KR20200071372A - Apparatus for generating three-dimensional shape information of an object to be measured - Google Patents

Abstract

According to an embodiment of the present invention, an apparatus for generating 3D shape information of an object to be measured comprises: a light source unit for emitting single wavelength light; a collimator for collimating the single wavelength light emitted from the light source unit; an optical splitter for splitting the single wavelength light, which has passed through the collimator, into object light and reference light; an optical mirror for reflecting the reference light split by the optical splitter; an image sensor which records an interference fringe formed by respectively transmitting, to the optical splitter, the object light reflected from the surface of the object to be measured and the reference light reflected by the optical mirror after being split by the optical splitter; and a processor which receives, from the image sensor, and stores an image including intensity information of an object hologram generated by converting the interference fringe, and generates 3D shape information of the surface of the object to be measured. The processor performs digital focusing of the image obtained from the image sensor by using a transfer function which depends on a digital distance value.

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 an object to be measured. More specifically, the present invention is a three-dimensional object to be measured from an image including intensity information of an object hologram generated by interference of the reference light reflected from the optical mirror and the object light reflected from the object to be measured 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, the digital holography microscope acquires 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 uses a light splitter to divide the light generated by the laser into two lights. At this time, one light (hereinafter referred to as reference light) is directed to the image sensor, and the other light (hereinafter referred to as object light) is reflected from the target object and directed to the above-described image sensor so that interference between the reference light and the object light occurs. do.

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

Conventional optical holography microscopy records the interference pattern according to the interference phenomenon between the reference light and the object light as a special film. At this time, when the reference light is irradiated to the special film having the interference fringe, the shape of the virtual object to be measured is restored to the position where the object to be measured is located.

Compared with 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 rather than an optical method. There is a difference.

On the other hand, the conventional digital holography microscope using a single wavelength laser light source has a problem that the minimum unit length of the measurement of the object is limited to the wavelength length of the laser. In order to compensate for this, another conventional digital holography microscope using a laser light source having two or more wavelengths has a problem in that it is not only possible to obtain a high-priced microscopic microscope, but also cannot obtain a three-dimensional shape of an object in real time.

In addition, the above-mentioned conventional digital holography microscopes generate a computer generated hologram (CGH) with a computer to restore the shape of the object to be measured, and display it on a spatial light modulator (SLM), and display the A 3D hologram image of the object was acquired by illuminating the reference light. However, this method not only requires the use of an expensive spatial light modulator (SLM), but also has a clear technical limitation by simply digitizing a special film in the above-described optical holography microscope.

To solve the problems of such conventional digital holography microscopes, for example, Republic of Korea Patent Publication No. 10-2016-0029606 (hereinafter referred to as "published prior art") proposes a digital holography microscope and a digital hologram image generation method. Hereinafter, a brief look at the disclosed prior art.

2 is a block diagram showing in detail a two-wavelength digital holography microscope device 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 objective unit 40, and 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 emitting unit 11 and a light source unit lens 12. The mixed light source light emitting unit 11 emits mixed light having a wavelength band distributed in several non-uniform bands. The light source unit lens 12 optically adjusts the mixed light generated by the mixed light source emitting unit 11 and makes it incident on the wavelength division unit 20.

The wavelength division unit 20 includes a first light splitter 21, a first filter plate 22, a second filter 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 divides it into two lights. At this time, the first light splitter 21 serves to divide the incident mixed light in different directions and proceed. The first filter plate 22 receives one of the light split by the first light splitter 21 to obtain a first light beam having a predetermined single wavelength. Here, light input to the first filter plate 22 is filtered while passing through the first filter plate 22, and a first ray having a single wavelength determined according to the characteristics of the first filter plate 22 is obtained. The second filter plate 23 receives the other one of the light split by the first optical splitter 21 in the same manner as the first filter plate 22, and has a second wavelength different from that of the first light filter Acquire rays. And the second ray is sent to the interference pattern acquisition unit 30. The first reflector 24 serves to receive the first light obtained from the first filter plate 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 filter plate 34, and a third reflector 35. The second light splitter 31 receives the first light input from the wavelength division unit 20 and divides the light into a first object light and a first reference light. At this time, the second light splitter 31 serves to divide the incident first light beams in different directions. The third light splitter 32 receives the second light beam in the same manner as the second light splitter 31 and divides it into a second object light and a second reference light. The second reflector 33 receives the first reference light, and sends the reflected first light to the second light splitter 31. The third filter plate 34 may receive the first reference light divided by the second light splitter 31 and send it to the second reflector 33, and receive the reflected first reflection reference light and send it to the second light splitter. In addition, the third filter plate 34 prevents the second object light from reaching the second reflector 33 when the second light splitter 31 reaches the second light splitter 31 and is partially divided to proceed toward the second reflector 33. . To this end, the third filter plate 34 is a filter plate having 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 light splitter 32, where the second reflector 33 and the third reflector 35 are the control unit 70 ) Can be configured to adjust the angle under control, so that an off-axis hologram can be implemented.

Meanwhile, the first object light and the second object light obtained as described above are converted into respective first reflection object light and second reflection object light through the following process and are sent to the image sensor unit 50. The second optical splitter 31 injects the first object light divided as described above into the object to be measured mounted on the objective unit 40, and further transmits the second object divided from the third optical splitter 32 Light is incident on the object to be measured. In this case, the reflected light reflecting the first object light incident from the object to be measured is referred to as the first reflected 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 reflected object light. The second light splitter 31 receives the first reflected object light and the second reflected object light reflected as described above and sends them to the third light splitter 32. The third light splitter 32 sends the first reflected object light and the second reflected object light input 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 light splitter 31 receives the first reflection reference light reflected from the second reflector 33 and sends it to the third light splitter 32. As described above, the third light splitter 32 receives the first reflection reference light sent from the second light splitter 31 and the second reflection reference light reflected from the third reflector 35, and then receives the image sensor unit 50 again. To send. Accordingly, after the first light reflection object light, the first light reflection reference light, the second light reflection object light and the second light reflection reference light are sent in the same direction to the image sensor unit 50 in the third light splitter 32, they interfere with each other. Interference patterns are generated.

Meanwhile, the second reflector 33 and the third reflector 35 are angled under the control of the control unit 70 in order to construct an off-axis system in which light rays of different wavelengths form different interference patterns. 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 reflecting reference light reflected from the second reflector 33 and the second reference reflecting from the third reflector 35 When the light is separated in the direction of the light, the first and second reflected reference light are combined with the first and second reflected object light reaching the image sensor unit 50 to form an interference pattern, each wavelength Very differently disjointed interference patterns are formed.

