JP2011095245A - Shape measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shape measuring device capable of improving measurement accuracy by an optical cutting method. <P>SOLUTION: In this shape measuring device, a rotation error around a driving shaft in the X-direction of an optical cutting probe 22 is detected, based on a difference of each Y-coordinate of each center position of a reference sphere 31 determined by twice measuring processings performed separately at a prescribed interval dz in the Z-direction. Further, a rotation error around the driving shaft in the Z-direction of the optical cutting probe 22 is detected by performing converging calculation, based on a difference of each Y-coordinate of each center position of the reference sphere 31 determined by twice measuring processings performed separately at a prescribed interval dx in the X-direction. A rotation error around the driving shaft in the Y-direction of the optical cutting probe 22 is detected, based on a difference of each X-coordinate of each center position of the reference sphere 31 determined by twice measuring processings performed separately at a prescribed interval dz in the Z-direction, or based on inclination to a reference surface of a plane determined by a measuring processing by performing the measuring processing by using the known reference surface 32 orthogonal to the Z-axis as a specimen. This invention can be applied to, for example, a three-dimensional measuring device by the optical cutting method. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a shape measuring apparatus, and more particularly to a shape measuring apparatus that can improve measurement accuracy by a light cutting method.

  Conventionally, in the light cutting method in which the line pattern is irradiated to measure the surface shape of the test object, the line pattern is scanned in a direction orthogonal to the line pattern irradiated to the test object, and according to the surface shape of the test object. The deformed line pattern is continuously imaged. And the data of the three-dimensional surface shape of a test object are constructed | assembled by performing the process which arranges the shape of the line pattern reflected on the image imaged continuously in a scanning direction.

  Moreover, in the measuring apparatus disclosed by patent document 1, a shape sensor is arrange | positioned by arrange | positioning a reference sphere in the location which does not interfere with the measurement on the base | substrate which mounts a test object, and measuring the center position of a reference sphere. A calibration operation for correcting the position of is performed.

JP 2009-14613 A

  By the way, in the measurement apparatus as described above, based on the premise that the line pattern is scanned in a direction orthogonal to the line pattern, from the image on which the test object irradiated with the line pattern is reflected, Three-dimensional surface shape data is constructed. Therefore, if the scanning direction is not exactly orthogonal to the line pattern, the three-dimensional surface shape of the test object cannot be accurately constructed, and the measurement accuracy is lowered.

  The present invention has been made in view of such a situation, and is intended to improve the measurement accuracy by the light cutting method.

  The shape measuring device of the present invention is a shape measuring device for measuring a three-dimensional surface shape of a test object, the irradiation means for projecting a line pattern on the test object, and the line pattern projected onto the test object Imaging means for imaging a test object, drive means for driving the irradiation means and the test object relatively along drive axes in the X, Y, and Z directions orthogonal to each other, and the driving The plurality of images sequentially captured by the imaging unit are acquired while the irradiation unit and the test object are relatively moved in the Y direction by the unit, and the plurality of images are copied to the plurality of images. The shape measurement data construction means for constructing the shape measurement data of the test object from the shape of the line pattern, the reference sphere formed in a spherical shape, and the rotation error of the attitude of the irradiation means with respect to each drive axis of the drive means Error detection to detect The error detection means acquires at least a plurality of shape measurement data obtained by the shape measurement data construction means, separated by a predetermined distance in the Z direction, with the reference sphere as the test object. Obtaining the center position of the reference sphere obtained from the shape measurement data for at least two of the plurality of shape measurement data, and based on the difference of the obtained center position of the reference sphere, the irradiation means A rotation error about the drive axis in the X direction with respect to the optical axis direction of the optical axis, and the shape measurement data construction unit is configured to measure the shape measurement data of the object based on the rotation error information obtained from the error detection unit. It is characterized by correcting.

  In the shape measuring apparatus of the present invention, at least a plurality of times of shape measurement data, which is performed while being separated by a predetermined distance in the Z direction with the reference sphere as the test object, are acquired, and at least two times of the plurality of times of shape measurement data are acquired. The center positions of the reference spheres obtained from the shape measurement data are acquired, and a rotation error around the drive axis in the X direction with respect to the optical axis direction is detected based on the difference between the acquired center positions of the reference spheres. Then, based on the obtained rotation error information, the shape measurement data of the test object is corrected.

  According to the shape measuring apparatus of the present invention, it is possible to improve the measurement accuracy by the light cutting method.

It is a perspective view which shows the structural example of one Embodiment of the shape measuring apparatus to which this invention is applied. It is a figure which shows the structural example of the optical cutting probe of a shape measuring apparatus. It is a figure explaining the process which detects the error of the attitude | position of the optical cutting probe with respect to a drive-axis coordinate system. It is a figure explaining the relationship between the rotation error around the X-axis and the measurement data of the reference sphere. It is a figure explaining the relationship between the rotation error around a Z-axis, and the measurement data of a reference sphere. It is a figure explaining the relationship between the rotation error around the Y-axis and the measurement data of the reference sphere. It is a flowchart explaining the rotation error detection process which detects the rotation error of an optical cutting probe.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing a configuration example of an embodiment of a shape measuring apparatus to which the present invention is applied.

