CN120928559A - Short focal ratio, wide spectral band, near-diffraction-limited reflective telescope system - Google Patents
Short focal ratio, wide spectral band, near-diffraction-limited reflective telescope systemInfo
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- CN120928559A CN120928559A CN202511348636.XA CN202511348636A CN120928559A CN 120928559 A CN120928559 A CN 120928559A CN 202511348636 A CN202511348636 A CN 202511348636A CN 120928559 A CN120928559 A CN 120928559A
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Abstract
本发明属于激光雷达望远镜技术领域，具体涉及短焦比宽谱段近衍射极限反射式望远系统，包括主反射镜：抛物面反射镜，有效通光口径为420mm，面形精度≤λ/20；次反射镜：双曲面反射镜，与所述主反射镜构成准格里高利式折反射光路结构；宽光谱校正镜组：位于次反射镜后光路中，包含至少一片超低色散材料透镜和至少一片自由曲面透镜；焦平面探测器；主反射镜以及次反射镜表面均镀制十五层以上梯度折射率膜，所述梯度折射率膜采用Al、SiO2、Si3N4叠层膜，所述梯度折射率膜厚公差<±3nm，所述梯度折射率膜平均反射率>98.5％；最大视场角0.0097°，角放大率‑25.793±0.5。本发明为机载激光雷达与深空探测提供近衍射极限的紧凑化解决方案。
This invention belongs to the field of lidar telescope technology, specifically relating to a short focal ratio, wide-spectrum, near-diffraction-limited reflective telescope system. It includes a primary mirror: a parabolic mirror with an effective aperture of 420 mm and a surface shape accuracy ≤ λ/20; a secondary mirror: a hyperboloid mirror, forming a quasi-Gregorian catadioptric optical path structure with the primary mirror; a wide-spectrum correction mirror assembly: located in the optical path behind the secondary mirror, comprising at least one ultra-low dispersion lens and at least one freeform lens; a focal plane detector; both the primary and secondary mirrors are coated with at least fifteen layers of gradient refractive index films, which are Al, SiO₂ , Si₃N₄ stacked films, with a thickness tolerance of < ±3 nm and an average reflectivity >98.5%; a maximum field of view of 0.0097° and an angular magnification of -25.793 ± 0.5. This invention provides a near-diffraction-limited compact solution for airborne lidar and deep space exploration.
Description
Technical Field
The invention belongs to the technical field of laser radar telescopes, and particularly relates to a short-focal-ratio wide-spectrum near diffraction limit reflection type telescopic system.
Background
The laser radar telescope belongs to one of telescope systems, and the structural form of the traditional telescope is simply divided into three types, namely refraction type, reflection type and refraction type. When the light transmission caliber D of the telescope is larger than or equal to phi 300mm, the telescope belongs to a large caliber telescope. The types of the large-caliber transmission materials are very few, so that most large-caliber telescopes adopt a reflection type structure. The focal ratio is a core performance parameter of the telescope, and has great influence on the function of the telescope.
The definition and calculation of the focal ratio, wherein the focal ratio (F value) is an important parameter of the telescope optical system, and is defined as the ratio of the focal length (F) to the caliber (D), and the calculation formula is F=f/D, and the ratio is similar to the aperture value of a camera lens, and directly influences the imaging brightness and the field size 12 of the telescope. For reflective telescopes, the focal ratio is one of the core parameters that need to be considered in design.
The focal ratio has the effects on the performance of the telescope, namely imaging brightness is directly influenced by focal ratio, F value is lower, brightness is higher, compared with the exposure time of an F/5 system is shortened by 75 percent compared with that of an F/10 system, the field of view is generally wider than that of the telescope, the field of view is smaller than that of the telescope, but the focal ratio is more suitable for observing punctiform celestial bodies, the optical design difficulty is higher than that of a large focal ratio (low F value) system, the image field and the image quality can be sacrificed, the available image field of the large focal ratio system is smaller under the same cost, the common focal ratio range of the large caliber telescope is the common focal ratio range of F/5 to F/11, and typical value examples of F/5 are as Star 130EQ (130 mm caliber, 650mm focal length) 5;f/7.9 are as Boguan observer 114/900 (114 mm caliber, 900mm focal length) 6;f/11 are as Star 80EQ (80 mm caliber, 900mm focal length) 7;
Therefore, the invention discloses a laser radar telescope with large caliber, wide spectrum and short focal ratio.
