Infrared spectrum signal acquisition system and method

Abstract

The invention provides an infrared spectral signal acquisition system and method.The system comprises a light path system, a main control computer, an intermediate infrared laser, a laser vibration meter and a sample displacement table, the intermediate infrared laser, the laser vibration meter and the sample displacement table are electrically connected with the main control computer, and the intermediate infrared laser is used for emitting intermediate infrared pulse laser which irradiates the surface of a to-be-measured sample through an intermediate infrared light path; a photo-thermal vibration signal is generated; the laser vibration meter is used for emitting vibration measurement laser, irradiating the vibration measurement laser to the surface of the to-be-measured sample through a vibration measurement light path and receiving a returned vibration signal; and the main control computer is used for adjusting laser signal parameters of the intermediate infrared laser and the laser vibration meter, controlling the sample displacement table to move and performing signal analysis processing on vibration signals acquired by the laser vibration meter. According to the invention, the laser vibration meter can detect the infrared spectrum signal, and the detection sensitivity of the sample surface signal is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of signal processing, and in particular to an infrared spectrum signal acquisition system and method. Background Art

[0002] Mid-infrared photothermal microscopy is an imaging tool that combines mid-infrared spectroscopy technology and photothermal effect. It uses the temperature change caused by the absorption of mid-infrared light of a specific wavelength to generate images.

[0003] At present, the collection of sample photothermal signals and images based on mid-infrared photothermal microscopy has the following technical defects:

[0004] 1. Insufficient detection sensitivity: The main reason is that the interaction between the mid-infrared light source and the sample is weak, resulting in low photothermal signal intensity. In addition, the commonly used detectors have limited response sensitivity to weak photothermal signals, which makes it difficult for mid-infrared photothermal microscopes to achieve detection sensitivity at the single molecule or single particle level similar to that of visible light-based photothermal microscopes, and cannot meet the needs of high-precision trace analysis.

[0005] 2. Limited spatial resolution: Currently, mid-infrared photothermal microscopes can achieve a resolution of hundreds of nanometers, but are limited by the diffraction limit and thermal diffusion, making further breakthroughs difficult.

[0006] 3. Low signal extraction efficiency: Current signal extraction methods mainly rely on indirect detection methods of temperature changes or refractive index changes. These methods have low response efficiency to tiny vibration signals on the sample surface, especially in a noisy environment, where the signal is easily masked and it is difficult to ensure a high signal-to-noise ratio.

[0007] 4. Low overall performance: The existing mid-infrared optical path system has a complex structure, which makes it easy for the mid-infrared light signal to lose light power due to absorption loss or scattering during transmission, thus reducing the overall performance of the photothermal microscope. Summary of the invention

[0008] In view of this, an object of the present invention is to provide an infrared spectrum signal acquisition system and method to solve at least one of the above technical problems.

[0009] In a first aspect, an infrared spectrum signal acquisition system is provided, comprising: an optical path system, a main control machine, and a mid-infrared laser electrically connected to the main control machine, a laser vibrometer, and a sample displacement stage, wherein the optical path system comprises a mid-infrared optical path and a vibrometer optical path;

[0010] The sample displacement stage is used to carry the sample to be tested;

[0011] The mid-infrared laser is used to emit mid-infrared pulsed laser and irradiate the surface of the sample to be tested through the mid-infrared optical path to generate photothermal vibration signals;

[0012] The laser vibrometer is used to emit a vibration measuring laser, irradiate the surface of the sample to be measured through the vibration measuring optical path, and receive the returned photothermal vibration signal;

[0013] The main control computer is used to adjust the laser signal parameters of the mid-infrared laser and the laser vibrometer, to control the movement of the sample displacement stage, and to perform signal analysis and processing on the photothermal vibration signals collected by the laser vibrometer.

[0014] Optionally, the mid-infrared optical path includes a plurality of first reflectors, a first dichroic mirror, a second dichroic mirror and a beam expander, and the plurality of first reflectors are respectively arranged between the mid-infrared laser and the first dichroic mirror, and between the beam expander and the second dichroic mirror according to preset angles.

