JP2016090479A - Measurement value correcting method, measurement value correcting program, and measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement value correcting method, a measurement value correcting program, and a measuring device, capable of obtaining highly-accurate measurement results about a measurement value by optimum correction.SOLUTION: A measurement value correcting method comprises the steps of: preparing a plurality of workpieces manufactured from the same design data; obtaining a first reference measurement value by measuring one of the plurality of workpieces as a master workpiece by a first measuring device; obtaining calibration data based on the difference between the first reference measurement value and the design data; obtaining a second reference measurement value by measuring the master workpiece by a second measuring device with high measurement accuracy; obtaining difference data which is the difference between the value obtained by correcting the first reference measurement value and the second reference measurement value using the calibration data; obtaining a target measurement value by measuring workpieces other than a master workpiece among the plurality of workpeices as the workpiece to be measured by the first measuring device; and obtaining a corrected measurement value by subtracting difference data from the value obtained by correcting the target measurement value using the calibration data.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a measurement value correction method, a measurement value correction program, and a measurement apparatus that correct a measurement value acquired by tracing the surface of a workpiece with a stylus.

  As a measuring device for measuring the shape of the surface of a workpiece, a shape measuring machine that traces the surface of the workpiece with a stylus and obtains a measurement value based on the displacement of the stylus is known. For example, in a pivot-type shape measuring machine in which the stylus moves in an arc around a fulcrum, the workpiece and the stylus are moved relative to each other in a predetermined direction with the stylus in contact with the surface of the workpiece, and the moving direction at that time is aligned. The shape (height) of the surface of the workpiece is obtained from the position and the displacement of the stylus.

  Here, in the shape measuring machine using the pivot type stylus, it is necessary to correct the measurement value in consideration of the arc motion of the stylus. For example, Patent Documents 1 to 5 disclose a correction method for a measuring apparatus using a pivot stylus. In any technique, an ideal spherical surface or cylindrical surface is used as a calibration reference.

Japanese Patent No. 2727067 Japanese Patent No. 5183848 Japanese Patent No. 5155533 Japanese Patent No. 3215325 US Pat. No. 5,150,314

  In recent years, in industrial products such as lenses, there is an increasing demand for high accuracy in workpiece contour measurement. For example, when measuring the contour of an aspheric lens, there is a product in which the shape error with respect to the design value is several tens of nm or less, and the sag amount is comparable to the dynamic range of the measuring device. In order to measure the contour of such a workpiece, calibration using a reference sphere with a very high sphericity is required in the measuring apparatus.

  However, in order to withstand product evaluation on the order of several tens of nm, a measuring apparatus having a high accuracy of at least several nm is required. Such a measuring device requires a long measuring time and is very expensive and difficult to obtain. In addition, maintenance is required to maintain high accuracy, and it is not realistic to always use it in a production line.

  An object of the present invention is to provide a measurement value correction method, a measurement value correction program, and a measurement apparatus capable of obtaining a highly accurate measurement result by optimal correction of a measurement value.

  In order to solve the above-described problems, the measurement value correction method of the present invention is a measurement value correction method for correcting a measurement value obtained by tracing the surface of a workpiece with a stylus of a measurement device, and is prepared from the same design data. A step of preparing a plurality of workpieces, a step of measuring one of the plurality of workpieces as a master workpiece by a first measuring device to obtain a first reference measurement value, and a first reference measurement value and design data A step of obtaining calibration data based on the difference, a step of obtaining a second reference measurement value by measuring the master workpiece with a second measurement device having a measurement accuracy higher than that of the first measurement device, and a first step using the calibration data. A step of obtaining difference data, which is a difference between a value obtained by correcting the reference measurement value and the second reference measurement value, and measuring the target workpiece by measuring a plurality of workpieces other than the master workpiece as a workpiece to be measured by the first measuring device. Obtaining a value, characterized by comprising a step of obtaining a corrected measured value by subtracting the differential data from the value obtained by correcting the target measured value, the using the calibration data.

  According to such a configuration, in order to obtain a reference measurement value using one of a plurality of workpieces produced from the same design data as a master workpiece, the shape of the workpiece to be measured produced from the same design data as the master workpiece is obtained. Optimal calibration data can be obtained. Further, the master work is measured by the second measuring apparatus having higher measurement accuracy than the first measuring apparatus, and the difference data from the measurement correction value of the master work by the first measuring apparatus is obtained. It can remove and can measure with the measurement accuracy equivalent to a 2nd measuring apparatus.

  In the measurement value correction method of the present invention, the stylus may be a pivot type that moves in an arc around a fulcrum. According to such a configuration, calibration data suitable for the operation of the pivot stylus can be obtained.

