JP7470521B2 - Parameter acquisition device and parameter acquisition method - Google Patents

Description

The present invention relates to a technique for measuring the displacement of a target surface of an object to be measured using a sampling moiré method. More specifically, the present invention relates to an apparatus and method for determining parameters used to measure the displacement of a target surface and inspecting the reliability of the parameters.

In the sampling moiré method, a regular pattern (e.g. a lattice pattern) is attached or projected onto the surface of the object to be measured (hereafter referred to as the target surface), and the displacement of the target surface is measured based on image data of the lattice pattern. That is, a process is performed to thin out pixels at regular intervals in the image data of the lattice pattern, and this process is performed multiple times by changing the starting point for thinning out pixels, thereby obtaining multiple moiré fringe images. The displacement of the target surface is calculated based on the change in the phase of the moiré fringes caused by these moiré fringe images.

Devices that use the sampling moiré method to measure the displacement of a target surface in this way are described in, for example, Patent Documents 1 and 2.

JP 2019-11984 A JP 2019-124561 A

In Patent Document 1, a camera that captures an image of a regular pattern on the target surface is mounted on a movable stage. Parameters (correction coefficients) used to determine the in-plane or out-of-plane displacement of the target surface are determined in advance as follows. At the reference time of the initial state, the stage is moved relative to the target surface. The in-plane or out-of-plane displacement of the target surface according to the moving distance of the stage is measured. A correction coefficient is determined based on the measured value and the moving distance of the stage. Then, during actual measurement, the corrected in-plane or out-of-plane displacement with the effects of errors removed is determined based on the in-plane or out-of-plane displacement measured by the sampling moiré method and the correction coefficients.

In Patent Document 2, a camera that captures an image of the target surface and a projection device that projects a regular pattern onto the target surface are mounted on a movable stage. In Patent Document 2, parameters (ratios) used to calculate the out-of-plane displacement of the target surface are calculated in advance as follows: The stage is moved relative to the target surface. The amount of phase change in the pattern at the measurement point on the target surface due to the moving distance of the stage is measured. A ratio is calculated based on the amount of phase change and the moving distance of the stage. Then, the phase of the pattern at the measurement point on the target surface is calculated by the sampling moiré method at each of the reference time and the actual measurement time, and the difference between the phase at the measurement time and the phase at the reference time is calculated, and the out-of-plane displacement is calculated based on this difference and the above ratio.

When using the above parameters in a device that measures the displacement of a target surface using the sampling moiré method, it is desirable to improve the reliability of the measured displacement of the target surface.

The inventors of the present invention focused on ensuring the accuracy of parameters (e.g., the above-mentioned correction coefficients or ratios) in order to obtain highly reliable displacement measurement values. In other words, the object of the present invention is to ensure the accuracy of parameters so as to obtain highly reliable displacement measurement values.

In order to achieve the above object, a parameter acquisition device according to the present invention comprises:
A camera that captures an image of a regular pattern on a target surface of an object to generate image data;
a data processing unit that calculates a displacement amount for a measurement point on the target surface by a sampling moiré method based on the image data;
A parameter acquisition device provided in a displacement acquisition device including a displacement calculation unit that calculates one or both of an in-plane displacement and an out-of-plane displacement of a measurement point based on an obtained displacement amount and a parameter obtained in advance,
a movable part on which the camera is mounted and which is movable in a predetermined direction;
A drive device that moves the movable part in the predetermined direction;
a control unit that performs parameter acquisition control on the drive device to move the movable unit in the predetermined direction by a control distance for parameter acquisition,
a displacement amount relating to the measurement point before and after the parameter acquisition control is obtained by the camera and the data processing unit;
a parameter calculation unit that calculates the parameter based on the displacement amount and a control distance for acquiring the parameter;
a distance measuring sensor that measures a distance actually moved by the movable part under an inspection control when the inspection control is performed on the driving device to move the movable part by a control distance for inspection in the predetermined direction; and
The apparatus further includes an index value calculation unit that calculates an index value indicating a difference between the movement distance measured by the distance measuring sensor and the inspection control distance, and outputs the calculated index value.

In order to achieve the above object, a parameter acquisition method according to the present invention includes a camera that captures an image of a regular pattern on a target surface of an object to generate image data;
a data processing unit that calculates a displacement amount for a measurement point on the target surface by a sampling moiré method based on the image data;
A parameter acquisition method for a displacement acquisition device including a displacement calculation unit that calculates one or both of an in-plane displacement and an out-of-plane displacement of a measurement point based on an acquired displacement amount and a parameter acquired in advance,
(A) providing a movable part on which the camera is installed and which is movable in a predetermined direction, and a drive device that moves the movable part in the predetermined direction;
(B) performing parameter acquisition control on the drive device by a control unit to move the movable part in the predetermined direction by a control distance for parameter acquisition;
(C) determining a displacement amount of the measurement point before and after the parameter acquisition control by the camera and the data processing unit;
(D) calculating the parameter by a parameter calculation unit based on the displacement amount and a control distance for obtaining the parameter;
(E) performing an inspection control on the drive device by the control unit to move the movable part in the predetermined direction by a control distance for inspection;
(F) measuring the distance that the movable part has actually moved by the inspection control using a distance measuring sensor;
(G) An index value indicating the difference between the movement distance measured by the distance measuring sensor and the control distance for inspection is calculated and output by an index value calculation unit.

According to the present invention, the control unit performs parameter acquisition control to move the movable part a predetermined distance in the predetermined direction, measures the amount of displacement at the measurement point caused by this, and determines the parameter based on the amount of displacement and the control distance for parameter acquisition. To ensure the reliability of this parameter, the present invention measures the distance actually moved by the movable part using inspection control, and determines and outputs an index value indicating the difference between that distance and the control distance for inspection.

Therefore, the reliability of the parameter accuracy can be evaluated based on the output index value. For example, if the index value is within an acceptable range, it can be determined that the parameter is highly reliable and that highly reliable displacement measurement values can be obtained.

On the other hand, if the index value is outside the allowable range, calibration can be performed to obtain a highly reliable displacement measurement value, for example by correcting the parameter value or by correcting the drive amount of the drive device using the parameter acquisition control of the control unit and re-determining the parameters.

1 shows the configuration of a displacement acquiring device to which the parameter acquiring device according to the first embodiment of the present invention can be applied. 11 is an explanatory diagram of a process for acquiring an in-plane correction coefficient which is a parameter. 13 is another explanatory diagram of the process of acquiring an in-plane correction coefficient which is a parameter. FIG. 11 is an explanatory diagram of a process for acquiring an out-of-plane correction coefficient which is a parameter. FIG. FIG. 13 is another explanatory diagram of the process of acquiring the out-of-plane correction coefficient which is a parameter. 13 is a flowchart showing a process in an initial state (reference time). 13 is a flowchart showing a process of movement in the z direction. 13 is a flowchart showing a process of movement in the x direction. 13 is a flowchart of a displacement acquisition process. 13 is a flowchart of a parameter inspection process. 1 shows the configuration of a displacement acquiring device to which a parameter acquiring device according to a second embodiment of the present invention can be applied. FIG. 11 is an explanatory diagram of a process for acquiring a ratio which is a parameter. 13 is a flowchart showing a parameter acquisition process and a displacement acquisition process. A target is shown provided on the laser irradiation surface of the movable part.

The embodiment of the present invention will be described with reference to the drawings. Note that common parts in each drawing are given the same reference numerals, and duplicated explanations will be omitted.

[First embodiment]
(Configuration of Displacement Acquisition Device)
FIG. 1 shows the configuration of a displacement acquisition device 100 to which a parameter acquisition device 200 according to a first embodiment of the present invention can be applied. The displacement acquisition device 100 measures the displacement of a surface of an object 1 to be measured (hereinafter also simply referred to as a 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 target surface 1a may be a flat surface or a curved surface. In one example, the object 1 is a motor case of a rocket motor, and the target surface 1a is the outer circumferential surface of the motor case. The displacement acquisition device 100 includes a camera 101, a data processing unit 103, a displacement calculation unit 105, and a storage unit 107.

The camera 101 captures an image of a regular pattern on the target surface 1a, thereby acquiring image data of the pattern. Here, the regular pattern is, for example, a lattice pattern, but other patterns may be used as long as they can generate moiré fringe image data, which will be described later. In addition, the pattern may be provided in advance on the target surface 1a.

The data processing unit 103 measures the amount of displacement of a measurement point (hereinafter also simply referred to as a measurement point) on the target surface 1a by the sampling moiré method based on the image data generated by the camera 101. In this embodiment, the amount of displacement of the measurement point is the in-plane displacement and out-of-plane displacement of the measurement point before correction. The in-plane displacement is the displacement in a direction along the target surface 1a. The out-of-plane displacement is the displacement of the measurement point in a direction intersecting (e.g. perpendicular to) the target surface 1a. Hereinafter, the in-plane displacement and out-of-plane displacement are also simply referred to as the in-plane displacement and out-of-plane displacement, respectively.

The displacement calculation unit 105 calculates one or both of the in-plane displacement and the out-of-plane displacement after correction of the measurement point based on the amount of displacement (in-plane displacement and out-of-plane displacement before correction) calculated by the data processing unit 103 and the parameters calculated in advance. In this embodiment, the direction seen by the camera 101 is set as a set direction (hereinafter also simply referred to as a set direction), and for each set direction (e.g., each of a plurality of set directions), the displacement of the measurement point existing in the set direction is calculated.

The luminance distribution I(x, y) of the image data acquired by the camera 101 is expressed by the following formula (1). Here, x and y indicate the x and y coordinates in an xyz coordinate system fixed to the camera 101. This xyz coordinate system may be a three-dimensional coordinate system whose z axis is parallel to the optical axis C of the camera 101 (the orientation of the camera 101). In the following, the x direction, y direction, and z direction refer to 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 formula (1), I(x, y) indicates the luminance of the coordinates (x, y) of a point on the target surface 1a. φ ₀ (x, y) is the initial phase. Q is the pitch Q(x, y) of the grid pattern in the image data in the x direction. _Ia is the amplitude of the luminance, and _Ib is the background luminance.

