Visible infrared dual-band refraction and reflection optical system based on free-form surface shared beam shrinking lens

Abstract

The utility model relates to an optical imaging system, in particular to a visible infrared dual-band refraction and reflection optical system based on a free-form surface shared beam shrinking lens. The technical problem that an existing total reflection type earth remote sensing system and a refraction and reflection type earth remote sensing optical system are difficult to meet the overall requirements of compactness, stray light, convenient adjustment and large view field is solved. The system comprises a beam shrinking unit, a dichroic mirror, a visible TDI imaging lens group, a reflecting mirror, an infrared TDI imaging lens group, a visible switching reflecting mirror and a visible area array imaging lens group, wherein the beam shrinking unit and the dichroic mirror are sequentially arranged along a light path; the visible TDI imaging lens group, the reflecting mirror and the infrared TDI imaging lens group are arranged on a reflecting light path of the dichroic mirror; the visible area array imaging lens group is arranged on a reflecting light path of the visible switching reflecting mirror; the beam shrinking unit comprises a primary mirror, a secondary mirror, an axis folding mirror and a third mirror which are sequentially arranged along a light path; the primary mirror and the secondary mirror are coaxially arranged; the included angle between the normal of the folding-axis mirror and the optical axis of the system is greater than 45 degrees; the third mirror is a free-form surface reflecting mirror, and emergent central view field light of the third mirror is perpendicular to primary and secondary mirror axes; and the dichroic mirror is arranged on an emergent light path of the third mirror.

Description

TECHNICAL FIELD

[0001] The utility model relates to an optical imaging system, concretely relates to a visible infrared dual waveband catadioptric optical system based on freeform surface shared beam-reducing mirror. BACKGROUND

[0002] With the development of space optical load technology and remote sensing inversion technology, in order to obtain more abundant detection target information, the demand of wide waveband detection is increasing. The visible light waveband in the space optical imaging device is mainly used for detecting land, sea and specific targets during the day; the middle wave infrared waveband is mainly used for detecting at night, and the optical imaging device covering dual wavebands can realize uninterrupted monitoring of target areas all day round. Since the space and weight of the aircraft carrying the space remote sensing optical system are limited, the compactness of the optical system is strictly required, the freeform surface has super strong aberration balancing capacity, can be effectively applied in compact optical system design, thus attracting many scholars to carry out design and research.

[0003] Compact space-to-ground remote sensing imaging optical systems mainly include two types: full reflection type space-to-ground remote sensing system and catadioptric space-to-ground remote sensing optical system. Among them, the full reflection type space-to-ground remote sensing system is divided into off-axis reflection type and on-axis reflection type, the on-axis reflection type has compact overall structure, and there is not only the obstruction of the secondary mirror to the primary mirror, but also the factors such as the opening hole to further obstruct the incident light of the three mirrors, which affects the energy utilization rate and signal-to-noise ratio of the system. The off-axis reflection type system does not have central obstruction, but the vertical axis size of the system is easy to exceed the envelope of the whole system. Since the focal plane of the space remote sensing optical system usually has optical splicing or mechanical splicing, it is required to adjust the lens to realize focusing, and the precision requirement of adjusting the reflecting mirror is higher, so the realization difficulty is also greater.

[0004] The catadioptric space-to-ground remote sensing optical system usually increases a transmission lens in the Cassegrain system or R-C system to correct aberration and expand the field of view, but since the requirement of stray light of the system is improved and the field of view of the system is continuously increased, the freeform surface can effectively increase the field of view, reduce the number of lenses, and effectively suppress stray light by changing the layout of the optical path, so it is necessary to develop a new type of visible infrared dual waveband compact catadioptric optical system based on freeform surface shared beam-reducing mirror, which can meet the overall requirements of compactness, stray light, convenient adjustment and large field of view by reasonable layout. UTILITY MODEL CONTENTS

[0005] The utility model aims at solving the technical problem that the existing full reflection type space-to-ground remote sensing system and catadioptric space-to-ground remote sensing optical system cannot meet the overall requirements of compactness, stray light, convenient adjustment and large field of view, and provides a visible infrared dual waveband catadioptric optical system based on freeform surface shared beam-reducing mirror.

[0006] In order to achieve the above object, the utility model adopts the following technical scheme:

[0007] The speciality of a visible infrared dual wave band catadioptric optical system based on a free-form surface shared beam-reducing mirror lies in comprising a beam-reducing unit, a dichroic mirror arranged in sequence along an optical path, a visible TDI imaging lens group arranged on the reflected light path of the dichroic mirror, an infrared TDI imaging lens group arranged on the transmitted light path of the dichroic mirror, a visible switching mirror and a visible area array imaging lens group arranged on the reflected light path of the visible switching mirror; the visible switching mirror is used for cutting into or out of the visible TDI imaging lens group; the infrared TDI imaging lens group is provided with a mirror;

[0008] The beam-reducing unit comprises a primary mirror, a secondary mirror, a fold mirror and a three-mirror arranged in sequence along the optical path; the primary mirror and the secondary mirror are coaxially arranged, and the axis is a primary-secondary mirror axis; the fold mirror is located on the side of the primary mirror away from the secondary mirror, and the included angle between the normal line of the fold mirror and the system optical axis is greater than 45 DEG; the three-mirror is a free-form surface mirror, and the outgoing central field of view light is perpendicular to the primary-secondary mirror axis; the dichroic mirror is arranged on the outgoing light path of the three-mirror;

