KR102553788B1 - Microscope system for quantifying birefringence of sample - Google Patents

Abstract

A microscope system for quantifying the optical anisotropy of a sample according to an embodiment of the present invention is a microscope system for providing quantitative information on the optical anisotropy of a sample, comprising: a light source unit emitting light; a polarization modulator for modulating a polarization form of light emitted from the light source unit; a polarization acquiring unit configured to detect the light modulated by the polarization modulating unit by irradiating the sample and classifying the light reflected or transmitted from the sample according to a polarization direction; and an image generating unit generating an image visualizing quantitative information about the optical anisotropy of the sample through the light detected by the polarization acquisition unit.

Description

Microscope system for quantifying the optical anisotropy of a sample {MICROSCOPE SYSTEM FOR QUANTIFYING BIREFRINGENCE OF SAMPLE}

The present invention relates to a microscope system for quantifying the optical anisotropy of a sample, and more particularly, by irradiating a sample with light modulated in a constant polarization state and calculating an image obtained by separating light reflected or transmitted from the sample along a polarization axis. It relates to a microscope system for quantifying the optical anisotropy of a sample.

Arithmetic microscopy is an imaging technology that simplifies the complex optical system of existing microscopes by using an optical numerical model-based arithmetic operation technique, and restores and provides information that general microscopes cannot provide, such as light intensity information as well as phase information. Representatively, there are differential phase-contrast imaging technology and Fourier ptychography technology. Differential phase contrast microscopy is an imaging technique that restores quantitative phase information of a transparent sample using several light intensity images acquired with two or more complementary light irradiation patterns, and Fourier ptychography technology irradiates the sample with plane waves of various angles, It is a technique for restoring large-area, high-resolution images by superimposing acquired images in Fourier space.

Birefringence is a phenomenon in which the refractive index is different in one medium according to the polarization state of light and is separated into two refracted lights, which occurs when irradiation light is incident on a medium having optical anisotropy. Semiconductor materials, composite materials, and biological samples have optical anisotropy.

Images of optical anisotropy are used to observe the crystal structure to determine the mechanical properties, biodegradability, and biocompatibility of the internal crystal structure of composite materials and semiconductor materials. In particular, silicon wafers and EUV masks required for semiconductor processes can find defects at an early stage through optical anisotropy measurement, and unnecessary processes can be minimized.

In addition, since biological tissues such as chromosomes, muscle tissues, and microtubules have optical anisotropy, their internal structures can be observed through optical anisotropy characteristic images. Therefore, the optically anisotropic characteristic image of a biological sample is more useful in that it is used in biological and medical fields and does not require a preprocessing process such as staining.

Optical anisotropy measurement techniques include polarization microscopy and interferometry-based techniques. The polarization microscope has a disadvantage in that stability and repeatability of image collection are low because a polarizing plate is provided between the irradiation unit and the measurement unit to acquire images while physically rotating the polarizing plate. To solve this problem, it is necessary to use an expensive electric variable retarder, but since it is an electric device, calibration is required according to the conditions of use. Since interferometry-based optical anisotropy measurement technology uses an interferometer, it requires a complicated optical system configuration and is vulnerable to disturbance.

The present invention is a microscope system that quantifies the optical anisotropy of a sample by modulating the polarization of light irradiated onto a sample, obtaining an image obtained by separating light reflected or transmitted from the sample along a polarization axis, and calculating the obtained image with a numerical model-based algorithm. provides

A microscope system for quantifying the optical anisotropy of a sample according to an embodiment of the present invention is a microscope system for providing quantitative information on the optical anisotropy of a sample, comprising: a light source unit emitting light; a polarization modulator for modulating a polarization form of light emitted from the light source unit; a polarization acquiring unit configured to detect the light modulated by the polarization modulating unit by irradiating the sample and classifying the light reflected or transmitted from the sample according to a polarization direction; and an image generating unit generating an image visualizing quantitative information about the optical anisotropy of the sample through the light detected by the polarization acquisition unit.