  The shape measuring device 11 is a three-dimensional measuring device that three-dimensionally measures the surface shape of the test object 12 by a light cutting method. In the shape measuring apparatus 11, the light cutting probe 22 scans in a direction orthogonal to the line pattern while irradiating the test object 12 placed on the surface plate 21 from the light cutting probe 22 with the line pattern. Then, the surface shape of the test object 12 is measured.

  The optical cutting probe 22 is moved in the Z direction along the vertical direction, and in the X direction and the Y direction orthogonal to each other as the Z stage 23 and the column 25 are driven. Hereinafter, a coordinate system composed of the X direction, the Y direction, and the Z direction as shown in FIG. 1 will be referred to as a drive axis coordinate system.

  That is, the light cutting probe 22 is attached to the lower end of a Z stage 23 elongated in the Z direction, and the Z stage 23 is attached to a column 25 having a beam portion 24 extending in the Y direction. The Z stage 23 is driven along the beam portion 24 of the column 25 and is driven along its longitudinal direction. The column 25 has a U-shape in which both ends of the beam portion 24 are supported by legs, and one leg is guided by a guide 26 provided on the surface plate 21 and is driven in the X direction. Of the leg portions of the column 25, the lower end of the leg portion on which the guide 26 is not provided is an air guide, for example.

  Further, the surface plate 21 has a position within the range where measurement by the optical cutting probe 22 is possible and does not interfere with the measurement of the test object 12, for example, a peripheral portion of the range where measurement on the surface plate 21 is possible. In addition, a reference sphere 31 and a reference surface 32 are arranged. The reference sphere 31 is a spherical member formed with a predetermined sphericity. The reference surface 32 is a plane formed with a predetermined flatness so as to be orthogonal to the Z axis.

  FIG. 2 is a diagram illustrating a configuration example of the light cutting probe 22 of the shape measuring apparatus 11.

  FIG. 2 shows a state in which the light cutting probe 22 irradiates the reference sphere 31 with a line pattern. The light cutting probe 22 includes an irradiation unit 41 that irradiates the reference sphere 31 with a line pattern, and an imaging unit 42 that images the reference sphere 31 irradiated with the line pattern.

  The optical cutting probe 22 is arranged such that the optical axis L1 of the optical system of the irradiation unit 41 and the optical axis L2 of the optical system of the imaging unit 42 are at a predetermined angle (for example, 45 °). 42 is incorporated. Further, the light cutting probe 22 is attached to the tip of the Z stage 23 in FIG. 1 so that the optical axis L1 of the irradiation unit 41 coincides with the Z direction and the longitudinal direction of the line pattern coincides with the X direction.

  The light emitting element 51 of the irradiation unit 41 is configured by, for example, an LED (Light Emitting Diode) or an LD (Laser Diode). The h-plane shown in FIG. 2 is a plane having an optical axis L1 perpendicular to the intersection of the optical axis L1 of the optical system of the irradiation unit 41 and the optical axis L2 of the imaging unit 42. The light beam emitted from the light emitting element 51 is stretched in the X direction by the line generator lens 53, and the cross-sectional shape of the light beam becomes a line pattern shape and is irradiated to the reference sphere 31. The line generator lens 53 can be constituted by, for example, a cylindrical lens.

  The imaging device 55 of the imaging unit 42 is configured by, for example, a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) sensor, and the reference sphere 31 irradiated with the line pattern via the imaging lens 54. Take an image. The imaging element 55 supplies image data obtained by imaging the reference sphere 31 to the control device 61 that performs various controls on the shape measuring device 11.

  The control device 61 includes a shape data construction unit 62, an error detection unit 63, and a drive control unit 64. The shape data construction unit 62 measures the three-dimensional surface shape of the reference sphere 31 based on the position of each part of the line pattern deformed according to the surface shape of the reference sphere 31 shown in the image from the image sensor 55. Build up. The shape data constructing unit 62 also corrects the measurement data based on error information detected by an error detecting unit 63 described later. As will be described later with reference to FIG. 3, the error detection unit 63 detects an error in the attitude of the optical cutting probe 22 with respect to the drive axis coordinate system in which the Z stage 23 and the column 25 of FIG. An error in the direction of the optical axis L1 of the optical system of the unit 41 is detected. The drive control unit 64 controls the drive of the Z stage 23 and the column 25 and moves the optical cutting probe 22 along the drive axis coordinate system.

  For example, when the drive control unit 64 drives the Z stage 23 and the optical cutting probe 22 moves in the Z direction, the measurable range W in the Z direction by the optical cutting probe 22 moves. The measurable range W in the Z direction by the light cutting probe 22 has the height h in the Z direction at the intersection of the optical axis L1 of the optical system of the irradiation unit 41 and the optical axis L2 of the optical system of the imaging unit 42 as the measurement center. This is a range in the Z direction (that is, a range that is W / 2 above the height h and W / 2 below the height h), and is a range determined by the viewing angle of the imaging unit 42.