[0009] The dichroic mirror is used for transmitting the outgoing light of the three-mirror to the mirror and the infrared TDI imaging lens group along the optical path, and reflecting the outgoing light of the three-mirror to the visible TDI imaging lens group, or reflecting the light to the visible area array imaging lens group when the visible switching mirror cuts into the visible TDI imaging lens group;

[0010] A visible TDI detection device is arranged on the outgoing light path of the visible TDI imaging lens group, so that the outgoing light of the visible TDI imaging lens group is imaged on the visible TDI detection device;

[0011] A visible light area array detector is arranged on the outgoing light path of the visible area array imaging lens group, so that the outgoing light of the visible area array imaging lens group is imaged on the visible light area array detector;

[0012] An infrared TDI detection device is arranged on the outgoing light path of the infrared TDI imaging lens group, and the outgoing light of the infrared TDI imaging lens group is imaged on the infrared TDI detection device by translating the infrared TDI imaging lens group.

[0013] Further, the primary mirror is a central or eccentric aperture even aspheric mirror, the surface of which is plated with silver film or gold film, the conic coefficient K is less than 0, the material is quartz or K9 or microcrystalline or silicon carbide, and the mirror F number is 0.5-1.5.

[0014] Further, the secondary mirror is an even aspheric mirror, the surface of which is plated with silver film or gold film, the conic coefficient K is less than 0, the material is quartz or K9 or microcrystalline or silicon carbide, and the mirror F number is 0.5-1.5.

[0015] Further, the fold mirror is a plane mirror, the surface of which is coated with silver film or gold film, and the material is quartz or K9 or microcrystalline or silicon carbide.

[0016] Further, the primary mirror is provided with a diaphragm; the conic coefficient K of the three mirrors is less than 0, expressed by XY polynomial, and the material is quartz or K9 or microcrystalline or silicon carbide; the dichroic mirror is a parallel flat plate coated with a dichroic film, and the material of the dichroic mirror is Silicon, Germanium or ZNSE or CLEARTRAN, and the reflectivity and transmissivity are both greater than 90%; the visible switching mirror is a plane mirror, and the material is quartz or K9 or microcrystalline or SiC.

[0017] Further, the visible TDI imaging lens group comprises a visible common lens front group and a visible imaging discrete rear group coaxially arranged in sequence along the optical path.

[0018] The visible common lens front group comprises six lenses coaxially arranged in sequence along the optical path, wherein the first lens is a plano-convex lens, the convex surface of which is a free curved surface with a conic coefficient K less than 0, expressed by XY polynomial, the third lens is a negative lens, and the remaining lenses are all spherical mirrors.

[0019] The visible imaging discrete rear group comprises three lenses coaxially arranged in sequence along the optical path, wherein one surface of the second lens is aspherical with a conic coefficient K greater than 0 and less than 1 without high-order terms; and the remaining lenses are all spherical mirrors.

[0020] The visible switching mirror is used to cut into or cut out between the visible common lens front group and the visible imaging discrete rear group; when the visible switching mirror is cut in, the reflected light of the dichroic mirror is transmitted to the visible switching mirror through the visible common lens front group and then reflected to the visible area array imaging lens group; when the visible switching mirror is cut out, the reflected light of the dichroic mirror is reflected to the visible TDI imaging lens group.

[0021] The visible area array imaging lens group has the same structure as the visible imaging discrete rear group.

[0022] The visible TDI imaging lens group adjusts the image quality and air pressure by adjusting the interval of the third lens of the visible common lens front group.

[0023] Further, the infrared TDI imaging lens group comprises two positive lens groups; the two positive lens groups have a primary image plane; one positive lens group comprises three lenses with positive, negative and positive focal powers arranged in sequence; the other positive lens group comprises three lenses with negative, positive and positive focal powers arranged in sequence; and the materials of the two positive lens groups are Silicon and / or Germanium.

[0024] The infrared TDI imaging lens group adjusts the air pressure by adjusting the position of the positive lens group located in front of the primary image plane.

[0025] Further, the translation amount T of the infrared TDI imaging lens group is calculated according to the following formula:

[0026]

[0027] In the formula, d is the thickness of the dichroic mirror, theta is the angle between the dichroic mirror and the horizontal plane, and n is the refractive index of the dichroic mirror.

[0028] Further, the visible TDI detection device comprises an optical splicing device and N visible TDI detectors; the optical splicing device comprises a plurality of splicing-fixed plane mirrors, the sizes and intervals of the plurality of plane mirrors are the same, and the materials of the plurality of plane mirrors are quartz, K9, microcrystalline or SiC; each visible TDI detector is arranged on a reflection light path or a transmission light path of the plane mirror.

[0029] Alternatively, the visible TDI detection device comprises N visible TDI detectors located on the same detection plane, the N visible TDI detectors are mechanically spliced and arranged in parallel to each other, there are a number of overlapping pixels not less than 10 along the splicing direction, and N is greater than or equal to 2.

[0030] Further, the infrared TDI detection device comprises M infrared TDI detectors located on the same detection plane, the M infrared TDI detectors are mechanically spliced and arranged in parallel to each other, there are a number of overlapping pixels not less than 10 along the splicing direction, and M is greater than or equal to 2; and a cold light stop is arranged on each infrared TDI detector.

[0031] The angle theta between the dichroic mirror and the horizontal plane is 45 degrees.

[0032] Advantages of the present application:

[0033] 1. The visible-infrared dual-band catadioptric optical system based on the free-form surface shared beam-reducing mirror utilizes a primary mirror, a secondary mirror, an axicon mirror and three mirrors to form a beam-reducing unit, and has good image quality; by adjusting the interval between the primary mirror and the secondary mirror and the eccentricity of the secondary mirror, the image quality after assembly and adjustment can be basically maintained unchanged, and the primary mirror and the secondary mirror are coaxially installed, and the combined center field of view has good image quality, which facilitates machining, detection and assembly.

