A catadioptric optical imaging system for an infrared star sensor

Abstract

The present invention provides a catadioptric optical imaging system for an infrared star sensor, which includes a reflecting mirror group and a correcting transmissive lens group. The reflecting mirror group includes a first reflecting mirror L1 and a second reflecting mirror L2 arranged coaxially in sequence along the light propagation direction. A light passing opening is provided at the center of the second reflecting mirror L2. The correcting transmissive lens group includes a first lens L3, a second lens L4, a third lens L5, a fourth lens L6, a fifth lens L7 and a sixth lens L8 arranged coaxially in sequence along the light propagation direction. The first lens L3 and the second lens L4 are arranged between the first reflecting mirror L1 and the second reflecting mirror L2. The third lens L5, the fourth lens L6, the fifth lens L7 and the sixth lens L8 are arranged on the side of the second reflecting mirror L2 away from the first reflecting mirror L1. In this way, the distortion value of the star sensor optical system can be effectively reduced, and thus the measurement accuracy and detection ability of the star sensor are improved.

Description

[0001] The present invention relates to a catadioptric optical imaging system for an infrared star sensor. This application claims priority. The application number of the prior application is: 202410857774.X, the title: A catadioptric optical imaging system for an infrared star sensor, and the priority date: June 28, 2024. Technical Field

[0002] The present invention relates to the technical field of optical systems, and particularly to a catadioptric optical imaging system for an infrared star sensor. Background Art

[0003] A star sensor is a high-precision optical attitude sensor with stars as the reference source and is currently the measurement instrument with the highest attitude measurement accuracy. Generally speaking, traditional visible light star sensors are greatly affected by background stray light and can only be used for out-of-atmosphere space or star measurement at night, and most of the optical systems are transmissive. With the rapid development of navigation technology, the application environment requirements for star sensors are also getting higher and higher.

[0004] Among them, the optical system is an important part in the development process of star sensors. However, the imaging distortion of the optical systems of existing star sensors is relatively large and the authenticity is poor, resulting in low detection accuracy of the optical systems.

[0005] Therefore, the present invention is committed to providing a catadioptric optical imaging system for an infrared star sensor to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a catadioptric optical imaging system for an infrared star sensor, which can effectively reduce the distortion value of the catadioptric optical imaging system by setting a reflecting mirror group and a correcting transmission lens group, ensure the imaging effect of the catadioptric optical imaging system of the star sensor, and further ensure the detection accuracy of the star sensor.

[0007] The technical solution provided by the present invention is as follows:

[0008] A catadioptric optical imaging system for an infrared star sensor includes a reflecting mirror group and a correcting transmission lens group. The reflecting mirror group includes a first reflecting mirror L1 and a second reflecting mirror L2 arranged coaxially in sequence along the light propagation direction. A light passing aperture is provided at the center of the second reflecting mirror L2;

[0009] The correction transmission lens group includes a first lens L3, a second lens L4, a third lens L5, a fourth lens L6, a fifth lens L7, and a sixth lens L8 that are coaxially arranged in sequence along the light propagation direction. The first lens L3 and the second lens L4 are arranged between the first mirror L1 and the second mirror L2. The third lens L5, the fourth lens L6, the fifth lens L7, and the sixth lens L8 are arranged on the side of the second mirror L2 away from the first mirror L1.

[0010] In some embodiments, the first lens L3, the second lens L4, the third lens L5, the fourth lens L6, the fifth lens L7, and the sixth lens L8 satisfy the following conditions:

[0011] 3.2 mm < d1 < 3.6 mm, 2.8 mm < d2 < 3.1 mm, 2.1 mm < d3 < 2.4 mm, 2.1 mm < d4 < 2.4 mm, 1.3 mm < d5 < 1.6 mm, 4.5 mm < d6 < 4.7 mm;

[0012] Wherein, d1 is the thickness of the first lens L3, d2 is the thickness of the second lens L4, d3 is the thickness of the third lens L5, d4 is the thickness of the fourth lens L6, d5 is the thickness of the fifth lens L7, and d6 is the thickness of the sixth lens L8.

[0013] In some embodiments, the material of the first lens L3 is N-PK52A, and the first lens L3 is a negative meniscus lens.

