JP2019011984A - Displacement acquisition device, displacement acquisition method, and program - Google Patents

Abstract

To reduce an error due to the inclination or a measuring direction of an object surface in measuring displacement of a measuring point on the object surface by using a sampling moire method.SOLUTION: A displacement acquisition device 10 comprises a displacement measuring device 3, a correction coefficient calculating device 5, and a displacement calculating device 9. The displacement measuring device 3 includes a camera 3a that picks up an image of the appearance of an object surface 1a, and a data processing unit 3b that obtains measurement displacement by a sampling moire method on the basis of the picked-up image. The correction coefficient calculating device 5 obtains a correction coefficient related to the measurement displacement. The displacement calculating device 9 calculates displacement of a measuring point after correction on the basis of the measurement displacement and correction coefficient. The relative positions of the camera 3a and object surface 1a are changed to obtain the correction coefficient. The displacement measuring device 3 measures displacement of the measuring point on the object surface 1a present in a setting direction due to the change as displacement for coefficient calculation. The correction coefficient calculating device 5 obtains the correction coefficient on the basis of the displacement for coefficient calculation and the amount of change in relative positions.SELECTED DRAWING: Figure 2

Description

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

  In the sampling moire method, a regular pattern (for example, a lattice pattern) is pasted on 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 image data of the lattice pattern. That is, in the lattice pattern image data, a process of thinning out pixels at a constant cycle is performed, and this process is performed only a plurality of times while changing the pixel thinning start point, thereby obtaining a plurality of moire fringe images. Based on the change in the phase of moire fringes generated by these moire fringe images, the displacement of the target surface is obtained.

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

In the formula (1), I (x) indicates the luminance of the one-dimensional coordinate x of one point in the target surface. φ (x) is the phase at the coordinate x. I _a is the luminance amplitude of the lattice pattern, and I _b is the background luminance. In order to generate moire fringes (that is, new stripe patterns) in the 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 lattice pattern period Q 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 thinning processes a plurality of times, but the thinning start point is changed. A plurality of images after thinning are obtained for a plurality of thinning processes (in FIG. 1, the starting point is indicated by k = 0, 1, 2, or 3).

  In the luminance interpolation processing, the luminance of the thinned pixels is linearly interpolated as shown in FIG. 1D in each thinned image. Thereby, a plurality of moire fringe image data is obtained. The period of the luminance distribution in each moire fringe image data is larger than the period of the lattice pattern and the luminance distribution of the image data in FIG. The luminance distribution of each moire fringe image data is expressed by the following equation (2).

In Expression (2), k is a thinning start point, and k = 0, 1, 2, or 3. φ _m (x) is the phase of the moire fringe at the coordinate x. Q is the pitch of the lattice pattern in the image data of FIG. 1B (that is, the interval between adjacent lattices), 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) of the phase φ _m (x) of the moire fringes, the in-plane displacement of the target surface (the displacement in the direction along the target surface) can be obtained. That is, when the actual pitch of the lattice 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 Patent Literature 1 and Non-Patent Literature 1, for example.

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 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, the target surface being 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 according to the inclination of the target surface.
(2) An error occurs in the displacement measurement value depending on the measurement direction. That is, the displacement at the measurement point on the target surface that exists in the optical axis direction of the camera when viewed from the camera, and the displacement at the measurement point on the target surface that exists in the direction inclined from the optical axis of the camera when viewed from the camera In the meantime, an error occurs in the measured value.
(3) An error occurs in the measurement value due to an error (aberration etc.) inherent to the camera.
(4) An error occurs in the measurement value due to an error in the actual pitch of the lattice pattern.

  Accordingly, an object of the present invention is to measure the inclination of the target surface, the measurement direction, the camera-specific error, and the actual pitch of the lattice pattern when measuring the displacement of the measurement point on the target surface using the sampling moire method. An object is to reduce a measurement error due to at least one of the errors.

In order to achieve the above object, according to the present invention, a displacement acquisition device for measuring the displacement of the target surface of an object,
A camera that images a regular pattern provided on the target surface, and a data processing unit that obtains a displacement of a measurement point on the target surface as a measurement displacement by a sampling moire method based on image data of the pattern captured by the camera A displacement measuring device comprising:
A correction coefficient calculation device for obtaining a correction coefficient related to the measured displacement;
A displacement calculating device that calculates a corrected displacement of the measurement point based on the measured displacement and the correction coefficient;
The measurement point is located in a setting direction viewed from the camera, and the correction coefficient is obtained for the setting 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 on the target surface existing in the setting direction due to this change as a coefficient calculation displacement,
The correction coefficient calculation device is provided with a displacement acquisition device for obtaining the correction coefficient based on the coefficient calculation displacement and the change amount of the relative position.

Moreover, according to the present invention, a displacement acquisition method for measuring the displacement of the target surface of an object,
(A) Obtaining image data by capturing a regular pattern provided on the target surface with a camera;
(B) A displacement of the measurement point on the target surface is determined as a measurement displacement by a sampling moire method based on the image data,
(C) calculating a corrected displacement of the measurement point based on the measured displacement and a correction coefficient;
The measurement point is located in a setting direction viewed from the camera, and the correction coefficient is obtained for the setting direction,
In order to obtain the correction factor,
(A) changing the relative position between the camera and the target surface;
(B) The displacement of the measurement point on the target surface existing in the set direction due to this change is measured as a coefficient calculation displacement,
(C) A displacement acquisition method for obtaining the correction coefficient based on the coefficient calculation displacement and the change amount of the relative position is provided.