[0034] 2. The visible-infrared dual-band catadioptric optical system based on the free-form surface shared beam-reducing mirror, the angle between the normal line of the axicon mirror and the optical axis of the system is greater than 45 degrees, so as to ensure that the central field of view light emitted after the light path of the off-axis field of view passes through the primary mirror, the secondary mirror, the axicon mirror and the three mirrors is perpendicular to the optical axis of the primary mirror and the secondary mirror, so that the system is compact and insensitive to tolerance.

[0035] 3. The utility model discloses a visible infrared dual waveband catadioptric optical system based on free-form surface shared beam-reducing mirror, the main mirror, the mirror are all even aspheric mirror, and mirror F number is all 0.5-1.5, further guarantee the compactness of system.

[0036] 4. The utility model discloses a visible infrared dual waveband catadioptric optical system based on free-form surface shared beam-reducing mirror, the visible light path sets the lens of adjusting image quality and air pressure as the third lens in visible shared lens front group, and the third lens selects negative lens, and the infrared light path sets the lens group before adjusting air pressure as primary image plane, compared with the optical system of adjusting link setting in mirror, the precision requirement of adjusting link is relatively lower, realizes more easily, and the cost is smaller.

[0037] 5. The utility model discloses a visible infrared dual waveband catadioptric optical system based on free-form surface shared beam-reducing mirror, has visible infrared dual waveband detection function, visible light array, surface array switching function (namely the cutout, cut-in of visible switching mirror) and the function of optical splicing to N visible linear array TDI detector. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is the structure schematic diagram of the utility model discloses a visible infrared dual waveband catadioptric optical system example based on free-form surface shared beam-reducing mirror;

[0039] Figure 2 It is the light path diagram of the utility model discloses a visible infrared dual waveband catadioptric optical system example based on free-form surface shared beam-reducing mirror;

[0040] Fig. 3 (a) is the YOZ plane light path diagram of the beam-reducing unit and dichroic mirror in the embodiment of the utility model;

[0041] Fig. 3 (b) is the XOY plane light path diagram of the beam-reducing unit and dichroic mirror in the embodiment of the utility model;

[0042] Fig. 3 (c) is the visible light transmission function diagram of the beam-reducing unit and dichroic mirror in the embodiment of the utility model;

[0043] Fig. 3 (d) is the infrared light transmission function diagram of the beam-reducing unit and dichroic mirror in the embodiment of the utility model;

[0044] Fig. 4 (a) is the YOZ plane light path diagram of visible TDI detection light path in the embodiment of the utility model;

[0045] Fig. 4 (b) is the XOY plane light path diagram of visible TDI detection light path in the embodiment of the utility model;

[0046] Fig. 4 (c) is the visible light transmission function diagram of visible TDI detection light path in the embodiment of the utility model;

[0047] Figure 4(d) is a point column diagram of different fields of view of the visible TDI detection light path in the embodiment of the present application;

[0048] Figure 4(e) is a transmission function diagram of the multispectral B1 segment visible TDI detection light path (spatial frequency is 71.43 lp / mm) in the embodiment of the present application;

[0049] Figure 4(f) is a transmission function diagram of the multispectral B2 segment visible TDI detection light path (spatial frequency is 71.43 lp / mm) in the embodiment of the present application;

[0050] Figure 4(g) is a transmission function diagram of the multispectral B3 segment visible TDI detection light path (spatial frequency is 71.43 lp / mm) in the embodiment of the present application;

[0051] Figure 4(h) is a transmission function diagram of the multispectral B4 segment visible TDI detection light path (spatial frequency is 71.43 lp / mm) in the embodiment of the present application;

[0052] Figure 5(a) is a YOZ plane light path diagram of the visible light area array detection light path in the embodiment of the present application;

[0053] Figure 5(b) is an XOY plane light path diagram of the visible light area array detection light path in the embodiment of the present application;

[0054] Figure 5(c) is a visible light transmission function diagram of the visible light area array detection light path in the embodiment of the present application;

[0055] Figure 5(d) is a point column diagram of different fields of view of the visible light area array detection light path in the embodiment of the present application;

[0056] Figure 6(a) is a YOZ plane light path diagram of the infrared TDI detection light path in the embodiment of the present application;

[0057] Figure 6(b) is an XOY plane light path diagram of the infrared TDI detection light path in the embodiment of the present application;

[0058] Figure 6(c) is an infrared light transmission function diagram of the infrared TDI detection light path in the embodiment of the present application;

[0059] Figure 6(d) is a point column diagram of different fields of view of the infrared TDI detection light path in the embodiment of the present application.

