KR102373935B1 - An Improved Holographic Reconstruction Apparatus and Method - Google Patents

Abstract

The disclosed holographic restoration apparatus includes: a first light splitter for splitting a single wavelength light from a light source into first and second transmitted split light; a plurality of optical mirrors reflecting the first transmitted split light; a second light splitter dividing the second transmitted split light into first and second reflected split lights; a reference light objective lens through which the second reflection split light passes; a positioning mirror through which the first reflected split light passing through the reference light objective lens is transmitted; The first transmitted split light passing through the measurement target object or the first reflected split light reflected from the measurement target object passes through the object light objective lens, and the second reflected split light reflected by the positioning mirror is a recording medium for recording an interference fringe formed by passing through the reference light objective lens and being transmitted to the second light splitter; and a processor for receiving and storing the image file generated by converting the interference fringe, wherein the light transmission or reflection object hologram is selectively acquired according to the mode. Various embodiments are possible.

Description

An Improved Holographic Reconstruction Apparatus and Method

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

More specifically, the present invention is an integrated system that integrates a transmission type system for measuring an object that transmits light and a reflection type system for measuring an object that reflects light. An improved hologram restoration apparatus and method capable of measuring digital holograms regardless of characteristics.

As is well known, holography is an imaging method devised for the purpose of improving the resolving power of an electron microscope, whereas conventional photography records only the distribution of the light and dark sides of an object, whereas holography is a wave of all information that light has. , that is, the amplitude and phase are simultaneously accumulated and reproduced. The principle is that the coherent light from the laser light source divides the beam splitter into two and one of them illuminates the subject. The reflected light reaches the holographic photosensitive material. This light beam is called object light. The other ray is diffused through the lens and directly illuminates the entire surface of the holographic photosensitive material. This light beam is called reference light or reference light (hereinafter referred to as "reference light"). In this way, the object light and the reference light interfere with each other on the holographic photosensitive material, creating a very delicate and complex interference pattern of about 500 to 1500 per 1 mm. A photograph in which the interference fringes are recorded is called a hologram. When the hologram made in this way is irradiated with the same light as the reference light, the interference pattern acts as a diffraction grating and the light is diffracted at a different location from the direction in which the reference light is incident. become together In this way, the first object light is reproduced in the hologram.

Therefore, if you look inside the regenerated wavefront, you can see the first object, but it looks as if the object is inside. Then, if you move the viewing point again, the position at which the object is visible also changes, so it looks as if you are looking at a three-dimensional picture. In addition, since the wavefront of the original object is regenerated, it can interfere with the wavefront from an object that is slightly deformed. Accordingly, such characteristics of holography have been applied and used in various fields.

For example, a digital holographic microscope is a microscope that measures the shape of an object using digital holography technology. A general microscope uses a general light source to illuminate an object and measure the intensity of light reflected or transmitted from the object to measure the shape of the object. If it is a measuring device, a digital holographic microscope is a device that measures the interference and diffraction of light that occurs when light is shined on an object, records it digitally, and restores the shape information of the object from this information.

In other words, digital holography technology generates light of a single wavelength, such as a laser, and splits it into two lights using a light splitter. One light (reference light) illuminates the image sensor directly, and the other light (object light) As the light transmitted or reflected from the measurement target is illuminated by the measurement target object, the image sensor causes interference between the reference light and the object light, and the interference pattern information of the light is recorded with the digital image sensor It is a technology for restoring the shape of a measurement target object by using a computer with the recorded interference fringe information.

On the other hand, in the case of the conventional optical holography technology, not digital holography, the interference fringe information of the light is recorded with a special film, and the reference light is irradiated onto the special film on which the interference fringe is recorded in order to restore the shape of the object to be measured. This is a method in which the shape of the virtual measurement object is restored to the location where the measurement object was originally located.

Compared with the conventional optical holography method, the digital holographic microscope measures the interference fringe information of light with a digital image sensor and stores it digitally, and the stored interference fringe information is numerically calculated using a computer device rather than an optical method. It is different in that it restores the shape of the object to be measured by processing it through

In a conventional digital holographic microscope, a laser light source of a single wavelength may be used first. However, when using a single laser light source, there is a problem in that the measurement resolution of the object, that is, the minimum measurement unit is limited by the wavelength of the laser light source used. In addition, when a laser light source of two or multiple wavelengths is used among existing digital holographic microscopes, the cost increases by using light sources having different wavelengths, or holographic images are sequentially acquired using light sources of different wavelengths. Therefore, there is a problem in that it is difficult to measure the three-dimensional change information of the object to be measured in real time.

In addition, in the above-described conventional digital holography technology, a computer generated hologram (CGH) is generated with a computer to restore the shape of the object to be measured, it is displayed on a spatial light modulator (SLM), and then a reference light is irradiated. , a three-dimensional holographic image of an object is obtained by diffraction of the reference light. In this case, since the use of an expensive spatial light modulator (SLM) (more than tens of thousands of won) is required, there is considerable difficulty in practical use.

A number of patent documents for solving the problems of the conventional digital holography technology are disclosed as follows.

