Polarized television camera imaging optical system

Abstract

This invention discloses an imaging optical system for a polarized television camera, comprising a four-channel imaging system, a four-channel polarizer, and four image sensors. The four-channel imaging system is arranged in a parallel 2×2 array, labeled as Channel I, Channel II, Channel III, and Channel IV. Each of the four-channel imaging systems includes a first lens, a second lens, a cemented lens, a fifth lens, a sixth lens, a seventh lens, and a folding prism. The front surface of the four-channel polarizer is etched with crosshairs, dividing the polarizer into four quadrants. The photosensitive surfaces of the four image sensors are all located at the focal plane of the imaging system. This invention utilizes a four-channel polarizer and a folding prism to construct a polarized television imaging system that can simultaneously acquire four images of the same scene with different polarization states, significantly reducing the deviation between the polarization angles of the four channels.

Description

Technical Field

[0001] This invention belongs to the field of optical design, and specifically relates to an imaging optical system for a polarized television camera. Background Technology

[0002] Polarization imaging is a novel optoelectronic imaging technology that combines imaging techniques with polarization measurement techniques. It can be used to improve the imaging quality of computer vision systems under adverse weather conditions such as fog and haze, and also to enhance target detection accuracy and image clarity. A polarization imaging system adds a polarization device to a basic imaging system, typically including an optical system, polarization components, and an image sensor. Considering the structure of polarization imaging systems, a relatively easy-to-implement polarization television imaging method is to acquire polarized light information using multi-channel separate polarization imaging. This information is then used to reconstruct and enhance the target scene, obtaining the target's two-dimensional spatial light intensity distribution and polarization characteristic distribution.

[0003] In separate polarization imaging, the optical paths are independent of each other. Typically, during use, the polarizer is rotated to make each optical axis present a different angle. However, this setup inevitably introduces deviations between the angles of each optical path, ultimately affecting subsequent image calibration, registration, and restoration. Therefore, solving the problem of poor image restoration due to polarization angle deviations is a pressing issue that needs to be addressed. Summary of the Invention

[0004] The purpose of this invention is to provide a polarization television camera imaging optical system to effectively solve the problem of large angular deviations in each optical path in a split multi-channel polarization imaging system.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a polarized television camera imaging optical system, comprising a four-channel imaging system, a four-channel polarizer, and four image sensors. The four-channel imaging system is arranged in a 2×2 array in parallel and is labeled as channel I, channel II, channel III, and channel IV, respectively. The four-channel imaging systems have the same structure, each including a cemented lens composed of a first lens, a second lens, a third lens, and a fourth lens, a fifth lens, a sixth lens, a seventh lens, and a folding prism. The front surface of the four-channel polarizer is engraved with crosshairs, dividing the polarizer into four quadrants, with the first quadrant corresponding to channel I, the second quadrant corresponding to channel II, the third quadrant corresponding to channel III, and the fourth quadrant corresponding to channel IV. The photosensitive surfaces of the four image sensors are all located at the focal plane of the imaging system, and respectively receive target information acquired by the imaging system.

[0006] Furthermore, the distance between the first lens and the second lens is 1.19 mm, the distance between the second lens and the cemented lens is 0.143 mm, the distance between the cemented lens and the fifth lens is 6 mm, the distance between the fifth lens and the sixth lens is 0.57 mm, the distance between the sixth lens and the seventh lens is 0.28 mm, the distance between the seventh lens and the folding prism is 1.4 mm, the distance between the folding prism and the four-channel polarizer is 1 mm, and the distance between the four-channel polarizer and the photosensitive surface of the image sensor is 2.57 mm.

[0007] Furthermore, the outline diameter of the first lens is 27mm, the outline diameter of the second lens is 25mm, the outline diameter of the cemented lens is 25mm, the outline diameter of the fifth lens is 17mm, the outline diameter of the sixth lens is 15mm, and the outline diameter of the seventh lens is 14mm.