[0060] Label explanation of the drawing:

[0061] 1 - primary mirror, 2 - secondary mirror, 3 - fold mirror, 4 - triplet, 5 - dichroic mirror, 6 - visible TDI imaging lens group, 7 - visible switching mirror, 8 - visible area array imaging lens group, 9 - infrared TDI imaging lens group, 10 - reflecting mirror. DETAILED DESCRIPTION

[0062] like Figure 1 , Figure 2 As shown, a visible-infrared dual-band catadioptric optical system based on a freeform surface shared beam-shrinking mirror includes a beam-shrinking unit, a dichroic mirror 5, and a visible TDI (Time Delay Integration) imaging lens group 6 arranged in sequence along the optical path; an infrared TDI imaging lens group 9 arranged in the transmission optical path of the dichroic mirror 5; a visible switching mirror 7; and a visible surface array imaging lens group 8 arranged in the reflection optical path of the visible switching mirror 7. The visible switching mirror 7 is used to cut into or out of the visible TDI imaging lens group 6; a mirror 10 is provided in the infrared TDI imaging lens group 9; the visible TDI imaging lens group 6 and the visible surface array imaging lens group 8 complete the visible surface array or TDI imaging system in a time-division multiplexing manner. The DI optical system imaging includes a beam-shrinking unit consisting of a primary mirror 1, a secondary mirror 2, a folding mirror 3, and a third mirror 4 arranged sequentially along the optical path. The primary mirror 1 and secondary mirror 2 are coaxially arranged, with this axis serving as the primary and secondary mirror axes, resulting in a central field of view with good image quality. This facilitates the implementation of related technologies such as processing, testing, and assembly. The folding mirror 3 is located on the side of the primary mirror 1 furthest from the secondary mirror 2, and its normal forms an angle greater than 45° with the system's optical axis. This ensures that the central field of view rays emitted by the incident light from the off-center field of view after passing through the primary mirror 1, secondary mirror 2, folding mirror 3, and third mirror 4 are perpendicular to the primary and secondary mirror axes. The third mirror 4 is a freeform surface mirror, and its emitted central field of view rays are perpendicular to the primary and secondary mirror axes, exhibiting both aperture off-axis and field of view off-axis characteristics. The beam-shrinking unit formed by the primary mirror 1, secondary mirror 2, folding mirror 3, and third mirror 4 has good image quality. By adjusting sensitive parameters such as the spacing between the primary mirror 1 and secondary mirror 2, and the eccentricity of the secondary mirror 2, the image quality of the beam-shrinking unit can be kept essentially unchanged after assembly. The dichroic mirror 5 is positioned on the outgoing light path of the three mirrors 4, and is at an angle of 45° to the horizontal plane. It splits the dual-band color light emitted from the beam-contraction unit, transmits infrared light, and reflects visible light. It has a transmittance of ≥95% in the infrared band and a reflectance of ≥95% in the visible light band.

[0063] Dichroic mirror 5 is used to sequentially transmit the outgoing light from the three mirrors 4 along the optical path to the infrared TDI imaging lens group 9 and the reflector 10, while simultaneously reflecting the outgoing light from the three mirrors 4 to the visible TDI imaging lens group 6, or reflecting the light to the visible surface array imaging lens group 8 when the visible switching reflector 7 enters the visible TDI imaging lens group 6; a visible TDI detection device is provided on the outgoing light path of the visible TDI imaging lens group 6, so that the outgoing light of the visible TDI imaging lens group 6 is imaged on the visible TDI detection device; a visible light surface array detector is provided on the outgoing light path of the visible surface array imaging lens group 8, so that the outgoing light of the visible surface array imaging lens group 8 is imaged on the visible light surface array detector; an infrared TDI detection device is provided on the outgoing light path of the infrared TDI imaging lens group 9, and by translating the infrared TDI imaging lens group 9, the outgoing light of the infrared TDI imaging lens group 9 is imaged on the infrared TDI detection device.

[0064] In order to ensure the compactness of the system, the primary mirror 1 is a central or eccentric aperture even aspheric mirror, the surface of which is coated with silver or gold film, the conic coefficient K is less than 0, and there are three high-order aspheric terms of 4, 6 and 8; the material is quartz or K9 or microcrystalline or silicon carbide, and the F number of the mirror surface is 0.5-1.5. The secondary mirror 2 is an even aspheric mirror, the surface of which is coated with silver or gold film, the conic coefficient K is less than 0, and there are three high-order aspheric terms of 4, 6 and 8; the material is quartz or K9 or microcrystalline or silicon carbide, and the F number of the mirror surface is 0.5-1.5. The folded mirror 3 is a plane mirror, the surface of which is coated with silver or gold film, and the aperture is arranged off-axis to reduce the size, and the shape has a reverse edge to avoid interference with the dichroic mirror 5; the material is quartz or K9 or microcrystalline or silicon carbide.

[0065] The third mirror 4 is a free-form surface mirror, which is arranged off-axis and has a certain inclination angle, so as to reduce the size and weight. The conic coefficient K is less than 0, and the XY polynomial is used to represent it, and there are 36 terms, only 20 terms of X even power and Y arbitrary power are non-zero, and the number of terms of the XY polynomial can be adjusted according to the requirement of aberration correction. The material of the third mirror 4 is quartz or K9 or microcrystalline or SiC.

[0066] The dichroic mirror 5 is a parallel plate, which is coated with a dichroic film and is placed obliquely, and the angle θ is generally 45°, which can be adjusted according to the requirement of system layout; the dichroic mirror 5 has a certain thickness d to ensure the stability of the system during processing, coating, assembly and use. The material of the dichroic mirror 5 is Silicon, Germanium or ZNSE or CLEARTRAN, and the reflectivity and transmissivity are both greater than 90%. The switching mirror 7 is a plane mirror, and the material is quartz or K9 or microcrystalline or SiC.

