KR102222859B1 - An Improved Holographic Reconstruction Apparatus and Method - Google Patents

Abstract

Disclosed holographic restoration apparatus includes: a first light splitter for dividing a single wavelength light of a light source unit into first and second transmitted 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 first and second reflected split light; A reference light objective lens for passing the second reflected split light; A position adjustment mirror through which the first reflected split light passing through the reference light objective lens is transmitted; The first transmission split light that passes through the measurement target object or the first reflection split light reflected from the measurement object passes through the object light objective lens, and the second reflection split light reflected from 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 optical splitter; And a processor configured to receive and store an image file generated by converting the interference fringe, wherein a hologram of a light transmitting or reflecting object is selectively acquired according to a 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 all-in-one system in which a transmissive system for measuring an object that transmits light and a reflective system for measuring an object that reflects light are integrated. It relates to an improved hologram restoration apparatus and method capable of measuring digital holograms regardless of their characteristics.

As is well known, holography is an imaging method devised for the purpose of improving the resolution of an electron microscope. Whereas conventional photographs record only the distribution of the bright and dark sides of an object, holography is a wave that contains all the information of light. In other words, it accumulates and reproduces both amplitude and image at the same time.The principle is that the coherent light emitted from the laser light source divides the beam splitter into two, and one of the rays illuminates the subject. The reflected light reaches the holographic photosensitive material. This ray is called object light. The other light is diffused through the lens and is directly projected onto the entire surface of the holographic photosensitive material. This ray is referred to as 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 500-1500 per 1mm. The picture recording this interference pattern is called a hologram. When the same beam of light as the reference light is applied to the hologram, the interference pattern acts as a diffraction grating, and the light is diffracted at a location different 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 reproduced wavefront, you can see the object for the first time, but it looks as if the object is in there. Then, if you move the point of view again, the position where the object is visible changes, so it looks as if you are viewing a three-dimensional picture. Also, since the original object's wavefront is reproduced, it can interfere with the wavefront from a very slightly deformed object. Therefore, such holography features are 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 is a microscope that measures the intensity of light reflected or transmitted from the object by shining a general light source on the object to determine the shape of the object. If it is a measuring device, a digital holography microscope is a device that measures the interference and diffraction of light that occurs when light is shining on an object, records it digitally, and restores the shape information of the object from these information.

In other words, digital holography technology generates light of a single wavelength, such as a laser, and divides it into two lights using an optical splitter, so that one light (reference light) shines directly on the image sensor, and the other light (object light) is As the light transmitted or reflected from the object to be measured shines on the image sensor, the reference light and the object light cause an interference phenomenon in the image sensor, and the interference pattern information of this light is recorded with a digital image sensor. And, it is a technology for restoring the shape of the object to be measured using a computer using the recorded interference fringe information.

Meanwhile, in the case of conventional optical holography technology other than digital holography, the interference pattern information of the light is recorded with a special film, and the reference light is illuminated on a special film on which the interference pattern 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 object to be measured is restored to the place where the object to be measured was originally located.

Compared with the conventional optical holography method, the digital holography microscope measures the interference pattern information of light with a digital image sensor and stores it digitally, and the stored interference pattern information is a numerical computation method using a computer device, etc., not an optical method. There is a difference in that it restores the shape of the object to be measured by processing through it.

Conventional digital holographic microscopes may first use a single wavelength laser light source. However, when a single laser light source is used, there is a problem that the measurement resolution of an object, that is, the minimum measurement unit is limited to the wavelength of the laser light source used. In addition, in the case of using a laser light source of two or multiple wavelengths among the existing digital holography microscopes, the cost increases by using light sources with different wavelengths, or holographic images are sequentially acquired using light sources of different wavelengths. Therefore, 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, and then displayed on a spatial light modulator (SLM) and then a reference light is illuminated. , The 3D holographic image of the object is obtained by diffraction of the reference light. In this case, since the use of an expensive (more than tens of thousands of won) spatial light modulator (SLM) 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 object to be measured and restoring the three-dimensional shape information of the object to be measured in real time by measuring and recording the hologram of the object to be measured in real time that changes over time. Is achieved, but still the following problems arise.

