KR102218015B1 - System for measuring Grating phase using calibration Grating in FPM - Google Patents

Abstract

The present invention relates to a diffraction grating phase measurement system and a measurement method using calibration grating in FPM, and more particularly, in the phase measurement system, a plurality of LED light sources are provided, and LED beams are sequentially applied to a measurement object at different angles. LED array to irradiate; A lens configured to collect the beam emitted from the measurement object irradiated with the LED beam; A photodetector for receiving light from the lens and acquiring a first image for each of a plurality of LED beams; And an analysis means for calculating a phase of the measurement object by positioning and stitching each of the first images in the spectral domain, wherein the analysis means stores the phase information of the calibration grating in advance, and the measurement object and the calibration grating After calculating the phase information for the object to be measured overlapping by combining, and removing the phase information of the calibration grating to measure the phase information for the object to be measured, a system for measuring the phase of a diffraction grating using calibration grating will be.

Description

Diffraction grating phase measurement system and measurement method using calibration grating in FPM {System for measuring Grating phase using calibration Grating in FPM}

The present invention relates to a diffraction grating phase measurement system and a measurement method using calibration grating in FPM.

Fourier Ptychographic Microscopy (FPM) is a phase retrieval method developed by Guoan Zheng in 2013. As with conventional digital holographic microscopy, the phase can be calculated without using a reference beam.

Since the FPM can perform phase calculation without a reference beam, the system can be compact, and since the signal beam/reference beam is not distinguished, there is a strong advantage against vibration.

In addition, conventional digital holographic microscopy has a low field of view (FOV) and depth of focus (DOF) when using a high NA objective lens to obtain high resolution, whereas FPM replaces the condenser lens with an LED array to achieve high resolution. By enabling the illumination angle, high resolution is obtained even with a low NA objective lens, so there is an advantage of having a wide FOV and DOF. In addition, since a high illumination angle is obtained with the LED array, a mechanical driving part is not required.

1 shows a configuration diagram of an FPM system 1, and FIG. 2 shows a spectrum of a measurement object. As shown in FIG. 1, the FPM system 1 transmits the LED array 10 composed of a plurality of LED light sources 11 irradiated to the measurement object 2 at different angles, and the measurement object 2 It comprises an objective lens 20 on which one LED beam is formed, a condensing lens 30, and a photodetector 40 that acquires an image of the LED beam irradiated onto the measurement object 2.

Using the LED array 10 composed of N LED light sources 11, beams of N different irradiation angles are sequentially irradiated onto the measurement object 2, and N images are stored in the photodetector 40.

And the analysis means FFT N images as shown in Fig. 2 (in Fig. 2, ○ is the spectrum of the signal focused by the objective lens through the beam from one LED), the angle of θx, θy in the spectral domain The phase is calculated by stitching while being placed on the one corresponding to the position.

At this time, the individual spectra that are stitched must have overlapping portions for proper phase convergence.

Japanese Laid-Open Patent 2016-530567 Japanese Laid-Open Patent 2018-504627

Accordingly, the present invention has been devised to solve the conventional problems as described above, and according to an embodiment of the present invention, in the case of having a sparse spectrum like a diffraction grating, an overlapping region in stitching due to a wide gap between the spectrum of signals When phase convergence is difficult because there is no phase information, the calibration grating with known phase information is measured together with the measurement object to calculate the phase of the measurement object and the calibration grating, and the phase information of the calibration grating is removed from the result. Its purpose is to provide a diffraction crystal measurement system and a measurement method using calibration grating in FPM that can calculate the phase information of a measurement object having a sparse spectrum.

Meanwhile, the technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems that are not mentioned are clearly to those of ordinary skill in the technical field to which the present invention belongs from the following It will be understandable.

A first object of the present invention is a phase measurement system, comprising: an LED array provided with a plurality of LED light sources and sequentially irradiating an LED beam onto a measurement object at different angles; A lens configured to collect the beam emitted from the measurement object irradiated with the LED beam; A photodetector for receiving light from the lens and acquiring a first image for each of a plurality of LED beams; And an analysis means for calculating a phase of the measurement object by positioning and stitching each of the first images in the spectral domain, wherein the analysis means stores the phase information of the calibration grating in advance, and the measurement object and the calibration grating Achieved as a diffraction grating phase measurement system using calibration grating in FPM, characterized in that the phase information of the measurement object is measured by removing the phase information of the calibration grating after calculating the phase information of the object to be measured by combining Can be.

And the measurement object may be characterized in that it has a sparse spectrum like a diffraction grating.

In addition, the analysis means may be characterized in that the first image is inverse Fourier transformed to obtain a spectrum and phase converged through an overlapping region to obtain phase information to generate a second image having phase information.

In addition, an overlapping region may not exist in the spectrum obtained by inverse Fourier transform of the first image of the measurement object.