[0014] In some embodiments, the materials of the second lens L4 and the fourth lens L6 are both ZNS, the second lens L4 is a positive meniscus lens, and the fourth lens L6 is a biconcave lens.

[0015] In some embodiments, the materials of the third lens L5 and the sixth lens L8 are both ZnSe, the third lens L5 is a negative meniscus lens, and the sixth lens L8 is a plano-convex lens.

[0016] In some embodiments, the material of the fifth lens L7 is JGS1, and the fifth lens L7 is a biconcave lens;

[0017] The first mirror L1 is made of optical glass N-FK5 material, and the second mirror L2 is made of silicon carbide material.

[0018] In some embodiments, the distance between the second mirror L2 and the first lens L3 is D2, where 95.8 mm < D2 < 96.1 mm; the distance between the first lens L3 and the second lens L4 is D3, where 3.9 mm < D3 < 4.2 mm; the distance between the second lens L4 and the third lens L5 is D4, where 16.1 mm < D4 < 16.4 mm; the distance between the third lens L5 and the fourth lens L6 is D5, where 3.9 mm < D5 < 4.2 mm; the distance between the fourth lens L6 and the fifth lens L7 is D6, where 1.5 mm < D6 < 1.75 mm; and the distance between the fifth lens L7 and the sixth lens L8 is D7, where 36.5 mm < D7 < 36.8 mm.

[0019] and / or

[0020] The distance between the first mirror L1 and the second mirror L2 is D1, where 112.5 mm < D1 ≤ 113 mm.

[0021] and / or

[0022] The aperture of the second mirror L2 is 105 mm.

[0023] In some embodiments, the first mirror L1 protrudes towards the second mirror L2, and the side of the second mirror L2 close to the first mirror L1 is concave.

[0024] In some embodiments, the radius of curvature of the first lens L3, the second lens L4, the third lens L5, the fourth lens L6, the fifth lens L7, and the sixth lens L8 satisfies the following conditions:

[0025] -15 mm < R S1 < -10 mm, -15 mm < R S2 < -10 mm;

[0026] 25 mm < R S3 < 30 mm, 550 mm < R S4 < 555 mm;

[0027] -15 mm < R S5 < -10 mm, -25 mm < R S6 < -20 mm;

[0028] 10 mm < R S7 < 15 mm, -50 mm < R S8 < 45 mm;

[0029] -15 mm < R S9 < -10 mm, 5 mm < RS10 < 10 mm;

[0030] 55 mm < R S11 < 60 mm, R S12 = ∞;

[0031] Wherein, R S1 and R S2 are respectively the radii of curvature of the front and rear surfaces of the first lens L3, R S3 and R S4 are respectively the radii of curvature of the front and rear surfaces of the second lens L4, R S5 and R S6 are respectively the radii of curvature of the front and rear surfaces of the third lens L5, R S7 and R S8 are respectively the radii of curvature of the front and rear surfaces of the fourth lens L6, R S9 and R S10 are respectively the radii of curvature of the front and rear surfaces of the fifth lens L7, R S11 and R S12 are respectively the radii of curvature of the front and rear surfaces of the sixth lens L8.

[0032] In some embodiments, a filter L9 is further provided on the side of the sixth lens L8 away from the fifth lens L7, the distance between the filter L9 and the sixth lens L8 is 15.92 mm, and the thickness of the filter L9 is 1.1 mm.

[0033] The catadioptric optical imaging system for an infrared star sensor provided by the present invention has the following beneficial effects:

[0034] 1. The catadioptric optical imaging system for an infrared star sensor provided by the present invention, by arranging a first mirror and a second mirror coaxially in sequence along the light propagation direction, and arranging the first lens L3 and the second lens L4 between the first mirror L1 and the second mirror L2, and arranging the third lens L5, the fourth lens L6, the fifth lens L7 and the sixth lens L8 on the side of the second mirror L2 away from the first mirror L1, adopting a catadioptric system, can significantly reduce the relative distortion and field of view within the full field of view of the working band, and has a smaller relative distortion and field of view compared with the optical system of a traditional star sensor, thereby improving the measurement accuracy of the star sensor.

