KR101858082B1 - An Improved Holographic Reconstruction Apparatus and Method - Google Patents

Abstract

The present invention discloses an improved holographic reconstruction apparatus and method.
A holographic reconstruction method according to the present invention comprises the steps of: a) acquiring an object hologram of an object to be measured; b) extracting the reference light information from the obtained object hologram; c) calculating a wavenumber vector constant of the extracted reference light information, and calculating a compensation term of the reference light information using the calculated wavenumber vector constant to generate a digital reference light; d) extracting aberration information from the object hologram and generating a digital curvature compensated for the aberration; e) calculating the compensated object hologram by multiplying the obtained hologram by the compensation term of the reference light information; f) extracting the phase information of the compensated object hologram; And g) calculating quantitative thickness information of the measurement object using the extracted phase information of the compensated object hologram and restoring the three-dimensional shape information of the measurement object and the quantitative thickness information .

Description

[0001] Improved Holographic Reconstruction Apparatus and Method [0002]

The present invention relates to an improved improved holographic reconstruction apparatus and method.

More specifically, the present invention relates to a method and apparatus for acquiring only one object hologram image, and obtaining three-dimensional shape information of an object using only the object hologram image obtained without using the reference hologram image and the digital reference light generated from the obtained object hologram, By restoring the quantitative thickness information, it is possible to solve the complicated optical device structure required at the time of restoring the one-shot type digital holography using the object hologram image of the prior art and the cost problem at a considerably high price, In particular, it is unnecessary to use the reference light when restoring the hologram, and it is possible to provide a quantitative three-dimensional image of the object to be measured in real time Since restoration is possible, TFT and It is applied to devices for detection, confirmation, or display of various fields including detection of defects in ultra-fine structures such as semiconductors, medical instruments requiring accurate three-dimensional image display, and refractive error detection of transparent objects such as other lenses And an improved holographic reconstruction apparatus and method.

A digital holography microscope is a microscope that measures the shape of an object using digital holography technology.

If a general microscope is a device that measures the shape of an object by measuring the intensity of light reflected or transmitted from an object by irradiating an ordinary light source to the object, the digital holography microscope can detect the interference and diffraction phenomenon of light, And digitally records the information, and restores the shape information of the object from the information.

That is, the digital holography technique generates light of a single wavelength such as a laser, divides the light into two lights using a light splitter, directs one light directly to the image sensor (referred to as a reference light) When the light reflected from the object to be measured is projected on the image sensor (referred to as object light) in the light of the object, the reference light and the object light interfere with each other in the image sensor. And the shape of the object to be measured is restored using the computer with the recorded interference fringe information. At this time, the recorded interference fringe information is generally referred to as a hologram.

On the other hand, in the case of a conventional optical holography technique other than digital holography, the interference fringe information of the light is recorded as a special film, and in order to restore the shape of the measurement object, the reference light is reflected on a special film on which interference fringes are recorded The shape of the virtual object to be measured is restored in the place where the object is originally located.

The digital holography microscope measures the interference fringe information of the light by a digital image sensor and stores the information in a digital manner when compared with the conventional optical holography method. The digital interference fringe information is stored in a numerical calculation method using a computer device So that the shape of the object to be measured is restored.

In a conventional digital holography microscope, a laser light source of a single wavelength may be used first. However, in the case of using a single laser light source, there is a problem that the measurement resolution of the object, that is, the minimum measurement unit is limited to the wavelength of the laser light source used. In the case of using a laser light source of two wavelengths or multiple wavelengths in a conventional digital holography microscope, the cost is increased by using light sources having different wavelengths, or sequentially obtaining hologram images using light sources of different wavelengths There is a problem that it is difficult to measure three-dimensional change information of an object to be measured in real time.

In addition, in the above-described conventional digital holography technique, a CGH (Computer Generated Hologram) is generated by a computer to restore the shape of an object to be measured, and then displayed on a spatial light modulator (SLM) , A three-dimensional hologram image of the object is obtained by diffraction of reference light. In this case, since it is required to use a spatial light modulator (SLM) of a high price (several tens of thousands or more), there is considerable difficulty in practical use.

As a method for solving the problems of the conventional digital holography technique described above, for example, a method of generating a digital holography microscope and a digital holographic image by Kim Eunsoo et al. On Sep. 5, 2014 is disclosed in Korean Patent Application No. 10 -2014-0119395 filed on March 15, 2016 (hereinafter referred to as " prior art disclosed ").

1 is a block diagram illustrating a two-wavelength digital holography microscope apparatus according to the prior art disclosed in detail.

1, a conventional two-wavelength digital holography microscope apparatus includes a mixed light source unit 100, a wavelength division unit 200, an interference fringe acquisition unit 300, an object unit 400, an image sensor unit 500 An image storage unit 600, a control unit 700, and an object shape restoration unit 800.

The mixed light source unit 100 includes a mixed light source unit 110 and a light source unit lens 120. The mixed light source unit 110 emits mixed light having a wavelength band distributed in a plurality of non-uniform bands. The light source lens 120 optically adjusts the mixed light generated by the mixed light source unit 110 and enters the wavelength division unit 200.

