Evaluation program and probe type surface property measuring machine

Abstract

To provide an evaluation program enabled to evaluate probe tip radius correction and a contour curve filter of a probe type surface property measuring machine more easily.SOLUTION: The present invention relates to an evaluation program for evaluating probe tip radius correction or a contour curve filter applied to measured cross-sectional curve data acquired by a probe type surface property measuring machine. The evaluation program causes a computer to execute: a contour curve generation step (S30) of generating a sinusoidal contour curve having a wavelength varying from a predetermined initial wavelength to a predetermined final wavelength; an evaluation curve generation step (S34) of applying at least one of the probe tip radius correction and contour curve filter to the contour curve to generate an evaluation curved; and a display step (S36) of displaying the evaluation curved on a screen.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to an evaluation program for evaluating a stylus tip radius correction calculation that removes or reduces the influence of the stylus tip radius on measured profile curve data acquired by a stylus surface texture measuring instrument, or a profile curve filter that extracts a roughness curve or a waviness curve, and to a stylus surface texture measuring instrument equipped with such an evaluation program. [Background technology]

[0002] The tip of a stylus used in a stylus-type surface texture measuring instrument typically has a radius of curvature of several microns. The ISO / JIS standard requires a stylus tip made of single-crystal diamond, conical, with a radius of 2 μm and an apex angle of 60°. Therefore, the measured profile data obtained when tracing a measurement surface with such a stylus is the locus of the center of a circle with a radius of 2 μm as it moves across the measurement surface while in contact with the surface, as shown in Figure 1. This locus will differ slightly from the actual shape of the measurement surface. ISO 21920-2:2021 adds a specification to compensate for the effect of the stylus tip radius on the measured profile data measured with a stylus having such a finite tip curvature radius. It is recommended that stylus-type surface texture measuring instruments be equipped with such stylus tip radius compensation.

[0003] Furthermore, when determining surface texture parameters such as the surface roughness and waviness of a measured surface based on the measured profile curve data, the measured profile curve data is filtered. As shown in Figure 2, for example, when determining surface roughness, wavelength components shorter than the roughness component, i.e., high-frequency components, are removed from the measured profile curve data using a low-pass filter with a cutoff value λs, and wavelength components longer than the roughness component, i.e., low-frequency components, are removed using a high-pass filter with a cutoff value λc, to obtain a roughness curve. When determining waviness, a low-pass filter with a cutoff value λc and a high-pass filter with a larger cutoff value λf are applied to obtain a waviness curve. Surface roughness and waviness, which are surface texture parameters, are calculated from these roughness and waviness curves.

[0004] As shown in Figure 3, the ISO / JIS standard specifies the above-mentioned stylus tip radius r tip , standard values for the cutoff values λs, λc, and the maximum sampling interval of the measurement data are predefined.

[0005] Stylus-type surface texture measuring instruments are typically equipped with the above-mentioned stylus tip radius correction and profile filter, but if these stylus radius correction and profile filter settings are not properly configured, appropriate measurement results cannot be obtained. Patent Document 1 discloses a surface roughness standard having a single blank with sinusoidal grooves of multiple different wavelengths or sinusoidal grooves in which the wavelength changes so that it exponentially decreases. By measuring this surface roughness standard with a stylus-type surface texture measuring instrument and filtering the acquired measured profile curve data to confirm that the amplitude transmission rate at the cutoff value λc set in the filter is 50%, it is possible to confirm that the filter settings are correct. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-158368 Summary of the Invention [Problem to be solved by the invention]

[0007] The measured profile data obtained by measuring a surface roughness standard with a stylus surface texture measuring instrument contains shape errors of the surface roughness standard and measurement errors of the stylus surface texture measuring instrument. Therefore, when using the measured profile data to evaluate the stylus tip radius correction or profile curve filter implemented in the stylus surface texture measuring instrument, the effects of shape errors and measurement errors may prevent accurate evaluation of the stylus tip radius correction or filter. Furthermore, if you want to evaluate over a wider wavelength range than the wavelength band of the sinusoidal grooves formed on the surface roughness standard, you will need to prepare a new standard.

