A catadioptric long focal length multi-vari-focal visible and low-light level optical system

Abstract

The application discloses a catadioptric long-focus multi-grade zoom visible light and low-light optical system, which comprises, in sequence from an object side to an image side, a reflecting objective group, an eyepiece group, a zoom group, a compensation group, a rear fixed group, a folding mirror, a filter group, a rotating mirror and a detector; the reflecting objective group, the eyepiece group, the zoom group, the compensation group, the rear fixed group, the folding mirror, the filter group and the rotating mirror are common groups of the visible light and low-light optical system; the rotating mirror is rotated by 90 degrees around the Y axis to realize time-sharing imaging of the visible light and low-light optical system; a secondary imaging rear group zoom structure form is adopted for an imaging channel, light aperture is greatly compressed through the reflecting objective group, and the zoom is realized through axial movement of lenses of the small-aperture zoom group and the compensation group along the optical axis in the secondary imaging rear group, so that the volume and weight are reduced. The application realizes design of a super-long-focus large-aperture zoom optical system in a very small space, and greatly reduces the volume and weight of the optical system.

Description

Technical Field

[0001] This invention belongs to the field of optical technology, specifically relating to a combined telephoto and reflective long focal length multi-zoom visible light and low light optical system. Background Technology

[0002] With the increasing demand for long-range target detection and identification, long focal length optical systems have become an indispensable component of various optoelectronic payloads. However, as focal lengths gradually increase, their size and weight also increase significantly. The urgent need for ultra-long focal length optical systems and their limited size and weight have become an increasingly prominent contradiction. Summary of the Invention

[0003] The purpose of this invention is to provide a combined telephoto and reflective long-focal-length multi-zoom visible light and low-light optical system. The visible light optical system and the low-light optical system share an imaging lens. Time-division imaging of visible light and low light is achieved by rotating a reflector in front of the image, thus resolving the contradiction between the focal length, size, and weight of the optical system.

[0004] The technical solution provided by this invention is as follows:

[0005] A catadioptric combined long focal length multi-zoom visible light and low light optical system, comprising, from object to image, a reflective objective lens group, an eyepiece group, a zoom group, a compensation group, a rear fixation group, a folding mirror, a filter group, a rotating mirror, and a detector.

[0006] Among them, the reflective objective lens group, eyepiece group, zoom group, compensation group, rear fixation group, folding mirror, filter group, and rotating mirror are shared by the visible light optical system and the low light optical system; the reflective objective lens group, eyepiece group, zoom group, compensation group, and rear fixation group are set along the Z-axis, the folding mirror is at a 45° angle to the Z-axis, and the rotating mirror is at a 45° angle to the Z-axis and is opposite to the folding mirror. Time-division imaging of the visible light optical system and the low light optical system is achieved by rotating the rotating mirror 90° around the Y-axis;

[0007] The imaging channel adopts a zoom structure after secondary imaging. The light aperture is greatly compressed by the reflective objective lens group. In the secondary imaging group, the zoom is achieved by moving the small-aperture zoom group and the compensation group lens along the optical axis, thereby reducing the size and weight.

[0008] Furthermore, the reflective objective lens assembly includes a Casio primary mirror and a Casio secondary mirror, with the Casio primary mirror being a parabolic surface and the Casio secondary mirror being a hyperboloid.

[0009] Furthermore, the primary mirror of the cassette reflector is fixed using a central support mounting method on the back.

[0010] Furthermore, the eyepiece assembly includes two meniscus lenses and a set of cemented lenses, namely a meniscus lanthanum crown material lens with negative optical power, a meniscus heavy flint material lens with positive optical power, and a heavy flint-heavy phosphorus crown material cemented lens with positive optical power.

[0011] Furthermore, the zoom group includes a meniscus lens, a biconvex lens, and a set of cemented lenses, which are a meniscus heavy flint material lens with positive optical power, a biconvex fluorite material lens with positive optical power, and a fluorite-flint cemented lens with positive optical power, respectively.

[0012] Furthermore, the compensation group includes one biconcave lens and two meniscus lenses, namely a meniscus heavy flint material lens with negative optical power, a meniscus heavy flint material lens with positive optical power, and a fluorite material lens with positive optical power.

[0013] Furthermore, the rear fixing assembly is a meniscus heavy phosphorus crown lens with positive optical power.

