JP7660280B2 - Measurement device and method - Google Patents

Description

The present invention relates to a measuring device and method, and in particular to a measuring device and method capable of measuring the shape of the inner surface of a cylindrical workpiece.

Conventionally, shape measuring devices have been proposed that measure the shape of the inner surface of a cylindrical workpiece without contact. For example, Patent Document 1 discloses a shape measuring device that places conical prisms inside a cylindrical workpiece so that their central axes coincide with each other, and deflects the measurement light at a right angle using the conical prism to irradiate the inner surface of the workpiece with the measurement light, thereby measuring the three-dimensional shape of the inner surface of the workpiece. The shape measuring device described in Patent Document 1 can measure the three-dimensional shape of the inner surface of a cylindrical workpiece without cutting it. Also, the shape measuring device described in Patent Document 1 can measure the shape of the entire circumferential direction of the cylindrical inner surface at once by emitting light in the entire circumferential direction centered on the central axis of the conical prism.

JP 2016-075577 A

However, with the shape measuring device described in Patent Document 1, when measuring the three-dimensional shape of the inner surface of a workpiece over a wide range in the height direction (Z direction), the relative position between the measurement area set on the inner surface of the workpiece and the shape measuring device needs to be changed in the Z direction. When scanning the inner surface of the workpiece from top to bottom, the magnification of the optical system deteriorates as the measurement area of the workpiece moves from top to bottom, and the spatial resolution deteriorates.

The present invention was made in consideration of these circumstances, and aims to provide a measuring device and method that can easily and accurately measure the shape of the inner surface of a workpiece over a wide range in the height direction.

In order to solve the above problem, the measuring device according to the first aspect of the present invention includes a rotating stage on which a cylindrical workpiece is placed, the rotating stage being rotatable around a rotation axis along the height direction of the workpiece, a linear stage being linearly movable in a linear movement direction perpendicular to the rotation axis of the rotating stage, a mirror member having a reflective surface inclined at 45° with respect to the rotation axis and the linear movement direction, the mirror member being fixed on the linear stage and arranged to pass through a hole formed in the rotating stage, and being linearly movable relative to a base on which the linear stage is mounted as the linear stage moves linearly, a white light interference microscope that irradiates the inner surface of the workpiece with measurement light by reflecting the measurement light on the reflective surface, thereby measuring the shape of the inner surface of the cylindrical workpiece, and a control unit that moves the measurement field irradiated with the measurement light along the height direction by linearly moving the linear stage, and moves the measurement field in the circumferential direction of the workpiece by rotating the rotating stage.

In the second aspect of the present invention, the measuring device is provided with an image processing unit that stitches together the measurement data for each measurement field of view.

The third aspect of the present invention is a measurement method for a measuring device including a rotating stage on which a cylindrical workpiece is placed, the rotating stage being rotatable around a rotation axis along the height direction of the workpiece, a linear stage being linearly movable in a linear movement direction perpendicular to the rotation axis of the rotating stage, a mirror member having a reflective surface inclined at 45° with respect to the rotation axis and the linear movement direction, the mirror member being fixed on the linear stage and arranged to pass through a hole formed in the rotating stage, and being linearly movable relative to a base on which the linear stage is provided as the linear stage moves linearly, and a white light interference microscope that irradiates the inner surface of the workpiece with measurement light by reflecting the measurement light from the reflective surface, thereby measuring the shape of the inner surface of the cylindrical workpiece, the method including the steps of moving the measurement field irradiated with the measurement light along the height direction by linearly moving the linear stage, and moving the measurement field in the circumferential direction of the workpiece by rotating the rotating stage.

The present invention makes it possible to measure the shape of the inner surface of a workpiece easily and accurately over a wide range in the height direction.

