KR102483163B1 - Apparatus for generating three-dimensional shape information of an object to be measured - Google Patents

Abstract

An embodiment of the present invention, a light source unit for emitting single-wavelength light, a collimator for collimating the single-wavelength light emitted from the light source unit, a light splitter for splitting the single-wavelength light passing through the collimator into object light and reference light, An object light objective lens passing the object light split by the light splitter, an optical mirror reflecting the reference light split by the light splitter, and an object to be measured mounted on one surface facing the object light objective lens A plate, a distance sensor disposed adjacent to the object light objective lens and detecting a distance between the object light objective lens and the plate, connected to the plate, and using a distance value sensed by the distance sensor to detect the distance between the object light objective lens and the object light objective lens. Interference fringes formed by passing the driving means for moving the plate relative to the lens, the object light reflected from the surface of the object to be measured through the object light objective lens, and the reference light reflected by the optical mirror, respectively, to the optical splitter. An image sensor for recording and a processor for receiving and storing an image including intensity information of an object hologram generated by converting the interference fringe in the image sensor and generating 3D shape information of the object to be measured It provides an apparatus for generating three-dimensional shape information of an object to be measured, comprising:

Description

Apparatus for generating three-dimensional shape information of an object to be measured}

The present invention relates to an apparatus for generating three-dimensional shape information of a measurement target object. More specifically, the present invention provides a three-dimensional image of the object to be measured from an image including intensity information of an object hologram generated by the interference of reference light reflected from an optical mirror and object light reflected from or transmitted through the object to be measured. It relates to a device for generating shape information.

A digital holography microscope refers to a microscope that acquires the shape of an object using digital holography technology.

If a general microscope is a device that acquires the shape of an object by acquiring reflected light reflected from the object, a digital holography microscope is a device that acquires the interference light and/or diffracted light generated by the object and acquires the shape of the object therefrom. to be.

A digital holography microscope uses a laser that generates light of a single wavelength as a light source, and splits the light generated by the laser into two beams using a beam splitter. At this time, one light (hereinafter referred to as reference light) is directed toward the image sensor, and the other light (hereinafter referred to as object light) is reflected from the target object and directed toward the image sensor, so that interference between the reference light and object light occurs. do.

The image sensor may record the interference pattern according to the interference phenomenon as a digital image and restore the 3D shape of the object to be measured from the recorded interference pattern. At this time, the interference pattern recorded by the image sensor is commonly referred to as a hologram.

Conventional optical holography microscopes record interference patterns according to the interference between reference light and object light with a special film. At this time, when the reference light is irradiated on the special film on which the interference fringes are recorded, the shape of the virtual object to be measured is restored to the position where the object to be measured is located.

Compared to the conventional optical holography microscope, the digital holography microscope digitizes (or digitizes) the interference pattern of light through an image sensor, and restores the shape of the object to be measured through electronic calculation of the interference pattern information, not optically. There is a difference in

Meanwhile, a conventional digital holography microscope using a laser light source of a single wavelength has a problem in that the minimum unit length for measuring an object is limited to the wavelength of the laser. In order to compensate for this, another conventional digital holography microscope using a laser light source of two or more wavelengths has a problem in that the manufacturing cost of the microscope is high and the three-dimensional shape of the object cannot be obtained in real time.

In addition, the above-described conventional digital holography microscopes generate a CGH (Computer Generated Hologram) with a computer to restore the shape of an object to be measured, display it on a Spatial Light Modulator (SLM), and A 3D holographic image of the object was obtained by illuminating a reference light. However, this method not only requires the use of an expensive spatial light modulator (SLM), but also has clear technical limitations because it is merely a digitization of a special film in the optical holography microscope described above.

In order to solve such problems of conventional digital holography microscopes, for example, Korean Patent Publication No. 10-2016-0029606 (hereinafter referred to as "disclosed prior art") proposes a digital holography microscope and a method for generating a digital holographic image. Hereinafter, the disclosed prior art will be briefly reviewed.

2 is a block diagram showing in detail a two-wavelength digital holography microscope apparatus according to the prior art.

Referring to FIG. 2, the conventional two-wavelength digital holography microscope device includes a mixed light source unit 10, a wavelength division unit 20, an interference pattern acquisition unit 30, an object unit 40, an image sensor unit 50, It includes an image storage unit 60, a control unit 70, and an object shape restoration unit 80.

The mixed light source unit 10 includes a mixed light source light emitting unit 11 and a light source unit lens 12 . The mixed light source light emitting unit 11 emits mixed light having wavelength bands distributed in several non-single bands. The light source unit lens 12 optically controls the mixed light generated by the mixed light source light emitting unit 11 and makes it incident to the wavelength division unit 20 .

The wavelength division unit 20 includes a first light splitter 21 , a first filtering plate 22 , a second filtering plate 23 and a first reflector 24 . The first light splitter 21 receives the mixed light incident from the mixed light source unit 10 and splits it into two lights. At this time, the first light splitter 21 serves to divide the incident mixed light into different directions and propagate them. The first light filter 22 receives one of the split lights from the first light splitter 21 and obtains a first light ray having a predetermined single wavelength. Here, the light input to the first filter plate 22 is filtered while passing through the first filter plate 22 , and a first light ray having a single wavelength determined according to the characteristics of the first filter plate 22 is obtained. In the same way as the first filter plate 22, the second light filter 23 receives the other light from among the light divided by the first light splitter 21, and receives the second light having a wavelength different from that of the first light ray. get the rays And the second light ray is sent to the interference fringe acquisition unit 30 . The first reflector 24 serves to receive the first light ray obtained from the first light filter 22 and reflect it to the interference pattern acquisition unit 30 .

The interference pattern acquisition unit 30 includes a second light splitter 31 , a third light splitter 32 , a second reflector 33 , a third light filter 34 , and a third reflector 35 . The second beam splitter 31 receives the first light ray input from the wavelength splitter 20 and splits it into a first object light and a first reference light. At this time, the second light splitter 31 serves to divide and propagate the incident first light beam in different directions. The third light splitter 32 also receives the second light ray and splits it into a second object light and a second reference light in the same manner as the second light splitter 31 . The second reflector 33 receives the first standard light and sends the reflected first reference light to the second light splitter 31 . The third light filter 34 receives the first reference light divided by the second light splitter 31 and sends it to the second reflector 33, and receives the reflected first reflection reference light and sends it to the second light splitter. In addition, the third light filter 34 prevents the second object light from reaching the second reflector 33 when a portion of the second object light reaches the second light splitter 31 and is split, so that a portion of the second object light travels in the direction of the second reflector 33. . To this end, the third filter plate 34 has the same characteristics as the first filter plate 22 in transmitting light. The third reflector 35 receives the second reference light and sends the reflected second reference light to the third beam splitter 32, where the second reflector 33 and the third reflector 35 are the controller 70 ), 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 the first and second object lights through the following process and sent to the image sensor unit 50 . The second beam splitter 31 causes the first object light divided as described above to be incident on the object to be measured mounted on the objective unit 40, and is divided from the third beam splitter 32 and sent to the second object light. 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 the first reflecting object light. In addition, the reflected light obtained by reflecting the second object light incident from the object to be measured is referred to as the second reflection object light. The second beam splitter 31 receives the reflected first and second reflection object lights as described above and sends them to the third beam splitter 32 . The third beam splitter 32 sends the first and second reflection object lights received as described above to the image sensor unit 50 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 50 through the following process. Specifically, the second beam splitter 31 receives the first reflection reference light reflected from the second reflector 33 and sends it to the third beam splitter 32 . As described above, the third beam splitter 32 receives the first reflection reference light sent from the second beam splitter 31 and the second reflection reference light reflected from the third reflector 35, and returns to the image sensor unit 50. send to Accordingly, after the first reflective object light, the first reflective reference light, the second reflective object light, and the second reflective reference light are all equally sent in the direction of the image sensor unit 50 in the third beam splitter 32, they mutually interfere with each other. Interference fringes are created.