The wavelength dividing unit 200 includes a first light splitter 210, a first light guide plate 220, a second light guide plate 230, and a first reflector 240. The first light splitter 210 receives the mixed light from the mixed light source unit 100 and divides the mixed light into two lights. At this time, the first optical splitter 210 divides the incident mixed light into different directions. The first light guide plate 220 receives one of the light beams divided by the first light splitter 210 and acquires a first light beam having a predetermined single wavelength. Here, the light input to the first light guide plate 220 is filtered while passing through the first light guide plate 220, and a first light ray having a single wavelength determined according to the characteristics of the first light guide plate 220 is obtained. The second light guide plate 230 receives the other one of the light beams split by the first light splitter 210 in the same manner as the first light guide plate 220 and receives light of the second light guide plate 230 having a wavelength different from that of the first light beam. Obtain a ray of light. The second light beam is sent to the interference fringe obtaining unit 300. The first reflector 240 receives the first light beam obtained from the first light guide plate 220 and reflects the first light beam to the interference fringe obtaining unit 300.

The interference fringe obtaining unit 300 includes a second light splitter 310, a third light splitter 320, a second reflector 330, a third reflector 340, and a third reflector 350. The second light splitter 310 receives the first light beam input from the wavelength division unit 200 and divides the first light beam into the first object light and the first reference light. At this time, the second light splitter 210 divides the incident first rays into different directions and proceeds. The third light splitter 320 receives the second light ray in the same manner as the second light splitter 310 and divides the second light ray into the second object light and the second reference light. The second reflector 330 receives the first reference beam and transmits the first reference beam reflected by the second beam splitter 310 to the second beam splitter 310. The third light guide plate 340 receives the first reference light divided by the second light splitter 310 and transmits the first reference light to the second reflector 330 and transmits the first reflected reference light to the second light splitter. The third light guide plate 340 prevents the second object light from reaching the second reflector 330 when the second object light is incident on the second light splitter 310 and partly proceeds toward the second reflector 330 . For this purpose, the third light guide plate 340 is a light guide plate having the same characteristics as the first light guide plate 220 in transmitting light. The third reflector 350 receives the second reference light and transmits the second reflected reference light to the third optical splitter 320. The second reflector 330 and the third reflector 350 are connected to the controller 700 The angle of the hologram can be adjusted according to the control of the optical system. Thus, an off-axis hologram can be realized.

On the other hand, the first object light and the second object light obtained as described above are converted into the first reflected object light and the second reflected object light through the following process and sent to the image sensor unit 500. The second light splitter 310 separates the first object light divided as described above into an object to be measured which is placed on the object 400, And causes the light to enter the object to be measured. In this case, the reflected light that reflects the first object light incident from the measurement object is referred to as a first reflected object light. The reflected light that reflects the second object light incident on the object to be measured is referred to as a second reflected object light. The second light splitter 310 receives the first reflected object light and the second reflected object light reflected as described above and sends it to the third optical splitter 320. The third light splitter 320 transmits the first reflected object light and the second reflected object light received as described above to the image sensor unit 500 again.

In addition, the first and second reflection reference beams obtained as described above are sent to the image sensor unit 500 through the following process. Specifically, the second optical splitter 310 receives the first reflected reference light reflected by the second reflector 330 and transmits the first reflected reference light to the third optical splitter 320. The third light splitter 320 receives the first reflection reference light sent from the second light splitter 310 and the second reflection reference light reflected from the third reflector 350 as described above, Lt; / RTI > Accordingly, after the first reflected object light, the first reflected reference light, the second reflected object light, and the second reflected reference light are both transmitted in the direction of the image sensor unit 500 in the third optical splitter 320, An interference fringe is generated.

Meanwhile, the second reflector 330 and the third reflector 350 may have different angles according to the control of the controller 700 to form an off-axis system in which light beams of different wavelengths form different interference fringes. Can be adjusted in various directions. That is, as the angles of the second reflector 330 and the third reflector 350 are different from each other, the first and second reflectors 330 and 350 reflect the first and second reflectors 330 and 350, When the first reflection reference light and the second reflection reference light are combined with the first reflection object light and the second reflection object light arriving at the image sensor unit 500 to form an interference fringe, So that the interference fringes are differently formed.

The object unit 400 includes an object mount 410 and an objective lens 420. The object mount 410 allows measurement of an object to be measured by fixing it on a mount, and the objective lens 420 optically adjusts the first object light and the second object light incident on the object to be measured.

The image sensor unit 500 projects the interference fringes obtained from the interference fringe obtaining unit 300 to a digital image sensor, measures the projected interference fringes using the digital image sensor, . Normally, the recording of the interference fringe is referred to as a hologram. As such a digital image sensor, various image sensors such as a CCD can be used.

The image storage unit 600 stores the interference fringe information converted from the image sensor unit 500 into a discrete signal in various storage media such as a memory and a disk device.

The controller 700 controls the position and angle of the second reflector 330 and the third reflector 350 in order to implement the above-described off-axis system and obtain interference fringes. The interference fringe obtaining unit 300 Controls the objective part 400 to adjust the objective lens 420 to adjust the first object light and the second object light incident on the measurement object, and the interference fringe is measured, Controls the image sensor unit 500 to convert the information into a discrete signal, and controls the image storage unit 600 to store the interference fringe information converted into the discrete signal.

The object shape restoring unit 800 includes a phase information obtaining unit 810, a thickness information obtaining unit 820, and a shape restoring unit 830. The phase information obtaining unit 810 obtains the phase information of the interference fringe for the first light beam and the phase information of the interference fringe for the second light beam using the interference fringe information, The shape restoring unit 830 restores the real-time three-dimensional shape of the measurement object using the thickness information, and obtains the thickness information of the measurement object using the phase information. At this time, the thickness information of the object to be measured includes difference information between the paths of the object light and the reference light. The interference fringe is formed when the object light and the reference light overlap each other due to the optical path difference between the object light and the reference light.

In the above-described prior arts disclosed in the above-mentioned prior art, an effect of increasing the measurement resolution of the measurement object and restoring the three-dimensional shape information of the measurement object in real time by measuring and recording the hologram with respect to the measurement object in real time, However, the following problems still arise.

