Calibration standards and calibration methods for shape measuring instruments

Abstract

To provide: standards for calibration which allow calibration (magnification calibration) of a shape measuring instrument to be performed highly accurately; and a method for calibrating the shape measuring instrument.SOLUTION: Standards (M1-M3) for calibration are used for the calibration of a shape measuring instrument (10), and comprise, respectively: outer circumferential parts (S1-S3) each having a cylindrical outer circumferential surface; cut parts (D1-D3) which are notched by prescribed cut amounts each from the cylindrical outer circumferential surface; and mitigated curved surface parts (E1-E3) which are each installed so as to connect from the outer circumferential part to the cut part and constructed in a curved shape protruding to the outside of the standard for calibration.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a calibration standard and a method for calibrating a shape measuring machine, and more particularly to a calibration standard used for calibrating a shape measuring machine for measuring the shape of a workpiece, and a method for calibrating a shape measuring machine. [Background technology]

[0002] Conventionally, there has been known a shape measuring machine that measures the shape (roundness, etc.) of a workpiece by rotating a probe and the workpiece relatively around a rotation axis. For example, Patent Document 1 discloses a technology for non-contact measurement of the shape of the inner and side surfaces of the center hole of a cylindrical workpiece placed on a rotary table. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-014656 Summary of the Invention [Problem to be solved by the invention]

[0004] With shape measuring instruments like those described above, a probe equipped with a non-contact optical sensor is used to measure the shape of the calibration standard, and a process called magnification calibration is required to correlate the output signal of the probe with the actual calibrated displacement (see, for example, Japanese Industrial Standards JIS B7451:1997, Annex 2).

[0005] FIG. 13 is a plan view (top view) for explaining magnification calibration using a calibration standard (flick master, hereinafter referred to as master).

[0006] As shown in FIG. 13, the master M0 has a cylindrical shape, and a flat portion (hereinafter referred to as D-cut portion D0) is formed on part of its side surface. In the following explanation, a two-dimensional polar coordinate system is used, with the center C0 (the central axis of the cylinder) of the cylindrical master M0 as the origin and a perpendicular line (hereinafter referred to as center line Lx) extending from the center C0 of the master M0 to the D-cut portion D0 as the X-axis. Here, the outer diameter (radius) R of the master M0 and the amount of cutting d of the D-cut portion D0 (the maximum distance between the extension line (dotted line) of the outer periphery of the master M0 and the D-cut portion D0) are known. In addition, the distance from the center C0 of the master M0 to the end D0 of the D-cut portion D0 is known. E The angle θ between the line extending to the center line Lx d is also known because it depends on the cutting amount d.

[0007] 13, when performing magnification calibration, measurement light B1 is emitted from an optical sensor provided at the tip of probe 30 to the surface of master M0, and reflected light B2 returning from the surface of master M0 is detected. Then, magnification calibration is performed using the detection result of reflected light B2 and known R and d. This enables the shape measuring instrument to accurately measure the shape and dimensions of the measurement target.

[0008] 13, the angle of measurement light B1 relative to the center line Lx is θ, the distance between the center C0 of master M0 and the incident position P0 of measurement light B1 is R(θ), and the angle (incident angle) of measurement light B1 relative to the normal direction (N0) of the surface of master M0 at the incident position P0 of measurement light B1 is φ(θ). In this case, the incident angle φ(θ) is expressed by the following equation (1):

[0009] Since the master M0 is symmetrical with respect to the X axis, the following description will only cover the area above the X axis (0°≦θ<180°), and will omit the area below the X axis (180°≦θ<360°).

[0010]

number

[0011] As shown in equation (1), θ ≥ θ d, that is, when the measurement light B1 is incident on the side surface of the cylinder, θ=0, but θ<θ d That is, when the measuring light B1 is incident on the D-cut portion D0, the incident angle φ(θ) changes.

[0012] Here, in order to accurately measure the shape of the master M0, it is necessary to ensure a sufficient amount of reflected light B2, so it is preferable that the incident angle φ(θ) is small. For example, if the numerical aperture of the optical sensor of the probe 30 is NA, it is preferable that φ(θ)≦arcsin(NA).

[0013] When the incident angle φ(θ) becomes large, the component of the reflected light B2 reflected or scattered by the D-cut portion D0 that returns to the optical sensor of the probe 30 decreases. In other words, the amount of reflected light B2 that can be used to measure the shape of the master M0 decreases. In particular, the amount of reflected light B2 that can be used to measure the shape of the master M0 decreases. E At and near the edge D0 of the D-cut portion D0, the incident angle φ(θ) becomes larger, and the amount of reflected light B2 that can be used for measuring the shape decreases. E At and near the center of the mirror, noise data is likely to occur due to a decrease in the amount of reflected light B2. If such noise data is included in the detection results of the master M0, an error will occur in the amount of removal d of the master M0, making it difficult to perform high-precision magnification calibration.

