Measuring device and hole position detection method

Abstract

To provide a measuring apparatus and a hole position detecting method capable of detecting a position of a hole in a workpiece.SOLUTION: A measuring apparatus 1 includes: a table 20 on which a workpiece 9 is placed; a stylus 41 that can be displaced in a direction intersecting a hole forming surface 92 of the workpiece 9; a movement control unit that controls a relative movement mechanism so as to scan the hole forming surface 92 in a direction toward the hole 91 with the stylus 41 contacting the hole forming surface 92; a displacement detection unit that detects the displacement of the stylus 41 while the stylus 41 scans the hole forming surface 92; a measuring unit that generates shape data of the hole forming surface 92 based on the displacement of the stylus 41; an edge detection unit that detects edge points corresponding to an edge of the hole 91 from the shape data; an edge coordinate calculation unit that calculates edge coordinates that are coordinates of the edge points with respect to the table 20; and a center coordinate calculation unit that calculates the center coordinates of a virtual circle passing through at least three edge coordinates as the center coordinates of the hole 91.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a measuring device and a hole position detection method. [Background technology]

[0002] Conventionally, measuring devices such as roundness measuring devices, surface roughness measuring devices, and contour measuring devices are known (see, for example, Patent Document 1). Such measuring devices measure the surface properties of a workpiece by detecting the displacement of a stylus that is in contact with the surface of the workpiece. When measuring the surface properties of the inner surface of a hole formed in the workpiece, the stylus is inserted into the hole in the workpiece and brought into contact with the inner surface of the hole. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-065751 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned measuring device, if the exact position of the hole in the workpiece is unknown, the measurer visually checks the position of the hole in the workpiece to prevent the stylus from coming into contact with the workpiece and being damaged. However, visually checking the position of the hole makes the measurement process more difficult, and the smaller the diameter of the hole in the workpiece, the more difficult it becomes to visually check the position of the hole, which can lead to the stylus coming into contact with the workpiece and being damaged.

[0005] An object of the present invention is to provide a measuring device and a hole position detection method capable of detecting the position of a hole in a workpiece. [Means for solving the problem]

[0006] The measuring device of the present invention comprises a table on which a workpiece having a surface with a circular hole formed therein is placed, a stylus that is displaceable in a direction intersecting the surface of the workpiece, a relative movement mechanism that moves the stylus relative to the table, a movement control unit that controls the relative movement mechanism so that the stylus abuts against the surface of the workpiece and scans the surface in a direction toward the hole, a displacement detection unit that detects the displacement of the stylus while the stylus scans the surface, a measurement unit that generates shape data of the surface based on the displacement of the stylus detected by the displacement detection unit, an edge detection unit that detects an edge point corresponding to an edge of the hole from the shape data, an edge coordinate calculation unit that calculates the edge coordinates, which are the coordinates of the edge point relative to the table, and a center coordinate calculation unit that calculates the center coordinates of a virtual circle passing through at least three of the edge coordinates as the center coordinate of the hole.

[0007] In the present invention, the center coordinates of a hole in a table can be calculated. Therefore, the stylus can be aligned with the center coordinates of the hole before being inserted into the hole, and the stylus can be prevented from contacting the workpiece during insertion. In addition, since there is no need to visually confirm the position of the hole in the workpiece, the workability of the measurement can be improved.

[0008] In the measuring apparatus of the present invention, it is preferable that the edge detection section detects, as the edge point, a point at which the shape data is displaced from a scanning start point by a preset amount. In the present invention, edge points can be easily detected without requiring complicated calculation processing. In addition, by setting the predetermined amount of displacement to a value greater than the surface roughness of the workpiece, erroneous detection of edge points can be suppressed.

[0009] In the measuring device of the present invention, it is preferable that the movement control unit further controls the relative movement mechanism so that the stylus is inserted into the hole while being aligned with the center coordinates. In the present invention, the operation of inserting the stylus into the hole in the workpiece is performed automatically, which can further improve the workability of measurement.