The objective part 40 includes an object holder 41 and an objective lens 42. The object holder 41 is fixed to the object to be measured to be measured, and the objective lens 42 optically adjusts the first object light and the second object light incident on the object to be measured.

The image sensor unit 50 projects the interference pattern obtained from the interference pattern acquisition unit 30 onto a digital image sensor, measures the projected interference pattern using the digital image sensor, and disperses the measured value. Convert to Usually, the interference fringe is recorded as a hologram. As the digital image sensor, various image sensors such as a CCD may be used.

The image storage unit 60 stores the interference fringe information converted from the image sensor unit 50 into discrete signals 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 position and angle of the second reflector 33 and the third reflector 35 to obtain an interference pattern, such as the interference pattern acquisition unit 30 ), and the objective 40 is controlled by adjusting the objective lens 42 to adjust the first object light and the second object light incident on the object to be measured. The image sensor unit 50 is controlled to allow information to be converted into a discrete signal, and the image storage unit 60 is controlled to store interference fringe information converted into a discrete signal.

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 pattern for the first ray and the interference pattern for the second ray by using the interference pattern information, respectively, and the thickness information acquisition unit 82 Obtains the thickness information of the object to be measured using the phase information, and the shape restoration unit 83 restores the real-time three-dimensional 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 between the paths of the object light and the reference light. Due to the optical path difference between the object light and the reference light, the interference pattern 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 still has the following problems.

Since the conventionally disclosed prior art uses a mixed light source having a wavelength band distributed in several bands, the wavelength division unit 20 divides the first and second light sources having different wavelengths to obtain at least two single wavelengths. To do so, the first filter plate 22, the second filter plate 23, and the first reflector 24 must be used.

In addition, the interference pattern acquisition unit 30 is a third light splitter 32 for dividing the second light source, a third reflector 35 for reflecting the second light source, and a second light source for the second reflector 33 The third filter plate 34 to block the incident light to be used additionally.

Therefore, the structure of the microscope is complicated, and this involves various problems such as an increase in manufacturing cost and an increase in design complexity. Therefore, a new method is needed to solve the above-mentioned problems while using a single wavelength light source.

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 Republic of Korea Patent No. 10-1139178 Republic of Korea 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, it is intended to accurately generate the three-dimensional shape information of the object to be measured by the acquisition of 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 information about the reference light from one hologram and curvature aberration information of optical elements and correcting the obtained object hologram in consideration of this.

In addition, the present invention seeks to solve the complex optical device structure and thus significant high cost problems.

Furthermore, the present invention seeks to detect defects of these structures with a high probability by accurately acquiring three-dimensional shapes of ultra-fine structures such as TFTs and semiconductors.

According to an embodiment of the present invention, a light source unit that emits single wavelength light, a collimator for collimating single wavelength light emitted from the light source unit, and an optical splitter for dividing the single wavelength light that has passed through the collimator into object light and reference light, The optical mirror reflecting the reference light divided by the optical splitter, the object light reflected from the surface of the object to be measured after being divided by the optical splitter, and the reference light reflected by the optical mirror are transmitted to the optical splitter, respectively. An image sensor that records the interference fringe formed and an image including the intensity information of the object hologram generated by converting the interference fringe from the image sensor are received and stored, and the three-dimensional shape of the surface of the object to be measured Including a processor for generating information, the processor performs digital focusing of the image obtained from the image sensor using a transfer function that depends on a digital distance value. Provided is an apparatus for generating three-dimensional shape information.

In one embodiment of the present invention, the object light divided by the optical divider is disposed on a path through which the object to be measured is seated, and is disposed adjacent to the optical divider, and the optical divider and the plate A distance sensor for sensing a distance to and a connection to the plate may further include driving means for moving the plate with respect to the optical splitter using an optical distance value detected by the distance sensor.

In one embodiment of the present invention, the plate includes an overlapping area overlapping with the object to be measured, and a non-overlapping area non-overlapping with the object to be measured, and the distance sensor is non-overlapping on one surface of the plate. The distance of the plate can be detected based on the area.

In one embodiment of the present invention, the processor may perform the digital focusing after moving the plate using the optical distance value detected by the distance sensor.

In one embodiment of the present invention, the processor detects an edge of the image obtained from the image sensor, extracts a contrast value of the detected edge, and digitally based on the extracted contrast value. Focusing can be performed.

In one embodiment of the present invention, the processor extracts a real image component corresponding to a real image among at least one frequency component included in the image, and is paired with the reference light based on the real image components ( conjugate) to generate a real image hologram including the correction light in relation to and the mounting information of the object to be measured, and based on the correction light, generate an intermediate hologram in which the information of the reference light is removed from the real image hologram, and the intermediate 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 increased in the intermediate hologram is generated, and the three-dimensional object of the measurement object is measured from the correction hologram. Shape information can be generated.

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

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

In particular, by generating information about the reference light and curvature aberration information of optical elements from one hologram and correcting the object hologram obtained by taking this into consideration, it is possible to generate three-dimensional shape information of an object to be measured with improved accuracy.

In addition, it is possible to solve the complicated optical device structure and thus a considerable high cost problem.

Furthermore, by accurately acquiring the three-dimensional shape of ultra-fine 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 device according to the disclosed prior art.
2A is a block diagram showing a schematic configuration of a holographic reconstruction apparatus according to a first embodiment of the present invention.
2B is a block diagram showing a schematic configuration of a holographic reconstruction apparatus according to a second embodiment of the present invention.
3A and 3B are diagrams for explaining a method in which a holographic reconstruction apparatus according to an embodiment of the present invention automatically focuses on an object M to be measured (outo-focusing).
3C to 3F are diagrams for explaining a method in which the holographic restoration apparatus focuses using digital focusing.
4A and 4B are diagrams for explaining a method of focusing by detecting an edge in an image of an object to be measured.
5A and 5B are views for explaining the 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 showing frequency components of an image of a part of the measurement target object illustrated in FIG. 6.
8 is a diagram for explaining a method of extracting frequency components corresponding to a real image from the frequency components illustrated in FIG. 7.
9A is a diagram showing the intensity of digital reference light.
9B is a diagram showing the phase of the reference light.
9C is a diagram showing the intensity of the correction light.
9D is a diagram showing the phase of the correction light.
10 is a diagram illustrating an exemplary actual hologram.
11 and 12 are diagrams for explaining a method for a processor to determine a curvature aberration correction term from an intermediate hologram according to an embodiment of the present invention.
13 is a diagram showing an example of a three-dimensional shape of a measurement object generated from a hologram.
14 is a flowchart illustrating a method of generating 3D shape information of an object to be measured performed by a holographic reconstruction apparatus according to an embodiment of the present invention.
15 and 16 are flowcharts of a method for removing noise in a holographic reconstruction apparatus according to embodiments of the present invention.