According to these patent documents, the effect of increasing the measurement resolution of the measurement object and measuring and recording the hologram of the measurement object that changes with time in real time to restore the three-dimensional shape information of the measurement object in real time is achieved, but the following problems still occur.

More specifically, Patent Document 1 entitled “Digital Holographic Microscope and Digital Holographic Image Generating Method” is a two-wavelength digital holographic microscope device, as shown in FIG. 1 , 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 light-emitting unit 110 and a light source unit lens 120, and the mixed light source light-emitting unit 110 emits mixed light having a wavelength band distributed in several non-uniform bands, and the light source unit The lens 120 optically adjusts the mixed light generated by the mixed light source emitting unit 110 , and makes it incident on the wavelength dividing unit 200 .

The wavelength divider 200 includes a first light splitter 210 , a first filter plate 220 , a second filter plate 230 , and a first reflector 240 . The first light splitter 210 receives the mixed light incident from the mixed light source unit 100 and splits it into two lights. In this case, the first light splitter 210 divides the incident mixed light in different directions to proceed. The first filtering plate 220 receives one light among the lights divided by the first light splitter 210 to obtain a first light beam having a predetermined single wavelength. Here, the light input to the first filtering plate 220 is filtered while passing through the first filtering plate 220 , and a first light beam having a single wavelength determined according to the characteristics of the first filtering plate 220 is obtained. The second filter plate 230 receives the other light among the lights divided by the first light splitter 210 in the same manner as the first filter plate 220 , and receives a second light having a wavelength different from the wavelength of the first light beam. get the beam And the second light beam is sent to the interference fringe acquisition unit 300 . The first reflector 240 serves to receive the first ray obtained from the first filtering plate 220 and reflect it to the interference fringe acquisition unit 300 .

The interference fringe acquisition unit 300 includes a second light splitter 310 , a third light splitter 320 , a second reflector 330 , a third filter plate 340 , and a third reflector 350 . The second light splitter 310 receives the first light beam input from the wavelength splitter 200 and splits it into a first object light and a first reference light. At this time, the second light splitter 210 serves to divide the incident first light beam in different directions and advance the light beam. The third light splitter 320 also receives the second light beam in the same manner as the second light splitter 310 and splits it into a second object light and a second reference light. The second reflector 330 receives the first reference light, and transmits the reflected first reference light to the second light splitter 310 . The third filter plate 340 receives the first reference light divided by the second light splitter 310 and sends it to the second reflector 330 , and receives the reflected first reflected reference light to the second light splitter 310 . can In addition, the third filter plate 340 blocks the progress of the second object light so that it does not reach the second reflector 330 when the second object light reaches the second light splitter 310 and is split so that some of the light travels in the direction of the second reflector 330 . . To this end, the third filter plate 340 is a filter plate having the same characteristics as the first filter plate 220 in transmitting light. The third reflector 350 receives the second reference light, and transmits the reflected second reference light to the third light splitter 320 , where the second reflector 330 and the third reflector 350 are the controller 700 ) can be configured so that the angle can be adjusted according to the control of an off-axis hologram.

Meanwhile, the first and second object lights obtained as described above are converted into first and second reflective object lights, respectively, and are sent to the image sensor unit 500 through the following process. The second light splitter 310 injects the first object light divided as described above to the measurement target object mounted on the objective unit 400 , and the second object is divided and sent from the third light splitter 320 . Light is incident on the measurement target object. In this case, the reflected light reflecting the first object light incident from the measurement target object is referred to as the first reflecting object light. In addition, the reflected light reflecting the second object light incident from the measurement target object is referred to as a second reflecting object light. The second light splitter 310 receives the first reflective object light and the second reflective object light reflected as described above and transmits them to the third light splitter 320 . The third light splitter 320 transmits the first reflective object light and the second reflective object light received as described above to the image sensor unit 500 again.

In addition, the first reflection reference light and the second reflection reference light obtained as described above are sent to the image sensor unit 500 through the following process. Specifically, the second light splitter 310 receives the first reflection reference light reflected from the second reflector 330 and transmits it to the third light splitter 320 . As described above, 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, and receives the image sensor unit 500 again. send to Accordingly, in the third light splitter 320, the first reflecting object light, the first reflecting reference light, the second reflecting object light, and the second reflecting reference light are all sent in the same direction to the image sensor unit 500, and then mutually interfere with each other. An interference fringe is created.

On the other hand, the second reflector 330 and the third reflector 350 are angled according to the control of the controller 700 in order to configure an off-axis system in which light rays of different wavelengths form different interference fringes. It is characterized in that it can be adjusted in multiple directions.

That is, as the angles of the second reflector 330 and the third reflector 350 are different from each other, the first reflection reference light reflected from the second reflector 330 and the second reference light reflected from the third reflector 350 are different from each other. When the separation occurs in the direction of the light, 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 reaching the image sensor unit 500 to form an interference fringe, each wavelength A different deaxially descaled interference fringe is formed.

The objective unit 400 includes an object holder 410 and an objective lens 420, the object holder 410 fixes the measurement target object to the holder to be measured, and the objective lens 420 is incident on the measurement target object The first object light and the second object light are optically adjusted.