[0010] The present invention is a hole position detection method for detecting the position of a hole formed on the surface of a workpiece in a measuring device comprising a table on which a workpiece is placed and a stylus that can be displaced in a direction intersecting the surface of the workpiece, the method comprising the steps of: a scanning step in which the stylus contacts the surface of the workpiece and scans the surface in a direction toward the hole; a displacement detection step in which the displacement of the stylus is detected during the scanning step; a measurement step in which shape data of the surface is generated based on the displacement of the stylus detected in the displacement detection step; an edge detection step in which an edge point corresponding to the edge of the hole is detected from the shape data; an edge coordinate calculation step in which edge coordinates, which are the coordinates of the edge point on the table, are calculated; and a center coordinate calculation step in which the center coordinates of a virtual circle passing through at least three of the edge coordinates are calculated as the center coordinate of the hole. According to the hole position detection method of the present invention, it is possible to achieve the same effects as those achieved by the above-mentioned measuring device of the present invention. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a side view showing a schematic diagram of a measuring device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view showing the measuring device. [Diagram 3] FIG. 4 is a block diagram showing a control unit of the measurement device. [Figure 4] 5 is a flowchart showing the procedure of a hole position detection method in the measuring device. [Diagram 5] 3 is a schematic diagram showing a state in which a stylus of the measuring device scans a hole forming surface of a workpiece. FIG. [Figure 6] 1A and 1B are schematic diagrams for explaining a method for detecting a hole in a workpiece. [Figure 7] FIG. 4 is a schematic diagram showing edge points in shape data. [Figure 8] 3A to 3C are schematic diagrams showing examples of a hole formation surface, edge coordinates, and hole center coordinates of a workpiece. [Figure 9]13A and 13B are schematic diagrams for explaining a modified example of a method for detecting a hole in a workpiece. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [Measuring device] 1 and 2 are diagrams that diagrammatically show a measurement device 1 according to one embodiment of the present invention. The measuring device 1 of this embodiment is a device that contacts a workpiece 9 (object to be measured) to measure the surface properties of the workpiece 9 (e.g., shape, roundness, surface roughness, etc.), and is equipped with a base 10, a table 20 installed on the upper surface of the base 10, a moving mechanism 30 installed adjacent to the table 20, a detector 40 supported by the moving mechanism 30, and a control unit 50 that controls the operation of each part.

[0013] The table 20 has a cylindrical main body 21 rotatably mounted on the base 10, and a disk-shaped mounting plate 22 mounted on the upper surface of the main body 21 so as to be movable in the horizontal direction. The main body 21 is provided with a motor-driven table rotation mechanism 23 (see FIG. 3), and the main body 21 can be rotated around a rotation axis Cr by the table rotation mechanism 23. The mounting plate 22 can rotate together with the main body 21, and a workpiece 9, which is an object to be measured, is placed on the mounting plate 22. The rotation axis Cr is arranged along the vertical direction.

[0014] An adjustment mechanism 24 is installed on the table 20 to perform an operation of aligning (centering and leveling) the rotation axis Cr of the table 20 with the central axis of the workpiece 9 (for example, the central axis of a circle formed by the outer circumferential surface of the workpiece 9 or the central axis of a hole in the workpiece 9). The adjustment mechanism 24 has a centering mechanism 241 that adjusts the arrangement of the mounting plate 22 relative to the main body 21 in the CX axis direction and the CY axis direction, and a leveling mechanism 242 that adjusts the inclination of the mounting plate 22 in the CX axis direction and the CY axis direction relative to the main body 21 (see FIG. 2). The centering mechanism 241 and the leveling mechanism 242 are each driven by a motor. The CX axis direction and the CY axis direction are perpendicular to the rotation axis Cr and perpendicular to each other, and form an orthogonal coordinate system (table coordinate system) set with respect to the table 20.

[0015] The table 20 is also provided with an angle sensor 25 (see FIG. 3) that detects a rotation angle θ of the table 20 relative to the base 10. The angle sensor 25 is, for example, a rotary encoder, and detects the rotation position of the table 20 relative to a reference rotation position as the rotation angle θ.

[0016] The movement mechanism 30 moves the detector 40 in the X-axis direction, the Y-axis direction, and the Z-axis direction relative to the base 10. The movement mechanism 30, together with the table rotation mechanism 23, constitutes the relative movement mechanism 11 (see FIG. 3), and can move the stylus 41 relative to the table 20. In this embodiment, the vertical direction is defined as the Z-axis direction, the direction approaching or moving away from the table 20 in a plane perpendicular to the Z-axis direction is defined as the X-axis direction, and the direction perpendicular to the Z-axis direction and the X-axis direction is defined as the Y-axis direction. The X-axis direction, Y-axis direction, and Z-axis direction form a three-axis Cartesian coordinate system (base coordinate system) with respect to the base 10.