Furthermore, according to the present invention, there is provided a program for executing processing for measuring a displacement of a target surface of an object,
A process for obtaining a 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;
Processing for obtaining a correction coefficient related to the measured displacement;
Based on the measurement displacement and the correction coefficient, the computer calculates the corrected displacement of the measurement point,
The measurement point is located in a setting direction viewed from the camera, and the correction coefficient is obtained for the setting direction,
In order to obtain the correction coefficient, when the relative position between the camera and the target surface is changed, the process for obtaining the correction coefficient includes:
Based on the image data obtained by imaging the pattern with the camera before this change and the image data obtained by imaging the pattern with the camera after this change, the change exists in the setting direction. Processing for measuring the displacement of the measurement point on the target surface as a coefficient calculation displacement;
A program is provided that includes processing for obtaining the correction coefficient based on the coefficient calculation displacement and the change amount of 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 on the target surface existing in the setting direction due to this change is measured as the coefficient calculation displacement. A correction coefficient is obtained based on the coefficient calculation displacement and the change amount of the relative position. This correction factor includes measurement errors due to the tilt of the target surface with respect to the plane perpendicular to the optical axis of the camera, measurement errors that depend on the direction of the measurement point viewed from the camera, errors inherent to the camera, and the actual grid pattern. At least one (for example, all) of pitch errors is reflected.
Therefore, by calculating the corrected displacement of the measurement point based on the measured displacement of the target surface and the correction coefficient, such a measurement error can be reduced or eliminated.

It is explanatory drawing of a sampling moire method. The structure of the displacement acquisition apparatus by embodiment of this invention is shown. It is explanatory drawing of the process which acquires in-plane correction coefficient _{Kux (x, y) and (DELTA) z} . It is explanatory drawing of the process which acquires in-plane correction coefficient _{Kux (x, y) and (DELTA) x} . It is explanatory drawing of the process which acquires an out-of-plane correction coefficient _{Ko (x, y) and (DELTA) z} . It is explanatory drawing of the process which acquires an out-of-plane correction coefficient _{Ko (x, y) and (DELTA) x} . It is a flowchart which shows the displacement acquisition method by embodiment of this invention. It is a flowchart which shows the process of the initial state in a correction coefficient acquisition process. It is a flowchart which shows the process of the z direction movement in a correction coefficient acquisition process. It is a flowchart which shows the process of the x direction movement in a correction coefficient acquisition process.

  Embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

[Configuration of displacement acquisition device]
FIG. 2 shows a configuration of the displacement acquisition apparatus 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 caused by a load acting on the object 1 or a displacement caused by 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 a displacement of a measurement point (hereinafter also simply referred to as a measurement point) on the target surface 1a based on the sampling moire method. In this embodiment, this displacement includes in-plane displacement and out-of-plane displacement. The in-plane displacement is a displacement in a 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) with the target surface 1a. The displacement measuring device 3 includes a camera 3a and a data processing unit 3b.

  The camera 3a acquires image data of this pattern by imaging a regular pattern provided on the target surface 1a. Here, the regular pattern is, for example, a lattice pattern, but may be another pattern as long as moire fringe image data described later can be generated.

  The data processing unit 3b calculates the displacement of the measurement point on the target surface 1a by the sampling moire method based on the pattern image data captured by the camera 3a. In the present embodiment, the displacement of the measurement point is obtained for each of a 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 an x coordinate and ay coordinate in an xyz coordinate system fixed to the camera 3a. The xyz coordinate system is a three-dimensional coordinate whose z axis is parallel to the optical axis C of the camera 3a (the direction of the camera 3a). Hereinafter, the x direction, the y direction, and the z direction mean a direction parallel to the x axis, a direction parallel to the y axis, and a direction parallel to the z axis in the above-described xyz coordinate system.

In Expression (4), I (x, y) represents 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 lattice pattern in the image data described above. I _a is the luminance amplitude, and I _b is the background luminance.

  The data processing unit 3b performs a thinning process and a luminance interpolation process on the above-described image data. In the present embodiment, the data processing unit 3b performs a thinning process and a luminance interpolation process for the x direction. In the thinning process, the data processing unit 3b samples and maintains the pixels of the image data at a predetermined sampling period (in this example, a period T close to the pattern period) in the x direction, and replaces 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 pixel based on the luminance of the pixels existing around this 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 thinning processes a plurality of times, but the thinning start point 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 on the above-described image data a plurality of times.
In this example, the data processing unit 3b generates T pieces of moire fringe image data by thinning-out processing in the x direction and luminance interpolation processing. These moire fringe image data are expressed by the following equation (5).

In Expression (5), k represents the starting point of thinning in the x direction. k takes values of 0, 1, 2,..., T−1.
The data processing unit 3b applies the discrete Fourier transform to the equation (5), and obtains the moire fringe phase φ _m (x, y) by the following equation (6).

