WO2020235883A1 - Système optique utilisant un modulateur spatial de lumière et procédé de mesure de propriétés physiques l'utilisant - Google Patents

Système optique utilisant un modulateur spatial de lumière et procédé de mesure de propriétés physiques l'utilisant Download PDF

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WO2020235883A1
WO2020235883A1 PCT/KR2020/006441 KR2020006441W WO2020235883A1 WO 2020235883 A1 WO2020235883 A1 WO 2020235883A1 KR 2020006441 W KR2020006441 W KR 2020006441W WO 2020235883 A1 WO2020235883 A1 WO 2020235883A1
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light
sample
optical system
spatial light
light modulator
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PCT/KR2020/006441
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English (en)
Korean (ko)
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박희재
김진용
김민규
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서울대학교산학협력단
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G01N21/211—Ellipsometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/02—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the intensity of light
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/08—Mirrors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/06—Illumination; Optics
    • G01N2201/063—Illuminating optical parts
    • G01N2201/0638—Refractive parts
    • G01N2201/0639—Sphere lens

Definitions

  • the present invention relates to an optical system using a spatial light modulator and to measurement of physical properties of a sample using the same.
  • Ellipsometry is a method of measuring the physical properties of a sample by using the change in polarization characteristics of light.
  • the measuring equipment using the ellipsometry method is called an ellipsometer. After the incident light is polarized into a desired shape and incident on the sample, the polarization state of light reflected from the sample (reflective ellipsometer) or transmitted (transmitted ellipsometer) is measured. It measures physical properties such as complex refractive index, dielectric function, electrical conductivity, and crystal state such as lattice structure.
  • a reflective ellipsometer can be used to measure the thickness of a multilayer thin film. Compared to other thin film thickness measurement methods, it is a non-contact-non-destructive method, is applicable to transparent materials or dielectric thin films, and has excellent resolution. In the spotlight, it is widely used in the display and semiconductor industries.
  • the Ellipsometric Microscope introduced by KR Neumaier in 2000, introduced a vertical microscope structure to enable high-magnification imaging, but the optical component was physically (manually or at least) to adjust the polarization state. There was a limit in that it had to be adjusted mechanically.
  • a position of a polarizer must be adjusted or a mirror that moves finely within the microscope must be arranged, and the physical movement of such an optical element itself causes vibration to cause noise. This is problematic in that there is a risk of breaking the optical alignment between optical elements, which are kept extremely sensitive, as well as to generate ).
  • the operator After each measurement, the operator has to spend a considerable amount of time to remove noise and restore optical alignment after each measurement, and it is difficult to secure reliability for each measurement. For this reason, elliptical polarization microscopes are not widely used until now.
  • An object of the present invention is to provide an optical system using a spatial light modulator and a method for measuring physical properties using the same.
  • the above object can be achieved by a method of measuring an optical system and physical properties including the features of the claims to be described later.
  • the optical system using the spatial light modulator according to the present invention When the optical system using the spatial light modulator according to the present invention is used, it is possible to measure the physical properties of a sample without driving a motor, and since the possibility of interference of noise due to mechanical manipulation is reduced, more accurate and fast measurement is possible.
  • the advantages of the conventional elliptical polarization microscope that is, the advantages of high lateral resolution and high resolution imaging are maintained in the optical system according to the present invention.
  • FIG. 1 is a conceptual diagram showing the basic structure of an elliptic system according to the prior art.
  • FIG. 2 is a conceptual diagram illustrating a general structure of an optical system, that is, an arrangement of optical elements and an optical path according to an embodiment of the present invention.
  • FIG. 3 is a conceptual diagram showing the structure of an optical system when a digital light projector or an LCoS microdisplay is used as a spatial light modulator in the optical system according to an embodiment of the present invention.
  • FIG. 4 is a conceptual diagram showing a structure of an optical system when a transmission type liquid crystal display is used as a spatial light modulator in the optical system according to an embodiment of the present invention.
  • 5 and 6 are conceptual diagrams illustrating a digital light projector that is an example of a spatial light modulator of an optical system and a digital micromirror device that is an element constituting the digital light projector according to an embodiment of the present invention.
  • FIG. 7 is a conceptual diagram showing a single device of an LCoS type microdisplay that is an example of a spatial light modulator of an optical system according to an embodiment of the present invention.
  • FIG. 8 is a conceptual diagram showing a single element of a transmission type liquid crystal display that is an example of a spatial light modulator of an optical system according to an embodiment of the present invention.