[0014] The graph in Figure 14 plots the incident angle φ(θ) (see equation (1)) when the radius R of the master M0 is 12.5 mm, the cutting amount d is 20 μm, and the numerical aperture NA of the probe 30 is 0.05 (acceptable angle (=arcsin(NA)) ≈ 3°).

[0015] As shown in FIG. 14, the end D0 of the D-cut portion D0 E At and around this point, the incident angle φ(θ) exceeds the allowable angle (≈3°). As a result, the amount of reflected light B2 that can be detected by the optical sensor of the probe 30 decreases, making it impossible to perform high-precision magnification calibration.

[0016] The present invention has been made in view of the above circumstances, and has as its object to provide a calibration standard and a calibration method for a shape measuring machine that are capable of calibrating the shape measuring machine (magnification calibration) with high precision. [Means for solving the problem]

[0017] In order to solve the above problems, a calibration standard according to a first aspect of the present invention is a calibration standard used for calibrating a shape measuring instrument, and comprises an outer periphery having a cylindrical outer surface, a cut portion cut out from the cylindrical outer surface by a predetermined amount, and a gentle curved surface portion extending from the outer periphery to the cut portion and configured in a convex curve on the outside of the calibration standard.

[0018] A calibration standard according to a second aspect of the present invention is the first aspect, wherein the cut portion is formed in a flat shape on a part of the outer peripheral surface of the cylindrical shape, and the gentle curved surface portion has a shape that follows a circle inscribed in both the outer peripheral surface of the cylindrical shape and the flat cut portion.

[0019] A calibration standard according to a third aspect of the present invention is the first aspect, in which the cut portion is formed in a line parallel to the central axis of the calibration standard on a part of the outer peripheral surface of the cylindrical shape, and the gradual curved surface portion has a curved shape in which the distance from the center of the calibration standard changes linearly with the angle with respect to a perpendicular line extending from the center of the calibration standard to the cut portion.

[0020] A calibration standard according to a fourth aspect of the present invention is the first aspect, wherein the cut portion is formed in a flat shape on a part of the outer peripheral surface of the cylindrical shape, and the gentle curve portion has a curved shape in which the distance from the center of the calibration standard changes linearly with the angle with respect to a perpendicular line extending from the center of the calibration standard to the cut portion.

[0021] A method for calibrating a shape measuring machine according to a fifth aspect of the present invention includes emitting measurement light from a probe of the shape measuring machine to a calibration standard of any one of the first to fourth aspects, detecting reflected light from the calibration standard using the probe, and calibrating magnification based on the detection result of the reflected light and the outer diameter and cutting amount of the calibration standard. [Effects of the Invention]

[0022] According to the present invention, by providing a gentle curved surface on the side of the cylindrical construction standard, the amount of reflected light during measurement of the cut portion can be secured, enabling highly accurate magnification calibration. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a front view showing a shape measuring instrument. [Figure 2] FIG. 2 is a block diagram showing the control system of the shape measuring machine. [Figure 3] FIG. 3 is a plan view (top view) showing a calibration standard (Flick Master) according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a plan view (top view) showing a calibration standard (Flick Master) according to the first embodiment of the present invention. [Figure 5] FIG. 5 is a partially enlarged plan view showing the transition curve according to the first embodiment of the present invention. [Figure 6] FIG. 6 is a graph showing an example of the calculation results of the incident angle φ(θ) in the calibration standard according to the first embodiment of the present invention. [Figure 7] FIG. 7 is a graph showing an example of the calculation results of the incident angle φ(θ) when the length of the D-cut portion is changed. [Figure 8] FIG. 8 is a plan view (top view) showing a calibration standard (Flick Master) according to the second embodiment of the present invention. [Figure 9] FIG. 9 is a partially enlarged plan view showing a transition curve according to the second embodiment of the present invention. [Figure 10] FIG. 10 is a graph showing an example of the calculation results of the incident angle φ(θ) in the calibration standard according to the second embodiment of the present invention. [Figure 11] FIG. 11 is a plan view (top view) showing a calibration standard (Flick Master) according to the third embodiment of the present invention. [Figure 12]FIG. 12 is a graph showing an example of the calculation results of the incident angle φ(θ) in the calibration standard according to the third embodiment of the present invention. [Figure 13] FIG. 13 is a plan view (top view) for explaining magnification calibration using a calibration standard (Flick Master). [Figure 14] FIG. 14 is a graph showing the relationship between the angle θ of the measurement light with respect to the X axis and the angle of incidence φ of the measurement light with respect to the surface of the master. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of a calibration standard and a method for calibrating a shape measuring instrument according to the present invention will be described with reference to the accompanying drawings.

