JP6977205B2 - Displacement acquisition device, displacement acquisition method, and program - Google Patents

Description

The present invention relates to a technique for measuring surface displacement of an object to be measured by using a sampling moire method.

In the sampling moire method, a regular pattern (for example, a grid pattern) is attached to the surface of an object to be measured (hereinafter referred to as a target surface), and the displacement of the target surface is measured based on the image data of the grid pattern. That is, in the image data of the lattice pattern, a process of thinning out the pixels is performed at a fixed cycle, and this process is performed only a plurality of times by changing the thinning start point of the pixels to acquire a plurality of moire fringe images. The displacement of the target surface is obtained based on the change in the phase of the moire fringes caused by these moire fringe images.

FIG. 1 is an explanatory diagram showing an example of the sampling moire method. FIG. 1 shows a one-dimensional case for simplicity. FIG. 1 (A) shows a lattice pattern attached to the surface of the object, and FIG. 1 (B) shows image data obtained by imaging this lattice pattern. The luminance distribution I in the image data of FIG. 1 (B) is represented by the following equation (1).

In the formula (1), I (x) indicates the luminance of one point in the target surface at the one-dimensional coordinate x. φ (x) is the phase at the coordinates x. I _a is the luminance amplitude of the grid pattern, and I _b is the background luminance. In order to generate moire fringes (that is, new fringe patterns) in an image, thinning processing and luminance interpolation processing are performed.

FIG. 1C shows an image after the thinning process. In the thinning process, pixels are sampled at a period T close to the period Q of the lattice pattern in the image, and pixels at other positions are thinned out. The thinning process is performed a plurality of times. The sampling period T is the same between the plurality of thinning processes, but the starting point of the thinning is changed. A plurality of images after decimation are obtained for each of a plurality of decimation processes (in FIG. 1, the start point is indicated by k = 0, 1, 2, or 3).

In the luminance interpolation process, the luminance of the thinned pixels is linearly interpolated as shown in FIG. 1 (D) in the image after each thinning process. As a result, a plurality of moire fringe image data can be obtained. The period of the luminance distribution in each moire fringe image data is larger than the period of the checkered pattern and the luminance distribution of the image data of FIG. 1 (B). The luminance distribution of each moire fringe image data is expressed by the following equation (2).

In equation (2), k is the thinning start point, and k = 0, 1, 2, or 3. φ _m (x) is the phase of the moire fringes at the coordinates x. Further, Q is the pitch of the grid pattern in the image data of FIG. 1 (B) (that is, the distance between adjacent grids), and T is the sampling period in the thinning process. Using a plurality of moire fringe image data having different phases, the phase φ _m (x) of the moire fringes is calculated by the discrete Fourier transform of the following equation (3).

_{By obtaining the change Δφ m} (x) in the phase φ _m (x) of the moire fringes, the in-plane displacement (displacement in the direction along the target surface) of the target surface can be obtained. That is, when the actual pitch of the grid pattern is p, the in-plane displacement U can be obtained by U = Δφ _m (x) · p / 2π. In the present application, the mark "・" means multiplication.

Such a sampling moire method is described in, for example, Patent Document 1 and Non-Patent Document 1.

Patent No. 4831703

"Development of Optical Out-of-plane Displacement Distribution Measurement Method Using Single Camera and Regular Pattern" Experimental Mechanics, Vol. 15, No. 4 (2015), pp. 309-314

However, in the measurement by the sampling moire method, at least one of the following measurement errors (1) to (4) occurs.
(1) The target surface may be tilted from a plane perpendicular to the optical axis of the camera. This inclination is due to, for example, that the target surface is a curved surface. In the image, even if the actual displacement of the target surface is the same, an error occurs in the measured value of the displacement depending on the inclination of the target surface.
(2) An error occurs in the measured value of displacement depending on the measurement direction. That is, the displacement at the measurement point on the target surface existing in the optical axis direction of the camera when viewed from the camera, and the displacement at the measurement point on the target surface existing in the direction tilted from the optical axis of the camera when viewed from the camera. There is an error in the measured value between them.
(3) An error occurs in the measured value due to an error (aberration, etc.) inherent in the camera.
(4) An error occurs in the measured value due to an error in the actual pitch of the grid pattern.

Therefore, an object of the present invention is to measure the inclination of the target surface, the measurement direction, the error peculiar to the camera, and the actual pitch of the lattice pattern when measuring the displacement of the measurement point on the target surface by using the sampling moire method. The purpose is to be able to reduce the measurement error due to at least one of the errors.

In order to achieve the above object, according to the present invention, it is a displacement acquisition device that measures the displacement of the object surface of an object.
A camera that captures a regular pattern on the target surface, and a data processing unit that obtains the displacement of the measurement point on the target surface as the measured displacement by the sampling moire method based on the image data of the pattern captured by the camera. Displacement measuring device with
A correction coefficient calculation device for obtaining a correction coefficient for the measured displacement, and a correction coefficient calculation device.
A displacement calculation device for calculating the corrected displacement of the measurement point based on the measurement displacement and the correction coefficient is provided.
The measurement point is located in the set direction as seen from the camera, and the correction coefficient is obtained for the set direction.
In order to obtain the correction coefficient, the relative position between the camera and the target surface is changed.
The displacement measuring device measures the displacement of the measurement point of the target surface existing in the set direction due to this change as the displacement for coefficient calculation.
The correction coefficient calculation device is provided with a displacement acquisition device that obtains the correction coefficient based on the displacement for calculating the coefficient and the amount of change in the relative position.

Further, according to the present invention, it is a displacement acquisition method for measuring the displacement of the object surface of an object.
(A) Image data is acquired by taking an image of a regular pattern provided on the target surface with a camera.
(B) Based on the image data, the displacement of the measurement point on the target surface is obtained as the measurement displacement by the sampling moire method.
(C) Based on the measured displacement and the correction coefficient, the corrected displacement of the measurement point is calculated.
The measurement point is located in the set direction as seen from the camera, and the correction coefficient is obtained for the set direction.
To obtain the correction coefficient
(A) By changing the relative position between the camera and the target surface,
(B) The displacement of the measurement point of the target surface existing in the set direction due to this change is measured as the displacement for coefficient calculation.
(C) Provided is a displacement acquisition method for obtaining the correction coefficient based on the displacement for calculating the coefficient and the amount of change in the relative position.

Further, according to the present invention, it is a program that executes a process for measuring the displacement of the object surface of an object.
A process of obtaining the displacement of a measurement point on the target surface as a measurement displacement by a sampling moire method based on image data obtained by imaging a regular pattern provided on the target surface with a camera.
The process of obtaining the correction coefficient for the measured displacement and
A computer is made to execute a process of calculating the corrected displacement of the measurement point based on the measurement displacement and the correction coefficient.
The measurement point is located in the set direction as seen from the camera, and the correction coefficient is obtained for the set direction.
When the relative position between the camera and the target surface is changed in order to obtain the correction coefficient, the process for obtaining the correction coefficient is:
Based on the image data obtained by capturing the pattern with a camera before this change and the image data obtained by capturing the pattern with a camera after this change, the pattern exists in the setting direction due to this change. The process of measuring the displacement of the measurement point on the target surface as the displacement for calculating the coefficient, and
A program is provided that includes a process of obtaining the correction coefficient based on the displacement for calculating the coefficient and the amount of change in the relative position.

According to the present invention described above, the relative position between the camera and the target surface is changed, and the displacement of the measurement point of the target surface existing in the setting direction due to this change is measured as the displacement for coefficient calculation. The correction coefficient is obtained based on the displacement for calculating the coefficient and the amount of change in the relative position. This correction coefficient includes measurement error due to the inclination of the target surface with respect to the plane perpendicular to the optical axis of the camera, measurement error depending on the direction of the measurement point seen from the camera, error specific to the camera, and the actual grid pattern. At least one (eg, all) of the pitch error is reflected.
Therefore, such measurement error can be reduced or eliminated by calculating the corrected displacement of the measurement point based on the measured displacement of the target surface and the correction coefficient.

It is explanatory drawing of the sampling moire method. The configuration of the displacement acquisition device according to the embodiment of the present invention is shown. It is explanatory drawing of the process of acquiring the in-plane correction coefficient _{Kux (x, y), Δz.} It is explanatory drawing of the process of acquiring the in-plane correction coefficient _{Kux (x, y), Δx.} It is explanatory drawing of the process of acquiring the out-of-plane correction coefficient _{Ko (x, y), Δz.} It is explanatory drawing of the process of acquiring the out-of-plane correction coefficient _{Ko (x, y), Δx.} It is a flowchart which shows the displacement acquisition method by embodiment of this invention. It is a flowchart which shows the processing of the initial state in the correction coefficient acquisition processing. It is a flowchart which shows the process of the z-direction movement in the correction coefficient acquisition process. It is a flowchart which shows the process of the x-direction movement in the correction coefficient acquisition process.