  • FIG. 9 is a conceptual diagram showing that the color and polarization state of the liquid crystal transmits differently according to the voltage applied to the transmissive LC cell, which is a single element of a transmissive liquid crystal display, which is an example of a spatial light modulator of an optical system according to an embodiment of the present invention. .
  • FIGS. 10 and 11 are conceptual diagrams for explaining characteristics of a rear focal plane in an optical system according to an embodiment of the present invention.
  • 12 and 13 are conceptual diagrams for explaining a relationship between incident light and reflected light in an optical system of an optical system according to an embodiment of the present invention.
  • 14 to 17 are conceptual diagrams for explaining a method of measuring physical properties by adjusting a position to be illuminated on a rear focal plane by a spatial light modulator in an optical system according to an exemplary embodiment of the present invention.
  • FIG. 1 is a conceptual diagram showing the basic structure of an elliptic system according to the prior art.
  • the light source on the left serves to generate and emit incident light, and various light sources having an intensity and wavelength of an LED, laser or other known type may be used.
  • the emitted incident light passes through a polarization state generator (PSG) to have a desired polarization state.
  • the polarization state generator may consist of one or more various optical elements, such as a polarizer, a compensator, also called a retarder, and a phase modulator. These optical elements and their role are well known to those skilled in the art. Like electric devices, it is possible to adjust the incident light to have a desired polarization state (linear polarization, circular polarization, elliptical polarization) by combining these optical devices.
  • the incident light passing through the polarization state generator is incident on the surface of the sample with a certain angle ( ⁇ i ).
  • Incident light is divided into transmissive light that passes through the sample from the sample surface and reflected light that is reflected from the sample.
  • the plane perpendicular to the sample determined by incident light and reflected light is called a plane of incidence.
  • Reflected light is not only the light directly reflected from the sample surface, but also the light transmitted through the upper sample surface after the above-described transmitted light travels inside the sample and is reflected from the surface with another medium disposed at the bottom of the sample, or It is reflected downwards, proceeds to the bottom, and is reflected again from the surface of the other medium at the bottom to form an overlapping form of light transmitted through the upper sample surface.
  • a polarized state analyzer is placed on the path of the reflected light to analyze the state, for example, by extracting only light of a specific polarization component. By measuring the intensity or the like, the state of the reflected light can be determined.
  • a photodetector at the end of the path of reflected light measures the intensity of light and converts it into an electrical signal.
  • the photodetector may be a photodiode, a CCD, etc., and generally cannot measure the component or phase of light, but only measure the intensity, but by adjusting the polarization state analyzer, for example, rotating the polarizer included in the polarization state analyzer. By doing so, it is possible to calculate the polarization state of light by allowing only light of a specific polarization state to pass through and sensing the intensity of light according to each polarization state.
  • the polarization state of light may be calculated by adjusting the incident light incident on the sample by rotating the polarizer included in the polarization state generator instead of the polarization state analyzer.
  • the state vector of light has the form of a 1 ⁇ 2 matrix.
  • the first row component of the matrix is p-polarized, that is, a transverse magnetic mode in which the direction of vibration of the magnetic field is perpendicular to the incident plane.
  • the second row component means s polarization, that is, a transverse electric mode (TE mode) in which the vibration direction of the electric field is perpendicular to the incident surface.
  • the p-polarized and s-polarized components are perpendicular to each other.
  • p polarized light is
  • s polarized light is
  • the given light can be completely represented by the intensity and phase of this p-polarized and s-polarized light.
  • optical elements and specimens through which light passes on the optical path can be represented as a 2 ⁇ 2 matrix, and become an operator (2 ⁇ 2 matrix) acting on a given vector of light (1 ⁇ 2 matrix).
  • the polarizer The compensator is And the sample is (assuming isotropic material) Becomes.
  • the state of light that is deformed while passing through an optical element or sample is compared to the action of transforming the light vector by an operator.
  • the polarization state generator or the polarization state analyzer is a combination of optical elements represented by the above 2 ⁇ 2 matrix, the whole may be expressed as a single 2 ⁇ 2 matrix by obtaining the product of the 2 ⁇ 2 matrix corresponding to the elements included therein. have.
  • the result of light coming out of the light source and passing through the polarization state generator, the sample, and the polarization state analyzer can be expressed as follows.
  • the light source (the vector on the far right) has only p polarization for convenience of discussion.