The image sensor unit 500 projects the interference fringe obtained by the interference fringe acquisition unit 300 onto a digital image sensor, measures the projected interference fringe using the digital image sensor, and converts the measured value to a discrete signal. convert to In general, a recording of the interference fringe is called a hologram. As such a digital image sensor, various image sensors such as a CCD may be used.

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

The control unit 700 implements the above-described off-axis system and controls the positions and angles of the second reflector 330 and the third reflector 350 to obtain the interference fringe, such as the interference fringe acquisition unit 300 ) and control the objective unit 400 such as adjusting the objective lens 420 to adjust the first and second object lights incident on the measurement target object, and the interference fringes are measured and applied thereto. The image sensor unit 500 is controlled to convert the information into a discrete signal, and the image storage unit 600 is controlled to store the interference fringe information converted into the discrete signal.

The object shape restoration unit 800 includes a phase information acquisition unit 810, a thickness information acquisition unit 820, and a shape restoration unit 830, and the phase information acquisition unit 810 uses the interference fringe information. The phase information of the interference fringe with respect to the first light beam and the phase information of the interference fringe with respect to the second light beam are respectively obtained, and the thickness information acquisition unit 820 obtains thickness information of the measurement target object using the phase information, , the shape restoration unit 830 restores the real-time three-dimensional shape of the measurement target object by using the thickness information. In this case, the thickness information of the object to be measured includes information on the difference between the paths traveled by the object light and the reference light, respectively. Due to the optical path difference between the object light and the reference light, the interference fringe is formed when the object light and the reference light overlap.

In Patent Document 1 disclosed as described above, since a mixed light source having a wavelength band distributed in several non-single bands is used, the wavelength division unit divides the first light beam and the second light beam having different wavelengths to obtain at least two or more single wavelengths. For division, the first filter plate, the second filter plate, and the first reflector must be used. In addition, the interference fringe acquisition unit includes a third light splitter for splitting the second light beam, a third reflector for reflecting the second light beam, and a third filter plate for blocking the second light beam from entering the second reflector. should be used Accordingly, there are still problems that the structure of the entire device becomes complicated, the overall optical noise of the device increases due to an increase in the use of optical elements, and the overall manufacturing cost is high.

Accordingly, as a new method for solving the above-described problems while using a light source of a single wavelength is required, a number of patent documents corresponding thereto have been disclosed.

However, the optical system of most disclosed patent documents can be broadly classified into a transmissive system that measures an object that transmits light to measure a digital hologram or a reflective system that reflects light.

More specifically, Patent Documents 2, 3, 5 and 6 are reflective measurement devices using two wavelengths, and only an object that reflects light can be measured, but Patent Document 2 requires lasers having two different wavelengths, and The optical interferometer system is complicated, patent document 3 requires two image sensors, uses white light with low coherence, and like patent document 2, the optical interferometer system is complicated, and patent document 5 like patent document 2 , lasers having two different wavelengths are required, and the optical interferometer system is complicated, and hologram generation is impossible due to the configuration of the proposed system. There is a problem that a laser is required and the optical interferometer system is complicated.

In addition, Patent Document 4 is a transmission type measuring device using one wavelength and can measure only an object that transmits light.

Therefore, in order to solve this problem, measurement was possible only by using a transmissive system and a reflective system according to the optical characteristics of the measurement target, such as an object that transmits light or an object that reflects light. In order to measure holograms, there is a problem that additional cost arises because expensive equipment worth hundreds of millions of won must be purchased each.

[Prior Patent Literature]

[Patent Literature]

1. Korea Patent No. 10-1634170 (Registered on June 22, 2016)

2. Korea Patent No. 10-1152798 (Registered on May 29, 2012)

3. Korean Patent No. 10-1139178 (Registered on April 16, 2012)

4. Korea Patent No. 10-1203699 (Registered on November 15, 2012)

5. Korean Patent Registration No. 10-1441245 (Registered on September 5, 2014)

6. Korean Patent Registration No. 10-1716452 (Registered on Mar. 8, 2017)

The present invention has been devised to solve the conventional problems as described above, and an object of the present invention is a transmission type system for measuring an object that transmits light, and a reflection type for measuring an object that reflects light An object of the present invention is to provide an improved holographic restoration device that can measure a digital hologram regardless of the optical properties of an object to be measured by a single integrated system that integrates the system.

