CN111580258A - Compact type large-view-field small-F # catadioptric optical system - Google Patents
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- G—PHYSICS
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- G02B17/00—Systems with reflecting surfaces, with or without refracting elements
- G02B17/08—Catadioptric systems
- G02B17/0836—Catadioptric systems using more than three curved mirrors
- G02B17/084—Catadioptric systems using more than three curved mirrors on-axis systems with at least one of the mirrors having a central aperture
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B17/00—Systems with reflecting surfaces, with or without refracting elements
- G02B17/08—Catadioptric systems
- G02B17/0836—Catadioptric systems using more than three curved mirrors
- G02B17/0844—Catadioptric systems using more than three curved mirrors off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry
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Abstract
The invention belongs to the field of optical imaging, and relates to a compact large-view-field small-F # catadioptric optical system. The method is mainly used for large-field high-resolution ground imaging. The problem of current remote sensing optical system can not satisfy the requirement that the formation of image visual field is big, working band is broad and compact structure simultaneously is solved. The device comprises a primary mirror, a secondary mirror, a third mirror, a fourth mirror and a compensation lens in sequence along the light propagation direction; inner holes are formed in the axial centers of the primary mirror, the secondary mirror and the third mirror, and the third mirror is embedded into the inner hole of the primary mirror; the four mirrors are embedded into the inner holes of the secondary mirrors; the light rays are reflected by the primary mirror, the secondary mirror, the third mirror and the fourth mirror in sequence in the propagation direction and then penetrate through the compensation lens to reach a focal plane for imaging; the primary mirror, the secondary mirror, the third mirror and the fourth mirror are even aspheric mirrors with the highest frequency of four times, and four even aspheric reflectors are adopted to convert the light path, so that the total length of the system is greatly reduced, and meanwhile, the primary mirror, the third mirror, the secondary mirror and the fourth mirror are integrally processed, the total lens quantity of the system is reduced, and the installation and adjustment difficulty of the system is reduced.
Description
Technical Field
The invention belongs to the field of optical imaging, and particularly relates to a compact large-view-field small-F # catadioptric optical system. The method is mainly used for large-view-field high-resolution ground imaging, and can also be used in the fields of urban safety monitoring, national soil general survey, disaster prevention and reduction and the like.
Background
With the development of optical technology, the importance of the field of optical remote sensing is increasing, and at the same time, higher performance requirements are placed on optical systems for remote sensing. In order to meet new performance requirements, the remote sensing optical system gradually develops towards the directions of long focal length, large caliber, wide spectrum band, large visual field, compact structure and the like, and the total reflection system has unique advantages in realizing the indexes. The traditional RC system has the advantages of long focal length, large caliber, compact structure, easy assembly and adjustment and the like, and because the transmission compensating mirror is adopted, the working waveband of the system is narrow, and the imaging field of view of the system is difficult to be enlarged; although the off-axis three-reflection optical system can realize the functions of long focal length, large caliber, wide spectrum band, large view field and the like, the installation and adjustment of a single system are complex, and the overall size is large. Meanwhile, in order to enlarge a field of view and correct aberration, an off-axis four-reflection structure is developed on the basis of off-axis three-reflection, so that the overall size of the system and the complexity of adjustment are further increased.
A compact large-view-field embedded catadioptric optical system is disclosed in CN 109459844A, which is applied by Jingjing, and has a complex Graigarie system, an intermediate image plane is arranged between secondary and tertiary mirrors, a more optimized system configuration is realized in a coaxial four-reflection mode, the whole structure is compact, the total length is less than 1/10 of an effective focal length, the total view field can reach 3 degrees, and the imaging quality is close to the diffraction limit. The specification gives an optical system with an entrance pupil diameter of 1250mm and a focal length of 7700mm, assuming that the obscuration ratio of the system is 1/3, the system equivalent F # -6.7. The system can be understood as a Gregorian system, and is characterized in that the compensating mirror is a reflector, and the integral imaging field of view is still not large after the reflector is used as the compensating mirror because the imaging field of view of the Gregorian system is small. The RC system is similar to the Gregorian system, except that there is no primary image plane and the imaging field of view is larger.
Therefore, the coaxial four-reflection optical system based on the RC system is provided according to the RC system, and has the characteristics of large imaging field of view, small system F #, compact system structure, wide working spectrum, high imaging quality and the like.
Disclosure of Invention
The invention aims to provide a compact large-visual-field small-F # catadioptric optical system to solve the problem that the existing remote sensing optical system cannot simultaneously meet the requirements of large imaging visual field, wide working waveband and compact structure.
The optical system has the characteristics of large imaging view field, small system F # and the like, and also has the characteristics of compact structure, wide working spectrum, high imaging quality, simplicity in assembly and adjustment and the like.
