Large-view-field image space telecentric underwater vision docking imaging optical system

Abstract

The invention discloses a large-view-field image space telecentric underwater vision docking imaging optical system. The optical system sequentially comprises a dome cover window, a front group lens, an iris diaphragm, a rear group lens and an optical filter, the front-group lens sequentially comprises a front-group first lens, a front-group second lens, a front-group third lens and a front-group fourth lens; the rear group lens sequentially comprises a rear group first lens, a rear group second lens, a rear group third lens and a rear group fourth lens; the variable diaphragm is positioned between the front-group fourth lens and the rear-group first lens; and an object space imaging light beam sequentially passes through the dome cover window, the front group of lenses, the variable diaphragm, the rear group of lenses and the optical filter to be imaged on the target surface of the gating camera. The system has the advantages of being large in view field, short in focal length, variable in F number, telecentric in image space and the like, clear imaging is achieved through rear set focusing and the variable F number, the system can be used for short-distance underwater vision docking recovery of a cross-domain aircraft, it is ensured that imaging can be clear in the docking process, and position calculation errors caused by image space focusing can be eliminated.

Description

Technical Field

[0001] The invention relates to an underwater optical system, in particular to a large-field-of-view image-space telecentric underwater visual docking imaging optical system. Background Art

[0002] Cross-domain aircraft is an important equipment for underwater and surface detection. Underwater docking and recovery of aircraft is an important function. The process includes two stages: long-range hydroacoustic or inertial navigation guidance and close-range underwater visual docking. In the close-range underwater visual docking stage, the underwater optoelectronic imaging unit is mainly used to image the cooperative target array, extract the target lattice coordinates, and calculate the distance and three-dimensional posture of the cross-domain aircraft relative to the recovery platform according to the lattice pattern. Studies have shown that the blue-green laser is in the underwater transmission "window" and has a strong ability to penetrate seawater. Therefore, underwater cooperative targets generally use LED lights with a wavelength of about 530nm, and the imaging band of the underwater visual docking imaging lens needs to match it. The imaging system is used for visual positioning and solution, and needs to have the characteristics of large field of view, large depth of field, fast focusing, image telecentricity, etc., to ensure clear imaging during the entire docking process and eliminate the solution error caused by image focusing.

[0003] Therefore, it is urgent to propose a large-field-of-view image-side telecentric underwater visual docking imaging optical system for visual positioning solution. It needs to have the characteristics of large field of view, large depth of field, fast focusing, image-side telecentricity, etc. to ensure clear imaging during the entire docking process and eliminate the solution error caused by image-side focusing. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a large-field-of-view image-side telecentric underwater visual docking imaging optical system for the defects in the prior art, which is used for the close-range underwater visual docking recovery of cross-domain aircraft, and its imaging band matches the cooperative target. The imaging system is used for visual positioning and solving, and needs to have the characteristics of large field of view, large depth of field, fast focusing, image-side telecentricity, etc., to ensure clear imaging during the entire docking process and eliminate the solving error caused by image-side focusing.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] The present invention provides a large-field-of-view image-space telecentric underwater visual docking imaging optical system, which comprises in sequence: a ball cover window, a front lens group, a variable diaphragm, a rear lens group and a filter; wherein:

[0007] The front lens group includes: the first lens of the front group, the second lens of the front group, the third lens of the front group, and the fourth lens of the front group; the rear lens group includes: the first lens of the rear group, the second lens of the rear group, the third lens of the rear group, and the fourth lens of the rear group; the variable aperture is located between the fourth lens of the front group and the first lens of the rear group;

[0008] The object imaging beam passes through the ball cover window, the front lens group, the variable aperture, the rear lens group and the filter in sequence to form an image on the target surface of the gated camera.

[0009] Furthermore, the spherical cover window of the present invention is a tempered concentric spherical cover window, which is used to isolate water and the lens, the left medium is water, and the right medium is air.

[0010] Furthermore, the four lenses of the front lens group of the present invention adopt a "2+2" structure, wherein: the first lens of the front lens group and the second lens of the front lens group are negative lenses made of high refractive index materials, and the third lens of the front lens group and the fourth lens of the front lens group are positive lenses made of low dispersion materials.

[0011] Furthermore, the rear lens group of the present invention has a total of four lenses, the first lens of the rear group is a double cemented negative lens, the second lens of the rear group is a plano-convex positive lens, the third lens of the rear group is a double convex positive lens, and the fourth lens of the rear group is a double cemented positive lens.

[0012] Furthermore, the working wavelength band of the optical system of the present invention is 505-545 nm, and the filter is used to filter out light in wavelength bands other than the working wavelength band.