An embodiment of the present invention will be described with reference to the drawings. In addition, the same reference numerals are given to the common parts in each figure, and duplicate description is omitted.

[Displacement acquisition device configuration]
FIG. 2 shows the configuration of the displacement acquisition device 10 according to the embodiment of the present invention. The displacement acquisition device 10 measures the displacement of the surface of the object 1 to be measured (hereinafter, also simply referred to as the target surface 1a). This displacement may be, for example, a displacement due to a load applied to the object 1 or a displacement due to the vibration of the object 1, but is not limited thereto. The displacement acquisition device 10 includes a displacement measurement device 3, a correction coefficient calculation device 5, and a displacement calculation device 9.

The displacement measuring device 3 obtains the displacement of the measuring point (hereinafter, simply referred to as the measuring point) on the target surface 1a based on the sampling moire method. In this embodiment, this displacement includes an in-plane displacement and an out-of-plane displacement. The in-plane displacement is a displacement in the direction along the target surface 1a. The out-of-plane displacement is the displacement of the measurement point in the direction intersecting (for example, orthogonal to) the target surface 1a. The displacement measuring device 3 has a camera 3a and a data processing unit 3b.

The camera 3a acquires image data of this pattern by taking an image of a regular pattern provided on the target surface 1a. Here, the regular pattern is, for example, a checkerboard pattern, but other patterns may be used as long as the moire fringe image data described later can be generated.

The data processing unit 3b obtains the displacement of the measurement point on the target surface 1a by the sampling moire method based on the image data of the pattern captured by the camera 3a. In the present embodiment, the displacement of the measurement point is obtained for each of the plurality of setting directions.

The luminance distribution I (x, y) of the image data acquired by the camera 3a is expressed by the following equation (4). Here, x and y indicate the x-coordinate and the y-coordinate in the xyz coordinate system fixed to the camera 3a. This xyz coordinate system is a three-dimensional coordinate whose z-axis is parallel to the optical axis C (direction of the camera 3a) of the camera 3a. In the following, the x-direction, the y-direction, and the z-direction mean the direction parallel to the x-axis, the direction parallel to the y-axis, and the direction parallel to the z-axis in the above-mentioned xyz coordinate system.

In the formula (4), I (x, y) indicates the luminance of the coordinates (x, y) of one point in the target surface 1a. φ ₀ (x, y) is the initial phase. Q is the pitch Q (x, y) in the x direction of the grid pattern in the above-mentioned image data. Further, I _a is the amplitude of the luminance, and I _b is the background luminance.

The data processing unit 3b performs thinning processing and luminance interpolation processing on the above-mentioned image data. In the present embodiment, the data processing unit 3b performs thinning processing and luminance interpolation processing in the x direction. In the thinning process, the data processing unit 3b samples and maintains the pixels of the image data in a predetermined sampling cycle (in this example, the cycle T close to the cycle of the pattern) in the x direction, and performs pixels at other positions. Thin out and delete. In the luminance interpolation process, the data processing unit 3b interpolates (for example, linear interpolation) the luminance of the thinned pixels based on the luminance of the pixels existing around the pixel.

The data processing unit 3b performs such thinning processing and luminance interpolation processing a plurality of times. The sampling period T is the same between the plurality of thinning processes, but the starting point of the thinning is changed. The data processing unit 3b generates a plurality of moire fringe image data corresponding to each of the plurality of times by performing the thinning process and the luminance interpolation process a plurality of times on the above-mentioned image data.
In this example, the data processing unit 3b generates T moire fringe image data by thinning processing in the x direction and luminance interpolation processing. These moire fringe image data are represented by the following equation (5).

In equation (5), k indicates the starting point of thinning in the x direction. k takes the values of 0, 1, 2, ..., T-1.
The data processing unit 3b applies the discrete Fourier transform to the equation (5), _{and obtains the phase φ m} (x, y) of the moire fringes by the following equation (6).

The data processing unit 3b can obtain the in-plane displacement of the target surface 1a by _{obtaining the change Δφ m (x, y) of the phase φ m} (x, y) of the moire fringes. That is, assuming that the lattice pattern is a pattern that is repeated at pitch p (constant intervals) in the x direction, the in-plane displacement U _x (x, y) is set to U _x (x, y) = Δφ _m (x, y). It can be obtained by p (x, y) / 2π (hereinafter, p (x, y) is also simply described as p, and U _x (x, y) is also described _{as U x).} U _x is an in-plane displacement along the x direction in the xyz coordinate system, in other words, an in-plane displacement in a plane parallel to the xz plane (including the xz plane) in the xyz coordinate system.
_{Here, φ m} (x, y) obtained in the initial state is defined _{as φ m0 (x, y), and φ m} (x, y) obtained at the time of measurement is defined as _{φ m} (x, y) as it is. In this case, Δφ _m is Δφ _m = φ _m (x, y) −φ _m0 (x, y).

The focal length of the camera 3a is f, the actual pitch of the lattice pattern provided on the target surface 1a is the above p, the pitch of the lattice in the image data is the above Q, and the camera 3a in the optical axis C direction of the camera 3a ( When the distance from the center of the objective lens of the camera 3a) to the lattice pattern (the surface of the target object 1) is Z, the following equation (7) holds.

Z = f ・ p / Q ・ ・ ・ (7)

Based on this equation (7), the data processing unit 3b obtains the out-of-plane displacement O of the measurement point by the following equation (8).

O = f ・ p / Q−f ・ p / Q ₀ ... (8)

Here, Q ₀ is the pitch in the x direction of the lattice pattern in the image data obtained by the camera 3a capturing the target surface 1a in the initial state, and Q is the pitch in the x direction of the target surface 1a captured by the camera 3a at the time of measurement. It is the pitch in the x direction of the lattice pattern in the obtained image data.

Q is calculated as follows. First, the following equation (9) holds from the above equation (5).
From this equation, the data processing unit 3b obtains Q. For example, the equation (9) is approximated by the following equation (10), and the data processing unit 3b obtains Q by the following equation (11) which is a modification of the equation (10).

In the equation (11), _{x + 1 of φ m} (x + 1, y) is the x coordinate of the pixel adjacent to the pixel (x coordinate) of interest for obtaining Q in the x axis direction, and φ _m (x-1, y). x-1 of y) is the x-coordinate of a pixel adjacent to the pixel of interest on the opposite side of the x-coordinate x + 1 in the x-axis direction. _{The data processing unit 3b obtains Q 0} by the same method as in the case of Q.

The correction coefficient calculation device 5 obtains a correction coefficient related to the measured displacement obtained by the displacement measuring device 3. Correction factor includes a plane correction factor K _u about plane displacement, and a plane correction factor K _o about out-of-plane displacement.

<In-plane correction coefficient>
3 and 4 are explanatory views of the process of acquiring the in- _{plane correction coefficient Ku.} In FIGS. 3 and 4, the xyz coordinate system is a three-dimensional coordinate system fixed to the camera 3a and has the above-mentioned x-axis, y-axis, and z-axis.

In FIGS. 3 and 4, the angle θ (x, y) indicates the above-mentioned setting direction as seen from the camera 3a. That is, the angle θ (x, y) is the angle formed by the optical axis C and the set direction. The angle α (x, y) indicates the inclination of the target surface 1a. That is, the angle α (x, y) indicates the angle formed by the x direction and the target surface 1a.

In order to obtain the in-plane correction coefficients _{Kux (x, y) and Δz} in the z direction, the relative positions of the camera 3a and the target surface 1a are changed by the amount of change Δz ₀ in the z direction as shown in FIG.

_{At this time, the in-plane displacements U 0x (x, y) and Δz due to Δz 0} in the plane parallel to the xz plane are based on the following equation, assuming that θ (x, y) is sufficiently small as shown in FIG. It can be approximated by 12).

U _{0x (x, y), Δz} = Δz ₀ · tan θ (x, y) / cosα (x, y) ... (12)

Based on the equation (12), the in- _{plane displacement U 0x (x, y) with respect to Δz 0} and the in-plane _{correction coefficients Kux (x, y) and Δz} as the volatility of Δz are expressed by the following equation (13). ..