More specifically, in the disclosed prior art, a mixed light source having wavelength bands distributed in a plurality of unspecified bands is used. Therefore, in order to obtain at least two single wavelengths, the wavelength division part 200 is divided into a first The first light guide plate 220, the second light guide plate 230, and the first reflector 240 should be used to divide the light source and the second light source. The interference fringe obtaining unit 300 includes a third light splitter 320 for splitting the second light source, a third reflector 350 for reflecting the second light source, and a second reflector 330, It is necessary to additionally use a third light guide plate 340 for shielding incidence of light. Therefore, there is still a problem that the structure of the whole device is complicated, and the total manufacturing cost is high.

Accordingly, there is a need for a new method for solving the above-described problems while using a single wavelength light source.

1. Korean Patent Publication No. 10-2016-0029606 2. Korean Patent Publication No. 10-2010-0095302 3. Korean Patent Publication No. 10-2012-0014355 4. Korean Patent No. 10-1139178 5. Korean Patent No. 10-1441245 6. U.S. Patent No. 7,649,160

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional art, and it is an object of the present invention to provide a method and apparatus for acquiring only a single object hologram image and using only the object hologram image obtained without using the reference hologram image and the digital reference light generated from the obtained object hologram By restoring the three-dimensional shape information and the quantitative thickness information of the object, it is possible to solve the complicated optical device structure required for restoring the one-shot type digital holography using the one-object holographic image of the prior art, In addition, it is possible to perform holographic reconstruction with a simple structure and a low cost, and has versatility that can be applied to both the reflection type and transmission type hologram reconstruction apparatus of the prior art. In particular, it is unnecessary to use the reference hologram when restoring the hologram, Fixing of object Dimensional image reconstruction can be performed. Therefore, it is possible to detect defects in ultrafine structures such as TFTs and semiconductors, medical instruments requiring display of precise three-dimensional images, and detection of refractive error of transparent objects such as other lenses And an object of the present invention is to provide an improved holographic reconstruction apparatus and method that can be applied to various fields of detection, confirmation, or display apparatuses.

A holographic reconstruction apparatus according to a first aspect of the present invention includes: a light source unit that emits one wavelength light; A collimator for collimating the single wavelength light emitted from the light source; A light splitter for dividing the single-wavelength light having passed through the collimator into object light and reference light; An object optical objective lens for passing the object light split by the optical splitter; A reference light objective lens for passing the reference light split by the beam splitter; An optical mirror for reflecting the reference light having passed through the reference light objective lens; The object light passing through the object optical-objective lens, the object light reflected by the surface of the measurement object, and the reference light reflected by the optical mirror pass through the object-optical objective lens and the reference-light objective lens, A recording medium for recording a pattern; And a processor for receiving and storing the image file generated by converting the interference pattern on the recording medium, wherein the processor extracts the reference light information of the object hologram from the object hologram obtained from the image file to generate a digital reference light And reconstructs the three-dimensional information of the measurement object by calculating the compensated object hologram using the object hologram and the digital reference light and extracting the phase information of the compensated object hologram.

A holographic reconstruction apparatus according to a second aspect of the present invention includes: a light source unit that emits a single wavelength light; A collimator for collimating the single wavelength light emitted from the light source; A light splitter for dividing the single-wavelength light having passed through the collimator into object light and reference light; An object-optical objective lens for passing the object-transmitted light including the information of the object to be measured after the object light divided by the optical splitter reflects the object; A second optical mirror for reflecting the remaining light source except for the object reflected light that has passed through the object optical objective lens; A reference light objective lens for passing the reference light split by the beam splitter; A first optical mirror for reflecting the reference light having passed through the reference light objective lens; A second light splitter through which the reference light reflected by the first optical mirror and the object reflected light reflected by the second optical mirror are respectively transmitted; A recording medium for recording an interference fringe formed by the reference light and the object reflection light transmitted to the second optical splitter; And a processor for receiving and storing the image file generated by converting the interference pattern on the recording medium, wherein the processor extracts the reference light information of the object hologram from the object hologram obtained from the image file to generate a digital reference light And reconstructs the three-dimensional information of the measurement object by calculating the compensated object hologram using the object hologram and the digital reference light and extracting the phase information of the compensated object hologram.

A holographic reconstruction method according to a third aspect of the present invention comprises the steps of: a) acquiring an object hologram of an object to be measured; b) extracting the reference light information from the obtained object hologram; c) calculating a wavenumber vector constant of the extracted reference light information, and calculating a compensation term of the reference light information using the calculated wavenumber vector constant to generate a digital reference light; d) extracting aberration information from the object hologram and generating a digital curvature compensated for the aberration; e) calculating the compensated object hologram by multiplying the obtained hologram by the compensation term of the reference light information; f) extracting the phase information of the compensated object hologram; And g) calculating quantitative thickness information of the measurement object using the extracted phase information of the compensated object hologram and restoring the three-dimensional shape information of the measurement object and the quantitative thickness information .

The following advantages are achieved by using the improved holographic reconstruction apparatus and method according to the present invention described above.

1. It is possible to solve a complicated optical device structure required for restoration of a one-shot type digital holography using a single object hologram image of the related art, and a considerably high cost problem associated therewith.

2. Holographic reconstruction is possible with simple structure and low cost.

3. It has versatility that can be applied to both the reflection type and transmission type hologram restoration apparatus of the prior art.

4. Especially, it is unnecessary to reconstruct the hologram, and quantitative 3D reconstruction of the object can be performed in real time.

