JP2002131027A - Measuring apparatus for interference of phase shift, method therefor and record medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring apparatus for interference of phase shift, a method therefor and a record medium capable of allowing a precise unwrap of phase wrap whose absolute value of the difference between a real phase value of a detected pixel and a phase value of other detected pixel next to the detected pixel is π or more and also capable of allowing a prevention of occurrences of unwrap errors. SOLUTION: In the method, a mean value of a corrected phase value ϕ1 by phase unwrap processing of a next detected pixel B (x, y-1) in the y direction on two-dimensional arrangement of the detected pixels equipped by an area sensor and a corrected phase value ϕ2 by phase unwrap processing of a next detected pixel C (x-1, y) in the x direction is determined as a predictive phase value ϕ4 of the detected pixel A (x, y), according to the parameter of an absolute value of the difference between the phase value ϕ4 and a phase value ϕ3 of the detected pixel A (x, y) which is calculated by a phase shift method, two-dimensional phase unwrap processing is performed to unwrap the phase value ϕ3 to a corrected phase value ϕ5 of the detected pixel A (x, y).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift interference measuring device and method, and a storage medium.

[0002]

2. Description of the Related Art Conventionally, there has been known a method of measuring a planar shape of an object by a non-contact method using a phase shift method.

In the phase shift method, based on light intensity distributions represented by at least three phase-shifted interference fringe images, a two-dimensional array of detection pixels is measured from a position to be measured on the surface of the object using a known shape analysis technique. The phase value φ (x, y) representing the height to the provided area sensor is calculated.

In the phase shift method, a part of light emitted from a light source is reflected by a reference surface, and another part of the light is reflected by a surface of a subject, so that a reflected image from the reference surface and a light reflected from the surface of the subject are reflected. An interference fringe is generated by causing interference with a reflected image. Next, at least three interference fringe images having a relative phase difference are acquired from the surface of the subject by the imaging device while performing a phase shift by a predetermined phase shift amount by the area sensor, and the acquired interference fringe images are acquired by the phase shift method. The phase value φ (x, y) is calculated based on

More specifically, the xy coordinates of the surface to be inspected are (x,
y), the phase value of the detection pixel (x, y) is φ (x, y), and the phase shift amount is δ _i , the light intensity distribution I _i (x,
formula y) _{is, I i (x, y)} = I B (x, y) + I A (x, y) cos [φ (x, y) + δ i] represented by ... (1). In equation (1), δ ₁ =
0, δ ₂ = α, by substituting _{δ 3 = β, I 1 (} x, y) = I B (x, y) + I A (x, y) cos [φ
_{(X, y)] I 2} (x, y) = I B (x, y) + I A (x, y) cos [φ
(X, y) + α] I 3 (x, y) = I B (x, y) + I A (x, y) cos [φ
(X, y) + β] is obtained. I _B (x, y) is the bias value of the interference fringe, I _A
(X, y) is an amplitude value, and I _{k (k = 1, 2, 3)} (x, y) is a measured value of the light intensity distribution of the interference fringes at each phase shift amount.

At this time, the phase value φ of the detection pixel (x, y) is
(X, y) is calculated by the following equation based on the measured value of the light intensity distribution of the interference fringes at each phase shift amount and each phase shift amount.

[0007]

(Equation 1) The phase value calculated by the phase shift method is as shown in FIG. 11 when represented by a one-dimensional model.

FIG. 11 is a one-dimensional graph for explaining the relationship between the phase value of each detection pixel calculated by the phase shift method and the corrected phase value of each detection pixel.

Since the phase value is folded in the range of the main value from -π to π (hereinafter, referred to as “wrap”), the light source is not illuminated with respect to the true phase value representing the height from the object surface to the area sensor. It contains an uncertain value that is an integral multiple of the wavelength period (2π). That is, there is a possibility that the phase value of each adjacent detection pixel on the surface of the subject becomes discontinuous (hereinafter, referred to as “phase wrap”). Therefore, the phase value of each detection pixel calculated by the phase shift method needs to be corrected using an uncertain value that is an integral multiple of 2π.

In the graph of FIG. 11, .largecircle. Represents the phase value of each detection pixel calculated (wrapped) by the phase shift method, and .DELTA. Represents the uncertainty value obtained by multiplying the calculated phase value of each detection pixel by an integral multiple of 2.pi. Is a phase value corrected so as to be continuous with the phase value of an adjacent detection pixel by using. Correcting the phase value of each detection pixel wrapped using an uncertainty value that is an integral multiple of 2π so as to be continuous with the phase value of an adjacent detection pixel is referred to as unwrapping. In the graph, for convenience of explanation, π is added to the phase value の of each detection pixel calculated by the phase shift method, and values from -π to π are displayed in the range of 0 to 2π.

Generally, when unwrapping the phase value of a wrapped detection pixel, the phase value of each detection pixel calculated by the phase shift method is represented by information on two-dimensional coordinates (hereinafter referred to as a “phase map”). (Hereinafter, referred to as “mapping”), and the phase value of the detected pixel (x, y) and x
In the direction, a detection pixel (x−
When the absolute value of the difference from the phase value of (1, y) exceeds π,
There is known a one-dimensional phase unwrapping method in which unwrapping is performed by adding or subtracting an integer multiple of 2π to or from the phase value of the detection pixel (x, y).

When measuring the planar shape of the subject, a one-dimensional phase unwrapping process is performed by sequentially scanning the entire area of the subject surface coordinates in the x direction.

