JPH08105717A - Method and apparatus for extracting phase from speckle image of object to be inspected - Google Patents

Abstract

PURPOSE: To simply and accurately measure the deformation and the distortion of an object to be inspected by generating a phase difference map due to the deformation based on a speckle image before or after the deformation of the object to be inspected and calculating the displacement amount at the each point. CONSTITUTION: A laser beam from an He-Ne laser 10 is split to two beams, an object 20 to be inspected is irradiated with each one or double beams, and the speckle image due to the irradiation is taken by a CCD camera 24. The image includes speckle images due to the irradiation of the double beams before and after the deformation, the speckle image by the irradiation of the first beam, the speckle image by the irradiation of the second beam, and dark noise, and the dark noise is removed from the respective images. An image processing computer 25 obtains the difference of the speckle images before and after the deformation, forms a phase difference map due to the deformation of the object 20 to be inspected, calculates the displacement amounts at the respective points, and then calculates the deformation and the distortion of the object 20 to be inspected by using a predetermined calculation formula.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for extracting a phase from a speckle image of an object to be inspected and an apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, as prior art in such a field, for example, (1) Journal of Physics E: S
scientific Instruments 1970
VoIume 3 p. 214-218, "Inte
rferometric displacement
measurement on scattering
surfaces utilizing speck
"le effect" (2) Optical Society of Ame
rica A / Vol. 7 No. 5 / May 199
0 p. 820-826 "Extraction o
f phase data from electro
nic speckle pattern inter
feromeric fringing a
single-phase-step method
d: anovel approach "(3) Applied Optics, Vol. 30,
No. 7/1 March 1991 p. 717-7
21 "Whole field in-plane
vibration analysis using
pulsed-stepped ESPI "and the like. That is, ESPI (E
electronic Speckle Pattern
Interferometry] has been used to attempt distortion analysis and displacement of the measurement surface of the inspection object, and vibration analysis of the inspection object.

FIG. 12 shows a double beam.
It is a schematic block diagram of an EAM or Dual beam) ESPI. In this figure, 1 is an inspection object (object), and the inspection object 1 is irradiated with a first laser beam I and a second laser beam II,
The CCD camera 2 images the irradiation part. At this time, C
All speckle images captured by the CD camera have positive values. Therefore, all corresponding mathematical expressions appearing below mean absolute values.

Then, both the image by the first laser beam I before the deformation of the inspection object 1 and the image by the second laser beam II become a speckle pattern, and the CCD camera has both of them. A speckle pattern as a superposition of speckle patterns can be obtained. Next, after the inspection object 1 is deformed, that is, non-uniformly displaced on the x and y planes, an image by the first laser beam I and an image by the second laser beam II are obtained.

At this time, the images obtained before and after the deformation
The intensity of can be generally expressed as a function of x and y
it can. Speckle image I of inspection object 1 before deformation_before
Is I_before= A₁ ²(X, y) + A₂ ²(X, y) + 2A₁(X, y) A₂ (X, y) cos θ + N_before (1) Speckle image I of the inspection object 1 after deformation_afterIs I_after= A₁ ²(X, y) + A₂ ²(X, y) + 2A₁(X, y) A₂ (X, y) cos (θ + φ) + N_after (2) However, A₁, A₂Is the first laser beam I and the second
The amplitude of the optical field of the laser beam II of
Speckle before deformation [on inspection object 1 (x, y)
Phase difference (initial phase difference), φ is the displacement component in the x direction
The phase difference introduced by u (x, y) (of the inspection object 1
Phase difference due to displacement), and N_before, N _afterEach
This is the noise. Generally, θ and φ are also functions of x and y.
You.

When the incident angles of the first laser beam I and the second laser beam II with respect to the inspection object 1 are both α, the phase difference φ due to deformation is a displacement component u in the x direction.
And has the following relationship. φ (x, y) = (2π / λ) · sin α · 2u (x, y) (3) where α is the incident angle of the first laser beam I and the second laser beam II, and λ is the laser The wavelength of light.

Next, 2 represented by the above equations (1) and (2)
Taking the difference between the intensities of the two speckle patterns, ΔI (x, y) = 2A ₁ (x, y) · A ₂ (x, y) [cos θ-cos from the above equations (1)-(2). (Θ + φ)] + ΔN = 4A ₁ (x, y) · A ₂ (x, y) sin [θ + (φ / 2)] sin (φ / 2) + ΔN (4) and the intensity corrected by the phase φ. The distribution is obtained.

However, ΔN is a noise difference before and after deformation and is usually ignored. Therefore, by analyzing the intensity distribution having the general form of the above equation (4), the phase φ (x, y) can be calculated as (x,
y (), and u (x,
If y) is calculated, the displacement of each point on the inspection object 1 due to the deformation can be obtained. This kind of analysis of deformation and displacement (vibration etc.) is generically called ESPI.

ΔI is generally an interference fringe pattern.
In the above description, the method of obtaining the phase difference φ introduced by the displacement component u (x, y) in the x direction by taking the difference between I _before and I _after has been described. It suffices if the phase difference φ can be extracted, and in addition to the method of taking the difference, the method of taking the sum or I _before
There is a method of correlating the speckle between I and I _after .

As a conventional method of extracting the phase difference φ,
Fourier transform (FFT) and phase step (PS) methods
Is used. (1) The FFT method is based on ΔI (x, y) in the above equation (4).
, The spatial dependence of φ / 2 to be obtained, that is, the space
Φ / 2 is extracted by utilizing the fact that the frequency is different from other variables.
It is something to try. That is, I_before＋ I_afterAlso
Is I_before-I _afterTo create a spatial frequency other than φ / 2
Except frequency components other than those on the frequency axis (frequency domain)
After the inverse Fourier transform, the ratio of the real part and the imaginary part of the FFT
The phase difference φ is obtained.

Usually, a carrier having a constant frequency in space is introduced to separate the frequency component to be obtained from unnecessary components. The above expression is expressed as follows.
Speckle image (light intensity distribution) to be analyzed in general
Has the following form. i (x, y) = a (x, y) + b (x, y) cos [2πf ₀ x + φ (x, y)] (10) where f ₀ is the frequency of the introduced carrier.

When the above equation (10) is modified,

[0013]

[Equation 1]

When Fourier transform of the above (11) is performed, as shown in FIG. 13, I (f, y) = A (f, y) + C ^* (f−f ₀ , y) +
It becomes C (f + f ₀ , y). Next, C ^* and A are removed, and C (f + f ₀ ,
When y) is shifted to the left in FIG. 13 by f ₀ on the frequency axis and inverse Fourier transform is performed, c (x, y) is obtained. If the ratio of the real part and the imaginary part is taken, the above (12) is obtained. As is clear from the equation, φ (x, y) = tan ⁻¹ [I _m [c (x, y)] / Re _e [c (x, y)]] (13) and the phase difference φ (x , Y) can be obtained.