  • the light source when light comes out of the light source, it can have both p-polarized and s-polarized components, but by placing a polarizing plate at the introduction part of the polarization state generator, it can be converted into a state vector having only a specific component as above.
  • the vector on the far right is the light from the light source
  • the matrix on the left is the transformation by the polarization state generator (PSG)
  • the matrix on the left is the sample
  • the two matrices on the left are the polarization state analyzer (PSA).
  • the leftmost matrix means that only light whose polarization direction matches the angle (A) of the polarization state analyzer is passed based on the incident surface of the polarization state analyzer.
  • the polarization state generator and the polarization state analyzer are composed of only a polarizer, and have a function of leaving only a linear polarization component corresponding to the axial angle of the polarizer, and P and A are variables representing the axial angle.
  • r p and r s contain information on various properties of a material, it is the goal of ellipsometry to find the values of r p and r s by adjusting the settings of the light source, polarization state generator, and polarization state analyzer.
  • the degree of matching may be based on, for example, a variance of an error between a numerical value according to a predicted value and an actual measured value, and those skilled in the art may set a standard for measuring the degree of matching in various ways.
  • FIG. 2 is a conceptual diagram illustrating a general structure of an optical system, that is, an arrangement of optical elements and an optical path according to an embodiment of the present invention.
  • a light source 110 and a spatial light modulator 120 are shown on the left side of the optical system 100.
  • the light source 110 and the spatial light modulator 120 can be combined in various forms, in FIG. 2 dealing with a general structure of an optical system, a diagram is replaced without showing an optical path.
  • FIGS. 3 and 4 dealing with a specific configuration of an optical system according to the type of spatial light modulator, the light source 110 and the spatial light modulator 120 will be shown in a separate form.
  • the light source 110 is a part that generates light that is a source of incident light of the optical system, and may generate and use light of a single wavelength or light having a spectrum of a certain range.
  • the spatial light modulator 120 is a device that modulates light in space to create a desired image. While the polarization state generator or the polarization state analyzer of FIG. 1 receives incident light and filters out only components of a specific polarization state or delays the phase by a predetermined amount, the spatial light modulator is a beam of a given light. With respect to the cross section, a specific portion passes light and a specific portion does not pass light, so that the input light is output in a state having a shape desired by the user.
  • a portion that becomes the smallest unit that allows or does not pass light is defined as a pixel, and the state in which each pixel passes light is on, and the state in which light does not pass is off. I will call it.
  • the spatial light modulator 120 may look like a surface light source or a display in which pixels are arranged in a certain array.
  • the pixels may have an arbitrary arrangement, for example, in the form of a two-dimensional rectangular array.
  • each pixel may correspond to a coordinate of a Cartesian coordinate system.
  • the pixels may be in the form of a two-dimensional circular array.
  • each pixel may correspond to the coordinates of the pole coordinate system.
  • the present invention is not limited to a specific arrangement method of each pixel of a spatial light modulator or a method of turning on/off the pixel, that is, a specific driving method.
  • the spatial light modulator 120 is not limited to a specific implementation method, and may be understood as referring to a device that creates and outputs an image desired by a user for input light.
  • the user can control the on/off of each pixel using a control module (not shown in the drawing) connected to the spatial light coordinate device, and accordingly, can draw a desired image as specified in advance.
  • a control module not shown in the drawing
  • An exemplary type of spatial light modulator 120 will be discussed in detail later.
  • the light modulated by the spatial light modulator 120 passes through the optional relay lenses 130a, 130b, which prevents the beam diameter on the optical path from becoming too wide and keeps the beam constant. It is intended to be limited within range.
  • a polarizer 130c and a compensator 130d are illustrated as examples. However, these are exemplary devices, and a person skilled in the art may construct other types of polarization state generators using other devices.
  • the light passing through the polarization state generator has a polarization state of a desired value, and in this state, the path is bent by the beam splitter 140 and goes to the bottom of the drawing.
  • the path of light passing through the objective lens is bent by the action of the lens, and is incident on the special point of the specimen 300. This completes the incident path.
  • the reflected light having a change in the polarization state by the sample at the point of incidence is emitted from the sample and passes through the objective lens 150 again, and then passes through the rear focal plane 200 and the beam splitter 140 and goes to the top of the drawing. And passes through elements corresponding to the polarization state analyzer.
  • a polarizer 160 is shown as an example.
