Substance spectrum low-temperature measurement system and method based on thermostat

Abstract

The invention provides a substance spectrum low-temperature measurement method based on a thermostat, and the system comprises a time-varying radiation module which is used for generating modulated light; the low-temperature photoacoustic module is used for focusing the modulated light and generating a photoacoustic signal; the automatic control module is used for controlling the intensity change of the modulated light and the temperature in the low-temperature photoacoustic module; and the signal detection module is used for detecting the photoacoustic signal to obtain the spectral characteristics of the to-be-detected sample. The high-power xenon lamp serves as a light source, the monochromator and the photochopper are adopted to achieve light modulation, intensity control over modulated light is carried out through the control end so as to obtain different photoacoustic signals, the photoacoustic cell is optimally designed through the optical fiber leading-in technology, the photoacoustic conversion capacity of the photoacoustic cell is improved, and the photoacoustic effect of the photoacoustic cell is improved. The sensitivity of the photoacoustic cell and the signal-to-noise ratio of the system are improved, meanwhile, the temperature of the photoacoustic cell is reasonably controlled by adopting a thermostat, spectral measurement of substances in a low-temperature state is realized, and finally, effective extraction of weak signals is realized by adopting a cross-correlation method.

Description

Technical Field

[0001] The present invention relates to the technical field of spectral low-temperature measurement, and in particular to a method for measuring the spectral low-temperature of a material based on a thermostat. Background Art

[0002] Photoacoustic spectroscopy is a technology that achieves spectral measurement by measuring the thermal properties of samples. It determines the heat generated by measuring the changes in the volume and pressure of the sample or the coupling parts in contact with the sample. It has the characteristics of high sensitivity and strong universality. It is particularly suitable for the detection of strongly scattering and non-transparent samples. It has been widely used in biomedicine, physics, chemistry and environmental monitoring. The photoacoustic spectroscopy technology has the following characteristics:

[0003] 1. The photoacoustic signal of photoacoustic detection directly depends on the amount of light energy absorbed by the material, so the interference of reflected light, scattered light, etc. on photoacoustic detection is very small. For weak absorption samples, the incident light power can be increased, thereby improving the signal-to-noise ratio of the detection. Therefore, it can be successfully used to detect the absorption or absorption spectrum of various samples, transparent or opaque solids, liquids, gases, powders, colloids, crystals or amorphous materials. At the same time, it is also the only method that can be used to detect the absorption spectrum of the sample surface; 2. In photoacoustic detection, the sample itself is both the object of study and the detector that absorbs electromagnetic radiation. Therefore, it can be studied in a very wide range of optical and electromagnetic wavelengths without changing the detection system, and the sample does not need to be pre-processed to destroy the initial state of the sample; 3. The photoacoustic signal is generated when the material molecules absorb the external incident energy modulated by intensity and transition from the excited state to the low energy state through a non-radiative process. Therefore, it is complementary to the radiation process and photochemical process after the material is excited. Therefore, the photoacoustic effect itself is an extremely sensitive and effective method for studying the fluorescence, photoelectric and photochemical phenomena of materials; 4. The photoacoustic effect is not only a spectroscopic technique that can be used to measure the absorption spectrum of materials, but also can be used to study relaxation processes, quantum efficiency of radiation processes, and to measure the thermal properties, elastic properties, film thickness and various non-spectral studies such as sub-surface thermal wave imaging of opaque materials.

[0004] However, the existing technology for measuring the performance parameters of materials at low temperatures is very limited. There are few studies on photoacoustic spectroscopy in low-temperature environments. The structure and use of the equipment used in low-temperature photoacoustic experiments are very complicated. In addition, there is an insurmountable noise influence from the boiling of low-temperature liquids. In addition, the sound signal is not transmitted from the slender tube to the micro-acoustic device outside the pool in an effective way, and is not very practical. Summary of the invention

[0005] In view of this, the present invention proposes a method for measuring low-temperature spectra of materials based on a thermostat to solve the problems existing in the above-mentioned prior art.