Meanwhile, the angles of the second reflector 33 and the third reflector 35 are controlled by the control unit 70 to form 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 33 and the third reflector 35 are different from each other, the first reference light reflected from the second reflector 33 and the second reference light reflected from the third reflector 35 A separation occurs in the direction of light, and when the first reflection standard light and the second reflection standard light are combined with the first and second reflection object lights reaching the image sensor unit 50 to form an interference fringe, each wavelength Differently off-axis interference fringes are formed.

The object unit 40 includes an object holder 41 and an objective lens 42 . The object holder 41 fixes the object to be measured on the holder to be measured, and the objective lens 42 optically adjusts the first and second object lights incident on the object to be measured.

The image sensor unit 50 projects the interference pattern acquired by the interference pattern acquisition unit 30 onto a digital image sensor, measures the projected interference pattern using the digital image sensor, and outputs the measured value as a discrete signal. convert to Generally, the recording of the interference fringes is called a hologram. As such a digital image sensor, various image sensors such as CCD may be used.

The image storage unit 60 stores interference fringe information converted into discrete signals by the image sensor unit 50 in various storage media such as a memory or a disk device.

The control unit 70 implements the above-described off-axis system and adjusts the positions and angles of the second reflector 33 and the third reflector 35 to acquire the interference fringes. ), and control the object part 40, such as adjusting the objective lens 42 to adjust the first and second object lights incident on the object to be measured, and the interference fringe is measured to determine the The image sensor unit 50 is controlled to convert information into discrete signals, and the image storage unit 60 is controlled to store interference pattern information converted into discrete signals.

The object shape restoration unit 80 includes a phase information acquisition unit 81, a thickness information acquisition unit 82, and a shape restoration unit 83. The phase information acquisition unit 81 acquires the phase information of the interference fringes for the first light ray and the phase information of the interference fringes for the second light ray using the interference fringe information, and the thickness information acquisition unit 82 obtains thickness information of the object to be measured using the phase information, and the shape restoration unit 83 restores the real-time 3D shape of the object to be measured using the thickness information. At this time, the thickness information of the object to be measured includes difference information of paths respectively traveled by the object light and the reference light. 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.

According to the disclosed prior art including the above, it is possible to improve measurement resolution and secure real-time image acquisition, but the following problems still occur.

Since a mixed light source having a wavelength band distributed in several bands is used in the previously disclosed prior art, the wavelength division unit 20 divides the first light source and the second light source having different wavelengths to obtain at least two or more single wavelengths. To do this, the first filtering plate 22, the second filtering plate 23, and the first reflector 24 must be used.

In addition, the interference pattern acquisition unit 30 includes a third light splitter 32 for splitting the second light source, a third reflector 35 for reflecting the second light source, and a second reflector 33 for the second light source. It is necessary to additionally use a third filter plate 34 for blocking the incident light.

Accordingly, the structure of the microscope becomes complicated, which entails various problems such as an increase in manufacturing cost and an increase in design complexity. Therefore, a new method for solving the above problems while using a light source of a single wavelength is required.

Republic of Korea Patent Publication No. 10-2016-0029606 Republic of Korea Patent Publication No. 10-2010-0095302 Republic of Korea Patent Publication No. 10-2012-0014355 Korean Patent No. 10-1139178 Korean Patent No. 10-1441245 U.S. Patent No. 7,649,160

The present invention is to solve the problems of the prior art as described above, and to accurately generate 3D shape information of a measurement target object by acquiring only one hologram.

In particular, the present invention seeks to generate three-dimensional shape information of an object to be measured with improved accuracy by generating reference light information and curvature aberration information of an object light objective lens from one hologram and correcting the obtained object hologram in consideration of the information.

The present invention also addresses the problem of complex optical device structures and consequently high costs.

Furthermore, the present invention seeks to detect defects of such structures with high probability by accurately acquiring the three-dimensional shape of ultrafine structures such as TFTs and semiconductors.

An embodiment of the present invention, a light source unit for emitting single-wavelength light, a collimator for collimating the single-wavelength light emitted from the light source unit, a light splitter for splitting the single-wavelength light passing through the collimator into object light and reference light, An object light objective lens passing the object light split by the light splitter, an optical mirror reflecting the reference light split by the light splitter, and an object to be measured mounted on one surface facing the object light objective lens A plate, a distance sensor disposed adjacent to the object light objective lens and detecting a distance between the object light objective lens and the plate, connected to the plate, and using a distance value sensed by the distance sensor to detect the distance between the object light objective lens and the object light objective lens. Interference fringes formed by passing the driving means for moving the plate relative to the lens, the object light reflected from the surface of the object to be measured through the object light objective lens, and the reference light reflected by the optical mirror, respectively, to the optical splitter. An image sensor for recording and a processor for receiving and storing an image including intensity information of an object hologram generated by converting the interference fringe in the image sensor and generating 3D shape information of the object to be measured It provides an apparatus for generating three-dimensional shape information of an object to be measured, comprising:

Another embodiment of the present invention, a light source unit for emitting single-wavelength light, a collimator for collimating the single-wavelength light emitted from the light source unit, a light splitter for splitting the single-wavelength light passing through the collimator into object light and reference light, A first optical mirror for reflecting the reference light split by the beam splitter, a second optical mirror for reflecting the object light split by the light splitter, and a traveling path of the object light reflected by the second optical mirror A plate disposed on one surface of a plate on which the object to be measured is seated, an object light objective lens through which the object light passes through the object to be measured and then transmits the object light including the information of the object to be measured, and the first optical mirror. A second beam splitter through which the reference light reflected by the object light and the object transmitted light passing through the objective lens are transmitted respectively, and an image recording an interference fringe formed by the reference light transmitted to the second beam splitter and the object transmitted light A sensor, a distance sensor disposed adjacent to the object light objective lens to detect a distance between the object light objective lens and the plate, connected to the plate, and using a distance value sensed by the distance sensor to detect a distance between the object light objective lens and the object light objective lens. An image including intensity information of an object hologram generated by converting the interference fringes in a driving means for moving the plate with respect to a lens and the image sensor is received and stored, and 3D shape information of the object to be measured is stored. It provides an apparatus for generating three-dimensional shape information of an object to be measured, including a processor that generates a.

In one embodiment of the present invention, the plate includes an overlapping area overlapping the measurement target object and a non-overlapping area overlapping the measurement target object, and the distance sensor includes the non-overlapping area of one side of the plate. The distance of the plate may be detected based on the area.

In one embodiment of the present invention, the processor moves the plate using the distance value sensed by the distance sensor, detects an edge of the image obtained from the image sensor, and contrast of the detected edge A contrast value may be extracted, and the driving unit may be controlled to adjust a distance between the plate and the object light objective lens based on the extracted contrast value.

In one embodiment of the present invention, a distance between the object light objective lens and the beam splitter may be constant.

In one embodiment of the present invention, the processor extracts real image components corresponding to a real image among at least one frequency component included in the image, and based on the real image components, the reference light and the conjugate ( conjugate) generating a real image hologram including a correction light having a relationship and mounting information of the object to be measured, generating an intermediate hologram in which information of the reference light is removed from the real image hologram based on the correction light, and generating the intermediate hologram After generating the curvature aberration correction information from the hologram, based on the curvature aberration correction information, a correction hologram in which the error due to the curvature aberration is reduced in the intermediate hologram is generated, and the three Dimensional shape information can be created.

Other aspects, features, and advantages other than those described above will become clear from the detailed description, claims, and drawings for carrying out the invention below.

According to one embodiment of the present invention made as described above, according to the present invention, it is possible to accurately generate 3D shape information of the object to be measured by acquiring only one hologram.

In particular, by generating information on the reference light and curvature aberration information of the object light objective lens from one hologram, and correcting the obtained object hologram in consideration of the information, it is possible to generate 3D shape information of the object to be measured with improved accuracy.

It can also solve the problem of complex optical device structure and consequently high cost.

Furthermore, by accurately acquiring the three-dimensional shape of ultrafine structures such as TFTs and semiconductors, defects in these structures can be detected with high probability.

Of course, the scope of the present invention is not limited by these effects.