The data processing unit 103 performs thinning and luminance interpolation on the above-mentioned image data. In this embodiment, the data processing unit 103 performs thinning and luminance interpolation in the x direction. In the thinning process, the data processing unit 103 samples and maintains pixels of the image data at a predetermined sampling period (period T close to the period of the pattern in this example) in the x direction, and thins out and deletes pixels in other positions. In the luminance interpolation process, the data processing unit 103 interpolates (for example, linearly interpolates) the luminance of the thinned pixel based on the luminance of the pixels surrounding this pixel.

The data processing unit 103 performs such thinning processing and brightness interpolation processing multiple times. The sampling period T is the same between the multiple thinning processing, but the start point of thinning (the start point of the pixels to be sampled) is changed. The data processing unit 103 performs the thinning processing and brightness interpolation processing multiple times on the above-mentioned image data, thereby generating multiple pieces of moiré fringe image data corresponding to each of the multiple times.
In this example, the data processing unit 103 generates T pieces of moire fringe image data by thinning out the images in the x direction and performing luminance interpolation. These pieces of moire fringe image data are expressed by the following equation (2).

In equation (2), k indicates the start point of thinning in the x direction, and takes the values 0, 1, 2, ..., T-1.
The data processing unit 103 applies a discrete Fourier transform to equation (2) to obtain the phase φ _m (x, y) of the moiré fringes using the following equation (3).

<In-plane displacement before correction>
The data processing unit 103 obtains the change Δφ _m (x, y) in the phase φ _m (x, y) of the moiré fringes to obtain the in-plane displacement of the target surface 1a. That is, assuming that the lattice pattern is a pattern that is repeated at a pitch (constant interval) in the x direction, the data processing unit 103 obtains the in-plane displacement U _x (x, y) by U _x (x, y) = Δφ _m (x, y) · p (x, y) / 2π. Hereinafter, the pitch p (x, y) of the lattice pattern is also simply written as p, U _x (x, y) is also written as U _x , and Δφ _m (x, y) is also written as Δφ _m . U _x is the in-plane displacement along the x direction in the xyz coordinate system, in other words, the in-plane displacement in a plane parallel to the xz plane or in the xz plane in the xyz coordinate system.
Here, if φ _m (x, y) obtained at the reference time in the initial state is defined as φ _m0 (x, y) and φ _m (x, y) obtained at the time of measurement is directly defined as φ _m (x, y), then Δφ _m is the in-plane displacement before correction and is expressed as Δφ _m = φ _m (x, y) - φ _m0 (x, y).

<Out-of-plane displacement before correction>
If the focal length of the camera 101 is f, the actual pitch of the grid pattern on the target surface 1a is p as above, the pitch of the grid in the image data is Q as above, and the distance from the camera 101 (the center of the objective lens of the camera 101) to the grid pattern (the surface of the target object 1) in the direction of the optical axis C of the camera 101 is Z, the following equation (4) holds.

Z = f p / Q ... (4)

Based on this equation (4), the data processing unit 103 calculates the out-of-plane displacement O of the measurement point before correction using the following equation (5).

O = f p / Q - f p / Q ₀ ... (5)

Here, _Q0 is the pitch in the x direction of the lattice pattern in the image data obtained by the camera 101 capturing the target surface 1a in the initial state (reference time), and Q is the pitch in the x direction of the lattice pattern in the image data obtained by the camera 101 capturing the target surface 1a during measurement.

Q can be calculated as follows: First, the following equation (6) is obtained from the above equation (2).
From this equation, the data processing unit 103 obtains Q. For example, equation (6) is approximated by the following equation (7), and the data processing unit 103 obtains Q from the following equation (8) obtained by modifying equation (7).

In equation (8), x+1 in φ _m (x+1, y) is the x coordinate of the pixel adjacent in the x-axis direction to the pixel (x coordinate) of interest for finding Q, and x-1 in φ _m (x-1, y) is the x coordinate of the pixel adjacent to the pixel of interest on the opposite side of the x-coordinate x+1 in the x-axis direction. Data processing unit 103 finds _Q0 in the same way as in the case of Q.

The displacement calculation unit 105 calculates one or both of the in-plane displacement and the out-of-plane displacement after correction based on the in-plane displacement and the out-of-plane displacement obtained by the data processing unit 103 and the parameters stored in the memory unit 107 provided in the displacement acquisition device 100. Here, the parameters are correction coefficients for removing the effects of errors contained in the in-plane displacement and the out-of-plane displacement before correction. The errors include measurement errors due to the inclination of the target surface 1a with respect to a plane perpendicular to the optical axis of the camera 101, measurement errors depending on the direction of the measurement point as seen from the camera 101, errors specific to the camera 101 (lens aberration, angle of view, etc.), and errors in the actual pitch of the lattice pattern. In addition, if the target surface 1a is a curved surface, errors due to the curved surface are also included in the in-plane displacement and the out-of-plane displacement before correction. The correction coefficients can remove these errors.

(Parameter Acquisition Device)
The parameter acquisition device 200 according to this embodiment is a device for acquiring the above-mentioned parameters (correction coefficients). The parameter acquisition device 200 includes a movable part 201, a driving device 203, a control part 205, a parameter calculation part 207, a distance measurement sensor 209, an index value calculation part 211, a determination part 213, and a correction part 215.

The camera 101 is installed on the movable part 201. The movable part 201 is movable in a predetermined direction. In this embodiment, the predetermined directions are the x direction and the z direction.

The driving device 203 moves the movable part 201 in a predetermined direction. In the example of FIG. 1, the driving device 203 has a moving stage 203a, a first driving unit 203b, and a second driving unit 203c. The moving stage 203a is provided with the movable part 201 so that it can move in the x direction. The first driving unit 203b is provided on the moving stage 203a and drives the movable part 201 in the x direction relative to the moving stage 203a (i.e., the target surface 1a). The second driving unit 203c is provided on a stationary structure and drives the moving stage 203a in the z direction relative to the stationary structure (i.e., the target surface 1a).

The control unit 205 performs parameter acquisition control on the drive device 203 to move the movable unit 201 in a predetermined direction by a control distance for parameter acquisition. At this time, the amount of displacement (in-plane displacement and out-of-plane displacement before correction in this embodiment) of the measurement point before and after the parameter acquisition control is found by processing of the camera 101 and the data processing unit 103.

The parameter calculation unit 207 calculates a parameter (a correction coefficient in this embodiment) based on the amount of displacement and the control distance for obtaining the parameter. The parameter calculation unit 207 stores the calculated parameter in the storage unit 107.

The control unit 205 also performs inspection control on the driving device 203 to move the movable unit 201 in a predetermined direction by a control distance for inspection. The control distance for inspection and the control distance for obtaining the above-mentioned parameters may be preset in the control unit 205 or may be input to the control unit 205 from the outside.

The distance measurement sensor 209 measures the distance that the movable part 201 actually moves in a predetermined direction under the inspection control, and outputs the measured distance to the index value calculation unit 211. The distance measurement sensor 209 may be a laser displacement sensor. The laser displacement sensor emits laser light in a predetermined direction toward the movable part 201, reflects it on the movable part 201, and measures the moving distance of the movable part 201 in the predetermined direction based on the reflected laser light. In one example, the laser displacement sensor focuses (concentrates) the reflected laser light that returns in a direction intersecting the emission direction of the laser light with a light receiving lens, and obtains the moving distance of the movable part 201 based on the change in the image position due to the inspection control. In another example, the laser displacement sensor measures the time from the time when the laser light is emitted to the time when the reflected laser light is received, and measures the moving distance of the movable part 201 based on the change in the time due to the inspection control. Alternatively, the laser displacement sensor may measure the moving distance of the movable part 201 by another method.

In the example of FIG. 1, the distance measurement sensor 209 includes a distance measurement sensor 209a that measures the movement distance of the movable part 201 in the z direction, and a distance measurement sensor 209b that measures the movement distance of the movable part 201 in the x direction.

The index value calculation unit 211 calculates and outputs an index value relating to the difference between the moving distance measured by the distance measurement sensor 209 and the control distance for inspection. This index value may be the difference or ratio between the moving distance measured by the distance measurement sensor 209 and the control distance for inspection. The control distance for inspection may be set in advance in the index value calculation unit 211, or may be input to the index value calculation unit 211 from the control unit 205.

The judgment unit 213 judges whether the index value output by the index value calculation unit 211 is within an acceptable range, and if the result of the judgment is negative, outputs the judgment result to the correction unit 215.

When the correction unit 215 receives the above judgment result from the judgment unit 213 that the index value output by the index value calculation unit 211 is outside the allowable range, the correction unit 215 corrects the parameters (correction coefficients) stored in the memory unit 107.

(How to calculate the correction coefficient)
<In-plane correction coefficient>
The correction coefficient as the parameter mentioned above includes an in-plane correction number for correcting the in-plane displacement. Figures 2 and 3 are explanatory diagrams of the process of acquiring the in-plane correction coefficient K _u . In Figures 2 and 3, the xyz coordinate system is a three-dimensional coordinate system fixed to the camera 101, and has the above-mentioned x-axis, y-axis, and z-axis.

In Figures 2 and 3, the angle θ(x, y) indicates the above-mentioned set direction as seen by the camera 101. That is, the angle θ(x, y) is the angle between 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 between the x direction and the target surface 1a.

To obtain the in-plane correction coefficient K _ux(x,y),Δz in the z direction, the camera 101 (i.e., the movable part 201) is moved by a predetermined distance Δz ₀ in the z direction with respect to the target surface 1a by the driving device 203 as shown in FIG.

In this case, the in-plane displacement U _{0x(x, y), Δz} due to Δz ₀ in a plane parallel to the xz plane can be approximated by the following equation (9) assuming that θ(x, y) is sufficiently small as shown in FIG.

_U0x(x,y),Δz = _Δz0 ·tanθ(x,y)/cosα(x,y) (9)

Based on equation (9), the in-plane correction coefficient K _{ux(x, y), Δz} as the rate of variation of the in-plane displacement U _{0x(x, y)} , Δz with respect to Δz ₀ is expressed by the following equation (10).

