JP2018205430A - Phase shift digital holography apparatus and program thereof - Google Patents

Abstract

To solve the problem in which since it is difficult to accurately move an optical path length of reference light in phase shift digital holography, an interference fringe image having an accurate phase shift amount cannot be obtained, and image quality of a reconstructed image deteriorates, and in which development of a technology to improve the image quality of the reconstructed image by detecting a phase shift amount of reference light due to low operation accuracy of a phase shift apparatus and correcting an interference fringe image is desired.SOLUTION: An interference fringe image between a laser beam irradiated on a measurement object and phase shifted reference light is recorded by a camera 2, and a phase shift amount due to low operating accuracy of a phase shift apparatus is detected from a regularity fringe pattern using a moire image processing technique. After the interference fringe image for the object recorded by a camera 1 is corrected by the detected phase shift amount, the interference fringe image is reconstructed, image quality of the reconstructed image is improved, and measuring accuracy is improved.SELECTED DRAWING: Figure 7

Description

  The present technology relates to an interference fringe image of a phase shift digital holography device.

In digital holography, an interference fringe image generated by object light and reference light is captured using an imaging device, and information on the amplitude distribution and phase distribution of the measurement target is obtained by calculating the interference fringe image on a computer.
The intensity information of the measurement target is obtained from the amplitude distribution, and the shape / displacement distribution of the measurement target is obtained from the phase distribution.

  However, there is a problem that there is a 0th-order diffracted light and a conjugate image (-1st-order diffracted light), which are components unnecessary for interference fringes, and the quality of the reproduced image deteriorates.

  Off-axis digital holography (Non-Patent Document 1) and phase-shift digital holography have been proposed as methods for removing these unnecessary components (Patent Document 1, Non-Patent Document 2).

In off-axis digital holography, the reference beam and the object beam are incident on the camera at a large crossing angle, and the desired image (+ 1st order diffracted beam) and the conjugate image are separated in the crossing angle direction of the reference beam and the object beam. The image can be reproduced.
An example of a reproduced image is shown in FIG.

  Although it is possible to extract only a desired image by using a spatial filter, off-axis digital holography has a problem that the measurement range is narrow because only a partial area of a reproduced image can be used.

On the other hand, phase shift digital holography records multiple interference fringe images generated by multiple phase-shifted reference beams and object beams, removes unnecessary image components by phase shift calculation, and reproduces only desired images. To do.
An example of the optical system is shown in FIG.

A phase shift device such as a piezo element with a mirror is introduced on the reference light side, and the phase shift device is driven by the control unit to shift the phase of the reference light on the imaging surface.
The calculation processing unit calculates the phase distribution of the object light and the amplitude distribution of the object light from the recorded interference fringe image, and displays them on the display unit.
Until now, many phase shift means have been proposed (Non-patent Document 3).

JP-A-10-268740 JP 2009-264852 A

J. W. Goodman and R. W. Lawrence, “Digital image formation from electronically detected holograms,” Applied. Physics. Letters. 11, pp. 325 77-79 (1967). Yamaguchi Ichirou and Tong Zhang, “Phase-shifting digital holography.” Optics Letters 22, 16, pp. 1268-1270 (1997). J.A.N. Buytaert and J.J.J.Dirckx, “Study of the performance of 84 phase-shifting algorithms for interferometry.” Journal of Optics, 40, 3, pp. 114-131 (2011). Y. Morimoto, et al., “Deformation measurement by phase-shifting digital holography,” Experimental Mechanics, 45, 1, pp. 65-70 (2005).

  Phase shift digital holography records a plurality of phase-shifted interference fringe images by moving the optical path length of the reference light along the optical axis with a nano-order accuracy using a phase shift device (Patent Document). 1).

As an example of realizing this technology, an experiment has been reported in which a high-precision piezo element with a mirror is used and displacement is measured in the nano order (Non-Patent Document 4).
Piezo elements that are currently on the market include an expensive and highly accurate Close loop type and an inexpensive but low-accuracy Open loop type.

The open loop type piezo element cannot accurately move the optical path length of the reference light as compared with the close loop type.
Therefore, there is a problem that an interference fringe image with an accurate phase shift amount cannot be obtained and the quality of the reproduced image is deteriorated.
Even a closed loop type piezo element may not operate correctly because it depends on the usage environment such as drive voltage.