  In the measurement value correction method of the present invention, the surface of the workpiece may be an aspherical surface. According to such a configuration, it is possible to obtain calibration data optimal for measuring an aspheric surface.

  In the measurement value correction method of the present invention, in the step of obtaining the calibration data, the parameter of the model equation for correcting the measurement value by the stylus is fitted from the relationship between the correction value by the model equation of the first reference measurement value and the design data. In the step of obtaining the first parameter and obtaining the corrected measurement value, the target specific value may be corrected using a model formula to which the first parameter is applied.

  According to such a configuration, calibration data can be included in the model equation for correcting the measurement value by the stylus, and a highly accurate corrected measurement value can be obtained by correcting the target measurement value using the model equation. Can do.

  A measurement value correction program according to the present invention is a measurement value correction program for correcting a measurement value obtained by tracing the surface of a workpiece with a stylus of a measuring device, and the computer is configured to include a plurality of workpieces created from the same design data. Means for obtaining a first reference measurement value obtained by measuring with one of the master work as a master work, means for calculating calibration data based on a difference between the first reference measurement value and the design data, Means for obtaining a second reference measurement value obtained by measuring the master work with a second measurement device having higher measurement accuracy than the first measurement device, a value obtained by correcting the first reference measurement value using calibration data, Means for obtaining difference data that is a difference from two reference measurement values, and obtaining target measurement values obtained by measuring with a first measuring device a plurality of workpieces other than the master workpiece as a workpiece to be measured That means, characterized in that to function as a unit, for calculating a corrected measurement value by subtracting the differential data from the corrected value of the target measured value using the calibration data.

  According to such a configuration, in order to obtain a reference measurement value using one of a plurality of workpieces produced from the same design data as a master workpiece, the shape of the workpiece to be measured produced from the same design data as the master workpiece is obtained. Optimal calibration data can be calculated by a computer. Further, the master workpiece is measured by the second measuring device having higher measurement accuracy than the first measuring device, the difference data from the measurement correction value of the master workpiece by the first measuring device is obtained, and the error by the first measuring device is obtained. It can remove and can measure with the measurement accuracy equivalent to a 2nd measuring apparatus.

  In the measurement value correction program of the present invention, the stylus may be a pivot type that performs an arc motion around a fulcrum. According to such a configuration, calibration data suitable for the operation of the pivot stylus can be calculated by the computer.

  In the measurement value correction program of the present invention, the surface of the workpiece may be an aspherical surface. According to such a configuration, calibration data that is optimal for aspheric measurement can be calculated by a computer.

  In the measurement value correction program of the present invention, the means for obtaining the calibration data fits the parameter of the model equation for correcting the measurement value by the stylus from the relationship between the correction value of the first reference measurement value by the model equation and the design data. Then, the means for obtaining the first parameter and obtaining the corrected measurement value may correct the target correction value using a model formula to which the first parameter is applied.

  According to such a configuration, the calibration data can be included in the model equation for correcting the measurement value by the stylus, and the corrected measurement value with high accuracy can be obtained by the computer by correcting the target measurement value using the model equation. Can be obtained.

  The measurement apparatus of the present invention includes a measurement unit that traces the surface of a workpiece with a stylus to obtain a measurement value, a calibration data acquisition unit that acquires calibration data, and a measurement value obtained by the measurement unit is corrected with the calibration data. A calibration data acquisition unit for acquiring a first reference measurement value measured by the first measurement device using one of a plurality of workpieces produced from the same design data as a master workpiece. A first reference value acquisition unit, a second reference value acquisition unit that acquires a second reference measurement value obtained by measuring a master work with a second measurement device having higher measurement accuracy than the first measurement device, and a first reference measurement value and design A first calculation unit that calculates calibration data based on a difference from the data; and difference data that is a difference between a value obtained by correcting the first reference measurement value using the calibration data and the second reference measurement value. A second computing unit for computing, The correction unit corrects the target measurement value measured by the first measuring apparatus using the calibration data as a measurement target workpiece other than the master workpiece among the plurality of workpieces, and subtracts the difference data from the corrected value. To obtain a corrected measurement value.

  According to such a configuration, in order to obtain a reference measurement value using one of a plurality of workpieces produced from the same design data as a master workpiece, the shape of the workpiece to be measured produced from the same design data as the master workpiece is obtained. Optimal calibration data can be obtained. Further, the master work is measured by the second measuring apparatus having higher measurement accuracy than the first measuring apparatus, and the difference data from the measurement correction value of the master work by the first measuring apparatus is obtained. It can remove and can measure with the measurement accuracy equivalent to a 2nd measuring apparatus.

  In the measurement apparatus of the present invention, the stylus may be a pivot type that moves in an arc around a fulcrum. According to such a configuration, calibration data suitable for the operation of the pivot stylus can be obtained.