(여기에서,

,
I_x : X 편광 축의 방향으로 분리된 광세기 영상, θ : 광축방향, δ : 위상지연)In addition, the optical anisotropy of the sample includes an optical axis direction and a phase retardation value of the sample. At this time, the optical axis direction and phase retardation value of the sample may be calculated through the following equation.

(From here,

,
I _x : optical intensity image separated in the direction of the X polarization axis, θ: optical axis direction, δ: phase retardation)

In addition, the light source unit includes an LED array or a laser.

In addition, the polarization acquisition unit includes a plurality of condensing lenses and a polarization camera configured to classify light reflected or transmitted from the sample according to a polarization direction and to detect respective intensities of the divided light.

In addition, the polarization acquisition unit detects a plurality of condensing lenses, a Wollaston prism that separates the light reflected or transmitted from the sample at a predetermined angle according to orthogonal polarization directions, and the separated light according to orthogonal polarization directions. It includes a camera including an image sensor for

In addition, the polarization acquisition unit further includes a field stop positioned between the plurality of condensing lenses.

In addition, the polarization acquisition unit may include a plurality of condensing lenses, a polarization beam splitter that reflects or transmits light reflected or transmitted from the sample according to orthogonal polarization directions, and a first unit that detects the first light reflected from the polarization beam splitter. It includes a camera, and a second camera that detects the second light transmitted through the polarization beam splitter.

The microscope system for quantifying the optical anisotropy of a sample according to the present invention obtains an image of light reflected or transmitted through a sample using an optical system having a simple structure, and quantifies the optical anisotropy by arithmetically processing the light intensity of the image with a numerical model algorithm. You can get one video.

The effects obtainable in the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description below. will be.

1 is a schematic configuration diagram of a microscope system for quantifying optical anisotropy of a sample according to an embodiment of the present invention.
2A is an example of a polarization acquisition unit of a microscope system for quantifying optical anisotropy of a sample according to an embodiment of the present invention.
2B is another example of a polarization acquisition unit of a microscope system for quantifying optical anisotropy of a sample according to an embodiment of the present invention.
2C is another example of a polarization acquisition unit of a microscope system for quantifying optical anisotropy of a sample according to an embodiment of the present invention.
3 illustrates visualization of quantitative information of optical anisotropy of a sample according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The terms used in this specification are terms defined in consideration of the functions of the present invention, and may vary according to the intention or custom of a user or operator. Therefore, definitions of these terms should be made based on the contents throughout this specification.

In addition, the embodiments disclosed below do not limit the scope of the present invention, but are merely exemplary of the components presented in the claims of the present invention, are included in the technical spirit throughout the specification of the present invention, and cover the scope of the claims. Embodiments including components that can be replaced as equivalents in components may be included in the scope of the present invention.

In the embodiments disclosed below, terms such as "first", "second", "one surface", and "other surface" are used to distinguish one component from another component, and the component is the term are not limited by Hereinafter, in describing the present invention, detailed descriptions of known technologies that may obscure the gist of the present invention will be omitted.

1 is a schematic configuration diagram of a microscope system for quantifying optical anisotropy of a sample according to an embodiment of the present invention.

Referring to FIG. 1 , a microscope system 1000 for quantifying the optical anisotropy of a sample according to an embodiment of the present invention includes a light source unit 100, a polarization modulator 200, a polarization acquisition unit 300, and an image generator. (400).

The light source unit 100 emits light to the sample, and a light source such as LED or laser may be used. For example, the light source unit 100 uses an LED array as a light source, and in the LED array, light emitting diodes are arranged at a constant pitch in a matrix structure.