[0008] Therefore, an object of the present invention is to provide an evaluation program that makes it easier to correct the stylus tip radius and evaluate the profile curve filter of a stylus surface texture measuring instrument, and a stylus surface texture measuring instrument in which such an evaluation program is implemented. [Means for solving the problem]

[0009] That is, the present invention provides: An evaluation program for evaluating a stylus tip radius correction or a profile curve filter applied to measured profile curve data acquired by a stylus-type surface texture measuring instrument, a contour curve generating step of generating a sinusoidal contour curve having a wavelength that varies from a predetermined initial wavelength to a predetermined final wavelength; an evaluation curve generating step of applying at least one of a stylus tip radius correction and a profile curve filter to the profile curve to generate an evaluation curve; a display step of displaying the evaluation curve on a screen; An evaluation program for causing a computer to execute the above is provided.

[0010] According to this evaluation program, it is possible to visually and easily confirm whether the applied stylus tip radius correction or profile curve filter was appropriate from the shape of the evaluation curve displayed on the screen. Furthermore, by appropriately setting the initial wavelength and final wavelength, which are the wavelength range of the profile curve, it is possible to easily confirm the characteristics of the stylus tip radius correction or profile curve filter in any wavelength range. Furthermore, since the profile curve can be generated by calculation in the program, it can be generated as an ideal curve that does not include shape errors or measurement errors. This makes it possible to evaluate the applied stylus tip radius correction or profile curve filter without being affected by shape errors or measurement errors.

[0011] Also, The contour curve generating step generating a sinusoidal reference curve having a constant amplitude and varying the wavelength from the initial wavelength to the final wavelength; determining a locus of a center of a circle having a predetermined radius when the circle moves while tangent to the reference curve; The locus is the contour curve; Including, The evaluation curve generating step may generate the evaluation curve by applying the stylus tip radius correction to the profile curve.

[0012] Furthermore, the display step may display the contour curve and the evaluation curve on the same graph on the screen.

[0013] moreover, The contour curve generating step TIFF2025120982000002.tif20170where z(x) is the height at position x (x≧0) in the longitudinal direction, A is the amplitude, Xe is the final position, λ0 is the initial wavelength, and λe is the final wavelength. The reference curve can be generated based on the following.

[0014] Also, The computer is further configured to execute an instantaneous wavelength calculation step of determining an instantaneous wavelength of the reference curve at a position of an extreme point of the reference curve whose radius of curvature coincides with or is closest to the radius of the circle, among the extreme points of the reference curve; The display step may display on the screen the position where the evaluation curve has the instantaneous wavelength.

[0015] moreover, the profile curve has a constant amplitude; the evaluation curve generating step generates the evaluation curve by applying the stylus tip radius correction to the profile curve; the computer is further caused to execute an instantaneous wavelength calculation step of determining an instantaneous wavelength of the profile curve at a position of an extreme point of the profile curve whose curvature radius coincides with or is closest to the stylus radius set by the stylus tip radius correction, The display step may display on the screen the position where the evaluation curve has the instantaneous wavelength.

[0016] moreover, The contour curve generating step TIFF2025120982000003.tif20170where z(x) is the height at position x (x≧0) in the longitudinal direction, A is the amplitude, Xe is the final position, λ0 is the initial wavelength, and λe is the final wavelength. The contour curve can be generated based on the following.

[0017] Also, the profile curve has a constant amplitude; The evaluation curve generating step may generate the evaluation curve by applying the contour curve filter to the contour curve.

[0018] moreover, The contour curve generating step TIFF2025120982000004.tif20170where z(x) is the height at position x (x≧0) in the longitudinal direction, A is the amplitude, Xe is the final position, λ0 is the initial wavelength, and λe is the final wavelength. The contour curve can be generated based on the following.