FIG. 12 is a diagram of a phase map on which the phase values of the respective detection pixels calculated by the phase shift method are mapped. FIG. 13 is a diagram showing all the detection pixels mapped on the phase map 1200 of FIG. FIG. 8 is a diagram for explaining scanning of a detection pixel in the x direction performed at the time of one-dimensional phase unwrapping processing for the phase value of FIG.

As shown in FIG. 13, one-dimensional phase unwrap processing is performed by sequentially scanning the detection pixels in the x direction. However, since the detection pixels are not scanned in the y direction, the detection pixels adjacent to each other in the y direction are detected. The phase value of the pixel may be a phase wrap. Therefore, in order to unwrap the phase values of adjacent detection pixels in the y direction, y
The scanning of the detection pixels is performed in the direction (FIG. 14). When the scanning of the detection pixel in the y direction is performed first,
Thereafter, scanning of the detection pixels is performed in the x direction.

[0015]

However, in the above-described method of adding or subtracting 2π when the absolute value of the phase value difference between adjacent detection pixels exceeds π, the true phase of each adjacent detection pixel is Assuming that the absolute value of the difference is equal to or smaller than π, if the absolute value of the difference exceeds π, 2π
However, when the absolute value of the difference between the true phase values of adjacent detection pixels is equal to or more than π, there is a problem that it is not possible to accurately unwrap to the true phase value.

Further, when performing a one-dimensional phase unwrapping process on the phase value of each detection pixel in the phase map, the detection pixel is first scanned in the x direction, and then the detection pixel is scanned in the y direction. When the phase values of all the detection pixels in the phase map are unwrapped by performing the above operation, even if the phase wrap in the y direction is eliminated as a result of the scanning of the detection pixels in the y direction, a new phase wrap in the x direction is obtained. (Less than,
(Referred to as “unwrap error”).

FIG. 15 is a diagram for explaining a phase map in which an unwrap error occurs.

In FIG. 15, all the phase values of the detected pixels in the phase map 1500 have not been subjected to one-dimensional phase unwrapping. At this time, when performing one-dimensional phase unwrapping processing on the phase value of the detection pixel in the phase map 1500, the detection pixel is first scanned in the x direction, and then the detection pixel is scanned in the y direction. , The phase value of the detected pixel (x, y) = (6, 6) is from 3π / 2 to π / 2.
, The phase difference (step) of π or more between 7π / 4 which is the phase value of the detected pixel (x, y) = (5, 6)
Occurs and an unwrap error occurs.

FIG. 16 is a three-dimensional schematic diagram for explaining the cause of the occurrence of the unwrap error.

In FIG. 16, as a result of the one-dimensional phase unwrapping process on the phase value of the detection pixel in the phase map 1500, the phase value of the detection pixel (6, 6) obtained by scanning the detection pixel in the x direction is 3π / 2, and the phase value of the detection pixel (6, 6) obtained by scanning the detection pixel in the y direction is π / 2, so that a step difference of π or more occurs even in the same detection pixel. .

FIG. 17 shows that when one-dimensional phase unwrapping is performed on the phase value of a detection pixel in the phase map, the detection pixel is first scanned in the x direction, and then the detection pixel in the y direction is scanned. FIG. 7 is a diagram illustrating an unwrap error in the x direction generated as a result of scanning.

When one-dimensional phase unwrapping is performed on the phase value of the detection pixel in the phase map, the detection pixel is first scanned in the y direction, and then the detection pixel is scanned in the x direction. When performing this, similarly, there is a problem that an unwrap error occurs in the y direction.

It is an object of the present invention to accurately unwrap a phase wrap in which the absolute value of the difference between the true phase value of a detection pixel and the phase value of another detection pixel adjacent to the detection pixel is π or more. An object of the present invention is to provide a phase shift interference measurement device and method capable of preventing occurrence of an unwrap error, and a storage medium.

[0024]

In order to achieve the above object, a phase shift interferometer according to claim 1 is generated based on an optical path length difference between reflected light from a surface of a subject and reference light from a reference surface. An area sensor having a two-dimensional array of detection pixels for detecting interference fringes, and an optical phase value in which an integer multiple of a light source wavelength period calculated based on the detected interference fringes is wrapped from the surface of the subject. Unwrapping means for unwrapping to a corrected phase value representing the height up to the detection pixel, the unwrapping means, the unwrapping means, the correction phase value of a plurality of other detection pixels in the vicinity of each detection pixel Based on the difference between the wrapped optical phase value and the obtained predicted phase value, the optical phase value of each detection pixel is calculated based on the predicted phase value of each detected pixel based on Wherein the unwrapping a positive phase value.

According to a second aspect of the present invention, there is provided a phase shift interferometer according to the first aspect.
The unwrapping unit calculates the predicted phase value of each of the detected pixels by using the corrected phase value of the other detected pixels in a first direction in the two-dimensional array and a second direction different from the first direction. , Based on the corrected phase value of the other detection pixel.

According to a third aspect of the present invention, there is provided a phase shift interference measuring apparatus according to the second aspect.
The detection pixels are adjacent to the other detection pixels in the first direction and the other detection pixels in the second direction.

According to a fourth aspect of the present invention, in the phase shift interference measuring apparatus according to the second or third aspect, the second direction is orthogonal to the first direction.