The polarization modulator 200 modulates the light emitted from the light source 100 into a constant polarization. The light emitted from the light source unit 100 may have a non-polarized light or a constant polarization form in which the oscillation of the electric field does not have a constant direction. In the present invention, irradiation light polarized in a predetermined direction is irradiated to a sample, and light reflected or transmitted through the sample is detected according to an orthogonal polarization direction, and the transfer function of the detection light reflecting the characteristics of the sample is a transfer function of the irradiation light. By comparing numerically with , the optical anisotropy characteristics of the sample are extracted. Accordingly, the polarization modulator 200 modulates the light emitted from the light source unit 100 in a pre-intended polarization form to simplify an arithmetic expression used by the image generator 400 to extract the optical anisotropy. According to an embodiment, the polarization modulator 200 modulates emission light such that circularly polarized light, particularly left circularly polarized light, is irradiated onto the sample. The polarization modulator 200 may use various combinations of optical instruments to modulate the light emitted from the light source into a desired polarization shape according to the polarization state.

For example, when the light source of the light source unit is a laser, the polarization modulator 200 includes a wave plate or a retarder for modulating a constant polarization into circular polarization, or a spatial light modulator (SLM). Light Modulator).

In addition, the polarization modulator 200 includes a linear polarizer and a wave plate or a retarder or a circular polarizer to modulate the unpolarized light into circularly polarized light, as another example, when the light source of the light source unit emits unpolarized light. can do.

The polarization acquisition unit 300 classifies and detects the light reflected or transmitted from the sample according to the polarization direction, converts the intensity of the separated light according to the polarization direction into an electrical signal, and transmits it to the image generator. Irradiation light having a certain intended polarization form is irradiated onto the sample, and the polarization form of the irradiation light is not maintained and the light reflected or transmitted from the sample is changed due to the optical anisotropy of the sample. In an embodiment, in a process in which circularly polarized light is irradiated onto a sample and reflected or transmitted through the sample, reflected light or transmitted light in which optical anisotropy of the sample is reflected may be elliptically polarized light. The polarization acquisition unit 300 may include an optical device that separates the light reflected or transmitted from the sample according to the polarization direction or a camera including an image sensor that detects the intensity of each separated light according to the orthogonal polarization direction as an electrical signal. there is.

2a to 2c illustrate one example, another example, and another example of a polarization acquisition unit of a microscope system for quantifying optical anisotropy of a sample according to an embodiment of the present invention.

Referring to FIG. 2A , in one example, the polarization acquisition unit 300 includes a plurality of condensing lenses and a polarization camera 321 that classifies light reflected or transmitted from a sample according to a polarization direction and detects the intensity of the divided light. do. The polarization acquisition unit 300 includes a first lens 311 that modulates the light passing through the sample 10 into parallel light and a second lens 312 that condenses the parallel light so that the polarization camera 321 is sensitive to it. It includes a plurality of condensing lenses. The polarization camera 321 classifies and detects the sensitized light into intensities according to components of the polarization directions of the 0 degree, 45 degree, 90 degree, and 135 degree axes, respectively, and restores the light intensity image. Referring to FIG. 2B , in another example, the polarization acquisition unit 300 includes a plurality of condensing lenses and a Wollaston prism that separates light reflected or transmitted from a sample at a predetermined angle along orthogonal polarization directions. ) 322, and a camera 332 including an image sensor for detecting light along separated orthogonal polarization directions.

The polarization acquisition unit 300 converts the light separated according to the polarization direction by the first lens 311 and the Wollaston prism 322, which modulate the light passing through the sample 10 into parallel light, to the camera 332, respectively. It includes a plurality of condensing lenses including a second lens 312 condensing light to be sensitive to the image sensor. The Wollaston prism 322 separates the reflected light or transmitted light reflecting the optically anisotropic characteristics of the sample into two linearly polarized lights having vibration planes orthogonal to each other and spaced apart at a predetermined angle. The light separated by the Wollaston prism 322 is sensitized at the same time by varying the area within the image sensor of the camera 332, so that the light reflected or transmitted through the sample is classified into intensities according to components of orthogonal polarization directions and detected. .

In this example, the polarization acquisition unit 300 includes a third lens (not shown) disposed between the first lens 311 and the Wollaston prism 322 in addition to the first lens 311 and the second lens 312 . It further includes, and a field stop (not shown) positioned between the first lens 311 and the third lens. The placement of the field stop and the aperture size are adjusted so that the light separated by the Wollaston prism is dimmed into the image sensor and the separated light is prevented from overlapping within the image sensor.