More specifically, Patent Document 1, entitled "Digital Holographic Microscope and Digital Holographic Image Generation 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 pattern 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 multiple bands that are not single, and the light source unit The lens 120 optically adjusts the mixed light generated by the mixed light source light emitting unit 110 and makes it incident on the wavelength dividing unit 200.

The wavelength splitter 200 includes a first light splitter 210, a first filter plate 220, a second filter plate 230, and a first reflector 240. The first optical splitter 210 receives the mixed light incident from the mixed light source unit 100 and divides it into two lights. At this time, the first optical splitter 210 serves to divide the incident mixed light in different directions and proceed. The first filter plate 220 receives one of the lights divided by the first light splitter 210 and acquires a first ray having a predetermined single wavelength. Here, the light input to the first filter plate 220 is filtered while passing through the first filter plate 220, and a first light beam having a single wavelength determined according to the characteristics of the first filter plate 220 is obtained. The second filter plate 230 receives the remaining one of the lights divided by the first light splitter 210 in the same manner as the first filter plate 220, and receives the second light having a wavelength different from that of the first light beam. Acquire a ray. And the second ray is sent to the interference fringe acquisition unit 300. The first reflector 240 serves to receive the first light beam acquired from the first filter plate 220 and reflect it to the interference fringe acquisition unit 300.

The interference fringe acquisition unit 300 includes a second optical splitter 310, a third optical splitter 320, a second reflector 330, a third filter plate 340, and a third reflector 350. The second optical splitter 310 receives the first light beam input from the wavelength splitter 200 and divides it into a first object light and a first reference light. At this time, the second optical splitter 210 serves to divide the incident first light beam in different directions and proceed. The third optical splitter 320 receives a second light beam in the same manner as the second optical 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 optical splitter 310. The third filter plate 340 receives the first reference light divided by the second optical splitter 310 and sends it to the second reflector 330, and receives the reflected first reflection reference light and sends it to the second optical splitter 310. I can. In addition, the third filter plate 340 prevents the second object light from reaching the second reflector 330 when the second object light reaches the second light splitter 310 and is split into light, so that a part of the light goes toward 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 optical splitter 320, where the second reflector 330 and the third reflector 350 are the controller 700 ), it is possible to implement an off-axis hologram by configuring the angle to be adjustable according to the control.

Meanwhile, the first object light and the second object light obtained as described above are converted into first and second reflective object light and transmitted to the image sensor unit 500 through the following process. The second optical splitter 310 causes the light of the first object divided as described above to be incident on the object to be measured mounted on the object unit 400, and is divided and transmitted from the third optical splitter 320. Light is incident on the object to be measured. In this case, the reflected light obtained by reflecting the first object light incident from the object to be measured is referred to as first reflective object light. In addition, the reflected light reflecting the second object light incident from the object to be measured is referred to as the second reflective object light. The second optical splitter 310 receives the reflected light from the first and second reflective objects as described above and sends them to the third optical splitter 320. The third optical splitter 320 sends the light of the first reflective object and the light of the second reflective object 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 transmitted to the image sensor unit 500 through the following process. Specifically, the second optical splitter 310 receives the first reflected reference light reflected from the second reflector 330 and sends it to the third optical splitter 320. The third optical splitter 320 receives the first reflection reference light sent from the second optical splitter 310 and the second reflection reference light reflected from the third reflector 350 as described above, and the image sensor unit 500 Send to Accordingly, from the third optical splitter 320, the first reflective object light, the first reflective reference light, the second reflective object light, and the second reflective reference light are all sent to the image sensor unit 500 in the same direction, and then interfere with each other. Interference fringes are 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 patterns. 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 become different from each other, the first reflection reference light reflected from the second reflector 330 and the second reference reflected from the third reflector 350 When a separation occurs in the direction of the light, 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 reaching the image sensor unit 500 to form an interference pattern, each wavelength Differently, it forms a deaxial interference pattern.