According to a fifth aspect of the present invention, in the phase shift interference measuring apparatus according to any one of the second to fourth aspects, the predicted phase value of each of the detection pixels is the first direction. And the average value of the corrected phase value of the other detection pixel in the second direction and the corrected phase value of the other detection pixel in the second direction.

According to a sixth aspect of the present invention, there is provided the phase shift interference measuring apparatus according to the first aspect.
The unwrapping unit calculates the predicted phase value of each of the detected pixels by using the corrected phase value of the other detected pixels in a first direction in the two-dimensional array and at least one of the corrected phase values different from the first direction. , Based on the corrected phase value of the other detection pixel in the direction of.

According to a seventh aspect of the present invention, in the phase shift interference measuring apparatus according to the sixth aspect,
The predicted phase value of each of the detected pixels is an average of the corrected phase value of the other detected pixel in the first direction and the corrected phase value of the other detected pixel in the at least one other direction. Value.

The phase shift interferometer according to claim 8 is the phase shift interferometer according to claim 1.
The unwrap means derives an approximate curve from the corrected phase values of two or more other detection pixels in a first direction in the two-dimensional array, and at least one other direction different from the first direction Deriving at least one other approximated curve from the corrected phase values of the two or more other detected pixels in the above, obtaining a predicted approximated phase value of each of the detected pixels based on the derived approximated curve, and The method is characterized in that the predicted phase value of each of the detection pixels is obtained based on the approximate phase value.

According to a ninth aspect of the present invention, in the phase shift interference measuring apparatus according to the eighth aspect,
The prediction phase value of each of the detection pixels is a value identified by the prediction approximate phase value.

According to a tenth aspect of the present invention, there is provided the phase shift interference measuring apparatus according to any one of the first to ninth aspects, wherein the unwrapping means includes the predicted phase value of each of the detected pixels and the When the difference from the optical phase value exceeds a predetermined value, the optical phase value of each detection pixel is added to or subtracted from the optical phase value by an integer multiple of the light source wavelength period to the corrected phase value. It is characterized by being modified.

According to a eleventh aspect of the present invention, there is provided the phase shift interference measuring method, wherein the interference fringes generated based on the optical path length difference between the reflected light from the object surface and the reference light from the reference surface are provided with two-dimensionally arranged detection pixels. A detection step of detecting by the area sensor, and representing a height from the surface of the subject to the detection pixel, the optical phase value wrapped by an integer multiple of the light source wavelength cycle calculated based on the detected interference fringes. An unwrapping step of unwrapping to a corrected phase value, wherein the unwrapping step includes predicting each of the detected pixels based on the corrected phase values of a plurality of other detected pixels near each of the detected pixels. Determining a phase value and, based on the difference between the wrapped optical phase value and the determined predicted phase value, unwraps the optical phase value of each detection pixel with the corrected phase value. Tsu characterized in that it flops.

In the phase shift interference measuring method according to a twelfth aspect, in the phase shift interference measuring method according to the eleventh aspect, the unwrapping step includes the steps of: And the corrected phase value of the other detected pixel in a second direction different from the first direction.

A phase shift interference measuring method according to a thirteenth aspect is the phase shift interference measuring method according to the twelfth aspect, wherein each of the detection pixels includes the other detection pixel in the first direction and the second direction. Is adjacent to the other detection pixel.

According to a fourteenth aspect of the present invention, in the phase shift interference measuring method according to the twelfth or thirteenth aspect, the second direction is orthogonal to the first direction.

According to a fifteenth aspect of the present invention, there is provided the phase shift interference measuring method according to any one of the twelfth to fourteenth aspects, wherein the predicted phase value of each detection pixel is in the first direction. And the average value of the corrected phase value of the other detection pixel in the second direction and the corrected phase value of the other detection pixel in the second direction.

According to a sixteenth aspect of the present invention, in the phase shift interference measuring method according to the eleventh aspect, in the unwrapping step, the unwrapping step calculates the predicted phase value of each of the detected pixels in the first two-dimensional array. And the corrected phase value of the other detection pixel in at least one other direction different from the first direction. .

In the phase shift interference measuring method according to a seventeenth aspect, in the phase shift interference measuring method according to the sixteenth aspect, the predicted phase value of each of the detection pixels is the same as that of the other detection pixels in the first direction. An average value of the corrected phase value and the corrected phase value of the another detection pixel in the at least one other direction.

In the phase shift interference measuring method according to the eighteenth aspect, in the phase shift interference measuring method according to the eleventh aspect, the unwrapping step includes detecting two or more of the other detections in a first direction in the two-dimensional array. Deriving an approximate curve from the corrected phase value of the pixel, and at least one other approximate curve from the corrected phase values of two or more other detected pixels in at least one other direction different from the first direction; Is derived, a predicted approximate phase value of each of the detected pixels is determined based on the derived approximate curve, and the predicted phase value of each of the detected pixels is determined based on the predicted approximate phase value.

In the phase shift interference measuring method according to a nineteenth aspect, in the phase shift interference measuring method according to the eighteenth aspect, the predicted phase value of each detection pixel is a value identified by the predicted approximate phase value. It is characterized by.

According to a twentieth aspect of the present invention, in the phase shift interference measuring method according to any one of the eleventh to nineteenth aspects, the unwrapping step includes the steps of: When the difference from the optical phase value exceeds a predetermined value, the optical phase value of each detection pixel is added to or subtracted from the optical phase value by an integer multiple of the light source wavelength period to the corrected phase value. It is characterized by being modified.

