Image acquisition method and system for dual-wavelength circular polarization camera

Abstract

The present invention discloses an image acquisition method and system for a dual-wavelength circular polarization camera, including: setting two independent nanosecond pulse laser sources to emit lasers of different wavelengths respectively; performing left-hand circular polarization and right-hand circular polarization processing on the two lasers respectively; integrating the two circularly polarized nanosecond pulse laser beams into one beam, wherein the two beams of light completely overlap and are coaxial; irradiating the integrated nanosecond pulse laser beam onto the target object, and collecting the reflected light through a dual-spectrum camera to form two images of different wavelengths; assigning weights to the images according to the importance of the polarization information, and using image fusion technology to generate a composite image. The present invention proposes an image acquisition method and system for a dual-wavelength circular polarization camera, which realizes efficient imaging in complex environments by setting two independent nanosecond pulse laser sources to emit short-wavelength and long-wavelength lasers respectively, and integrating the two laser beams into one beam after performing left-hand and right-hand circular polarization processing on the two laser beams.

Description

Technical Field

[0001] The present invention relates to the technical field of optical elements and systems, and in particular to the field of polarization, and specifically to an image acquisition method and system for a dual-wavelength circular polarization camera. Background Art

[0002] Circularly polarized light is a polarized light whose polarization direction moves in a circle. The trajectory of the vector endpoint is a circle. The endpoint of the electric field vector describes a spiral line in space as time changes. When this spiral line rotates clockwise, it is called right-hand circular polarization; when it rotates counterclockwise, it is called left-hand circular polarization. The light vector size remains unchanged and rotates at a certain frequency. Compared with linearly polarized light, circularly polarized light has more complex polarization characteristics. When circularly polarized light passes through certain media, its left-handed and right-handed components may be absorbed to different degrees. This phenomenon is called circular dichroism.

[0003] In specific application scenarios, especially when shooting smooth objects such as water surfaces, glass surfaces, and metal surfaces, when light hits non-metallic surfaces, reflection occurs. These reflected lights contain strong linear polarization components. By using a circular polarizing filter, these reflected lights can be selectively blocked, thereby reducing reflections and glare and improving image clarity. Since unnecessary reflected light is reduced, the colors in the image are more vivid, increasing the color saturation and contrast of the photo.

[0004] When encountering smoke, fog or other obstructions, the existing technology has limited penetration ability and often has difficulty in obtaining clear images. In addition, the image quality will be significantly reduced in extreme light and dark environments or different types of weather conditions. When trying to penetrate opaque or semi-transparent obstacles for imaging, the existing technology cannot provide sufficiently clear and detailed image information, which affects the quality of the final analysis and decision-making.

[0005] Therefore, it is necessary to improve the image acquisition method and system of the dual-wavelength circular polarization camera in the prior art to solve the above problems. Summary of the invention

[0006] The present invention overcomes the shortcomings of the prior art and provides an image acquisition method and system for a dual-wavelength circular polarization camera, aiming to solve the problems of limited penetration ability, poor imaging quality, and difficulty in effectively processing reflections and glare in the prior art in complex environments and special application scenarios.

[0007] To achieve the above object, the technical solution adopted by the present invention is: an image acquisition method of a dual-wavelength circular polarization camera, comprising:

[0008] S1. Setting two independent nanosecond pulse laser sources to emit lasers of different wavelengths respectively;

[0009] S2, performing left-hand circular polarization processing on the short-wavelength laser and performing right-hand circular polarization processing on the long-wavelength laser;

[0010] S3, integrating two circularly polarized nanosecond pulse laser beams into one beam, wherein the two beams completely overlap and are coaxial;

[0011] S4, irradiating the integrated nanosecond pulse laser beam onto the target object, and collecting the reflected light through a dual-spectrum camera to form two images with different wavelengths;

[0012] S5. Assign weights to images according to the importance of polarization information, and use image fusion technology to generate a composite image to preserve the effects of two circular polarizations and form a high-quality image output.

[0013] In a preferred embodiment of the present invention, in step S1, one of the two independent nanosecond pulse laser sources is a short-wavelength blue or green laser source with an operating wavelength range of 400-600nm; the other is a long-wavelength red or infrared laser source with an operating wavelength of 620-1550nm;

[0014] The pulse width of the nanosecond pulse laser source is 10 -10 ~10 -9 s, the repetition frequency is 5-10kHz, the pulse width and repetition frequency of the two wavelengths of nanosecond pulse lasers are consistent; the camera is equipped with a synchronous control system, which uses an external trigger signal or a built-in synchronization circuit to ensure the simultaneity of the two laser pulses.

[0015] In a preferred embodiment of the present invention, the energy density of the short-wavelength laser is 10-30 mJ / cm 3 ; For long-wavelength lasers, the energy density is 30-80mJ / cm 3 , for infrared lasers, the energy density is 50-200mJ / cm 3 .