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

The image sensor unit 500 projects the interference pattern obtained by the interference pattern acquisition unit 300 onto a digital image sensor, measures the projected interference pattern using the digital image sensor, and measures the measured value as a discrete signal. Convert to Usually, the recording of the interference pattern is called a hologram. Various image sensors such as CCD can be used as such a digital image sensor.

The image storage unit 600 stores interference fringe information converted into a 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 adjusts the positions and angles of the second reflector 330 and the third reflector 350 in order to obtain the interference fringe. ) And controlling the objective part 400 such as adjusting the objective lens 420 to adjust the first object light and the second object light incident on the object to be measured, and the interference pattern is measured 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 a 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 pattern information to Each of the phase information of the interference fringe for the first ray and the phase information of the interference pattern for the second ray is obtained, and the thickness information acquisition unit 820 obtains thickness information of the object to be measured using the phase information, , The shape restoration unit 830 restores a real-time three-dimensional shape of the object to be measured using the thickness information. In this case, the thickness information of the object to be measured includes information on the difference between the paths of the object light and the reference light, respectively. The interference pattern is formed when the object light and the reference light overlap due to the difference in the optical path between the object light and the reference light.

In Patent Document 1 disclosed as described above, since a mixed light source having a wavelength band distributed in several non-uniform bands is used, the wavelength dividing unit generates first and second rays having different wavelengths in order to obtain at least two single wavelengths. To divide, a first filter plate, a second filter plate, and a first reflector must be used. In addition, the interference fringe acquisition unit further includes a third optical splitter for dividing 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, the overall structure of the device is complicated, the optical noise of the device is increased due to the increase in the use of optical elements, and the overall manufacturing cost is still high.

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

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

More specifically, Patent Documents 2, 3, 5, and 6 are reflective measuring devices using two wavelengths and can measure only objects that reflect light, but Patent Document 2 requires lasers having two different wavelengths. The optical interferometer system is complex, Patent Document 3 requires two image sensors, uses white light with low coherence, and the optical interferometer system is complicated as in Patent Document 2, and Patent Document 5 is similar to Patent Document 2. In addition, a laser having two different wavelengths is required, and the optical interferometer system is complex, and it is impossible to generate a hologram due to the configuration of the proposed system, and Patent Document 6 also uses two different wavelengths as in Patent Document 2. Branches require a laser and the optical interferometer system has a complex problem.

In addition, Patent Document 4 is a transmission-type measuring device using one wavelength and can measure only an object that transmits light, but there is a problem in that an error occurs due to a time delay because two images are required to be photographed.

Therefore, to solve this problem, measurement was possible only by using a transmission-type system and a reflection-type system according to the optical characteristics of the object to be measured, 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 problems arise because expensive equipment worth hundreds of millions of dollars per unit must be purchased.

[Prior Patent Literature]

[Patent Literature]

1. Korean Patent Registration No. 10-1634170 (registered on June 22, 2016)

2. Korean Patent Registration No. 10-1152798 (registered on May 29, 2012)

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

4. Korean Patent Registration 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. 08, 2017)

The present invention has been devised to solve the conventional problems as described above, and an object of the present invention is a transmissive system for measuring an object that transmits light, and a reflective type for measuring an object that reflects light. It is to provide an improved holographic restoration apparatus capable of measuring digital holograms regardless of the optical properties of an object to be measured by a single integrated system incorporating the system.

In addition, another object of the present invention is a transmission mode for measuring an object that transmits light and a reflection mode for measuring an object that reflects light in order to measure a digital hologram regardless of the optical properties of the object to be measured. It is to provide an improved holographic restoration method so that you can choose.