[0025] [First embodiment] (shape measuring machine) First, the schematic configuration of the shape measuring machine will be described with reference to Figures 1 and 2. Figure 1 is a front view showing the shape measuring machine.

[0026] The shape measuring machine 10 shown in FIG. 1 is a device capable of measuring the outer shape of a workpiece W and the inner shape (roundness, etc.) of a small hole H formed in a cylindrical workpiece W. In the example shown in FIG. 1, the small hole H is a through-hole formed along the central axis of the workpiece W. The inner diameter of the small hole H is extremely small (for example, an inner diameter of 500 μm or less). In FIG. 1, the X, Y, and Z directions are mutually perpendicular, the X direction is a horizontal direction, the Y direction is a horizontal direction perpendicular to the X direction, and the Z direction is a vertical direction.

[0027] As shown in FIG. 1, the shape measuring instrument 10 includes a main body base 12, a stage rotation mechanism 14, a stage 18, a column 20, a carriage 22, an arm 24, a displacement detector 26, a detector drive mechanism 28, and a control device 50.

[0028] The stage rotation mechanism (high-precision rotation mechanism) 14 is a rotation mechanism for rotating the workpiece W around a rotation axis C, and rotates a stage 18 (described later) with high precision around the rotation axis C parallel to the Z direction. The stage rotation mechanism 14 includes a rotor 16 rotatably mounted on the main body base 12, and the stage 18 is supported on the upper surface of the rotor 16. The stage rotation mechanism 14 includes a motor (not shown) that rotates the rotor 16 with high precision around the rotation axis C, and an encoder (not shown) that detects the rotation angle of the rotor 16.

[0029] The stage 18 is used to place the workpiece W. The stage 18 may be used to directly support and fix the workpiece W, or may be used to support and fix the workpiece W via a workpiece setting jig (not shown).

[0030] The stage 18 is supported on the support surface (upper surface) of the rotating body 16, and is configured to be rotatable integrally with the rotating body 16 around the rotation axis C. As a result, the workpiece W supported and fixed on the stage 18 can be rotated integrally with the stage 18 around the rotation axis C. The stage 18 and the rotating body 16 are an example of a "stage rotation mechanism."

[0031] The stage 18 is equipped with a linear motion mechanism and a tilting mechanism (neither of which is shown). The linear motion mechanism moves the stage 18 in the X and Y directions by driving a motor (not shown), thereby adjusting the position of the stage 18 in the XY plane (horizontal plane) perpendicular to the rotation axis C. The tilting mechanism rotates the stage 18 in the X and Y directions by driving a motor (not shown), thereby adjusting the tilt of the stage 18 with respect to the XY plane.

[0032] A column (support) 20 extending parallel to the Z direction is erected on the main body base 12. The lower end of the column 20 is fixed to the upper surface of the main body base 12.

[0033] The carriage 22 is supported by the column 20 so as to be movable in the Z direction. The carriage 22 is configured to be movable in the Z direction by being driven by a motor (not shown).

[0034] The arm 24 is supported by the carriage 22 so as to be movable in the X and Y directions. The arm 24 is configured to be movable in the horizontal direction (X and Y directions) by a linear motion mechanism 70 and a busbar extension mechanism 72 (see FIG. 2). The linear motion mechanism 70 and the busbar extension mechanism 72 each include a drive source (motor, etc.) for moving the arm 24 in the horizontal direction.

[0035] Scales are provided on the sides of the arm 24 and the column 20 along the X and Z directions, respectively. The control device 50 can detect the position of the probe 30 in the X and Z directions by reading the graduations on these scales using a sensor (not shown).

[0036] The displacement detector 26 is supported by the arm 24 via a detector drive mechanism 28. The displacement detector 26 has a probe 30. The probe 30 detects the shape of the surface of the workpiece W (the outer surface or the inner surface of a hole H formed in the workpiece W). The probe 30 according to this embodiment is a non-contact probe that can detect the surface shape of the workpiece W without coming into contact with the surface of the workpiece W.

[0037] The type of non-contact probe 30 is not particularly limited as long as it can detect the surface shape of the workpiece W without contacting the surface of the workpiece W. As the non-contact probe, for example, a probe to which various methods such as a laser interferometer, a white light interferometer, SD-OCT (Spectral Domain-Optical Coherence Tomography) or SS-OCT (Swept Source-Optical Coherence Tomography) can be used.