Disclosure of Invention
The invention aims to provide a short-focal-ratio wide-spectrum near diffraction limit reflection type telescopic system which can provide a compact solution of near diffraction limit for airborne laser radar and deep space detection.
The technical scheme adopted by the invention is as follows:
A short-focal-ratio wide-spectrum near-diffraction-limited reflective telescopic system, comprising:
The main reflector is a parabolic reflector, the effective light transmission caliber is 420mm, and the surface shape precision is less than or equal to lambda/20, wherein lambda=632.8 nm;
The secondary reflector is a hyperbolic reflector and forms a quasi-Grignard high-interest refraction and reflection light path structure with the main reflector;
The wide spectrum correction lens group is positioned in the rear light path of the secondary reflector and comprises at least one ultra-low dispersion material lens and at least one free-form surface lens;
a focal plane detector, wherein a response wave band covers 400-1700nm;
The total focal length F of the system and the focal length F 1 of the main reflector meet 3<f/F 1 <4, and the focal ratio of the system is F3.57;
The wide spectrum performance is that the working wave band covers 0.355 mu m ultraviolet light-1.5 mu m near infrared light, more than ten layers of gradient refractive index films are plated on the surfaces of a main reflector and a secondary reflector, the gradient refractive index films adopt Al and SiO 2、Si3N4 laminated films, the film thickness tolerance of the gradient refractive index films is < +/-3 nm, and the average reflectivity of the gradient refractive index films is more than 98.5%;
the maximum field angle is 0.0097 degrees, and the angle amplification rate is-25.793 +/-0.5.
Preferably, the wide spectrum correction lens group is composed of three lenses, and sequentially comprises:
The first positive lens is made of calcium fluoride (CaF 2) and has an Abbe number more than or equal to 95;
the second negative lens is made of fused quartz and is glued with the first positive lens (31) to form an achromatic double-glued lens;
And the third free-form surface lens has a surface formula:
Where c is the inverse radius of curvature, k is the conic coefficient, A 4-A20 is the even aspheric coefficient, and |A 4|>10-5mm-3.
Preferably, the main reflector adopts a lightweight structure, and comprises:
The honeycomb core layer is made of silicon carbide composite material, and the surface density is less than or equal to 30kg/m 2;
a surface reflection layer, namely a chemical vapor deposition SiC coating, wherein the thickness is more than or equal to 200 mu m;
and the active supporting component is at least 6 groups of piezoelectric actuator arrays and corrects the surface shape error of the main mirror surface to be less than or equal to lambda/50 in real time.
Preferably, the total length L of the system and the diameter D of the main reflector are L less than or equal to 0.6D, and the distance between the secondary reflector and the main reflector is less than or equal to 0.25D.
Preferably, the method further comprises:
the multi-wavelength laser emission module comprises output wavelengths of 532nm, 1064nm and 1550nm;
And the synchronous control unit is used for switching the laser wavelength and the reading time sequence of the focal plane detector according to a time division multiplexing mode.
Preferably, the included angle θ between the telescope and the optical axis of the laser emission module is less than or equal to 0.1 °, and the conjugated imaging relationship is satisfied:
Wherein f tel is the focal length of the telescope, d obj is the target distance, and d laser is the distance from the laser emitting end to the primary mirror of the telescope.
Preferably, the MTF value of the system is reduced by less than or equal to 10% at the spatial frequency of 50lp/mm under the temperature range of-40 ℃ to 60 ℃, and the wide-spectrum correction lens group is configured to be in the wave band range of 400-1700nm, so that the chromatic aberration delta f of the system is less than or equal to 0.05mm and the curvature of field is less than or equal to 0.1mm.
The invention has the technical effects that:
According to the invention, through the collaborative design of the quasi-Grignard high-definition structure and the free-form surface wide-spectrum correction lens group, F3.57 short focal ratio and 0.355-1.5 mu m ultra-wide spectrum coverage are realized under the light aperture of only 420mm, the average reflectivity breaks through 98.5% by high-precision gradient refractive index coating, the total length of the system is compressed to 252mm by matching with a silicon carbide lightweight main lens and real-time piezoelectric deformation correction, the MTF attenuation of a full temperature range of-40 ℃ to 60 ℃ is ensured to be less than or equal to 10%, the innovative multi-wavelength laser timing control technology is combined with sub-arc second angular resolution, 532nm/1064nm/1550nm spectral dimension information can be synchronously acquired, high-precision multi-dimensional detection of terrains, vegetation and atmosphere can be completed by single scanning, the comprehensive performance is improved by 60% optical efficiency and 30% edge view resolution compared with the traditional system, and a compact solution of near diffraction limit is provided for airborne laser radar and space detection.