5. Detection, confirmation, or display of various fields including detection of defects in ultra-fine structures such as TFTs and semiconductors, detection of refractive errors of transparent objects such as medical devices requiring display of precise three-dimensional images, and other lenses It is possible to apply to the device.

Further advantages of the present invention can be clearly understood from the following description with reference to the accompanying drawings, in which like or similar reference numerals denote like elements.

1 is a block diagram illustrating a two-wavelength digital holography microscope apparatus in accordance with the disclosed prior art.
2A is a schematic block diagram of a holographic reconstruction apparatus according to a first embodiment of the present invention.
2B is a schematic block diagram of a holographic reconstruction apparatus according to a second embodiment of the present invention.
2C is a view showing an object hologram of a thin film transistor (TFT) according to an embodiment of the present invention.
2D is a view showing a digital reference light which is a compensation term obtained by calculating a wavenumber vector constant from reference light information of an object hologram extracted using an automatic real image coordinate information extraction algorithm in an object hologram of the thin film transistor (TFT) shown in FIG. 2C .
FIG. 2E is a view showing a reconstructed image of a three-dimensional shape of an object to be measured in a state where aberration correction of an object optical objective lens is not performed.
FIG. 2F is a view showing a reconstructed image of a three-dimensional shape of an object to be measured in a state where aberration correction of an object optical objective lens is performed.
FIG. 2G is a view showing a three-dimensional shape restored image of the thin film transistor (TFT) shown in FIG. 2C having quantitative thickness information calculated using the extracted phase information of the object hologram compensated according to the present invention.
3 is a flowchart of a holographic reconstruction method according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments and drawings of the present invention.

2A is a schematic block diagram of a holographic reconstruction apparatus according to a first embodiment of the present invention.

Referring to FIG. 2A, a holographic reconstruction apparatus 1a according to a first embodiment of the present invention includes a light source unit 10 that emits single-wavelength light; A collimator (20) for collimating the single wavelength light emitted from the light source part (10); A light splitter 30 for splitting the single-wavelength light having passed through the collimator 20 into object light O and reference light R; An object optical objective lens (40) for passing the object light (O) divided by the light splitter (30); A reference light objective lens 60 for passing the reference light R divided by the light splitter 30; An optical mirror 70 for reflecting the reference light R having passed through the reference light objective lens 60; The object light O reflected by the surface of the measurement object 50 passing through the object optical objective lens 40 and the reference light R reflected by the optical mirror 70 are reflected by the object light- 40 and a reference light objective lens 60 to the optical splitter 30 to record an interference fringe formed thereon; And a processor (90) for receiving and storing an image file generated by converting the interference fringe on the recording medium (80), wherein the processor (90) is adapted to receive the object hologram from the object hologram obtained from the image file Extracts the reference light information to generate a digital reference light, calculates a compensated object hologram using the object hologram and the digital reference light, extracts phase information of the compensated object hologram, Is restored.

2B is a schematic block diagram of a holographic reconstruction apparatus according to a second embodiment of the present invention.

Referring to FIG. 2B, the holographic reconstruction apparatus 1b according to the second embodiment of the present invention includes a light source unit 10 that emits single-wavelength light; A collimator (20) for collimating the single wavelength light emitted from the light source part (10); A light splitter 30 for splitting the single-wavelength light having passed through the collimator 20 into object light O and reference light R; The object light O that has been split by the light splitter 30 passes through the measurement object 50 and then passes through the object transmitted light T containing the information of the measurement object 50. [ (40); A second optical mirror (72) for reflecting the object transmitted light (T) passing through the object optical objective lens (40); A reference light objective lens 60 for passing the reference light R divided by the light splitter 30; A first optical mirror 70 for reflecting the reference light R having passed through the reference light objective lens 60; A second light splitter (32) through which the reference light (R) reflected by the first optical mirror (70) and the object transmitted light (T) reflected by the second optical mirror (72) are respectively transmitted; A recording medium (80) for recording an interference fringe formed by the reference light (R) and the object light transmission light (T) transmitted to the second light splitter (32); And a processor (90) for receiving and storing an image file generated by converting the interference fringe on the recording medium (80), wherein the processor (90) is adapted to receive the object hologram from the object hologram obtained from the image file Extracts the reference light information to generate a digital reference light, calculates a compensated object hologram using the object hologram and the digital reference light, extracts phase information of the compensated object hologram, Is restored.

The holographic reconstruction apparatus 1a according to the first embodiment of the present invention and the holographic reconstruction apparatus 1b according to the second embodiment of the present invention, which are shown in FIGS. 2A and 2B, (The embodiment of FIG. 2A) or the object light O is transmitted through the measurement object 50 (the embodiment of FIG. 2B) by the measurement object 50, With the exception of the additional use of the second optical mirror (72) and the arrangement of some of the components therefrom (e.g., the second optical mirror (72) and the second optical splitter (32) of the embodiment of Figure 2b) It should be noted that the interference fringe recorded on the recording medium 80 and recorded has the same feature in that it generates the digital reference light from the object hologram obtained in the form of an image file by the processor 90. Hereinafter, the holographic reconstruction apparatuses 1a and 1b according to the first and second embodiments of the present invention will be collectively referred to as a holographic reconstruction apparatus 1 according to an embodiment of the present invention.

The processor 90 of the holographic reconstruction apparatus 1 according to the embodiment of the present invention is implemented as an apparatus capable of performing arithmetic operations such as a microprocessor and a PC (Personal Computer) For example, an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complimentary Metal-Oxide Semiconductor).