Hereinafter, various embodiments of the present disclosure are described in connection with the accompanying drawings. Various embodiments of the present disclosure may have various modifications 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 modifications and/or equivalents or substitutes included in the spirit and scope of the various embodiments of the present disclosure. In connection with the description of the drawings, similar reference numerals have been used for similar elements.

Expressions such as “include” or “may include” that may be used in various embodiments of the present disclosure indicate the existence of a corresponding function, operation, or component disclosed, and additional one or more functions, operations, or The components and the like are not limited. Also, in various embodiments of the present disclosure, terms such as “include” or “have” are intended to indicate that there are features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, It should be understood that one or more other features or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

In various embodiments of the present disclosure, expressions such as “or” include any and all combinations of 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 elements of various embodiments, but do not limit the elements. Does not. For example, the above expressions do not limit the order and/or importance of the components. The above expressions can be used to distinguish one component from another component. For example, the first user device and the second user device are both user devices and represent different user devices. For example, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component without departing from the scope of rights of various embodiments of the present disclosure.

When a component is said to be "connected" to or "connected" to another component, the component may be directly connected to or connected to the other component, but may not be connected to the component. It will be understood that other new components may exist between the other components. On the other hand, when it is mentioned that an element is "directly connected" or "directly connected" to another component, it will be understood that no other new component exists between the one component and the other components. You should be able to.

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

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which various embodiments of the present disclosure pertain.

Terms, such as those defined in a commonly used dictionary, should be interpreted as having meanings consistent with meanings in the context of related technologies, and are ideally or excessively formal unless explicitly defined in various embodiments of the present disclosure. It is not interpreted as meaning.

2A is a block diagram showing a schematic configuration of a 3D shape information generating apparatus 300A according to a first embodiment of the present invention.

In the present invention, the'three-dimensional shape information generating device' means a holographic restoring device that acquires a hologram (hereinafter referred to as'object hologram') for an object to be measured and analyzes and/or displays the obtained object hologram. Can be. Hereinafter, the names of the 3D shape information generating device and the holographic restoration device will be used interchangeably.

For example, the holography restoring apparatus 300A may be a device that is disposed on a semiconductor manufacturing line, obtains an object hologram of the produced semiconductor, and determines whether the semiconductor is integrity from the obtained object hologram. However, this is exemplary and the spirit of the present invention is not limited thereto.

On the other hand, in the present invention,'object hologram (Hologram)' is a hologram that can be generated from an image obtained by the holographic reconstruction apparatus 300A, and may mean a hologram before various processing by the holography reconstruction apparatus 300A is performed. have. Detailed description thereof will be described later.

Referring to FIG. 2A, the holographic reconstruction 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 single wavelength light emitted from the light source unit 310 ), a light splitter 330 for dividing the single wavelength light passing through the collimator 320 into object light O and reference light R, and an optical mirror reflecting the reference light R divided by the light splitter 330 (370), the object light (O) reflected from the surface of the object to be measured (M) after being divided by the light splitter (330) and the reference light (R) reflected from the optical mirror (370) are respectively the light splitter (330) The image sensor 380 records the interference fringe formed by being transmitted to the image sensor, and receives and stores an image including the intensity information of the object hologram generated by converting the interference fringe from the image sensor 380, and measures the object. It may include a processor 390 for generating three-dimensional shape information of the object (M). Here, the object M to be measured may be a substrate, and the substrate will be described below as the object M to be measured.

On the other hand, the holographic restoration apparatus 300A according to the first embodiment of the present invention is disposed on a path through which the object light O divided by the light splitter 330 passes, and a plate for mounting the object M to be measured ( 351), is disposed adjacent to the optical splitter 330, is connected to the distance sensor 357 and the plate 351 to detect the distance between the optical splitter 330 and the plate 351, the distance sensor 357 Drive means 353 for moving the plate 351 with respect to the optical splitter 330 using the detected optical distance value may be further included.

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. Further, the processor 390 may focus using at least one of optical focusing and digital focusing. 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 holographic reconstruction apparatus 300B according to a second embodiment of the present invention.

Referring to FIG. 2B, the holographic reconstruction 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 single wavelength light emitted from the light source unit 310 ), a light splitter 330 for dividing the single wavelength light passing through the collimator 320 into object light O and reference light R, and a first for reflecting the reference light R divided by the light splitter 330 The optical mirror 370, the second optical mirror 372 reflecting the object light O divided by the light splitter 330, the reference light R reflected by the first optical mirror 370 and the object light ( After the O) passes through the object M to be measured, the reference light R transmitted to the second light splitter 332 and the second light splitter 332 through which the object transmitted light including the information of the measurement object M is transmitted, respectively. ) And the image sensor 380 that records the interference fringes formed by the object transmitted light, and the image sensor 380 converts the interference fringes and receives and stores an image including the intensity information of the object hologram. It may include a processor 390 for generating three-dimensional shape information of the object to be measured (M).

Of course, even in this second embodiment, 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.

2A and 2B, the holographic restoring apparatus 300A according to the first embodiment of the present invention and the holographic restoring apparatus 300B according to the second embodiment of the present invention are respectively measured by the object light O. The fact that the object M is reflected (the embodiment of FIG. 2A) or the object light O transmits the object M to be measured (the embodiment of FIG. 2B) and some components thereof (e.g. It has substantially the same configuration except for the additional use of the second optical mirror 372 and the second light splitter 332 of the embodiment of FIG. 2B and the placement of some components accordingly).

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

Hereinafter, the holographic reconstruction apparatuses 300A and 300B according to the first and second embodiments of the present invention will be collectively described as the holographic reconstruction apparatus 300.

The holographic reconstruction apparatus 300 according to embodiments of the present invention is characterized in that it does not include an object light objective lens between the light splitter 330 and the object M to be measured. The holographic restoring apparatus 300 according to embodiments of the present invention does not include an object light objective lens, and thus can minimize the use of elements compared to a system including the object light objective lens, thereby reducing the size of the entire system. In addition, through this, it is possible to implement an effect of reducing noise generated from an optical element.

Meanwhile, the processor 390 of the holographic restoring apparatus 300 according to an embodiment of the present invention may include all kinds of apparatus capable of processing data. For example, the processor 390 may refer to a data processing device embedded in hardware having physically structured circuits to perform functions represented by codes or instructions included in a program.

As an example of such a data processing device embedded in hardware, a microprocessor, a central processing unit (CPU), a processor core, a multiprocessor, and an application-specific integrated (ASIC) Circuit), FPGA (Field Programmable Gate Array), and the like, 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 with at least one image sensor, such as a Charge Coupled Device (CCD), a Complimentary Metal-Oxide Semiconductor (CMOS), for example.