  In the measuring apparatus of the present invention, the surface of the workpiece may be an aspherical surface. According to such a configuration, it is possible to obtain calibration data optimal for measuring an aspheric surface.

  In the measurement apparatus of the present invention, the first calculation unit fits the parameter of the model formula for correcting the measurement value by the stylus based on the relationship between the correction value by the model formula of the first reference measurement value and the design data, and the first parameter The correction unit may correct the target measurement value using a model formula to which the first parameter is applied.

  According to such a configuration, calibration data can be included in the model equation for correcting the measurement value by the stylus, and a highly accurate corrected measurement value can be obtained by correcting the target measurement value using the model equation. Can do.

(A) And (b) is a schematic diagram which illustrates the structure of the measuring apparatus which concerns on this embodiment. It is a functional block diagram of the measuring apparatus which concerns on this embodiment. (A) And (b) is a figure explaining the measured value correction method which concerns on this embodiment. It is the figure which represented the pick-up mechanism of the pivot type stylus geometrically. It is a flowchart which illustrates the main routine of a measured value correction program. It is a flowchart which illustrates the subroutine of a measured value correction program. (A)-(f) is a figure which shows the sensitivity curve of the parameter with respect to a detection position.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same members are denoted by the same reference numerals, and the description of the members once described is omitted as appropriate.

〔measuring device〕
FIG. 1A and FIG. 1B are schematic views illustrating the configuration of a measurement apparatus according to this embodiment. FIG. 1A shows a configuration diagram of the measuring apparatus 1, and FIG. 1B shows a block diagram of the computer 30.

  As shown in FIG. 1A, the measuring apparatus 1 according to this embodiment measures the position (height) of the surface of the workpiece W by tracing the surface of the workpiece W, which is a measurement target, with the stylus 10. It is a device to do. The measurement apparatus 1 includes a stylus 10, a detection unit 20, and a computer 30. The workpiece W is arranged on the stage ST. The workpiece W and the stylus 10 are provided so as to be relatively movable in one direction. By this relative movement, the stylus 10 traces the surface of the workpiece W. In the present embodiment, the relative movement direction of the workpiece W and the stylus 10 is the X-axis direction. A direction orthogonal to the X axis (a direction orthogonal to the reference surface of the stage ST) is defined as a Z axis direction. In the measuring apparatus 1, the workpiece W is fixed to the stage ST, and the stylus 10 moves in the X-axis direction.

  The stylus 10 is a pivot type that moves in an arc around a predetermined fulcrum 10a. The arc motion of the stylus 10 is performed along the XZ plane. The detection unit 20 detects a motor 21 serving as a drive source for moving the stylus 10 in the X-axis direction, an X-axis detection unit 22 that detects a position of the stylus 10 in the X-axis direction, and a position of the stylus 10 in the Z-axis direction. And a Z-axis detection unit 23 for

  The motor 21 applies a driving force to a driving mechanism (not shown) in accordance with an instruction from the computer 30 to move the stylus 10 in the X-axis direction. The X-axis detection unit 22 detects the position along the X-axis of the stylus 10 that moves in the X-axis direction during measurement and sends the detected position to the computer 30. A probe 11 is provided at the tip of the stylus 10. By moving the stylus 10 in the X-axis direction, the probe 11 advances while contacting the surface of the workpiece W.

  The Z-axis detector 23 detects the position along the Z-axis of the stylus 10 that moves in an arc following the surface shape of the workpiece W during measurement, and sends it to the computer 30. With such a configuration, in the measuring apparatus 1, the height (position in the Z-axis direction) along the trace line of the probe 11 that contacts the surface of the workpiece W corresponds to the position along the X-axis of the stylus 10. Can be obtained. Thereby, the surface shape of the workpiece | work W along a trace line is obtained. Further, for example, by performing the same measurement by moving the stage ST in the Y-axis direction (direction orthogonal to the X-axis direction and the Z-axis direction), the three-dimensional shape of the surface of the workpiece W can be obtained.

  As illustrated in FIG. 1B, the computer 30 includes a CPU (Central Processing Unit) 31, interfaces 32 a to 32 c, an output unit 33, an input unit 34, a main storage unit 35, and a sub storage unit 36.

  The CPU 31 controls each unit by executing various programs. The interfaces 32 a to 32 c are parts that perform information input / output with the detection unit 20. In the present embodiment, detection information from the Z-axis detection unit 23 of the detection unit 20 is taken in via the interface 32a. In addition, an instruction is given to the motor 21 of the detection unit 20 via the interface 32b. Further, the detection information from the X-axis detection unit 22 of the detection unit 20 is taken in via the interface 32c. Note that the computer 30 may be connected to a local area network (LAN) or a wide area network (WAN) via an interface (not shown).