[0016] In a preferred embodiment of the present invention, in step S2, the polarization processing step includes:

[0017] S21, placing a linear polarizer in the path of the nanosecond pulse laser so that the output beam becomes linearly polarized light, and adjusting the angle of the polarizer until the maximum intensity of the beam passes through;

[0018] For short-wavelength laser sources, use ultraviolet or visible light polarizers; for long-wavelength laser sources, use infrared polarizers;

[0019] S22, a quarter wave plate is arranged after the linear polarizer; the phase delay of the quarter wave plate is λ / 4, where λ is the laser wavelength;

[0020] For short-wavelength nanosecond pulse lasers, the fast axis of the quarter-wave plate is rotated 45 degrees relative to the linear polarization direction, converting the linearly polarized light into left-handed circularly polarized light;

[0021] For long-wavelength nanosecond pulse lasers, the axial rotation direction of the quarter-wave plate is opposite to that of the short-wavelength laser, rotating at an angle of -45 degrees relative to the linear polarization direction to generate right-handed circularly polarized light;

[0022] S23. Check the polarization state of the output light beam, evaluate the polarization quality, and adjust the polarization parameters until the polarization effect is optimal; evaluate by quantifying the intensity and ellipticity of the output light beam. The closer the ellipticity is to 0, the closer the polarization effect is to a perfect circle, and the better the effect.

[0023] In a preferred embodiment of the present invention, in step S3, the two circularly polarized light beams are integrated by a beam combiner, and the beam combiner is one of a dichroic mirror or a polarization beam splitter cube.

[0024] In a preferred embodiment of the present invention, one side of the dichroic mirror can reflect short-wavelength laser light, and the other side can transmit long-wavelength laser light; two beam combiners are provided, including: a first beam combiner and a second beam combiner;

[0025] The first beam combiner is at an angle of 45 degrees to the horizontal and is located on the optical path of the short-wavelength laser. The surface capable of reflecting the short-wavelength laser is close to the short-wavelength laser light source, so that the first beam combiner reflects the short-wavelength laser vertically downward.

[0026] The second beam combiner is located at the intersection of the long-wavelength laser and the reflected short-wavelength laser, with an angle of 45 degrees to the horizontal. The surface of the second beam combiner that can transmit the long-wavelength laser is close to the long-wavelength laser light source, so that the long-wavelength laser can be transmitted horizontally, and the short-wavelength laser is reflected twice to combine into a laser beam with the long-wavelength laser.

[0027] In a preferred embodiment of the present invention, a filter is arranged in the imaging optical path of the dual-spectrum camera to filter out unnecessary spectral components and improve the contrast and clarity of the image.

[0028] In a preferred embodiment of the present invention, in step S5, image fusion is performed based on polarization information:

[0029] The dual-spectrum camera captures the reflected light signals of the target object after the short-wavelength and long-wavelength lasers are irradiated, forming two images with different wavelengths.

[0030] The characteristics of left-handed circularly polarized light extracted from short-wavelength images: Among them, E S is the ellipticity of short-wavelength left-handed circularly polarized light, I LCP,S and I RCP,S are the intensities of short-wavelength left-handed circularly polarized light and right-handed circularly polarized light, respectively;

[0031] The characteristics of long wavelength images to extract right-handed circularly polarized light: Among them, E L is the ellipticity of long-wavelength right-handed circularly polarized light, I RCP,L and I LCP,L are the intensities of long-wavelength right-handed circularly polarized light and left-handed circularly polarized light, respectively;

[0032] According to the importance of polarization information, a weight ω is assigned to each image. S +ω L =|E S |+|E L |=1;

[0033] Two images can be fused in a variety of ways, including weighted average fusion, pseudo color mapping fusion, and multi-layer fusion based on deep learning to generate a composite image.

[0034] In a preferred embodiment of the present invention, weighted average fusion generates a comprehensive image

[0035] IF(x,y)=ωS·IS(x,y)+ωL·IL(x,y); where (x,y) is the pixel coordinate of the image, IS, IL are the short-wavelength image and the long-wavelength image.

[0036] The present invention provides an image acquisition system for a dual-wavelength circular polarization camera, comprising:

[0037] Dual-wavelength laser source, including two independent nanosecond pulse laser sources, one for improving the penetration of obstructions such as smoke and fog, and the other for improving image quality and detail capture;

[0038] The polarization processing module includes a linear polarizer and a quarter-wave plate, which are used to perform left-hand circular polarization processing on short-wavelength nanosecond pulse lasers and right-hand circular polarization processing on long-wavelength nanosecond pulse lasers to achieve polarization conversion of the lasers;

[0039] The beam combiner module combines two circularly polarized light beams into one beam, ensuring that the two beams completely overlap and are coaxial;

[0040] Irradiation and imaging module: The integrated nanosecond pulse laser beam passes through the beam expander to illuminate the target object, and the dual-spectrum camera captures and records the light signal reflected from the target object to generate images of different wavelengths;

[0041] The image processing module assigns weights to two images of different wavelengths according to the importance of polarization information and uses image fusion technology to generate a composite image.