[0038] The detector drive mechanism 28 is interposed between the arm 24 and the displacement detector 26. The detector drive mechanism 28 includes a linear motion mechanism and a tilt mechanism (neither of which is shown). The linear motion mechanism moves the displacement detector 26 in the X and Y directions by driving a motor (not shown), thereby adjusting the position of the probe 30 in an XY plane (horizontal plane) perpendicular to the rotation axis C. The tilt mechanism rotates the displacement detector 26 around the X and Y directions by driving a motor (not shown), thereby adjusting the tilt of the probe 30 with respect to the XY plane. Therefore, by adjusting the position and tilt of the probe 30 in the horizontal direction (X and Y directions) using the detector drive mechanism 28 (linear motion mechanism and tilt mechanism), it is possible to perform relative positioning (probe alignment) between the probe 30 and the rotation axis C.

[0039] The detector driving mechanism 28 also includes a driving source (for example, a motor) for rotating around a rotation axis (probe rotation axis) AX. The detector driving mechanism 28 is an example of a "probe rotation mechanism."

[0040] FIG. 2 is a block diagram showing the control system of the shape measuring machine.

[0041] The control device 50 controls the operation of each part of the profile measuring machine 10 (including the operation of measuring the surface profile of the workpiece W and the probe alignment operation described below). The control device 50 is realized by, for example, a general-purpose computer such as a personal computer or a microcomputer. The control device 50 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), a storage device (for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive)), an input / output interface, etc. In the control device 50, various programs such as a control program stored in the storage device are loaded into the RAM, and the programs loaded into the RAM are executed by the CPU, thereby realizing the functions of each part in the profile measuring machine 10 and executing various arithmetic processing or control processing via the input / output interface.

[0042] The control device 50 is provided with an operation unit 52 (for example, a keyboard and a mouse) that accepts operation input from a user, and a display unit 54 that displays an operation UI (User Interface) and detection results.

[0043] As shown in FIG. 2, the control device 50 includes a displacement calculation unit 56 and a drive control unit 58.

[0044] The displacement calculation unit 56 calculates the displacement of the workpiece W based on the detection results of the displacement of the surface of the workpiece W detected by the displacement detector 26, and measures the shape of the surface of the workpiece W (for example, the outer shape of the workpiece W or the roundness of the hole H, etc.).

[0045] The drive control unit 58 controls the linear motion mechanism 70 , the busbar extension mechanism 72 , the detector drive mechanism 28 and the stage rotation mechanism 14 to adjust the relative positions of the workpiece W and the probe 30 .

[0046] (Magnification calibration method) Next, we will explain a method for calibrating the magnification in the profile measuring instrument 10. Figures 3 and 4 are plan views (top views) showing a calibration standard (flick master, hereinafter referred to as master) according to the first embodiment of the present invention.

[0047] When calibrating the magnification of the profile measuring machine 10, first, the master M1 is placed on the stage 18 so that its center C1 (the central axis of the cylinder) coincides with the rotation axis C of the stage 18 (see FIGS. 3 and 4). Then, the stage rotation mechanism 14, the detector drive mechanism 28, and the carriage 22 are controlled to adjust the relative position between the workpiece W and the probe 30, while the probe 30 emits measurement light B1 toward the master M1 and detects the light reflected from the master M1 to measure the profile of the master M1. Next, the magnification is calibrated using the detection result of the light reflected from the master M1 and the known outer diameter (radius) R and cutting amount d of the master M1.

[0048] (calibration standard) Next, the master M1 will be described.

[0049] As shown in FIGS. 3 and 4, the master M1 according to this embodiment has a cylindrical shape, and a flat portion (an example of a cut portion, hereinafter referred to as a D-cut portion D1) is formed by cutting out a predetermined amount d from a portion of its outer periphery (outer peripheral surface, side surface) S1. A curved side surface (a relaxation curve portion, hereinafter referred to as a relaxation curve) E1 is formed between the cylindrical side surface S1 of the master M1 and the D-cut portion D1. Here, the outer diameter (radius) R of the master M1 and the amount of removal d of the D-cut portion D1 (the maximum distance between the extension line (dotted line) of the outer periphery of the master M1 and the D-cut portion D1) are known. In addition, if the relaxation curve E1 were not present, the end D1 of the virtual D-cut portion D1 (dashed line portion) would be E Y coordinate of L D is also known because it depends on the cutting amount d.

