Micro-area scanning imaging device and measurement method

Abstract

The present invention discloses a micro-area scanning imaging device and measurement method, comprising a laser, a dual-axis scanning galvanometer SM that focuses the laser light on a sample S, a cubic beam splitter CB, and a microscope objective lens OB. The cubic beam splitter CB splits the signal light reflected from the sample S after the laser is irradiated onto the sample S and transmits it to a sample signal detector SD. A plate-shaped beam splitter PB is provided between the cubic beam splitter CB and the sample signal detector SD to further split the signal light to a laser detector PD. During the measurement process, a two-dimensional characteristic light signal map of the surface of the sample S is first obtained based on the sample signal detector SD. Then, a blank substrate is placed in the area to be measured, and a two-dimensional reflected light signal map of the substrate in the same area as the sample S is obtained based on the laser detector PD. The two-dimensional characteristic light signal map is normalized based on the two-dimensional reflected light signal map to obtain the normalized two-dimensional characteristic light signal map, and a two-dimensional spatial scanning map of the physical properties of the sample S is further drawn. The present invention is suitable for collecting signals such as fluorescence spectroscopy, Raman spectroscopy, and second harmonic generation. By performing two-dimensional laser scanning on the sample surface, high-resolution imaging of micro-areas of various materials is achieved.

Description

Technical Field

[0001] The present invention relates to the field of optical measurement, and in particular to a micro-area scanning imaging device and a measuring method. Background Art

[0002] Microscopic optical technology can perform non-contact, non-destructive analysis of materials at the micron scale, obtaining multi-dimensional information such as the material's microstructure, physical properties, and chemical composition through optical detection. Compared with traditional large-scale characterization methods, microscopic optics is particularly adept at analyzing the spatial heterogeneity of tiny samples. For example, based on scanning imaging capabilities, it can collect optical characteristic signals of two-dimensional materials (such as Raman spectroscopy, fluorescence, and frequency-doubled light) to obtain spatial distribution information on the surface of two-dimensional materials. This is particularly critical in the characterization of inhomogeneous materials, analysis of local stress distribution, and research on the performance of nanodevices.

[0003] However, building a scanning imaging device and measurement solution with high stability, fast sampling capability and high data accuracy faces certain technical challenges. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a micro-area scanning imaging device and a measurement method for achieving high-resolution imaging of material micro-areas.

[0005] Technical solution: To achieve the above-mentioned purpose, the present invention provides a micro-area scanning imaging device, comprising a laser Laser, wherein a dual-axis scanning galvanometer SM and a microscope objective lens OB for converging the laser onto a sample S are sequentially arranged on the laser optical path where the laser Laser emits the laser light, and a cubic beam splitter CB is provided between the dual-axis scanning galvanometer SM and the microscope objective lens OB for splitting the signal light reflected after the laser is irradiated onto the sample S to the sample signal detector SD for signal collection, and a plate beam splitter PB is provided on the optical path where the signal light is located between the cubic beam splitter CB and the sample signal detector SD for further splitting the signal light to the laser detector PD for signal collection.

[0006] A reflecting mirror M1 is provided on the laser light path between the dual-axis scanning galvanometer mirror SM and the cubic beam splitter CB, for reflecting the laser light deflected by the dual-axis scanning galvanometer mirror SM to the cubic beam splitter CB.

[0007] Among them, a scanning lens SL and a sleeve lens TL are provided on the laser light path between the dual-axis scanning galvanometer SM and the cubic beam splitter CB, or on the laser light path between the dual-axis scanning galvanometer SM and the reflector M1, so as to collimate the laser beam deflected by the dual-axis scanning galvanometer SM and ensure that the laser beam is vertically incident on the sample within the entire scanning range, providing uniform focusing.

[0008] The cubic beam splitter CB and the plate beam splitter PB are non-polarizing beam splitters, and the transmission and reflection splitting ratio is 10:90.

[0009] The sample signal detector SD is a spectrometer, a photomultiplier tube, etc., and the laser detector PD is a photodetector.

[0010] A reflector I is added to the upstream optical path of the cubic beam splitter CB to introduce LED light into the laser optical path, and a reflector II is added to the downstream optical path of the cubic beam splitter CB to introduce signal light into the camera CM for image capture of the sample S.