[0008] Furthermore, the first lens is a biconvex lens with a focal length range of 25mm ≤ f ≤ 30mm; the second lens is a meniscus lens with a focal length range of -45mm ≤ f ≤ -50mm; the third lens is a biconvex lens with a focal length range of 10mm ≤ f ≤ 15mm; the fourth lens is a biconcave lens with a focal length range of -18mm ≤ f ≤ -22mm; the fifth lens is a biconvex lens with a focal length range of 20mm ≤ f ≤ 26mm; the sixth lens is a meniscus lens with a focal length range of 280mm ≤ f ≤ 310mm; and the seventh lens is a plano-concave lens with a focal length range of -7mm ≤ f ≤ -10mm.

[0009] Furthermore, the folding prism is made of H-BaK7 material. The incident end face A and the exit end face D of the folding prism are parallel to each other, and the reflecting surface B and the reflecting surface C are parallel to each other. The reflecting surface forms a 45° angle with the incident and exit end faces. Surfaces E, F, G and H are all cemented surfaces. The angle between surface E and surface F is 135°±1′, the angle between surface F and surface G is 90°±1′, and the angle between surface G and surface H is 135°±1′.

[0010] Furthermore, the thickness of the four-channel polarizer is 1 mm, and polarizing films are deposited in the middle of the four quadrants into which the polarizer is divided. The polarizing films are 15 mm × 15 mm in size, linearly polarized, with a wavelength range of 400 nm to 700 nm, an extinction coefficient of 9000:1, and a transmittance of 53%. The polarization axis direction of the first quadrant is set to 0°, the polarization axis direction of the second quadrant is set to 45°, the polarization axis direction of the third quadrant is set to 90°, and the polarization axis direction of the fourth quadrant is set to 135°.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes a four-channel polarizer and a folding prism to construct a polarization television imaging system, which can simultaneously acquire four images of the same scene with different polarization states, and greatly reduces the deviation between the polarization angles of the four channels. It features a simple optical path, compact structure, high reliability, good image restoration effect, and low cost. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the single-channel optical system of the present invention; Figure 2 This is a schematic diagram of the folding prism structure of the present invention; Figure 3 This is a front view of the four-channel imaging system of the present invention; Figure 4 This is a schematic diagram of the four-channel polarizer of the present invention; Figure 5 This is the MTF curve of the single-channel optical system of the present invention; Figure 6 This is a dot diagram of the single-channel optical system of the present invention; Figure 7 This is a distortion diagram of the single-channel optical system of the present invention; The reference numerals in the figure are as follows: 1. First lens; 2. Second lens; 3. Cemented lens; 301. Third lens; 302. Fourth lens; 4. Fifth lens; 5. Sixth lens; 6. Seventh lens; 7. Folding prism; 8. Four-channel polarizer; 9. Photosensitive surface of image sensor. Detailed Implementation

[0013] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0014] See Figure 1 and Figure 4 The polarization television camera imaging optical system of this embodiment includes a four-channel imaging system, a four-channel polarizer, and four image sensors.

[0015] See Figure 1 and Figure 3 The four imaging systems are arranged in a parallel 2×2 array and are labeled as Channel I, Channel II, Channel III, and Channel IV, respectively. The imaging systems of the four channels have the same structure, each including a cemented lens 3 composed of a first lens 1, a second lens 2, a third lens 301, and a fourth lens 302, a fifth lens 4, a sixth lens 5, a seventh lens 6, and a folding prism 7.

[0016] The dimensions of each lens are as follows: the outline diameter of the first lens 1 is 27mm, the outline diameter of the second lens 2 is 25mm, the outline diameter of the cemented lens 3 is 25mm, the outline diameter of the fifth lens 4 is 17mm, the outline diameter of the sixth lens 5 is 15mm, and the outline diameter of the seventh lens 6 is 14mm.