[0050] In the following description, a two-dimensional polar coordinate system is used in which the center C1 of the master M1 (the central axis of the cylinder) is the origin and the perpendicular line extending from the center C1 of the master M1 to the D-cut portion D1 is the X-axis.

[0051] Since the master M1 is symmetrical with respect to the X-axis, the following description will only cover the transition curve E1 above the X-axis (0°≦θ<180°), and will omit the description of the transition curve E1 below the X-axis (180°≦θ<360°).

[0052] 3 and 4, the transition curve E1 is part of an inscribed circle IC1 that is inscribed in both the side surface S1 and the D-cut portion D1 of the master M1. The points of contact between the side surface S1 of the master M1 and the inscribed circle IC1 and the D-cut portion D1 are designated as P1 and P2, respectively.

[0053] If the coordinates of the center C10 of the inscribed circle IC1 are (x0, y0) and the radius is r, the inscribed circle IC1 is expressed by the following formula (2).

[0054] (x-x0) 2 +(y-y0) 2 =r 2 …(2) The radius r of the inscribed circle IC1 can be expressed using known variables as follows: First, since the inscribed circle IC1 is inscribed in the D-cut portion D1, the following equations (3) and (4) are obtained.

[0055] x0=(Rdr) …(3) y0=L …(4) In equation (4), L is the Y coordinate of the inscribed circle IC1 and the inscribed D-cut portion D1 at the inscribed point P2. Here, L can be determined arbitrarily. For example, if L is the length (L D ), the effect of the transition curve E1 can be obtained while ensuring a sufficient length for the D-cut portion D1.

[0056] Next, since the inscribed circle IC1 is inscribed in the side surface S1 of the master M1, the following equation (5) is obtained.

[0057]

number

[0058] By solving equation (5) for r using equations (3) and (4), we obtain the following equation (6).

[0059] r=R-(L 2 -d 2 ) / 2d …(6) Next, the distance R(θ) between the center C10 of the inscribed circle IC1 and a point on the transition curve E1 can be expressed in known variables as follows:

[0060] First, from Figures 3 and 4, the point (x, y) on the transition curve E1 is (R(θ) cos θ, R(θ) sin θ). Substituting this into equation (1) for the inscribed circle IC1, we obtain the following equation (7).

[0061] (R(θ)cosθ-x0) 2 +(R(θ)sinθ-y0) 2 =r 2 …(7) By transforming equation (7), the following equation (8) is obtained.

[0062] R(θ) 2 -2(x0cosθ+y0cosθ)R(θ)+(x0 2 +y0 2 -r 2 )=0…(8) When equation (8) is solved for R(θ), the following equation (9) is obtained.

[0063]

number

[0064] By substituting r from equation (6) into equation (9), R(θ) can be calculated using only the known variables (R, d, L, x0, and y0) and θ.

[0065] Next, as shown in Figure 4, the normal to the surface of the master M1 at the incident position P0 of the measurement light B1 is defined as N1, and the angle (incident angle) of the measurement light B1 with respect to the normal N1 is defined as φ(θ). The incident angle φ(θ) can be expressed in known variables as follows:

[0066] FIG. 5 is a partially enlarged plan view of the transition curve E1.

[0067] As shown in Fig. 5, consider the incident position P0 of the measurement light B1 and point P3 on the transition curve E1 that is Δθ away from the incident position P0. In Fig. 5, if Δθ is sufficiently small (Δθ ≒ 0), then R(θ) tan Δθ ≒ R(θ) Δθ. In this case, the incident angle φ(θ) is expressed by the following equation (10).

[0068] φ(θ)=arctan[{R(θ+Δθ)-R(θ)} / (R(θ)Δθ)] …(10) (Example of calculation result of incident angle φ(θ)) 6 is a graph showing an example of the calculation results of the incident angle φ(θ) in the master M1 according to the first embodiment. Graph F1 in FIG. 6 plots the incident angle φ(θ) when the radius R of the master M1 is 12.5 mm, the cutting amount d is 20 μm, and the numerical aperture NA of the measurement optical system of the probe 30 is 0.05 (acceptable angle (=arcsin(NA))≈3°). In FIG. 6, the Y coordinate of the boundary (inner tangent point P2) between the D-cut portion D1 and the relaxation curve E1, i.e., the length L which is half the length of the D-cut portion D1, is taken as the length (L) of the virtual D-cut portion D1 (dashed line portion). D ) is half of the original size (L=1 / 2L) D ).