[0017] Specifically, the moving mechanism 30 includes a column 31 erected on the base 10, a slider 32 provided movably in the Z-axis direction relative to the column 31, a Z-axis drive unit (not shown) that drives the slider 32 in the Z-axis direction, an arm 33 provided movably in the X-axis direction relative to the slider 32, an X-axis drive unit (not shown) that drives the arm 33 in the X-axis direction, a detector support unit 34 provided movably in the Y-axis direction relative to the arm 33 and supporting the detector 40, and a Y-axis drive unit (not shown) that drives the detector support unit 34 in the Y-axis direction. Each of the Z-axis drive unit, the X-axis drive unit, and the Y-axis drive unit includes a motor, and a ball screw mechanism or a rack-and-pinion mechanism connected to the motor.

[0018] The moving mechanism 30 is also provided with a position sensor 35 (see FIG. 3) that detects the position of the detector 40 in the base coordinate system. The position sensor 35 includes, for example, a Z scale that detects the position of the slider 32 in the Z axis direction, an X scale that detects the position of the arm 33 in the X axis direction, and a Y scale that detects the position of the detector support part 34 in the Y axis direction.

[0019] The moving mechanism 30 is also provided with a rotation mechanism (not shown) for changing the attitude of the detector 40. This rotation mechanism changes the attitude of the detector 40, for example, by rotating the detector support part 34 about a rotation axis Cx provided on the arm 33 along the X-axis direction.

[0020] The detector 40 has a stylus 41 and a displacement detection unit 42 . The stylus 41 comes into contact with the surface of the workpiece 9 in the Z-axis direction or the X-axis direction, and can be displaced along the surface of the workpiece 9. In addition, the attitude of the stylus 41 with respect to the displacement detection unit 42 can be changed depending on the content of the measurement. The displacement detection unit 42 supports the stylus 41 so that it can be displaced, and detects the displacement of the stylus 41 .

[0021] The control unit 50 is configured by a computer and includes a memory, an arithmetic circuit, etc. The control unit 50 functions as a movement control unit 51, a measurement unit 52, and a hole position detection unit 53, as shown in Fig. 3, by the arithmetic circuit executing various programs recorded in the memory.

[0022] The movement control unit 51 controls the relative position of the stylus 41 with respect to the workpiece 9 by controlling the movement mechanism 30 or the table rotation mechanism 23 .

[0023] The measuring unit 52 can measure the surface properties (eg, shape, roundness, surface roughness, etc.) of the workpiece 9 based on the displacement of the stylus 41 detected by the displacement detecting unit . For example, the measurement unit 52 can measure the surface properties of the workpiece 9 based on the displacement of the stylus 41 detected by the displacement detection unit 42 and the position of the detector 40 detected by the position sensor 35. The measurement unit 52 can also measure the roundness of the workpiece 9 based on the displacement of the stylus 41 detected by the displacement detection unit 42 and the rotation angle θ of the table 20 detected by the angle sensor 25.

[0024] The hole position detection unit 53 detects the position of a hole when the hole is formed on the surface of the workpiece 9. The hole position detection unit 53 includes an edge detection unit 531, an edge coordinate calculation unit 532, and a center coordinate calculation unit 533, which will be described later.

[0025] [Hole position detection method] The measuring device 1 of this embodiment implements a hole position detection method for detecting the position of a hole when measuring the inner surface of the hole in the workpiece 9. This hole position detection method will be described with reference to the flowchart of FIG. 5, the hole 91 in the workpiece 9 opens in a hole forming surface 92, which is a planar surface of the workpiece 9, and is formed along an arbitrary central axis Ch with respect to the workpiece 9 as the center. The cross section of the hole 91 intersecting with the central axis Ch is circular.

[0026] As a preparation before carrying out the hole position detection method of this embodiment, the workpiece 9 is placed on the table 20 so that the center axis Ch of the hole 91 is along the Z-axis direction. The center axis Ch of the hole 91 is preferably placed near the rotation axis Cr, but does not have to coincide with the rotation axis Cr. Moreover, the diameter of the tip of stylus 41 used in measuring device 1 is smaller than the diameter of the cross-sectional shape of hole 91. Moreover, detector 40 has its posture adjusted by a turning mechanism and is disposed at an angle with respect to the Z-axis direction.