Another object of the present invention is to measure a digital hologram regardless of the optical characteristics of the object to be measured, a transmission mode for measuring an object that transmits light, and a reflection mode for measuring an object that reflects light To provide an improved holographic restoration method to select

In order to achieve the above object, an improved holographic restoration apparatus according to an aspect of the present invention includes a light source unit emitting a single wavelength light; a first light splitter for splitting the single wavelength light emitted from the light source into a first transmitted split light and a second transmitted split light; a plurality of optical mirrors for reflecting the first transmitted split light split by the first light splitter; a second light splitter dividing the second transmitted light split by the first light splitter into a first reflected split light and a second reflected split light; an object light objective lens for passing the first transmitted split light transmitted through the measurement target object after being reflected by the plurality of optical mirrors or the first reflected split light split by the second light splitter; a reference light objective lens for passing the second reflection split light divided by the second light splitter; a positioning mirror through which the second reflection split light passing through the reference light objective lens is transmitted; The first split beam transmitted through the measurement target or the first split split beam reflected from the surface of the measurement target, and the second split beam reflected from the positioning mirror passing through the reference beam objective lens a recording medium for recording an interference fringe formed by passing through the object light objective lens and the reference light objective lens, respectively, and transmitted to the second light splitter; and a processor for receiving and storing an image file generated by transforming the interference fringe transmitted from the recording medium, wherein a light transmission object hologram and a light reflection object hologram are transmitted by the processor in a transmission mode and selectively acquired according to the reflective mode.

An improved holographic restoration method according to another aspect of the present invention comprises: a) selecting two measurement modes of an object hologram of a measurement target object (S1); b) measuring the object hologram according to the selected mode (S2); c) removing direct current, virtual image, and aberration information of the measured object hologram (S3); d) extracting the phase information of the object hologram (S4); and e) restoring three-dimensional shape information and quantitative size (thickness) information of the measurement target object (S5).

Through the means for solving the above problems, the improved holographic restoration apparatus and method of the present invention provides the following effects.

1. It is possible to solve the complex optical device structure required for one-shot digital holographic restoration using a single object holographic image of the prior art and a significant high cost problem.

2. Holographic restoration is possible with a simple structure and low cost.

3. It has versatility that can be applied to both reflective and transmissive hologram restoration devices of the prior art.

4. In particular, the use of reference light is unnecessary when restoring holograms, and quantitative 3D image restoration of the measurement target is possible in real time.

5. Detection, confirmation, or display in various fields, including devices for detecting defects in ultra-fine structures such as TFTs and semiconductors, medical devices requiring precise three-dimensional image display, and other transparent objects such as lenses for refractive index error detection It can be applied to the device for

6. A digital hologram can be measured regardless of the optical characteristics of a measurement target by selectively selecting a transmission mode and a reflection mode by one integrated system that integrates the conventional reflective and transmissive hologram restoration devices, so additional cost can solve the problem.

Further advantages of the present invention may become apparent 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 in detail a two-wavelength digital holographic microscope apparatus according to the disclosed prior art.
2 is a schematic block diagram illustrating an improved holographic restoration apparatus according to a preferred embodiment of the present invention.
3 is a flowchart illustrating an improved holographic restoration method according to an embodiment of the present invention.
4 is a flowchart illustrating in detail a specific implementation step of step S3 among the improved holographic restoration method of FIG. 3 .

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. In this case, it should be noted that the same components in the accompanying drawings are denoted by the same reference numerals as much as possible. In the description of the present invention, when it is determined that a detailed description of a related configuration or function is unnecessary, the detailed description thereof will be omitted.

Referring to FIG. 2 showing an improved holographic restoration apparatus according to an embodiment of the present invention, the improved holographic restoration apparatus 1 according to an embodiment of the present invention measures an object that transmits light It may be an All-in-one type Digital Holographic Microscopy that selectively executes a transmission-type mode that measures light and a reflection-type mode that measures an object that reflects light.

An improved holographic restoration apparatus 1 according to an embodiment of the present invention includes a light source unit 10 emitting a single wavelength light; a first light splitter 20 for splitting the single wavelength light emitted from the light source unit 10 into a first transmitted split light T1 and a second object transmitted light T2; a plurality of optical mirrors (30, 31) for reflecting the first transmitted split light (T1) divided by the first light splitter (20); a second light splitter (60) for splitting the second transmitted split light (T2) split by the first light splitter (20) into a first reflected split light (R1) and a second reflected split light (R2); The first transmitted split light T1 that passes through the measurement target object 40 after being reflected by the plurality of optical mirrors 30 and 31 or the first split light split by the second light splitter 60 an object light objective lens 50 for passing the reflected split light R1; a reference light objective lens (51) for passing the second reflection split light (R2) divided by the second light splitter (60); a positioning mirror 70 through which the second reflection split light R2 passing through the reference light objective lens 51 is transmitted; The first transmitted split light T1 passing through the measurement target object 40 or the first reflected split light R1 reflected from the surface of the measurement target object 40, and the reference light objective lens 51 The second reflection split light R2 passed through and reflected from the positioning mirror 70 passes through the object light objective lens 50 and the reference light objective lens 51, respectively, and the second light splitter 60 a recording medium 80 for recording the interference fringes transmitted to and formed; and a processor 90 for receiving and storing an image file generated by converting the interference fringe transmitted from the recording medium 80 .

The processor 90 of the holographic restoration apparatus 1 according to the embodiment of the present invention described above is implemented as a device capable of arithmetic operations such as, for example, a microprocessor, a personal computer (PC), and the recording medium 80 ) may be implemented as, for example, an image sensor such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS).

