Fiber integrated modulation underwater long-distance optical detection system

Abstract

The invention relates to the technical field of underwater optical imaging, in particular to a fiber integrated modulation underwater long-distance optical detection system, a laser illumination optical module is used for emitting two beams of light with an included angle to an underwater target water body area, the two beams of light form spatial variation interference fringes in the target water body area, and light and shade alternate illumination light is generated; the Sabortus imaging optical module is used for shooting a target water body area under the illumination light according to Sabortus imaging conditions to obtain an underwater space image; and the circuit control core group is used for controlling the laser illumination optical module to emit two beams of light and collecting underwater space images from the Sabortus imaging optical module. According to the invention, a fiber integrated modulation fiber interferometer structure is introduced as a light source output regulation and control module, so that an emergent beam forms an angle to realize space interference, the regulation and control performance of a light source part of a traditional Saborne imaging laser radar is effectively improved, the size and weight are effectively reduced, and the Saborne imaging laser radar has the advantages and characteristics of low cost and stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of underwater optical imaging, and particularly relates to a fiber integrated modulation underwater long-distance optical detection system. BACKGROUND

[0002] The existing underwater detection technology can be divided into in-situ detection technology and sampling off-line detection technology. Compared with the off-line sampling detection of limited samples, the in-situ detection in a complex wide range such as deep sea has more value. Among the many in-situ detection technologies, not only can the actual information of the water sample be detected online, but some can also search and explore the geological and mineral resources of the seabed and the ocean floor. In this process, the increasing application requirements put forward higher requirements on the information acquisition range and capacity of the underwater detection technology.

[0003] The in-situ detection technology method based on acoustics and optics has more practical value in a large range of complex and variable water environments. Although the acoustic detection method can achieve lower transmission loss in water, it still lags behind the optical detection method in the resolution limit. Among the existing various underwater high-resolution optical detection technologies, the active excitation type underwater optical detection technology has better environmental background resistance and application potential in turbid water and deep sea dark environment. However, the current active detection technology is always difficult to be effectively applied due to the problems of high cost, large size, complex system and other issues of the gate selection type hardware. At the same time, although the current Shashima imaging lidar technology is low in cost, the regulation and control ability of the continuous laser illumination light source is poor, and the signal analysis still relies on the direct collection of traditional image sensors. The signal-to-noise ratio of long-distance detection is poor, and it is difficult to break through the limit of traditional underwater detection distance. SUMMARY

[0004] Therefore, the present application aims to provide a fiber integrated modulation underwater long-distance optical detection system, which improves the regulation and control of the existing Shashima imaging lidar light source part, introduces a fiber integrated modulation optical fiber interferometer structure as a light source output regulation and control module, and relies on the fiber integrated modulation optical fiber interferometer structure to increase the regulation and control of the traditional Shashima imaging lidar light source part, effectively reduce the size and weight, and have the advantages of low cost and stability.

[0005] To achieve the above purpose, the technical scheme of the present application is as follows: The application discloses an underwater long-distance optical detection system integrated with fiber modulation, which comprises a laser illumination optical module, a Scheimpflug imaging optical module and a circuit control core group.

[0006] Further, the laser illumination optical module comprises a laser unit, a first laser arm and a second laser arm; the first laser arm and the second laser arm receive laser from the laser unit and emit laser to the target water area at an included angle, so that the two beams of light form spatially varying interference fringes in the target water area.

[0007] Further, the laser unit comprises a laser light source and a light source fiber splitter; the light source fiber splitter splits the laser from the laser light source into first laser and second laser, and transmits the first laser into the first laser arm and the second laser into the second laser arm.

[0008] Further, the first laser arm comprises a first fiber splitter and a first fiber collimator group; the first fiber collimator group comprises a plurality of first fiber collimators arranged in parallel; the first fiber splitter splits the first laser, and inputs the split laser into the corresponding first fiber collimator; and the first fiber collimator emits the collimated laser into the target water area.

[0009] Further, the second laser arm comprises a piezoelectric ceramic structure, a second fiber splitter and a second fiber collimator group; the second fiber collimator group comprises a plurality of second fiber collimators arranged in parallel and having the same number as the first fiber collimators; the light exit angle between the first fiber collimators and the second fiber collimators satisfies the condition of forming spatially varying interference fringes; the second fiber splitter splits the second laser, and inputs the split laser into the corresponding second fiber collimator; and the second fiber collimator emits the collimated laser into the target water area; the optical fibers between the light source fiber splitter and the second fiber splitter are wound on the piezoelectric ceramic structure; the piezoelectric ceramic structure adjusts the stretching and shrinking of the wound optical fibers, changes the arm length of the second laser arm, and further adjusts the light and dark change of the illumination light.