[0011] The dual-axis scanning galvanometer SM includes two reflective mirrors SM1 and SM2 , which are driven by a driving device to deflect and are used to perform two-dimensional scanning on the surface of the sample S in the X-axis and Y-axis directions.

[0012] The present invention provides a measurement method based on the above-mentioned micro-area scanning imaging device, comprising the following steps:

[0013] S1. Place the substrate carrying the sample S in the test area;

[0014] S2. Start the laser Laser and adjust the microscope objective lens OB to focus the laser on the surface of the sample S. Set the scanning angle range and angle step of the dual-axis scanning galvanometer SM on the X and Y axes to make the laser beam scan the surface of the sample S point by point. Obtain a two-dimensional characteristic light signal map of the surface of the sample S based on the sample signal detector SD.

[0015] S3. Place a blank substrate in the area to be measured, repeat the laser scanning process in S2, and obtain a two-dimensional reflected light signal map in the same area on the substrate as the surface of the sample S in S2 based on the laser detector PD;

[0016] S4, performing normalization processing on the two-dimensional characteristic light signal graph based on the two-dimensional reflected light signal graph to obtain a normalized two-dimensional characteristic light signal graph;

[0017] S5. Based on the normalized two-dimensional characteristic light signal image, analyze the sample physical property parameters corresponding to each pixel point and draw a two-dimensional spatial scanning image of the physical properties of sample S.

[0018] The method for obtaining the normalized two-dimensional characteristic light signal image in S4 is:

[0019] First, the two-dimensional reflected light signal image is normalized, that is, the maximum intensity value in the two-dimensional reflected light signal image is found, and the intensity values ​​of all pixels in the two-dimensional reflected light signal image are divided by the maximum intensity value to obtain a normalized two-dimensional reflected light signal image;

[0020] If the characteristic light signal has a linear relationship with the incident light intensity, such as fluorescence and Raman scattering, then divide the intensity value of each pixel point in the two-dimensional characteristic light signal map by the intensity value at the corresponding position in the normalized two-dimensional reflected light signal map to obtain the normalized two-dimensional characteristic light signal map; if the characteristic light signal has a square relationship with the incident light intensity, such as the second harmonic signal, then divide the intensity value of each pixel point in the two-dimensional characteristic light signal map by the square value of the intensity at the corresponding position in the normalized two-dimensional reflected light signal map to obtain the normalized two-dimensional characteristic light signal map.

[0021] Among them, the method of drawing a two-dimensional spatial scanning diagram of the physical properties of sample S based on the two-dimensional characteristic light signal diagram after normalization in S5 is: analyzing the physical property information of sample S based on the two-dimensional characteristic light signal diagram after normalization, including molecular vibration, structure, symmetry, fluorescence properties, etc., to obtain the spatial distribution information of the physical property parameters of sample S.

[0022] Beneficial effects: The present invention has the following advantages: 1. The present invention can perform two-dimensional laser scanning on the sample surface to achieve high-resolution imaging of material micro-regions; 2. The present invention is suitable for signal acquisition such as fluorescence spectroscopy, Raman spectroscopy and second harmonic generation; 3. The present invention introduces a laser detector PD to normalize the signal light collected by the sample signal detector SD, thereby reducing the sample signal error caused by the change in incident light intensity brought by the scanning laser, so that the collected signal light more accurately reflects the actual optical properties of the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the optical path structure of this device;

[0024] Figure 2 Based on Figure 1 Schematic diagram of the optical path structure in which a reflector is added to the device to realize image acquisition of sample S;

[0025] Figure 3 The image data is obtained by collecting the intensity signal of the reflected light from MoS2 on the silicon oxide / silicon substrate and normalizing it.

[0026] Figure 4 Collect imaging data for second harmonic generation signal intensity, fluorescence spectrum, and Raman spectrum of MoS2 on SiO2 / Si substrates. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is described in detail below with reference to the embodiments and drawings.