Referring again to FIGS. 2A and 2B, the holography restoring apparatus 300 according to an embodiment of the present invention is for generating three-dimensional shape information of an object M to be seated on a plate 351, For example, it may be used for the purpose of examining the presence or absence of pattern defects after the deposition process by generating 3D shape information of the semiconductor substrate. At this time, the optical configuration of the holographic reconstruction apparatus 300 constructs a system in a state in which the distance between each component is set in advance to generate accurate 3D shape information.

Here, the optical configuration of the holographic reconstruction apparatus 300A according to the first embodiment includes a collimator 320, an optical splitter 330, an optical mirror 370, and an image sensor 380, according to the second embodiment The holographic reconstruction apparatus 300B may include a collimator 320, a light splitter 330, a second light splitter 332, a first optical mirror 370, a second optical mirror 372, and an image sensor 380. Can be.

Therefore, the above-described optical configuration is fixedly positioned as previously set, and in order to inspect a plurality of objects M to be measured, it is necessary to measure while changing the objects M to be measured on the plate 351. For example, the distance between the image sensor 380 and the optical splitter 330 or the distance between the image sensor 380 and the second optical splitter 332 may be constant. At this time, since the plate 351 continuously moves to set the object M to be measured, the above-described optical configuration, in particular, the focus with the optical splitter 330 may be out of focus. The holographic reconstruction apparatus 300 according to an embodiment of the present invention includes a distance sensor 357 to automatically solve the above-described problem, and attempts to automatically focus on the object M to be measured. In particular, the holographic graph reconstruction apparatus 300 according to an embodiment of the present invention uses an optical focusing as well as digital focusing in the absence of an object light objective lens to the object M to be measured. I want to focus on.

The distance sensor 357 according to an embodiment of the present invention may be located adjacent to the light splitter 330 to detect the distance between the light splitter 330 and the plate 351. For example, the distance sensor 357 emits a laser toward the plate 351, detects a laser reflected back from the plate 351, and measures a distance to the plate 351 by detecting a returned laser (Laser Range) Finder), but the technical idea of the present invention is not limited thereto. As another embodiment, the distance sensor 357 is disposed on the plate 351, it may be provided as a sensor for detecting the displacement of the plate 351.

On the other hand, the distance sensor 357 may detect a direct distance between the optical splitter 330 and the plate 351, but if the distance between the distance sensor 357 and the optical splitter 330 is known in advance, the distance sensor By measuring the distance from 357 to the plate 351, the distance between the optical splitter 330 and the plate 351 can also be derived. When directly measuring the distance between the optical splitter 330 and the plate 351, the position of the distance sensor 357 should be disposed at the same height position as the optical splitter 330 with respect to the measurement direction. At this time, the position of the distance sensor 357 may be disposed at the same height position with respect to the exit surface from which the object light O divided from the light splitter 330 is emitted, as described above, with the light splitter 330 This is not necessary if the distance to the distance sensor 357 is known in advance.

On the other hand, the plate 351, when the object to be measured (M) is seated, the overlapping area (A1, see FIG. 3A) overlapping the object to be measured (M), and the non-overlapping area non-overlapping with the object (M) (A2, see FIG. 3A). The holographic restoring apparatus 300 according to an embodiment of the present invention may adjust the macroscopic distance between the plate 351 and the optical splitter 330 using a distance sensor 357, wherein the object to be measured (M) When measuring in an overlapping region, the distance may vary depending on the height of the object M to be measured.

The holographic restoration apparatus 300 according to an embodiment of the present invention aims to generate accurate three-dimensional information of an object M to be measured, and is based on an object M to be deposited or formed with different heights. By measuring the distance, it is possible to detect the distance to the plate 351 based on the non-overlapping area (A2) made of a plane of constant height. The holographic restoring apparatus 300 may measure a distance from a preset position in the non-overlapping area A2 to the plate 351, and for this purpose, a vision camera (not shown) for confirming the correct position of the plate 351 City) may be further included. The holography restoration apparatus 300 uses a vision camera (not shown) to set the position of the plate 351 in the planar direction (xy), and then uses the distance sensor 357 to be perpendicular to the planar direction (xy). Macroscopic distances in one height direction (z direction) can be measured.

Meanwhile, the driving means 353 is connected to the plate 351 and may move the plate 351 relative to the optical splitter 330 using the optical distance value detected 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 drive means 353 may include an actuator such as a motor or hydraulic cylinder. Although not shown, the holographic restoration apparatus 300 further includes one or more guide members (not shown) for guiding the vertical movement of the plate 351 by the driving means 353, so that the plate 351 moves up and down. When it can, it can stably support without twisting.

3A and 3B are diagrams for explaining a method in which the holographic restoration apparatus 300 according to an embodiment of the present invention automatically focuses the object M to be measured (outo-focusing). 3F is a diagram for explaining a method in which the holographic reconstruction apparatus 300 focuses using digital focusing.

Referring to FIG. 3A, when the object M to be measured is seated on the plate 351, the holography restoration apparatus 300 first uses a distance sensor 357 to determine the distance between the plate 351 and the optical splitter 330. Distance can be detected. At this time, the distance sensor 357 detects the distance to the plate 351 and generates a first signal S1. As described above, the optical splitter 330 and the distance sensor 357 are at the same height position. If present, the first signal S1 may be a signal including distance information between the optical splitter 330 and the plate 351. Alternatively, when the distance sensor 357 is at a different height position from the optical splitter 330, the first signal S1 may be a signal including distance information to 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 position between the distance sensor 357 and the optical splitter 330 is different, the location information of the distance sensor 357 and the optical splitter 330 may be stored in advance in the processor 390. Using the stored information and the first signal S1, the height position of the plate 351 can be adjusted.

Referring to FIG. 3B, the holography restoring apparatus 300 measures an image of a measurement object M that is macroscopically adjusted through the above-described method, and performs digital focusing on the acquired image to focus Can fit. Here, digital focusing calculates an image while changing a digital distance value based on an image acquired in the processor 390 without movement of an optical configuration, and based on the most focused image among the calculated images. It means to generate three-dimensional shape information of the surface of the object to be measured.

In this specification, digital focusing may perform a focusing process on an image obtained from the image sensor 380 using a transfer function that depends on a digital distance value. Here, the transfer function can be expressed as follows.

[Equation 1]

Since the holographic reconstruction apparatus 300 according to embodiments of the present invention uses a coherent laser of a single wavelength as a light source, a digital distance value to perform digital focusing on an image obtained from the image sensor 380 The calculated image can be generated by changing (d).