[0006] On the one hand, to achieve the above-mentioned purpose, the present invention proposes a thermostat-based material spectrum low-temperature measurement system, including a time-varying radiation module, a low-temperature photoacoustic module, an automatic control module, and a signal detection module;

[0007] The time-varying radiation module, the low-temperature photoacoustic module and the signal detection module are connected in sequence, and the automatic control module is connected to the time-varying radiation module, the low-temperature photoacoustic module and the signal detection module respectively;

[0008] The time-varying radiation module is used to generate modulated light;

[0009] The low-temperature photoacoustic module is used to focus the modulated light and generate a photoacoustic signal;

[0010] The automatic control module is used to control the intensity change of the modulated light and the temperature in the low-temperature photoacoustic module;

[0011] The signal detection module is used to detect the photoacoustic signal and obtain the spectral characteristics of the sample to be tested.

[0012] Furthermore, the time-varying radiation module includes a xenon lamp, a monochromator and a chopper;

[0013] The xenon lamp generates white light, the monochromator splits the white light to generate monochromatic light, and the chopper modulates the light to generate modulated light with periodic intensity changes.

[0014] Furthermore, the low-temperature photoacoustic module includes a low-temperature photoacoustic cell and an optical fiber window. The low-temperature photoacoustic cell is provided with an optical fiber and a sample to be tested. The modulated light is focused through the optical fiber window and transmitted to the sample to be tested through the optical fiber, and the sample to be tested is periodically heated to generate a photoacoustic signal.

[0015] The photoacoustic cell adopts optical fiber introduction technology to irradiate modulated light to the surface of the sample to be tested. The cell body is made of brass, the cell wall is designed as a cylindrical double-cavity structure, and rubber is used between the inner and outer cavities for O-ring sealing.

[0016] Further, the automatic control module includes a thermostat and a control end, the thermostat is arranged in the low-temperature photoacoustic module, and is used to control the temperature in the low-temperature photoacoustic cell, the control end is used to control the luminous power of the xenon lamp and the spectroscopic parameters of the monochromator in the time-varying radiation module, control the amplification parameters of the lock-in amplifier in the signal detection module, control the temperature setting value of the thermostat, and is also used to analyze the photoelectric signal using the cross-correlation detection principle;

[0017] The spectroscopic parameters include wavelength scanning range and detector sensitivity, and the amplification parameters include amplification factor and sensitivity.

[0018] Furthermore, the control end uses serial port RS232 characters to transmit data with the phase-locked amplifier, uses PCT7422 interface to transmit data with the monochromator, and uses serial port RS232 binary characters to transmit data with the thermostat.

[0019] Furthermore, the signal detection module includes a microphone and a phase-locked amplifier. The photoacoustic signal is detected by the microphone and then transmitted to the phase-locked amplifier for amplification. The amplified photoacoustic signal is then transmitted to the control end in the automatic control module for analysis.

[0020] On the other hand, to achieve the above object, the present invention proposes a method for measuring low temperature spectra of materials based on a thermostat, comprising the following steps:

[0021] The automatic control module controls the time-varying radiation module to generate modulated light with periodically varying intensity;

[0022] The low-temperature photoacoustic module focuses the modulated light and transmits it to the sample to be tested to generate a photoelectric signal;

[0023] The signal detection module detects and analyzes the photoelectric signal to obtain the spectral characteristics of the sample to be tested.

[0024] Furthermore, the process in which the automatic control module controls the time-varying radiation module to generate modulated light with periodically varying intensity includes:

[0025] Generate white light by a xenon lamp, split the white light by a monochromator to generate monochromatic light, and modulate the monochromatic light by a chopper to generate modulated light;

[0026] The light emitting power of the xenon lamp and the spectroscopic parameters of the monochromator are adjusted through the control end to generate modulated light with periodic intensity changes.

[0027] Furthermore, the process of the low-temperature photoacoustic module focusing the modulated light and transmitting it to the sample to be tested includes:

[0028] The modulated light is focused through the optical fiber window and transmitted to the sample to be tested in the photoacoustic cell through the optical fiber to heat the sample to be tested. The temperature value of the thermostat is set by the control end to control the temperature in the photoacoustic cell and generate a photoelectric signal.