[0014] Furthermore, the filter group consists of 7 filters, which can be used in a time-division manner by rotating around the Z-axis; the wavelengths of the 7 filters are: 450nm~1000nm, 450nm~650nm, 780nm~1000nm, 810nm±10nm, 850nm±20nm, 880nm±10nm and polarizer.

[0015] Furthermore, the folding mirror is made of quartz.

[0016] Furthermore, the visible light optical system operates in the 450–850 nm wavelength range, while the low-light optical system operates in the 520 nm–1000 nm wavelength range. The visible light optical system is compatible with a 1920×1080 resolution detector with 4.5 μm × 4.5 μm pixels, and offers four focal length / F-stop variations: 600 mm / F3.33, 1200 mm / F6.67, 1900 mm / F10.6, and 3200 mm / F17.8. The low-light optical system is compatible with a 1280×720 resolution detector with 4.5 μm × 4.5 μm pixels, and offers four focal length / F-stop variations: 600 mm / F3.33, 1200 mm / F6.67, 1900 mm / F10.6, and 3200 mm / F17.8.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0018] The catadioptric combined long focal length multi-range zoom optical system of the present invention comprises two parts: a visible light optical system and a low-light optical system. The two share an imaging optical system, and time-division imaging of the two is achieved by rotating a mirror in front of the visible light detector and the low-light detector. The imaging channel adopts a secondary imaging and post-group zoom structure, which greatly compresses the light aperture through a reflective objective lens group. After the first image point, a small-aperture refractive lens is used for zooming. Compared with conventional transmissive front-group zoom long focal length large-aperture optical systems, the optical system of the present invention achieves the design of an ultra-long focal length large-aperture zoom optical system in a very small space, greatly reducing the size and weight of the optical system. Attached Figure Description

[0019] Figure 1 is a schematic diagram of the optical system according to an embodiment of the present invention;

[0020] Figure 2 is a transfer function diagram of the optical system according to an embodiment of the present invention;

[0021] Figure 3 is a diffusion pattern of the optical system according to an embodiment of the present invention.

[0022] In the diagram: 1-Reflective objective lens group, 11-Cassette primary mirror, 12-Cassette secondary mirror, 2-Eyepiece group, 21-First meniscus lens, 22-Second meniscus lens, 23-First cemented lens, 3-Magnification group, 31-Third meniscus lens, 32-Biconvex lens, 33-Second cemented lens, 4-Compensation group, 41-Biconcave lens, 42-Fourth meniscus lens, 43-Fifth meniscus lens, 5-Rear fixed group, 6-Folding mirror, 7-Filter group, 8-Rotating mirror, 9-Detector. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] This invention provides a catadioptric combined long focal length multi-zoom visible / low light optical system. The system consists of two parts: a visible light optical system and a low light optical system, both sharing an imaging optical system. Time-division imaging of the two detectors is achieved through rotating mirrors in front of them. The imaging channel employs a secondary imaging post-group zoom structure. The primary objective lens is a Casio reflector system, rapidly compressing the large-aperture beam. In the secondary imaging post-group, a small-aperture zoom group and a compensation group lens move along the optical axis to achieve zoom, reducing the system's size and weight. This allows for the design of an ultra-long focal length optical system within a very small space, with overall dimensions ≤384mm×194mm×201mm (length×width×height) and a weight of less than 6.5kg.

[0025] The catadioptric combined long focal length multi-range zoom visible light / low light optical system of the present invention, as shown in Figures 1 and 2, includes, from the object side to the image side, a reflective objective lens group 1, an eyepiece group 2, a zoom group 3, a compensation group 4, a rear fixation group 5, a folding mirror 6, a filter group 7, a rotating mirror 8, and a detector 9.

[0026] The reflective objective lens group 1, eyepiece group 2, zoom group 3, compensation group 4, rear fixation group 5, folding mirror 6, filter group 7, and rotating mirror 8 are shared by the visible light and low-light optical systems. Switching between the visible light and low-light optical systems is achieved by rotating the rotating mirror 8 90° around the Y-axis. The visible light optical system operates in the wavelength range of 450–850 nm, while the low-light optical system operates in the wavelength range of 520 nm–1000 nm. Therefore, the optical system of this invention corrects aberrations within the 450 nm–1000 nm wavelength range.