  • the reflected light passing through the polarization state analyzer passes through the eyepiece 170 and reaches the light detector 180.
  • the light reaching the photodetector is converted into an electrical signal, and the optical device, for example, the polarizer 130c, is rotated to measure the change in intensity of the photodetector accordingly to analyze the physical properties of the above-described sample.
  • the paths of the incident light and the reflected light and the configuration of the above-described elements are exemplary, and those skilled in the art can design an optical system suitable for the purpose by varying the combination of optical elements while maintaining the essential configuration of the present invention. It is included.
  • FIG. 3 is an optical system in the case of using a digital light projector (DLP) or a liquid crystal on silicon (LCoS) microdisplay as the spatial light modulator 120 in the optical system according to an embodiment of the present invention. It is a conceptual diagram showing the structure of. The detailed structure and operation method of the digital light projector will be described in detail in FIGS. 5 and 6 and the related description, and the specific structure and operation method of the LCoS type microdisplay will be described in detail in FIG. 7 and the related description.
  • DLP digital light projector
  • LCDoS liquid crystal on silicon
  • the light source 110 is not arranged coaxially or in a straight line with the spatial light modulator 120 in the optical path.
  • the light source 110 is incident on the spatial light modulator 120 at an oblique angle and then reflected.
  • the digital light projector and the LCoS microdisplay are exemplified as the case where the light source 110 is not arranged coaxially or in a straight line with the spatial light modulator 120, but other spatial light modulators 120 are also similar. Alternatively, it may be used in other ways, and all such modifications are included in the scope of the present invention.
  • FIG. 4 is a conceptual diagram showing the structure of an optical system when a transmissive liquid crystal display is used as the spatial light modulator 120 in the optical system according to an embodiment of the present invention.
  • the specific structure and operation of the transmissive liquid crystal display will be dealt with in detail in Fig. 8 and the related description.
  • the light source 110 is disposed in front of the spatial light modulator 120 in a coaxial or straight line with the spatial light modulator 120 in an optical path. Accordingly, the light emitted from the light source 110 passes through the spatial light modulator 120.
  • the light source 110 is arranged coaxially or in a straight line with the spatial light modulator 120, and only a transmissive liquid crystal display is given as an example, but the spatial light modulator 120 of another method may be used in a similar manner or in a different manner. , All such modifications are included in the scope of the present invention.
  • FIGS. 2 to 4 only a specific combination of the light source 110 and the spatial light modulator 120 is shown in FIGS. 2 to 4, but the present invention is not limited to a specific combination method of both devices.
  • the present invention can be implemented for any spatial light modulator 120.
  • a structure and operation method of an exemplary spatial light modulator 120 usable in the present invention will be described.
  • FIG. 5 and 6 illustrate a digital optical projector that is an example of a spatial light modulator 120 of an optical system according to an embodiment of the present invention, and a digital micromirror device (DMD) that is an element constituting the digital light projector. It is a conceptual diagram.
  • the digital optical projector shown in FIG. 5 is a digital micromirror device arranged in an array, and the digital micromirror device is a micro-sized mirror made of a micro electro-mechanical system (MEMS). . That is, in a digital light projector, each digital micromirror device serves as a pixel.
  • the digital micromirror device constitutes an array of 1024 columns and 768 rows, but the number of columns and rows constituting the array is exemplary, and may have any other number of columns and rows.
  • the digital light projector according to an embodiment of the present invention may be implemented through an arbitrary device, for example, a digital light projector manufactured by Texas Instruments.
  • two digital micromirror devices 120 are shown. There is an electrode under the digital micromirror device 120 to receive an electrical signal from the outside, and a reflector is provided at the top to reflect light. When an electric signal is applied to the lower electrode, the hinge supporting the upper reflector is bent, and the angle of the reflector is adjusted.
  • Light 121 from the outside is reflected by the projection lens 122 and emitted to the outside according to the angle of the reflector 120 of the digital micrometer device, or is reflected by the light absorption plate 123 and is absorbed without being emitted to the outside. do.
  • the digital micromirror device shown on the right reflects the light 121 to the projection lens 122
  • the digital micromirror device shown on the left reflects the light 121 to the light absorbing plate 123.
  • the pixels corresponding to the digital micromirror device shown on the right appear to be in the on state to emit light
  • the pixels corresponding to the digital micromirror device shown on the left do not emit light. It appears to be in the off state.