In addition, the analysis means obtains a spectrum by inverse Fourier transform of the first image of the combined measurement object in which the measurement object and the calibration grating overlap, and phase converges through the overlapping region to obtain phase information of the combined measurement object. You can do it.

And the analysis means may be characterized in that the phase information of the measurement object is obtained by removing the phase information of the calibration grating from the phase information of the combined measurement object.

In addition, it may be characterized in that it comprises an LED control unit for controlling the plurality of the LED light source to sequentially irradiate the measurement object.

A second object of the present invention is to provide a method for measuring a phase, comprising: a first step of storing phase information of calibration grating; A second step of preparing a combined measurement object by overlapping the calibration grating on the measurement object; A third step of sequentially irradiating an LED beam onto the combined measurement object at different angles through the LED array; A fourth step of collecting the beam emitted from the combined measurement object irradiated with the LED beam from the lens; A fifth step of receiving, by a photodetector, light from the lens and obtaining a first image for each of a plurality of LED beams; And a sixth step of calculating the phase of the combined measurement object by positioning and stitching each of the first images in the spectral domain, and measuring phase information of the measurement object by removing phase information of the calibration grating. It can be achieved as a diffraction grating phase measurement method using calibration grating in the FPM, characterized in that it comprises.

And in the third step, it may be characterized in that the LED control unit controls the plurality of LED light sources to sequentially irradiate the combined measurement object.

In addition, in the sixth step, the analysis means obtains a spectrum by inverse Fourier transforming the first image of the combined measurement object in which the measurement object and the calibration grating are overlapped, and phase converges through the overlapping region to perform phase information of the combined measurement object. And removing phase information of the calibration grating from the phase information of the combined measurement object to obtain phase information of the measurement object.

In the case of having a sparse spectrum such as a diffraction grating, when phase convergence is difficult because there is no overlapping region in stitching due to a wide gap between the spectrum of signals, a system for measuring diffraction crystals using calibration grating in an FPM according to an embodiment of the present invention and According to the measurement method, the phase information of the measurement object and the calibration grating is calculated by measuring the calibration grating with known phase information together with the measurement object, and the phase information of the calibration grating is removed from the result, and finally the spectrum sparse like a diffraction grating. It has the effect of calculating the phase information of the object to be measured.

On the other hand, the effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those of ordinary skill in the art from the following description. I will be able to.

The following drawings attached to the present specification illustrate a preferred embodiment of the present invention, and serve to further understand the technical idea of the present invention together with the detailed description of the present invention, so the present invention is limited to the matters described in such drawings. It is limited and should not be interpreted.
1 is a configuration diagram of an FPM system,
2 is a spectrum graph of a measurement object,
3 is an FPM system for calculating phase information of a measurement object having a sparse spectrum like a diffraction grating,
4 is a spectrum graph of a measurement object having a sparse spectrum like a diffraction grating,
5 is a configuration diagram of a diffraction grating phase measurement system using calibration grating in an FPM according to an embodiment of the present invention;
6 is a spectral distribution of a diffraction grating measurement object, a spectral distribution of calibration grating, and a spectral distribution in which the diffraction grating measurement object and the calibration grating are converted,
7 is an image of a measurement object and a calibration grating, and a Fourier transformed spectrum,
8 shows an image of a spectrum obtained by converting a measurement object and a calibration grating, and an image of a measurement object from which phase information of the calibration grating is removed.

The above objects, other objects, features, and advantages of the present invention will be easily understood through the following preferred embodiments related to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed contents may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

In the present specification, when a component is referred to as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. In addition, in the drawings, the thickness of the components is exaggerated for effective description of the technical content.

Embodiments described herein will be described with reference to cross-sectional views and/or plan views, which are ideal exemplary views of the present invention. In the drawings, the thicknesses of films and regions are exaggerated for effective description of technical content. Therefore, the shape of the exemplary diagram may be modified by manufacturing technology and/or tolerance. Accordingly, embodiments of the present invention are not limited to the specific form shown, but also include a change in form generated according to the manufacturing process. For example, an area shown at a right angle may be rounded or may have a shape having a predetermined curvature. Accordingly, the regions illustrated in the drawings have properties, and the shapes of the regions illustrated in the drawings are intended to illustrate a specific shape of a device region and are not intended to limit the scope of the invention. In various embodiments of the present specification, terms such as first and second are used to describe various elements, but these elements should not be limited by these terms. These terms are only used to distinguish one component from another component. The embodiments described and illustrated herein also include complementary embodiments thereof.

The terms used in the present specification are for describing exemplary embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless specifically stated in the phrase. As used in the specification, "comprises" and/or "comprising" does not exclude the presence or addition of one or more other elements.