[0042] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0043] (1) The present invention proposes an image acquisition method and system for a dual-wavelength circularly polarized camera. By setting two independent nanosecond pulse laser sources to emit short-wavelength and long-wavelength lasers respectively, and integrating the two laser beams into one beam after left-handed and right-handed circular polarization processing, efficient imaging in complex environments is achieved. It not only significantly enhances the ability to penetrate obstructions such as smoke and fog, but also improves the image quality and the accuracy of detail capture. It is particularly suitable for detecting substances with circular dichroism.

[0044] (2) The present invention sets up two independent nanosecond pulse laser sources to emit short-wavelength and long-wavelength lasers respectively, and performs different circular polarization treatments on the two lasers; the short-wavelength laser is used to improve the penetration effect on obstructions such as smoke and fog, while the long-wavelength laser focuses on improving image quality and detail capture; the combination of these two laser sources with different characteristics realizes high-quality imaging in complex environments, which not only enhances the penetration of obstacles, but also ensures clarity and contrast. Compared with the existing technology, it further achieves the effect of maintaining stable output under harsh conditions.

[0045] (3) The present invention performs left-hand circular polarization on short-wavelength lasers and right-hand circular polarization on long-wavelength lasers, and uses linear polarizers and quarter-wave plates to achieve precise polarization conversion, thereby ensuring that the light beam can penetrate obstacles to the greatest extent and reduce scattering losses, so that the system can provide a deeper imaging depth in the presence of suspended particles, while improving signal intensity and image contrast. Compared with the prior art, the ability to obtain clear images in complex environments is further enhanced.

[0046] (4) The present invention combines two circularly polarized laser beams into one beam through a beam combiner, ensuring that the two beams are completely overlapped and coaxial. A dichroic mirror or a polarization beam splitter cube is used to reflect or transmit light of corresponding wavelengths according to the wavelength separation characteristics, thereby achieving optimal beam overlap. The precise beam combining design ensures that the target object is illuminated by uniform dual-wavelength light, improves the consistency and accuracy of imaging, and further enhances the stability and reliability of the system compared to the prior art.

[0047] (5) Steps S4 and S5 of the present invention together constitute an efficient image acquisition and fusion mechanism. In S4, the integrated nanosecond pulse laser beam is irradiated onto the target object, and the image formed by the reflected light is captured by the dual-spectrum camera; S5 allocates weights based on the importance of polarization information and uses multiple image fusion technologies to generate a comprehensive image, which not only retains the effects of the two circular polarizations, but also forms a high-quality final output. Compared with the prior art, the resolution and detail performance of the image are further improved, especially in application scenarios that require high-precision distinction between moving objects and backgrounds.

[0048] (5) The present invention applies right-handed circularly polarized light to long-wavelength laser light, which is suitable for detecting materials with circular dichroism. It can optimize image quality and detail capture without causing overheating, and provides additional information to accurately characterize the unique properties of these materials. In addition, because long-wavelength laser light can more easily penetrate the interior of materials and is less affected by surface reflection, it is suitable for tasks requiring deep detection or high-resolution imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0050] Figure 1 is a flow chart of a preferred embodiment of the present invention;

[0051] Figure 2 is a schematic diagram of an optical element according to a preferred embodiment of the present invention;

[0052] In the figure: 1. Short-wavelength nanosecond pulse laser; 2. Linear polarizer; 3. Quarter-wave plate; 4. First beam combiner; 5. Second beam combiner; 6. Beam expander; 7. Long-wavelength nanosecond pulse laser; 8. Dual-spectrum camera; 9. Target object. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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. 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.

[0054] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0055] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, "multiple" means two or more.

[0056] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0057] Application Overview:

[0058] Existing technologies face problems such as limited penetration, slow imaging speed, low temporal resolution, and difficulty in effectively dealing with reflections and glare in complex environments and special application scenarios. In particular, when faced with obstructions such as smoke and fog, traditional imaging systems find it difficult to maintain high-quality image output; at the same time, their performance cannot meet the requirements when it is necessary to quickly capture dynamic targets or distinguish moving objects from the background with high precision; in addition, for the detection of specific materials with circular dichroism, single-wavelength lasers cannot provide enough information to accurately characterize the unique properties of these materials.