  In order to put a phase shift digital holography measurement device into practical use at low cost using an open loop type piezo element, the phase shift amount of the reference light due to the low operation accuracy of the phase shift device is detected and the interference fringe image is corrected. Therefore, it is desired to develop a technique for improving the quality of a reproduced image. In addition, in order to achieve more accurate measurement even in measurement devices using expensive Close loop type piezo elements, the image quality of the reproduced image is improved by detecting the phase shift amount of the reference light and correcting the interference fringe image. Technology development is desired.

  As shown in FIG. 3, in the present invention, an interference fringe image of the laser beam extracted by the beam splitter and the phase-shifted reference beam before irradiating the measurement target is recorded by the camera 2.

On the other hand, the camera 1 records an interference fringe image of the reflected light from the measurement target and the phase-shifted reference light (Step 1).
When two plane waves (or approximate plane waves) interfere with each other, a regular stripe pattern is generated.

  FIG. 4 shows an example of a regular stripe pattern recorded by the camera 2.

  From the regular stripe pattern recorded by the camera 2, an amount of phase shift due to low operation accuracy of a phase shift device such as a piezo element is detected by an image processing method (Step 2).

  Then, the interference fringe image recorded by the camera 1 shown in FIG. 5 is corrected with the shift amount detected by the camera 2 (Step 3) and reproduced (Step 4), thereby improving the image quality of the reproduced image and improving the measurement accuracy. Can do.

The present invention is applicable to all phase shift digital holography using a phase shift device.
In the example shown in FIG. 3, reflected light of object light is used, but transmitted light may be used.

Specifically, the following means can be provided.
(1)
The interference light 1 between the light emitted from the light source (hereinafter referred to as light source light) and the reference light from the phase shift device in which a predetermined phase shift amount is set to the phase of the light source light is changed in the predetermined phase shift amount. A phase shift digital holography method for analyzing the phase of the reference light from the interference fringe image 1 (multiple times is 1 to n times, where n is a natural number of 3 or more),
The method, wherein the predetermined phase shift amount set for the reference light is corrected by a phase shift amount obtained from the analysis of the interference fringe image 1.
(2)
The method according to (1), wherein the phase shift digital holography is a four-stage phase shift digital holography, and the plurality of times is four times.
(3)
The method according to (2), wherein the phase shift device includes any one of a piezo element, a wedge prism, a quarter wavelength plate, and a half wavelength plate.
(4)
The method according to (3), wherein the phase shift amount is obtained by analyzing interference fringes reflected in the interference fringe image 1 using a moire method.
(5)
Further, from the interference fringe image 2 obtained by irradiating the object light with the light source light and reflecting the interference light 2 between the object light reflected through the object and the reference light and the reference light, or a plurality of times by changing the predetermined phase shift amount, A method of phase shift digital holography for reproducing a holographic image of the object using the phase of the reference light corrected by the phase shift amount analyzed by the method according to any one of (1) to (4) .

(6)
The program according to any one of (1) to (4), wherein the analysis is executed, or a storage medium storing the program.
(7)
(5) A phase shift digital holography method according to (5), wherein a holographic image of the object is reproduced, or a storage medium storing the program.

(8)
A phase shift holographic image processing apparatus comprising a light source, a beam splitter 1, a beam splitter 2, a phase shift device, and a correction imaging device 1 (camera 2),
Light emitted from the light source (hereinafter referred to as light source light) is split into two light source lights by the beam splitter 2,
The light source light becomes reference light by a phase shift device in which a predetermined phase shift amount is set,
The light source light and the reference light are incident on a beam splitter 1 to become interference light 1,
The imaging device 1 captures the interference fringe image 1 from the interference light 1,
The phase according to any one of (1) to (4), wherein the predetermined phase shift amount set in the reference light is corrected with a phase shift amount obtained from the analysis. Shift holographic image processing device.
The upper correction imaging device 1 refers to the camera 2 of the embodiment described above and described below.
(9)
The image processing apparatus according to (8) further includes a measurement imaging device 2 (camera 1) connected to the beam splitter 2, a beam splitter 3 for splitting a part of the light source light, and a part of the reference light. A beam splitter 4 for splitting light and a display device;
The light source light spectrally separated by the beam splitter 3 becomes object light reflected on or transmitted through the object,
The object light and the reference light split by the beam splitter 4 are configured to enter the beam splitter 2 and become interference light 2,
In the image processing device, the holographic image 2 of the object reproduced by using the phase of the reference light corrected by the phase shift amount is displayed on the display device. A phase shift digital holography measuring device characterized by displaying.
The imaging device 2 for measurement above refers to the camera 1 of the embodiment described above and described below.
(10)
A phase shift digital holography measuring device comprising the image processing device according to (8).