FIG. 1 is a block diagram showing a measurement device according to an embodiment of the present invention. FIG. 2 is a diagram showing a procedure for scanning the inner surface of a workpiece in the height direction (Z direction). FIG. 3 is a diagram showing a procedure for scanning the inner surface of a workpiece in the height direction (Z direction) and the circumferential direction. FIG. 4 is a flowchart showing a measurement method according to an embodiment of the present invention. FIG. 5 is a flow chart showing the Z direction measurement process of FIG.

Below, an embodiment of the measurement device and method according to the present invention will be described with reference to the attached drawings.

[Configuration of measuring device]
FIG. 1 is a block diagram showing a measurement device according to an embodiment of the present invention.

The measuring device 1 according to this embodiment is a device for measuring the shape (including surface roughness, three-dimensional shape, contour, etc.) of a workpiece (object to be measured) W placed on a stage ST, and includes a stage ST, a control device 10, and a white light interference microscope 50. In the following explanation, a three-dimensional Cartesian coordinate system is used in which the plane along the mounting surface of the stage ST on which the workpiece W is placed is defined as the XY plane, and the height direction is defined as the Z direction.

(Stage ST)
First, the stage ST on which the workpiece W is placed will be described.

As shown in FIG. 1, the stage ST includes a rotation stage ST1, a linear stage ST2, and a base ST3.

The linear stage ST2 is provided on a base ST3 and is capable of linear movement relative to the base ST3. In other words, the rotation stage ST1 and the linear stage ST2 are structured to move linearly in the linear movement direction (X direction) relative to the base ST3. A beveled cylindrical mirror member M is fixed to the linear stage ST2.

The rotating stage ST1 is mounted on the linear stage ST2 so as to be rotatable around the Z axis. A hole H with a larger diameter than the mirror member M is formed in the rotating stage ST1, and the mirror member M is disposed so as to pass through this hole H. The mirror member M is capable of linear movement relative to the base ST3 in conjunction with the linear movement of the linear stage ST2.

As shown in Fig. 1, when measuring the inner surface W _in of the workpiece W, the cylindrical workpiece W to be measured is placed so as to overlap with a hole H formed in the rotating stage ST1. Here, in the example shown in Fig. 1, the optical axis AX (see Fig. 2(b)) of the objective part 64 and the central axis of the hole H formed in the rotating stage ST1 coincide with each other. Furthermore, the central axis of the workpiece W is held by a holding means (e.g., a clamp, etc.) (not shown) so as to coincide with the central axis of the rotating stage ST1.

The measurement light L0 emitted from the white light interference microscope 50 is reflected by the reflecting surface _MS of the mirror member M and reaches the inner surface W _in of the workpiece W. This makes it possible to measure the surface roughness of the inner surface W _in of the workpiece W.

In this embodiment, the mirror member M has an obliquely cut cylindrical shape, but the present invention is not limited to this. For example, it may have an obliquely cut polygonal prism shape, a cone shape, or a polygonal pyramid shape, or it may have a structure in which a reflector of any shape is supported by a pillar.

(Control device 10)
Next, the control device 10 of the measuring device 1 will be described.

The control device 10 is a device that controls each part of the white light interference microscope 50 and processes the results of measurements made by the white light interference microscope 50, and includes a control unit 12, an input/output unit 14, a memory unit 16, and a signal processing unit 18. The control device 10 can be realized by a general-purpose computer such as a personal computer or a workstation.

The control unit 12 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The control unit 12 receives operation input from an operator via the input/output unit 14 and controls each unit of the control device 10. The control unit 12 also controls the output of the light source unit 52 of the white light interference microscope 50 to adjust the amount of illumination light irradiated onto the workpiece W. The control unit 12 controls the drive of the rotation stage drive unit 80 and the linear stage drive unit 82 to operate the stages ST1 and ST2, and adjusts the observation target position (measurement position) of the workpiece W (see Figures 2 and 5). The control unit 12 also controls the relative position (distance) in the height direction (Z direction) between the lens barrel 56 and the stage ST1. The control unit 12 is an example of the control unit and image processing unit of the present invention.

