Underwater imaging device based on hollow square ring laser illumination

Abstract

The invention discloses an underwater imaging device based on hollow square ring laser illumination, which comprises a transmitting optical system, a receiving optical system, a system controller and an image display, and is characterized in that the transmitting optical system comprises a laser group, an annular light modulation module and an annular lens modulation module and is used for realizing underwater laser illumination; the receiving optical system is composed of a low-illumination imaging detector and a zoom imaging lens, and is used for collecting target information light in different imaging view fields to realize underwater imaging; the system controller is respectively connected and communicated with the transmitting optical system and the receiving optical system, and is used for coordinating and controlling each module in the device; and the image display is used for displaying images under the control of the system controller. The device has the advantages of being low in cost, small in size, low in energy consumption, high in portability, clear in imaging and the like, can be flexibly applied to underwater security monitoring, handheld camera equipment, underwater robot imaging load and the like, and has wide market space.

Description

Technical Field

[0001] The invention relates to the technical field of underwater lighting and imaging equipment, and in particular to an underwater imaging device based on hollow square ring laser lighting. Background Art

[0002] Underwater optical imaging has a wide range of application needs in underwater topographic mapping, fishery farming, environmental monitoring, underwater operations and other fields. Compared with acoustic, microwave and other means, it has the advantages of high imaging resolution, good imaging color, and rich information acquisition in underwater short-distance detection tasks. In the process of underwater imaging, due to the strong absorption effect of water on natural light, the underwater environment is mostly dominated by dark light, and it is usually necessary to increase active lighting to enhance the environment and target reflected light for imaging.

[0003] Common active lighting methods include wide-spectrum LEDs and halogen lamps. Such light sources have high overall power consumption, single lighting methods, low conversion efficiency, and poor transmission directionality. Due to the use of large-angle divergent lighting methods, there is a serious intersection between the lighting and imaging optical paths, which introduces a large amount of backscattered light into the imaging field of view, resulting in blurred imaging, especially difficult to meet the needs of active lighting for imaging in turbid water bodies. In addition, due to the wide-spectrum characteristics of the light source, the selective absorption of the water body causes serious attenuation of the lighting energy, resulting in limited irradiation distance. Although the lighting distance can be increased by increasing the lighting power, it also causes serious energy waste. Lasers have the advantages of narrow spectrum, good directionality, and concentrated energy, and are good underwater lighting sources. Although the interference of backscattered light can be reduced to a certain extent through distance gating, synchronous scanning and other technologies, such as distance gating, synchronous scanning and other technologies, such as frequency-doubled Nd: YAG lasers or argon ion lasers, such imaging systems usually require light sources with narrow spectrum, high energy, good coherence, and high stability. Therefore, there are generally disadvantages such as expensive light source cost, large size, and complex system, which cannot meet the needs of practical applications. Therefore, the lighting method, power consumption, cost, volume and weight, and complexity of the light source are important factors affecting the performance of existing underwater imaging devices. Summary of the invention

[0004] The purpose of the present invention is to provide an underwater imaging device based on hollow square ring laser lighting, which has the advantages of low cost, small size, low energy consumption, high portability, clear imaging, etc. It can be flexibly used for multiple purposes such as underwater security monitoring, handheld camera equipment, underwater robot imaging payload, etc., and has a broad market space.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] An underwater imaging device based on hollow square ring laser illumination, the device comprising a transmitting optical system, a receiving optical system, a system controller and an image display, wherein:

[0007] The transmitting optical system includes a laser group, an annular light modulation module and an annular lens modulation module, which are used to realize underwater laser illumination. The beam diameter, spot shape and divergence angle of the laser beam emitted by the laser group are modulated by the annular light modulation module to form an annular hollow laser with adjustable edge thickness; and the annular lens modulation module adjusts the pitch angle of the illumination laser beam without affecting the imaging light collection;

[0008] The receiving optical system consists of a low-light imaging detector and a zoom imaging lens, which is used to collect target information light under different imaging fields of view to achieve underwater imaging;

[0009] The system controller is connected and communicated with the transmitting optical system and the receiving optical system respectively, and includes an embedded microcontroller, a clock module, an operational amplifier module and a communication module, and is used to coordinate and control various modules in the device, including laser light output switch, optical power adjustment, laser beam expansion diameter adjustment, laser divergence adjustment, laser pitch adjustment and lens zoom, so as to realize automatic control of the imaging process;

[0010] The image display is used for displaying images under the control of the system controller.

