Large-view-field high-resolution optical system based on super-large area array detector

Abstract

The invention provides a large-field-of-view high-resolution optical system based on an ultra-large area array detector. The large-field-of-view high-resolution optical system comprises an optical filter, a front group lens, a diaphragm, a rear group lens and an image plane, the front group lens has negative focal power; the rear group lens has positive focal power; the diaphragm is located between the front group of lens and the rear group of lens, the front group of lens, the diaphragm and the rear group of lens are coaxially designed, and a large-view-field light beam from a target sequentially passes through the optical filter, the front group of lens, the diaphragm and the rear group of lens to be converged and imaged on an image plane of the system. According to the invention, a complicated double-Gaussian structure and a full-spherical design are adopted, the focal power of each component is reasonably distributed, the refractive index dispersion characteristics are optimally matched, the front and rear groups of lenses are combined for aberration correction, the large-aperture, large-field-of-view and high-resolution imaging performance is realized, the imaging quality, distortion and image surface illumination in the full field of view are ensured, and the imaging quality is improved. The length and the aperture of the lens are effectively controlled, and ultra-large area array high-resolution imaging is realized by using a single optical system.

Description

Technical Field

[0001] The invention belongs to the field of optical technology, and relates to a large-field-of-view high-resolution optical system, and in particular to a large-field-of-view high-resolution imaging optical system based on an ultra-large array detector. Background Art

[0002] Gigapixel cameras have the characteristics of "large scenes, wide-angle coverage, and ultra-high resolution". They can grasp the dynamics of the entire scene in one picture and can also achieve long-distance monitoring capabilities with a large field of view. They have broad application prospects in astronomical observation, aerospace remote sensing and other fields.

[0003] Currently, optical systems that can achieve billion / multi-billion pixel resolution include the GigaPan panoramic shooting system designed and developed by a team from Carnegie Mellon University in the United States, which acquires billion-pixel images through scanning with a small-field-of-view camera and image stitching; the multi-scale billion-pixel camera AWARE-2 developed by Duke University in the United States has a field of view of 120°. The camera's main mirror is concentric and surrounded by an array of 98 small cameras, and the number of effective pixels in the acquired image is as high as one billion; the billion-pixel camera developed by the Defense Advanced Research Projects Agency (DARPA) is a collection of 100 to 150 small cameras; the "billion-pixel array" super camera carried by the Gaia probe developed by the European Space Agency has a payload consisting of two telescopes, a focal plane and related electronic equipment, and the focal plane array of the two telescopes consists of 106 CCDs with 4500x1966 pixels. In addition, the Chinese patent with publication number CN106254741A discloses "a large-field-of-view, high-resolution, multi-gigapixel remote sensing camera", including four imaging optical path components, which achieve full coverage of the large field of view through image stitching; the Chinese patent with publication number CN109040601A discloses "a multi-scale unstructured billion-pixel VR panoramic photography system", including a wide-field-of-view annular camera array and a narrow-field-of-view annular camera array, a multi-camera image stitching device, and a VR display device. The multi-camera image stitching device uses the ZNCC algorithm to perform multi-scale fusion of multiple wide-field-of-view images and multiple narrow-field-of-view images according to the calibration parameter matrix to generate a billion-pixel annular image, thereby realizing the acquisition and display of billion-pixel VR panoramic videos.

[0004] It can be seen that the reported billion / multi-billion-pixel cameras either use small field of view scanning plus image stitching, or small camera array imaging plus image stitching to achieve high-resolution imaging; but small field of view scanning cannot achieve fast real-time imaging; and although small camera arrays can achieve large field of view and multi-billion-pixel real-time imaging, they are limited by high system complexity and poor stability. In addition, multiple detectors make the system large in size and weight, and image stitching is difficult and costly. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention proposes a large-field-of-view, high-resolution optical system based on an ultra-large area array detector. Based on the currently available billion-pixel large area array detector, a single optical system is used to match the ultra-large area array detector to achieve billion-pixel large-field-of-view, high-resolution imaging.