K _{ux (x, y), Δz} = tanθ (x, y) / cosα (x, y) ... (13)


Since θ (x, y) and α (x, y) are unknown in equation (13), _{Kux (x, y) and Δz} can be obtained from θ (x, y) and α (x, y). Although not, Δz ₀ is known, and U _{0x (x, y) and Δz} are obtained by the displacement measuring device 3. Therefore, in the present embodiment, _{Kux (x, y) and Δz} are obtained by the following equation (14).

K _{ux (x, y), Δz} = U _{0x (x, y), Δz} / Δz ₀ ... (14)

plane correction factor _{K ux} x direction _{(x, y),} in order to determine the _{[Delta] x,} the relative position of the camera 3a and the target surface 1a, as shown in FIG. 4, is changed by the change amount [Delta] x ₀ in the x direction.

At this time, the in-plane displacements U _{0x (x, y) and Δx due to Δx 0} in the plane parallel to the xz plane are expressed by the following equation (15) as shown in FIG.

U _{0x (x, y), Δx} = Δx ₀ / cosα (x, y) ... (15)

Based on the equation (15), the in- _{plane displacement U 0x (x, y) with respect to Δx 0} and the in-plane _{correction coefficients Kux (x, y) and Δx} as the volatility of Δx are expressed by the following equation (16). ..

K _{ux (x, y), Δx} = 1 / cosα (x, y) ... (16)

Since α (x, y) is unknown in equation (16), _{Kux (x, y) and Δx} cannot be obtained from α (x, y), but Δx ₀ is known and U _{0x ( x, y) and Δx} are obtained by the displacement measuring device 3. Therefore, in the present embodiment, _{Kux (x, y) and Δx} are obtained by the following equation (17).

K _{ux (x, y), Δx} = U _{0x (x, y), Δx} / Δx ₀ ... (17)

<Out-of-plane correction coefficient>
5 and 6 are explanatory views of a process of obtaining out-of-plane correction factor K _o. In FIGS. 5 and 6, the xyz coordinate system, the angle θ (x, y), and the angle α (x, y) are the same as in FIGS. 3 and 4.

In order to obtain the out-of-plane correction coefficients _{Ko (x, y) and Δz} in the z direction, the relative positions of the camera 3a and the target surface 1a are changed by the amount of change Δz ₀ in the z direction as shown in FIG.

At this time, the out-of-plane displacements O _{0 (x, y) and Δz due to Δz 0} can be approximated by the following equation (18), assuming that θ (x, y) is sufficiently small as shown in FIG.

O _{0 (x, y), Δz} = Δz ₀ · {1 + tanθ (x, y) · tanα (x, y)} / cos {α (x, y) + θ (x, y)} ... (18)


Based on the equation (18), out-of-plane displacement _{O 0} for Delta] z _{0 (x, y),} plane correction coefficient as a rate of change in _{Delta] z K o (x, y),} a _{Delta] z,} the following equation (19) Represent.

_{Ko (x, y), Δz} = {1 + tanθ (x, y) · tanα (x, y)} / cos {α (x, y) + θ (x, y)} ... (19)

Since θ (x, y) and α (x, y) are unknown in equation (19), K _0z cannot be obtained from θ (x, y) and α (x, y), but Δz ₀ is. It is known, and O _{0 (x, y) and Δz} are obtained by the displacement measuring device 3. Therefore, in this embodiment _{, Ko (x, y) and Δz} are obtained by the following equation (20).

_{Ko (x, y), Δz} = O _{0 (x, y), Δz} / Δz ₀ ... (20)

plane correction factor K _o x direction _{(x, y),} in order to determine the _{[Delta] x,} the relative position of the camera 3a and the target surface 1a, as shown in FIG. 6, is changed by the change amount [Delta] x ₀ in the x direction.

At this time, the out-of-plane displacements O _{0 (x, y) and Δx} are expressed by the following equation (21) as shown in FIG.

O _{0 (x, y), Δx} = Δx ₀ · tanα (x, y) / cos {α (x, y) + θ (x, y)} ... (21)


Based on the equation (21), out-of-plane displacement _{O 0} for [Delta] x _{0 (x, y),} plane correction coefficient as a rate of change _{[Delta] x K o (x, y),} the _{[Delta] x,} the following equation (22) Represent.

_{Ko (x, y), Δx} = tanα / cos {α + θ (x, y)} ... (22)

Since α (x, y) is unknown in equation (22), _{Ko (x, y) and Δx} cannot be obtained from α (x, y), but Δx ₀ is known and O _{0 ( x, y) and Δx} are obtained by the displacement measuring device 3. Therefore, in this embodiment _{, Ko (x, y) and Δx} are obtained by the following equation (23).

_{Ko (x, y), Δx} = O _{0 (x, y), Δx} / Δx ₀ ... (23)

<Process to obtain correction coefficient>
By the above, the correction coefficient _{K ux (x, y),} Δz, K o (x, y), in order to determine the _{Delta] z,} the relative position of the camera 3a and the target surface 1a, the optical axis C parallel to the z-direction Change by the amount of change Δz ₀ . Next, the displacement measuring device 3 obtains the in- _{plane displacement U 0x (x, y), Δz} and the out-of-plane displacement O _{0 (x, y), Δz} as the coefficient calculation displacement according to the _{change amount Δz 0.} Thereafter, the correction coefficient calculating unit 5, Delta] z ₀ and _{U 0x (x, y),} K ux as plane correction factor _{K u} on the basis of the _{Δz (x, y), Δz} = U 0x (x, y), calculates _Δz / _{Δz 0, Δz 0} and _{O 0 (x, y),} K o as plane correction factor _{K o} based on the _{Δz (x, y), Δz} = O 0 (x, y), Δz / Δz ₀ is calculated.

Further, the correction coefficient _{K ux (x, y),} Δx, K o (x, y), in order to determine the _{[Delta] x,} to the relative position of the camera 3a and the target surface 1a is changed by the change amount [Delta] x ₀ in the x direction. Next, the displacement measuring device 3 obtains the in- _{plane displacement U 0x (x, y), Δx} and the out-of-plane displacement O _{0 (x, y), Δx} as the coefficient calculation displacement according to the _{change amount Δx 0.} Thereafter, the correction coefficient calculating unit 5, [Delta] x ₀ and _{U 0x (x, y),} K as in-plane correction factor _{K u} on the basis of _{Δx ux (x, y),} Δx = U 0x (x, y), calculates _Δx / _{Δx 0, Δx 0} and _{O 0 (x, y),} K o as plane correction factor _{K o} based on _{Δx (x, y), Δx} = O 0 (x, y), Δx / Δx ₀ is calculated.

As described above, the correction coefficient calculation unit 5, correction coefficient _{K ux (x, y),} Δz, K o (x, y), Δz, K ux (x, y), Δx, K o (x, y _{), Δx} is obtained in advance and stored in the storage device 7.

After that, when measuring the displacement of the measurement point on the target surface 1a, the displacement calculation device 9 measures the in-plane displacement U _x and the out-of-plane displacement O as the measured displacement, and these in-plane displacement U _x and the out-of-plane displacement O , the correction coefficient _{K ux (x, y),} Δz, K ux (x, y), Δx, K o (x, y), Δz, K o (x, y), on the basis of the _{[Delta] x,} corrected displacement The displacement Δz in the z direction and the displacement Δx in the x direction are calculated by the following equations (24) and (25).

Δz = ( _{Kux (x, y), Δx} · _{OK o (x, y), Δz} · U _x ) / ( _{Kux (x, y), Δx} · _{Ko (x, y), Δz} − K _{ux (x, y), Δz} · _{Ko (x, y), Δx} ) ... (24)

Δx = ( _{Ko (x, y), Δz} · U _x −K _{ux (x, y), Δz} · O) / ( _{Kux (x, y), Δx} · _{Ko (x, y), Δz} − K _{ux (x, y), Δz} · _{Ko (x, y), Δx} ) ... (25)

Equations (24) and (25) are derived from the following relational expressions (26) and relational expression (27).

U _x = K _{ux (x, y), Δx} · Δx + K _{ux (x, y), Δz} · Δz ... (26)

O = _{Ko (x, y), Δx} · Δx + _{Ko (x, y), Δz} · Δz ... (27)

In the present embodiment, the displacement acquisition device 10 may include a drive device 11 as shown in FIG. The drive device 11 changes the relative position between the camera 3a and the target surface 1a by moving the camera 3a. In this case, the amount of change in the relative displacement described above is the amount of movement of the camera 3a by the drive device 11. In the above example, the drive device 11 can move the camera 3a in the x-direction and the z-direction. _{The correction coefficient calculation device 5 obtains a correction coefficient based on the movement amount (Δz 0} or Δx _{0 in the} above example) set in advance or detected by the detectors 12a and 12b and the displacement for coefficient calculation.

