Atomic fluorescence terahertz thermometry device and method

Abstract

This invention provides an atomic fluorescence terahertz temperature measurement device, comprising a filtering module, an atomic fluorescence conversion module, and a temperature measurement data processing module connected sequentially via an optical signal. The filtering module modulates and filters the target thermal radiation signal to obtain a terahertz signal. The atomic fluorescence conversion module converts the terahertz signal into visible light fluorescence and acquires the fluorescence intensity signal through a PDA detector. The temperature measurement data processing module performs phase-sensitive detection between the visible light fluorescence intensity signal and a reference signal provided by a chopper using a lock-in amplifier, extracting the effective target signal with the same frequency as the reference signal from the visible light fluorescence intensity signal, amplifying it, and simulating the temperature of the object under test. This invention, through the synergistic effect of the filtering module and the lock-in amplifier module, converts the thermal radiation signal into an optical signal, extracts the effective signal from the noise background, improves the signal-to-noise ratio, and simultaneously improves the temperature measurement efficiency, sensitivity, and resolution.

Description

Technical Field

[0001] This invention relates to the field of temperature measurement technology, and in particular to a temperature measurement technology. Background Technology

[0002] Terahertz technology, as a rapidly developing emerging technology in recent years, possesses unique advantages such as strong penetration, minimal damage to living organisms, and the ability to reflect the vibration and rotation information of matter molecules. It has shown great potential in imaging, detection, and communication. Among these, traditional terahertz thermal radiation imaging technology images based on the terahertz waves emitted by the object being measured, without the need for an active light source. It has seen initial applications in covert detection and non-destructive testing, becoming one of the research hotspots in the field of temperature measurement.

[0003] The core principle of traditional terahertz thermal radiation measurement technology is that any object with a temperature above absolute zero (-273.15℃) radiates electromagnetic waves, and the radiation intensity in the terahertz band is quantitatively correlated with the object's temperature (following Planck's blackbody radiation law). This technology receives the terahertz waves radiated by the object using a terahertz detector, converts them into electrical signals, processes the signals to obtain a terahertz thermal radiation image of the object, and finally calculates the object's temperature based on the correlation between radiation intensity and temperature.

[0004] Current mainstream terahertz thermal radiation temperature measurement technologies have several drawbacks: extremely low signal sensitivity, insufficient accuracy at low temperatures, and susceptibility to interference from inherent noise (such as thermal noise and current noise) and environmental noise (such as background terahertz radiation) when faced with weak thermal radiation signals, making signal extraction difficult. They also have poor environmental adaptability and weak anti-interference capabilities. These technologies have extremely stringent requirements for the measurement environment, and background terahertz radiation, electromagnetic interference, and humidity changes in the environment can all seriously affect the measurement results.

[0005] Therefore, developing a terahertz temperature measurement system that can overcome the above limitations and achieve high sensitivity, high resolution, strong anti-interference, and wide temperature range applicability has become an urgent need in the field of temperature measurement technology. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an atomic fluorescence terahertz thermometry device and method with high sensitivity, high resolution, strong anti-interference, and wide temperature range applicability.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: On one hand, the present invention provides an atomic fluorescence terahertz temperature measuring device, comprising a filtering module, an atomic fluorescence conversion module, and a temperature measurement data processing module connected in sequence via optical signals. The filtering module is used to frequency modulate and filter the target thermal radiation signal to obtain a filtered terahertz signal. The atomic fluorescence conversion module receives the modulated and filtered terahertz signal and converts it into visible fluorescence, and collects the visible fluorescence intensity signal through a PDA detector. The temperature measurement data processing module is used to perform phase-sensitive detection on the visible light fluorescence intensity signal and the reference signal provided by the chopper through a lock-in amplifier, extract the effective target signal in the visible light fluorescence intensity signal that is in the same frequency as the reference signal, amplify the effective target signal, and calculate and simulate the temperature of the object under test based on the amplified effective target signal.

[0008] Preferably, the filtering module includes a chopper, a lens group, and a filter connected in sequence via optical signals.

[0009] Preferably, the filter is a narrowband filter with a bandwidth of 10G.

[0010] Preferably, the atomic fluorescence conversion module includes an atomic gas chamber and a PDA detector. The cesium atoms in the atomic gas chamber are excited by three laser beams to produce fluorescence. The three laser beams are stabilized and locked by saturated absorption stabilization and EIT stabilization respectively, which excites the atoms in the atomic gas chamber to the Rydberg state and produces Rydberg fluorescence. The filtered terahertz signal interacts with the atoms to transfer the atoms to the Rydberg state and produce visible light fluorescence. The PDA detector uses the visible light fluorescence intensity.