  • an electric signal using an electric circuit connected to the lower electrode of each digital micromirror device, it is possible to turn on/off the light of the individual digital micromirror device.
  • the hinge angle when the signal is on, the hinge angle is adjusted to direct light to the projection lens 122, and when the signal is off, the hinge angle can be adjusted so that the light is reflected to the light absorbing plate 123. have. Turning on and off of the electric signal and light may be made to correspond to the opposite, and all such variations are within the scope of the present invention.
  • each pixel of the digital light projector can be turned on/off by a signal from the outside using, for example, a computer, so that a light source having a desired shape, such as a circle, a square, or even a text or picture, can be used. It can be generated, and by controlling this signal at a constant refresh rate based on predetermined data, a light source corresponding to a moving picture can be created.
  • the LCoS type microdisplay is similar to the digital optical projector shown in FIG. 5 in that individual elements are arranged in an array, but the individual elements are not a digital micromirror device but an LCoS element. That is, in the LCoS microdisplay, the LCoS device serves as a pixel.
  • FIG. 7 is a conceptual diagram showing a single device (hereinafter referred to as an “LCoS device”) of an LCoS type microdisplay that is an example of a spatial light modulator of an optical system according to an embodiment of the present invention.
  • an LCoS device a single device of an LCoS type microdisplay that is an example of a spatial light modulator of an optical system according to an embodiment of the present invention.
  • the LCoS device shown in FIG. 7 is substantially similar to a single device of a known liquid crystal display (LCD) in terms of its structure, but differs somewhat in that it is formed on a silicon substrate instead of a glass substrate.
  • a CMOS element 127 is disposed on the silicon substrate, a reflective film, a liquid crystal 126, an alignment film, a transparent electrode 125, and a glass plate to protect the liquid crystal from physical damage from the outside are disposed on the silicon substrate.
  • the polarizing plate 124 is disposed obliquely in consideration of the angle of incident light from.
  • FIG. 8 is a conceptual diagram showing a single element (hereinafter referred to as a'transmissive LC cell') of a transmissive liquid crystal display that is an example of a spatial light modulator of an optical system according to an embodiment of the present invention.
  • the transmissive LC cell shown in FIG. 8 has a structure similar to a cell of a liquid crystal display known in the art, and is presented in a simplified form by omitting some structures such as transparent electrodes for description. Compared with the LCoS device of FIG. 7, it can be recognized that both sides are made of glass.
  • a liquid crystal 129 is disposed between both glass plates 128 (more generally, a material capable of transmitting light other than glass) And a voltage source V(t) is connected between the liquid crystals.
  • the liquid crystal 129 when no voltage is applied to the transmissive LC cell, the liquid crystal 129 is arranged in a disordered direction, whereas when a voltage is applied in Fig. 8(b), the liquid crystal 129 is in the same direction.
  • the liquid crystal 129 may or may not be aligned depending on whether a voltage is applied, and may or may not transmit light depending on the alignment state. Therefore, each transmissive LC cell can be turned on/off by applying or not applying a voltage to each transmissive LC cell.
  • the spatial light modulator 120 has been described as being a separate element separated from the polarization state generator.
  • the polarization state generator 120 is depicted as a separate device separated from the devices 130a to 130d corresponding to the polarization state generator.
  • the spatial light modulator 120 may perform part or all of the function of changing the polarization state by itself according to its structure.
  • polarization state generator 120 may combine an element that plays the role of such a polarization state generator with a single element of the polarization state generator 120, or combines an element that plays the role of a polarization state generator integrally with the entire device of the polarization state generator 120. It can be envisioned, and all of these configurations are included in the scope of the present invention.
  • FIG. 9 is a conceptual diagram showing that the color and polarization state of the liquid crystal transmits differently according to the voltage applied to the transmissive LC cell, which is a single element of a transmissive liquid crystal display, which is an example of a spatial light modulator of an optical system according to an embodiment of the present invention. .
  • polarizing plates are added to the left and right (arrows indicate polarization directions).
  • the light incident from the left passes through the left polarizing plate, only the polarized light passes through, and the polarization state changes through the liquid crystal, and only the light of the polarization direction component determined by the right polarizing plate passes through the right polarizing plate and leaves the device. do.
  • Light incident from the left passes through the left polarizing plate and only the light of the polarized component passes. This light is incident on the liquid crystal, but because the liquid crystal is not aligned, it passes through the liquid crystal without changing the polarization direction.