[0011] A hollow square ring laser lighting device, the device comprising a ring light modulation module and a ring lens modulation module, wherein:

[0012] The annular light modulation module is composed of a collimating and expanding lens group, a linear light lens, and a convex lens, and is used to modulate a high-energy light beam with a fixed divergence angle emitted by each semiconductor laser tube. The specific modulation process is: first, collimation and beam expansion are performed to convert the light beam into a collimated parallel light with an adjustable spot diameter; then, the linear light lens is used to modulate the circular spot into a divergent "I" linear spot, and the convex lens coaxial with the linear light lens at the rear end is moved to adjust the divergence angle of the "I" linear spot to obtain a beam of parallel linear laser; wherein, each light source and the annular light modulation module can obtain a beam of parallel "I" linear light with an adjustable divergence angle, and then through the effective combination of the upper, lower, left, and right four laser beams, a hollow square ring laser with adjustable edge width and divergence angle is formed;

[0013] The annular lens modulation module is composed of a group of coaxial hollow annular lenses. By adjusting the distance between the two lenses, the pitch angle of the hollow square ring laser generated by the laser group and the annular light modulation module can be adjusted, thereby achieving a high match between the illumination divergence angle and the imaging field angle, thereby improving the illumination and imaging effects.

[0014] It can be seen from the technical solution provided by the present invention that the above-mentioned device has the advantages of low cost, small size, low energy consumption, high portability, clear imaging, etc. It can be flexibly used for multiple purposes such as underwater security monitoring, handheld camera equipment, underwater robot imaging payload, etc., and has a broad market space. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0016] Figure 1 A schematic diagram of the structure of an underwater imaging device based on hollow square ring laser illumination provided by an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of the principle of horizontal illumination and imaging optical paths of the device according to an embodiment of the present invention;

[0018] Figure 3 Schematic diagram of light beam modulation by a linear light lens according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] like Figure 1 The figure shows a schematic diagram of the structure of an underwater imaging device based on hollow square ring laser illumination provided by an embodiment of the present invention, wherein the device includes a transmitting optical system, a receiving optical system, a system controller and an image display, wherein:

[0021] The transmitting optical system includes a laser group, an annular light modulation module and an annular lens modulation module, which are used to realize underwater laser illumination. The beam diameter, spot shape and divergence angle of the laser beam emitted by the laser group are modulated by the annular light modulation module to form an annular hollow laser with adjustable edge thickness; and the annular lens modulation module adjusts the pitch angle of the illumination laser beam without affecting the imaging light collection;

[0022] The receiving optical system consists of a low-light imaging detector and a zoom imaging lens, which is used to collect target information light under different imaging fields of view to achieve underwater imaging;

[0023] The system controller is connected and communicated with the transmitting optical system and the receiving optical system respectively, and includes an embedded microcontroller, a clock module, an operational amplifier module and a communication module, and is used to coordinate and control various modules in the device, including laser light output switch, optical power adjustment, laser beam expansion diameter adjustment, laser divergence adjustment, laser pitch adjustment and lens zoom, so as to realize automatic control of the imaging process;

[0024] The image display is used for displaying images under the control of the system controller.

[0025] In a specific implementation, the device also includes a housing for sealing, connecting, protecting, and fixing other modules, and providing necessary counterweight for the overall device.

[0026] In the transmitting optical system, the laser group adopts semiconductor laser tubes, which are respectively distributed at the upper, lower, left and right positions of the receiving optical system; the present embodiment adopts semiconductor green laser tubes, which have the advantages of low cost, small size, light weight, low power consumption, easy integration, etc. The light output power of a single tube can reach 500mW, and the overall electrical power is less than 10W. Compared with wide-spectrum lighting sources such as high-power LEDs, it not only significantly reduces the lighting power consumption, but also has higher transmission efficiency and anti-attenuation ability underwater due to the better directionality and narrower spectrum width of the laser beam, so the lighting distance is farther; compared with all-solid-state lasers and argon ion lasers, etc., semiconductor green laser tubes not only have smaller size and cost advantages, but also have smaller coherence and diffraction effects on underwater imaging;