[0015] Optionally, the beam expander includes a first off-axis parabolic mirror and a second off-axis parabolic mirror, and the focal lengths of the first off-axis parabolic mirror and the second off-axis parabolic mirror are twice as long.

[0016] Optionally, the vibrometer optical path includes a plurality of second reflectors, a second dichroic mirror and a third dichroic mirror, and the second reflectors are respectively arranged between the laser vibrometer and the third dichroic mirror, and between the third dichroic mirror and the second dichroic mirror according to preset angles.

[0017] Optionally, the system also includes a green light LED and a navigation optical path, the green light LED is used to irradiate the emitted LED green light to the surface of the sample to be tested via the navigation optical path, and the LED green light is used to assist the mid-infrared laser in positioning on the surface of the sample to be tested; the navigation optical path includes a third reflector and the first dichroic mirror in the mid-infrared optical path and the optical elements thereafter.

[0018] Optionally, the first to third reflectors are all gold film reflectors.

[0019] Optionally, the system also includes an image sensor and a lighting device, and the optical path system also includes an imaging light path and an illumination light path. The image sensor and the lighting device are electrically connected to the main control machine respectively. The lighting device is used to illuminate the sample surface through the illumination light path, and the image sensor is used to collect an optical image of the sample surface through the imaging light path.

[0020] Optionally, the optical path system further comprises a reflective objective lens, which is arranged between the end of each optical path and the sample displacement stage, and is used to focus the light beam of each optical path onto the sample surface and collect the vibration-measuring light reflected from the sample surface.

[0021] Optionally, the system further comprises a lock-in amplifier, the input of the lock-in amplifier is respectively connected to the mid-infrared laser and the laser vibrometer, and the output of the lock-in amplifier is connected to the main control computer.

[0022] In a second aspect, a method for collecting infrared spectrum signals is provided, the method comprising:

[0023] The mid-infrared pulse laser emitted by the mid-infrared laser is irradiated onto the surface of the sample to be tested through a mid-infrared optical path to generate a photothermal vibration signal;

[0024] The vibrometer laser emitted by the laser vibrometer is irradiated onto the surface of the sample to be tested through the vibrometer optical path to collect the photothermal vibration signal of the surface of the sample to be tested.

[0025] The present invention provides an infrared spectrum signal acquisition system and method, which includes: an optical path system, a main control machine and a mid-infrared laser electrically connected to the main control machine, a laser vibrometer, and a sample displacement stage, wherein the mid-infrared laser is used to emit a mid-infrared pulse laser, and irradiate the surface of the sample to be tested through the mid-infrared optical path to generate a photothermal vibration signal; the laser vibrometer is used to emit a vibration measurement laser, and irradiate the surface of the sample to be tested through the vibration measurement optical path and receive the returned photothermal vibration signal; the main control machine is used to adjust the laser signal parameters of the mid-infrared laser and the laser vibrometer, and is also used to control the movement of the sample displacement stage, and is also used to perform signal analysis and processing on the vibration signal collected by the laser vibrometer. The present invention combines the laser vibrometer with the mid-infrared laser, utilizes the high sensitivity and non-contact characteristics of the laser Doppler vibrometer technology, accurately captures the tiny vibration signal caused by the mid-infrared photothermal effect on the surface of the sample to be tested, and improves the detection sensitivity to the picometer level, thereby improving the detection sensitivity of the photothermal vibration signal on the sample surface.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 The structure framework diagram of the infrared spectrum signal acquisition system provided by the embodiment of the present invention is shown;

[0029] Figure 2 A structural framework diagram of an infrared spectrum signal acquisition system provided by another embodiment of the present invention is shown;

[0030] Figure 3 A structural framework diagram of an infrared spectrum signal acquisition system provided by another embodiment of the present invention is shown;

[0031] Figure 4A structural framework diagram of an infrared spectrum signal acquisition system provided by another embodiment of the present invention is shown;

[0032] Figure 5 A schematic diagram showing the structure of an optical path system provided by an embodiment of the present invention is shown;