The data processing unit 3b can determine the in-plane displacement of the target surface 1a by determining 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 a pitch p (a constant interval) in the x direction, the in-plane displacement U _x (x, y) is expressed as U _x (x, y) = Δφ _m (x, y). It can be obtained by p (x, y) / 2π (hereinafter, p (x, y) is simply written as p and U _x (x, y) is also written as U _x ). U _x is an in-plane displacement along the x direction in the xyz coordinate system. In other words, U _x is an in-plane displacement in a plane (including the xz plane) parallel to the xz plane in the xyz coordinate system.
Here, φ _m (x, y) obtained in the initial state is taken as φ _m0 (x, y), and φ _m (x, y) found at the time of measurement is taken 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 grid pattern provided on the target surface 1a is p, the grid pitch in the image data is 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) is established.

Z = f · p / Q (7)

Based on the 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 imaging the target surface 1a in the initial state by the camera 3a, and Q is the image of the target surface 1a captured by the camera 3a during measurement. This is the pitch in the x direction of the lattice pattern in the obtained image data.

Q is obtained as follows. First, the following equation (9) is established from the above equation (5).
From this equation, the data processing unit 3b calculates 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) obtained by modifying the equation (10).

In Expression (11), x + 1 of φ _m (x + 1, y) is an x coordinate of a pixel adjacent to the pixel of interest (x coordinate) for obtaining Q in the x-axis direction, and φ _m (x−1, y) x-1 in y) is an x coordinate of a pixel adjacent to the pixel of interest on the opposite side to the x coordinate x + 1 in the x-axis direction. In the same way as for Q, the data processing unit 3b obtains the Q _0.

The correction coefficient calculation device 5 obtains a correction coefficient related to the measured displacement obtained by the displacement measurement 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 factor>
3 and 4 are explanatory diagrams of processing for obtaining the in-plane correction coefficient _Ku . 3 and 4, the xyz coordinate system is a three-dimensional coordinate system fixed to the camera 3a, and has the above-described x-axis, y-axis, and z-axis.

  3 and 4, the angle θ (x, y) indicates the above-described setting direction as viewed from the camera 3a. That is, the angle θ (x, y) is an angle formed by the optical axis C and the setting direction. The angle α (x, y) indicates the inclination of the target surface 1a. That is, the angle α (x, y) indicates an angle formed between the x direction and the target surface 1a.

In order to obtain the in-plane correction coefficient K _{ux (x, y), Δz} in the z direction, the relative position between the camera 3a and the target surface 1a is changed by the change amount Δz ₀ in the z direction as shown in FIG.

At this time, in-plane displacements U _{0x (x, y) and Δz} due to Δz ₀ in a plane parallel to the xz plane are as follows, _assuming that θ (x, y) is sufficiently small as shown in FIG. 12).

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

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

K _{ux (x, y), Δz} = tan θ (x, y) / cos α (x, y) (13)


Since θ (x, y) and α (x, y) are unknown in equation (13), K _{ux (x, y) and Δz} are obtained from θ (x, y) and α (x, y). However, Δz ₀ is already known, and U _{0x (x, y), Δz} is obtained by the displacement measuring device 3. Therefore, in the present embodiment, K _{ux (x, y) and Δz} are obtained by the following equation (14).

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

In order to obtain the in-plane correction coefficients K _{ux (x, y) and Δx} in the x direction, the relative position between the camera 3a and the target surface 1a is changed by the change amount Δx ₀ in the x direction as shown in FIG.

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

U _{0x (x, y), Δx} = Δx ₀ / cos α (x, y) (15)

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

K _{ux (x, y), Δx} = 1 / cos α (x, y) (16)

Since α (x, y) is unknown in Equation (16), K _{ux (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 this embodiment, K _{ux (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 factor>
5 and 6 are explanatory views of a process of obtaining out-of-plane correction factor K _o. 5 and 6, the xyz coordinate system, the angle θ (x, y), and the angle α (x, y) are the same as those in FIGS. 3 and 4.

In order to obtain the out-of-plane correction coefficients K _{o (x, y) and Δz} in the z direction, the relative position between the camera 3a and the target surface 1a is changed by a change amount 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 + tan θ (x, y) · tan α (x, y)} / cos {α (x, y) + θ (x, y)} (18)


Based on the equation (18), the out-of-plane correction coefficients K _{o (x, y) and Δz} as the fluctuation rates of the out-of-plane displacement O _{0 (x, y) and Δz} with respect to Δz _{0 are} expressed by the following equation (19). Represent.

K _{o (x, y), Δz} = {1 + tan θ (x, y) · tan α (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), Δz} is obtained by the displacement measuring device 3. Therefore, in this embodiment, K _{o (x, y) and Δz} are obtained by the following equation (20).

K _{o (x, y), Δz} = O _{0 (x, y), Δz} / Δz ₀ (20)

In order to obtain the out-of-plane correction coefficients K _{o (x, y) and Δx} in the x direction, the relative position between the camera 3a and the target surface 1a is changed by the change amount Δx ₀ in the x direction as shown in FIG.

