JP2021192022A - Space measurement error detector of optical three-dimensional shape measurement device, space measurement error detection method and correction method thereof, optical three-dimensional shape measurement device, space measurement error calibration method of optical three-dimensional shape measurement device, and probing performance detection-purpose plane standard of optical three-dimensional shape measurement device - Google Patents

Abstract

To provide a space measurement error detector of an optical three-dimensional shape measurement device and a space measurement error detection method thereof that serve as a length measurement error detector complying with JISB7440-8, scan a measurement object with measurement light emitted from an optical comb distance meter, and thereby measure a three-dimensional shape of an object non-contactly.SOLUTION: A space measurement error detector of an optical three-dimensional shape measurement device comprises: a plurality of inspection balls 120; and a substrate 110 in which the plurality of inspection balls are two-dimensionally arrayed. The inspection ball is machined to a true sphere with a prescribed diameter, and is made of a steel ball having a screw hole 121 shorter in depth than the diameter, and a titanium nitride film is deposited on a surface. In the substrate, two or more through-holes 111 are formed through which a screw part 130 to be screwed into the screw hole is penetrated, and a bevelled process 112 is applied to a surface contacting with the inspection ball above the through-hole. In a state contacting with the bevelled part of the substrate, the inspection ball is tightly fixed by the screwing from a rear side of the substrate, and at least one of each center coordinate, an inter-ball distance, sphericity or the diameter of the plurality of inspection balls is known.SELECTED DRAWING: Figure 11

Description

The present invention is a spatial measurement error inspector and spatial measurement of an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner by scanning the measurement light emitted from the optical comb distance meter to the object to be measured. The present invention relates to an error detection method, a correction method, an optical three-dimensional shape measuring device, a spatial measurement error calibration method of the optical three-dimensional shape measuring device, and a plane standard for probing performance inspection of the optical three-dimensional shape measuring device.

Conventionally, distance measurement by an optical principle using a laser beam has been known as a distance measurement method capable of measuring a distance at a precise point. In a laser rangefinder that measures the distance to an object using laser light, the object to be measured is based on the difference between the time when the laser light is emitted and the time when the reflected laser light that hits the measurement target is detected by the light receiving element. The distance to is calculated (see, for example, Patent Document 1). Further, for example, the drive current of the semiconductor laser is modulated by a triangular wave or the like, and the reflected light of the object is received by using a photodiode embedded in the semiconductor laser element, and the sawtooth appearing in the photodiode output current. Distance information is obtained from the number of main waves of the state wave.

A laser range finder is known as a device for measuring an absolute distance from a certain point to a measurement point with high accuracy. For example, Patent Document 1 describes a rangefinder that measures a distance from a time difference between an interference signal of a reference light and an interference signal of a measurement light.

With conventional absolute rangefinders, it is difficult to realize a practical absolute rangefinder that can measure long distances with high accuracy, and in order to obtain high resolution, it is necessary to return to the origin like a laser displacement meter, so it is suitable for absolute distance measurement. There was only a method that was not suitable.

The present inventors detect the interference light between the reference light radiated to the reference surface and the measurement light radiated to the measurement surface by the reference light detector, and also detect the reference light reflected by the reference surface and the measurement surface. The interference light with the measurement light reflected by is detected by the measurement light detector, and the distance to the reference plane and the measurement from the time difference between the two interference signals obtained by the reference light detector and the measurement light detector. We have previously proposed an optical comb distance meter, a distance measuring method, and an optical three-dimensional shape measuring device that can be performed with high accuracy and in a short time by obtaining the difference in distance to the surface (for example,). See Patent Document 2).

In the optical three-dimensional shape measuring device, the measurement object emitted from the optical comb distance meter is irradiated to the measurement object through a scanning optical system such as a galvano mirror or a polygon mirror that scans the measurement light in one or two dimensions for measurement. The optical comb distance meter, in which the reflected light of the measurement light reflected by the object is returned via the scanning optical system, acquires the three-dimensional shape information of the measurement surface as the distance information to the measurement surface. An optical scanner using a telecentric optical system such as a telecentric f-θ lens is used to irradiate a measurement object with measurement light from a direction perpendicular to a virtual plane.

Conventionally, the correction of an optical scanner for a two-dimensional scan is generally performed as follows using a calibration reference device whose three-dimensional coordinates are calibrated.

As shown in FIG. 24, the coordinates of the grid points of the calibration reference device 200 are (X _Gi , Y _Gj , Z _Gk ). If the reference device has coordinates created in a grid pattern on a plane, X _Gi and Y _Gj are the coordinates of the XY reference device, and Z _Gk is the height at which the reference device is installed. The surface to be the Z reference plane may be processed so that the XY coordinates can be identified. Alternatively, a Z reference plane and an XY reference device may be prepared separately. Even if the Z reference plane and the XY reference device are different, the coordinates (X _i , Y _j , Z _k ) seen from the scanner side and the coordinates of the grid points of the calibration reference device can be measured under the same conditions. The relationship (X _i , Y _j , Z _k ) can be obtained. Here, X _i and Y _j are the XY coordinates assumed by the scanner, and Z _k is the value of the height before correction output by the shape measuring instrument.

First, the XY reference device is measured at multiple heights, and _{the Z dependence (X i} , Y _j , Z _{k ) between the XY coordinates (X i} , Y _j ) assumed by the scanner and the coordinates of the grid points of the calibration reference device. ).
Next, when the Z reference plane is measured, the relationship between _{the coordinates (height distribution) (X i} , Y _j , Z _{k ) seen from the scanner side and the installation height (Z G} k) of the Z reference plane can be obtained. By synthesizing the two, the relationship between the coordinates seen from the scanner side and the coordinates of the grid points of the calibration standard can be obtained via the _{common (X i} , Y _j).

Here, a rough surface having a small specular reflection component and a high flatness can be used as the Z reference plane. Height distribution data that does not include specular reflection is obtained by making slight angles around the X-axis and around the Y-axis. The virtual plane shape is obtained by averaging them. When measuring the XY reference device, if the specular reflection component does not affect the extraction of the grid points in the XY reference period, the reference device may be aligned with the virtual plane for measurement.

Since the coordinates of the grid points (X _Gi , Y _Gj , Z _Gk ) are visible as the coordinates (height distribution) (X _i , Y _j , Z _k ) seen from the scanner side, the amount of correction for the coordinates of the grid points (ΔX _i , ΔY _j , ΔZ _k ) = (X _Gi −X _i , Y _Gj −Y _j , Z _Gk −Z _k )
If the amount of correction is obtained for all grid points, ΔX _i = X _MCAL (X _i , Y _j , Z _k ) as a set of correction data at the grid points.
ΔY _j = Y _MCAL (X _i , Y _j , Z _k )
ΔZ _k = Z _MCAL (X _i , Y _j , Z _k )
Is obtained. Since this data contains only the correction amount of the grid points, it is necessary to obtain the correction amount other than the grid points by interpolation. Based on the set of correction data, each is fitted with the XY coordinates viewed from the scanner side, the value of height Z, a high-order polynomial of (X, Y, Z) or other appropriate function, and corrected as a coefficient of that polynomial. Save the data. Each fitted function is ΔX _i = X _FCAL (X, Y, Z)
ΔY _j = Y _FCAL (X, Y, Z)
ΔZ _k = Z _FCAL (X, Y, Z)
If, arbitrary coordinates as seen from the scanner side _{(X A, Y A, Z} A) ΔX by the correction amount interpolation in _{A = X FCAL (X A,} Y A, Z A)
_{ΔY A = Y FCAL (X A} , Y A, Z A)
_{ΔZ A = Z FCAL (X A} , Y A, Z A)
Will be. In a normal usage environment, the beam leaving the scanner travels in a straight line toward the measurement target, so it can be considered that Z is represented by a linear equation.

When the telecentricity of the scanner optical system (vertical downhill characteristics, matching condition with the normal of the virtual plane, etc.) is high and the Z dependence of the XY coordinates is so small that it can be ignored, the Z dependence disappears from the correction data. Therefore, it is sufficient to acquire the coordinates of the calibration reference device only at one height that is easy to measure (for example, the height of Z = 0 or the height of the beam focal point).

If the correction amount is obtained for all the grid points at Z = 0, then ΔX _i = X _MCAL (X _i , Y _j , 0) as a set of correction data at the grid points.
ΔY _j = Y _MCAL (X _i , Y _j , 0)
ΔZ _k = Z _MCAL (X _i , Y _j , 0)
Is obtained. The ΔZ _i is not limited to the grid points, and the entire plane data can be used. The amount of correction other than the grid points is obtained by interpolation. Based on the set of correction data, each is fitted with a high-order polynomial of XY coordinates (X, Y) viewed from the scanner side or other appropriate function, and the correction data is saved as a coefficient of the polynomial. Each fitted function is ΔX = X _FCAL (X, Y)
ΔY = Y _FCAL (X, Y)
ΔZ = Z _FCAL (X, Y)
If, arbitrary coordinates as seen from the scanner side _{(X A, Y A, Z} A) ΔX A = X FCAL by the correction amount interpolation in _{(X A, Y} A)
_{ΔY A = Y FCAL (X A} , Y A)
_{ΔZ A = Z FCAL (X A} , Y A)
Will be.

It may be considered as a case where the correction formula is defined in the general form including the Z dependence and the coefficient related to the term representing the Z dependence is zero.