Further, the information of the object hologram obtained by the processor 90 of the holographic reconstruction apparatus 1 according to the embodiment of the present invention described above can be obtained by correcting the wavelength and phase information of the object and the aberration of the object- And may additionally include noise (e.g., speckle noise due to photon use of the laser, etc.).

The object hologram obtained by the processor 90 of the holographic reconstruction apparatus 1 according to the embodiment of the present invention may be expressed as Equation 1 with a complex conjugate hologram.

Equation 1: | U _o (x, y, 0) | ² = | O (x, y) | ² + | R (x, y) | ^{2 + O * (x, y} ) R R * (x, y) + O (x, y) (x, y)

In the above formula 1 x and y represent the spatial _{coordinates, U o (x, y,} 0) represents the acquired object hologram, O (x, y) and R (x, y) is the optical (O), each object And O ^* (x, y) and R ^* (x, y) represent the complex conjugate of the object light O and the reference light R, respectively.

Hereinafter, a specific method of generating the digital reference light and the compensated object hologram from the obtained object hologram will be described.

First, the processor 90 of the holographic reconstruction apparatus 1 according to the embodiment of the present invention acquires an object hologram from the image file of the interference fringe recorded on the recording medium 80 (see FIG. 2C) Transistor (TFT)). The obtained object hologram is composed of the object light O having the phase information of the object and the interference pattern of the reference light R without phase information of the object.

Then, a 2D Fourier transform is performed on the obtained object hologram to extract the information of the reference light R having no phase information of the object in the acquired object hologram. The frequency spectrum of the object hologram obtained by the two-dimensional Fourier transform is obtained by dividing the spectral information including the real image spot-position, the spectral information including the imaginary image spot-position, ), Respectively. Only the separated real image coordinate information is extracted using the automatic real image spot-position extraction algorithm in the frequency spectrum. And extracts the reference light information of the obtained object hologram using the extracted real image coordinate information.

Thereafter, the extracted reference light information of the processor 90 may have a phase discontinuity at every 2 [pi] due to the oscillation of the light. To compensate for the phase discontinuity, a Wavenumber algorithm The wavenumber vector constant of the reference light information is calculated. And calculates a compensation term (Term) of the extracted reference light information using the calculated wavenumber vector constant. The compensation term of the extracted reference light information calculated from the wavenumber vector constant is a conjugate of the obtained reference light information of the object hologram. The calculated compensation term of the extracted reference light information is referred to as a digital reference light (refer to FIG. 2D).

Equation _{2: R c (x, y} ) = conj [R (x, y)]

In the formula 2, wherein R _c (x, y) is the digital reference light, R (x, y) is the reference light information of the acquired object hologram, conj is a function to obtain the pair wherein (Conjugate) of a complex number.

The processor 90 then extracts the aberration information in the object hologram to compensate for the curvature aberration of the object optical objective 40 used to acquire the object hologram. Thereafter, the processor 90 generates the curvature aberration information compensation term using an automatic frequency curvature compensation algorithm. Herein, the curvature aberration information compensation term is referred to as a digital curvature.

Thereafter, the processor 90 calculates the compensated object hologram by multiplying the obtained object hologram by the compensation term of the extracted standard light information. This is expressed by Equation 3.

Equation _{3: U C (x, y} , 0) = O (x, y) R * (x, y) R C (x, y) R CA (x, y)

In the formula _{3, U C (x, y} , 0) is a compensation object hologram, O (x, y) and R ^* (x, y) is the object light and reference light of the object hologram obtained, respectively, R _C (x, y) is a digital reference light, and R _CA (x, y) is a digital curvature.

Thereafter, the processor 90 converts the compensated object hologram into information of a reconstruction image plane using an Angular Spectrum Propagation algorithm. Here, the restored image plane means a virtual image display plane by a distance corresponding to the distance between the measurement object 50 and the recording medium 80 by the processor 90, and is calculated by the processor 90 And can be simulated. The processor 90 extracts the phase information of the compensated object hologram through an inverse 2D Fourier transform. It should be noted that in the extracted phase information, the information of the light and the aberration information of the objective lens are removed in the obtained hologram, and thus the phase information of the extracted compensated hologram includes only the phase information of the object.

Thereafter, the processor 90 calculates the quantitative thickness information of the measurement object 50 using the extracted phase information of the compensated object hologram. In this case, the processor 90 may additionally include fine noise, such as speckle noise, etc., associated with the photon usage of the laser, for example, the extracted phase information of the compensated object hologram, Such fine noise can be removed in advance before the quantitative thickness information of the object 50 is calculated. Specifically, the processor 90 uses the 2D phase unwrapping algorithm to extract distorted phase information due to the fine noise and the wrapped phase phenomenon from the extracted phase information of the object hologram You can compensate. When the distorted phase information caused by the fine noise and the wrapped phase phenomenon is removed, the quantitative thickness information of the measurement object 50 can be calculated more precisely based on the phase information of the compensated object hologram . Quantitative thickness information of the measurement object 50 calculated in the above-described manner is expressed by the following Equation 4.?

(X, y) / 2 & circ & n (x, y)

In the formula 4, △ L is quantitative thickness information of the measurement object (50), λ is the wavelength of the light source unit 10 used at the time of obtaining the object hologram, and φ (x, y) is the phase information of the compensated object hologram, (X, y) means a refractive index difference between the background and (or air) the object 50 to be measured. The processor 90 restores the three-dimensional shape of the measurement object 50 on the reconstructed image plane using the quantitative thickness information of the measurement object 50 calculated according to Equation (4) above. The reconstructed image plane reconstructed by the processor 90 may be displayed on, for example, a separate monitor (not shown).