In order to achieve the above object, an improved holographic restoration apparatus according to an embodiment of the present invention includes a light source unit that emits light of a single wavelength; A first light splitter for dividing the single wavelength light emitted from the light source unit into a first transmission split light and a second transmission split light; A plurality of optical mirrors reflecting the first transmitted and divided light divided by the first optical splitter; A second optical splitter for dividing the second transmitted light split by the first optical splitter into a first reflected split light and a second reflected split light; A body light objective lens for passing the first split light transmitted through the object to be measured 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 reflected and split light split by the second light splitter; A position adjustment mirror through which the second reflected split light passing through the reference light objective lens is transmitted; The first transmitted split light transmitted through the measurement target object or the first reflected split light reflected from the surface of the measurement target object, and the second reflected split light reflected from the positioning mirror after passing through the reference light 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 optical splitter; And a processor configured to receive and store an image file generated by converting the interference fringe transmitted from the recording medium, wherein a light transmission object hologram and a light reflection object hologram are converted into a transmission mode. And selectively acquired according to the reflective mode.

An improved holographic restoration method according to another aspect of the present invention includes: a) selecting two measurement modes of an object hologram of an object to be measured (S1); b) measuring the object hologram according to the selected mode (S2); c) removing DC, virtual image, and aberration information of the measured object hologram (S3); d) extracting phase information of the object hologram (S4); And e) restoring 3D shape information and quantitative size (thickness) information of the object to be measured (S5).

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

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

2. Holographic restoration is possible with 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, it is not necessary to use reference light when restoring a hologram, and it is possible to restore a quantitative 3D image of an object to be measured in real time.

5. Detection, confirmation, or display in various fields including devices for detecting defects of ultra-fine structures such as TFTs and semiconductors, medical devices that require precise 3D image display, and detection of refractive index errors of transparent objects such as other lenses. It can be applied to the device.

6. Digital hologram can be measured irrespective of the optical characteristics of the object to be measured by selectively selecting the transmission mode and the reflection mode by one integrated system incorporating the conventional reflective and transmissive hologram restoration devices. You can solve the problem.

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

1 is a block diagram showing in detail a two-wavelength digital holographic microscope apparatus according to the disclosed prior art.
2 is a schematic block diagram showing an improved holographic restoration apparatus according to an exemplary embodiment of the present invention.
3 is a flowchart showing an improved holographic restoration method according to an embodiment of the present invention.
FIG. 4 is a detailed flowchart illustrating a detailed implementation step of step S3 of 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 indicated by the same reference numerals as possible. Further, in describing the present invention, when it is determined that a detailed description of a related configuration or function is unnecessary, a 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 mode and a reflection mode for measuring 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 for emitting a single wavelength light; A first light splitter 20 for dividing the single wavelength light emitted from the light source unit 10 into a first transmission split light T1 and a second object transmission light T2; A plurality of optical mirrors (30, 31) reflecting the first transmitted split light (T1) divided by the first light splitter (20); A second optical splitter (60) for dividing the second transmitted split light (T2) divided by the first optical splitter (20) into a first reflected split light (R1) and a second reflected split light (R2); After being reflected by the plurality of optical mirrors (30, 31), the first transmitted split light (T1) transmitted through the measurement target object (40) or the first split by the second light splitter (60) An object light objective lens 50 through which the reflected split light R1 passes; A reference light objective lens 51 for passing the second reflected split light R2 divided by the second light splitter 60; A position adjustment mirror 70 through which the second reflected and split light R2 passing through the reference light objective lens 51 is transmitted; The first transmission split light T1 that passes through the measurement target object 40 or the first reflection split light R1 reflected from the surface of the measurement target object 40, and the reference light objective lens 51 The second reflected split light R2 that has 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 an interference fringe that is 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 a microprocessor, a personal computer (PC), etc., and the recording medium 80 ) May be implemented by, for example, an image sensor such as a Charge Coupled Device (CCD) or Complimentary Metal-Oxide Semiconductor (CMOS).