[0017] The optical parameters of each lens are as follows: The first lens 1 is a biconvex lens with a focal length range of 25mm≤f≤30mm; the center thickness of the first lens 1 is 2mm, the radius of curvature R of the S1 surface is 35.74, the radius of curvature R of the S2 surface is -29.8, the refractive index of the optical material is 1.618, and the Abbe number is 63.4. The second lens 2 is a meniscus lens with a focal length range of -45mm≤f≤-50mm; the center thickness of the second lens 2 is 0.7mm, the radius of curvature R of the S3 surface is -29.15, the radius of curvature R of the S4 surface is -97.13, the refractive index of the optical material is 1.847, and the Abbe number is 23.8. The third lens 301 is a biconvex lens with a focal length range of 10mm≤f≤15mm. The center thickness of the third lens 301 is 3mm, the radius of curvature R of the S5 surface is 14.27, the radius of curvature R of the S6 surface is -19.55, the refractive index of the optical material is 1.593, and the Abbe number is 68.3. The fourth lens 302 is a biconcave lens with a focal length range of -18m≤f≤-22mm; the center thickness of the fourth lens 302 is 0.6mm, the radius of curvature R of the S6 surface is -19.55, the radius of curvature R of the S7 surface is 39.49, the refractive index of the optical material is 1.64, and the Abbe number is 60.2. The fifth lens 4 is a biconvex lens with a focal length range of 20mm≤f≤26mm; the center thickness of the fifth lens 4 is 1mm, the radius of curvature R of the S8 surface is 15.72, the radius of curvature R of the S9 surface is 199.34, the refractive index of the optical material is 1.74, and the Abbe number is 28.3. The sixth lens 5 is a meniscus lens with a focal length range of 280mm≤f≤310mm; the center thickness of the sixth lens 5 is 0.86mm, the radius of curvature R of the S10 surface is -15.42, the radius of curvature R of the S11 surface is -14.77, the refractive index of the optical material is 1.743, and the Abbe number is 49.2. The seventh lens 6 is a plano-concave lens with a focal length range of -7mm≤f≤-10mm. The center thickness of the seventh lens 6 is 0.57mm, the radius of curvature R of the S12 surface is 131.99, the radius of curvature R of the S13 surface is 6.63, the refractive index of the optical material is 1.786, and the Abbe number is 44.2.

[0018] See Figure 2The folding prism 7 is made of H-BaK7. Its incident and exit surfaces A and D are parallel, as are its reflecting surfaces B and C. The reflecting surfaces form a 45° angle with the incident and exit surfaces. Surfaces E, F, G, and H are all cemented surfaces. The angle between surface E and surface F is 135°±1′, the angle between surface F and surface G is 90°±1′, and the angle between surface G and surface H is 135°±1′. Light enters the folding prism 7 from the incident surface A, undergoes two reflections, and exits from the exit surface D.

[0019] See Figure 4 The four-channel polarizer 8 has a thickness of 1 mm, and its front surface is etched with crosshairs, dividing the polarizer into four quadrants. A polarizing film, 15 mm × 15 mm in size, is deposited in the middle of each of the four quadrants. The polarizing film is linearly polarized, with a wavelength range of 400 nm to 700 nm, an extinction coefficient of 9000:1, and a transmittance of 53%. The first quadrant corresponds to channel I, with a polarization axis of 0°; the second quadrant corresponds to channel II, with a polarization axis of 45°; the third quadrant corresponds to channel III, with a polarization axis of 90°; and the fourth quadrant corresponds to channel IV, with a polarization axis of 135°.

[0020] The relative positions of the various optical elements are as follows: the distance between the first lens 1 and the second lens 2 is 1.19 mm; the distance between the second lens 2 and the cemented lens 3 is 0.143 mm; the distance between the cemented lens 3 and the fifth lens 4 is 6 mm; the distance between the fifth lens 4 and the sixth lens 5 is 0.57 mm; the distance between the sixth lens 5 and the seventh lens 6 is 0.28 mm; the distance between the seventh lens 6 and the folding prism 7 is 1.4 mm; the distance between the folding prism 7 and the four-channel polarizer 8 is 1 mm; and the distance between the four-channel polarizer 8 and the photosensitive surface of the image sensor 9 is 2.57 mm.

[0021] The photosensitive surfaces of the four image sensors 9 are all located at the focal plane of the imaging system. The photosensitive surfaces of the image sensors 9 receive the target information acquired by each channel and restore the image through back-end image processing.

[0022] The optical system of this invention comprises four independent optical lenses assembled together using folding prisms and polarizers. It can simultaneously acquire four images with different polarization states, and finally, through image decoding and other processing, restore a clear image. The four-channel polarizer is divided into four quadrants, and through coating, the angles of the polarization films in each quadrant are 0°, 45°, 90°, and 135°, respectively. The use of integral coating effectively avoids the influence of polarization angle errors during assembly and adjustment. Figure 5 , Figure 6 and Figure 7 The image quality of the single-channel optical system is presented, demonstrating that the single-channel imaging quality is good.