According to the present invention, it is possible to detect the phase shift amount of the reference light due to the low operation accuracy of the phase shift device such as a piezo element, and it is possible to perform highly accurate three-dimensional shape / displacement measurement.
The present invention can be applied to phase shift digital holography that requires a phase shift device.
It can greatly contribute to the practical application of phase shift digital holography and can be expected to contribute to the realization of industrial inspection of products, measurement of material shape, and thermo / mechanical deformation measuring device.

It is a related figure of the reproduction image and spatial frequency of off-axis digital holography. It is an optical example of a well-known phase shift digital holography device. It is a block diagram which shows schematic structure of the phase shift digital holography measuring apparatus which concerns on Embodiment 1 of this invention. 2 is an example of a high-contrast interference fringe pattern obtained from a specular object recorded by a camera 2 in the first embodiment. 2 is an interference fringe image including information (amplitude and phase) of a measurement object recorded by the camera 1 in the first embodiment. It is a flowchart figure which concerns on Embodiment 1 of this invention. It is a block diagram which shows a different structure of the phase shift digital holography measuring device which concerns on Embodiment 1 of this invention. It is a block diagram which shows schematic structure at the time of measuring a transmission type | mold object in the phase shift digital holography measuring device which concerns on Embodiment 1 of this invention. It is a block diagram which shows schematic structure of the phase shift digital holography measuring device which concerns on Embodiment 2 of this invention. It is a block diagram which shows schematic structure at the time of measuring the transmitted light of the phase shift digital holography measuring device which concerns on Embodiment 2 of this invention. It is a block diagram which shows schematic structure of the phase shift digital holography measuring device which concerns on Embodiment 3 of this invention. It is a block diagram which shows schematic structure at the time of measuring the transmitted light of the phase shift digital holography measuring device which concerns on Embodiment 3 of this invention. In Example 1, object image information (upper: amplitude distribution, lower: phase distribution) reproduced by the present invention (left) and the prior art (right). In Example 2, it is the luminance information (amplitude distribution) of the object image reproduced | regenerated by this invention and the prior art. In Example 2, it is a figure which compares the noise of the image reproduced | regenerated by this invention and the prior art.

(Embodiment 1)
Embodiment 1 of the present invention will be described below with reference to the accompanying drawings.

  FIG. 3 is a block diagram illustrating a schematic configuration of the phase shift digital holography measuring apparatus according to the first embodiment of the present invention.

This measuring device includes a light source, an objective lens, a lens, beam splitters 1, 2, 3, 4, mirrors 1, 2, piezo elements with mirrors, cameras 1, 2, measurement object, control unit, arithmetic processing unit, and display unit. I have.
This measurement apparatus shifts the phase of the reference light by moving the piezo element with a mirror.

  A part of the light emitted from the light source is incident on the camera 2 through the objective lens, the lens, the beam splitters 2 and 4, the mirror 2, and the beam splitter 1, and a part of the emitted light is measured by the beam splitters 2 and 4. The reflected light from the measurement target is incident on the camera 1.

  The other part of the light emitted from the light source is irradiated to the piezo element with a mirror through the objective lens, the lens, and the beam splitters 2 and 3, and a part of the reflected light from the piezo element with the mirror is the beam splitter 3 and the mirror. 1. The light enters the camera 2 through the beam splitter 1, and a part of the light enters the camera 1 through the beam splitters 3 and 2.

  FIG. 6 is a flowchart according to the first embodiment of the present invention. By moving the piezo element with a mirror in the control unit, the camera 1 and the camera 2 record a plurality of phase-shifted interference fringe images.