[0069] 6, in this embodiment, the incident angle φ(θ) is less than the allowable angle (≈3°) even at the boundary (inner tangent point P2) between the D-cut portion D1 and the transition curve E1 and in the vicinity thereof. Therefore, a sufficient amount of reflected light can be secured that can be detected by the optical sensor of the probe 30, and the shape of the master M1 can be measured with high accuracy, allowing for high-accuracy magnification calibration.

[0070] In addition, the transition curve E1 of the master M1 according to this embodiment is circular and therefore easy to manufacture. Furthermore, since there are no inflection points in the shape of the side surface of the transition curve E1 of the master M1, the measured shape waveform is stable, and the shape of the master M1 can be measured with high accuracy.

[0071] Furthermore, according to this embodiment, the length (2L) of the D-cut portion D1 can be adjusted arbitrarily, so that an optimum geometric shape can be adopted depending on the numerical aperture NA of the probe 30.

[0072] Fig. 7 is a graph showing an example of the calculation results of the incident angle φ(θ) when the length (2L) of the D-cut portion D1 is changed. Note that the calculation parameters for the graph in Fig. 7 are the same as those in Fig. 6: radius R of master M1 = 12.5 mm, cutting amount d = 20 μm, and numerical aperture NA of the measurement optical system of probe 30 = 0.05 (acceptable angle (= arcsin(NA)) ≈ 3°).

[0073] As shown in FIG. 7, graphs F1-1 to F1-3 are graphs in which the length (2L) of the D-cut portion D1 is L=1 / 4L. D ,L=1 / 2L D ,L=3 / 4L D In all of the graphs F1 to F3, the incident angle φ(θ) is less than the allowable angle (≈3°).

[0074] As shown in Figure 7, the maximum incident angle φ(θ) increases as the length (2L) of the D-cut portion D1 increases, and conversely, the maximum incident angle φ(θ) decreases as the length (2L) of the D-cut portion D1 decreases.

[0075] Therefore, in this embodiment, the length (2L) of the D-cut portion D1 can be optimized according to the numerical aperture NA of the probe 30. For example, as shown in graph F1-3, increasing the length (2L) of the D-cut portion D1 allows the D-cut portion D1 (straight portion) to be longer, thereby stabilizing the measured waveform. On the other hand, as shown in graph F1-1, decreasing the length (2L) of the D-cut portion D1 reduces the maximum value of φ(θ), enabling high-precision measurement even when the numerical aperture NA of the probe 30 is small.

[0076] [Second embodiment] Next, a second embodiment of the present invention will be described. The second embodiment differs from the first embodiment in the shape of the master M2. The shape measuring machine 10 and its configuration method are the same as those of the first embodiment, so a description thereof will be omitted.

[0077] (calibration standard) Fig. 8 is a plan view (top view) showing a calibration standard (flick master) according to a second embodiment of the present invention. Fig. 8 also shows an extension line (dotted line) of the cylindrical outer peripheral surface S2 of the master M2 and the D-cut portion D0 (dashed line) shown in Fig. 13.

[0078] 8, the master M2 according to this embodiment has a cylindrical shape, and a curved side surface (transition curve) E2 is formed on a part of its outer periphery (outer periphery surface, side surface) S2. The outer diameter (radius) R of the master M2 and the distance d between the side surface E2 of the master M2 and the intersection point PI with the X-axis (hereinafter referred to as the cutting amount) are known.

[0079] As shown in FIG. 8, in this embodiment, the cut portion D2 is formed at the intersection point PI in the form of a line parallel to the central axis (C2) of the master M2.

[0080] In the following description, a two-dimensional polar coordinate system is used in which the center C2 of the master M2 (the central axis of the cylinder) is the origin and the X axis is a line extending to the intersection PI between the side surface E2 of the master M2 and the X axis.

[0081] As shown in FIG. 8, the master M2 is symmetrical with respect to the X axis, so only the upper side of the X axis (0°≦θ<180°) will be described, and the lower side of the X axis (180°≦θ<360°) will not be described.

[0082] For master M2, the distance R(θ) from the center C2 of master M2 to the surface is expressed by the following equation (11): As shown in equation (11), side surface S2 (θ≧θ0) has a cylindrical shape with a radius R, while side surface E2 (θ<θ0) has a curved shape that changes linearly with the angle θ. Hereinafter, of side surface E2 (θ<θ0), the portion above the X-axis will be referred to as the linear change curve E2(+), and the portion below the X-axis will be referred to as the linear change curve E2(-).

[0083]

number

[0084] In equation (11), angle θ0 represents the angle (switching angle) of point P5, which is the boundary between side surface S2 of the cylindrical shape of master M2 and linear change curve E2(+).

[0085] FIG. 9 is a partially enlarged plan view showing the linear change curve E2(+).