  Further, when the drive control unit 64 drives the column 25 and the light cutting probe 22 moves in the X direction, the measurement region viewed from the Z direction moves in the X direction. This measurement region is an XY plane (including an intersection point between the optical axis L1 of the optical system of the irradiation unit 41 and the optical axis L2 of the optical system of the imaging unit 42) when a line pattern along the X direction is scanned in the Y direction. That is, it is an area (an area surrounded by a dotted line in FIG. 3B described later) irradiated with a line pattern on the XY plane at the height h.

  In the shape measuring apparatus 11 configured as described above, the light cutting probe 22 is moved under the control of the drive control unit 64 and the three-dimensional surface shape of the test object 12 is measured. That is, the light cutting probe 22 is scanned in the Y direction while irradiating the test object 12 with the line pattern along the X direction, and the shape data construction unit 62 projects the images continuously captured by the imaging unit 42. The three-dimensional shape data of the test object 12 is constructed by performing the process of arranging the shape of the line pattern to be arranged in the scanning direction.

  As described above, the shape measuring device 11 constructs three-dimensional shape data of the test object 12, but the optical cutting with respect to the reference coordinate axis set by the shape measuring device 11 due to an assembly error of the shape measuring device 11 or the like. A slight error may occur in the posture of the probe 22. Therefore, when an error has occurred in the posture of the light cutting probe 22, the surface of the test object 12 must be processed unless processing for constructing the three-dimensional shape data of the test object 12 is performed in consideration of the error. The position of the shape cannot be measured accurately.

  Therefore, the shape measuring apparatus 11 measures the reference sphere 31 and the reference surface 32 before measuring the test object 12, and based on the measurement result, the error in the attitude of the optical cutting probe 22 with respect to the drive axis coordinate system. In particular, processing for detecting a rotation error Rx around the X axis, a rotation error Ry around the Y axis, and a rotation error Rz around the Z axis as errors in the optical axis direction of the irradiation unit 41 (rotation of the flowchart of FIG. 7 described later) Error detection processing) is performed. In this embodiment, an example in which a coordinate system is set for the drive axis will be described. However, the present invention can be applied to other coordinate systems.

  Next, a process for detecting an error in the posture of the optical cutting probe 22 with respect to the drive axis coordinate system will be described with reference to FIG.

  3A is a diagram for explaining processing for detecting the rotation error Rx around the X axis, FIG. 3B is a diagram for explaining processing for detecting the rotation error Rz around the Z axis, and FIG. 3C is a diagram showing the Y axis. It is a figure explaining the process which detects the surrounding rotation error Ry.

  First, a process for detecting the rotation error Rx around the X axis will be described.

  For example, a distance from an attachment reference position serving as a reference when the light cutting probe 22 is attached to the Z stage 23 to the center of the reference sphere 31 is Lx. Then, the optical cutting with respect to the coordinates of the center position of the reference sphere 31 obtained from the surface shape data of the reference sphere 31 when the optical cutting probe 22 is ideally attached to the drive axis coordinate system without causing an error. The error (ΔX, ΔY, ΔZ) of the coordinates of the center position of the reference sphere 31 obtained from the surface shape data of the reference sphere 31 when the rotation error Rx around the X axis occurs in the probe 22 is expressed by the following equation (1). It is represented by

(ΔX, ΔY, ΔZ)
= (0, Lx × sin (Rx), Lx × (cos (Rx) −1))
≒ (0, Lx x Rx, 0)
... (1)

  However, in Formula (1), since it is estimated that the rotation error Rx around the X-axis generated in the shape measuring apparatus according to the present embodiment is a minute amount, first-order approximation is performed.

  As shown in Expression (1), if the distance Lx is known, the surface shape data of the reference sphere 31 is measured, and the coordinates of the center position of the sphere are calculated, whereby the rotation error Rx around the X axis is calculated. Can be calculated. However, it is difficult to accurately measure the distance Lx.

  Therefore, in the process of detecting the rotation error Rx around the X axis, as shown in FIG. 3A, the surface shape of the reference sphere 31 is measured twice by moving the position of the optical cutting probe 22 in the Z direction at an interval dz. The coordinates of the center position are calculated for each measurement. That is, two measurements are performed such that the line pattern is irradiated to two measurement regions (two regions surrounded by a dotted line in FIG. 3A) that are separated by a distance dz in the Z direction.

  Here, if the distance from the attachment reference position in the first measurement to the center of the reference sphere 31 is Lx1, and the distance from the attachment reference position in the second measurement to the center of the reference sphere 31 is Lx2, the first measurement. The error (ΔX1, ΔY1, ΔZ1) of the center coordinate of the reference sphere 31 and the error (ΔX2, ΔY2, ΔZ2) of the center coordinate of the reference sphere 31 in the second measurement are expressed by the following equation (2). .

(ΔX1, ΔY1, ΔZ1) ≈ (0, Lx1 × Rx, 0)
(ΔX2, ΔY2, ΔZ2) ≈ (0, Lx2 × Rx, 0)
... (2)

  Therefore, the rotation error Rx around the X axis can be obtained from the following equation (3) from the equation (2).