The improved holographic restoration apparatus 1 according to an embodiment of the present invention generates a light transmission object hologram and a light reflection object hologram by the processor 90 according to the transmission type mode and the reflection type mode. It can be obtained selectively. That is, the processor 90 of the integrally improved holographic restoration apparatus 1 according to an embodiment of the present invention variably adjusts the position of the position adjustment mirror 70, so that light in the transmissive mode and the reflective mode It compensates for the optical path difference. Accordingly, the light transmitting object hologram or the light reflecting object hologram may be transmitted to the processor 90 through the recording medium 80 (eg, CCD) to be acquired in the form of an image file.

More specifically, in the holographic restoration apparatus 1 according to an embodiment of the present invention, in the transmission mode for measuring an object that transmits light, the light emitted from the laser, which is the light source unit 10, passes through the first light splitter 20 . It is divided into the first transmitted split light T1 and the second transmitted split light T2.

The first transmitted split light T1 is reflected by the plurality of optical mirrors 30 and 31, respectively, is transmitted to the measurement object 40, passes through the measurement object 40, and then the object light objective lens ( 50) to the second light splitter 60. In the embodiment of the present invention, the plurality of optical mirrors 30 and 31 are exemplified as being implemented with two optical mirrors, but those skilled in the art will fully understand that it may be implemented with three or more optical mirrors. Meanwhile, the second transmitted split light T2 passes through the second light splitter 60 and the reference light objective lens 51 , is reflected by the position adjustment optical mirror 70 , and then passes through the reference light objective lens 51 again to the second It goes to the light splitter 60 .

The first and second transmitted split beams T1 and T2 met by the second light splitter 60 form an interference fringe (light-transmitting object hologram) for the light-transmitting portion of the measurement target object 40 . . Here, the first transmitted split light T1 corresponds to the object light of the light transmitting object hologram, and the second transmitted divided light T2 corresponds to the reference light of the light transmitting object hologram.

On the other hand, in the reflective mode for measuring an object reflecting light, the light emitted from the laser, which is the light source unit 10 , passes through the first light splitter 20 into the first transmitted split light T1 and the second transmitted split light T2 . is divided into

The second transmitted light T2 is divided into the first reflection split light R1 and the second reflection split light R2 by the second light splitter 60 . The first reflection split light R1 passes through the object light objective lens 50 , is reflected from the measurement target object 40 , passes through the object light objective lens 50 again, and is directed to the second light splitter 60 . The second reflection split light R2 passes through the reference light objective lens 51 and is reflected by the positioning optical mirror 70 , and the reflected light passes through the reference light objective lens 51 again to the second light splitter 60 . Head to

The first reflection split beam R1 and the second reflection split beam R2 met by the second light splitter 60 form an interference fringe (light reflection object hologram) for the portion reflecting the light of the measurement target object 40 . will form Here, the first reflection split light R1 corresponds to the object light of the light reflecting object hologram, and the second reflection divided light R2 corresponds to the reference light of the light reflecting object hologram.

At this time, by adjusting the position of the position adjustment mirror 70 by, for example, the processor 90 implemented by a PC, the optical path difference of light generated in the transmissive mode and the reflective mode is corrected. The light transmitting object hologram and the light reflecting object hologram are respectively transmitted to the PC which is the processor 90 through the CCD as the recording medium 80 and are acquired in the form of an image file.

When the light transmission mode is selected and measured by the holographic restoration apparatus 1 according to the above-described embodiment of the present invention, the obtained light transmitting object hologram is in the portion through which the light of the measurement target object 40 is transmitted. It is an interference pattern for The light-transmitting object hologram thus obtained may be expressed as a complex conjugated hologram as shown in Equation 1 below.

Equation 1:

는 획득한 빛 투과 물체 홀로그램을 나타내고,

는 빛 투과 물체 홀로그램의 물체광과 기준광을 나타내고,

는 빛 투과 물체 홀로그램의 물체광과 기준광의 복소 공액을 나타낸다.where x and y represent spatial coordinates,

represents the obtained light-transmitting object hologram,

represents the object light and the reference light of the light-transmitting object hologram,

represents the complex conjugate of the object light and the reference light of the light-transmitting object hologram.

On the other hand, when the light reflection mode is selected and the measurement is performed, the obtained light reflection object hologram is an interference fringe of the light reflection portion of the measurement target object 40 . The light reflecting object hologram thus obtained may be expressed as a complex conjugated hologram as shown in Equation 2 below.

Equation 2:

는 획득한 빛 반사 물체 홀로그램을 나타내고,

는 빛 반사 물체 홀로그램의 물체광과 기준광을 나타내고,

는 빛 반사 물체 홀로그램의 물체광과 기준광의 복소 공액을 나타낸다.where x and y represent spatial coordinates,

represents the obtained light-reflecting object hologram,

represents the object light and the reference light of the light-reflecting object hologram,

represents the complex conjugate of the object light and the reference light of the light-reflecting object hologram.

Hereinafter, a specific method for reconstructing a three-dimensional shape of an object from the obtained two types of object holograms will be described.