[0029] Furthermore, the process of the signal detection module detecting and analyzing the photoelectric signal includes:

[0030] The photoacoustic signal is detected by a microphone and then transmitted to a phase-locked amplifier for amplification, and the amplified photoacoustic signal is transmitted to a control end in an automatic control module, and the control end analyzes the photoelectric signal using a cross-correlation detection principle.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The invention uses a high-power xenon lamp as a light source, adopts a monochromator and a chopper to realize light modulation, and controls the intensity of the modulated light through a control end to realize the acquisition of different photoacoustic signals, and adopts an optical fiber introduction technology to optimize the design of the photoacoustic cell to improve its photoacoustic conversion ability, so that the photoacoustic signal measured by the photoacoustic cell can be detected by directly entering a phase-locked amplifier without passing through a preamplifier. The sensitivity of the photoacoustic cell and the signal-to-noise ratio of the system are improved, and a thermostat is used to reasonably control the temperature of the photoacoustic cell to realize the spectrum measurement of the material under low temperature state, and finally the effective extraction of weak signals is realized according to the cross-correlation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0034] Figure 1 Schematic diagram of the structure of a material spectrum low-temperature measurement system in an embodiment of the present invention;

[0035] Figure 2 Schematic diagram of the process of low-temperature measurement of material spectrum in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] Embodiment 1

[0038] This embodiment proposes a thermostat-based material spectrum low-temperature measurement system, such as Figure 1 As shown, it includes a time-varying radiation module, a cryogenic photoacoustic module, an automatic control module, and a signal detection module;

[0039] The time-varying radiation module, the low-temperature photoacoustic module and the signal detection module are connected in sequence, and the automatic control module is connected to the time-varying radiation module, the low-temperature photoacoustic module and the signal detection module respectively;

[0040] The time-varying radiation module is used to generate modulated light;

[0041] The low-temperature photoacoustic module is used to focus the modulated light and generate a photoacoustic signal;

[0042] The automatic control module is used to control the intensity change of the modulated light and the temperature in the low-temperature photoacoustic module;

[0043] The signal detection module is used to detect the photoacoustic signal and obtain the spectral characteristics of the sample to be tested.

[0044] Furthermore, the time-varying radiation module described in this embodiment includes a xenon lamp, a monochromator and a chopper; the xenon lamp generates white light, the monochromator splits the white light to generate monochromatic light, and the chopper modulates the light to generate modulated light with periodic intensity changes.

[0045] As a preferred embodiment, the xenon lamp used in this embodiment is a high-pressure short-arc xenon lamp, the light source luminous power is 350W, equipped with an independent current regulator, the spectrum range is between 270nm and 1000nm, the lamp tube has the advantages of high radiation, multi-line spectrum, high radiation energy in the ultraviolet region, long life, high optical quality, etc., its shell is made of high temperature resistant, transparent, stable quartz glass, the electrodes of the lamp are divided into cathode and anode, the cathode is made of thoriated tungsten or barium tungsten material with good electron emission performance, and the anode is made of high temperature resistant tungsten material. In order to dissipate a large amount of heat generated by electron bombardment through radiation energy, the anode body is significantly larger than the cathode body and is processed into a heat dissipation groove. The lamp is filled with 5 to 8 atmospheres of xenon gas. In arc discharge, the energy lost by elastic collision between electrons and gas is inversely proportional to the atomic weight of the gas, so compared with other inert gases, xenon gas has less loss during arc discharge and high luminous efficiency. At the same time, the ionization potential of xenon gas is low, and the voltage drop near the electrode is small during discharge, which can extend the life of the electrode. At the same time, the high-pressure arc lamp not only has a high luminous efficiency, but also can obtain a continuous broadband spectrum. This broadband spectrum is caused by the pressure broadening effect and is more suitable for spectral detection technology.

[0046] As a preferred embodiment, the chopper uses a dual-frequency chopper disc, which can modulate two beams of light at the same time to obtain two modulation frequencies. Two cable sockets are used to output reference voltage signals of two frequencies, which is suitable for laser, optical or microwave measurement systems in various occasions. In order to be more flexible and convenient to use, a special form is adopted in which the chopper disc is separated from the control part, and the optical path hole of the chopper disc can be rotated at any angle and the height can be adjusted.