[0006] The technical solution of the present invention is:

[0007] The large-field-of-view high-resolution optical system based on the ultra-large array detector comprises a filter, a front lens group, an aperture, a rear lens group and an image plane;

[0008] The front lens group has negative focal power; the rear lens group has positive focal power; the aperture is located between the front lens group and the rear lens group, and the aperture hole center is located on the optical axis; the image plane is located on the side of the rear lens group away from the aperture, and the filter is located on the side of the front lens group away from the aperture; the front lens group, the aperture and the rear lens group are coaxially designed, and the large field of view light beam from the target is sequentially converged to the image plane of the system through the filter, the front lens group, the aperture and the rear lens group;

[0009] The front lens group includes, from the object side to the image side, the following:

[0010] Objective lens 1 has negative optical power and the object side is convex;

[0011] Objective lens 2, with positive power and a convex object side surface;

[0012] Objective lens 3 has negative optical power and is in the form of a cemented lens, which is composed of a first cemented negative lens and a first cemented positive lens from the object side to the image side; the first cemented negative lens has negative optical power and is a double concave lens; the first cemented positive lens has positive optical power and is a double convex lens;

[0013] Objective lens 4 has negative optical power and is in the form of a cemented lens, which is composed of a second cemented positive lens and a second cemented negative lens from the object side to the image side; the second cemented positive lens has positive optical power and is a double convex lens; the second cemented negative lens has negative optical power and is a double concave lens;

[0014] Objective lens 5 has positive focal power and is in the form of a cemented lens, which is composed of a third cemented positive lens and a third cemented negative lens from the object side to the image side; the third cemented positive lens has positive focal power and is a double convex lens; the third cemented negative lens has negative focal power and is a meniscus lens;

[0015] The rear lens group includes, from the object side to the image side,

[0016] Objective lens 6, having positive optical power and a convex object side surface;

[0017] Objective lens seven, having positive power and a convex object side surface;

[0018] Objective lens eight has positive focal power and is in the form of a cemented lens, and is composed of a fourth cemented negative lens and a fourth cemented positive lens from the object side to the image side; the fourth cemented negative lens has negative focal power and is a meniscus lens; the fourth cemented positive lens has positive focal power and is a double convex lens;

[0019] Objective lens nine has positive power and is in the form of a cemented lens, which is composed of a fifth cemented negative lens and a fifth cemented positive lens from the object side to the image side; the fifth cemented negative lens has negative power and is a double concave lens; the fifth cemented positive lens has positive power and is a double convex lens;

[0020] Objective lens ten has negative optical power and the object side is concave.

[0021] Beneficial Effects

[0022] The present invention uses a single large-field-of-view high-resolution optical system matched with a single ultra-large array detector to achieve billion-pixel high-resolution imaging. The overall technical effect is reflected in the following aspects:

[0023] (1) The single large field of view and high resolution optical system adopts a full spherical surface design, which reduces the difficulty of processing and assembly, shortens the development cycle, and reduces costs.

[0024] (ii) A single large field of view and high resolution optical system that takes into account both a large field of view and high resolution, which is conducive to long-distance target detection and recognition under a large field of view.

[0025] (3) A single large field of view and high resolution optical system solves the problem of poor real-time performance caused by small field of view scanning; it does not require high-precision layout and control of multiple camera arrays, which reduces the difficulty of mechanical design and installation; it avoids image stitching and fusion, reducing the difficulty of image processing technology; it reduces volume and weight, and reduces costs.

[0026] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0028] Figure 1 It is a schematic diagram of the composition and optical path of an optical system in a specific embodiment of the present invention.

[0029] Figure 2 It is a modulation transfer function characteristic curve diagram of the optical system in a specific embodiment of the present invention.

[0030] Figure 3It is a relative illumination curve diagram of an optical system in a specific embodiment of the present invention.

[0031] Figure 4 It is a graph showing the optical distortion characteristics of an optical system in a specific embodiment of the present invention.

[0032] Figure 5 It is the field curvature of the optical system in a specific embodiment of the present invention (4 microns, which is less than the indicator requirement of 5.2 microns). DETAILED DESCRIPTION

[0033] Embodiments of the present invention are described in detail below. The embodiments are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0034] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] This embodiment is based on the already available billion-pixel large-area array detector, and uses a single optical system to match the ultra-large-area array detector to achieve billion-pixel large-field-of-view high-resolution imaging. The design difficulty of the imaging optical system with large relative aperture, large field of view and ultra-high resolution is much greater than that of a general imaging lens.

[0037] First, for a billion-pixel large-array detector, the pixel size is 0.7μm and the spatial resolution is as high as 714lp / mm. Therefore, the matching optical system also needs high spatial resolution, and the modulation transfer function (MTF) of the optical system is required to be greater than 0.2@714lp / mm, which greatly increases the difficulty of aberration correction. In addition, the diffraction limit 1 / λF of the optical system needs to be improved. # , under the condition of a certain working wavelength λ, the F number needs to be reduced, and the F number is closely related to the focal depth Δ of the optical system (Δ=±2λF 2), that is, the smaller the F number, the smaller the focal depth Δ. The target surface of a billion-pixel large-array detector has a certain flatness error (5 microns), so the focal depth of the optical system must be greater than 5 microns. Therefore, in order to balance the contradiction between the depth of focus and the diffraction limit, the optical system F number is set to 1.6, which belongs to a large relative aperture system and also increases the difficulty of aberration correction. When the F number is 1.6, the focal depth Δ is 5.2μm, so the field curvature of the optical system needs to be less than 5.2μm.