(2) Next, the PS (phase step) method will be described. The PS method artificially introduces the phase difference ψ _i before and after the deformation of the inspection object instead of the phase difference φ due to the deformation, and thereby increases the number of equations to obtain the phase difference φ. Is. That is, the speckle image of the inspection object after deformation is I _i ′ _after = A ₁ ² + A ₂ ² + 2A ₁ A ₂ cos (θ + φ + Ψ _i ) ... (14) _i = 1, 2, 3 where θ: initial Phase difference φ: Phase difference due to deformation of the inspection object Ψ _i It is a known phase difference that is artificially introduced. Usually, since there are three unknowns, i is 1, 2,
3 is required.

In order to facilitate normal calculation, Ψ ₁ = −
Let Ψ, Ψ ₂ = 0 and Ψ ₃ = Ψ. Then, the phase difference φ due to the deformation to be obtained is θ + φ = tan ⁻¹ [(I _{1 after} −I _{3 after} ) (cos Ψ −1) / (I _{1 after} + I _{3 after} −2I _{2 after} ) sin Ψ] (15 ) Θ = tan ⁻¹ [(I _{1 before} −I _{3 before} ) (cos Ψ −1) / (I _{1 before} + I _{3 before} −2I _{2 before} ) sin Ψ] (16)

[0017]

However, the above-mentioned prior art has the following problems. (1) Both of the FFT method and the PS method are optical systems for extracting the phase difference φ due to deformation of the inspection object, that is, in the case of the FFT method, a mechanism for introducing spatial carriers, and in the case of the PS method , A phase shifter, that is, a mechanism for introducing the phase difference Ψ is required.

(2) At the same time, a procedure related to measurement is required. That is, in the case of the FFT method, it is necessary to insert an operation for introducing a spatial carrier, and in the case of the PS method, it is necessary to insert a phase modulator. (3) The FFT method requires a long calculation time to process image data. (4) In the FFT method, the unnecessary term is removed on the frequency axis, but there is a possibility that a part of the required signal may be lost.

(5) In the PS method, the error of the phase difference ψ introduced appears as the error of the phase difference φ due to the deformation of the inspection object. For example, if liquid crystal is used as the phase shifter, the amount of phase shift will change due to changes in environmental temperature.
In order to solve the above problems, the present invention can easily and accurately extract the phase difference due to the deformation of the inspection object based on the speckle images before and after the deformation of the inspection object. An object of the present invention is to provide a method for extracting a phase from a speckle image of the above and an apparatus therefor.

[0020]

The present invention achieves the above objects.
(1) Phase extraction method from speckle image of inspection object
The first laser with an incident angle equal to the inspection object
Beam and a second laser beam to irradiate the inspection
Speckle image of the object before deformation I_beforeCCD camera
And the step of blocking the second laser beam
Subject to inspection by irradiation with only the first laser beam
Speckle image before deformation I_{1 before}To CCD camera
The step of taking in and blocking the first laser beam
The inspection object by irradiation with only the second laser beam
Of the speckle image before deformation I_{2 before}The CCD camera
Step to install and put a cap on the CCD camera
To capture dark noise, and the inspection object
First laser beam and second laser with an incident angle equal to
Beam and irradiate the
Kur image I_afterCapturing the image into the CCD camera,
Block the second laser beam and shield the first laser beam
Speckle after deformation of the inspection object due to irradiation with only
Image I_{1 after}The step of taking the image into the CCD camera,
The first laser beam is blocked and the second laser beam
Speckle image after deformation of the inspection object due to irradiation
I_{2 af ter}To the CCD camera, and
Cap the CCD camera to capture dark noise
Steps and speckles captured in each of the above
The dark noise is eliminated from the image, and the noise is eliminated.
Speckle image I of the inspection object before deformation_{before nf}And no
Speckle after deformation of the inspection object with erased noise
Image I_{after nf}And the inspection object from which the noise has been eliminated
Of the first laser beam before deformation
Image I_{1 before nf}And the inspection target from which noise has been eliminated
Specifications only by the second laser beam before the deformation of the object
Le Statue I_{2 be fore nf}And the inspection pair from which the noise has been eliminated
After the deformation of the elephant
Kur image I_{1 after nf}And the inspection where the noise was eliminated
After the deformation of the object, only the second laser beam
Kickle Statue I_{2 after nf}And the step of getting
Speckle image I of the erased inspection object before deformation
_{before nf}Deformation of the inspection object from which noise is eliminated
Later speckle image I_{afte r nf}Sum of speckle image with
_addAnd the inspection pair from which the noise has been eliminated.
Speckle image before transformation of elephant I_{before nf}And the noise disappears
Speckle image I of the removed inspection object after deformation
_{after nf}Difference of speckle image with_subStep to get
And the sum of the speckle image I_addNoise is removed from
Of the first laser beam before deformation of the inspected object
Speckle image I_{1 before nf}And the noise is erased
Of the second laser beam before the deformation of the inspected object
Speckle image I_{2 before nf}And the noise is erased
Of the first laser beam after deformation of the inspected object
Speckle image I_{1 after nf}And the noise is erased
Of the second laser beam after the deformation of the inspected object
Speckle image I_{2 after nf}And speckle statue
Sum of corrected speckle image I_{add mod}
To obtain I_subAnd I_{add mod}At
Those who do not affect the phase difference due to the deformation of the inspection object
Select the orientation and select the CCD camera
Take a row of cells and arrange their pixels and parallel neighboring pixels.
The step of averaging the pixel sequence,
I for each cell_subAnd I_{add mod}Take the ratio of
n^-1And a step of calculating

(2) In the phase extraction method from the speckle image of the inspection object described in (1) above, a direction that does not affect the phase difference due to the deformation of the inspection object in I _sub and I _{add mod} described above. Is selected, and the pixels of the CCD camera are arranged perpendicularly to that direction, and the averaging in the step of averaging the pixel and the parallel adjacent pixel array is performed by averaging a plurality of pixels in the vertical direction with respect to the pixel array. This is done by selecting the line.