Specifically, referring back to FIGS. 2 to 4 , as described above, in order to remove direct current and virtual image information from the light transmitting object hologram (S21 in FIG. 3 ) obtained by selecting the transmissive mode by the processor 90, 2 A 2D Fourier transform is performed (S3 in FIG. 3).

In the transmissive mode, the frequency spectrum of the light transmitting object hologram obtained by the two-dimensional Fourier transform is the real image of the light transmitting object hologram, the imaginary image of the light transmitting object hologram, and direct current (DC) information. It appears separated (S31 in FIG. 4). In order to remove the virtual image and direct current (DC) information of the separated light-transmitting object hologram, for example, an automatic real image spot-position extraction algorithm is used from the real image spot-position information. It is applied to extract the phase information (S3 in FIG. 3 and S32 in FIG. 4).

Thereafter, reference light information of the light-transmitting object hologram is extracted using a frequency filtering algorithm (S33 in FIG. 4).

In order to calculate a compensation term of the extracted reference light information, a wavenumber vector constant of the extracted reference light information is calculated ( S34 of FIG. 4 ). A compensation term of the extracted reference light information is calculated using the calculated wavenumber vector constant (S35 of FIG. 4). In this case, the compensation term of the extracted reference light information is the conjugate term of the light-transmitting object hologram.

Thereafter, aberration information is extracted from the light-transmitting object hologram to compensate for the aberration of the object light objective lens 51 used for measuring the hologram ( S36 of FIG. 4 ). To this end, for example, an aberration information compensation term is generated using an automatic frequency aberration compensation algorithm.

A compensated light-transmitting object hologram is obtained by multiplying the extracted reference light information compensation term and aberration information compensation term by the light-transmitting object hologram ( S5 in FIG. 3 and S37 in FIG. 4 ).

On the other hand, even in the case of the reflective mode, the light reflective object hologram obtained by the two-dimensional Fourier transform is obtained by applying the same method as the above-described transmissive mode to obtain the compensated light reflective object hologram. The compensated light-transmitting object hologram and the compensated light-reflecting object hologram obtained in this way can be expressed as Equations 3 and 4, respectively.

Equation 3:

Equation 4:

및

는 각각 보상된 빛 투과 물체 홀로그램, 및 보상된 빛 반사 물체 홀로그램이고,

는 빛 투과 물체 홀로그램의 물체광 및 기준광이며,

는 빛 반사 홀로그램의 물체광 및 기준광이고,

는 빛 투과 물체 홀로그램의 기준광 정보의 보상 항이고,

는 빛 투과 물체 홀로그램의 수차(curvature) 정보 보상 항이며,

는 빛 반사 물체 홀로그램의 기준광 정보의 보상 항이고,

는 빛 반사 물체 홀로그램의 수차(curvature) 정보 보상 항을 의미한다.here,

and

are a compensated light-transmitting object hologram, and a compensated light-reflecting object hologram, respectively,

is the object light and reference light of the light-transmitting object hologram,

is the object light and reference light of the light reflection hologram,

is the compensation term of the reference light information of the light-transmitting object hologram,

is the aberration information compensation term of the light-transmitting object hologram,

is the compensation term of the reference light information of the light reflecting object hologram,

denotes a compensation term for aberration information of a light reflecting object hologram.

The compensated light-transmitting object hologram represented by Equation 3 is converted into information of a reconstruction image plane using an angular spectrum propagation algorithm.

Phase information is extracted from the transform-compensated object hologram through inverse 2D Fourier transform. At this time, the phase information obtained is the information other than the phase information of the light-transmitting part of the measurement target object 40 possessed by the obtained light-transmitting object hologram (ie, light information, object light of the objective lens 50). aberration information) is removed, and only phase information of a portion that transmits light of the measurement target object 40 is included.

The same method is applied to the compensated light-reflecting object hologram to extract phase information. The phase information obtained at this time is the information other than the phase information of the portion reflecting the light of the measurement target object 40 possessed by the acquired light reflection object hologram (that is, light information, object light of the objective lens 50) aberration information) is removed, and only phase information of a portion reflecting light of the measurement target object 40 is included.

The phase information of the portion that transmits the extracted light and the phase information of the portion that reflects the extracted light of the measurement target object 40 are distorted phase information using a 2D phase unwrapping algorithm Compensate for each, and calculates quantitative thickness information of the measurement target object 40 using this (S5 in FIG. 3). This quantitative thickness information can be expressed as in Equation 5 below.

Equation 5:

*

은 측정 대상 물체(40)의 정량적인 두께 정보이고,

는 물체 홀로그램 획득 시 사용한 광원의 파장이며,

는 측정 대상 물체(40)의 빛을 투과하는 부분의 위상 정보이고,

는 측정 대상 물체(40)의 빛을 반사하는 부분의 위상 정보이며,

는 측정 대상 물체(40)와 공기의 굴절률 차이를 의미한다. 계산된 물체의 정량적인 두께 정보를 이용하여 물체의 3차원 형상을 복원한다.here,

is quantitative thickness information of the measurement target object 40,

is the wavelength of the light source used to acquire the object hologram,

is the phase information of the portion that transmits the light of the measurement target object 40,

is the phase information of the part that reflects the light of the measurement target object 40,

denotes a difference in refractive index between the measurement target object 40 and air. The three-dimensional shape of the object is restored using the calculated quantitative thickness information of the object.

