Large field of view small f# high precision star sensor optical system

Abstract

In order to realize the requirement of a star sensor optical system to a large field of view, long focal length and small F# optical system, the application provides a large field of view, small F# and high precision star sensor optical system, which comprises a diaphragm and a primary mirror, a secondary mirror, a first lens, a second lens and a third lens which are sequentially arranged along an optical path from an object side to an image side; the diaphragm is located on the secondary mirror; the primary mirror is a Mangin mirror; an object side imaging light beam sequentially passes through the primary mirror, the secondary mirror, the first lens, the second lens and the third lens and is finally imaged on a detector. The system takes into account the imaging quality and the miniaturization of the optical system.

Description

Technical Field

[0001] The present invention relates to a large field of view and small F# high-precision star sensor optical system, which is an engineering and high-precision star sensor optical imaging system suitable for long-term application in high and low orbits of the aerospace space environment. Background Art

[0002] The optical sensor optical system uses starry sky imaging and uses the invariance of the spacing and azimuth information of stars as a reference system for inertial attitude navigation and positioning of aircraft. Since it has the advantages of high measurement accuracy and no drift during long-term use, it has obtained great development since its successful development.

[0003] In recent years, with the development and progress of optical technology, higher requirements have also been put forward for the imaging quality, volume, field of view, etc. of star sensor optical systems. Summary of the Invention

[0004] In order to meet the requirements of the star sensor optical system for a large field of view, long focal length, and small F# optical system, the present invention proposes a catadioptric star sensor optical system using an aspheric Mangin mirror, which兼顾 the imaging quality of the optical system and the lightweight and miniaturization of the volume.

[0005] The technical solution of the present invention is as follows:

[0006] A large field of view and small F# high-precision star sensor optical system, which is characterized in that it includes an aperture stop and a primary mirror, a secondary mirror, a first lens, a second lens, and a third lens sequentially arranged along the optical path from the object side to the image side;

[0007] The above aperture stop is located on the secondary mirror;

[0008] The above primary mirror is a Mangin mirror;

[0009] The object-side imaging light beam sequentially passes through the primary mirror, the secondary mirror, the first lens, the second lens, and the third lens and finally forms an image on the detector.

[0010] Further, it is defined that the surface first reached by the light is the front surface of each lens, and the surface later reached by the light is the back surface of each lens;

[0011] The radius of curvature R1 of the front surface of the primary mirror is -f’ < R1 < -0.5f’, and the radius of curvature R2 of the back surface of the primary mirror is -f’ < R2 < -0.5f’;

[0012] The radius of curvature of the front surface of the secondary mirror is -0.5f’ < R3 < 0;

[0013] The radius of curvature R4 of the front surface of the above first lens is 0 < R4 < 0.2f’, and the radius of curvature R5 of the back surface of the first lens is -0.5f’ < R5 < 0;

[0014] The radius of curvature R6 of the front surface of the second lens is 0 < R6 < 0.2f', and the radius of curvature R7 of the rear surface of the second lens is 0 < R7 < 0.5f'.

[0015] The radius of curvature R8 of the front surface of the third lens is 0 < R8 < 0.2f', and the radius of curvature R9 of the rear surface of the third lens is 0 < R9 < 0.5f'.

[0016] Furthermore, the focal length f'1 of the first lens is 0 < f'1 < 0.2f'.

[0017] The focal length f'2 of the second lens is -0.5f' < f'2 < 0.

[0018] The focal length f'3 of the third lens is 0 < f'3 < 0.5f'.

[0019] Among them, f' is the focal length of the optical system.

[0020] Furthermore, the conic coefficient of the reflecting surface of the primary mirror is -0.99, and the central thickness is 15 mm.

[0021] The conic coefficient of the reflecting surface of the secondary mirror is -10.7.

[0022] The refractive index n1 of the first lens is: 1.5 < n1 < 1.7.

[0023] The refractive index n2 of the second lens is: 1.7 < n2 < 1.9.