[0010] Furthermore, the Shash imaging optical module includes an image sensor and an imaging lens group. The light beam from the target water area passes through the imaging lens group and enters the image sensor for imaging, thus obtaining an underwater space image. The three planes—the plane where the target surface of the image sensor is located, the central plane of the imaging lens group, and the longitudinal plane of the target water area—converge at a point.

[0011] Furthermore, the circuit control core group includes an industrial computer and a piezoelectric ceramic control driver; wherein, the industrial computer is used to control the laser source to emit laser light and to receive underwater space images from the image sensor; the piezoelectric ceramic control driver is used to control the piezoelectric ceramic structure to adjust the extension and retraction of the wound optical fiber.

[0012] Furthermore, the watertight outer shell structure includes a cylindrical support shell, an imaging receiving optical window, and an output laser illumination window. The imaging receiving optical window and the output laser illumination window are located in the cylindrical support shell. The cylindrical support shell houses and seals the laser illumination optical module, the Saxony imaging optical module, and the circuit control core group. The laser emitted by the laser illumination optical module illuminates the target water area through the output laser illumination window, and the beam generated in the target water area enters the Saxony imaging optical module through the imaging receiving optical window.

[0013] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) The fiber-integrated modulation underwater long-distance optical detection system created by the present invention fully combines the advantages of fiber-integrated modulation devices and Saxony imaging. It integrates the compactness, layout flexibility, and integrated modulation operability of fiber interferometer with the high relative aperture and tilted large depth of field characteristics of Saxony imaging, breaks through the limitation of the deterioration of the backscattering signal-to-noise ratio in long-distance detection, and realizes spatial dynamic structure illumination in the spatial depth direction of laser light source with low-cost fiber components, which improves the problems of poor controllability and insufficient resolution of traditional Saxony imaging illumination light source. (2) In the fiber-integrated modulation underwater long-distance optical detection system created by the present invention, the dual fiber collimators are tilted to realize dynamic structural illumination of the depth direction of the water body to be measured, and with the high-speed modulation of piezoelectric ceramics, the problem of the degradation of the signal-to-noise ratio of underwater long-distance imaging can be effectively improved. (3) In the fiber-integrated modulation underwater long-distance optical detection system created by the present invention, the watertight shell structure meets the requirements of wide and narrow lateral observation range, as well as the requirements of use in shallow water areas, turbid water bodies or deep sea high pressure environments. Relying on the high stability of fiber optic integrated devices and the Saxophone imaging system module, it can achieve highly reliable, highly stable and long-life underwater applications. Attached Figure Description

[0014] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A schematic diagram of the structure of the fiber-integrated modulation underwater long-range optical detection system described in the embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the laser illumination optical module described in the embodiment of the present invention; Figure 3 A schematic diagram illustrating the working principle of the fiber-integrated modulation underwater long-range optical detection system described in an embodiment of the present invention.

[0015] Explanation of reference numerals in the attached figures: 1. Laser source; 2. Fiber optic splitter for the source; 3. First fiber optic splitter; 4. First fiber optic collimator; 5. Piezoelectric ceramic structure; 6. Second fiber optic splitter; 7. Second fiber optic collimator; 8. Image sensor; 9. Imaging lens assembly; 10. Industrial computer; 11. Piezoelectric ceramic control driver; 12. Cylindrical support housing; 13. Imaging receiving optical window; 14. Outgoing laser illumination window. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0018] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] like Figure 1 and Figure 2 As shown in the embodiment of the present invention, the fiber-integrated modulation underwater long-range optical detection system includes a laser illumination optical module, a Safran imaging optical module, a circuit control core group, and a watertight shell structure. The laser illumination optical module emits two beams of light at an angle to an underwater target water body region. The two beams form spatially varying interference fringes in the target water body region, producing alternating bright and dark illumination light. The Safran imaging optical module is used to photograph the target water body region under the illumination light according to Safran imaging conditions, obtaining an underwater spatial image. The circuit control core group controls the laser illumination optical module to emit the two beams of light and collects the underwater spatial image from the Safran imaging optical module. The watertight shell structure is used to seal the laser illumination optical module, the Safran imaging optical module, and the circuit control core group.