[0028] like Figure 1As shown, a micro-area scanning imaging device described in the present invention includes a laser Laser, a biaxial scanning galvanometer SM, a cubic beam splitter CB, a microscope objective lens OB, a plate beam splitter PB, a sample S, a laser detector PD, and a sample signal detector SD. The biaxial scanning galvanometer SM is located in the laser optical path where the laser beam emitted by the laser Laser is located, and performs angular deflection on the laser beam in the XY axis direction. The deflected laser beam is adjusted by the microscope objective lens OB and converges on the sample S. In order to further obtain the signal light (or scattered light, fluorescence, and frequency-doubled light, etc.) reflected after the laser beam is irradiated on the sample S, a cubic beam splitter CB is added to the optical path between the biaxial scanning galvanometer SM and the microscope objective lens OB, and a plate beam splitter PB is provided on the optical path of the signal light reflected by the cubic beam splitter CB to further split the signal light to the laser detector PD and the sample signal detector SD for signal acquisition.

[0029] A reflector M1 can be further provided on the laser optical path between the dual-axis scanning galvanometer SM and the cubic beam splitter CB. The reflector M1 reflects the laser beam deflected by the dual-axis scanning galvanometer SM to the cubic beam splitter CB, thereby ensuring that the sample S is located on a horizontal plane while facilitating the installation of other components, thereby making the overall structure of the device more compact and improving the space utilization of the device.

[0030] A scanning lens SL and a tube lens TL can be further added to the laser optical path between the dual-axis scanning galvanometer SM and the cubic beam splitter CB, or to the laser optical path between the dual-axis scanning galvanometer SM and the reflector M1, to collimate the laser beam deflected by the dual-axis scanning galvanometer SM, to ensure that the laser beam is perpendicular to the sample within the entire scanning range, to provide uniform focusing, and thus to ensure high-quality scanning imaging on the sample.

[0031] In this embodiment, the laser is polarized light, and a 532nm low-noise single-longitudinal-mode laser can be used to achieve highly stable output, reducing variations in beam energy and power caused by mode drift and mode hopping, thereby ensuring the stability of the optical scanning imaging process. Other light sources can also be switched to other types, such as pulsed lasers, to meet the needs of optical testing for detecting second harmonic generation (i.e., frequency-doubled light).

[0032] The cubic beam splitter CB and the plate beam splitter PB are non-polarizing beam splitters. In this embodiment, the cubic beam splitter CB can adopt a splitting ratio of 10:90 for transmitted light and reflected light. After the laser beam on the laser light path passes through the cubic beam splitter CB, 10% of the laser light converges to the sample S. After the signal light formed by the reflection of the surface of the sample S passes through the cubic beam splitter CB, 90% of the signal light is used for subsequent detector collection. The cubic beam splitter CB is composed of two prisms, which can reduce the deviation of the passing light beam. At the same time, the single reflecting surface can also avoid ghosting. The plate beam splitter PB can also adopt a splitting ratio of 10:90, wherein, after splitting, 10% of the signal light is captured by the laser detector PD, and the remaining 90% of the signal light is captured by the sample signal detector SD.

[0033] The Sample Signal Detector (SD) can select devices such as spectrometers and photomultiplier tubes based on the characteristics of the optical signal to be collected, thereby obtaining detailed spatial distribution information on the surface of a specific sample material. Spectrometers are characterized by high sensitivity, high resolution, and versatility, and can collect optical signals including Raman spectra, fluorescence spectra, and frequency-doubled optical spectra, thereby achieving high-resolution scanning imaging of different optical signal spectra. Photomultiplier tubes are used to collect optical signals generated by second harmonic generation. Unlike the frequency-doubled optical spectra collected by spectrometers, photomultiplier tubes have extremely high sensitivity, high signal-to-noise ratio, and ultra-fast time response, enabling fast, high-quality scanning imaging of frequency-doubled optical signals.

[0034] In this embodiment, the laser detector PD is a photodetector with high sensitivity, low noise, and low power consumption. It is used to efficiently capture variations in signal light intensity. Its function is to normalize the signal collected by the sample signal detector SD to eliminate the effects of changes in incident laser intensity caused by angular deviations of the light beam entering the entrance pupil of the microscope objective OB. This reduces errors caused by light intensity variations, ensuring that the collected optical signal more accurately reflects the actual optical properties of the sample.