[0027] First, the measuring device 1 scans and measures the hole forming surface 92 of the workpiece 9 in one direction (step S1). 5, the movement control unit 51 controls the moving mechanism 30 to bring the stylus 41 into contact with an arbitrary scanning start point Ps on the hole formation surface 92 with a predetermined pressure. Thereafter, the movement control unit 51 controls the moving mechanism 30 to move the stylus 41 along the X-axis direction toward the hole 91 and scan the hole formation surface 92 (scanning step). Note that the scanning line from the scanning start point Ps toward the hole 91 does not need to pass through the center of the hole 91, allowing rough positioning. During scanning of the hole forming surface 92, the displacement detection unit 42 detects the displacement of the stylus 41 in the Z-axis direction (displacement detection step), and the position sensor 35 detects the position of the detector 40 in the base coordinate system. The measurement unit 52 generates shape data Sm indicating the shape of the hole forming surface 92 of the workpiece 9 based on the detection values ​​input from the displacement detection unit 42 and the position sensor 35 (measurement step).

[0028] 6, the stylus 41 scanning the hole formation surface 92 is displaced in the Z-axis direction when it drops from the hole formation surface 92 into the hole 91. When the stylus 41 completely reaches the hole 91, the movement control unit 51 detects that the pressure applied to the stylus 41 from the workpiece 9 has dropped below a predetermined pressure, and the scanning of the hole formation surface 92 is terminated.

[0029] 7, the edge detection unit 531 detects edge points Pn corresponding to the edges of the hole 91 from the shape data Sm generated in step S1 (step S2; edge detection step). Specifically, the edge detection unit 531 detects, as the edge point Pn, a data point when the shape data Sm is displaced by a predetermined amount D from the scanning start point Ps. Here, the predetermined amount D is an arbitrary displacement amount that is set in advance, and is preferably set to a value larger than the range that includes the surface roughness of the hole formation surface 92 so as to avoid erroneous detection of the edge point Pn.

[0030] Next, the edge coordinate calculation unit 532 calculates the coordinates (edge ​​coordinates) of the edge point Pn in the table coordinate system (step S3; edge coordinate calculation step). For example, the edge coordinate calculation unit 532 can calculate the edge coordinates by acquiring the coordinates of the edge point Pn in the base coordinate system from the shape data Sm, and converting the coordinates in the base coordinate system into coordinates in the table coordinate system based on the rotation angle θ of the table 20 detected by the angle sensor 25 and the origin position of the table coordinate system in the base coordinate system (the position of the rotation axis Cr).

[0031] Next, the control unit 50 determines whether or not three or more edge coordinates have been calculated (step S4). If the number of edge coordinates is less than three (step S4; No), the movement control unit 51 controls the table rotation mechanism 23 to rotate the table 20 by an arbitrary angle (for example, 120 degrees). Then, the movement control unit 51 controls the movement mechanism 30 to position the stylus 41 at the same base coordinates as at the start of the previous step S1. As a result, the scanning start point Ps of the hole formation surface 92 in the next step S1 is changed from the scanning start point Ps of the hole formation surface 92 in the previous step S1 (step S5). That is, the scanning direction is changed from that in the previous step S1.

[0032] Thereafter, the above-mentioned steps S1 to S4 are performed again. According to this flow, as shown in Fig. 8, the stylus 41 scans the hole formation surface 92 of the workpiece 9 sequentially along a plurality of mutually different directions toward the hole 91. As a result, a plurality of edge points Pn (P1 to P3 in Fig. 8) are detected, and the edge coordinates of each edge point Pn are calculated.

[0033] When three or more edge coordinates are calculated (step S4; Yes), the center coordinate calculation unit 533 selects any three edge coordinates (for example, the coordinates of edge points P1 to P3). Then, as shown in Fig. 8, the center coordinate calculation unit 533 calculates the center coordinates Ph (CXph, CYph) of a virtual circle VC that passes through the three edge coordinates (CXp1, CYp1), (CXp2, CYp2), and (CXp3, CYp3) (step S6; center coordinate calculation step). This calculation method can use a general circle equation, so details will be omitted. The center coordinate Ph (CXph, CYph) of the imaginary circle VC calculated here corresponds to the position of the center axis Ch of the hole 91 of the workpiece 9 on the table 20 (center coordinate of the hole 91). Therefore, the center coordinate calculation unit 533 calculates the center coordinate of the imaginary circle VC, whereby the center coordinate of the hole 91 is found. This completes the flow of the hole position detection method of this embodiment.