[0033] Figure 6 A schematic diagram of the process of the infrared spectrum signal acquisition method provided by an embodiment of the present invention is shown;

[0034] FIG. 7( a ) shows the test comparison results of the PS film provided by the embodiment of the present invention;

[0035] FIG. 7( b ) shows the test comparison results of the PMMA film provided in the embodiment of the present invention;

[0036] FIG. 7( c ) shows a FA provided by an embodiment of the present invention. 0.9 Cs 0.1 Test comparison results of PbI3 perovskite films;

[0037] Figure 8 The test results of different areas of the photoresist film sample provided by the embodiment of the present invention are shown.

[0038] Explanation of the main component symbols: 101, main control computer; 102, laser vibrometer; 103, mid-infrared laser; 104, sample displacement stage; 105, lighting equipment; 106, CMOS camera; 107, green light LED; 108, phase-locked amplifier; 200, optical path system; 201, vibrometer optical path; 202, mid-infrared optical path, 203, illumination optical path, 204, imaging optical path; 205, navigation optical path; 301, first reflector; 302, first dichroic mirror; 303, beam expander; 304, second dichroic mirror; 305, reflective objective lens; 306, second reflector; 307, third dichroic mirror; 308, third reflector; 309, lens; 310, fourth reflector; 311, beam splitter. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0040] Considering the following technical defects in collecting sample optical images based on mid-infrared photothermal microscopy:

[0041] 1. Insufficient detection sensitivity: The main reason is that the interaction between the mid-infrared light source and the sample is weak, resulting in low photothermal signal intensity. In addition, the commonly used detectors have limited response sensitivity to weak photothermal signals, which makes it difficult for mid-infrared photothermal microscopes to achieve detection sensitivity at the single molecule or single particle level similar to that of visible light-based photothermal microscopes, and cannot meet the needs of high-precision trace analysis.

[0042] 2. Limited spatial resolution: Currently, mid-infrared photothermal microscopes can achieve a resolution of hundreds of nanometers, but are limited by the diffraction limit and thermal diffusion, making further breakthroughs difficult.

[0043] 3. Low signal extraction efficiency: Current signal extraction methods mainly rely on indirect detection methods of temperature changes or refractive index changes. These methods have low response efficiency to tiny vibration signals on the sample surface, especially in a noisy environment, where the signal is easily masked and it is difficult to ensure a high signal-to-noise ratio.

[0044] 4. Low overall performance: The existing mid-infrared optical path system has a complex structure, which makes it easy for the mid-infrared light signal to lose light power due to absorption loss or scattering during transmission, thus reducing the overall performance of the photothermal microscope.

[0045] Based on this, an embodiment of the present invention provides an infrared spectrum signal acquisition system, which is described below through an embodiment.

[0046] The embodiment of the present invention provides an infrared spectrum signal acquisition system, such as Figure 1 As shown, the system includes: an optical path system 200 , a main control machine 101 , a mid-infrared laser 103 electrically connected to the main control machine 101 , a laser vibrometer 102 , and a sample displacement stage 104 , wherein the optical path system 200 includes a mid-infrared optical path and a vibration measuring optical path 201 .

[0047] The sample displacement stage 104 is used to carry the sample to be tested and the auxiliary system to complete the photothermal imaging test;

[0048] The mid-infrared laser 103 is used to emit mid-infrared pulse laser and irradiate the surface of the sample to be tested through the mid-infrared light path to generate a photothermal vibration signal.

[0049] The laser vibrometer 102 is used to emit a vibration measuring laser, and irradiate the surface of the sample to be measured through the vibration measuring optical path 201 and receive the returned photothermal vibration signal.

[0050] The main control machine 101 is used to adjust the laser signal parameters of the mid-infrared laser 103 and the laser vibrometer 102 , to control the movement of the sample displacement stage 104 , and to perform signal analysis and processing on the vibration signal collected by the laser vibrometer 102 .