[0013] Furthermore, the focal length of the lens of the optical system of the present invention is 8.6 mm, the minimum F number is 2.5, the maximum field of view is 80°, and the variable F number is achieved by adjusting the size of the variable aperture.

[0014] Furthermore, the optical system of the present invention is an image-space telecentric system, and the telecentricity is better than 0.1°.

[0015] Furthermore, the optical system of the present invention performs focusing through four lenses of the rear lens group to achieve underwater imaging at a distance from 0.4 m to infinity.

[0016] Furthermore, the structural parameters of the optical system of the present invention are specifically as follows:

[0017] The dome cover window has a curvature radius of 75 and a thickness of 10 on surface S1; a curvature radius of 65 and a thickness of 17 on surface S2;

[0018] The first lens of the front group has a curvature radius of 86.5 on the surface S3 and a thickness of 8; a curvature radius of 24.62 on the surface S4 and a thickness of 8.4;

[0019] The second lens of the front group has a curvature radius of 1900 on surface S5 and a thickness of 3.6; a curvature radius of 42.53 on surface S6 and a thickness of 22.4;

[0020] The third lens of the front group has a curvature radius of -95.35 on surface S7 and a thickness of 5; a curvature radius of -41.6 on surface S8 and a thickness of 12.35;

[0021] The fourth lens of the front group has a curvature radius of 66.2 on surface S9 and a thickness of 7; a curvature radius of -66.2 on surface S10 and a thickness of 23;

[0022] The curvature radius of the variable aperture is ∞ and the thickness is 9;

[0023] The first lens of the rear group has a curvature radius of -10.2 and a thickness of 2.5 on the surface S11; a curvature radius of -85.45 and a thickness of 5.5 on the surface S12; a curvature radius of -14.63 and a thickness of 0.35 on the surface S13;

[0024] The second lens of the rear group has a curvature radius of 2405 on surface S14 and a thickness of 5.2; a curvature radius of -18.65 on surface S15 and a thickness of 1.4;

[0025] The third lens of the rear group has a curvature radius of 142.55 on surface S16 and a thickness of 8.2; a curvature radius of -54.52 on surface S17 and a thickness of 0.4;

[0026] The fourth lens of the rear group has a curvature radius of 43.52 on surface S18 and a thickness of 8.2; a curvature radius of -24.62 on surface S19 and a thickness of 3; a curvature radius of -421.24 on surface S20 and a thickness of 5.5;

[0027] Filter, the curvature radius of surface S21 is ∞, and the thickness is 2; the curvature radius of surface S22 is ∞, and the thickness is 10;

[0028] The unit is mm.

[0029] Furthermore, the adjustment method of the optical system of the present invention comprises:

[0030] Utilizing a short focal length, large F-number system, it has the characteristic of a large depth of field when focusing on close objects, from a long distance of 50m to a close distance of 0.4m. Through the rear lens focusing group, the 50m target and the 0.8m target are focused, achieving clear imaging within the range of 50m to 0.4m, and achieving rapid and clear focusing on cooperative targets.

[0031] The outstanding features and significant beneficial effects of the present invention are: the imaging optical system of the present invention has the characteristics of large field of view, short focal length, variable F number and image telecentricity. The system can achieve clear imaging in the range of 50m to 0.4m through rear group focusing and variable F number, and can be used for close-range underwater visual docking and recovery of cross-domain aircraft, ensuring clear imaging during the entire docking process, and the image telecentric optical path can eliminate the position solution error caused by image focusing. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0033] Figure 1 is a schematic diagram of an optical system of the present invention;

[0034] In the figure, 1-protective window, 2-first lens of the front group, 3-second lens of the front group, 4-third lens of the front group, 5-fourth lens of the front group, 6-variable aperture, 7-first lens of the rear group, 8-second lens of the rear group, 9-third lens of the rear group, 10-fourth lens of the rear group, 11-filter;

[0035] Figure 2 Schematic diagram of the lens and lens surface of the present invention;

[0036] Figure 3 A two-dimensional diagram of the optical system of the present invention;

[0037] Figure 4 This is the MTF diagram of the optical system of the present invention at 80lp / mm.

[0038] Figure 5 This is the MTF diagram of the optical system of the present invention when it is focused at a close distance of 0.4m and at 80lp / mm. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] Example 1

[0041] like Figure 1 As shown, the embodiment of the present invention has a large field of view image-side telecentric underwater visual docking imaging optical system, with a focal length of 8.6mm, a minimum F number of 2.5, and a field of view of up to 80°. The embodiment of the present invention is an image-side telecentric system, and the telecentricity is better than 0.1°. The entire system has eight lenses, a ball cover window 1, a variable aperture 6, and a filter 11, which include the ball cover window 1, a front group, a rear group, and a filter 11 in sequence, wherein: the front group includes a front group first lens 2, a front group second lens 3, a front group third lens 4, and a front group fourth lens 5, a total of four lenses, the rear group includes a rear group first lens 7, a rear group second lens 8, a rear group third lens 9, and a rear group fourth lens 10, a total of four lenses, and the last piece is a filter 11.