[0022] In some embodiments, the laser illumination optical module includes a laser unit, a first laser arm, and a second laser arm. The first and second laser arms receive laser light from the laser unit and then emit laser light at an angle towards the target water area, causing the two beams to form spatially varying interference fringes in the target water area. In this invention, the first and second laser arms form an optical fiber integrated interferometer modulation structure. The light emitted from the first and second laser arms forms a certain angle in the underwater target water area, and the two emitted laser beams strictly overlap at an angle in the target water area, thus forming spatially varying interference fringes and creating alternating bright and dark illumination light in the target water area.

[0023] The laser unit includes a laser source 1 and a light source fiber splitter 2. The light source fiber splitter 2 splits the laser from the laser source 1 into a first laser and a second laser, and transmits the first laser to a first laser arm and the second laser to a second laser arm.

[0024] like Figure 2As shown, the first laser arm includes a first fiber optic splitter 3 and a first fiber optic collimator group. The first fiber optic collimator group includes multiple first fiber optic collimators 4 arranged in parallel. The first fiber optic splitter 3 splits the first laser beam and inputs the split laser beam into the corresponding first fiber optic collimator 4. The first fiber optic collimator 4 directs the collimated laser beam into the target water region. It should be noted that the length of the first laser arm is defined as the length of the transmission path of the laser beam from the light source fiber optic splitter 2 to the first fiber optic collimator 4.

[0025] like Figure 2As shown, the second laser arm includes a piezoelectric ceramic structure 5, a second fiber optic splitter 6, and a second fiber optic collimator group. The second fiber optic collimator group includes parallel second fiber optic collimators 7, the same number as the first fiber optic collimators 4, and the light exit angle between the first fiber optic collimators 4 and the second fiber optic collimators 7 satisfies the condition for forming spatially varying interference fringes. Consistent with the length of the first laser arm, the length of the second laser arm is defined as the length of the transmission path of the light beam from the light source fiber optic splitter 2 to the second fiber optic collimator 7. The second fiber optic splitter 6 splits the second laser beam and inputs the split laser beam into the corresponding second fiber optic collimator 7, which then directs the collimated laser beam into the target water area. The optical fiber between the light source fiber optic splitter 2 and the second fiber optic splitter 6 is wound around the piezoelectric ceramic structure 5. By adjusting the extension and retraction of the wound optical fiber, the piezoelectric ceramic structure 5 changes the arm length of the second laser arm, achieving dynamic and precise adjustment and control of the arm length difference between the first and second laser arms, thereby adjusting the brightness of the illumination light. In some other embodiments, the optical fibers connected to the light source fiber splitter 2 and the first fiber collimator 4 and the second fiber collimator 7 can be simultaneously wound around the piezoelectric ceramic structure 5. However, it is necessary to ensure that the expansion and contraction of the optical fibers in the two laser arms are inconsistent during the piezoelectric ceramic expansion process of the piezoelectric ceramic structure 5. This ensures that the modulation function of the interferometer modulation structure formed by the first and second laser arms is effectively realized, thus achieving fiber-integrated modulation. The arrangement of the first and second fiber collimator groups in this invention, without increasing the number of piezoelectric ceramic structures 5, effectively compensates for the narrow output light path and the narrow lateral width of the target water body area. The parallel arrangement of the fiber collimators in the first and second fiber collimator groups effectively avoids additional interference fringes, preventing image resolution confusion. Furthermore, to improve the differential modulation of the added channels, the first and second fiber collimators forming an angle with the output light can be set as a single fiber collimator group, with different interference path differences between different groups of fiber collimators. Meanwhile, all optical components in the laser illumination optical module are wavelength-dependent. Given that blue-green light has the lowest transmission loss in water, with an attenuation coefficient of approximately 0.4 dB / m, laser source 1 in the blue-green light band should be selected under normal working conditions. In special working scenarios and for applications such as biological phototaxis analysis, laser source 1 in other corresponding bands can be used. Other optical components in the laser illumination optical module are selected in conjunction with the blue-green light band.