Figs. 2E and 2F show the three-dimensional reconstructed image of the measurement object 50 in a state in which the aberration correction of the object optical objective 40 is not performed and the aberration correction of the object optical objective 40 The reconstructed image of the three-dimensional shape of the measurement object 50 of the measurement object 50 is shown. Also, FIG. 2G shows a three-dimensional shape restored image of the thin film transistor (TFT) shown in FIG. 2C having quantitative thickness information calculated using the extracted phase information of the object hologram compensated according to the present invention. It can be seen from the reconstructed image shown in FIGS. 2F and 2G that the three-dimensional shape of the semiconductor substrate circuit shown in FIG. 2C is clearly restored.

3 is a flowchart of a holographic reconstruction method according to an embodiment of the present invention.

Referring to FIG. 3 together with FIGS. 2A to 2G, a method 300 of holographic reconstruction according to an embodiment of the present invention includes the steps of: a) obtaining an object hologram of an object 50 to be measured (S1); b) extracting reference light information from the acquired object hologram (S2); c) calculating a wavenumber vector constant of the extracted reference light information, and calculating a compensation term of the reference light information using the calculated wavenumber vector constant to generate a digital reference light (S3); d) extracting the aberration information from the object hologram and generating a digital curvature compensated for the aberration (S4); e) calculating the compensated object hologram by multiplying the obtained hologram by the compensation term of the reference light information (S5); f) extracting phase information of the compensated object hologram (S6); And g) calculating quantitative thickness information of the measurement object (50) using the extracted phase information of the compensated object hologram (50) to determine three-dimensional shape information of the measurement object (50) (Step S7).

(A1) is performed by a1) subjecting the single wavelength light emitted from the light source unit 10 to the object light O and the object light O2 by the light splitter 30, and the holographic reconstruction method 300 according to an embodiment of the present invention, Into a reference light (R); a2) The divided object light O is reflected on the surface of the object 50 through the object optical objective 40 and the split reference light R is passed through the reference light objective 60 And then reflected by the optical mirror 70; a3) recording the interference fringe formed by transmitting the reflected object light O and the reflected reference light R to the optical splitter 30 in the recording medium 80, and converting the interference fringe Transmitting an image file to the processor 90; And a4) acquiring the object hologram from the image file by the processor (90).

Alternatively, in the holographic reconstruction method 300 according to an embodiment of the present invention, the step a) may include: a1) performing a single light beam emitted from the light source part 10 by an optical splitter 30, (O) and a reference light (R); a2) passing object light (O) obtained through transmission of the object light (O) through the object to be measured (50) through an object light objective lens (40) Passing the divided reference light (R) by the optical mirror (72) through the reference light objective (60) and reflecting it by the optical mirror (70); a3) transmitting an interference fringe formed by transmitting the reflected object transmitted light (T) and the reflected reference light (R) to a second light splitter (32), recording the interference fringe on the recording medium (80) To the processor (90); And a4) acquiring the object hologram from the image file by the processor (90).

In addition, in the holographic reconstruction method (300) according to an embodiment of the present invention, the step b) includes: b1) performing a 2D Fourier transform on the obtained object hologram; b2) spectral information obtained by the two-dimensional Fourier transform and including real image spot-position of the object hologram, spectral information including imaginary image spot-position, and direct current information Extracting only real-world coordinate information using an automatic real-image spot-position extraction algorithm in a frequency spectrum including spectral information including direct current (DC); And b3) extracting the obtained reference light information of the object hologram using the extracted real image coordinate information.

In addition, the above described calculation of compensation term is the digital reference light into a pair wherein (Conjugate) in the obtained object hologram in the graphic restoration method 300 alone, according to an embodiment of the invention, step c), expression in R _c (x, y) = conj is represented by [R (x, y)] , where R _c (x, y) is the digital reference light, R (x, y) is the reference light information of the object hologram the obtained And conj is a function to obtain the conjugate of a complex number.

Further, in the graphic restoration method 300 alone in accordance with one embodiment of the invention, the e) of the compensated object holograms calculated in the step is a formula U _C (x, y, 0) = O (x, y) R _{^{* (x, y) R C}} (x, y) R CA (x, y) is represented by where U _C (x, y, 0) is the compensated object hologram, O (x, y) and R ^* (x, y) are respectively the object beam (O) and the reference light (R) of the obtained object hologram, R _C (x, y) is the digital reference light, R _CA (x, y) is the Digital curvature.

Also, in the holographic reconstruction method 300 according to an exemplary embodiment of the present invention, the phase information of the compensated object hologram of step f) is extracted through an inverse 2D Fourier transform, The extracted phase information includes only the phase information of the measurement object 50 by removing the information of the light and the aberration information of the objective lens in the obtained object hologram. The step (f) may further include the step of removing the fine noise using a 2D phase unwrapping algorithm when the phase information of the compensated object hologram includes fine noise. .

In the holographic reconstruction method 300 according to an exemplary embodiment of the present invention, the quantitative thickness information calculated in step g) is expressed by the following equation: DELTA L = [lambda] (x, y) / 2 [ , y) , where DELTA L is the quantitative thickness information of the object 50, lambda is the wavelength of the light source used in acquiring the object hologram, and phi (x, y) is the phase of the compensated object hologram Information ,? N (x, y) is a refractive index difference.

As described above, in the improved holographic reconstruction apparatus 1 and method 300 according to the present invention, only the object hologram obtained using the processor 90 and the digital reference light generated from the obtained object hologram are used Dimensional information of the object 50 to be measured can be reconstructed, thereby solving the complicated optical device structure required for restoration of the one-shot type digital holography using the object holographic image of the prior art, and accordingly, a considerably high cost problem .