[0011] Preferably, the wavelengths of the three laser beams are 852nm, 1470nm, and 822nm, respectively.

[0012] Preferably, the temperature data processing module includes a lock-in amplifier and a computer. The lock-in amplifier is used to amplify the visible light fluorescence intensity. The computer calculates the temperature relationship curve of the visible light fluorescence intensity based on the relationship between the amplified visible light fluorescence intensity and temperature, and simulates the temperature of the object being measured.

[0013] On the other hand, the present invention provides an atomic fluorescence terahertz temperature measurement method, which applies the above-mentioned atomic fluorescence terahertz temperature measurement device, characterized by comprising the following steps: Step S1: The thermal radiation signal emitted by the analyte is input to the filtering module, where it is frequency modulated and filtered to obtain the filtered terahertz signal, which is then input to the atomic fluorescence conversion module. Step S2: The atomic fluorescence conversion module receives the modulated and filtered terahertz signal and converts it into visible fluorescence, and collects the visible fluorescence intensity signal through a PDA detector; Step S3: The temperature measurement data processing module performs phase-sensitive detection on the visible light fluorescence intensity signal through a lock-in amplifier and a reference signal provided by a chopper, extracts the effective target signal in the visible light fluorescence intensity signal that has the same frequency as the reference signal, amplifies the effective target signal, and calculates and simulates the temperature of the object under test based on the amplified effective target signal.

[0014] Preferably, in step S1, the filtering module modulates the signal at the output port of the signal under test through the chopper, and then uses a combination of a narrow bandwidth filter with a bandwidth of 10G and a waveguide to filter out interference noise, filter the infrared signal, and generate an effective terahertz signal in the terahertz band.

[0015] Preferably, in step S2, cesium atoms in the atomic gas cell are excited by three laser beams to generate fluorescence, and the three laser beams are stabilized and locked by saturated absorption frequency stabilization and EIT frequency stabilization respectively, so that the atoms in the gas cell are excited to the Rydberg state and generate Rydberg fluorescence. The terahertz signal interacts with the atoms to transfer the atoms to the Rydberg state. When the atoms de-excite, they emit visible light fluorescence, and the intensity of visible light fluorescence is collected by a PDA detector.

[0016] Preferably, in step S3, the effective target signal is amplified by a phase-locked loop (PLL).

[0017] The above-mentioned solution of the present invention includes at least the following beneficial effects: the present invention converts thermal radiation signals into optical signals through the synergistic effect of the filtering module and the lock-in amplification module, extracts effective signals from the noise background, and the filtering technology further removes interference noise in the signal, thereby improving the signal-to-noise ratio of the signal; The target signal is amplified by the temperature measurement data processing module and then processed by the algorithm to obtain the curve of fluorescence intensity versus temperature change. This realizes the conversion of thermal radiation signal into optical signal and then calculates the temperature of the object being measured, which greatly improves temperature measurement efficiency, sensitivity and resolution. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an atomic fluorescence terahertz temperature measuring device.

[0019] Figure 2 This is a flowchart of a method for atomic fluorescence terahertz thermometry.

[0020] Names of the components in the diagram: I-Filtering module, II-Atomic fluorescence conversion module, III-Temperature measurement data processing module; 1-Sample stage, 2-Chopper, 3-Lens group, 4-Filter, 5-Atomic gas cell, 6-PDA detector, 7-Lock-in amplifier, 8-Computer. Detailed Implementation

[0021] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0022] like Figure 1 An atomic fluorescence terahertz temperature measuring device includes a filtering module, an atomic fluorescence conversion module, and a temperature measurement data processing module connected in sequence via optical signals. The filtering module is used to frequency modulate and filter the target thermal radiation signal to obtain a filtered terahertz signal. The atomic fluorescence conversion module receives the modulated and filtered terahertz signal and converts it into visible fluorescence, and collects the visible fluorescence intensity signal through a PDA detector. The temperature measurement data processing module is used to perform phase-sensitive detection on the visible light fluorescence intensity signal and the reference signal provided by the chopper through a lock-in amplifier, extract the effective target signal in the visible light fluorescence intensity signal that is in the same frequency as the reference signal, amplify the effective target signal, and calculate and simulate the temperature of the object under test based on the amplified effective target signal.