[0067] The primary mirror 1 and the secondary mirror 2 are coaxial, and after the combination of the two, the central field of view is perfectly imaged; when the two are combined and adjusted, there is no need to process a compensation lens group or CGH for adjustment, which is conducive to the implementation of the adjustment technology. The beam-reducing unit composed of the primary mirror 1, the secondary mirror 2, the folded mirror 3 and the third mirror 4 is a visible and infrared dual-band beam-reducing system with perfect image quality, which is conducive to the implementation of the combination and adjustment of the beam-reducing unit. First, the combination and adjustment of the primary mirror 1 and the secondary mirror 2 are completed, and then the adjustment of the folded mirror 3 is completed in combination with the theodolite, and then the adjustment of the third mirror 4 is completed. Since the beam-reducing unit has perfect image quality, there is no need to process a compensation lens group or CGH for adjustment, and the image quality of the outgoing parallel light can be controlled to complete the adjustment; finally, if the image quality of the outgoing parallel light still does not meet the requirement of the overall image quality of the beam-reducing unit, the interval between the primary mirror 1 and the secondary mirror 2 and the eccentricity of the secondary mirror 2 are adjusted to ensure that the image quality of the entire beam-reducing unit after adjustment meets the requirement.

[0068] The visible TDI imaging lens group 6 includes a visible common lens front group and a visible imaging discrete rear group coaxially arranged in sequence along the optical path; the visible common lens front group includes six lenses coaxially arranged in sequence along the optical path, wherein the first lens is a plano-convex lens, the convex surface is a free-form surface, the conic coefficient K of the surface is less than 0, is expressed by an XY polynomial, and has a total of 36 terms, only 20 terms of X even power and Y arbitrary power terms are non-zero; the number of terms of the XY polynomial can be adjusted according to the aberration correction requirement, only the terms of X even power and Y arbitrary power are non-zero, so that the lens surface is a transmission lens surface with one axis symmetry, and the remaining lenses are all spherical mirrors; the visible imaging discrete rear group includes three lenses coaxially arranged in sequence along the optical path, wherein one surface of the second lens is an aspheric surface, the conic coefficient K is greater than 0 and less than 1, and there is no high-order term; the remaining lenses are all spherical mirrors.

[0069] If the position of the third lens in the visible common lens front group is finely adjusted to compensate for the changes in temperature and air pressure to fully adapt to the changes, the third lens is a negative lens to meet the image quality requirement. Compared with the existing system in which the adjustment link is arranged in the secondary mirror 2, the accuracy requirement of the adjustment link is relatively low, the implementation is easier, the cost is smaller, and the economy of the system implementation is improved.

[0070] The visible common lens front group and the visible imaging discrete rear group are coaxially arranged, and there is a large air gap between the two, which can allow the switching mirror 7 to cut in and cut out. When the visible switching mirror 7 cuts in between the visible common lens front group and the visible imaging discrete rear group, the reflected light of the dichroic mirror 5 is transmitted to the visible switching mirror after being transmitted by the visible common lens front group, and is reflected to the visible area array imaging lens group 8. When the visible switching mirror 7 cuts out of the visible common lens front group and the visible imaging discrete rear group, the reflected light of the dichroic mirror 5 is reflected to the visible TDI imaging lens group 6; the visible area array imaging lens group 8 has the same structure as the visible imaging discrete rear group.

[0071] The infrared TDI imaging lens group 9 has a secondary imaging function, which ensures the pupil matching of the system without increasing the size of the system primary mirror 1; the infrared TDI imaging lens group 9 includes two positive lens groups; the two positive lens groups have a primary image surface; one positive lens group includes three lenses with positive, negative and positive focal powers arranged in sequence; the other positive lens group includes three lenses with negative, positive and positive focal powers arranged in sequence; the materials of the two positive lens groups are Silicon and / or Germanium. In order to achieve 100% matching with the cold shield, four surfaces of the six lenses are aspheric surfaces, the conic coefficient K is 0, and there are three high-order aspheric terms of the fourth, sixth and eighth. The lens material, the number of aspheric surfaces and the positions of the aspheric surfaces can be adjusted according to the overall requirement of the system.

[0072] The visible TDI detection device comprises an optical splicing device and a plurality of visible TDI detectors; the optical splicing device comprises a plurality of splicing fixed plane mirrors, the sizes and intervals of the plurality of plane mirrors are the same, and the materials of the plurality of plane mirrors are quartz, K9, microcrystal or SiC; each visible TDI detector is arranged on a reflection light path or a transmission light path of the plane mirror; the optical splicing device can solve the problem of the limitation of the size of the detector and the requirement of a large field of view. The optical splicing device has the function of optically splicing N visible TDI detectors, and N is greater than or equal to 2. The waveband of the plane mirror can be adjusted according to requirements, so that the optical splicing device can be expanded to different wavebands and different numbers of detectors. In other embodiments, the visible TDI detection device can also use four visible TDI detectors located in the same detection plane, the four visible TDI detectors are mechanically spliced, and are staggered in a triangular shape. In order to meet the requirement of compact miniaturization of the system, the pixel size of the selected single visible TDI detector is small, and the number of pixels is close to ten thousand, which still cannot directly cover the size of the image surface; the optical splicing method is adopted, and 2*2 visible TDI detectors can complete large field of view visible multispectral TDI push-broom imaging through the method of transmission and reflection mirror 10 interval array.

[0073] The infrared TDI detection device comprises M infrared TDI detectors located in the same detection plane; the M infrared TDI detectors are mechanically spliced, and when M is equal to 2, the M infrared TDI detectors are arranged in parallel, and when M is equal to 3, the M infrared TDI detectors are arranged in a triangular shape; a cold light diaphragm is arranged on each infrared TDI detector; the lens of the infrared TDI imaging lens group 9 for adjusting the air pressure of the infrared light path is a lens group located in front of a primary image surface; compared with the system in which the adjusting link is arranged on the secondary mirror 2, the adjusting link has relatively low accuracy requirement, is easier to realize, has smaller cost, and improves the economy of system implementation.