(3) The inspection object space described in (2) above.
In the phase extraction method from the Kickle image, the line book
The number depends on increasing the aperture of the CCD camera.
It can be reduced. (4) For phase extraction method from speckle image of inspection object
The first laser with an incident angle equal to the inspection object
Beam and a second laser beam to irradiate the inspection
Speckle image of the object before deformation I_beforeCCD camera
And the step of blocking the second laser beam
Subject to inspection by irradiation with only the first laser beam
Speckle image before deformation I_{1 before}To CCD camera
The step of taking in and blocking the first laser beam
The inspection object by irradiation with only the second laser beam
Of the speckle image before deformation I_{2 before}The CCD camera
Step to install and put a cap on the CCD camera
To capture dark noise, and the inspection object
First laser beam and second laser with an incident angle equal to
Beam and irradiate the
Kur image I_afterCapturing the image into the CCD camera,
Block the second laser beam and shield the first laser beam
Speckle after deformation of the inspection object due to irradiation with only
Image I_{1 after}The step of taking the image into the CCD camera,
The first laser beam is blocked and the second laser beam
Speckle image after deformation of the inspection object due to irradiation
I_{2 af ter}To the CCD camera, and
Cap the CCD camera to capture dark noise
Steps and speckles captured in each of the above
The dark noise is eliminated from the image, and the noise is eliminated.
Speckle image I of the inspection object before deformation_{before nf}And no
Speckle after deformation of the inspection object with erased noise
Image I_{after nf}And the inspection object from which the noise has been eliminated
Of the first laser beam before deformation
Image I_{1 before nf}And the inspection target from which noise has been eliminated
Specifications only by the second laser beam before the deformation of the object
Le Statue I_{2 be fore nf}And the inspection pair from which the noise has been eliminated
After the deformation of the elephant
Kur image I_{1 after nf}And the inspection where the noise was eliminated
After the deformation of the object, only the second laser beam
Kickle Statue I_{2 after nf}And the step of getting
Speckle image I of the erased inspection object before deformation
_{before nf}Deformation of the inspection object from which noise is eliminated
Later speckle image I_{afte r nf}Sum of speckle image with
_addAnd the inspection pair from which the noise has been eliminated.
Speckle image before transformation of elephant I_{before nf}And the noise disappears
Speckle image I of the removed inspection object after deformation
_{after nf}Difference of speckle image with_subStep to get
And the sum of the speckle image I_addNoise is removed from
Of the first laser beam before deformation of the inspected object
Speckle image I_{1 before nf}And the noise is erased
Of the second laser beam before the deformation of the inspected object
Speckle image I_{2 before nf}And the noise is erased
Of the first laser beam after deformation of the inspected object
Speckle image I_{1 after nf}And the noise is erased
Of the second laser beam after the deformation of the inspected object
Speckle image I_{2 after nf}And speckle statue
Sum of corrected speckle image I_{add mod}
To obtain mI_subFrom the nI
_{add mod}By subtracting (where m, n are positive
Integer), to obtain the phase difference map due to the deformation of the inspection object
Steps.

(5) The inspection object space described in (4) above.
In the phase extraction method from the Kickle image, the phase difference map
The contrast of the image is optimized by adjusting the aperture. (6) For phase extraction device from speckle image of inspection object
The first laser with an incident angle equal to the inspection object
Means for irradiating the laser beam and the second laser beam,
First shutter capable of blocking the first laser beam
And a second shutter capable of blocking the second laser beam
And a CCD for capturing the speckle image of the inspection object
Processing speckle images from the camera and this CCD camera
Image processing computer
With the first laser beam at an incident angle equal to the inspection object
Irradiation with a second laser beam changes the object to be inspected.
Means for obtaining speckle image before shaping and second laser beam
Before irradiating only the first laser beam with the light shielded
Means for obtaining a speckle image of the inspection object before deformation,
The first laser beam is blocked and the second laser beam
Speckle image of the inspection object before deformation due to irradiation
And a cap on the CCD camera.
Means for obtaining background noise and equal incidence on the inspection object
The first laser beam and the second laser beam at an angle
Irradiate and obtain a speckle image of the inspection object after deformation
Means and a first laser for blocking the second laser beam
Beam after irradiation of only the beam
Means to obtain peckle image and shield the first laser beam
Then, the inspection pair by irradiating only the second laser beam
Means for obtaining a deformed speckle image of the elephant, and the CCD
A means to get dark noise by attaching a cap to the camera,
From the speckle image captured in each of the above
Noise is eliminated and the noise of the inspection object is changed.
Shaped speckle image I_{before nf}And the noise is erased
Speckle image I of the inspection object after deformation _{after nf}
And the first before deformation of the inspection object from which noise is eliminated
Image of the speckle by only the laser beam I
_{1 before nf}And the object to be inspected from which noise has been eliminated
Speckle image with only the second laser beam before deformation
I_{2 before nf}And the inspection object from which the noise has been eliminated
Of the first laser beam only after the deformation of the
Image I_{1 after nf}And the inspection target from which noise has been eliminated
Specifications only by the second laser beam after the deformation of the object
Le Statue I_{2 after nf}And the noise is eliminated
Speckle image I of the inspection object before deformation_{before nf}
After the deformation of the inspection object from which noise and noise have been eliminated,
Kur image I_{after nf}Sum of speckle image with_addGet
And a means for removing the noise before the deformation of the inspection object
Speckle image I_{before nf}And the noise is eliminated
Speckle image I of deformed inspection object_{after nf}With
Kickle Difference I_subOf the speckle image
Sum I_addFrom the
Speckle image I by only the first laser beam before shaping
_{1 before nf}And the noise of the inspection object
Speckle image I with only the second laser beam before shaping
_{2 before nf}And the noise of the inspection object
Speckle image I by only the shaped first laser beam
_{1 after nf}And the noise of the inspection object
Speckle image I by only the second laser beam after shaping
_{2 after nf}Is corrected by subtracting the sum of the speckle image of
Sum of speckle image I_{add mod}Means for obtaining
_subAnd I_{add mod}In the case of the deformation of the inspection object
Select a direction that does not affect the phase difference, and drop in that direction.
Directly arrange the pixels of the CCD camera, and
Average for pixel rows in parallel with adjacent pixels
Means for performing the conversion, and the I_subAnd I
_{add mod}The phase due to the deformation of the inspection object
And means for obtaining a difference.

(7) Position from the speckle image of the inspection object
In the phase extraction device, at an incident angle equal to the inspection object
Irradiation with a first laser beam and a second laser beam
Means and a first laser beam that can shield the first laser beam
Shutter and second that can block the second laser beam
And the speckle image of the inspection object
CCD camera to insert and specifications from this CCD camera
An image processing computer that processes
And a first laser with an incident angle equal to the inspection object.
Beam and a second laser beam to irradiate the inspection
A means for obtaining a speckle image of the object before deformation, and a second laser
The laser beam is blocked and only the first laser beam is illuminated.
Obtain the speckle image before deformation of the inspection object by irradiation
Means and a second laser for blocking the first laser beam
-Beam only irradiation before the deformation of the inspection object
Means for obtaining peckle image and cap for the CCD camera
To obtain dark noise by attaching the
First laser beam and second laser with equal incidence angles
Specifications after the beam is irradiated and the inspection object is deformed
And a means for obtaining an image of the
The inspection object by irradiation with only one laser beam
A means for obtaining a deformed speckle image and a first laser beam
By irradiating only the second laser beam with the beam shielded
Means for obtaining a deformed speckle image of the inspection object,
Get dark noise by attaching a cap to the CCD camera
And the speckle image captured in each of the above.
The dark noise from the
Speckle image of the object before deformation I_{before nf}And the noise
The deformed speckle image I of the inspection object from which the
_{after nf}The noise of the inspection object
Speckle image I by only the first laser beam before shaping
_{1 before nf}And the object to be inspected from which noise has been eliminated
Speckle image with only the second laser beam before deformation
I_{2 before nf}And the inspection object from which the noise has been eliminated
Of the first laser beam only after the deformation of the
Image I_{1 after nf}And the inspection target from which noise has been eliminated
Specifications only by the second laser beam after the deformation of the object
Le Statue I_{2 after nf}And the noise is eliminated
Speckle image I of the inspection object before deformation_{before nf}
After the deformation of the inspection object from which noise and noise have been eliminated,
Kur image I_{after nf}Sum of speckle image with_addGet
And a means for removing the noise before the deformation of the inspection object
Speckle image I_{before nf}And the noise is eliminated
Speckle image I of deformed inspection object_{after nf}With
Kickle Difference I_subOf the speckle image
Sum I_addFrom the
Speckle image I by only the first laser beam before shaping
_{1 before nf}And the noise of the inspection object
Speckle image I with only the second laser beam before shaping
_{2 before nf}And the noise of the inspection object
Speckle image I by only the shaped first laser beam
_{1 after nf}And the noise of the inspection object
Speckle image I by only the second laser beam after shaping
_{2 after nf}Is corrected by subtracting the sum of the speckle image of
Sum of speckle image I_{add mod}Means for obtaining
_subFrom the nI_{add mod}By subtracting (
Where m and n are positive integers), depending on the deformation of the inspection object.
And a means for obtaining a phase difference map.