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 tan α (x, y) / cos {α (x, y) + θ (x, y)} (21)


Based on the equation (21), the out-of-plane correction coefficients K _{o (x, y) and Δx} as the fluctuation rates of the out-of-plane displacement O _{0 (x, y) and Δx} with respect to Δx _{0 are} expressed by the following equation (22). Represent.

K _{o (x, y), Δx} = tan α / cos {α + θ (x, y)} (22)

Since α (x, y) is unknown in Equation (22), K _{o (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, K _{o (x, y) and Δx} are obtained by the following equation (23).

K _{o (x, y), Δx} = O _{0 (x, y), Δx} / Δx ₀ (23)

<Process for obtaining correction coefficient>
Thus, in order to obtain the correction coefficients K _{ux (x, y), Δz} , K _{o (x, y), Δz} , the relative position between the camera 3a and the target surface 1a is set in the z direction parallel to the optical axis C. only the change amount Δz ₀ changing. Next, the displacement measuring device 3 obtains in-plane displacements U _{0x (x, y), Δz} and out-of-plane displacements O _{0 (x, y), Δz} as coefficient calculation displacements based on the change amount Δz ₀ . Thereafter, the correction coefficient calculation device 5 uses K _{ux (x, y), Δ z} = U _{0x (x, y),} as the in-plane correction coefficient K _u based on Δz ₀ and U _{0x (x, y), Δz .} 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 in-plane displacements U _{0x (x, y), Δx} and out-of-plane displacements O _{0 (x, y), Δx} as coefficient calculation displacements based on the change amount Δx ₀ . Thereafter, the correction coefficient calculation device 5 uses K _{ux (x, y), Δx} = U _{0x (x, y),} as an in-plane correction coefficient K _u based on Δx ₀ and U _{0x (x, y), Δx .} It 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 device 5 uses the correction coefficients 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.

Thereafter, when the measurement of the displacement of the measurement points in the subject surface 1a, the displacement calculating unit 9 measures the in-plane displacement U _x and out-of-plane displacement O as measured displacement, and these plane displacement U _x and out-of-plane displacement O , Correction coefficients K _{ux (x, y), Δz} , K _{ux (x, y), Δx} , K _{o (x, y), Δz} , K _{o (x, y), Δx} 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 = (K _{ux (x, y), Δx} · O−K _{o (x, y), Δz} · U _x ) / (K _{ux (x, y), Δx} · K _{o (x, y), Δz} − K _{ux (x, y), Δz} · K _{o (x, y), Δx} ) (24)

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

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

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

O = K _{o (x, y), Δx} · Δx + K _{o (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 driving 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 relative displacement described above is the amount of movement of the camera 3a by the driving device 11. In the above-described example, the driving 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 coefficient calculation displacement.

  In the example of FIG. 2, the drive device 11 is provided with a camera 3a, a first stage 11a that can move in the z direction, a first motor 11b that drives the first stage 11a in the z direction, and can move in the x direction. A second stage 11c provided on the first stage 11a and a second motor 11d provided on the first stage 11a and driving 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 illustrating a displacement acquisition method according to an embodiment of the present invention. This displacement acquisition method is performed using the displacement acquisition device 10 described above. This displacement acquisition method has 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 setting direction due to this change is measured as a coefficient calculation displacement by the displacement measuring device 3. To do.
Next, in the correction coefficient acquisition process, the correction coefficient calculation device 5 obtains a correction coefficient based on the coefficient calculation displacement and the amount of relative position change.

  In a specific example, the correction coefficient acquisition process includes an initial state process, a z-direction movement process, and an x-direction movement process.

<Initial processing>
FIG. 8 is a flowchart showing the processing in the initial state. The process 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-described 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, based on the plurality of moire fringe image data obtained in step S2, uses the above equation (6) to determine the phase of the moire fringes at the measurement point (x, y) φ _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 determines the pitch Q ₀ (x, y) in the x direction of the lattice pattern existing in the set direction in the image data obtained in step S1 from the above formulas (9) to (9). According to 11), identification is performed based on the area of the image data corresponding to the set 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, the focal length f of the camera 3a, and the actual pitch p (x, y) of the lattice pattern in the x direction, the data processing unit 3b obtains the position z ₀ = f · p (x, y) / Q ₀ (x, y) in the z direction of the measurement point existing in the set direction. 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).

Steps S4 and S5 described above are performed for each of a plurality of setting directions. That is, in step S4, the pitch Q ₀ (x, y) of the lattice pattern existing in each setting direction is specified, and in step S5, the position z ₀ in each setting direction corresponds to the setting direction. It calculates _| requires based on Q0 (x, y).

<Z-direction movement processing>
FIG. 9 is a flowchart showing the z-direction movement process. The z-direction movement process 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 by a minute amount Δz ₀ in the z direction from the state of step S1 (ie, the reference position). Change by the amount Δz ₀ . Δz ₀ may be not less than 1/500 of the above-described p (x, y) and not more than the pitch p (x, y). Δz ₀ is, for example, about 1 mm.
In step S7, the camera 3a acquires image data by imaging 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-described thinning process and luminance interpolation process only a plurality of times on the image data obtained in step S7.
In step S9, the data processing unit 3b, based on the plurality of moire fringe image data obtained in step S8, calculates the moire fringes at the measurement point (x, y) existing in the setting direction according to the above equation (6). The phase φ _m (x, y) is obtained. This φ _m (x, y) is hereinafter referred to as φ _mz (x, y).