[0074] The primary mirror 1, the secondary mirror 2, the fold mirror 3, the three-mirror 4, the dichroic mirror 5, the infrared TDI imaging lens group 9 and the reflection mirror 10 form an infrared subsystem; an exit pupil of the infrared subsystem is an infrared diaphragm, which is arranged on a cold shield of the infrared TDI detector, can realize 100% cold light diaphragm matching, and ensures that the imaging light beams are all in the reflection area of the primary mirror 1 by controlling the position of an entrance pupil of the infrared light; the infrared TDI detector is a finished mechanical spliced infrared detector. The primary mirror 1, the secondary mirror 2, the fold mirror 3, the three-mirror 4, the dichroic mirror 5, the visible TDI imaging lens group 6, the visible switching reflection mirror 7 and the visible area array imaging lens group 8 form a visible subsystem, and a diaphragm of the visible subsystem is arranged on the primary mirror 1.

[0075] After the infrared light beam transmits through the parallel plate (dichroic mirror 5) with a certain thickness and inclination angle, it enters the infrared TDI imaging lens group 9 and the infrared TDI detector for imaging. In order to ensure the image quality of the system and eliminate the influence of the optical axis of the system, the infrared TDI imaging lens group 9 needs to be translated as a whole, and the translation direction is consistent with the translation direction of the transmission optical axis of the dichroic mirror 5. The translation amount T can be obtained according to the refractive index n, thickness d and inclination angle θ of the dichroic mirror 5 (i.e. the parallel plate) through the following formula:

[0076]

[0077] The utility model discloses a kind of visible infrared dual-band catadioptric optical systems based on free-form surface common condenser mirror, combine visible TDI detector, infrared TDI detector and a visible area array detector, space-to-ground remote sensing imaging is realized, can be observed all day long;The entrance pupil aperture D of this system=Φ650.0mm, the angle of view is-1 °, the aperture Φ1 of primary mirror 1=650mm, the reflection aperture Φ2 of secondary mirror 2=195.0mm, obscuration ratio is 0.3, the visible focal length f of visible TDI detector='3600mm, the angle of view is ±0.86 ° × ±0.15 °, visible TDI detector is multispectral line array detector, with full color spectrum, multispectral B1~B4 five spectrum, wherein, full color spectrum range is 0.45 μm~0.8 μm, the spectral range of multispectral B1 is 0.45 μm~0.52 μm, the spectral range of multispectral B2 is 0.52 μm~0.59 μm, the spectral range of multispectral B3 is 0.63 μm~0.69 μm, the spectral range of multispectral B4 is 0.77 μm~0.89 μm;The angle of view of visible light area array detector is ±0.31 ° × ±0.22 °, spectral range is 0.45 μm~0.89 μm, rear working distance is 68.977mm;The infrared focal length f of infrared TDI detector='2010mm, the angle of view is ±0.86 ° × ±0.1 °, spectral range is 2.9 μm~5.4 μm.

[0078] In the embodiment, the parallel light beam first passes through the coaxial primary mirror 1 and secondary mirror 2, then passes through the off-axis fold mirror 3 to enter the off-axis three-mirror 4, is converted into a small-aperture condenser light path, and after passing through the dichroic mirror 5, the transmitted infrared light passes through the secondary imaging infrared TDI imaging lens group 9 to form an image on the focal plane of the infrared linear array TDI detector; the reflected visible light passes through the visible common lens front group, the visible imaging discrete rear group and the second visible imaging discrete rear group to reach the large-field-of-view visible TDI detector image plane; after the visible switching mirror 7 is switched in, the visible light passes through the visible area array imaging lens group 8 to reach the visible area array detector image plane. The optical parameters of the primary mirror 1, the secondary mirror 2, the fold mirror 3, the three-mirror 4 and the dichroic mirror 5 are shown in Table 1.1.

[0079] Table 1.1

[0080] Surface type Radius Thickness Glass Refractive mode Comment Object plane Spherical Infinite Infinite 1 (stop) Even aspherical -1328.273 -502.609 Reflective Primary mirror 1 2 Even aspherical -241.066 803.88 Reflective Secondary mirror 2 3 Spherical Infinite 332.21 Reflective Tilted mirror 3 4 Freeform 588.056000 374.40 Reflective Tertiary mirror 4 5 Spherical Infinite Reflective Exit pupil

[0081] The optical parameters of TDI imaging lens group 6 are detailed in Table 1.2:

[0082] Table 1.2

[0083]

[0084]

[0085] The optical parameters of the infrared TDI imaging lens group 9 and the infrared TDI detector are detailed in Table 1.3:

[0086] Table 1.3

[0087]

[0088] Figure 3(a) , 3(b) Figure 3(c) shows the in-YOZ and in-XOY plane optical path diagrams of the beam-shrinking unit and dichroic mirror 5 in this embodiment of the present invention when light is incident on the beam-shrinking unit; Figure 3(d) shows the infrared optical path diagram of the beam-shrinking unit and dichroic mirror 5 in this embodiment of the present invention, where various colors represent the visible light path function of different fields of view, the horizontal axis is the spatial frequency in cycles / mrad, and the vertical axis is the path function value, which is dimensionless;