The input/output unit 14 includes an operating member (e.g., a keyboard, a pointing device, etc.) for receiving operational input from the operator, and a display unit (e.g., a liquid crystal display, etc.) for displaying the results of the measurement of the workpiece W by the white light interference microscope 50, etc.

The signal processing unit 18 acquires a detection signal from the detector 76 of the white light interference microscope 50, performs signal processing on this detection signal, and calculates the shape and amplitude of the interference fringes, etc.

The memory unit 16 is a storage device for storing programs for controlling the white light interference microscope 50 and for processing measurement data such as the measurement results of the workpiece W, as well as the measurement data. For example, a hard disk drive (HDD) or a solid state drive (SSD) can be used as the memory unit 16.

(White Light Interference Microscope 50)
Next, a description will be given of the white light interference microscope 50 of the measuring device 1. In the following description, an example in which the inner surface W _in of a cylindrical workpiece W is measured will be described.

The white light interference microscope 50 includes a light source unit 52, a light guide 54, and a lens barrel 56. A turret 62 is attached to the lower end of the lens barrel 56, and a detector 76 is attached to the upper end of the lens barrel 56. Multiple objective units 64 (three in the example shown in FIG. 1) are attached to the turret 62. The interference objective lenses 66 included in the multiple objective units 64 have mutually different magnifications, and by rotating the turret 62, it is possible to switch between the interference objective lenses 66 used to measure the workpiece W.

The light source unit 52 is a light source that outputs white light, and is, for example, a halogen lamp, a laser light source, or an LED (Light Emitting Diode) light source. Here, white light is light that is a mixture of visible light rays with wavelengths in the visible light region (wavelengths of approximately 400 nm to approximately 720 nm), and may be, for example, light that is a mixture of three colors (three primary colors) of red, green, and blue in an appropriate ratio.

The light guide 54 is a member that forms an optical path that propagates the white light output from the light source unit 52 to the lens barrel 56, and is, for example, an optical fiber.

The lens barrel 56 has a coaxial epi-illumination optical system. An illumination lens 58, a beam splitter 60, an imaging lens 72, and an aperture 74 are arranged in the lens barrel 56. The relative position (distance) in the height direction (Z direction) between the lens barrel 56 and the stage ST1 can be changed by the control unit 12. Note that in the example shown in FIG. 1, the lens barrel 56 is moved in the Z direction, but a Z direction drive mechanism may be provided on the base ST3 to move the stage ST1, or both may be movable.

The illumination lens 58 has an optical system that guides (images) the white light (illumination light) that enters the lens barrel 56 via the light guide 54 to the pupil position of the interference objective lens 66. The illumination light output from the illumination lens 58 is reflected by the beam splitter 60 and guided to the objective section 64.

The illumination light guided through the beam splitter 60 is guided to the exit side of the objective unit 64 by the interference objective lens 66. The component (measurement light L0) of the illumination light guided to the exit side of the objective unit 64 that passes through the half mirror 68 is guided inside the cylindrical workpiece W placed on the stage ST1, and then reflected by the reflecting surface M _S of the mirror member M to reach the inner surface W _in of the workpiece W and is reflected. Then, the first reflected light L1 from the inner surface W _in of the workpiece W passes through the half mirror 68 and reaches the imaging lens 72. On the other hand, the component (second reflected light L2) of the illumination light guided to the exit side of the objective unit 64 that is reflected by the half mirror 68 is guided to the reference mirror 70 and reflected. The reference mirror 70 is arranged at a position conjugate with the focal position of the exit side (workpiece W side) of the interference objective lens 66. The second reflected light L 2 from the reference mirror 70 is reflected by the half mirror 68 and reaches the imaging lens 72 .

The imaging lens 72 has an optical system that forms an image of the reflected light L1 from the inner surface W _in of the workpiece W and the second reflected light L2 from the reference mirror 70 on the light detection surface of the detector 76.