[0051] In the embodiment of the present invention, the mid-infrared laser 103 uses a QCL laser, which can achieve single-wavelength output in the range of 5.5 μm-8 μm, a repetition rate range of 0-3 MHz, and an output power of up to 500 mW. The laser vibrometer 102 can use an OFV-505 / 5000 high-performance single-point laser vibrometer 102, and the wavelength of the output light is 633 nm.

[0052] Specifically, the mid-infrared laser 103 is connected to the main control machine 101 via a USB interface to achieve control of pulse width, pulse power, pulse frequency modulation and other functions. The laser vibrometer 102 is composed of an optical head and a controller. The optical head is mainly an interference optical path system 200 based on the Doppler effect, and the controller plays the role of parameter setting and data acquisition and processing. The controller outputs the received vibration measurement signal in the form of voltage through the BNC interface.

[0053] In addition, the LabView program can be used in the main control machine 101 to precisely control the displacement of the sample displacement stage 104 in the XYZ direction. By controlling the movement of the sample displacement stage 104, the movement of the sample to be tested is achieved, so that the system can test the laser vibration measurement signals at different positions under the movement of the sample displacement stage 104, and cooperate with the system to complete the photothermal imaging test.

[0054] The main control computer 101 analyzes and processes the received vibration signal to obtain parameters such as the vibration speed, vibration amplitude, and vibration acceleration of the sample to be tested.

[0055] In actual application design, the entire spectral signal acquisition system is placed on a vibration isolation air cushion to reduce the impact of environmental vibration on the measurement.

[0056] The embodiment of the present invention combines the laser vibrometer 102 with the mid-infrared laser 103, and utilizes the high sensitivity and non-contact characteristics of the laser Doppler vibrometer technology to accurately capture the tiny vibration signals on the surface of the sample to be tested caused by the mid-infrared photothermal effect, thereby increasing the detection sensitivity to the picometer level, thereby improving the detection sensitivity of the photothermal vibration signals on the sample surface.

[0057] In order to facilitate the intuitive observation of the optical changes on the sample surface, such as Figure 2 As shown, the embodiment of the present invention also designs an imaging optical path, an illumination optical path, an image sensor and an illumination device 105. The image sensor and the illumination device 105 are electrically connected to the main control computer 101 respectively. The illumination device 105 emits LED white light to illuminate the sample surface through the illumination optical path to assist the image sensor in collecting an optical image of the sample surface. The image sensor can use a CMOS camera 106 to collect an optical image of the sample surface through the imaging optical path.

[0058] In one example, the illumination light path uses two lenses 309 to focus and collimate the light path, providing uniform sample illumination for the imaging plane. The imaging light path uses another lens 309 and a beam splitter to perform imaging and LED white light beam combination.

[0059] However, the imaging resolution of the conventional mid-infrared photothermal microscope is limited by the optical diffraction limit and cannot meet the imaging requirements of some nanoscale samples. Therefore, the embodiment of the present invention improves the optical path system 200 and designs a high numerical aperture reflective objective lens 305, which is arranged between the end of each optical path and the sample displacement stage 104 to focus the light beams of each optical path onto the sample surface.

[0060] The embodiment of the present invention breaks through the diffraction limit by combining the laser vibrometer 102 with the reflective objective lens 305 with a high numerical aperture and an optimized optical path, and achieves an imaging resolution capability far higher than the optical diffraction limit. The reason why the imaging resolution can be improved by the reflective objective lens 305 with a high numerical aperture is that the numerical aperture is one of the key parameters affecting the resolution of the optical system. By using an objective lens with a high numerical aperture, more light angles can be collected, thereby improving the resolution capability of the system. The reflective objective lens 305 usually has a higher numerical aperture than the transmissive objective lens because they can use a wider angle range to collect light from the sample.

[0061] The existing optical paths are complex in design and prone to optical power loss or scattering problems, which makes system debugging difficult and the system performance stability insufficient. Therefore, the present invention optimizes each optical path, and the optimized structure is shown in the following embodiment.