Rx = (ΔY1−ΔY2) / (Lx1−Lx2)
... (3)

  Here, the distances Lx1 and Lx2 are set and measured so that the difference (Lx1−Lx2) between the distances Lx1 and Lx2 in the measurement performed twice is the distance dz moved in the Z direction of the light cutting probe 22. When the above is performed, the above equation (3) is expressed by the following equation (4).

Rx = (Y1-Y2) / dz
... (4)

  However, in Formula (4), Y1 is the Y coordinate of the center of the reference sphere 31 in the first measurement, and Y2 is the Y coordinate of the center of the reference sphere 31 in the second measurement. As described above, the rotation error Rx around the X axis is measured twice by changing the position of the light cutting probe 22 in the Z direction at the interval dz, and the Y coordinate of the reference sphere 31 obtained by the two measurements. It can be obtained from the difference between Y1 and Y coordinate Y2.

  Here, with reference to FIG. 4, it will be described that a difference occurs between the Y coordinate Y1 and the Y coordinate Y2 of the measurement data of the reference sphere 31 due to the rotation error Rx around the X axis.

  4A schematically shows a line pattern irradiated on the reference sphere 31 in the first measurement process, and FIG. 4B shows a line pattern irradiated on the reference sphere 31 in the second measurement process. It is shown schematically. As shown in the figure, the optical cutting probe 22 is tilted around the X axis with a rotation error Rx, and the surface of the reference sphere 31 is irradiated with a line pattern tilted with the rotation error Rx with respect to the Z axis.

  Then, in the shape data construction unit 62 (FIG. 2), on the premise that the light cutting probe 22 is not inclined (the optical axis of the irradiation unit 41 is set parallel to the Z axis), that is, the surface of the reference sphere 31 Suppose that the three-dimensional shape data of the test object 12 is constructed on the basis of the first and second measurement data on the assumption that the line pattern irradiated to the Z axis is the same as viewed from the X direction. . In this case, since the processing is actually performed on the assumption that the line pattern inclined with respect to the Z-axis is along the Z-axis, as shown in FIG. 4C, the shape data constructed based on the first measurement data The position is shifted in the Y direction between the (circular indicated by the solid line) and the shape data (circular indicated by the broken line) constructed based on the second measurement data. As described above, an error occurs in the measurement of the reference sphere 31 due to a shift in the projection direction of the line pattern (rotation error Rx).

  Therefore, based on the difference between the Y coordinate Y1 and the Y coordinate Y2 of each shape data, the rotation error Rx is obtained from the above equation (4), and the rotation error Rx is applied to apply the three-dimensional shape of the reference sphere 31. By performing the process of constructing data, the shape of the reference sphere 31 is accurately measured, that is, as shown by the two-dot chain line in FIG. 4C, the reference sphere 31 in an ideal position where no error occurs. Shape data can be obtained.

  In addition, an arbitrary value can be selected as the diameter of the reference sphere 31, but it is desirable to select a value that is twice or more the interval dz. For example, when the measurable range W is 20 mm and the distance dz is 20 mm, if the diameter of the reference sphere 31 is 40 mm or more, the measurement is performed so that the measurable ranges W do not overlap. Further, even when the diameter of the reference sphere 31 is less than 40 mm, the measurement can be performed with the interval dz narrowed.

  Next, in the process of detecting the rotation error Rz around the Z axis, similarly to the process of detecting the rotation error Rx around the X axis, the surface shape of the reference sphere 31 is measured twice, and for each measurement result. Calculate the coordinates of the center position. That is, in the process of detecting the rotation error Rz around the Z axis, as shown in FIG. 3B, the position of the optical cutting probe 22 is moved in the X direction by the interval dx, and the coordinates of the center position of the reference sphere 31 are set twice. taking measurement. That is, two measurements are performed such that the line pattern is irradiated to two measurement regions (two regions surrounded by a dotted line in FIG. 3B) whose center positions are separated by a distance dx in the X direction.

  For example, the distance from the optical axis L1 of the optical system of the irradiation unit 41 to the center of the reference sphere 31 when viewed from the Z direction is Lz. Then, the optical cutting with respect to the coordinates of the center position of the reference sphere 31 obtained from the surface shape data of the reference sphere 31 when the optical cutting probe 22 is ideally attached to the drive axis coordinate system without causing an error. The error (ΔX, ΔY, ΔZ) of the coordinates of the center position of the reference sphere 31 obtained from the surface shape data of the reference sphere 31 when the rotation error Rz around the Z axis occurs in the probe 22 is expressed by the following equation (5). It is represented by

(ΔX, ΔY, ΔZ)
= (Lz × (cos (Rz) −1), Lz × sin (Rz), 0)
≒ (0, Lz x Rz, 0)
... (5)

  However, in the equation (5), the first order approximation is performed because the rotation error Rz around the Z axis is a minute amount.

  Then, as shown in FIG. 3B, the second measurement is performed by changing the position of the light cutting probe 22 by the distance dx in the X direction, and the rotation error Rx around the X axis is obtained. If the Y coordinate of the center of the reference sphere 31 in Y is Y1, and the Y coordinate of the center of the reference sphere 31 in the second measurement is Y2, the rotation error Rz around the Z axis is obtained by the following equation (6).