(8) In the phase extraction device from the speckle image of the inspection object described in (6) or (7) above, the CCD camera has a diaphragm whose aperture can be adjusted.

[0026]

According to the present invention, (A) as shown in FIG. 2, to the CCD camera of the speckle image before the deformation of the inspection object, (1) the speckle image I _before ,
(2) Speckle image I _{1 before} , (3) Speckle image I
_{2 before} , (4) _Import dark noise _before .

Next, (5) speckle image I _after , (6) speckle image I _{1 after} , (7) speckle image I _{2 after} , to the CCD camera of the speckle image of the inspection object after deformation.
(8) Capture the dark noise _after respectively. Then (9)
I _{before nf} from which noise has been eliminated and I
_{after nf} , I _{1 before nf} , I _{2 before nf} ,
Obtain I _{1 after nf} and I _{2 after nf} .

Next, (10) I _add , that is, I _{before nf}
Get + I _{after nf} . Then, (11) I _sub , that is, I
_{before nf-Get} I _{after nf} . Then, (12) I
_{add mod} , that is, I _add − (I _{1 before nf} + I
_{2 before nf} + I _{1 after nf} + I _{2 after nf} ). Next, (13) I _sub and I _{add mod} are averaged in a direction that does not affect the phase difference φ with respect to the arrangement of pixels of the CCD cameras that are in parallel and close to each other.

Next, (14) Phase difference φ, that is, tan ^-1
Calculate (I _sub / I _{add mod} ). (B) As shown in FIG. 3, (21) speckle image I _before , to the CCD camera of the speckle image of the inspection object before deformation.
(22) Speckle image I _{1 before} , (23) Speckle image I
_{2 before} and (24) Dark noise _before are imported respectively.

Next, (25) speckle image I _after , (26) speckle image I _{1 after} , (27) speckle image I _{2 after} , to the CCD camera of the speckle image after deformation of the inspection object,
(28) Take in dark noise _after respectively. Then (2
9) I _{before nf} from which noise has been eliminated and I
_{after nf} , I _{1 before nf} , I _{2 before nf} ,
Obtain I _{1 after nf} and I _{2 after nf} .

Next, (30) I _add , that is, I _{before nf}
Get + I _{after nf} . Then, (31) I _sub , that is, I
_{before nf-Get} I _{after nf} . Then, (32) I
_{add mod} , that is, I _add − (I _{1 before nf} + I
_{2 before nf} + I _{1 after nf} + I _{2 after nf} ). Then, nI _{add mod} is subtracted from (33) mI _sub (where m and n are positive integers) to obtain a phase difference map due to the deformation of the inspection object.

The speckle image captured by the CCD camera at each step is stored in the frame memory built in the image processing computer 25. The amount of speckle image is adjusted by the speckle image read from the frame memory. It can be executed by the adjusting operation of. Therefore, it is possible to easily and accurately obtain the deformation or distortion of the inspection object by extracting the phase difference due to the deformation of the inspection object, calculating the displacement amount at each point from it, and using a predetermined calculation formula. You can

In particular, an application for obtaining the time derivative of deformation, that is, a constant and sufficiently short time step Δt
It is possible to obtain an excellent effect in an application in which the measurement of displacement in is required.

[0034]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an overall configuration diagram of a phase extracting apparatus from a speckle image on a detection surface of an inspection object showing an embodiment of the present invention. The device shown here is merely an example, and the device of the present invention is not limited to this.

In this figure, 10 is a He-Ne laser, and the laser beam output from this He-Ne laser 1 is reflected by reflecting mirrors 11 and 12, and a first laser beam 21 which goes straight by a beam splitter 15.
And a second laser beam 22 traveling downward,
The laser 21 is reflected by the reflecting mirror 13 and passes through the objective lens 16 to make an incident angle α (here, for example, 45 degrees).
The inspection object 20 is irradiated with.

On the other hand, the second laser beam 22 is reflected by the reflecting mirror 14 through the objective lens 17, and the object to be inspected at an incident angle α (here, for example, 45 degrees) from the side opposite to the first laser beam 21. Irradiate 20. Furthermore, the first
The laser beam 21 of the
The second laser beam 22 can be opened and closed by the second shutter 19. The shutters 18 and 19 are controlled to be opened and closed in synchronization with each other by the control device 26.

The first laser beam 21 and the second laser beam 21
The detection surface of the inspection object illuminated by the laser beam 22 is imaged by the CCD camera 24 through the diaphragm 28 and the lens 23 whose aperture can be adjusted. The speckle image captured by the CCD camera 24 is processed by the image processing computer 25 and can be monitored by the monitor 27.

The phase extracting method from the speckle image on the detection surface of the inspection object showing the embodiment of the present invention will be described below with reference to FIG. Here, in order to avoid the complexity of the formula, the formula is expressed on the assumption that the amplitudes A ₁ and A ₂ of the optical electric fields before and after the deformation of the inspection object by the irradiation of both laser beams are equal to each other. Also, at each step CCD
The speckle image captured by the camera is stored in the frame memory built in the image processing computer 25, and the adjustment of the speckle image can be performed by the adjustment operation of the speckle image read from the frame memory. .

(1) First, the speckle image I _before of the above-described deformation of the inspection object, that is, A of the above equation (1).
₁ ² (x, y) + A ₂ ² (x, y) + 2A ₁ (x, y)
CCD camera 24 for A ₂ (x, y) cos θ + N _before
Take in. (2) Next, by blocking the second laser beam 22 with the second shutter 19, A ₁ ² _before + N _before , which is I _{1 before} , and the first laser beam 2
By blocking 1 with the first shutter 18, A ₂ ² _before + N _before , which is I _{2 before} , is taken into the CCD camera 24.

(3) Next, a cap (not shown) is attached to the CCD camera 24 to turn dark noise (dark no).
capture). (4) The same operations as (1) to (3) above are performed after deformation.
That is, I _after , that is, A in the above equation (2)
₁ ² (x, y) + A ₂ ² (x, y) + 2A ₁ (x, y)
A ₂ (x, y) cos (θ + φ) + N _after is taken into the CCD camera 24.