[0062] Based on the above embodiments, Figure 5As shown, the mid-infrared optical path includes a plurality of first reflectors 301, a first dichroic mirror 302, a second dichroic mirror 304 and a beam expander 303. The plurality of first reflectors 301 are respectively arranged between the mid-infrared laser 103 and the first dichroic mirror 302, and between the beam expander 303 and the second dichroic mirror 304 according to preset angles.

[0063] In the embodiment of the present invention, the number and specific installation angle of the first reflective mirrors 301 can be adaptively adjusted according to the distance and spatial position between the mid-infrared laser 103 and the sample displacement stage 104 .

[0064] In a feasible implementation, the beam expander 303 includes a first off-axis parabolic mirror and a second off-axis parabolic mirror, and the focal lengths of the first off-axis parabolic mirror and the second off-axis parabolic mirror are twice each other. The first off-axis parabolic mirror focuses the incident mid-infrared laser, and then diverges and expands the beam by 2 times before being collimated into parallel light output by the second off-axis parabolic mirror, which is used to reduce the discrete angle of the mid-infrared laser and meet the numerical aperture requirements of the reflective objective lens 305.

[0065] In a feasible implementation, the first reflector 301 is a gold film reflector, the reflectivity of which is greater than 98%, thereby greatly reducing the loss of each optical signal in the optical path.

[0066] The optical transmission path of the mid-infrared optical path is as follows: the mid-infrared laser emitted by the mid-infrared laser 103 is reflected to the first dichroic mirror 302 via a plurality of first reflectors 301, and the mid-infrared laser is transmitted through the high transmittance of the first dichroic mirror 302 to reduce the power loss of the mid-infrared laser; then, the mid-infrared laser transmitted by the first dichroic mirror 302 passes through the beam expander 303, and then is reflected and guided to the second dichroic mirror 304 via a plurality of first reflectors 301; the mid-infrared laser is reflected to the reflective objective lens 305 via the reflection of the second dichroic mirror 304, and is focused by the reflective objective lens 305 and irradiated to the surface of the sample to be measured.

[0067] Since mid-infrared laser is invisible to the naked eye, in order to facilitate the positioning of mid-infrared laser on the surface of the sample to be tested, such as Figure 3 As shown, the embodiment of the present invention further designs a green light LED 107 and a navigation optical path 205. The green light LED 107 is used to irradiate the emitted LED green light to the surface of the sample to be tested via the navigation optical path 205. The LED green light is used to assist the mid-infrared laser in positioning on the surface of the sample to be tested.

[0068] In order to simplify the optical path design, in a feasible implementation, as Figure 5 As shown, the present invention combines the LED green light and the mid-infrared laser beams through the first dichroic mirror 302 for transmission, that is, the navigation optical path 205 and the mid-infrared optical path are partially combined. Figure 2 As shown, the navigation optical path 205 includes a third reflector 308 and a first dichroic mirror 302 in the mid-infrared optical path and the optical elements thereafter. The optical transmission path of the navigation optical path 205 is as follows: the LED green light is reflected to the first dichroic mirror 302 via the third reflector 308, and is combined with the mid-infrared laser after being reflected by the second dichroic mirror 304. The combined LED green light and the mid-infrared laser are incident on the reflective objective lens 305 after passing through the beam expander 303, a plurality of first reflectors 301, and the second dichroic mirror 304 in sequence.

[0069] The third reflector 308 also adopts a gold film reflector, and the light path is simplified through the beam combining of the first dichroic mirror 302, thereby further reducing the power loss.

[0070] Based on the above embodiments, Figure 5 As shown, the vibrometer optical path 201 includes a plurality of second reflectors 306 , a second dichroic mirror 304 and a third dichroic mirror 307 . The second reflectors 306 are respectively arranged between the laser vibrometer 102 and the third dichroic mirror 307 , and between the third dichroic mirror 307 and the second dichroic mirror 304 at preset angles.

[0071] In the embodiment of the present invention, the number and specific installation angle of the second reflective mirrors 306 can be adaptively adjusted according to the distance and spatial position between the laser vibrometer 102 and the sample displacement stage 104 .