[0027] The catadioptric combined long-focal-length multi-zoom optical system employs a secondary imaging structure. It significantly compresses the light aperture through a reflective objective lens group 1, and then uses a small-aperture refractive lens for zooming after the first image point. The visible light optical system is adapted to a 1920×1080 resolution detector with a pixel size of 4.5μm×4.5μm, offering four focal length / F-stop variations: 600mm / F3.33, 1200mm / F6.67, 1900mm / F10.6, and 3200mm / F17.8. The low-light optical system is adapted to a 1280×720 resolution detector with a pixel size of 4.5μm×4.5μm, also offering four focal length / F-stop variations: 600mm / F3.33, 1200mm / F6.67, 1900mm / F10.6, and 3200mm / F17.8.

[0028] The reflecting objective lens assembly consists of a Casio primary mirror 11 and a Casio secondary mirror 12, with a focal length of 474.6 mm. The optical system aperture is located at the Casio secondary mirror. The Casio primary mirror 11 is parabolic, and the Casio secondary mirror 12 is hyperboloid. After combination, the on-axis RMS surface shape error is better than 1 / 40λ (λ=632.8nm), and they are individually adjusted using an interferometer. The Casio primary mirror is fixed using a back-center support mounting method. Compared with the side wall support of the mirror chamber, the advantages of the back-center support are that the mirror is less affected by temperature changes and external forces, and the overall size is reduced; it also improves the accuracy of the cylinder shaft fit during the installation of the central spindle, thereby improving the initial installation accuracy of the primary and secondary mirrors and reducing the workload of assembly and adjustment.

[0029] Eyepiece group 2 consists of a first meniscus lens 21, a second meniscus lens 22, and a first cemented lens 23, with a focal length of 74.56 mm. The zoom group consists of a third meniscus lens 31, a biconvex lens 32, and a second cemented lens 33, with a focal length of 40.4 mm and a zoom travel of 76.16 mm. Compensation group 4 consists of a biconcave lens 41, a fourth meniscus lens 42, and a fifth meniscus lens 43, with a focal length of -355.12 mm and a zoom travel of 75.33 mm. The rear fixed group 5 is a single lens with a focal length of 166.53 mm. The filter group 7 consists of seven filters, with the following working wavelengths: 450nm~1000nm, 450nm~650nm, 780nm~1000nm, 810nm±10nm, 850nm±20nm, 880nm±10nm, and a polarizer. Custom filters can be replaced according to different working conditions.

[0030] Specifically, the catadioptric combined long focal length multi-range zoom visible light / low light optical system of this embodiment consists of, from the object side to the image side, a reflective objective lens group 1, an eyepiece group 2, a zoom group 3, a compensation group 4, a rear fixed group 5, a folding mirror 6, a filter group 7, a rotating mirror 8, and a detector 9. Figure 1(a) is a structural diagram of the visible light optical system, and Figure 1(b) is a structural diagram of the low light optical system.

[0031] The system comprises a shared group for both the visible light and low-light optical systems, consisting of a reflective objective lens group 1, an eyepiece group 2, a zoom group 3, a compensation group 4, a rear fixed group 5, a folding mirror 6, a filter group 7, and a rotating mirror 8. Switching between the two systems can be achieved within 1 second by rotating the rotating mirror 8 90° around the Y-axis. The visible light optical system operates in the 450–850 nm wavelength range, while the low-light optical system operates in the 520 nm–1000 nm wavelength range. Therefore, the optical system corrects aberrations within the 450 nm–1000 nm wavelength range, and the optical system's aperture stop is located at the secondary mirror of the Casio mirror.

[0032] The visible light optical system is compatible with a 1920×1080 resolution detector with 4.5μm×4.5μm pixels, and offers four focal length / F-stop variations: 600mm / F3.33, 1200mm / F6.67, 1900mm / F10.6, and 3200mm / F17.8. The low-light optical system is compatible with a 1280×720 resolution detector with 4.5μm×4.5μm pixels, and offers four focal length / F-stop variations: 600mm / F3.33, 1200mm / F6.67, 1900mm / F10.6, and 3200mm / F17.8.

[0033] The reflecting objective lens group 1 consists of a Casio primary mirror 11 and a Casio secondary mirror 12, with a focal length of 474.6 mm. The Casio primary mirror is parabolic, and the Casio secondary mirror is hyperboloid. After combination, the on-axis RMS surface shape error is better than 1 / 40λ (λ=632.8nm), and they are individually assembled and adjusted using an interferometer. The Casio primary mirror is fixed by a back-center support. Compared with the side wall support of the mirror chamber, the back-center support has the advantages of being less affected by temperature changes and external forces, and reducing the overall size; it also improves the accuracy of the cylinder shaft fit during the installation of the central spindle, thereby improving the initial installation accuracy of the primary and secondary mirrors and reducing the workload of assembly and adjustment.