[0023] Specifically, the filtering module includes a chopper 2, a lens group 3, and a filter 4 connected in sequence via optical signals. The filter 4 is a narrowband filter with a bandwidth of 10G.

[0024] The object to be tested is placed stably in the center of the sample stage 1. The height of the sample stage 1 can be adjusted according to the shape and size of the object to be tested to ensure that the radiation area of ​​the object to be tested is on the same horizontal line as the subsequent optical path.

[0025] The working principle of the filtering module is as follows: Chopper 2 is turned on, and the modulation frequency is set to 100Hz (square wave output, duty cycle 50%) through its matching control software. The blade speed of chopper 2 is confirmed to be stable (speed error ≤ ±2%) to ensure uniform modulation of thermal radiation signal. Then, the signal is passed through a narrowband filter 4 with a bandwidth of 10G. The center frequency of filter 4 is matched with the 321GHz terahertz band to ensure that infrared band (1~10μm) and visible light signals can be effectively filtered out, while retaining terahertz signal.

[0026] The filtered terahertz signal from filter 4 can directly enter the atomic gas chamber 5. In this embodiment, the terahertz signal enters the atomic gas chamber 5 after being reflected by a mirror. In actual operation, the specific connection settings are determined according to the actual application scenario.

[0027] The atomic fluorescence conversion module includes an atomic gas chamber 5 and a PDA detector 6. In the atomic gas chamber, cesium atoms are excited by three laser beams to generate fluorescence. The three laser beams are frequency-stabilized and locked using saturable absorption and EIT stabilization, respectively, exciting the atoms in the atomic gas chamber to the Rydberg state, producing Rydberg fluorescence. The filtered terahertz signal interacts with the atoms, causing them to transfer to the Rydberg state, generating visible fluorescence. The PDA detector uses the intensity of this visible fluorescence. The wavelengths of the three laser beams are 852 nm, 1470 nm, and 822 nm, respectively.

[0028] Specifically, cesium atoms in atomic gas chamber 5 are lasers with three wavelengths used for laser frequency locking. Using the 852nm probe light, 1470nm coupling light, and 822nm Rydberg light, a saturated absorption frequency stabilization optical path (for the 852nm laser) and an EIT frequency stabilization optical path (for the 1470nm laser) are constructed. The 852nm laser is split into two beams via a PBS, and optical mirrors are used to make them collide within the atomic gas chamber to achieve saturated absorption frequency stabilization. The 852nm laser and the 1470nm laser collide within the atomic gas chamber to achieve EIT frequency stabilization. Finally, the three laser beams of 852nm, 1470nm, and 822nm collide within the atomic gas chamber to achieve EIT frequency stabilization for the 852nm laser. Within the atomic chamber 5, cesium atoms undergo a three-step excitation process using three laser beams, sequentially completing energy level transitions (from the ground state to an intermediate state, then to an excited state, and finally to the initial Rydberg state). The terahertz waves, after passing through a filtering module, interact with the cesium atoms in chamber 5, incoherently transferring them from the initial Rydberg state to a specific Rydberg state. When the atoms de-excite from this specific Rydberg state, the spontaneously emitted fluorescence is emitted in the visible light band and received by a PDA detector 6.

[0029] The temperature measurement data processing module includes a lock-in amplifier 7 and a computer 8. The lock-in amplifier 7 is used to amplify the visible light fluorescence intensity. The computer 8 obtains the visible light fluorescence intensity temperature relationship curve by analyzing the relationship between the amplified visible light fluorescence intensity and temperature, and calculates and simulates the temperature of the object being measured.

[0030] Specifically, the PDA detector 6 in the atomic fluorescence conversion module is connected to the lock-in amplifier 7. The 100Hz square wave signal output by the chopper 2 is used as the reference signal and connected to the "reference input" terminal of the lock-in amplifier 7 through another BNC signal line. The amplification factor of the lock-in amplifier 7 is set to 104 times (which can be flexibly adjusted according to the fluorescence signal intensity), and the integration time is 10ms to ensure that the effective fluorescence signal with the same frequency and phase as the reference signal can be accurately extracted.

[0031] The lock-in amplifier 7 uses phase-sensitive detection technology to perform multiplication and integration on the input fluorescence signal and the reference signal, filter out noise that is not at the same frequency as the reference signal (such as environmental radiation interference and detector noise), extract the effective fluorescence signal and amplify it according to a certain ratio; the amplified effective signal is transmitted to the computer 8 via a USB data cable.

