JP6550621B2 - Spatial position measuring method and apparatus using tracking type laser interferometer - Google Patents

Description

  The present invention relates to a spatial position measuring method and apparatus using a tracking laser interferometer, and in particular, during the measurement of a plurality of positions, which is suitable for use in measuring spatial correction parameters of a three-dimensional coordinate measuring machine (CMM). The present invention relates to a spatial position measuring method and apparatus using a tracking laser interferometer, which can perform high-accuracy measurement using a position measurement result even if the position of the tracking laser interferometer body is shifted.

  As tracking type laser interferometers for measuring displacement and position of the moving body with high accuracy while tracking the moving body, there are ones described in Patent Documents 1 to 3. These tracking type laser interferometers are used when measuring CMM spatial correction parameters and calibrating machine tools, and this correction / calibration target (CMM Z-axis spindle tip or machining tool) is a measurement target. A retroreflector (retroreflector) is attached.

  FIG. 1 shows a configuration example of a tracking type laser interferometer. The tracking type laser interferometer 40 includes a retroreflector 42 fixed to the moving body 22 that is a measurement object, a tracking type laser interferometer main body 50 including a laser light source 60, an optical measurement device 70, and a two-axis rotation device 80. A control device (hereinafter referred to as a rotation mechanism control device) 82 of the biaxial rotation device 80 is configured. The biaxial rotating device 80 includes biaxial rotating mechanisms orthogonal to each other, and has an angle detector (not shown) on each axis. The laser beam 74 is guided from the laser light source 60 to the optical measuring device 70 using the optical fiber 62. The optical measurement apparatus 70 includes a laser interference (measurement) meter 72 (hereinafter simply referred to as a laser interferometer) 72 that measures a distance (ie, length) L from the reference point O to the retroreflector 42, and tracking of the retroreflector 42. It comprises the tracking optical device 76 used in control.

  The retroreflector 42 is an optical element in which the optical axes of incident light and reflected light are parallel, and the optical axes of incident light and reflected light are point-symmetric with respect to the center of the retroreflector 42. Therefore, when incident light is incident on a position away from the reflection center of the retroreflector 42, the reflected light returns to a position shifted with respect to the incident light. The tracking optical device 76 has a light position detector 78 that observes the amount of deviation between the incident light and the reflected light, detects the amount of deviation, and sends it to the rotation mechanism control device 82.

  In the rotation mechanism control device 82, a signal (amount of deviation between incident light and reflected light) sent from the tracking optical device 76 and an angle output from an angle detector on each rotation axis of the biaxial rotation mechanism. Using a signal, the two-axis rotating device 80 is controlled so that the amount of deviation falls within a predetermined range.

  A laser interferometer 72 attached to a biaxial rotating device 80 constituted by an orthogonal biaxial rotating mechanism interferes with the light returned from the retroreflector 42 and detects a change in intensity of the interfering light in phase. The rotation center (intersection point) of the two-axis rotation mechanism is taken as a reference point O, and the distance L from the reference point O to the retroreflector 42 is measured via the rotation mechanism control device 82.

  With this configuration, in the measurement by the tracking laser interferometer 40, the angle signal of the biaxial rotating device 80 and the distance information (L) observed by the laser interferometer 72 are obtained as measured values. When these measured values are used, the tracking laser interferometer 40 can be used as an apparatus for measuring three-dimensional coordinates.

  Further, by using a plurality of tracking type laser interferometers 40, three-side length measurement can be performed by using only the distance information (L) observed by the laser interferometer 72 to obtain a three-dimensional coordinate value. it can.

  On the other hand, the applicants have proposed techniques for performing spatial correction in order to increase the measurement accuracy of CMM in Patent Documents 4 and 5.

  Furthermore, a method of measuring a spatial correction parameter of a CMM to be corrected using a tracking laser interferometer is also known. In this method, as described in Non-Patent Document 1, the space correction parameter of CMM is calculated using the principle of multi-lateration (multi-side measurement). When the principle of multilateration is used, the spatial correction parameter is calculated from only the information on the distance (length) without using the information on the angle obtained by the rotary encoder that increases the error at a long distance. In addition, the tracking laser interferometer body is moved, and the length is usually measured from four or more locations.

In Non-Patent Document 1, as illustrated in FIG. 2, length measurement is performed from four arrangement positions of P ₁ , P ₂ , P ₃ , and P ₄ . The position of the retro-reflector is changed from each arrangement position (P ₁ , P ₂ , P ₃ , P ₄ ), and usually several tens to several hundreds of points are measured, and CMM spatial correction is performed from the measured data. Find the parameters.