K _{ux(x,y), Δz} = tan θ(x,y) / cos α(x,y) ... (10)

In formula (10), θ(x,y) and α(x,y) are unknown, so K _{ux(x,y), Δz} cannot be obtained from θ(x,y) and α(x,y), but Δz ₀ is known, and U _{0x(x,y), Δz} can be obtained as the in-plane displacement before correction as described above. Therefore, in this embodiment, K _{ux(x,y), Δz} are obtained by the following formula (11).

K _{ux (x, y), Δz} = U _{0 x (x, y), Δz} / Δz ₀ ... (11)

To obtain the in-plane correction coefficient K _ux(x,y),Δx in the x direction, the camera 101 (i.e., the movable part 201) is moved by an amount of change _Δx0 in the x direction relative to the target surface 1a by the driving device 203 as shown in FIG.

At this time, the in-plane displacement U _{0x(x, y), Δx} due to Δx ₀ in a plane parallel to the xz plane is expressed by the following equation (12), as shown in FIG.

_{U0x(x,y), Δx} = _Δx0 /cosα(x,y) ... (12)

Based on equation (12), the in-plane correction coefficient K _{ux(x, y), Δx} as the rate of variation of the in-plane displacement U _{0x(x, y),} Δx relative to Δx ₀ is expressed by the following equation (13).

K _{ux(x,y), Δx} =1/cos α(x,y) ... (13)

In formula (13), α(x, y) is unknown, so 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} can be obtained as the in-plane displacement before correction as described above. Therefore, in this embodiment, K _{ux(x, y) and Δx} are obtained by the following formula (14).

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

<Out-of-plane correction coefficient>
The correction coefficient as the parameter mentioned above includes an out-of-plane correction number for correcting the out-of-plane displacement. Figures 4 and 5 are explanatory diagrams of the process of acquiring the out-of-plane correction coefficient K _o . In Figures 4 and 5, the xyz coordinate system, the angle θ(x, y), and the angle α(x, y) are the same as those in Figures 2 and 3.

In order to obtain the out-of-plane correction coefficient K _{o(x, y),Δz} in the z direction, the relative position between the camera 101 and the target surface 1a is changed by a predetermined distance Δz ₀ in the z direction as shown in FIG.

At this time, the out-of-plane displacement O _{0 (x, y), Δz} due to Δz ₀ can be approximated by the following equation (15) 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)} ... (15)

Based on equation (15), the out-of-plane correction coefficient K _{o(x, y),Δz} as the rate of variation of the out-of-plane displacement O _{0(x, y)} ,Δz relative to Δz ₀ is expressed by the following equation (16).

K _{o(x,y), Δz} = {1 + tan θ(x,y) · tan α(x,y)} / cos {α(x,y) + θ(x,y)} ... (16)

In formula (16), θ(x,y) and α(x,y) are unknown, so K _0z cannot be obtained from θ(x,y) and α(x,y), but Δz ₀ is known, and O _{0(x,y), Δz} are obtained as the out-of-plane displacement before correction as described above. Therefore, in this embodiment, K _{o(x,y), Δz} are obtained by the following formula (17).

K _{o (x, y), Δz} = O _{0 (x, y), Δz} / Δz ₀ ... (17)

To obtain the out-of-plane correction coefficient K _o(x,y),Δx in the x direction, the relative position between the camera 101 and the target surface 1a is changed in the x direction by an amount of change Δx ₀ as shown in FIG.

At this time, the out-of-plane displacement O _{0 (x, y), Δx} is expressed by the following equation (18), as shown in FIG.

O _{0 (x, y), Δx} = Δx ₀ tan α (x, y) / cos {α (x, y) + θ (x, y)} ... (18)

Based on equation (18), the out-of-plane correction coefficient K _{o(x, y), Δx as the rate of variation of the out-of-plane displacement O 0(x, y), Δx with respect} to Δx 0 is expressed by the following equation (19).

K _o(x,y),Δx = tan α/cos{α+θ(x,y)} (19)

In formula (19), α(x, y) is unknown, so 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} can be obtained as the out-of-plane displacement before correction as described above. Therefore, in this embodiment, K _{o(x, y) and Δx} are obtained by the following formula (20).

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

(How to get parameters)
A parameter acquisition method according to this embodiment will be described below. The parameter acquisition method includes processing of the initial state, processing of movement in the z direction, and processing of movement in the x direction.

<Initial state processing>
6 is a flowchart showing the process in the initial state (reference time). The process in the initial state includes steps S1 to S5.

In step S1, the camera 101 at the reference position captures an image of the grid pattern on the target surface 1a to obtain image data.

In step S2, the data processing unit 103 performs the above-mentioned thinning process and brightness interpolation process multiple times on the image data obtained in step S1 to generate multiple moiré fringe image data.

In step S3, the data processing unit 103 obtains the phase φ _m (x, y) of the moiré fringes at the measurement point (x, y) by the above-mentioned formula (3) based on the multiple moiré fringe image data obtained in step S2. This φ _m (x, y) is hereinafter referred to as φ _m0 (x, y).

Meanwhile, in step S4, the data processing unit 103 specifies the pitch _Q0 (x,y) in the x direction of the lattice pattern existing in the set direction as seen from the camera 101 in the image data obtained in step S1, based on the area of the image data corresponding to the set direction, in accordance with the above-mentioned equations (6) to (8). At this time, Q is replaced with _Q0 (x,y) in equations (6) to (8).
In step S5, the data processing unit 103 calculates the z-direction position z0 of the measurement point in the set direction, _z0 =f·p(x,y)/Q0(x,y), based on the pitch _Q0 (x,y) determined in step S4, the focal length f of the camera 101, and the actual pitch p(x,y) of the grid pattern in the x _- direction. Note that f and p(x,y) are known. Note that the origin of the z-axis is assumed to be at the camera 101 (same below).

The above-mentioned steps S4 and S5 may be performed for each of a plurality of set directions. That is, in step S4, the pitch _Q0 (x,y) in the x direction of the lattice pattern present in each set direction may be specified, and in step S5, the position _z0 of the measurement point for each set direction may be obtained based on _Q0 (x,y) corresponding to the set direction.

<Processing of z-direction movement>
7 is a flowchart showing the process of the movement in the z direction, which includes steps S6 to S15.

In step S6, from the state of step S1, the control unit 205 performs parameter acquisition control on the driving device 203 to move the movable unit 201 (i.e., the camera 101 at the reference position) in the z direction by a control distance Δz ₀ for parameter acquisition. Δz ₀ may be 1/500 or more of the above-mentioned p(x, y) and may be less than or equal to the pitch p(x, y). Δz ₀ is, for example, about 1 mm.
In step S7, the camera 101 captures an image of the lattice pattern on the target surface 1a to obtain image data.

In step S8, the data processing unit 103 performs the above-mentioned thinning process and luminance interpolation process a plurality of times on the image data obtained in step S7, thereby generating a plurality of pieces of moire fringe image data.
In step S9, the data processing unit 103 obtains the phase φm(x,y) of the moiré fringes at the measurement point (x,y) in the set direction using the multiple moiré fringe image data obtained in step S8, using the above-mentioned formula (3). This _φm (x,y) is hereinafter referred _to as _φmz (x,y).

In step S10, the in-plane displacements U _{0x(x,y), Δz} before correction due to Δz ₀ are obtained. Step S10 has steps S10a and S10b. In step S10a, the data processing unit 103 obtains Δφ _m (x,y) by Δφ m (x,y) = φ _mz (x,y) - _{φ m0} (x,y). In step S10b, the data processing unit 103 obtains the in-plane displacements U _{0x(x,y), Δz} due to Δz ₀ by U 0x(x,y) _{, Δz} = p(x,y) · Δφ _{m (x,y) / 2π. Here, Δφ m (} x,y) is the one obtained in step S10a. Note that this in-plane displacement U _{0x(x, y), Δz} is the in-plane displacement of the measurement point (x, y) located in the set direction (hereinafter also referred to as the in-plane displacement U _{0x(x, y), Δz} corresponding to the set direction), and φ _mz (x, y) and φ _m0 (x, y) are phases corresponding to the set direction.

In step S11, based on the control distance Δz ₀ in step S6 and U _{0x(x, y), Δz} calculated in step S10, the parameter calculation unit 207 calculates the in-plane correction coefficient K _{ux(x, y), Δz} for the set direction by K _{ux(x, y), Δz} = U _{0x(x, y), Δz} / Δz _0. The control distance Δz ₀ may be input to the parameter calculation unit 207 from the control unit 205, or may be set in advance in the parameter calculation unit 207.

The above-mentioned steps S10 and S11 may be performed for each of the multiple set directions. That is, in step S10, the in-plane displacements U _{0x(x,y),Δz of the multiple measurement points (x,y} ) that exist in each of the multiple set directions are obtained, and in step S11, the in-plane correction coefficients K _ux(x,y),Δz for each set direction may be calculated based on the in-plane displacements U _0x(x,y),Δz corresponding to the set direction and stored in the storage unit 107.

On the other hand, in step S12, the data processing unit 103 specifies the pitch _Q1 in the x direction of the lattice pattern existing in the set direction in the image data obtained in step S7 based on the area of the image data corresponding to the set direction in accordance with the above-mentioned expressions (6) to (8). At this time, Q is replaced with _Q1 in (6) to (8).

In step S13, the data processing unit 103 calculates the z-direction position _z1 = f·p(x, y)/ _Q1 of the measurement point in the set direction based on the pitch Q1 identified in step _S12 , the focal length f of the camera 101, and the actual pitch p(x, y) of the grid pattern.

In step S14, the data processing unit 103 calculates the out-of-plane displacement O _{0 (x,y) ,Δz due to Δz 0 from} O 0(x,y),Δz =z ₁ -z ₀ based on z ₀ calculated in step S5 and z 1 calculated in step S13.
In step S15, based on the control distance Δz ₀ in step S6 and O _{0(x, y), Δz} calculated in step S14, the parameter calculation unit 207 calculates the out-of-plane correction coefficient K _{o(x, y), Δz} before correction by K _{o(x, y), Δz} = O _{0(x, y), Δz} / Δz ₀ , and stores the calculated coefficient in the storage unit 107.