[0038] Secondly, the ultra-large array (diagonal 32mm) detector requires the matching optical system to have a large field of view (diagonal field of view 80°), and the image plane illumination at the maximum field of view cannot be less than 70%, and the image plane illumination of the off-axis field of view E = E0cos 4 w (E0 is the illumination of the on-axis point, w is the field of view angle) decreases rapidly with the increase of the field of view angle. If a conventional optical system is used, the image plane illumination of the off-axis field of view can only reach 34% of the on-axis field of view, which is far below the required 70%. Therefore, the design needs to control the off-axis field of view aberration while taking into account the illumination requirements, which greatly increases the difficulty of aberration correction.

[0039] From the aberration theory, we know that spherical aberration is proportional to the cube of the relative aperture, and coma is proportional to the square of the relative aperture. Therefore, it is more difficult to correct the spherical aberration and coma of the system with large relative aperture; distortion is proportional to the cube of the field of view, and field curvature and astigmatism are proportional to the square of the field of view. Therefore, it is more difficult to correct the distortion, field curvature and astigmatism of the system with large field of view; in addition, for the system with large relative aperture and large field of view, chromatic aberration correction is also a difficult point, and as the relative aperture and field of view of the optical system increase, its higher-order aberrations will increase significantly.

[0040] From the analysis, it can be seen that the large relative aperture and large field of view system needs to correct all monochromatic aberrations and chromatic aberrations, and the ultra-high resolution puts higher requirements on the image quality of the system. Therefore, how to optimize the initial structure, optimize and balance various aberrations, and improve the imaging quality of the system are key technologies that need to be focused on.

[0041] In this embodiment, a double Gaussian structure is used as the initial design structure. The double Gaussian structure is a symmetrical structure, and the vertical axis aberration (coma, distortion and magnification chromatic aberration) can be well corrected. Therefore, when designing, it is mainly necessary to consider the correction of spherical aberration, field curvature, astigmatism, and chromatic aberration. The complex double Gaussian structure can reduce the high-order spherical aberration of the off-axis field of view and the high-order spherical aberration of the aperture on the axis at the same time, and can obtain higher imaging quality under the condition of large relative aperture and large field of view. The image-side telecentric structure can make the convergence angle of the off-axis field of view and the on-axis field of view consistent on the image plane, reduce the occlusion and vignetting of the off-axis field of view, and ensure the uniformity of the illumination of the image plane.

[0042] Therefore, this embodiment ultimately adopts the idea of ​​combining a complex double Gaussian structure with an image-side telecentric structure. On the basis of the complex double Gaussian structure, the angle of the outgoing light of the off-axis field of view is optimized and controlled so that the convergence angle of the off-axis field of view and the on-axis field of view on the image plane is consistent, thereby ensuring the uniformity of the illumination of the large-field-of-view image plane.

[0043] The specific optical system structure is as follows: Figure 1 As shown, it includes a filter 1, a front lens group 2, an aperture 3, a rear lens group 4 and an image plane 5. The filter 1 is located at the front end of the optical system and is used to control the width of the transmission spectrum, cut off the non-imaging spectrum, and improve the contrast of the image plane; the imaging wide spectrum is converged on the image plane 5 after passing through the filter 1, the front lens group 2, the aperture 3, and the rear lens group 4.

[0044] The front lens group 2 includes, from the object side to the image side:

[0045] Objective lens 2-1 has negative optical power and its object side surface is convex;

[0046] Objective lens 2-2 has positive power and a convex object side surface;

[0047] Objective lens 3 2-3 has negative optical power and is a cemented lens, which is composed of a cemented negative lens 2-3a and a cemented positive lens 2-3b; the cemented negative lens 2-3a has negative optical power and is a double concave lens; the cemented positive lens 2-3b has positive optical power and is a double convex lens;

[0048] Objective lens 4 2-4 has negative optical power and is a cemented lens, which is composed of a cemented positive lens 2-4a and a cemented negative lens 2-4b; the cemented positive lens 2-4a has positive optical power and is a double convex lens; the cemented negative lens 2-4b has negative optical power and is a double concave lens;

[0049] Objective lens five 2-5 has positive optical power and is a cemented lens, consisting of a cemented positive lens 2-5a and a cemented negative lens 2-5b; the cemented positive lens 2-5a has positive optical power and is a double convex lens; the cemented negative lens 2-5b has negative optical power and is a meniscus lens.

