Echo model construction method for single-photon laser detection device

Abstract

The invention relates to a method for constructing an echo model of a single-photon laser detection device, and belongs to the technical field of imaging detection of the single-photon laser detection device. By inputting the target scene model or the intensity map and the depth map of the target scene and inputting relevant parameters in an actual detection system, the echo model based on actual target scene detection can be quickly generated, an important theoretical basis is provided for actual detection, and the process of parameter trial and error in an actual experiment is reduced. Wherein the constructed echo has the characteristics of two imaging echo models of a free mode and a gating mode in a real detection environment, and can quickly and comprehensively deal with the construction of the echo imaging model of the laser detection device in two different detection modes.

Description

Technical Field

[0001] The present invention belongs to the technical field of imaging detection of single-photon laser detection devices, and in particular relates to a method for constructing an echo model of a single-photon laser detection device. Background Art

[0002] In recent years, under the continuous demand for weak echo long-distance non-cooperative target detection, single-photon laser detection devices (also known as photon counting laser detection devices) have been applied and developed, which can meet the detection needs of tens to hundreds of kilometers. Compared with traditional linear PIN and APD laser ranging radars, single-photon laser detection devices mainly use high-sensitivity single-photon detectors (usually including single-photon avalanche diodes SPAD, photomultiplier tubes PMT and superconducting nanowire single-photon detectors SNSPD) and time-correlated single-photon counting technology. It has the ability to detect single photons and can realize the detection of non-cooperative targets under long-distance weak echoes, which has important application value.

[0003] The single-photon laser detection device is a new type of ultra-sensitive photoelectric detection technology with the ability to respond to a single photon. Its theoretical detection process is relatively complex, involving multiple physical processes such as laser light source, atmospheric transmission channel, target scattering characteristics, photoelectric signal conversion, etc. Single-photon detection usually has two working modes, namely free mode and gated mode. Among them, the free mode does not impose additional restrictions on the detector. After responding to the photon counting signal, the detector enters the dead time quenching, and after the quenching is completed, the next detection can be carried out; the gated mode applies a gate signal to the detector to control the detector to work at a specific time. The detector is in a dormant state at other times. The single-photon detector can only respond to the photon counting signal once during the gated time. The two modes have different echo probability models, and their echo model construction methods are different. So far, no specific method for constructing the echo model of a single-pixel single-photon scanning imaging laser detection device based on the free mode and a single-photon imaging laser detection device based on the gated mode has been proposed, which hinders the development of the detection technology of the single-photon laser detection device. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] The technical problem to be solved by the present invention is: in order to provide theoretical guidance for detection of single-photon imaging laser detection devices in actual environments, a method for constructing an echo model of a single-photon laser detection device is provided.

[0006] (II) Technical solution

[0007] In order to solve the above technical problems, the present invention provides a method for constructing an echo model of a single-photon laser detection device, comprising the following steps:

[0008] Step 1: Obtain the target scene model;

[0009] Step 2: Extracting the target scene intensity map and depth map that match the actual detection array size from the acquired target scene model;

[0010] Step 3: Preprocess the intensity map and depth map of the target scene to obtain the number of echo photons and distance value of each pixel;

[0011] Step 4: Combine the echo photon rate equation, background noise, dark counts, and detector detection efficiency to obtain the relationship between the actual echo photoelectron number and time distribution of each pixel;

[0012] Step 5: According to the relationship between the actual echo photoelectron number and time distribution, the single photon detection time grid counting principle and Poisson distribution, the distribution relationship of each pixel echo count over time is obtained;

[0013] Step 6: Based on the time distribution relationship of each pixel echo count, combined with the Monte Carlo method, obtain the data of N pulse detections for each pixel;

[0014] Step 7: Using the N pulse detection data counted for each pixel, generate the detector's single echo target range image, multiple pulse accumulation target range image, and target intensity image.

[0015] Preferably, the target scene model acquired in step one contains true intensity information and true depth information of the target scene, and is acquired through data from an open source laser detection device designed based on actual target scene simulation or based on actual target scene detection.

[0016] Preferably, step 2 is to scale the original intensity map and the depth map to obtain an image that matches the actual detection array size.