The above-mentioned steps S12 to S15 are performed for each of the set directions in the image data. That is, in step S13, the z-direction position _z1 of the measurement point (x, y) existing in each set direction is obtained based on _Q1 corresponding to the set direction, in step S14, the out-of-plane displacement O0 _{(x, y), Δz} for each set direction is calculated based on the position _z1 and the position _z0 corresponding to the set direction, and in step S15, the out-of-plane correction coefficient K0 _{(x, y), Δz} for each set direction is calculated based on the out-of-plane displacement O0 _{(x, y), Δz} corresponding to the set direction and stored in the storage unit 107.

<Processing of x-direction movement>
8 is a flowchart showing the process of the x-direction movement, which includes steps S16 to S25.

In step S16, the control unit 205 performs parameter acquisition control on the driving device 203 to move the movable unit 201 (i.e., the camera 101 at the reference position) in the x direction by a control distance Δx ₀ for parameter acquisition. When continuing after the process of moving in the z direction, the camera 101 is moved in the z direction by -Δz ₀ to return the position of the camera 101 to the state of step S1, and then the camera 101 is moved in the x direction by the control distance Δx _0. As a result, the relative position between the camera 101 and the target surface 1a is changed in the x direction by the control distance Δx ₀ from the state of step S1. Δx ₀ may be 1/500 or more of the above-mentioned p(x, y) and less than the pitch p(x, y). Δx ₀ is, for example, about 1 mm in size.
In step S17, the camera 101 captures an image of the lattice pattern on the target surface 1a to obtain image data.

In step S18, the data processing unit 103 performs the above-mentioned thinning process and luminance interpolation process a plurality of times on the image data obtained in step S17, thereby generating a plurality of frames of moire fringe image data.
In step S19, the data processing unit 103 obtains the phase φm(x,y) of the moiré fringes at the measurement point (x,y) in the set direction using the multiple moiré fringe image data obtained in step S18, using the above-mentioned formula (3). This _φm (x,y) is hereinafter referred to _{as φmx} (x,y).

In step S20, the in-plane displacements U _{0x(x,y), Δx} before correction due to Δx ₀ are obtained. Step S20 has steps S20a and S20b. In step S20a, the data processing unit 103 obtains Δφ _m (x,y) by Δφ m (x,y) = φ _mx (x,y) _- φ _m0 (x,y). In step S20b, the data processing unit 103 obtains the in-plane displacements U _{0x(x,y), Δx} due to Δx ₀ by U 0x(x,y), _Δx = p(x,y) · Δφ _{m (x,y) / 2π. Here, Δφ m (} x,y) is the one obtained in step S20a. This in-plane displacement U _{0x(x, y), Δx} is the in-plane displacement of the measurement point (x, y) located in the set direction (hereinafter also referred to as the in-plane displacement U _{0x(x, y), Δx} corresponding to the set direction), and φ _mx (x, y) and φ _m0 (x, y) are the phases corresponding to this set direction.

In step S21, based on the control distance _Δx0 in step S16 and U _{0x(x,y), Δx} calculated in step S20, the parameter calculation unit 207 calculates the in-plane correction coefficient K _{ux(x,y), Δx} by K _{ux(x,y), Δx} = U _{0x(x,y), Δx} /Δx _0. The control distance _Δx0 may be input to the parameter calculation unit 207 from the control unit 205, or may be set in advance in the parameter calculation unit 207.

The above-mentioned steps S20 and S21 may be performed for each of a plurality of set directions. That is, in step S20, the in-plane displacements U _{0x(x,y), Δx of a plurality of measurement points (x,} y) that exist in each of the plurality of set directions may be obtained, and in step S21, the in-plane correction coefficients K _{ux(x,y), Δx} for each set direction may be 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 unit 103 specifies the pitch _Q2 in the x direction of the lattice pattern existing in the set direction in the image data obtained in step S17 based on the area of the image data corresponding to the set direction in accordance with the above-mentioned formulas (6) to (8). At this time, Q is replaced with _Q2 in formulas (6) to (8).
In step S23, the data processing unit 103 determines the z-direction position _z2 = f·p(x, y)/ _Q2 of the measurement point in the set direction based on the pitch Q2 identified in step _S22 , the focal length f of the camera 101, and the actual pitch p(x, y) of the grid pattern in the x direction.
In step S24, the parameter calculation unit 207 calculates the out-of-plane displacement O _{0 (x,y) , Δx} due to Δx ₀ from O 0(x,y), Δx = z ₂ - z ₀ based on z ₀ calculated in step S5 and z 2 calculated in step S23.

In step S25, based on the control distance _Δx0 in step S16 and O0 _{(x,y), Δx} calculated in step S24, the parameter calculation unit 207 calculates the out-of-plane correction coefficient K0 _{(x,y), Δx} by K0 _{(x,y), Δx} = _{O0(x,y), Δx} / _Δx0 , and stores the calculated coefficient in the storage unit 107.

The above-mentioned steps S22 to S25 may be performed for each of the set directions in the image data. That is, in step S23, the position _z2 in the z direction of the measurement point (x, y) existing in each set direction is obtained based on _Q2 corresponding to the set direction, in step S24, the out-of-plane displacement O0 _{(x, y), Δx} for each set direction is calculated based on the position _z2 and the position _z0 corresponding to the set direction, and in step S25, the out-of-plane correction coefficient K0 _{(x, y), Δx} for each set direction is calculated based on the out-of-plane displacement O0 _{(x, y), Δx} corresponding to the set direction and stored in the storage unit 107.

(Displacement acquisition process)
9 is a flowchart of the displacement acquisition process that is performed when measurement is performed after time has elapsed from the reference time in the initial state described above. This displacement acquisition process has steps S26 to S33.

In step S26, the camera 101 in the above-mentioned reference position captures an image of the lattice pattern on the target surface 1a, thereby acquiring image data.
In step S27, the data processing unit 103 performs the above-mentioned thinning process and luminance interpolation process a plurality of times on the image data obtained in step S26, thereby generating a plurality of frames of moire fringe image data.
In step S28, the data processing unit 103 obtains the phase φ m (x, y) of the moiré fringes at the measurement point (x, y) in the set direction using the multiple moiré fringe image data obtained in step S27, using the above-mentioned equation ( ₃ ).

In step S29, the data processing unit 103 obtains the in-plane displacement U _x . Step S29 includes steps S29a and S29b. In step S29a, the data processing unit 103 obtains Δφ _m (x, y) by Δφ _m (x, y) = φ _m (x, y) - φ m0 (x, y). 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 may be φ _m (x, y) obtained in advance at another reference time. In step S29b, the data processing unit 103 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 multiple set directions. That is, in step S28, the phases φ _m (x, y) of the multiple measurement points (x, y) present in each of the multiple set directions are obtained, and in step S29, the in-plane displacement U _x for each set direction is calculated 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 103 specifies the pitch Q in the x direction of the lattice pattern existing in the set direction in the image data obtained in step S26, based on the area of the image data existing in the set direction.
In step S31, based on the pitch Q identified in step S30, the focal length f of the camera 101, and the actual pitch p(x, y) of the grid pattern in the x direction, the data processing unit 103 determines the z-direction position z = f p(x, y)/Q of the measurement point (x, y) located in the set direction.
In step S32, the data processing unit 103 calculates the out-of-plane displacement O in the set direction based on the z calculated in step S31 by O = z - z _0. Here, z ₀ is the z ₀ calculated in step S5, but it may be z ₀ of the initial state calculated in advance at the other reference time.

The above-mentioned steps S30 to S32 are performed for each of the multiple set directions. That is, in step S31, the z-direction position z of the measurement point (x, y) in each set direction is obtained based on Q corresponding to the set direction, and in step S32, the out-of-plane displacement O for each set direction is calculated based on the position z and position _z0 corresponding to the set direction.

In step S33, the displacement calculation unit 105 calculates a corrected out-of-plane displacement Δz in the z direction and a corrected in-plane displacement Δx in the x direction based on the in-plane displacement _Ux as the measured displacement obtained in step S29, the out-of-plane displacement O as the measured displacement obtained in step S32, and the correction coefficients K _{ux(x, y), Δz ,} K _{ux( x, y), Δx , K o(x, y), Δz , K o(x, y),} Δx stored in the storage unit 107, using the following equations (21) and (22).

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} ) (21)

Δx=(K _ux(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 ) (22)

Equations (21) and (22) are derived from the following relations (23) and (24).

U _x =K _{ux ( x, y ), Δx} · Δx +K _{ux ( x, y ), Δz} · Δz ... (23)

O = K _{o (x, y), Δx} · Δx + K _{o (x, y), Δz} · Δz ... (24)

Step S33 is performed for each set direction. That is, for each set direction, corrected displacements Δz and Δx are calculated based on the in-plane displacement _Ux and 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 , K o(x,y),} Δx.
In addition, in the memory unit 107, the correction coefficients K _{ux(x, y), Δz} , K _{ux(x, y), Δx} , K _{o(x, y), Δz} , K _{o(x, y), Δx} are stored in association with the set direction by the data processing unit 103 for each set direction.

(Parameter inspection process)
10 is a flowchart of a parameter inspection process for inspecting the correction coefficients stored in the storage unit 107. The parameter inspection process includes steps S41 to S45. Note that the parameter acquisition method according to the present embodiment may include the parameter inspection process.

In step S41, the control unit 205 performs inspection control on the driving device 203 to move the movable unit 201 by an inspection control distance in a predetermined direction (z direction or x direction).
In step S42, the distance that the movable part 201 has actually moved under the inspection control in step S41 is measured by the distance measuring sensor 209.

In step S43, an index value (e.g., the difference or ratio between the movement distance measured in step S42 and the control distance for inspection in step S41) is calculated by the index value calculation unit 211, and the calculated difference is output by the index value calculation unit 211.

In step S44, the unit 213 determines whether the index value output in step S43 is within the allowable range, and if the result of the determination is negative, the result is output and the process proceeds to step S45. If the result of the determination is positive, that is, if the difference output in step S43 is within the allowable range, the parameter inspection process is terminated.

In step S45, the correction coefficient is corrected by the correction unit 215 based on the control distance for inspection in step S41 and the movement distance measured in step S42.

If the predetermined direction in which the movable part 201 is moved in step S41 is the z direction, the control distance for inspection in step S41 is _Δzα , the movement distance measured in step S42 is _Δzβ , and in step S45, the correction coefficient K _{ux(x, y), Δz} is multiplied by _Δzα / _Δzβ to correct K _{ux(x, y), Δz} , and the correction coefficient K _{o(x, y), Δz} is multiplied by _Δzα / _Δzβ to correct K _{o(x, y), Δz} .