Patent No. 2603429 gazette U.S. Pat. No. 6,147,748 Patent No. 4776454 Patent No. 2902285 Patent No. 4675047

Kenta Umetsu et al., Geometric calibration of a coordinate measuring machine using a laser tracking system, Measurement Science and Technology, Vol. 16, 2005, p.2466-2472.

  However, in the conventional technique, if the position of the tracking type laser interferometer main body is shifted due to an unintended external force during measurement, an error due to the influence of this positional shift is generated in the spatial correction parameter of the obtained CMM. There's a problem.

For example, the measurement of the length from one installation position P ₁ to the retroreflector, consider a case where 100 times while changing the position of the retroreflector. Between the end of the 50th measurement and the start of the 51st measurement, the cable is pulled by the cable, or the table on which the tracking laser interferometer body is mounted moves due to inertia, etc. Suppose that the position of the tracking type laser interferometer main body is shifted. Since the conventional tracking laser interferometer cannot determine that the position of the tracking laser interferometer body has shifted, the position of the tracking laser interferometer body does not change, and the position of the retroreflector has changed. , I handle the 51st to 100th data. As a result, in the conventional method, the calculated space correction parameter is affected by the error due to the positional deviation.

  The present invention has been made to solve the above-mentioned conventional problems. For example, during the measurement of a plurality of positions such as measurement of a spatial correction parameter of the CMM, the position of the tracking type laser interferometer main body due to an unintended external force or the like is detected. It is an object of the present invention to make it possible to utilize position measurement results without affecting the values of space correction parameters and the like which are calculated even if they deviate.

The present invention provides a retroreflector attached to a moving body, irradiates the retroreflector with laser light, and uses the interference of the laser light reflected in the return direction by the retroreflector to reduce the distance to the retroreflector. A laser interferometer to detect, a tracking optical device having an optical position detector for detecting a positional deviation of the optical axis of the laser light, a biaxial rotation mechanism orthogonal to each other capable of changing the emitting direction of the laser light, An angle detector disposed on each axis of the biaxial rotation mechanism, and when the movable body moves, the optical axis position shift of the laser beam reflected in the return direction from the retroreflector is detected as the optical position. A tracking type laser interferometer that is detected by a detector and controls the biaxial rotation mechanism so that the positional deviation of the laser optical axis falls within a predetermined range is used. Move the measuring point, in detecting the position of each measurement point, detecting a deviation of the arrangement position of the tracking type laser interferometer during the measurement at the same measurement point, detecting a deviation of該配installation position When the same measurement point is used, the spatial position measurement method using the tracking type laser interferometer is characterized in that the arrangement position of the tracking type laser interferometer main body is treated as different data before and after the deviation. The above-mentioned problem is solved.

  Here, the space correction parameter of the coordinate measuring machine can be determined by the tracking laser interferometer using the moving body as a spindle tip of the coordinate measuring machine.

The present invention also provides a retroreflector attached to a moving body, irradiates the retroreflector with laser light, and uses the interference of the laser light reflected in the return direction by the retroreflector to reach the retroreflector. Laser interferometer for detecting distance, optical device for tracking having optical position detector for detecting positional deviation of optical axis of laser beam, biaxial rotation orthogonal to each other capable of changing emission direction of laser beam And an angle detector disposed on each axis of the biaxial rotating mechanism, and when the movable body moves, the positional deviation of the optical axis of the laser beam reflected in the return direction from the retroreflector is detected by the light position detector, and has been tracking type laser interferometer to positional deviation of the laser beam axis for controlling the two-axis turning mechanism so as to fall within a predetermined range, measured at the same measuring point A position sensor for detecting a deviation of the arrangement position of該追tail type laser interferometer in the middle, with該追tail type laser interferometer, by moving the movable body in a plurality of measuring points, detecting the position of each measurement point when, upon detection of the deviation of the arrangement position of the add tail type laser interferometer by the position sensor during the measurement at the same measurement point can be the same measuring point, the tracking type before and after the shift The present invention provides a spatial position measuring apparatus using a tracking type laser interferometer, characterized in that it comprises data processing means for handling data with different arrangement positions of a laser interferometer body.

  According to the present invention, even when the position of the tracking laser interferometer main body is shifted due to an unintended external force or the like during measurement of a plurality of positions such as measurement of a spatial correction parameter of the CMM, The position measurement results can be used without affecting the values. Therefore, the reliability of the space correction parameter or the like measured by the tracking laser interferometer is improved.