[0019] Furthermore, the contour curve generating step can generate the contour curve by extending the curve of the formula (1) into an area where x<0 so that the wavelength is equal to or greater than the initial wavelength.

[0020] The present invention also provides a stylus-type surface texture measuring instrument including a computer on which any one of the above-described evaluation programs is implemented.

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an evaluation program and a stylus-type surface texture measuring instrument according to the present invention will be described below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram showing a sine wave curve and the locus of the center of a circle moving along it. [Figure 2] 10 is a graph showing amplitude transmissibility. [Figure 3] FIG. 1 is a diagram showing the cutoff value, stylus tip radius, and maximum sampling interval defined in the ISO / JIS standard. [Figure 4] 4 is a flowchart showing the operation of an evaluation program according to the first embodiment of the present invention. [Figure 5] 4 is a graph showing a contour curve in the first embodiment. [Figure 6] 6 is a graph showing an evaluation curve obtained by applying a contour curve filter to the contour curve of FIG. 5. [Figure 7] 10 is a graph showing a contour curve extended in the negative direction in the evaluation program according to the second embodiment of the present invention. [Figure 8] 8 is a graph showing an evaluation curve obtained by applying a contour curve filter to the contour curve of FIG. 7. [Figure 9] 10 is a first flowchart showing the operation of an evaluation program according to the third embodiment. [Figure 10] 10 is a second flowchart showing the operation of the evaluation program according to the third embodiment. [Figure 11] 10 is a graph showing a reference curve in the third embodiment. [Figure 12] 12 is a graph showing a contour curve generated from the reference curve of FIG. 11. [Figure 13] 13 is a graph showing an evaluation curve obtained by applying an appropriate stylus tip radius correction to the profile curve of FIG. 12. [Figure 14] FIG. 14 is an enlarged view of part A in FIG. [Figure 15] 13 is a graph showing an evaluation curve obtained by applying an inappropriate stylus tip radius correction to the profile curve of FIG. 12. [Figure 16] 10 is a flowchart showing the operation of an evaluation program according to a fourth embodiment of the present invention. [Figure 17] 12 is a graph showing an evaluation curve obtained by applying stylus tip radius correction to the reference curve in FIG. 11 as a contour curve. [Figure 18] FIG. 10 is a diagram showing a contour curve expanded into three dimensions. [Figure 19] 19 is a diagram showing a three-dimensional evaluation curve obtained by applying a contour curve filter to the three-dimensional contour curve of FIG. 18. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] An evaluation program according to a first embodiment of the present invention operates to evaluate a profile curve filter applied to measured cross-sectional curve data of a stylus-type surface texture measuring instrument. The operation of the evaluation program will be described below with reference to the flowchart shown in FIG. 4. In this embodiment, the evaluation program is installed in a computer included in the stylus-type surface texture measuring instrument and executed by the computer. However, the evaluation program may also be installed in a computer separate from the stylus-type surface texture measuring instrument and executed thereon.

[0024] First, a sinusoidal profile curve having a wavelength that changes from an initial wavelength to a final wavelength is generated (S10). In this embodiment, the profile curve is generated as a sinusoidal curve having a constant amplitude and whose wavelength changes exponentially from the initial wavelength to the final wavelength, using the following equation (1): TIFF2025120982000005.tif20170 where z(x) is the height at position x (x≧0) in the longitudinal direction, A is the amplitude, Xe is the final position, λ0 is the initial wavelength, and λe is the final wavelength. In this embodiment, the amplitude A is set to 1 μm, the final position Xe is set to 15,000 μm, the initial wavelength λ0 is set to 10 μm, and the final wavelength λe is set to 8,000 μm. The sampling interval is 0.5 μm. The generated profile is shown in FIG. 5. Note that the above parameters in equation (1) can be arbitrarily set and changed depending on the profile filter to be evaluated.