1 is a block diagram showing in detail a two-wavelength digital holography microscope apparatus according to the prior art disclosed.
2A is a block diagram showing a schematic configuration of a holography restoration apparatus according to a first embodiment of the present invention.
2B is a block diagram showing a schematic configuration of a holography restoration apparatus according to a second embodiment of the present invention.
3A and 3B are diagrams for explaining a method of automatically focusing (outo-focusing) on a measurement target object M by the holography restoration apparatus according to an embodiment of the present invention.
4A and 4B are diagrams for explaining a method of focusing by detecting an edge in an image of a measurement target.
5A and 5B are diagrams for explaining the external appearance of an exemplary object to be measured.
6 is an example of an image of a portion of an object to be measured.
FIG. 7 is a diagram illustrating frequency components of an image of a portion of the object to be measured shown in FIG. 6 .
FIG. 8 is a diagram for explaining a method of extracting frequency components corresponding to a real image from the frequency components shown in FIG. 7 .
9A is a diagram illustrating the intensity of digital reference light.
9B is a diagram illustrating a phase of a reference light.
9C is a diagram showing the intensity of correction light.
9D is a diagram showing the phase of correction light.
10 is a diagram illustrating an exemplary real-image hologram.
11 and 12 are views for explaining a method of determining a curvature aberration correction term from an intermediate hologram by a processor according to an embodiment of the present invention.
13 is a diagram illustrating an example of a 3D shape of a measurement target object generated from a hologram.
14 is a flowchart for explaining a method of generating 3D shape information of a measurement target performed by a holography restoration apparatus according to an embodiment of the present invention.
15 and 16 are flowcharts of a noise removal method of a holography restoration apparatus according to embodiments of the present invention.

Hereinafter, various embodiments of the present disclosure will be described in conjunction with the accompanying drawings. Various embodiments of the present disclosure may have various changes and various embodiments, and specific embodiments are illustrated in the drawings and related detailed descriptions are described. However, this is not intended to limit the various embodiments of the present disclosure to specific embodiments, and should be understood to include all changes and/or equivalents or substitutes included in the spirit and technical scope of the various embodiments of the present disclosure. In connection with the description of the drawings, like reference numerals have been used for like elements.

Expressions such as “include” or “may include” that may be used in various embodiments of the present disclosure indicate the presence of disclosed functions, operations, or components, and may include one or more additional functions, operations, or components. components, etc. are not limited. In addition, in various embodiments of the present disclosure, terms such as "include" or "have" are intended to designate that there are features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, It should be understood that it does not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

In various embodiments of this disclosure, expressions such as “or” include any and all combinations of the words listed together. For example, "A or B" may include A, may include B, or may include both A and B.

Expressions such as "first", "second", "first", or "second" used in various embodiments of the present disclosure may modify various components of various embodiments, but do not limit the components. don't For example, the above expressions do not limit the order and/or importance of corresponding components. The above expressions may be used to distinguish one component from another. For example, the first user device and the second user device are both user devices and represent different user devices. For example, a first element may be termed a second element, and similarly, a second element may also be termed a first element, without departing from the scope of rights of various embodiments of the present disclosure.

When an element is referred to as being "connected" or "connected" to another element, the element may be directly connected or connected to the other element, but with the other element. It should be understood that other new components may exist between the other components. On the other hand, when an element is referred to as being “directly connected” or “directly connected” to another element, it will be understood that no new element exists between the element and the other element. should be able to

Terms used in various embodiments of the present disclosure are only used to describe a specific embodiment, and are not intended to limit various embodiments of the present disclosure. Singular expressions include plural expressions unless the context clearly dictates otherwise.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments of the present disclosure belong.

Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in various embodiments of the present disclosure, ideal or excessively formal. not interpreted as meaning

2A is a block diagram showing a schematic configuration of a holography restoration apparatus 300A according to a first embodiment of the present invention.

In the present invention, a 'holography restoration device' may refer to a device that acquires a hologram (hereinafter referred to as an 'object hologram') of an object to be measured, and analyzes and/or displays the obtained object hologram.

For example, the holography restoration device 300A may be a device disposed in a semiconductor manufacturing line, obtaining an object hologram of a semiconductor being produced, and determining whether the semiconductor is integrity based on the obtained object hologram. However, this is an example and the spirit of the present invention is not limited thereto.

Meanwhile, in the present invention, an 'object hologram' is a hologram that can be generated from an image acquired by the holography restoration device 300A, and can mean a hologram before various processes by the holography restoration device 300A are performed. there is. A detailed description of this will be given later.

Referring to FIG. 2A , the holography restoration apparatus 300A according to the first embodiment of the present invention includes a light source unit 310 emitting single-wavelength light, and a collimator 320 for collimating the single-wavelength light emitted from the light source unit 310. ), a light splitter 330 that splits the single-wavelength light passing through the collimator 320 into object light O and reference light R, and an object that passes the object light O divided by the light splitter 330. The objective lens 340, the optical mirror 370 for reflecting the reference light R divided by the beam splitter 330, and the object M to be measured are placed on one surface facing the object light objective lens 340. The plate 351, which is disposed adjacent to the object light objective lens 340, is connected to the distance sensor 357 and the plate 351 for detecting the distance between the object light objective lens 340 and the plate 351, a driving means 353 for moving the plate 351 relative to the object light objective lens 340 using the distance value sensed by the distance sensor 357; The object light O passed through the objective lens 340 and reflected on the surface of the object 350 and the reference light R reflected by the optical mirror 370 are transmitted to the beam splitter 330, respectively. An image sensor 380 that records the interference fringe formed by the image sensor 380 and an image including intensity information of an object hologram generated by converting the interference fringe in the image sensor 380 is received and stored, and an object to be measured (M ) may include a processor 390 generating 3D shape information. Here, the object to be measured (M) may be a substrate, and hereinafter, the substrate will be described as the object (M) to be measured.

Meanwhile, the holography reconstruction apparatus 300A according to the first embodiment of the present invention may further include a reference light objective lens (not shown) passing the reference light R divided by the beam splitter 330 .

At this time, the processor 390 may generate 3D information of the object M to be measured from the image acquired by the image sensor 380 . A detailed description of the operation of the processor 390 will be described later.

2B is a block diagram showing a schematic configuration of a holography restoration apparatus 300B according to a second embodiment of the present invention.

Referring to FIG. 2B , the holography restoration apparatus 300B according to the second embodiment of the present invention includes a light source unit 310 emitting single wavelength light, and a collimator 320 for collimating the single wavelength light emitted from the light source unit 310. ), a beam splitter 330 that splits the single-wavelength light passing through the collimator 320 into object light O and reference light R, and a first beam that reflects the reference light R divided by the beam splitter 330. An optical mirror 370, a second optical mirror 372 for reflecting the object light O divided by the beam splitter 330, and a propagation path of the object light O reflected by the second optical mirror 372 Disposed on the plate 351, on one surface of which the object M to be measured is seated, and after the object light O passes through the object M to be measured, the object transmitted light including the information of the object M to be measured is transmitted. A second beam splitter 332 through which the passing object light objective lens 340, the reference light R reflected by the first optical mirror 370 and the object transmitted light passing through the object light objective lens 340 are transmitted, respectively; An image sensor 380 that records an interference fringe formed by the reference light R transmitted to the second beam splitter 332 and the light transmitted through the object, disposed adjacent to the object light objective lens 340, and the object light objective lens 340 ) and the plate 351, the distance sensor 357 is connected to the plate 351 and the plate 351 is connected to the object light objective lens 340 using the distance value detected by the distance sensor 357. ) Receives and stores an image including intensity information of an object hologram generated by converting an interference pattern in the driving unit 353 and the image sensor 380 that move the 3D image of the object M to be measured. It may include a processor 390 that generates shape information.

Of course, even in this second embodiment, the processor 390 may generate 3D information of the object M to be measured from an image acquired by the image sensor 380 . A detailed description of the operation of the processor 390 will be described later.