[0023] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An imaging optical system for a polarized television camera, characterized in that, The system includes a four-channel imaging system, a four-channel polarizer, and four image sensors. The four-channel imaging system is arranged in a 2×2 array in parallel and is labeled as channel I, channel II, channel III, and channel IV, respectively. The four-channel imaging systems have the same structure and each includes a cemented lens (3), a fifth lens (4), a sixth lens (5), a seventh lens (6), and a folding prism (7), which are composed of a first lens (1), a second lens (2), a third lens (301), and a fourth lens (302). The front surface of the four-channel polarizer (8) is engraved with cross lines to divide the polarizer into four quadrants, with the first quadrant corresponding to channel I, the second quadrant corresponding to channel II, the third quadrant corresponding to channel III, and the fourth quadrant corresponding to channel IV. The photosensitive surfaces of the four image sensors (9) are all located at the focal plane of the imaging system and receive the target information collected by the imaging system.

2. The polarization television camera imaging optical system according to claim 1, characterized in that, The distance between the first lens (1) and the second lens (2) is 1.19 mm, the distance between the second lens (2) and the cemented lens (3) is 0.143 mm, the distance between the cemented lens (3) and the fifth lens (4) is 6 mm, the distance between the fifth lens (4) and the sixth lens (5) is 0.57 mm, the distance between the sixth lens (5) and the seventh lens (6) is 0.28 mm, the distance between the seventh lens (6) and the folding prism (7) is 1.4 mm, the distance between the folding prism (7) and the four-channel polarizer (8) is 1 mm, and the distance between the four-channel polarizer (8) and the photosensitive surface of the image sensor (9) is 2.57 mm.

3. The polarization television camera imaging optical system according to claim 1, characterized in that, The first lens (1) has an outline diameter of 27 mm, the second lens (2) has an outline diameter of 25 mm, the cemented lens (3) has an outline diameter of 25 mm, the fifth lens (4) has an outline diameter of 17 mm, the sixth lens (5) has an outline diameter of 15 mm, and the seventh lens (6) has an outline diameter of 14 mm.

4. The polarization television camera imaging optical system according to claim 3, characterized in that, The first lens (1) is a biconvex lens with a focal length range of 25mm≤f≤30mm; the second lens (2) is a meniscus lens with a focal length range of -45mm≤f≤-50mm; the third lens (301) is a biconvex lens with a focal length range of 10mm≤f≤15mm; the fourth lens (302) is a biconcave lens with a focal length range of -18mm≤f≤-22mm; the fifth lens (4) is a biconvex lens with a focal length range of 20mm≤f≤26mm; the sixth lens (5) is a meniscus lens with a focal length range of 280mm≤f≤310mm; and the seventh lens (6) is a plano-concave lens with a focal length range of -7mm≤f≤-10mm.

5. The polarization television camera imaging optical system according to claim 1, characterized in that, The folding prism (7) is made of H-BaK7. The incident end face A and the exit end face D of the folding prism (7) are parallel to each other, the reflecting surface B and the reflecting surface C are parallel to each other, and the reflecting surface forms a 45° angle with the incident and exit end faces. The E surface, F surface, G surface and H surface are all glued surfaces. The angle between the E surface and the F surface is 135°±1′, the angle between the F surface and the G surface is 90°±1′, and the angle between the G surface and the H surface is 135°±1′.

6. The polarization television camera imaging optical system according to claim 1, characterized in that, The thickness of the four-channel polarizer (8) is 1 mm. Polarizing films are deposited in the middle of the four quadrants of the polarizer. The polarizing films are 15 mm × 15 mm in size, linearly polarized, with a wavelength range of 400 nm to 700 nm, an extinction coefficient of 9000:1, and a transmittance of 53%. The polarization axis of the first quadrant is set to 0°, the polarization axis of the second quadrant is set to 45°, the polarization axis of the third quadrant is set to 90°, and the polarization axis of the fourth quadrant is set to 135°.

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