[0035] 2. The catadioptric optical imaging system for an infrared star sensor provided by the present invention has a distortion value less than 0.005%, reduces the overall optical length, has a more compact structure, is conducive to applications on multiple platforms, can be applied to multiple fields such as infrared monitoring and situation awareness, and has a wider range of applicability. In addition, the catadioptric optical system has a large aperture and a small field of view. Increasing the aperture can increase the target energy entering the catadioptric optical system and improve the ability to extract optical signals under strong backgrounds. Reducing the field of view can reduce the adverse effects of the atmospheric background on star observation, thereby meeting the requirements of the optical system for all-weather star detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above characteristics, technical features, advantages and their implementation manners of the present solution will be further described below in a clear and understandable manner in combination with the drawings to illustrate the preferred embodiments.

[0037] Figure 1 is a schematic structural diagram of a catadioptric optical imaging system for an infrared star sensor provided by the present invention;

[0038] Figure 2 is the spot diagram of each field of view of a catadioptric optical imaging system for an infrared star sensor provided by the present invention;

[0039] Figure 3 is the distortion diagram of the optical system of a catadioptric optical imaging system for an infrared star sensor provided by the present invention;

[0040] Figure 4 is the field curvature diagram of the optical system of a catadioptric optical imaging system for an infrared star sensor provided by the present invention;

[0041] Figure 5 is the MTF resolution curve diagram of a catadioptric optical imaging system for an infrared star sensor provided by the present invention;

[0042] Figure 6 is the relative illumination diagram of a catadioptric optical imaging system for an infrared star sensor provided by the present invention;

[0043] Figure 7 is the optical path diagram of a catadioptric optical imaging system for an infrared star sensor provided by the present invention.

[0044] Description of the reference numerals in the drawings:

[0045] The first reflector L1, the second reflector L2, the first lens L3, the second lens L4, the third lens L5, the fourth lens L6, the fifth lens L7, the sixth lens L8, and the filter L9. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will describe the specific embodiments of the present invention with reference to the accompanying drawings. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings, and other embodiments can also be obtained.

[0047] To make the drawings concise, only the parts related to the present invention are schematically shown in each drawing, and they do not represent the actual structure of the product. In addition, to make the drawings concise and easy to understand, in some drawings, for components with the same structure or function, only one of them is schematically shown, or only one of them is labeled. In this article, "one" not only means "only this one", but also means "more than one" situation.

[0048] In this article, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0049] In addition, in the description of this application, the terms "first", "second", etc. are only used for distinguishing descriptions, and cannot be understood as indicating or implying relative importance.

[0050] In one embodiment, a catadioptric optical imaging system for an infrared star sensor is described. By setting a mirror group and a correction transmissive lens group, the distortion value and the field of view of the catadioptric optical imaging system are significantly reduced, the detection accuracy of the star sensor is improved, and thus the detection effect of the star sensor is improved.

[0051] Specifically, referring to the accompanying drawings of the specification Figure 1 , Figure 7 , a catadioptric optical imaging system for an infrared star sensor includes a mirror group and a correction transmissive lens group. The mirror group includes a first mirror L1 and a second mirror L2. The first mirror L1 and the second mirror L2 are coaxially arranged in sequence along the direction of light propagation, and a light passing aperture is opened at the center of the second mirror L2, and the light passing aperture of the second mirror L2 is coaxial with the mirror group and the correction transmissive lens group. In addition, the distance between the first mirror L1 and the second mirror L2 is 113 mm.

[0052] Accordingly, the correction transmission lens group includes a first lens L3, a second lens L4, a third lens L5, a fourth lens L6, a fifth lens L7, and a sixth lens L8. The first lens L3, the second lens L4, the third lens L5, the fourth lens L6, the fifth lens L7, and the sixth lens L8 are arranged in sequence along the optical axis in the direction of light propagation. The first lens L3 and the second lens L4 are arranged between the first reflector L1 and the second reflector L2, and the second lens L4 is located on the side of the first lens L3 closer to the second reflector L2. The third lens L5, the fourth lens L6, the fifth lens L7, and the sixth lens L8 are arranged on the side of the second reflector L2 away from the first reflector L1.

[0053] It can be understood that, referring to the accompanying drawings of the specification Figure 6 , through the settings of the reflector group and the correction transmission lens group, when using this catadioptric optical imaging system, when the object imaging light enters the catadioptric optical imaging system, it first irradiates on the second reflector L2. After reflection on the second reflector L2, the imaging light irradiates on the first reflector L1, and then is reflected on the first reflector L1 and enters the correction transmission lens group, passing through the first lens L3, the second lens L4, the third lens L5, the fourth lens L6, the fifth lens L7, and the sixth lens L8 in sequence.