  The recorded interference fringe image data is read into an arithmetic processing unit and subjected to arithmetic processing. The interference fringe image recorded by the camera 2 is an interference fringe between light before irradiating the measurement target and reference light, and has a regular stripe pattern.

  First, the shift amount of the reference light set by using an image processing method such as the moire method (for example, Patent Document 2) and the phase shift amount due to the low operation accuracy of the piezo element are calculated from these striped patterns.

  Next, the interference fringe image recorded by the camera 1 is corrected using the calculated phase shift amount.

Next, the correction means will be described in detail.
Light emitted from the light source is irradiated onto the measurement target, and object light is generated.
The object light is incident on the camera, and the complex amplitude of the object light on the imaging surface of the camera is expressed by Expression (1).

In Expression (1), φ corresponds to the phase distribution of the object light on the imaging surface, and A corresponds to the amplitude distribution of the object light on the imaging surface. i is an imaginary unit in the complex number display.
The complex amplitude of the reference light on the imaging surface is expressed by Expression (2).

In the formula (2), φ _R corresponds to the phase data of the reference light on the imaging surface, A _R corresponds to the amplitude data of the reference light on the imaging surface.
The object light and the reference light interfere with each other on the imaging surface, an interference fringe image is generated, and interference fringe image data (luminance value) recorded by the camera is expressed by Expression (3).

In the formula (3), * means conjugation, | U | ² + | U _R | ² is zero-order diffracted light, UU * _R is a desired image component, and U * U _R is a conjugate image component.

In phase shift digital holography, it is necessary to shift the phase of the reference light and record a plurality of phase-shifted interference fringe images.
Here, the correction means will be described by taking four-stage phase shift digital holography (Non-Patent Document 2) as an example.

  The four-stage phase shift digital holography records four interference fringe images having a phase shift amount different by π / 2.

First, the phase φ _{R of the} reference light is set to 0, and one interference fringe image is recorded.

Next, the phase φ _R of the reference light is shifted by π / 2 by moving the mirrored piezo element, and an interference fringe image in which the phase of the reference light is shifted by π / 2, π, 3π / 2 is recorded. .
When it is assumed that the phase shift is accurately performed every π / 2 due to the movement of the piezo element, the phase distribution and the amplitude distribution of the object light on the imaging surface can be obtained by the four-stage phase shift calculation formula.

  Finally, Fresnel calculation is performed to calculate the phase distribution and amplitude distribution of the object light on the object plane, and display on the display unit (Non-Patent Document 2).

  However, there are many cases where the set phase cannot be accurately shifted due to the low operation accuracy of the piezo element and the characteristics of nonlinearity.

In this case, the phase shift amount of the reference light from the second sheet is not π / 2 but π / 2 + Δδ ₁ , π + Δδ ₂ , 3π / 2 + Δδ ₃ .
Δδ ₁ , Δδ ₂ , and Δδ ₃ are deviation amounts from the set phase shift amount, and cause an error when reproducing the amplitude / phase distribution of the object light.

  By substituting the phase shift amounts of these reference lights into Equation (3), new equations for calculating the phase distribution and amplitude distribution of the object light can be obtained from the simultaneous equations.

  In the case of 4-step phase shift digital holography, the phase distribution and amplitude distribution of the object light on the imaging surface are expressed by equations (4) and (5), respectively.

Here, the functions I of the first and second terms of M, and the first and second terms of N, respectively, change the phase of the reference light to 0, π + Δδ ₂ , 3π / 2 + Δδ ₃ , π / 2. + .DELTA..delta an interference fringe image data obtained by shifting the _1.

In the present invention, deviation amounts Δδ ₁ , Δδ ₂ , and Δδ ₃ with respect to the phase shift amount set from the stripe pattern recorded by the camera 2 are calculated using Equation (3), and a ₁ to. a ₄ is obtained.

By substituting the four phase-shifted interference fringe image data and a _{1 to} a ₄ into equations (4) and (5), the phase distribution and amplitude distribution of the object light on the imaging surface can be calculated.

  By performing the Fresnel calculation, the phase distribution and the amplitude distribution of the object light on the object plane are calculated and displayed on the display unit.