If the scanner scans in a single direction, for example a line parallel to the X-axis, and measures the entire shape by another means of transportation in the Y-axis direction, then one line in the two-dimensional scan Make corrections as if they were scanned. If the scan line is distorted with respect to the line parallel to the X axis, the XY coordinates need to be corrected. By combining the X-axis line scan and the Y-axis movement, the XY reference device is scanned with the minimum width required for coordinate calibration in the Y-axis direction, and correction data is acquired by the same method as the two-dimensional scan.

In addition, JIS B 7440, which defines the accuracy test method for three-dimensional coordinate measuring machines, is provided as the JIS standard, and non-contact probing, which determines the corrected measurement point according to the principle of optical distance measurement as JIS B 7440-8. It defines a coordinate measuring machine with an optical distance sensor, which is a system.

Then, by using a block gauge and a sphere, which are standard lengths, the static scale calibration and the sphere measurement are performed at the same time to integrate the scale error of each axis including the operation performance of the detector. A CMM calibration gauge that can be calibrated for the purpose has been proposed (see, for example, Patent Document 3).

In the disclosed technique of Patent Document 3, CMM calibration is performed by placing and fixing a sphere on the surface of a block gauge whose absolute value of the length between the first end face and the second end face is guaranteed as a national standard. Make up the gauge. When using, a CMM stylus is applied to the first end face at three or more points to identify the plane of the first end face, and then a three-point stylus is applied to the equatorial part of the sphere and also to the pole point to hit the first end face. The center coordinates of the sphere from the plane and the diameter of the sphere are specified, and then the stylus is applied to the second end face to correct the above-mentioned specific values of the second end face and the sphere, and the coordinates of the three-dimensional space of the sphere are accurately specified. Use the CMM calibration gauge.

A CMM (coordinate measuring machine) is a measuring instrument for measuring dimensions and shapes with the assistance of a computer using discrete X, Y, and Z coordinate points existing in a three-dimensional space. The object to be measured placed on the platen and the probe attached to the tip of the Z-axis in the measuring instrument are relatively moved in the three-dimensional directions of X, Y, and Z, and the moment when the probe comes into contact with the object to be measured is captured. This is a three-dimensional measuring instrument that reads the coordinate values in each feed axis direction using this moment as an electrical trigger and measures the dimensions and shape by a computer.
Further, by providing a first sphere row arranged on the surface of a substrate having a flat upper surface and a second sphere row arranged at an angle with respect to the upper surface of the substrate, the three-dimensional coordinate measuring machine can be accurately measured. It has been proposed to construct a three-dimensional coordinate measuring instrument gauge for evaluation (see, for example, Patent Document 4).

Japanese Unexamined Patent Publication No. 2001-343234 Japanese Patent No. 5231883 Japanese Patent No. 3005681 Japanese Unexamined Patent Publication No. 2012-58057

By the way, an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner by scanning the measurement light radiated to the object to be measured from the optical comb distance meter proposed by the present inventors. Then, the measurement of the irradiation position on the measurement object of the measurement light irradiated to the measurement object via the optical comb interferometer can be performed with high accuracy and in a short time, but the measurement is performed via the optical scanner. Since the object is irradiated with the measurement light, there is a measurement error due to scanning distortion by the optical scanner.

In an optical scanner installed in an optical three-dimensional shape measuring device, in general, the curved surface of a lens or mirror cannot be completely equidistant on a virtual plane due to the deviation from the ideal shape or the influence of the refractive index. However, the height is often different between the central part and the peripheral part of the field of view, as seen in the curvature of field. An optical three-dimensional shape measuring device equipped with an optical scanner with an ideal telecentric optical system whose main optical axis is parallel to the optical axis at any location in the optical system can measure a high-precision reference plane like a mirror. However, it is possible to correct the height data of the object to be measured without error by using the correction data so that the plane obtained as the measurement result looks like a plane.

However, in reality, the measurement light emitted to the object to be measured via the optical scanner is slightly affected by the deviation from the ideal optical system and the wavelength dispersion of the material with respect to the optical axis at each location. It is inclined to, and it becomes a distorted state distributed in one or two dimensions.

Further, when a material having a large wavelength dispersion is included in the scanning optical system, the group delay may be distributed within the beam diameter of the measurement light.

In an optical scanner that emits measurement light slightly inclined with respect to the optical axis for each location and an optical scanner that includes a material with a large wavelength dispersion in the scanning optical system, mirror reflection occurs when calibrated using a mirror. Only a part of the reflected light component of the measurement light contributes to the generation of the interference signal in the optical comb distance meter.

If the optical comb distance meter can detect all of the reflected light reflected by the measurement object of the measurement light applied to the measurement object, the distance of the locus of the center of the optical axis of the measurement light can be measured with high accuracy. However, if only a part of the reflected light can be detected, an error will occur in the distance calculated from the locus of the center of the optical axis of the measured light.

As described above, the raw shape data obtained by the optical three-dimensional shape measuring device without coordinate correction includes an error in the coordinates and the distance in space. The error is due to the non-linearity of the scanner, the distortion of the optical system, the deviation from the telecentricity, and the aberration. Therefore, it is correct to detect the spatial error distribution with an inspection device that serves as a coordinate reference separately from the shape measurement of the object to be measured and have it as correction data, and correct the coordinates of the measurement result and the movement of the scanner. It is necessary to convert to coordinate values and correct (calibrate) the data.

In addition, it is necessary to detect spatial errors by an inspector whose true values of coordinates and length are determined in order to evaluate the coordinate measurement performance of the corrected (calibrated) optical 3D shape measuring device. .. JIS B 7440-8 Optical non-contact three-dimensional measuring instrument "Product geometric characteristic specifications (GPS) -Acceptance inspection and periodic inspection of coordinate measurement system (CMS) -Part 8: Coordinate measuring instrument with optical distance sensor" An inspection method that complies with is desirable.

In view of the conventional circumstances as described above, the inventors of the present invention have made a special application for a calibration method of an optical scanner device capable of acquiring calibration data capable of correcting distortion of a scanning optical system that irradiates a measurement object with measurement light. It is proposed earlier as 2020-001699.

Further, the disclosed techniques of Patent Document 3 and Patent Document 4 are for calibrating a contact-type coordinate measuring instrument that measures by applying a stylus, and is a non-contact optical three-dimensional shape measuring device. No consideration is given to the calibration of.

In JIS B 7440-8, "Inspection standard equipment is used to evaluate the probing error using an inspection standard equipment made of steel or ceramics. An inspection standard equipment made of other appropriate materials is used. Inspecting with inspection standards of different materials may result in different probing errors due to differences in optical characteristics such as surface reflectance light penetration (volume scattering), color, and scattering characteristics. Therefore, the material of the inspection standard used must be recorded. The surface roughness of the inspection standard used to evaluate the probing error is negligibly small compared to the corresponding maximum tolerance. Must be. "

Therefore, an object of the present invention is to function as a length measurement error inspector compliant with JIS B 7440-8 in view of the conventional circumstances as described above, and scan the measurement light radiated to the measurement object from the optical comb distance meter. It is an object of the present invention to provide a spatial measurement error inspection device and a spatial measurement error detection method of an optical three-dimensional shape measuring device for measuring a three-dimensional shape of an object in a non-contact manner.

Another object of the present invention is for calibration of an optical three-dimensional shape measuring device for detecting deviation from a telecentric optical system and obtaining data necessary for coordinate correction and calibration (calibration). To provide a spatial measurement error tester and a calibration method.

In addition, we provide an optical three-dimensional shape measuring device capable of performing three-dimensional shape measurement with less error by removing the influence of distortion of the scanning optical system that irradiates the measurement object with measurement light, and a spatial measurement error calibration method thereof. To do.

Further, another object of the present invention is an optical three-dimensional shape measuring device capable of performing three-dimensional shape measurement with less error by removing the influence of distortion of a scanning optical system that irradiates a measurement object with measurement light. To provide a flat surface standard for probing performance inspection.

Other objects of the invention, the specific advantages obtained by the present invention, will be further clarified from the description of the embodiments described below.

The present invention is a spatial measurement error inspector of an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner by scanning the measurement light radiating to the object to be measured from an optical comb distance meter. A steel ball having a plurality of test balls and a substrate on which the test balls are arranged two-dimensionally, the test ball is processed into a true sphere to a predetermined diameter and has a screw hole having a depth shorter than the diameter. A titanium nitride film is formed on the surface of the substrate, and the substrate has two or more through holes through which the screw screwed into the screw holes is penetrated, and the upper part of the through holes is on the surface in contact with the inspection ball. The plurality of inspection balls are chamfered, and the plurality of inspection balls are arranged two-dimensionally and are screwed and fixed from the back side of the substrate in a state of being in contact with the chamfered portion of the substrate, respectively. It is characterized in that at least one of each center coordinate, intersphere distance, sphericity or diameter of each of the above is known.

In the spatial measurement error inspection device of the optical three-dimensional shape measuring device according to the present invention, the inspection ball is screwed and fixed in a state of being pressed by the elastic element against the chamfered portion of the substrate with a predetermined pressing force. Can be assumed to be.

In the spatial measurement error inspection device of the optical three-dimensional shape measuring device according to the present invention, the plurality of inspection balls have a predetermined diameter within 3 mm to 6.8 mm and a predetermined pitch within 3 mm to 6.8 mm. It can be assumed that they are arranged in two dimensions.