In the example of FIG. 2, the drive device 11 can move in the x direction with the first stage 11a in which the camera 3a is installed and can move in the z direction, and the first motor 11b that drives the first stage 11a in the z direction. A second stage 11c provided in the first stage 11a and a second motor 11d provided in the first stage 11a to drive the second stage 11c in the x direction with respect to the first stage 11a are provided.

[Displacement acquisition method]
FIG. 7 is a flowchart showing a displacement acquisition method according to the embodiment of the present invention. This displacement acquisition method is performed using the displacement acquisition device 10 described above. This displacement acquisition method includes a correction coefficient acquisition process and a measurement process.

In the correction coefficient acquisition process, the relative position between the camera 3a and the target surface 1a is changed, and the displacement of the measurement point of the target surface 1a existing in the set direction due to this change is measured as the displacement for coefficient calculation by the displacement measuring device 3. do.
Next, in the correction coefficient acquisition process, the correction coefficient calculation device 5 obtains the correction coefficient based on the displacement for coefficient calculation and the amount of change in the relative position.

In a specific example, the correction coefficient acquisition process includes a process of an initial state, a process of moving in the z direction, and a process of moving in the x direction.

<Processing of initial state>
FIG. 8 is a flowchart showing the processing in the initial state. The processing in the initial state includes steps S1 to S5.

In step S1, the camera 3a at the reference position acquires image data by imaging the lattice pattern of the target surface 1a.
In step S2, the data processing unit 3b generates a plurality of moire fringe image data by performing the above-mentioned thinning process and luminance interpolation process only a plurality of times on the image data obtained in step S1.
In step S3, the data processing unit 3b on the basis of the plurality of moire fringe image data obtained in step S2, the above-mentioned equation (6), of the moire fringes at the measurement point (x, y) a phase phi _{m (x} , Y). This φ _m (x, y) will be referred to as φ _m0 (x, y) below.
_{On the other hand, in step S4, the data processing unit 3b sets the pitch Q 0} (x, y) of the lattice pattern existing in the setting direction in the x direction in the image data obtained in step S1 in the above equations (9) to (9). According to 11), the image data is specified based on the area of the image data corresponding to the setting direction. _{At this time, Q is replaced with Q 0} (x, y) in (9) to (11).
In step S5, based on the pitch _Q 0 (x, y) specified in step S4 and the focal length f of the camera 3a, the actual pitch p (x, y) of the grid pattern in the x-direction and the data processing unit _{In 3b, the position z 0} = f · p (x, y) / Q ₀ (x, y) of the measurement point existing in the set direction in the z direction is obtained. Note that f and p (x, y) are known. It is assumed that the origin of the z-axis is in the camera 3a (the same applies hereinafter).

The above-mentioned steps S4 and S5 are performed for each of the plurality of setting directions. _{That is, in step S4, the pitch Q 0} (x, y) in the x direction of the grid pattern existing in each setting direction is specified, and in step S5, the position z ₀ for each setting direction corresponds to the setting direction. Obtained _{based on Q 0} (x, y).

<Processing of movement in z direction>
FIG. 9 is a flowchart showing the process of moving in the z direction. The process of moving in the z direction includes steps S6 to S15.

In step S6, the relative position between the camera 3a and the surface of the target object 1 is changed in the z direction by _{, for example, moving the camera 3a in the z direction by a minute amount Δz 0} from the state of step S1 (that is, the reference position). Change by the amount Δz _0. Δz ₀ may be 1/500 or more of the above-mentioned p (x, y) and may be pitch p (x, y) or less. Δz ₀ has a size of, for example, about 1 mm.
In step S7, the camera 3a acquires image data by photographing the lattice pattern of the target surface 1a.

In step S8, the data processing unit 3b generates a plurality of moire fringe image data by performing the above-mentioned thinning process and brightness interpolation process only a plurality of times on the image data obtained in step S7.
In step S9, the data processing unit 3b uses the above equation (6) to determine the moire fringes at the measurement points (x, y) existing in the setting direction based on the plurality of moire fringe image data obtained in step S8. Find the phase φ _m (x, y). This φ _m (x, y) will be referred to as φ _mz (x, y) below.

In step S10, the data processing unit 3b obtains the in-plane displacement U _{0x (x, y) and Δz due to Δz 0.} Step S10 includes step S10a and step S10b. In step S10a, the data processing portion _{3b, Δφ m (x, y)} = φ mz (x, y) -φ m0 (x, y) by, obtaining the Δφ _m (x, y). In step S10b, the data processing unit 3b has U _{0x (x, y), Δz} = p (x, y) · Δφ _m (x, y) / 2π, and the in-plane displacement U _{0x (x, y ) due to Δz 0. ), Δz} . Here, Δφ _m (x, y) is obtained in step S10a. The in-plane displacement U _{0x (x, y), Δz} is the in-plane displacement of the measurement point (x, y) existing in the set direction (hereinafter, the in-plane displacement U _{0x (x, y) corresponding to the set direction). ), Δz} ), and φ _mz (x, y) and φ _m0 (x, y) are the phases corresponding to the setting direction.

In step S11, based on the amount of change Δz _{0 in step S6 and U 0x (x, y), Δz} obtained in step S10, the data processing unit 3b sets the in-plane correction coefficient K _{ux ( x, y), Δz} are calculated by _{Kux (x, y), Δz} = U _{0x (x, y), Δz} / Δz _0. The amount of change Δz ₀ is set in advance and stored in, for example, the storage device 7, or is detected by the detector 12a and input from the detector 12a to the correction coefficient calculation device 5 (the same applies hereinafter).

The above-mentioned steps S10 and S11 are performed for each of the plurality of setting directions. _{That is, in step S10, in-plane displacements U 0x (x, y) and Δz} of a plurality of measurement points (x, y) existing in each of the plurality of setting directions are obtained, and in step S11, in-plane correction for each setting direction is obtained. The coefficients K _{ux (x, y), Δz} are calculated based on the in-plane displacement U _{0x (x, y), Δz corresponding to the set direction.}

On the other hand, in step S12, the data processing portion 3b, the setting in the image data obtained in step S7, the pitch to Q ₁ x direction of the grating pattern that exists in the set direction, in accordance with the above equation (9) to (11) It is specified based on the area of the image data corresponding to the direction. In this case, replace Q to _{Q 1} in (9) to (11).
In step S13, the data processing unit 3b includes a pitch _{Q 1} specified in step S12, on the basis of the focal length f of the camera 3a, the actual pitch p (x, y) of the grid pattern and are present in the set direction _{Find the position z 1} = f · p (x, y) / Q ₁ of the measurement point in the z direction.
In step S14, the data processing unit 3b, based on _{z 1} and obtained in _{z 0} and the step 13 obtained in step _{S5, O 0 (x, y} ), by _{Delta] z} = _z 1 -z _0, by Delta] z ₀ The out-of-plane displacement O _{0 (x, y), Δz} is obtained.
In step S15, a variation Delta] z ₀ in step S6, _{O 0} obtained in step S14 _{(x, y),} based on the _{Delta] z,} the correction coefficient calculating unit 5, out-of-plane correction factor _{K o (x, y ), Δz} is calculated by _{Ko (x, y), Δz} = O _{0 (x, y), Δz} / Δz _0.

The above-mentioned steps S12 to S15 are performed for each of the setting directions in the image data. _{That is, in step S13, the position z 1} of the measurement point (x, y) existing in each setting direction in the z direction is _{obtained based on Q 1} corresponding to the setting direction, and in step S14, the surface for each setting direction is obtained. The outer displacements O _{0 (x, y) and Δz are calculated based on the position z 1} and the position z ₀ corresponding to the set direction, and in step S15, the out-of-plane correction coefficient _{Ko (x, x,) for each set direction is calculated. y) and Δz} are calculated based on the out-of-plane displacement O0 _{(x, y) and Δz corresponding to the set direction.}

<Processing of movement in x direction>
FIG. 10 is a flowchart showing the process of moving in the x direction. The process of moving in the x direction includes steps S16 to S25.