  The present invention is not limited to four-stage phase shift digital holography but can be applied to phase shift digital holography using all phase shift devices (Non-patent Document 3). Different phase shift methods have different phase shift calculation formulas for obtaining a phase distribution and an amplitude distribution. If the amount of phase shift deviation is known, it is substituted into the corresponding phase shift calculation formula, and the phase distribution and amplitude distribution of the object light are calculated using the new formula.

The system shown in FIG. 3 can perform the same function even with the configuration shown in FIGS.
FIG. 7B is a diagram in which a configuration for calculating a phase shift amount is extracted.
Further, in the measurement of the transmission object, the phase shift digital holography measurement according to the first embodiment of the present invention can be performed from the system configuration shown in FIG.

(Embodiment 2)
Embodiment 2 of the present invention will be described below with reference to the accompanying drawings.
FIG. 9 is a block diagram showing a schematic configuration of a digital holography measurement apparatus according to Embodiment 2 of the present invention.

This measuring device includes a light source, objective lenses 1 and 2, lenses 1 and 2, beam splitters 1 2, 3, 4 and 5, mirrors 1, 2, 3 and 4, cameras 1 and 2, a wedge prism, an object to be measured, A control unit, an arithmetic processing unit, and a display unit are provided.
In this measurement apparatus, the phase of the reference light is shifted using the thickness of the wedge prism.

In this system, the light incident on the camera 1 is the following two.
The light emitted from the light source is irradiated to the measurement target via the beam splitter 1, the objective lens 1, the lens 1, the beam splitter 2, and the mirror 2, and the reflected light from the measurement target is incident on the camera 1 as the object light S2. .

  The light emitted from the light source enters the camera 1 as reference light S1 through the beam splitter 1, mirror 1, wedge prism, objective lens 2, lens 2, and beam splitters 3 and 4.

On the other hand, the light incident on the camera 2 is the following two.
Light emitted from the light source enters the camera 2 as object light S4 through the beam splitter 1, the objective lens 1, the lens 1, the beam splitter 2, the mirror 3, and the beam splitter 5.

  The light emitted from the light source is incident on the camera 2 as reference light S3 via the beam splitter 1, mirror 1, wedge prism, objective lens 2, lens 2, beam splitter 3, mirror 4, and beam splitter 5. .

The phase of the reference light is shifted by changing the thickness of the wedge prism, and a plurality of phase-shifted interference fringe images are recorded by the camera 1 and the camera 2.
In the flow shown in FIG. 6, the phase distribution and amplitude distribution of the measurement target are calculated and displayed on the display unit.
FIG. 10 is a block diagram showing a schematic configuration when measuring transmitted light of the phase shift digital holography measuring apparatus according to the second embodiment of the present invention.

(Embodiment 3)
Embodiment 3 of the present invention will be described below with reference to the accompanying drawings.
FIG. 11 is a block diagram showing a schematic configuration of a phase shift digital holography measurement apparatus according to Embodiment 3 of the present invention.

This measuring device consists of a light source, objective lenses 1 and 2, lenses 1 and 2, beam splitters 1, 2, 3, 4 and 5, mirrors 1, 2, 3 and 4, camera 1, camera 2, and a quarter-wave plate. , A half-wave plate, a measurement target, a control unit, an arithmetic processing unit, and a display unit.
This measurement apparatus shifts the phase of the reference light by rotating the quarter wavelength plate and the half wavelength plate.

The following two lights are incident on the camera 1.
The light emitted from the light source passes through the polarizing plate and becomes linearly polarized light, which is irradiated onto the measurement target via the beam splitter 1, the objective lens 1, the lens 1, the beam splitter 2, and the mirror 2, and is reflected from the measurement target. Is incident on the camera 1 through the beam splitter 4 as object light S2.

  The light emitted from the light source is transmitted through the polarizing plate, the beam splitter 1, the mirror 1, the half-wave plate, the quarter-wave plate, the objective lens 2, the lens 2, and the beam splitters 3 and 4 and the reference light S1. Is incident on the camera 1.

On the other hand, the light incident on the camera 2 is the following two.
Light emitted from the light source passes through the polarizing plate and becomes linearly polarized light, and passes through the beam splitter 1, the objective lens 1, the lens 1, the beam splitter 2, the mirror 3, and the beam splitter 5 as object light S 4 to the camera 2. Incident.