In the spatial measurement error inspection device of the optical three-dimensional shape measuring device according to the present invention, the plurality of inspection balls are arranged two-dimensionally at the inter-sphere distance position selected only for the section used in the JIS standard inspection. Can be.

In the spatial measurement error inspection device of the optical three-dimensional shape measuring device according to the present invention, the plurality of inspection spheres have five different maximum lengths of 26.4 mm or more and 40 mm or less in the two-dimensional direction on the surface of the substrate. It can be assumed that they are arranged two-dimensionally at the inter-ball distance positions corresponding to at least one of the inspection lengths.

In the spatial measurement error inspection device of the optical three-dimensional shape measuring device according to the present invention, the plurality of inspection balls have a maximum length of 42.3 mm or more and 64 mm or less in the diagonal direction and have five different inspection lengths. It can be assumed that they are arranged two-dimensionally at the distance positions between spheres corresponding to at least one.

In the spatial measurement error inspection device of the optical three-dimensional shape measuring device according to the present invention, at least one calibration value, nominal value, or design value of each center coordinate, intersphere distance, sphericity, or diameter of the plurality of inspection spheres. Can be clarified.

The present invention is a method for detecting a spatial measurement error of an optical three-dimensional shape measuring device that measures a three-dimensional shape of an object in a non-contact manner by scanning the measurement light emitted from an optical comb distance meter to a measurement object. ,
Three-dimensional shape measurement is performed using the optical space measurement error tester as the measurement object with the optical three-dimensional shape measuring device to be inspected, and the center coordinates, inter-sphere distance, and true of the plurality of test spheres obtained as the measurement results. At least one difference between the information on the sphericity or diameter and the information on the center coordinates, the distance between spheres, the sphericity or the diameter of the plurality of inspection spheres calibrated in advance is the above-mentioned optical three-dimensional shape measuring device to be inspected. It is characterized in that it is detected as a spatial measurement error of.

The present invention is a correction method for an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner by scanning the measurement light emitted from the optical comb distance meter to the object to be measured, and is to be corrected. Using the optical three-dimensional shape measuring device, the optical space measurement error tester is placed at a plurality of height positions as a measurement object, three-dimensional shape measurement is performed, and a plurality of notes obtained as measurement results at each height position are obtained. At least one of information on each center coordinate, intersphere distance, sphericity or diameter of the test sphere and information on each center coordinate, intersphere distance, sphericity or diameter of the plurality of pre-calibrated test spheres. It is characterized in that the difference is detected as a spatial measurement error of the corrected optical three-dimensional shape measuring device and correction data is acquired.

The present invention is an optical three-dimensional shape measuring device, and is an optical system that scans measurement light to irradiate a measurement object based on the correction data acquired by the correction method of the optical three-dimensional shape measuring device. It is characterized by comprising a correction processing means for correcting distortion.

The present invention is a spatial measurement error calibration method for an optical three-dimensional shape measuring device, in which a corrected optical three-dimensional shape measuring device is used as an optical three-dimensional shape measuring device to be inspected to acquire correction data. Three-dimensional shape measurement is performed using an optical space measurement error tester different from the spatial measurement error tester as the measurement target, and the center coordinates, inter-sphere distance, sphericity, or sphericity of each of the multiple test balls obtained as the measurement results. Spatial measurement of at least one difference between the diameter information and each center coordinate, intersphere distance, sphericity or diameter information of the plurality of inspection spheres calibrated in advance by the optical three-dimensional shape measuring device to be inspected. It is characterized by detecting it as an error.

The present invention is a planar standard for probing performance inspection of an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner by scanning the measurement light emitted from the optical comb distance meter to the object to be measured. Therefore, it is characterized in that a titanium nitride film is formed on a precision-polished ceramic flat surface.

According to the present invention having the above-mentioned feature points, a plurality of steel balls each having a true sphere processed to a predetermined diameter and having screw holes having a depth shorter than the above diameter, and having a titanium nitride film formed on the surface thereof. The inspection ball of No. 1 has two or more through holes through which the screw screwed into the screw hole is formed, and contacts the chamfered portion of the substrate on which the surface in contact with the inspection ball is chamfered at the upper part of the through holes. In this state, it is screwed and fixed from the back side of the substrate, and at least one of the center coordinates, intersphere distance, sphericity or diameter of each of the plurality of inspection balls is pre-calibrated, so that the object is non-contact. It is possible to detect the spatial measurement error of the optical three-dimensional shape measuring device that measures the three-dimensional shape with high accuracy, and it is measured from the optical com distance meter as a length measurement error inspection device compliant with JIS B 7440-8. By scanning the measurement light that irradiates the object, it is possible to provide a spatial measurement error inspector and a spatial measurement error detection method of an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner.

Further, according to the present invention, a space for calibration (calibration) of an optical three-dimensional shape measuring device for detecting deviation from the telecentric optical system and collecting data necessary for coordinate correction and calibration (calibration). Measurement error inspectors and calibration methods can be provided.

Further, according to the present invention, an optical three-dimensional shape measuring device and its space capable of performing three-dimensional shape measurement with less error by removing the influence of distortion of the scanning optical system that irradiates the measurement object with measurement light. A measurement error calibration method can be provided.

Further, according to the present invention, the probing performance of an optical three-dimensional shape measuring device capable of performing three-dimensional shape measurement with less error by removing the influence of distortion of the scanning optical system that irradiates the measurement object with the measurement light. A flat surface standard for inspection can be provided.

It is a block diagram which shows the basic structure of the optical 3D shape measuring apparatus 100 to which this invention is applied. It is a block diagram which shows the structure of the optical comb rangefinder provided in the said optical three-dimensional shape measuring apparatus. It is a perspective view schematically showing the state of the calibration process in the case where the optical scanner device in the above optical three-dimensional shape measuring device is a one-dimensional scanner provided with a scanning optical system that scans the measurement light in one direction. A perspective view schematically showing the state of the height distribution obtained as a measurement result according to the deviation of the locus of the scanned points from the X axis when the shape of the reference plane for calibration is measured by the above one-dimensional scanner. Yes, (A) shows the case where the tilt angle θ of the reference plane is positive, and (B) shows the case where the tilt angle θ of the reference plane is negative. It is a perspective view schematically showing the state of the calibration process in the case where the optical scanner device in the above optical three-dimensional shape measuring device is a two-dimensional scanner provided with a scanning optical system that scans measurement light in two directions. It is a perspective view which shows the state of the reference plane of the calibration standard in the calibration process of the 2D scanner, (A) shows the state which the reference plane is tilted + θ about the X axis, (B) is The state where the reference plane is tilted by −θ around the X axis is shown, (C) shows the state where the reference plane is tilted by + φ around the Y axis, and (D) shows the state where the reference plane is tilted by −φ around the Y axis. (E) shows a virtual plane with θ = 0 degrees and φ = 0 degrees. The scan linearity of a scan optical system that scans one-dimensionally in the X direction with a galvano scanner using a telecentric lens made of a single material, and the results of this scan optical system make titanium nitride with high flatness. It is a characteristic diagram showing the result of measuring the one-dimensional shape by tilting the ceramic substrate on which the film was formed by ± 1 degree in the Y direction, (A) shows the measurement result of the linearity of the scan, and (B) shows the ceramic. It is a plot of the difference between the results of measuring the one-dimensional shape of the substrate. It is a characteristic diagram which shows the discrepancy between the measurement result of a plane mirror and the measurement of the ceramic substrate on which the titanium nitride film which is a rough surface is formed, and (A) is a characteristic diagram when (B) of FIG. 7 is measured. It is a plot of the difference between the data measured by the plane mirror from the data (TiN + 1 degree), and (B) is from the data (TiN-1 degree) when (B) in FIG. 7 is measured. It is a plot of the difference of the data measured by the plane mirror, and (C) shows the average value of (A) of FIG. 8 and (B) of FIG. It is a bird's-eye view which shows the plane standard for probing performance inspection placed on the surface plate. It is a bird's-eye view which shows the spatial measurement error inspection apparatus to which this invention is applied which is formed by arranging a plurality of inspection spheres two-dimensionally on a substrate. It is a figure which is provided for the explanation of the structure of the space measurement error inspection device, (A) is a plan view of a substrate, (B) is a side view schematically showing the disassembled state of this space measurement error inspection device, (C). Is a side view schematically showing a state in which this spatial measurement error inspection device is assembled and attached to a base substrate. It is a perspective view which shows typically the installation state at the time of performing the inter-ball distance measurement by the said space measurement error inspection device, and (A) shows the state which installed the space measurement error inspection device parallel to the XY plane of the measurement space. , (B) shows the state where the spatial measurement error inspector is lifted from the state shown in (A) to the other corner side on the diagonal line centering on one point of the four corners, and (C) shows the state where the side surface is further lifted. Shows. Three types of spatial measurement attached to the base board as a spatial measurement error inspector used for calibrating a three-dimensional shape measuring device whose measurement range is a three-dimensional space of length (40 mm) x width (40 mm) x height (30 mm). It is a bird's-eye view showing an error inspection device. It is a bird's-eye view which shows the state which the said three kinds of space measurement error inspection instruments are placed on the surface plate of an optical three-dimensional shape measuring apparatus. Space with 28 test balls arranged and fixed on the board Space indicating the numbers (0 to 27) assigned to the 28 test balls referred to when explaining the analysis results of the measurement data by the measurement error tester. It is a bird's-eye view of a measurement error inspection device. It is a figure which provides the explanation about the analysis of the measurement data by a spatial measurement error inspection device. It is the figure which showed the relationship between the center coordinate and the height obtained as the analysis result of the measurement data by looking at the spatial measurement error inspector from above. It is the figure which emphasized the error of the locus of the locus of the center of a sphere obtained as the analysis result of the measurement data. It is a figure which shows the locus of the center of a sphere in the X cross section obtained as the analysis result of the measurement data. It is a figure which shows the locus of the center of a sphere in the Y cross section obtained as the analysis result of the measurement data. It is a figure which shows the inter-ball distance obtained as the analysis result of the measurement data, (A) shows the inter-ball distance of No. 0 and No. 1, (B) shows the inter-ball distance of No. 0 and No. 5. (C) shows the distance between the balls 0 and 6, (D) shows the distance between the balls 0 and 22, and (E) shows the distance between the balls 0 and 27. Rmax = 0.6 (range of 60% of top surface diameter), Rmax = 0.7 (range of 70% of top surface diameter), Rmax = of intersphere distance based on No. 0 obtained as the analysis result of measurement data. It is a figure which shows the reproducibility at 0.8 (the range of 60% of the upper surface diameter), Rmax = 0.9 (the range of 90% of the upper surface diameter), and (A) is the distance between spheres at a height of 97.5 mm. The variation is shown, (B) shows the variation of the ball-to-ball distance at a height of 87.5 mm, and (C) shows the variation of the ball-to-ball distance at a height of 77.5 mm). Rmax = 0.6 (range of 60% of top diameter) and Rmax = 0.7 (range of 70% of top diameter) of center coordinates (radius of center point inclusion sphere) obtained as a result of analysis of measurement data , Rmax = 0.8 (range of 60% of top surface diameter), Rmax = 0.9 (range of 90% of top surface diameter), (A) is the center point inclusion sphere diameter (high). 97.5 mm), (B) indicates a center point inclusion sphere (height 87.5 mm), and (C) indicates a center point inclusion sphere (height 77.5 mm). It is a schematic plan view of the calibration standard generally used for the calibration of the optical scanner of a two-dimensional scan conventionally.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The common components will be described with reference numerals in the drawings. Further, the present invention is not limited to the following examples, and it goes without saying that the present invention can be arbitrarily modified without departing from the gist of the present invention.