In the holography restoration device 300A according to the first embodiment and the holography restoration device 300B according to the second embodiment shown in FIGS. 2A and 2B, respectively, object light O is measured. The fact that the target object M is reflected (the embodiment of FIG. 2A) or the object light O is transmitted through the object M to be measured (the embodiment of FIG. 2B) and some components (for example, It has substantially the same configuration except for the additional use of the second optical mirror 372 and the second light splitter 332 and the arrangement of some components accordingly) of the embodiment of FIG. 2B.

In particular, it should be noted that the image has the same feature in that the image is acquired by the image sensor 380 and the processor 390 generates the reference light R from the acquired image.

Hereinafter, the holography restoration devices 300A and 300B according to the first and second embodiments of the present invention will be collectively referred to as the holography restoration device 300 and described.

Meanwhile, the processor 390 of the holography reconstruction device 300 according to an embodiment of the present invention may include all types of devices capable of processing data. For example, the processor 390 may refer to a data processing device embedded in hardware having a physically structured circuit to perform functions expressed by codes or instructions included in a program.

As an example of such a data processing device built into the hardware, a microprocessor, a central processing unit (CPU), a processor core, a multiprocessor, an application-specific integrated (ASIC) Circuit) and FPGA (Field Programmable Gate Array), but the scope of the present invention is not limited thereto.

In addition, the image sensor 380 according to an embodiment of the present invention may be implemented as at least one image sensor such as, for example, a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS).

Referring back to FIGS. 2A and 2B , the holography restoration apparatus 300 according to an embodiment of the present invention is for generating 3D shape information of an object M to be measured placed on a plate 351, For example, by generating 3D shape information of a semiconductor substrate, it can be used for the purpose of inspecting pattern defects after a deposition process. At this time, the optical component of the holography restoration device 300 builds a system in a state where the distance between each component is set in advance in order to generate accurate 3D shape information.

Here, the optical configuration of the holography restoration apparatus 300A according to the first embodiment includes a collimator 320, a light splitter 330, an object light objective lens 340, an optical mirror 370, and an image sensor 380. The holography restoration apparatus 300B according to the second embodiment includes a collimator 320, a light splitter 330, a second light splitter 332, an object light objective lens 340, a first optical mirror 370, A second optical mirror 372 and an image sensor 380 may be included.

Therefore, the above-described optical configuration is fixedly disposed as the position is set in advance, and in order to inspect a plurality of objects M to be measured, the objects M to be measured on the plate 351 must be alternately measured. For example, a distance between the object light objective lens 340 and the beam splitter 330 or a distance between the object light objective lens 340 and the second beam splitter 332 may be constant. At this time, since the plate 351 continuously moves to seat the object M to be measured, the above-described optical configuration, in particular, the object light objective lens 340 may be out of focus. The holography restoration apparatus 300 according to an embodiment of the present invention includes the distance sensor 357 to automatically focus on the object M to be measured to solve the above problem.

The distance sensor 357 according to an embodiment of the present invention may be positioned adjacent to the object light objective lens 340 to detect a distance between the object light objective lens 340 and the plate 351 . For example, the distance sensor 357 emits a laser beam toward the plate 351, detects the reflected laser beam from the plate 351, and measures the distance to the plate 351 (Laser Range Sensor). Finder), but the technical spirit of the present invention is not limited thereto. As another embodiment, the distance sensor 357 may be disposed on the plate 351 and may be provided as a sensor that detects the displacement of the plate 351 .

Meanwhile, the distance sensor 357 may directly detect the distance between the object light objective lens 340 and the plate 351, but the distance between the distance sensor 357 and the object light objective lens 340 is known in advance. In this case, the distance between the object light objective lens 340 and the plate 351 may be derived by measuring the distance from the distance sensor 357 to the plate 351 . In the case of directly measuring the distance between the object light objective lens 340 and the plate 351, the position of the distance sensor 357 should be placed at the same height as the object light objective lens 340 in the measurement direction.

On the other hand, when the object M to be measured is placed on the plate 351, the overlapping area (A1, see FIG. 3A) overlapping the object M and the non-overlapping area overlapping the object M (A2, see FIG. 3A). The holography restoration apparatus 300 according to an embodiment of the present invention can adjust the macroscopic distance between the plate 351 and the object light objective lens 340 by using the distance sensor 357. At this time, the object to be measured ( When measuring in an area where M) overlaps, the distance may vary according to the height of the object M to be measured.

The purpose of the holography restoration device 300 according to an embodiment of the present invention is to generate accurate 3D information of the object M to be measured, based on the object M to be measured, which can be deposited or formed with different heights. Without measuring the distance, the distance to the plate 351 can be sensed based on the non-overlapping area A2 consisting of a plane with a constant height. The holography restoration device 300 may measure the distance from a pre-set position in the non-overlapping area A2 to the plate 351, and for this purpose, a vision camera (not shown) for confirming the exact position of the plate 351. city) may be further included. The holography restoration device 300 sets the position of the plate 351 in the plane direction (x-y) using a vision camera (not shown), and then uses the distance sensor 357 to set the position perpendicular to the plane direction (x-y). A macroscopic distance in one height direction (z direction) can be measured.

Meanwhile, the driving unit 353 is connected to the plate 351 and can move the plate 351 with respect to the object light objective lens 340 using the distance value sensed by the distance sensor 357 . The driving means 353 may move the position of the plate 351 with respect to the height direction (z direction) of the plate 351 . The driving means 353 may include an actuator such as a motor or a hydraulic cylinder. Although not shown, the holography restoration apparatus 300 further includes one or more guide members (not shown) for guiding the up and down movement of the plate 351 by the drive unit 353 so that the plate 351 moves up and down. It can be supported stably without twisting when it becomes.

3A and 3B are diagrams for explaining a method in which the holography restoration apparatus 300 according to an embodiment of the present invention automatically focuses (outo-focusing) on a measurement target object M, and FIGS. 4A and 3B 4B is a diagram for explaining a method of focusing by detecting an edge in an image of a measurement target object M. Referring to FIG.

Referring to FIG. 3A , the holography restoration apparatus 300, when the object M to be measured is placed on the plate 351, first moves the plate 351 and the object light objective lens 340 using the distance sensor 357. distance between them can be detected. At this time, the distance sensor 357 detects the distance to the plate 351 and generates the first signal S1. As described above, the object light objective lens 340 and the distance sensor 357 are at the same height. When in the position, the first signal S1 may be a signal including distance information between the object light objective lens 340 and the plate 351 . Alternatively, when the distance sensor 357 is at a different height from the object light objective lens 340, the first signal S1 may be a signal including distance information between the distance sensor 357 and the plate 351. .

The processor 390 may receive the first signal S1 from the distance sensor 357 and control the driving means 353 to adjust the height of the plate 351 according to the first signal S1. If the height positions between the distance sensor 357 and the object light objective lens 340 are different, positional information of the distance sensor 357 and the object light objective lens 340 may be previously stored in the process 390. The height position of the plate 351 may be adjusted using previously stored information and the first signal S1.

Referring to FIG. 3B, the holography restoration apparatus 300 measures the image of the object M to be measured macroscopically whose position is adjusted through the above-described method, and the edge of the image obtained from the image sensor 380 can be detected. The holography reconstruction apparatus 300 may measure a preliminary image of the object M to be measured through the image sensor 380 prior to measuring an image for generating 3D shape information of the actual object M to be measured. there is.

When such a preliminary image is provided, the processor 390 may detect an edge included in all preliminary images and extract a contrast value of the detected edge. In this case, the processor 390 may detect edge pixels in the image using an edge detection algorithm. The goal of edge detection is to recognize each point in a digital image where the image intensity changes sharply. During the edge detection process, discontinuities are detected and can assist the system in recognizing important events, such as focusing automatically. can Edge detection may be one of the important steps in processing such as image processing, image analysis, image pattern recognition, and computer vision.

For example, the processor 390 measures the x-direction brightness and color change rate and the y-direction brightness and color change rate of the pixels in the preliminary image obtained from the image sensor 380, and detects pixels at a point where the change rate is large as edge pixels can do. Thereafter, the processor 390 may control the driving unit 353 to adjust the distance between the plate 351 and the object light objective lens 340 based on the extracted contrast value.