  • the light passing through the liquid crystal reaches the right polarizing plate, and the right polarizing plate has a polarization direction perpendicular to the left polarizing plate. For example, when the polarization direction of the left polarizing plate is 45 degrees, the polarization direction of the right polarizing plate is 135 degrees.
  • the light reaching the right polarizing plate has a polarization direction perpendicular to the right polarizing plate, it cannot pass through the right polarizing plate. As a result, when viewed from the outside, this pixel does not emit light, so it appears black, and the pixel is turned off.
  • FIG. 9B to 9E illustrate a state in which a voltage is applied to the liquid crystal and the liquid crystal is aligned as the applied voltage increases.
  • the strength of the applied voltage may have a continuous value, and the liquid crystal may have not only completely aligned or completely aligned states, but also continuous intermediate states.
  • the degree to which the polarization state of the light passing through the left polarizing plate and incident on the liquid crystal is changed by the liquid crystal increases.
  • Fig. 9(e) in which the liquid crystals are completely aligned, the polarization direction rotates 90 degrees while the light incident from the left passes through the liquid crystal. As a result, the polarization direction coincides with the polarization direction of the right polarizing plate.
  • the liquid crystal is phase modulated.
  • the spatial light modulator 120 has an element that performs spatial light modulation in a different way instead of a liquid crystal, and a phase modulator exists at the beginning of the polarization state generator separated from the spatial light modulator 120. Will have. That is, due to the liquid crystal of the spatial light modulator 120, the spatial light modulator 120 plays a part of the polarization state generator.
  • the spatial light modulator 120 performs some or all of the functions of the polarization state generator. It should be understood as what can be done.
  • FIGS. 10 and 11 are conceptual diagrams for explaining characteristics of a rear focal plane 200 in an optical system according to an embodiment of the present invention.
  • FIG. 10 is for explaining that light incident on the rear focal plane 200 at the same point is incident on the sample 300 at the same angle.
  • the rear focal plane 200 of FIG. 2 the objective lens 150 (indicated by being simplified with lines for convenience of explanation), and the sample 300 are shown.
  • Three light paths are shown at points A and B on the optical path, respectively.
  • the solid lines from A and B indicate the left point of the rear focal plane 200, and the broken line indicates the center point of the rear focal plane 200.
  • the double-dashed line is passing through the right point of the rear focal plane 200.
  • the light rays (solid line) passing through the left side of the rear focal plane 200 at points A and B are incident at an angle of ⁇ from the left when entering the sample 300 through the objective lens 150, and the rear focus
  • the light ray (dashed line) passing through the center of the plane 200 is vertically incident on the sample 300 through the objective lens 150, and the light ray (double-dotted line) passing through the right side of the rear focal plane 200 is the objective.
  • the incident is incident at an angle of ⁇ from the right.
  • the light rays passing through the left side of the rear focal plane 200 (solid line) and the light rays passing through the right side of the rear focal plane 200 (dashed-dotted line) are from the central axis of the objective lens 150 at the rear focal plane 200. It passes through a point separated by an equidistant distance, and as a result, it can be seen that the incident angle to the sample 300 is the same.
  • the light rays passing through the same point of the rear focal plane 200 are incident on the specimen 300 at the same angle, and this angle is determined according to the distance from the central axis of the objective lens 150.
  • FIG. 11 is for explaining that even light from another point on the specimen 300 meets at a point on the rear focal plane 200. This principle can be seen by reversing the path of the light beam in FIG. 10.
  • FIG. 11 a sample 300, an objective lens 150 (simplified and indicated by lines for convenience of explanation), and a rear focal plane 200 are shown.
  • the light from different points A and B on the sample 300 rises to the left at the same angle (solid line), rises vertically (dashed line), or rises to the right (double-dotted line), and the starting point from sample 300 Despite this difference, since the angles were the same, they meet at the same points on the rear focal plane 200, that is, a, b, and c, respectively.
  • 12 and 13 are conceptual diagrams for explaining a relationship between incident light and reflected light in an optical system of an optical system according to an embodiment of the present invention.
  • the rear focal plane 200, the objective lens 150, and the sample 300 are shown.
  • the sample 300 is located at a point separated by the focal length f of the objective lens 150.
  • a light ray (solid line, broken line) passing through the rear focal plane 200 passes through the objective lens 150 and enters the sample 300. You can see the same point.