[0034] [Insert stylus] After carrying out the above-described hole position detection method, the measuring device 1 can insert the stylus 41 into the hole 91 and perform any measurement of the inner surface of the hole 91 (such as the shape, roundness, or surface roughness).

[0035] A method for inserting the stylus 41 will now be briefly described. First, the attitude of the detector 40 is adjusted by the rotation mechanism, and the detector 40 is disposed along the Z-axis direction. As a result, the stylus 41 is disposed along the depth direction of the hole 91. Furthermore, the movement control unit 51 controls the movement mechanism 30 and the table rotation mechanism 23 to align the stylus 41 with the center coordinates of the hole 91 in the table 20. For example, the movement control unit 51 controls the table rotation mechanism 23 so that the table 20 is located at the rotation reference position, and controls the movement mechanism 30 so that the stylus 41 is located at the center coordinates of the hole 91 when the table 20 is at the rotation reference position. Thereafter, the movement control unit 51 controls the movement mechanism 30 to lower the stylus 41. As a result, the stylus 41 is inserted into the hole 91.

[0036] After the stylus 41 is inserted into the hole 91, the measuring device 1 may perform centering so that the central axis Ch of the hole 91 coincides with the rotation axis Cr of the table 20. The centering may be performed by a conventional method. Alternatively, the adjustment mechanism 24 may be adjusted using the central coordinates of the hole 91 so that the central coordinates of the hole 91 coincide with the rotation axis Cr of the table 20.

[0037] 〔effect〕 In this embodiment, as described above, the central coordinates of the hole 91 in the table 20 can be detected. Therefore, the stylus 41 can be aligned with the central coordinates of the hole 91 before being inserted into the hole 91, and the stylus 41 can be prevented from contacting the workpiece 9 during insertion. Also, since there is no need to visually confirm the position of the hole 91 in the workpiece 9, the workability of the measurement can be improved.

[0038] The edge detection unit 531 of this embodiment detects, as an edge point Pn, a data point when the shape data Sm is displaced a predetermined amount D from the scanning start point Ps. According to this method, the edge point Pn corresponding to the edge of the hole 91 can be easily detected without requiring complicated calculation processing. In addition, by setting the predetermined amount of displacement D to a value larger than the surface roughness of the workpiece 9, erroneous detection of the edge point Pn can be suppressed.

[0039] The movement control unit 51 of this embodiment controls the movement mechanism 30 so that the stylus 41 is inserted into the hole 91 while being aligned with the center coordinates of the hole 91. This allows the operation of inserting the stylus 41 into the hole 91 in the workpiece 9 to be performed automatically, further improving the workability of the measurement.

[0040] [Modifications] The present invention is not limited to the above-described embodiment, and modifications within the scope of the present invention are included in the present invention.

[0041] In the above embodiment, the movement control unit 51 ends the scanning of the hole forming surface 92 when the stylus 41 reaches the hole 91. As a variation of this embodiment, the movement control unit 51 may cause the stylus 41 to scan the hole forming surface 92 so as to cross the hole 91, without ending the scanning even when the stylus 41 reaches the hole 91, as shown in FIG. In this case, the shape data Sm is displaced in the Z-axis direction at the timing when the stylus 41 falls from the hole formation surface 92 into the hole 91, and at the timing when the stylus 41 rises from the hole 91 onto the hole formation surface 92. Based on the shape data Sm, the edge detection unit 531 can detect, as edge points Pn, a data point at a point in time displaced a predetermined amount D from the scanning start point Ps, and a data point at a start point after that point in time displaced the predetermined amount D to the same position in the Z-axis direction as the scanning start point Ps. According to this modified example, by scanning the hole forming surface 92 of the workpiece 9 in any two directions, a total of four edge points Pn can be detected.

[0042] In the embodiment, the edge detection unit 531 detects a point at which the shape data Sm is displaced from the scanning start point Ps by a preset amount D as the edge point Pn, but the method of detecting the edge point Pn is not limited to this. For example, the position of the hole formation surface 92 may be calculated from the shape data Sm, and a point at which the shape data Sm is displaced from the position by a preset amount may be detected as the edge point Pn.