Rz = (Y1-Y2) / dx
... (6)

  As described above, the rotation error Rz around the Z axis is measured twice by changing the position of the light cutting probe 22 in the X direction at the interval dx, and the center of the reference sphere 31 obtained by the two measurements is measured. It can be obtained from the difference between the Y coordinate Y1 and the Y coordinate Y2.

  Here, with reference to FIG. 5, it will be described that a difference occurs between the Y coordinate Y1 and the Y coordinate Y2 of the measurement data of the reference sphere 31 due to the rotation error Rz around the Z axis.

  FIG. 5A schematically shows a line pattern irradiated on the reference sphere 31 in the first measurement process, and FIG. 5B shows a line pattern irradiated on the reference sphere 31 in the second measurement process. It is shown schematically. As shown in the figure, the optical cutting probe 22 (the line pattern irradiated by it) is inclined with a rotation error Rz around the Z axis, and the surface of the reference sphere 31 is inclined with the rotation error Rz with respect to the X axis. Each pattern is irradiated.

  Therefore, when the three-dimensional shape data of the test object 12 is constructed based on the first and second measurement data without considering the rotation error Rz, as shown in FIG. 5C, the first measurement data The position data in the Y direction is misaligned between the shape data constructed based on (circle indicated by a solid line) and the shape data constructed based on the second measurement data (circle indicated by a broken line). End up. As described above, an error occurs in the measurement of the reference sphere 31 due to the deviation of the projection direction of the line pattern (rotation error Rz).

  Therefore, based on the difference between the Y coordinate Y1 and Y coordinate Y2 of each shape data, the rotation error Rz is obtained from the above equation (6), and the rotation error Rz is applied to apply the three-dimensional shape of the reference sphere 31. By performing the process of constructing the data, the shape data of the reference sphere 31 at an ideal position where no error occurs can be obtained as shown by a two-dot chain line in FIG. 5C.

  By the way, the line light is irradiated to different areas on the surface of the reference sphere 31 in the first measurement process and the second measurement process. Therefore, depending on the sphericity of the reference sphere 31, the rotation error Rz is accurately set. It can be difficult to find. For example, a value different from the actual rotation error Rz may be calculated due to a subtle difference in the surface shape to be measured between the first measurement process and the second measurement process.

  That is, when obtaining the rotation error Rx around the X axis, as shown in FIG. 4, the areas irradiated with the line pattern overlap in the first measurement process and the second measurement process, and are substantially the same. Since the rotation error Rx can be obtained from the measurement result of the surface, the rotation error Rx can be obtained accurately. On the other hand, when obtaining the rotation error Rz around the Z-axis, as shown in FIG. 5, the area irradiated with the line pattern is different between the first measurement process and the second measurement process. Accuracy will be reduced.

  Therefore, the shape measuring apparatus 11 performs a convergence calculation that is repeatedly performed until the value converges while applying the rotation error Rz that has already been obtained. For example, first, the rotation error Rz is set to 0, and measurement processing is performed twice to obtain the rotation error Rz. Then, the rotation error Rz is applied to perform two measurement processes to obtain a new rotation error Rz, and a change in the new rotation error Rz (difference from the rotation error Rz obtained one time before) is obtained. The process for obtaining the rotation error Rz is repeated until a predetermined threshold value, for example, 10 seconds or less is reached. By obtaining the rotation error Rz in this way, an accurate rotation error Rz can be obtained, and thereby the measurement accuracy of the test object 12 can be improved.

  Further, as the diameter of the reference sphere 31, an arbitrary value can be selected, but it is desirable to select a value that is twice or more the interval dx. For example, when the width of the measurement region in the X direction is 20 mm and the distance dx is 20 mm, the measurement is performed so that the measurement regions do not overlap if the diameter of the reference sphere 31 is 40 mm or more. Further, even when the diameter of the reference sphere 31 is less than 40 mm, the measurement can be performed with the interval dx narrowed.

  Next, a process for detecting the rotation error Ry around the Y axis will be described.

  The rotation error Ry around the Y axis is detected by measuring the reference plane 32 with the optical cutting probe 22 as shown in FIG. 3C. As described above, the reference surface 32 is a plane formed with a predetermined flatness so as to be orthogonal to the Z axis. In addition, for example, without providing the reference surface 32, an arbitrary part of the plane of the surface plate 21 is measured at about 3 to 10 points using a touch probe (not shown), and the plane defined by the measurement is used as a reference. It may be a surface.

  Then, assuming that the rotation angle around the Y axis of the reference surface 32 is Ry0 (known value) and the rotation angle around the Y axis of the reference surface 32 measured by the optical cutting probe 22 is Ryp, a rotation error around the Y axis. Ry is calculated | required by following Formula (7).

Ry = Ryp−Ry0
... (7)

  Here, for example, as the size of the reference surface 32, there is a size that includes the length of the line pattern irradiated to the reference surface 32 in the X direction, for example, a size of 20 mm or more. Good. The size of the reference surface 32 is not limited with respect to the Y direction.