The technical scheme of the invention is to provide a compact large-view-field small-F # catadioptric optical system, which is characterized in that: the device comprises a primary mirror, a secondary mirror, a third mirror, a fourth mirror and a compensation lens in sequence along the light propagation direction; the diaphragm is arranged on the secondary mirror;
inner holes are formed in the axial centers of the primary mirror, the secondary mirror and the third mirror, the third mirror is embedded into the inner hole of the primary mirror, and the peripheral surface of the third mirror is tightly attached to the wall of the inner hole of the primary mirror; the four mirrors are embedded into the inner holes of the secondary mirrors, and the peripheral surfaces of the four mirrors are tightly attached to the hole walls of the inner holes of the secondary mirrors; the compensation lens is positioned in the inner hole of the three mirrors, and a gap is formed between the compensation lens and the wall of the inner hole of the three mirrors; the light rays are reflected by the primary mirror, the secondary mirror, the third mirror and the fourth mirror in sequence in the propagation direction and then penetrate through the compensation lens to reach a focal plane for imaging;
the primary mirror, the secondary mirror, the third mirror and the fourth mirror are even aspheric mirrors with the highest degree of times of four, and the surface of the compensation lens is a spherical surface;
the central distances between the primary mirror and the secondary mirror, between the secondary mirror and the third mirror, and between the third mirror and the fourth mirror are equal.
Furthermore, the curvature radius of the primary mirror is-76.80 mm, the center distance between the primary mirror and the secondary mirror is 38.70mm, the conic coefficient of the primary mirror is-1.00, and the quadratic coefficient of the primary mirror is 3.8340e-3The coefficient of the fourth order term of the secondary mirror is 1.9887e-8。
Further, the curvature radius of the secondary mirror is-35.05 mm, the center distance between the secondary mirror and the third mirror is 38.70mm, the conconic coefficient of the secondary mirror is-1.16, the quadratic coefficient of the secondary mirror is 0.0106, and the quartic coefficient of the secondary mirror is-2.3981 e-7。
Furthermore, the curvature radius of the three mirrors is-17.52 mm, the distance between the three mirrors and the four mirrors is 38.70mm, the conic coefficient of the three mirrors is-1.02, the quadratic coefficient of the three mirrors is 0.0262, and the quartic coefficient of the three mirrors is-4.9931 e-7。
Further, the curvature radius of the four mirrors is-13.68 mm, the distance between the four mirrors and the compensation lens is 40.58mm, the conic coefficient of the four mirrors is-0.97, the quadratic coefficient of the four mirrors is 0.03468, and the quadratic coefficient of the four mirrors is 7.9750e-7。
Furthermore, the material of the compensating lens is fused quartz, the curvature radius of the front surface is 33.26mm, the curvature radius of the rear surface is 29.60mm, and the center thickness of the lens is 2.00 mm.
The invention has the beneficial effects that:
1. the invention adopts four even-order aspheric reflectors to fold the light path, so that the total length of the system is greatly reduced, and meanwhile, the primary mirror and the tertiary mirror, and the secondary mirror and the four mirrors are integrally processed, so that the total lens number of the system is reduced, and the difficulty in system installation and adjustment is reduced;
2. the central intervals between the primary mirror and the secondary mirror, between the secondary mirror and the third mirror, and between the third mirror and the fourth mirror are equal, so that the coincidence of the optical axis positions of the primary mirror and the third mirror, and between the secondary mirror and the fourth mirror is ensured, the rise difference generated during the integral processing of the primary mirror and the third mirror, and between the secondary mirror and the fourth mirror is favorably reduced, and the difficulty of optical processing and optical detection during the integral processing of the primary mirror and the third mirror, and between the secondary mirror and the fourth mirror is reduced;
3. compared with the coaxial four-reflection optical system mentioned in the background, the full field of view of the optical system reaches 5 DEG under the characteristics of compact system structure, high imaging quality and wide working spectrum band, the effective F # of the system is reduced to 1.70, and the transfer function at 100lp/mm is higher than 0.4.
Drawings
FIG. 1 is a schematic diagram of an optical system according to the present invention;
FIG. 2 is a schematic diagram of the optical path structure of the optical system of the present invention;
FIG. 3 is an MTF curve for an optical system of the present invention;
FIG. 4 is a speckle pattern of the optical system of the present invention;
FIG. 5 is a graph of field curvature distortion for an optical system of the present invention;
the reference numbers in the figures are: 1-a primary mirror; 2-secondary mirror, 3-tertiary mirror, 4-quaternary mirror, 5-compensation lens, 6-focal plane.
Detailed Description
The invention is further described with reference to the following figures and specific embodiments.
As shown in fig. 1, which is a schematic structural diagram of the optical system of the present embodiment, a combined mirror of a primary mirror 1 and a tertiary mirror 3, a combined mirror of a secondary mirror 2 and a quaternary mirror 4, and a compensation lens 5 are disposed on an optical path.