[0032] The fluorescence intensity amplitude is obtained through lock-in amplifier 7, and the fluorescence intensity amplitude map is extracted by computer 8. A preset "fluorescence intensity-temperature" calibration curve is called, and the fluorescence intensity amplitude is fitted and calculated using the least squares method to obtain the real-time temperature value of the object under test. Then, by repeatedly probing the object at different temperatures, the intensity distribution map of the thermal radiation amplitude signal with different temperatures is reconstructed. If the temperature distribution of the object under test needs to be obtained, the sample stage 1 can use a digitally controlled translation stage. By moving the object under test, fluorescence intensity signals at different positions are collected. Based on the signal amplitude at each position, combined with the calibration curve, the thermal radiation intensity distribution map and temperature distribution map of the object under test are reconstructed and can be displayed on the computer screen in real time.

[0033] In summary, this device employs a filtering module and a temperature data processing module to jointly filter and amplify the signal. A chopper is placed after the object under test to provide a modulation signal. The chopper modulates the signal into a high-frequency square wave signal (or a sine wave signal, depending on the chopper type; this system uses a square wave signal). This signal is then filtered by a narrowband filter with a bandwidth of 10G and transmitted to the "signal input" terminal of the lock-in amplifier. A reference square wave of the same frequency generated by the same signal generator is connected to the "reference input" terminal of the lock-in amplifier, which extracts the target signal. The lock-in amplifier module uses an OE2031 lock-in amplifier with a measurement frequency of 10μHz-10MHz. Its working principle is based on phase-sensitive detection technology, performing multiplication and integration operations on the input signal and the reference signal. The reference signal is in phase and frequency with the effective signal in the measured signal. In this way, the lock-in amplifier can extract the effective signal in phase and frequency with the reference signal from the noise background and amplify it, effectively suppressing noise interference and greatly improving the detection accuracy and reliability of the signal.

[0034] like Figure 2 As shown, an atomic fluorescence terahertz thermometry method is described. The logic of the method and device is as follows: object temperature → terahertz wave radiation intensity → Rydberg atomic fluorescence intensity → (filtering + latching) purified signal → temperature deduction from calibration curve.

[0035] Specifically, the method involves the following steps: Step S1: The thermal radiation signal emitted by the analyte is input to the filtering module, where it is frequency modulated and filtered to obtain the filtered terahertz signal, which is then input to the atomic fluorescence conversion module. In step S1, the filtering module filters the thermal radiation signal of the object under test. The thermal radiation signal under test is frequency modulated at the output port of the signal under test by a chopper. Then, a combination of a narrow bandwidth filter with a bandwidth of 10G and a waveguide is used to filter out interference noise from the thermal radiation signal under test, filter out infrared signals, retain the effective signal in the terahertz band, and obtain the terahertz signal.

[0036] Step S2: The atomic fluorescence conversion module receives the modulated and filtered terahertz signal and converts it into visible fluorescence, and collects the visible fluorescence intensity signal through a PDA detector; In step S2, the signal after passing through the filtering module enters the atomic gas chamber in the atomic fluorescence conversion module. Cesium atoms in the atomic gas chamber are excited by three laser beams to generate fluorescence. The three laser beams are stabilized and locked by saturated absorption frequency stabilization and EIT frequency stabilization respectively, exciting the atoms in the gas chamber to the Rydberg state and generating Rydberg fluorescence. The terahertz signal interacts with the atoms to transfer the atoms to the Rydberg state. When the atoms de-excite, they emit visible fluorescence, and the intensity of the visible fluorescence is collected by a PDA detector.

[0037] Step S3: The temperature measurement data processing module performs phase-sensitive detection on the visible light fluorescence intensity signal through a lock-in amplifier and a reference signal provided by a chopper, extracts the effective target signal in the visible light fluorescence intensity signal that has the same frequency as the reference signal, amplifies the effective target signal, and calculates and simulates the temperature of the object under test based on the amplified effective target signal.

[0038] The acquired fluorescence intensity signal is passed through a lock-in amplifier and compared with a reference signal provided by a chopper using the same lock-in amplifier for phase-sensitive detection. The effective target signal with the same frequency as the reference signal is extracted and amplified to improve the signal-to-noise ratio. The signal acquired by the PDA detector, after lock-in amplification, yields a thermal radiation intensity signal with an even higher signal-to-noise ratio. The amplitude signal is analyzed using computer software, and based on the relationship between atomic fluorescence intensity and temperature, a temperature curve is obtained to calculate and simulate the temperature of the measured object.

