Spectrum detection data acquisition system and method based on FPGA+SOM

Abstract

The application discloses a spectrum detection data acquisition system and method based on FPGA+SOM, and relates to the technical fields of spectrum detection and data acquisition.The system comprises an optical system, a SOM module and an FPGA module.Laser emitted by a laser in the optical system is transmitted to a photomultiplier tube after oscillation in an optical resonant cavity, the photomultiplier tube converts the optical signal into an electrical signal, i.e., a PMT signal, and sends the PMT signal to the FPGA module, the FPGA module sends a TTL signal to the laser of the optical system for modulating the laser, the FPGA module pre-processes the PMT signal, and sends the pre-processed data to the SOM module, and a spectrum algorithm is arranged in the SOM module, and the pre-processed data is calculated by using the spectrum algorithm.The application is based on the FPGA+SOM architecture mode, and can meet the requirement of fast data processing and has rich external interface resources.

Description

Technical Field

[0001] This invention relates to the field of spectral detection and data acquisition technology, and in particular to a spectral detection data acquisition system and method based on FPGA+SOM. Background Technology

[0002] Currently, with the development of semiconductor chip technology, spectroscopic detection instruments are gradually moving towards miniaturization, fast response, and high sensitivity. Therefore, the iterative development of data acquisition systems is particularly important for spectroscopic detection technology. In data acquisition systems, microcontrollers are typically used as the core, but with the development of FPGA chips in recent years, FPGAs are increasingly being adopted as the core of data acquisition systems to meet the demands of high-speed processing.

[0003] FPGAs, as programmable gate circuits, possess both the fast response and programmability of hardware circuits, leading to their widespread application. While FPGAs offer significant advantages in parallel data processing, their performance in floating-point operations is limited by accuracy and throughput issues. Spectroscopic applications require complex floating-point operations, including nonlinear and exponential data fitting, to achieve system functionality. Therefore, data acquisition systems for spectroscopy typically require an FPGA paired with a multi-core processor. The FPGA handles fast parallel data processing, while the multi-core processors handle complex floating-point operations.

[0004] Currently, the main system architectures are FPGA+ARM and FPGA+DSP. The FPGA+ARM architecture offers high integration, but its disadvantages include relatively low speed and data processing capabilities. While algorithm implementation on DSPs is easier and development costs are lower, and DSP-based processing technologies are widely used in target tracking, radar, sonar, and communications, DSPs have limited external interface resources, making them unable to meet more complex control requirements.

[0005] Chinese Patent Publication No. CN115191989A discloses an integrated human breath detection system based on laser spectroscopy. In this system, a wavelength-tunable semiconductor laser (TDLAS) source emits infrared light of different wavelength bands modulated by wavelength. This light is collected into an optical fiber via a fiber coupler and then split into two infrared laser beams of equal intensity by an optical fiber splitter. One beam irradiates a gas sample containing a marker gas in a sampling chamber, while the other beam is attenuated by an optical fiber attenuator to match the output intensity of the air chamber. A MEMS-SPI spectrometer collects the spectral signals of the infrared light emitted by the different wavelength bands after absorption by the marker gas. Simultaneously, the same sensor system collects the differential signal after passing through the optical fiber attenuator. An FPGA processor performs calculations on the differential digital signal and analyzes the concentration of the marker gas in the sample. However, this patent finds that using an FPGA processor alone cannot handle complex floating-point operations. Furthermore, in situations with high sampling rates, large amounts of data, and complex processing environments, data congestion can occur, making it unsuitable for practical applications.

[0006] Chinese Patent Publication No. CN116660899A discloses a near-field target ISAR imaging system and device based on FPGA+DSP. The system uses an FPGA chip to receive echo data and corresponding parameter information within each pulse; calculates the time-domain and frequency-domain compensation coefficients of the echo data; and compensates the echo data based on these coefficients to obtain the data compensation result. Two multi-core DSP chips alternately receive the data compensation result within one cycle, and perform autofocus processing on the data compensation result within each cycle using a multi-core synchronous parallel processing method to obtain the imaging waveform data, ultimately forming the image. This patent fully utilizes the advantages of FPGA's parallel data processing and the complex floating-point operations and multi-core parallel processing advantages of multi-core DSPs, optimizing the allocation of processing tasks in the imaging algorithm. Although FPGA+DSP can achieve complex floating-point operations, the limited external interface resources of DSPs cannot meet complex control requirements, making it unsuitable for most applications requiring complex control, and also presenting significant development challenges.

[0007] SOM refers to a modular system that provides various core components of an embedded processing system, including CPU, GPU, memory, Wi-Fi, wireless communication, scalable GPIO, and peripherals, on a single printed circuit board (PCB). Summary of the Invention

[0008] To overcome the shortcomings of the prior art, the present invention provides a spectral detection data acquisition system based on FPGA+SOM. Based on the FPGA+SOM architecture, it not only meets the requirements of fast data processing, but also has abundant external interface resources.