[0050] The rear lens group 4 includes, from the object side to the image side, the following:

[0051] Objective lens 64-1, having positive optical power and a convex object side surface;

[0052] Objective lens 74-2, having positive optical power and a convex object side surface;

[0053] Objective lens eight 4-3 has positive focal power and is a cemented lens, which is composed of a cemented negative lens 4-3a and a cemented positive lens 4-3b; the cemented negative lens 4-3a has negative focal power and is a meniscus lens; the cemented positive lens 4-3b has positive focal power and is a double convex lens;

[0054] Objective lens nine 4-4 has positive focal power and is a cemented lens, which is composed of a cemented negative lens 4-4a and a cemented positive lens 4-4b; the cemented negative lens 4-4a has negative focal power and is a double concave lens; the cemented positive lens 4-4b has positive focal power and is a double convex lens;

[0055] Objective lens 10 4-5 has negative optical power and the object side is concave.

[0056] The components of the front lens group 2 of the optical system adopt a coaxial design; the components of the rear lens group 4 adopt a coaxial design; the front lens group 2, the aperture 3 and the rear lens group 4 also adopt a coaxial design.

[0057] This embodiment adopts the above optical system composition, uses the structural change of the thick lens to correct the field curvature, uses the bending of the thin lens to correct the spherical aberration, changes the distance between the two thick lenses to correct the astigmatism, and introduces the cemented surface in the thick lens to correct the chromatic aberration. In order to further meet the large relative aperture and ensure the imaging quality, the meniscus thin lens is complicated into a double cemented lens. This structure can reduce the high-order spherical aberration of the off-axis field of view and the high-order spherical aberration of the aperture on the axis at the same time, and can obtain higher imaging quality in the case of a larger field of view. The point array spot of the full field of view is controlled within 0.7 microns of a pixel, ensuring MTF>0.2@714lp / mm.

[0058] When optimizing the design, the field curvature coefficient is calculated and its absolute value is gradually reduced until the field curvature is less than the index requirement. When the field curvature is reduced, the astigmatism is also controlled. In addition, when optimizing the design, the angle of the outgoing light of the off-axis field of view is also controlled to make the convergence angle of the off-axis field of view and the on-axis field of view on the image plane consistent (that is, to achieve the image side telecentric structure), thereby ensuring the uniformity of the illumination of the large field of view image plane.

[0059] Finally, the curvature radius r, center thickness d, refractive index N and Abbe number V of each surface of the above optical system device satisfy the following table:

[0060] Surface number Radius of curvature r Center thickness d Refractive index N Abbe number V S1 -- 8 51 64 S2 -- 5 -- -- S3 2595.99 6.5 43 95 S4 27.28 -- -- -- S5 30.9 12 64 33 S6 29.11 -- -- -- S7 -29.31 4 51 60 S8 75.34 14 20 25 S9 -219.8 -- -- -- S10 85.9 12 65 50 S11 -39.36 7 74 27 S12 88.15 -- -- -- S13 38.46 15 48 70 S14 -28.05 3 85 32 S15 -167.7 -- -- -- S16 123.59 6 94 18 S17 -278.85 -- -- -- S18 -220.8 7.2 43 95 S19 -36.9 -- -- -- S20 22.18 5 20 25 S21 16.218 13 49 81 S22 95.51 -- -- -- S23 -80.53 2.6 20 25 S24 15.56 14 92 20 S25 -32.21 -- -- -- S26 -30.13 2.6 94 18 S27 -257.48 12 -- -- S28 -- -- -- --

[0061] The focal length of the optical system that meets the above conditions is f'=25, and the total optical length from the filter to the image plane is TTL=183 mm.

[0062] In order to verify the performance of the optical system, the optical system in this embodiment is simulated for optical performance, and its modulation transfer function characteristic curve is as follows: Figure 2As shown, the relative illumination curve is Figure 3 As shown in the figure, the optical distortion characteristic curve is as follows Figure 4 As shown, the field curvature is Figure 5 shown.