In describing the specific embodiments below, a number of specific contents have been prepared to explain the invention in more detail and to aid understanding. However, readers who have knowledge in this field to the extent that they can understand the present invention can recognize that it can be used without these various specific contents. In some cases, it is mentioned in advance that parts that are commonly known in describing the invention and are not largely related to the invention are not described in order to prevent confusion without any reason in describing the invention.

Hereinafter, the configuration, function, and measurement method of the diffraction grating phase measurement system 100 using calibration grating in the FPM according to an embodiment of the present invention will be described.

First, FIG. 3 shows an FPM system for calculating phase information of a measurement object 2 having a sparse spectrum like a diffraction grating. 4 shows a spectrum graph of a measurement object having a sparse spectrum like a diffraction grating.

3 and 4, in the case of measuring phase information through a PEM system for a measurement object 2 (hereinafter, a diffraction grating measurement object) having a sparse spectrum like a diffraction grating, an overlapping area between the spectra Since this does not exist, there is a problem in that phase information cannot be obtained because phase convergence is difficult.

The diffraction grating phase measurement system 100 using calibration grating in the FPM according to the embodiment of the present invention includes a plurality of LED light sources 11, and an LED array that sequentially irradiates an LED beam to a measurement object at different angles ( 10), and a plurality of LED light source 11 is configured to include an LED control unit for controlling the sequentially irradiated to the object (2). Therefore, it is configured so that the LED beams of N different irradiation angles (θx, θy) can be sequentially irradiated onto the measurement object 2 using the LED array 10 composed of the N LED light sources 11.

And, including an objective lens 20 and a condensing lens 30 configured to collect the beam emitted from the measurement object 2 irradiated with the LED beam, the photodetector 40 receives light from the lens, and each of the plurality of LED beams A first image of is acquired. This first image corresponds to a state in which phase information has disappeared.

Therefore, the analysis means calculates the phase of the measurement object by positioning and stitching each of the first images in the spectral domain.

Analysis means according to an embodiment of the present invention stores the phase information of the calibration grating (3) in advance, overlaps the diffraction grating measurement object (2) and the calibration grating (3), and provides phase information for the combined measurement object (4). After calculation, the phase information of the calibration grating 3 is removed, and the phase information of the diffraction grating measurement object 2 is measured.

5 is a block diagram of a diffraction grating phase measurement system 100 using calibration grating in an FPM according to an embodiment of the present invention. And FIG. 6 shows the spectral distribution of the diffraction grating measurement object, the spectral distribution of the calibration grating, and the spectral distribution in which the diffraction grating measurement object and the calibration grating are converted.

As shown in FIG. 6, it can be seen that there is no overlapping region in the spectrum for each of the first images of the single grating measurement object 2. However, the phase information for the calibration grating (3) is known in advance, and there is an overlapping area in the spectrum of the combined measurement object (4) where the calibration grating (3) and the diffraction grating measurement object (2) are overlapped, so that the phase information is recovered and acquired. You can see that you can.

7 shows an image of a measurement object and calibration grating, and a Fourier transformed spectrum. 8 shows an image of a spectrum obtained by converting a measurement object and a calibration grating, and an image of a measurement object from which phase information of the calibration grating is removed. The upper left of FIG. 7 is the first image of the diffraction grating measurement object, the upper right corresponds to the first image of the calibration measurement object, the lower left is an inverse Fourier transform of the first image of the diffraction grating measurement object, and the lower right is It is an inverse Fourier transform of the first image of the calibration measurement object.

In addition, the left side of FIG. 8 shows the spectrum with the phase information of the combined measurement object in which the calibration grating and the diffraction grating measurement object overlap, and the right side shows an image with the phase information of the diffraction grating measurement object from which the phase information of the calibration grating is removed. will be.

As shown in FIG. 5, the analysis means according to an embodiment of the present invention obtains a spectrum by inverse Fourier transform of each of the plurality of first images acquired by the photodetector 40, and performs phase convergence through the overlapping region. It is configured to obtain information to generate a second image having phase information.

As mentioned above, since there is no overlapping region in the spectrum obtained by inverse Fourier transform of the first image of the diffraction grating measurement object 2 alone, it is difficult to measure the phase information of the diffraction grating measurement object 2.

Therefore, the analysis means obtains a spectrum by inverse Fourier transform of the first image of the combined measurement object 4 in which the diffraction grating measurement object 2 and the calibration grating 3 are overlapped, and phase converges through the overlapping region to obtain a combined measurement object. It is configured to obtain the phase information of (4).

That is, the analysis means obtains the phase information of the diffraction grating measurement object 2 by removing the phase information of the calibration grating 3 from the phase information of the combined measurement object 4.

Hereinafter, a method of measuring a phase of a diffraction grating using calibration grating in PM will be described.