In step S16, the state of step S1 (or reference position), for example, a camera 3a by moving in the x direction by a very small amount [Delta] x _0, the relative position of the camera 3a and the target surface 1a, the x-direction to the change amount [Delta] x Change by _0. When continuing after the processing of moving in the z direction, the camera 3a is _{moved in the z direction by −Δz 0} to return the position of the camera 3a to the state of step S1, and then the camera 3a is moved in the x direction by a minute amount Δx _0. Move it. Thus, from the state of step S1, the relative position of the camera 3a and the target surface 1a, is changed by the change amount [Delta] x ₀ in the x direction. [Delta] x ₀ is above of p (x, y) be 1/500 or more pitch p (x, y) may be less. [Delta] x ₀ is, for example, a size of about 1 mm.
In step S17, the camera 3a acquires image data by photographing the lattice pattern of the target surface 1a.

In step S18, the data processing unit 3b generates a plurality of moire fringe image data by performing the above-mentioned thinning process and luminance interpolation process only a plurality of times on the image data obtained in step S17.
In step S19, the data processing unit 3b uses the above equation (6) to determine the moire fringes at the measurement points (x, y) existing in the setting direction based on the plurality of moire fringe image data obtained in step S18. Find the phase φ _m (x, y). This φ _m (x, y) will be referred to as φ _mx (x, y) below.

In step S20, the data processing unit 3b obtains the in-plane displacement U _{0x (x, y) and Δx due to Δx 0.} Step S20 includes step S20a and step S20b. In step S20a, the data processing unit 3b _{obtains Δφ m} (x, y) by _{Δφ m} (x, y) = φ _mx (x, y) −φ _m0 (x, y). In step S20b, the data processing portion _{3b, U 0x (x, y)} , Δx = p (x, y) · Δφ m (x, y) / 2π , the plane displacement by Δx _{0 U 0x (x, y ), Δx} . Here, Δφ _m (x, y) is obtained in step S20a. The in-plane displacement U _{0x (x, y), Δx} is the in-plane displacement of the measurement point (x, y) existing in the set direction (hereinafter, the in-plane displacement U _{0x (x, y) corresponding to the set direction), It} is also referred to as _{Δx), and φ mx} (x, y) and φ _m0 (x, y) are phases corresponding to this setting direction.

In step S21, the data processing unit 3b sets the in-plane correction coefficient K _{ux (x, y) based on the amount of change Δx 0 in step S16 and U 0x (x, y), Δx} obtained in step S20. _{, Δx} is calculated by _{Kux (x, y), Δx} = U _{0x (x, y), Δx} / Δx _0. Variation [Delta] x ₀ is stored is set in advance, for example, the storage device 7, or may be input from the detector 12b is detected by the detector 12b in the correction coefficient calculating unit 5 (hereinafter the same).

The above-mentioned steps S20 and S21 are performed for each of the plurality of setting directions. _{That is, in step S20, in-plane displacements U 0x (x, y) and Δx} of a plurality of measurement points (x, y) existing in each of the plurality of setting directions are obtained, and in step S21, in-plane correction for each setting direction is obtained. The coefficients K _{ux (x, y), Δx} are calculated based on the in-plane displacements U _{0x (x, y), Δx corresponding to the set direction.}

On the other hand, in step S22, the data processing portion 3b, the setting in the image data obtained in step S17, the pitch _{Q 2} in the x direction of the grating pattern that exists in the set direction, in accordance with the above equation (9) to (11) It is specified based on the area of the image data corresponding to the direction. In this case, replace Q to _{Q 2} in (9) to (11).
In step S23, the data processing unit 3b on the basis of the pitch _{Q 2} to which specified in step S22, the focal length f of the camera 3a, the actual pitch p (x, y) of the grid pattern in the x-direction and setting a direction _{The position z 2} = f · p (x, y) / Q ₂ of the measurement point existing in the z direction is obtained.
In step S24, the data processing unit 3b, based on the _{z 2} obtained in _{z 0} and the step 23 obtained in step _S5, the _{O 0 (x, y),} Δx = z 2 -z 0, by [Delta] x ₀ The out-of-plane displacements O _{0 (x, y) and Δx} are obtained.
In step S25, the data processing unit 3b has an out-of-plane correction coefficient _{Ko (x, y) based on the amount of change Δx 0 in step S16 and O 0 (x, y), Δx} obtained in step S24. _{, Δx} is calculated by _{Ko (x, y), Δx} = O _{0 (x, y), Δx} / Δx _0.

The above-mentioned steps S22 to S25 are performed for each of the setting directions in the image data. _{That is, in step S23, the position z 2} in the z direction of the measurement point (x, y) existing in each setting direction is _{obtained based on Q 2} corresponding to the setting direction, and in step S24, the surface for each setting direction is obtained. The outer displacements O _{0 (x, y) and Δx are calculated based on the position z 2} and the position z ₀ corresponding to the set direction, and in step S25, the out-of-plane correction coefficient _{Ko (x, x, for each set direction) is calculated. y) and Δx} are calculated based on the out-of-plane displacements O0 _{(x, y) and Δx corresponding to the set direction.}

<Measurement processing>
In the displacement acquisition method according to the present embodiment, the measurement process is performed after the correction coefficient acquisition process described above. The measurement process includes steps S26 to S33 as shown in FIG.

In step S26, the camera 3a at the reference position acquires image data by imaging the lattice pattern of the target surface 1a.
In step S27, the data processing unit 3b generates a plurality of moire fringe image data by performing the above-mentioned thinning process and luminance interpolation process only a plurality of times on the image data obtained in step S26.
In step S28, the data processing unit 3b uses the above equation (6) to determine the moire fringes at the measurement points (x, y) existing in the setting direction based on the plurality of moire fringe image data obtained in step S27. Find the phase φ _m (x, y).

In step S29, the data processing unit 3b obtains the plane displacement _{U x.} Step S29 has step S29a and step S29b. In step S29a, the data processing portion _{3b, Δφ m (x, y)} = φ m (x, y) -φ m0 (x, y) by Δφ _m (x, y) is determined. Here, φ _m (x, y) is obtained in step S28, and φ _m0 (x, y) is φ _m (x, y) obtained in step S3, but at another time point in advance. _{It may be φ m} (x, y) in the obtained initial state. In step S29b, the data processing unit 3b obtains the in- _{plane displacement U x by U x} = p (x, y) · Δφ _m (x, y) / 2π. Here, Δφ _m (x, y) is obtained in step S29a.

The above-mentioned steps S28 and S29 are performed for each of the plurality of setting directions. _{That is, in step S28, the phase φ m} (x, y) of a plurality of measurement points (x, y) existing in each of the plurality of setting directions is obtained, and in step S29, the in-plane displacement U _x for each setting direction is determined. corresponding to the setting direction φ _m (x, y) and φ _m0 (x, y) is calculated based on.

On the other hand, in step S30, the data processing unit 3b specifies the pitch Q in the x direction of the lattice pattern existing in the setting direction in the image data obtained in step S26 based on the region of the image data existing in the setting direction. do.
In step S31, the data processing unit 3b moves in the setting direction based on the pitch Q specified in step S30, the focal length f of the camera 3a, and the actual pitch p (x, y) of the grid pattern in the x direction. The position z = f · p (x, y) / Q in the z direction of the existing measurement point (x, y) is obtained.
In step S32, the data processing unit 3b obtains the out-of-plane displacement O in the set direction by _{O = z−z 0 based on the z obtained in step S31.} Here, z ₀ is the z ₀ determined in step S5, it may be a z ₀ of previously determined initial state at other times.

The above-mentioned steps S30 to S32 are performed for each of the plurality of setting directions. That is, in step S31, the position z of the measurement point (x, y) existing in each setting direction in the z direction is obtained based on the Q corresponding to the setting direction, and in step S32, the out-of-plane displacement for each setting direction is obtained. O is calculated based on the position z and the position z _{0 corresponding to the setting direction.}

In step S33, the displacement calculating unit 9, a plane displacement U _x as measured displacement calculated in step S29, and the plane displacement O as measured displacement obtained in step S32, correction stored in the storage device 7 factor _{K ux (x, y),} Δz, K ux (x, y), Δx, K o (x, y), Δz, K o (x, y), based on the _{[Delta] x,} as a corrected displacement The displacement Δz in the z direction and the displacement Δx in the x direction are calculated by the above equations (24) and (25).

Step S33 is performed for each setting direction. That is, for each set direction in-plane displacement corresponding to the setting direction _{U x} and out-of-plane displacement O and the correction coefficient _{K ux (x, y),} Δz, K ux (x, y), Δx, K o (x _{, Y), Δz, Ko (x, y), Δx,} and the corrected displacements Δz and Δx are calculated.
Incidentally, in the storage device 7, for each setting direction, the correction coefficient _{K ux (x, y),} Δz, K ux (x, y), Δx, K o (x, y), Δz, K o (x, _{y) and Δx} are stored in association with the setting direction.