  The light emitted from the light source passes through a polarizing plate, a beam splitter 1, a mirror 1, a half-wave plate, a quarter-wave plate, an objective lens 2, a lens 2, a beam splitter 3, a mirror 4, and a beam splitter 5. , And enters the camera 2 as reference light S3.

  By rotating the half-wave plate and the quarter-wave plate, the phase of the reference light is shifted, and a plurality of phase-shifted interference fringe images can be recorded by the camera 1 and the camera 2.

In the flow shown in FIG. 6, the phase distribution and amplitude distribution of the measurement target are calculated and displayed on the display unit.
FIG. 12 is a block diagram showing a schematic configuration when measuring transmitted light using the phase shift digital holography measuring apparatus according to Embodiment 3 of the present invention.

Example 1 based on Embodiment 1 shown in FIG. 8 will be described.
The measurement target is a flat object on which characters “AIST NDG” are printed, and the central portion is slightly curved toward the camera 1 side.

A laser light source having a wavelength of 633 nm was used as the light source.
The cameras 1 and 2 are provided with an image pickup element having a pixel number of 512 × 512 and a pixel size of 3.45 μm, and a reflection mirror including a fine movement mirror using a piezoelectric element.

  The distance from the measurement object to the camera 1 was set to 100 mm.

Using the above parameters, a computer simulation was performed as follows.
First, the amplitude and phase distribution of the object are generated by a computer.

By the Fresnel calculation, the object light from the object surface propagates a distance of 100 mm, and the amplitude and phase distribution of the object light on the imaging surface are obtained.
Interference with reference light having an initial phase value of 0 and an amplitude value of 1 generates a first interference fringe image.

Next, the phase of the reference light is shifted by (1 + 0.2 * rand) π / 2 to generate three interference fringe images.
Here, rand is a random number from 0 to 1.
That is, a maximum phase shift of 20% occurs.

(Validity check)
As a result of the prior art, in the measurement apparatus shown in FIG. 8, an image was reproduced from four phase-shifted holograms recorded by the camera 1 without correction.
In order to confirm the effectiveness of the present invention, it was compared with the results of the prior art.

(Evaluation result 1)
FIG. 13 shows luminance information of object images reproduced in the present invention and the prior art, respectively.
According to the present invention, the calculated shift amounts Δδ ₁ , Δδ ₂ , and Δδ ₃ of the phase shift were 0.32017 (radian), 0.0331 (radian), and 0.0842 (radian).

Mean square error (RMSE) calculations were performed for the present invention and the prior art.
The results are shown in Table 1.

In Table 1, amplitude RMSE and phase RMSE mean errors in amplitude information and phase information, and the smaller the numerical value, the higher the accuracy.
From this result, it can be seen that the measurement apparatus according to the present invention can obtain amplitude and phase information with higher accuracy than the prior art.

Example 2 based on Embodiment 1 as shown in FIG. 3 will be described.
The measurement target is the surface on which the number 1 of a 1-yen coin is written.

As the light source, a laser light source having a wavelength of 532 nm was used.
The cameras 1 and 2 are provided with an image sensor having a pixel number of 2448 × 2048 and a pixel size of 3.45 μm, and the reflection mirror includes a fine movement mirror using a piezo element.
The distance from the measurement object to the camera 1 was set to 198 mm.

  By moving the mirrored piezo element, four interference fringe images were recorded, and the images were reproduced and compared with the prior art and the inventive technique, respectively.

(Evaluation result 2)
FIG. 14 shows luminance information of an object image reproduced by the present invention and the prior art.
According to the present invention, the calculated shift amounts Δδ ₁ , Δδ ₂ , and Δδ ₃ of the phase shift were −0.5371 (radian), 0.6414 (radian), and 0.0128 (radian).

FIGS. 14A and 14B are all images reproduced by the present invention and the prior art.
FIGS. 14C and 14D are images enlarged by adjusting the contrast of the square portions of FIGS. 14A and 14B, respectively.
The experimental results obtained from the prior art have a lot of noise (conjugate image components), and the quality of the reproduced image is deteriorated.