If the predetermined direction in which the movable part 201 is moved in step S41 is the x direction, the control distance for inspection in step S41 is _Δxα , the movement distance measured in step S42 is _Δxβ , and in step S45, the correction coefficient K _{ux(x, y), Δx} is multiplied by _Δxα / _Δxβ to correct K _{ux(x, y), Δx} , and the correction coefficient K _{o(x, y), Δx} is multiplied by _Δxα / _Δxβ to correct K _{o(x, y), Δx} .

The above-described steps S41 to S45 may be performed for each of the cases where the predetermined direction in which the movable part 201 is moved in step S41 is the z direction and where the predetermined direction in which the movable part 201 is moved in step S41 is the x direction.

The above is processing (called xz processing) for each plane parallel to the xz plane (i.e., the plane for each xy coordinate value). However, xz processing may also be performed for one plane parallel to the xz plane (including the xz plane).

[yz processing]
In addition to the above-mentioned xz processing, processing on each plane parallel to the yz plane (called yz processing) may also be performed. The yz processing is the same as the above-mentioned xz processing except that x is replaced with y and y is replaced with x (i.e., x and y are swapped), so a detailed description thereof will be omitted. However, the contents that overlap between the xz processing and the yz processing (for example, the processing for calculating the out-of-plane displacement O and the processing for calculating the correction coefficient K _oz ) may be performed in either the xz processing or the yz processing. Furthermore, when (x, y) representing the xy coordinates is replaced, it becomes (y, x), but since this is the same as (x, y), (x, y) is not replaced.

In the xz process, as described above, the correction coefficients K _{ux(x,y), Δz} , K _{ux(x,y), Δx} , K _{o(x,y), Δz} , K _{o(x,y), Δx} are calculated in advance and stored in the storage unit 107.
Furthermore, in the yz processing, similarly to the xz processing, the correction coefficients K _{uy(x,y), Δz} , K _{uy(x,y), Δy} , K _{o(x,y), Δy} are calculated in advance and stored in the storage unit 107 .

In step S33, the displacement calculation unit 105 calculates, as post-correction displacements, an out-of-plane displacement Δz in the z direction, an in-plane displacement Δx in the x direction, and an in-plane displacement Δy in the y direction, based on the correction coefficients stored in the storage unit 107. That is, the displacement calculation unit 105 calculates Δz, Δx, and Δy as solutions to simultaneous equations with three unknowns expressed by the following equations (25) to (27).

U _x =K _{ux ( x, y ), Δx} · Δx +K _{ux ( x, y ), Δy} · Δy +K _{ux ( x, y ), Δz} · Δz ... (25)

U _y =K _{uy (x, y), Δx} · Δx + K _{uy (x, y), Δy} · Δy + K _{uy (x, y), Δz} · Δz ... (26)

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

In these equations, _Ux is an in-plane displacement (measured displacement) along the x direction obtained in the xz process, _Uy is an in-plane displacement (measured displacement) along the y direction obtained in the yz process, and K _ux(x,y),Δy and K _uy(x,y),Δx are obtained in advance as follows: K _ux(x,y),Δy is obtained by the following additional process in the yz process. The additional process includes the following processes (a1) to (a6).

(a1) The control unit 205 performs control to move the movable unit 201 (camera 101) in the y direction by a control distance _Δy0 for parameter acquisition from the state of step S1 described above. This process (a1) may be step S16 of the yz process.
(a2) Next, the camera 101 captures an image of the lattice pattern on the target surface 1a to obtain image data.
(a3) After that, the data processing unit 103 performs the above-mentioned thinning process and luminance interpolation process on this image data a plurality of times to generate a plurality of pieces of moire fringe image data.
(a4) Next, the data processing unit 103 calculates the phase φm(x,y) of the moiré fringes in _the x direction at the measurement point (x,y) in the set direction based on the multiple moiré fringe image data using the above-mentioned equation (6). This _φm (x,y) is hereinafter referred to as _φmx (x,y).

(a5) After that, the data processing unit 103 obtains the in-plane displacement U _0x(x,y),Δy along the x direction due to Δy ₀ by U _0x(x ,y),Δy =p(x,y)·{φ _mx (x,y)-φ _m0 (x,y)}/2π. 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) are the phases in the x direction corresponding to this set direction. φ _m0 (x,y) is the phase in the initial state.
(a6) Based on the control distance _Δy0 in (a1) above and U _0x(x,y),Δy calculated in (a5) above, the parameter calculation unit 207 calculates an in-plane correction coefficient K _ux(x,y),Δy by K _ux(x,y),Δy = U _0x(x,y),Δy / _Δy0 , and stores the calculated coefficient in the storage unit 107. The control distance _Δy0 is set in advance in the parameter calculation unit 207, or is input from the control unit 205 to the parameter calculation unit 207. Note that in the storage unit 107, K _ux(x,y),Δy is stored for each set direction in association with the set direction.

K _{uy (x, y), Δx} can be obtained by the following additional process in the xz process, similar to the above additional process for obtaining K _{ux (x, y), Δy} . This additional process includes the following processes (b1) to (b6).

(b1) From the state of step S1, for example, by moving the movable part 201 (camera 101) by a minute amount Δx ₀ in the x direction, the relative position between the camera 101 and the target surface 1a is changed in the x direction by a control distance Δx ₀ for parameter acquisition. This process (b1) may be step S16 of the xz process.
(b2) Next, the camera 101 captures an image of the lattice pattern on the target surface 1a to obtain image data.
(b3) Thereafter, the data processing unit 103 performs the above-mentioned thinning process and luminance interpolation process on this image data a plurality of times to generate a plurality of pieces of moire fringe image data.
(b4) Next, the data processing unit 103 calculates the phase φm(x,y) of the moiré fringes in the y direction at the measurement point (x,y) in the set direction based on the multiple moiré fringe image data using the above-mentioned equation (6) with x and y interchanged. This _φm (x,y) is hereinafter referred to _{as φmy} (x,y).

(b5) After that, the data processing unit 103 obtains the in-plane displacement U _{0y(x,y), Δx} along the y direction due to Δx ₀ by U _{0y(x,y), Δx = p(x,y) · {φ my (x,y) - φ m0 (x,y)} / 2π. Here, the in-plane displacement U 0y(x,y) , Δx is} the in-plane displacement of the measurement point (x,y) existing in the set direction, and φ _my (x,y) and φ _m0 (x,y) are the phases corresponding to this set direction. φ _m0 (x,y) is the phase of the initial state.
(b6) Based on the control distance _Δx0 in (b1) above and U _{0y(x,y), Δx} calculated in (b5) above, the parameter calculation unit 207 calculates an in-plane correction coefficient K _{uy(x,y), Δx} by K _{uy(x,y), Δx} = U _{0y(x,y), Δx} / _Δx0 , and stores it in the storage unit 107. The control distance _Δx0 is set in advance in the parameter calculation unit 207, or is input to the parameter calculation unit 207 from the control unit 205. Note that in the storage unit 107, K _{uy(x,y), Δx} is stored for each set direction in association with the set direction.

Furthermore, the above-mentioned parameter inspection process may be performed for each of the z, x, and y directions as follows:

For the z direction, the control distance for inspection in step S41 is _Δzα , the movement distance measured in step S42 is _Δzβ , and in step S45, the correction coefficients K _{ux(x, y), Δz} , K _{uy(x, y), Δz} , K _{o(x, y), and Δz} are multiplied by _Δzα / _Δzβ to correct the correction coefficients.

For the x direction, the control distance for inspection in step S41 is _Δxα , the movement distance measured in step S42 is _Δxβ , and in step S45, the correction coefficients K _{ux(x,y), Δx} , K _{uy(x,y), Δx} , K _{o(x,y), Δx} are multiplied by _Δxα / _Δxβ to correct the correction coefficients.

The control distance for inspection in step S41 is _Δyα , the movement distance measured in step S42 is _Δyβ , and in step S45, the correction coefficients K _{ux(x, y), Δy} , K _{uy(x, y), Δy} , K _{o(x, y), Δy are} multiplied by _Δyα / _Δyβ to correct the correction coefficients.

(Effects of the First Embodiment)
According to the first embodiment, the influence of various errors can be generally corrected by the parameters (each correction coefficient) corrected by the correction unit 215. That is, the influence of the inclination of the target surface 1a, the error in the installation angle of the camera 101, the angle of view of the camera 101, the error in the pitch of the pattern on the target surface 1a, and the error in the calculated values of the in-plane displacement and the out-of-plane displacement caused by the lens aberration of the camera 101, etc. can be generally corrected.

[Second embodiment]
11 shows the configuration of a displacement acquisition device 100 to which a parameter acquisition device 200 according to a second embodiment of the present invention can be applied. The second embodiment differs from the first embodiment in the points described below. Points of the second embodiment that are not described below may be the same as those of the first embodiment. In the second embodiment, the displacement acquisition device 100 obtains the out-of-plane displacement of the target surface 1a.

The displacement acquisition device 100 includes a projection device 202 that projects a regular pattern onto the target surface 1a. The projection device 202 is provided on the movable part 201. The phase of the pattern projected in the same projection direction as seen from the projection device 202 is the same regardless of the distance between the position where the pattern is projected and the projection device 202.

The camera 101 captures the pattern projected onto the target surface 1a by the projection device 202, and generates captured image data. The data processing unit 103 uses the sampling moiré method based on this image data to determine the amount of displacement at the measurement point on the target surface 1a. In the second embodiment, the amount of displacement is also the amount of phase change (the amount of phase change in the moiré fringes) at the measurement point.

The camera 101 captures an image of the pattern projected onto the target surface 1a, thereby acquiring image data of the pattern. The orientation of the camera 101 (i.e., the direction of the optical axis C2) may or may not be parallel to the measurement direction (z direction) of the out-of-plane displacement. The camera 101 is disposed at a distance from the projection device 202 in a direction intersecting the measurement direction. Also, the orientation of the camera 101 may be shifted from the orientation of the projection device 202 (i.e., the direction of the optical axis C1) as shown in FIG. 3.