[0009] To achieve the above objectives, the present invention adopts the following technical solution, including:

[0010] The spectral detection data acquisition system based on FPGA+SOM includes: optical system, SOM module, and FPGA module;

[0011] The optical system includes a laser, an optical resonant cavity, and a photomultiplier tube (PMT) arranged along the direction of light transmission. The laser emitted by the laser is transmitted to the photomultiplier tube after oscillation in the optical resonant cavity. The photomultiplier tube is used to convert the optical signal into an electrical signal, i.e., the PMT signal, and then sends the PMT signal to the FPGA module.

[0012] The FPGA module is used to generate TTL signals and send the TTL signals to the laser in the optical system for laser modulation.

[0013] The FPGA module preprocesses the PMT signal and sends the preprocessed data to the SOM module; the SOM module is equipped with a spectral algorithm, which is used to calculate the preprocessed data.

[0014] Preferably, the FPGA module includes: a TTL generation module, an AD acquisition module, a TTL status judgment module, and an accumulation and summing module one;

[0015] The TTL generation module is used to generate a fixed frequency TTL signal and send the periodic TTL signal to the laser and the TTL status judgment module respectively.

[0016] The TTL state determination module is used to determine the state of the TTL signal in each cycle, including the states of low level, high-low level, falling edge, and rising edge; the TTL state determination module sends the determination result to the accumulation and summing module one;

[0017] The AD acquisition module is used to receive the PMT signal and perform AD acquisition (analog-to-digital conversion) on the PMT signal to obtain the PMT digital signal; the AD acquisition module sends the PMT digital signal to the accumulation and summing module one;

[0018] The summation module extracts the valid PMT digital signal from the PMT digital signal for each cycle based on the TTL signal state in each cycle. After accumulating the valid PMT digital signals for N cycles, the summation module averages the valid PMT digital signals from the N cycles by dividing the sum by the number of cycles N to obtain the averaged valid PMT digital signal. The summation module then sends the averaged valid PMT digital signal to the SOM module.

[0019] Preferably, the summation module extracts the first valid PMT digital signal from the PMT digital signal when the TTL signal is low in each cycle, averages the first valid PMT digital signals of N cycles, and sends the averaged first valid PMT digital signal to the SOM module.

[0020] The SOM module includes a CRDS spectral algorithm, which calculates the absorption coefficient of the analyte using the ring-down time. Specifically, the SOM module uses the first PMT digital signals received in the background and sample phases respectively to perform exponential fitting to obtain the ring-down times for the background and sample phases, and calculates the absorption coefficient using the following formula:

[0021]

[0022] In the formula, α is the absorption coefficient of the analyte, τ0 is the ringing time in the background stage, τ is the ringing time in the sample stage, and c is the speed of light; wherein, in the background stage, a gas without the analyte is introduced into the optical resonant cavity; and in the sample stage, a gas containing the analyte is introduced into the optical resonant cavity.

[0023] Preferably, the accumulation and summation module extracts the second effective PMT digital signal from the PMT digital signal at the rising edge of the TTL signal in each cycle, averages the second effective PMT digital signals of N cycles, and sends the averaged second effective PMT digital signal to the SOM module.

[0024] The SOM module includes a CEAS spectral algorithm, which calculates the absorption coefficient of the analyte using direct transmitted light intensity. Specifically, the SOM module averages the amplitude values ​​of the second effective PMT digital signals received in the background and sample phases to obtain the direct transmitted light intensity values ​​for both phases, and then calculates the absorption coefficient using the following formula:

[0025]

[0026] In the formula, α is the absorption coefficient of the analyte, I0 is the direct transmitted light intensity in the background stage, I is the direct transmitted light intensity in the sample stage, c is the speed of light, and τ0 is the ringing time in the background stage; wherein, in the background stage, a gas without the analyte is introduced into the optical resonant cavity; and in the sample stage, a gas containing the analyte is introduced into the optical resonant cavity.

[0027] Preferably, the FPGA module includes: a TTL generation module, an AD acquisition module, a digital phase-locked loop module, and an accumulation and summing module 2;

[0028] The TTL generation module is used to generate a fixed frequency TTL signal and send the periodic TTL signal to the laser.

[0029] The AD acquisition module is used to receive the PMT signal and perform AD acquisition (analog-to-digital conversion) on the PMT signal to obtain the PMT digital signal; the AD acquisition module sends the PMT digital signal to the digital phase-locked module.

[0030] The digital phase-locked module is used to demodulate and reduce noise in the PMT digital signal to obtain the amplitude value of the demodulated signal; the digital phase-locked module sends the demodulated signal to the accumulation and summing module two.

[0031] After the second accumulation and summing module accumulates N cycles of demodulated signal, it accumulates the demodulated signal of N cycles and then averages it, that is, it divides the accumulated signal by the number of cycles N to obtain the averaged demodulated signal; the second accumulation and summing module sends the averaged demodulated signal to the SOM module.

[0032] Preferably, in the background stage, a gas without the analyte is introduced into the optical resonant cavity; in the sample stage, a gas containing the analyte is introduced into the optical resonant cavity.

[0033] The SOM module includes an AM-CEAS spectral algorithm, which calculates the absorption coefficient of the analyte using the demodulated signal amplitude value. Specifically, the SOM module obtains the demodulated signal amplitude values ​​for the background and sample stages using the demodulated signals received in the background and sample stages, respectively, and calculates the absorption coefficient using the following formula:

[0034]

[0035] In the formula, α is the absorption coefficient of the analyte, R0 is the amplitude of the demodulated signal in the background stage, R is the amplitude of the demodulated signal in the sample stage, c is the speed of light, and τ0 is the ringing time in the background stage.

[0036] Preferably, the SOM module sends program control instructions to the FPGA module, and the program control instructions are used to control whether the current test stage is the background stage or the sample stage; the FPGA module controls the switching between the background stage and the sample stage of the optical system according to the program control instructions, that is, controls the gas introduced into the optical resonator of the optical system.

[0037] Preferably, the optical system is specifically configured along the light transmission direction with a laser, an optical isolator, a high-reflection mirror one, an optical resonant cavity, a high-reflection mirror two, a filter, and a photomultiplier tube;

[0038] The laser emitted by the laser passes through the optical isolation and enters the optical resonant cavity composed of high-reflection mirror one and high-reflection mirror two. After reflecting back and forth in the optical resonant cavity, the laser passes through high-reflection mirror two and is received by the photomultiplier tube. A filter is placed between high-reflection mirror two and photomultiplier tube. The photomultiplier tube converts the received optical signal into an electrical signal, namely the PMT signal, and finally transmits the PMT signal to the FPGA module through the signal line.

[0039] A modulated laser refers to a laser that uses a TTL signal as its signal source. The laser switches on and off based on the state of the TTL signal. The laser turns on at the rising edge of the TTL signal; it is in the on state when the TTL signal is high; it turns off at the falling edge of the TTL signal; and it is in the off state when the TTL signal is low.

[0040] Preferably, the FPGA module sends the preprocessed data to the SOM module through the transmission module; the transmission module uses a PCI_e IP core.

[0041] This invention also provides a spectral detection data acquisition method based on FPGA+SOM, applicable to the aforementioned spectral detection data acquisition system based on FPGA+SOM. The method includes the following specific steps:

[0042] S1, the SOM module confirms that the current test stage is the background stage, and the FPGA module controls the introduction of gas without the test substance into the optical resonator of the optical system.

[0043] S2, the FPGA module generates a TTL signal and sends it to the laser in the optical system; the laser in the optical system turns on at the rising edge of the TTL signal; the laser is on when the TTL signal is high; the laser turns off at the falling edge of the TTL signal; the laser is off when the TTL signal is low; the laser emitted by the laser is transmitted to the photomultiplier tube after oscillation in the optical resonant cavity. The photomultiplier tube converts the optical signal into an electrical signal, namely the PMT signal, and sends the PMT signal to the FPGA module; the FPGA module preprocesses the PMT signal and sends the preprocessed data to the SOM module;

[0044] S3, the SOM module calculates the relevant parameters of the background stage based on the spectral algorithm after receiving the preprocessed data.

[0045] S4, the SOM module confirms that the current test stage is the sample stage, and the FPGA module controls the introduction of gas containing the substance to be tested into the optical resonant cavity of the optical system.

[0046] S5, the FPGA module generates a TTL signal and sends it to the laser in the optical system. The laser in the optical system turns on at the rising edge of the TTL signal; the laser is on when the TTL signal is high; the laser turns off at the falling edge of the TTL signal; the laser is off when the TTL signal is low. The laser light emitted by the laser is transmitted to a photomultiplier tube (PMT) after oscillation in the optical resonant cavity. The PMT converts the optical signal into an electrical signal and sends it to the FPGA module. The FPGA module preprocesses the PMT signal and sends the preprocessed data to the SOM module.

[0047] S6, the SOM module calculates the relevant parameters of the sample stage based on the spectral algorithm after receiving the preprocessed data.

[0048] After obtaining the relevant parameters of the background stage and the sample stage, the S7 and SOM modules calculate the absorption coefficient of the analyte based on the spectral algorithm.

[0049] The advantages of this invention are:

[0050] (1) This invention proposes a new architecture, namely FPGA+SOM, which can realize fast data processing. The underlying layer uses FPGA programming to realize high-speed parallel operation, and the Windows system is embedded in the SOM. It can utilize rich Windows development resources. The combination of the two avoids the shortcomings of FPGA in complex floating-point operation and fills the shortcomings of SOM in data parallel processing, making full use of the advantages of FPGA parallel data processing and SOM complex floating-point operation.

[0051] (2) The present invention can realize complex control application scenarios, such as switching control between background stage and sample stage, real-time data processing, real-time calculation of absorption coefficient, and real-time display of absorption coefficient curve on user interface.

[0052] (3) The present invention is based on the FPGA+SOM architecture, which not only meets the requirements of fast data processing, but also has rich external interface resources. The SOM integrates Ethernet interface, multiple USB interface, HDMI interface and PCI_e data transmission interface, etc.

[0053] (4) The Windows development environment embedded in SOM is more user-friendly for developers. In addition, the algorithm design can simultaneously implement multiple spectral algorithms such as CRDS, CEA, and AM-CEAS to meet the needs of different detection scenarios.

[0054] (5) The FPGA transmission module adopts the PCI_e IP core, which is a fast data transmission protocol. It can quickly acquire and process the data after the FPGA to transmit it to the SOM for the next step of complex floating-point processing, which largely avoids the situation of FPGA data blocking and improves the real-time performance of the data.

[0055] (6) Setting up a digital phase-locked loop module in the FPGA can further improve the system integration and realize multiple spectral detections such as AM-CEAS. Attached Figure Description

[0056] Figure 1 This is an architecture diagram of a spectral detection data acquisition system based on FPGA+SOM.

[0057] Figure 2 This is a structural diagram of the optical system.

[0058] Figure 3 This is the architecture diagram of the FPGA module.

[0059] Figure 4 The diagram shows the signals.

[0060] Figure 5 This is a schematic diagram of the extraction of the first valid PMT digital signal.

[0061] Explanation of reference numerals in the attached figures:

[0062] 1-Optical system; 2-SOM module; 3-Communication module; 4-Controlled module; 5-FPGA module;

[0063] 11-Laser; 12-Optical isolation; 13-High-reflection mirror one; 14-Optical resonator; 15-High-reflection mirror two; 16-Filter; 17-Photomultiplier tube;

[0064] 41-TTL generation module; 42-AD acquisition module; 43-Digital phase-locked loop module; 44-Accumulation and summation module II; 45-Transmission module; 46-Accumulation and summation module I; 47-TTL status judgment module. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] Depend on Figure 1As shown, the spectral detection data acquisition system based on FPGA+SOM includes: optical system 1, SOM module 2, communication module 3, controlled module 4, and FPGA module 5.

[0067] Depend on Figure 2 As shown, the optical system 1 includes a laser 11, an optical isolator 12, a high-reflection mirror 13, an optical resonator 14, a high-reflection mirror 15, a filter 16, and a PMT (photomultiplier tube) 17 arranged sequentially along the light transmission direction.

[0068] The laser emitted by laser 11, i.e., free-space light, passes through optical isolation 12 and enters the optical resonant cavity 14, which consists of high-reflection mirror 13 and high-reflection mirror 15. The function of optical isolation 12 is to prevent laser 11 from being damaged by the laser reflected back and forth by high-reflection mirror 13 and high-reflection mirror 15. After being reflected back and forth in the optical resonant cavity 14, the laser passes through high-reflection mirror 15 and is received by photomultiplier tube 17. A filter 16 is placed between high-reflection mirror 15 and photomultiplier tube 17 to prevent interference from external stray light. Photomultiplier tube 17 converts the received optical signal into an electrical signal, i.e., a PMT signal, and finally transmits the PMT signal to FPGA module 5 through a signal line.

[0069] The FPGA module 5 internally generates a fixed-frequency (5kHz-35kHz) TTL signal and sends it to the laser 11 in the optical system 1 for laser modulation. The TTL signal includes four states: rising edge, high level, falling edge, and low level. In this embodiment, the amplitude of the low-level TTL signal is 0V, and the amplitude of the high-level TTL signal is 5V. Laser modulation means that the TTL signal serves as the signal source for modulating the laser 11. The laser 11 performs switching actions according to the TTL signal state. At the rising edge of the TTL signal, the laser 11 turns on; at the high level, the laser 11 is in the on state; at the falling edge of the TTL signal, the laser 11 turns off; and at the low level, the laser 11 is in the off state.

[0070] FPGA module 5 receives the PMT signal from photomultiplier tube 17 of optical system 1 and preprocesses the PMT signal. FPGA module 5 then sends the preprocessed data to SOM module 2 via communication module 3. SOM module 2 performs complex floating-point operations and includes a spectral algorithm to calculate the absorption coefficient of the analyte based on the PMT signal in the background and sample phases. Specifically, in the background phase, a dry gas without the analyte is introduced into the optical resonant cavity 14 of optical system 1; in the sample phase, a gas containing the analyte is introduced into the optical resonant cavity 14 of optical system 1.

[0071] The SOM module 2 issues program control instructions to the FPGA module 5 through the communication module 3. The program control instructions are used to control whether the current test stage is the background stage or the sample stage. The FPGA module 5 controls the three-way solenoid valve in the controlled module 4 according to the program control instructions, thereby controlling the gas introduced into the optical resonator 14 of the optical system 1 and realizing the switching between the background stage and the sample stage in the optical system 1.

[0072] As Figure 3 shown, the FPGA module 5 mainly includes a TTL generation module 41, an AD acquisition module 42, a digital phase-locked module 43, an accumulation and summation module II 44, a transmission module 45, an accumulation and summation module I 46, and a TTL state judgment module 47.

[0073] The TTL generation module 41 is used to generate TTL signals with a fixed frequency and send the periodic TTL signals to the laser 11 and the TTL state judgment module 47 respectively. In this embodiment, the TTL signal is as Figure 4 shown in (a) of

[0074] The AD acquisition module 42 is used to receive the PMT signal and perform AD acquisition (i.e., analog-to-digital conversion) on the PMT signal to obtain the PMT digital signal that can be processed inside the FPGA module 5. The AD acquisition module 42 sends the PMT digital signal to the accumulation and summation module I 46 and the digital phase-locked module 43 respectively. In this embodiment, the PMT digital signal is as Figure 4 shown in (c) of

[0075] The TTL state judgment module 47 is used to judge the state of the TTL signal in each period, including the states of low level, high and low level, falling edge and rising edge, and send the judgment result, that is, the state of the TTL signal in each period, to the accumulation and summation module I 46. Among them, the specific method for judging the state of the TTL signal is as follows: The TTL values of 1 and 0 represent the high-level state and low-level state of the TTL signal respectively. The change from 1 to 0 represents the falling edge state; the change from 0 to 1 represents the rising edge state; the TTL state judgment module 47 reads the TTL signal value sent by the TTL generation module 41 at the current sampling point, that is, the TTL signal value A at the current sampling point, and compares it with the TTL signal value sent by the TTL generation module 41 at the previous moment, that is, the TTL signal value B at the previous sampling point. If A < B, it means that the TTL signal is in the falling edge state and the laser 11 is in the closed transition state; if A = B = 0, it means that the TTL signal is in the low-level state and the laser 11 is in the closed state; if A > B, it means that the TTL signal is in the rising edge state and the laser 11 is in the open transition state; if A = B = 1, it means that the TTL signal is in the high-level state and the laser 11 is in the open state.

[0076] The summation module 46 extracts the first valid PMT digital signal when the TTL signal is low from the PMT digital signal according to the TTL signal state in each cycle, thus obtaining the first valid PMT digital signal in each cycle. After accumulating the first valid PMT digital signal in N cycles, the summation module 46 performs bit-by-bit summation and then averages the first valid PMT digital signal in N cycles, that is, the summation is divided by the number of cycles N to obtain the averaged first valid PMT digital signal; the summation module 46 sends the averaged first valid PMT digital signal to the SOM module 2 through the transmission module 45. In this embodiment, the TTL signal is as follows: Figure 4 As shown in (a) above, the PMT digital signal is as follows: Figure 4 As shown in (c) in the diagram. Figure 5 As shown, the circled area represents the extracted first valid PMT digital signal. Furthermore, when the TTL signal is high / low, the PMT digital signal exhibits a level-wise form; when the TTL signal is at a falling / rising edge, the PMT digital signal exhibits an exponential function form.

[0077] The summation module 46 extracts the second valid PMT digital signal at the rising edge of the TTL signal from the PMT digital signal according to the TTL signal state in each cycle, thus obtaining the second valid PMT digital signal in each cycle. After accumulating the second valid PMT digital signal in N cycles, the summation module 46 performs bit-by-bit summation and then averages the bit-by-bit signals, i.e., the summation is divided by the number of cycles N to obtain the averaged second valid PMT digital signal. The summation module 46 then sends the averaged second valid PMT digital signal to the SOM module 2 through the transmission module 45.

[0078] The digital phase-locked loop module 43 is used to demodulate and reduce noise in the PMT digital signal to obtain a demodulated signal. The digital phase-locked loop module 43 sends the demodulated signal to the accumulation and summing module 44. In this embodiment, the original demodulated signal is as follows: Figure 4 As shown in (b) above, the demodulated signal after noise reduction is as follows: Figure 4 As shown in (d) in the figure.

[0079] After accumulating N cycles of demodulated signal, the summation module 2 (44) performs bit-by-bit summation and then averages the N cycles of demodulated signal. That is, the summation is divided by the number of cycles N to obtain the averaged demodulated signal. The summation module 2 (44) then sends the averaged demodulated signal to the SOM module 2 via the transmission module 45, thereby obtaining the amplitude and phase angle of the demodulated signal. In this embodiment, the transmission module 45 uses a packaged PCI_e high-speed data transmission IP core. As a fast data transmission protocol, it can quickly transmit the pre-processed data acquired by the FPGA to the SOM for further complex floating-point processing, largely avoiding FPGA data blocking and improving data real-time performance.

[0080] In this invention, the SOM module 2 embeds a Windows development environment, which can provide multiple spectral algorithms such as CRDS, CEA, and AM-CEAS.

[0081] The CRDS spectral algorithm calculates the absorption coefficient of the analyte using its ring-down time. Specifically, the SOM module 2 uses the first effective PMT digital signals received during the background and sample phases to perform exponential fitting to obtain the ring-down times for both phases, and then calculates the absorption coefficient using the following formula:

[0082]

[0083] In the formula, α is the absorption coefficient of the analyte, τ0 is the ring-down time obtained by exponential fitting of the first effective PMT digital signal in the background stage, τ is the ring-down time obtained by exponential fitting of the first effective PMT digital signal in the sample stage, and c is the speed of light (in m / s).

[0084] The CEAS spectral algorithm calculates the absorption coefficient by directly transmitting light intensity. Specifically, the SOM module 2 averages the amplitude values ​​of the second effective PMT digital signals received in the background and sample phases to obtain the direct transmitted light intensity values ​​for both phases. The absorption coefficient is then calculated using the following formula:

[0085]

[0086] In the formula, α is the absorption coefficient of the analyte, I0 is the direct transmitted light intensity in the background stage, I is the direct transmitted light intensity in the sample stage, c is the speed of light (in m / s), and τ0 is the ringing time in the background stage.

[0087] The AM-CEAS spectral algorithm calculates the absorption coefficient by using the amplitude values ​​of the demodulated signal. Specifically, the SOM module 2 obtains the amplitude values ​​of the demodulated signals received in the background and sample phases, respectively, and calculates the absorption coefficient using the following formula:

[0088]

[0089] In the formula, α is the absorption coefficient of the analyte, R0 is the amplitude of the demodulated signal in the background stage, R is the amplitude of the demodulated signal in the sample stage, c is the speed of light (in m / s), and τ0 is the ringing time in the background stage.

[0090] The above spectral algorithms can simultaneously perform three calculations of the absorption coefficient, and the output frequency can be changed by the frequency of the TTL signal and the number of periods N used for averaging, achieving high throughput output.

[0091] The spectral detection data acquisition method based on FPGA+SOM of the present invention includes the following specific steps:

[0092] S1, SOM module 2 confirms that the current test stage is the background stage, sends program control instructions to FPGA module 5 and controls the introduction of gas without the test substance into the optical resonant cavity 14 of optical system 1 through FPGA module 5.

[0093] S2, FPGA module 5 generates a TTL signal and sends it to laser 11 in optical system 1. Laser 11 in the optical system turns on at the rising edge of the TTL signal; laser 11 is in the on state when the TTL signal is high; laser 11 turns off at the falling edge of the TTL signal; laser 11 is in the off state when the TTL signal is low. The laser emitted by laser 11 is transmitted to photomultiplier tube 17 after oscillation in optical resonant cavity 14. Photomultiplier tube 17 converts the optical signal into an electrical signal, i.e., a PMT signal, and sends the PMT signal to FPGA module 5. FPGA module 5 preprocesses the PMT signal and sends the preprocessed data to SOM module 2. In this embodiment, the preprocessed data is either the extracted valid PMT signal or the demodulated signal obtained by demodulation.

[0094] S3, SOM module 2 calculates the preprocessed data received in the background stage based on the spectral algorithm to obtain relevant parameters for the background stage. In this embodiment, the relevant parameters are the ring-down time, the direct transmitted light intensity value, or the demodulated signal amplitude value.

[0095] S4, SOM module 2 confirms that the current test stage is the sample stage, and controls the optical resonant cavity 14 of optical system 1 to introduce gas containing the substance to be tested through FPGA module 5.

[0096] S5, FPGA module 5 generates a TTL signal and sends it to laser 11 in optical system 1; laser 11 in optical system turns on the laser at the rising edge of the TTL signal; laser 11 is in the on state when the TTL signal is high; laser 11 turns off the laser at the falling edge of the TTL signal; laser 11 is in the off state when the TTL signal is low; the laser emitted by laser 11 is transmitted to photomultiplier tube 17 after oscillation in optical resonant cavity 14. Photomultiplier tube 17 is used to convert the optical signal into an electrical signal, namely PMT signal, and sends the PMT signal to FPGA module 5; FPGA module 5 preprocesses the PMT signal and sends the preprocessed data to SOM module 2.

[0097] S6, SOM module 2 calculates the relevant parameters of the sample stage based on the spectral algorithm after the preprocessed data received in the sample stage.

[0098] S7, after obtaining the relevant parameters for the background and sample stages respectively, the SOM module 2 calculates the absorption coefficient of the analyte based on a spectroscopic algorithm. In this embodiment, CRDS, CEA, or AM-CEAS spectroscopic algorithms can be used.

[0099] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A spectral detection data acquisition system based on FPGA+SOM, characterized in that, The application relates to an optical system (1), a SOM module (2) and an FPGA module (5). The optical system (1) comprises a laser (11), an optical resonant cavity (14) and a PMT (17) arranged along the light transmission direction; the laser (11) transmits laser light to the PMT (17) after the laser light is oscillated by the optical resonant cavity (14); the PMT (17) is used for converting the optical signal into an electrical signal, i.e. a PMT signal, and sending the PMT signal to the FPGA module (5); The FPGA module (5) is used for generating a TTL signal and sending the TTL signal to the laser (11) of the optical system (1) to modulate the laser (11); The FPGA module (5) pre-processes the PMT signal and sends the pre-processed data to the SOM module (2); the SOM module (2) is provided with a spectrum algorithm, and the spectrum algorithm is used for calculating the pre-processed data; The SOM module (2) is provided with a CRDS spectrum algorithm; the FPGA module (5) comprises an accumulation sum module (46); the accumulation sum module (46) extracts a first effective PMT digital signal in each cycle when the TTL signal is at a low level from the PMT digital signal; Alternatively, the SOM module (2) is provided with a CEAS spectrum algorithm; the FPGA module (5) comprises an accumulation sum module (46); the accumulation sum module (46) extracts a second effective PMT digital signal in each cycle when the TTL signal is at a rising edge from the PMT digital signal. The FPGA module (5) comprises a TTL generation module (41), an AD acquisition module (42), a TTL state judgment module (47) and an accumulation sum module (46); 2.The FPGA+SOM based spectral detection data acquisition system of claim 1, wherein, The TTL generation module (41) is used for generating a TTL signal with a fixed frequency and sending the periodic TTL signal to the laser (11) and the TTL state judgment module (47); The TTL state judgment module (47) is used for judging the state of the TTL signal in each cycle, including the states of a low level, a high-low level, a falling edge and a rising edge; the TTL state judgment module (47) sends the judgment result to the accumulation sum module (46); The AD acquisition module (42) is used for receiving the PMT signal, performing AD acquisition, i.e. analog-digital conversion, on the PMT signal to obtain a PMT digital signal; and sending the PMT digital signal to the accumulation sum module (46). ​ The accumulation summation module one (46) extracts valid PMT digital signals in each cycle from the PMT digital signals according to TTL signal states in each cycle; the accumulation summation module one (46) obtains an average valid PMT digital signal by averaging valid PMT digital signals in N cycles after accumulating the valid PMT digital signals in the N cycles; and the accumulation summation module one (46) sends the average valid PMT digital signal to the SOM module (2).

3. The FPGA + SOM based spectral probe data acquisition system according to claim 2, wherein, The accumulation summation module one (46) extracts first valid PMT digital signals in each cycle when the TTL signal is at a low level from the PMT digital signals, averages the first valid PMT digital signals in N cycles, and sends the average first valid PMT digital signal to the SOM module (2). The SOM module (2) is provided with a CRDS spectrum algorithm, the CRDS spectrum algorithm calculates the absorption coefficient of the to-be-measured substance by using the ring-down time; wherein the SOM module (2) obtains the ring-down time of the background stage and the sample stage by performing exponential fitting on the first PMT digital signals received in the background stage and the sample stage, respectively, and calculates the absorption coefficient by the following formula: wherein is the absorption coefficient of the substance to be measured, is the decay time of the background phase, is the decay time of the sample phase, is the speed of light; wherein, in the background phase, a gas not containing the substance to be measured is passed through the optical resonator (14); in the sample phase, a gas containing the substance to be measured is passed through the optical resonator (14). 4.The FPGA+SOM based spectral detection data acquisition system of claim 2, wherein, The accumulation summation module one (46) extracts second valid PMT digital signals in each cycle when the TTL signal is at a rising edge from the PMT digital signals, averages the second valid PMT digital signals in N cycles, and sends the average second valid PMT digital signal to the SOM module (2). The SOM module (2) is provided with a CEAS spectrum algorithm, the CEAS spectrum algorithm calculates the absorption coefficient of the to-be-measured substance by using the direct transmission light intensity; wherein the SOM module (2) obtains the direct transmission light intensity values of the background stage and the sample stage by taking the average of the amplitude values of the second valid PMT digital signals received in the background stage and the sample stage, respectively, and calculates the absorption coefficient by the following formula: wherein is the absorption coefficient of the substance to be measured, is the directly transmitted light intensity of the background phase, is the directly transmitted light intensity of the sample phase, is the speed of light, is the decay time of the background phase; wherein, in the background phase, a gas not containing the substance to be measured is passed through the optical resonator (14); in the sample phase, a gas containing the substance to be measured is passed through the optical resonator (14).

5. The FPGA + SOM based spectral probe data acquisition system as claimed in claim 1, wherein, The FPGA module (5) comprises a TTL generation module (41), an AD acquisition module (42), a digital phase-locked loop module (43), and an accumulation summation module two (44). The TTL generation module (41) is configured to generate a TTL signal with a fixed frequency and send the periodic TTL signal to the laser (11). The AD acquisition module (42) is configured to receive a PMT signal, perform AD acquisition, i.e., analog-to-digital conversion, on the PMT signal, and obtain a PMT digital signal; and the AD acquisition module (42) sends the PMT digital signal to the digital phase-locked loop module (43). The digital phase-locked loop module (43) is configured to demodulate and denoise the PMT digital signal to obtain the amplitude value of the demodulated signal; and the digital phase-locked loop module (43) sends the demodulated signal to the accumulation summation module two (44). The second accumulation sum module (44) obtains the average demodulation signal by accumulating and averaging the demodulation signal of N periods after accumulating the demodulation signal of N periods; and the second accumulation sum module (44) sends the average demodulation signal to the SOM module (2).

6. The FPGA + SOM based spectral probe data acquisition system according to claim 5, wherein, In the background stage, the optical resonant cavity (14) is filled with a gas containing no measured substance; in the sample stage, the optical resonant cavity (14) is filled with a gas containing the measured substance; The SOM module (2) is provided with an AM-CEAS spectrum algorithm, which calculates the absorption coefficient of the measured substance by using the demodulation signal amplitude value; wherein the SOM module (2) obtains the demodulation signal amplitude values of the background stage and the sample stage by using the demodulation signals received in the background stage and the sample stage, and calculates the absorption coefficient by the following formula: wherein is the absorption coefficient of the substance to be measured, is the demodulated signal amplitude value of the background phase, is the demodulated signal amplitude value of the sample phase, is the speed of light, is the decay time of the background phase.

7. The FPGA + SOM based spectral probe data acquisition system according to claim 1, wherein, The SOM module (2) sends a program control instruction to the FPGA module (5), and the program control instruction is used to control the current test stage to be the background stage or the sample stage; and the FPGA module (5) controls the switching of the background stage and the sample stage of the optical system (1) according to the program control instruction, that is, controls the gas filled into the optical resonant cavity (14) of the optical system (1).

8. The FPGA + SOM based spectral probe data acquisition system according to claim 1, wherein, The optical system (1) is specifically provided with a laser (11), an optical isolator (12), a high-reflection mirror one (13), an optical resonant cavity (14), a high-reflection mirror two (15), a filter (16) and a photomultiplier tube (17) along the light transmission direction; The laser emitted by the laser (11) passes through the optical isolator (12) into the optical resonant cavity (14) composed of the high-reflection mirror one (13) and the high-reflection mirror two (15); the laser is received by the photomultiplier tube (17) after being reflected back and forth in the optical resonant cavity (14) and passing through the high-reflection mirror two (15), and the filter (16) is placed between the high-reflection mirror two (15) and the photomultiplier tube (17); the photomultiplier tube (17) converts the received optical signal into an electrical signal, that is, a PMT signal, and finally transmits the PMT signal to the FPGA module (5) through a signal line; The modulated laser (11) means that the TTL signal is used as the signal source of the modulated laser (11), and the laser (11) realizes the opening and closing actions according to the state of the TTL signal; the laser (11) completes the opening action at the rising edge of the TTL signal; the laser (11) is in the opened state under the high level state of the TTL signal; the laser (11) completes the closing action at the falling edge of the TTL signal; and the laser (11) is in the closed state under the low level state of the TTL signal.

9. The FPGA + SOM based spectral probe data acquisition system according to claim 1, wherein, The FPGA module sends the preprocessed data to the SOM module (2) through a transmission module (45); and the transmission module adopts a PCI_e IP core.

10. A spectral detection data acquisition method based on FPGA+SOM, characterized in that, The method comprises the following specific steps: S1, the SOM module (2) confirms that the current test stage is a background stage, and controls the optical resonant cavity (14) of the optical system (1) to pass in a gas without the to-be-tested substance through the FPGA module (5); S2, the FPGA module (5) generates a TTL signal and sends the TTL signal to the laser (11) of the optical system (1); the laser (11) in the optical system completes the opening of the laser at the rising edge of the TTL signal; in the high level state of the TTL signal, the laser (11) is in an open state; the laser (11) completes the closing of the laser at the falling edge of the TTL signal; in the low level state of the TTL signal, the laser (11) is in a closed state; the laser emitted by the laser (11) is transmitted to the photomultiplier tube (17) after oscillation through the optical resonant cavity (14), the photomultiplier tube (17) is used for converting the optical signal into an electrical signal, that is, a PMT signal, and sending the PMT signal to the FPGA module (5); the FPGA module (5) pre-processes the PMT signal and sends the pre-processed data to the SOM module (2); S3, the SOM module (2) calculates the pre-processed data received in the background stage based on a spectrum algorithm to obtain related parameters of the background stage; S4, the SOM module (2) confirms that the current test stage is a sample stage, and controls the optical resonant cavity (14) of the optical system (1) to pass in a gas containing the to-be-tested substance through the FPGA module (5); S5, the FPGA module (5) generates a TTL signal and sends the TTL signal to the laser (11) of the optical system (1); the laser (11) in the optical system completes the opening of the laser at the rising edge of the TTL signal; in the high level state of the TTL signal, the laser (11) is in an open state; the laser (11) completes the closing of the laser at the falling edge of the TTL signal; in the low level state of the TTL signal, the laser (11) is in a closed state; the laser emitted by the laser (11) is transmitted to the photomultiplier tube (17) after oscillation through the optical resonant cavity (14), the photomultiplier tube (17) is used for converting the optical signal into an electrical signal, that is, a PMT signal, and sending the PMT signal to the FPGA module (5); the FPGA module (5) pre-processes the PMT signal and sends the pre-processed data to the SOM module (2); S6, the SOM module (2) calculates the pre-processed data received in the sample stage based on a spectrum algorithm to obtain related parameters of the sample stage; S7, after obtaining the related parameters of the background stage and the sample stage respectively, the SOM module (2) calculates the absorption coefficient of the to-be-tested substance based on a spectrum algorithm.

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