[0027] The annular light modulation module is composed of a collimating and expanding lens group, a linear light lens, and a convex lens, and is used to modulate a high-energy light beam with a fixed divergence angle emitted by each semiconductor laser tube. The specific modulation process is: first, collimation and beam expansion are performed to convert the light beam into a collimated parallel light with an adjustable spot diameter; then, the linear light lens is used to modulate the circular spot into a divergent "I" linear spot, and the convex lens coaxial with the linear light lens at the rear end is moved to adjust the divergence angle of the "I" linear spot to obtain a beam of parallel linear laser; wherein, each light source and the annular light modulation module can obtain a beam of parallel "I" linear light with an adjustable divergence angle, and then through the effective combination of the upper, lower, left, and right four laser beams, a hollow square ring laser with adjustable edge width and divergence angle is formed;

[0028] like Figure 2The figure shows the schematic diagram of the horizontal illumination and imaging optical path principle of the device according to the embodiment of the present invention, which includes: 1-device housing; 2-left semiconductor laser tube; 3-left collimating beam expander group; 4-left linear light lens; 5-left convex lens; 6-hollow ring lens group; 7, 8 hollow ring lenses; 9-right semiconductor laser tube; 10-right collimating beam expander group; 11-camera; 12-right linear light lens; 13-zoom lens; 14-right convex lens. Reference Figure 2 :The divergent illumination laser is modulated into a linear laser beam, and a square ring illumination laser is formed to match the imaging field of view. During the illumination process, the influence of the illumination light path and water backscattering in the imaging field of view can be effectively reduced, and the imaging quality can be enhanced. Linear light lens ( Figure 2 4 and 12) in the figure use a Powell lens, and the linear beam generated is more concentrated in energy than the traditional divergent illumination light. However, due to the structural defects of the ordinary cylindrical lens, the linear effect is limited by the non-uniform Gaussian laser beam.

[0029] like Figure 3 The figure shows a schematic diagram of the light beam modulation of the line light lens according to the embodiment of the present invention, 15 is the incident laser beam of the line light lens; 16 is the linear laser beam modulated by the line light lens; 17 is the incident laser cross section of the line light lens; 18 is the exit laser cross section of the line light lens. The line light lens is designed based on a complex two-dimensional aspheric curve, and the arc top of the surface is designed. By generating a large amount of spherical aberration, the light is redistributed along a straight line, the light in the central area is reduced, and the light intensity at the end of the line is increased, so that the energy distribution of the modulated linear laser is more uniform.

[0030] The annular lens modulation module is composed of a group of coaxial hollow annular lenses, such as Figure 2 As shown in 7 and 8, by adjusting the distance between the two lenses, the pitch angle of the hollow square ring laser generated by the laser group and the annular light modulation module can be adjusted, thereby achieving a high match between the illumination divergence angle and the imaging field angle, thereby improving the illumination and imaging effects. Since the middle of the annular lens is a hollow structure, the target reflected light can directly enter the imaging module without refraction, effectively realizing the multiplexing of the illumination and imaging optical paths, avoiding redundant reflective devices, and making the entire optical path structure more compact, effectively compressing the internal space of the device.

[0031] In a specific implementation, the imaging detector of the receiving optical system has low illumination and wide dynamic range, and the minimum sensitivity in color mode is 0.001 Lux, so as to better adapt to the underwater dark light environment; the zoom imaging lens has an electrically controllable function and ensures that the imaging field of view angle is ≤ the annular laser divergence angle.

[0032] In addition, the annular light modulation module can modulate and generate square annular, circular annular or polygonal annular illumination laser, and the corresponding light source for generating the annular laser beam is a single laser or a combination of multiple lasers using a beam splitting structure.

[0033] The linear light lens in the annular light modulation module can be a Powell lens, a cylindrical lens, a wave mirror or a DOE diffraction element; the semiconductor laser source is replaced by a narrow spectrum monochromatic light source with a small divergence angle.

[0034] The collimating beam expanding lens group in the annular light modulation module can be replaced by a combination of concave and convex lens groups;

[0035] The embedded microcontroller in the system controller can be replaced by a DSP processor or a system on chip.