Drawings
FIG. 1 is a diagram of the optical path of a telescope in the short-focal-ratio wide-band near diffraction limit reflection type telescopic system of the present invention;
fig. 2 is a schematic view of MTF of the short-focal-length wide-band near diffraction limit reflection type telescopic system of the present invention.
Detailed Description
The present invention will be specifically described with reference to examples below in order to make the objects and advantages of the present invention more apparent. It should be understood that the following text is intended to describe only one or more specific embodiments of the invention and does not limit the scope of the invention strictly as claimed.
As shown in fig. 1, the short-focal-ratio wide-band near diffraction limit reflection type telescopic system includes:
The main reflector is a parabolic reflector, the effective light transmission caliber is 420mm, and the surface shape precision is less than or equal to lambda/20, wherein lambda=632.8 nm;
The secondary reflector is a hyperbolic reflector and forms a quasi-Grignard high-interest refraction and reflection light path structure with the main reflector;
The wide spectrum correction lens group is positioned in the rear light path of the secondary reflector and comprises at least one ultra-low dispersion material lens and at least one free-form surface lens;
a focal plane detector, wherein a response wave band covers 400-1700nm;
The total focal length F of the system and the focal length F 1 of the main reflector meet 3<f/F 1 <4, and the focal ratio of the system is F3.57;
The wide spectrum performance is that the working wave band covers 0.355 mu m ultraviolet light-1.5 mu m near infrared light, more than ten layers of gradient refractive index films are plated on the surfaces of a main reflector and a secondary reflector, the gradient refractive index films adopt Al and SiO 2、Si3N4 laminated films, the film thickness tolerance of the gradient refractive index films is < +/-3 nm, and the average reflectivity of the gradient refractive index films is more than 98.5%;
the maximum field angle is 0.0097 degrees, and the angle amplification rate is-25.793 +/-0.5.
According to the invention, the high-efficiency light collection and aberration control of the ultraviolet-near infrared ultra-wide spectrum band are realized by combining the quasi-Grignard structure with the wide spectrum correction lens group. In the invention, the short focal ratio of F3.57 remarkably improves the optical efficiency, the signal-to-noise ratio is more than or equal to 6dB compared with the traditional system, the gradient refractive index film of the Al/SiO 2/Si3N4 lamination ensures that the average reflectivity of the 400-1700nm wave band is more than 98.5%, solves the problem of energy loss in a wide spectrum band, and the angle amplification rate-25.793 +/-0.5 ensures the consistency of a field of view and avoids scanning distortion.
Preferably, the wide spectrum correction lens group is composed of three lenses, and sequentially comprises:
The first positive lens is made of calcium fluoride (CaF 2) and has an Abbe number more than or equal to 95;
the second negative lens is made of fused quartz and is bonded with the first positive lens to form an achromatic double-bonded lens;
And the third free-form surface lens has a surface formula:
Where c is the inverse radius of curvature, k is the conic coefficient, A 4-A20 is the even aspheric coefficient, and |A 4|>10-5mm-3.
The three-piece type correcting lens group cooperatively inhibits wide-spectrum chromatic aberration and off-axis astigmatism. In the invention, caF 2 +fused quartz cemented lens eliminates axial chromatic aberration, Δf is less than or equal to 0.02mm@400-1700nm, free-form surface higher order item A 4-A20 compensates edge field wavefront difference to less than or equal to 0.03λ, near diffraction limit imaging is realized, and MTF is more than or equal to 0.55@50lp/mm;
preferably, the main reflector adopts a lightweight structure, and comprises:
The honeycomb core layer is made of silicon carbide composite material, and the surface density is less than or equal to 30kg/m 2;
a surface reflection layer, namely a chemical vapor deposition SiC coating, wherein the thickness is more than or equal to 200 mu m;
and the active supporting component is at least 6 groups of piezoelectric actuator arrays and corrects the surface shape error of the main mirror surface to be less than or equal to lambda/50 in real time.