[0025] Next, a profile filter is applied to the profile to generate an evaluation curve (S20). The profile filter in this embodiment is a bandpass filter for obtaining a roughness curve, with a cutoff value λs set to 2.5 μm and a cutoff value λc set to 800 μm. By applying this profile filter, wavelength components smaller than the cutoff value λs (2.5 μm) and wavelength components larger than the cutoff value λc (800 μm) are removed. The evaluation curve generated by applying the profile filter to the profile is as shown in FIG. 6. The evaluation program displays this evaluation curve on the screen (S30).

[0026] By checking this evaluation curve on the screen, the user can easily confirm whether the applied profile filter is appropriate. Specifically, since the amplitude is reduced to 50% at instantaneous wavelengths of 2.5 μm and 800 μm, the cutoff values λs and λc are 2.5 μm and 800 μm, respectively, and it can be easily confirmed that the applied profile filter is operating as intended. It can also be easily confirmed how attenuation occurs across the entire wavelength range.

[0027] The evaluation program according to the second embodiment of the present invention differs from the evaluation program according to the first embodiment in the method of generating a profile. When a profile filter is applied, the filter's terminal effect can cause unintended changes at both ends of the profile. For this reason, the wavelength ranges at both ends where the terminal effect appears are omitted from the evaluation curve shown in FIG. 6 of the first embodiment. Therefore, the amplitude transfer characteristics of the profile filter cannot be confirmed in those wavelength ranges. Extending the profile is an effective way to reduce the influence of such a filter's terminal effect. However, if the initial wavelength is further reduced from the current 1 μm to extend the profile toward shorter wavelengths (toward the negative x-axis of the graph), a sampling interval of 0.5 μm, as specified in the ISO / JIS standard (FIG. 2), would include wavelengths shorter than the 1 μm wavelength corresponding to the Nyquist frequency. This would result in aliasing, making it impossible to properly reproduce the waveform. Therefore, in this embodiment, to solve this problem, the profile is generated using the following equation (2) instead of equation (1): As in the first embodiment, the parameters in equation (2) are set as follows: amplitude A = 10 μm, final position Xe = 15,000 μm, initial wavelength λ0 = 1 μm, and final wavelength λe = 8,000 μm. The sampling interval is 0.5 μm. The contour curve is generated within the range of -1,000≦x≦15,000. The generated contour curve is shown in FIG. 7. In this contour curve, the wavelength increases as x decreases in the x<0 region. Therefore, although this contour curve extends into the x<0 region, the wavelength remains equal to or greater than the initial wavelength (1 μm) at all positions. When a contour curve filter similar to that used in the first embodiment is applied to the contour curve in FIG. 7, the evaluation curve obtained is shown in FIG. 8. This evaluation curve also confirms the amplitude transfer characteristics around a wavelength of 1 μm. Instead of the curve based on equation (2), a curve connecting the curve of equation (1) in the range of x≧0 and the curve of the following equation (3) in the range of x<0 may be used as the contour curve. TIFF2025120982000007.tif13170Equation (3) is a sinusoidal curve with a constant wavelength of initial wavelength λ0.

[0028] In the above embodiment, the profile filter is a band-pass filter for obtaining a roughness curve, but it may also be a band-pass filter for obtaining a waviness curve. In this case, the cutoff values are λc and λf. Alternatively, any other filter such as a high-pass filter or a low-pass filter may be used.

[0029] The operation of an evaluation program for evaluating the stylus tip radius correction applied to the measured profile curve data of a stylus-type surface texture measuring instrument according to the third embodiment of the present invention will be described below with reference to the flowchart shown in FIG.

