movable parts that can be displaced in a plurality of directions. In this case, the number of calibration directions (the number of reflectors, the arrangement pattern, and the arrangement location in the equipment to be calibrated) and the number of specific positions are appropriately changed according to the type of the device to be calibrated, the standard of calibration, and the like.

10 ... 3D measuring machine,
14 ... Surface plate,
24 ... Probe head,
24L ... Laser head,
35 ... 1st drive unit,
36 ... 2nd drive unit,
40 ... Calibration device body,
42 ... Optical frequency comb light source,
43 ... Etalon,
44 ... Pulse interferometer,
47 ... Laser probe,
48 ... Photodetector,
50 ... Hikari Com,
50A ... Measurement light,
50B ... Reference light,
54 ... Optical path difference variable part,
57 ... Reflector,
58 ... Scanning stage,
59 ... Reflective coated surface,
60 ... Computer,
61 ... Integrated control unit,
62A ... Control information,
62B ... Calibration program,
63A ... Position / attitude control unit,
63B ... Positioning control unit,
65 ... Scanning control unit,
67 ... Positioning accuracy measuring unit,
80A, 80B ... Ball lens,
D1, D2 ... Calibration direction,
C1 to C6 ... Optical fiber cable,
P0 ... Alignment position,
P1 to P5 ... Specific position

Claims (7)

In a calibration device that calibrates a device to be calibrated that has movable parts that can be displaced in multiple directions.
An optical head provided in the movable portion and whose position and posture can be displaced freely,
When a plurality of reflectors are arranged in the device to be calibrated in an arrangement pattern corresponding to a plurality of calibration directions, the position and orientation of the optical head are controlled to align the optical head with respect to the reflector. 1 control unit and
An optical frequency comb light source that emits an optical comb having a repetition frequency,
The optical comb emitted from the optical frequency comb light source is branched into a measurement light and a reference light, the measurement light is emitted from the optical head to the reflector, and the reference light is emitted to a reference surface at a predetermined position. An interference optical system that outputs an optical interference signal between the measurement light received by the optical head from the reflector and the reference light reflected by the reference surface.
When a position having a spatial interval determined based on the repetition frequency is set as a specific position, the movable portion is driven to move from the reflector to the specific position along the calibration direction corresponding to the reflector. A second control unit that positions the optical head and
An optical path difference variable unit provided in the interference optical system that changes the optical path difference between the optical path of the measurement light and the optical path of the reference light each time the optical head is positioned at the specific position by the second control unit. When,
A signal detection unit that detects the optical interference signal output from the interference optical system while the change in the optical path difference by the optical path difference variable unit is being executed.
For each reflector, the first control unit, the optical frequency comb light source, the second control unit, the optical path difference variable unit, and the third control unit that repeatedly operates the signal detection unit.
A calibration device equipped with. A positioning accuracy measuring unit for measuring the positioning accuracy of the optical head by the movable unit for each specific position based on the detection result of the signal detecting unit and the change in the optical path difference due to the optical path difference variable unit is provided.
The calibration device according to claim 1, wherein the third control unit repeatedly operates the positioning accuracy measuring unit for each reflector. The calibration device according to claim 1 or 2, wherein the optical path difference variable unit changes the optical path difference within a certain range centered on a predetermined reference. The calibration device according to any one of claims 1 to 3, wherein the optical path of the measurement light and the optical path of the reference light pass through a common optical path. The calibration device according to any one of claims 1 to 4, wherein the optical path of the measurement light and the optical path of the reference light are each composed of an optical fiber cable. In a calibration method for calibrating a device to be calibrated that has movable parts that can be displaced in multiple directions.
With a plurality of reflectors arranged in the device to be calibrated and an optical head attached to the movable portion in an arrangement pattern corresponding to a plurality of calibration directions, the first control unit moves the position and orientation of the optical head. The first step of aligning the optical head with respect to the reflector by controlling
The second step of emitting an optical comb having a repeating frequency from an optical frequency comb light source, and
The interfering optical system branches the optical comb into measurement light and reference light, emits the measurement light from the optical head to the reflector, and emits the reference light to a reference surface at a predetermined position, and the reflection A third step of outputting an optical interference signal between the measurement light received by the optical head from the body and the reference light reflected by the reference surface.
When a position having a spatial interval determined based on the repetition frequency is set as a specific position, the second control unit drives the movable portion to follow the calibration direction corresponding to the reflector from the reflector. A fourth step of positioning the optical head at each specific position, and
A fifth step in which the optical path difference variable unit changes the optical path difference between the optical path of the measurement light and the optical path of the reference light each time the optical head is positioned at the specific position.
A sixth step in which the signal detection unit detects the optical interference signal output from the interference optical system while the change in the optical path difference by the optical path difference variable unit is being executed.
A seventh step in which the third control unit repeatedly executes each step from the first step to the sixth step for each reflector.
Calibration method with. It has an eighth step of measuring the positioning accuracy of the optical head by the movable unit for each specific position based on the detection result of the signal detection unit and the change of the optical path difference by the optical path difference variable unit.
The calibration method according to claim 6, wherein the third control unit repeatedly operates the eighth step for each reflector.

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