The aperture 74 is provided between the imaging lens 72 and the detector 76, and blocks a portion of the first reflected light L1 and the second reflected light L2 that are guided from the imaging lens 72 to the detector 76.

The detector 76 includes a light detection array element (hereinafter referred to as an image sensor), such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). The detector 76 generates an analog or digital detection signal indicating the light intensity detected by each light receiving element of the image sensor, and outputs the signal to the signal processing unit 18. This allows an image of the inner surface W _in of the workpiece W to be acquired. The detector 76 also acquires an interference waveform (interferogram) of each pixel of this image.

The detector 76 receives the first reflected light L1 from the inner surface W _in of the workpiece W and the second reflected light L2 from the reference mirror 70 to generate a detection signal and output it to the signal processing unit 18.

The signal processing unit 18 acquires a detection signal from the detector 76 of the white light interference microscope 50, performs predetermined signal processing on this detection signal, and calculates the shape and amplitude of the interference fringes. Here, the brightness change curve (interference waveform) obtained when the interference objective lens 66 is scanned in the height direction (Z direction) is called an interferogram.

The control unit 12 measures the shape and surface roughness of the inner surface W _in of the workpiece W based on the shape and amplitude of the interference fringes calculated by the signal processing unit 18 when the interference objective lens 66 is scanned in the height direction (Z direction). Specifically, the control unit 12 measures the shape and surface roughness of the inner surface W _in of the workpiece W by utilizing the difference between the distance between the inner surface W _in of the workpiece W and the half mirror 68 and the distance between the reference mirror 70 and the half mirror 68 (hereinafter referred to as the optical path difference). Such a measurement method is called a vertical scanning method (VSI: Vertical Scanning Interferometry). The vertical scanning method is described in, for example, U.S. Patent No. 4,340,306. The vertical scanning method is standardized by the International Organization for Standardization (ISO) as CSI (Coherence Scanning Interferometry) (ISO25178-604:2013).

When the optical path difference changes, the phase difference between the first reflected light L1 and the second reflected light L2 changes, and the interference fringes change according to the change in phase difference. When the optical path difference is zero, that is, when the light is focused on the inner surface W _in of the workpiece W, no phase difference occurs between the first reflected light L1 and the second reflected light L2. Therefore, the interference intensity becomes maximum, and the amplitude of the interference fringes becomes maximum. On the other hand, when the optical path difference increases, the interference intensity decreases.

The control unit 12 acquires, for example, the position (Z-axis height) in the height direction (Z direction) of the interference objective lens 66 when the amplitude of the interference fringes calculated by the signal processing unit 18 is maximum. Here, the position in the height direction of the interference objective lens 66 when the amplitude of the interference fringes is maximum can be obtained from the envelope in the interferogram. Then, the control unit 12 calculates the height position (focus position) of the inner surface W _in of the workpiece W based on the position of the interference objective lens 66, and measures the shape, surface roughness, etc. of the inner surface W _in of the workpiece W. The control unit 12 is capable of storing the results of this measurement in the memory unit 16 and displaying them on the display unit of the input/output unit 14.

The method for measuring the height position of the inner surface W _in of the workpiece W is not limited to VSI or CSI. For example, a frequency domain analysis (FDA) or a phase shifting interferometry (PSI) may be applied as a method for measuring the height position of the inner surface W _in of the workpiece W. The frequency domain method is a method for obtaining the height position of the inner surface W _in of the workpiece W by Fourier transforming the interferogram and obtaining the gradient of the phase with respect to the wave number near the peak position of the amplitude spectrum. The frequency domain method is described in, for example, U.S. Pat. No. 5,398,113. The phase shifting method is a method for obtaining the height position of the inner surface W _in of the workpiece W based on the change in the density value of the pixel when the focal position of the interference objective lens 66 is shifted in the optical axis direction. The phase shift method is described, for example, in J.H. Bruning et al.: "Digital Wavefront Measuring Interferometer for Testing Optical Surfaces and Lenses, Applied Optics, Vol. 13, Issue 11, pp. 2693-2703 (1974)."