A storage medium according to a twenty-first aspect of the present invention is a readable storage medium for storing a program for executing a phase shift interference measurement method, wherein the program is configured to include a reflected light from a surface of a subject and a reference from a reference surface. A detection module for detecting an interference fringe generated based on a difference in optical path length with light by an area sensor including detection pixels in a two-dimensional array, and an integer multiple of a light source wavelength cycle calculated based on the detected interference fringes. An unwrap module for unwrapping the wrapped optical phase value to a corrected phase value representing a height from the object surface to the detection pixel, wherein the unwrap module includes a plurality of other components near each of the detection pixels. Determining a predicted phase value of each of the detected pixels based on the corrected phase value of the detected pixel, and calculating the wrapped optical phase value and the determined predicted phase. Wherein the unwrapping said optical phase values of the respective detection pixels in the corrected phase value based on the difference between.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a phase shift interferometer according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing a schematic configuration of a phase shift interference measurement apparatus according to a first embodiment of the present invention.

In FIG. 1, a phase shift interferometer 10 according to the present embodiment mainly supports a light source 11 composed of a red semiconductor laser, a beam splitter 12, a reference surface 13, and a reference surface 13, and It comprises a reference surface minute displacement mechanism 14 composed of elements, a displacement mechanism control device 15 connected to the displacement mechanism 14, and an imaging device 16.

The laser light emitted from the light source 11 enters the beam splitter 12 via the objective lens 17.
The light transmitted through the beam splitter 12 is collimated by the collimator lens 18 and illuminates the reference surface 13.
Part of the light is reflected on the surface of the reference surface 13, and light transmitted through the reference surface 13 is reflected on the surface to be measured of the measurement object 19.

As a result, the light reflected by the surface of the reference surface 13 and the light reflected by the surface to be measured of the measurement object 19 are separated by the reference surface 1
3 again to form interference light. Then, the light is again guided downward by the beam splitter 12 via the collimator lens 18 in the drawing. This light is transmitted through the imaging lens 2
0 forms an image on the light receiving surface of the imaging device 16.

The result of imaging by the imaging device 16 is sent to an image processing device 22 provided in the control computer 21.
It can be visually observed by the monitor 23.

Further, the displacement mechanism control device 15 applies a desired voltage to the reference surface minute displacement mechanism 14, and the reference surface minute displacement mechanism 14 displaces the reference surface 13 according to the voltage applied to the piezo element. This causes a phase shift.

Hereinafter, the phase unwrapping process executed by the phase shift interference measuring apparatus according to the first embodiment of the present invention having the above-described configuration will be described.

In this processing, a predicted phase value of each detected pixel is obtained based on the phase values of the other detected pixels adjacent to each detected pixel after the phase unwrapping process, and the predicted phase value is calculated by the phase shift method. The phase value of each detection pixel calculated by the phase shift method based on the difference from the phase value (optical phase value) of each detection pixel is unwrapped.

This processing is executed when unwrapping the phase value of the detected pixel on the phase map 1200 in FIG. 12 to which the phase value calculated by the phase shift method is mapped, for example.

FIG. 2 is a flowchart of the phase unwrapping process executed by the phase shift interference measuring device according to the first embodiment of the present invention.

First, as shown in FIG.
At 00, a one-dimensional phase unwrapping process is performed by scanning the detection pixel (1,1) in the first row (first column in the y direction) from the detection pixel (m, 1) in the x direction (step S201) Then, as shown in FIG. 4, scanning is performed in the y direction from the detection pixel (1, 1) in the first column (the first column in the x direction) to the detection pixel (1, n). A one-dimensional phase unwrap process is performed (step S2
02).

Steps S201 and S2 in FIG.
The two-dimensional phase unwrapped phase values of the first row and each detection pixel of the first row obtained in step 02 are obtained by the control computer 2.
1 is stored in a memory (not shown) built in the memory 1.

Next, a two-dimensional phase unwrapping process, which will be described later, is performed on the detection pixels (2, 2) to the detection pixels (m, n) in the range indicated by oblique lines in FIG. 5 (step S203).

Hereinafter, the two-dimensional phase unwrapping process executed in step S203 of FIG. 2 will be described.

FIG. 6 is a flowchart of the two-dimensional phase unwrapping process executed in step S203 of FIG.

First, a template kernel core as shown in FIG. 7 is converted into a detected pixel A (x, y) calculated by the phase shift method and not yet subjected to the phase unwrapping process.
(2, 2), detection pixel B (x, y-1) already phase unwrapped = (2, 1), detection pixel C (x-1, y) already phase unwrapped (1,
2).

Referring to this template kernel core, the predicted phase value φ ₄ of the detected pixel (2, 2) is converted into the corrected phase value φ ₁ of the detected pixel (2, 1) after the phase unwrapping process. By using the corrected phase value φ ₂ that has been subjected to the phase unwrapping process and stored in the memory of the detection pixel (1, 2), the following equation (2): φ ₄ = (φ ₁ + φ ₂ ) / 2 (2) Is calculated as an average value of the corrected phase value φ ₁ and the corrected phase value φ ₂ (step S601), and the calculated predicted phase value φ ₄
And the detection pixel (2, 2) calculated by the phase shift method.
The absolute value parameter n of the difference between the phase value phi ₃ 2), the following equation (3) n = [(φ 4 -φ 3) / π] is calculated by ...... (3) (step S602). Note that [(φ ₄ −φ
₃ ) / π] is an integer part (Gaussian symbol) of a real number (φ ₄ −φ ₃ ) / π.