[0059] In order to solve the above problems, the present application proposes an image acquisition method and system for a dual-wavelength circularly polarized camera; by using two laser sources with different wavelengths, one wavelength is used to improve the penetration effect on specific obstacles, and the other wavelength is focused on improving image quality and detail capture, which can improve the adaptability to various materials and environmental conditions, and can also enhance the penetration and clarity of imaging, and optimize the physical properties of different objects.

[0060] Exemplary methods:

[0061] like Figure 1As shown, an image acquisition method of a dual-wavelength circular polarization camera includes:

[0062] S1. Setting two independent nanosecond pulse laser sources to emit lasers of different wavelengths respectively;

[0063] S2, performing left-hand circular polarization processing on the short-wavelength laser and performing right-hand circular polarization processing on the long-wavelength laser;

[0064] S3, integrating two circularly polarized nanosecond pulse laser beams into one beam, wherein the two beams completely overlap and are coaxial;

[0065] S4, irradiating the integrated nanosecond pulse laser beam onto the target object, and collecting an image formed by the reflected light through a dual-spectrum camera;

[0066] S5. Based on the reflected light signal captured by the dual-spectrum camera, two images with different wavelengths are formed respectively. A weight is assigned to each image according to the importance of the polarization information, and an image fusion technology is used to generate a composite image to retain the effects of the two circular polarizations and form a high-quality image output.

[0067] In step S1, of the two independent nanosecond pulse laser sources, one is a short-wavelength blue or green laser source, which is used to improve the penetration effect of smoke, fog and other obstructions, and the operating wavelength range is 400-600nm; the other is a long-wavelength red or infrared laser source, which is used to improve image quality and detail capture, and the operating wavelength is 620-1550nm.

[0068] The pulse width of the nanosecond pulse laser source is 10 -10 ~10 -9 s, the repetition frequency is 5-10kHz, the pulse width and repetition frequency of the two wavelengths of nanosecond pulse laser are consistent; the camera is equipped with a synchronization control system, which uses an external trigger signal or a built-in synchronization circuit to ensure the simultaneity of the two laser pulses;

[0069] The energy density of short-wavelength nanosecond pulse laser is 10-30mJ / cm 3 For applications that require penetration of smoke, fog and other obstructions, sufficient energy density can be ensured to penetrate the obstacles while maintaining a low energy level to reduce scattering and thermal effects; for long-wavelength nanosecond pulse lasers, the energy density for red lasers is 30-80mJ / cm 3 , for infrared lasers, the energy density is 50-200mJ / cm 3 The higher energy density is designed to optimize image quality and detail capture without causing overheating. For the near-infrared band, higher energy density helps to increase the penetration depth of different materials, and due to its longer wavelength, it can better avoid some reflection and scattering problems.

[0070] Short-wavelength laser sources, including blue light or green light, have higher energy density and better directionality due to their shorter wavelengths, higher scattering ratios and smaller absorption coefficients, and are therefore more likely to penetrate obstructions such as smoke and fog. Long-wavelength laser sources, including red light or infrared light, have better thermal effects and penetration depths due to their longer wavelengths compared to short-wavelength lasers, reduce surface reflections and have better penetration capabilities into the internal structures of materials, and are suitable for improving image quality and capturing details.

[0071] In step S2, the short-wavelength nanosecond pulse laser is subjected to left-hand circular polarization processing; the long-wavelength nanosecond pulse laser is subjected to right-hand circular polarization processing;

[0072] like Figure 2 As shown, the polarization processing steps include:

[0073] S21, placing a linear polarizer in the path of the nanosecond pulse laser so that the output beam becomes linearly polarized light, and adjusting the angle of the polarizer until the beam passes through with maximum intensity; when the beam is parallel to the transmission axis of the polarizer, the light intensity is maximum, and the linear polarization effect is optimal at this time;

[0074] For short-wavelength laser sources, use ultraviolet or visible light polarizers; for long-wavelength laser sources, use infrared polarizers;

[0075] S22, a quarter wave plate is arranged after the linear polarizer; the phase delay of the quarter wave plate is λ / 4, where λ is the laser wavelength;

[0076] For short-wavelength nanosecond pulse lasers, the fast axis of the quarter-wave plate is rotated 45 degrees relative to the linear polarization direction, converting the linearly polarized light into left-handed circularly polarized light;

[0077] For long-wavelength nanosecond pulse lasers, the axial rotation direction of the quarter-wave plate is opposite to that of the short-wavelength laser, rotating at an angle of -45 degrees relative to the linear polarization direction to generate right-handed circularly polarized light;

[0078] S23, check the polarization state of the output light beam, evaluate the polarization quality, and adjust the polarization parameters until the polarization effect is optimal; the evaluation is performed by quantifying the intensity and ellipticity of the output light beam. The closer the ellipticity is to 0, the closer the polarization effect is to a perfect circle, and the better the effect;

[0079] Short-wavelength lasers have higher energy density and better directionality. When left-handed circularly polarized light is used, light loss due to scattering can be further reduced. In the presence of smoke, fog or other suspended particles, left-handed circularly polarized light can penetrate these obstacles more deeply, providing a deeper imaging depth, enabling the system to capture clearer target images in harsh environments. More light can reach the target and be reflected back instead of being scattered in other directions, thereby improving signal strength and image contrast.