When measuring the shape of the inner surface W _in of the workpiece W, scanning along the Z direction is performed by the linear stage driving unit 82. The linear stage driving unit 82 includes a driving mechanism (e.g., an actuator) for linearly moving the rotation stage ST1 and the linear stage ST2 in the X direction relative to the base ST3.

Scanning along the circumferential direction of the workpiece W is performed by the rotating stage driving unit 80. The rotating stage driving unit 80 is equipped with a driving mechanism (e.g., an actuator, etc.) for rotating the rotating stage ST1 around the Z axis.

The control unit 12 sequentially captures images of the inner surface W _in of the workpiece W using the rotary stage drive unit 80 and the linear stage drive unit 82. The control unit 12 can then stitch together the sequentially captured images to create a composite image of the entire measurement range of the workpiece W (see, for example, JP 2020-159759 A). This makes it possible to measure the shape of the entire measurement range of the workpiece W.

[Scanning procedure of the inner surface W _in of the workpiece W]
Next, a scanning procedure for measuring the inner surface W _in of a cylindrical workpiece W will be described.

2 is a diagram (front view and partial cross-sectional view) showing the procedure for scanning the inner surface W _in of the workpiece W in the height direction (Z direction). In FIG. 2, (b) shows a state in which the central axis of the mirror member M coincides with the optical axis AX of the objective section 64, and (a) and (c) show states in which the cylindrical workpiece W and mirror member M have each been linearly moved in the ±X direction with (b) as a reference. The central axis of the workpiece W is arranged to coincide with the central axis of the rotating stage ST1.

2, the reflecting surface _MS of the mirror member M is inclined at 45° with respect to the Z axis (the rotation axis of the rotating stage ST1) and the X axis (direction of linear movement), and the measurement light L0 irradiated to the workpiece W is bent at a right angle by the reflecting surface _MS and enters the inner surface W _in of the workpiece W. The irradiation position (observation target position) of the measurement light L0 irradiated to the workpiece W can be changed in the Z direction by moving the linear stage ST2 in the X direction by the linear stage driving unit 82.

As shown in FIG. 2B, when the reflecting surface M _S of the mirror member M is at a position M _S (0), the irradiation position V(0) of the measuring light L0 becomes the measurable area (hereinafter referred to as the measurement field of view).

2B, the distance from the objective lens 64 to the arrival position (reflection position) P(0) of the measurement light L0 on the reflecting surface _MS is designated as Z, and the distance from position P(0) to position V(0) is designated as X. In this case, the optical path length D(0) from the objective lens 64 to position V(0) is given by D(0) = Z + X.

2(a), when the rotary stage ST1 also moves ΔX in the +X direction in conjunction with the linear movement of the linear stage ST2, the inner surface W _in of the workpiece W moves from position W _in (0) to position W _in (+) by ΔX in the +X direction, and the reflecting surface M _S of the mirror member M moves from position M _S (0) to position M _S (+) by ΔX in the +X direction. In this case, the irradiation position of the measurement light L0 moves upward (to the +Z side) by ΔZ, and the measurement field of view becomes V(+).

2A, the distance from the objective lens 64 to the arrival position P(+) of the measurement light L0 on the reflecting surface _MS is (Z-ΔZ), and the distance from position P(+) to position V(+) is (X+ΔX). In this case, the optical path length D(+) from the objective lens 64 to position V(+) is D(+)=(Z-ΔZ)+(X+ΔX). Here, since the inclination angle of the reflecting surface MS is 45°, ΔX=ΔZ. Therefore, D(+)=Z+X.