In addition, the second laser beam 22 is
By blocking with the shutter 19, I
_{1 after}Is A₁ ² _after+ N_afterAnd the first ray
The beam 21 is blocked by the first shutter 18.
By I_{2 after}Is A ₂ ² _after+ N
_afterAnd are taken into the CCD camera 24. Change
Incorporate dark noise into
Mu.

[0042] (4) taken in step _{I before, I after, I 1} before, I 2 befo re, I
Dark noise (dark noise) captured in (3) and (4) above from each of _{1 after} and I _{2 after}
Subtract e). That is, here, I _{before nf} , I
_{after nf} , A ₁ ² _{before nf} , A ₂ ² _{before nf} , A
₁ ² _{after nf} and A ₂ ² _{after nf} can be obtained. Where n. f indicates noise-free in which noise is eliminated.

(5) Next, the speckle image I _{before nf} of the inspection object from which noise is eliminated and _before deformation and the speckle image I _{after nf of} the inspection object from which noise is eliminated are deformed.
Get the sum of. I _add = I _{before nf} + I _{after nf In} addition, a speckle image I _{before nf} of the inspection object in which noise is eliminated and _before deformation and a speckle image I _{after nf} of the inspection object in which noise is eliminated are formed. Get the difference.

I_sub= I_{before nf}-I_{after nf} These are the components of the image processing computer 25.
I in the frame memory _{before nf}Remember another
I in the frame memory_{after nf}Memorize
Image processing comp.
The computer 25 performs arithmetic processing.

(6) From the speckle image I _add to A ₁ ²
_{before nf} ＋ A ₂ ² _{before nf} ＋ A ₁ ² _{after nf} ＋ A
₂ ² _{After nf} is subtracted. This is called I _{add mod} .
Although the speckle image I _sub is not corrected,
Call it _{sub mod} . [(Mod: modified means the correction.) (7) From the above, I _{add mod} = 4A ₁ (x, y) A ₂ (x, y) cos [θ + (φ / 2)] co s (φ / 2) (5) I _{sub mod} = 4A ₁ (x, y) A ₂ (x, y) sin [θ + (φ / 2)] sin (φ / 2) (6) is obtained.

(8) A direction perpendicular to the interference fringes of I _{sub mod} and I _{add mod} (see FIG. 5) is selected, and the arrangement of adjacent pixels parallel to that direction, that is, the phase difference φ
Average for directions that do not affect. Here, in FIG. 4, the left end of a rectangular inspection object (for example, a metal body) 31 is fixed by a fixing portion 32, and the right end of the inspection object 31 receives a mechanical stress F in the right direction, and the inspection object is It shows how the object 31 is deformed, and the I of the inspection object 31 is shown.
The image of the _{sub mod} is as shown in FIG. In addition,
FIG. 5B is a similar I _{sub mod} image in a state where the deformation has progressed after a certain time has elapsed.

Therefore, as shown in FIG. 5B, attention is paid to an interference fringe having a constant phase difference φ, for example, f ₁ , and a pixel array perpendicular to this interference fringe is taken. For pixels and parallel pixel arrays in parallel,
That is, the pixel array of 5 to 10 is averaged in the direction that does not affect the phase difference φ. At this time, the number of pixel arrays to be averaged is determined by the relative relationship between the frequency of spatial fluctuation of the initial phase difference θ and the width of the pixel, which will be described later.

Here, in order to make it easier to understand, as shown in FIG. 6, the lower left corner of the rectangular inspection object 41 is provided with a screw 42.
When the deformation is performed in a state of being fixed and rotatable by, that is, when the deformation is made by the minute angle δ, (x, y) is displaced to (x ′, y ′), and the displacement u is u = x′−x x = rcos θ x ′ = rcos (θ + δ) = rcos θ cos δ−r sin θ sinδ where δ << 1 ∴sin δ≈δ, cos δ≈1 x′≈rcos θ−δr sin θ ∴u = x′−x = rcos θ−δr sr rcosθ = −δrsinθ By the way, rsinθ = y ∴u = −δy, and the displacement u is proportional to y, as shown in FIG.
An image of each equation can be shown as shown in (c). That is, u is proportional to y, so the interference fringes are parallel and evenly spaced.

Therefore, the averaging is performed using 5 to 10 pixel rows that are perpendicular to the interference fringes and are parallel to each other. Then, when averaging is not performed [line (x = 250) is 1
In the case of a book], as shown in FIG. 8, the phase angle φ (radian) under the vertical pixel number, that is, the displacement (u)
However, as shown in FIG. 9, in the case of five lines (x = 250 to 254), the initial phase angle θ (radian) at each pixel, that is, cos (θ + φ) and sin ( The term (θ + φ) is averaged, and the effect of the phase angle φ, that is, the degree of inclination of displacement becomes clear.
Furthermore, as shown in FIG. 10, ten lines (x = 25
In the case of 0 to 259), the initial phase angle θ (radian) under the vertical pixel number is more averaged, and the inclination degree of displacement becomes clear.

This averaging operation is performed by _adding I _{add mod} and I _{sub mod.}
Do both. Thereby, the term including the initial phase angle θ in the above equations (5) and (6) becomes a constant due to the randomness of the initial phase angle θ. <I _{add mod} > = <4 A ₁ (x, y) A ₂ (x, y)><cos [θ + (φ / 2)]> cos (φ / 2) (7) = C _add cos (φ / 2) <I _{sub mod} > = C _sub sin (φ / 2) (8) Here, C _add = C _sub = <4 A ₁ (x, y) A ₂ (x, y)><cos [θ + (Φ / 2)]> = <4A ₁ (x, y) A ₂ (x, y)><sin [θ + (φ / 2)]> As is clear from the above equation, <cos [θ + (φ / 2)]> ≉ <sin [θ + (φ / 2)]> holds, the averaging must be performed in a sufficiently wide region as compared with the spatial variation of θ. That is, if it is shown by a general formula,

[0051]

[Equation 2]

On the other hand, θ is 0 on average within one speckle size.
The spatial area to be averaged depends on the speckle size because it changes from ˜2π. That is, the smaller the speckle size, the smaller the spatial spread of ξ ₀ for the same Θ. Now, if the spatial extent is the speckle size and sigma _S, because of the order Shitashiguma _S, if the pixel size of the image plane and sigma _P, the number k _av of pixels to be subjected to averaging, k _av = Θ σ _S / σ _P. Further, σ _S is approximately σ _S = 0.6λ / N. It is expressed as A = 0.6λl _i / d.

Where λ is the laser wavelength, d is the aperture radius of the diaphragm, l _i is the distance between the lens and the image plane, and N. A: Numerical aperture (see FIG. 11). In FIG. 11, 2
Reference numeral 9 denotes an image plane on which pixels are arranged. Other points are shown in Figure 1.
As shown in. Therefore, the number k _av of pixels to be averaged is k _av = (Θ · 0.6λl _i ) / (d · σ _P ), and is inversely proportional to the opening radius d if the pixel size σ _P is constant.