[0054] In this embodiment, through the settings of the reflector group and the correction transmission lens group, the distortion value of this catadioptric optical imaging system can be significantly reduced. Compared with some optical systems for star sensors in the prior art, the distortion value is significantly reduced, and the detection accuracy of the star sensor is significantly improved.

[0055] In addition, the distance between the second reflector L2 and the first lens L3 is D2, 95.8 mm < D2 < 96.1 mm; the distance between the first lens L3 and the second lens L4 is D3, 3.9 mm < D3 < 4.2 mm; the distance between the second lens L4 and the third lens L5 is D4, 16.1 mm < D4 < 16.4 mm; the distance between the third lens L5 and the fourth lens L6 is D5, 3.9 mm < D5 < 4.2 mm; the distance between the fourth lens L6 and the fifth lens L7 is D6, 1.5 mm < D6 < 1.75 mm; the distance between the fifth lens L7 and the sixth lens L8 is D7, 36.5 mm < D7 < 36.8 mm.

[0056] Accordingly, the distance between the first reflector L1 and the second reflector L2 is D1, where 112.5 mm < D1 ≤ 113 mm. Additionally, compared with traditional transmissive optical systems, the aperture of the second reflector L2 of this catadioptric optical system is 105 mm, which is relatively large. It can further meet the star detection requirements under strong background conditions during the day, enhance the target energy entering the optical system, thereby collecting more light, resulting in clearer and brighter imaging, and improving the ability of the catadioptric optical system to extract starlight signals under a strong sky background.

[0057] Furthermore, the distance between the first reflector L1 and the second reflector L2 is 113 mm. Correspondingly, the distance between the second reflector L2 and the first lens is 96 mm, the distance between the first lens L3 and the second lens L4 is 4 mm, the distance between the second lens L4 and the third lens L5 is 16.3 mm, the distance between the third lens L5 and the fourth lens L6 is 4 mm, the distance between the fourth lens L6 and the fifth lens L7 is 1.6 mm, and the distance between the fifth lens L7 and the sixth lens L8 is 36.56 mm.

[0058] In one embodiment, based on the previous embodiment, this embodiment further describes the correction transmissive lens group. Among them, along the light propagation direction, the first lens L3 is successively provided with a first surface S1 and a second surface S2, the second lens L4 is successively provided with a third surface S3 and a fourth surface S4, the third lens L5 is successively provided with a fifth surface S5 and a sixth surface S6, the fourth lens L6 is successively provided with a seventh surface S7 and an eighth surface S8, the fifth lens L7 is successively provided with a ninth surface S9 and a tenth surface S10, and the sixth lens L8 is successively provided with an eleventh surface S11 and a twelfth surface S12. Correspondingly, the radius of curvature of the first lens L3, the second lens L4, the third lens L5, the fourth lens L6, the fifth lens L7, and the sixth lens L8 satisfies the following conditions:

[0059] -15 mm < R S1 < -10 mm, -15 mm < R S2 < -10 mm;

[0060] 25 mm < R S3 < 30 mm, 550 mm < R S4 < 555 mm;

[0061] -15 mm < R S5 < -10 mm, -25 mm < R S6 < -20 mm;

[0062] 10 mm < R S7 < 15 mm, -50 mm < R S8 < 45 mm;

[0063] -15 mm < R S9 < -10 mm, 5 mm < R S10 < 10 mm;

[0064] 55 mm < R S11 < 60 mm, R S12 = ∞;

[0065] R S1 and R S2 respectively represent the radii of curvature of the front and rear surfaces of the first lens L3, R S3 and R S4 respectively represent the radii of curvature of the front and rear surfaces of the second lens L4, R S5 and R S6 respectively represent the radii of curvature of the front and rear surfaces of the third lens L5, R S7 and R S8 respectively represent the radii of curvature of the front and rear surfaces of the fourth lens L6, R S9 and R S10 respectively represent the radii of curvature of the front and rear surfaces of the fifth lens L7, R S11 and R S12 respectively represent the radii of curvature of the front and rear surfaces of the sixth lens L8.