4A and 4B, when the macroscopic distance of the plate 351 is adjusted by the distance sensor 357, the image sensor 380 obtains a preliminary image of the object M to be measured, and then the processor ( 390), and at this time, the processor 390 may detect an edge from the preliminary image. The processor 390 may extract the contrast value of the detected edge while microscopically adjusting the height of the plate 351 through the driving unit 353 . As shown in FIG. 4A, when the focus is out of focus, blur occurs at the edge and the contrast value is low, and when the focus is right as shown in FIG. 4B, the contrast value at the edge is relatively becomes high with

As an embodiment, the processor 390 microscopically adjusts the drive unit 353 to find the highest contrast value, places the plate 351 at a height corresponding to the value, and then the actual image required for generating 3D shape information. can measure As another example, the processor 390 may position the plate 351 at a height having a contrast value corresponding to a preset reference range.

In addition, when comparing the contrast values, the processor 390 may compare contrast values at one point of an edge or average contrast values of the entire edge to compare average values.

As described above, the holography restoration apparatus 300 according to an embodiment of the present invention can automatically adjust the focus with the object M to be measured through the movement of the plate 351 . The holography restoration apparatus 300 can implement efficient auto focusing by macroscopically moving the plate 351 using the distance sensor 357 and then microscopically moving the plate 351 using an edge. can

5A and 5B are diagrams for explaining the external appearance of an exemplary object to be measured 350 . When the object to be measured 350 is the substrate M, deposition materials may be formed on the substrate M along the mask pattern. Since the thin film pattern deposited on the substrate M has a somewhat complex shape, the simplified pattern shown in FIGS. 5A and 5B will be described as an example for convenience of explanation.

As shown in FIGS. 5A and 5B , the object to be measured 350 may include rectangular parallelepiped structures 51A to 51I disposed at predetermined intervals on one surface. In other words, the object to be measured 350 may include rectangular parallelepiped structures 51A to 51I protruding in the Z direction on a plane parallel to the X-Y plane.

Hereinafter, the holography restoration device 300 irradiates the object light O in a direction perpendicular to the surface of the object to be measured 350 on which the rectangular parallelepiped structures 51A to 51I are disposed, thereby generating an image of the object to be measured 350. It is explained on the premise of obtaining

First, the image sensor 380 according to an embodiment of the present invention may obtain an image of the measurement target object 350 .

In the present invention, the 'Image' of the object to be measured 350 is the intensity information at each position of the object hologram (U0(x,y,0)) of the object to be measured 350 (that is, | (U0(x,y,0)| ² ), and can be expressed as Equation 2 below.

[Equation 2]

Here, the object hologram Uo(x,y,0) represents the phase information at each x,y point of the object to be measured, and x, y are coordinates in the space where the object to be measured is placed perpendicular to the object light (O). Represents the coordinates defining the plane to be, O (x, y) and R (x, y) represent the object light (O) and reference light (R), respectively, O * (x, y) and R * (x, y) represents a complex conjugate of the object light O and the reference light R, respectively.

For example, the image sensor 380 acquires an image as shown in FIG. 5 for a part (eg, a part including 51A and 51B) of the object to be measured 350 shown in FIGS. 5A and 5B. can

Since the image acquired by the image sensor 380 includes intensity information at each position of the object hologram U0(x,y,0) as described above, the general image acquired by the image sensor 380 It may be different from the image of the object to be measured 350 (that is, photographed only with the object light O).

Referring to Equation 1, the object hologram U0(x,y,0) does not include the object light 0 including the phase information of the object to be measured 350 at each point and the phase information of the object to be measured. It may be generated by interference of the reference light R, which is not visible.

In addition, the object hologram (U0 (x, y, 0)) is the object light objective lens (340 ) may further include an error and noise (for example, speckle noise due to the use of photons of a laser) due to an aberration of .

Accordingly, the processor 390 according to an embodiment of the present invention may perform various calculation processes as described below in order to remove the above-described error and noise from the image obtained by the image sensor 380 .

The processor 390 according to an embodiment of the present invention may check frequency components of an image acquired by the image sensor 380 . For example, the processor 390 may perform a 2D Fourier Transform on the image to check frequency components of the image.

In other words, the processor 90 calculates the frequency components included in the image including intensity information (ie, |(U0(x,y,0)| ² ) for each position of the object hologram U0(x,y,0). At this time, the image may include a frequency component corresponding to a real image, a frequency component corresponding to an imaginary image, and a DC component.

Of course, the image may further include various components in addition to the above-described three components (frequency component corresponding to the real image, frequency component and DC component corresponding to the virtual image). For example, the image may further include frequency components due to noise. However, this is an example and the spirit of the present invention is not limited thereto.

The processor 390 according to an embodiment of the present invention may extract only components corresponding to the real image from among the identified frequency components. At this time, the processor 390 may extract components corresponding to the real image in various ways.

For example, the processor 390 extracts components (hereafter referred to as peak components) having a peak value in the size of the component from frequency components included in the image, and extracts a peak component corresponding to the real image from among the extracted peak components. Components within the frequency difference of plasticity can be extracted as components corresponding to the real image.

In this case, the processor 390 may determine components corresponding to the real image in various ways based on the peak component corresponding to the real image. For example, the processor 90 may determine frequency components in a cross region including a peak component among frequency components corresponding to the real image as components corresponding to the real image. In this case, the length of the cross section from the peak component may be determined based on a distance difference value between a frequency component corresponding to the real image and a frequency component corresponding to the origin. For example, however, this is illustrative and the spirit of the present invention is not limited thereto.

In an optional embodiment, the processor 390 may extract only components corresponding to the real image from frequency components included in the hologram using an automatic real image spot-position extraction algorithm.

In the present invention, 'extracting' a specific frequency component may mean extracting the frequency of the corresponding frequency component and the size (or intensity) of the corresponding frequency component.

FIG. 7 is a diagram illustrating frequency components of an image of a portion of the object to be measured 350 shown in FIG. 6 .

As described above, the processor 390 can check the frequency components of the image acquired by the image sensor 380, and accordingly, the processor 390 determines the frequency component 911 corresponding to the real image and the frequency component corresponding to the virtual image. Various frequency components including 912 and DC component 913 can be identified.

Also, the processor 390 may extract only the frequency component 911 corresponding to the real image from among the identified components. At this time, the processor 390 removes noise from a frequency component corresponding to the real image. Specifically, the processor 390 removes frequency components located in the direction of the interference fringe and the normal direction of the interference fringe as noise, for example, as shown in FIGS. 8A, 8B, 8C, and 8D, corresponding to the real image. Frequency components in the cross region centered on the peak component may be determined as components corresponding to the real image. At this time, the direction of the cross section is rotated according to the direction of the interference fringes.

The processor 390 according to an embodiment of the present invention may generate digital reference light from frequency components corresponding to the real image extracted through the above process. Looking at this in more detail, the processor 390 may calculate the propagation direction and wave number of the digital reference light based on the frequency components corresponding to the real image. In other words, the processor 390 may calculate the wavenumber vector of the digital reference light.

In addition, the processor 390 generates a digital reference light based on the propagation direction and wavenumber (or wavenumber vector) of the digital reference light, and the conjugate term of the generated digital reference light (R(x,y)) as in Equation 3 below By obtaining, the correction light Rc(x,y) can be generated.

[Equation 3]

Rc(x,y)= conj[R(x,y)]

At this time, R(x,y) represents the digital reference light generated based on the frequency components corresponding to the real image, and Rc(x,y) represents the correction light.