In step S10, the data processing unit 3b calculates an in-plane displacement U _{0x (x, y), Δz} due to Δz ₀ . Step S10 has 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 uses U _{0x (x, y), Δz} = p (x, y) · Δφ _m (x, y) / 2π, and thus the in-plane displacement U _{0x (x, y} by 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). _{) And Δz} ), and φ _mz (x, y) and φ _m0 (x, y) are phases corresponding to the set direction.

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

Steps S10 and S11 described above are performed for each of a 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 a 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) and Δz} are calculated based on the in-plane displacements U _{0x (x, y) and 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 A position z ₁ of the measurement point in the z direction = f · p (x, y) / Q ₁ is obtained.
In step S14, the data processing unit 3b performs O _{0 (x, y), Δz} = z ₁ −z ₀ based on z ₀ obtained in step S5 and z ₁ obtained in step 13, and Δz ₀ The out-of-plane displacement O _{0 (x, y), Δz} is obtained.
In step S15, the correction coefficient calculation device 5 calculates the out-of-plane correction coefficient K _{o (x, y )} based on the change amount Δz ₀ in step S6 and O _{0 (x, y) and Δz} obtained in step S14. _{), Δz} is calculated by K _{o (x, y), Δz} = O _{0 (x, y), Δz} / Δz ₀ .

Steps S12 to S15 described above are performed for each setting direction in the image data. That is, calculated on the basis of the measurement points present in each set direction in step S13 (x, y) position z ₁ of z-direction, the Q ₁ corresponding to the setting direction, in step S14, the surface of each set direction The external displacement O _{0 (x, y), Δz} is 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 K _{o (x, y) and Δz} are calculated based on the out-of-plane displacement O _{0 (x, y) and Δz} corresponding to the set direction.

<X-direction movement processing>
FIG. 10 is a flowchart showing x-direction movement processing. The x-direction movement process 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 process of moving in the z direction, the camera 3a is moved by −Δz ₀ in the z direction to return the position of the camera 3a to the state of step S1, and then the camera 3a is moved by a minute amount Δx _{0 in the} x direction. Move. 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. Δx ₀ may be not less than 1/500 of the above-described p (x, y) and not more than the pitch p (x, y). Δx ₀ is about 1 mm, for example.
In step S17, the camera 3a acquires image data by imaging 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-described 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, based on the plurality of moire fringe image data obtained in step S18, calculates the moire fringes at the measurement point (x, y) existing in the setting direction according to the above equation (6). The phase φ _m (x, y) is obtained. This φ _m (x, y) is hereinafter referred to as φ _mx (x, y).

In step S20, the data processing unit 3b obtains in-plane displacements U _{0x (x, y) and Δx} due to Δx ₀ . Step S20 has step S20a and step S20b. In step S20a, the data processing unit 3b obtains Δφ _m (x, y) from Δφ _m (x, y) = φ _mx (x, y) −φ _m0 (x, y). In step S20b, the data processing unit 3b uses U _{0x (x, y), Δx} = p (x, y) · Δφ _m (x, y) / 2π, and thus the in-plane displacement U _{0x (x, y} by Δx _{0 ), Δx} . Here, Δφ _m (x, y) is obtained in step S20a. The in-plane displacements U _{0x (x, y) and Δx} are the in-plane displacements of measurement points (x, y) existing in the set direction (hereinafter referred to as in-plane displacements U _{0x (x, y),} (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 determines the in-plane correction coefficient K _{ux (x, y)} based on the change amount Δx ₀ in step S16 and U _{0x (x, y) and Δx} obtained in step S20. _{, Δx} is calculated by K _{ux (x, y), Δx} = U _{0x (x, y), Δx} / Δx ₀ . The change amount Δx ₀ is set in advance and stored in the storage device 7, for example, or detected by the detector 12b and input from the detector 12b to the correction coefficient calculation device 5 (the same applies hereinafter).

Steps S20 and S21 described above are performed for each of a 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) respectively existing in a plurality of setting directions are obtained, and in step S21, in-plane correction for each setting direction is performed. The coefficients K _{ux (x, y) and Δx} are calculated based on the in-plane displacements U _{0x (x, y) and 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 in the z direction of the measurement point existing in is obtained.
In step S24, the data processing unit 3b uses O _{0 (x, y), Δx} = z ₂ −z ₀ based on z ₀ obtained in step S5 and z ₂ obtained in step 23, and Δx ₀ The out-of-plane displacement O _{0 (x, y), Δx} is obtained.
In step S25, a variation [Delta] x ₀ in step S16, _{O 0} calculated in step S24 _{(x, y),} based on the _{[Delta] x,} the data processing unit 3b is out-of-plane correction factor _{K o (x, y) , Δx} are calculated from K _{o (x, y), Δx} = O _{0 (x, y), Δx} / Δx ₀ .

Steps S22 to S25 described above are performed for each setting direction in the image data. That is, calculated on the basis of the measurement points present in each set direction in step S23 (x, y) position z ₂ in the z direction, the Q ₂ to which corresponding to the setting direction, in step S24, the surface of each set direction The outer displacement O _{0 (x, y), Δx} is 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 K _{o (x, y) and Δx} are calculated based on the out-of-plane displacements O _{0 (x, y) and Δx} corresponding to the set direction.