[0035] like Figure 2 As shown, in this embodiment, a reflector I can be further added to the upstream optical path of the cubic beam splitter CB to introduce LED light into the laser light path. A reflector II can be added to the downstream optical path to guide signal light to the camera CM, enabling image capture of the sample S. This facilitates observation of the sample surface and facilitates subsequent selection of an appropriate optical scanning imaging area. When the laser detector PD and sample signal detector SD are subsequently used for signal light acquisition, reflectors I and II can be removed.

[0036] Microscope objective lens OB can be focused to converge the laser beam at a specific detection location on the surface of sample S, further enabling detection of sample S, particularly of uneven surfaces or microstructures. In this embodiment, microscope objective lens OB can achieve a 40x resolution, while a high numerical aperture ensures high spot resolution. Therefore, a numerical aperture of 0.6 is used to achieve high-resolution scanning of up to 1 micron, thereby acquiring physical property distribution information on the sample surface at the micron scale.

[0037] The dual-axis scanning galvanometer (SM) consists of two mirrors, SM1 and SM2, which are deflected by a drive mechanism, respectively, to scan the sample S along the X and Y axes. The drive mechanism uses a moving magnetic actuator as the rotor, which utilizes the torque generated by an energized coil in a magnetic field to drive the rotor's deflection. Unlike conventional rotary motors, the galvanometer's rotor is subjected to a reset torque proportional to the angle at which the rotor deviates from its equilibrium position. When a constant current is applied to the coil, the rotor deflects until the electromagnetic torque equals the reset torque, at which point the rotor stops deflecting. This design enables the scanning galvanometer (SM) to achieve high-speed, high-precision scanning, enabling detection of the optical properties of the sample S surface at the micrometer scale. By adjusting the scanning angle range and angular step size of the dual-axis scanning galvanometer (SM) in the X and Y axes, and combining it with the focusing function of the microscope objective (OB), two-dimensional scanning of the sample S surface is possible.

[0038] This embodiment provides a method for measuring reflected light intensity based on the above device, specifically:

[0039] (1) Place the substrate carrying the sample S in the test area;

[0040] (2) Start the laser, set the scanning angle range and angle step of the dual-axis scanning galvanometer SM on the X-axis and Y-axis, adjust the microscope objective lens OB so that the laser beam converges on the surface of the sample S, move the laser beam to scan the surface of the sample S point by point, and use the sample signal detector SD to collect signal light to obtain a two-dimensional characteristic light signal map of the surface of the sample S;

[0041] (3) placing a blank substrate in the area to be measured, repeating the laser scanning process in step (2), and collecting reflected light using a laser detector PD, thereby obtaining a two-dimensional reflected light signal map in the same area on the substrate as the surface of the sample S in step (2);

[0042] (4) Based on the two-dimensional reflected light signal graph, the two-dimensional characteristic light signal graph is normalized, specifically:

[0043] First, the two-dimensional reflected light signal image is normalized, that is, the maximum intensity value in the two-dimensional reflected light signal image is found, and the intensity values ​​of all pixels in the two-dimensional reflected light signal image are divided by the maximum intensity value to obtain a normalized two-dimensional reflected light signal image;

[0044] If the characteristic light signal has a linear relationship with the incident light intensity, such as fluorescence and Raman scattering, the intensity value of each pixel point in the two-dimensional characteristic light signal image is divided by the intensity value at the corresponding position in the normalized two-dimensional reflected light signal image to obtain the normalized two-dimensional characteristic light signal image; if the characteristic light signal has a square relationship with the incident light intensity, such as the second harmonic signal, the intensity value of each pixel point in the two-dimensional characteristic light signal image is divided by the square value of the intensity at the corresponding position in the normalized two-dimensional reflected light signal image to obtain the normalized two-dimensional characteristic light signal image.

[0045] (5) Based on the normalized two-dimensional characteristic light signal image and the physical property information of sample S it carries (such as molecular vibration, structure, symmetry, fluorescence, etc.), a two-dimensional spatial scanning diagram of the physical property parameters of sample S is drawn.