This means that the number k _{av of} pixels to be averaged can be adjusted by adjusting the aperture of the diaphragm. However, if the aperture is made too large and σ _S becomes too small, the resolution of the speckle pattern by the pixels of finite width σ _P is reduced, and the recognition accuracy of the speckle pattern before and after the displacement is reduced accordingly. Therefore, in reality, the lower limit of σ _S is this recognition accuracy,
In other words, it is determined by the good correlation of the speckle patterns before and after the displacement, and the upper limit of σ is suppressed by the number of pixels k _av that can be averaged. Incidentally, the upper limit of k _av is often restricted by a condition that does not affect the phase difference φ, and when the fringes of the interference fringes of I _sub and I _{add mod} are not parallel as in the example shown in FIG. Especially, it is important to keep k _av small.

(9) Then, for each pixel of the CCD camera, that is, for all (x, y), the ratios of the above (7) and (8) are taken and its tan ^-1 is calculated. That is, [φ (x, y) / 2] = tan ⁻¹ [<I _{sub mod} > / <I _{add mod} >] (9) With such a configuration, the fringes of the interference fringes in the speckle image are The phase difference φ of can be continuously and accurately evaluated.

The displacement u (x, y) can be obtained by using φ (x, y) thus obtained and (3) above. Next, processing of image pickup data and image processing showing the second embodiment of the present invention will be described. First
In the embodiment, in (8) above, a direction perpendicular to the fringe of the interference fringes of I _{sub mod} and I _{add mod} is selected, and the average of the array of adjacent cells (pixels of the CCD camera) parallel to the direction is selected. From this, the terms including the initial phase angle θ in the above equations (5) and (6) are made constant from the randomness of the initial phase angle θ, and every pixel of the CCD camera, that is, all ( The ratio of (7) and (8) is taken for x, y) to calculate tan ⁻¹ . In the second embodiment, the following processing is performed to deform the inspection object. To obtain the phase difference map. That is, (1) I _{add mod} is subtracted from the I _sub . That is,
Calculate I _sub −I _{add mod} . This is [4A
₁ (x, y) A ₂ (x, y) sin [θ + (φ / 2)]
sin (φ / 2)] − [4A ₁ (x, y) A ₂ (x,
y) cos [θ + (φ / 2)] cos (φ / 2)], and a locus at which this value becomes 0, that is, tan (φ / 2) = 1, that is, φ / 2 by obtaining the interference fringes
= Π / 4, 3π / 4, 5π / 4, ... is a dark peak (dar
It is possible to obtain a phase difference map due to the deformation of the inspection object, which is defined as k peak).

(2) In place of (1) above, 2I _sub -I
_{Compute add mod} . According to this, 2sin (φ /
2) = cos (φ / 2): tan (φ / 2) = 1/2. (3) Instead of (1) above, I _sub -2I _{add mod} is calculated. According to this, sin (φ / 2) = 2cos
(Φ / 2): tan (φ / 2) = 2. When generalized, it becomes mI _sub −nI _{add mod} (where m and n are positive integers). When mI _sub −nI _{add mod} = 0, msin (φ / 2) = ncos (φ / 2) ∴tan (φ / 2) = n / m, and a phase difference map having a dark peak of φ / 2 that satisfies this equation is obtained.

In the second embodiment, since the pixels are not averaged, it is important to adjust the speckle size by the control of the controller 26 for the aperture diameter of the diaphragm 28 of the CCD camera 24 in FIG. That is, by selecting an appropriate speckle size σ _S , the speckle image contrast (correlat) before and after the displacement of the inspection object can be determined.
Ion) can be achieved at the same time, and a sufficiently high Θ (Θπ <ξ ₀ <(Θ + 1) π can be obtained within one pixel, which results in cos (θ + φ) ≈sin (θ + φ).
And the fringe of the interference pattern resulting from mI _sub −nI _{add mod} , that is, the contrast of the phase difference map is improved.

As described above, the obtained phase difference map can be monitored by displaying an image on the monitor 27. As described above, by configuring the second embodiment, it is possible to reduce the arithmetic processing and to speed up the data processing more than the first embodiment. That is, a phase difference map can be obtained by a single operation for the phase difference φ defined in advance by m and n.

The present invention is not limited to the above embodiments, and various modifications can be made based on the spirit of the present invention, and these modifications are not excluded from the scope of the present invention.

[0061]

As described in detail below, according to the present invention, the following effects can be obtained. ADVANTAGE OF THE INVENTION According to this invention, the deformation | transformation or distortion of an inspection target object can be extracted simply and correctly, and the phase difference by the deformation | transformation of an inspection target object can be extracted.

In particular, an application for obtaining the time derivative of deformation, that is, a constant and sufficiently short time step Δt
It is possible to obtain an excellent effect in an application in which the measurement of displacement in is required. In this way, the deformation or distortion of the inspection object can be accurately captured. For example, the mechanical strength of a reactor pressure vessel and the state of high-speed deformation can be detected rapidly and accurately and analyzed, and the effects brought by it are vast and remarkable.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a phase extraction apparatus from a speckle image of an inspection object showing an embodiment of the present invention.

FIG. 2 is a flowchart of a phase extraction method from a speckle image of an inspection target according to an embodiment of the present invention.

FIG. 3 is a flowchart of a method of extracting a phase from a speckle image of an inspection target according to another embodiment of the present invention.

FIG. 4 is a plan view of an inspection object showing an embodiment of the present invention.

FIG. 5 is a diagram showing a speckle subtraction image of an inspection object showing an embodiment of the present invention.

FIG. 6 is a plan view of another inspection object showing the embodiment of the present invention.

FIG. 7 is a diagram showing a speckle subtraction image and an addition image of another inspection target according to the embodiment of the present invention.

FIG. 8 is a diagram (No. 1) showing the relationship between the vertical pixel and the phase difference of the speckle image of another inspection object showing the embodiment of the present invention.

FIG. 9 is a diagram (No. 2) showing the relationship between the vertical pixel and the phase difference of the speckle image of another inspection target according to the embodiment of the present invention.

FIG. 10 is a diagram (part 3) showing the relationship between the vertical pixel and the phase difference of the speckle image of another inspection target according to the embodiment of the present invention.

FIG. 11 is an explanatory diagram of speckle size of a CCD camera.

FIG. 12 is a conventional double beam.
It is a schematic block diagram of m or Dual beam) ESPI.

FIG. 13 is an explanatory diagram of phase extraction from a speckle image by a conventional Fourier transform method.