[0024] The refractive index n3 of the third lens is: 1.4 < n5 < 1.6.

[0025] Furthermore, the back working distance of the large field of view, small F# and high-precision star sensor optical system is greater than 9 mm.

[0026] Furthermore, in order to effectively resist the complex particle irradiation in space, the primary mirror material is made of fused quartz.

[0027] The beneficial effects of the present invention are:

[0028] 1. The primary mirror of the optical system of the present invention adopts the structure of a Mangin mirror, and the aperture stop is placed on the secondary mirror, which simplifies the system structure and ensures the imaging quality at the same time.

[0029] 2. The primary mirror of the optical system of the present invention selects the fused quartz JGS1 primary mirror. The excellent anti-irradiation performance of JGS1 can effectively resist the complex particle irradiation in space and further improve the imaging quality.

[0030] 3. Using the optical system of the present invention can achieve the following indicators:

[0031] (1) The imaging field of view is large, and the imaging quality can be guaranteed within the 4° imaging field of view;

[0032] (2) The system F# is small, and the system F# ≤ 1.7 can be achieved;

[0033] (3) Within the full field of view, the distortion is controlled within 2% within the imaging object distance range and the imaging temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic structural diagram of the optical system of the embodiment;

[0035] Where the reference numerals are: 1, primary mirror; 2, secondary mirror; 3, first lens; 4, second lens; 5, third lens;

[0036] Figure 2 It is the spot diagram of the image plane of the optical system of the embodiment;

[0037] Figure 3 It is the curve graph of the energy of the image plane circumscribing circle of the optical system of the embodiment;

[0038] Figure 4 It is the field curvature and distortion curve of the optical system of the embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the specific embodiments of the present invention in detail with reference to the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present invention shall fall within the scope of protection of the present invention.

[0040] Refer to Figure 1 , which is the large field of view, small F#, and high-precision star sensor optical system of this embodiment. The system is arranged in sequence along the optical axis with the primary mirror 1, secondary mirror 2, first lens 3, second lens 4, and third lens 5; the aperture stop is on the secondary mirror 2, and the primary mirror 1 adopts the structure of a Mankin mirror;

[0041] Among them, the optical characteristics of the primary mirror 1 are:

[0042] The primary mirror 1 is a Mankin mirror, and fused quartz is used as the primary mirror material, -f’ < R1 < -0.5f’, -f’ < R2 < -0.5f’. In this embodiment, R1 = -383.4 mm, R2 = -379.3 mm, the conic coefficient of the reflecting surface is -0.99, and D1 = 15 mm.

[0043] The optical characteristics of the secondary mirror 2 are:

[0044] -0.5f’ < R3 < 0. In this embodiment, R3 = -274.6 mm, the conic coefficient of the reflecting surface is -20.0, and D2 = -100.9 mm.

[0045] The optical characteristics of the first lens 3 are as follows:

[0046] 0 < f’1 < 0.2f’, 1.5 < n1 < 1.7, 0 < R4 < 0.2f’, -0.5f’ < R5 < 0. In this embodiment, R4 = 29.2 mm, R5 = -36.6 mm, D3 = 9.2 mm, D4 = 4.0 mm.

[0047] The optical characteristics of the second lens 4 are as follows:

[0048] -0.5f’ < f’2 < 0, 1.7 < n2 < 1.9, 0 < R6 < 0.2f’, 0 < R7 < 0.5f’. In this embodiment, R6 = 129.3 mm, R7 = 95.3 mm, D5 = 5.0 mm, D6 = 4.0 mm.

[0049] The optical characteristics of the third lens 5 are as follows:

[0050] 0 < f’3 < 0.5f’, 1.4 < n5 < 1.6, 0 < R8 < 0.2f’, 0 < R9 < 0.5f’. In this embodiment, R8 = 45.5 mm, R9 = 43.2 mm, D7 = 9.2 mm, D8 = 10.0 mm.