The improved holographic restoration apparatus 1 according to an embodiment of the present invention uses the processor 90 to convert a light transmission object hologram and a light reflection object hologram according to a transmission mode and a reflection mode. Can be obtained selectively. That is, the processor 90 of the holographic restoration apparatus 1 improved integrally according to an embodiment of the present invention variably adjusts the position of the position adjustment mirror 70, thereby reducing light in the transmissive mode and the reflective mode. It corrects the difference in light path. 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, a CCD) to obtain an image file.

More specifically, in the holographic restoration apparatus 1 according to an embodiment of the present invention, in a transmission mode in which an object transmitting light is measured, light emitted from the laser, which is the light source unit 10, passes through the first optical splitter 20. It is divided into a first transmission split light T1 and a second transmission 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 object to be measured 40, passes through the object to be measured, and then passes through the object to be measured. 50) to the second optical splitter 60. In the embodiment of the present invention, although it is illustrated that the plurality of optical mirrors 30 and 31 are implemented with two optical mirrors, those skilled in the art will fully understand that it can 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 positioning optical mirror 70, and then passes through the reference light objective lens 51 again. It is directed to the optical splitter 60.

The first and second transmitted split lights T1 and T2 met by the second light splitter 60 form an interference fringe (a light transmitting object hologram) with respect to the light-transmitting portion of the object 40 to be measured. . Here, the first transmission split light T1 corresponds to the object light of the light-transmitting object hologram, and the second transmission split light T2 corresponds to the reference light of the light-transmitting object hologram.

On the other hand, in the reflection mode in which an object that reflects light is measured, light emitted from the laser, which is the light source unit 10, passes through the first light splitter 20 to the first transmitted split light T1 and the second transmitted split light T2. It is divided into

The second transmitted light T2 is divided into a first reflected and divided light R1 and a second reflected and divided light R2 by the second light splitter 60. The first reflected 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, and is directed to the second light splitter 60. The second reflected 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 and passes through the second light splitter 60. Heading to

The first reflected split light R1 and the second reflected split light R2 met by the second light splitter 60 form an interference fringe (a light reflection object hologram) with respect to the part of the object 40 that reflects light. Formed. Here, the first reflected split light R1 corresponds to the object light of the light-reflecting object hologram, and the second reflected split light R2 corresponds to the reference light of the light-reflecting object hologram.

At this time, the position of the positioning mirror 70 is adjusted by, for example, a processor 90 implemented as a PC, thereby correcting the difference in the optical path of light generated in the transmissive mode and the reflective mode. The light-transmitting object hologram and the light-reflecting object hologram are transferred to a PC, which is the processor 90, through a CCD, which is a recording medium 80, respectively, and are obtained in the form of image files.

When measuring by selecting a light transmission mode by the holographic restoration apparatus 1 according to an embodiment of the present invention described above, the obtained light-transmitting object hologram is applied to the light-transmitting portion of the object 40 to be measured. For interference pattern. The light-transmitting object hologram obtained in this way may be expressed as Equation 1 below as a complex conjugated hologram.

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 acquired light-transmitting object hologram,

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

Denotes 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 measured, the obtained light reflection object hologram is an interference fringe with respect to a part of the object 40 that reflects light. The light-reflecting object hologram thus obtained may be expressed as Equation 2 below as a complex conjugated hologram.

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 acquired light reflective object hologram,

Represents the object light and the reference light of the light reflective object hologram,

Denotes the complex conjugate of the object light and the reference light of the light reflective object hologram.

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

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

In the case of the transmissive mode, the frequency spectrum of the hologram of the light-transmitting object obtained by the 2D Fourier transform is the real image of the hologram of the light-transmitting object, the Imaginary image of the hologram of the light-transmitting object, and Direct Current (DC) information It appears separately (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. Apply to extract the phase information (S3 in Fig. 3 and S32 in Fig. 4).