  • the light rays passing through the same point of the rear focal plane 200 are incident on the sample 300 at the same angle, and when the radial distance from the central axis of the objective lens 150 is the same, that is, the broken lines on the left and right sides in FIG. , Or in the case of the left and right solid lines, the value of the incident angle is the same.
  • FIG. 13 is a conceptual diagram illustrating a correlation between incident light incident on each point on the rear focal plane 200 in a polar coordinate system centered on the central axis of the objective lens 150 and reflected light accordingly.
  • Incident light by the optical system according to an embodiment of the present invention all have the same polarization before incidence of the objective lens 150 and the sample 300, for example, polarization in the x-axis direction in this example (solid line).
  • each incident light is an angle in the polar coordinate system centered on the central axis of the objective lens 150 ( ), the direction of the incident surface is different (dashed lines between 1 and 1', 2 and 2', 3 and 3', and 4 and 4', respectively), and the components of p polarization and s polarization As a result, the polarization component of the reflected light is also different.
  • the incident light 1 passes through the objective lens 150 and enters the specimen 300 in a path curved in the -x-axis direction, and as a result, the incident surface (broken line between 1 and 1') becomes parallel to the polarization direction.
  • the polarization of the reflected light comes out with the same polarization direction as the polarization direction of the incident light (1').
  • the incident light 3 passes through the objective lens 150 and enters the specimen 300 in a path curved in the -y axis direction, and as a result, the incident surface (broken line between 3 and 3') becomes completely perpendicular to the polarization direction. , it means that there is only s polarization, and the reflected light comes out without mixing the p polarization component (regardless of the phase change) (3').
  • the position on the rear focal plane 200 is the radius (r) and the angle (r) on the polar coordinate system with the central axis of the objective lens 150 as the origin.
  • angle ( ) it is possible to adjust the components of the p-polarized light and the s-polarized light incident on the sample 300, and by adjusting the radius r, the angle of incidence ( ⁇ ) incident on the sample 300 can be adjusted.
  • 14 to 17 are conceptual diagrams for explaining a method of measuring physical properties by adjusting a position to be illuminated on the rear focal plane 200 by the spatial light modulator 120 in an optical system according to an embodiment of the present invention. .
  • the coordinate plane of FIG. 14 represents a position on the rear focal plane 200.
  • the spatial light modulator 120 it is possible to enter the incident light only at a specific point on the rear focal plane 200 by using the spatial light modulator 120.
  • the size of a specific point may vary depending on the number of pixels and the area per pixel of the spatial light modulator 120, and the spatial light modulator 120 in which a larger number of pixels are integrated, that is, a higher resolution, is narrower.
  • the incident light can pass only at more precise points.
  • the radius is fixed to r 1 on the polar coordinate system of the rear focal plane 200, and the angle ( The incident light is irradiated while varying) from 0 to 360 degrees, and the reflected light accordingly is measured (path 1).
  • the incident angle of the incident light irradiated to the sample 300 is fixed accordingly, and a value at which the polarization component changes as the angle changes is incident on the sample 300.
  • the method of adjusting the angle can be measured continuously from 0 to 360 degrees, or discretely measured for specific angles such as 0, 45, and 90 degrees, and the measurement direction is also the direction in which the angle increases (counterclockwise ) (Fig. 14) or in a decreasing direction (clockwise) (Fig. 15).
  • the interval between the change value and the measured angle may vary depending on the resolution of the spatial light modulator 120.
  • the change value may be a value in which the radius increases or decreases, and the change value itself may vary according to the radius.
  • the radius can increase gradually, such as 1 -> 2 -> 3 -> 4, or it can decrease to 4 -> 3 -> 2 -> 1, and change like 10 -> 15 -> 18 -> 20 However, the increase may decrease or vice versa.
  • the measurement of the reflected light as described above may be exemplarily implemented through the following sequence: For a polar coordinate system whose origin is the lens center axis in the back focal plane of the objective lens, a radius value is set.
  • the primary variable and the angular (radian) value are set as secondary variables, the secondary variable is changed from 0 to 360 degrees, and the primary variable is changed at a predetermined value for each cycle of change of the secondary variable.
  • the angle ( ) Is fixed and the radius (r) is changed.
  • the measurement of the reflected light as described above can be implemented through the following sequence: For a polar coordinate system with the lens center axis as the origin at the rear focal plane of the objective lens, the angle value is the primary variable and the radius value is the secondary variable. And changing a secondary variable by a change value determined according to the resolution of the spatial light modulator at a predetermined value, and changing the primary variable from 0 degrees to 360 degrees for each change cycle of each secondary variable.