[0047] Furthermore, the low-temperature photoacoustic module described in this embodiment includes a low-temperature photoacoustic cell and an optical fiber window. The low-temperature photoacoustic cell is provided with an optical fiber and a sample to be tested. The modulated light is focused through the optical fiber window and transmitted to the sample to be tested through the optical fiber, and the sample to be tested is periodically heated to generate a photoacoustic signal.

[0048] As a preferred embodiment, a significant difference between microphone photoacoustic cell detection technology and other photoacoustic detection technologies is that it has a closed cavity equipped with a microphone and placed in the sample to be tested, i.e., the photoacoustic cell. Since the energy conversion process of light energy-heat energy-acoustic energy in the detection process all occurs in the photoacoustic cell, the design of the photoacoustic cell and the quality of the performance are very important for the improvement and improvement of the photoacoustic detection signal-to-noise ratio. According to the difference in the working mode of the photoacoustic cell, it can be usually divided into two categories: resonant photoacoustic cell and non-resonant photoacoustic cell. The photoacoustic cell that does not have resonance in both acoustics and optics is called a non-resonant photoacoustic cell. The present embodiment adopts a non-resonant optical fiber introduction photoacoustic cell, which adopts the optical fiber introduction technology to concentrate the modulated light on the sample surface to avoid the influence of the photoacoustic effect of the cell wall. At the same time, in order to reduce the influence of the acoustic noise of the boiling solution, the cell wall of the photoacoustic cell is designed as a cylindrical double-cavity structure, and rubber is used between the inner and outer cavities to carry out O-ring sealing, which greatly reduces the noise influence of the system and the outside world through this design, ensures good sound sealing, and reduces the influence of external vibration at the same time.

[0049] As a preferred embodiment, the optical fiber includes a buffer coating, a cladding and a core, wherein the buffer coating, cladding and core are stacked, the buffer coating and cladding are used to protect the optical fiber, the core is used to conduct photoelectric signals, and the refractive index of the core is greater than the refractive index of the cladding.

[0050] Furthermore, the signal detection module includes a microphone and a phase-locked amplifier. The photoacoustic signal is detected by the microphone and then transmitted to the phase-locked amplifier for amplification. The amplified photoacoustic signal is then transmitted to the control end in the automatic control module for analysis.

[0051] The signals output by various photoacoustic detectors are all weak signals, and the signals are easily submerged in noise. In order to extract the signal from the noise, a corresponding weak signal detector must be used. This embodiment uses a phase-locked amplifier, which is also called a phase-locked analyzer. But in fact, its input is an alternating signal, and its output is a DC signal. The phase-locked amplifier is actually an analog correlator. The main part of its noise suppression is the correlator. The correlator is composed of a multiplier and an integrator. The weak signal is extracted by using the mutual irrelevance of the signal and the noise. Since the noise is irrelevant to the signal, the phase of the reference signal can be adjusted so that the phase difference between it and the input signal is 0, thereby maximizing the output signal.

[0052] Furthermore, the automatic control module of this embodiment includes a thermostat and a control end, wherein the thermostat is arranged in the low-temperature photoacoustic module and is used to control the temperature in the low-temperature photoacoustic cell, and the control end is used to control the luminous power of the xenon lamp and the spectroscopic parameters of the monochromator in the time-varying radiation module, control the amplification parameters of the lock-in amplifier in the signal detection module, control the temperature setting value of the thermostat, and is also used to analyze the photoelectric signal using the cross-correlation detection principle;

[0053] The control end uses serial port RS232 characters to carry out data transmission with the phase-locked amplifier, uses PCT7422 interface to carry out data transmission with the monochromator, and uses serial port RS232 binary characters to carry out data transmission with the thermostat;