  As described above, the shape measuring apparatus 11 can detect the rotation error Rx around the X axis, the rotation error Ry around the Y axis, and the rotation error Rz around the Z axis.

  That is, the error detection unit 63 drives the optical cutting probe 22 via the drive control unit 64 so as to perform the measurement with respect to the reference sphere 31, and performs two measurements at positions spaced apart by dz in the Z direction. Then, based on the Y coordinate of the center position of the reference sphere 31 obtained by each measurement, the above formula (4) is calculated to calculate the rotation error Rx around the X axis. In addition, the error detection unit 63 drives the optical cutting probe 22 via the drive control unit 64 so as to perform the measurement for the reference sphere 31, and performs two measurements at positions separated by an interval dx in the X direction. Then, based on the Y coordinate of the center position of the reference sphere 31 obtained by each measurement, the above formula (6) is calculated to calculate the rotation error Rz around the Z axis. Further, the error detection unit 63 drives the optical cutting probe 22 via the drive control unit 64 so as to perform the measurement with respect to the reference surface 32, and the inclination of the plane obtained by the measurement with respect to the reference surface 32 is adjusted. Based on this, a rotation error Ry around the Y axis is calculated.

  Then, the shape data construction unit 62 performs processing for constructing the three-dimensional shape of the test object 12 by arranging the shapes of the line patterns shown in the images continuously captured by the imaging unit 42 in the scanning direction. In this case, each rotation error is reflected. For example, the shape data construction unit 62 performs processing for arranging the shape of the line pattern shown in the images continuously captured by the imaging unit 42 in the scanning direction in a tilted state according to the rotation error. As described above, by reflecting the rotation error detected by the error detection unit 63, it is assumed that a slight error (deviation in the projection direction of the line pattern) occurs in the posture of the optical cutting probe 22 with respect to the drive axis coordinate system. In addition, the surface shape of the test object 12 can be accurately measured, and the measurement accuracy can be improved.

  Further, as described above, when detecting the rotation error Rz around the Z axis, the measurement is performed twice so that a part of the measurement region viewed from the Z direction (the dotted line region in FIG. 3B) overlaps, The influence of the shape of the reference sphere 31 being not a perfect sphere can be eliminated from the two measurement results. On the other hand, when the rotation error Rz around the Z axis is detected, the measurement is performed twice so that the measurement region viewed from the Z direction (the dotted line region in FIG. 3B) does not overlap, so that the rotation error Rz around the Z axis. Can be detected in detail (with high resolution).

  By the way, in the above-described embodiment, the rotation error Rx around the X axis and the rotation error Rz around the Z axis are detected using the reference sphere 31 as the measurement target, and the rotation around the Y axis is performed using the reference plane 32 as the measurement target. Although the error Ry is detected, for example, the rotation error Ry around the Y axis can be detected using the reference sphere 31 as a measurement target.

  That is, when detecting the rotation error Rx around the X axis, two measurements are performed at positions spaced apart by dz in the Z direction, and based on the Y coordinate of the center position of the reference sphere 31 obtained by each measurement, The above equation (4) is calculated. Based on the X coordinate of the center position of the reference sphere 31 obtained at this time, the following equation (8) is calculated to obtain the rotation error Ry around the Y axis. Can be sought.

Ry = (X1-X2) / dz
... (8)

  However, in Formula (8), X1 is the X coordinate of the center of the reference sphere 31 in the first measurement, and X2 is the X coordinate of the center of the reference sphere 31 in the second measurement. As described above, the rotation error Ry around the Y axis is measured twice by changing the position of the light cutting probe 22 in the Z direction at the interval dz, and the X coordinate of the reference sphere 31 obtained by the two measurements. It can be obtained from the difference between X1 and X coordinate X2.

  Here, with reference to FIG. 6, it will be described that a difference occurs between the X coordinate X1 and the X coordinate X2 of the measurement data of the reference sphere 31 due to the rotation error Ry around the Y axis.

  6A and 6B schematically show a line pattern irradiated on the reference sphere 31 in the first and second measurements, and the light cutting probe 22 is tilted around the Y axis with a rotation error Ry. Yes. In the first measurement and the second measurement, the optical cutting probe 22 is moved at an interval dz in the Z direction. However, since the posture of the optical cutting probe 22 is tilted around the Y axis by a rotation error Ry, the measurement region interval ( The distance between the two-dot chain lines shown in FIGS. 6A and 6B is different from the distance dz.

  Accordingly, when the three-dimensional shape data of the test object 12 is constructed based on the first and second measurement data without considering the rotation error Ry, as shown in FIG. 6C, the first measurement data The position in the X direction is misaligned between the shape data constructed based on (circle shown by a solid line) and the shape data built based on the second measurement data (circle shown by a broken line). End up. As described above, an error occurs in the measurement of the reference sphere 31 due to the deviation of the projection direction of the line pattern (rotation error Ry).