The processor 390 extracts the normal line of the interference fringe and the direction lines Line1 and Line2 parallel to the interference fringe corresponding to the peak component 911P from the frequency components 911 corresponding to the real image. The processor 390 determines areas including Line1 and Line2 as noise areas (Noise1, Noise2, Noise3, and Noise4). The processor 390 may extract frequency components distributed in areas other than noise areas. The processor 90 may extract frequency components corresponding to the noise-removed real image using a pattern excluding the noise region. As shown in FIG. 8C , the processor 90 may remove noise using a cross-shaped pattern (Pattern1) that excludes frequency components distributed on Line1 and Line2. At this time, the processor 90 generates a cross-shaped pattern (Pattern1) based on a predetermined ratio of the distance difference value between the origin component 913 and the frequency component 911 corresponding to the real image, for example, 1/3 times R. can decide

The processor 90 may set various patterns for removing noise areas. As shown in FIG. 8D, noise of a frequency component corresponding to a real image may be generated by using a pattern (Pattern2) whose width increases as it approaches the peak component of the frequency component 911 corresponding to the real image.

Since the digital reference light (R(x,y)) and the correction light (Rc(x,y)) have a conjugate relationship, the intensity is the same as shown in FIGS. 9A and 9C, and as shown in FIGS. 9B and 9D Likewise, the phase may be reversed. Here, FIG. 9A is a diagram showing the intensity of the digital reference light R(x,y), FIG. 9B is a diagram showing the phase of the reference light, and FIG. 9C shows the intensity of the correction light Rc(x,y). FIG. 9D is a diagram showing the phase of the correction light.

The generated correction light Rc(x,y) may be used for correction of a real image hologram Um(x,y,0) described later.

Meanwhile, the 'digital reference light' is light having the same properties as the reference light R generated from light of a single wavelength by the light splitter 330, and is restored by the processor 390 from an image acquired by the image sensor 380. It may be a virtual light.

The processor 390 according to an embodiment of the present invention may generate a real image hologram based on the frequency components corresponding to the real image extracted through the above process. For example, the processor 390 may generate a real image hologram as shown in FIG. 9 by performing an inverse 2D Fourier transform on frequency components corresponding to the real image.

At this time, the real hologram can be expressed as Equation 4 below.

[Equation 4]

Um(x,y,0)=O(x,y)R*(x,y)

Here, Um(x,y,0) represents the real hologram, O(x,y) represents the object light O, and R*(x,y) represents the complex conjugate of the reference light R.

Meanwhile, such a real hologram (Um(x,y,0)), in addition to information on the height of the object to be measured 350, information on the reference light R and errors due to aberration of the object light objective lens 340 can include

Therefore, the processor 390 according to an embodiment of the present invention considers the effect of the reference light R and the error due to the aberration of the object light objective lens 340 from the real hologram Um(x,y,0). A calibration hologram Uc(x,y,0) may be generated.

For example, the processor 90 generates a term for correction light (Rc(x,y)) and a term for curvature aberration correction (Rca(x ,y)) to generate the calibration hologram Uc(x,y,0).

[Equation 5]

Uc(x,y,0)=Um(x,y,0)Rc(x,y)Rca(x,y)

Here, Uc(x,y,0) denotes a correction hologram from which information on the reference light R and aberration information of the object light objective lens 340 are removed, and Um(x,y,0) denotes a real hologram, Rc(x,y) represents a term for correction light, and Rca(x,y) represents a term for curvature aberration correction.

Meanwhile, the processor 390 according to an embodiment of the present invention may generate the aforementioned term Rca(x,y) for curvature aberration correction in various ways.

For example, the processor 390 calculates 3 values of the object to be measured 350 from a hologram obtained by multiplying a real hologram (Um(x,y,0)) with only a term (Rc(x,y)) for the correction light (hereinafter referred to as an intermediate hologram). A dimensional shape may be generated, and a term for curvature aberration correction (Rca(x,y)) may be generated from the generated 3D shape.

Looking at this in more detail, the processor 390 may determine at least one parameter for determining the curvature aberration correction term from the 3D shape of the object to be measured 350 generated from the intermediate hologram. At this time, the parameters may include, for example, the coordinates and radius of the center point defining the hemispherical curved surface.

11 and 12 are diagrams for explaining how the processor 390 determines a curvature aberration correction term from an intermediate hologram according to an embodiment of the present invention.

For convenience of explanation, it is assumed that the image sensor 380 acquires an image of the rectangular parallelepiped structure 51D of FIG. 3B and the processor 390 generates an intermediate hologram of the structure 51D according to the above process. do. It is also assumed that the 3D shape 920 of the structure 51D generated from the intermediate hologram of the structure 51D is as shown in FIG. 10 .

Under the above assumption, the processor 390 according to an embodiment of the present invention may determine at least one parameter for determining the curvature aberration correction term from the 3D shape 920 . For example, the processor 390 can determine the coordinates (Cx, Cy) of the center point of the hemispherical curved surface and the radius (r) of the curved surface from the curve on the I-I cross section of the three-dimensional shape 920 as shown in FIG. 12 as parameters. . At this time, the processor 390 according to an embodiment of the present invention may determine the position and / or direction of the cutting plane such as the I-I cross section to include the center point of the 3D shape 920 (ie, the center point of the hemispherical shape). Also, the processor 390 may determine that a cut plane such as the I-I section is parallel to the traveling direction of the object light 0.

The processor 390 according to an embodiment of the present invention may generate (or determine) a curvature aberration correction term based on at least one parameter determined by the above process. For example, the processor 390 creates a curved surface in a three-dimensional space by referring to the coordinates (Cx, Cy) of the center point of the curved surface and the radius (r) of the curved surface, and from the created curved surface, the phase correction of each x, y point will be reflected. The curvature aberration correction term may be generated (or determined) in a manner of generating information.

In an alternative embodiment, the processor 390 may determine a correction term from an intermediate hologram of an object to be measured (eg, an object having the same z value at all x and y coordinates) whose shape is known in advance.

In the case of a measurement target object whose shape is known in advance, since z values at each x and y point are known in advance, the processor 390 calculates the 3D shape of the measurement target object generated from the intermediate hologram and the known shape of the measurement target object. The correction term may be determined by checking the difference between z values at each x and y point. However, this is an example and the spirit of the present invention is not limited thereto.

The processor 390 according to an embodiment of the present invention may generate a 3D shape of the object to be measured 350 based on the calibration hologram Uc(x,y,0). In other words, the processor 390 may calculate the height of the object in the z direction at each x and y point.

For example, the processor 90 may convert the correction hologram Uc(x,y,0) into information on the restored image plane. In this case, the restored image plane means a virtual image display plane corresponding to the distance between the measurement target object and the image sensor by the processor, and may be a virtual plane calculated and simulated by the processor 90.

The processor 390 may calculate the height of the object in the z direction at the x and y points from the restored information in consideration of the reconstructed image plane, as shown in FIGS. 13A, 13B, and 13C. 13A shows a result of restoration without removing noise from frequency components, FIG. 13B shows a restoration result of removing noise using a cross-shaped pattern (Pattern1), and FIG. 13C shows a restoration result of removing noise using Pattern2. . A1, A2, and A3 represent height values in the Z direction as planar graphs. It can be seen that A1 has a large change in the height value in the z direction because noise is not removed, and A2 and A3 show little change in the height value in the z direction.

When using a cross-shaped pattern, the processor 390 may extract a frequency component according to Equation 5 below.

[Equation 5]

13A, 13B, and 13C illustrate three-dimensional shapes of two rectangular parallelepiped structures 51A and 51B disposed on the object to be measured 350 .

14 is a flowchart illustrating a method of generating 3D shape information of an object to be measured 350 performed by the holography restoration apparatus 300 according to an embodiment of the present invention. Hereinafter, description of contents overlapping with those described in FIGS. 2 to 13 will be omitted, but will be described with reference to FIGS. 2 to 13 together.

The holography restoration apparatus 300 according to an embodiment of the present invention may obtain an image of the measurement target object 350 (S1201).

In the present invention, the 'Image' of the object to be measured 350 is the intensity information at each position of the object hologram (U0(x,y,0)) of the object to be measured 350 (that is, | (U0(x,y,0)| ² ), and can be expressed as in Equation 2 above.

For example, the holography reconstruction apparatus 300 acquires an image as shown in FIG. 6 for a portion of the measurement target object 350 shown in FIGS. 5A and 5B (eg, a portion including 51A and 51B) can do.