  The output unit 33 is a part that outputs a result processed by the computer 30. As the output unit 33, for example, a display or a printer (not shown) is used. The input unit 34 is a part that receives information from an operator. For the input unit 34, for example, a keyboard, a joystick, and a mouse (not shown) are used. Further, the input unit 34 includes a function of reading information recorded on the recording medium MM.

  For example, a RAM (Random Access Memory) is used for the main storage unit 35. As a part of the main storage unit 35, a part of the sub storage unit 36 may be used. For example, a hard disk drive (HDD) or a solid state drive (SSD) is used for the secondary storage unit 36. The secondary storage unit 36 may be an external storage device connected via a network.

FIG. 2 is a functional block diagram of the measuring apparatus according to the present embodiment.
The functional block of the measuring apparatus 1 includes a measurement unit 110, a calibration data acquisition unit 120, a correction unit 130, an output unit 140, and a control unit 150. Among these, the measurement unit 110 includes a motor control unit 111 and a detection control unit 112. The calibration data acquisition unit 120 includes a first reference value acquisition unit 1211, a second reference value acquisition unit 1212, a first calculation unit 1221, and a second calculation unit 1222.

  The motor control unit 111 of the measurement unit 110 gives an instruction for controlling the rotation of the motor 21. The detection control unit 112 controls the X-axis detection unit 22 and the Z-axis detection unit 23 to acquire the X-axis coordinate value and the Z-axis coordinate value (measurement value) sent from them.

  The calibration data acquisition unit 120 is a part that acquires calibration data for correcting the measurement value acquired by the measurement unit 110. The first reference value acquisition unit 1211 of the calibration data acquisition unit 120 uses the one of a plurality of workpieces W made from the same design data as a master workpiece, and measures the surface of this master workpiece with the stylus 10. Get a reference measurement. The second reference value acquisition unit 1212 of the calibration data acquisition unit 120 acquires a second reference measurement value obtained by measuring the surface of the same master work as described above using another measurement device. Here, as another measuring device, one that has higher measurement accuracy than the measuring device 1 according to the present embodiment and has been calibrated is used.

  The first calculation unit 1221 of the calibration data acquisition unit 120 calculates the calibration data based on the difference between the first reference measurement value acquired by the first reference value acquisition unit 1211 and the design data. The second calculation unit 1222 is a difference between the value obtained by correcting the first reference measurement value using the calibration data calculated by the first calculation unit 1221 and the second reference measurement value acquired by the second reference value acquisition unit 1212. Calculate some difference data.

  The correction unit 130 corrects the measurement value acquired by the measurement unit 110 with the calibration data obtained by the calculation by the first calculation unit 1221, and subtracts the difference data calculated by the second calculation unit 1222 from the corrected value. This is the part that calculates the corrected measurement value.

  The output unit 140 is a part that outputs measurement results. The control unit 150 is a part that controls the measurement unit 110, the calibration data acquisition unit 120, the correction unit 130, and the output unit 140.

  In the measuring apparatus 1 having such a functional block, the measurement value on the surface of the workpiece W can be corrected with the calibration data, and a measurement result in which an error is suppressed can be obtained. In particular, in order to obtain a reference measurement value using one of a plurality of workpieces W made from the same design data as a master workpiece, the calibration is optimum for the shape of another workpiece W made from the same design data as the master workpiece. Data can be obtained. Furthermore, in order to measure the master work by another measuring apparatus having higher measurement accuracy than the measuring apparatus 1 according to the present embodiment and obtain difference data from the measurement correction of the master work by the measuring apparatus 1, an error caused by the measuring apparatus 1 Thus, measurement can be performed with a measurement accuracy equivalent to that of another high-precision measurement device.

[Measurement value correction method]
Next, a measurement value correction method including acquisition of calibration data will be described.
Here, a method for correcting a measurement value using the measurement apparatus 1 will be described as an example.
First, as shown in FIG. 3A, a plurality of works W1, W2, W3,..., Wn prepared from the same design data DT are prepared. Next, one of the produced workpieces W1, W2, W3,..., Wn is set as a master workpiece. Here, as an example, the work W1 is a master work. Then, the surface of the master work is measured by the measuring unit 110 of the measuring apparatus 1 to obtain a first reference measurement value. The first reference measurement value is acquired by the first reference value acquisition unit 1211.