The present invention is applied to, for example, an optical three-dimensional shape measuring device 100 having a configuration as shown in FIG.

FIG. 1 is a block diagram showing a basic configuration of an optical three-dimensional shape measuring device 100 to which the present invention is applied.

The optical three-dimensional shape measuring device 100 includes an optical comb distance meter 10, an optical scanner device 20 that scans an object 50 with measurement light S2 emitted from the optical comb distance meter 10, and an optical comb distance meter 10. A signal processing device 30 for measuring an absolute distance to a plurality of points of a measurement object 50 based on an output to obtain a stereoscopic image is provided.

The optical comb distance meter 10 measures the distance using, for example, an optical frequency comb interferometer, as shown in the block diagram of FIG. 2, and is emitted from the first and second optical comb light sources 11 and 12. Two optical frequency combs with different center frequencies and frequency intervals are periodically modulated in intensity or phase, and are measured via the interference optical system 13 as interfering reference light S1 and measurement light S2 having different modulation periods. The reference light detector 16 detects the interference light S3 with the measurement light S2 incident on the optical path 15, and the reference light S1 and the measurement light S2 incident on the reference light path 14 and the measurement optical path 15 are the reference optical path 14 and the measurement optical path. The interference light S4 between the reference light S1'and the measurement light S2'reciprocating back and forth between 15 is detected by the measurement light detector 17, and the interference light S3 is detected by the reference light detector 16 by the signal processing unit 18. From the time difference between the interference signal and the interference signal in which the interference light S4 is detected by the measurement light detector 17, the distance L1 of the reference light path 14 to which the reference light S1 reciprocates and the measurement light S2 are determined from the light speed and the refractive index at the measurement wavelength. The difference in the distance L2 of the reciprocating measurement optical path 15 can be obtained. There are multiple types of interferometers and detectors.

The optical scanner device 20 irradiates the surface of the object to be measured 50 with the measurement light S2 emitted from the optical comb distance meter 10 while scanning the surface, and returns the reflected light from the surface to the optical comb distance meter 10. The scanning optical system 21 that scans the measurement object 50 with the measurement light S2 emitted from the optical comb distance meter 10 and the measurement light S2 deflected by the scanning optical system 21 are focused and perpendicular to the measurement object 50. A scan optical system 23 including a telecentric condensing optical system 22 that irradiates light from a direction is provided.

The signal processing device 30 controls the optical scanner device 20 to scan the laser beam, and at the same time, acquires the distance information to the measurement object 50 measured by the optical comb rangefinder 10 to the beam irradiation position and its location. The three-dimensional shape of the object to be measured 50 is measured in a non-contact manner by accumulating the distances at a plurality of points.

Then, as shown in FIG. 3, the optical scanner device 20 in the optical three-dimensional shape measuring device 100 is scanned when it is a one-dimensional scanner provided with a scanning optical system 23A that scans the measurement light S2 in one direction. With reference to the state in which the sheet-shaped flat surface 41 created by the measurement light S2 and the calibration reference plane 40A of the calibration reference device 40 are perpendicular to each other, the reference plane 40A is set at an angle θ0 around the X axis (scanning direction of the measurement light S2). Correction data can be obtained by scanning the measurement light S2 that irradiates the reference plane 40A of the calibration reference device 40 from the optical comb distance meter 10 and measuring the shape of the reference plane 40A. It will be done.

Here, the reference plane 40 is slightly tilted so as not to detect the specular reflection component, and the required angle θ0 differs depending on the beam diameter. When the beam diameter is 100 μm, it is sufficient to incline the reference plane 40A once around the X axis (scanning direction of the measurement light S2).

For the calibration of the optical scanner device 20, a reference plane 40A having a high flatness but containing a diffuse reflection component and a small specular reflection component, such as a machined surface having a good flatness or a ceramic substrate coated with titanium nitride (TiN). 40, and a calibration reference device 40 whose coordinate position on the reference plane 40 has been calibrated in advance is used. As shown in the bird's-eye view of FIG. 9, the calibration reference device 40 has a probing having a calibration reference plane 40A having a flatness of 0.2 μm in which a titanium nitride film is formed on a precision-polished ceramic plane. A plate made with the same specifications as the flat surface standard for performance inspection was placed on the surface plate 60 and used.

The signal processing device 30 in the optical three-dimensional shape measuring device 100 controls the optical scanner device 20 to scan the laser beam, and at the same time, the reference plane 40A of the calibration reference device 40 measured by the optical comb distance meter 10. The three-dimensional shape of the reference plane 40A is measured by acquiring the distance information up to and accumulating the beam irradiation position and the distance to the location at a plurality of points, and the reference plane obtained by the optical comb distance meter 10. Based on the shape measurement result of 40A, a correction process is performed using the error of the coordinate position based on the shape measurement result as the correction data with respect to the coordinate position on the pre-calibrated reference plane 40A.

Here, FIG. 4 shows that when the shape of the reference plane 40A of the calibration reference device 40 is measured by the one-dimensional scanner, the locus of the scanned points is obtained as a measurement result according to the deviation from the X axis. It is a perspective view which shows the state of the height distribution schematically, (A) shows the case where the inclination angle θ of the reference plane 40A is positive, and (B) shows the case where the inclination angle θ of the reference plane 40A is negative. ing.

That is, in the correction process of the optical scanner device 20 by the signal processing device 30, when the optical scanner device 20 is a one-dimensional scanner including a scanning optical system 23A that scans the measurement light S2 in one direction, the locus of the scanned points is If it deviates from the X-axis, it is detected as a height deviation, and if it is curved in the positive direction of the Y-axis, as shown in FIG. 4A, if the angle θ is positive, it is in the Z-axis direction. The height distribution F1 of is convex upward, and when it is curved in the positive direction of the X axis, as shown in FIG. 4B, if the angle θ is negative, the height distribution F2 in the Z axis direction is negative. Since is convex downward, the height fluctuation caused by the curvature of the scan line and the inclination of the reference plane 40A by measuring the shape of the calibration reference plane 40A at a positive / negative angle θ and taking the summed average of the height distribution. Can be offset.

Further, as shown in FIG. 5, the optical scanner device 20 in the optical three-dimensional shape measuring device 100 is a two-dimensional scanner provided with a scanning optical system 23B that scans the measurement light S2 in two directions in the X-axis direction. A reference plane around the X axis (scanning direction of the measurement light S2) with reference to the state in which the sheet-shaped flat surface 41X created by the measurement light S2 scanned in 1 and the calibration reference plane 40A of the calibration reference device 40 are perpendicular to each other. The 40A is tilted by an angle θ0, and the sheet-shaped plane 41Y created by the measurement light S2 scanned in the Y-axis direction and the calibration reference plane 40A of the calibration reference device 40 are referenced around the Y-axis as a reference. By scanning the measurement light S2 irradiating the reference plane 40A of the calibration reference device 40 from the optical comb distance meter 10 with the plane 40A tilted by an angle φ0, the shape of the reference plane 40A is measured. The correction data is acquired.