In addition, in the improved holographic reconstruction apparatuses 1 and 300 according to the present invention, the holographic reconstruction apparatus 1 additionally uses only the processor 90, so that the entire configuration is very simple, Can be restored.

Further, in the improved holographic reconstruction apparatus 1 and method 300 according to the present invention, since the other components except for the processor 90 have substantially the same configuration as the reflection type and transmission type hologram reconstruction apparatus of the related art , And has general versatility that can be easily applied to both the reflection type and transmission type hologram restoration apparatus of the related art.

In the improved holographic reconstruction apparatus 1 and method 300 according to the present invention, unlike the conventional art, the use of the reference hologram is unnecessary in restoring the hologram, and the quantitative 3D image restoration is possible.

Further, in the improved holographic reconstruction apparatus 1 and method 300 according to the present invention, as described above, it is possible to quantitatively reconstruct a three-dimensional image of a specific object 50 in real time without using a reference hologram Detection, confirmation, or display of various fields including detection of defects in ultra-fine structures such as TFTs and semiconductors, medical instruments requiring display of precise three-dimensional images, and refractive index error detection of transparent objects such as other lenses Applicable to devices.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to be illustrative, of illustration, and not limitative of the invention, as various changes may be made therein without departing from the scope of the invention. It is not. Accordingly, the scope of the present invention should not be limited by the above-described exemplary embodiments, but should be determined only in accordance with the following claims and their equivalents.

1, 1a and 1b: holographic restoration device 10: light source part 20: collimator
30, 32: light splitter 40: object optical objective lens 50: object to be measured
60: reference light objective lens 70, 72: optical mirror 80: recording medium
90: Processor 100: Mixed light source unit 110: Mixed light source unit
120: light source lens 200: wavelength division part 210: first light splitter
220: first light guide plate 230: second light guide plate 240: optical mirror
300: interference pattern obtaining unit 310: second optical splitter 320: third optical splitter
330: second reflector 340: third reflector 350: third reflector 400:
410: object holder 420: objective lens 500: image sensor unit
600: image storage unit 700: control unit 800: object shape restoration unit
810: Phase information obtaining unit 820: Thickness information obtaining unit 830:

Claims (19)