2(c), when the rotary stage ST1 also moves ΔX in the -X direction in conjunction with the linear movement of the linear stage ST2, the inner surface W _in of the workpiece W moves from position W _in (0) to position W _in (-) which is moved ΔX in the -X direction, and the reflecting surface M _S of the mirror member M moves from position M _S (0) to position M _S (-) which is moved ΔX in the -X direction. In this case, the irradiation position of the measurement light L0 moves downward (to the -Z side) by ΔZ, and the measurement field of view becomes V(-).

2(c), the distance from the objective lens 64 to the arrival position P(-) of the measurement light L0 on the reflecting surface _MS is (Z+ΔZ), and the distance from the position P(-) to the position V(-) is (X-ΔX). In this case, the optical path length D(+) from the objective lens 64 to the position V(-) is D(+) = (Z-ΔZ) + (X+ΔX) = Z+X.

In this way, by repeating the linear movement to sequentially scan the inner surface W _in of the workpiece W, it is possible to obtain measurement data for the entire measurement range in the Z direction. As shown in Fig. 2, in this embodiment, scanning in the Z direction is performed by linear movement of the mirror member M, so the distance from the objective part 64 to the inner surface W _in of the workpiece W does not change before and after the linear movement (D(0) = D(-) = D(+)). Therefore, even if the inner surface W _in of the workpiece W is scanned from the top to the bottom, there is no need to refocus, so the shape of the inner surface W _in of the workpiece W can be accurately and easily measured over a wide range in the height direction.

FIG. 3 is a diagram showing a procedure for scanning the inner surface W _in of the workpiece W in the height direction (Z direction) and the circumferential direction.

When the linear stage ST2 is moved sequentially in the -X direction, the measurement visual field moves to positions V(1,1), V(1,2), ..., V(1,N) in the order shown in FIG. 3. Here, the linear movement amount ΔX and the number of repetitions (number of movements) N of the linear movement are determined by the shape and size of the measurement visual field V(i,j) and the size Z _m of the overlapping area (pixel group used for alignment. For example, see JP 2020-159759 A) for stitching together the measurement data (image). In the example shown in FIG. 3, since the measurement visual field V(i,j) is approximately rectangular, the linear movement amount ΔX and the number of repetitions N of the linear movement are determined by the measurement target range (Z-direction measurement range) Z _A in the Z direction, the Z-direction dimension Z _V of the measurement visual field V(i,j), and the size Z _m of the overlapping area for stitching together the measurement data (image). In this case, the linear movement amount ΔX is Z _V -Z _m . The number of repetitions N of the linear movement is determined within a range where N×Z _V −(N−1)×Z _m ≧Z _A. Depending on the shape of the measurement visual field V(i, j), Z _m may differ between the top and bottom.

When scanning of the entire Z-direction measurement range Z _A is completed, the rotation stage ST1 is rotated by a rotation angle θ around the Z axis to scan the next rows V(2,1), V(2,2), ..., V(2,N). Here, the rotation angle θ is determined by the shape and size of the measurement field V(i,j) and the size C _m of the overlapping area for stitching together the measurement data (images). In the example shown in FIG. 3, since the measurement field V(i,j) is substantially rectangular, the number of repetitions M of the rotational movement is determined by the circumferential length C _A of the inner surface W _in of the workpiece W, the circumferential dimension C _V of the measurement field V(i,j), and the size C _m of the overlapping area for stitching together the measurement data (images). In this case, the number of repetitions M of the rotational movement is determined within a range where M × C _V - (M - 2) × C _m ≧ C _A. Note that C _m may differ between the left and right depending on the shape of the measurement field V(i,j).

As described above, by repeating scanning in the Z direction and the circumferential direction, the entire measurement target range of the inner surface W _in of the workpiece W can be measured.