3C is an image focused by an optical focusing method, and FIG. 3D is an image obtained through the image sensor 380 by moving the optical distance from the image of FIG. 3C upward 100 um. Referring to FIGS. 3C and 3D, it can be seen that the measurement target object M in the optically focused image has an edge portion blurred by moving the optical distance.

3E and 3F are images generated using a transfer function by moving the digital distance value d 100 um and 200 um downward based on the blurred image of FIG. 3d, respectively. Referring to FIG. 3E, when the image taken by optically moving upward 100 um from the focused image is calculated by applying a digital distance value d to 100 um below using a digital focusing technique, it is illustrated in FIG. 3C. As can be seen, it can be seen that the optically focused image acquires almost the same results.

In addition, referring to FIG. 3F, the digital image value (d) is calculated by applying a digital distance value (d) 200 μm below the optical focal length using a digital focusing technique to move the image taken by optically moving 100 um upward from the focused image. If it does, unlike FIG. 3C, it can be confirmed that the blurred image is generated because it is out of focus. That is, the holographic restoring apparatus 300 according to the embodiments of the present invention can focus in the same manner as the optical focusing by the digital focusing technique described above, and through this, it is not necessary to have an object light objective lens. The configuration of can be simplified.

Meanwhile, FIGS. 4A and 4B are diagrams for explaining a method of detecting and focusing an edge in an image of an object M to be measured.

4A and 4B, the holographic restoration apparatus 300 according to embodiments of the present invention can automatically focus as well as focus manually when using digital focusing. At this time, the holography restoring apparatus 300 may detect an edge of an image generated by digital focusing, and perform a focusing operation based on this.

In other words, the processor 390 may generate a calculated calculated image while changing the digital distance value d by using the image acquired from the image sensor 380 and detect an edge of the calculated image. Before measuring the image for generating the 3D shape information of the actual measurement target object M, the holographic restoration apparatus 300 uses the distance sensor 357 to focus macroscopically on the measurement target object M. Can measure the macroscopic image of

When such a macroscopic image is provided, the processor 390 detects an edge included in the generated calculated images while changing the digital distance value d, and calculates the contrast value of the detected edge. Can be extracted. At this time, 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 whose image intensity changes sharply, discontinuities are detected during the edge detection process, and assist the system to recognize important events, such as automatically focusing. Can be. 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 may measure the x-direction brightness and color change rate, and the y-direction brightness and color change rate of pixels in the calculated image calculated by digital focusing to detect pixels having a large change rate as edge pixels. have. In one embodiment, the processor 390 may use the most focused computational image as the focus image based on the extracted contrast value. Or, as another embodiment, the processor 390 acquires a digital distance value d corresponding to the most focused calculated image based on the extracted contrast value, and the light and the plate 351 in which the macroscopic focus distance is set. The driving means 353 may be controlled so that the distance between the dividers 330 is controlled by the digital distance value d.

In other words, when the macroscopic distance of the plate 351 is adjusted by the distance sensor 357, the image sensor 380 acquires a macroscopic image of the object M to be measured and provides it to the processor 390, At this time, the processor 390 may detect an edge of the calculated images calculated by digital focusing from the macroscopic image. As shown in FIG. 4A, when focus is not achieved, a blur is generated at an edge, so the contrast value is low. When focus is achieved as shown in FIG. 4B, the contrast value at the edge is relative to FIG. 4A. It becomes high.

In one embodiment, the processor 390 may select a focus image having the highest contrast value among edges of calculated images, and derive a digital distance value d corresponding to the selected focus image. Thereafter, the processor 390 may microscopically adjust the height of the plate 351 through the driving means 353 to correspond to the digital distance value d derived by digital focusing. Thereafter, the processor 390 may measure the actual image required to generate the 3D shape information after placing the plate 351 at a height corresponding to the derived digital distance value d. In another embodiment, 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 above-described contrast value, the processor 390 may compare the contrast values at one point of the edge, or average the contrast values of the entire edge to compare the average values.

As described above, the holographic restoring apparatus 300 according to an embodiment of the present invention can obtain a focus image by adjusting focus microscopically by optical focusing and then focusing microscopically by digital focusing. In particular, the holography reconstruction apparatus 300 may automatically implement digital focusing using edge detection.

5A and 5B are diagrams for explaining the 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 complicated shape, the simplified pattern shown in FIGS. 5A and 5B will be described below as an example for convenience of description.

As shown in FIGS. 5A and 5B, the object to be measured 350 may include rectangular parallelepiped structures 51A to 51I arranged on one surface at predetermined intervals. 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 apparatus 300 irradiates the object light O in a direction perpendicular to the surface on which the structures 51A to 51I of the rectangular parallelepiped structure of the object to be measured 350 are disposed, and thus the image of the object to be measured 350 It will be described on the premise of obtaining.

First, the image sensor 380 according to an embodiment of the present invention may acquire an image of the object 350 to be measured.

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) with respect to the object to be measured 350 (ie | (U0(x,y,0)| ² ), and may be expressed as Equation 2 below.

[Equation 2]

Here, the object hologram Uo(x,y,0) represents 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 and perpendicular to the object light O O(x,y) and R(x,y) denote object light O and reference light R, respectively, and O*(x,y) and R*(x, y) represents the complex conjugate of the object light O and the reference light R, respectively.

For example, the image sensor 380 may acquire an image as shown in FIG. 5 for a portion of the object to be measured 350 shown in FIGS. 5A and 5B (for example, a portion including 51A and 51B). Can be.

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 image sensor 380 acquires the general It may be different from the image of the object to be measured 350 (that is, photographed only with 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 350 to be measured at each point and the phase information of the object to be measured. It may be generated by the interference of the reference light (R).

In addition, the object hologram (U0(x,y,0)) is in addition to the phase information (ie, height information of the object) at each point (ie, each x,y point) of the object 350 to be measured, according to aberration of optical elements. Errors and noise (eg, speckle noise due to the use of a photon of a laser) may be further included.

Accordingly, the processor 390 according to an embodiment of the present invention may perform various calculation processes as described below to remove the above-described error and noise from the image acquired 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 uses the frequency components included in the image including the intensity information for each position of the object hologram U0(x,y,0) (that is, |(U0(x,y,0)| ² ). 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 three components described above (the frequency component corresponding to the real image, the frequency component corresponding to the virtual image, and the DC component). For example, the image may further include frequency components due to noise. However, this is exemplary 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 world from the identified frequency components. At this time, the processor 390 may extract components corresponding to the actual image in various ways.

For example, the processor 390 extracts components having a peak value (hereinafter referred to as peak components) among the frequency components included in the image, and a peak component corresponding to a real image among the extracted peak components. Components within the frequency difference of firing can be extracted as components corresponding to the actual 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, among the frequency components corresponding to the real image, frequency components in the cross region including the peak component as components corresponding to the real image. At this time, the length of the cross region 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 exemplary and the spirit of the present invention is not limited thereto.