Block diagram showing a configuration example of a conventional tracking type laser interferometer The perspective view which shows the measurement state of the space correction parameter of CMM using the conventional tracking type laser interferometer The perspective view showing the principal part composition of the embodiment of the measuring device concerning the present invention An enlarged sectional view of part IV of FIG. 3 as viewed from the side Front view showing the retro reflector mounted on the CMM Flow chart showing the processing procedure of the embodiment The perspective view which shows the state which is measuring the space correction parameter of CMM in the said embodiment Diagram showing the state of data as well

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments and examples. In addition, the constituent elements in the embodiments and examples described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in the so-called equivalent range. Furthermore, the constituent elements disclosed in the embodiments and examples described below may be appropriately combined or may be appropriately selected and used.

  An embodiment of a measurement apparatus using a tracking laser interferometer for carrying out the present invention is shown in FIGS.

  In this embodiment, in the tracking type laser interferometer 40 similar to the conventional example shown in FIG. 1, FIG. 3 (a perspective view showing a main part configuration) and FIG. As shown in the figure, a two-dimensional scale 92 is arranged as a position sensor for detecting the arrangement position of the base plate 90 on the lower side of the base plate 90 of the tracking type laser interferometer main body 50, and data processing is performed. When the arrangement position of the tracking laser interferometer body 50 is changed during the measurement by the apparatus 94, the arrangement position of the tracking laser interferometer body 50 is treated as different data before and after the change. In the figure, 81 is a holder.

  The retro-reflector 42 of the tracking type laser interferometer 40 is disposed at the tip (lower end in the figure) of the Z-axis spindle 38 of the CMM 30 as shown in FIG. In FIG. 5, 32 is a surface plate of the CMM 30, 34 is a portal column that moves on the surface plate 32 in the Y-axis direction before and after the figure, and 36 is a left and right X in the figure on the portal column 34. The Z-axis spindle 38 moves on the slider 36 in the vertical Z-axis direction in the drawing.

  The two-dimensional scale 92 is an encoder that detects two-dimensional movement of a measurement object, and can use, for example, MICSYS manufactured by Mitutoyo Corporation. These two-dimensional encoders are encoders that measure relative displacement with respect to a plane opposite to the two-dimensional encoder, and can detect displacement in two directions orthogonal to each other within the plane. As a two-dimensional encoder, it is also possible to use, for example, a mouse for a personal computer.

Two displacement amounts output from this two-dimensional encoder are denoted by δx _s and δy _s .

Hereinafter, a case where the spatial accuracy correction of the CMM 30 to be corrected is performed using the sequential multilateration method will be described. Sequential multi-lateration is a method of performing multi-lateration using one tracking laser interferometer 40. As shown in FIG. 2, tracking laser interference is sequentially performed at the arrangement positions P _{1 to} P _4. It is a method of placing measurement main body 50 and performing measurement.

Retro a tracking type laser interferometer 50, is first fixed to the arrangement position _{P 1} on the platen 32 of the correction of the target CMM30, as shown in FIG. 5, the tip of the Z axis spindle 38 of the correction target CMM30 A reflector 42 is attached.

  Thereafter, measurement is performed according to the flowchart shown in FIG.

That is, first, to move the retroreflector 42 in the Z-axis spindle 38 tip to the first measurement point _{U 1} by operating the CMM30 at step 100.

Then in step 110, the displacement amount .delta.x _s, .delta.y _s and, initialized by resetting the value of the counter _{E T} to zero. Here, the value of the counter E _T is a variable indicating the number of times the tracking type laser interferometer 50 is shifted during the measurement.

Next, at step 120, the distance d ₁ at the measurement point U ₁ of the retroreflector 42 is measured by the tracking laser interferometer 40. At the same time, the coordinate U _CMM1 of the measurement point U ₁ is measured by the CMM 30 to be corrected.

Next, in step 130, it is determined whether or not the tracking type laser interferometer main body 50 has shifted during measurement. Specifically, using the data processing device 94 of the tracking type laser interferometer 40, the tracking type laser interferometer body in which the square root δS of the square sum of the displacements δx _s and δy _s of the two-dimensional scale 92 is set in advance. A comparison is made as to whether the threshold value δS _L (for example, 0.2 μm) of 50 shift amounts is exceeded or not.

If delta] S ≦ delta] S _L at the decision result in the step 130 is positive, the process proceeds to a tracking type laser interferometer main body 50 is determined not to shift in the measurement step 140, the distance _{d 1,} the coordinate _{U CMM1,} and this time the value _{E T1} of the counter _{E T,} is stored in the data processing apparatus 94 of the tracking type laser interferometer 40.