[0080] Long-wavelength lasers have better thermal effects and penetration depth, are easier to penetrate into materials, and are less affected by surface reflections. Right-handed circularly polarized light can help optimize interactions with materials, especially when detecting substances with circular dichroism. Right-handed circularly polarized light can provide additional information to accurately characterize the unique properties of these materials. For long-wavelength lasers, right-handed circularly polarized light is suitable for application scenarios that require high resolution and detail capture, and can optimize image quality and detail capture without causing overheating.

[0081] In step S3, the two circularly polarized light beams are combined by a beam combiner, which is a dichroic mirror or a polarization beam splitter cube. The dichroic mirror is suitable for the case where the wavelength separation is large, and can reflect light in one wavelength range and allow light in another wavelength range to pass. The polarization beam splitter cube combines the light based on the polarization state, and is used to combine two light beams with orthogonal polarization states.

[0082] The beam combiner controls the refraction and transmission of the two lasers and is placed at the intersection of the two laser paths to achieve optimal beam overlap.

[0083] Specifically, a dichroic mirror is selected as a beam combiner, one side of the dichroic mirror can reflect short-wavelength laser light, and the other side can transmit long-wavelength laser light; two beam combiners are provided;

[0084] The first beam combiner is at an angle of 45 degrees to the horizontal and is located on the optical path of the short-wavelength laser. The surface capable of reflecting the short-wavelength laser is close to the short-wavelength laser light source, so that the first beam combiner reflects the short-wavelength laser vertically downward.

[0085] The second beam combiner is located at the intersection of the long-wavelength laser and the reflected short-wavelength laser, with an angle of 45 degrees to the horizontal. The surface of the second beam combiner that can transmit the long-wavelength laser is close to the long-wavelength laser light source, so that the long-wavelength laser can be transmitted horizontally, and the short-wavelength laser is reflected twice and combined with the long-wavelength laser into a laser beam, retaining the original polarization effect.

[0086] Check the beam quality after combining, including parameters such as intensity distribution and ellipticity, to ensure that the two beams completely overlap and are coaxial.

[0087] In step S4, the integrated nanosecond pulse laser beam is passed through a beam expander so that it can evenly illuminate the target object. The beam expander can adjust the diameter and divergence angle of the laser beam to ensure that the laser beam has an appropriate spot size and uniformity when irradiating the target object.

[0088] In the imaging optical path of the dual-spectral camera, filters are set to filter out unnecessary spectral components to improve the contrast and clarity of the image; the dual-spectral camera captures and records the light signals reflected back after the short-wavelength and long-wavelength lasers irradiate the target object, respectively, thereby forming two images of different wavelengths, and then performs image fusion to retain the effects of the two circularly polarized lights, thereby forming a high-quality image.

[0089] In step S5, image fusion is performed based on polarization information:

[0090] The dual-spectrum camera captures the reflected light signals of the target object after the short-wavelength and long-wavelength lasers are irradiated, forming two images with different wavelengths.

[0091] The characteristics of left-handed circularly polarized light extracted from short-wavelength images: Among them, E S is the ellipticity of short-wavelength left-handed circularly polarized light, I LCP,S and I RCP,S are the intensities of short-wavelength left-handed circularly polarized light and right-handed circularly polarized light, respectively;

[0092] The characteristics of long wavelength images to extract right-handed circularly polarized light: Among them, E L is the ellipticity of long-wavelength right-handed circularly polarized light, I RCP,L and I LCP,L are the intensities of long-wavelength right-handed circularly polarized light and left-handed circularly polarized light, respectively;

[0093] According to the importance of polarization information, a weight ω is assigned to each image. S +ω L =|E S |+|E L |=1;

[0094] Two images can be fused in a variety of ways, including weighted average fusion, pseudo color mapping fusion, and multi-layer fusion based on deep learning to generate a comprehensive image;

[0095] Specifically, taking weighted average fusion as an example, a comprehensive image is generated

[0096] IF(x,y)=ωS·IS(x,y)+ωL·IL(x,y); where (x,y) is the pixel coordinate of the image, IS, IL are the short-wavelength image and the long-wavelength image.