[Description of sign]

 10 He-Ne laser 11, 12, 13, 14 Reflecting mirror 15 Beam splitter 16, 17 Objective lens 18 First shutter 19 Second shutter 20 Inspection object 21 First laser beam 22 Second laser beam 23 Lens 24 CCD camera 25 Image processing computer 26 Control device 27 Monitor 28 Aperture 29 Image plane 32 Fixed part 41, 31 Inspection object 42 Screw

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Lini Widia Stuty Indonesia 40143 Bandung Jalan Captain Abdul Hamidu Number 37 (72) Inventor Anung Kusnowo Republic of Indonesia 15310 Tangerang Serpong Complex Cypsip Techblock 4 Number J-3 (3) 72) Inventor Eddi Turi Asututi Republic of Indonesia 15310 Tangerang Serpong Compreak Psupip Tech Block 2 Number G-7

Claims (8)

[Claims] 1. A method for extracting a phase from a speckle image of an inspection object, comprising: (a) irradiating the inspection object with a first laser beam and a second laser beam at an incident angle equal to each other; Speckle image _before deformation I _before
In a CCD camera, and (b) Speckle image I of the inspection object before being deformed by irradiating only the first laser beam with the second laser beam blocked.
Step of capturing _{1 before} into the CCD camera, (c)
Capturing a speckle image I _{2 before before} deformation of the inspection object by irradiating only the second laser beam while blocking the first laser beam into a CCD camera;
(D) Capping the CCD camera to capture dark noise, and (e) irradiating the inspection object with a first laser beam and a second laser beam at the same incident angle to inspect the inspection object. Capturing the speckle image I _{after after} deformation into the CCD camera, (f)
Capturing a speckle image I _{1 after} the deformed speckle image I _{1 after} of the inspection object by irradiating only the first laser beam with the second laser beam _blocked, into a CCD camera;
(G) capturing the speckle image I _{2 after} the deformation of the inspection object by irradiating only the second laser beam with the first laser beam _blocked, into the CCD camera, and (h) the CCD camera Attaching a cap to capture dark noise, and (i) erasing the dark noise from the speckle images captured in each of them, and speckle image I _{before nf of} the noise-erased non-deformed inspection object of the inspection object. , A speckle image I _{after nf} of the inspection object after the deformation of the noise, and a speckle image I _{1 before nf of the} inspection object before deformation of the inspection object of which the noise is eliminated. , only the second laser beam and speckle image I _{2 before nf} due before deformation of the test object which noise has been erased, the inspection object which the noise has been erased after deformation And obtaining only the speckle image I _{1 af ter nf} by 1 of the laser beam, and a second laser beam only by speckle image I _{2 after nf} after deformation of the test object which noise has been erased, ( j) A speckle image I _{before nf of the} inspection object in which noise is eliminated and a deformed speckle image I of the inspection object in which noise is eliminated.
obtaining a sum I _add of the speckle image with _{after nf,} and (k) transforming the speckle image I _{before nf before} deformation of the inspection object from which noise has been eliminated and the inspection object from which noise has been eliminated Obtaining a difference I _sub between the speckle image I _{after nf} and the speckle image I _{after nf,} and (l) a sum I _add of the speckle images, from the sum I _add of the speckle images before the deformation of the inspection object Of the speckle image I _{1 before nf} by the laser beam only and the noise of the inspection object before the deformation of the inspection object of the second laser beam only by the second laser beam I _{2 before nf} and the noise of the inspection object Of the speckle image I _{1 after nf} only by the first laser beam _after the deformation and the speckle image I _{2 after nf} by the second laser beam after the deformation of the inspection object from which the noise is erased Subtract sum of images Then, the step of obtaining the sum I _{add mod} of the corrected speckle images, and (m) the direction that does not affect the phase difference due to the deformation of the inspection object is selected in I _sub and I _{add mod} , and the direction thereof is selected. The pixel array of the CCD camera is taken perpendicularly to, and the pixel and the parallel pixel array are averaged, and (n) the ratio of I _sub and I _{add mod} is taken for each pixel, t
and a step of calculating an ⁻¹ , the phase extraction method from the speckle image of the inspection object. 2. The phase extraction method from a speckle image of an inspection object according to claim 1, wherein the averaging in step (m) does not affect a phase difference due to deformation of the inspection object. A phase extraction method from a speckle image of an inspection object, which is performed by selecting a plurality of lines in a vertical direction with respect to the arrangement of the pixels. 3. The method for extracting a phase from a speckle image of an inspection object according to claim 2, wherein the number of lines can be reduced by increasing the aperture of the CCD camera. Phase extraction method from speckle image of target. 4. A method of extracting a phase from a speckle image of an inspection object, comprising: (a) irradiating the inspection object with a first laser beam and a second laser beam at an incident angle equal to each other, Speckle image _before deformation I _before
In a CCD camera, and (b) Speckle image I of the inspection object before being deformed by irradiating only the first laser beam with the second laser beam blocked.
Step of capturing _{1 before} into the CCD camera, (c)
Capturing a speckle image I _{2 before before} deformation of the inspection object by irradiating only the second laser beam while blocking the first laser beam into a CCD camera;
(D) Capping the CCD camera to capture dark noise, and (e) irradiating the inspection object with a first laser beam and a second laser beam at the same incident angle to inspect the inspection object. Capturing the speckle image I _{after after} deformation into the CCD camera, (f)
Capturing a speckle image I _{1 after} the deformed speckle image I _{1 after} of the inspection object by irradiating only the first laser beam with the second laser beam _blocked, into a CCD camera;
(G) capturing the speckle image I _{2 after} the deformation of the inspection object by irradiating only the second laser beam with the first laser beam _blocked, into the CCD camera, and (h) the CCD camera Attaching a cap to capture dark noise, and (i) erasing the dark noise from the speckle images captured in each of them, and speckle image I _{before nf of} the noise-erased non-deformed inspection object of the inspection object. , A speckle image I _{after nf} of the inspection object after the deformation of the noise, and a speckle image I _{1 before nf of the} inspection object before deformation of the inspection object of which the noise is eliminated. , only the second laser beam and speckle image I _{2 before nf} due before deformation of the test object which noise has been erased, the inspection object which the noise has been erased after deformation And obtaining only the speckle image I _{1 af ter nf} by 1 of the laser beam, and a second laser beam only by speckle image I _{2 after nf} after deformation of the test object which noise has been erased, ( j) A speckle image I _{before nf of the} inspection object in which noise is eliminated and a deformed speckle image I of the inspection object in which noise is eliminated.
obtaining a sum I _add of the speckle image with _{after nf,} and (k) transforming the speckle image I _{before nf before} deformation of the inspection object from which noise has been eliminated and the inspection object from which noise has been eliminated Obtaining a difference I _sub between the speckle image I _{after nf} and the speckle image I _{after nf,} and (l) a sum I _add of the speckle images, from the sum I _add of the speckle images before the deformation of the inspection object Of the speckle image I _{1 before nf} by the laser beam only and the noise of the inspection object before the deformation of the inspection object of the second laser beam only by the second laser beam I _{2 before nf} and the noise of the inspection object Of the speckle image I _{1 after nf} only by the first laser beam _after the deformation and the speckle image I _{2 after nf} by the second laser beam after the deformation of the inspection object from which the noise is erased Subtract sum of images And (b) subtracting the nI _{add mod} from the mI _sub (where m and n are positive integers) to obtain the sum I _{add mod} of the corrected speckle images. And a step of obtaining a phase difference map according to the deformation of the object, the method for extracting the phase from the speckle image of the inspection object. 5. The method for extracting a phase from a speckle image of an inspection object according to claim 4, wherein the contrast of the phase difference map is optimized by adjusting the aperture. Phase extraction method from image. 6. A phase extraction device from a speckle image of an inspection object, comprising: (a) means for irradiating the inspection object with a first laser beam and a second laser beam at an incident angle equal to each other; b) a first shutter capable of shielding the first laser beam, (c) a second shutter capable of shielding the second laser beam, and (d) a CCD camera for capturing the speckle image of the inspection object. And (e) the C