The data processing unit 3b and the correction coefficient calculation device 5 described above can be realized by, for example, a computer, a program, and a storage medium. In this case, the program causes the computer to execute each of the above-mentioned processes of the data processing unit 3b and the correction coefficient calculation device 5. In this case, the storage medium is a computer-readable medium (for example, a computer hard disk, a CD-ROM, etc.) that stores a program non-temporarily.

The above is the processing (referred to as xz processing) relating to each plane parallel to the xz plane (that is, the plane for each value of the xy coordinate). However, xz processing may be performed on one plane (including the xz plane) parallel to the xz plane.

[Yz processing]
In addition to the xz process described above, a process related to each plane parallel to the yz plane (referred to as yz process) may also be performed. The yz process is the same as the above-mentioned xz process and the contents in FIGS. 2 to 10 (except for the variable step S33) in which x is read as y and y is read as x (that is, x and y are replaced with each other). Therefore, the detailed explanation is omitted. However, the content that overlaps between the xz process and the yz process (for example, the process of obtaining the out-of-plane displacement O or the _{process of obtaining the} correction coefficient Koz) may be performed by either the xz process or the yz process. Further, when (x, y) representing the xy coordinates is read as (y, x), this is the same as (x, y), so (x, y) is not read.

In xz processing, as described above, the correction coefficient calculation unit 5, correction coefficient _{K ux (x, y),} Δz, K ux (x, y), Δx, K o (x, y), Δz, K o _{(X, y) and Δx} are obtained in advance and stored in the storage device 7.
Further, in the yz process, as in the xz process, the correction coefficient calculation device 5 has a correction coefficient K _{ui (x, y), Δz} , K _{ui (x, y), Δy} , _{Ko (x, y), Δy.} Is obtained in advance and stored in the storage device 7.

In step S33, the displacement calculation device 9 obtains the displacement Δz in the z direction, the displacement Δx in the x direction, and the displacement Δy in the y direction as the corrected displacement based on each correction coefficient stored in the storage device 7. That is, the displacement calculation device 9 obtains Δz, Δx, and Δy as solutions of the three-dimensional simultaneous equations represented by the following equations (28) to (30).

U _x = K _{ux (x, y), Δx} · Δx + K _{ux (x, y), Δy} · Δy + K _{ux (x, y), Δz} · Δz ... (28)

U _y = K _{ui (x, y), Δx} · Δx + K _{ui (x, y), Δy} · Δy + K _{ui (x, y), Δz} · Δz ... (29)

O = _{Ko (x, y), Δx} · Δx + _{Ko (x, y), Δy} · Δy + _{Ko (x, y), Δz} · Δz ... (30)

In these equations, U _x is the in-plane displacement (measured displacement) along the x direction obtained by the displacement measuring device 3 in the xz process, and U _y is the y direction obtained by the displacement measuring device 3 in the yz process. It is an in-plane displacement (measured displacement) along the above _, and _{Kux (x, y), Δy and Kui (x, y), Δx} are obtained in advance as follows _{, and Kux (x, y), Δy.} Is obtained by the following additional processing in the yz processing. The additional processing includes the following processes (a1) to (a6).

(A1) from the state of the above step S1, by moving by a small amount [Delta] y ₀ For example a camera 3a in the y direction, the relative position of the camera 3a and the target surface 1a, is changed by the change amount [Delta] y ₀ in the y-direction .. This process (a1) may be step S16 of the yz process.
(A2) Next, the camera 3a acquires image data by photographing the lattice pattern of the target surface 1a.
(A3) After that, the data processing unit 3b generates a plurality of moire fringe image data by performing the above-mentioned thinning process and luminance interpolation process only a plurality of times on the image data.
(A4) Next, the data processing unit 3b is based on the plurality of moire fringe image data in the x direction at the measurement points (x, y) existing in the set direction according to the above equation (6). Find the phase φ _m (x, y) of the moire fringes. This φ _m (x, y) will be referred to as φ _mx (x, y) below.

(A5) After that, the data processing unit 3b is subjected to _{Δy by U 0x (x, y), Δy} = p (x, y) · {φ _mx (x, y) −φ _m0 (x, y)} / 2π. _{In- plane displacement U 0x (x, y), Δy} along the x direction due to 0 is obtained. Here, the in-plane displacements U _{0x (x, y) and Δy} are in-plane displacements of the measurement points (x, y) existing in the setting direction, and φ _mx (x, y) and φ _{m 0 (x, y).} ) Is the phase in the x direction corresponding to this setting direction. φ _m0 (x, y) is the initial phase.
(A6) Based on the change amount Δy _{0 in the above (a1) and the U 0x (x, y), Δy} obtained in the above (a5), the data processing unit 3b has an in-plane correction coefficient _{Kux (x). , Y), Δy} are calculated by _{Kux (x, y), Δy} = U _{0x (x, y), Δy} / Δy _0. The amount of change Δy ₀ is set in advance and stored in, for example, the storage device 7, or is detected by the detector 12b and input from the detector to the correction coefficient calculation device 5. _{In the storage device 7, Kux (x, y) and Δy} are stored in association with each setting direction for each setting direction.

K _{ui (x, y) and Δx} are obtained by the next additional process in the xz process, similarly to the above-mentioned additional process for _{obtaining K ux (x, y) and Δy.} This additional process has the following processes (b1) to (b6).

(B1) from the state of step S1, for example a camera 3a by moving in the x direction by a very small amount [Delta] x _0, the relative position of the camera 3a and the target surface 1a, is changed by the change amount [Delta] x ₀ in the x direction. This process (b1) may be step S16 of the xz process.
(B2) Next, the camera 3a acquires image data by photographing the lattice pattern of the target surface 1a.
(B3) After that, the data processing unit 3b generates a plurality of moire fringe image data by performing the above-mentioned thinning process and luminance interpolation process only a plurality of times on the image data.
(B4) Next, the data processing unit 3b uses the above-mentioned equation (6) in which x and y are exchanged based on the plurality of moire fringe image data, and the measurement points (x, y) existing in the setting direction. _{The phase φ m} (x, y) of the moire fringes in the y direction is obtained. This φ _m (x, y) will be referred to as φ _my (x, y) below.

(B5) After that, the data processing unit 3b is subjected to _{Δx by U 0y (x, y), Δx} = p (x, y) · {φ _my (x, y) −φ _m0 (x, y)} / 2π. _{In- plane displacement U 0y (x, y), Δx} along the y direction due to 0 is obtained. Here, the in-plane displacements U _{0y (x, y) and Δx} are the in-plane displacements of the measurement points (x, y) existing in the setting direction, and φ _my (x, y) and φ _{m 0 (x, y).} ) Is the phase corresponding to this setting direction. φ _m0 (x, y) is the initial phase.
(B6) and the change amount [Delta] x ₀ of the above (b1), the (b5) in the obtained _{U 0y (x, y),} based on the _{[Delta] x,} the data processing unit 3b has an in-plane correction factor _{K uy (x , Y), Δx} are calculated by _{Kuy (x, y), Δx} = U _{0y (x, y), Δx} / Δx _0. Variation [Delta] x ₀ is stored is set in advance, for example, the storage device 7, or may be input from the detector 12b is detected by the detector 12b in the correction coefficient calculating unit 5. _{In the storage device 7, Kui (x, y) and Δx} are stored in association with each setting direction for each setting direction.

The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the scope of the technical idea of the present invention.
For example, in the above description, the relative position between the camera 3a and the target surface 1a is changed by moving the camera 3a, but the relative position between the camera 3a and the target surface 1a is changed by moving the object 1. You may.