Next, the absolute value parameter n of the calculated difference
Is determined whether or not is greater than 1 (predetermined value) (step S603). If it is greater than 1, the detection pixel (2, 2)
A correction phase value phi ₅ of and calculated by the following equation _{(4) φ 5 = φ 3} -2nπ ...... (4) ( step S606), the modified phase value phi
After storing ₅ in the memory, the process ends. on the other hand,
If the calculated absolute value parameter n of the difference is equal to or smaller than 1, the process proceeds to step S604.

[0064] At step S604, the absolute value parameter n of the calculated difference is -1 is determined whether or not (a predetermined value) is smaller than when less than -1, the correction phase value phi ₅ the following formula (5) φ ₅ = φ ₃ + 2nπ (5) (step S607), and the corrected phase value φ
After storing ₅ in the memory, the process ends. on the other hand,
When the calculated absolute value parameter n of the difference is −1 or more, that is, when −1 ≦ n ≦ 1, the phase value φ ₃ calculated by the phase shift method is set as the corrected phase value φ ₅ (step S60).
5) After the data is stored in the memory, the present process ends.

Next, the processing of FIG. 6 described above is performed in the second row (y
The two-dimensional phase unwrapping process is performed on each detection pixel in the second row by sequentially executing the detection pixel (3, 2) to the detection pixel (m, 2) in the direction (second column).

Thereafter, the above-described processing of FIG. 6 is sequentially performed on each of the detection pixels from the third row to the n-th row, so that the phase unwrapping process of the detection pixels on the phase map 1200 is performed.

According to the first embodiment, the corrected phase value φ ₁ by the phase unwrapping process of the adjacent detection pixel B (x, y−1) in the y direction and the adjacent detection pixel C (x−1) in the x direction , y) as the predicted phase value φ _{4 of the} detection pixel A (x, y) by the phase correction value φ _{2 obtained} by the phase unwrapping process, and the predicted phase value φ ₄ and the calculated value obtained by the phase shift method. detection pixel a (x, y) is performed two-dimensional phase unwrapping process of unwrapping the phase values phi ₃ to modify the phase value phi ₅ based on the parameters of the absolute value of the difference between the phase value phi ₃ of the true detection pixels In addition to accurately unwrapping a phase wrap having an absolute value of π or more of a difference between the phase value of the detection pixel and the phase value of another detection pixel adjacent to the detection pixel, occurrence of an unwrap error can be prevented.

In the first embodiment, the above-described FIG.
Is sequentially performed on each of the detection pixels from the second row to the n-th row, but the above-described processing in FIG. 6 is performed on each of the detection pixels from the second column (the second column in the x direction) to the m-th column. May be sequentially executed.

FIG. 8 is a diagram showing a result of the phase unwrapping process by the above-described phase shift interference measuring apparatus according to the first embodiment of the present invention. As compared with FIG. 17, the unwrap error is avoided and the original normal object surface shape is calculated.

Next, a description will be given of a phase shift interference measuring apparatus according to a second embodiment of the present invention.

The schematic configuration of the phase shift interference measuring device according to the second embodiment of the present invention is the same as the schematic configuration of the phase shift interference measuring device according to the first embodiment of the present invention.

The phase unwrapping process executed by the phase shift interference measuring device according to the second embodiment is basically the same as the phase unwrapping process executed by the phase shift interference measuring device according to the first embodiment. Pixel A (x, y) in step S601
Only the method of calculating the predicted phase value φ ₄ is different.

Hereinafter, a method of calculating the predicted phase value φ ₄ of the detected pixel A (x, y) in step S601 according to the second embodiment will be described.

First, a template kernel core as shown in FIG. 9 is divided into a detection pixel A (x, y) that has not yet undergone phase unwrapping and a detection pixel G (x−3, y) that has already undergone phase unwrapping. , Detection pixel E (x−2, y)
And a detection pixel row in the x direction composed of a detection pixel C (x−1, y), a detection pixel J (x−3, y−3), and a detection pixel I (x−2, y) which have been similarly unwrapped. -2)
And a detection pixel row in the xy direction including the detection pixel H (x-1, y-1), a detection pixel F (x, y-3), and a detection pixel D (x, y) which have been similarly unwrapped. -2)
And a detection pixel row in the y direction including the detection pixels B (x, y-1).

Referring to the template kernel core, the predicted phase value φ ₄ of the detected pixel A (x, y) is converted to all the detected pixels in the template kernel core of FIG. Calculated by averaging the phase values of the detection pixels J after the phase unwrapping process (for example, by summation or geometric mean).

According to the second embodiment, the detection pixel B
Since the predicted phase value φ ₄ of the detection pixel A (x, y) is calculated by averaging the phase values of the detection pixel J after the phase unwrap processing, the accuracy of the correction phase value φ ₅ can be improved.

The number of detection pixels forming the template kernel core may be larger or smaller than the number of detection pixels forming the template kernel core shown in FIG. It may be four or more.

Next, a description will be given of a phase shift interference measuring apparatus according to a third embodiment of the present invention.

The schematic configuration of the phase shift interference measuring apparatus according to the third embodiment of the present invention is the same as the schematic configuration of the phase shift interference measuring apparatus according to the first embodiment of the present invention.

