Three-Dimensional Imaging Method and System for Underwater Targets Based on Dynamic Intensity Variation

Abstract

The present invention discloses an underwater three-dimensional target imaging method and system based on dynamic intensity variation. The system includes an active light source array, an optical image sensor, and a control system. The control system includes a light source intensity control module and a control module; the light source intensity control module is connected to the active light source array to control the light source intensity of the point light sources in the active light source array to vary periodically. The light source intensity control module is connected to the control module, and the optical image sensor is connected to the control module to implement functions of image storage and analysis and processing. With the periodic variation of the light source intensity, the target parts at different distances will successively reach the signal-to-noise ratio at which the reflected light can be collected. The control system synthesizes the distance information of different parts of these target images to obtain the distance information of all targets under the maximum light intensity within the field of view, thereby realizing three-dimensional contour imaging. The technical solution of the invention is simple, applicable to underwater imaging in rivers, lakes, and oceans, and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of underwater imaging, and particularly relates to a three-dimensional imaging method and system for underwater targets based on dynamic intensity change. Background Art

[0002] In recent years, with the continuous exploration of the ocean and lake fields by people, underwater imaging has become increasingly important. Underwater imaging has become an important research direction in the fields of optics and oceanography. However, due to the complexity and uncertainty of the underwater situation, and the influence of the absorption and scattering effects of water bodies on the imaging quality, the quality of underwater imaging is still not satisfactory. Currently, underwater imaging is mainly divided into several methods: one is underwater active illumination imaging, which uses high-power active illumination equipment to ensure the absolute energy of the imaging echo signal under high loss; another is underwater laser scanning imaging, which samples the target by combining laser illumination with line scanning or point scanning and then splices the signals according to the positions to obtain the grayscale image of the target. However, due to its multiple samplings, the imaging speed of this method is relatively slow; there is also an underwater range-gated imaging technology, which uses an active pulse illumination method to make the time difference between the backscattered light and the target reflected light reaching the imaging receiving device. By controlling the opening and closing of the imaging shutter, the light beams in the time period when the non-target reflected light beams arrive are isolated outside the receiving device, and only the light signals in the time period when the target reflected light beams arrive are received, so as to achieve the purpose of excluding the interference of stray light, improving the signal-to-noise ratio of the received data, and further increasing the imaging distance and improving the imaging quality. However, this technology can only obtain the targets at a preset distance in a single imaging. All of the above imaging methods are improved designs for underwater interference, and can only collect the two-dimensional information of the target object and cannot achieve the imaging of the three-dimensional contour.

[0003] Therefore, there is still a large room for exploration in the field of underwater imaging, and a more convenient and highly sensitive three-dimensional imaging method for underwater targets is needed. Summary of the Invention

[0004] Based on this, in view of the above problems, the present invention proposes a three-dimensional imaging method and system for underwater targets based on dynamic intensity change.

[0005] The present invention proposes a three-dimensional imaging method for underwater targets based on dynamic intensity change, including the following steps:

[0006] Irradiate an underwater target with a light source whose intensity changes periodically;

[0007] Obtain the image information of the underwater target. When the intensity of the light source gradually changes, the parts of the underwater target at farther distances will successively reach the signal-to-noise ratio at which the reflected light can be collected, so as to realize the successive imaging of underwater targets at different distances;

[0008] The three-dimensional contour imaging algorithm based on the visible light attenuation characteristic synthesizes the target image information and the maximum imaging distance under the current light source intensity to realize the three-dimensional contour imaging of the underwater target.

[0009] Optionally, the step of irradiating the underwater target with the light source whose intensity changes periodically includes:

[0010] By adjusting the output level of the light source intensity control module, the light source intensity of the point light source in the active light source array is controlled to change periodically.

[0011] Optionally, the active light source array includes a plurality of light source lens groups arranged in a circular pattern around the optical image sensor. All the light source lens groups are set on the same plane. At the same time, the front ends of all the light source lens groups and the front end of the optical image sensor are aligned on the same plane. There is a certain interval between the light source lens group and the optical image sensor, and there is also a certain interval between adjacent two light source lens groups. The light source lens group contains a point light source and a corresponding lens. The irradiation ranges of different light source lens groups have a certain outward deflection angle, and there is a certain overlapping part between the irradiation ranges of each different light source lens group.