The projection device 202 and the camera 101 are disposed on the movable part 201 at a distance from each other in a direction intersecting the measurement direction, and are attached to the movable part 201 in a state in which the orientation of the projection device 202 and the orientation of the camera 101 are shifted from each other. This keeps the distance between the projection device 202 and the camera 101 constant, and fixes the orientation of the projection device 202 and the orientation of the camera 101 relative to each other.

The data processing unit 103 obtains a phase change amount related to the pattern at a measurement point on the target surface 1a using the sampling moiré method based on image data of the pattern captured by the camera 101. That is, similarly to the first embodiment, the phase at the measurement point (x, y) on the target surface 1a is defined as the above-mentioned φ _m (x, y), the data processing unit 103 defines the φ _m (x, y) obtained at the reference time as φ _m0 (x, y) and the φ _m (x, y) obtained at the measurement time as φ _m2 (x, y), and obtains the phase change amount Δφ _m (x, y) at the measurement point (x, y) by Δφ _m (x, y) = φ _m2 (x, y) - φ _m0 (x, y).

The projection device 202 and the camera 101 may be placed on a plane (hereinafter referred to as the measurement point plane) that is parallel to the xz plane and includes the measurement point (x, y), or may be placed at a position shifted from the measurement point plane by an amount that is sufficiently small compared to the distance between the projection device 202 and the camera 101 and the target surface 1a.

The displacement calculation unit 105 calculates the out-of-plane displacement of the measurement point as a measurement displacement based on the displacement amount Δφ _m (x, y) calculated by the data processing unit 103 and parameters calculated in advance and stored in the storage unit 107 (described in detail later). This parameter is the ratio of the amount of change in the distance in the measurement direction (z direction) between the projection device 202 and camera 101 (i.e., the movable part 201) and the target surface 1a to a value representing the amount of phase change of the pattern at the measurement point (x, y).

Figure 12 is an explanatory diagram of the process of obtaining the above ratio. In Figure 12, the xyz coordinate system is the same as in Figure 11. In Figure 12, the measurement point (x, y) on the target surface 1a is located in a set direction as seen from the camera 101.

The distance between the projection device 202 and the camera 101 and the target surface 1a is changed in the z direction by moving the movable part 201 in the z direction by the driving device 203 (second driving part 203C). The change in the distance is ΔZ _0. Due to this change in the distance, in FIG. 12, the positional relationship between the projection device 202 and the camera 101 and the target surface 1a changes from the positional relationship between the projection device 202 and the camera 101 and the target surface 1a shown by the solid line to the positional relationship between the projection device 202 and the camera 101 and the target surface 1a shown by the dashed line. As a result, the phase of the pattern projected by the projection device 202 on the target surface 1a changes by Δφ _m0 (x, y) at the measurement point (x, y) existing in the set direction as seen from the camera 101. The following approximation formula (28) holds for this Δφ _m0 (x, y).

Each symbol in this formula (28) is as follows. θ1 is the angle between the direction of the measurement point (x, y) seen from the projection device 202 (optical axis C1 in the example of FIG. 12) and the measurement direction of the out-of-plane displacement (optical axis C2, i.e., z direction in FIG. 12). θ2 is the angle between the direction of the measurement point (x, y) seen from the camera 101 (set direction) and the measurement direction of the out-of-plane displacement. However, since the angles on the left and right sides of the measurement point (x, y) in FIG. 12 are positive and negative, respectively, θ1 is a positive value and θ2 is a negative value. Since FIG. 12 shows an example, θ1 and θ2 may be either positive or negative. P is the pitch of the lattice pattern projected onto the target surface 1a, and ΔZ ₀ is the distance by which the projection device 202 and the camera 101 are moved. The angles θ1 and θ2 and the pitch P may respectively be the angle and pitch on a plane (measurement point plane) parallel to the xz plane in the above-mentioned xyz coordinate system.

Here, the distance between the projection device 202 and the camera 101 and the target surface 1a is sufficiently large with respect to _ΔZ0 , so the angles θ1 and θ2 and the pitch P are considered to be the same before and after the projection device 202 and the camera 101 are moved. Therefore, the ratio of the pitch P to (tan θ1-tan θ2) can be considered to be constant. The ratio (tan θ1-tan θ2)/P multiplied by 2π is expressed by the following equation (29), which is a modification of equation (28).

In equation (29), since the amount of phase change Δφ _m0 (x, y) and the amount of movement ΔZ ₀ are measurable, it is possible to obtain 2π(tan θ1-tan θ2)/P. That is, at the reference time, the distance ΔZ ₀ by which the projector 202 and the camera 101 are moved and the resulting amount of phase change Δφ _m0 (x, y) at the measurement point (x, y) are measured, and Δφ _m0 (x, y)/ΔZ ₀ can be obtained in advance as 2π(tan θ1-tan θ2)/P.

The storage unit 107 stores the previously calculated K=Δφ _m0 (x, y)/ΔZ ₀ as a parameter (ratio) for out-of-plane displacement calculation. Therefore, at the time of measurement when time has elapsed from the reference time, the displacement calculation unit 105 can calculate the out-of-plane displacement ΔZ of the measurement point (x, y) using the ratio K. That is, in the formula (29), ΔZ ₀ is replaced with the out-of-plane displacement ΔZ, and Δφ _m0 (x, y) is replaced with the phase change amount Δφ _m (x, y) at the time of measurement, and the out-of-plane displacement ΔZ of the measurement point (x, y) can be calculated by the following formula (30) obtained by modifying the formula (29). Here, K is equal to 2π(tan θ1-tan θ2)/P as described above.
Note that θ1, θ2, P, and K can be expressed as θ1(x, y), θ2(x, y), P(x, y), and K(x, y), respectively, but for simplicity, these are simply written as θ1, θ2, P, and K.

The control unit 205 performs parameter acquisition control on the driving device 203 to move the movable part 201 in a predetermined direction (z direction) by a control distance _ΔZ0 for parameter acquisition at the reference time of the target surface 1a. As a result, the driving device 203 moves the movable part 201 in the z direction. The above-mentioned phase change amount Δφ _m0 (x, y) for the measurement point before and after the parameter acquisition control is found by processing by the camera 101 and the data processing unit 103.

The parameter calculation unit 207 calculates a ratio K between the control distance ΔZ ₀ for parameter acquisition and the amount of phase change Δφ _m0 (x, y) by K = Δφ _m0 (x, y)/ΔZ _0. The parameter calculation unit 207 stores the ratio K thus calculated in the storage unit 107.

The displacement calculation unit 105 calculates the out-of-plane displacement ΔZ as follows. First, at the time of measurement when time has passed from the reference time, the phase change amount Δφ _m (x, y) related to the pattern at the measurement point (x, y) is calculated by the processing of the camera 101 and the data processing unit 103 as described above. This phase change amount Δφ _m (x, y) is the difference between the phase φ _m0 (x, y) related to the pattern at the measurement point (x, y) at the reference time and the phase φ _m2 (x, y) related to the pattern at the measurement point (x, y) at the measurement time. That is, the data processing unit 103 calculates Δφ _m (x, y) from Δφ _m (x, y) = φ _m2 (x, y) - φ _m0 (x, y). Next, the displacement calculation unit 105 calculates the out-of-plane displacement ΔZ of the measurement point (x, y) from the above formula (30), i.e., ΔZ = Δφ _m (x, y) / K, based on this phase change Δφ _m (x, y) and the ratio K stored in the storage unit 107. Note that the data processing unit 103 stores the above phase φ _m0 (x, y) at the measurement point (x, y) calculated for the reference time.

Figure 13 is a flowchart showing the parameter acquisition process and the displacement acquisition process according to the second embodiment. The parameter acquisition process is performed at a reference time and includes steps S51 to S55. Note that the parameter acquisition method according to the second embodiment may include the parameter acquisition process and a parameter inspection process described below.

In step S51, a phase φ _m0 (x, y) of the pattern projected at a measurement point (x, y) on the target surface 1a in the set direction is obtained as follows: With the projection device 202 and the camera 101 in a reference position, the projection device 202 projects a pattern onto the target surface 1a, and the camera 101 captures the projected pattern to generate image data. The data processing unit 103 generates multiple moiré fringe image data by performing the above-mentioned thinning process and brightness interpolation process multiple times on this image data. Based on the multiple moiré fringe image data generated, the data processing unit 103 obtains the phase φ _m (x, y) of the moiré fringes at the measurement point (x, y) as the phase φ _m0 (x, y) of the pattern.

In step S52, the control unit 205 performs parameter acquisition control on the driving device 203 to move the movable part 201 in a predetermined direction (z direction) by a control distance ΔZ ₀ for parameter acquisition at the reference time of the target surface 1a.

In step S53, the phase φ _m1 (x, y) of the pattern projected at the measurement point (x, y) on the target surface 1a in the set direction is obtained as follows. With the projection device 202 and the camera 101 in the position moved in step S52, the projection device 202 projects a pattern onto the target surface 1a, and the camera 101 captures the projected pattern to generate image data. Based on this image data, the data processing unit 103 generates multiple moiré fringe image data in the same manner as in step S51, and obtains the phase φ _m (x, y) of the moiré fringes at the measurement point (x, y) as the phase φ _m1 (x, y) of the pattern based on the multiple moiré fringe image data. After completing step S53, the driving device 203 moves the projection device 202 and the camera 101 from the changed position to the reference position.

In step S54, the data processing unit 103 calculates the difference Δφ _m0 (x, y) between the phase φ _m0 (x, y) of the pattern calculated in step S1 and the phase φ _m1 (x, y) of the pattern calculated in step S3 as the amount of phase change using Δφ _m0 (x, y) = φ _m1 (x, y) - φ _m0 (x, y).

In step S55, the parameter calculation unit 207 calculates a ratio K between the control distance _ΔZ0 for acquiring the parameters in step S2 and the phase change amount Δφ _m0 (x, y) calculated in step S54 as a parameter by K=Δφ _m0 (x, y)/ _ΔZ0 , and stores the ratio in the storage unit 107. The control distance _ΔZ0 is set in advance in the parameter calculation unit 207, or is input from the control unit 205 to the parameter calculation unit 207.