Inner holes are formed in the axial centers of the primary mirrors 1, the three mirrors 3 are embedded into the inner holes of the primary mirrors, and the peripheral surfaces of the three mirrors are tightly attached to the wall of the inner hole of the primary mirror; inner holes are formed in the axial centers of the secondary mirrors 2, the four mirrors 4 are embedded into the inner holes of the secondary mirrors 2, and the peripheral surfaces of the four mirrors 4 are tightly attached to the wall of the inner hole of the secondary mirror 2; the axial center of the three mirrors 3 is also provided with an inner hole, and the compensating lens is positioned in the inner hole of the three mirrors and has a clearance with the wall of the inner hole of the three mirrors. The system diaphragm is located on the secondary mirror 2, and no intermediate image plane exists in the system. The light rays sequentially pass through the primary mirror 1, the secondary mirror 2, the three-mirror 3, the four-mirror 4 and the compensation lens 5 in the propagation direction and then reach the focal plane 6.
In the compact large-field-of-view small-F # catadioptric optical system, a main mirror 1,The four reflectors of the secondary mirror 2, the three mirror 3 and the four mirror 4 are even aspheric mirrors with the highest degree of times of four, and the surfaces of the compensation lens 5 are spherical surfaces; the curvature radius of the primary mirror 1 is-76.80 mm, the distance between the primary mirror 1 and the secondary mirror 2 is 38.70mm, the conic coefficient of the primary mirror 1 is-1.00, and the quadratic coefficient of the primary mirror 1 is 3.8340e-3The coefficient of the fourth order term of the secondary mirror 2 is 1.9887e-8(ii) a The curvature radius of the secondary mirror 2 is-35.05 mm, the distance between the secondary mirror 2 and the third mirror 3 is 38.70mm, the concic coefficient of the secondary mirror 2 is-1.16, the quadratic coefficient of the secondary mirror 2 is 0.0106, and the quartic coefficient of the secondary mirror 2 is-2.3981 e-7(ii) a The radius of curvature of the three mirror 3 is-17.52 mm, the distance between the three mirror 3 and the four mirror 4 is 38.70mm, the conic coefficient of the three mirror 3 is-1.02, the quadratic coefficient of the three mirror 3 is 0.0262, and the quartic coefficient of the three mirror 3 is-4.9931 e-7(ii) a The curvature radius of the four-mirror 4 is-13.68 mm, the distance between the four-mirror 4 and the compensating lens 5 is 40.58mm, the conconic coefficient of the four-mirror 4 is-0.97, the quadratic coefficient of the four-mirror 4 is 0.03468, and the quadratic coefficient of the four-mirror 4 is 7.9750e-7(ii) a The material of the compensation lens is fused quartz, the surface where the light beam firstly reaches is defined as the front surface of the compensation lens, the curvature radius of the front surface of the compensation lens is 33.26mm, the curvature radius of the rear surface of the compensation lens is 29.60mm, and the central thickness of the compensation lens is 2.00 mm.
The system focal length of the optical system provided by the embodiment is 192mm, the imaging field of view is 5 degrees, the working waveband is 400-900nm, the effective F # of the system is 1.70 (minus central obscuration), and the whole field of view has no vignetting. As shown in FIG. 3 and FIG. 5, the MTF is close to the diffraction limit in the whole field of view in the 400-900nm band, and the relative distortion is less than 0.2%.
Claims (6)
1. A compact type large-visual-field small-F # catadioptric optical system is characterized in that: the optical system sequentially comprises a main mirror (1), a secondary mirror (2), a third mirror (3), a fourth mirror (4) and a compensation lens (5) along the light propagation direction; the diaphragm is arranged on the secondary mirror;
inner holes are formed in the axial centers of the primary mirror (1), the secondary mirror (2) and the third mirror (3), the third mirror (3) is embedded into the inner hole of the primary mirror (1), and the peripheral surface of the third mirror (3) is tightly attached to the wall of the inner hole of the primary mirror (1); the four mirror (4) is embedded into the inner hole of the secondary mirror (2), and the peripheral surface of the four mirror (4) is tightly attached to the wall of the inner hole of the secondary mirror (2); the compensation lens (5) is positioned in an inner hole of the three mirrors (3), and a gap is formed between the compensation lens and the wall of the inner hole of the three mirrors (3); the light rays sequentially pass through the primary mirror (1), the secondary mirror (2), the third mirror (3) and the fourth mirror (4) in the propagation direction, are reflected and then penetrate through the compensation lens (5) to reach a focal plane for imaging;
the primary mirror (1), the secondary mirror (2), the third mirror (3) and the fourth mirror (4) are even aspheric mirrors with the highest degree of times of four, and the surface of the compensation lens (5) is a spherical surface;
the central distances between the primary mirror (1) and the secondary mirror (2), between the secondary mirror (2) and the third mirror (3), and between the third mirror (3) and the fourth mirror (4) are equal.