[0012] Optionally, there are two working modes for the periodic change of the light source intensity:

[0013] In the first working mode, the point light sources in the active light source array are lit up in sequence and the light source intensity changes periodically. After imaging respectively, the images at different angles and distances are comprehensively analyzed to realize three-dimensional imaging within a relatively wide angle range. At this time, the light source intensity of the active light source array during each imaging is the light source intensity of the point light source.

[0014] In the second working mode, the point light sources in the active light source array are lit up simultaneously and the light source intensity changes periodically. The optical image sensor images the overlapping part of the areas covered by all the point light sources, and the images at different distances in the overlapping part are comprehensively analyzed to realize three-dimensional imaging within a relatively long distance range; at this time, the light source intensity of the active light source array during each imaging is the superposition of the light source intensities of all the point light sources.

[0015] Optionally, the three-dimensional contour imaging algorithm based on the visible light attenuation characteristic is specifically as follows:

[0016] Set the initial value I0 of the light source intensity of the point light source, set the step value ΔI of the light source intensity of the point light source and the number of iterations n = 1, I n = I n-1 +ΔI is the light source intensity of the point light source after the nth iteration, S n is the target range within the current maximum imaging distance found by using the optical image sensor to collect image information and through the edge detection algorithm after the nth iteration;

[0017] Compare the target ranges obtained from imaging after two adjacent iterations. When the light source intensity changes periodically according to a specific step value, if the range of S n-1 is greater than the range of S n , the imaging is interfered by invalid information, n = n - 1, and the previous imaging is performed again; if the range of S n-1 is equal to or less than the range of S n , n = n + 1;

[0018] According to the attenuation model of light in water, calculate the maximum imaging distance D n at the current light source intensity I n ;

[0019] When the light source intensity of the point light source changes to the maximum intensity I max or the minimum intensity I min , the iteration stops. According to the maximum imaging distance D n at the light source intensity I n and the corresponding target range S n , as well as the coverage angle range of the point light source, determine the three-dimensional data information of the underwater target and realize three-dimensional contour imaging.

[0020] Optionally, the specific calculation method of the maximum imaging distance D n at the light source intensity I n is as follows:

[0021]

[0022] where α is the attenuation coefficient of light propagation underwater, which is related to the type of water and the water depth; C reflect is the surface reflection coefficient of the target object; S sensor is the minimum signal-to-noise ratio that the optical image sensor can image; P i is the current noise of the optical image sensor; B BS is the backscattering coefficient underwater, which is related to the type of water and the water depth.

[0023] Optionally, the specific formation method of the three-dimensional contour imaging information includes: storing the image information of different light source intensities in a three-dimensional matrix, the size of the matrix is the number of horizontal pixels × the number of vertical pixels × the number of pixels in the depth direction, where the number of horizontal pixels and the number of vertical pixels are determined by the optical image sensor, and the number of pixels in the depth direction is equal to the number of iterations n. Each value corresponds to an imaging information point in the three-dimensional contour image. The three-dimensional matrix is a plurality of two-dimensional matrices in the depth direction, each matrix is S n , and each light intensity I n corresponds to a two-dimensional matrix in the depth direction, and its depth value is D n, fill this three-dimensional matrix in the order of depth change to obtain the required three-dimensional contour imaging information.

[0024] An underwater target three-dimensional imaging system based on dynamic intensity change, comprising: an active light source array, an optical image sensor and a control system, the control system is connected to the active light source array and the optical image sensor, the active light source array includes a number of light source lens groups arranged in a circular pattern around the optical image sensor, all the light source lens groups are arranged on the same plane, there is a certain interval between the light source lens group and the optical image sensor, and there is also a certain interval between adjacent two light source lens groups, the light source lens group contains a point light source and a corresponding lens;

[0025] When the light source with periodically changing light source intensity of the active light source array irradiates an underwater target; the optical image sensor acquires the image information of the underwater target. When the light source intensity gradually changes, the parts of the underwater target at farther distances will successively reach the signal-to-noise ratio of the reflected light that can be collected, so as to realize the sequential imaging of underwater targets at different distances; the control system, based on the three-dimensional contour imaging algorithm of the visible light attenuation characteristic, comprehensively combines the target image information with the light source maximum distance information at the corresponding light source intensity to realize the three-dimensional contour imaging of the underwater target.

[0026] Optionally, the illumination ranges of different light source lens groups have a certain outward deflection angle, and there is a certain overlapping part between the illumination ranges of each different light source lens group.

[0027] Optionally, the periodically changing light source intensity has two working modes:

[0028] In the first working mode, which is suitable for three-dimensional imaging at relatively short distances, the point light sources in the light source lens group are lit up in sequence and the light source intensity changes periodically. After imaging respectively, the images at different angles and distances are comprehensively analyzed to realize three-dimensional imaging within a relatively wide angle range. At this time, the light source intensity of the active light source array during each imaging is the light source intensity of the point light source.

[0029] In the second working mode, which is suitable for three-dimensional imaging at relatively long distances, the point light sources in the light source lens group are lit up simultaneously and the light source intensity changes periodically. The optical image sensor images the overlapping part of the coverage areas of all the point light sources, and comprehensively analyzes the images at different distances in the overlapping part to realize three-dimensional imaging within a relatively long distance range; at this time, the light source intensity of the active light source array during each imaging is the superposition of the light source intensities of all the point light sources.

[0030] Beneficial effects:

[0031] The present invention adjusts the maximum imaging distance by controlling the light source intensity. When the light source intensity gradually changes from low to high or from high to low, target parts at different distances will successively reach the signal-to-noise ratio of the reflected light that can be collected, so as to achieve target information acquisition, and combines with a three-dimensional contour imaging algorithm based on the visible light attenuation characteristic to realize three-dimensional contour imaging. The technical solution of the present invention is simple, with low implementation cost, convenient to use, applicable to underwater imaging in rivers, lakes and oceans, and has good application prospects. Description of the Drawings

[0032] Figure 1 It is a schematic diagram of the overall structure of the three-dimensional underwater target imaging system of the present invention;

[0033] Figure 2 It is a schematic diagram of the overall structure of the light source lens group of the present invention;

[0034] Figure 3 It is a schematic diagram of the irradiation ranges of two working modes of the present invention;

[0035] Figure 4 It is a flowchart of the three-dimensional underwater target imaging method based on dynamic intensity change of the present invention.

[0036] In the figure: active light source array 1, light source lens group 11, point light source 111, lens 112, optical image sensor 2, control system 3, light source intensity control module 31, digital-to-analog conversion chip 311, operational amplifier 312, feedback resistor 313, reference resistor 314, input resistor 315, control module 32. Detailed Embodiments

[0037] To make the present invention more obvious and understandable, preferred embodiments are provided below in conjunction with the accompanying drawings for detailed description as follows.

[0038] As Figure 1 shown, the embodiment of the present invention first provides a three-dimensional underwater target imaging system based on dynamic intensity change, including an active light source array 1, an optical image sensor 2 and a control system 3. The control system 3 includes a light source intensity control module 31 and a control module 32; the light source intensity control module 31 controls and drives the light source intensity in the active light source array to change periodically according to a specific step, and the control module 32 stores and comprehensively analyzes the image information at different angles and distances obtained from the optical image sensor; the light source with periodically changing light source intensity in the active light source array 1 irradiates the underwater target image, and the optical image sensor 2 collects the underwater target image information at different distances for imaging.

[0039] The light source intensity control module 31 is connected to the active light source array 1 to control the light source intensity in the active light source array 1 to change periodically; the control module 32 is connected to the light source intensity control module 31, and the control module 32 is connected to the optical image sensor 2.

[0040] In this embodiment, the control module 32 is an Arduino Mega 2560. In other embodiments, the control module can be other single-chip microcomputers or microcomputers.

[0041] As Figure 2 shown, the active light source array 1 includes a plurality of light source lens groups 11 arranged in a circular pattern around the optical image sensor 2. All the light source lens groups 11 are arranged on the same plane. At the same time, the front ends of all the light source lens groups 11 and the front end of the optical image sensor 2 are aligned on the same plane. There is a certain interval between the light source lens group 11 and the optical image sensor 2, and there is also a certain interval between adjacent two light source lens groups 11. Each light source lens group 11 includes a point light source 111 and a corresponding lens 112.

[0042] In this embodiment, the number of the light source lens groups 11 is 8, which are evenly arranged around the optical image sensor 2 in a circular pattern. The model of the optical image sensor 2 is the CMOS image sensor OV2640 produced by OmniVision.

[0043] In other embodiments, the number of the light source lens groups 11 can be one or more, and multiple light source lens groups 11 can be arranged in other arrangements.

[0044] The point light source 111 in the light source lens group 11 is an omnidirectional light source. The point light source in this embodiment uses a white LED lamp. The deflection directions of the light beams by the lenses 112 in each light source lens group 11 are different. Therefore, the emitted light of different point light sources 111 has a certain outward deflection angle after passing through the lens 112, and can illuminate target objects in a wider angle range; at the same time, the illumination ranges of different light source lens groups 11 have a certain overlapping area at the central position.

[0045] In other embodiments, the point light source can be a metal halide lamp or a high-pressure sodium lamp.

[0046] Under the control and drive of the light source intensity control module 31, the light source intensity of the point light source 111 changes periodically from low to high or from high to low according to a specific step; in this embodiment, the light source intensity of the point light source 111 has a linear relationship with the working power of the point light source 111: light source intensity = luminous efficiency * working power. In this embodiment, the luminous efficiency of the point light source 111 is 180 lm / W; the working power of the point light source 111 is controlled by the light source intensity control module 31 and changes periodically from low to high or from high to low. In this embodiment, the light source intensity step value from low to high is 0.3 watts. When the light source intensity is a specific value, targets within the maximum imaging distance from the optical image sensor 2 can be captured to reflect light and be imaged. As the light source intensity increases, the optical image sensor 2 can image targets in sequence from near to far. By integrating these target images with the corresponding distance information and using a three-dimensional contour imaging algorithm based on the visible light attenuation characteristics, three-dimensional contour imaging can be achieved.

[0047] This system has two working modes:

[0048] In the first working mode, which is suitable for three-dimensional imaging at relatively short distances, the point light sources in the light source lens group are lit up in sequence and the light source intensity changes periodically. After imaging respectively, the images at different angles and distances are comprehensively analyzed to achieve three-dimensional imaging within a relatively wide angle range. At this time, the light source intensity of the active light source array during each imaging is the light source intensity of the point light source.

[0049] In the second working mode, which is suitable for three-dimensional imaging at relatively long distances, the point light sources in the light source lens group are lit up simultaneously and the light source intensity changes periodically. The optical image sensor images the overlapping part of the areas covered by all the point light sources, and comprehensively analyzes the images at different distances in the overlapping part to achieve three-dimensional imaging within a relatively long distance range; at this time, the light source intensity of the active light source array during each imaging is the superposition of the light source intensities of all the point light sources.

[0050] The embodiment of the present invention also provides a three-dimensional imaging method for underwater targets based on dynamic intensity changes. Please refer to Figure 4 , including:

[0051] Step S10, irradiating an underwater target with a light source whose light source intensity changes periodically;

[0052] Step S20, obtaining image information of the underwater target. When the light source intensity gradually changes, the parts of the underwater target at farther distances will sequentially reach the signal-to-noise ratio at which the reflected light can be collected, so as to achieve sequential imaging of underwater targets at different distances.

[0053] Step S30: Based on the three-dimensional contour imaging algorithm of visible light attenuation characteristics, the target image information is integrated with the maximum imaging distance at the current light source intensity to achieve three-dimensional contour imaging of the underwater target.

[0054] Specifically, in this embodiment, the light source intensity of the point light source 111 changes periodically from low to high according to a specific step value under the control and drive of the light source intensity control module 31, illuminating the underwater target. In other embodiments, the light source intensity of the point light source changes periodically from high to low according to a specific step value under the control and drive of the light source intensity control module, illuminating the underwater target.

[0055] When the light source intensity is at a specific value, only the target within the maximum imaging distance from the optical image sensor 2 can capture the reflected light and form an image. As the light source intensity increases, the optical image sensor 2 can sequentially image the targets from near to far. The control module 32 integrates these target images with the corresponding distance information and uses the three-dimensional contour imaging algorithm based on visible light attenuation characteristics to achieve three-dimensional contour imaging.

[0056] The three-dimensional contour imaging algorithm based on visible light attenuation characteristics is specifically as follows:

[0057] Step S31: Set the initial value I0 of the light source intensity of the point light source, set the step value ΔI of the light source intensity of the point light source, and the number of iterations n = 1. I n = I n-1 + ΔI is the light source intensity of the point light source after the nth iteration. S n is the target range within the current maximum imaging distance found by using the optical image sensor for image information acquisition and through the edge detection algorithm after the nth iteration.

[0058] Step S32: Compare the target ranges obtained by imaging in two adjacent iterations. When the light source intensity changes periodically according to a specific step value, if the range of S n-1 is greater than the range of S n , the imaging is interfered by invalid information, n = n - 1, and the previous imaging is performed again; if the range of S n-1 is equal to or less than the range of S n , n = n + 1;

[0059] Step S33: Calculate the maximum imaging distance D n at the current light source intensity I n according to the attenuation model of light in water;

[0060] Step S33: When the light source intensity of the point light source changes to the maximum intensity I max or the minimum intensity I min , the iteration stops. According to the light source intensity I nThe maximum imaging distance D under n and the corresponding target range S n , and the coverage angle range of the point light source, to determine the three-dimensional data information of the underwater target and achieve three-dimensional contour imaging.

[0061] The light source intensity I n The maximum imaging distance D under n The calculation method is specifically as follows:

[0062]

[0063] Where α is the attenuation coefficient of underwater light propagation, which is related to the type of water and the water depth; C reflect is the surface reflection coefficient of the target object; S sensor is the minimum signal-to-noise ratio that the optical image sensor can image; P i is the current noise of the optical image sensor; B BS is the backscattering coefficient underwater, which is related to the type of water and the water depth.

[0064] The three-dimensional image information is stored in a three-dimensional matrix, and the size of the matrix is the number of horizontal pixels × the number of vertical pixels × the number of pixels in the depth direction. Among them, the number of horizontal pixels and the number of vertical pixels are determined by the optical image sensor, and the number of pixels in the depth direction is equal to the number of iterations n. Each value corresponds to an imaging information point in the three-dimensional contour image. The three-dimensional matrix is multiple two-dimensional matrices in the depth direction, and each matrix is S n , and each light intensity I n corresponds to a two-dimensional matrix in the depth direction, and its depth value is D n , and this three-dimensional matrix is filled in the order of depth change to obtain the required three-dimensional contour imaging information.

[0065] As Figure 3 shown, the underwater target three-dimensional imaging system has two working modes:

[0066] In the first working mode, which is suitable for three-dimensional imaging at relatively short distances, the point light source 111 in the light source lens group 11 is lit up in sequence and the light source intensity is adjusted. After the optical image sensor 2 images respectively, the control module 32 comprehensively analyzes the images at different angles and distances to achieve three-dimensional imaging within a relatively wide angle range. At this time, the light source intensity of the active light source array 1 during each imaging is the light source intensity of the point light source 111;

[0067] In the second working mode, which is suitable for three-dimensional imaging at relatively long distances, the point light sources 111 in the light source lens group 11 are simultaneously turned on and the light source intensity is adjusted. The optical image sensor 2 images the overlapping part of the coverage areas of all the point light sources 111, and the control module 32 comprehensively analyzes the images at different distances to achieve three-dimensional imaging within a relatively long distance range; at this time, the light source intensity of the active light source array 1 during each imaging is the superposition of the light source intensities of all the point light sources 111.

[0068] The above are only the preferred examples of the present invention and do not impose any formal limitations on the present invention. Any person skilled in the relevant art may use the disclosed technical content to make changes or modifications into equivalent examples of equivalent changes. However, as long as they do not depart from the technical solution content of the present invention, any simple modifications, equivalent changes, and modifications made to the above examples based on the technical essence of the present invention still fall within the protection scope of the present invention.

Claims

1. A three-dimensional imaging method for underwater targets based on dynamic intensity change, characterized in that The method includes the following steps: irradiating an underwater target with a light source whose light source intensity changes periodically;. Obtaining image information of the underwater target. When the light source intensity gradually changes, the parts of the underwater target at farther distances will successively reach the signal-to-noise ratio of the reflected light that can be collected, so as to realize the sequential imaging of underwater targets at different distances; Based on a three-dimensional contour imaging algorithm for the visible light attenuation characteristic, integrating the target image information with the maximum imaging distance at the current light source intensity to realize three-dimensional contour imaging of the underwater target. Among them, the three-dimensional contour imaging algorithm based on the visible light attenuation characteristic is specifically: Setting the initial value I0 of the light source intensity of the point light source, setting the light source intensity step value ΔI of the point light source and the number of iterations n = 1. In = In-1 + ΔI is the light source intensity of the point light source after the nth iteration. Sn is the target range within the current maximum imaging distance found by using an optical image sensor to collect image information and through an edge detection algorithm after the nth iteration; Comparing the target ranges obtained by imaging after two adjacent iterations. When the light source intensity changes periodically according to a specific step value, if the range of Sn-1 is greater than the range of Sn, the imaging is interfered by invalid information, n = n - 1, and the previous imaging is performed again; if the range of Sn-1 is equal to or less than the range of Sn, n = n + 1; Calculating the maximum imaging distance Dn at the current light source intensity In according to the attenuation model of light in water; After the light source intensity of the point light source changes to the maximum intensity Imax or the minimum intensity Imin, the iteration stops. According to the maximum imaging distance Dn and the corresponding target range Sn at the light source intensity In, and the coverage angle range of the point light source, three-dimensional data information of the underwater target is formed to realize three-dimensional contour imaging.

2. The three-dimensional imaging method for underwater targets based on dynamic intensity change according to claim 1, wherein The step of irradiating the underwater target with the light source whose light source intensity changes periodically includes: Controlling the light source intensity of the point light source in the active light source array to change periodically by adjusting the output level of the light source intensity control module.

3. The three-dimensional imaging method for underwater targets based on dynamic intensity change according to claim 2, wherein, The active light source array includes a plurality of light source lens groups arranged in a circular arrangement around the optical image sensor. All the light source lens groups are arranged on the same plane. At the same time, the front ends of all the light source lens groups and the front end of the optical image sensor are aligned on the same plane. There is a certain interval between the light source lens group and the optical image sensor, and there is also a certain interval between adjacent two light source lens groups. The light source lens group includes a point light source and a corresponding lens. The irradiation ranges of different light source lens groups have a certain outward deflection angle, and there is a certain overlapping part between the irradiation ranges of each different light source lens group.

4. The three-dimensional imaging method for underwater targets based on dynamic intensity variation according to claim 2 or 3, characterized in that, There are two working modes for the periodic change of the light source intensity: In the first working mode, the point light sources in the active light source array are sequentially lit and the light source intensity changes periodically. After imaging respectively, the images at different angles and distances are comprehensively analyzed to realize three-dimensional imaging within a relatively wide angle range. At this time, the light source intensity of the active light source array during each imaging is the light source intensity of the point light source; In the second working mode, the point light sources of the active light source array are simultaneously turned on and the light source intensity changes periodically. The optical image sensor images the overlapping part of the areas covered by all the point light sources, and comprehensively analyzes the images at different distances in the overlapping part to achieve three-dimensional imaging within a relatively long distance range. At this time, the light source intensity of the active light source array during each imaging is the superposition of the light source intensities of all the point light sources.

5. A three-dimensional imaging method for underwater targets based on dynamic intensity variation according to claim 1, characterized in that, The specific calculation method for the maximum imaging distance Dn under the light source intensity In is as follows: Where α is the attenuation coefficient of underwater light propagation, which is related to the type of water and the water depth; Creflect is the surface reflection coefficient of the target object; Ssensor is the minimum signal-to-noise ratio at which the optical image sensor can image; Pi is the current noise of the optical image sensor; BBS is the backscattering coefficient underwater, which is related to the type of water and the water depth.

6. A three-dimensional imaging method for underwater targets based on dynamic intensity change according to claim 1, characterized in that, The specific method for forming the three-dimensional contour imaging information includes: the image information at different light source intensities is stored in a three-dimensional matrix, the size of which is the number of horizontal pixels × the number of vertical pixels × the number of pixels in the depth direction. Among them, the number of horizontal pixels and the number of vertical pixels are determined by the optical image sensor, and the number of pixels in the depth direction is equal to the number of iterations n. Each value corresponds to an imaging information point in the three-dimensional contour image. The three-dimensional matrix is a plurality of two-dimensional matrices in the depth direction. Each matrix is Sn, and each light intensity In corresponds to a two-dimensional matrix in the depth direction, and its depth value is Dn. Fill this three-dimensional matrix in the order of depth change to obtain the required three-dimensional contour imaging information.

7. An underwater target three-dimensional imaging system based on dynamic intensity change, characterized in that Including: An active light source array, an optical image sensor, and a control system. The control system is connected to the active light source array and the optical image sensor. The active light source array includes a number of light source lens groups arranged in a circular pattern around the optical image sensor. All the light source lens groups are arranged on the same plane. There is a certain interval between the light source lens groups and the optical image sensor, and there is also a certain interval between adjacent light source lens groups. Each light source lens group includes a point light source and a corresponding lens. When the light source with a periodically changing light source intensity of the active light source array irradiates an underwater target; the optical image sensor acquires the image information of the underwater target. When the light source intensity gradually changes, the parts of the underwater target at farther distances will successively reach the signal-to-noise ratio at which the reflected light can be collected, so as to achieve sequential imaging of underwater targets at different distances. The control system combines the target image information with the maximum distance information of the light source under the corresponding light source intensity based on the three-dimensional contour imaging algorithm of the visible light attenuation characteristic to achieve three-dimensional contour imaging of the underwater target. Among them, the three-dimensional contour imaging algorithm based on the visible light attenuation characteristic is specifically as follows: Set the initial value I0 of the light source intensity of the point light source, set the light source intensity step value ΔI of the point light source, and the number of iterations n = 1. In = In-1 + ΔI is the light source intensity of the point light source after the nth iteration. Sn is the target range within the current maximum imaging distance found by using the optical image sensor to collect image information and through the edge detection algorithm after the nth iteration. Compare the target ranges obtained from imaging after two adjacent iterations. When the light source intensity changes periodically according to a specific step value, if the range of Sn-1 is greater than the range of Sn, the imaging is interfered by invalid information, n = n - 1, and the previous imaging is performed again; if the range of Sn-1 is equal to or less than the range of Sn, n = n + 1; According to the attenuation model of light in water, calculate the maximum imaging distance Dn at the current light source intensity In; After the light source intensity of the point light source changes to the maximum intensity Imax or the minimum intensity Imin, the iteration stops. According to the maximum imaging distance Dn and the corresponding target range Sn at the light source intensity In, as well as the coverage angle range of the point light source, three-dimensional data information of the underwater target is formed to achieve three-dimensional contour imaging.

8. The three-dimensional imaging system for underwater targets based on dynamic intensity variation according to claim 7, characterized in that: The illumination ranges of different light source lens groups have a certain outward deflection angle, and there is a certain overlapping part between the illumination ranges of each different light source lens group.

9. The three-dimensional imaging system for underwater targets based on dynamic intensity change according to claim 8, characterized in that, The periodic change of the light source intensity has two working modes: In the first working mode, the point light sources in the light source lens group are turned on in sequence and the light source intensity changes periodically. After imaging respectively, the images at different angles and distances are comprehensively analyzed to achieve three-dimensional imaging in a relatively wide angle range. At this time, the light source intensity of the active light source array during each imaging is the light source intensity of the point light source; In the second working mode, the point light sources in the light source lens group are turned on simultaneously and the light source intensity changes periodically. The optical image sensor images the overlapping part of the coverage areas of all point light sources, and the images at different distances in the overlapping part are comprehensively analyzed to achieve three-dimensional imaging in a relatively long distance range; at this time, the light source intensity of the active light source array during each imaging is the superposition of the light source intensities of all point light sources.

Images