<Measurement process>
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-described 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, based on the plurality of moire fringe image data obtained in step S27, calculates the moire fringes at the measurement point (x, y) existing in the setting direction according to the above equation (6). The phase φ _m (x, y) is obtained.

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. 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.

Steps S28 and S29 described above are performed for each of a plurality of setting directions. That is, in step S28, the phases φ _m (x, y) of a plurality of measurement points (x, y) existing in a plurality of setting directions are obtained, and in step S29, the in-plane displacement U _x in each setting direction is calculated. Calculation is performed based on φ _m (x, y) and φ _m0 (x, y) corresponding to the set direction.

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 based on the region of the image data existing in the setting direction in the image data obtained in step S26. To do.
In step S31, 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 lattice pattern in the x direction, the data processing unit 3b moves in the set direction. A position z = f · p (x, y) / Q in the z direction of an 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 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.

Steps S30 to S32 described above are performed for each of a plurality of setting directions. That is, in step S31, the position z in the z direction of the measurement point (x, y) existing in each setting direction is obtained based on Q corresponding to the setting direction, and in step S32, the out-of-plane displacement in each setting direction. O is calculated based on the position z and the position z ₀ corresponding to the set 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 Based on the coefficients K _{ux (x, y), Δz} , K _{ux (x, y), Δx} , K _{o (x, y), Δz} , K _{o (x, y), Δx} , 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, the in-plane displacement U _x and the out-of-plane displacement O corresponding to the set direction and the correction coefficients K _{ux (x, y), Δz} , K _{ux (x, y), Δx} , K _{o (x , Y), Δz, Ko (x, y), Δx} , the corrected displacements Δz and Δx are calculated.
In the storage device 7, the correction coefficients K _{ux (x, y), Δz} , K _{ux (x, y), Δx} , K _{o (x, y), Δz} , K _{o (x, y)} are set for each setting direction _{. y) and Δx} are stored in association with the set 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 the above-described 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 or a CD-ROM) that stores the program non-temporarily.

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

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

In the xz process, as described above, the correction coefficient calculation device 5 uses the correction coefficients 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, similarly to the xz process, the correction coefficient calculation device 5 performs correction coefficients K _{uy (x, y), Δz} , K _{uy (x, y), Δy} , K _{o (x, y), Δy.} Is obtained in advance and stored in the storage device 7.

In step S <b> 33, the displacement calculation device 9 obtains a displacement Δz in the z direction, a displacement Δx in the x direction, and a displacement Δy in the y direction as post-correction displacements based on each correction coefficient stored in the storage device 7. That is, the displacement calculating device 9 obtains Δz, Δx, and Δy as a solution of the ternary simultaneous equations expressed 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 uy (x,} y), Δx · Δx + K uy (x, y), Δy · Δy + K uy (x, y), Δz · Δz ··· (29)

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

In these equations, U _x is an in-plane displacement (measurement displacement) along the x direction obtained by the displacement measuring device 3 in the xz processing, and U _y is a y direction obtained by the displacement measuring device 3 in the yz processing. , K _{ux (x, y), Δy} and K _{ux (x, y), Δx} are obtained in advance as follows: K _{ux (x, y), Δy} Is obtained by the following additional processing in the yz processing. The additional process 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 imaging the lattice pattern of the target surface 1a.
(A3) Thereafter, the data processing unit 3b generates a plurality of moire fringe image data by performing the above-described thinning process and luminance interpolation process only a plurality of times on this image data.
(A4) Next, the data processing unit 3b, based on the plurality of moire fringe image data, in the x direction at the measurement point (x, y) existing in the set direction according to the above equation (6). The phase of moiré fringes φ _m (x, y) is obtained. This φ _m (x, y) is hereinafter referred to as φ _mx (x, y).

(A5) Thereafter, the data processing unit 3b determines that U _{0x (x, y), Δy} = p (x, y) · {φ _mx (x, y) −φ _m0 (x, y)} / 2π An in-plane displacement U _{0x (x, y), Δy} along the x direction due to ₀ is obtained. Here, the in-plane displacement U _{0x (x, y), Δy} is the in-plane displacement of the measurement point (x, y) existing in the set direction, and φ _mx (x, y) and φ _m0 (x, y). ) Is a phase in the x direction corresponding to the set direction. φ _m0 (x, y) is the phase in the initial state.
(A6) On the basis of the change amount Δy ₀ in (a1) and U _{0x (x, y), Δy} obtained in (a5), the data processing unit 3b _{calculates the in-} plane correction coefficient K _{ux (x , Y), Δy} is calculated by K _{ux (x, y), Δy} = U _{0x (x, y), Δy} / Δy ₀ . The change amount Δy ₀ is set in advance and stored in the storage device 7, for example, or detected by the detector 12 b and input from the detector to the correction coefficient calculation device 5. In the storage device 7, K _{ux (x, y) and Δy} are stored in association with the setting direction for each setting direction.