The displacement acquisition process is performed at the time of measurement when time has elapsed from the reference time, and includes steps S56 to S58.

In step S56, the phase related to the pattern projected at the measurement point (x, y) on the target surface 1a existing in the set direction is obtained as follows: With the projection device 202 and the camera 101 (movable part 201) in the same reference position as when the projection and image capturing were performed in step S51, the projection device 202 projects a pattern onto the target surface 1a, and the camera 101 captures the projected pattern to generate image data. Based on this image data, the data processing unit 103 generates multiple moiré fringe image data as in step S51, and obtains the phase φ _m (x, y) of the moiré fringes at the measurement point (x, y) as the phase φ _m2 (x, y) related to the pattern based on the multiple moiré fringe image data.

In step S57, the data processing unit 103 calculates the difference Δφ _m (x, y) between the phase φ _m0 (x, y) of the pattern calculated in step S51 and the phase φ _m2 (x, y) of the pattern calculated in step S56 as the phase change amount using Δφ _m (x, y) = φ _m2 (x, y) - φ _m0 (x, y).

In step S58, the displacement calculation unit 105 calculates the out-of-plane displacement ΔZ of the measurement point (x, y) based on the ratio K calculated in step S55 and stored in the memory unit 107 and the phase change amount Δφ _m (x, y) calculated in step S57, using ΔZ = Δφ _m (x, y)/K.

(Parameter inspection process)
The parameter inspection process for inspecting the above-mentioned parameters in the second embodiment is similar to that in the first embodiment shown in the flowchart of Fig. 10, so the parameter inspection process in the second embodiment will be described with reference to Fig. 10. This parameter inspection process has steps S41 to S45.

In step S41, the control unit 205 performs inspection control on the driving device 203 to move the movable part 201 by an inspection control distance _Δzα in a predetermined direction (z direction).
In step S42, the distance that the movable part 201 has actually moved under the inspection control in step S41 is measured by the distance measuring sensor 209.

In step S43, an index indicating the difference between the movement distance Δz _β measured in step S42 and the control distance Δz _α for inspection in step S41 (for example, the difference or ratio between the two) is calculated by the index value calculation unit 211, and the calculated index is output by the index value calculation unit 211.

In step S44, the unit 213 judges whether the index value output in step S43 is within the allowable range, and if the result of the judgment is negative, the result is output and the process proceeds to step S45. If the result of the judgment is positive, that is, if the index value output in step S43 is within the allowable range, the parameter inspection process is terminated.

In step S45, based on the control distance _Δzα for inspection in step S41 and the movement distance _Δzβ measured in step S42, the correction unit 215 corrects the parameter (ratio K) stored in the storage unit 107. That is, the ratio is corrected by multiplying the parameter K by _Δzα / _Δzβ . The corrected parameter is stored in the storage unit 107 as a corrected parameter, and is used in the displacement acquisition process (step S58) that is performed subsequently.

The above-mentioned parameter acquisition process, displacement acquisition process, and parameter inspection process may be performed for one set direction, or the above-mentioned parameter acquisition process, displacement acquisition process, and parameter inspection process may be performed for each of multiple set directions.

(Effects of the Second Embodiment)
According to the second embodiment, similarly to the first embodiment, the influence of various errors can be entirely corrected by the parameters (each correction coefficient) corrected by the correction unit 215 .

[Target indicating the target position for laser light irradiation]
In each of the above-described embodiments, when the distance measurement sensor 209 is a laser displacement sensor, a target 301 indicating a target position of irradiation with the laser light may be provided on the movable part 201. Fig. 14 is a diagram showing a laser irradiation surface 201a of the movable part 201 as viewed in a predetermined direction (z direction or x direction in Fig. 1, z direction in Fig. 11) in Fig. 1 or Fig. 11. The laser irradiation surface 201a is a surface on which the laser light from the laser displacement sensor 209 hits.

As shown in FIG. 14, a target 301 (circle in this figure) is provided at the movable part 201 at the location where the laser light from the laser displacement sensor 209 hits. The spot of the laser light that hits the laser irradiation surface 201a (black circle in FIG. 14) can be visually recognized by a person. The target 301 indicates the irradiation target position of the laser light. The target 301 is provided so that it can be visually recognized by a person. The target 301 is located on a straight line extending from the laser irradiation position of the laser displacement sensor 209 in the above-mentioned specified direction. In addition, a position deviation display 302 that indicates the position deviation from the target 301 is provided around the target 301. The position deviation display 302 may indicate the distance that is offset from the target 301. In the example of FIG. 14, the position deviation display 302 is a display of multiple concentric circles with a known radius centered on the target 301.

By providing such a target 301 and position deviation indicator 302, it is possible to check whether the direction in which the movable part 201 moves deviates from the above-mentioned predetermined direction. For example, before performing the above-mentioned step 42, the laser light from the laser displacement sensor 209 attached to the stationary structure is made to strike the target 301. After that, after the movable part 201 moves in the above-mentioned step 41, a person can visually check whether the position where the laser light is irradiated by the laser displacement sensor 209 in step S42 deviates from the target 301. At this time, if there is a position deviation indicator 302, the amount of deviation can be easily obtained.

If the position where the laser light is irradiated is deviated from the target 301, the movement direction of the movable part 201 deviates from the above-mentioned predetermined direction, so the driving device 203 can be adjusted so that the movement direction of the movable part 201 is accurately aligned with the above-mentioned predetermined direction.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the technical concept of the present invention. For example, any of the following modified examples 1 to 3 may be adopted alone, or modified examples 1 to 3 may be adopted in any combination. In this case, the points not described below are the same as those described above.

(Modification 1)
The determination unit 213 and the correction unit 215 may be omitted. In this case, the index value calculation unit 211 may output the index value to a display device, for example. This causes the display device to display the index value. A person can check whether the index value is within an allowable range by looking at the displayed index value. If the index value is outside the allowable range, for example, the control distance for parameter acquisition set in the control unit can be adjusted, and the parameter acquisition process can be performed again.

(Modification 2)
In the above description, the correction unit 215 corrects the parameters, but the correction unit 215 may also correct the driving amount of the driving device 203 by the parameter acquisition control of the control unit 205 based on the movement distance measured by the distance measurement sensor 209 and the control distance for inspection.

For example, the control unit 205 controls a driver (see FIG. 1 or FIG. 11) to control the number of pulses input from the driver to a stepping motor (e.g., stepping motor 203b or 203c) which is the driving device 203, and the stepping motor drives (moves) the movable part 201 by an amount of drive corresponding to the number of input pulses. In this case, in this modification, the correction unit 215 corrects the number of pulses input from the driver to the stepping motor based on the movement distance measured by the distance measurement sensor 209 and the control distance for inspection.

(Modification 3)
The inspection control may be a parameter acquisition control, and the control distance for the inspection may be a parameter acquisition control. In other words, the inspection control may be a movement control that also serves as a parameter acquisition control (hereinafter simply referred to as a movement control), and the inspection control distance may be the same control distance as the parameter acquisition control distance (hereinafter referred to as a common control distance).

The amount of displacement of the measurement point before and after the movement control is found by processing by the camera 101 and the data processing unit 103. Next, a parameter (the correction coefficient in the first embodiment, and the ratio in the second embodiment) is found by the parameter calculation unit 207 based on the amount of displacement and the common control distance.

Meanwhile, the distance that the movable part 201 has actually moved in a predetermined direction due to the movement control is measured by the distance measurement sensor 209. Next, an index value indicating the difference between the movement distance and the common control distance is calculated by the index value calculation unit 211, and the index value is output by the index value calculation unit 211.

The judgment unit 213 judges whether the output index value is within an acceptable range, and if the result of the judgment is negative, the result may be output by the judgment unit 215. If the result of this judgment is negative, the parameter calculated by the parameter calculation unit 207 may be corrected by the correction unit 215 based on the common control distance and the movement distance measured by the distance measurement sensor 209. That is, the parameter may be calculated by performing movement control once, and this parameter may be corrected.

Therefore, in the first embodiment, the same movement control not only serves as the parameter acquisition control in step S6 or S16 described above, but also as the inspection control in step S41 described above. After the movement control is performed, a process of determining the correction coefficient as a parameter (steps S7 to S15 or steps S17 to S25 described above) and a process of correcting the determined parameter (steps S42 to S45 described above) may be performed. At this time, steps S42 to S44 may be performed in parallel with steps S7 to S15 or steps S17 to S25 described above.

Similarly, in the second embodiment, the same movement control not only serves as the parameter acquisition control in step S52 described above, but also as the inspection control in step S41 described above. After the movement control is performed, a process for determining the ratio as a parameter (steps S53 to S55 described above) and a process for correcting the determined parameter (steps S42 to S45 described above) may be performed. At this time, steps S42 to S44 may be performed in parallel with steps S53 to S55 described above.