The phase unwrapping process executed by the phase shift interference measuring device according to the third embodiment is basically the same as the phase unwrapping process executed by the phase shift interference measuring device according to the first embodiment. Pixel A (x, y) in step S601
Only the method of calculating the predicted phase value φ ₄ is different.

Hereinafter, a method of calculating the predicted phase value φ ₄ of the detected pixel A (x, y) in step S601 according to the third embodiment will be described with reference to FIG. The template kernel core used in step S601 is the same as the template kernel core of FIG. 9 used in the above-described second embodiment.

FIG. 10 shows a detection pixel A (x, x) executed by the phase shift interferometer according to the third embodiment of the present invention.
It is a diagram for explaining a method of calculating the predicted phase value phi ₄ of y).

In FIG. 10, first, the detection pixel G (x−
3, y), detection pixel E (x−2, y) and detection pixel C (x
-1, y) based on the phase unwrapped phase values and coordinates of each detection pixel in the detection pixel row in the x direction consisting of x, y, and y.
Then, a predicted approximate phase value φ ₄₁ of the detected pixel A (x, y) is calculated based on the first approximate curve and the coordinates of the detected pixel A (x, y).

Next, detection pixels J (x-3, y-3),
Detection pixel I (x-2, y-2) and detection pixel H (x-1,
y-1), a second approximate curve is derived based on the phase unwrapped phase values and the coordinates of the respective detection pixels in the detection pixel row in the xy direction composed of y-1). based on the coordinates of the pixel a (x, y), it calculates the predicted approximate phase value phi ₄₂ of the detection pixel a (x, y).

Further, each of the detection pixels in the detection pixel row in the y direction including the detection pixel F (x, y-3), the detection pixel D (x, y-2) and the detection pixel B (x, y-1) A third approximate curve is derived based on each phase value and each coordinate after the phase unwrap processing, and the third approximate curve and the detection pixel A
Based on the coordinates of (x, y), a predicted approximate phase value φ ₄₃ of the detection pixel A (x, y) is calculated.

Thereafter, the predicted approximate phase value φ ₄₁ ,
identifying phi ₄₂ and phi ₄₃ (e.g., by averaging method or least square method) to calculate the predicted phase value phi ₄ by (step S601).

According to the third embodiment, first, a first approximation curve is derived based on each phase value and each coordinate of each detection pixel in the detection pixel row in the x direction after phase unwrap processing, Next, a second approximate curve is derived based on each phase value and each coordinate of the phase unwrapped phase of each detection pixel in the detection pixel row in the xy direction, and further, each detection pixel in the detection pixel row in the y direction. Derives a third approximation curve based on each phase value and each coordinate after the phase unwrapping process, and predicts a detection pixel A (x, y) calculated based on the derived first to third approximation curves Approximate phase value φ ₄₁ ,
detected by identifying phi ₄₂ and phi ₄₃ pixel A (x,
Since obtaining the predicted phase value phi ₄ of y), the adjacent detection pixels B, C, corrected phase value of the phase difference is even more 2π detection pixel A with modified phase value of H (x, y) φ ₅ Can be calculated accurately.

Further, the predicted phase value φ ₄ of the detected pixel A (x, y) may be obtained using two or more approximate curves, and each approximate curve is a phase unwrapping process of two or more detected pixels. It may be derived based on each phase value and each coordinate already processed.

Further, an arbitrary storage medium storing a program for executing the above-described phase unwrapping processing method supplies the above-mentioned program to the above-mentioned phase shift interference measurement apparatus, and controls the control computer 21 of the phase shift interference measurement apparatus.
Either a CPU (not shown) or an MPU (not shown) may execute the program. Examples of a storage medium for supplying the program include a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, MO, magnetic tape,
There is a nonvolatile memory card or a ROM.

Further, instead of any one of the control computer 21, the CPU or the MPU, a circuit (not shown) which operates similarly to the above may realize the above-described embodiment.

The program supplied by the storage medium is written into a memory (not shown) provided in a function expansion board (not shown) inserted into the control computer 21 or a function expansion unit (not shown) connected to the control computer 21. After that, a CPU or the like (not shown) provided in the function expansion board or the function expansion unit may execute a part or all of the program.

In addition, an OS or the like running on the control computer 21 may execute some or all of the above programs.

[0093]

As described in detail above, according to the phase shift interference measuring apparatus of the first aspect, the phase shift interference measuring method of the eleventh aspect, and the storage medium of the twenty-first aspect, the area sensor is provided. A predicted phase value of each detected pixel is obtained based on the corrected phase values of a plurality of other detected pixels near each detected pixel in the two-dimensional array of the detected pixels, and the wrapped optical phase value and the obtained predicted phase value are obtained. And the optical phase value of each detection pixel is unwrapped to the corrected phase value based on the difference between the absolute value of the difference between the true phase value of the detection pixel and the phase value of another detection pixel adjacent to the detection pixel. Can accurately unwrap phase wraps that are greater than or equal to π, and can also prevent the occurrence of unwrap errors.

According to the phase shift interference measuring apparatus of the sixth aspect and the phase shift interference measuring method of the sixteenth aspect,
A corrected phase value of another detected pixel in a first direction in a two-dimensional array of detected pixels included in the area sensor and a corrected phase value of another detected pixel in at least one other direction different from the first direction. Based on the difference between the wrapped optical phase value and the obtained predicted phase value, the optical phase value of each detected pixel is unwrapped to the corrected phase value. The accuracy of the corrected phase value of the pixel can be improved.