  Next, calibration data is acquired based on the difference between the first reference measurement value and the design data DT. The calibration data is calculated by the first calculation unit 1221 of the calibration data acquisition unit 120. FIG. 3B is a diagram illustrating the difference between the design data DT and the measured value MD of the master work. The horizontal axis in FIG. 3B is the coordinate in the X-axis direction, and the vertical axis is the coordinate in the Z-axis direction. The measurement value MD of the master work is acquired as a Z-axis coordinate corresponding to each of a plurality of X-axis coordinates. The first calculation unit 1221 obtains the difference between the Z-axis coordinate value of each measurement value MD and the Z-axis coordinate of the design data DT corresponding to the measurement value MD, and calculates the parameter of the model function by, for example, the least square method. To do. The parameter of this model function becomes calibration data.

  Next, the surface of the same master work as before is measured by another measuring device having higher measurement accuracy than the measuring device 1 to obtain a second reference measurement value. The second reference measurement value is acquired by the second reference value acquisition unit 1212. In addition, what is necessary is just to perform the measurement of the masterwork by another measuring apparatus once.

  Next, difference data which is a difference between a value obtained by correcting the first reference measurement value using the calibration data and the second reference measurement value is obtained. The difference data is calculated by the second calculation unit 1222 of the calibration data acquisition unit 120. The difference data includes a measurement error between the measurement apparatus 1 and another measurement apparatus with higher measurement accuracy.

  Next, the measurement unit 110 uses the workpieces W2, W3,..., Wn other than the master workpiece among the plurality of workpieces W1, W2, W3,. Target measurement value).

  Next, the correction unit 130 corrects the target measurement value using the calibration data. That is, the corrected measurement value is obtained by a model function to which the parameter obtained previously from the coordinate value in the Z-axis direction of the target measurement value is applied. Further, the corrected measurement value is obtained by subtracting the difference data from the corrected measurement value. This corrected measurement value becomes the measurement result of the measurement apparatus 1. In such a measurement value correction method, since the correction is obtained by correcting the calibration data obtained from the master work produced from the same design data DT, the accuracy is determined by the calibration data optimum for the shape of the work to be measured. A high measurement result. Furthermore, if the target measurement value is corrected using the calibration data and then corrected using the difference data, even the measurement value obtained by the measurement device 1 has the same accuracy as that measured by another measurement device with high measurement accuracy. The measurement result which has can be obtained.

  Here, when the design data DT of the workpiece W is, for example, a spherical surface, one of the plurality of workpieces W1, W2, W3,..., Wn produced from the design data DT is used as a master workpiece and calibration data and And the measurement value of the workpiece to be measured other than the master workpiece produced from the same design data DT is corrected with the calibration data. Since the workpiece to be measured and the master workpiece are created from the same design data DT, the calibration data obtained from the master workpiece is the optimum calibration data for the workpiece to be measured created from the same design data DT. .

Furthermore, in order to obtain the second reference measurement value by another measurement device having higher measurement accuracy than the measurement device 1 and obtain difference data from the corrected measurement value of the measurement device 1, the error due to the measurement device 1 can be removed. Thus, even the measurement apparatus 1 can perform measurement with the same measurement accuracy as another measurement apparatus.

  This embodiment is particularly effective when the design data DT is an aspheric surface. That is, when the design data DT is an aspherical surface, in order to acquire calibration data and difference data, generally a highly accurate spherical master work is used. However, it is difficult to prepare a highly accurate spherical master work. In this respect, in the present embodiment, one of a plurality of workpieces W1, W2, W3,..., Wn produced from the same aspherical design data DT is used as a master workpiece. There is no need to prepare. Further, since one of a plurality of workpieces W1, W2, W3,..., Wn produced from the same aspherical design data DT is used as a master workpiece, calibration data and difference data are acquired. A highly accurate measurement result can be obtained by correction using calibration data and difference data.

  When a master workpiece is selected from a plurality of workpieces W1, W2, W3,..., Wn produced from the same aspherical design data DT, the design data is the largest of the plurality of workpieces W1, W2, W3,. It is desirable to use a master work with a small error from DT. This makes it possible to perform correction with higher accuracy.

(Pivot stylus)
Here, acquisition of specific calibration data in the measuring apparatus 1 using the pivot type stylus 10 will be described.
FIG. 4 is a view geometrically showing a pickup mechanism of a pivot type stylus.
In the pickup mechanism using the pivot type stylus 10, it is necessary to calibrate the measurement value in consideration of the arc motion of the stylus 10.

Assuming that the coordinates in the X-axis direction and the coordinates in the Z-axis direction of the measurement data obtained by using the pickup mechanism of the pivot stylus 10 are (x _m , z _m ), the correct measurement position (x _r , z _r ) is These are obtained by Equation 1 and Equation 2.

  In Equations 1 and 2, g is a gain coefficient, l is a length from the fulcrum 10a of the stylus 10 to the tip of the arm (arm length), and h is a length from the arm tip of the stylus 10 to the probe 11 (edge length). (See FIG. 4).