In an optional embodiment, the processor 390 may extract only components corresponding to a real image from among 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 frequency component and the magnitude (or intensity) of the frequency component.

FIG. 7 is a diagram showing frequency components of an image for a portion of the measurement target object 350 shown in FIG. 6.

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

In addition, the processor 390 may extract only the frequency component 911 corresponding to the actual condition among the identified components. At this time, the processor 390 removes noise from the frequency component corresponding to the actual image. Specifically, the processor 390 removes, as noise, the frequency components located in the direction of the interference fringe and the normal direction of the interference fringe, thereby corresponding to the real image as shown in FIGS. 8A, 8B, 8C, and 8D. The frequency components in the cross region centered on the peak component can be determined as components corresponding to the actual image. At this time, the direction of the cross region is rotated according to the direction of the interference fringe.

The processor 390 according to an embodiment of the present invention may generate digital reference light from frequency components corresponding to a real image extracted by the above-described 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 actual 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 wave number (or wave vector) of the digital reference light, and generates a conjugate term of the digital reference light (R(x,y)) generated 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 digital reference light generated based on frequency components corresponding to the real image, and Rc(x,y) represents correction light.

The processor 390 extracts a normal line of the interference fringe and direction lines (Line1, 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 regions including Line1 and Line2 as noise regions (Noise1, Noise2, Noise3, and Noise4). The processor 390 may extract frequency components distributed in regions excluding noise regions. The processor 90 may extract frequency components corresponding to the reality in which noise is removed using a pattern excluding the noise region. As shown in FIG. 8C, the processor 90 may remove noise using a cross-shaped pattern (Pattern1) excluding frequency components distributed in Line1 and Line2. At this time, the processor 90 generates a cross-shaped pattern (Pattern1) based on a constant ratio of the distance difference value between the origin component 913 and the actual frequency component 911, for example, 1/3 times R. Can decide.

The processor 90 may set various patterns to remove the noise region. As illustrated in FIG. 8D, the noise of the frequency component corresponding to the real image may be performed by using a pattern (Pattern2) that is wider 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, as shown in FIGS. 9A and 9C, the intensity is the same, as shown in FIGS. 9B and 9D. Likewise, the phases can 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 is 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 the actual hologram Um(x,y,0) described later.

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

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

In this case, the hologram may be represented by Equation 4 below.

[Equation 4]

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

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

Meanwhile, such a hologram Um(x,y,0) may include errors related to aberrations of optical elements and information about the reference light R, in addition to information about the height of the object to be measured 350.

Therefore, the processor 390 according to an embodiment of the present invention takes into account the influence by the reference light R and the error due to the aberration of the optical elements, thereby correcting the corrected hologram Uc() from the hologram Um(x,y,0). x,y,0)).

For example, the processor 90 may include a term (Rc(x,y)) for correction light and a term for correction of curvature aberration (Rca(x) in the actual hologram (Um(x,y,0)) as shown in Equation 5 below. ,y)) to generate a correction 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) represents a correction hologram in which information about the reference light R and aberration information of optical elements are removed, Um(x,y,0) represents a real hologram, and Rc(x,y) ) Denotes a term for correction light, and Rca(x,y) denotes a term for curvature aberration correction.

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

For example, the processor 390 may actually measure the hologram Um(x,y,0) multiplied by only the term Rc(x,y) for the correction light from the hologram (hereinafter, the intermediate hologram) 3 of the object to be measured 350 A dimensional shape may be generated, and a term Rca(x,y) for curvature aberration correction 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 a curvature aberration correction term from the three-dimensional shape of the measurement target object 350 generated from the intermediate hologram. At this time, the parameter may include, for example, a coordinate and a radius of a center point defining a hemispherical curved surface.

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

For convenience of description, it is assumed that the image sensor 380 acquires an image of the cuboid-shaped structure 51D of FIG. 3B, and the processor 390 generates an intermediate hologram for the structure 51D according to the above-described process. do. It is also assumed that the three-dimensional shape 920 of the structure 51D generated from the intermediate hologram for the structure 51D is as shown in FIG. 10.

Under the assumptions described above, the processor 390 according to an embodiment of the present invention may determine at least one parameter for determining a curvature aberration correction term from the three-dimensional shape 920. For example, the processor 390 may determine, as parameters, the coordinates (Cx, Cy) of the center point of the hemispherical surface and the radius (r) of the surface from the curve on the II section of the three-dimensional shape 920 as shown in FIG. 12. . At this time, the processor 390 according to an embodiment of the present invention may determine the position and/or direction of the cutting surface such that the cutting surface such as the I-I cross section includes the center point of the three-dimensional shape 920 (ie, the center point of the hemispherical shape). Also, the processor 390 may determine that a cutting surface such as an I-I cross 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-described process. For example, the processor 390 refers to the coordinates (Cx, Cy) of the center point of the curved surface and the radius (r) of the curved surface to generate a curved surface in 3D space, and is reflected in the phase correction of each x,y point from the generated curved surface. A curvature aberration correction term may be generated (or determined) by generating information.

In an optional 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 in all x and y coordinates) whose shape is known in advance.

In the case of an object to be measured in advance of the shape, since the z value at each of the x and y points is known in advance, the processor 390 determines the three-dimensional shape of the object to be measured generated from the intermediate hologram and the shape of the object to be measured. The correction term can also be determined by checking the difference in z values at each x and y point. However, this is exemplary 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 three-dimensional shape of the object 350 to be measured based on the correction hologram Uc(x,y,0). In other words, the processor 390 may calculate the height in the z direction of the object at each x and y point.

For example, the processor 90 may convert the corrected hologram Uc(x,y,0) into information on a reconstructed image plane. In this case, the reconstructed image plane refers to a virtual image display plane corresponding to a 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 processor 90.

The processor 390 may calculate the height in the z direction of the object at points x and y as shown in FIGS. 13A, 13B, and 13C from the restored information in consideration of the reconstructed image plane. FIG. 13A shows the result of restoring without removing noise from the frequency component, and FIG. 13B shows the result of removing noise using the cross-shaped pattern (Pattern1), and FIG. 13C shows the result of removing noise using Pattern2. . A1, A2, and A3 represent the height value in the Z direction as a flat graph. It can be seen that A1 has no noise, so that the height value in the z direction is large, and A2 and A3 have little change in the height value in the z direction.

When the cross-shaped pattern is used, the processor 390 may extract frequency components according to Equation 6 below.