In the correction process of the optical scanner device 20 by the signal processing device 30, when the optical scanner device 20 is a two-dimensional scanner provided with a scan optical system 23B that scans the measurement light S2 in two directions, the curvature of the scan line is curved depending on the scanning location. Since they are different, as shown in FIG. 6, the influence is excluded by the post-processing by measuring by tilting the X-axis and the Y-axis in the positive and negative directions.

6 (A), (B), (C), (D), and (E) of FIG. 6 are cases where the optical scanner device 20 is a two-dimensional scanner including a scanning optical system 23B that scans the measurement light S2 in two directions. It is a perspective view which shows the state of the reference plane 40A of the calibration standard 40 in the correction process schematically, (A) shows the state which the reference plane 40A is tilted + θ about the X axis, and (B) is the reference plane. 40A is tilted by −θ around the X axis, (C) is the state where the reference plane 40A is tilted by + φ around the Y axis, and (D) is the state where the reference plane 40A is tilted by −φ around the Y axis. (E) shows a virtual plane 40B with θ = 0 degrees and φ = 0 degrees.

That is, when the line that should exist parallel to the X-axis is curved in the positive direction of the Y-axis, as shown in FIG. 6A, the angle θ ₀ around the X-axis is positive and negative for each of the positive and negative axes. The height distributions F1 and F2 in the direction are measured.

If the line to be present parallel to the Y axis is curved in the positive direction of the X axis, as shown in (C) of FIG. 6, the angle phi ₀ of the Y-axis around positive and negative, respectively, in the Z-axis direction The height distributions F3 and F4 are measured.

In this way, by measuring the shape of the calibration reference plane 40A at positive and negative angles θ0 and φ0 (4 times in total) and taking the averaging of the height distribution, the height generated by the curvature of the scan line and the inclination of the reference plane. Fluctuations can be offset.

That is, as shown in (A), (B), (C), (D), and (E) of FIG. 6, measurement is performed with a total of four tilt angles, ± θ around the X axis and ± φ around the Y axis. As shown in FIG. 6 (E), the measurement data of the virtual plane 40B having θ = 0 degrees and φ = 0 degrees can be obtained from the added average of the obtained data, and the diffuse reflection from the reference plane 40A of the rough surface can be obtained. It is possible to acquire data whose main component is, that is, data that is not affected by specular reflection.

Here, the result of measuring the linearity of the scan for the scan optical system that scans one-dimensionally in the X direction with a galvano scanner using a telecentric lens made of a single material, and the flatness of the scan optical system are obtained by this scan optical system. The results of measuring the one-dimensional shape by tilting the ceramic substrate on which the high titanium nitride film is formed by ± 1 degree in the Y direction are shown in FIGS. 7A and 7B.

FIG. 7A shows the measurement result of the linearity of the scan when one-dimensional scanning is performed in the X direction with a galvano scanner using a telecentric lens made of a single material capable of scanning a width of 160 mm. Deviance from the straight line is observed in the linearity.

In FIG. 7B, a ceramic substrate on which a highly flat titanium nitride film is formed is placed perpendicular to the beam at the focal position of the optical system and at the center of the scan, and then tilted by +1 degree in the Y direction. The result of measuring the one-dimensional shape of the time (X-axis rotation about the straight line where the plane formed by the measurement light scanned in the X-axis direction and the plane on which the titanium nitride film is formed intersects) is (TiN + 1 degree). On the contrary, the result of measuring the one-dimensional shape when tilted by -1 degree in the Y direction is taken as (TiN-1 degree), and the difference between them ((TiN-1 degree)-(TiN + 1 degree)) is plotted. Is.

The measurement result shown in FIG. 7 (B) has a strong correlation with the measurement result shown in FIG. 7 (A), and the difference between (TiN-1 degree) and (TiN + 1 degree) is not derived from the linearity of the scan. This is because it has the effect of canceling the distortion component of the scan, and the linearity of the scan becomes conspicuous.

That is, the measurement result of (B) in FIG. 7 proves that when the height of the plane placed at an angle with respect to the laser beam is measured, the deviation component from the linearity of the scan is included in the shape data. is doing.

Further, (A) and (B) in FIG. 8 show the difference between the data obtained by measuring the plane mirror from the data (TiN + 1 degree) and the data (TiN-1 degree) when (B) in FIG. 7 was measured. It is a plot, and FIG. 8C shows the average value of FIG. 8A and FIG. 8B.

Since the sign of the linearity of the scan is reversed when tilted by +1 degree in the Y direction and when tilted by -1 degree, (C) in FIG. 8 which is the average value of (A) in FIG. 8 and (B) in FIG. ) Cancels the distortion component due to the linearity of the scan. Therefore, the strain represented by (C) in FIG. 8 represents the discrepancy between the measurement result of the planar mirror and the measurement of the ceramic substrate on which the titanium nitride film, which is a rough surface, is formed. The main causes of this divergence are the imperfections of the telecentric lens and the wavelength dispersion of the lens material.

The signal processing device 30 in the optical three-dimensional shape measuring device 100 has a reference plane 40A having a high flatness but containing a diffused reflection component, and a calibration reference device 40 whose coordinate positions on the reference plane 40A are calibrated in advance. Is installed in a state where the reference plane 40A is slightly tilted, and the measurement light S2 irradiating the reference plane 40A of the calibration reference device 40 from the optical comb distance meter 10 is scanned by the optical scanner device 20 to obtain the light. The shape of the reference plane 40A is measured using the diffused reflection component of the measurement light S2'reflected from the reference plane 40A by the comb distance meter 10, and the shape of the reference plane 40A obtained by the optical comb distance meter 10 is measured. Based on the result, the distance measurement by the optical comb distance meter 10 is performed by performing correction processing using the error of the coordinate position based on the shape measurement result with respect to the coordinate position on the pre-calibrated reference plane 40A as the correction data. As the data, it is possible to acquire the three-dimensional shape measurement data of the measurement object in which the distortion of the scan optical system is corrected.

That is, in the optical three-dimensional shape measuring device 100, the signal processing device 30 scans the measurement light S2 irradiating the measurement object 50 from the optical comb distance meter 10 with the optical scanner device 20 to scan the optical comb. It has a function as a correction processing means for acquiring the three-dimensional shape measurement data of the measurement object 50 in which the spatial distribution of the group delay of the scan optical system 23 is corrected as the distance measurement data by the distance meter 10. Is high, but has a reference plane containing a diffused reflection component, and correction data is acquired using a calibration reference device 40 whose coordinate position on the reference plane 40A is calibrated in advance, and the measurement is applied to the measurement object 50. By correcting the distortion of the scan optical system 23 due to the inclination of the light S2 with respect to the optical axis based on the correction data, the influence of the distortion of the scan optical system 23 that irradiates the measurement object 50 with the measurement light S2 is removed. It is possible to perform three-dimensional shape measurement with little error.

The format of the correction data is the data (ΔX, ΔY, ΔZ) itself for converting the three-dimensional coordinate data (X, Y, Z) of the measured data into the corrected coordinates (X + ΔX, Y + ΔY, Z + ΔZ) of the table. A method of holding in the form or a method of holding (ΔX, ΔY, ΔZ) in the form of a function of (X, Y, Z) can be considered. In the case of the function form, it is also possible to hold the correction data in the form of the coefficients of the function that approximates the polynomial.

In this optical three-dimensional shape measuring device 100, the signal processing device 30 has a reference plane 40A having a high flatness but containing a diffused reflection component, and a calibration reference whose coordinate position on the reference plane 40A is calibrated in advance. The device 40 is installed in a state where the reference plane 40A is slightly tilted, and the measurement light S2 to be applied from the optical comb distance meter 10 to the reference plane 40A of the calibration reference device 40 is scanned by the optical scanner device 20. The shape of the reference plane 40A is measured using the diffused reflection component of the measurement light S2'reflected from the reference plane 40A by the optical comb distance meter 10, and the reference plane 40A obtained by the optical comb distance meter 10 is obtained. Based on the shape measurement result, the correction method of the optical scanner device according to the present invention is executed, in which the error of the coordinate position based on the shape measurement result with respect to the coordinate position on the pre-calibrated reference plane 40A is used as correction data.

In the correction method of the optical scanner device 20, when the scanning locus on the reference plane 40A by the measurement light S2 irradiated on the reference plane 40A of the calibration reference device 40 deviates from the straight line, the reference is positive or negative with respect to the reference. At the tilt angle of the plane 40A, the shape of the reference plane 40A can be measured by using the diffuse reflection component of the measurement light S2'reflected from the reference plane 40A by the optical comb distance meter 10.

Further, in the correction method of the optical scanner device 20, when the optical scanner device 20 is a one-dimensional scanner, the calibration reference device with respect to the plane formed by the measurement light S2 scanned by the optical scanner device 20. With respect to the state in which the reference plane 40A of 40 is vertical as a reference, the above-mentioned positive and negative with respect to the reference obtained by inclining the reference plane 40A around the axis with respect to the straight line where the plane formed by the measurement light S2 and the reference plane 40A intersect. At the tilt angle of the reference plane 40A, it is possible to take the summed average of the two height distributions obtained by measuring the shape of the reference plane 40A.