  In this specific example, Equation 1 and Equation 2 are used as model equations, the gain coefficient g, the arm length l, and the edge length h are used as parameters, and the parameters are determined from the relationship between the correction value based on the model equation of the reference measurement value and the design data DT. Perform fitting.

That is, first, to measure the surface of the master work by the stylus 10 of the pivot to obtain reference measured value _{^{(x k m, z k m}} ). Here, k = 1, 2,..., N. Next, reference measurement value _{^{(x k m, z k m}} ), corrected by the number 1 and number 2. Then, the correction value obtained by the correction and the design data DT are aligned in the X-axis direction (best fit), and the shortest distance after the best fit (or the difference in coordinate values in the Z-axis direction) is used as an evaluation amount. Each parameter (gain coefficient g, arm length l, and edge length h) is estimated so that the sum of squares of the verification error is minimized.

  If the measurement values of the workpiece to be measured are corrected using the equations 1 and 2 in which each parameter is estimated, a corrected measurement value reflecting the calibration data obtained by the measurement of the master workpiece can be obtained. As described above, the calibration data can be included in the model formula by fitting each parameter of the model formula based on the arc motion of the pivot type stylus 10. Therefore, if the measured value of the workpiece to be measured created with the same design data DT as the master workpiece used for acquiring the calibration data is corrected with the model formula, it is possible to perform correction with the optimal calibration data.

  Although not described above, correction including the shape of the tip of the probe 11 provided at the tip of the stylus 10 may be performed. For the correction related to the tip shape of the probe 11, for example, a technique described in Japanese Patent No. 4372759 may be applied.

[Measurement value correction program]
Next, the measurement value correction program will be described.
The measurement value correction method described above may be realized by a measurement value correction program executed by the CPU 31 of the computer 30.
5 and 6 are flowcharts illustrating the measurement value correction program.
First, as shown in step S101 of FIG. 5, the first reference measurement value is acquired. That is, the computer 30 uses one of a plurality of workpieces W1, W2, W3,..., Wn produced from the same design data DT as a master workpiece, and measures the master workpiece measured by the stylus 10 (first reference). (Measurement value) is acquired.

  Next, as shown in step S102, calibration data is calculated. The computer 30 executes a process of calculating calibration data based on the difference between the first reference measurement value acquired previously and the design data DT of the master work. This process is performed by a subroutine shown in FIG.

  First, as shown in step S201 in FIG. 6, processing for setting an initial value of the first parameter is performed. For example, when Equation 1 and Equation 2 are used as model equations and the gain coefficient g, arm length l, and edge length h are parameters, the geometrical values according to the design values of the stylus 10 for these parameters (first parameters) are used. Set the correct value as the initial value.

  Next, as shown in step S202, the first reference measurement value is corrected. That is, the master workpiece measurement value (first reference measurement value) acquired in step S101 is corrected by the above formulas 1 and 2 to calculate a correction value.

  Next, as shown in step S203, the correction value and the design data DT are aligned. In this alignment, the X-axis alignment (best fit) between the correction value of the first reference measurement value by the master work and the design data DT is performed. For example, the coordinate value in the X-axis direction of the first reference measurement value needs to be corrected according to the shape of the measuring element 11 by the shape (such as a sphere) of the measuring element 11 of the stylus 10. This correction is alignment (best fit).

  Next, as shown in step S204, error matching is performed. The error collation is a process for obtaining a shortest distance (or a difference in coordinate values in the Z-axis direction) between the correction value after the best fit and the design data DT as a collation error.

  Next, as shown in step S205, the first parameter is updated. Here, a process of changing the parameter (first parameter) of the model formula is performed so that the collation error obtained in the previous step S204 is reduced. For example, in the above formulas 1 and 2, the gain coefficient g, the arm length l, and the edge length h are adjusted in the model formula.

  Next, as shown in step S206, it is determined whether or not the collation error is minimum. That is, after adjusting the first parameter in step S205, the collation error is obtained again. If the collation error is not the minimum, the processing from step S202 to step S205 is repeated. The determination as to whether or not the collation error is minimum may be made based on, for example, whether or not the collation error is within a preset range. When the collation error is minimized, the first parameter is determined as shown in step S207.

  Next, the process returns to step S103 in FIG. In step S103, the second reference measurement value is acquired. Here, the same master work as before is measured by another measuring device having higher measurement accuracy than the measuring device 1 to obtain the second reference measured value. In addition, when the measurement of the master work has already been performed and the measurement result is stored in the memory, or when the measurement of the master work is performed by another measuring device and the measurement result is stored in the memory. The measurement result stored in the memory may be read out as the second reference measurement value.