Thereafter, reference light information of the hologram of the light transmitting object 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 in FIG. 4). A compensation term of the extracted reference light information is calculated using the calculated wave number vector constant (S35 in FIG. 4). In this case, a compensation term of the extracted reference light information is a conjugate term of a light transmitting object hologram.

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

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

Meanwhile, even in the case of the reflective mode, the light reflective object hologram obtained by the 2D Fourier transform is also obtained by applying the same method as in the above-described transmission 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 manner can be expressed as Equations 3 and 4 below, 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

Is 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 the reference light of the light reflection hologram,

Is the compensation term of the reference light information of the hologram of the light transmitting object,

Is the compensation term for the aberration information of the hologram of the light transmitting object,

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

Denotes a compensation term for curvature information of a hologram of a light reflecting object.

The compensated light-transmitting object hologram represented by Equation 3 is converted into information on a reconstruction image plane using each spectral propagation algorithm.

Phase information is extracted from the transform-compensated object hologram through Inverse 2D Fourier Transform. The phase information obtained at this time is the remaining information (i.e., information of light, object light of the objective lens 50) except for the phase information of the part of the object to be measured 40 that transmits light of the acquired light-transmitting object hologram. Aberration information) is removed, and includes only the phase information of the portion of the object 40 that transmits light.

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 remaining information (i.e., light information, object light objective lens 50) except for the phase information of the part reflecting light of the measurement target object 40 that the acquired light-reflecting object hologram has. Aberration information) is removed, and includes only the phase information of the part reflecting light of the object 40 to be measured.

The phase information of the part of the measurement object 40 that transmits the extracted light and the phase information of the part that reflects the extracted light is distorted using a 2D phase unwrapping algorithm. Each is compensated for, and the quantitative thickness information of the object to be measured 40 is calculated using this (S5 in FIG. 3). This quantitative thickness information may be expressed as 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 object 40 to be measured,

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

Is the phase information of the portion of the object to be measured 40 that transmits light,

Is the phase information of the part reflecting light of the object to be measured 40,

Denotes a difference in refractive index between the object 40 to be measured and air. The three-dimensional shape of the object is restored using the calculated quantitative thickness information of the object.

3 is a flowchart showing 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 an object to be measured 40 (S1); b) measuring the object hologram according to the selected measurement mode (S2); c) removing DC, virtual image, and aberration information of the measured object hologram (S3); d) extracting phase information of the object hologram (S4); And e) restoring 3D shape information and quantitative size (thickness) information of the object 40 to be measured (S5).

In the holographic restoration method according to an embodiment of the present invention described above, 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 conjugated hologram corresponding to the interference fringe of the light-transmitting portion of the object to be measured 40, expressed by Equation 1 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 acquired light-transmitting object hologram,

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

Denotes 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 conjugated hologram corresponding to the interference fringe of the part reflecting light of the object to be measured 40, 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 acquired light reflective object hologram,

Represents the object light and the reference light of the light reflective object hologram,

Denotes the complex conjugate of the object light and the reference light of the light reflective object hologram.

In the holographic restoration method according to an embodiment of the present invention described above, when the measured object hologram is a light-transmitting object hologram, step c) includes c1) in order to remove DC and virtual image information from the light-transmitting object hologram. The frequency spectrum of the light-transmitting object hologram obtained by performing 2D Fourier Transform is separated into Real image, 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 used by 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 wave number vector constant; c6) extracting curvature information from the light transmitting object hologram to compensate for the aberration of the object light objective lens 50 used when 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 each spectral spreading algorithm. .

In this case, step c6) includes generating a curvature information compensation term using an automatic frequency curvature compensation algorithm; And obtaining the compensated light-transmitting object hologram by multiplying the light-transmitting object hologram by the compensation term of the extracted reference light information and the aberration information compensation term.