[0072] In a feasible implementation, the second reflector 306 also uses a gold film reflector to reduce the loss of the vibration measurement signal in the optical path.

[0073] like Figure 2 As shown, the optical transmission path of the vibration measuring optical path 201 is: the vibration measuring laser emitted by the vibration measuring laser is reflected to the third dichroic mirror 307 via the second reflector 306, reflected by the third dichroic mirror 307, reflected to another second reflector 306, and then reflected to the second dichroic mirror 304 via the second reflector 306, transmitted through the second dichroic mirror 304, the vibration measuring laser is combined with the LED green light and the mid-infrared laser, and the combined light beam is incident on the reflective objective lens 305, and is focused by the reflective objective lens 305 and irradiated to the sample surface.

[0074] The entire optical path of the optimized vibration measuring optical path 201 is less than 50 cm, which greatly reduces energy loss.

[0075] In another embodiment, in order to simplify the optical path design, as Figure 5As shown, the imaging light path and the illumination light path are partially combined with the vibration measuring light path 201 through the third dichroic mirror 307, the LED white light emitted by the lighting device 105 is focused and collimated by two lenses 309 and then incident on the fourth reflector 310, reflected by the fourth reflector 310 to the beam splitter, split by the beam splitter, a part of the LED white light is incident on the third dichroic mirror 307, transmitted through the third dichroic mirror 307 and combined with the vibration measuring laser, and then passed through the second The dichroic mirror 304 transmits, and the second dichroic mirror 304 combines the LED white light, the vibrometric laser, the mid-infrared laser and the LED green light and then injects them into the reflective objective lens 305. The vibrometric laser reflected by the sample is guided to the second dichroic mirror 304 via the reflective objective lens 305. The second dichroic mirror 304 reflects the vibrometric laser through the sample, and the vibrometric laser is then reflected to the laser vibrometer 102 via the third dichroic mirror 307. The vibrometric laser interferes with the reference beam through the laser Doppler effect, and then the vibrometric signal is obtained. In addition, the visible light reflected by the sample is transmitted to the CMOS camera 106 via the imaging optical path for imaging.

[0076] In actual application design, each optical element in each optical path is fixed on marble. This is because marble material has lower thermal expansion absorption and good vibration absorption characteristics, which can effectively reduce the interference of external vibration sources on the optical system.

[0077] The embodiment of the present invention optimizes the optical path structure by using a gold film reflector and a plurality of dichroic mirrors, thereby greatly reducing power loss and improving the stability and usability of the system.

[0078] In order to verify the reliability of the optimized optical path system, a set of experimental data is used to verify it.

[0079] Three organic films with characteristic absorption peaks in the range of 1510 cm-1 to 1790 cm-1 were selected as standard verification samples. The three sample films are: PS (Polystyrene, polystyrene) film, PMMA (Polymethyl Methacrylate, polymethyl methacrylate) film, FA 0.9 Cs 0.1 PbI3 perovskite film; a comparative test was carried out using the V-PSC (Visible Photoacoustic Scanning Confocal microscopy) and FTIR (Fourier Transform Infrared Spectroscopy) of the present invention to verify the feasibility and reliability of the optical path system design.

[0080] As shown in Figure 7(a), in the PS film, both FTIR and V-PSC can clearly detect the characteristic absorption peak of the benzene ring skeleton vibration at 1600 cm-1;

[0081] As shown in Figure 7(b), in the PMMA films, characteristic absorption peaks originating from C=O stretching vibration are shown around 1730 cm-1;

[0082] As shown in Figure 7(c), in FA 0.9 Cs 0.1 In the PbI3 perovskite film, both FTIR and V-PSC detected the characteristic absorption peak of C=N stretching vibration originating from FA+ at 1712cm-1, and the two showed good consistency.

[0083] Based on the above test results, it is proved that the mid-infrared photothermal microscopy technology is consistent with the FTIR test results, which further illustrates the rationality of the optical path design of the embodiment of the present invention and its reliability in practical applications. Therefore, it is shown that the characteristic absorption signal of thin film FA+ can be accurately and effectively obtained through the optimized optical path system.