[0026] In some other embodiments, the first laser arm may output only a single laser beam, in which case the first fiber optic splitter 3 is not required for beam splitting. Specifically, for example... Figure 1As shown, the first laser arm includes a first fiber collimator 4. Correspondingly, in the first laser arm, the first laser output from the light source fiber splitter 2 is collimated by the first fiber collimator 4 and directly enters the target water area. If the first laser arm only outputs one laser beam, the second laser arm must correspond to the first laser arm and output only one laser beam. Only then can the lasers output by the first and second laser arms form an angle in the target water area, thereby forming spatially varying interference fringes. Specifically, the second laser arm includes a piezoelectric ceramic structure 5 with a fiber ring wound around it and a second fiber collimator 7. The second laser output from the light source fiber splitter 2 in the laser unit enters the second fiber collimator 7 after passing through the wound fiber ring. The second fiber collimator 7 then directs the collimated laser into the target water area.

[0027] The Shapiro imaging optical module comprises an image sensor 8 and an imaging lens group 9. A beam of light from the target water area passes through the imaging lens group 9 and enters the image sensor 8 for imaging, resulting in an underwater spatial image. The Shapiro imaging optical module must satisfy the Shapiro imaging condition, namely, the plane containing the target surface of the image sensor 8, the central plane of the imaging lens group 9, and the longitudinal plane of the target water area must converge at a single point. The imaging lens group 9 can be a complex imaging lens group composed of multiple lenses, not limited to single-lens imaging, but its ray geometry analysis can be compared to that of a single lens. A core advantage of the Shapiro imaging optical module is that it does not need to worry about the depth of field as in traditional imaging lens designs. Generally, the depth of field is inversely proportional to the relative aperture of the optical lens; that is, the larger the relative aperture, the smaller the depth of field. In traditional optical systems, this undoubtedly limits the high-throughput light collection and detection capabilities of underwater scenes. However, in the Shapiro imaging optical structure, the depth of field changes with the longitudinal angle, thus the Shapiro imaging optical lens group can achieve a larger relative aperture (smaller F-number) effect.

[0028] The core circuit control unit includes an industrial computer 10 and a piezoelectric ceramic control driver 11. The industrial computer 10 is used to control the laser source 1 to emit laser light and to receive underwater space images from the image sensor 8. The piezoelectric ceramic control driver 11 is used to control the piezoelectric ceramic structure 5 to adjust the extension and retraction of the wound optical fiber.

[0029] The watertight housing structure includes a cylindrical support housing 12, an imaging receiving optical window 13, and an output laser illumination window 14. The imaging receiving optical window 13 and the output laser illumination window 14 are disposed on the cylindrical support housing 12. The cylindrical support housing 12 houses and seals the laser illumination optical module, the Saxony imaging optical module, and the circuit control core assembly. The laser emitted by the laser illumination optical module illuminates the target water area through the output laser illumination window 14, and the beam generated in the target water area enters the Saxony imaging optical module through the imaging receiving optical window 13.

[0030] In this embodiment of the invention, for engineering considerations during application, pressure resistance needs to be fully considered in deep-sea conditions. Therefore, the cylindrical support shell 12 is designed as a cylindrical structure. The imaging receiving optical window 13 and the laser illumination output window 14 are primarily made of trapezoidal frustum acrylic or sapphire material, with specific design tailored to the operating water depth. The thickness-to-diameter ratio is often used as an empirical parameter for calculation and analysis. Furthermore, in ultra-high pressure operating environments, this embodiment of the invention designs the cylindrical support shell 12 protecting the laser illumination optical module and the Saxony imaging optical module as a separate double-cylinder structure. This reduces the difficulty of shell structure design and the required cylinder wall thickness. Additionally, the imaging receiving optical window 13 and the laser illumination output window 14 are coated with an anti-reflection film that matches the wavelength of the laser emitted by the laser source 1.

[0031] In this embodiment of the invention, the system structure can adopt an offline working mode powered by a built-in battery, or it can use a tail cable for remote control of the underwater laboratory or the surface platform, but watertight penetration and watertight cable deployment are required.

[0032] The specific working principle of the system created by this invention is as follows: Figure 3 As shown, in traditional underwater Schaperone imaging applications, due to water absorption and scattering, the oblique backscattered or reflected signals gradually weaken with increasing depth, leading to a gradual deterioration of the signal-to-noise ratio and a corresponding decrease in underwater detection capability. Essentially, the signal-to-noise ratio differs significantly between near and far locations, placing high demands on the detector's dynamic range; it is difficult to achieve breakthroughs in detection distance when the detector is fixed. In this invention, spatial interference fringes can be formed in the target water area through integrated optical fiber modulation. Furthermore, by controlling the piezoelectric ceramic drive and changing the arm length difference between the two laser arms, the signal-to-noise ratio in the target water area is dynamically adjusted. This modulated signal-to-noise ratio change enhances the resolution of distant optical signals, overcoming the challenge of long-distance detection.