[0030] First, a sinusoidal profile curve is generated, having a wavelength that varies from a predetermined initial wavelength to a final wavelength (profile curve generation step: S30). In this embodiment, the profile curve is generated as shown in FIG. 10. Specifically, a sinusoidal reference curve having a constant amplitude and whose wavelength varies exponentially from the initial wavelength to the final wavelength is generated using the above-mentioned equation (1) (S30-1). In this embodiment, the amplitude A is set to 10 μm, the final position Xe is set to 16,000 μm, the initial wavelength λ0 is set to 8 μm, and the final wavelength λe is set to 80 μm. The generated reference curve is shown in FIG. 11. This reference curve corresponds to the ideal cross-sectional shape of the surface roughness standard block. Note that the above parameters in equation (1) can be arbitrarily set and changed depending on the stylus tip radius correction to be evaluated. Next, the locus of the center of a circle having a predetermined radius is determined when the circle moves tangent to the reference curve (S30-2). The radius of the circle is set to the same size as the radius of curvature of the tip of the conical stylus of the stylus-type surface texture measuring instrument. In this embodiment, the radius of the circle is set to 2 μm, but other sizes may be used depending on the stylus used. As in FIG. 1, the trajectory runs along the reference curve (sinusoidal curve) at a distance of radius (2 μm) from the reference curve, and has a shape slightly different from the reference curve. This trajectory corresponds to the measured cross-sectional curve obtained when a surface roughness standard having a reference curve is scanned with a stylus whose tip radius of curvature is the same as the radius of the circle (2 μm). The trajectory obtained in this manner is used as the profile curve (S30-3). The generated profile curve is shown in FIG. 12.

[0031] Next, the instantaneous wavelength of the reference curve at the extreme point of the reference curve whose radius of curvature R coincides with or is closest to the radius of the circle (2 μm) is calculated (instantaneous wavelength calculation step: S32). The relationship between the radius of curvature R and the wavelength λ is given by Equation (4). TIFF2025120982000008.tif13170From equation (4), the instantaneous wavelength λt when the radius of curvature R is 2 μm is calculated to be approximately 28.1 μm.As can be seen from Figure 12, the bottom end of the profile curve gradually rises from the position of the instantaneous wavelength λt (approximately 28.1 μm) toward the shorter wavelength side (toward position x = 0).This is because in the wavelength region less than 28.1 μm, a circle with a radius of 2 μm (i.e., the tip of the stylus) cannot reach the extreme point on the bottom, and as the wavelength becomes shorter, the position that the circle can reach becomes higher.

[0032] Next, stylus tip radius correction is applied to the profile curve to generate an evaluation curve (evaluation curve generation step: S34). Stylus tip radius correction corrects for the influence of a stylus with a finite tip radius from the measured cross-sectional curve data acquired by tracing the measurement surface with a stylus with a constant radius of curvature at its tip. Details are described in ISO21920-2:2021, so a detailed explanation will be omitted here. The obtained evaluation curve is shown in Figure 13.

[0033] Next, the evaluation curve shown in FIG. 13 is displayed on the screen (display step: S36). In this embodiment, the position where the evaluation curve has the above-mentioned instantaneous wavelength λt (approximately 28.1 μm) is also displayed on the screen. This allows the user to easily confirm that appropriate stylus tip radius correction has been applied, from the shape of the evaluation curve, where the lower end rises as the wavelength becomes shorter than the instantaneous wavelength λt. In this embodiment, the profile curve is also displayed on the same graph as the evaluation curve. FIG. 14 shows an enlarged view of the profile curve and evaluation curve displayed on the screen. From FIG. 14, it can be seen that the evaluation curve obtained by applying stylus radius correction to the profile curve, which was asymmetrical in the upper and lower directions due to the influence of the stylus, has become a vertically symmetrical sinusoidal curve. This evaluation curve substantially coincides with the reference curve in FIG. 11. In other words, the influence of the stylus tip radius contained in the profile curve has been appropriately removed by the stylus radius correction, and the original reference curve has been reproduced. By viewing this evaluation curve on the screen, the user can easily visually confirm that appropriate stylus tip radius correction has been applied.