[0066] Furthermore, on the basis of the previous embodiment, the thicknesses of the first lens L3, the second lens L4, the third lens L5, the fourth lens L6, the fifth lens L7 and the sixth lens L8 satisfy the following conditions:

[0067] The thickness d1 of the first lens L3 is 3.2 mm < d1 < 3.6 mm, the thickness of the second lens L4 is 2.8 mm < d2 < 3.1 mm, the thickness of the third lens L5 is 2.1 mm < d3 < 2.4 mm, the thickness of the fourth lens L6 is 2.1 mm < d4 < 2.4 mm, the thickness of the fifth lens L7 is 1.3 mm < d5 < 1.6 mm, and the thickness of the sixth lens L8 is 4.5 mm < d5 < 4.7 mm.

[0068] The thickness d1 of the first lens L3 = 3.5 mm, the thickness d2 of the second lens L4 = 2.9 mm, the thickness d3 of the third lens L5 = 2.3 mm, the thickness d4 of the fourth lens L6 = 2.3 mm, the thickness d5 of the fifth lens L7 = 1.5 mm, and the thickness d6 of the sixth lens L8 = 4.6 mm.

[0069] In one embodiment, refer to the accompanying drawings of the specification Figure 1 , Figure 6, on the side of the sixth lens L8 away from the fifth lens L7, a filter L9 with a thickness of 1.1 mm is further provided, and the distance between the filter L9 and the sixth lens L8 is 15.92 mm. The material of the filter L9 is SAPPHIRE.

[0070] In addition, a detector is provided on the side of the filter L9 away from the sixth lens L8, and the distance between the filter L9 and the detector is 5.5 mm. The light after the action of the mirror group and the correction transmission lens group enters the detector after the action of the filter L9.

[0071] In one embodiment, this embodiment further describes the mirror group and the correction transmission lens group. Among them, the first mirror L1 protrudes towards the direction close to the second mirror L2, and the side of the second mirror L2 close to the first mirror L1 is concave.

[0072] In addition, the material of the first lens L3 is N-PK52A material, and the first lens L3 is a negative meniscus lens. The second lens L4 and the fourth lens L6 are both made of ZNS material, and the second lens L4 is a positive meniscus lens, and the fourth lens L6 is a biconcave lens. The third lens L5 and the sixth lens L8 are both made of ZnSe material, the third lens L5 is a negative meniscus lens, and the sixth lens L8 is a plano-convex lens. The fifth lens L7 is made of JGS1 material, and the fifth lens L7 is a biconcave lens. The first mirror L1 is made of optical glass N-FK5 material, and the second mirror L2 is made of silicon carbide material. The total optical length of the mirror group and the correction transmission component is not greater than 200 mm.

[0073] It should be noted that the first lens L3 functions to eliminate a large contribution to the system spherical aberration, the second lens L4 functions to eliminate a large contribution to the system spherical aberration, the third lens L5 functions to eliminate a large contribution to the system spherical aberration, the fourth lens L6 functions to eliminate a large contribution to the system coma and astigmatism, the fifth lens L7 functions to eliminate a large contribution to the system coma and astigmatism, and the sixth lens L8 functions to eliminate a large contribution to the system field curvature and distortion.

[0074] In one embodiment, this embodiment further describes the first mirror LI and the second mirror L2. Among them, the surface types of the first mirror L1 and the second mirror L2 are both hyperboloids, and the surface types satisfy the following formula:

[0075]

[0076] Among them, z is the sagittal height of the first mirror L1 or the second mirror L2, c is the paraxial curvature, k is the quadratic coefficient, and r is the radial variable. The coordinate data adopts the following right-handed coordinate system, with the horizontal right direction as the +Z axis, the vertical inward direction as the +X axis, and the upward direction as the +Y axis. The paraxial curvatures of the first mirror L1 and the second mirror L2 are defined as follows: if the center of the sphere is on the left side of the mirror body, the paraxial curvature is negative; if the center of the sphere is on the right side of the mirror body, the paraxial curvature is positive.