[0017] Preferably, in step three, the target scene intensity map and depth map are preprocessed to obtain the number of echo photons and distance values ​​that conform to each pixel in the actual target scene. The preprocessing is divided into two cases. One is that the extracted intensity map and depth map of the target scene are absolute intensity maps and depth maps in the real target scene. In this case, the actual number of photons and distance values ​​corresponding to each pixel in the actual target scene are obtained through the fixed relationship between energy and photons and the 1:1 correspondence between the depth map and the distance value; the second case is that the extracted intensity map and depth map of the target scene are based on the relative intensity map and depth map in the real target scene, that is, the intensity distribution grayscale map and the target depth distribution grayscale map. At this time, the intensity distribution grayscale map and the target depth distribution grayscale map are normalized, and then multiplied with the maximum number of echo photons and the maximum detection distance value in the actual target scene (which can be obtained based on system parameters, laser detection device equations, and target scenes), so as to obtain the number of echo photons and the corresponding distance value of each pixel evaluated based on the actual target scene.

[0018] Preferably, in step 4, the number of echo photons of each pixel and the corresponding distance value are substituted into the photon rate equation to obtain the distribution of the number of laser echo photons on the time axis, wherein the photon rate equation is as follows:

[0019]

[0020] Where N s is the number of echo photons, c is the speed of light, R is the distance from the target to the laser detection device, σ represents the standard deviation of the laser Gaussian distribution, and is related to the laser pulse width t fwhm (Full width at half maximum of pulse laser) is: σ = t fwhm / 2.355;

[0021] At the same time, considering the influence of background noise, dark counts and detector efficiency in the actual detection scene, the total photoelectron echo rate equation of each pixel, that is, the distribution of the number of echo photoelectrons over time, is obtained as follows:

[0022] N(t)=N s (t)·η+N b ·η+N d (2)

[0023] Where N s is the number of echo photons, N b is the background noise intensity, η is the photon detection efficiency of the detector, N d is the dark count noise intensity.

[0024] Preferably, in step five, the number of photoelectrons in each time grid Δt, i.e., N(t)·Δt, is obtained based on the photoelectron echo rate equation and the single-photon detection time grid counting principle; and then combined with the Poisson distribution, the distribution relationship of the echo count of each pixel over time is obtained. At this time, under different detection modes, i.e., free mode and gated mode, the distribution relationship of the echo count of each pixel over time is different, and the effects displayed are different.

[0025] Preferably, in step six, based on the distribution relationship of the echo count of each pixel over time, combined with the Monte Carlo method, the transformation process of the Poisson distribution is performed N times to achieve data acquisition of N pulse detections, and different detection modes also have different effects.

[0026] Preferably, in step seven, the N pulse detection data counted for each pixel are used to combine all pixels to generate a single target echo range image, a multiple pulse accumulated target range image, and a multiple pulse accumulated target intensity image, respectively. The generated image types include a free mode and a gated mode, thereby completing the construction of the echo model of the single-photon laser detection device under two different detection modes.

[0027] Preferably, the method is applied in the field of imaging detection technology of single-photon laser detection devices.

[0028] 10. A system for implementing the method.

[0029] (III) Beneficial effects

[0030] 1) The present invention provides a method for constructing an echo model of a single-photon laser detection device. By inputting a target scene model or an intensity map and a depth map of the target scene, and inputting relevant parameters in an actual detection system, an echo model based on actual target scene detection can be quickly generated, which provides an important theoretical basis for actual detection and reduces the process of parameter trial and error in actual experiments.

[0031] 2) The present invention provides a method for constructing an echo model of a single-photon laser detection device, wherein the constructed echo has the characteristics of two imaging echo models, namely, a free mode and a gated mode in a real detection environment, and can quickly and comprehensively cope with the construction of echo imaging models of laser detection devices under two different detection modes.