  Next, as shown in step S104, the difference data is calculated. The computer 30 executes a process of calculating difference data that is a difference between the value obtained by correcting the first reference measurement value using the calibration data obtained in step S102 and the second reference measurement value obtained in step S103. .

  Next, as shown in step S105, the target measurement value is acquired. That is, an object obtained by measuring the surface of the workpiece to be measured by the stylus 10 of the measuring apparatus 1 except for the master workpiece among the plurality of workpieces W1, W2, W3,..., Wn produced from the same design data DT. Execute the process to obtain the measured value.

  Next, as shown in step S106, the target measurement value is corrected. Here, the target measurement value is corrected by the model equation to which the calibration data (first parameter) calculated in step S102 is applied, and the corrected measurement value is obtained by subtracting the difference data obtained in step S104 from the corrected value. Calculate.

  According to such a measured value correction program, calibration data is acquired using one of a plurality of workpieces W1, W2, W3,..., Wn produced from the same design data DT as a master workpiece, and this calibration Data can be reflected in the model formula. Thereby, it becomes possible for the computer 30 to calculate the measurement result by the correction most suitable for the shape of the workpiece to be measured created from the same design data DT as the master workpiece.

  Furthermore, since the difference data is subtracted from the value corrected with the calibration data to obtain a corrected measurement value, the error component of the measurement device 1 with respect to another measurement device with high measurement accuracy can be removed. However, it becomes possible to perform highly accurate measurement.

  In the fitting of the parameter (first parameter) in the measurement value correction program, a parameter having low sensitivity to positional accuracy among a plurality of parameters may be excluded from the fitting target.

FIGS. 7A to 7F are diagrams showing parameter sensitivity curves with respect to detection positions. FIGS. 7A, 7C, and 7E are parameter sensitivity curves with respect to detection positions in the X-axis direction, and FIG. , (D), and (f) are sensitivity curves of parameters with respect to detection positions in the Z-axis direction.
FIG. 7A shows the coordinate change (differential value) of the gain coefficient g in the X-axis direction, and FIG. 7B shows the coordinate change (differential value) of the gain coefficient g in the Z-axis direction. FIG. 7C shows the coordinate change (differential value) of the arm length l in the X-axis direction, and FIG. 7D shows the coordinate change (differential value) of the arm length l in the Z-axis direction. FIG. 7E shows coordinate changes (differential values) in the X-axis direction of the edge length h, and FIG. 7F shows coordinate changes (differential values) in the Z-axis direction of the edge length h.

  Referring to the sensitivity curves of the parameters shown in FIGS. 7A to 7F, it can be seen that the sensitivity of the arm length l is the lowest among the gain coefficient g, the arm length l, and the edge length h. Therefore, even if the arm length l is excluded when fitting the parameters, the influence is small. Thus, by excluding (fixing) low-sensitivity parameters from the fitting target, the convergence time required for parameter optimization processing can be shortened.

  Note that the measurement value correction program described above may be recorded on a computer-readable recording medium MM or distributed via a network.

  As described above, according to the measurement value correction method, the measurement value correction program, and the measurement apparatus 1 according to the embodiment, it is possible to obtain a highly accurate measurement result by optimal correction of the measurement value.

  In addition, although this embodiment and its specific example were demonstrated above, this invention is not limited to these examples. For example, in the present embodiment, the measuring device 1 and the measuring method using the pivot type stylus 10 are taken as an example, but the measuring device 1 and the measuring method using the stylus 10 other than the pivot type are also applicable. What is necessary is just to use what was matched with the mechanism of the stylus 10 as a model formula of correction | amendment. In addition, the above-described embodiments or specific examples thereof, and those in which those skilled in the art appropriately added, deleted, and changed the design of the above-described embodiments, and combinations of the features of each embodiment as appropriate are also included in the gist of the present invention. As long as it is provided, it is included in the scope of the present invention.

  As described above, the present invention can be suitably used for a shape measuring device that measures the surface shape of the workpiece W, a height measuring device that measures the surface height, a surface roughness measuring device, and the like.