[0086] As shown in Figure 9, consider the incident position P0 of the measurement light B1 and point P6 on the linear change curve E2, which is Δθ away from the incident position P0. Let N2 be the normal to the surface of the master M2 at the incident position P0 of the measurement light B1, and φ(θ) be the angle (incident angle) of the measurement light B1 with respect to the normal N2. In Figure 9, if Δθ is sufficiently small (Δθ ≒ 0), then R(θ) tan Δθ ≒ R(θ) Δθ. In this case, the incident angle φ(θ) is expressed by the following equation (12):

[0087] φ(θ)=arctan[{R(θ+Δθ)-R(θ)} / (R(θ)Δθ)] …(12) By substituting the equation for the linear change curve E2(+)(0≦θ<θ0) of equation (11) into equation (12), the following equation (13) is obtained.

[0088] φ(θ)=arctan[d / {Rθ0-(θ0-θ)d}] …(13) From equation (13), the following equation (14) is obtained.

[0089] φ(θ)~d / (Rθ0) …(14) From equation (14), the incident angle φ(θ) is constant regardless of θ.

[0090] (Example of calculation result of incident angle φ(θ)) Fig. 10 is a graph showing an example of calculation results of the incident angle φ(θ) on the master M2 according to the second embodiment. Graph F2 in Fig. 10 plots the incident angle φ(θ) when the radius R of the master M2 is 12.5 mm, the removal amount d is 20 μm, the numerical aperture NA of the measurement optical system of the probe 30 is 0.05 (acceptable angle (=arcsin(NA))≈3°), and the switching angle θ0 is 10°.

[0091] 10, in this embodiment, the incident angle φ(θ) is less than the allowable angle (≈3°) even at and near the boundary (point P5) between the cylindrical side surface S2 of the master M2 and the linear change curve E2. Therefore, a sufficient amount of reflected light can be detected by the optical sensor of the probe 30, and the shape of the master M2 can be measured with high accuracy, allowing for high-precision magnification calibration.

[0092] Furthermore, according to this embodiment, as shown in equation (14), the incident angle φ(θ) of the measurement light B1 is approximately constant regardless of θ, so the reflection angle of the measurement light B1 can be made constant and small, thereby enabling high-quality and uniform measurement.

[0093] [Third embodiment] Next, a third embodiment of the present invention will be described. The second embodiment differs from the first and second embodiments in the shape of the master M3. The shape measuring machine 10 and its configuration method are the same as those of the first embodiment, so a description thereof will be omitted.

[0094] (calibration standard) Fig. 11 is a plan view (top view) showing a calibration standard (flick master) according to a second embodiment of the present invention. Fig. 11 also shows an extension line (dotted line) of the cylindrical outer peripheral surface S3 of master M3 and the D-cut portion D0 (dashed line) shown in Fig. 13.

[0095] As shown in Figure 11, the master M3 according to this embodiment is cylindrical, and a flat portion (an example of a cut portion, hereinafter referred to as a D-cut portion D3) is formed on part of its outer periphery (outer peripheral surface, side surface) S3. A curved side surface (a relaxation curve, hereinafter referred to as a linear change curve) E3 is formed between the cylindrical side surface S3 of the master M3 and the D-cut portion D3. Here, the outer diameter (radius) R of the master M3 and the distance d between the side surface E3 of the master M3 and the intersection P9 of the X-axis (hereinafter referred to as the cutting amount) are known.

[0096] In the following description, a two-dimensional polar coordinate system is used in which the center C3 of the master M3 (the central axis of the cylinder) is the origin and the perpendicular line extending from the center C3 of the master M3 to the D-cut portion D3 is the X-axis.

[0097] As shown in FIG. 11, the master M3 is symmetrical with respect to the X axis, so only the upper side of the X axis (0°≦θ<180°) will be described, and the lower side of the X axis (180°≦θ<360°) will not be described.

[0098] In master M3, the distance R(θ) from the center C2 of master M3 to the surface is expressed by the following equation (15). As shown in equation (15), side surface S3 (θ≧θ0) is cylindrical with a radius R, while D-cut portion D3 (θ<θ1) is flat. Furthermore, side surface E3 (θ1≦θ<θ0) between the cylindrical side surface S3 of master M3 and D-cut portion D3 has a curved shape that changes linearly with the angle θ. Hereinafter, the portion of side surface E3 (θ1≦θ<θ0) above the X-axis will be referred to as the linear change curve E3(+), and the portion below the X-axis will be referred to as the linear change curve E3(-).