[0032] 3) The present invention provides a method for constructing an echo model of a single-photon laser detection device. In the absence of actual detection environment conditions, the simulation model is close to the echo model of the single-photon laser detection device for actual detection, which has important application significance for internal field simulation, data testing, data optimization, and algorithm verification. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 : A schematic diagram of a method for constructing an echo model of a single-photon laser detection device;

[0034] Figure 2 : Target scene model intensity and depth grayscale images; (a) is the target scene model intensity grayscale image, (b) is the target scene model depth grayscale image;

[0035] Figure 3 : Intensity and depth grayscale images of the target scene model after scaling; (a) is the intensity grayscale image of the target scene model after scaling, and (b) is the depth grayscale image of the target scene model after scaling;

[0036] Figure 4 : Pseudo-color images of the number of photons and distance of the extracted target scene echo; (a) is a pseudo-color image of the number of photons of the extracted target scene echo, (b) is a pseudo-color image of the distance of the extracted target scene echo;

[0037] Figure 5 : The distribution relationship between the number of echo photoelectrons of the first pixel on the upper left and time;

[0038] Figure 6: The relationship between the echo count distribution over time in the free mode and the gated mode for the first pixel on the upper left; (a) is the echo count distribution over time in the free mode, and (b) is the echo count distribution over time in the gated mode;

[0039] Figure 7 : The relationship between the distribution of echo statistics counts over time in the free mode and the gated mode for the first pixel on the upper left; (a) is the distribution of echo statistics counts over time in the free mode, and (b) is the distribution of echo statistics counts over time in the gated mode;

[0040] Figure 8 : Free mode range image and gated mode range image constructed under single pulse detection; (a) is the free mode range image of single pulse detection, (b) is the gated mode range image of single pulse detection;

[0041] Fig. 9 : Distance diagram of 100, 500, and 1000 pulse accumulation statistics in free mode; (a) is 100 pulse accumulation, (b) is 500 pulse accumulation, and (c) is 1000 pulse accumulation;

[0042] Fig.10 : Intensity diagram of 100, 500, and 1000 pulse accumulation statistics in free mode; (a) is 100 pulse accumulation, (b) is 500 pulse accumulation, and (c) is 1000 pulse accumulation;

[0043] Fig.11 : Distance diagram of 100, 500, and 1000 pulse accumulation statistics in gated mode; (a) is 100 pulse accumulation, (b) is 500 pulse accumulation, and (c) is 1000 pulse accumulation;

[0044] Fig.12 : Intensity diagram of 100, 500, and 1000 pulse accumulation statistics in gated mode; (a) is 100 pulse accumulation, (b) is 500 pulse accumulation, and (c) is 1000 pulse accumulation. DETAILED DESCRIPTION

[0045] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples.

[0046] In order to provide theoretical guidance for the detection of single-photon imaging laser detection devices in actual environments, the present invention proposes a method for constructing a laser detection device echo model for the needs of internal field simulation, data testing, data optimization, algorithm verification, etc., which includes the construction of imaging echo models of two detection modes, free mode and gated mode. The constructed echo has the characteristics of two imaging echo models of free mode and gated mode in the real detection environment, provides simulation data based on actual environment detection, and provides necessary debugging data for single-photon data optimization and imaging algorithm. The construction method uses a three-dimensional model of the target, combines a photon echo model, a single-photon detection model and a Monte Carlo method, and adds corresponding noise to reproduce the real detection process of the single-photon laser detection device, realizes single-photon imaging detection based on actual scenes, and provides necessary theoretical support for the actual detection of the single-photon laser detection device. In addition, the data generated based on the simulation can more effectively verify the effect of the single-photon denoising imaging algorithm, provide a convenient way for data optimization of the single-photon laser detection device, and lay an important foundation for the development of the single-photon laser detection device.

[0047] Figure 1 This is a schematic diagram of a method for constructing an echo model of a single-photon laser detection device of the present invention. Please refer to Figure 1 , the method specifically includes the following steps:

[0048] Step 1: Obtain the target scene model. The target scene model contains the true value intensity information and true value depth information of the target scene. The target scene model is obtained through actual target scene simulation design or open source laser detection device data based on actual target scene detection. Select an open source target scene data model such as Figure 2 As shown, a grayscale image of its intensity and depth distribution is included.

[0049] Step 2: Extract the target scene intensity map and depth map that match the actual detection array size from the established target model. Figure 2 Scaling is performed to obtain an image that matches the actual detection array size, such as Figure 3 shown.

[0050] Step 3: Preprocess the intensity map and depth map of the target scene to obtain the echo photon number and distance value that conforms to each pixel in the actual target scene. The preprocessing is divided into two cases. One is that the intensity map and depth map of the extracted target scene are the absolute intensity map and depth map of the real target scene. In this case, the actual photon number and distance value corresponding to each pixel in the actual target scene can be obtained through the fixed relationship between energy and photons and the 1:1 correspondence between the depth map and the distance value. In the second case, the intensity map and depth map of the extracted target scene are based on the relative intensity map and depth map of the real target scene, namely, the intensity distribution grayscale map and the target depth distribution grayscale map. At this time, the intensity distribution grayscale map and The target depth distribution grayscale image is normalized, and then multiplied with the maximum echo photon number and the maximum detection distance value in the actual target scene (which can be obtained based on the system parameters, the laser detection device equation, and the target scene), and then the number of photons per pixel and the distance value based on the actual target scene evaluation are obtained. The first preprocessing is consistent with the real corresponding model of the target scene, and no complex processing method is required. Therefore, the second preprocessing is adopted in the present invention to perform actual scene evaluation. It is assumed that, through the system parameters, the laser detection device equation and the target parameters, the number of photons at the strongest echo in the target scene is about 0.02, and the corresponding time is about 100ns, that is, the distance is about 10m. The pseudo-color photon echo image and the distance image are as shown in Figure 4 shown.

[0051] Step 4: Substitute the echo photon number and corresponding distance value of each pixel into the photon rate equation to obtain the distribution of the laser echo photon number on the time axis. At the same time, for the actual detection scenario, considering the influence of background noise, dark counts and detector efficiency, the total photoelectron echo rate equation of each pixel can be obtained, that is, the distribution of the echo photoelectron number over time.

[0052] Step 5: According to the echo photoelectron rate equation and the single photon detection time grid counting principle, the number of photoelectrons in each time grid Δt can be obtained, that is, N(t)·Δt. Assuming that the background noise photon counting rate is 633.3kHz, the photon detection efficiency is 0.3, the dark counting rate is 10kHz, the acquisition time resolution (time grid Δt) is 1ns, the photon detection efficiency is 0.3, the pulse width is 6ns, and the time axis length is 200ns, under single pulse detection, the echo photoelectron number of the first pixel in the upper left corner is distributed over time as shown below: Figure 5 shown.

[0053] Combined with Poisson distribution, the distribution relationship of each pixel echo count over time can be obtained. At this time, in different detection modes, namely free mode and gated mode, the distribution relationship of each pixel echo count over time is different, and the display effect is different. Based on the above parameters, assuming that the door detection time is 0.1ms, the distribution relationship of the echo count of the first pixel in the upper left free mode and gated mode over time is as follows Figure 6 As shown, its characteristics conform to the free mode and gated mode concepts.

[0054] Step 6: Based on the time distribution relationship of each pixel echo count, combined with the Monte Carlo method, the transformation process of Poisson distribution is performed N times, and the data acquisition of N pulse detections can be realized. Different detection modes also have different effects. At this time, in order to better demonstrate different accumulation effects, the open gate detection time is set to 200ns, and the number of accumulated pulses is 1000. The time distribution relationship of the echo statistical count of the first pixel in the upper left free mode and gated mode is as follows Figure 7 As shown, it can be found that the gated mode obviously decreases after the door opening detection time, and the characteristics of both are consistent with the definition of their detection modes.

[0055] Step 7: Finally, using the N pulse detection data counted for each pixel, all pixels are combined to generate a single target echo range image, a multiple pulse accumulation target range image, and a multiple pulse accumulation target intensity image. The generated image types include free mode and gated mode, and then the single-photon laser detection device echo model construction under two different detection modes is completed. Under the influence of background noise and dark counts, the free mode range image and gated mode range image constructed under single pulse detection are as follows: Figure 8 As shown in the figure; in single pulse detection, single photon detection only has a response, and its intensity image cannot be known. Statistics can be performed under multiple pulses, and the peak method can be used to obtain the distance image and intensity image. The distance image constructed by accumulating statistics of 100, 500, and 1000 pulses in the free mode is as follows Fig. 9 As shown, the intensity of 100, 500, and 1000 pulse accumulation statistics in the constructed free mode is as follows Fig.10 As shown; the distance image constructed by accumulating 100, 500, and 1000 pulses in the gated mode is as follows Fig.11 As shown, Fig.12 It is the intensity image of the accumulated statistics of 100, 500, and 1000 pulses in gated mode.

[0056] This method generates simulation data based on the actual detection environment and realizes single-photon imaging detection based on actual scenes, which provides important theoretical support for actual detection and a convenient way to optimize the data of single-photon laser detection devices.

[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for constructing an echo model of a single-photon laser detection device, characterized in that: The following steps are involved: Step 1: Obtain the target scene model; Step 2: Extracting the target scene intensity map and depth map that match the actual detection array size from the acquired target scene model; Step 3: Preprocess the intensity map and depth map of the target scene to obtain the number of echo photons and distance value of each pixel; Step 4: Combine the echo photon rate equation, background noise, dark counts, and detector detection efficiency to obtain the relationship between the actual echo photoelectron number and time distribution of each pixel; Step 5: According to the relationship between the actual echo photoelectron number and time distribution, the single photon detection time grid counting principle and Poisson distribution, the distribution relationship of each pixel echo count over time is obtained; Step 6: Based on the time distribution relationship of each pixel echo count, combined with the Monte Carlo method, obtain the data of N pulse detections for each pixel; Step 7: Using the N pulse detection data counted for each pixel, generate the detector's single echo target range image, multiple pulse accumulation target range image, and target intensity image.

2. The method according to claim 1, characterized in that The target scene model obtained in step 1 contains the true intensity information and the true depth information of the target scene, and is obtained through data from an open source laser detection device based on a simulation design based on an actual target scene or based on detection of an actual target scene.

3. The method according to claim 1, characterized in that Step 2: Scaling the original intensity map and depth map to obtain an image that matches the actual detection array size.

4. The method according to claim 2, characterized in that In step three, the intensity map and depth map of the target scene are preprocessed to obtain the number of echo photons and distance values ​​that conform to each pixel in the actual target scene. The preprocessing is divided into two cases. One is that the extracted intensity map and depth map of the target scene are absolute intensity maps and depth maps in the real target scene. In this case, the actual number of photons and distance values ​​corresponding to each pixel in the actual target scene are obtained through the fixed relationship between energy and photons and the 1:1 correspondence between the depth map and the distance value; the second case is that the extracted intensity map and depth map of the target scene are based on the relative intensity map and depth map in the real target scene, that is, the intensity distribution grayscale map and the target depth distribution grayscale map. At this time, the intensity distribution grayscale map and the target depth distribution grayscale map are normalized, and then multiplied with the maximum number of echo photons and the maximum detection distance value in the actual target scene, so as to obtain the number of echo photons and the corresponding distance value of each pixel evaluated based on the actual target scene.

5. The method according to claim 3, characterized in that In step 4, the number of echo photons of each pixel and the corresponding distance value are substituted into the photon rate equation to obtain the distribution of the number of laser echo photons on the time axis, where the photon rate equation is as follows: Where N s is the number of echo photons, c is the speed of light, R is the distance from the target to the laser detection device, σ represents the standard deviation of the laser Gaussian distribution, and is related to the laser pulse width t fwhm The relationship is: σ = t fwhm / 2.355; At the same time, considering the influence of background noise, dark counts and detector efficiency in the actual detection scene, the total photoelectron echo rate equation of each pixel, that is, the distribution of the number of echo photoelectrons over time, is obtained as follows: N(t)=N s (t)·η+N b ·n+N d (2) Where N s is the number of echo photons, N b is the background noise intensity, η is the photon detection efficiency of the detector, N d Dark counts.

6. The method according to claim 5, characterized in that In step 5, based on the photoelectron echo rate equation and the single-photon detection time grid counting principle, the number of photoelectrons in each time grid Δt, namely N(t)·Δt, is obtained; and then combined with the Poisson distribution, the distribution relationship of the echo count of each pixel over time is obtained.

7. The method according to claim 6, characterized in that In step six, based on the distribution relationship of the echo count of each pixel over time, combined with the Monte Carlo method, the transformation process of the Poisson distribution is performed N times to achieve data acquisition of N pulse detections.

8. The method according to claim 7, characterized in that Step seven: Using the N pulse detection data counted for each pixel, all pixels are combined to generate a single target echo range image, a multiple pulse accumulated target range image, and a multiple pulse accumulated target intensity image. The generated image types include free mode and gated mode, thereby completing the construction of the echo model of the single-photon laser detection device under two different detection modes.

9. The method according to any one of claims 1 to 8, characterized in that The method is applied in the field of imaging detection technology of single-photon laser detection devices.

10. A system for implementing the method according to any one of claims 1 to 9.

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