[0046] This device can achieve high-resolution optical imaging of micro-areas and is compatible with various optical detection technologies including fluorescence spectroscopy, Raman spectroscopy, and second harmonic generation. For example, in the above-mentioned embodiment, when the device is used to collect fluorescence spectra, Raman spectra, etc., the sample signal detector SD is a spectrometer, and a 532-nanometer excitation light source is used to obtain the luminescence properties and phonon vibration information of the sample. When the device is used to collect second harmonic generation signals, the sample signal detector SD can use a photomultiplier tube, and by using an 810-nanometer femtosecond pulse excitation light source, information such as the symmetry of the sample can be obtained. In the above optical detection technologies, the laser detector PD is a photodetector that can provide normalized processed data.

[0047] Taking 300 nanometers of molybdenum disulfide on silicon oxide / silicon substrate as an example, the device and measurement method are used to realize spatial scanning imaging of the sample, wherein the laser wavelength of the laser is 532 nanometers or 810 nanometers. Figure 3 As shown, Figure 3 (a) is a white light image of the sample; Figure 3 (b) is a two-dimensional image of the intensity distribution of the reflected light signal directly collected by the laser detector PD in the sample area, in which there is an obvious reflected background intensity distribution; Figure 3 (c) is a two-dimensional graph of the sample light signal intensity after normalization processing of the reflected light signal on a blank substrate. The results show that the reflected background intensity distribution is eliminated, and high-quality scanning imaging of the sample reflected light signal intensity is successfully achieved, demonstrating the reliability of the normalization processing.

[0048] The scanning imaging results of the characteristic light signal of MoS2 are as follows Figure 4As shown, Figure 4 (a) is a white light image of the sample, with the area with a thickness of 1-4 layers marked; Figure 4 (b) A two-dimensional plot of the normalized second harmonic generation (SHG) signal intensity distribution captured by a photomultiplier tube. SHG is a second-order nonlinear optical effect. An 810-nanometer femtosecond pulsed laser source was used. For MoS2, samples with odd layers exhibit significant SHG signals due to the violation of spatial inversion symmetry, while samples with even layers exhibit almost no SHG signals due to their spatial inversion symmetry. This allows for the acquisition of spatially resolved information, such as the number of layers and symmetry of the sample.

[0049] Figure 4 (c) is the normalized two-dimensional distribution of fluorescence spectrum intensity collected by the spectrometer. Figure 4 (d) shows the fluorescence spectrum at a specific location in the corresponding two-dimensional image. Based on the fluorescence spectrum of MoS2, the more layers there are, the weaker the fluorescence signal. This allows us to further determine the number of layers in the sample, thereby obtaining the spatial distribution of the sample's layers and fluorescence properties.

[0050] Figure 4 (e) is the two-dimensional distribution diagram of the normalized Raman spectrum intensity collected by the spectrometer. Figure 4 (f) is a two-dimensional diagram of the energy difference distribution of the two characteristic peaks of MoS2 Raman spectrum at 370-430 wavenumbers. Figure 4 (g) is the Raman spectrum at a specific location in the corresponding two-dimensional image. MoS2 is known to have two Raman-active phonon peaks between 370 and 430 wavenumbers, and the integrated intensity and energy difference of these two peaks are both layer-number dependent. For each pixel position scanned by the laser, the Raman signal intensity is integrated within the 370-430 wavenumber range, and the energy difference between the two peaks within this wavenumber range is analyzed. This provides information on the spatial distribution of the sample's Raman signal intensity and the energy difference between the Raman peaks.