[0077] In addition, the optical data of the mirror group and the correction transmission lens group are specifically as follows:

[0078] Table 1 Optical system data:

[0079]

[0080]

[0081] It can be understood that through the first lens L3, the second lens L4, the third lens L5, the fourth lens L6, the fifth lens L7 and the sixth lens L8 provided by the above embodiments, the field of view of the catadioptric optical system can be significantly reduced, thereby reducing the adverse effects of the external environment on the optical system. In this way, through the design of the mirror group and the correction transmission lens group, the catadioptric optical system has the characteristics of a large aperture and a small field of view. The influence of background stray light on the optical system is small, and it can extract weak starlight signals under a strong sky background when measuring stars during the day, meeting the requirements of all-day star detection. In addition, while increasing the aperture and reducing the field of view, the catadioptric optical system also significantly reduces the distortion value, enabling the optical system to not only meet the all-day star observation requirements but also significantly improve the detection accuracy.

[0082] For the distortion degree of a catadioptric optical imaging system for an infrared star sensor provided by the present invention, it represents the deformation between the actual image plane and the ideal image plane. The distortion diagram of the optical system is as Figure 3 shown, and the curve is the distortion value from zero degree to the full field of view. Figure 3 The ordinate of represents the field of view, and the abscissa represents the relative distortion percentage. The optical system of the present invention has the advantage of low distortion. Its central wavelength is 1.5 μm, and the distortion is less than 0.005%. Therefore, the optical system provided by the present invention can significantly reduce the distortion value.

[0083] In addition, Figure 4 is the field curvature diagram. Field curvature refers to the bending of the image field, which means that after a flat object passes through the optical system, the image plane formed by focusing all the flat object points does not coincide with the ideal image plane but presents a curved image plane. Figure 4 The ordinate of is the field of view, and the abscissa represents the field curvature. Its central wavelength is 1.5 μm, and the field curvature < 0.2 mm.

[0084] For the optical system provided by the present invention, it can be applied to observe stars all day long within the atmosphere. Due to the influence of atmospheric scattering during the day, the influence is small in the short-wave band of 0.9 - 1.7 μm. Therefore, this band is selected as the detection band. The spot diagrams of each field of view of the optical system are as follows Figure 2 shown, which is used as a reference for the imaging quality of the system. Figure 2 In it, OBG represents the field of view, IMA represents the spot diagram of the image point of the optical system. The spot radius of each field of view is given in the figure. The root mean square value of the spot radius in the 1.838 field of view (half field of view 0.919) is at most 10.857 μm, and the diameter is 21.714 μm, which is equivalent to the diagonal size of 21.2 μm of the detector pixel, meeting the imaging requirements.

[0085] Characterize the relative illuminance of the optical system provided by the present invention in order to accurately consider the influence of the exit pupil radiation and solid angle. Refer to the attached drawings of the specification Figure 6 It represents the ratio of the illuminance at each field position on the image plane to the illuminance of the central field of view. Figure 6 The ordinate of Figure 6 represents the illuminance value, and the abscissa represents the field of view. It can be seen from

[0086] that the change of illuminance within the entire field of view is not obvious, and the illuminance is uniform. Figure 5 shown. The MTF (Modulation Transfer Function) of different fields of view. In the MTF resolution curve diagram in the figure, the horizontal axis represents the image height, and the vertical axis represents the contrast, and its range is from 0 to 1. It can be known from Figure 5 that the MTF is better than 0.3, meeting the imaging quality requirements.

[0087] It should be noted that the above-mentioned embodiments can be freely combined according to needs. The above is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A catadioptric optical imaging system for an infrared star sensor, characterized in that: It includes a reflector group and a correction transmission mirror group, wherein the reflector group includes a first reflector L1 and a second reflector L2 which are coaxially arranged in sequence along the light propagation direction, and a light opening is opened at the center of the second reflector L2; The correction transmission lens group includes a first lens L3, a second lens L4, a third lens L5, a fourth lens L6, a fifth lens L7 and a sixth lens L8 which are coaxially arranged in sequence along the light propagation direction, the first lens L3 and the second lens L4 are arranged between the first reflector L1 and the second reflector L2, the third lens L5, the fourth lens L6, the fifth lens L7 and the sixth lens L8 are arranged on a side of the second reflector L2 away from the first reflector L1; In the catadioptric optical imaging system, only the first reflector L1, the second reflector L2, the first lens L3, the second lens L4, the third lens L5, the fourth lens L6, the fifth lens L7 and the sixth lens L8 have optical power, the first lens L3 and the third lens L5 are both negative meniscus lenses, the second lens L4 is a positive meniscus lens, the fifth lens L7 is a double concave lens, the sixth lens L8 is a plano-convex lens, the curvature radii of the front and rear surfaces of the fourth lens L6 are set to RS7 and RS8 respectively, and 10mm<RS7<15mm, -50mm<RS8<45mm, the first reflector L1 is convex in the direction close to the second reflector L2, and the side of the second reflector L2 close to the first reflector L1 is concave.