[0089] like Figure 4(a) , 4(b) As shown, under conventional pushbroom imaging conditions, visible light is reflected by the dichroic mirror 5 and enters the visible TDI imaging lens group 6, finally forming an image on the visible TDI detector; Figure 4(c) is a visible light transfer function diagram of the visible TDI detector optical path in this embodiment of the invention, where various colors represent the visible light transfer function of different fields of view, the horizontal axis is the spatial frequency in cycles / mm, and the vertical axis is the transfer function value, which is dimensionless; Figure 4(d) is a visible point array diagram of different fields of view of the visible TDI detector optical path in this embodiment of the invention; from Figure 4(c) , 4(d)As can be seen from Figure 4(e), the visible multispectral B1 segment transfer function is greater than 0.3 at a spatial frequency of 142.9 lp / mm, indicating good consistency of the blur spot across all fields of view and near-limit image quality. Figure 4(f) shows that the visible multispectral B2 segment transfer function is greater than 0.5 at a spatial frequency of 71.43 lp / mm, indicating excellent image quality; Figure 4(g) shows that the visible multispectral B1 transfer function is greater than 0.47 at a spatial frequency of 71.43 lp / mm, indicating excellent image quality; and Figure 4(h) shows that the visible multispectral B4 transfer function is greater than 0.3 at a spatial frequency of 71.43 lp / mm, indicating excellent image quality.

[0090] like Figure 5(a) , 5(b) As shown, in the imaging condition of the discrete target region of interest, a visible switching mirror 7 is inserted between the dichroic mirror 5 and the visible array imaging lens group 8. Visible light, after being reflected by the dichroic mirror 5, enters the visible array imaging lens group 8 and is finally imaged onto the visible light array detector. Figure 5(c) is a visible light transfer function diagram of the visible light array detector optical path in this embodiment, where various colors represent the visible light transfer function of different fields of view. The horizontal axis represents the spatial frequency in cycles / mm, and the vertical axis represents the transfer function value, which is dimensionless. Figure 5(d) is a dot plot of the visible light array detector optical path in different fields of view in this embodiment. Figure 5(c) , 5(d) It can be seen that the visible transfer function is greater than 0.32 at a spatial frequency of 110 lp / mm, the consistency of the blur spot is good across the fields of view, and the image quality is close to the limit.

[0091] like Figure 6(a) , 6(b) As shown, under conventional push-broom imaging conditions, visible light enters the infrared TDI imaging lens group 9 after being transmitted through the dichroic mirror 5, and finally images onto the infrared TDI detector; Figure 6(c) is a visible light transfer function diagram of the infrared TDI detection optical path in this embodiment of the present invention, where various colors represent infrared light transfer functions of different fields of view, the horizontal axis is the spatial frequency in cycles / mm, and the vertical axis is the transfer function value, which is dimensionless; Figure 6(d) is a dot plot of the infrared TDI detection optical path in different fields of view in this embodiment of the present invention, from Figure 6(c) , 6(d) It can be seen that the infrared transfer function is greater than 0.35 at a spatial frequency of 25 lp / mm, the consistency of the blur spot is good across all fields of view, and the image quality is close to the limit.

[0092] The utility model discloses a visible infrared double wave band catadioptric optical system based on free-form surface shared beam-reducing mirror, can reach better image quality level, and processing, assembly are relatively simple. Its envelope size is 800 (X direction) * 750 (Y direction) * 870 (Z direction is system optical axis direction), and the effective aperture of optical system is 650, and visible focal length is 3600, and focal length ratio is 4.137:1, and system layout is compact.

Claims

1. A visible-infrared dual-band catadioptric optical system based on a freeform surface shared condenser lens, characterized in that: The system comprises, in sequence along the light path, a beam-reducing unit, a dichroic mirror (5), a visible TDI imaging lens group (6) arranged on the reflected light path of the dichroic mirror (5), an infrared TDI imaging lens group (9) arranged on the transmitted light path of the dichroic mirror (5), a visible switching mirror (7), and a visible area array imaging lens group (8) arranged on the reflected light path of the visible switching mirror (7); the visible switching mirror (7) is used to cut into or out of the visible TDI imaging lens group (6); the infrared TDI imaging lens group (9) is provided with a mirror (10); The beam-reducing unit comprises, in sequence along the light path, a primary mirror (1), a secondary mirror (2), a folded mirror (3), and a three-mirror (4); the primary mirror (1) and the secondary mirror (2) are coaxially arranged, and the axis is the primary-secondary mirror axis; the folded mirror (3) is located on the side of the primary mirror (1) away from the secondary mirror (2), and the angle between the normal line of the folded mirror (3) and the system optical axis is greater than 45°; the three-mirror (4) is a free-form surface mirror, and the outgoing central field of view light is perpendicular to the primary-secondary mirror axis; the dichroic mirror (5) is arranged on the outgoing light path of the three-mirror (4); The dichroic mirror (5) is used to transmit the outgoing light of the three-mirror (4) to the infrared TDI imaging lens group (9) and the mirror (10) along the light path, and reflect the outgoing light of the three-mirror (4) to the visible TDI imaging lens group (6), or reflect the light to the visible area array imaging lens group (8) when the visible switching mirror (7) cuts into the visible TDI imaging lens group (6); A visible TDI detection device is arranged on the outgoing light path of the visible TDI imaging lens group (6), so that the outgoing light of the visible TDI imaging lens group (6) is imaged on the visible TDI detection device; A visible light area array detector is arranged on the outgoing light path of the visible area array imaging lens group (8), so that the outgoing light of the visible area array imaging lens group (8) is imaged on the visible light area array detector; An infrared TDI detection device is arranged on the outgoing light path of the infrared TDI imaging lens group (9), and the outgoing light of the infrared TDI imaging lens group (9) is imaged on the infrared TDI detection device by translating the infrared TDI imaging lens group (9).