Claims

1. A measurement method for a micro-area scanning imaging device, characterized in that: The following steps are involved: S1. Place the substrate carrying the sample S in the test area; S2. Start the laser Laser and adjust the microscope objective lens OB to focus the laser on the surface of the sample S. Set the scanning angle range and angle step of the dual-axis scanning galvanometer SM on the X and Y axes to make the laser beam scan the surface of the sample S point by point. Obtain a two-dimensional characteristic light signal map of the surface of the sample S based on the sample signal detector SD. S3. Place a blank substrate in the area to be measured, repeat the laser scanning process in S2, and obtain a two-dimensional reflected light signal map in the same area on the substrate as the surface of the sample S in S2 based on the laser detector PD; S4, performing normalization processing on the two-dimensional characteristic light signal graph based on the two-dimensional reflected light signal graph to obtain a normalized two-dimensional characteristic light signal graph; S5. Based on the normalized two-dimensional characteristic light signal image, analyze the sample physical property parameters corresponding to each pixel point and draw a two-dimensional spatial scanning image of the physical properties of sample S; The micro-area scanning imaging device includes a laser Laser. A dual-axis scanning galvanometer SM and a microscope objective lens OB are sequentially arranged on the laser light path where the laser Laser emits the laser light, and are used to focus the laser light on the sample S. A cubic beam splitter CB is provided between the dual-axis scanning galvanometer SM and the microscope objective lens OB, and is used to split the signal light reflected after the laser is irradiated on the sample S to the sample signal detector SD for signal collection. A plate beam splitter PB is provided on the signal light light path between the cubic beam splitter CB and the sample signal detector SD, and is used to further split the signal light to the laser detector PD for signal collection.

2. The measuring method according to claim 1, wherein The method for obtaining the normalized two-dimensional characteristic light signal image in S4 is: First, the two-dimensional reflected light signal image is normalized, that is, the maximum intensity value in the two-dimensional reflected light signal image is found, and the intensity values ​​of all pixels in the two-dimensional reflected light signal image are divided by the maximum intensity value to obtain a normalized two-dimensional reflected light signal image; If the characteristic light signal has a linear relationship with the incident light intensity, such as fluorescence and Raman scattering, the intensity value of each pixel in the two-dimensional characteristic light signal image is divided by the intensity value at the corresponding position in the normalized two-dimensional reflected light signal image to obtain the normalized two-dimensional characteristic light signal image; If the characteristic light signal has a square relationship with the incident light intensity, such as the second harmonic signal, the intensity value of each pixel in the two-dimensional characteristic light signal image is divided by the square value of the intensity at the corresponding position in the normalized two-dimensional reflected light signal image to obtain the normalized two-dimensional characteristic light signal image.

3. The measuring method according to claim 1, wherein The method for drawing a two-dimensional spatial scanning diagram of the physical properties of sample S based on the two-dimensional characteristic light signal diagram after normalization in S5 is: analyzing the physical property information of sample S based on the two-dimensional characteristic light signal diagram after normalization, including molecular vibration, structure, symmetry, and fluorescence properties, to obtain the spatial distribution information of the physical property parameters of sample S.

4. The measuring method according to claim 1, wherein A reflecting mirror M1 is provided on the laser light path between the biaxial scanning galvanometer mirror SM and the cubic beam splitter CB, for reflecting the laser light deflected by the biaxial scanning galvanometer mirror SM to the cubic beam splitter CB.

5. The measuring method according to claim 1 or 4, characterized in that: A scanning lens SL and a sleeve lens TL are provided on the laser optical path between the dual-axis scanning galvanometer SM and the cubic beam splitter CB, or between the dual-axis scanning galvanometer SM and the reflector M1, to collimate the laser beam deflected by the dual-axis scanning galvanometer SM and ensure that the laser beam is vertically incident on the sample within the entire scanning range, providing uniform focusing.

6. The measuring method according to claim 1, characterized in that The cubic beam splitter CB and the plate beam splitter PB are non-polarizing beam splitters, and the transmission and reflection splitting ratio is 10:

90.

7. The measuring method according to claim 1, characterized in that The sample signal detector SD is a spectrometer or a photomultiplier tube, and the laser detector PD is a photodetector.

8. The measurement method according to claim 1, characterized in that A reflector I is added to the upstream optical path of the cubic beam splitter CB to introduce LED light into the laser optical path, and a reflector II is added to the downstream optical path of the cubic beam splitter CB to introduce signal light into the camera CM for image capture of the sample S.

9. The measuring method according to claim 1, wherein: The dual-axis scanning galvanometer SM includes two reflective mirrors SM1 and SM2 , which are driven by a driving device to deflect and are used to perform two-dimensional scanning on the surface of the sample S in the X-axis and Y-axis directions.

Images