K _{ui (x, y) and Δx} are obtained by the following additional process in the xz process, similarly to the above-described additional process for _obtaining K _{ux (x, y) and Δy} . This additional process includes 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 imaging the lattice pattern of the target surface 1a.
(B3) Thereafter, the data processing unit 3b generates a plurality of moire fringe image data by performing the above-described thinning process and luminance interpolation process only a plurality of times on the image data.
(B4) Next, the data processing unit 3b, based on the plurality of moiré fringe image data, calculates the measurement point (x, y) existing in the set direction according to the above equation (6) in which x and y are interchanged. Then, the phase φ _m (x, y) of the moire fringes in the y direction is obtained. This φ _m (x, y) is hereinafter referred to as φ _my (x, y).

(B5) After that, the data processing unit 3b determines that U _{0y (x, y), Δx} = p (x, y) · {φ _my (x, y) −φ _m0 (x, y)} / 2π, Δx An 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 in-plane displacements of the measurement point (x, y) existing in the set direction, and φ _my (x, y) and φ _m0 (x, y). ) Is a phase corresponding to this setting direction. φ _m0 (x, y) is the phase in the initial state.
(B6) Based on the change amount Δx ₀ in (b1) and U _{0y (x, y), Δx} obtained in (b5), the data processing unit 3b determines the in-plane correction coefficient K _{uy (x , Y), Δx} is calculated by K _{uy (x, y), Δx} = U _{0y (x, y), Δx} / Δx ₀ . The change amount Δx ₀ is set in advance and stored in the storage device 7, for example, or detected by the detector 12 b and input from the detector 12 b to the correction coefficient calculation device 5. In the storage device 7, for each setting direction, K _{uy (x, y) and Δx} are stored in association with the setting direction.

The present invention is not limited to the above-described embodiments, and various changes 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. However, the relative position between the camera 3a and the target surface 1a is changed by moving the object 1. May be.

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

Claims (8)

A displacement acquisition device that measures the displacement of a target surface of an object,
A camera that images a regular pattern provided on the target surface, and a data processing unit that obtains a displacement of a measurement point on the target surface as a measurement displacement by a sampling moire method based on image data of the pattern captured by the camera A displacement measuring device comprising:
A correction coefficient calculation device for obtaining a correction coefficient related to the measured displacement;
A displacement calculating device that calculates a corrected displacement of the measurement point based on the measured displacement and the correction coefficient;
The measurement point is located in a setting direction viewed from the camera, and the correction coefficient is obtained for the setting 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 on the target surface existing in the setting direction due to this change as a coefficient calculation displacement,
The correction coefficient calculation apparatus is a displacement acquisition apparatus that calculates the correction coefficient based on the coefficient calculation displacement and the amount of change in the relative position. For each of the plurality of setting directions,
The displacement measuring device obtains the coefficient calculation displacement,
The correction coefficient calculation device obtains the correction coefficient based on the coefficient calculation displacement and the change amount of the relative position,
The displacement acquisition according to claim 1, wherein the displacement calculation device calculates the corrected displacement based on the measured displacement of the measurement point existing in the setting direction and the correction coefficient for the setting direction. apparatus. Each of the measurement 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 based on the out-of-plane displacement included in the coefficient calculation displacement. The displacement acquisition device according to claim 1 or 2, wherein K _o is obtained. 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 obtains the in-plane displacement U _{0x (x, y), Δz} and the out-of-plane displacement O _{0 (x, y), Δz} included in the coefficient calculation displacement based on the change amount Δz _0. ,
The correction coefficient calculating device includes K _{ux (x, y), Δz} = U _{0x (x, y),} which is included in the in-plane correction coefficient K _u based on Δz ₀ , U _{0x (x, y), and Δz . Δz} / Δz ₀ is calculated, and K _{o (x, y) and Δz} = O _{0 (x, y)} included in the out-of-plane correction coefficient K _o based on Δz ₀ , O _{0 (x, y), and Δz. , Δz} / Δz ₀ ,
In order to obtain the correction coefficient, the relative position between the camera and the target surface is changed by the change amount Δx ₀ in the x direction perpendicular to the z direction,
The displacement measuring device obtains in-plane displacements U _{0x (x, y), Δx} and out-of-plane displacements O _{0 (x, y), Δx} included in the coefficient calculation displacement based on the change amount Δx ₀ ,
The correction coefficient calculating device includes K _{ux (x, y), Δx} = U _{0x (x, y),} included in the in-plane correction coefficient K _u based on Δx ₀ , U _{0x (x, y), and Δx . Δx} / Δx ₀ is calculated, and based on Δx ₀ and O _{0 (x, y), Δx} , K _{o (x, y)} as the out-of-plane correction coefficient K _{o , Δx} = O _{0 (x, y),} Calculate _Δx / Δx ₀ ,
The displacement calculating device includes an in-plane displacement U _x and an out-of-plane displacement O included in the measured displacement, and the correction coefficients K _{ux (x, y), Δz} , K _{ux (x, y), Δx} , _{Ko ( x, y), Δz} , K _{o (x, y), Δx,} and the displacement Δz in the z direction and the displacement Δx in the x direction as the post-correction displacement,
Δz = (K _{ux (x, y), Δx} · O−K _{o (x, y), Δz} · U _x ) / (K _{ux (x, y), Δx} · K _{o (x, y), Δz} − K _{ux (x, y), Δz} · K _{o (x, y), Δx} )
Δx = (K _{o (x, y), Δz} · U−K _{ux (x, y), Δz} · O) / (K _{ux (x, y), Δx} · K _{o (x, y), Δz} −K _{ux (x, y), Δz} · K _{o (x, y), Δx} )
The displacement acquisition device according to claim 3, which is calculated by: 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 includes the in-plane displacements U _{0x (x, y), Δz} and U _{0y (x, y), Δz} and the out-of-plane displacements O included in the coefficient calculation displacements based on the change amount Δz _{0. 0 (x, y), Δz} is obtained, and U _{0x (x, y), Δz} and U _{0y (x, y), Δz} are in-plane displacements along the x direction and the y direction, respectively.
The correction coefficient calculation device includes K _{ux (x, y),} included in the in-plane correction coefficient K _u based on Δz ₀ and U _{0x (x, y), Δz} and U _{0y (x, y), Δz . Δz} = U _{0x (x, y), Δz} / Δz ₀ and K _{uy (x, y), Δz} = U _{0y (x, y), Δz} / Δz ₀ are calculated, and Δz ₀ and O _{0 (x, y ), Δz} , K _{o (x, y), Δz} = O _{0 (x, y), Δz} / Δz ₀ included in the out-of-plane correction coefficient K _o are calculated,
In order to obtain the correction coefficient, the relative position between the camera and the target surface is changed by the change amount Δx _{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} , 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 calculating device includes K _{ux (x, y), Δx} = U _{0x (x, y),} included in the in-plane correction coefficient K _u based on Δx ₀ , U _{0x (x, y), and Δx .} 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 Based on 0} , O _{0 (x, y), Δx} , K _{o (x, y), Δx} = O _{0 (x, y), Δx} / Δx ₀ as the out-of-plane correction coefficient K _o are calculated,
In order to obtain the correction coefficient, the relative position between the camera and the target surface is changed by the change amount Δy _{0 in the} y direction,
Said displacement measuring apparatus, according to the amount of change [Delta] y _0, the plane displacement included in the coefficient calculation displacement _{U 0y (x, y),} Δy and _{U 0x (x, y),} Δy and out-of-plane displacement _{O 0 ( x, y), Δy} , and U _{0y (x, y), Δy} and U _{0x (x, y), Δy} are in-plane displacements along the y direction and the x direction, 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), calculating a _{[Delta] y} / [Delta] y _0, to calculate the [Delta] y ₀ and _{U 0x (x, y),} based on _{Δy K ux (x, y)} , Δy = U 0x (x, y), Δy / Δy 0, Δy _{Based on 0} , O _{0 (x, y), Δy, Ko (x, y), Δy} = O _{0 (x, y), Δy} / Δy ₀ as the out-of-plane correction coefficient K _o are calculated,
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 displacements U _x and U _y and out-of-plane displacements 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, Based on K _{ux (x, y), Δy} , K _{o (x, y), Δy} , the corrected displacement in the z direction Δz, the displacement in the x direction Δx, and the displacement in the y direction Δy