[0043] In the embodiment, the measuring device 1 functions as a roundness measuring machine. In a variation of this embodiment, the measuring device 1 does not have to function as a roundness measuring machine, and the table 20 may be a linear motion table that moves in the X-axis direction or the Y-axis direction relative to the base 10. In this case, the movement control unit 51 may control a movement mechanism of a linear motion table on which the workpiece 9 is placed, thereby moving the stylus 41 relative to the workpiece 9. That is, the relative movement mechanism of the present invention may include a movement mechanism of the linear motion table. For example, in the above-mentioned step S1, the movement control unit 51 may control the movement mechanism of the linear motion table to cause the stylus 41 to scan the hole formation surface 92 of the workpiece 9. Also, in the above-mentioned step S5, the movement control unit 51 may change the scanning start point Ps by controlling the movement mechanism of the linear motion table. Even with this modification, the position of the hole 91 in the workpiece 9 can be detected, similarly to the above embodiment.

[0044] In addition, in the above embodiment, a surface texture measuring machine that measures the surface texture of the workpiece 9 is exemplified as the measuring device 1, but the present invention is not limited to this. The measuring device of the present invention may be any measuring device having a stylus, such as a three-dimensional measuring device capable of scanning measurement. [Explanation of symbols]

[0045] 1...measuring device, 10...base, 11...relative movement mechanism, 20...table, 21...main body, 22...mounting plate, 23...table rotation mechanism, 24...adjustment mechanism, 241...centering mechanism, 242...leveling mechanism, 25...angle sensor, 30...movement mechanism, 31...column, 32...slider, 33...arm, 34...detector support part, 35...position sensor, 40...detector, 41...stylus, 42...displacement detection part, 5 0...control unit, 51...movement control unit, 52...measurement unit, 53...hole position detection unit, 531...edge detection unit, 532...edge coordinate calculation unit, 533...center coordinate calculation unit, 9...workpiece, 91...hole, 92...hole formation surface, Ch...center axis, Cr...rotation axis, D...predetermined amount, P1...edge point, P2...edge point, P3...edge point, Pn...edge point, Ps...scanning start point, Sm...shape data, VC...virtual circle, θ...rotation angle.

Claims

1. a table on which a workpiece having a surface on which a circular hole is formed is placed; a stylus displaceable in a direction intersecting the surface of the workpiece; a relative movement mechanism for moving the stylus relative to the table; a movement control unit that controls the relative movement mechanism so that the stylus contacts the surface of the workpiece and scans the surface in a direction toward the hole; a displacement detector for detecting a displacement of the stylus while the stylus scans the surface; a measurement unit that generates shape data of the surface based on the displacement of the stylus detected by the displacement detection unit; an edge detection unit that detects edge points corresponding to edges of the holes from the shape data; an edge coordinate calculation unit that calculates edge coordinates that are coordinates of the edge point with respect to the table; a center coordinate calculation unit that calculates, as a center coordinate of the hole, a center coordinate of a virtual circle that passes through at least three of the edge coordinates.

2. 2. The measuring device according to claim 1, wherein the edge detection section detects, as the edge point, a point at which the shape data is displaced from a scanning start point by a preset amount.

3. The measuring device according to claim 1 or 2, wherein the movement control unit further controls the relative movement mechanism so that the stylus is inserted into the hole while being aligned with the center coordinates.

4. A hole position detection method for detecting a position of a hole formed on a surface of a workpiece in a measuring device including a table on which a workpiece is placed and a stylus displaceable in a direction intersecting a surface of the workpiece, the method comprising: a scanning step in which the stylus contacts the surface of the workpiece and scans the surface in a direction toward the hole; a displacement detection step of detecting a displacement of the stylus during the scanning step; a measurement step of generating shape data of the surface based on the displacement of the stylus detected in the displacement detection step; an edge detection step of detecting edge points corresponding to edges of the holes from the shape data; an edge coordinate calculation step of calculating edge coordinates which are coordinates of the edge points in the table; A center coordinate calculation step is carried out to calculate center coordinates of a virtual circle passing through at least three of the edge coordinates as center coordinates of the hole. A hole position detection method comprising:

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