[0054] Correlation detection technology is a technology that uses the characteristics of signal correlation and noise randomness to remove noise and detect signals through correlation operations. Since signal and noise are independent processes, according to the definition of correlation function, the signal is only related to the signal itself and not to the noise, and the noise is generally unrelated, so this correlation principle can be used to suppress noise and extract signals. The autocorrelation function is used to measure the correlation between two random processes. If the occurrence of two random processes is independent of each other (such as signal and random noise), the cross-correlation function will be a constant, which is equal to the product of the average values ​​of the two random functions. If one of the average values ​​is zero, the cross-correlation function is zero everywhere. Since the pulse width of the pulse signal in the alarm is very small, only a dozen nanoseconds, it is difficult to grasp the delay time t when using autocorrelation, and the anti-interference performance of cross-correlation detection is better than that of autocorrelation detection. Usually, cross-correlation is based on the known repetition period or frequency of the received signal, and a reference signal with the same repetition period as the signal is sent at the receiving end, and the reference signal is correlated with the input signal mixed with noise. In the spectral low temperature detection system, after the modulated pump beam is input into the photoacoustic cell, the sample is heated periodically and the vibration of the adjacent thin layer of air is converted into a photoacoustic signal, which is detected by the detection sensor and transmitted to the phase-locked amplifier to be correlated with the reference signal with the same frequency output by the chopper. In this way, the weak photoacoustic signal buried in the noise is extracted, and the signal-to-noise ratio of the detection is improved.

[0055] Embodiment 2

[0056] This embodiment proposes a method for measuring the low temperature spectrum of a substance based on a thermostat, such as Figure 2 As shown, the following steps are included:

[0057] The automatic control module controls the time-varying radiation module to generate modulated light with periodically varying intensity;

[0058] The low-temperature photoacoustic module focuses the modulated light and transmits it to the sample to be tested to generate a photoelectric signal;

[0059] The signal detection module detects and analyzes the photoelectric signal to obtain the spectral characteristics of the sample to be tested.

[0060] Furthermore, the process in which the automatic control module controls the time-varying radiation module to generate modulated light with periodically varying intensity includes:

[0061] Generate white light by a xenon lamp, split the white light by a monochromator to generate monochromatic light, and modulate the monochromatic light by a chopper to generate modulated light;

[0062] The light emitting power of the xenon lamp and the spectroscopic parameters of the monochromator are adjusted through the control end to generate modulated light with periodic intensity changes.

[0063] Furthermore, the process of the low-temperature photoacoustic module focusing the modulated light and transmitting it to the sample to be tested includes:

[0064] The modulated light is focused through the optical fiber window and transmitted to the sample to be tested in the photoacoustic cell through the optical fiber to heat the sample to be tested. The temperature value of the thermostat is set by the control end to control the temperature in the photoacoustic cell and generate a photoelectric signal.

[0065] Furthermore, the process of the signal detection module detecting and analyzing the photoelectric signal includes:

[0066] The photoacoustic signal is detected by a microphone and then transmitted to a phase-locked amplifier for amplification, and the amplified photoacoustic signal is transmitted to a control end in an automatic control module for analysis.

[0067] The invention uses a high-power xenon lamp as a light source, adopts a monochromator and a chopper to realize light modulation, and controls the intensity of the modulated light through a control end to realize the acquisition of different photoacoustic signals, and adopts an optical fiber introduction technology to optimize the design of the photoacoustic cell to improve its photoacoustic conversion ability, so that the photoacoustic signal measured by the photoacoustic cell can be detected by directly entering a phase-locked amplifier without passing through a preamplifier. The sensitivity of the photoacoustic cell and the signal-to-noise ratio of the system are improved, and a thermostat is used to reasonably control the temperature of the photoacoustic cell to realize the spectrum measurement of the material under low temperature state, and finally the effective extraction of weak signals is realized according to the cross-correlation method.

[0068] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. As for the method disclosed in the embodiment, since it corresponds to the system disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0069] 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-described embodiments, those skilled in the art should understand that any person skilled in the art can still modify the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or perform equivalent replacements on some of the technical features thereof; 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 subject to the protection scope of the claims.

Claims

1. A thermostat-based material spectrum low-temperature measurement system, characterized in that: It includes time-varying radiation module, cryogenic photoacoustic module, automatic control module and signal detection module; The time-varying radiation module, the low-temperature photoacoustic module and the signal detection module are connected in sequence, and the automatic control module is connected to the time-varying radiation module, the low-temperature photoacoustic module and the signal detection module respectively; The time-varying radiation module is used to generate modulated light; The low-temperature photoacoustic module is used to focus the modulated light and generate a photoacoustic signal; The automatic control module is used to control the intensity change of the modulated light and the temperature in the low-temperature photoacoustic module; The signal detection module is used to detect the photoacoustic signal and obtain the spectral characteristics of the sample to be tested.