[0042] The variable aperture 6 is located between the fourth lens of the front group 5 and the first lens of the rear group 7. The variable F number can be changed by adjusting the size of the variable aperture 6.

[0043] The spherical cover window 1 used in the embodiment of the present invention is a tempered concentric spherical cover window, which can withstand 3MPa hydrostatic pressure and is used to isolate water and the lens. The left medium is water and the right medium is air.

[0044] The first lens 7 and the fourth lens 10 of the rear group in the embodiment of the present invention are cemented lenses, which are used to correct system aberrations. The embodiment of the present invention realizes the image telecentric optical path through the four lenses of the rear group and performs focusing. The working band of the embodiment of the present invention is 505-545nm, and the last piece is a filter 11, which can filter out light of other bands.

[0045] The embodiment of the present invention utilizes a short focal length and a large F number system, and when focusing on close objects clearly, it also has the characteristic of a large depth of field. From a long distance of 50m to a close distance of 0.4m, the focusing group only needs to focus on a 50m target and a 0.8m target to achieve clear imaging within the range of 50m to 0.4m. Using this focusing strategy, rapid and clear focusing on cooperative targets can be achieved.

[0046] Figure 2 Schematic diagram of the lens and lens surface of the present invention. Furthermore, the optical lens materials are all common visible light glass materials with excellent performance and abundant stock.

[0047] The front four lenses adopt a "2+2" structure, where the first two lenses are negative lenses made of high refractive index materials, and the rear two lenses are positive lenses made of low dispersion materials. The rear group has a total of four lenses, the first lens of the rear group is a double-cemented negative lens, the second lens of the rear group is a plano-convex positive lens, the third lens of the rear group is a double-convex positive lens, and the fourth lens of the rear group is a double-cemented positive lens.

[0048] Example 2

[0049] The embodiment of the present invention further provides the specific parameters of the optical system structure of the present invention in more detail based on embodiment 1: Table 1 shows the lens curvature radius, thickness, lens spacing and material of the entrance pupil pre-underwater laser imaging optical system structure parameters;

[0050] Table 1 Structural parameters of the pre-pupil underwater laser imaging optical system

[0051]

[0052]

[0053] Figure 3 It is a two-dimensional image of an underwater infinitely distant target imaged by the optical system of the present invention;

[0054] Figure 4 This is the MTF diagram of the optical system of the present invention at 80lp / mm.

[0055] Figure 5 This is the MTF diagram of the optical system of the present invention when it is focused at a close distance of 0.4m and at 80lp / mm.

[0056] In summary, the present invention discloses a large-field-of-view image-space telecentric underwater visual docking imaging optical system, a large-field-of-view image-space telecentric underwater visual docking imaging optical system, which adopts a one-time imaging structure to realize an image-space telecentric design, and a telecentricity better than 0.1°. The system is used for underwater visual docking imaging, and the working band is 505-545nm. The system consists of a spherical cover window, four lenses in the front group, four lenses in the rear group, a variable iris and a filter, wherein the variable iris is located between the fourth lens in the front group and the first lens in the rear group, and the first lens in the rear group and the fourth lens in the rear group are both cemented lenses, which are used for aberration correction to realize image-space telecentricity. The focal length of the optical lens of the present invention is 8.6mm, the minimum F number is 2.5, the full field of view is 80°, the variable F number can be achieved through the variable iris, and the focusing can be performed through the four lenses in the rear group. The system utilizes a short focal length and large F number system. When focusing on close objects, it also has a large depth of field. From a long distance of 50m to a close distance of 0.4m, the focusing group only needs to focus on the 50m target and the 0.8m target to achieve clear imaging within the range of 50m to 0.4m. Using this focusing strategy, rapid and clear focusing on cooperative targets can be achieved.

[0057] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0058] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A large-field-of-view image-space telecentric underwater visual docking imaging optical system, characterized in that: The optical system comprises in sequence: a spherical cover window (1), a front lens group, a variable aperture (6), a rear lens group and a filter (11); wherein: The front lens group includes, in sequence: a front first lens group (2), a front second lens group (3), a front third lens group (4), and a front fourth lens group (5); the rear lens group includes, in sequence: a rear first lens group (7), a rear second lens group (8), a rear third lens group (9), and a rear fourth lens group (10); the variable aperture (6) is located between the front fourth lens group (5) and the rear first lens group (7); The object-side imaging light beam passes through the ball cover window (1), the front lens group, the variable aperture (6), the rear lens group and the filter (11) in sequence to form an image on the target surface of the gated camera.