  • a measurement can be performed using another sequence. I can.
  • each pixel is arranged in a row-column order, that is, A sequence can be configured in a continuous manner, such as from column 1 to the last column of row 1, column 1 to last column of row 2, ... (FIG. 17).
  • the last column and the last row may be determined according to the horizontal and vertical resolution of the array of pixels constituting the spatial light modulator 120.
  • the direction of sweeping each row-column may be different.
  • a sequence may be formed in a form that continues from the last row to the first row and/or from the last column to the first column.
  • the measurement of reflected light according to the above method can be implemented through the following sequence: For a Cartesian coordinate system whose origin is the central axis of the objective lens at the rear focal plane of the objective lens, the row is the primary variable, With a column as a secondary variable, a secondary variable is changed between the number of columns of the array of one or more pixels in column 1, and the primary variable is an array of the one or more pixels in row 1 for each change cycle of the secondary variable A sequence that changes between the number of rows of.
  • This alternative sequence may be, for example, a sequence from the top left to the bottom right while drawing a horizontal line, similar to the scanning of an electron gun of a CRT TV, and the same sequence as the control signal of each pixel of the spatial light modulator 120 is input. Because it can, there is an advantage that the coding of the sequence is simpler. However, compared to the sequence according to the polar coordinate system, the order of each measurement value, the incident angle, and the polarization state are mixed without being correlated. Therefore, after the measurement, it is necessary to rearrange the data according to the incident angle and the polarization state.
  • the optical system in order to change the polarization component of incident light, at least one optical element on the polarization state generator or the polarization state analyzer has to be manually or mechanically moved. Compared with the conventional technology, it has an advantage that the optical system can be operated without generating physical vibration. Although there may be a mechanical movement of the pixels included in the spatial light modulator 120, the vibration caused by this is substantially small to a level that is difficult to detect. Therefore, noise due to vibration is reduced and the reliability of the measured value is improved.
  • Another advantage of the method for measuring physical properties by an optical system according to an embodiment of the present invention is that the on/off of a specific pixel in the spatial light modulator 120 described above is performed in a virtually automated sequence through an electronic device such as a computer connected to the outside. Because of this, faster and more convenient measurements are possible compared to previous manual or mechanical operation. That is, the movement of the position of light on the above-described rear focal plane 200 can be automated by a computer simply by coding a sequence specifying a pixel to be turned on by the spatial light modulator 120, and this sequence is preprogrammed. You can also use the old one. Therefore, the need for direct manipulation by the user is significantly reduced.
  • the optical system using the spatial light modulator according to the present invention When the optical system using the spatial light modulator according to the present invention is used, it is possible to measure the physical properties of a sample without driving a motor, and since the possibility of interference of noise due to mechanical manipulation is reduced, more accurate and fast measurement is possible.
  • the advantages of the conventional elliptical polarization microscope that is, the advantages of high lateral resolution and high resolution imaging are maintained in the optical system according to the present invention.

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Abstract

L'invention concerne un système optique pour mesurer les propriétés physiques d'un échantillon, comprenant : un modulateur spatial de lumière pour moduler, en une lumière de la forme prédéfinie d'une première image, une section transversale de faisceau de lumière reçue en provenance d'une source de lumière ; un générateur d'état de polarisation, qui reçoit la lumière modulée par le modulateur spatial de lumière de façon à faire passer celle-ci dans un premier état de polarisation prédéfini ; un objectif qui reçoit la lumière passée dans le premier état de polarisation de façon à amener celle-ci à être incidente sur l'échantillon, et qui reçoit la lumière réfléchie par l'échantillon ; un analyseur d'état de polarisation, qui reçoit la lumière réfléchie par l'échantillon pour être reçue par l'objectif et qui traverse ainsi l'objectif, de façon à la faire passer dans un second état de polarisation prédéfini ; et un photodétecteur, qui reçoit la lumière passée dans le second état de polarisation de façon à convertir celle-ci en un signal électrique.
PCT/KR2020/006441 2019-05-17 2020-05-15 Système optique utilisant un modulateur spatial de lumière et procédé de mesure de propriétés physiques l'utilisant WO2020235883A1 (fr)

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KR102270190B1 (ko) * 2020-04-03 2021-06-28 서울대학교산학협력단 공간 광 변조기를 이용한 각도 분해 분광반사계
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