2. The thermostat-based material spectrum low-temperature measurement system according to claim 1, characterized in that: The time-varying radiation module includes a xenon lamp, a monochromator and a chopper; The xenon lamp generates white light, the monochromator splits the white light to generate monochromatic light, and the chopper modulates the light to generate modulated light with periodic intensity changes.

3. The thermostat-based material spectrum low-temperature measurement system according to claim 1, characterized in that: The low-temperature photoacoustic module comprises a low-temperature photoacoustic cell and an optical fiber window. An optical fiber and a sample to be tested are arranged in the low-temperature photoacoustic cell. The modulated light is focused through the optical fiber window and transmitted to the sample to be tested through the optical fiber, and the sample to be tested is periodically heated to generate a photoacoustic signal. The photoacoustic cell uses optical fiber introduction technology to focus the modulated light on the surface of the sample to be tested. The cell body is made of brass, the cell wall is designed as a cylindrical double-cavity structure, and rubber is used between the inner and outer cavities for O-ring sealing.

4. The thermostat-based material spectrum low-temperature measurement system according to claim 1, characterized in that: The automatic control module includes a thermostat and a control end. The thermostat is arranged in the low-temperature photoacoustic module and is used to control the temperature in the low-temperature photoacoustic cell. The control end is used to control the luminous power of the xenon lamp and the spectroscopic parameters of the monochromator in the time-varying radiation module, control the amplification parameters of the lock-in amplifier in the signal detection module, control the temperature setting value of the thermostat, and is also used to analyze the photoelectric signal using the cross-correlation detection principle. The spectroscopic parameters include wavelength scanning range and detector sensitivity, and the amplification parameters include amplification factor and sensitivity.

5. The thermostat-based material spectrum low-temperature measurement system according to claim 4, characterized in that: The control end uses serial port RS232 characters to transmit data with the phase-locked amplifier, uses PCT7422 interface to transmit data with the monochromator, and uses serial port RS232 binary characters to transmit data with the thermostat.

6. The thermostat-based material spectrum low-temperature measurement system according to claim 1, characterized in that: The signal detection module includes a microphone and a phase-locked amplifier. The photoacoustic signal is detected by the microphone and then transmitted to the phase-locked amplifier for amplification. The amplified photoacoustic signal is then transmitted to the control end in the automatic control module for analysis.

7. A method for measuring low temperature spectra of materials based on the system according to any one of claims 1 to 6, characterized in that: The following steps are involved: The automatic control module controls the time-varying radiation module to generate modulated light with periodically varying intensity; The low-temperature photoacoustic module focuses the modulated light and transmits it to the sample to be tested to generate a photoelectric signal; The signal detection module detects and analyzes the photoelectric signal to obtain the spectral characteristics of the sample to be tested.

8. The thermostat-based low-temperature material spectrum measurement method according to claim 7, characterized in that: The process of the automatic control module controlling the time-varying radiation module to generate modulated light with periodically varying intensity includes: Generate white light by a xenon lamp, split the white light by a monochromator to generate monochromatic light, and modulate the monochromatic light by a chopper to generate modulated light; The light emitting power of the xenon lamp and the spectroscopic parameters of the monochromator are adjusted through the control end to generate modulated light with periodic intensity changes.

9. The thermostat-based low-temperature material spectrum measurement method according to claim 7, characterized in that: The process of the low temperature photoacoustic module focusing the modulated light and transmitting it to the sample to be tested includes: The modulated light is focused through the optical fiber window and transmitted to the sample to be tested in the photoacoustic cell through the optical fiber to heat the sample to be tested. The temperature value of the thermostat is set by the control end to control the temperature in the photoacoustic cell and generate a photoelectric signal.

10. The thermostat-based low-temperature material spectrum measurement method according to claim 7, characterized in that: The process of the signal detection module detecting and analyzing the photoelectric signal includes: The photoacoustic signal is detected by a microphone and then transmitted to a phase-locked amplifier for amplification, and the amplified photoacoustic signal is transmitted to a control end in an automatic control module, and the control end analyzes the photoelectric signal using a cross-correlation detection principle.

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