[0034] The eyepiece group 2 has a combined focal length of 74.56 mm and consists of two meniscus lenses and a set of cemented lenses. These are a meniscus lanthanum-corona material lens with negative optical power, a meniscus heavy flint material lens with positive optical power, and a heavy flint-heavy phosphorus-corona material cemented lens with positive optical power. The primary image point is located 2.75 mm in front of the eyepiece group.

[0035] The zoom group has a combined focal length of 40.4mm and consists of a meniscus lens, a biconvex lens, and a set of cemented lenses. These lenses are a meniscus heavy flint lens with positive optical power, a biconvex fluorite lens with positive optical power, and a fluorite-flint cemented lens with positive optical power. The zoom group has a travel distance of 76.16mm.

[0036] The compensation group 4 has a combined focal length of -355.12mm and consists of one biconcave lens and two meniscus lenses: a meniscus heavy flint lens with negative optical power, a meniscus heavy flint lens with positive optical power, and a fluorite lens with positive optical power. The compensation group's travel distance is 75.33mm.

[0037] The rear fixed group 5 has a focal length of 166.53mm and is a meniscus heavy phosphorus crown lens with positive optical power.

[0038] The folding mirror 6 is made of quartz, with its normal at a 45° angle to the optical axis. Its main function is to fold the light path and increase space utilization.

[0039] The 7 filter bands are: 450nm~1000nm, 450nm~650nm, 780nm~1000nm, 810nm±10nm, 850nm±20nm, 880nm±10nm and polarizer. Custom filters can be replaced according to different working conditions.

[0040] The rotating mirror 8 rotates around the Y-axis at a rotation angle of 90°, enabling time-division imaging of the visible light optical system and the low-light optical system.

[0041] The specific design parameters of the optical system in this embodiment are shown in Table 1, and Table 2 is a table of transfer function values ​​for the dual-channel mid-wave infrared optical system in this embodiment.

[0042] Table 1. Design parameters of the refracting-reflection combined long focal length multi-zoom optical system in specific embodiments.

[0043]

[0044]

[0045]

[0046] Table 2 Transfer function values ​​of the dual-channel mid-wave infrared optical system in specific embodiments.

[0047]

[0048] In Tables 1 and 2, radius of curvature refers to the radius of curvature of each lens surface, thickness or spacing refers to the lens thickness or the distance between adjacent lens surfaces, material refers to the material used in the lens, and air refers to the medium between two lenses being air.

[0049] Figures 2 and 3 are optical simulation data diagrams of the optical system in this embodiment. Figure 2(a) shows the transfer function curve of the short-focus optical system (600mm) at 100 lp / mm, Figure 2(b) shows the transfer function curve of the medium-focus optical system (1200mm) at 100 lp / mm, Figure 2(c) shows the transfer function curve of the long-focus optical system (1900mm) at 50 lp / mm, and Figure 2(d) shows the transfer function curve of the super-long-focus optical system (3200mm) at 30 lp / mm. The horizontal axis represents the number of line pairs per millimeter, and the vertical axis represents the contrast value. Figure 3(a) shows the blur pattern of the short-focus optical system (600mm) of this invention, Figure 3(b) shows the blur pattern of the medium-focus optical system (1200mm) of this invention, Figure 3(c) shows the blur pattern of the long-focus optical system (1900mm) of this invention, and Figure 3(d) shows the blur pattern of the super-long-focus optical system (3200mm) of this invention.

[0050] In summary, this invention belongs to the field of optical technology and relates to a catadioptric combined long focal length multi-zoom visible light / low light optical system. The catadioptric combined long focal length multi-zoom visible light / low light optical system consists of, from object side to image side, a reflective objective lens group, an eyepiece group, a zoom group, a compensation group, a rear fixation group, a folding mirror, a filter group, a rotating mirror, and a detector. The reflective objective lens group, eyepiece group, zoom group, compensation group, rear fixation group, folding mirror, filter group, and rotating mirror are shared by both the visible light and low light optical systems. Switching between the visible light and low light optical systems is achieved by rotating the rotating mirror 90° around the Y-axis. The visible light optical system is adapted to a 1920×1080 resolution detector with 4.5μm×4.5μm pixels, offering four focal length / F-stop variations: 600mm / F3.33, 1200mm / F6.67, 1900mm / F10.6, and 3200mm / F17.8. The low-light optical system is adapted to a 1280×720 resolution detector with 4.5μm×4.5μm pixels, also offering four focal length / F-stop variations: 600mm / F3.33, 1200mm / F6.67, 1900mm / F10.6, and 3200mm / F17.8. The filter assembly consists of seven filters that rotate around the Z-axis, enabling time-division multiplexing of the filters.