Since the image acquired by the holography restoration apparatus 300 includes intensity information at each position of the object hologram U0(x,y,0) as described above, the holography restoration apparatus 300 acquires It may be different from a general image of the object to be measured 350 (that is, photographed only with the object light O).

Referring to Equation 2, the object hologram U0(x,y,0) does not include the object light 0 including the phase information of the object to be measured 350 at each point and the phase information of the object to be measured. It may be generated by interference of the reference light R, which is not visible.

In addition, the object hologram (U0 (x, y, 0)) is the object light objective lens (340 ) may further include an error and noise (for example, speckle noise due to the use of photons of a laser) due to an aberration of .

Therefore, the holography restoration apparatus 300 according to an embodiment of the present invention may perform the calculation process of steps S1202 to S1207 in order to remove the above-described error and noise from the image obtained by the holography restoration apparatus 300. .

The holography restoration apparatus 300 according to an embodiment of the present invention may check frequency components of an image acquired by the holography restoration apparatus 300 (S1202). For example, the holography restoration apparatus 300 may perform a 2D Fourier Transform on an image to check frequency components of the image.

In other words, the holography restoration apparatus 300 is a frequency included in an image including intensity information (that is, |(U0(x,y,0)| ² ) for each position of the object hologram U0(x,y,0). In this case, the image may include a frequency component corresponding to a real image, a frequency component corresponding to an imaginary image, and a DC component.

Of course, the image may further include various components in addition to the above-described three components (frequency component corresponding to the real image, frequency component and DC component corresponding to the virtual image). For example, the image may further include frequency components due to noise. However, this is an example and the spirit of the present invention is not limited thereto.

The holography restoration apparatus 300 according to an embodiment of the present invention may extract only components corresponding to the real image from among the identified frequency components (S1203). In this case, the holography restoration apparatus 300 may extract components corresponding to the real image in various ways.

For example, the holography reconstruction apparatus 300 extracts components having a peak value (hereafter referred to as peak components) in the size of a component among frequency components included in an image, and extracts a peak corresponding to the real image from among the extracted peak components. Components within a frequency difference between the component and firing can be extracted as components corresponding to the real image.

In this case, the holography restoration apparatus 300 may determine components corresponding to the real image in various ways based on peak components corresponding to the real image. For example, the holography reconstruction apparatus 300 may determine frequency components in a cross region centered on a peak component corresponding to the real image as components corresponding to the real image. However, this is an example and the spirit of the present invention is not limited thereto.

In an optional embodiment, the holography reconstruction apparatus 300 may extract only components corresponding to the real image from frequency components included in the hologram by using an automatic real image spot-position extraction algorithm.

In the present invention, 'extracting' a specific frequency component may mean extracting the frequency of the corresponding frequency component and the size (or intensity) of the corresponding frequency component.

Referring back to FIG. 7 , the holography restoration apparatus 300 may check the frequency components of the image obtained by the holography restoration apparatus 300, and accordingly, the holography restoration apparatus 300 may check the frequency components 911 corresponding to the real image. ), and various frequency components including a frequency component 912 and a DC component 913 corresponding to the virtual image can be identified.

Also, the holography reconstruction apparatus 300 may extract only the frequency component 911 corresponding to the real image from among the identified components. At this time, the holography reconstruction apparatus 300 may determine frequency components 911B in the cross section centered on the peak component 911A corresponding to the real image as components corresponding to the real image, as shown in FIG. 7 .

The holography restoration apparatus 300 according to an embodiment of the present invention may generate digital reference light from frequency components corresponding to the real image extracted through the above process (S1204). Looking at this in more detail, the holography restoration apparatus 300 may calculate the propagation direction and wave number of the digital reference light based on frequency components corresponding to the real image. In other words, the holography restoration apparatus 300 may calculate the wave number vector of the digital reference light.

In addition, the holography restoration apparatus 300 generates a digital reference light based on the propagation direction and wavenumber (or wavenumber vector) of the digital reference light, and generates the digital reference light R(x,y) generated as in Equation 3 above. The correction light Rc(x,y) can be generated by obtaining a conjugate term.

Since the digital reference light (R(x,y)) and the correction light (Rc(x,y)) have a conjugate relationship, the intensity is the same as shown in FIGS. 9A and 9C, and as shown in FIGS. 9B and 9D Likewise, the phase may be reversed. Here, FIG. 9A is a diagram showing the intensity of the digital reference light R(x,y), FIG. 9B is a diagram showing the phase of the reference light, and FIG. 9C shows the intensity of the correction light Rc(x,y). FIG. 9D is a diagram showing the phase of the correction light.

The generated correction light Rc(x,y) may be used for correction of a real image hologram Um(x,y,0) described later.

On the other hand, the 'digital reference light' is light having the same properties as the reference light R generated from light of a single wavelength by the light splitter 330 described above, and the holography restoration apparatus 300 obtains it by the holography restoration apparatus 300. It may be a virtual light restored from an image.

The holography restoration apparatus 300 according to an embodiment of the present invention may also generate a real image hologram based on the frequency components corresponding to the real image extracted through the above process (S1204). For example, the holography reconstruction apparatus 300 may generate a real image hologram as shown in FIG. 10 by performing an inverse 2D Fourier transform on frequency components corresponding to the real image. At this time, the real hologram can be expressed as in Equation 3 above.

The holography restoration apparatus 300 according to an embodiment of the present invention may generate an intermediate hologram to generate a term for curvature aberration correction (Rca(x,y)) (S1205). For example, the holography restoration apparatus 300 may generate an intermediate hologram by multiplying the real hologram Um(x,y,0) by the correction light term Rc(x,y). The generated intermediate hologram may be used to generate curvature aberration correction information in step S1206.

The holography restoration apparatus 300 according to an embodiment of the present invention generates a 3D shape of the object to be measured 350 from the intermediate hologram generated in step S1205, and a term for curvature aberration correction from the generated 3D shape ( Rca(x,y)) can be generated (S1206). Looking at this in more detail, the holography restoration apparatus 300 may determine at least one parameter for determining the curvature aberration correction term from the 3D shape of the object to be measured 350 generated from the intermediate hologram. At this time, the parameters may include, for example, the coordinates and radius of the center point defining the hemispherical curved surface.

Referring back to FIGS. 11 and 12 , a method of determining a curvature aberration correction term from an intermediate hologram by the holography restoration apparatus 300 according to an embodiment of the present invention will be described. For convenience of explanation, the holography restoration apparatus 300 acquires an image of the rectangular parallelepiped structure 51D of FIG. Suppose you have created It is also assumed that the 3D shape 920 of the structure 51D generated from the intermediate hologram of the structure 51D is as shown in FIG. 11 .

Under the above assumption, the holography reconstruction apparatus 300 according to an embodiment of the present invention may determine at least one parameter for determining the curvature aberration correction term from the 3D shape 920 . For example, the holography restoration apparatus 300 determines the coordinates (Cx, Cy) of the center point of the hemispherical curved surface and the radius (r) of the curved surface from the curve on the I-I cross section of the 3D shape 920 as shown in FIG. 12 as parameters. can At this time, the holography restoration apparatus 300 according to an embodiment of the present invention may determine the position and/or direction of the cut plane such as the I-I cross section to include the center point of the 3D shape 920 (ie, the center point of the hemispherical shape). . In addition, the holography restoration apparatus 300 may determine a cut plane such as an I-I section to be parallel to the traveling direction of the object light 0 .

The holography restoration apparatus 300 according to an embodiment of the present invention may generate (or determine) a curvature aberration correction term based on at least one parameter determined by the above process. For example, the holography reconstruction apparatus 300 creates a curved surface in a 3D space by referring to the coordinates (Cx, Cy) of the center point of the curved surface and the radius (r) of the curved surface, and phase correction of each x, y point from the generated curved surface The curvature aberration correction term may be generated (or determined) in a manner that generates information to be reflected.

In an optional embodiment, the holography restoration apparatus 300 may determine a correction term from an intermediate hologram of an object to be measured (for example, an object having the same z value at all x and y coordinates) whose shape is known in advance.