[0036] The embodiment of the present invention further provides a hollow square ring laser lighting device, the device comprising a ring light modulation module and a ring lens modulation module, wherein:

[0037] The annular light modulation module is composed of a collimating and expanding lens group, a linear light lens, and a convex lens, and is used to modulate a high-energy light beam with a fixed divergence angle emitted by each semiconductor laser tube. The specific modulation process is: first, collimation and beam expansion are performed to convert the light beam into a collimated parallel light with an adjustable spot diameter; then, the linear light lens is used to modulate the circular spot into a divergent "I" linear spot, and the convex lens coaxial with the linear light lens at the rear end is moved to adjust the divergence angle of the "I" linear spot to obtain a beam of parallel linear laser; wherein, each light source and the annular light modulation module can obtain a beam of parallel "I" linear light with an adjustable divergence angle, and then through the effective combination of the upper, lower, left, and right four laser beams, a hollow square ring laser with adjustable edge width and divergence angle is formed;

[0038] The annular lens modulation module is composed of a group of coaxial hollow annular lenses. By adjusting the distance between the two lenses, the pitch angle of the hollow square ring laser generated by the laser group and the annular light modulation module can be adjusted, thereby achieving a high match between the illumination divergence angle and the imaging field angle, thereby improving the illumination and imaging effects.

[0039] In a specific implementation, the annular light modulation module modulates and generates square ring, circular ring or polygonal ring illumination laser, and the corresponding light source for generating the annular laser beam is a single laser or a combination of multiple lasers using a beam splitting structure.

[0040] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to professional and technical personnel in the field.

[0041] In summary, the device described in the embodiment of the present invention has the following advantages:

[0042] 1. The ring light modulation module generates a hollow ring illumination laser that matches the rectangular imaging field of view. During the illumination process, the overlap between the illumination light path and the imaging field of view can be effectively reduced. The forward scattered light of the hollow ring illumination laser is used for field illumination, which avoids the interference of the backscattered interference light on the target reflected light, thus significantly improving the imaging quality and imaging distance of the image sensor, especially enhancing the adaptability to turbid water bodies.

[0043] 2. The light source in the device uses a low-cost, lightweight semiconductor laser as the lighting source, which is small in size and low in power consumption. Compared with high-power LED and other wide-spectrum lighting sources, the spectrum of the light source is narrower, the transmission direction is stronger, and the energy is more concentrated. It can more effectively reduce the absorption attenuation of water bodies, improve energy utilization, and reduce lighting power consumption;

[0044] 3. The present invention generates a linear laser beam through modulation of a linear light lens. Compared with the energy of the traditional divergent illumination light, the energy is more concentrated, and the divergence angle and width of the laser beam are adjustable, which can better adapt to the annular light modulation module of different underwater environments. The linear light lens preferably adopts a Powell linear light lens to modulate the divergent illumination laser into a linear laser beam. Compared with the ordinary cylindrical lens, the linear effect is reduced by the limitation of the uneven Gaussian laser beam;

[0045] 4. The hollow annular lens module of the present invention is a hollow structure, so the target reflected light can directly enter the imaging module without refraction, effectively realizing the multiplexing of the illumination and imaging light paths, avoiding redundant reflective devices, and making the device light path structure more compact;

[0046] 5. The device of the present invention has the advantages of low cost, small size, low energy consumption, high portability, clear imaging, etc. It can be flexibly used for multiple purposes such as underwater security monitoring, handheld camera equipment, underwater robot imaging payload, etc., and has a broad market space.

[0047] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. An underwater imaging device based on hollow square ring laser illumination, characterized in that: The device comprises a transmitting optical system, a receiving optical system, a system controller and an image display, wherein: The transmitting optical system includes a laser group, an annular light modulation module and an annular lens modulation module, which are used to realize underwater laser illumination. The beam diameter, spot shape and divergence angle of the laser beam emitted by the laser group are modulated by the annular light modulation module to form an annular hollow laser with adjustable edge thickness; and the annular lens modulation module adjusts the pitch angle of the illumination laser beam without affecting the imaging light collection; The receiving optical system consists of a low-light imaging detector and a zoom imaging lens, which is used to collect target information light under different imaging fields of view to achieve underwater imaging; The system controller is connected and communicated with the transmitting optical system and the receiving optical system respectively, and includes an embedded microcontroller, a clock module, an operational amplifier module and a communication module, and is used to coordinate and control various modules in the device, including laser light output switch, optical power adjustment, laser beam expansion diameter adjustment, laser divergence adjustment, laser pitch adjustment and lens zoom, so as to realize automatic control of the imaging process; The image display is used for displaying images under the control of the system controller.