[0034] When stylus tip radius correction with a tip radius of 3 μm is applied to the profile curve in Figure 11, the evaluation curve displayed on the screen has a shape with its upper end lowered in the short wavelength range, as shown in Figure 15. This indicates that appropriate correction has not been made because stylus tip radius correction with a tip radius of 3 μm has been mistakenly applied to a profile curve obtained when measuring with a stylus with a 2 μm radius of curvature of the stylus tip. From the shape of this evaluation curve, the user can easily confirm that the stylus tip radius correction is not appropriate.

[0035] The operation of an evaluation program for evaluating stylus tip radius correction applied to measured profile curve data of a stylus-type surface texture measuring instrument according to a fourth embodiment of the present invention will be described with reference to the flowchart shown in FIG.

[0036] The evaluation program according to the fourth embodiment of the present invention differs from the evaluation program according to the third embodiment in the method for generating a contour curve. In this embodiment, a contour curve is generated using Equation (1) (contour curve generating step: S40). This contour curve is the same as the reference curve (FIG. 11) generated using Equation (1) in the third embodiment. Next, the instantaneous wavelength of the contour curve is calculated at the extreme point of the contour curve where the radius of curvature R coincides with or is closest to the radius of the circle (2 μm) (instantaneous wavelength calculating step: S42). As in the third embodiment, the instantaneous wavelength λt when the radius of curvature R is 2 μm is calculated from Equation (4) above, resulting in approximately 28.1 μm. Next, an evaluation curve is generated by applying the same stylus tip radius correction as in the third embodiment to the contour curve (evaluation curve generating step: S44). The resulting evaluation curve is shown in FIG. 17. The evaluation program displays this evaluation curve on the screen (display step: S46). In this embodiment, the position where the evaluation curve has the above-mentioned instantaneous wavelength λt (approximately 28.1 μm) is also displayed on the screen.

[0037] When stylus tip radius correction is applied to a profile curve that does not include the influence of the stylus tip radius, as shown in Figure 17, the bottom of the evaluation curve remains constant, while the top gradually declines from the instantaneous wavelength λt (approximately 28.1 μm) toward the shorter wavelength side (toward distance x = 0). On the other hand, if stylus tip radius correction with a tip radius of 3 μm is applied, the curve begins to decline from wavelengths greater than the instantaneous wavelength λt toward the shorter wavelength side. Specifically, the instantaneous wavelength at the position where the radius of curvature of the extreme point of the curve in Figure 11 is 3 μm is approximately 34.4 μm, so the curve's top gradually declines from the wavelength of 34.4 μm toward the shorter wavelength side. The user can confirm that the appropriate stylus tip radius correction has been applied by visually confirming that the evaluation curve displayed on the screen is a curve whose top gradually declines from the appropriate instantaneous wavelength λt toward the shorter wavelength side.

[0038] In the above embodiment, each curve is displayed two-dimensionally, but it may be displayed three-dimensionally. The following equation (5) is an equation obtained by expanding equation (1) three-dimensionally. TIFF2025120982000009.tif29170The three-dimensional surface shown in Fig. 18 is a contour curve when the amplitude A in equation (5) is 1 μm, the initial wavelength λ0 is 2 μm, and the final wavelength λe is 500 μm. Fig. 19 is an evaluation curve when a contour curve filter with a cutoff value λs of 25 μm is applied to the contour curve of Fig. 18.

[0039] A stylus-type surface texture measuring instrument according to one embodiment of the present invention includes a computer on which the above-described evaluation program is implemented. The evaluation program in this embodiment is capable of both evaluating the profile curve filter and evaluating the stylus tip radius correction. In other embodiments, the evaluation program may be configured to execute only one of the evaluation of the profile curve filter and the evaluation of the stylus tip radius correction.