DESCRIPTION OF SYMBOLS 1 ... Measuring apparatus 10 ... Stylus 10a ... Supporting point 11 ... Measuring element 20 ... Detection part 21 ... Motor 22 ... X-axis detection part 23 ... Z-axis detection part 30 ... Computer 31 ... CPU
32a, 32b, 32c ... interface 33 ... output unit 34 ... input unit 35 ... main storage unit 36 ... sub storage unit 110 ... measurement unit 111 ... motor control unit 112 ... detection control unit 120 ... calibration data acquisition unit 130 ... correction unit 140 ... output unit 150 ... control unit 1211 ... first reference value acquisition unit 1212 ... second reference value acquisition unit 1221 ... first calculation unit 1222 ... second calculation unit DT ... design data MD ... measured value MM ... recording medium ST ... Stage W ... Work

Claims (12)

A measurement value correction method for correcting a measurement value obtained by tracing the surface of a workpiece with a stylus of a measurement device,
Preparing multiple workpieces made from the same design data;
Measuring one of the plurality of workpieces as a master workpiece with a first measuring device to obtain a first reference measurement value;
Obtaining calibration data based on a difference between the first reference measurement value and the design data;
Measuring the master work with a second measuring device having higher measurement accuracy than the first measuring device to obtain a second reference measurement value;
Obtaining difference data that is a difference between a value obtained by correcting the first reference measurement value using the calibration data and the second reference measurement value;
Measuring the first measurement device as a measurement target workpiece other than the master workpiece among the plurality of workpieces to obtain a target measurement value;
Subtracting the difference data from a value obtained by correcting the target measurement value using the calibration data to obtain a corrected measurement value;
A measurement value correction method characterized by comprising:   The measurement value correcting method according to claim 1, wherein the stylus is a pivot type that moves in an arc around a fulcrum.   The measurement value correction method according to claim 1, wherein the surface of the workpiece is an aspherical surface. In the step of obtaining the calibration data, a parameter of a model formula for correcting the measurement value by the stylus is fitted from the relationship between the correction value of the first reference measurement value by the model formula and the design data, and the first parameter is obtained. Seeking
The measurement value according to claim 1, wherein in the step of obtaining the corrected measurement value, the target measurement value is corrected using the model formula to which the first parameter is applied. Correction method. A measurement value correction program for correcting a measurement value obtained by tracing the surface of a workpiece with a stylus of a measurement device,
Computer
Means for obtaining a first reference measurement value obtained by measuring one of a plurality of workpieces produced from the same design data as a master workpiece by a first measuring device;
Means for calculating calibration data based on a difference between the first reference measurement value and the design data;
Means for obtaining a second reference measurement value obtained by measuring the master work with a second measurement device having higher measurement accuracy than the first measurement device;
Means for obtaining difference data which is a difference between a value obtained by correcting the first reference measurement value using the calibration data and the second reference measurement value;
Means for acquiring an object measurement value obtained by measuring by the first measuring device as a measurement object work other than the master work among the plurality of works;
Means for calculating a corrected measurement value by subtracting the difference data from a value obtained by correcting the target measurement value using the calibration data;
A measured value correction program characterized in that it functions as   6. The measured value correction program according to claim 5, wherein the stylus is a pivot type that moves in a circular arc around a fulcrum.   The measured value correction program according to claim 5 or 6, wherein the surface of the work is an aspherical surface. In the means for obtaining the calibration data, the parameter of the model formula for correcting the measurement value by the stylus is fitted from the relationship between the correction value of the first reference measurement value by the model formula and the design data, and the first parameter is obtained. Seeking
The measurement value according to claim 5, wherein the means for obtaining the corrected measurement value corrects the target measurement value using the model formula to which the first parameter is applied. Correction program. A measurement unit that traces the surface of the workpiece with a stylus to obtain measurement values;
A calibration data acquisition unit for acquiring calibration data;
A correction unit for correcting the measurement value obtained by the measurement unit with the calibration data;
With
The calibration data acquisition unit includes:
A first reference value acquisition unit that acquires a first reference measurement value measured by the first measurement device using one of a plurality of workpieces produced from the same design data as a master workpiece;
A second reference value acquisition unit for acquiring a second reference measurement value obtained by measuring the master work with a second measurement device having higher measurement accuracy than the first measurement device;
A first calculation unit for calculating calibration data based on a difference between the first reference measurement value and the design data;
A second calculation unit that calculates difference data that is a difference between a value obtained by correcting the first reference measurement value using the calibration data and the second reference measurement value;
The correction unit is
A target measurement value measured by the first measuring device as a measurement target workpiece other than the master workpiece among the plurality of workpieces is corrected using the calibration data, and corrected by subtracting the difference data from the corrected value. A measuring device characterized by obtaining a measured value.   The measuring apparatus according to claim 9, wherein the stylus is a pivot type that moves in a circular arc around a fulcrum.   The measuring apparatus according to claim 9, wherein a surface of the workpiece is an aspherical surface. The first calculation unit obtains a first parameter by fitting a parameter of a model formula for correcting the measurement value by the stylus from a relationship between the correction value of the first reference measurement value by the model formula and the design data. ,
The measurement apparatus according to claim 9, wherein the correction unit corrects the target measurement value using the model formula to which the first parameter is applied.

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