FIG. 15 shows a comparison of pixel values in line segments MM ′ and NN ′ shown in FIGS. 14 (c) and 14 (d).
In the present invention in which accurate phase shift calculation is performed, the pixel value is low and the variation is small, so that it is understood that the conjugate component can be removed.

  From the above, it can be seen that the present invention can be used to correct the phase shift error and improve the quality of the reproduced image and the phase calculation accuracy.

  The objects to which the present invention can be applied include three-dimensional measurement of cells and living bodies, three-dimensional deformation measurement of semiconductors and materials, and inspection of thin film and fine processing in industrial fields such as microfabrication, biomedicine, material manufacturing, and electronic packaging. .

1 BS, BS1, BS2, BS3, BS4, BS5, BS6: Beam splitter 2 L, L1, L2: Lens 3 OB, OB1, OB2: Objective lens 4 M, M1, M2, M3, M4: Mirror 5 S1: Camera Reference light 6 incident on 1 S2: Object light 7 incident on the camera 1 S3: Reference light 8 incident on the camera 2 S4: Object light 9 incident on the camera 2 P: Polarizing plate 10 QWP: 1/4 wavelength plate 11 HWP: 1/2 wavelength plate 12 Control unit 13 Processing unit 14 Display unit 15 Light source 16 Piezo element 17 with mirror 17 Camera 1
18 Camera 2
19 Measurement object 20 Wedge prism

Claims (10)

The interference light 1 between the light emitted from the light source (hereinafter referred to as light source light) and the reference light from the phase shift device in which a predetermined phase shift amount is set to the phase of the light source light is changed in the predetermined phase shift amount. A phase shift digital holography method for analyzing the phase of the reference light from the interference fringe image 1 (multiple times is 1 to n times, where n is a natural number of 3 or more),
The method, wherein the predetermined phase shift amount set for the reference light is corrected by a phase shift amount obtained from the analysis of the interference fringe image 1.   The method of claim 1, wherein the phase shift digital holography is a four-stage phase shift digital holography, and the plurality of times is four times.   The method according to claim 2, wherein the phase shift device includes any one of a piezo element, a wedge prism, a quarter wavelength plate, and a half wavelength plate.   The method according to claim 3, wherein the phase shift amount is obtained by analyzing an interference fringe reflected in the interference fringe image 1 using a moire method.   Further, from the interference fringe image 2 obtained by irradiating the object light with the light source light and reflecting the interference light 2 between the object light reflected through the object and the reference light and the reference light, or a plurality of times by changing the predetermined phase shift amount, 5. A phase-shift digital holography method for reproducing a holographic image of the object using the phase of the reference light corrected by the phase shift amount analyzed by the method according to claim 1. .   The program according to any one of claims 1 to 4, wherein the analysis is executed, or a storage medium on which the program is recorded.   6. A phase shift digital holography method according to claim 5, wherein a holographic image of the object is reproduced, or a storage medium storing the program. A phase shift holographic image processing device comprising a light source, a beam splitter 1, a beam splitter 2, a phase shift device, and an image pickup device 1 for correction,
Light emitted from the light source (hereinafter referred to as light source light) is split into two light source lights by the beam splitter 2,
The light source light becomes reference light by a phase shift device in which a predetermined phase shift amount is set,
The light source light and the reference light are incident on a beam splitter 1 to become interference light 1,
The imaging device 1 captures the interference fringe image 1 from the interference light 1,
The phase according to any one of claims 1 to 4, wherein the predetermined phase shift amount set in the reference light is corrected with a phase shift amount obtained from the analysis. Shift holographic image processing device. 9. The image processing apparatus according to claim 8, further comprising a measurement imaging device connected to the beam splitter, a beam splitter for splitting a part of the light source light, and a beam splitter for splitting a part of the reference light. 4 and a display device,
The light source light spectrally separated by the beam splitter 3 becomes object light reflected on or transmitted through the object,
The object light and the reference light split by the beam splitter 4 are configured to enter the beam splitter 2 and become interference light 2,
In the image processing device, the holographic image 2 of the object reproduced by using the phase of the reference light corrected by the phase shift amount is displayed on the display device. A phase shift digital holography measuring device characterized by displaying. A phase shift digital holography measuring apparatus comprising the image processing apparatus according to claim 8.

Images