[0040] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. The order in which each processing step is performed does not necessarily have to be the order shown in the flowchart. For example, the instantaneous wavelength calculation step may be performed after the evaluation curve generation step, or these steps may be performed simultaneously. Furthermore, the reference curve (or profile curve) may be generated so as to change linearly from the initial wavelength to the final wavelength, or so as to change from a long wavelength to a short wavelength. [Explanation of symbols]

[0041] A amplitude R radius of curvature Xe final position λ wavelength λs, λc, λf cutoff values λc cutoff value λ0 initial wavelength λe final wavelength λt instantaneous wavelength

Claims

1. An evaluation program for evaluating a stylus tip radius correction or a profile curve filter applied to measured profile curve data acquired by a stylus-type surface texture measuring instrument, a contour curve generating step of generating a sinusoidal contour curve having a wavelength that varies from a predetermined initial wavelength to a predetermined final wavelength; an evaluation curve generating step of applying at least one of a stylus tip radius correction and a profile curve filter to the profile curve to generate an evaluation curve; a display step of displaying the evaluation curve on a screen; An evaluation program for running the above on a computer.

2. The contour curve generating step generating a sinusoidal reference curve having a constant amplitude and varying the wavelength from the initial wavelength to the final wavelength; determining a locus of a center of a circle having a predetermined radius when the circle moves while tangent to the reference curve; The locus is the contour curve; Including, 2. The evaluation program according to claim 1, wherein the evaluation curve generating step generates the evaluation curve by applying the stylus tip radius correction to the profile curve.

3. 3. The evaluation program according to claim 2, wherein said display step displays said contour curve and said evaluation curve on the same graph on said screen.

4. The contour curve generating step where z(x) is the height at position x (x≧0) in the longitudinal direction, A is the amplitude, Xe is the final position, and λ ０ is the initial wavelength, λ is the final wavelength, 3. The evaluation program according to claim 2, wherein the reference curve is generated based on:

5. The computer is further configured to execute an instantaneous wavelength calculation step of determining an instantaneous wavelength of the reference curve at a position of an extreme point of the reference curve whose radius of curvature coincides with or is closest to the radius of the circle, among the extreme points of the reference curve; 3. The evaluation program according to claim 2, wherein said display step displays a position where said evaluation curve has said instantaneous wavelength on said screen.

6. the profile curve has a constant amplitude; the evaluation curve generating step generates the evaluation curve by applying the stylus tip radius correction to the profile curve; the computer is further caused to execute an instantaneous wavelength calculation step of determining an instantaneous wavelength of the profile curve at a position of an extreme point of the profile curve whose curvature radius coincides with or is closest to the stylus radius set by the stylus tip radius correction, 2. The evaluation program according to claim 1, wherein said display step displays a position where said evaluation curve has said instantaneous wavelength on said screen.

7. The contour curve generating step where z(x) is the height at position x (x≧0) in the longitudinal direction, A is the amplitude, Xe is the final position, and λ ０ is the initial wavelength, λ is the final wavelength, 7. The evaluation program according to claim 6, wherein the contour curve is generated based on the following formula:

8. the profile curve has a constant amplitude; 2. The evaluation program according to claim 1, wherein the evaluation curve generating step generates the evaluation curve by applying the contour curve filter to the contour curve.

9. The contour curve generating step where z(x) is the height at position x (x≧0) in the longitudinal direction, A is the amplitude, Xe is the final position, and λ ０ is the initial wavelength, λ is the final wavelength, 9. The evaluation program according to claim 8, wherein the profile curve is generated based on the following equation:

10. 10. The evaluation program according to claim 9, wherein the contour curve generating step generates the contour curve by extending the curve of the formula (1) into a region where x<0 so that the wavelength is equal to or greater than the initial wavelength.

11. A stylus-type surface texture measuring instrument comprising a computer on which the evaluation program according to any one of claims 1 to 10 is implemented.

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