On the other hand, if δS> δS _L and the determination result in step 130 is negative, it is determined that the tracking laser interferometer main body 50 has shifted during measurement, and the process returns to step 120 to repeat the measurement. However, prior to re-measure, and change the value of the counter E _T in step 150 to 1, for initialization reset to 0 the value of the displacement amount .delta.x _s and .delta.y _s in step 160.

Next, in step 200, the CMM 30 is operated to move the retro reflector 42 to the next measurement point U _m (for example, the second measurement point U ₂ ).

  Next, in step 210, it is determined whether or not the tracking type laser interferometer main body 50 is shifted while the retroreflector 42 is moving, in the same manner as in step 130.

If δS ≦ δS _L and the determination result in step 210 is positive, it is determined that the tracking laser interferometer body 50 is not displaced during the movement of the retroreflector 42, and the process proceeds to step 220, where the tracking laser interferometer 40 is moved. The distance d _m (d _{2 in} the case of the second point) to the _{retroreflector 42 and} the coordinates U _CMMm (the second point U _{2 in} the case of the second point) of the measurement point U _m (U _{2 in} the case of the second point) are measured. In the case of, make a measurement of U _CMM2 ) at the same time.

On the other hand, if the decision result in the step 210 in delta] S> delta] S _L is negative, it is determined that the tracking type laser interferometer 50 is shifted during the movement of the retroreflector 42, the value of the counter E _T in step 230, it The value is changed to a value obtained by adding 1 to the previous value E _Tm−1 (E _{T1 in} the case of the second point), and the displacements δx _s and δy _s are reset to 0 in step 240 and initialized. Thereafter, the process proceeds to step 220, (in the case of second point _{U CMM2)} (in the case of second point _{d 2)} the distance _d m between the coordinate _{U Cmmm} simultaneously performing measurement values.

  After completion of step 220, the process proceeds to step 250, and the same determination as in the previous step 210 is performed. If the determination result in step 250 is negative, the process proceeds to steps 260 and 270, and the same processing as in the previous steps 230 and 240 is performed.

On the other hand, if the decision result in the step 250 is positive, the process proceeds to step 280, the measured _{d m, U Cmmm,} and the value _{E Tm} of the counter _{E T} of this time, the tracking type laser interferometer 40 data processing apparatus 94 To remember.

The procedure of steps 200 to 280 is repeated until the determination result of step 290 for checking whether the measurement has been completed at all the measurement points U _m becomes positive, and all the predetermined measurement points U _{1 to} U _m are determined. to perform the measurement by moving the retroreflector 42, a distance _d 1 to d _m to retroreflector 42, the correction coordinate _U measuring points _U 1 ~U _m measured at CMM30 eligible CMM1 _{~U Cmmm,} and a counter _{E T} Value _ETm is stored.

When measured from the installation position P ₁ of the step 100 to 290 is completed, then moving the tracking type laser interferometer 50 similarly perform the measurement from the disposed position P _2, the then likewise disposed position make measurements from P ₃ and disposed position _{P 4.}

When the measurement from the arrangement positions P _{1 to} P ₄ is completed, the spatial accuracy parameter of the CMM 30 is calculated using the measured data. At the time of this calculation, if the position of the tracking laser interferometer main body 50 is shifted during the measurement, the data before and after the shift is arranged differently from the original arrangement position (for example, P ₁ ). It is handled as data measured from a position (for example, P ₅ ), and the calculation of the spatial accuracy parameter of the CMM 30 is performed.

For example, when the tracking type laser interferometer main body 50 is installed at the installation position P ₁ and the position of the retroreflector 42 is changed and m = 100 measurements are performed, m = 50th measurement from the start of measurement. There is no positional displacement of the tracking type laser interferometer main body 50 until the end, and after the m = 50th measurement is completed, the tracking type laser interferometer main body is generated by an unintended external force until the 51st measurement starts. It is assumed that the position of 50 shifts by δS _L or more. Further, it is assumed that no positional deviation of δS _L or more occurs after the end of m = 100 measurements.