An image processing computer for processing a speckle image from a CD camera is provided, and (f) the first laser beam and the second laser beam are irradiated at the same incident angle to the inspection object to inspect the inspection object. Means for obtaining a speckle image before deformation, (g) a means for shielding the second laser beam and obtaining a speckle image before deformation of the inspection object by irradiation with only the first laser beam, )
Means for obtaining a speckle image of the inspection object before being deformed by irradiating only the second laser beam by blocking the first laser beam, and (i) means for obtaining dark noise by attaching a cap to the CCD camera (J) means for irradiating the inspection object with a first laser beam and a second laser beam at an incident angle equal to each other to obtain a deformed speckle image of the inspection object; Means for shielding the second laser beam to obtain a deformed speckle image of the inspection object by irradiation with only the first laser beam;
Means for obtaining a speckle image after deformation of the inspection object by irradiating only the second laser beam by blocking the first laser beam, and (m) means for obtaining dark noise by attaching a cap to the CCD camera And (n) dark noise is erased from the speckle image captured in each of them, and the speckle image I _{before nf} of the inspection object before deformation in which noise is erased and the inspection object in which noise is erased Speckle image I _{after nf after} deformation of the object, speckle image I _{1 before nf of} only the first laser beam before deformation of the inspection object in which noise is erased, and inspection object in which noise is erased The speckle image I _{2 before nf of} only the second laser beam _before the deformation of the object and the speckle image I of only the first laser beam after the deformation of the inspection object from which the noise is erased _{1 af ter nf} ,
A means for obtaining a speckle image I _{2 after nf} by only the second laser beam _after the deformation of the inspection object from which noise has been deleted, and (o) a specification before the deformation of the inspection object from which noise has been deleted Image I _{before nf} and speckle image I after deformation of the inspection object from which noise is eliminated
means for obtaining the sum I _add of speckle images with _{after nf} ,
(P) Difference I of speckle image between the speckle image I _{before nf of the} inspection object in which noise is eliminated and _before deformation and the speckle image I _{after nf} of the inspection object in which noise is eliminated. means for obtaining _sub , and (q) speckle image I _{1 before nf} and noise erased by only the first laser beam before deformation of the inspection object from which noise has been erased, from the sum I _add of the speckle images The speckle image I _{2 before nf of the processed} object to be inspected only by the second laser beam _before deformation and the speckle image I _{1 of the} object to be inspected after deformation of the inspection object in which noise is eliminated _{after nf} and noise by subtracting the sum of the speckle image of the second laser beam only by speckle image I _{2 after nf} after deformation of the object to be examined is erased, the sum of the corrected speckle image I and means for obtaining the _{add mod,} r)
In I _sub and I _{add mod} , a direction that does not affect the phase difference due to the deformation of the inspection object is selected, and the pixels of the CCD camera are arranged perpendicularly to the direction.
Means for averaging the pixel as well as parallel adjacent pixel rows; (s) the I for each pixel
A phase extraction device from a speckle image of an inspection object, comprising means for obtaining a phase difference due to deformation of the inspection object by taking a ratio of _sub and I _{add mod} . 7. A phase extracting apparatus for speckle images of an inspection object, comprising: (a) means for irradiating the inspection object with a first laser beam and a second laser beam at an incident angle equal to each other; b) a first shutter capable of shielding the first laser beam, (c) a second shutter capable of shielding the second laser beam, and (d) a CCD camera for capturing the speckle image of the inspection object. And (e) the C
An image processing computer for processing a speckle image from a CD camera is provided, and (f) the first laser beam and the second laser beam are irradiated at the same incident angle to the inspection object to inspect the inspection object. Means for obtaining a speckle image before deformation, (g) a means for shielding the second laser beam and obtaining a speckle image before deformation of the inspection object by irradiation with only the first laser beam, )
Means for obtaining a speckle image of the inspection object before being deformed by irradiating only the second laser beam by blocking the first laser beam, and (i) means for obtaining dark noise by attaching a cap to the CCD camera (J) means for irradiating the inspection object with a first laser beam and a second laser beam at an incident angle equal to each other to obtain a deformed speckle image of the inspection object; Means for shielding the second laser beam to obtain a deformed speckle image of the inspection object by irradiation with only the first laser beam;
Means for obtaining a speckle image after deformation of the inspection object by irradiating only the second laser beam by blocking the first laser beam, and (m) means for obtaining dark noise by attaching a cap to the CCD camera And (n) dark noise is erased from the speckle image captured in each of them, and the speckle image I _{before nf} of the inspection object before deformation in which noise is erased and the inspection object in which noise is erased Speckle image I _{after nf after} deformation of the object, speckle image I _{1 before nf of} only the first laser beam before deformation of the inspection object in which noise is erased, and inspection object in which noise is erased The speckle image I _{2 before nf of} only the second laser beam _before the deformation of the object and the speckle image I of only the first laser beam after the deformation of the inspection object from which the noise is erased _{1 af ter nf} ,
A means for obtaining a speckle image I _{2 after nf} by only the second laser beam _after the deformation of the inspection object from which noise has been deleted, and (o) a specification before the deformation of the inspection object from which noise has been deleted Image I _{before nf} and speckle image I after deformation of the inspection object from which noise is eliminated
means for obtaining the sum I _add of speckle images with _{after nf} ,
(P) Difference I of speckle image between the speckle image I _{before nf of the} inspection object in which noise is eliminated and _before deformation and the speckle image I _{after nf} of the inspection object in which noise is eliminated. means for obtaining _sub , and (q) speckle image I _{1 before nf} and noise erased by only the first laser beam before deformation of the inspection object from which noise has been erased, from the sum I _add of the speckle images The speckle image I _{2 before nf of the processed} object to be inspected only by the second laser beam _before deformation and the speckle image I _{1 of the} object to be inspected after deformation of the inspection object in which noise is eliminated _{after nf} and noise by subtracting the sum of the speckle image of the second laser beam only by speckle image I _{2 after nf} after deformation of the object to be examined is erased, the sum of the corrected speckle image I and means for obtaining the _{add mod,} r)
Inspection means for obtaining a phase difference map by deformation of the inspection object by subtracting the nI _{add mod} from the mI _sub (where m and n are positive integers). Phase extraction device from speckle image of target. 8. The phase extraction device for speckle images of an inspection object according to claim 6 or 7, wherein the CCD camera has a diaphragm whose aperture can be adjusted. Phase extraction device from image.