[0033] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0034] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A fiber-integrated modulated underwater long-range optical detection system, characterized in that, include: The laser illumination optical module is used to emit two beams of light at an angle to an underwater target water body area. The two beams of light form spatially varying interference fringes in the target water body area, producing alternating bright and dark illumination light. The Saxophone imaging optical module is used to capture images of the target water body area under illumination light according to the Saxophone imaging conditions, thereby obtaining underwater spatial images. The circuit control core group is used to control the laser illumination optical module to emit two beams of light and to collect underwater space images from the Saxony imaging optical module; A watertight housing structure is used to seal the laser illumination optical module, the Saxony imaging optical module, and the circuit control core assembly.

2. The fiber-integrated modulation underwater long-range optical detection system according to claim 1, characterized in that, The laser illumination optical module includes a laser unit, a first laser arm, and a second laser arm. The first laser arm and the second laser arm receive laser light from the laser unit and then emit laser light at an angle toward the target water body area, so that the two beams of light form spatially varying interference fringes in the target water body area.

3. The fiber-integrated modulation underwater long-range optical detection system according to claim 2, characterized in that, The laser unit includes a laser source and a fiber optic splitter. The fiber optic splitter splits the laser from the laser source into a first laser and a second laser, and transmits the first laser to a first laser arm and the second laser to a second laser arm.

4. The fiber-integrated modulation underwater long-range optical detection system according to claim 3, characterized in that, The first laser arm includes a first fiber optic splitter and a first fiber optic collimator group. The first fiber optic collimator group includes multiple first fiber optic collimators arranged in parallel. The first fiber optic splitter splits the first laser beam and inputs the split laser beam into the corresponding first fiber optic collimator. The first fiber optic collimator directs the collimated laser beam into the target water area.

5. The fiber-integrated modulation underwater long-range optical detection system according to claim 4, characterized in that, The second laser arm includes a piezoelectric ceramic structure, a second fiber beam splitter, and a second fiber collimator group. The second fiber collimator group includes parallel second fiber collimators, the same number as the first fiber collimators, and the light emission angle between the first fiber collimator and the second fiber collimator satisfies the condition for forming spatially varying interference fringes. The second fiber optic splitter splits the second laser beam and inputs the split laser beam into the corresponding second fiber optic collimator. The second fiber optic collimator then directs the collimated laser beam into the target water area. The optical fiber between the light source fiber splitter and the second fiber splitter is wound on a piezoelectric ceramic structure. The piezoelectric ceramic structure adjusts the extension and retraction of the wound optical fiber, changes the arm length of the second laser arm, and thus adjusts the brightness of the illumination light.

6. The fiber-integrated modulation underwater long-range optical detection system according to claim 5, characterized in that, The Shashka imaging optical module includes an image sensor and an imaging lens group. The light beam from the target water body region passes through the imaging lens group and enters the image sensor for imaging, thus obtaining an underwater space image. The three planes—the plane where the target surface of the image sensor is located, the central plane of the imaging lens group, and the longitudinal plane of the target water body region—converge at a point.

7. The fiber-integrated modulation underwater long-range optical detection system according to claim 6, characterized in that, The core circuit control unit includes an industrial computer and a piezoelectric ceramic control driver; the industrial computer is used to control the laser source to emit laser light and to receive underwater space images from the image sensor; the piezoelectric ceramic control driver is used to control the piezoelectric ceramic structure to adjust the extension and retraction of the wound optical fiber.

8. The fiber-integrated modulation underwater long-range optical detection system according to claim 1, characterized in that, The watertight housing structure includes a cylindrical support housing, an imaging receiving optical window, and an output laser illumination window. The imaging receiving optical window and the output laser illumination window are located in the cylindrical support housing. The cylindrical support housing houses and seals the laser illumination optical module, the Saxony imaging optical module, and the circuit control core group. The laser emitted by the laser illumination optical module illuminates the target water area through the output laser illumination window, and the beam generated in the target water area enters the Saxony imaging optical module through the imaging receiving optical window.

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