  Therefore, based on the difference between the X coordinate X1 and the X coordinate X2 of each shape data, the rotation error Ry is obtained from the above equation (8), and the rotation error Ry is applied to apply the three-dimensional shape data of the reference sphere 31. By performing the process of constructing, the shape data of the reference sphere 31 at an ideal position where no error occurs can be obtained as shown by a two-dot chain line in FIG. 6C.

  As described above, the shape measuring apparatus 11 calculates the rotation error Rx around the X axis from the difference between the Y coordinate Y1 and the Y coordinate Y2 of the shape data, based on two measurements at positions separated by a distance dz in the Z direction. The rotation error Ry around the Y axis can be detected from the difference between the X coordinate X1 and the X coordinate X2 of the shape data.

  Next, FIG. 7 is a flowchart for explaining a rotation error detection process in which the shape measuring apparatus 11 detects a rotation error of the light cutting probe 22. For example, the shape measuring apparatus 11 is set so that the rotation error detection process is executed at the time of activation, and the process is started when the user activates the shape measuring apparatus 11.

  In step S11, the drive control unit 64 controls the drive of the Z stage 23 and the column 25, and the measurement process is performed on two measurement areas separated by a distance dz in the Z direction with the reference sphere 31 as a measurement target. Proceed to step S12.

  In step S12, the shape data construction unit 62 determines the three-dimensional surface shape of the reference sphere 31 based on the line pattern of the image obtained by the measurement process performed twice with a gap dz in the Z direction in step S11. Build the data. Then, the error detection unit 63 calculates the above equation (4) based on the difference in the coordinates of the center position of the reference sphere 31 obtained by the two measurement processes, so that the X axis of the light cutting probe 22 is calculated. A rotation error Rx around is calculated. Similarly, the error detection unit 63 calculates the rotation error Ry around the Y axis of the optical cutting probe 22 by calculating the above-described equation (8).

  After the process of step S12, the process proceeds to step S13, where the drive control unit 64 controls the drive of the Z stage 23 and the column 25, and two measurement regions separated by a distance dx in the X direction with the reference sphere 31 as a measurement target. Measurement processing is performed, and the process proceeds to step S14.

  In step S <b> 14, the shape data construction unit 62 determines the three-dimensional surface shape of the reference sphere 31 based on the line pattern of the image obtained by the measurement process performed twice at the interval dx in the X direction in step S <b> 13. Build the data. Then, the error detection unit 63 calculates the above equation (6) based on the difference in the coordinates of the center position of the reference sphere 31 obtained by the two measurement processes, whereby the Z axis of the light cutting probe 22 is calculated. A surrounding rotation error Rz is calculated.

  After the process of step S14, the process proceeds to step S15, and it is determined whether or not the change amount of the rotation error Rz is equal to or less than a predetermined threshold value (for example, 10 seconds). Here, the amount of change in the rotation error Rz refers to the rotation error Rz obtained in the immediately preceding step S14 when the processing of steps S13 to S16 is looped, and the rotation error Rz obtained one time before that. It is the difference of. If the process in step S14 is the first time and the process has not yet looped, it is determined in step S15 that the change in the rotation error Rz is not less than or equal to a predetermined threshold value. That is, the processes in steps S13 to S16 are looped at least once.

  If it is determined in step S15 that the change in the rotation error Rz is not less than or equal to the predetermined threshold value (greater than the threshold value), the process proceeds to step S16. In step S <b> 16, the error detection unit 63 stores the rotation error Rz calculated in the previous step S <b> 14 in a memory built in the shape data construction unit 62. Thereby, in the subsequent processing, when the shape data of the reference sphere 31 is constructed, processing to which the rotation error Rz is applied is performed. After the process of step S16, the process returns to step S13, and the same process is repeated thereafter. That is, the process of building the shape data of the reference sphere 31 by applying the rotation error Rz and obtaining the rotation error Rz is repeated.

  On the other hand, if it is determined in step S15 that the change in the rotation error Rz is equal to or less than the predetermined threshold, the process proceeds to step S17. In step S17, the error detection unit 63 uses the rotation error Rx and the rotation error Ry obtained in step S12, and the rotation error Rz obtained by the convergence calculation so as to be equal to or less than a predetermined threshold value, as the shape data construction unit 62. Is stored in the built-in memory. Thus, the rotation error Rx, the rotation error Ry, and the rotation error Rz are applied when executing the process of constructing the shape data with the test object 12 as the measurement target. After the process of step S17, the rotation error detection process is terminated.

  As described above, the shape measuring apparatus 11 can detect the rotation error Rx, the rotation error Ry, and the rotation error Rz. Accordingly, the three-dimensional surface shape data of the test object 12 is obtained from the shape of the line pattern reflected in a plurality of images continuously captured by the image sensor 55 by reflecting each detected rotation error. By performing the construction process, the surface shape of the test object 12 can be accurately measured.

  In particular, by calculating the rotation error Rz by convergence calculation, the accuracy of the calculated rotation error Rz can be improved, and more accurate measurement can be performed.