[Equation 6]

13A, 13B, and 13C, three-dimensional shapes of two cuboid-shaped structures 51A and 51B disposed on the object to be measured 350 are exemplarily illustrated.

14 is a flowchart illustrating a method of generating three-dimensional shape information of a measurement target object 350 performed by the holographic restoration apparatus 300 according to an embodiment of the present invention. Hereinafter, descriptions 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 holographic reconstruction apparatus 300 according to an embodiment of the present invention may acquire an image of the object 350 to be measured (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) with respect to the object to be measured 350 (ie | (U0(x,y,0)| ² ), and may be represented by Equation 2 described above.

For example, the holographic restoration apparatus 300 acquires an image as shown in FIG. 6 for a portion of the object to be measured 350 shown in FIGS. 5A and 5B (for example, a portion including 51A and 51B). can do.

Since the image acquired by the holographic reconstruction apparatus 300 includes intensity information at each position of the object hologram U0(x,y,0) as described above, the holographic reconstruction apparatus 300 is obtained It may be different from the image of the object 350 to be measured (ie, 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 350 to be measured at each point and the phase information of the object to be measured. It may be generated by the interference of the reference light (R).

In addition, the object hologram (U0(x,y,0)) is in addition to the phase information (ie, height information of the object) at each point (ie, each x,y point) of the object 350 to be measured, according to aberration of optical elements. Errors and noise (eg, speckle noise due to the use of a photon of a laser) may be further included.

Therefore, the holographic reconstruction apparatus 300 according to an embodiment of the present invention may perform the calculation process of steps S1202 to S1207 to remove the above-described error and noise from the image acquired by the holographic reconstruction apparatus 300. .

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

In other words, the holographic reconstruction apparatus 300 includes the intensity information for each position of the object hologram U0(x,y,0) (that is, the frequency included in the image including |(U0(x,y,0)| ² )) Components may be identified, wherein 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 three components described above (the frequency component corresponding to the real image, the frequency component corresponding to the virtual image, and the DC component). For example, the image may further include frequency components due to noise. However, this is exemplary and the spirit of the present invention is not limited thereto.

The holographic reconstruction apparatus 300 according to an embodiment of the present invention may extract only components corresponding to a real image from the identified frequency components (S1203 ). At this time, the holographic reconstruction apparatus 300 may extract components corresponding to the actual image in various ways.

For example, the holographic reconstruction apparatus 300 extracts components having a peak value (hereinafter referred to as peak components) among the frequency components included in the image, and a peak corresponding to a real image among the extracted peak components Components within the frequency difference between the component and the firing can be extracted as components corresponding to the actual condition.

At this time, the holographic reconstruction apparatus 300 may determine components corresponding to the actual image in various ways based on a peak component corresponding to the actual image. For example, the holographic 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 exemplary and the spirit of the present invention is not limited thereto.

In an optional embodiment, the holographic reconstruction apparatus 300 may extract only components corresponding to the real image from among the 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 frequency component and the magnitude (or intensity) of the frequency component.

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

Also, the holographic reconstruction apparatus 300 may extract only the frequency component 911 corresponding to the real image from the identified components. In this case, the holographic reconstruction apparatus 300 may determine frequency components 911B in the cross region centered on the peak component 911A corresponding to the real image as components corresponding to the real image, for example, as illustrated in FIG. 7.

The holographic reconstruction apparatus 300 according to an embodiment of the present invention may generate digital reference light from frequency components corresponding to a real image extracted by the above-described process (S1204). Looking at this in more detail, the holographic reconstruction apparatus 300 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 holography restoration apparatus 300 may calculate the wavenumber vector of the digital reference light.

In addition, the holographic reconstruction apparatus 300 generates digital reference light based on the propagation direction and wave number (or wave vector) of the digital reference light, and the digital reference light R(x,y) generated as in Equation 3 above. By obtaining the conjugate term, correction light Rc(x,y) can be generated.

Since the digital reference light R(x,y) and the correction light Rc(x,y) have a conjugate relationship, as shown in FIGS. 9A and 9C, the intensity is the same, as shown in FIGS. 9B and 9D. Likewise, the phases can 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 is 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 the actual hologram Um(x,y,0) described later.

Meanwhile, the'digital reference light' is light having the same properties as the reference light R generated by the above-described optical splitter 330 from light of a single wavelength, and the holographic restoring device 300 is obtained by the holographic restoring device 300. It may be a virtual light reconstructed from an image.

The holographic restoring apparatus 300 according to an embodiment of the present invention may also generate a real image hologram based on frequency components corresponding to the real image extracted by the above-described process (S1204). For example, the holographic reconstruction apparatus 300 may generate an actual hologram as shown in FIG. 10 by performing an inverse 2D Fourier transform on frequency components corresponding to the actual image. In this case, the hologram may be represented by Equation 3 described above.

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

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

Referring again to FIGS. 11 and 12, a method for determining a correction term for curvature aberration from an intermediate hologram by the holographic reconstruction apparatus 300 according to an embodiment of the present invention will be described. For convenience of description, the holographic reconstruction apparatus 300 acquires an image of the rectangular parallelepiped structure 51D of FIG. 5B, and the holographic reconstruction apparatus 300 acquires an intermediate hologram for the structure 51D according to the above-described process. It is assumed to have been created. It is also assumed that the three-dimensional shape 920 of the structure 51D generated from the intermediate hologram for the structure 51D is as shown in FIG. 11.

Under the assumptions described above, the holographic reconstruction apparatus 300 according to an embodiment of the present invention may determine at least one parameter for determining a curvature aberration correction term from the three-dimensional shape 920. For example, the holographic reconstruction apparatus 300 determines the coordinates (Cx, Cy) of the center point of the hemispherical curved surface and the radius (r) of the curved surface as parameters from the curve on the II section of the three-dimensional shape 920 as shown in FIG. 12. Can be. At this time, the holographic restoration apparatus 300 according to an embodiment of the present invention may determine the position and/or direction of the cut surface such that the cut surface, such as the II cross section, includes the center point of the three-dimensional shape 920 (ie, the center point of the hemispherical shape). . Also, the holography restoring apparatus 300 may determine that a cutting surface such as an I-I cross section is parallel to the traveling direction of the object light 0.

The holographic 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-described process. For example, the holography restoration apparatus 300 generates a curved surface in three-dimensional space with reference to the coordinates (Cx, Cy) of the center point of the curved surface and the radius (r) of the curved surface, and corrects the phase of each x,y point from the generated curved surface. A method of correcting a curvature aberration may be generated (or determined) in a manner of generating information to be reflected.

In an optional embodiment, the holographic reconstruction apparatus 300 may determine a correction term from an intermediate hologram of an object to be measured (eg, an object having the same z value in all x and y coordinates) that knows the shape in advance.