Referring to FIG. 2C , in another example, the polarization acquisition unit 300 includes a plurality of condensing lenses and a polarization beam splitter (PBS) that reflects or transmits light reflected or transmitted from the specimen 10 according to orthogonal polarization directions. 323, a first camera 333 for detecting the first light reflected by the polarization beam splitter 323 and a second camera 334 for detecting the second light transmitted through the polarization beam splitter 323. .

The polarization acquisition unit 300 includes a first lens 311 that modulates the light passing through the sample 10 into parallel light and a second lens 312 that collects the parallel light so that the image sensor is exposed to the parallel light through a polarization beam splitter. It includes a plurality of condensing lenses including a. The polarization beam splitter 323 separates the reflected light or the transmitted light reflecting the optically anisotropic characteristics of the sample into two linearly polarized first and second lights having vibration planes orthogonal to each other. Since the light split by the polarization beam splitter 323 travels in directions orthogonal to each other, two cameras are required to detect the split light in this example. Light reflected or transmitted through the sample by each image sensor included in the first camera and the second camera is detected as an intensity according to a component of an orthogonal polarization direction.

The image generator 400 generates an image visualizing quantitative information about the optical anisotropy of the sample through the light detected by the polarization acquisition unit 300 . The polarization acquisition unit 300 converts the intensity of each light separated according to the polarization direction into an electrical signal and transmits it to the image generator 400, which is transmitted to the image generator 400 based on a pre-stored numerical model-based algorithm. The quantitative optical anisotropy property information of the sample is extracted through the operation of Here, the optical anisotropy of the sample includes an optical axis direction and a phase retardation value of the sample.

The image generator 400 may be a computing device capable of calculating and processing the electric signal transmitted from the polarization acquisition unit 300 .

The image generator 400 may use different numerical model-based algorithms according to the characteristics of the sample or the method of the polarization acquisition unit. For example, FPM (Fourier Ptychographic Microscopy), which restores large-area, high-resolution light absorption and optical phase images by irradiating light at various angles and superimposing acquired light information into Fourier space, and PTF (Phase Transfer Function) according to the irradiated light pattern There is an algorithm that can be applied to DPC (Differential Phase Contrast)-based QPI (Quantitative Phase Imaging) that restores a high-sensitivity optical phase image using .

In one embodiment, when the image generator 400 irradiates circularly polarized light to a sample and separates light reflected or transmitted through the sample according to an orthogonal polarization direction to detect each light intensity of the separated light, That is, in the case of the embodiments shown in FIGS. 2B and 2C , the optical anisotropy information of the sample, that is, the optical axis direction and the phase delay value of the sample may be quantitatively extracted using the following equations.

The electric field of each separated light obtained by irradiating a sample with circularly polarized light and separating the light reflected or transmitted through the sample according to the orthogonal polarization direction is as shown in Equation 1.

Equation 1

,

,

, 및

는 직교하는 편광 방향에 따라 분리된 광 각각의 전기장의 진폭 및 위상이고,

는 광학적 이방성 시료를 모델링한 Jones 매트릭스이다. here,

,

,

, and

is the amplitude and phase of the electric field of each light separated along the orthogonal polarization direction,

is the Jones matrix modeling the optically anisotropic sample.

In order to extract the optical axis direction and phase retardation, which are the optical anisotropy of the sample, Equation 1 is converted to the Stokes parameter, that is, Equation 2.

Equation 2

) 및 위상 지연(

)의 공간적 분포는 수학식 3과 같이 추출된다. Optical axis direction of the sample (

) and phase delay (

) The spatial distribution of Equation 3 is extracted.