According to the phase shift interference measuring apparatus of the eighth aspect and the phase shift interference measuring method of the eighteenth aspect,
An approximate curve is derived from the corrected phase values of two or more other detection pixels in the first direction in the two-dimensional array of the detection pixels provided in the area sensor, and the approximate curve is derived in at least one other direction different from the first direction. Deriving at least one other approximate curve from the corrected phase values of one or more other detected pixels;
A predicted approximate phase value of each detected pixel is determined based on the derived approximate curve, a predicted phase value of each detected pixel is determined based on the predicted approximate phase value, and a wrapped optical phase value and the determined predicted phase are calculated. Since the optical phase value of each detected pixel is unwrapped with the corrected phase value based on the difference from the detected value, the corrected phase value of the detected pixel is accurately calculated even if the phase difference between adjacent detected pixels is 2π or more. be able to.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a schematic configuration of a phase shift interference measurement device according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a phase unwrapping process performed by the phase shift interference measurement device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a range in which a one-dimensional phase unwrap process of a first row of a phase map 1200 in FIG. 12 is performed.

FIG. 4 is a diagram illustrating a range in which a one-dimensional phase unwrapping process of a first column of a phase map 1200 in FIG. 12 is performed.

FIG. 5 is a diagram illustrating a range in which a two-dimensional phase unwrapping process is performed in the phase map 1200 of FIG. 12;

FIG. 6 is a flowchart showing a process executed in step S203 of FIG. 2;
It is a flowchart of a dimensional phase unwrap process.

FIG. 7 is a diagram illustrating a template kernel core created at the time of a two-dimensional phase unwrapping process performed by the phase shift interference measurement device according to the first embodiment of the present invention.

FIG. 8 is a diagram illustrating a result of a phase unwrapping process performed by the phase shift interference measurement device according to the first embodiment of the present invention.

FIG. 9 is a diagram illustrating a template kernel core created at the time of a two-dimensional phase unwrapping process performed by the phase shift interference measurement device according to the second embodiment of the present invention.

FIG. 10 is a diagram illustrating a method of calculating a predicted phase value φ ₄ of a detection pixel A (x, y) performed by the phase shift interference measurement apparatus according to the third embodiment of the present invention.

FIG. 11 is a one-dimensional graph illustrating the relationship between the phase value of each detection pixel calculated by the phase shift method and the corrected phase value of each detection pixel.

FIG. 12 is a diagram of a phase map on which phase values of each detection pixel calculated by the phase shift method are mapped.

FIG. 13 is a diagram illustrating scanning of the detection pixels in the x direction performed at the time of the one-dimensional phase unwrapping process on the phase values of all the detection pixels mapped on the phase map 1200 in FIG. 12;

14 is a diagram illustrating scanning of the detection pixels in the y-direction performed in the one-dimensional phase unwrapping process on the phase values of all the detection pixels mapped on the phase map 1200 in FIG.

FIG. 15 is a diagram illustrating a phase map in which an unwrap error occurs.

FIG. 16 is a three-dimensional schematic diagram illustrating a cause of occurrence of an unwrap error.

FIG. 17 is a diagram showing an unwrap error in the x direction.

[Explanation of symbols]

 1200, 1500 Topological map

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[Procedure amendment]

[Submission date] October 30, 2000 (2000.10.
30)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

Continuing from the front page (72) Inventor Yasushi Ueshima F-term (reference) 2F064 AA09 CC00 FF01 GG22 GG70 HH03 2F065 AA54 DD00 FF51 GG04 JJ03 JJ26 LL46 LL57 QQ47 AQ07 5A BA02 BB04 BC04 CA17 CB11 DC20 5B057 BA02 BA15 BA19 CA08 CA12 CA16 CB08 CB13 CB16 CH08 CH11 DA17

Claims (21)