In the case of an object to be measured that knows the shape in advance, since the z value at each of the x and y points is known in advance, the holography restoring apparatus 300 can measure the three-dimensional shape of the object to be measured and the object to be measured from the intermediate hologram. The correction term can also be determined by checking the difference in z values at each x and y point of the shape. However, this is exemplary and the spirit of the present invention is not limited thereto.

The holographic restoring apparatus 300 according to an embodiment of the present invention takes a correction hologram Uc from a real hologram Um(x,y,0) in consideration of an error caused by aberrations of optical elements and an effect caused by the reference light R (x,y,0)) may be generated (S1207). For example, the holographic reconstruction apparatus 300 has a term (Rc(x,y)) for correcting light and a term for correcting curvature aberration (Rca) in the actual hologram (Um(x,y,0)) as in Equation 5 described above. By multiplying by (x,y)), a correction hologram Uc(x,y,0) can be generated. In this case, the term Rc(x,y) for the correction light may be generated in step S1204, and the term Rca(x,y) for curvature aberration correction may be generated in step S1206.

The holographic restoring 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 corrected hologram Uc(x,y,0) (S1208 ). In other words, the holographic reconstruction apparatus 300 may calculate the height of the object at each x and y point in the z direction.

For example, the holographic reconstruction apparatus 300 may convert the corrected hologram Uc(x,y,0) into information on the reconstructed image surface. In this case, the reconstructed image plane refers to a virtual image display plane corresponding to a 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 holographic reconstruction apparatus 300. .

The holographic reconstruction apparatus 300 may calculate the height in the z direction of the object at the x and y points from the reconstructed information in consideration of the reconstructed image plane. In FIG. 13, three-dimensional shapes of two rectangular parallelepiped structures 51A and 51B disposed on the object to be measured 350 are exemplarily illustrated.

15 and 16 are flowcharts of a method for removing noise in the holographic reconstruction apparatus 300 according to embodiments of the present invention.

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

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

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

In S12033, the holography restoration apparatus 300 removes noise from the first frequency component to extract a frequency component corresponding to the real image.

In another embodiment, the holography restoring apparatus 300 may set a pattern to remove noise and use the pattern to extract a frequency component corresponding to the real image.

In S12034, the holographic 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 S12035, the holographic reconstruction apparatus 300 generates a cross-region pattern including the peak component of the first frequency component. In S12036, the holographic reconstruction apparatus 300 extracts, among the first frequency components, frequency components included in the cross-region pattern.

The mathematical expression to which the cross-region pattern is applied is as follows. The holographic reconstruction apparatus 300 may extract frequency components included in the cross-region pattern according to Equation 7 below.

[Equation 7]

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

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

In another embodiment, the holographic reconstruction apparatus 1 may give different weights according to the position of the filtering region with hemispherical filtering in order to more effectively remove noise. For example, the holographic reconstruction apparatus 1 may multiply a weight less than 1 as it moves further from the center.

[Equation 8]

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

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

Meanwhile, the computer program may be specially designed and configured for the present invention or may be known and available to those skilled in the computer software field. Examples of computer programs may include not only machine language codes created by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like.

As described above, the holographic reconstruction apparatus 300 according to an embodiment of the present invention, that is, the holographic reconstruction apparatus 300, can accurately generate three-dimensional shape information of an object to be measured by acquiring one hologram. have. The above-described holographic reconstruction apparatus 300 can simplify components while generating accurate 3D shape information through the above-described methods, and is disposed inside the in-line deposition equipment to perform inspection in real time on an in-line process. Enable.

The specific implementations described in the present invention are exemplary embodiments, and do not limit the scope of the present invention in any way. For brevity of the specification, descriptions of conventional electronic configurations, control systems, software, and other functional aspects of the systems may be omitted. In addition, the connection or connection members of the lines between the components shown in the drawings are illustrative examples of functional connections and/or physical or circuit connections. It can be represented as a connection, or circuit connections. In addition, unless specifically mentioned, such as "essential", "important", etc., it may not be a necessary component for the application of the present invention.

Therefore, the spirit of the present invention is not limited to the above-described embodiment, and should not be determined, and the scope of the spirit of the present invention, as well as the claims to be described later, as well as all ranges that are equivalent to or equivalently changed from the claims. Would belong to

300, 300A, 300B: Holographic restoration device
310: light source unit
320: collimator
330,332: Optical splitter
350: object to be measured
370,372: Optical mirror
380: image sensor
390: processor

Claims (6)

A light source unit that emits single wavelength light;
A collimator for collimating single wavelength light emitted from the light source unit;
An optical splitter for dividing the single wavelength light passing through the collimator into object light and reference light;
An optical mirror reflecting the reference light divided by the light splitter;
An image sensor that records an interference fringe formed by transmitting the object light reflected from the surface of the object to be measured and the reference light reflected by the optical mirror to the light splitter after being divided by the light splitter; And
A processor for receiving and storing an image including intensity information of an object hologram generated by converting the interference fringe from the image sensor, and generating three-dimensional shape information of the surface of the object to be measured.
The processor performs digital focusing of the image obtained from the image sensor using a transfer function that depends on a digital distance value, and a device for generating three-dimensional shape information of an object to be measured. According to claim 1,
A plate disposed on a path through which the object light divided by the optical splitter passes, and seating the object to be measured;
A distance sensor disposed adjacent to the optical divider and detecting a distance between the optical divider and the plate; And
And a driving means connected to the plate and moving the plate with respect to the optical splitter using an optical distance value detected by the distance sensor. According to claim 2,
The plate includes an overlapping area overlapping the measurement object and a non-overlapping area non-overlapping with the measurement object,
The distance sensor detects the distance of the plate based on the non-overlapping area on one surface of the plate, and the apparatus for generating 3D shape information of the object to be measured. According to claim 3,
The processor moves the plate using the optical distance value sensed by the distance sensor, and then performs the digital focusing. According to claim 4,
The processor detects an edge of the image obtained from the image sensor, extracts a contrast value of the detected edge, and performs the digital focusing based on the extracted contrast value. 3D shape information generating device. According to claim 1,
The processor extracts a real image component corresponding to a real image among at least one frequency component included in the image, and corrects the correction light in the conjugate relationship with the reference light based on the real image components and the A real hologram including mounting information of a measurement target object is generated, and based on the correction light, an intermediate hologram in which the information of the reference light is removed from the real hologram is generated, and curvature aberration correction information is generated from the intermediate hologram. Thereafter, based on the curvature aberration correction information, an object to be measured that generates a corrected hologram with improved error due to curvature aberration in the intermediate hologram and generates the three-dimensional shape information of the object to be measured from the corrected hologram 3D shape information generating device.

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