[0097] Example systems:

[0098] An image acquisition system for a dual-wavelength circular polarization camera, comprising:

[0099] Dual-wavelength laser source, including two independent nanosecond pulse laser sources, one for improving the penetration of obstructions such as smoke and fog, and the other for improving image quality and detail capture;

[0100] The polarization processing module includes a linear polarizer and a quarter-wave plate, which are used to perform left-hand circular polarization processing on short-wavelength nanosecond pulse lasers and right-hand circular polarization processing on long-wavelength nanosecond pulse lasers to achieve polarization conversion of the lasers;

[0101] The beam combiner module combines two circularly polarized light beams into one beam, ensuring that the two beams completely overlap and are coaxial;

[0102] Irradiation and imaging module: The integrated nanosecond pulse laser beam passes through the beam expander to illuminate the target object, and the dual-spectrum camera captures and records the light signal reflected from the target object to generate images of different wavelengths;

[0103] The image processing module assigns weights to two images of different wavelengths according to the importance of polarization information and uses image fusion technology to generate a composite image.

[0104] Experiments were conducted on an image acquisition method for a dual-wavelength circular polarization camera:

[0105] Embodiment 1:

[0106] An image acquisition method for a dual-wavelength circular polarization camera, comprising:

[0107] S1, set up two independent nanosecond pulse laser sources;

[0108] Short wavelength laser source: blue laser source is used, the working wavelength range is 450nm, the pulse width is 10ns, the repetition frequency is 7kHz, and the energy density of short wavelength laser is 20mJ / cm 3 ;

[0109] Long wavelength laser source: A red laser source is used with an operating wavelength of 650nm, a pulse width of 10ns, and a repetition frequency of 7kHz; the energy density of the long wavelength laser is 60mJ / cm 3 ;

[0110] Synchronous control system: using external trigger signal to ensure the simultaneity of two laser pulses;

[0111] S2, performing left-hand circular polarization and right-hand circular polarization processing on the two lasers respectively;

[0112] Place an ultraviolet polarizer in the path of the short-wavelength laser and adjust the angle so that the beam passes through with maximum intensity; set a quarter-wave plate after the ultraviolet polarizer, and rotate the fast axis 45 degrees relative to the linear polarization direction to generate left-handed circularly polarized light;

[0113] For long-wavelength lasers, an infrared polarizer and a quarter-wave plate are used to rotate the fast axis by -45 degrees relative to the linear polarization direction, generating right-handed circularly polarized light;

[0114] S3, integrating two circularly polarized nanosecond pulse laser beams into one beam;

[0115] Use a dichroic mirror as a beam combiner;

[0116] The first beam combiner: with an angle of 45 degrees to the horizontal, located on the short-wavelength laser optical path, reflects the short-wavelength laser vertically downward;

[0117] The second beam combiner is located at the intersection of the long-wavelength laser and the reflected short-wavelength laser, with an angle of 45 degrees to the horizontal. It transmits the long-wavelength laser, and at the same time the short-wavelength laser is reflected twice and combined with the long-wavelength laser into one beam;

[0118] S4, irradiating the integrated nanosecond pulse laser beam onto the target object through a beam expander, and collecting the reflected light through a dual-spectrum camera to form two images with different wavelengths;

[0119] S5. Assign weights to the images according to the importance of the polarization information, and use weighted average fusion technology to generate a composite image.

[0120] Embodiment 2:

[0121] An image acquisition method for a dual-wavelength circular polarization camera, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0122] The energy density of short-wavelength laser is 10mJ / cm 3 ;

[0123] Embodiment three:

[0124] An image acquisition method for a dual-wavelength circular polarization camera, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0125] The energy density of short-wavelength laser is 30mJ / cm 3 ;

[0126] Embodiment 4:

[0127] An image acquisition method for a dual-wavelength circular polarization camera, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0128] The energy density of long wavelength laser is 40mJ / cm 3 ;

[0129] Embodiment five:

[0130] An image acquisition method for a dual-wavelength circular polarization camera, the same points as those in the second embodiment are not repeated here, and the difference between this embodiment and the second embodiment is that;

[0131] The energy density of long wavelength laser is 40mJ / cm 3 ;

[0132] Embodiment six:

[0133] An image acquisition method for a dual-wavelength circular polarization camera, the same points as those in the third embodiment are not described in detail, and the difference between this embodiment and the third embodiment is that;

[0134] The energy density of long wavelength laser is 40mJ / cm 3 ;

[0135] Embodiment seven:

[0136] An image acquisition method for a dual-wavelength circular polarization camera, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0137] The energy density of long wavelength laser is 80mJ / cm 3 ;

[0138] Embodiment eight:

[0139] An image acquisition method for a dual-wavelength circular polarization camera, the same points as those in the second embodiment are not repeated here, and the difference between this embodiment and the second embodiment is that;

[0140] The energy density of long wavelength laser is 80mJ / cm 3 ;

[0141] Embodiment nine:

[0142] An image acquisition method for a dual-wavelength circular polarization camera, the same points as those in the third embodiment are not described in detail, and the difference between this embodiment and the third embodiment is that;