2. A catadioptric optical imaging system for an infrared star sensor according to claim 1, characterized in that: The first lens L3, the second lens L4, the third lens L5, the fourth lens L6, the fifth lens L7 and the sixth lens L8 meet the following conditions: 3.2mm<d1<3.6mm, 2.8mm<d2<3.1mm, 2.1mm<d3<2.4mm, 2.1mm<d4<2.4mm, 1.3mm<d5<1.6mm, 4.5mm<d6<4.7mm; Wherein, d1 is the thickness of the first lens L3, d2 is the thickness of the second lens L4, d3 is the thickness of the third lens L5, d4 is the thickness of the fourth lens L6, d5 is the thickness of the fifth lens L7, and d6 is the thickness of the sixth lens L8.

3. A catadioptric optical imaging system for an infrared star sensor according to claim 2, characterized in that: The material of the first lens L3 is N-PK52A.

4. The catadioptric optical imaging system for an infrared star sensor according to claim 3, characterized in that: The second lens L4 and the fourth lens L6 are both made of ZNS.

5. The catadioptric optical imaging system for an infrared star sensor according to claim 4, characterized in that: The third lens L5 and the sixth lens L8 are both made of ZNSE.

6. The catadioptric optical imaging system for an infrared star sensor according to claim 5, characterized in that: The material of the fifth lens L7 is JGS1; The first reflector L1 is made of optical glass N-FK5, and the second reflector L2 is made of silicon carbide.

7. A catadioptric optical imaging system for an infrared star sensor according to any one of claims 1 to 6, characterized in that: The distance between the second reflector L2 and the first lens L3 is D2, 95.8mm<D2<96.1mm, the distance between the first lens L3 and the second lens L4 is D3, 3.9mm<D3<4.2mm, the distance between the second lens L4 and the third lens L5 is D4, 16.1mm<D4<16.4mm, the distance between the third lens L5 and the fourth lens L6 is D5, 3.9mm<D5<4.2mm, the distance between the fourth lens L6 and the fifth lens L7 is D6, 1.5mm<D6<1.75mm, the distance between the fifth lens L7 and the sixth lens L8 is D7, 36.5mm<D7<36.8mm; and / or The distance between the first reflector L1 and the second reflector L2 is D1, 112.5 mm < D1 ≤ 113 mm; and / or The aperture of the second reflector L2 is 105 mm.

8. The catadioptric optical imaging system for an infrared star sensor according to claim 7, characterized in that: The curvature radii of the first lens L3, the second lens L4, the third lens L5, the fifth lens L7 and the sixth lens L8 satisfy the following conditions: -15mm<RS1<-10mm, -15mm<RS2<-10mm; 25mm<RS3<30mm, 550mm<RS4<555mm; -15mm<RS5<-10mm, -25mm<RS6<-20mm; -15mm<RS9<-10mm, 5mm<RS10<10mm; 55mm<RS11<60mm, RS12=∞; Among them, RS1 and RS2 are the curvature radii of the front and rear surfaces of the first lens L3, RS3 and RS4 are the curvature radii of the front and rear surfaces of the second lens L4, RS5 and RS6 are the curvature radii of the front and rear surfaces of the third lens L5, RS9 and RS10 are the curvature radii of the front and rear surfaces of the fifth lens L7, and RS11 and RS12 are the curvature radii of the front and rear surfaces of the sixth lens L8.

9. The catadioptric optical imaging system for an infrared star sensor according to claim 8, characterized in that: A filter L9 is further disposed on a side of the sixth lens L8 away from the fifth lens L7. The distance between the filter L9 and the sixth lens L8 is 15.92 mm, and the thickness of the filter L9 is 1.1 mm.

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