[Claims] An area sensor including a two-dimensional array of detection pixels for detecting interference fringes generated based on a difference in optical path length between light reflected from the surface of the subject and reference light from a reference surface; Unwrapping means for unwrapping an optical phase value in which an integer multiple of the light source wavelength period calculated based on the interference fringes is wrapped into a corrected phase value representing a height from the object surface to the detection pixel. In the interference measurement apparatus, the unwrapping unit obtains a predicted phase value of each of the detection pixels based on the corrected phase values of a plurality of other detection pixels in the vicinity of each of the detection pixels, and the wrapped optical phase A phase shift interferometer for unwrapping the optical phase value of each of the detection pixels with the corrected phase value based on a difference between the detected phase value and the calculated predicted phase value. 2. The method according to claim 2, wherein the unwrapping unit calculates the predicted phase value of each of the detected pixels by using the corrected phase value of the other detected pixels in a first direction in the two-dimensional array and the first direction. 2. The phase shift interference measuring apparatus according to claim 1, wherein the value is obtained based on the corrected phase value of the another detection pixel in a different second direction. 3. The phase shift interference according to claim 2, wherein each of the detection pixels is adjacent to the other detection pixel in the first direction and the other detection pixel in the second direction. measuring device. 4. The phase shift interference measuring apparatus according to claim 2, wherein the second direction is orthogonal to the first direction. 5. The predicted phase value of each of the detected pixels includes the corrected phase value of the other detected pixel in the first direction and the corrected phase value of the other detected pixel in the second direction. 3. The average value of
5. The phase shift interference measuring apparatus according to any one of claims 4 to 4. 6. The unwrapping unit calculates the predicted phase value of each of the detected pixels by using the corrected phase values of the other detected pixels in a first direction in the two-dimensional array and the first direction. The phase shift interference measurement apparatus according to claim 1, wherein the determination is performed based on the corrected phase value of the other detection pixel in at least one different direction. 7. The predicted phase value of each of the detected pixels includes the corrected phase value of the other detected pixel in the first direction and the corrected phase value of the other detected pixel in the at least one other direction. 7. The phase shift interference measuring apparatus according to claim 6, wherein the average value is a phase value. 8. The unwrapping unit derives an approximate curve from the corrected phase values of two or more of the other detection pixels in a first direction in the two-dimensional array, and derives an approximate curve different from the first direction. Deriving at least one other approximated curve from the corrected phase values of two or more other detected pixels in one other direction, and calculating a predicted approximated phase value of each of the detected pixels based on the derived approximated curve; 2. The phase shift interference measuring apparatus according to claim 1, wherein the estimated phase value of each of the detection pixels is obtained based on the estimated approximate phase value. 9. The phase shift interference measuring apparatus according to claim 8, wherein the predicted phase value of each of the detected pixels is a value identified by the predicted approximate phase value. 10. The unwrapping means, when a difference between the predicted phase value and the optical phase value of each detection pixel exceeds a predetermined value, adds the optical phase value to an integral multiple of the light source wavelength period. The phase shift interference measurement apparatus according to any one of claims 1 to 9, wherein the optical phase value of each of the detection pixels is corrected to the corrected phase value by adding or subtracting. 11. A detecting step of detecting an interference fringe generated based on an optical path length difference between a reflected light from a surface of a subject and a reference light from a reference surface by an area sensor including detection pixels in a two-dimensional array; An unwrapping step of unwrapping an optical phase value in which an integer multiple of the light source wavelength period calculated based on the detected interference fringes is wrapped to a corrected phase value representing a height from the subject surface to the detection pixel. In the phase shift interference measurement method having, the unwrapping step determines a predicted phase value of each of the detected pixels based on the corrected phase values of a plurality of other detected pixels in the vicinity of each of the detected pixels, and the wrapped. Phase shifting interference wherein the optical phase value of each of the detection pixels is unwrapped with the corrected phase value based on a difference between an optical phase value and the calculated predicted phase value. Measuring method. 12. The unwrapping step includes the step of: combining the predicted phase value of each of the detected pixels with the corrected phase values of the other detected pixels in a first direction in the two-dimensional array; 12. The phase shift interference measurement method according to claim 11, wherein the determination is performed based on the corrected phase value of the another detection pixel in a different second direction. 13. The detection pixel according to claim 12, wherein each of the detection pixels is adjacent to the other detection pixel in the first direction and the other detection pixel in the second direction.
The described phase shift interference measurement method. 14. The phase shift interference measuring method according to claim 12, wherein the second direction is orthogonal to the first direction. 15. The predicted phase value of each of the detection pixels is:
The average value of the corrected phase value of the other detection pixel in the first direction and the correction phase value of the other detection pixel in the second direction. The phase shift interference measurement method according to claim 1. 16. The unwrapping step includes the step of: estimating the predicted phase value of each of the detected pixels by comparing the corrected phase value of the other detected pixels in a first direction in the two-dimensional array with the first direction. 12. The phase shift interference measurement method according to claim 11, wherein the determination is performed based on the corrected phase value of the another detection pixel in at least one different direction. 17. The prediction phase value of each of the detection pixels is:
17. The average value of the corrected phase value of the another detection pixel in the first direction and the corrected phase value of the other detection pixel in the at least one other direction. The described phase shift interference measurement method. 18. The method according to claim 18, wherein the unwrapping step derives an approximate curve from the corrected phase values of two or more other detection pixels in a first direction in the two-dimensional array.
2 in at least one other direction different from the direction of
Deriving at least one other approximate curve from the corrected phase values of the one or more other detected pixels, determining a predicted approximate phase value of each of the detected pixels based on the derived approximate curve, and 12. The phase shift interference measurement method according to claim 11, wherein the predicted phase value of each of the detection pixels is obtained based on a value. 19. The predicted phase value of each of the detection pixels is:
19. The phase shift interference measurement method according to claim 18, wherein the value is identified by the predicted approximate phase value. 20. The unwrapping step, wherein when the difference between the predicted phase value and the optical phase value of each detection pixel exceeds a predetermined value, the optical phase value is set to an integral multiple of the light source wavelength period. 20. The phase shift interference measurement method according to claim 11, wherein the optical phase value of each of the detection pixels is corrected to the corrected phase value by adding or subtracting. 21. A readable storage medium for storing a program for executing a phase shift interference measurement method,
The program generates an interference fringe generated based on an optical path length difference between the reflected light from the object surface and the reference light from the reference surface.
A detection module that detects an area sensor having detection pixels in a three-dimensional array, and an optical phase value in which an integer multiple of a light source wavelength cycle calculated based on the detected interference fringes is wrapped, from the object surface; An unwrap module for unwrapping to a corrected phase value representing a height up to a pixel, wherein the unwrap module is configured to detect each of the detected pixels based on the corrected phase values of a plurality of other detected pixels near each of the detected pixels. And unwrapping the optical phase value of each of the detection pixels with the corrected phase value based on a difference between the wrapped optical phase value and the obtained predicted phase value. Storage medium.