[0143] The energy density of long wavelength laser is 80mJ / cm 3 ;

[0144] Comparative Example 1:

[0145] An image acquisition method for a dual-wavelength circular polarization camera, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0146] This comparative example only uses right-handed circular polarization;

[0147] Comparative Example 2:

[0148] An image acquisition method for a dual-wavelength circular polarization camera, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0149] This comparative example only uses left-handed circular polarization;

[0150] Comparative Example 3:

[0151] An image acquisition method for a dual-wavelength circular polarization camera, the same points as those in the first embodiment are not described in detail, and the difference between this embodiment and the first embodiment is that;

[0152] This comparative example does not use circular polarization.

[0153] Experimental Example 1:

[0154] This experiment uses Examples 1 to 9 and Comparative Examples 1 to 3 as experimental objects, and evaluates the clarity and contrast of the collected images;

[0155] Objectively evaluate the clarity of a system by measuring its modulation transfer function, which is a measure of the system's ability to transfer spatial frequencies. It is determined by taking a standard edge or line pair chart and analyzing the spatial frequency response of the output image.

[0156] The peak signal-to-noise ratio compares the original image and the processed image based on the mean square error. The higher the peak signal-to-noise ratio, the closer it is to 50, the better the image quality.

[0157] Table 1 Experimental picture collection

[0158]

[0159]

[0160] Examples 1 to 9 all use a dual-wavelength solution combined with left- and right-handed circularly polarized light, and their clarity and contrast are significantly higher than solutions that only use a single wavelength or no polarization, indicating that the technology of dual-wavelength combined with circularly polarized light can significantly improve the imaging quality of the image.

[0161] Due to its higher energy density and better directionality, short-wavelength lasers can more easily penetrate obstructions such as smoke and fog, providing a deeper imaging depth. When the energy density of short-wavelength lasers is too low, the clarity and contrast will decrease. When the energy density is too high, although the clarity is slightly improved, it may not necessarily bring a significant increase in contrast. This is because short-wavelength lasers are mainly used to penetrate obstacles. Too high energy density may cause more scattering or thermal effects, which is not conducive to imaging quality.

[0162] Long wavelength lasers are essential for improving image quality and capturing details. Examples 4 to 9 demonstrate the effects of different long wavelength laser energy densities. Higher energy density helps improve image quality while maintaining better contrast because long wavelength lasers have better penetration depth and are less affected by surface reflections, making them suitable for capturing details.

[0163] By combining the two polarization states, the impact of scattered light can be effectively reduced, the interaction with materials can be optimized, and additional information can be provided to characterize substances with circular dichroism.

[0164] The above is based on the ideal embodiment of the present invention. Through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. An image acquisition method for a dual-wavelength circular polarization camera, characterized in that: Includes steps: S1. Setting two independent nanosecond pulse laser sources to emit lasers of different wavelengths respectively; S2, performing left-hand circular polarization processing on the short-wavelength laser and performing right-hand circular polarization processing on the long-wavelength laser; S3, integrating two circularly polarized nanosecond pulse laser beams into one beam, wherein the two beams completely overlap and are coaxial; S4, irradiating the integrated nanosecond pulse laser beam onto the target object, and collecting the reflected light through a dual-spectrum camera to form two images with different wavelengths; S5, assigning weights to images according to the importance of polarization information, and using image fusion technology to generate a composite image to preserve the effects of two circular polarizations and form a high-quality image output; In step S5, image fusion is performed based on polarization information: The dual-spectrum camera captures the reflected light signals of the target object after the short-wavelength and long-wavelength lasers are irradiated, forming two images with different wavelengths. The characteristics of left-handed circularly polarized light extracted from short-wavelength images: Among them, E S is the ellipticity of short-wavelength left-handed circularly polarized light, I LCP,S and I RCP,S are the intensities of short-wavelength left-handed circularly polarized light and right-handed circularly polarized light, respectively; The characteristics of long wavelength images to extract right-handed circularly polarized light: Among them, E L is the ellipticity of long-wavelength right-handed circularly polarized light, I RCP,L and I LCP,L are the intensities of long-wavelength right-handed circularly polarized light and left-handed circularly polarized light, respectively; According to the importance of polarization information, a weight ω is assigned to each image. S +ω L =|E S |+|E L |=1; The two images are fused in a variety of ways, including weighted average fusion, pseudo color mapping fusion, and multi-layer fusion based on deep learning to generate a composite image.