Equation 3

Although the extraction of quantitative optical anisotropy characteristics of the sample using the Jones matrix has been described above, dichroism occurs when acquiring light intensity images according to more polarization directions and calculating them using the Mueller matrix Additional optical anisotropic properties can be obtained as

In one embodiment, the image generator 400 irradiates the sample with circularly polarized light and separates the light reflected or transmitted through the sample according to polarization directions of 0 degree, 45 degree, 90 degree and 135 degree polarization axes. In the case of detecting each light intensity of the detected light, that is, in the case of the embodiment shown in FIG. 2A, the optical anisotropy information of the sample, that is, the optical axis direction and phase delay value of the sample can be quantitatively extracted using the following equations. can

Equation 4

는 X 편광 축의 방향으로 분리된 광세기 영상이고,

는 시료의 광축 방향이고,

는 위상 지연이다. 시료의 광축 방향() 및 위상 지연(

)은 수학식 5과 같이 얻을 수 있다. in Equation 4

Is the optical intensity image separated in the direction of the X polarization axis,

is the optical axis direction of the sample,

is the phase delay. Optical axis direction of the sample ( ) and phase delay (

) can be obtained as in Equation 5.

Equation 5

3 illustrates visualization of quantitative information of optical anisotropy of a sample according to an embodiment of the present invention.

Referring to FIG. 3 , (a) to (c) of FIG. 3 are images obtained by averaging intensities of light separated according to orthogonal polarization directions of light reflected or transmitted through a transparent sample. 3 (d) to (f) provide the optical anisotropy, that is, the optical axis direction and phase retardation value of the sample extracted by the microscope system according to an embodiment of the present invention in the form of a two-dimensional map. Here, the optical axis direction is shown in color and the phase retardation value in dark. Accordingly, it can be confirmed that the characteristics of the sample having optical anisotropy can be quantified and visualized by the microscope system for quantifying the optical anisotropy of the sample according to the present invention.

3 (a) to (d) use UAD (uric acid dihydrate) as a sample, FIG. 3 (b) to (e) use UA (anhydrous uric acid) as a sample, and FIG. 3 (c) to (f) take a mixture of UAD and UA as a sample.

Claims (7)

In a microscope system that provides quantitative information on the optical anisotropy of a sample,
a light source unit that emits light;
a polarization modulator for modulating a polarization form of light emitted from the light source unit;
a polarization acquiring unit configured to detect the light modulated by the polarization modulating unit by irradiating the sample and classifying the light reflected or transmitted from the sample according to a polarization direction; and
And an image generator for generating an image visualizing quantitative information on the optical anisotropy of the sample through the light detected by the polarization acquisition unit,
The optical anisotropy of the sample includes an optical axis direction and a phase retardation value of the sample,
The optical axis direction and phase retardation value of the sample is calculated through the following equation, the microscope system for quantifying the optical anisotropy of the sample.

(From here,

,
I _x : optical intensity image separated in the direction of the X polarization axis, θ: optical axis direction, δ: phase retardation)
delete The method of claim 1,
A microscope system for quantifying the optical anisotropy of a sample, wherein the light source unit includes an LED array or a laser.
The method of claim 1,
The polarization acquisition unit,
A microscope system for quantifying optical anisotropy of a sample, comprising a plurality of condensing lenses and a polarization camera configured to classify light reflected or transmitted from the sample according to a polarization direction and detect respective intensities of the separated light.
The method of claim 1,
The polarization acquisition unit,
a plurality of condensing lenses;
A Wollaston prism that separates the light reflected or transmitted from the sample at a predetermined angle according to the orthogonal polarization direction, and
A microscope system for quantifying optical anisotropy of a sample, comprising a camera including an image sensor for detecting light along the separated orthogonal polarization direction.
The method of claim 5,
The polarization acquisition unit,
A microscope system for quantifying optical anisotropy of a sample, further comprising a field stop positioned between the plurality of condensing lenses.
The method of claim 1,
The polarization acquisition unit,
a plurality of condensing lenses;
A polarization beam splitter for reflecting or transmitting light reflected or transmitted from the sample according to orthogonal polarization directions;
A first camera for detecting the first light reflected by the polarization beam splitter, and
A microscope system for quantifying optical anisotropy of a sample, comprising a second camera for detecting second light transmitted through the polarization beam splitter.

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