2. The visible-infrared dual-band catadioptric optical system based on a free-form surface shared beam-reducing mirror according to claim 1, wherein the primary mirror (1) is a central or eccentric aperture even aspheric mirror, the surface of which is coated with a silver or gold film, the conic coefficient K is less than 0, the material is quartz or K9 or microcrystalline or silicon carbide, and the mirror F number is 0.5-1.

5.

3. The visible-infrared dual-band catadioptric optical system based on a free-form surface shared beam-reducing mirror according to claim 2, wherein the secondary mirror (2) is an even aspheric mirror, the surface of which is coated with a silver or gold film, the conic coefficient K is less than 0, the material is quartz or K9 or microcrystalline or silicon carbide, and the mirror F number is 0.5-1.

5.

4. The visible-infrared dual-band catadioptric optical system based on a free-form surface shared beam-reducing mirror according to claim 3, wherein ​ ​ The fold mirror (3) is a plane mirror, the surface of which is coated with silver or gold film, and the material is quartz or K9 or microcrystalline or silicon carbide.

5. The visible-infrared dual-band catadioptric optical system based on a free-form surface common condenser lens according to claim 4, wherein: The main mirror (1) is provided with a diaphragm; The conic coefficient K of the three-mirror (4) is less than 0, and the three-mirror (4) is expressed by an XY polynomial, and the material is quartz or K9 or microcrystalline or silicon carbide; The dichroic mirror (5) is a parallel plate, and a dichroic film is coated on the dichroic mirror (5), and the material of the dichroic mirror (5) is Silicon, Germanium or ZNSE or CLEARTRAN, and the reflectivity and transmissivity are greater than 90%; The visible switching mirror (7) is a plane mirror, and the material is quartz or K9 or microcrystalline or SiC.

6. The visible-infrared dual-band catadioptric optical system based on a free-form surface common condenser lens according to any one of claims 1 to 5, wherein: The visible TDI imaging lens group (6) comprises a visible common lens front group and a visible imaging discrete rear group which are coaxially arranged in sequence along an optical path; The visible common lens front group comprises six lenses which are coaxially arranged in sequence along an optical path, wherein the first lens is a plano-convex lens, the convex surface of which is a free-form surface, the conic coefficient K of which is less than 0 and is expressed by an XY polynomial, the third lens is a negative lens, and the remaining lenses are spherical mirrors; The visible imaging discrete rear group comprises three lenses which are coaxially arranged in sequence along an optical path, wherein one surface of the second lens is an aspherical surface, the conic coefficient K of which is greater than 0 and less than 1 and has no high-order term, and the remaining lenses are spherical mirrors; The visible switching mirror (7) is used to cut into or cut out between the visible common lens front group and the visible imaging discrete rear group, when the visible switching mirror (7) cuts in, the reflected light of the dichroic mirror (5) is transmitted to the visible switching mirror (7) through the visible common lens front group, and then reflected to the visible area array imaging lens group (8), when the visible switching mirror (7) cuts out, the reflected light of the dichroic mirror (5) is reflected to the visible TDI imaging lens group (6); The visible area array imaging lens group (8) has the same structure as the visible imaging discrete rear group; The visible TDI imaging lens group (6) adjusts the image quality and air pressure by adjusting the interval of the third lens of the visible common lens front group.

7. The visible-infrared dual-band catadioptric optical system based on a free-form surface common condenser lens according to claim 6, wherein: The infrared TDI imaging lens group (9) comprises two positive lens groups, and the two positive lens groups have an intermediate image plane, one positive lens group comprises three lenses, and the refractive powers of the three lenses are arranged in positive, negative and positive order respectively, and the other positive lens group comprises three lenses, and the refractive powers of the three lenses are arranged in negative, positive and positive order respectively, and the materials of the two positive lens groups are Silicon and / or Germanium; The infrared TDI imaging lens group (9) adjusts the air pressure by adjusting the position of the positive lens group located in front of the intermediate image plane.

8. The visible-infrared dual-band catadioptric optical system based on a free-form surface common condenser lens according to claim 1, wherein: The translation amount T of the infrared TDI imaging lens group (9) is calculated according to the following formula: In the formula, d is the thickness of the dichroic mirror (5), θ is the angle between the dichroic mirror (5) and the horizontal plane, and n is the refractive index of the dichroic mirror (5).

9. The visible-infrared dual-band catadioptric optical system based on a freeform surface shared condenser lens according to claim 8, characterized in that: The visible TDI detection device comprises an optical splicing device and N visible TDI detectors; the optical splicing device comprises a plurality of splicing fixed plane mirrors, the sizes and intervals of the plane mirrors are the same, and the materials of the plane mirrors are quartz, K9, microcrystalline or SiC; each visible TDI detector is arranged on a reflection light path or a transmission light path of the plane mirror; Alternatively, the visible TDI detection device comprises N visible TDI detectors located on the same detection plane, the N visible TDI detectors are mechanically spliced and arranged in parallel with each other, there are at least 10 overlapping pixels along the splicing direction, and N is greater than or equal to 2.

10. The visible-infrared dual-band catadioptric optical system based on a freeform surface shared condenser lens according to claim 9, characterized in that: The infrared TDI detection device comprises M infrared TDI detectors located on the same detection plane, the M infrared TDI detectors are mechanically spliced and arranged in parallel with each other, there are at least 10 overlapping pixels along the splicing direction, and M is greater than or equal to 2; and a cold light stop is arranged on each infrared TDI detector; The angle θ between the dichroic mirror (5) and the horizontal plane is 45°.

Images