Meanwhile, even in the case of the reflective mode, the light reflective object hologram obtained by the 2D Fourier transform is also obtained by applying the same method as in the above-described transmission 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 represented 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 reflective object hologram,

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

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

Is the compensation term of the reference light information of the hologram of the light transmitting object,

Is the compensation term for the aberration information of the hologram of the light transmitting object,

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

Denotes a compensation term for curvature information of a hologram of a light reflecting object.

In the holographic restoration 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 Inverse 2D Fourier Transform, The phase information obtained here is the remaining information (i.e., light information, object information, etc.) except for the phase information of the light transmitting or reflecting part of the light-transmitting object hologram or the light-reflecting object hologram. Aberration information of the optical objective lens 50) includes only phase information of a portion of the target object 40 from which light is transmitted or reflected.

In the holographic restoration method according to the embodiment of the present invention described above, the step e) is the extracted phase information of the part that transmits light or the extracted phase information of the part that reflects light of the measurement object 40 Compensating for each of the distorted phase information using a 2D phase unwrapping algorithm; Calculating quantitative thickness information of the object to be measured 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 represented 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 object 40 to be measured,

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,

Means the difference in the refractive index between the object and the 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 problem of a complex optical device structure required for restoration of a one-shot digital holography using a single object holographic image of the prior art, and a considerable costly cost.

Further, 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 entire configuration is very simple and it is possible to restore the holographic at low cost. .

Further, 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 those of the reflective and transmissive hologram restoration apparatus of the prior art. Since it has a configuration, it has versatility that can be easily applied to both reflective and transmissive hologram restoration apparatuses of the prior art.

In addition, in the improved holographic restoration apparatus 1 and method according to the present invention, unlike the prior art, in particular, the use of reference light is not required when reconstructing the hologram, and quantitative 3D image restoration of the object 40 to be measured in real time. This is possible.

In addition, in the improved holographic restoration apparatus 1 and method according to the present invention, since it is possible to quantitatively restore a three-dimensional image of the object 40 to be measured in real time without using a reference light as described above, TFTs and semiconductors Applicable to a variety of detection, confirmation, or display devices including devices for detecting defects with ultra-fine structures such as, medical devices requiring precise 3D image display, and detection of refractive index errors of transparent objects such as lenses. It is possible.

Moreover, in the improved holographic restoration apparatus 1 and method according to the present invention, a transmission mode and a reflection mode are selectively selected and measured by a single integrated system incorporating a reflective and transmissive hologram restoration apparatus of the prior art. Since digital holograms can be measured regardless of the optical properties of the object, additional cost problems can be solved.

The embodiments have been described above with respect to the present invention, but the present invention is not limited thereto, and modifications and variations can be implemented within the scope of the technical idea 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 optical splitter
70: positioning mirror 80: recording medium
90: processor

Claims (1)

In the holographic restoration device,
A light source unit that emits light of a single wavelength;
A first light splitter for dividing the single wavelength light emitted from the light source unit into a first split light and a second split light;
A plurality of optical mirrors reflecting the first transmitted and divided light divided by the first optical splitter;
A second optical splitter for dividing the second transmitted split light divided by the first optical splitter into first reflected split light and second reflected split light;
An object light objective lens for passing the first split light transmitted through the object to be measured 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 reflected and split light split by the second light splitter;
A position adjustment mirror through which the second reflected split light passing through the reference light objective lens is transmitted;
The first transmission split light that passes through the measurement target object or the first reflection split light reflected from the surface of the measurement target object, and the second reflection split light reflected from the positioning mirror after passing through the reference light 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 optical splitter; And
Including a processor for receiving and storing the image file generated by converting the interference fringe transmitted from the recording medium,
Selectively acquiring a light transmission object hologram and a reflection object hologram according to a transmission mode and a reflection mode by the processor.
Holographic restoration device.

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