[0099]

number

[0100] In equation (15), angle θ0 indicates the angle (switching angle) of point P7 at the boundary between the cylindrical side surface S3 of master M3 and the linear change curve E3(+), and angle θ1 indicates the angle (switching angle) of point P8 at the boundary between the linear change curve E3(+) and the D-cut portion D3.

[0101] Here, θ1 is a non-zero angle that satisfies the condition of the following equation (16).

[0102] (Rd) / cosθ1=R-(1-θ1 / θ0)d …(16) By approximately solving equation (16), the following equation (17) is obtained.

[0103] θ1=2d / (Rd)θ0…(17) (Example of calculation result of incident angle φ(θ)) Fig. 12 is a graph showing an example of the calculation results of the incident angle φ(θ) in the master M3 according to the third embodiment. Note that Fig. 12 also shows the graph F1-2 (see Fig. 7) according to the first embodiment for comparison.

[0104] Graph F3 in FIG. 12 is obtained when the radius R of the master M3 is 12.5 mm, the cutting amount d is 20 μm, the numerical aperture NA of the measurement optical system of the probe 30 is 0.05 (allowable angle (=arcsin(NA)) ≈ 3°), the switching angle θ0 is 6.3°, and the length (2L) of the D-cut portion D3 is L=1 / 2L. D The incident angle φ(θ) is plotted as

[0105] 13, according to this embodiment, although the incident angle φ(θ) becomes large at the D-cut portion D3, φ(θ) quickly becomes a small, constant value when it enters the region of the linear change curve E3. Therefore, according to this embodiment, it is possible to reduce the angle region where φ(θ) is large, where measurement quality tends to deteriorate, and to further improve the measurement quality of magnification calibration.

[0106] [Variations] In the above embodiment, a portion of a circle (E1) or a linear change curve (E2 and E3) is used as an example of a transition curve, but examples of the transition curve are not limited to these. For example, it is also possible to use known shapes such as a clothoid curve or an n-th order function (n is a natural number of 2 or more, for example, a cubic curve), or a curve that is convex outward from the masters M1 to M3. Furthermore, a pseudo transition curve may be formed using one or more straight lines.

[0107] In the above embodiment, the masters M1 to M3 each have one D-cut portion D1 to D3 formed on their side surface, but a plurality of D-cut portions D1 to D3 may be formed. [Explanation of symbols]

[0108] 10...shape measuring machine, 12...main body base, 14...stage rotation mechanism, 16...rotating body, 18...stage, 20...column, 22...carriage, 24...arm, 26...displacement detector, 28...detector drive mechanism, 30...probe, 32...camera, 34...camera bracket, 50...control device, 52...operation unit, 54...display unit, 56...displacement calculation unit, 58...drive control unit, 60...imaging control unit, 70...linear motion mechanism, 72...busbar extraction mechanism, M1 to M3...calibration standard (Flick Master)

Claims

1. A calibration standard used for calibrating a shape measuring machine, an outer circumferential portion having a cylindrical outer circumferential surface; a cut portion formed by cutting out a predetermined amount from the outer peripheral surface of the cylindrical shape; a gentle curved surface portion that is provided so as to connect the outer periphery portion to the cut portion and that is configured in a curved shape that is convex outward from the calibration standard; A calibration standard comprising:

2. The cut portion is formed in a flat shape on a part of the outer circumferential surface of the cylindrical shape, 2. The calibration standard according to claim 1, wherein the gentle curved surface portion has a shape that follows a circle inscribed in both the cylindrical outer circumferential surface and the flat cut portion.

3. the cut portion is formed in a line parallel to the central axis of the calibration standard on a part of the outer circumferential surface of the cylindrical shape, 2. The calibration standard according to claim 1, wherein the gentle curved surface portion has a curved shape in which the distance from the center of the calibration standard changes linearly with the angle with respect to a perpendicular line extending from the center of the calibration standard to the cut portion.

4. The cut portion is formed in a flat shape on a part of the outer circumferential surface of the cylindrical shape, 2. The calibration standard according to claim 1, wherein the gentle curved surface portion has a curved shape in which the distance from the center of the calibration standard changes linearly with the angle with respect to a perpendicular line extending from the center of the calibration standard to the cut portion.

5. a method for detecting a reflected light from the calibration standard according to any one of claims 1 to 4, wherein a measurement light is emitted from a probe of a shape measuring machine to the calibration standard according to any one of claims 1 to 4, and the reflected light from the calibration standard is detected using the probe; A method for calibrating a shape measuring machine, wherein magnification calibration is performed based on the detection result of the reflected light and the outer diameter and cutting amount of the calibration standard.

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