[0039] It should be noted that this device is a device corresponding to the above method. All implementation methods in the above method embodiments are applicable to this embodiment and can achieve the same technical effect.

[0040] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An atomic fluorescence terahertz thermometer, characterized in that, This includes a filtering module, an atomic fluorescence conversion module, and a temperature data processing module, which are connected sequentially via optical signals. The filtering module is used to frequency modulate and filter the target thermal radiation signal to obtain a filtered terahertz signal. The atomic fluorescence conversion module receives the modulated and filtered terahertz signal and converts it into visible fluorescence, and collects the visible fluorescence intensity signal through a PDA detector. The temperature measurement data processing module is used to perform phase-sensitive detection on the visible light fluorescence intensity signal and the reference signal provided by the chopper through a lock-in amplifier, extract the effective target signal in the visible light fluorescence intensity signal that is in the same frequency as the reference signal, amplify the effective target signal, and calculate and simulate the temperature of the object under test based on the amplified effective target signal.

2. The atomic fluorescence terahertz thermometer as described in claim 1, characterized in that, The filtering module includes a chopper, a lens group, and a filter connected in sequence via optical signals.

3. The atomic fluorescence terahertz thermometer as described in claim 2, characterized in that, The filter is a narrowband filter with a bandwidth of 10G.

4. The atomic fluorescence terahertz thermometer as described in claim 1, characterized in that, The atomic fluorescence conversion module includes an atomic gas chamber and a PDA detector. The cesium atoms in the atomic gas chamber are excited by three laser beams to produce fluorescence. The three laser beams are stabilized and locked by saturated absorption stabilization and EIT stabilization respectively, which excites the atoms in the atomic gas chamber to the Rydberg state and produces Rydberg fluorescence. The filtered terahertz signal interacts with the atoms to transfer the atoms to the Rydberg state and produce visible light fluorescence. The PDA detector uses the visible light fluorescence intensity.

5. The atomic fluorescence terahertz thermometer as described in claim 4, characterized in that, The three laser beams have wavelengths of 852nm, 1470nm, and 822nm, respectively.

6. The atomic fluorescence terahertz thermometer as described in claim 1, characterized in that, The temperature measurement data processing module includes a lock-in amplifier and a computer. The lock-in amplifier is used to amplify the visible light fluorescence intensity. The computer calculates the temperature relationship curve of the visible light fluorescence intensity based on the relationship between the amplified visible light fluorescence intensity and temperature, and simulates the temperature of the object being measured.

7. An atomic fluorescence terahertz thermometry method, employing an atomic fluorescence terahertz thermometry device as described in any one of claims 1-6, characterized in that, Includes the following steps: Step S1: The thermal radiation signal emitted by the analyte is input to the filtering module, where it is frequency modulated and filtered to obtain the filtered terahertz signal, which is then input to the atomic fluorescence conversion module. Step S2: The atomic fluorescence conversion module receives the modulated and filtered terahertz signal and converts it into visible fluorescence, and collects the visible fluorescence intensity signal through a PDA detector; Step S3: The temperature measurement data processing module performs phase-sensitive detection on the visible light fluorescence intensity signal through a lock-in amplifier and a reference signal provided by a chopper, extracts the effective target signal in the visible light fluorescence intensity signal that has the same frequency as the reference signal, amplifies the effective target signal, and calculates and simulates the temperature of the object under test based on the amplified effective target signal.

8. The atomic fluorescence terahertz thermometry method as described in claim 7, characterized in that, In step S1, the filtering module modulates the frequency of the signal at the output port of the signal under test through the chopper, and then uses a combination of a narrow bandwidth filter with a bandwidth of 10G and a waveguide to filter out interference noise, filter infrared signals, and generate an effective terahertz signal in the terahertz band.

9. The atomic fluorescence terahertz thermometry method as described in claim 7, characterized in that, In step S2, cesium atoms in the atomic gas chamber are excited by three laser beams to generate fluorescence. The three laser beams are then frequency-locked using saturated absorption frequency stabilization and EIT frequency stabilization to excite the atoms in the gas chamber to the Rydberg state, generating Rydberg fluorescence. The terahertz signal interacts with the atoms, causing them to transfer to the Rydberg state. When the atoms de-excite, they emit visible fluorescence, and the intensity of the visible fluorescence is collected by a PDA detector.

10. The atomic fluorescence terahertz thermometry method as described in claim 7, characterized in that, In step S3, the effective target signal is amplified by a phase-locked loop.

Images