3 is a flowchart illustrating an improved holographic restoration method according to an embodiment of the present invention.

2 and 3 , an improved holographic restoration method according to an embodiment of the present invention includes: a) selecting two measurement modes of an object hologram of a measurement target object 40 (S1); b) measuring the object hologram according to the selected measurement mode (S2); c) removing direct current, virtual image, and aberration information of the measured object hologram (S3); d) extracting the phase information of the object hologram (S4); and e) restoring three-dimensional shape information and quantitative size (thickness) information of the measurement target object 40 (S5).

In the above-described holographic restoration method according to an embodiment of the present invention, step b) includes measuring an object hologram in a light transmission mode (S21) or measuring an object hologram in a light reflection mode (S22) can do.

In addition, the light transmitting object hologram obtained in the measuring step (S21) of the light transmitting mode is a complex conjugate hologram corresponding to the interference fringe of the light transmitting portion of the measurement target object 40, and is expressed by Equation 1 below. can be

Equation 1:

는 획득한 빛 투과 물체 홀로그램을 나타내고,

는 빛 투과 물체 홀로그램의 물체광과 기준광을 나타내며,

는 빛 투과 물체 홀로그램의 물체광과 기준광의 복소 공액을 나타낸다.where x and y represent spatial coordinates,

represents the obtained light-transmitting object hologram,

represents the object light and the reference light of the light-transmitting object hologram,

represents the complex conjugate of the object light and the reference light of the light-transmitting object hologram.

On the other hand, the light reflecting object hologram obtained in the measuring step (S22) of the light reflection mode is a complex conjugate hologram corresponding to the interference fringe of the light reflecting portion of the measurement target object 40, and is expressed by Equation 2 below. can be

Equation 2:

는 획득한 빛 반사 물체 홀로그램을 나타내고,

는 빛 반사 물체 홀로그램의 물체광과 기준광을 나타내며,

는 빛 반사 물체 홀로그램의 물체광과 기준광의 복소 공액을 나타낸다.where x and y represent spatial coordinates,

represents the obtained light-reflecting object hologram,

represents the object light and reference light of the light-reflecting object hologram,

represents the complex conjugate of the object light and the reference light of the light-reflecting object hologram.

In the above-described holographic restoration method according to an embodiment of the present invention, when the measured object hologram is a light-transmitting object hologram, step c) is performed in c1) to remove direct current and virtual image information from the light-transmitting object hologram. Separating the frequency spectrum of the light-transmitting object hologram obtained by performing 2D Fourier Transform into a real image, an imaginary image, and direct current information of the light-transmitting object hologram step; c2) In order to remove the virtual image and direct current (DC) information of the separated light-transmitting object hologram, the real image spot-position is extracted using an automatic real image spot-position extraction algorithm. applying and extracting; c3) extracting reference light information of the light-transmitting object hologram using a frequency filtering algorithm; c4) calculating a wavenumber vector constant of the extracted reference light information; c5) calculating a compensation term of the extracted reference light information using the calculated wavenumber vector constant; c6) extracting aberration information from the light-transmitting object hologram to compensate for the aberration of the object light objective lens 50 used for measuring the object hologram; and c7) converting the light-transmitting object hologram, in which the compensation term and the aberration information are compensated, into information of a reconstruction image plane using an Angular Spectrum Propagation algorithm. .

In this case, step c6) may include generating an aberration information compensation term using an automatic frequency aberration compensation algorithm; and multiplying the extracted reference light information compensation term and the aberration information compensation term by the light transmitting object hologram to obtain the compensated light transmitting object hologram.

On the other hand, even in the case of the reflective mode, the light reflective object hologram obtained by the two-dimensional Fourier transform is obtained by applying the same method as the above-described transmissive mode to obtain the compensated light reflective object hologram.

In the holographic restoration method according to an embodiment of the present invention, the compensated light-transmitting object hologram or the compensated light-reflecting object hologram may be expressed by Equation 3 or Equation 4 below.

Equation 3:

Equation 4:

는 보상된 빛 투과 물체 홀로그램이고,

는 보상된 빛 반사 물체 홀로그램이고,

는 빛 투과 물체 홀로그램의 물체광 및 기준광이며,

는 빛 반사 홀로그램의 물체광 및 기준광이고,

는 빛 투과 물체 홀로그램의 기준광 정보의 보상 항이며,

는 빛 투과 물체 홀로그램의 수차(curvature) 정보 보상 항이고,

는 빛 반사 물체 홀로그램의 기준광 정보의 보상 항이며,

는 빛 반사 물체 홀로그램의 수차(curvature) 정보 보상 항을 의미한다.here,

is the compensated light-transmitting object hologram,

is the compensated light-reflecting object hologram,

is the object light and reference light of the light-transmitting object hologram,

is the object light and reference light of the light reflection hologram,

is the compensation term of the reference light information of the light-transmitting object hologram,

is the aberration information compensation term of the light-transmitting object hologram,

is the compensation term of the reference light information of the light reflecting object hologram,

denotes a compensation term for aberration information of a light reflecting object hologram.