1 Object, 1a Target surface, 3 Displacement measuring device, 3a Camera, 3b Data processing unit, 5 Correction coefficient calculation device, 7 Storage device, 9 Displacement calculation device, 10 Displacement acquisition device, 11 Drive device, 11a First stage, 11b 1st motor, 11c 2nd stage, 11d 2nd motor, C optical axis

Claims (7)

A displacement acquisition device that measures the displacement of the target surface of an object.
A camera that captures a regular pattern on the target surface, and a data processing unit that obtains the displacement of the measurement point on the target surface as the measured displacement by the sampling moire method based on the image data of the pattern captured by the camera. Displacement measuring device with
A correction coefficient calculation device for obtaining a correction coefficient for the measured displacement, and a correction coefficient calculation device.
A displacement calculation device for calculating the corrected displacement of the measurement point based on the measurement displacement and the correction coefficient is provided.
The measurement point is located in the set direction as seen from the camera, and the correction coefficient is obtained for the set direction.
In order to obtain the correction coefficient, the relative position between the camera and the target surface is changed.
The displacement measuring device measures the displacement of the measurement point of the target surface existing in the set direction due to this change as the displacement for coefficient calculation.
The correction coefficient calculation unit, the coefficient and calculation displacement, based on the amount of change in the relative position, determined Me said correction coefficient,
The amount of change in the relative position between the camera and the target surface in the direction parallel to the optical axis of the camera is defined as the first change amount, and the camera and the target surface in the direction orthogonal to the optical axis of the camera. The amount of change in the relative position of is used as the second amount of change, and the correction coefficient is
The first in-plane correction coefficient as the fluctuation rate of the in-plane displacement with respect to the first change amount, the second in-plane correction coefficient as the fluctuation rate of the in-plane displacement with respect to the second change amount, and the first change. Includes a first out-of-plane correction factor as the rate of change in out-of-plane displacement with respect to the quantity and a second out-of-plane correction factor as the rate of change in out-of-plane displacement with respect to the second amount of change.
The displacement calculation device is
Along the target surface based on the in-plane displacement and the out-of-plane displacement included in the measured displacement, the first and second in-plane correction coefficients, and the first and second out-of-plane correction coefficients. The in-plane displacement of the measurement point in the direction is calculated as the corrected displacement, or
It intersects the target surface based on the in-plane displacement and the out-of-plane displacement included in the measured displacement, the first and second in-plane correction coefficients, and the first and second out-of-plane correction coefficients. A displacement acquisition device that calculates the out-of-plane displacement of the measurement point in the direction as the corrected displacement. A displacement acquisition device that measures the displacement of the target surface of an object.
A camera that captures a regular pattern on the target surface, and a data processing unit that obtains the displacement of the measurement point on the target surface as the measured displacement by the sampling moire method based on the image data of the pattern captured by the camera. Displacement measuring device with
A correction coefficient calculation device for obtaining a correction coefficient for the measured displacement, and a correction coefficient calculation device.
A displacement calculation device for calculating the corrected displacement of the measurement point based on the measurement displacement and the correction coefficient is provided.
The measurement point is located in the set direction as seen from the camera, and the correction coefficient is obtained for the set direction.
In order to obtain the correction coefficient, the relative position between the camera and the target surface is changed.
The displacement measuring device measures the displacement of the measurement point of the target surface existing in the set direction due to this change as the displacement for coefficient calculation.
The correction coefficient calculation device obtains the correction coefficient based on the displacement for calculating the coefficient and the amount of change in the relative position.
Each of the measured displacement and the coefficient calculation displacement includes an in-plane displacement in a direction along the target surface and an out-of-plane displacement in a direction intersecting the target surface.
The correction factor may include a plane correction factor K _u about plane displacement, and a plane correction factor K _o about out-of-plane displacement,
The correction coefficient calculation device obtains an in-plane correction coefficient _Ku based on the in-plane displacement included in the coefficient calculation displacement, and an out-of-plane correction coefficient based on the out-of-plane displacement included in the coefficient calculation displacement. determine the K _o,
In order to obtain the correction coefficient, the relative position between the camera and the target surface is changed by the _{change amount Δz 0 in the z direction parallel to the optical axis of the camera.}
Said displacement measuring apparatus, according to the amount of change Delta] z _0, the in-plane displacement _{U 0x} included in displacement the coefficient calculation _{(x, y),} the out of plane displacement _{O 0} and _{Δz (x, y),} obtains a _{Delta] z} ,
The correction coefficient calculation unit, Delta] z ₀ and _{U 0x (x, y),} K ux included in the in-plane correction factor _{K u} on the basis of the _{Δz (x, y), Δz} = U 0x (x, y), calculates _Δz / _{Δz 0, Δz 0} and _{O 0 (x, y),} K o contained in the out of plane correction factor _{K o} based on the _{Δz (x, y), Δz} = O 0 (x, y) _{, Δz} / Δz ₀ ,
Wherein in order to determine the correction factor, the relative position between the camera and the object surface, the amount of change [Delta] x ₀ only is changed in the x-direction perpendicular to the z-direction,
The displacement measuring device obtains the in- _{plane displacement U 0x (x, y), Δx} and the out-of-plane displacement O _{0 (x, y), Δx} included in the coefficient calculation displacement according to the _{change amount Δx 0} .
The correction coefficient calculation unit, [Delta] x ₀ and _{U 0x (x, y),} K ux included in the in-plane correction factor _{K u} on the basis of the _{Δx (x, y), Δx} = U 0x (x, y), calculates _Δx / _{Δx 0, Δx 0} and _{O 0 (x, y),} K o contained in the out of plane correction factor _{K o} based on _{Δx (x, y), Δx} = O 0 (x, y) _{, Δx} / Δx ₀ ,
The displacement calculating unit, the measurement and the out-of-plane displacement O-plane displacement _{U x} contained in the displacement, the correction coefficient _{K ux (x, y),} Δz, K ux (x, y), Δx, K o ( _{x, y), Δz, K} o (x, y), based on the _{[Delta] x,} the z-direction displacement Delta] z and x direction of the displacement [Delta] x as the corrected displacement,
Δz = ( _{Kux (x, y), Δx} · _{OK o (x, y), Δz} · U _x ) / ( _{Kux (x, y), Δx} · _{Ko (x, y), Δz} − K _{ux (x, y), Δz} · _{Ko (x, y), Δx} )
Δx = ( _{Ko (x, y), Δz} · U−K _{ux (x, y), Δz} · O) / ( _{Kux (x, y), Δx} · _{Ko (x, y), Δz} −K _{ux (x, y), Δz} · _{Ko (x, y), Δx} )
Displacement acquisition device calculated by. A displacement acquisition device that measures the displacement of the target surface of an object.
A camera that captures a regular pattern on the target surface, and a data processing unit that obtains the displacement of the measurement point on the target surface as the measured displacement by the sampling moire method based on the image data of the pattern captured by the camera. Displacement measuring device with
A correction coefficient calculation device for obtaining a correction coefficient for the measured displacement, and a correction coefficient calculation device.
A displacement calculation device for calculating the corrected displacement of the measurement point based on the measurement displacement and the correction coefficient is provided.
The measurement point is located in the set direction as seen from the camera, and the correction coefficient is obtained for the set direction.
In order to obtain the correction coefficient, the relative position between the camera and the target surface is changed.
The displacement measuring device measures the displacement of the measurement point of the target surface existing in the set direction due to this change as the displacement for coefficient calculation.
The correction coefficient calculation device obtains the correction coefficient based on the displacement for calculating the coefficient and the amount of change in the relative position.
Each of the measured displacement and the coefficient calculation displacement includes an in-plane displacement in a direction along the target surface and an out-of-plane displacement in a direction intersecting the target surface.
The correction factor may include a plane correction factor K _u about plane displacement, and a plane correction factor K _o about out-of-plane displacement,
The correction coefficient calculation device obtains an in-plane correction coefficient _Ku based on the in-plane displacement included in the coefficient calculation displacement, and an out-of-plane correction coefficient based on the out-of-plane displacement included in the coefficient calculation displacement. determine the K _o,
Assuming that the z direction of the three-dimensional coordinate system xyz is the direction of the optical axis of the camera.
In order to obtain the correction coefficient, the relative position between the camera and the target surface is changed by the _{change amount Δz 0 in the z direction parallel to the optical axis of the camera.}
The displacement measuring device has the in- _{plane displacements U 0x (x, y), Δz} and U _{0y (x, y), Δz} and the out-of-plane displacement O included in the coefficient calculation displacement due to the _{change amount Δz 0. 0 (x, y) and Δz} are obtained, and U _{0x (x, y), Δz} and U _{0y (x, y), Δz} are in-plane displacements along the x and y directions, respectively.
The correction coefficient calculation unit, Delta] z ₀ and _{U 0x (x, y),} Δz and _{U 0y (x, y),} K contained in said plane correction factor _{K u} on the basis of the _{Δz ux (x, y), Δz} = U _{0x (x, y), Δz} / Δz ₀ and _{Kui (x, y), Δz} = U _{0y (x, y), Δz} / Δz ₀ are calculated, and Δz ₀ and O _{0 (x, y) are calculated. ),} to calculate the _{K o (x, y),} Δz = O 0 (x, y), Δz / Δz 0 contained in the out of plane correction factor _{K o} based on _{Delta] z,}
Wherein in order to determine the correction factor, the relative position between the camera and the object surface, is changed by the change amount [Delta] x ₀ in the x direction,
Said displacement measuring apparatus, according to the amount of change [Delta] x _0, the plane is included in the coefficient calculation displacement displacement _{U 0x (x, y),} Δx and _{U 0y (x, y),} Δx and out-of-plane displacement _{O 0 ( x, y), Δx} are obtained, and U _{0x (x, y), Δx} and U _{0y (x, y), Δx} are in-plane displacements along the x and y directions, respectively.
The correction coefficient calculation unit, [Delta] x ₀ and _{U 0x (x, y),} K ux included in the in-plane correction factor _{K u} on the basis of the _{Δx (x, y), Δx} = U 0x (x, y), calculates _Δx / _{Δx 0, Δx 0} and _{U 0y (x, y),} based on _{Δx K uy (x, y)} , Δx = U 0y (x, y), calculates _Δx / _{Δx 0, Δx 0} and _{O 0 (x, y),} to calculate the _{K o (x, y),} Δx = O 0 (x, y), Δx / Δx 0 as the out-of-plane correction factor _{K o} based on the _{[Delta] x,}
Wherein in order to determine the correction factor, the relative position between the camera and the object surface, is changed by the change amount [Delta] y ₀ in the y direction,
The displacement measuring device has in- _{plane displacements U 0y (x, y), Δy} and U _{0x (x, y), Δy} and out-of-plane displacement O _{0 (} x, y) included in the coefficient calculation displacement due to the _{change amount Δy 0. x, y), Δy} are obtained, and U _{0y (x, y), Δy} and U _{0x (x, y), Δy} are in-plane displacements along the y and x directions, respectively.
The correction coefficient calculation unit, [Delta] y ₀ and _{U 0y (x, y),} K uy included in the in-plane correction factor _{K u} on the basis of _{Δy (x, y), Δy} = U 0y (x, y), _{Calculate Δy} / Δy ₀ , calculate _{Kux (x, y), Δy} = U _{0x (x, y), Δy} / Δy ₀ based on _{Δy 0} and U _{0x (x, y), Δy} , and Δy. ₀ and _{O 0 (x, y),} to calculate the _{K o (x, y),} Δy = O 0 (x, y), Δy / Δy 0 as the out-of-plane correction factor _{K o} based on the _{[Delta] y,}
The measuring displacement comprises a plane displacement U _y and out-of-plane displacement O along the plane displacement U _x and y direction along the x-direction,
The displacement calculation device includes in-plane displacement U _x , U _y and out-of-plane displacement O _{included in the measured displacement, and the correction coefficients K ux (x, y), Δz} , K _{ui (x, y), Δz} , _{K o (x, y),} Δz, K ux (x, y), Δx, K uy (x, y), Δx, K o (x, y), Δx, K uy (x, y), Δy, _{K ux (x, y),} Δy, K o (x, y), based on the _{[Delta] y,} the z-direction displacement Δz and x direction of the displacement Δx and y-direction displacement [Delta] y as the corrected displacement