At this time, the recorded m = 1 to 50 th counter value of _{E T} when the measurement, i.e. _E T1 _{to E T50} is 0, the counter value of _{E T} in the case of 51 th to 100 th measurement ( E _{T51 to} E _T100 ) is 1. Using this, the distance of 51 th to 100 th measurement data (d _m and coordinates U _Cmmm), as shown in FIGS. 7 and 8, the new arrangement position instead of from the installation position P ₁ so far as measured from P ₅ to calculate the spatial accuracy parameters CMM30. At this time, the position of the disposed position P _5, like the other arrangement position P ₁ to P _4, determined by solving the simultaneous equations of the measured data of length.

  When the number of positional deviations is n, the number of new arrangement positions P is similarly increased by n to calculate the spatial accuracy parameter of the CMM 30.

By using the apparatus and method shown in the above embodiment, the position of the tracking type laser interferometer 50, when displaced preset threshold value delta] S _L or more, it is possible to detect this. Further, the data before and after the threshold delta] S _L further displacement occurs, by disposing position P of the tracking type laser interferometer 50 is to calculate the spatial correction parameter CMM30 handled as different data, and the like unintentional external force, Even if the position of the tracking type laser interferometer body 50 is displaced, the calculated spatial correction parameter is not affected by this displacement. Therefore, the reliability of the space correction parameter measured by the tracking laser interferometer 40 is improved.

  In the embodiment, the present invention is used to measure the spatial accuracy correction parameter of the CMM. However, the application target of the present invention is not limited to this, and a mobile object is measured by using a tracking laser interferometer. The present invention can be similarly applied when moving to a point and detecting the position of each measurement point from the same arrangement position.

30 ... 3D coordinate measuring machine (CMM)
32 ... Surface plate 38 ... Z-axis spindle 40 ... Tracking laser interferometer 42 ... Retro reflector 50 ... Tracking laser interferometer body 70 ... Optical measuring device 72 ... Laser interference (measurement) meter 74 ... Laser light 76 ... For tracking The optical device 78 ... light position detector 80 ... two-axis turning unit 81 ... holder 90 ... base plate 92 ... 2-dimensional scale 94 ... data processing unit O ... reference point _{P 1, P 2, P 3} , P 4, P 5 ... Installation position

Claims (3)

Retroreflector attached to a moving object, laser interference that irradiates the retroreflector with laser light and detects the distance to the retroreflector using interference of the laser light reflected in the return direction by the retroreflector Length measuring device, tracking optical device having optical position detector for detecting positional deviation of optical axis of laser beam, biaxial rotation mechanism orthogonal to each other capable of changing emission direction of laser beam, biaxial rotation An angle detector disposed on each axis of the mechanism, and when the movable body moves, the optical position detector detects a displacement of the optical axis of the laser beam reflected in the return direction from the retroreflector. A tracking laser interferometer configured to control the biaxial rotation mechanism so that the positional deviation of the laser optical axis falls within a predetermined range, and the moving body is set at a plurality of measurement points. And moving, in detecting the position of each measurement point,
Detect deviations in the placement position of the tracking type laser interferometer main body during measurement at the same measurement point ,
Upon detecting a deviation of該配installation position can be the same measuring point, a tracking type laser interferometer, characterized in that the handle arrangement position of the tracking type laser interferometer before and after the deviation as different data Spatial position measurement method using   The space using the tracking laser interferometer according to claim 1, wherein the moving body is a spindle tip of a coordinate measuring machine, and a spatial correction parameter of the coordinate measuring machine is obtained by the tracking laser interferometer. Position measurement method. Retroreflector attached to a moving object, laser interference that irradiates the retroreflector with laser light and detects the distance to the retroreflector using interference of the laser light reflected in the return direction by the retroreflector A length measuring instrument, a tracking optical device having an optical position detector for detecting a positional deviation of the optical axis of the laser beam, a two-axis rotation mechanism orthogonal to each other capable of changing the emission direction of the laser beam, the two-axis rotation An angle detector disposed on each axis of the mechanism, and when the movable body moves, the optical position detector detects a displacement of the optical axis of the laser beam reflected in the return direction from the retroreflector. A tracking laser interferometer configured to control the biaxial rotation mechanism so that the positional deviation of the laser optical axis is within a predetermined range;
A position sensor that detects a displacement of the arrangement position of the tracking laser interferometer during measurement at the same measurement point ;
Using該追tail type laser interferometer, by moving the movable body in a plurality of measuring points, when detecting the position of each measurement point, add tail type laser interferometer by the position sensor during the measurement at the same measurement point When detecting the displacement of the arrangement position of the meter body, data processing means that treats the arrangement position of the tracking laser interferometer body as different data before and after the deviation, even at the same measurement point ,
A spatial position measuring device using a tracking type laser interferometer characterized by comprising: