Laser spectrum detection system and control method thereof

Abstract

The invention relates to the technical field of laser spectrum detection, in particular to a laser spectrum detection system and a control method thereof, and the system comprises a main control board, a laser and a detector; the detector is connected with the main control board through the variable gain amplifier, the main control board is connected with the laser, and a light path is formed between the laser and the detector; the laser is used for emitting a laser signal according to a laser instruction of the main control board, so that the laser signal penetrates through to-be-detected gas on a light path to obtain a target laser signal; the detector is used for receiving a target laser signal and outputting an electric signal according to the target laser signal; the variable gain amplifier is used for periodically amplifying the electric signals and outputting a plurality of amplified electric signals to the main control board; and the main control board is also used for determining a target electric signal from the plurality of amplified electric signals under the condition that the electric signals are determined to be unsaturated signals, and obtaining the concentration of the gas to be detected according to the target electric signal. Through the system, the detection accuracy is improved, and the anti-interference capability of the system is enhanced.

Description

Technical Field

[0001] This invention relates to the field of laser spectroscopy detection technology, and in particular to a laser spectroscopy detection system and its control method. Background Technology

[0002] Laser gas absorption spectroscopy (TDLAS) is a gas analysis technique based on laser spectroscopy. It quantifies the concentration of a analyte gas by detecting its absorption characteristics to a specific wavelength of laser light. The core principle is to use a tunable semiconductor laser as the light source, rapidly tuning the laser wavelength within a specific narrow band to precisely match the absorption peak of the analyte gas. When the laser passes through the analyte gas, the gas molecules absorb wavelengths that match its absorption spectrum, resulting in a decrease in light intensity. The remaining light intensity is then received by a detector, and the intensity and shape of the absorption spectrum are calculated to ultimately deduce the concentration of the analyte gas.

[0003] However, in some relatively variable application scenarios, such as those with obstructions, laser gas absorption spectroscopy is prone to weak detection signals. If the photosensitive element of the detector is not saturated, the output signal may become saturated or have an excessively low voltage amplitude during amplification due to an inappropriate amplification factor in the amplifier circuit. This, in turn, reduces the accuracy of the gas concentration detection. Summary of the Invention

[0004] This application provides a laser spectral detection system and its control method, which at least solves the above-mentioned technical problems in the prior art. It achieves the technical effects of setting a reasonable amplification factor for the detector's detection signal, outputting an appropriate amplifier's electrical signal, and then calculating the accurate concentration of the gas to be measured based on the electrical signal, thereby improving the detection accuracy and enhancing the system's anti-interference ability.

[0005] In a first aspect, embodiments of the present invention provide a laser spectral detection system, comprising: a main control board, a laser, a detector, and a variable gain amplifier; the detector is connected to the main control board through the variable gain amplifier, the main control board is also connected to the laser, and an optical path is formed between the laser and the detector;

[0006] The main control board is used to send laser commands to the laser and to send turn-on commands to the variable gain amplifier;

[0007] The laser is used to emit a laser signal according to the laser command, so that the laser signal passes through the gas to be tested in the optical path to obtain the target laser signal;

[0008] The detector is used to receive the target laser signal and output an electrical signal according to the target laser signal;

[0009] The variable gain amplifier is used to periodically amplify the electrical signal and output multiple amplified electrical signals to the main control board. The periodic amplification process is a process of gradually amplifying the electrical signal according to a preset amplification ratio.

[0010] The main control board is also used to determine a target electrical signal from a plurality of amplified electrical signals when the electrical signal is determined to be an unsaturated signal, and to obtain the concentration of the gas to be measured based on the target electrical signal.

[0011] Optionally, determining the target electrical signal from the plurality of amplified electrical signals includes:

[0012] In each of the amplified electrical signals, if the amplitude of the amplified electrical signal is within the set amplitude range and the amplified electrical signal does not have a clipping phenomenon, then the amplified electrical signal is determined to be a qualified electrical signal.

[0013] If the number of qualified electrical signals is one, then the qualified electrical signal is determined as the target electrical signal;

[0014] If there are multiple qualified electrical signals, the qualified electrical signal with the largest amplitude is determined as the target electrical signal.

[0015] Optionally, the main control board is further configured to: after determining the target electrical signal a preset number of times, output the amplification factor corresponding to the target electrical signal to the variable gain amplifier;

[0016] The variable gain amplifier is further configured to: take the corresponding amplification factor as the current amplification factor, and perform amplification processing based on the current amplification factor, so as to facilitate the amplification processing of subsequent electrical signals.

[0017] Optionally, it also includes: an optical power attenuator, which is connected to the main control board and is disposed on the optical path;

[0018] The optical power attenuator is used to attenuate the laser signal to different degrees to obtain an attenuated laser signal, so that the attenuated laser signal can pass through the gas to be tested in the optical path to obtain the target laser signal, thereby preventing the detector from outputting a saturated signal based on the target laser signal.

[0019] Optionally, the optical power attenuator is a chopper, with the input end of the chopper aligned with the output end of the laser and the output end of the chopper aligned with the input end of the detector. The main control board is connected to the chopper via a motor, and the chopper can rotate under the drive of the motor.

[0020] The chopper wheel includes multiple sectors with different optical power attenuation rates. When the chopper wheel rotates, the input ends of the sectors with different optical power attenuation rates are aligned with the output ends of the laser, and the output ends of the sectors with different optical power attenuation rates are aligned with the input ends of the detector.

[0021] Optionally, the optical power attenuator is an adjustable optical attenuator, which is electrically connected to the main control board. The adjustable optical attenuator is used to perform optical power attenuation processing on the laser signal to different degrees to obtain the attenuated laser signal.

[0022] Optionally, the main control board is further used for:

[0023] Acquire the laser signal, the optical power attenuation rate of the optical power attenuator, and the target laser signal;

[0024] Based on the negative feedback control method, the laser signal, the optical power attenuation rate of the optical power attenuator, and the target laser signal are processed to obtain the target optical power attenuation rate;

[0025] The target optical power attenuation rate is output to the optical power attenuator;

[0026] The optical power attenuator is used to: take the target optical power attenuation rate as the current optical power attenuation rate, and perform optical power attenuation processing on the laser signal based on the current optical power attenuation rate to obtain the attenuated laser signal.

[0027] Optionally, the variable gain amplifier is further configured to: amplify the electrical signal according to the current amplification factor of the variable gain amplifier, and output the amplified electrical signal, wherein the amplified electrical signal is the electrical signal corresponding to the current amplification factor;

[0028] The main control board is also used to: acquire the electrical signal corresponding to the current amplification factor;

[0029] Based on the negative feedback control method, the electrical signal corresponding to the current amplification factor and the set electrical signal range are processed to obtain the target amplification factor, and the target amplification factor is output to the variable gain amplifier so that the electrical signal corresponding to the target amplification factor is consistent with the set target electrical signal;

[0030] The variable gain amplifier is further configured to: use the target amplification factor as the current amplification factor, and perform amplification processing based on the current amplification factor, so as to facilitate amplification processing of subsequent electrical signals.

[0031] Optionally, the laser is an electroabsorption modulated laser.

[0032] Based on the same inventive concept, in a second aspect, the present invention also provides a control method for a laser spectral detection system, applied to the laser spectral detection system as described in the first aspect, the control method comprising:

[0033] A laser signal is emitted by a laser, and the laser signal passes through the gas to be measured in the optical path between the laser and the detector to obtain the target laser signal.

[0034] The detector receives the target laser signal and outputs an electrical signal based on the target laser signal.

[0035] The electrical signal is periodically amplified by a variable gain amplifier, and multiple amplified electrical signals are output to the main control board. The periodic amplification process is a process of gradually amplifying the electrical signal according to a preset amplification ratio.

[0036] If the electrical signal is determined to be an unsaturated signal, a target electrical signal is determined from the plurality of amplified electrical signals, and the concentration of the gas to be measured is obtained based on the target electrical signal.

[0037] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0038] In this embodiment of the invention, a variable gain amplifier is installed between the detector and the main control board of the laser spectral detection system. This amplifier periodically amplifies the electrical signal output by the detector, resulting in multiple amplified electrical signals sent to the main control board. The main control board then determines a suitable target electrical signal based on these multiple amplified signals from the variable gain amplifier and obtains the concentration of the gas to be measured from the target signal. Thus, even when the photosensitive element of the detector is not saturated with the detection signal, the detection signal (i.e., the electrical signal) output by the photosensitive element is amplified by the variable gain amplifier to produce an amplified electrical signal with a suitable amplitude, i.e., the target electrical signal. The concentration of the gas to be measured is then analyzed with high accuracy based on the target electrical signal, improving the accuracy and precision of the gas concentration detection. Furthermore, the overall system configuration enhances the anti-interference capability of the entire photodetection process, especially its resistance to optical path interference. Attached Figure Description

[0039] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0040] Figure 1 A schematic diagram of the laser spectral detection system in an embodiment of the present invention is shown;

[0041] Figure 2 This invention provides a schematic diagram of the structure of an obstruction a with a slight degree of obstruction in the optical path, as shown in an embodiment of the invention.

[0042] Figure 3 A schematic diagram of the structure of an obstruction b with a moderate degree of obstruction in the optical path is shown in an embodiment of the present invention;

[0043] Figure 4 A schematic diagram of the structure of an obstruction c with a severe degree of obstruction on the optical path is shown in an embodiment of the present invention;

[0044] Figure 5 A schematic diagram of the structure of a laser spectral detection system with a chopper wheel according to an embodiment of the present invention is shown;

[0045] Figure 6 A schematic diagram of the structure of a blockage a with a slight degree of obstruction in the optical path of a laser spectral detection system with a chopper wheel in an embodiment of the present invention is shown.

[0046] Figure 7 A schematic diagram of a laser spectral detection system with a chopper wheel in an embodiment of the present invention is shown, showing a blockage b with a moderate degree of obstruction in the optical path.

[0047] Figure 8 A schematic diagram of the structure of an obstruction c with a severe degree of obstruction is shown in the optical path of the laser spectral detection system with a chopper wheel in an embodiment of the present invention.

[0048] Figure 9 A schematic diagram of the structure of a laser spectral detection system with an adjustable optical attenuator according to an embodiment of the present invention is shown;

[0049] Figure 10 A schematic flowchart of the control method for the laser spectral detection system in an embodiment of the present invention is shown. Detailed Implementation

[0050] 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.

[0051] Example 1

[0052] The first embodiment of the present invention provides a laser spectral detection system, such as... Figure 1 As shown, it includes: a main control board, a laser, a detector, and a variable gain amplifier. The detector is connected to the main control board via the variable gain amplifier, and the main control board is also connected to the laser, forming an optical path between the laser and the detector.

[0053] The main control board sends laser commands to the laser and activation commands to the variable gain amplifier. The laser command instructs the laser to emit laser light, while the activation command puts the variable gain amplifier into operation.

[0054] A laser is used to emit a laser signal according to a laser command, so that the laser signal passes through the gas to be tested in the optical path to obtain the target laser signal. It should be noted that when the laser signal passes through the gas to be tested in the optical path, the gas to be tested will absorb a portion of the laser signal, and the remaining laser signal is the target laser signal, which is received by the detector (i.e., the photosensitive element of the detector).

[0055] A detector is used to receive target laser signals and output electrical signals based on those signals. The detector outputs a detection signal based on the received target laser signal, which is presented in the form of electrical signals such as voltage or current.

[0056] A variable gain amplifier is used to periodically amplify electrical signals and output multiple amplified electrical signals to the main control board. The periodic amplification process involves gradually amplifying the electrical signals according to a preset amplification ratio.

[0057] The main control board is also used to determine the target electrical signal from multiple amplified electrical signals when the electrical signal is determined to be an unsaturated signal, and to obtain the concentration of the gas to be measured based on the target electrical signal.

[0058] In this embodiment, a variable gain amplifier is placed between the detector and the main control board of the laser spectroscopy detection system to periodically amplify the electrical signal output by the detector, outputting multiple amplified electrical signals to the main control board. This allows the main control board to determine a suitable target electrical signal based on the multiple amplified electrical signals output by the variable gain amplifier, and then obtain the concentration of the gas to be measured from the target electrical signal. Thus, even when the photodetector's photosensitive element is not saturated, the photodetector's output signal (i.e., electrical signal) is amplified by the variable gain amplifier through a suitable amplification factor during the amplification process, resulting in an amplified electrical signal with an appropriate signal amplitude, i.e., the target electrical signal. Based on the target electrical signal, the concentration of the gas to be measured can be analyzed with high accuracy, improving the accuracy and precision of the gas concentration detection. Furthermore, the overall system setup enhances the anti-interference capability of the entire photodetection process, especially its resistance to optical path interference.

[0059] Below, in conjunction with Figure 1 The control process of the laser spectral detection system in this embodiment is described in detail below:

[0060] The laser is installed on one side of the test scene, and the detector is installed on the other side, forming an optical path between them. The test scene can be set according to actual needs. For example, if the test scene is a highway, and the goal is to measure the alcohol content in a driver's vehicle, the laser is installed on one side of the highway, and the detector is installed on the other side. The test scene may contain the gas to be measured, and there may also be obstructions. These obstructions may randomly block the optical path between the laser and the detector to varying degrees, affecting the detector's absorption of the measurement intensity along the optical path, thus affecting the concentration analysis of the gas to be measured. Taking the test scene as a highway, to measure the alcohol content in a driver's vehicle, when the driver drives through the optical path, the entire vehicle or its windows act as obstructions, and the alcohol molecules exhaled by the driver diffuse throughout the vehicle. The laser signal emitted by the laser passes through the vehicle; the alcohol molecules absorb part of the laser signal, and the remaining laser signal is the target laser signal, which is received by the detector. Based on the received target laser signal, the detector outputs an electrical signal, such as... Figure 1 The waveform output by the detector in the image.

[0061] When detecting the concentration of the gas to be tested, the main control board of this system sends a periodic scanning drive voltage signal, such as... Figures 1 to 4 The first waveform in the diagram allows adjustment of the laser current, changing the wavelength of the laser signal emitted by the laser, and enabling the detection of the concentration of different gases to be tested.

[0062] When the electrical signal is determined to be unsaturated, a variable gain amplifier is used to periodically amplify the electrical signal output from the detector, outputting multiple amplified electrical signals to the main control board, such as... Figure 1 The waveform output by the variable gain amplifier is shown. Periodic amplification is a process of gradually amplifying the electrical signal according to a preset amplification ratio. The preset amplification ratio and its order can be set according to actual needs. An unsaturated electrical signal means that the detector output signal does not exhibit clipping. Clipping occurs when the top of the electrical signal waveform is cut off. An unsaturated electrical signal is formed because the detector's photosensitive element itself is not subjected to an excessively strong laser signal.

[0063] For example, a variable gain amplifier has amplification factors of 800, 400, 200, and 100 times within one cycle. After acquiring electrical signal A, the variable gain amplifier amplifies signal A by 800, 400, 200, and 100 times respectively within one cycle, resulting in four amplified electrical signals: 800A, 400A, 200A, and 100A. These four amplified electrical signals are then output to the main control board.

[0064] In this way, the electrical signal output from the detector is periodically amplified by a variable gain amplifier, resulting in multiple amplified electrical signals sent to the main control board. The main control board then determines the appropriate amplified electrical signal and its amplitude, thereby analyzing the concentration of the gas to be measured. This improves the accuracy and precision of the gas concentration detection and enhances the anti-interference capability of the entire optical detection process.

[0065] When the electrical signal is determined to be unsaturated, the main control board determines the target electrical signal from multiple amplified electrical signals, and the concentration of the gas to be measured is obtained based on the target electrical signal.

[0066] Specifically, since some amplified electrical signals output by the variable gain amplifier may be saturated or have excessively low amplitude, the main control board needs to determine the target electrical signal from these multiple amplified signals. The specific process is as follows:

[0067] After receiving multiple amplified electrical signals, the main control board evaluates each signal. If the amplitude of each amplified signal is within the set amplitude range and does not exhibit clipping, it indicates that the signal is neither a saturated signal nor a signal with excessively low amplitude, and is therefore classified as a compliant signal. The set amplitude range can be configured according to actual requirements. If the amplitude of the amplified signal is outside the set amplitude range or exhibits clipping, it indicates that the signal is either a saturated signal or a signal with excessively low amplitude, and is therefore classified as a non-compliant signal, requiring its rejection.

[0068] After identifying the qualified signals, if there is only one qualified electrical signal, it is designated as the target electrical signal. If there are multiple qualified electrical signals, the qualified electrical signal with the largest amplitude is designated as the target electrical signal. Therefore, the target electrical signal is an electrical signal that does not exhibit clipping and whose amplitude falls within the set amplitude range.

[0069] Example 1 illustrates the control process of the main control board: Figure 1 As shown, the laser signal has a relatively high optical power when there are no obstructions in the optical path. The detector outputs four amplified electrical signals: 800A1, 400A1, 200A1, and 100A1, to the main control board. The main control board evaluates each of these amplified electrical signals. The main control board determines that amplified signal 100A1 is the target signal, meaning that amplified signal 100A1 does not exhibit clipping and its amplitude is within the set amplitude range.

[0070] Example 2, such as Figure 2 As shown, when there is a slight obstruction (i.e., high transmittance) in the optical path, the detector outputs four amplified electrical signals: 800A2, 400A2, 200A2, and 100A2, to the main control board. The main control board evaluates each of these amplified signals. The main control board determines that amplified signals 100A2 and 200A2 are both compliant signals, meaning they do not exhibit clipping and their amplitudes are within the set range. Since the amplitude of 200A2 is greater than that of 100A2, resulting in a better waveform and stronger anti-interference capability, which facilitates the concentration analysis of the gas to be measured, amplified signal 200A2 is selected as the target signal.

[0071] Example 3, such as Figure 3As shown, when there is a moderately obstructed object b (i.e., moderately transparent) in the optical path, the detector outputs four amplified electrical signals: 800A3, 400A3, 200A3, and 100A3, to the main control board. The main control board evaluates each of these amplified signals. It determines that amplified signal 400A3 is the target signal, meaning it does not exhibit clipping and its amplitude is within the set amplitude range. In this case, 800A3 is a saturated signal, while 100A3 and 200A3 are signals with excessively low amplitude or amplitudes outside the set amplitude range.

[0072] Example 4, such as Figure 4 As shown, when there is a severe obstruction (i.e., low transmittance) on the optical path, the detector outputs four amplified electrical signals: 800A4, 400A4, 200A4, and 100A4, to the main control board. The main control board evaluates each of these amplified signals. The main control board determines that amplified signal 800A4 is the target signal, meaning that amplified signal 800A4 does not exhibit clipping and its amplitude is within the set amplitude range.

[0073] After determining the target electrical signal, the main control board can invert the concentration based on the Lambert-Beer Law. The specific calculation process can employ either the direct absorption method or the wavelength modulation method, which is not limited here.

[0074] In this embodiment, when the detector's photosensitive element is not saturated with the detection signal, and regardless of any obstructions, the main control board determines the target electrical signal based on multiple amplified electrical signals obtained by periodically amplifying the detector's output electrical signal using a variable gain amplifier. The concentration of the gas to be measured is then obtained based on this target electrical signal. The target electrical signal is one without clipping and with an amplitude within a set range, ensuring the accuracy and quality of the calculated data, thereby improving the accuracy and precision of the gas concentration detection. Furthermore, the overall system configuration enhances the anti-interference capability of the entire photodetection process.

[0075] Furthermore, after the main control board has performed the target electrical signal selection operation a preset number of times, it can output the corresponding amplification factor of the target electrical signal to the variable gain amplifier. The preset number of times can be set according to actual needs. The variable gain amplifier uses the corresponding amplification factor as the current amplification factor and performs amplification processing based on the current amplification factor to facilitate subsequent electrical signal amplification.

[0076] Specifically, the first process is executed as follows: the detector receives the target laser signal and outputs a first electrical signal based on it. A variable gain amplifier periodically amplifies this first electrical signal, outputting multiple amplified signals to the main control board. The main control board determines the first target electrical signal from these multiple amplified signals and obtains the first concentration of the gas to be measured based on it. Next, the second process is executed: the detector receives the target laser signal and outputs a second electrical signal based on it. The variable gain amplifier periodically amplifies this second electrical signal, outputting multiple amplified signals to the main control board. The main control board determines the second target electrical signal from these multiple amplified signals and obtains the second concentration of the gas to be measured based on it. This process is repeated until the main control board, after performing the target signal determination operation a preset number of times, outputs the amplification factor corresponding to the target electrical signal to the variable gain amplifier. A variable gain amplifier uses the corresponding amplification factor as its current amplification factor and performs amplification based on this current amplification factor to facilitate the amplification of subsequent electrical signals. For example, if a variable gain amplifier uses a corresponding amplification factor of 400 as its current amplification factor, all subsequent electrical signals will be amplified at a factor of 400. The variable gain amplifier updates its current amplification factor through this operation after executing at the current amplification factor for a set duration or a specified number of executions. The set duration and specified number of executions can be set according to actual needs.

[0077] This operation is more suitable for stable test scenarios where the difference in the target electrical signal is small each time, indicating that the amplification factor corresponding to the target electrical signal is consistent. Controlling the variable gain amplifier to use the corresponding amplification factor for subsequent electrical signal amplification processing improves the system's detection efficiency and the variable gain amplifier's amplification efficiency. This operation can be selectively adopted according to actual needs.

[0078] The control process of the laser spectral detection system in this embodiment is described below:

[0079] The only difference between Control Process 2 and Control Process 1 is that Control Process 2 obtains the amplification factor of the variable gain amplifier on the main control board and the amplification process of the variable gain amplifier; the rest of the processes are the same.

[0080] A variable gain amplifier amplifies an electrical signal based on its current gain and outputs an amplified electrical signal, which is the signal corresponding to the current gain.

[0081] The main control board acquires the electrical signal corresponding to the current amplification factor of the variable gain amplifier. Based on negative feedback control methods, such as PID (Proportion Integral Differential) and the binary search method, it processes the electrical signal corresponding to the current amplification factor and a set electrical signal range to obtain the target amplification factor. This target amplification factor is then output to the variable gain amplifier, ensuring that the electrical signal corresponding to the target amplification factor matches the set target electrical signal. The set target electrical signal can be set according to actual needs. The set electrical signal range can be set based on the difference range between the set target electrical signal and the target signal. The variable gain amplifier uses the target amplification factor as the current amplification factor and amplifies the signal based on this current amplification factor to facilitate amplification of subsequent electrical signals.

[0082] Specifically, taking the PID method as a negative feedback control method as an example, the main control board reads the amplified electrical signal and adjusts the amplification factor of the variable gain amplifier in real time through the PID negative feedback algorithm. The amplified electrical signal is gradually adjusted to approach the target electrical signal, ensuring that the difference between the amplified electrical signal and the target electrical signal falls within the set electrical signal range, ultimately achieving convergence and obtaining the target amplification factor. For example, the main control board reads an amplified electrical signal of 3V, corresponding to an amplification factor of 100, and the target electrical signal is 10V. The difference between 3V and 10V is not within the set electrical signal range of -0.5V to +0.5V. Using the PID method, the current amplification factor of the variable gain amplifier is adjusted from 100 to 110. After adjusting the current amplification factor of the variable gain amplifier, the main control board reads an amplified electrical signal of 3.3V, corresponding to an amplification factor of 110, and the target electrical signal is 10V. The difference between 3.3V and 10V is not within the set electrical signal range of -0.5V to +0.5V. By analogy, continue to adjust the current amplification factor of the variable gain amplifier until the difference between the amplified electrical signal and the set target electrical signal is within the set electrical signal range, so as to achieve real-time adjustment of the current amplification factor of the variable gain amplifier.

[0083] The variable gain amplifier uses the target amplification factor as the current amplification factor and performs amplification based on this current factor. This allows for automatic negative feedback adjustment of the variable gain amplifier's amplification factor when obstructions with varying transmittance randomly appear in the optical path, ensuring the amplified electrical signal carries a stable amplitude, which is beneficial for detecting the concentration of the analyte gas. This operation is more suitable for varied testing scenarios, broadening the application scenarios, improving the system's applicability and versatility, increasing detection efficiency, and enhancing its anti-interference capabilities.

[0084] In this embodiment, the control process three of the laser spectral detection system combines control process one and control process two. For example, in the startup phase, control process one is used to determine the current amplification factor of the variable gain amplifier. Then, control process two is used to adjust the current amplification factor of the variable gain amplifier in real time. This real-time control of the variable gain amplifier ensures that the amplified electrical signal carries a stable amplitude, which is beneficial for the concentration detection of the gas to be measured, improves the detection efficiency of the system, and enhances the anti-interference capability of the system.

[0085] Example 2

[0086] Based on Embodiment 1, this embodiment adds an optical power attenuator to address the problem that the detector's output detection signal (i.e., electrical signal) becomes saturated due to excessively strong laser signals affecting the detector's photosensitive element. In other words, it resolves the issue of a saturated electrical signal. A saturated electrical signal output by the detector indicates that the signal exhibits clipping.

[0087] The system in this embodiment also includes an optical power attenuator. The optical power attenuator is connected to the main control board and is positioned along the optical path. The optical power attenuator is used to perform different degrees of optical power attenuation on the laser signal to obtain an attenuated laser signal (e.g., ...). Figures 5-8 The second waveform in the image is used to allow the attenuated laser signal to pass through the gas to be tested in the optical path, thereby obtaining the target laser signal (e.g., waveform ②). Figures 5-8 The third waveform in the image is used to prevent the detector from outputting a saturated electrical signal based on the target laser signal. The attenuated laser signal passes through the gas to be tested in the optical path. The gas absorbs a portion of the attenuated laser signal, and the remaining attenuated laser signal is the target laser signal, which is received by the detector. Figures 5-8 The fourth waveform in the diagram represents the electrical signal output by the detector. Figures 5-8 Waveform ⑤ in the diagram represents the amplified electrical signal output by the variable gain amplifier.