U _x = K _{ux (x, y), Δx} · Δx + K _{ux (x, y), Δy} · Δy + K _{ux (x, y), Δz} · Δz

U _y = K _{ui (x, y), Δx} · Δx + K _{ui (x, y), Δy} · Δy + K _{ui (x, y), Δz} · Δz

O = _{Ko (x, y), Δx} · Δx + _{Ko (x, y), Δy} · Δy + _{Ko (x, y), Δz} · Δz

Displacement acquisition device obtained as a solution of three simultaneous equations represented by. For each of the plurality of setting directions
The displacement measuring device obtains the displacement for calculating the coefficient, and obtains the displacement.
The correction coefficient calculation device obtains the correction coefficient based on the displacement for calculating the coefficient and the change amount of the relative position.
One of claims 1 to 3, wherein the displacement calculation device calculates the corrected displacement based on the measured displacement of the measurement point existing in the set direction and the correction coefficient for the set direction . Displacement acquisition device according to paragraph 1. A drive device for changing the relative position between the camera and the target surface by moving the camera is provided.
The change amount of the relative position is the movement amount of the camera by the drive device.
The correction coefficient calculation device obtains the correction coefficient based on the movement amount set in advance or detected by the detector and the displacement for calculating the coefficient, according to any one of claims 1 to 4. The displacement acquisition device described. It is a displacement acquisition method that measures the displacement of the object surface of an object.
(A) Image data is acquired by taking an image of a regular pattern provided on the target surface with a camera.
(B) Based on the image data, the displacement of the measurement point on the target surface is obtained as the measurement displacement by the sampling moire method.
(C) Based on the measured displacement and the correction coefficient, the corrected displacement of the measurement point is calculated.
The measurement point is located in the set direction as seen from the camera, and the correction coefficient is obtained for the set direction.
To obtain the correction coefficient
(A) By changing the relative position between the camera and the target surface,
(B) The displacement of the measurement point of the target surface existing in the set direction due to this change is measured as the displacement for coefficient calculation.
(C) The correction coefficient is obtained based on the displacement for calculating the coefficient and the amount of change in the relative position.
The amount of change in the relative position between the camera and the target surface in the direction parallel to the optical axis of the camera is defined as the first change amount, and the camera and the target surface in the direction orthogonal to the optical axis of the camera. The amount of change in the relative position of is used as the second amount of change, and the correction coefficient is
The first in-plane correction coefficient as the fluctuation rate of the in-plane displacement with respect to the first change amount, the second in-plane correction coefficient as the fluctuation rate of the in-plane displacement with respect to the second change amount, and the first change. Includes a first out-of-plane correction factor as the rate of change in out-of-plane displacement with respect to the quantity and a second out-of-plane correction factor as the rate of change in out-of-plane displacement with respect to the second amount of change.
In (C) above
Along the target surface based on the in-plane displacement and the out-of-plane displacement included in the measured displacement, the first and second in-plane correction coefficients, and the first and second out-of-plane correction coefficients. The in-plane displacement of the measurement point in the direction is calculated as the corrected displacement, or
It intersects the target surface based on the in-plane displacement and the out-of-plane displacement included in the measured displacement, the first and second in-plane correction coefficients, and the first and second out-of-plane correction coefficients. A displacement acquisition method for calculating the out-of-plane displacement of the measurement point in the direction as the corrected displacement. A program that executes processing to measure the displacement of the object surface of an object.
A process of obtaining the displacement of a measurement point on the target surface as a measurement displacement by a sampling moire method based on image data obtained by imaging a regular pattern provided on the target surface with a camera.
The process of obtaining the correction coefficient for the measured displacement and
A computer is made to execute a process of calculating the corrected displacement of the measurement point based on the measurement displacement and the correction coefficient.
The measurement point is located in the set direction as seen from the camera, and the correction coefficient is obtained for the set direction.
When the relative position between the camera and the target surface is changed in order to obtain the correction coefficient, the process for obtaining the correction coefficient is:
Based on the image data obtained by capturing the pattern with a camera before this change and the image data obtained by capturing the pattern with a camera after this change, the pattern exists in the setting direction due to this change. The process of measuring the displacement of the measurement point on the target surface as the displacement for calculating the coefficient, and
The coefficient and calculation displacement, based on the amount of change in the relative position, seen including a process of obtaining the correction factor,
The amount of change in the relative position between the camera and the target surface in the direction parallel to the optical axis of the camera is defined as the first change amount, and the camera and the target surface in the direction orthogonal to the optical axis of the camera. The amount of change in the relative position of is used as the second amount of change, and the correction coefficient is
The first in-plane correction coefficient as the fluctuation rate of the in-plane displacement with respect to the first change amount, the second in-plane correction coefficient as the fluctuation rate of the in-plane displacement with respect to the second change amount, and the first change. Includes a first out-of-plane correction factor as the rate of change in out-of-plane displacement with respect to the quantity and a second out-of-plane correction factor as the rate of change in out-of-plane displacement with respect to the second amount of change.
In the process of calculating the corrected displacement of the measurement point,
Along the target surface based on the in-plane displacement and the out-of-plane displacement included in the measured displacement, the first and second in-plane correction coefficients, and the first and second out-of-plane correction coefficients. The in-plane displacement of the measurement point in the direction is calculated as the corrected displacement, or
It intersects the target surface based on the in-plane displacement and the out-of-plane displacement included in the measured displacement, the first and second in-plane correction coefficients, and the first and second out-of-plane correction coefficients. A program that calculates the out-of-plane displacement of the measurement point in the direction as the corrected displacement.

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