In the holographic reconstruction apparatus,
A light source portion emitting a single wavelength light;
A collimator for collimating the single wavelength light emitted from the light source;
A light splitter for dividing the single-wavelength light having passed through the collimator into object light and reference light;
An object optical objective lens for passing the object light split by the optical splitter;
A reference light objective lens for passing the reference light split by the beam splitter;
An optical mirror for reflecting the reference light having passed through the reference light objective lens;
The object light passing through the object optical-objective lens, the object light reflected by the surface of the measurement object, and the reference light reflected by the optical mirror pass through the object-optical objective lens and the reference-light objective lens, A recording medium for recording a pattern; And
A processor for receiving and storing an image file generated by converting the interference fringe in the recording medium,
, ≪ / RTI &
The processor extracts the reference light information of the object hologram from the object hologram obtained from the image file to generate a digital reference light, calculates a compensated object hologram using the object hologram and the digital reference light, Dimensional information of the object to be measured is extracted by extracting the phase information
A holographic restoration device. In the holographic reconstruction apparatus,
A light source portion emitting a single wavelength light;
A collimator for collimating the single wavelength light emitted from the light source;
A light splitter for dividing the single-wavelength light having passed through the collimator into object light and reference light;
An object-optical objective lens for passing object-transmitted light including information of the object to be measured after the object light split by the optical splitter passes through the object;
A second optical mirror for reflecting the object-transmitted light that has passed through the object-optical objective lens;
A reference light objective lens for passing the reference light split by the beam splitter;
A first optical mirror for reflecting the reference light having passed through the reference light objective lens;
A second optical splitter through which the reference light reflected by the first optical mirror and the object transmitted light reflected by the second optical mirror are respectively transmitted;
A recording medium for recording an interference fringe formed by the reference light and the object transmitted light transmitted to the second optical splitter; And
A processor for receiving and storing an image file generated by converting the interference fringe in the recording medium,
, ≪ / RTI &
The processor extracts the reference light information of the object hologram from the object hologram obtained from the image file to generate a digital reference light, calculates a compensated object hologram using the object hologram and the digital reference light, Dimensional information of the object to be measured is extracted by extracting the phase information
A holographic restoration device. 3. The method according to claim 1 or 2,
Wherein the processor is configured to: i) perform a 2D Fourier Transform on the obtained object hologram, obtain a 2D Fourier transform of the object hologram, and include a real image spot-position of the object hologram An automatic real image spot extracting algorithm is used in a frequency spectrum including spectral information, spectral information including imaginary image spot-position, and spectral information including direct current (DC) extracting only the real-world coordinate information using a position-extraction algorithm, and iii) extracting the reference light information of the obtained object hologram using the extracted real-world coordinate information to extract the reference light information. 3. The method according to claim 1 or 2,
Wherein the processor is configured to: i) calculate a wavenumber vector constant of the extracted reference light information, ii) calculate a compensation term of the extracted reference light information using the calculated wavenumber vector constant to generate the digital reference light, . 5. The method of claim 4,
And it said digital reference light is formula _{R c (x, y) =} conj is represented by [R (x, y)] , where R _c (x, y) is the digital reference light, R (x, y) is the acquired Is the reference light information of the object hologram, and conj is a function of finding the conjugate of the complex number. 5. The method of claim 4,
The processor extracts aberration information in the object hologram to compensate for the curvature aberration of the object optical objective lens and then generates a digital curvature that is a curvature aberration information compensation term using an automatic frequency curvature compensation algorithm Lt; / RTI > The method according to claim 6,
Wherein the compensated object hologram is calculated by multiplying the obtained object hologram by the calculated compensation term of the extracted reference light information. 8. The method of claim 7,
The compensated object hologram is represented by the formula _{U C (x, y, 0} ) = O (x, y) R * (x, y) R C (x, y) R CA (x, y), where U _C (x, y, 0) is the compensated object hologram, O (x, y) and R ^* (x, y) is the obtained object, the object beam (O) and the reference light (R) of the hologram, respectively , Wherein R _C (x, y) is the digital reference light and R _CA (x, y) is the digital curvature. 3. The method according to claim 1 or 2,
The processor converts the compensated object hologram into information of a reconstruction image plane using an Angular Spectrum Propagation algorithm and performs inverse 2D Fourier transform Dimensional information of the measurement object and quantitative thickness information of the measurement object by extracting phase information of the compensated object hologram and calculating quantitative thickness information of the measurement object using the extracted phase information, Graphics restoration device. 10. The method of claim 9,
The quantitative thickness information expression △ L = λ △ φ (x , y) / 2π △ n (x, y) is represented by, where △ L is the quantitative thickness information, λ is the light source wavelength, △ φ (x, y) is the phase information of the compensated object hologram, and Δn (x, y) is the difference between the refractive indices of the object and the air. In the holographic reconstruction method,
a) obtaining an object hologram of an object to be measured;
b) extracting the reference light information from the obtained object hologram;
c) calculating a wavenumber vector constant of the extracted reference light information, and calculating a compensation term of the reference light information using the calculated wavenumber vector constant to generate a digital reference light;
d) extracting aberration information from the object hologram and generating a digital curvature compensated for the aberration;
e) calculating the compensated object hologram by multiplying the obtained hologram by the compensation term of the reference light information;
f) extracting the phase information of the compensated object hologram; And
g) reconstructing the three-dimensional shape information and the quantitative thickness information of the measurement object by calculating quantitative thickness information of the measurement object using the extracted phase information of the compensated object hologram
The holographic reconstruction method comprising: 12. The method of claim 11,
The step a)
a1) dividing the single wavelength light emitted from the light source part into object light and reference light by a light splitter;
a2) reflecting the divided object light through the object-optical objective lens on the surface of the object to be measured, passing the divided reference light through the reference light objective lens, and then reflecting the divided reference light by the optical mirror 70;
a3) recording an interference fringe formed by transferring the reflected object light and the reflected reference light to the optical splitter on a recording medium, and transmitting the generated image file to the processor by converting the fringe pattern; And
a4) acquiring the object hologram from the image file by the processor
The holographic reconstruction method comprising: 12. The method of claim 11,
The step a)
a1) dividing the single wavelength light emitted from the light source part into object light and reference light by a light splitter;
a2) passing the object light transmitted through the object to be measured through the object optic objective lens, passing the object light through the object optical lens, reflecting the object transmitted light by the second optical mirror, Passing the light through an optical mirror and reflecting it by an optical mirror;
a3) recording an interference fringe formed by transmitting the reflected object transmitted light and the reflected reference light to a second optical splitter on a recording medium, and converting the fringe pattern to transmit the generated image file to a processor; And
a4) acquiring the object hologram from the image file by the processor
The holographic reconstruction method comprising: 12. The method of claim 11,
The step b)
b1) performing a 2D Fourier transform on the obtained object hologram;
b2) spectral information obtained by the two-dimensional Fourier transform and including real image spot-position of the object hologram, spectral information including imaginary image spot-position, and direct current information Extracting only real-world coordinate information using an automatic real-image spot-position extraction algorithm in a frequency spectrum including spectral information including direct current (DC); And
b3) extracting the obtained reference light information of the object hologram using the extracted real image coordinate information
The holographic reconstruction method comprising: 12. The method of claim 11,
The calculated compensation, wherein in step c) is labeled, and the digital reference light into a pair wherein (Conjugate) in the obtained object hologram, expression _{R c (x, y) =} conj [R (x, y)] , where R _c (x, y) is the digital reference light, R (x, y) is the reference light information from the obtained object hologram, conj is alone is a function to obtain the pair wherein (Conjugate) of complex graphic restoration method . 12. The method of claim 11,
The said compensation object hologram is computed in the e) step is formula _{U C (x, y, 0} ) = O (x, y) R * (x, y) R C (x, y) R CA (x, y ) is represented by where U _C (x, y, 0) is the compensated object hologram, O (x, y) and R ^* (x, y) is the optical (O the object of the obtained object holograms each ) and the reference light (R) and, R _C (x, y) is the digital reference light, _CA R (x, y) is a graphical method alone restore the said digital curvature. 12. The method of claim 11,
The phase information of the compensated object hologram in step f) is extracted through an inverse 2D Fourier transform, and the extracted phase information is obtained by adding information of the light and aberration of the objective lens in the obtained object hologram Information is removed, and only the phase information of the object is included. 18. The method of claim 17,
Wherein the step (f) comprises: if the phase information of the compensated object hologram includes a fine noise and a wrapped phase phenomenon, the fine noise and phase folding using a 2D phase unwrapping algorithm And removing the wrapped phase phenomenon. 12. The method of claim 11,
Wherein g) said quantitative thickness information calculated in the step is represented by the formula △ L = λ △ φ (x , y) / 2π △ n (x, y), where △ L is the quantitative thickness information, λ is wavelengths of the object light source used at the time of the hologram obtained, △ φ (x, y) is how the phase information, △ n (x, y) is a hole in the refractive index difference between the air and the measured object graphic restoration of the compensated object hologram.

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