Further, in the correction method of the optical scanner device 20, when the optical scanner device 20 is a two-dimensional scanner, the plane formed by the measurement light S2 scanned by the optical scanner device 20 in the X-axis direction is described above. With the reference plane 40A of the calibration reference device 40 as a reference, the reference plane around the axis is a straight line where the plane formed by the measurement light scanned in the X-axis direction S2 and the reference plane 40A intersect. The shape of the reference plane 40A is measured at the tilt angle of the reference plane positive and negative with respect to the reference in which the 40A is tilted, and the plane formed by the measurement light S2 scanned in the Y-axis direction by the optical scanner device 20. On the other hand, with the reference plane 40A of the calibration reference device 40 as a reference, the plane formed by the measurement light S2 scanned in the Y-axis direction and the straight line where the reference plane 40A intersects are taken around the axis. It is possible to take the summed average of the four height distributions obtained by measuring the shape of the reference plane 40A at the tilt angle of the reference plane 40A which is positive or negative with respect to the reference obtained by inclining the reference plane 40A. ..

Further, in the three-dimensional shape measuring device 100, the signal processing device 30 is used to perform correction processing for correcting the distortion of the scan optical system 23 in the optical scanner device 20, but as described above, the correction of the optical scanner device according to the present invention is performed. As a correction processing means for correcting the distortion of the scan optical system 23 that scans the measurement light S2 to irradiate the measurement object 50 based on the correction data acquired by the method, for example, the correction data acquired in advance is used as a storage means. Even if the optical scanner device 20 is provided with a correction data supply means that is stored and supplies correction data to the signal processing device 30 of the optical three-dimensional shape measuring device 100 and the signal processing unit 18 of the optical comb distance meter 10. good.

Here, in the calibration of the optical scanner device 20 in the three-dimensional shape measuring device 100, a probing having a calibration reference plane 40A having a flatness of 0.2 μm in which a titanium nitride film is formed on a precision-polished ceramic plane. A calibration standard 40, which is a planar standard for performance inspection, was used. For example, a spatial measurement error inspection in which a plurality of inspection balls 120 are arranged two-dimensionally on a substrate 110 having a structure as shown in the bird's-eye view of FIG. The vessel 140 can be used.

This space measurement error tester 140 is designed to be used for calibrating the three-dimensional shape measuring device 100 whose measurement range is a three-dimensional space of length (40 mm) × width (40 mm) × height (30 mm). , Vertical (6) x horizontal (6) 36 inspection balls 120 are arranged and fixed at the grid point position. Vertical (60 mm) x horizontal (60 mm) x height (15 mm) substrate 110 is fixed as a ball fixing block. Prepare as.

11A and 11B are views for explaining the structure of the spatial measurement error inspection device 140, where FIG. 11A is a plan view of the substrate 120 and FIG. 11B schematically shows a state in which the spatial measurement error inspection device 140 is disassembled. A side view, (C) is a side view schematically showing a state in which the spatial measurement error inspection device 140 is assembled and attached to the base substrate 150.

As shown in FIG. 11B, the plurality of inspection balls 120 in the spatial measurement error inspection device 140 are each spherically machined to have a predetermined diameter D, and have a screw hole 121 having a depth d shorter than the D diameter. It is made of a stainless steel ball or a carbon steel ball, and has a titanium nitride film formed on its surface.

The substrate 110 is made of a material such as iron or SUS whose coefficient of thermal expansion is within the range specified in the JIS standard.

As shown in the plan views of FIGS. 11A and 11B, the substrate 120 is penetrated by a screw 130 screwed into the screw hole 121 at a grid point position where 36 inspection balls 120 are arranged and fixed. The through hole 111 is formed, and the surface of the through hole 111 in contact with the inspection ball 110 is chamfered.

The plurality of inspection balls 120 are two-dimensionally arranged on the substrate 110, and are fixed by screws 130 from the back side of the substrate 110 in a state of being in contact with the chamfered portion 112 of the substrate 110, respectively.

The plurality of inspection balls 120 are screwed to the substrate 110 in a state where the hemisphere and the chamfered surface are in contact with each other inside the chamfered portion 112 and the positions are stable.

Here, since the inspection ball 120 is pulled from the back side of the substrate 110 toward the center of the chamfered portion 112 by the screw 130, the inspection ball 120 is mounted on the substrate with a constant force using the screw 130 with the spring washer 131. The force that presses against 110 works.

The spatial measurement error inspection device 140 assembled by arranging and fixing the plurality of inspection balls 120 on the substrate 110 in this way has the center coordinates, inter-sphere distance, sphericity, or sphericity of each of the plurality of inspection balls 110. At least one of the diameters is precalibrated and mounted on the base substrate 150 in a calibrated state.

The spatial measurement error inspector 140 can freely adjust its posture while the substrate 110 is supported at three points by the height adjusting screws 160 via mounting holes 115A, 115B, and 115C provided at three locations on the substrate 110. It is attached and screwed to the base substrate 150 via the support frame 170.

Here, in the JIS standard, PD: probing direction, GAS: least squares fitting sphere, PC: point group, CGAS1: least squares fitting sphere center 1, CGAS2: minimum, as a case of measuring by the unidirectional method by point group measurement. The unidirectional measurement of the dimensional inspection standard, which defines the center 2 of the squared fitting ball and has a spherical measuring surface such as a ball plate or ball bar, measures the sphere by a point group and determines the distance between the centers by the least squares fitting. including. For each measurement line to be inspected, the short dimensional inspection standard must be measured 15 times in total by the bidirectional method. It is specified with reference to 3.

However, in the above-mentioned three-dimensional shape measuring device 100, it is not possible to measure a sphere by a point cloud by a bidirectional method, so the method of inspecting the distance measurement error between spheres specified in Annex JD is adopted. ..

That is, the figure JD of Annex JD. In the 1-ball inspection standard, DP: the diameter of the inspection standard and LP: the diameter of the inspection standard are applied to the least squares ball, and the distance error between balls is ES _{. I try} to decide JIS. That is, the center position of each sphere is determined from the least squares sphere, the distance between spheres L _mas is calculated as the distance between the centers of the measured spheres, and the difference between _{the calculated measured value L mes} and the calibration value L _{cal (L mes).} -L _cal ) is the distance error between balls ES _. It shall be _JIS.

In addition, according to the JIS standard, five different inspection lengths are installed at seven different positions (positions and directions) in the measurement space of the coordinate measuring machine, and each length is measured three times, for a total of 105. The text stipulates that multiple measurements must be taken. Then, as the positions of the inspection standard in FIG. 7-the essential four-direction positions (1 to 4) and the directions are the diagonal directions of the space, and the remaining three default positions (6 to 7) are the coordinates. It is positioned along each axis of the system.

Further, according to the JIS standard, the default value of the diameter of the inspection standard sphere must be 10 mm or more and 51 mm or less. If the diameter of the standard sphere for inspection is significantly smaller than the range of the sensor area, the number of measurement points that can be acquired may be insufficient, and the strain of the measured value of the sensor may not be evaluated correctly. If the measurement range on the inspection standard sphere is less than 66% of the range of the sensor area, the probing performance inspection standard plane must be measured. With the agreement of the manufacturer and the user, a sphere having a diameter of more than 51 mm may be used instead of the standard plane for probing performance inspection. It is stipulated in the text that the measurement range on the probing performance inspection standard plane or large diameter inspection standard sphere must be at least 66% of the range of the sensor area.

As described above, the space measurement error tester 140 is used for calibrating the three-dimensional shape measuring device 100 having a three-dimensional space of length (40 mm) × width (40 mm) × height (30 mm) as a measurement range. It was designed, for example, because the length of 66% of the inspection range of 40 mm in the horizontal (X) direction and the vertical (Y) direction is 26.4 mm, as shown in Fig. 7-the position of the inspection standard according to the JIS standard. For 5 different inspections with a maximum length of 26.4 mm or more and 40 mm or less in the horizontal (X) axis direction corresponding to No. 5 and the vertical (Y) axis direction corresponding to No. 6 of the specified required 7 directions. Six test balls 120 are arranged and placed on the substrate 110 so as to give a length.

Further, since the length of 66% of the diagonal inspection range of 64.0 mm is 42.3 mm, the maximum length is set to 42.3 mm or more and 64.0 mm or less, and FIG. 7-for inspection according to JIS standard. Six inspection balls 120 are placed on the substrate 110 so as to provide five different inspection lengths diagonally corresponding to Nos. 1 to 4 of the required 7 directions defined as the position of the standard. It is installed in an array.

The inspection balls 120 may be arranged on a straight line at substantially equal intervals, and even if they are not on a straight line, a plurality of inspection balls 120 are arranged at positions offset in parallel with the straight line to set an inspection length. You can also do it.

Here, this spatial measurement error inspection device 140 has five different inspections in the height (Z) axis direction of No. 7 of the seven essential directions defined as the position of the inspection standard in FIG. 7-JIS standard. Since it is not possible to give a length, a block gauge shall be used.

Then, as described above, in the inspection of the distance measurement error between balls specified in Annex JD adopted in the three-dimensional shape measuring device 100, which cannot measure the sphere by the point group by the bidirectional method, the sphere is used. Distance measurement error ES _{. JIS} evaluation is specified by measuring the inspection standard with a spherical surface at seven positions and postures in the inspection measurement range described in Annex JC in the case of the entire measurement area or non-orthogonal coordinate measuring machine. Figure of Annex JD JD. The placement and orientation of the inspection standard with the spherical surface shown in 2 is recommended. The total number of points for acquiring and evaluating coordinate values on the surface of each sphere of the spherical inspection standard is 25 points or more, but the maximum score is not limited, and the distance between the spheres of the spherical inspection standard to be used. L _{If P} is less than 66% of the maximum measurable length in each side of the measuring instrument to be used, Figure JD Annex JD. As shown in 3, it is said that the inspection standard by the spherical surface is moved without changing the posture, and the measurement is performed in several times within the region of 66% or more of the length of each side. the distance is to be set so as not to exceed the spherical distance L _P of the inspection standards due to the spherical used.