In the case of a measurement target object whose shape is known in advance, since the z value at each x and y point is known in advance, the holography restoration apparatus 300 calculates the 3D shape of the measurement target object generated from the intermediate hologram and the known measurement target object. The correction term may be determined by checking the difference in z values at each x and y point of the shape. However, this is an example and the spirit of the present invention is not limited thereto.

The holography restoration apparatus 300 according to an embodiment of the present invention considers the effect of the reference light R and the error due to the aberration of the object lens 340 to obtain a real hologram (Um(x,y,0)) A correction hologram (Uc(x,y,0)) may be generated from (S1207). For example, the holography restoration apparatus 300, as shown in Equation 5 above, includes a correction light term (Rc(x,y)) and a curvature aberration correction term (Rca) in the real hologram (Um(x,y,0)) A calibration hologram Uc(x,y,0) can be generated by multiplying by (x,y). In this case, the term for correction light (Rc(x,y)) may be generated in step S1204, and the term for curvature aberration correction (Rca(x,y)) may be generated in step S1206.

The holography restoration apparatus 300 according to an embodiment of the present invention may generate 3D shape information of the object to be measured 350 based on the correction hologram Uc(x,y,0) (S1208). In other words, the holography restoration apparatus 300 may calculate the height of the object in the z direction at each x and y point.

For example, the holography restoration apparatus 300 may convert the correction hologram Uc(x,y,0) into information of a reconstructed image plane. At this time, the reconstructed image plane means a virtual image display plane corresponding to the distance between the object to be measured and the image sensor by the processor, and may be a virtual plane calculated and simulated by the holography restoration apparatus 300. .

The holography reconstruction apparatus 300 may calculate the height of the object in the z direction at the x and y points from the restored information in consideration of the reconstructed image plane, as shown in FIG. 13 . 13 shows three-dimensional shapes of two rectangular parallelepiped structures 51A and 51B disposed on the object to be measured 350 by way of example.

15 and 16 are flowcharts of a noise removal method of the holography restoration apparatus 300 according to embodiments of the present invention.

The holography restoration apparatus 300 according to an embodiment of the present invention may extract only components corresponding to the real image from among the identified frequency components (S1203).

In S12031, the holography reconstruction apparatus 300 determines a first frequency component corresponding to the real image included in the image, a second frequency component corresponding to the virtual image, and a third frequency component corresponding to the origin.

In operation S12032, the holography reconstruction apparatus 300 calculates the direction of the interference fringe and the normal direction from the first frequency component, and determines a frequency component located in the direction of the interference fringe and the normal direction as noise.

In S12033, the holography reconstruction apparatus 300 extracts a frequency component corresponding to a real image by removing noise from the first frequency component.

In another embodiment, the holography restoration apparatus 300 may set a pattern from which noise is removed and extract a frequency component corresponding to a real image using the pattern.

In operation S12034, the holography reconstruction apparatus 300 determines a first frequency component corresponding to the real image included in the image, a second frequency component corresponding to the virtual image, and a third frequency component corresponding to the origin.

In operation S12035, the holography restoration apparatus 300 generates a cross domain pattern including a peak component of the first frequency component. In S12036, the holography reconstruction apparatus 300 extracts frequency components included in the cross domain pattern from among the first frequency components.

Equation using the cross region pattern is as follows. The holography reconstruction apparatus 300 may extract frequency components included in the cross domain pattern according to Equation 7 below.

[Equation 7]

Here, ms is the size of the cross domain pattern, xc is the X coordinate of the peak component, and yc is the Y coordinate of the peak component. R refers to a number proportional to a distance between a frequency component corresponding to a real image and an origin component. For example, R may be distance/3, distance/2, and the like.

The size (ms) of the cross domain pattern is determined based on the origin component and the distance between the real image and the corresponding frequency component, but the size of the cross domain pattern can be adjusted for efficient removal of noise components. The size of the cross domain pattern can be optimized through an iterative noise removal process.

In another embodiment, in order to remove noise more efficiently, the holography reconstruction apparatus 1 may set different weights depending on the location of the filtering region through hemispherical filtering. For example, the holography restoration apparatus 1 may multiply a weight smaller than 1 as the distance from the center increases.

[Equation 8]

Here, R refers to a number proportional to the distance between the frequency component corresponding to the real image and the origin component. For example, R may be distance/3 , distance/2 , and the like.

Embodiments according to the present invention described above may be implemented in the form of a computer program that can be executed on a computer through various components, and such a computer program may be recorded on a computer-readable medium. In this case, the medium may store a program executable by a computer. Examples of media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical image sensors such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and ROM, RAM, flash memory, etc. configured to store program instructions.

Meanwhile, the computer program may be specially designed and configured for the present invention, or may be known and usable to those skilled in the art of computer software. An example of a computer program may include not only machine language code generated by a compiler but also high-level language code that can be executed by a computer using an interpreter or the like.

As described above, the holographic restoration apparatus 300 according to an embodiment of the present invention, in other words, the holography restoration apparatus 300 can accurately generate 3D shape information of the object to be measured by acquiring one hologram. there is. The holography reconstruction device 300 described above can generate accurate 3D shape information through the above-described methods while simplifying its components, so that it can be placed inside an in-line deposition equipment to perform inspection in real-time in an in-line process. make it possible

Specific implementations described in the present invention are examples and do not limit the scope of the present invention in any way. For brevity of the specification, description of conventional electronic components, control systems, software, and other functional aspects of the systems may be omitted. In addition, the connection of lines or connecting members between the components shown in the drawings are examples of functional connections and / or physical or circuit connections, which can be replaced in actual devices or additional various functional connections, physical connection, or circuit connections. In addition, if there is no specific reference such as "essential" or "important", it may not necessarily be a component necessary for the application of the present invention.

Therefore, the spirit of the present invention should not be limited to the above-described embodiments and should not be determined, and all scopes equivalent to or equivalently changed from the claims as well as the claims described below are within the scope of the spirit of the present invention. will be said to belong to

300, 300A, 300B: holography restoration device
310: light source unit
320: collimator
330,332 optical splitter
340 object light objective lens
350: object to be measured
360: reference light objective lens
370,372: optical mirror
380: image sensor
390: processor

Claims (4)

a light source unit emitting single wavelength light;
a collimator for collimating the single wavelength light emitted from the light source unit;
a light splitter splitting the single wavelength light passing through the collimator into object light and reference light;
an object light objective lens passing the object light divided by the light splitter;
an optical mirror for reflecting the reference light split by the light splitter;
a plate on which an object to be measured is seated on a surface facing the object light objective lens;
a distance sensor disposed adjacent to the object light objective lens to detect a distance between the object light objective lens and the plate;
a driving unit connected to the plate and moving the plate relative to the object light objective lens using a distance value sensed by the distance sensor;
an image sensor for recording an interference fringe formed when the object light passing through the object light objective lens and reflected from the surface of the object to be measured and the reference light reflected by the optical mirror are transferred to the optical splitter; and
A processor for receiving and storing an image including intensity information of an object hologram generated by converting the interference fringe in the image sensor, and generating 3D shape information of the object to be measured;
The processor moves the plate using the distance value sensed by the distance sensor, detects an edge of the image obtained from the image sensor, extracts a contrast value of the detected edge, and and controlling the driving means to adjust a distance between the plate and the object light objective lens based on the extracted contrast value.
delete According to claim 1
An apparatus for generating three-dimensional shape information of an object to be measured, wherein a distance between the object light objective lens and the beam splitter is constant.
According to claim 1
The processor extracts real image components corresponding to a real image from among at least one frequency component included in the image, and based on the real image components, a correction light having a conjugate relationship with the reference light and the A real image hologram including mounting information of an object to be measured is generated, an intermediate hologram in which information of the reference light is removed from the real image hologram is generated based on the correction light, and curvature aberration correction information is generated from the intermediate hologram. Then, based on the curvature aberration correction information, a correction hologram in which an error due to curvature aberration is reduced in the intermediate hologram is generated, and the 3D shape information of the object to be measured is generated from the correction hologram. 3D shape information generating device.

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