2. The compact, large field of view, small F # catadioptric optical system of claim 1, wherein: the curvature radius of the primary mirror (1) is-76.80 mm, the center distance between the primary mirror (1) and the secondary mirror (2) is 38.70mm, the conconic coefficient of the primary mirror (1) is-1.00, and the quadratic coefficient of the primary mirror (1) is 3.8340e-3The coefficient of the fourth order term of the secondary mirror (2) is 1.9887e-8。
3. A compact large field-of-view small F # catadioptric optical system as defined by claim 2 wherein: the curvature radius of the secondary mirror (2) is-35.05 mm, the center distance between the secondary mirror (2) and the third mirror (3) is 38.70mm, the conconic coefficient of the secondary mirror (2) is-1.16, the quadratic coefficient of the secondary mirror (2) is 0.0106, and the quartic coefficient of the secondary mirror (2) is-2.3981 e-7。
4. A compact large field-of-view small F # catadioptric optical system as defined by claim 3, wherein: the curvature radius of the three mirror (3) is-17.52 mm, the distance between the three mirror (3) and the four mirror (4) is 38.70mm, the conconic coefficient of the three mirror (3) is-1.02, the quadratic coefficient of the three mirror (3) is 0.0262, and the quartic coefficient of the three mirror (3) is-4.9931 e-7。
5. A compact, large field of view, small F # catadioptric light as defined in claim 4An optical system, characterized by: the curvature radius of the four-mirror (4) is-13.68 mm, the distance between the four-mirror (4) and the compensation lens (5) is 40.58mm, the conconic coefficient of the four-mirror (4) is-0.97, the quadratic coefficient of the four-mirror (4) is 0.03468, and the quartic coefficient of the four-mirror (4) is 7.9750e-7。
6. The compact, large-field-of-view, small-F # catadioptric optical system of claim 5, wherein: the material of the compensating lens (5) is fused quartz, the curvature radius of the front surface is 33.26mm, the curvature radius of the rear surface is 29.60mm, and the center thickness is 2.00 mm.
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CN202010475040.7A CN111580258B (en) | 2020-05-29 | Compact type large-view-field small-F# refraction and reflection optical system |
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Publication number | Priority date | Publication date | Assignee | Title |
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CN113031238A (en) * | 2021-04-14 | 2021-06-25 | 中国科学院长春光学精密机械与物理研究所 | Multi-mirror integrated large-view-field long-focus off-axis four-mirror optical system |
CN116755232A (en) * | 2023-08-14 | 2023-09-15 | 苏州简测科技有限公司 | Catadioptric optical lens |
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CN107966804A (en) * | 2017-12-30 | 2018-04-27 | 苏州大学 | Four speculum telephotolens of compact long-focus |
CN207924243U (en) * | 2017-12-30 | 2018-09-28 | 苏州大学 | Four speculum telephotolens of compact long-focus |
CN109459844A (en) * | 2018-09-07 | 2019-03-12 | 北京空间机电研究所 | A kind of big visual field inter-embedding type optical system of total reflection of compact |
CN212364708U (en) * | 2020-05-29 | 2021-01-15 | 中国科学院西安光学精密机械研究所 | Compact type large-view-field small-F # catadioptric optical system |
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
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US20150346022A1 (en) * | 2014-06-03 | 2015-12-03 | Tsinghua University | Off-axial three-mirror optical system with freeform surfaces |
CN107966804A (en) * | 2017-12-30 | 2018-04-27 | 苏州大学 | Four speculum telephotolens of compact long-focus |
CN207924243U (en) * | 2017-12-30 | 2018-09-28 | 苏州大学 | Four speculum telephotolens of compact long-focus |
CN109459844A (en) * | 2018-09-07 | 2019-03-12 | 北京空间机电研究所 | A kind of big visual field inter-embedding type optical system of total reflection of compact |
CN212364708U (en) * | 2020-05-29 | 2021-01-15 | 中国科学院西安光学精密机械研究所 | Compact type large-view-field small-F # catadioptric optical system |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
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CN113031238A (en) * | 2021-04-14 | 2021-06-25 | 中国科学院长春光学精密机械与物理研究所 | Multi-mirror integrated large-view-field long-focus off-axis four-mirror optical system |
CN116755232A (en) * | 2023-08-14 | 2023-09-15 | 苏州简测科技有限公司 | Catadioptric optical lens |
CN116755232B (en) * | 2023-08-14 | 2023-10-20 | 苏州简测科技有限公司 | Catadioptric optical lens |
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