  In the rotation error detection process described with reference to the flowchart of FIG. 7, the measurement process (step S13) is repeated for two measurement regions separated by a distance dx in the X direction. However, this measurement process may not be repeated. . That is, the measurement process is performed only once, the shape data is constructed using the obtained rotation error Rz using the measurement result, and the rotation error Rz is calculated again by repeating the calculation for obtaining the rotation error Rz. It can be converged.

  Further, a correspondence relationship between the difference between the coordinates of the center position of the reference sphere 31 obtained by performing the measurement process and the rotation error Rz is calculated in advance by simulation, for example, and a table in which the correspondence relationship is registered is stored. Thus, the rotation error Rz may be obtained with reference to the table.

  In the present embodiment, the measurement method of measuring the surface shape of the reference sphere 31 twice and calculating the coordinates of the center position of the reference sphere 31 from each measurement has been described. The shape is measured two or more times, and the shape measurement data for two times is selected from the plurality of shape measurement data acquired thereby, and the coordinates of the center position of the reference sphere 31 are determined from the two times of shape measurement data. You may make it calculate.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

  DESCRIPTION OF SYMBOLS 11 Shape measuring device, 12 Test object, 21 Surface plate, 22 Optical cutting probe, 23 Z stage, 24 Beam part, 25 Column, 31 Reference sphere, 32 Reference surface, 41 Irradiation unit, 42 Imaging unit, 51 Light emitting element, 52 condenser lens, 53 line generator lens, 54 imaging lens, 55 imaging device, 61 control device, 62 shape data construction unit, 63 error detection unit, 64 drive control unit

Claims (8)

In the shape measuring device that measures the surface shape of the test object,
An irradiation means for projecting a line pattern onto the test object;
Imaging means for imaging the object on which the line pattern is projected;
Driving means for driving the irradiating means and the test object relatively along drive axes in the X direction, the Y direction, and the Z direction orthogonal to each other;
While the driving unit moves the irradiation unit and the test object relative to each other in the Y direction, a plurality of images sequentially captured by the imaging unit are acquired and copied to the plurality of images. Shape measurement data construction means for constructing shape measurement data of the test object from the shape of the line pattern,
A reference sphere formed in a spherical shape;
An error detecting means for detecting a rotation error of the attitude of the irradiation means with respect to each drive shaft of the driving means,
The error detection means acquires at least a plurality of times of shape measurement data performed by being separated by a predetermined interval in the Z direction obtained by the shape measurement data construction means using the reference sphere as a test object, and the plurality of times The center position of the reference sphere obtained from the shape measurement data of at least two times among the shape measurement data is acquired, and based on the difference of the acquired center position of the reference sphere with respect to the optical axis direction of the irradiation means Detecting a rotation error around the drive shaft in the X direction;
The shape measurement data construction unit corrects the shape measurement data of the test object based on rotation error information obtained from the error detection unit. The error detection means obtains at least a plurality of shape measurement data obtained by the shape measurement data construction means that are separated by a predetermined distance in the X direction, and at least two of the plurality of shape measurement data. The center position of the reference sphere obtained from the shape measurement data is acquired, and based on the difference of the acquired center position of the reference sphere, the rotation error about the drive axis in the Z direction with respect to the optical axis direction of the irradiation means The shape measuring device according to claim 1, wherein the shape measuring device is detected. The error detection unit is configured to perform the irradiation based on a difference in the center position of the reference sphere obtained from shape measurement data for at least two times among the plurality of shape measurement data performed at a predetermined interval in the Z direction. The shape measuring apparatus according to claim 1, wherein a rotation error around the drive axis in the Y direction of the means is detected. The error detection unit is configured to rotate the Y unit in the Y direction based on an inclination of a plane represented by shape measurement data obtained using a known reference plane orthogonal to the Z axis as a test object with respect to the reference plane. The shape measuring apparatus according to claim 1, wherein a rotation error is detected. The error detection unit detects an optical axis of the optical system of the irradiation unit and an optical axis of the optical system of the imaging unit when detecting a rotation error around the drive axis in the Z direction with respect to the optical axis direction of the irradiation unit. From the shape measurement data of the two times obtained by setting the predetermined interval so that a part of the measurement area which is the area irradiated with the line pattern overlaps on the XY plane including the intersection of The shape measuring apparatus according to claim 1, wherein a center position is acquired. The error detection unit detects an optical axis of the optical system of the irradiation unit and an optical axis of the optical system of the imaging unit when detecting a rotation error around the drive axis in the Z direction with respect to the optical axis direction of the irradiation unit. From the two-time shape measurement data obtained by setting the predetermined interval so as to avoid the overlapping of the measurement areas which are areas irradiated with the line pattern on the XY plane including the intersection of the reference sphere, The shape measuring device according to any one of claims 1 to 4, wherein the center position is acquired. The error detecting means calculates the rotation error around the drive axis in the Z direction of the irradiating means while applying the rotation error around the drive axis in the Z direction that has already been obtained until the value converges. The shape measuring device according to claim 1, wherein the shape measuring device is repeatedly performed. The shape measuring apparatus according to claim 1, wherein the irradiation unit and the imaging unit are held in the same casing, and the driving unit drives the casing.

Images