In the above example, the Z-direction scanning and the circumferential scanning are performed in the order of V(1,1) to V(1,N), V(2,1) to V(2,N), ..., V(M,1) to V(M,N), but the scanning order is not limited to the above example. A more efficient scanning order can be selected depending on the shape and size of the workpiece W. For example, the Z-direction scanning order may be reversed in alternate rows (V(1,1) to V(1,N), V(2,N) to V(2,1), V(3,1) to V(3,N), ...). Also, the circumferential scanning may be performed first (for example, V(1,1) to V(M,1), V(M,2), V(1,2) to V(M-1,2), V(M-1,3), ...).

[Measurement method]
FIG. 4 is a flow chart showing a measurement method according to an embodiment of the present invention, and FIG. 5 is a flow chart showing the Z direction measurement process of FIG.

First, the workpiece W is placed on the rotating stage ST1 (step S10), and the optical system (lens tube 56) of the white light interference microscope 50 and the workpiece W are moved relative to each other in the Z direction to adjust the focus (step S12). In step S10, the central axis of the workpiece W is positioned so as to coincide with the optical axis AX of the objective section 64. Then, the focusing in step S12 is performed in a state in which the central axis of the mirror member M and the optical axis AX of the objective section 64 are aligned (see FIG. 2(b)).

Next, the Z-direction measurement range _ZA on the inner surface W _in of the workpiece W is set by the input/output unit 12 (step S14).

Next, the amount of movement ΔX, the number of movements N, and the rotation angle θ of the linear stage are calculated based on the size of the measurement field of view V(i, j) (step S16).

Next, a repetition parameter i for circumferential scanning is initialized to i=1 (step S18), and the Z-direction measurement range Z _A (measurement field of view V(i, j)) of the workpiece is sequentially measured (step S20).

As shown in FIG. 5, in step S20 (Z-direction measurement process), first, the Z-direction scanning repetition parameter j is initialized to j = 1 (step S200), and the measurement field of view V (1, 1) is measured (step S202). Next, the linear stage ST2 is moved by ΔX (No in step S204, step S206), j = j + 1 is set (step S208), and the measurement field of view V (1, 2) is measured (step S202).

As described above, steps S202 to S208 are repeated to measure the Z-direction measurement range Z _A (measurement field of view V(1,1) to V(1,N)) of the workpiece W. Then, when j=N and measurement of the Z-direction measurement range Z _A (measurement field of view V(1,1) to V(1,N)) of the workpiece W is completed (Yes in step S204), the measurement data of the Z-direction measurement range Z _A (measurement field of view V(1,1) to V(1,N)) of the inner surface W _in of the workpiece W is pieced together (step S210).

In this way, after the Z-direction measurement process (step S20) has been performed, as shown in FIG. 4, if i=M is not met, i.e., if measurement of the entire circumference of the workpiece W has not been completed (No in step S22), the rotating stage ST1 is rotated by θ (step S24), i=i+1 is set (step S26), and the Z-direction measurement range Z _A of the workpiece W (measurement field of view V(2,1) to V(2,N)) is measured.

As described above, steps S20 to S26 are repeated to repeatedly scan the workpiece W in the circumferential direction. Then, when i=M is reached and measurement of the entire circumference of the workpiece W is completed (Yes in step S22), the measurement data for the entire circumference of the workpiece is stitched together (step S28). This makes it possible to obtain measurement data (composite image) for the entire measurement range of the inner surface W _in of the workpiece W.

According to this embodiment, there is no need to refocus when scanning the inner surface W _in of the workpiece W from top to bottom, so the shape of the inner surface W _in of the workpiece W can be measured accurately and easily over a wide range in the vertical direction.

In the example shown in FIG. 5, images are stitched together for each loop of the Z-direction measurement process, but all measurement data may be stitched together after the measurement of the entire circumference is completed (step S28). Also, if circumferential scanning is performed first, circumferential stitching may be performed first.