The lightweight structure and the active support solve the problem of deformation of the mirror surface with the large caliber of 420 mm. The silicon carbide honeycomb core layer with the surface density less than or equal to 30kg/m 2 reduces the weight of the mirror body by 60 percent, improves the maneuverability, and the piezoelectric actuator array corrects the thermal deformation/gravity deformation in real time, the surface shape precision is stabilized in lambda/50, and the imaging stability of the extreme environment at-40 ℃ to 60 ℃ is ensured.
Preferably, the total length L of the system and the diameter D of the main reflector are L less than or equal to 0.6D, and the distance between the secondary reflector and the main reflector is less than or equal to 0.25D.
In the invention, the compact light path design breaks through the volume limitation of a short focal ratio system. The total length L is less than or equal to 0.6D (252 mm), so that the volume of the system is reduced by 70% compared with the same-focal-length refractive telescope, the distance between the primary mirror and the secondary mirror is less than or equal to 0.25D (105 mm), stray light interference is inhibited, and the signal to noise ratio is more than or equal to 3dB.
Preferably, the system further comprises:
the multi-wavelength laser emission module comprises output wavelengths of 532nm, 1064nm and 1550nm;
And the synchronous control unit is used for switching the laser wavelength and the reading time sequence of the focal plane detector according to a time division multiplexing mode.
In the invention, the multi-wavelength laser and the time sequence control realize the enhancement of spectrum dimension information. The three-wavelength switching of 532/1064/1550nm synchronously acquires vegetation water content (1550 nm), aerosol distribution (532 nm) and topographic data (1064 nm), the time division multiplexing time sequence control avoids multi-wavelength crosstalk, and the target classification precision is improved to 95%.
Preferably, the included angle θ between the telescope and the optical axis of the laser emission module is less than or equal to 0.1 °, and the conjugated imaging relationship is satisfied:
Wherein f tel is the focal length of the telescope, d obj is the target distance, and d laser is the distance from the laser emitting end to the primary mirror of the telescope.
In the invention, the optical axis conjugate design optimizes the laser-receiving optical path matching performance. The included angle theta of the optical axis is less than or equal to 0.1 degree, so that the superposition ratio of the laser spot and the receiving view field is more than or equal to 99 percent, the conjugated imaging relation formula ensures that the distance measurement error at the position of 10km is less than or equal to 5cm, and the mapping precision of a 1:50000 scale is met.
Preferably, the MTF value of the system is reduced by less than or equal to 10% at the spatial frequency of 50lp/mm under the temperature range of-40 ℃ to 60 ℃, and the wide-spectrum correction lens group is configured to be in the wave band range of 400-1700nm, so that the chromatic aberration delta f of the system is less than or equal to 0.05mm and the curvature of field is less than or equal to 0.1mm.
In the invention, temperature drift inhibition and aberration control ensure the near diffraction limit performance of the full working condition. MTF is reduced by less than or equal to 10% at-40 ℃ to 60 ℃ to avoid thermal defocusing, refocusing is not needed, chromatic aberration Δf is less than or equal to 0.05mm and field curvature is less than or equal to 0.1mm to ensure that the total field energy concentration (EE 80) is more than or equal to 90%, and high-resolution spectral analysis is supported.
According to the invention, the F3.57 short focal ratio and the 0.355-1.5 mu m ultra wide spectrum coverage are realized under the light-passing caliber of only 420mm by the cooperative design of the quasi-Grignard high-definition structure and the free-form surface wide spectrum correction mirror group, the high-precision gradient refractive index coating enables the average reflectivity to break through 98.5%, the total length of the system is compressed to 252mm and the full-temperature-range MTF attenuation of minus 40-60 ℃ is ensured to be less than or equal to 10% by matching with the silicon carbide light-weight main mirror and the real-time piezoelectric deformation correction, the innovative multi-wavelength laser timing control technology is combined with the sub-arc second level angular resolution, 532nm/1064nm/1550nm spectral dimension information can be synchronously acquired, so that the high-precision multi-dimensional detection of terrains, vegetation and atmosphere can be completed by single scanning, the comprehensive performance is improved by 60% of optical efficiency and 30% of edge view field resolution compared with the traditional system, and a compact solution of near diffraction limit is provided for airborne laser radar and deep space detection.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention. Structures, devices and methods of operation not specifically described and illustrated herein, unless otherwise indicated and limited, are implemented according to conventional means in the art.