[0051] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0052] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A catadioptric long focal length multi- range zoom visible and low light level optical system, characterized in that, From object side to image side, the components are as follows: reflective objective lens group, eyepiece group, zoom group, compensation group, rear fixation group, folding mirror, filter group, rotating mirror, and detector. Among them, the reflective objective lens group, eyepiece group, zoom group, compensation group, rear fixation group, folding mirror, filter group, and rotating mirror are shared by the visible light optical system and the low light optical system; the reflective objective lens group, eyepiece group, zoom group, compensation group, and rear fixation group are set along the Z-axis, the folding mirror is at a 45° angle to the Z-axis, and the rotating mirror is at a 45° angle to the Z-axis and is opposite to the folding mirror. Time-division imaging of the visible light optical system and the low light optical system is achieved by rotating the rotating mirror 90° around the Y-axis; The reflective objective lens group includes a Casio primary mirror and a Casio secondary mirror. The eyepiece group is located between the Casio primary mirror and the Casio secondary mirror, and the primary image point is located in front of the eyepiece group. The imaging channel adopts a zoom structure after secondary imaging. The light aperture is greatly compressed by the reflective objective lens group. In the secondary imaging group, the zoom is achieved by moving the small-aperture zoom group and the compensation group lens along the optical axis, thereby reducing the size and weight. The eyepiece assembly consists of two meniscus lenses and a set of cemented lenses, namely a meniscus lanthanum crown material lens with negative optical power, a meniscus heavy flint material lens with positive optical power, and a heavy flint-heavy phosphorus crown material cemented lens with positive optical power. The zoom group includes a meniscus lens, a biconvex lens, and a set of cemented lenses, which are a meniscus heavy flint material lens with positive optical power, a biconvex fluorite material lens with positive optical power, and a fluorite-flint cemented lens with positive optical power, respectively. The compensation group consists of one biconcave lens and two meniscus lenses, namely a meniscus heavy flint material lens with negative optical power, a meniscus heavy flint material lens with positive optical power, and a fluorite material lens with positive optical power. The rear fixed assembly is a meniscus heavy phosphorus crown lens with positive optical power.

2. The catadioptric long-FL multi-FL-zoom VIS and SWIR optical system of claim 1, wherein, The primary mirror of the Casio mirror is a parabolic surface, and the secondary mirror is a hyperboloid.

3. The catadioptric long-FL multi-FL-zoom VIS and SWIR optical system of claim 2, wherein, The primary mirror of the cassette reflector is fixed using a central support mounting method on the back.

4. The telephoto and reflective combined long focal length multi-zoom visible light and low light optical system according to claim 1, characterized in that, The filter group consists of 7 filters, which can be used in a time-division manner by rotating around the Z-axis; the 7 filter bands are: 450nm~1000nm, 450nm~650nm, 780nm~1000nm, 810nm±10nm, 850nm±20nm, 880nm±10nm and polarizer.

5. The telephoto and low-light optical system with multiple zoom ranges and telephoto lenses according to claim 1, characterized in that, The folding mirror is made of quartz.

6. The telephoto and reflective combined long focal length multi-zoom visible light and low light optical system according to claim 1, characterized in that, The visible light optical system operates in the 450–850 nm wavelength range, while the low-light optical system operates in the 520 nm–1000 nm wavelength range. The visible light optical system is compatible with a 1920×1080 resolution detector with 4.5 μm × 4.5 μm pixels, and offers four focal length / F-stop options: 600 mm / F3.33, 1200 mm / F6.67, 1900 mm / F10.6, and 3200 mm / F17.

8. The low-light optical system is compatible with a 1280×720 resolution detector with 4.5 μm × 4.5 μm pixels, and offers four focal length / F-stop options: 600 mm / F3.33, 1200 mm / F6.67, 1900 mm / F10.6, and 3200 mm / F17.8.

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