1...measuring device, 10...control device, 12...control unit, 14...input/output unit, 16...storage unit, 18...signal processing unit, 50...white light interference microscope, 52...light source unit, 54...light guide, 56...lens barrel, 58...illumination lens, 60...beam splitter, 62...turret, 64...objective unit, 66...interference objective lens, 68...half mirror, 70...reference mirror, 72...imaging lens, 74...diaphragm, 76...detector, 80...rotary stage drive unit, 82...linear stage drive unit, ST...stage, ST1...rotary stage, ST2...linear stage, ST3...base, M...mirror member

Claims (2)

A rotation stage on which a cylindrical workpiece is placed, the rotation stage being rotatable around a rotation axis along a height direction of the workpiece;
a linear motion stage that is linearly movable in a linear motion direction perpendicular to a rotation axis of the rotation stage;
a mirror member having a reflection surface inclined at 45° with respect to the rotation axis and the linear movement direction, the mirror member being fixed on the linear movement stage and disposed so as to pass through a hole formed in the rotation stage, and being linearly movable with respect to a base on which the linear movement stage is provided in association with the linear movement of the linear movement stage;
a white light interference microscope that reflects a measurement light on the reflecting surface to irradiate the measurement light onto the inner surface of the workpiece, thereby measuring the shape of the inner surface of the cylindrical workpiece;
a control unit that moves a measurement field of view irradiated with the measurement light along the height direction by linearly moving the linear stage, and moves the measurement field of view in a circumferential direction of the workpiece by rotating the rotation stage;
an image processing unit that stitches together the measurement data for each measurement field of view;
Equipped with
When the number of repetitions of the linear movement of the linear stage is N, the measurement target range in the height direction of the workpiece is Z _A , the measurement field of view is V, the height direction dimension of the measurement field of view is Z _V , and the size of the overlapping area for joining the measurement data in the height direction is Z _m ,
The number of repetitions N of the linear movement is determined within a range where N×Z _V −(N−1)×Z _m ≧Z _A ;
When the number of times the rotational movement of the rotating stage is repeated is M, the circumferential length of the inner surface of the work is C _A , the circumferential dimension of the measurement field of view is C _V , and the size of the overlapping area for joining the measurement data in the rotational direction is C _m ,
The number of times M of repetition of the rotational movement is determined within the range of M×C _v −(M−2)×C _m ≧C _A. A rotation stage on which a cylindrical workpiece is placed, the rotation stage being rotatable around a rotation axis along a height direction of the workpiece;
a linear motion stage that is linearly movable in a linear motion direction perpendicular to a rotation axis of the rotation stage;
a mirror member having a reflection surface inclined at 45° with respect to the rotation axis and the linear movement direction, the mirror member being fixed on the linear movement stage and disposed so as to pass through a hole formed in the rotation stage, and being linearly movable with respect to a base on which the linear movement stage is provided in association with the linear movement of the linear movement stage;
A measurement method for a measurement apparatus including a white light interference microscope that irradiates an inner surface of the workpiece with a measurement light by reflecting the measurement light on the reflecting surface, thereby measuring a shape of the inner surface of the cylindrical workpiece, comprising:
moving a measurement field of view irradiated with the measurement light along the height direction by linearly moving the linear stage;
moving the measurement field of view in a circumferential direction of the workpiece by rotating the rotary stage;
A step of stitching together the measurement data for each measurement field of view;
Including,
When the number of repetitions of the linear movement of the linear stage is N, the measurement target range in the height direction of the workpiece is Z _A , the measurement field of view is V, the height direction dimension of the measurement field of view is Z _V , and the size of the overlapping area for joining the measurement data in the height direction is Z _m ,
The number of repetitions N of the linear movement is determined within a range where N×Z _V −(N−1)×Z _m ≧Z _A ;
When the number of times the rotational movement of the rotating stage is repeated is M, the circumferential length of the inner surface of the work is C _A , the circumferential dimension of the measurement field of view is C _V , and the size of the overlapping area for joining the measurement data in the rotational direction is C _m ,
A measurement method in which the number of times M the rotational movement is repeated is determined within a range that satisfies M×C _v −(M−2)×C _m ≧C _A.

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