Claims (7)
1. The short-focal-ratio wide-spectrum near diffraction limit reflection type telescopic system is characterized by comprising the following components:
The main reflector is a parabolic reflector, the effective light transmission caliber is 420mm, and the surface shape precision is less than or equal to lambda/20, wherein lambda=632.8 nm;
The secondary reflector is a hyperbolic reflector and forms a quasi-Grignard high-interest refraction and reflection light path structure with the main reflector;
The wide spectrum correction lens group is positioned in the rear light path of the secondary reflector and comprises at least one ultra-low dispersion material lens and at least one free-form surface lens;
a focal plane detector, wherein a response wave band covers 400-1700nm;
The total focal length f of the system and the focal length f 1 of the main reflector meet 3<f/f 1 <4;
The wide spectrum performance is that the working wave band covers 0.355 mu m ultraviolet light-1.5 mu m near infrared light, more than ten layers of gradient refractive index films are plated on the surfaces of a main reflector and a secondary reflector, the gradient refractive index films adopt Al and SiO 2、Si3N4 laminated films, the film thickness tolerance of the gradient refractive index films is < +/-3 nm, and the average reflectivity of the gradient refractive index films is more than 98.5%;
the maximum field angle is 0.0097 degrees, and the angle amplification rate is-25.793 +/-0.5.
2. The short-focal-ratio wide-band near diffraction-limit reflection type telescopic system as claimed in claim 1, wherein said wide-spectrum correction lens group is composed of three lenses, in order, comprising:
The first positive lens is made of calcium fluoride (CaF 2) and has an Abbe number more than or equal to 95;
the second negative lens is made of fused quartz and is glued with the first positive lens (31) to form an achromatic double-glued lens;
And the third free-form surface lens has a surface formula:
Where c is the inverse radius of curvature, k is the conic coefficient, A 4-A20 is the even aspheric coefficient, and |A 4|>10-5mm-3.
3. The short-focal-ratio wide-band near diffraction-limit reflecting type telescopic system as claimed in claim 2, wherein said main mirror is of a lightweight structure, comprising:
The honeycomb core layer is made of silicon carbide composite material, and the surface density is less than or equal to 30kg/m 2;
a surface reflection layer, namely a chemical vapor deposition SiC coating, wherein the thickness is more than or equal to 200 mu m;
and the active supporting component is at least 6 groups of piezoelectric actuator arrays and corrects the surface shape error of the main mirror surface to be less than or equal to lambda/50 in real time.
4. The short-focal-ratio wide-band near diffraction-limited reflective telescopic system as claimed in claim 3, wherein the total length L of said system and the diameter D of the main reflector satisfy L≤0.6D, and the distance between the sub-reflector and the main reflector is≤0.25D.
5. The short-focal-ratio wide-band near-diffraction-limited-reflection type telescopic system according to claim 4, further comprising:
the multi-wavelength laser emission module comprises output wavelengths of 532nm, 1064nm and 1550nm;
And the synchronous control unit is used for switching the laser wavelength and the reading time sequence of the focal plane detector according to a time division multiplexing mode.
6. The short-focal-ratio wide-spectrum near diffraction limit reflection type telescopic system as claimed in claim 5, wherein an included angle θ between the telescope and an optical axis of the laser emission module is less than or equal to 0.1 °, and the conjugated imaging relationship is satisfied:
Wherein f tel is the focal length of the telescope, d obj is the target distance, and d laser is the distance from the laser emitting end to the primary mirror of the telescope.
7. The short-focal-ratio wide-band near diffraction-limit reflection type telescopic system as claimed in claim 6, wherein the MTF value of the system is reduced by less than or equal to 10% at a spatial frequency of 50lp/mm at a temperature range of-40 ℃ to 60 ℃, and the wide-spectrum correction lens group is configured to ensure that the chromatic aberration Δf of the system is less than or equal to 0.05mm and the field curvature is less than or equal to 0.1mm in a wave band range of 400 nm to 1700 nm.
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| CN202511348636.XA CN120928559A (en) | 2025-09-21 | 2025-09-21 | Short focal ratio, wide spectral band, near-diffraction-limited reflective telescope system |
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| CN202511348636.XA CN120928559A (en) | 2025-09-21 | 2025-09-21 | Short focal ratio, wide spectral band, near-diffraction-limited reflective telescope system |
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