Then, as described above, the spatial measurement error inspection device 140 is used in the diagonal direction corresponding to No. 1 to No. 4 of the seven essential directions defined as the position of the inspection standard in FIG. 7-JIS standard. Six inspection balls 120 are arranged and installed on the substrate 110 so that the maximum length is 42.3 mm or more and 64.0 mm or less and five different inspection lengths are given, and the lateral (X) axis corresponding to No. 5 is provided. Six inspection balls 120 are arranged and installed on the substrate 110 so as to give five different inspection lengths with a maximum length of 26.4 mm or more and 40 mm or less in the direction and the vertical (Y) axis corresponding to No. 6. Therefore, as shown in (A) of FIG. 12, by installing the measurement space parallel to the XY plane, the 5th (horizontal (X) axis) direction and the 6th specified in the text of the JIS standard are provided. Not only can it be used to measure length in the (vertical (Y) axis) direction, but it can also be used in the 2nd (horizontal (Y) axis) and 3rd (depth (Y) axis) directions specified in Annex JD. It can be used to measure the length in.

Further, as shown in FIG. 12B, the spatial measurement error inspector 140 lifts the other corners diagonally around one of the four corners from the state shown in FIG. 12A. This makes it possible to measure the length in the 1st to 4th (diagonal axis) directions of the 7 essential directions specified as the position of the inspection standard in Fig. 7-the JIS standard specified in the main text of the JIS standard. In addition to being able to be used, the figure JD of Annex JD specified in Annex JD. It can be used to measure the length of the space diagonal shown in 2, for example, in the 7th (BH) direction. It should be noted that this measurement may be combined with lifting the side surface and rotating around the Z axis.

Further, as shown in FIG. 12 (C), the spatial measurement error inspector 140 is obtained by lifting the side surface to obtain the figure JD of the annex JD specified in the annex JD. It can be used for measuring the length of the space diagonal shown in 2, for example, the number 4, 5, and 6 in the space diagonal direction.

Here, as shown in FIG. 13, a space measurement error inspector used for calibrating the three-dimensional shape measuring device 100 having a three-dimensional space of length (40 mm) × width (40 mm) × height (30 mm) as a measurement range. As 140, a spatial measurement error inspector 140A equipped with an inspection ball 120A having a diameter D of 1/4 inch made of a stainless steel ball having a titanium nitride film formed on its surface, and a stainless steel having a titanium nitride film formed on its surface. Three types of space measurement error tester 140B, which is equipped with a test ball 120B having a diameter D of 5/32 inches and which is made of spheres, and 140C, which is a space measurement error tester which is equipped with a test ball 120C made of ceramic spheres whose diameter D is 1/4 inch, are created. Then, it was attached to the base substrate 150, and as shown in FIG. 14, the shapes of the inspection balls 120A, 120B, and 120C of the spatial measurement error inspection devices 140A, 140B, and 140C were measured by the optical three-dimensional shape measuring device 100. Since the surface of the inspection ball 120C made of a ceramic sphere provided in the spatial measurement error inspection device 140C is a mirror surface, the light intensity of the return light of the measurement light by the three-dimensional shape measuring device 100 is the central region of the inspection sphere 120C. However, it was extremely low in the peripheral area and was easily affected by noise, making it unsuitable for three-dimensional shape measurement.

On the other hand, in the inspection balls 120A and 120B made of stainless steel balls having a titanium nitride film formed on the surface of the spatial measurement error inspection devices 140A and 140B, the measurement light emitted from the three-dimensional shape measuring device 100 is used. Is moderately diffused on the surface of the inspection sphere, and although the light intensity of the return light decreases in the peripheral region with respect to the central region of the inspection sphere 120C, it is not easily affected by noise, and the three-dimensional shape measurement can be performed properly. ..

In the spatial measurement error inspection device 140, by arranging the inspection balls 120 as closely as possible within the range where the center coordinates of the steel balls can be calculated, the reference coordinate points can be increased and the reliability as the correction data can be improved.

However, if the diameter D of the inspection ball 120 is too small, the number of measurement data on the upper surface of the sphere decreases and the accuracy of spherical fitting deteriorates, which is not preferable. The diameter D of the inspection ball 120 is about 4 mm to 6.5 mm. preferable.

Further, it is desirable that the inspection ball 120 is arranged more finely than the spatial frequency / period of the error to be calibrated.

The diameter D of the inspection ball 120 can be used for most calibrations by selecting a value of 10 mm or less when correcting a coordinate error due to a general optical system (lens, reflector) that scans 40 mm × 40 mm.

The spatial measurement error inspection device 140 may be configured to select and set the inter-ball distance only in the section used in the JIS standard inspection.

Further, when the spatial measurement error inspection device 140A attached to the base substrate 150 was subjected to three-dimensional shape measurement by the optical three-dimensional shape measuring device 100 and the acquired measurement data was analyzed, the following results were obtained. Was done. Each of the plurality of inspection balls 120A in the spatial measurement error inspection device 140A has known center coordinates, inter-sphere distance, and diameter, and for example, a design value, a nominal value, or a calibration value is known.

As shown in FIG. 15, the analysis results of the measurement data will be described below with reference to the numbers (0 to 27) assigned to the 28 inspection balls 120A arranged and fixed on the substrate 110A.

In the analysis of the measurement data, as shown in FIG. 16, one corrected binary data is divided into element data including one sphere, and the inspection sphere is fitted in each element, so that the center of the sphere with the upper left of the element as the origin is used. The relative coordinates of were obtained, and the relative coordinates were converted to absolute coordinates with the upper left of the original data as the origin, and the height dependence of the center coordinates was graphed. Data of approximately 50% to 90% of the diameter of the sphere seen from the top was used for the fit.

FIG. 17 is a diagram showing the locus of the center of the sphere obtained as a result of analysis of the measurement data, and shows the relationship between the coordinates of the center of the sphere and the height. In FIG. 17, since the error is small compared to the dimension of XY, it is inconspicuous, and the center coordinates of each inspection sphere appear to be parallel.

FIG. 18 is a diagram showing the locus of the center of the sphere obtained as a result of analysis of the measurement data. Shows the height dependence of.

FIG. 19 is a diagram showing the locus of the center of the sphere in the X cross section obtained as the analysis result of the measurement data, and the error is emphasized by reducing the XY dimension to 1/20 while keeping the magnitude of the error. It shows the height dependence of the sphere center coordinates. In FIG. 19, the beam ejection range expands downward. There is a difference of 0.2 mm in the X coordinate at the top and bottom.

FIG. 20 is a diagram showing the locus of the center of the sphere in the Y cross section obtained as the analysis result of the measurement data, and the error is emphasized by reducing the XY dimension to 1/20 while keeping the magnitude of the error. It shows the height dependence of the sphere center coordinates. In FIG. 20, the beam emission angle is inclined as a whole, and the beam emission range is narrowed slightly downward. The change in the Y coordinate is about 0.1 mm, but the error in the distance between the spheres seems small.

21 is a diagram showing the distance between balls obtained as a result of analysis of measurement data, (A) shows the distance between balls 0 and 1, and (B) shows the distance between balls 0 and 5. The distance is shown, (C) shows the distance between the balls 0 and 6, (D) shows the distance between the balls 0 and 22, and (E) shows the distance between the balls 0 and 27. Shows. According to the analysis result of the measurement data, the design value of the distance between adjacent spheres is 6.8 ± 0.05 mm, which is in the range of 6.75 to 6.75 mm. As shown in FIG. 26B, the distance between the 0th and 5th balls is 34.0 ± 0.05 mm, which is in the range of 33.95 to 34.055 mm. The error in the distance between balls in the X direction is large between No. 0 and No. 5, and the error in the distance between balls in the Y direction is small between No. 6 and No. 22.

FIG. 22 shows Rmax = 0.6 (range of 60% of the upper surface diameter) and Rmax = 0.7 (range of 70% of the upper surface diameter) of the intersphere distance with reference to No. 0 obtained as the analysis result of the measurement data. ), Rmax = 0.8 (range of 60% of the top surface diameter), Rmax = 0.9 (range of 90% of the top surface diameter), (A) is a diagram showing reproducibility at a height of 97.5 mm. The variation in the distance between balls is shown, (B) shows the variation in the distance between balls at a height of 87.5 mm, and (C) shows the variation in the distance between balls at a height of 77.5 mm.

The variation in the distance between spheres was evaluated by changing the calculation conditions from the same binary data, and the measurement width (maximum-minimum) of 10 times was used as an index. The result of Rmax = 0.9 is relatively stable. The reproducibility of the distance between spheres is about 1 μm near the focal point regardless of the direction.

FIG. 23 shows Rmax = 0.6 (range of 60% of the upper surface diameter) and Rmax = 0.7 (70 of the upper surface diameter) of the center coordinates (radius of the center point inclusion sphere) obtained as the analysis result of the measurement data. % Range), Rmax = 0.8 (60% range of top surface diameter), Rmax = 0.9 (90% range of top surface diameter), and (A) includes the center point. The sphere diameter (97.5 mm) is shown, (B) shows a center point containing sphere (87.5 mm), and (C) shows a center point containing sphere (77.5 mm).