[0088] There are three specific examples of optical power attenuators, as shown below:

[0089] The first type, such as Figure 5 As shown, the optical power attenuator is a chopper. The input end of the chopper is aligned with the output end of the laser, and the output end of the chopper is aligned with the input end of the detector. The main control board is connected to the chopper via a motor, and the chopper can rotate under the drive of the motor. The chopper includes multiple sectors with different optical power attenuation rates. When the chopper rotates, the input ends of the sectors with different optical power attenuation rates are aligned with the output end of the laser, and the output ends of the sectors with different optical power attenuation rates are aligned with the input end of the detector. The number of sectors of the chopper and the optical power attenuation rate of each sector can be set according to actual needs.

[0090] For example, such as Figure 5 As shown, the chopper wheel has four sectors, with optical power attenuation rates of 0, 1 / 2, 1 / 4, and 1 / 8 for each sector. The sectors of the chopper wheel can be divided into four sectors: the first sector (0), the second sector (1 / 2), the third sector (1 / 4), and the fourth sector (1 / 8). When the chopper wheel rotates to align the first sector with the laser output, since the first sector has a power attenuation rate of 0, it does not attenuate the laser signal, and the attenuated laser signal power is 100%. When the chopper wheel rotates to align the second sector with the laser output, the power attenuation rate is 1 / 2, and the attenuated laser signal power is 50%. When the chopper wheel rotates to align the third sector with the laser output, the power attenuation rate is 1 / 4, and the attenuated laser signal power is 25%. When the chopper rotates to the fourth sector aligned with the laser output, the optical power attenuation rate of the fourth sector is 1 / 8, and the optical power of the attenuated laser signal is 12.5% ​​of the laser signal.

[0091] like Figure 5 As shown, in this embodiment of the system with a chopper, when there are no obstructions in the optical path, the optical power of the attenuated laser signal formed after the laser signal passes through the first to the third sector is too high, causing the electrical signal output by the detector to be a saturated signal. When the optical power of the attenuated laser signal formed after the laser signal passes through the fourth sector is appropriate, the amplitude of the electrical signal output by the detector is reasonable. Therefore, the chopper is rotated to the fourth sector to align with the output end of the laser.

[0092] like Figure 6 As shown, in this embodiment of the system with a chopper, when there is a slight obstruction (i.e., high transmittance) in the optical path by an obstruction 'a', the optical power of the attenuated laser signal formed after the laser signal passes through the first sector to the second sector is too high, causing the electrical signal output by the detector to be a saturated signal. When the optical power of the attenuated laser signal formed after the laser signal passes through the third sector is appropriate, the amplitude of the electrical signal output by the detector is reasonable. When the optical power of the attenuated laser signal formed after the laser signal passes through the fourth sector is too low, the amplitude of the electrical signal output by the detector is too low. Therefore, the chopper is rotated to the third sector to align with the output end of the laser.

[0093] like Figure 7As shown, in this embodiment of the system with a chopper, when there is a moderately obstructed object b (i.e., moderately transparent) in the optical path, the optical power of the attenuated laser signal formed after the laser signal passes through the first sector is too high, resulting in a saturated electrical signal output by the detector. When the optical power of the attenuated laser signal formed after the laser signal passes through the second sector is appropriate, the amplitude of the electrical signal output by the detector is reasonable. When the optical power of the attenuated laser signal formed after the laser signal passes through the third and fourth sectors is too low, the amplitude of the electrical signal output by the detector is too low. Therefore, the chopper rotates to align with the output end of the laser in the second sector.

[0094] like Figure 8 As shown, the system of this embodiment with a chopper is applied when there is a severe obstruction (i.e., low transmittance) in the optical path by an obstruction c. When the optical power of the attenuated laser signal formed after the laser signal passes through the first sector is appropriate, the amplitude of the electrical signal output by the detector is reasonable. Therefore, the chopper rotates to align the first sector with the output end of the laser.

[0095] When the optical power attenuator is a chopper, the main control board can control the chopper to rotate to a suitable sector to align with the laser based on the electrical signal and / or the target electrical signal, which is beneficial for the concentration detection of the gas to be tested. This avoids the detector outputting a saturated signal based on the target laser signal, improves the system's anti-interference performance against optical path interference, and enhances the system's detection efficiency and accuracy.

[0096] The second type, such as Figure 9 As shown, the optical power attenuator is an adjustable optical attenuator. The adjustable optical attenuator is electrically connected to the main control board and is used to attenuate the optical power of the laser signal to different degrees, resulting in an attenuated laser signal. For example, if the main control board needs to control the optical power attenuation rate of the laser signal to 48.8%, then the optical power attenuation rate of the adjustable optical attenuator is directly set to 48.8%, so that the optical power of the attenuated laser signal is 48.8% of the original laser signal. In this way, the adjustable optical attenuator can achieve more precise control over the optical power of the laser signal, making the electrical signal output by the detector more accurate, thereby increasing the accuracy and precision of the detection concentration of the gas to be measured, improving the anti-interference performance of the system against optical path interference, and enhancing the detection efficiency and accuracy of the system. Furthermore, Figure 9 Waveform ⑥ in the diagram represents the control signal generated by the main control board to the adjustable optical attenuator. This control signal can adjust the optical power attenuation rate of the adjustable optical attenuator.

[0097] The third type is a laser that integrates the function of emitting laser signals with the function of adjusting the optical power attenuation rate of the laser signal using an optical power attenuator, such as an electro-absorption modulated laser (EML laser). EML lasers have advantages such as high speed, low distortion, long-distance transmission capability, wider application scenarios, higher precision, better detection effect, low cost, and low power consumption.

[0098] A laser spectral detection system with an optical power attenuator can not only solve the problem of excessively high laser power, leading to an overly strong laser signal received by the detector and consequently a saturated electrical signal output, but also address the issue of an unsaturated electrical signal output by the detector, caused by an unreasonable amplification factor in the amplifier circuit, resulting in a saturated signal or an excessively low amplitude amplified signal. Furthermore, the laser spectral detection system with an optical power attenuator further improves the system's anti-interference capability against optical path interference and enhances the detection accuracy and efficiency of the analyte gas.

[0099] The control process of the laser spectral detection system with an optical power attenuator in this embodiment is described below. Specifically, the process of the main control board controlling the current optical power attenuation rate of the optical power attenuator is added to control processes one, two, and three of Embodiment 1. The process of the main control board controlling the current optical power attenuation rate of the optical power attenuator is as follows:

[0100] The main control board acquires the laser signal, the optical power attenuation rate of the optical power attenuator, and the target laser signal. Based on a negative feedback control method, such as PID, binary, or AI control, it processes the laser signal, the optical power attenuation rate of the optical power attenuator, and the target laser signal to obtain the target optical power attenuation rate. This target optical power attenuation rate is then output to the optical power attenuator. The optical power attenuator uses the target optical power attenuation rate as its current optical power attenuation rate and, based on this current rate, performs optical power attenuation processing on the laser signal to obtain the attenuated laser signal.

[0101] Specifically, taking the PID method as a negative feedback control method as an example, the optical power attenuator is a chopper. The main control board, based on the PID method, processes the laser signal, the optical power attenuation rate of the optical power attenuator, and the target laser signal to obtain the target optical power attenuation rate. The main control board controls the chopper to rotate until the sector corresponding to the target optical power attenuation rate is aligned with the output end of the laser.

[0102] The optical power attenuator can be an adjustable optical attenuator or, in this embodiment, a direct EML laser. The main control board uses a PID method to process the laser signal, the optical power attenuation rate of the optical power attenuator, and the target laser signal to obtain the target optical power attenuation rate. This target optical power attenuation rate is then directly output to the adjustable optical attenuator or the EML laser.

[0103] By employing a PID algorithm, the optical power attenuation rate of the optical power attenuator is controlled in real time, achieving baseline control of the laser signal and preventing excessive laser power from causing saturation in the detector's output signal. This improves the overall system's resistance to optical path interference and also enhances the detection accuracy and efficiency of the analyte gas.

[0104] Furthermore, in the control process of the laser spectral detection system with an optical power attenuator in this embodiment, if adjusting only the optical power attenuation rate of the optical power attenuator or only adjusting the amplification factor of the variable gain amplifier cannot obtain a suitable target electrical signal, then the optical power attenuation rate of the optical power attenuator is first adjusted to prevent the electrical signal output by the detector from being a saturated signal. Then, the amplification factor of the variable gain amplifier is adjusted to ensure the main control board obtains a suitable target electrical signal, reducing electrical signal noise and interference, thereby accurately determining the concentration of the gas to be analyzed. This further improves the detection accuracy and efficiency of the gas to be analyzed.

[0105] Example 3

[0106] Based on the same inventive concept, the third embodiment of the present invention also provides a control method for a laser spectral detection system, applied to the laser spectral detection system described in Embodiment 1 or Embodiment 2, such as... Figure 10 As shown, the control method includes:

[0107] S201, a laser signal is emitted through a laser, so that the laser signal passes through the gas to be measured in the optical path between the laser and the detector to obtain the target laser signal;

[0108] S202, the detector receives the target laser signal and outputs an electrical signal based on the target laser signal;

[0109] S203, through a variable gain amplifier, the electrical signal is periodically amplified and multiple amplified electrical signals are output to the main control board. The periodic amplification process is a process of gradually amplifying the electrical signal according to a preset amplification ratio.

[0110] S204, if the electrical signal is determined to be an unsaturated signal, a target electrical signal is determined from the plurality of amplified electrical signals, and the concentration of the gas to be measured is obtained based on the target electrical signal.

[0111] Since the control method of the laser spectral detection system described in this embodiment is the same control method used in implementing the laser spectral detection system of Embodiment 1 or 2 of this application, those skilled in the art can understand the specific implementation method and various variations of the control method of the laser spectral detection system in this embodiment based on the laser spectral detection system described in Embodiment 1 or 2 of this application. Therefore, how the control method of this laser spectral detection system implements the laser spectral detection system of Embodiment 1 or 2 of this application will not be described in detail here. As long as those skilled in the art implement the control method used in the laser spectral detection system of Embodiment 1 or 2 of this application, they are all within the scope of protection of this application.

[0112] Those skilled in the art will understand that although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0113] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A laser spectral detection system, characterized in that, include: Main control board, laser, detector and variable gain amplifier; The detector is connected to the main control board via the variable gain amplifier, and the main control board is also connected to the laser, forming an optical path between the laser and the detector; The main control board is used to send laser commands to the laser and to send turn-on commands to the variable gain amplifier; The laser is used to emit a laser signal according to the laser command, so that the laser signal passes through the gas to be tested in the optical path to obtain the target laser signal; The detector is used to receive the target laser signal and output an electrical signal according to the target laser signal; The variable gain amplifier is used to periodically amplify the electrical signal and output multiple amplified electrical signals to the main control board. The periodic amplification process is a process of gradually amplifying the electrical signal according to a preset amplification ratio. The main control board is also used to determine a target electrical signal from a plurality of amplified electrical signals when the electrical signal is determined to be an unsaturated signal, and to obtain the concentration of the gas to be measured based on the target electrical signal.

2. The laser spectral detection system as described in claim 1, characterized in that, Determining the target electrical signal from the plurality of amplified electrical signals includes: In each of the amplified electrical signals, if the amplitude of the amplified electrical signal is within the set amplitude range and the amplified electrical signal does not have a clipping phenomenon, then the amplified electrical signal is determined to be a qualified electrical signal. If the number of qualified electrical signals is one, then the qualified electrical signal is determined as the target electrical signal; If there are multiple qualified electrical signals, the qualified electrical signal with the largest amplitude is determined as the target electrical signal.

3. The laser spectral detection system as described in claim 2, characterized in that, The main control board is also used to: after determining the target electrical signal a preset number of times, output the amplification factor corresponding to the target electrical signal to the variable gain amplifier; The variable gain amplifier is further configured to: take the corresponding amplification factor as the current amplification factor, and perform amplification processing based on the current amplification factor, so as to facilitate the amplification processing of subsequent electrical signals.

4. The laser spectral detection system as described in claim 3, characterized in that, Also includes: An optical power attenuator is connected to the main control board and is disposed on the optical path; The optical power attenuator is used to attenuate the laser signal to different degrees to obtain an attenuated laser signal, so that the attenuated laser signal can pass through the gas to be tested in the optical path to obtain the target laser signal, thereby preventing the detector from outputting a saturated signal based on the target laser signal.

5. The laser spectral detection system as described in claim 4, characterized in that, The optical power attenuator is a chopper, with the input end of the chopper aligned with the output end of the laser and the output end of the chopper aligned with the input end of the detector. The main control board is connected to the chopper via a motor, and the chopper can rotate under the drive of the motor. The chopper wheel includes multiple sectors with different optical power attenuation rates. When the chopper wheel rotates, the input ends of the sectors with different optical power attenuation rates are aligned with the output ends of the laser, and the output ends of the sectors with different optical power attenuation rates are aligned with the input ends of the detector.

6. The laser spectral detection system as described in claim 4, characterized in that, The optical power attenuator is an adjustable optical attenuator, which is electrically connected to the main control board. The adjustable optical attenuator is used to perform optical power attenuation processing on the laser signal to different degrees to obtain the attenuated laser signal.

7. The laser spectral detection system as described in any one of claims 4 to 5, characterized in that, The main control board is also used for: Acquire the laser signal, the optical power attenuation rate of the optical power attenuator, and the target laser signal; Based on the negative feedback control method, the laser signal, the optical power attenuation rate of the optical power attenuator, and the target laser signal are processed to obtain the target optical power attenuation rate; The target optical power attenuation rate is output to the optical power attenuator; The optical power attenuator is used to: take the target optical power attenuation rate as the current optical power attenuation rate, and perform optical power attenuation processing on the laser signal based on the current optical power attenuation rate to obtain the attenuated laser signal.

8. The laser spectral detection system as described in claim 7, characterized in that, The variable gain amplifier is further configured to: amplify the electrical signal according to the current amplification factor of the variable gain amplifier, and output the amplified electrical signal, wherein the amplified electrical signal is the electrical signal corresponding to the current amplification factor; The main control board is also used to: acquire the electrical signal corresponding to the current amplification factor; Based on the negative feedback control method, the electrical signal corresponding to the current amplification factor and the set electrical signal range are processed to obtain the target amplification factor, and the target amplification factor is output to the variable gain amplifier so that the electrical signal corresponding to the target amplification factor is consistent with the set target electrical signal; The variable gain amplifier is further configured to: use the target amplification factor as the current amplification factor, and perform amplification processing based on the current amplification factor, so as to facilitate amplification processing of subsequent electrical signals.

9. The laser spectral detection system as described in claim 1, characterized in that, The laser is an electroabsorption modulated laser.

10. A control method for a laser spectral detection system, characterized in that, The control method, applied to the laser spectral detection system as described in any one of claims 1-9, comprises: A laser signal is emitted by a laser, and the laser signal passes through the gas to be measured in the optical path between the laser and the detector to obtain the target laser signal. The detector receives the target laser signal and outputs an electrical signal based on the target laser signal. The electrical signal is periodically amplified by a variable gain amplifier, and multiple amplified electrical signals are output to the main control board. The periodic amplification process is a process of gradually amplifying the electrical signal according to a preset amplification ratio. If the electrical signal is determined to be an unsaturated signal, a target electrical signal is determined from the plurality of amplified electrical signals, and the concentration of the gas to be measured is obtained based on the target electrical signal.

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