[0084] In addition, the acquisition of mid-infrared spectra by laser vibrometer can keenly detect changes in the physical and chemical properties of local areas of the sample. The following specific experiments are used to verify this:

[0085] The CMOS camera was used to perform spectrum sampling tests on the edge area of ​​the photoresist film. The infrared spot was used to mark the spectrum sampling position, and the infrared spectra of different areas of the sample were collected, such as Figure 8 As shown, from top to bottom are the characteristic absorption signal curves of the four regions of the sample a, b, c, and d. Region a is the base region, and no obvious infrared absorption signal is detected; regions b and c correspond to thinner and thicker film regions, respectively, and characteristic absorption signals of varying degrees appear in their spectra. In particular, region d exhibits the strongest photothermal signal, indicating that its light absorption characteristics are significantly enhanced. This phenomenon may be related to the fact that the film thickness in region d is the thickest, making its absorption of mid-infrared light and photothermal conversion efficiency the highest. There may be special local effects in the edge region, such as material accumulation, stress concentration, or differences in crystal structure, which together contribute to significant changes in the signal.

[0086] The experimental results show that the laser vibrometer can keenly detect changes in the physical and chemical properties of local areas of the sample, providing a powerful tool for studying the microscopic properties of thin film materials.

[0087] The current methods for extracting vibration signals from sample surfaces mainly rely on indirect detection methods of temperature changes or refractive index changes. These methods have low response efficiency to tiny vibration signals on the sample surface, especially in a noisy environment, where the signal is easily masked and it is difficult to ensure a high signal-to-noise ratio. Therefore, based on the above embodiments, Figure 4 As shown, the system is also designed with a phase-locked amplifier 108, the input of the phase-locked amplifier 108 is respectively connected to the mid-infrared laser 103 and the laser vibrometer 102, and the output of the phase-locked amplifier can be connected to the main control computer 101 via USB.

[0088] The phase-locked amplifier sets the detection frequency to the same as the excitation frequency of the mid-infrared laser through the coherent detection method. It can accurately extract the laser vibration measurement signal of the sample in the noise background and optimize the signal-to-noise ratio of the acquired signal.

[0089] In a feasible implementation, in order to achieve efficient control and data processing of the spectral signal acquisition system, a software interface integrating spectral acquisition, imaging and signal optimization can be developed based on the LabVIEW platform. The software interface is divided into three modules: spectral acquisition, imaging operation and signal optimization. Each module has a clear function, which is convenient for experimental operation and data analysis.

[0090] Specifically, in the spectrum acquisition module, the spectrum acquisition band range, spectrum acquisition step size, and integration time of each sampling point can be set. The interface displays the spectrum data curve in real time, which is convenient for observing signal changes and quickly adjusting parameters. In the imaging operation module, the imaging resolution, scanning range and step size can be set, and the distribution characteristics of the photothermal signal on the sample surface can be displayed in the form of a pseudo-color map. In the signal optimization module, it is mainly used to control the XYZ axis movement of the sample displacement platform, and to achieve automatic focusing and optimal signal acquisition by adjusting the relative position between the sample and the vibration laser light source. The development of this software interface effectively improves the automation level and operational efficiency of the system.

[0091] Based on the same inventive concept, a spectral signal acquisition method is provided, such as Figure 6 As shown, the method includes:

[0092] Step S601: irradiating the surface of the sample to be tested with a mid-infrared pulse laser emitted by a mid-infrared laser through a mid-infrared optical path to generate a photothermal vibration signal.

[0093] Step S602: irradiating the surface of the sample to be measured with the vibration measuring laser emitted by the laser vibrometer through the vibration measuring optical path to collect the vibration signal of the surface of the sample to be measured.

[0094] In the embodiment of the present invention, the mid-infrared optical path and the vibration measuring optical path can adopt the optimized optical path in the above embodiment. The specific collection process refers to the light transmission process of each optical path in the above embodiment, which will not be repeated here.

[0095] In the embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of devices or units can be electrical, mechanical or other forms.