The spatial measurement error tester 140 is known to have at least one of the center coordinates, intersphere distance, sphericity or diameter of each of the plurality of test balls 120, for example, a design value, a nominal value or a calibration value is known. As a result, the spatial measurement error of the optical three-dimensional shape measuring device 100 that measures the three-dimensional shape of an object in a non-contact manner can be detected with high accuracy, and the length measurement error inspection device conforms to JIS B 7440-8. A spatial measurement error inspector for an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner by scanning the measurement light emitted from the optical comb distance meter to the object to be measured. And a method for detecting spatial measurement errors can be provided.

That is, in performing spatial measurement error detection of an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner by scanning the measurement light emitted from the optical comb distance meter to the object to be measured, it is inspected. The optical three-dimensional shape measuring device 100 performs three-dimensional shape measurement using the optical space measurement error inspection device 140 as a measurement object, and each center coordinate, inter-sphere distance, and true sphere of a plurality of inspection spheres 120 obtained as measurement results. The optical three-dimensional shape measuring device to be inspected is the difference between the degree or diameter information and at least one difference between the center coordinates of each of the plurality of inspection spheres 120 calibrated in advance, the distance between spheres, the sphericity or the diameter information. It can be detected as a spatial measurement error of 100.

In addition, when correcting an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner by scanning the measurement light emitted from the optical comb distance meter to the object to be measured, the corrected optical three-dimensional device is used. With the shape measuring device 100, the optical space measurement error inspection device 140 is placed at a plurality of height positions as a measurement object, three-dimensional shape measurement is performed, and a plurality of inspection balls 120 obtained as measurement results at each height position. At least one difference between the information on each center coordinate, the distance between spheres, the sphericity or the diameter and the information on the center coordinates, the distance between spheres, the sphericity or the diameter of each of the plurality of pre-calibrated test balls is described above. Corrected data can be acquired by detecting it as a spatial measurement error of the optical three-dimensional shape measuring device 100 to be corrected.

Further, the optical three-dimensional shape measuring device 100 whose correction data is acquired by the correction method using the optical space measurement error inspection device 140 corrects the distortion of the optical system that scans the measurement light irradiating the measurement object. By providing the processing means, it is possible to remove the influence of the distortion of the scanning optical system that irradiates the measurement object with the measurement light and perform the three-dimensional shape measurement with less error.

Further, the optical space measurement error according to the present invention, which is different from the spatial measurement error inspection device 140 used for acquiring the correction data, using the corrected optical three-dimensional shape measuring device 100 as the optical three-dimensional shape measuring device to be inspected. Three-dimensional shape measurement is performed using an inspection device as a measurement object, and the above-mentioned plurality of inspections calibrated in advance with information on the center coordinates, intersphere distance, sphericity, or diameter of the plurality of inspection balls 120 obtained as measurement results. To calibrate the spatial measurement error of the calibrated optical three-dimensional shape measuring device 100 by detecting at least one difference from the information of each center coordinate, the distance between spheres, the sphericity or the diameter of the sphere 120. Can be done.

10 optical comb distance meter, 11, 12 first and second optical comb light sources, 13 interference optics, 14 reference optical path, 15 measurement optical path, 16 reference optical detector, 17 measurement optical detector, 18 signal processing unit, 20 Optical scanner device, 21 scanning optical system, 22 telecentric condensing optical system, 23, 23A, 23B scanning optical system, 30 signal processing device, 40 calibration reference device, 40A reference plane, 40B virtual plane, 50 measurement object, 60 Platen, 100 Optical three-dimensional shape measuring device, 110, 110A board, 111 through hole, 112 chamfer, 115A, 115B, 115C mounting hole, 120, 120A, 120B, 120C inspection ball, 121 screw hole, 130 screw, 131 Spring washer, 140, 140A, 140B, 140C Optical space measurement error tester, 150 base board, 160 height adjustment screw, 170 support frame

Claims (12)

It is a spatial measurement error inspector of an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner by scanning the measurement light emitted from the optical comb distance meter to the object to be measured.
With multiple test balls,
A substrate in which the above inspection balls are arranged two-dimensionally is provided.
The inspection ball is formed into a true sphere with a predetermined diameter, is composed of a steel ball having a screw hole with a depth shorter than the above diameter, and has a titanium nitride film formed on the surface thereof.
The substrate has two or more through holes through which the screws screwed into the screw holes are penetrated, and the surface in contact with the inspection ball is chamfered at the upper part of the through holes.
The plurality of inspection balls are arranged two-dimensionally and are screwed and fixed from the back side of the substrate in a state where they are in contact with the chamfered portion of the substrate.
A spatial measurement error inspection device for an optical three-dimensional shape measuring device, characterized in that at least one of the center coordinates, the distance between spheres, the sphericity, or the diameter of each of the plurality of inspection spheres is known. The optical three-dimensional shape measuring apparatus according to claim 1, wherein the inspection ball is screwed and fixed in a state of being pressed by a repulsive element against a chamfered portion of the substrate. Spatial measurement error tester. Claim 1 or claim, wherein the plurality of test balls have a predetermined diameter within 3 mm to 6.8 mm and are arranged two-dimensionally at a predetermined pitch within 3 mm to 6.8 mm. 2. The spatial measurement error inspection device of the optical three-dimensional shape measuring device according to 2. The invention according to any one of claims 1 to 3, wherein the plurality of inspection balls are arranged two-dimensionally at the inter-ball distance position selected only for the section used in the JIS standard inspection. Spatial measurement error inspector for optical 3D shape measuring device. The plurality of inspection balls are two-dimensionally located on the surface of the substrate in a two-dimensional direction, each having a maximum length of 26.4 mm or more and 40 mm or less and corresponding to at least one of five different inspection lengths. The spatial measurement error inspector of the optical three-dimensional shape measuring apparatus according to claim 4, wherein they are arranged. The plurality of inspection balls are arranged two-dimensionally in the inter-ball distance position corresponding to at least one of five different inspection lengths having a maximum length of 42.3 mm or more and 64 mm or less in the diagonal direction. The spatial measurement error inspection device of the optical three-dimensional shape measuring apparatus according to claim 4 or 5. The optical three-dimensional shape according to claim 6, wherein the calibration value or the nominal value or the design value of each center coordinate, the distance between the spheres, the sphericity, and the diameter of the plurality of inspection spheres is clarified. Spatial measurement error inspection device for measuring devices. It is a spatial measurement error detection method of an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner by scanning the measurement light emitted from the optical comb distance meter to the object to be measured.
Using the optical three-dimensional shape measuring device to be inspected, three-dimensional shape measurement is performed using the spatial measurement error inspector of the optical three-dimensional shape measuring device according to any one of claims 1 to 7 as a measurement object. , Each center coordinate, intersphere distance, sphericity or diameter information of each of the plurality of inspection spheres obtained as a measurement result and each center coordinate, intersphere distance, sphericity or diameter of the plurality of inspection spheres calibrated in advance. A method for detecting a spatial measurement error of an optical three-dimensional shape measuring device, which comprises detecting at least one difference from the diameter information as a spatial measurement error of the optical three-dimensional shape measuring device to be inspected. It is a correction method of an optical three-dimensional shape measuring device that measures the three-dimensional shape of an object in a non-contact manner by scanning the measurement light emitted from the optical comb rangefinder to the object to be measured.
The optical space measurement error inspector according to any one of claims 1 to 6 is placed at a plurality of height positions as a measurement object by a corrected optical three-dimensional shape measuring device, and three-dimensional shape measurement is performed. And the information on the center coordinates, inter-sphere distance, sphericity or diameter of the plurality of test balls obtained as the measurement result at each height position, and the center coordinates and spheres of the plurality of test balls calibrated in advance. An optical three-dimensional shape characterized by detecting at least one difference from information on distance, sphericity, or diameter as a spatial measurement error of the corrected optical three-dimensional shape measuring device and acquiring correction data. Correction method for measuring devices. Correction means for correcting the spatial distribution of distortion of the optical system that scans the measurement light irradiating the measurement object based on the correction data acquired by the correction method of the optical three-dimensional shape measuring device according to claim 8. An optical three-dimensional shape measuring device characterized by being equipped with. Claims 1 to 6 different from the spatial measurement error inspection device used for acquiring the correction data by using the corrected optical three-dimensional shape measuring device according to claim 9 as the optical three-dimensional shape measuring device to be inspected. Three-dimensional shape measurement is performed using the optical space measurement error tester of the optical three-dimensional shape measuring device according to any one of the above items as a measurement object, and the center coordinates and spheres of the plurality of test balls obtained as the measurement results. At least one difference between the information on the distance, the sphericity or the diameter and the information on the center coordinates, the distance between the spheres, the sphericity or the diameter of the plurality of inspection spheres calibrated in advance is the above-mentioned optical tertiary to be inspected. A spatial measurement error calibration method for an optical three-dimensional shape measuring device, characterized in that it is detected as a spatial measurement error of the original shape measuring device. It is a plane standard for probing performance inspection of an optical 3D shape measuring device that measures the 3D shape of an object in a non-contact manner by scanning the measurement light emitted from the optical comb rangefinder to the object to be measured.
A flat surface standard for probing performance inspection of an optical three-dimensional shape measuring device, characterized in that a titanium nitride film is formed on a precision-polished ceramic flat surface.

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