In the holographic reconstruction method according to an embodiment of the present invention described above, step d) is implemented as a step of extracting phase information from a transform-compensated object hologram through an Inverse 2D Fourier Transform, The phase information obtained here is information other than the phase information of the portion that transmits or reflects the light of the measurement target object 40 possessed by the obtained light transmitting object hologram or light reflecting object hologram (ie, light information, object The aberration information of the optical objective lens 50) includes only the phase information of the portion that transmits or reflects the light of the measurement target object 40 from which it has been removed.

In the above-described holographic restoration method according to an embodiment of the present invention, step e) is the extracted phase information of the portion that transmits the light of the measurement target object 40 or the extracted phase information of the portion that reflects the light compensating for each distorted phase information using a 2D phase unwrapping algorithm; calculating quantitative thickness information of the measurement target object 40 using the compensated phase information; and restoring the three-dimensional shape of the measurement target object 40 by using the calculated quantitative thickness information of the object.

The calculated thickness information may be expressed by Equation 5 below.

Equation 5:

은 측정 대상 물체(40)의 정량적인 두께 정보이고,

는 물체 홀로그램 획득 시 사용한 광원의 파장이며,

는 물체의 빛을 투과하는 부분의 위상 정보이고,

는 물체의 빛을 반사하는 부분의 위상 정보이고,

는 물체와 공기의 굴절률 차이를 의미한다.here,

is quantitative thickness information of the measurement target object 40,

is the wavelength of the light source used to acquire the object hologram,

is the phase information of the part that transmits the light of the object,

is the phase information of the part that reflects the light of the object,

is the difference in refractive index between an object and air.

As described above, in the improved holographic restoration apparatus 1 and method according to the present invention, the digital reference hologram calculated from the object hologram is directly generated using the processor 90, Since the dimensional information can be restored, it is possible to solve the complex optical device structure required for one-shot digital holography restoration using a single object holographic image of the prior art and a significant high cost problem accordingly.

In addition, according to the improved holographic restoration apparatus 1 and method according to the present invention, since the restoration apparatus additionally uses only the processor 90, the overall configuration thereof is very simple and it is possible to restore the holographic at a low cost. .

In addition, in the improved holographic restoration apparatus 1 and method according to the present invention, other components except for the processor 90 and the positioning mirror 70 are substantially the same as the reflective and transmissive hologram restoration apparatuses of the prior art. Since it has a configuration, it has versatility that can be easily applied to both reflective and transmissive hologram restoration devices of the prior art.

In addition, in the improved holographic restoration apparatus 1 and method according to the present invention, in particular, unlike the prior art, the use of reference light is unnecessary when hologram restoration is performed, and quantitative 3D image restoration of the measurement target object 40 in real time This is possible.

In addition, in the improved holographic restoration apparatus 1 and method according to the present invention, quantitative three-dimensional image restoration of the measurement target object 40 is possible in real time without using the reference light as described above, so TFT and semiconductor Applicable to detection, confirmation, or display devices in various fields, including devices for detecting defects with ultra-fine structures, medical devices requiring precise 3D image display, and other transparent objects such as lenses possible.

Furthermore, in the improved holographic restoration apparatus (1) and method according to the present invention, the transmission mode and the reflection mode are selectively selected and measured by a single integrated system that integrates the reflection type and transmission type hologram restoration apparatus of the prior art. Since the digital hologram can be measured regardless of the optical properties of the object, it is possible to solve the additional cost problem.

Although the present invention has been described with reference to embodiments, it is not necessarily limited thereto, and modifications and variations are possible within the scope of the technical spirit of the present invention.

10: light source unit 20: first light splitter
30: first optical mirror 31: second optical mirror
40: object to be measured 50: object light objective lens
51: reference light objective lens 60: second light splitter
70: positioning mirror 80: recording medium
90: processor

Claims (1)

In the holographic restoration apparatus,
a light source unit emitting single wavelength light;
a first splitter for splitting the single wavelength light emitted from the light source into a first split light and a second split light;
a plurality of optical mirrors reflecting the first transmitted split light;
a second light splitter for dividing the second transmitted split light into a first reflected split light and a second reflected split light;
The first transmitted split light transmitted through the measurement target after being reflected by the plurality of optical mirrors and the first reflected split light reflected from the surface of the measurement target after being split by the second light splitter a passing object light objective lens;
a reference light objective lens through which the second reflection split light passes;
a positioning mirror through which the second reflection split light passing through the reference light objective lens is transmitted;
The first transmitted split light passing through the measurement target object or the first reflected split light reflected from the surface of the measurement target object passes through the object light objective lens, and the second reflection split beam reflected by the positioning mirror a recording medium for recording an interference fringe formed when light passes through the reference light objective lens and is transmitted to the second light splitter; and
A processor for receiving and storing an image file generated by transforming the interference fringe transmitted from the recording medium;

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