[0096] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0097] In addition, each functional unit in the embodiment provided by the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0098] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0099] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0100] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0101] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0102] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-mentioned embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-mentioned embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. They should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. An infrared spectrum signal acquisition system, characterized in that: include: An optical path system, a main control machine, and a mid-infrared laser, a laser vibrometer, and a sample displacement stage electrically connected to the main control machine, wherein the optical path system includes a mid-infrared optical path and a vibrometer optical path; The sample displacement stage is used to carry the sample to be tested; The mid-infrared laser is used to emit mid-infrared pulse laser, and irradiate the surface of the sample to be tested through the mid-infrared optical path to generate a photothermal vibration signal; The laser vibrometer is used to emit a vibration measuring laser, and irradiate the surface of the sample to be measured through the vibration measuring optical path and receive the returned photothermal vibration signal; The main control machine is used to adjust the laser signal parameters of the mid-infrared laser and the laser vibrometer, to control the movement of the sample displacement stage, and to perform signal analysis and processing on the photothermal vibration signal collected by the laser vibrometer.

2. The infrared spectrum signal acquisition system according to claim 1, characterized in that: The mid-infrared optical path includes a plurality of first reflectors, a first dichroic mirror, a second dichroic mirror and a beam expander. The plurality of first reflectors are respectively arranged between the mid-infrared laser and the first dichroic mirror, and between the beam expander and the second dichroic mirror according to preset angles.

3. The infrared spectrum signal acquisition system according to claim 2, characterized in that: The beam expander includes a first off-axis parabolic mirror and a second off-axis parabolic mirror, and the focal lengths of the first off-axis parabolic mirror and the second off-axis parabolic mirror are twice each other.

4. The infrared spectrum signal acquisition system according to claim 2, characterized in that: The vibrometer optical path includes a plurality of second reflectors, the second dichroic mirror and a third dichroic mirror. The second reflectors are respectively arranged between the laser vibrometer and the third dichroic mirror, and between the third dichroic mirror and the second dichroic mirror according to preset angles.

5. The infrared spectrum signal acquisition system according to claim 4, characterized in that: The system also includes a green light LED and a navigation optical path. The green light LED is used to irradiate the emitted LED green light to the surface of the sample to be tested via the navigation optical path. The LED green light is used to assist the mid-infrared laser in positioning on the surface of the sample to be tested. The navigation optical path includes a third reflector and a first dichroic mirror in the mid-infrared optical path and the optical elements thereafter.

6. The infrared spectrum signal acquisition system according to claim 5, characterized in that: The first to third reflecting mirrors are all gold film reflecting mirrors.

7. The infrared spectrum signal acquisition system according to claim 1, characterized in that: The system also includes an image sensor and a lighting device. The optical path system also includes an imaging optical path and an illumination optical path. The image sensor and the lighting device are electrically connected to the main control machine respectively. The lighting device is used to illuminate the sample surface through the illumination optical path, and the image sensor is used to collect an optical image of the sample surface through the imaging optical path.

8. The infrared spectrum signal acquisition system according to any one of claims 1 to 7, characterized in that: The optical path system also includes a reflective objective lens, which is arranged between the end of each optical path and the sample displacement stage and is used to focus the light beam of each optical path onto the sample surface and collect the vibration measurement light reflected by the sample surface.

9. The infrared spectrum signal acquisition system according to claim 1, characterized in that: The system further comprises a lock-in amplifier, the input of which is respectively connected to the mid-infrared laser and the laser vibrometer, and the output of which is connected to the main control computer.

10. A method for collecting infrared spectrum signals, characterized in that: Applied to the infrared spectrum signal acquisition system according to any one of claims 1 to 9, the method comprising: The mid-infrared pulse laser emitted by the mid-infrared laser is irradiated onto the surface of the sample to be tested through a mid-infrared optical path to generate a photothermal vibration signal; The vibrometer laser emitted by the laser vibrometer is irradiated onto the surface of the sample to be tested through the vibrometer optical path to collect the photothermal vibration signal of the surface of the sample to be tested.

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