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

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

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

The displacement acquisition device according to claim 3, which is obtained as a solution of a ternary simultaneous equation represented by: A drive device for changing the relative position between the camera and the target surface by moving the camera;
The amount of change in the relative position is the amount of movement of the camera by the driving device,
6. The correction coefficient calculation device according to claim 1, wherein the correction coefficient calculation device obtains the correction coefficient based on the movement amount set in advance or detected by a detector and the coefficient calculation displacement. 7. The displacement acquisition device described. A displacement acquisition method for measuring the displacement of a target surface of an object,
(A) Obtaining image data by capturing a regular pattern provided on the target surface with a camera;
(B) A displacement of the measurement point on the target surface is determined as a measurement displacement by a sampling moire method based on the image data,
(C) calculating a corrected displacement of the measurement point based on the measured displacement and a correction coefficient;
The measurement point is located in a setting direction viewed from the camera, and the correction coefficient is obtained for the setting direction,
In order to obtain the correction factor,
(A) changing the relative position between the camera and the target surface;
(B) The displacement of the measurement point on the target surface existing in the set direction due to this change is measured as a coefficient calculation displacement,
(C) A displacement acquisition method for obtaining the correction coefficient based on the coefficient calculation displacement and the change amount of the relative position. A program for executing processing for measuring the displacement of the target surface of an object,
A process for obtaining a 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;
Processing for obtaining a correction coefficient related to the measured displacement;
Based on the measurement displacement and the correction coefficient, the computer calculates the corrected displacement of the measurement point,
The measurement point is located in a setting direction viewed from the camera, and the correction coefficient is obtained for the setting direction,
In order to obtain the correction coefficient, when the relative position between the camera and the target surface is changed, the process for obtaining the correction coefficient includes:
Based on the image data obtained by imaging the pattern with the camera before this change and the image data obtained by imaging the pattern with the camera after this change, the change exists in the setting direction. Processing for measuring the displacement of the measurement point on the target surface as a coefficient calculation displacement;
A program including processing for obtaining the correction coefficient based on the coefficient calculation displacement and the change amount of the relative position.

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