1 Object 1a Target surface 100 Displacement acquisition device 101 Camera 103 Data processing unit 105 Displacement calculation unit 107 Memory unit 200 Parameter acquisition device 201 Movable unit 202 Projection device 203 Driving device 203a Moving table 203b First driving unit 203c Second driving unit 205 Control unit 207 Parameter calculation unit 209, 209a, 209b Distance measurement sensor 211 Index value calculation unit 213 Determination unit 215 Correction unit 301 Target 302 Position deviation display

Claims (14)

A camera that captures an image of a regular pattern on a target surface of an object to generate image data;
a data processing unit that calculates a displacement amount for a measurement point on the target surface by a sampling moiré method based on the image data;
A parameter acquisition device provided in a displacement acquisition device including a displacement calculation unit that calculates one or both of an in-plane displacement of the measurement point in a direction along the target surface and an out-of-plane displacement of the measurement point in a direction perpendicular to the target surface based on an acquired displacement amount and a previously acquired parameter,
a direction of an optical axis of the camera or a direction perpendicular to the optical axis direction is defined as a predetermined direction, and the parameter is a rate of variation of one or both of the in-plane displacement and the out-of-plane displacement with respect to a position change of the camera with respect to the target surface in the predetermined direction;
a movable part on which the camera is mounted and which is movable in the predetermined direction;
A drive device that moves the movable part in the predetermined direction;
a control unit that performs parameter acquisition control on the drive device to move the movable unit in the predetermined direction by a control distance for parameter acquisition,
a displacement amount relating to the measurement point before and after the parameter acquisition control is obtained by the camera and the data processing unit;
a parameter calculation unit that calculates the parameter based on the displacement amount and a control distance for acquiring the parameter;
a distance measuring sensor that measures a distance actually moved by the movable part under an inspection control when the inspection control is performed on the driving device to move the movable part by a control distance for inspection in the predetermined direction; and
a correction unit that corrects the parameters based on the inspection control distance and the movement distance measured by the distance measuring sensor. an index value calculation unit that calculates an index value indicating a difference between the moving distance measured by the distance measuring sensor and the control distance for inspection, and outputs the calculated index value;
a determination unit that determines whether the index value output by the index value calculation unit is within an allowable range and outputs the result when the result of the determination is negative;
2 . The parameter acquisition device according to claim 1 , wherein when the result of the judgment by the judgment unit is negative, the correction unit corrects the parameter based on the inspection control distance and the movement distance measured by the distance measuring sensor. A camera that captures an image of a regular pattern on a target surface of an object to generate image data;
a data processing unit that calculates a displacement amount for a measurement point on the target surface by a sampling moiré method based on the image data;
a displacement calculation unit that calculates one or both of an in-plane displacement and an out-of-plane displacement of the measurement point based on the obtained displacement amount and a parameter obtained in advance,
a movable part on which the camera is mounted and which is movable in a predetermined direction;
A drive device that moves the movable part in the predetermined direction;
a control unit that performs parameter acquisition control on the drive device to move the movable unit in the predetermined direction by a control distance for parameter acquisition,
a displacement amount relating to the measurement point before and after the parameter acquisition control is obtained by the camera and the data processing unit;
a parameter calculation unit that calculates the parameter based on the displacement amount and a control distance for acquiring the parameter;
a distance measuring sensor that measures a distance actually moved by the movable part under an inspection control when the inspection control is performed on the driving device to move the movable part by a control distance for inspection in the predetermined direction; and
A parameter acquisition device comprising: a correction unit that corrects a drive amount of the drive device under the parameter acquisition control of the control unit based on a movement distance measured by the distance measuring sensor and a control distance for inspection. an index value calculation unit that calculates an index value indicating a difference between the moving distance measured by the distance measuring sensor and the control distance for inspection, and outputs the calculated index value;
a determination unit that determines whether the index value output by the index value calculation unit is within an allowable range and outputs the result when the result of the determination is negative;
4. The parameter acquisition device according to claim 3, wherein when the result of the determination by the determination unit is negative, the correction unit corrects the drive amount based on the inspection control distance and the movement distance measured by the distance measuring sensor. The parameter acquisition device according to any one of claims 1 to 4, wherein the distance measurement sensor is a laser displacement meter that emits laser light in the predetermined direction toward the movable part, reflects it off the movable part, and measures the movement distance of the movable part in the predetermined direction based on the reflected laser light. 6. The parameter acquisition device according to claim 5 , wherein a target indicating a target position for irradiation with the laser light from the laser displacement meter is provided on the movable portion at a location where the laser light from the laser displacement meter hits. 7. The parameter acquisition device according to claim 1 , wherein the inspection control is the parameter acquisition control, and the inspection control distance is the parameter acquisition control distance. the data processing unit obtains, as the displacement amount, the in-plane displacement and the out-of-plane displacement before correction;
The parameter acquisition device according to any one of claims 1 to 7, wherein the displacement calculation unit calculates one or both of the in-plane displacement and the out-of-plane displacement after correction based on the in-plane displacement and the out- of -plane displacement obtained by the data processing unit and the parameters. A camera that captures an image of a regular pattern on a target surface of an object to generate image data;
a data processing unit that calculates a displacement amount for a measurement point on the target surface by a sampling moiré method based on the image data;
a displacement calculation unit that calculates an out-of-plane displacement of the measurement point based on the obtained displacement amount and a parameter obtained in advance,
a movable part on which the camera is mounted and which is movable in a predetermined direction;
A drive device that moves the movable part in the predetermined direction;
a control unit that performs parameter acquisition control on the drive device to move the movable unit in the predetermined direction by a control distance for parameter acquisition,
a displacement amount relating to the measurement point before and after the parameter acquisition control is obtained by the camera and the data processing unit;
a parameter calculation unit that calculates the parameter based on the displacement amount and a control distance for acquiring the parameter;
a distance measuring sensor that measures a distance actually moved by the movable part under an inspection control when the inspection control is performed on the driving device to move the movable part by a control distance for inspection in the predetermined direction; and
an index value calculation unit that calculates an index value indicating a difference between the moving distance measured by the distance measuring sensor and the control distance for inspection, and outputs the calculated index value;
The displacement acquisition device includes a projection device provided on the movable part, the projection device projects the pattern on the target surface,
the data processing unit determines a phase change amount related to the pattern as the amount of displacement;
the parameter is a ratio between an amount of change in distance between the projection device and the camera and the target surface and a value representing an amount of phase change in the pattern at the measurement point due to the change in distance;
The displacement calculation unit calculates an out-of-plane displacement based on the amount of phase change obtained by the data processing unit and the ratio. A camera that captures an image of a regular pattern on a target surface of an object to generate image data;
a data processing unit that calculates a displacement amount for a measurement point on the target surface by a sampling moiré method based on the image data;
A parameter acquisition method for a displacement acquisition device including a displacement calculation unit that calculates one or both of an in-plane displacement of the measurement point in a direction along the target surface and an out-of-plane displacement of the measurement point in a direction perpendicular to the target surface based on an acquired displacement amount and a previously acquired parameter, the method comprising:
a direction of an optical axis of the camera or a direction perpendicular to the optical axis direction is defined as a predetermined direction, and the parameter is a rate of variation of one or both of the in-plane displacement and the out-of-plane displacement with respect to a position change of the camera with respect to the target surface in the predetermined direction;
(A) providing a movable section on which the camera is mounted and which is movable in the predetermined direction, and a drive device that moves the movable section in the predetermined direction;
(B) performing parameter acquisition control on the drive device by a control unit to move the movable part in the predetermined direction by a control distance for parameter acquisition;
(C) determining a displacement amount of the measurement point before and after the parameter acquisition control by the camera and the data processing unit;
(D) calculating the parameter by a parameter calculation unit based on the displacement amount and a control distance for obtaining the parameter;
(E) performing an inspection control on the drive device by the control unit to move the movable part in the predetermined direction by a control distance for inspection;
(F) measuring the distance that the movable part has actually moved by the inspection control using a distance measuring sensor;
(G) A parameter acquisition method, comprising: correcting the parameters by a correction unit based on the inspection control distance and the movement distance measured by the distance measuring sensor. A camera that captures an image of a regular pattern on a target surface of an object to generate image data;
a data processing unit that calculates a displacement amount for a measurement point on the target surface by a sampling moiré method based on the image data;
a displacement calculation unit that calculates one or both of an in-plane displacement and an out-of-plane displacement of the measurement point based on the obtained displacement amount and a parameter obtained in advance,
(A) providing a movable part on which the camera is installed and which is movable in a predetermined direction, and a drive device that moves the movable part in the predetermined direction;
(B) performing parameter acquisition control on the drive device by a control unit to move the movable part in the predetermined direction by a control distance for parameter acquisition;
(C) determining a displacement amount of the measurement point before and after the parameter acquisition control by the camera and the data processing unit;
(D) calculating the parameter by a parameter calculation unit based on the displacement amount and a control distance for obtaining the parameter;
(E) performing an inspection control on the drive device by the control unit to move the movable part in the predetermined direction by a control distance for inspection;
(F) measuring the distance that the movable part has actually moved by the inspection control using a distance measuring sensor;
(G) A parameter acquisition method in which a correction unit corrects the drive amount of the drive device by the parameter acquisition control of the control unit based on the movement distance measured by the distance measuring sensor and the control distance for inspection. A camera that captures an image of a regular pattern on a target surface of an object to generate image data;
a data processing unit that calculates a displacement amount for a measurement point on the target surface by a sampling moiré method based on the image data;
a displacement calculation unit that calculates an out-of-plane displacement of the measurement point based on the obtained displacement amount and a parameter obtained in advance,
(A) providing a movable part on which the camera is installed and which is movable in a predetermined direction, and a driving device for moving the movable part in the predetermined direction, and providing a projection device for projecting the pattern on the target surface on the movable part;
(B) performing parameter acquisition control on the drive device by a control unit to move the movable part in the predetermined direction by a control distance for parameter acquisition;
(C) determining the displacement amount with respect to the measurement point before and after the parameter acquisition control by the camera and the data processing unit;
(D) calculating the parameter by a parameter calculation unit based on the displacement amount and a control distance for obtaining the parameter;
(E) performing an inspection control on the drive device by the control unit to move the movable part in the predetermined direction by a control distance for inspection;
(F) measuring the distance that the movable part has actually moved by the inspection control using a distance measuring sensor;
the parameter is a ratio between an amount of change in distance between the projection device and the camera and the target surface and a value representing an amount of phase change in the pattern at the measurement point due to the change in distance, the amount of displacement in the measurement point is an amount of phase change in the pattern,
The parameter acquisition method, wherein the displacement calculation unit calculates an out-of-plane displacement based on the amount of phase change obtained by the data processing unit and the ratio. The control for inspection is a common control that is the same as the control for parameter acquisition, and the control distance for inspection is a common control distance that is the same as the control distance for parameter acquisition,
The steps (B) and (E) are common steps in which the common control for moving the movable part by the common control distance in the predetermined direction is performed by the control part on the driving device as the inspection control and the parameter acquisition control,
In the step (C), the displacement amount regarding the measurement point before and after the common control is obtained by the camera and the data processing unit;
In the step (D), the parameter calculation unit calculates the parameter based on the displacement amount and the common control distance;
The parameter acquisition method according to any one of claims 10 to 12, wherein in (F), the distance actually moved by the movable part under the common control is measured by the distance measurement sensor . The parameter acquisition method according to claim 13 , wherein the displacement acquisition device includes an index value calculation unit, and an index value indicating a difference between the movement distance measured by the distance measuring sensor and the common control distance is calculated and output by the index value calculation unit.

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