First, the phase information of the calibration grating (3) is stored. Then, the calibration grating (3) is superimposed on the diffraction grating measurement object (2) to prepare a combined measurement object (4).

And the LED beam is irradiated to the combined measurement object 4 sequentially at different angles through the LED array 10. At this time, the LED control unit controls the plurality of LED light sources 11 to be sequentially irradiated onto the combined measurement object 4.

Then, the objective lens 20 and the condensing lens 30 collects the beam emitted from the combined measurement object 4 to which the LED beam is irradiated, and the photodetector 40 receives light from the condensing lens 30 and receives a plurality of LEDs. A first image for each beam is acquired. The phase information disappears from the first image.

In addition, the analysis means calculates the phase of the combined measurement object 4 by positioning and stitching each of the first images in the spectral domain, and removing the phase information of the calibration grating 3 to obtain phase information for the diffraction grating measurement object 2 Is measured.

That is, the analysis means acquires a spectrum by inverse Fourier transform of the first image of the combined measurement object 4 in which the diffraction grating measurement object 2 and the calibration grating 3 overlap, and performs phase convergence through the overlapping area to measure the combination. Phase information of the object 4 is acquired, and phase information of the calibration grating 3 is removed from the phase information of the combined measurement object 4 to obtain the phase information of the diffraction grating measurement object 2.

In addition, the above-described apparatus and method are not limitedly applicable to the configuration and method of the above-described embodiments, but all or part of each of the embodiments may be selectively combined so that various modifications can be made to the embodiments. It can also be configured.

1: FPM system
2: Measurement object
3: Calibration grating
4: binding measurement object
10: LED array
11: LED light source
20: objective lens
30: condensing lens
40: photodetector
Diffraction grating phase measurement system using calibration grating at 100:FPM

Claims (10)

In the phase measurement system,
An LED array provided with a plurality of LED light sources and sequentially irradiating an LED beam onto the object to be measured at different angles;
A lens configured to collect the beam emitted from the measurement object irradiated with the LED beam;
A photodetector for receiving light from the lens and acquiring a first image for each of a plurality of LED beams; And
And an analysis means for calculating a phase of the measurement object by stitching each of the first images in a spectral domain,
The analysis means stores the phase information of the calibration grating in advance, calculates the phase information of the measurement object overlapped by combining the measurement object and the calibration grating, and then removes the phase information of the calibration grating to determine the phase of the measurement object. Measure information,
The measurement object is a diffraction grating phase measurement system using a calibration grating in FPM, characterized in that it has a sparse spectrum like a diffraction grating.
delete The method of claim 1,
The analysis means generates a second image with phase information by obtaining phase information by inverse Fourier transform of the first image to obtain a spectrum, and phase convergence through an overlapping region. Diffraction grating phase measurement system.
The method of claim 3,
A diffraction grating phase measurement system using calibration grating in an FPM, characterized in that no overlapping region exists in the spectrum obtained by inverse Fourier transform of the first image of the measurement object.
The method of claim 4,
The analysis means obtains a spectrum by inverse Fourier transform of the first image of the combined measurement object in which the measurement object and the calibration grating are overlapped, and phase converges through the overlapping region to obtain phase information of the combined measurement object. Diffraction grating phase measurement system using calibration grating in FPM.
The method of claim 5,
The analysis means is a diffraction grating phase measurement system using calibration grating in FPM, characterized in that the phase information of the calibration grating is removed from the phase information of the combined measurement object to obtain phase information of the measurement object.
The method of claim 1,
A diffraction grating phase measurement system using a calibration grating in an FPM, characterized in that it comprises an LED control unit that controls the plurality of LED light sources to be sequentially irradiated to the measurement object.
In the phase measurement method,
A first step of storing phase information of calibration grating;
A second step of preparing a combined measurement object by overlapping the calibration grating on the measurement object;
A third step of sequentially irradiating an LED beam onto the combined measurement object at different angles through the LED array;
A third step of collecting the beam emitted from the combined measurement object irradiated with the LED beam from the lens;
A fourth step of receiving, by a photodetector, light from the lens and obtaining a first image for each of a plurality of LED beams; And
A fifth step of calculating the phase of the combined measurement object by positioning and stitching each of the first images in the spectral domain, and measuring phase information of the measurement object by removing phase information of the calibration grating; and,
In the third step, the LED control unit controls a plurality of the LED light sources to sequentially irradiate the combined measurement object,
In the fifth step, the analysis means obtains a spectrum by inverse Fourier transforming the first image of the combined measurement object in which the measurement object and the calibration grating are overlapped, and phase-converges through the overlapping area to perform phase information of the combined measurement object And obtaining phase information of the measurement object by removing the phase information of the calibration grating from the phase information of the combined measurement object. 14. A method of measuring a diffraction grating phase using a calibration grating in an FPM, characterized in that.
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