[0051] Here, f’ is the focal length of the optical system, f’1, f’2, and f’3 are the focal lengths of the first lens 3, the second lens 4, and the third lens 5 respectively, n1, n2, and n3 are the refractive indices of the glasses used for the first lens 3, the second lens 4, and the third lens 5 respectively, R1, R2, …, R9 are the radii of curvature of the 9 optical surfaces from front to back, and D1, D2, …, D8 are the central thicknesses and central intervals of the 9 optical surfaces from front to back.

[0052] As Figures 2 to 4 , it can be seen that the system focal length of the optical system provided in this embodiment is approximately 470 mm, the field angle is greater than 4.5°, the effective entrance pupil diameter is greater than 80 mm, and the system F# ≤ 5.1. There is no vignetting in the full field of view, and there is no cemented surface. In the wavelength range of 470 nm - 900 nm, the diameter of the 80% energy encirclement circle in the full field of view is ≤ 12 um. At the alignment position, the imaging quality is close to the diffraction limit, and the relative distortion is less than 0.1%.

[0053] This invention can also be applied to fields such as space target surveillance and space debris detection, which require optical systems with large field angles and small F#.

Claims

1. A high-precision star sensor optical system with a large field of view and a small F#, characterized in that: It consists of a diaphragm, a primary mirror, a secondary mirror, a first lens, a second lens, and a third lens that are sequentially arranged along the optical path from the object side to the image side; The diaphragm is located on the secondary mirror; The primary mirror is of a Mangin mirror structure; The object-side imaging light beam sequentially passes through the primary mirror, the secondary mirror, the first lens, the second lens, and the third lens and finally forms an image on the detector; Define the surface that the light first reaches as the front surface of each lens, and the surface that the light later reaches as the rear surface of each lens; The first lens has a positive optical angle, the object side is convex, and the image side is convex; The second lens has a negative optical angle, the object side is convex, and the image side is concave; The third lens has a positive optical angle, the object side is convex, and the image side is concave; The radius of curvature R1 of the front surface of the primary mirror is -f' < R1 < -0.5f', and the radius of curvature R2 of the rear surface of the primary mirror is -f' < R2 < -0.5f'; The radius of curvature of the front surface of the secondary mirror is -0.5f' < R3 < 0; The radius of curvature R4 of the front surface of the first lens is 0 < R4 < 0.2f', and the radius of curvature R5 of the rear surface of the first lens is -0.5f' < R5 < 0; The radius of curvature R6 of the front surface of the second lens is 0 < R6 < 0.2f', and the radius of curvature R7 of the rear surface of the second lens is 0 < R7 < 0.5f'; The radius of curvature R8 of the front surface of the third lens is 0 < R8 < 0.2f', and the radius of curvature R9 of the rear surface of the third lens is 0 < R9 < 0.5f'; Where f' is the focal length of the optical system.

2. The large-field small F# high-precision star sensor optical system according to claim 1, wherein: The focal length f'1 of the first lens is 0 < f'1 < 0.2f'; The focal length f'2 of the second lens is -0.5f' < f'2 < 0; The focal length f'3 of the third lens is 0 < f'3 < 0.5f'; Where f' is the focal length of the optical system.

3. The large-field small F# high-precision star sensor optical system according to claim 2, wherein: The conic coefficient of the reflecting surface of the primary mirror is -0.99, and the central thickness is 15 mm; The conic coefficient of the reflecting surface of the secondary mirror is -10.7; The refractive index n1 of the first lens is: 1.5 < n1 < 1.7; The refractive index n2 of the second lens is: 1.7 < n2 < 1.9; The refractive index n3 of the third lens is: 1.4 < n5 < 1.

6.

4. The large field-of-view, small F# high-precision star sensor optical system according to claim 3, characterized in that: The back working distance is greater than 9 mm.

5. The large field-of-view, small F# high-precision star sensor optical system according to any one of claims 1-4, characterized in that: The primary mirror material is made of fused quartz.

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