2. The large-field-of-view image-space telecentric underwater visual docking imaging optical system according to claim 1, characterized in that: The spherical cover window (1) is a tempered concentric spherical cover window, which is used to isolate water and the lens, the left medium is water, and the right medium is air.

3. The large field of view image space telecentric underwater visual docking imaging optical system according to claim 1, characterized in that: The four lenses of the front lens group adopt a "2+2" structure, wherein the first lens (2) and the second lens (3) of the front lens group are negative lenses made of high refractive index materials, and the third lens (4) and the fourth lens (5) of the front lens group are positive lenses made of low dispersion materials.

4. The large field of view image space telecentric underwater visual docking imaging optical system according to claim 1, characterized in that: The rear lens group has four lenses in total, the first lens (7) of the rear lens group is a double cemented negative lens, the second lens (8) of the rear lens group is a plano-convex positive lens, the third lens (9) of the rear lens group is a double convex positive lens, and the fourth lens (10) of the rear lens group is a double cemented positive lens.

5. The large field of view image space telecentric underwater visual docking imaging optical system according to claim 1, characterized in that: The working wavelength band of the optical system is 505-545 nm, and the filter (11) is used to filter out light in wavelength bands other than the working wavelength band.

6. The large-field-of-view image-space telecentric underwater visual docking imaging optical system according to claim 1, characterized in that: The lens focal length of the optical system is 8.6 mm, the minimum F number is 2.5, the maximum field of view is 80°, and the variable F number can be achieved by adjusting the size of the variable iris (6).

7. The large field of view image-space telecentric underwater visual docking imaging optical system according to claim 1, characterized in that: The optical system is an image-space telecentric system with a telecentricity better than 0.1°.

8. The large field of view image-space telecentric underwater visual docking imaging optical system according to claim 1, characterized in that: The optical system focuses through the four lenses of the rear lens group to achieve underwater imaging from 0.4m to infinity.

9. The large field of view image-space telecentric underwater visual docking imaging optical system according to claim 1, characterized in that: The structural parameters of the optical system are as follows: The spherical cover window (1) has a surface S1 with a curvature radius of 75 and a thickness of 10, and a surface S2 with a curvature radius of 65 and a thickness of 17; The first lens (2) of the front group has a surface S3 with a radius of curvature of 86.5 and a thickness of 8; a surface S4 with a radius of curvature of 24.62 and a thickness of 8.4; The second lens (3) of the front group has a surface S5 with a radius of curvature of 1900 and a thickness of 3.6; a surface S6 with a radius of curvature of 42.53 and a thickness of 22.4; The third lens (4) of the front group has a curvature radius of -95.35 on the surface S7 and a thickness of 5; a curvature radius of -41.6 on the surface S8 and a thickness of 12.35; The fourth lens (5) of the front group has a curvature radius of 66.2 on the surface S9 and a thickness of 7; a curvature radius of -66.2 on the surface S10 and a thickness of 23; The curvature radius of the variable aperture (6) is ∞, and the thickness is 9; The first lens (7) of the rear group has a surface S11 with a curvature radius of -10.2 and a thickness of 2.5; a surface S12 with a curvature radius of -85.45 and a thickness of 5.5; a surface S13 with a curvature radius of -14.63 and a thickness of 0.35; The second lens (8) of the rear group has a curvature radius of 2405 on the surface S14 and a thickness of 5.2; a curvature radius of -18.65 on the surface S15 and a thickness of 1.4; The third lens (9) of the rear group has a surface S16 with a radius of curvature of 142.55 and a thickness of 8.2; a surface S17 with a radius of curvature of -54.52 and a thickness of 0.4; The fourth lens (10) of the rear group has a curvature radius of 43.52 on the surface S18 and a thickness of 8.2; a curvature radius of -24.62 on the surface S19 and a thickness of 3; a curvature radius of -421.24 on the surface S20 and a thickness of 5.5; The filter (11) has a surface S21 with a curvature radius of ∞ and a thickness of 2; a surface S22 with a curvature radius of ∞ and a thickness of 10; The unit is mm.

10. The large-field-of-view image-space telecentric underwater visual docking imaging optical system according to claim 1, characterized in that: The adjustment method of the optical system includes: Utilizing a short focal length, large F-number system, it has the characteristic of a large depth of field when focusing on close objects, from a long distance of 50m to a close distance of 0.4m. Through the rear lens focusing group, the 50m target and the 0.8m target are focused, achieving clear imaging within the range of 50m to 0.4m, and achieving rapid and clear focusing on cooperative targets.

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