2. The underwater imaging device based on hollow square ring laser illumination according to claim 1, characterized in that: In the transmitting optical system, the laser group adopts semiconductor laser tubes, which are respectively distributed at the upper, lower, left and right positions of the receiving optical system; The annular light modulation module is composed of a collimating and expanding lens group, a linear light lens, and a convex lens, and is used to modulate a high-energy light beam with a fixed divergence angle emitted by each semiconductor laser tube. The specific modulation process is: first, collimation and beam expansion are performed to convert the light beam into a collimated parallel light with an adjustable spot diameter; then, the linear light lens is used to modulate the circular spot into a divergent "I" linear spot, and the convex lens coaxial with the linear light lens at the rear end is moved to adjust the divergence angle of the "I" linear spot to obtain a beam of parallel linear laser; wherein, each light source and the annular light modulation module can obtain a beam of parallel "I" linear light with an adjustable divergence angle, and then through the effective combination of the upper, lower, left, and right four laser beams, a hollow square ring laser with adjustable edge width and divergence angle is formed; The annular lens modulation module is composed of a group of coaxial hollow annular lenses. By adjusting the distance between the two lenses, the pitch angle of the hollow square ring laser generated by the laser group and the annular light modulation module can be adjusted, thereby achieving a high match between the illumination divergence angle and the imaging field angle, thereby improving the illumination and imaging effects.

3. The underwater imaging device based on hollow square ring laser illumination according to claim 1, characterized in that: The imaging detector of the receiving optical system has low illumination and wide dynamic range, and the minimum sensitivity in color mode is 0.001 Lux, so as to better adapt to the underwater dark light environment; The zoom imaging lens has an electrically controllable function and ensures that the imaging field angle is ≤ the annular laser divergence angle.

4. The underwater imaging device based on hollow square ring laser illumination according to claim 1, characterized in that: The annular light modulation module is used for modulating and generating square annular, circular annular or polygonal annular illumination laser, and the corresponding light source for generating the annular laser beam is a single laser or a combination of multiple lasers using a beam splitting structure.

5. The underwater imaging device based on hollow square ring laser illumination according to claim 2, characterized in that: The linear light lens in the annular light modulation module adopts a Powell lens, a cylindrical lens, a wave mirror or a DOE diffraction element; The semiconductor laser source is replaced by a light source with a narrow spectrum, monochromatic color and a small divergence angle.

6. The underwater imaging device based on hollow square ring laser illumination according to claim 2, characterized in that: The collimating beam expanding lens group in the annular light modulation module can be replaced by a combination of concave and convex lens groups; The embedded microcontroller in the system controller can be replaced by a DSP processor or a system on chip.

7. A hollow square ring laser lighting device, characterized in that: The device comprises a ring light modulation module and a ring lens modulation module, wherein: The annular light modulation module is composed of a collimating and expanding lens group, a linear light lens, and a convex lens, and is used to modulate a high-energy light beam with a fixed divergence angle emitted by each semiconductor laser tube. The specific modulation process is: first, collimation and beam expansion are performed to convert the light beam into a collimated parallel light with an adjustable spot diameter; then, the linear light lens is used to modulate the circular spot into a divergent "I" linear spot, and the convex lens coaxial with the linear light lens at the rear end is moved to adjust the divergence angle of the "I" linear spot to obtain a beam of parallel linear laser; wherein, each light source and the annular light modulation module can obtain a beam of parallel "I" linear light with an adjustable divergence angle, and then through the effective combination of the upper, lower, left, and right four laser beams, a hollow square ring laser with adjustable edge width and divergence angle is formed; The annular lens modulation module is composed of a group of coaxial hollow annular lenses. By adjusting the distance between the two lenses, the pitch angle of the hollow square ring laser generated by the laser group and the annular light modulation module can be adjusted, thereby achieving a high match between the illumination divergence angle and the imaging field angle, thereby improving the illumination and imaging effects.

8. The hollow square ring laser lighting device according to claim 7, characterized in that: The annular light modulation module is used for modulating and generating square annular, circular annular or polygonal annular illumination laser, and the corresponding light source for generating the annular laser beam is a single laser or a combination of multiple lasers using a beam splitting structure.

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