[0063] Figure 2 It is the modulation transfer function characteristic curve of the optical system in this embodiment. The horizontal axis is the spatial frequency in lp / mm, and the vertical axis is the modulation degree of the image point and the object point. Curve F1: Diff.Limit is the diffraction limit of the optical system; the transfer function curve corresponding to the on-axis light when the field of view angle is 0° is F1, and F2, F3, F4, F5, and F6 are the transfer function curves corresponding to the off-axis field of view. The field of view angle corresponding to F2 is 12.3°, the field of view angle corresponding to F3 is 20.5°, the field of view angle corresponding to F4 is 28.7°, the field of view angle corresponding to F5 is 32.8°, and the field of view angle corresponding to F6 is 41°. From Figure 2 It can be seen that at a spatial frequency of 714lp / mm, the diffraction limit of the optical transfer function in this embodiment is close to 0.3, the optical transfer function of the on-axis field of view is greater than 0.25, the optical transfer function of the maximum field of view is greater than 0.23, and the optical transfer function of the full field of view is between 0.23 and 0.25, which is close to the diffraction limit.

[0064] Figure 3 : is the relative illumination curve of the optical system in this embodiment, the horizontal axis is the field angle, and the vertical axis is the relative illumination. The relative illumination is used to evaluate the uniformity of the image brightness, which is the ratio of the off-axis field of view to the on-axis field of view. The relative illumination of the optical system in this embodiment is 72% when the maximum field of view is 41°.

[0065] Figure 4 : is the optical distortion curve of the optical system in this embodiment. The optical distortion value of the maximum field of view is -0.18, which meets the distortion requirement of a large field of view.

[0066] Figure 5 The field curvature of the optical system in this embodiment is 4 microns, which is smaller than the indicator requirement of 5.2 microns.

[0067] It can be seen that this embodiment adopts a complex double Gaussian structure and a full spherical surface design, reasonably distributes the optical power of each component, optimizes and matches its refractive index dispersion characteristics, and jointly performs aberration correction on the front and rear lens groups. It has large aperture, large field of view, and high-resolution imaging performance, ensuring the imaging quality, distortion and image plane illumination in the full field of view. The length and aperture of the lens are also effectively controlled, and ultra-large array high-resolution imaging is achieved using a single optical system.

[0068] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A large field of view and high resolution optical system based on a very large array detector, characterized by: From the object side to the image side, it includes filter, front lens group, aperture, rear lens group and image plane; The front lens group has negative focal power; the rear lens group has positive focal power; the front lens group, the aperture and the rear lens group are coaxially designed, and the large field of view light beam from the target is sequentially converged to the image plane of the system through the filter, the front lens group, the aperture and the rear lens group; The front lens group includes, from the object side to the image side, the following: Objective lens 1 has negative optical power and the object side is convex; Objective lens 2, with positive power and a convex object side surface; Objective lens 3 has negative optical power and is in the form of a cemented lens, which is composed of a first cemented negative lens and a first cemented positive lens from the object side to the image side; the first cemented negative lens has negative optical power and is a double concave lens; the first cemented positive lens has positive optical power and is a double convex lens; Objective lens 4 has negative optical power and is in the form of a cemented lens, which is composed of a second cemented positive lens and a second cemented negative lens from the object side to the image side; the second cemented positive lens has positive optical power and is a double convex lens; the second cemented negative lens has negative optical power and is a double concave lens; Objective lens 5 has positive focal power and is in the form of a cemented lens, which is composed of a third cemented positive lens and a third cemented negative lens from the object side to the image side; the third cemented positive lens has positive focal power and is a double convex lens; the third cemented negative lens has negative focal power and is a meniscus lens; The rear lens group includes, from the object side to the image side, Objective lens 6, having positive optical power and a convex object side surface; Objective lens seven, having positive power and a convex object side surface; Objective lens eight has positive focal power and is in the form of a cemented lens, and is composed of a fourth cemented negative lens and a fourth cemented positive lens from the object side to the image side; the fourth cemented negative lens has negative focal power and is a meniscus lens; the fourth cemented positive lens has positive focal power and is a double convex lens; Objective lens nine has positive power and is in the form of a cemented lens, which is composed of a fifth cemented negative lens and a fifth cemented positive lens from the object side to the image side; the fifth cemented negative lens has negative power and is a double concave lens; the fifth cemented positive lens has positive power and is a double convex lens; Objective lens ten has negative optical power and the object side is concave.

2. According to claim 1, a large field of view and high resolution optical system based on a very large area array detector is characterized in that: The field curvature is corrected by using the structural change of the thick lens, the spherical aberration is corrected by using the bending of the thin lens, the astigmatism is corrected by changing the distance between the two thick lenses, and the chromatic aberration is corrected by introducing a cemented surface in the thick lens. The meniscus thin lens is complicated into a double cemented lens, so that the high-order spherical aberration of the off-axis field of view and the high-order spherical aberration of the aperture on the axis can be reduced at the same time.

3. According to claim 2, a large field of view and high resolution optical system based on a very large area array detector is characterized in that: The radius of curvature r, center thickness d, refractive index N and Abbe number V of each surface of the optical system component are: 。

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