2. The image acquisition method of a dual-wavelength circular polarization camera according to claim 1, characterized in that: In step S1, of the two independent nanosecond pulse laser sources, one is a short-wavelength blue or green laser source with an operating wavelength range of 400-600nm; the other is a long-wavelength red or infrared laser source with an operating wavelength of 620-1550nm; The pulse width of the nanosecond pulse laser source is 10 -10 ~10 -9 s, the repetition frequency is 5-10kHz, the pulse width and repetition frequency of the two wavelengths of nanosecond pulse lasers are consistent; the camera is equipped with a synchronous control system, which uses an external trigger signal or a built-in synchronization circuit to ensure the simultaneity of the two laser pulses.

3. The image acquisition method of a dual-wavelength circular polarization camera according to claim 2, characterized in that: The energy density of short-wavelength laser is 10-30mJ / cm 3 ; For long-wavelength lasers, the energy density is 30-80mJ / cm 3 , for infrared lasers, the energy density is 50-200mJ / cm 3 .

4. The image acquisition method of a dual-wavelength circular polarization camera according to claim 1, characterized in that: In step S2, the polarization processing step includes: S21, placing a linear polarizer in the path of the nanosecond pulse laser so that the output beam becomes linearly polarized light, and adjusting the angle of the polarizer until the maximum intensity of the beam passes through; For short-wavelength laser sources, use ultraviolet or visible light polarizers; for long-wavelength laser sources, use infrared polarizers; S22, a quarter wave plate is arranged after the linear polarizer; the phase delay of the quarter wave plate is λ / 4, where λ is the laser wavelength; For short-wavelength nanosecond pulse lasers, the fast axis of the quarter-wave plate is rotated 45 degrees relative to the linear polarization direction, converting the linearly polarized light into left-handed circularly polarized light; For long-wavelength nanosecond pulse lasers, the axial rotation direction of the quarter-wave plate is opposite to that of the short-wavelength laser, rotating at an angle of -45 degrees relative to the linear polarization direction to generate right-handed circularly polarized light; S23. Check the polarization state of the output light beam, evaluate the polarization quality, and adjust the polarization parameters until the polarization effect is optimal; evaluate by quantifying the intensity and ellipticity of the output light beam. The closer the ellipticity is to 0, the closer the polarization effect is to a perfect circle, and the better the effect.

5. The image acquisition method of a dual-wavelength circular polarization camera according to claim 1, characterized in that: In step S3, the two circularly polarized light beams are combined by a beam combiner, which is a dichroic mirror or a polarization beam splitter cube.

6. The image acquisition method of a dual-wavelength circular polarization camera according to claim 5, characterized in that: One side of the dichroic mirror can reflect short-wavelength laser light, and the other side can transmit long-wavelength laser light; two beam combiners are provided, including: a first beam combiner and a second beam combiner; The first beam combiner is at an angle of 45 degrees to the horizontal and is located on the optical path of the short-wavelength laser. The surface capable of reflecting the short-wavelength laser is close to the short-wavelength laser light source, so that the first beam combiner reflects the short-wavelength laser vertically downward. The second beam combiner is located at the intersection of the long-wavelength laser and the reflected short-wavelength laser, with an angle of 45 degrees to the horizontal. The surface of the second beam combiner that can transmit the long-wavelength laser is close to the long-wavelength laser light source, so that the long-wavelength laser can be transmitted horizontally, and the short-wavelength laser is reflected twice to combine into a laser beam with the long-wavelength laser.

7. The image acquisition method of a dual-wavelength circular polarization camera according to claim 1, characterized in that: In the imaging light path of the dual-spectrum camera, filters are set to filter out unnecessary spectral components and improve the contrast and clarity of the image.

8. The image acquisition method of a dual-wavelength circular polarization camera according to claim 1, characterized in that: Weighted average fusion to generate a composite image IF(x,y)=ωS·IS(x,y)+ωL·IL(x,y); where (x,y) is the pixel coordinate of the image, IS, IL are the short-wavelength image and the long-wavelength image.

9. An image acquisition system for a dual-wavelength circular polarization camera, based on the image acquisition method for a dual-wavelength circular polarization camera according to any one of claims 1 to 8, characterized in that: Dual-wavelength laser source, including two independent nanosecond pulse laser sources, one for improving the penetration of obstructions such as smoke and fog, and the other for improving image quality and detail capture; The polarization processing module includes a linear polarizer and a quarter-wave plate, which are used to perform left-hand circular polarization processing on short-wavelength nanosecond pulse lasers and right-hand circular polarization processing on long-wavelength nanosecond pulse lasers to achieve polarization conversion of the lasers; The beam combiner module combines two circularly polarized light beams into one beam, ensuring that the two beams completely overlap and are coaxial; Irradiation and imaging module: The integrated nanosecond pulse laser beam passes through the beam expander to illuminate the target object, and the dual-spectrum camera captures and records the light signal reflected from the target object to generate images of different wavelengths; The image processing module assigns weights to two images of different wavelengths according to the importance of polarization information and uses image fusion technology to generate a composite image.

Images