A super large field of view dual-band aperture multiplexing optical remote sensing camera

Abstract

The present application relates to a kind of super large field of view dual-band aperture multiplexing type optical remote sensing camera, belong to optical remote sensing technical field.The optical remote sensing camera of the present application includes the visible light optical system and infrared optical system of common main mirror and secondary mirror;Visible light optical system includes in optical path direction: main mirror, secondary mirror, visible light three mirrors, fold mirror and visible light focal plane;Infrared optical system includes in optical path direction: main mirror, secondary mirror, infrared three mirrors and infrared focal plane.The super large field of view dual-band aperture multiplexing type optical remote sensing camera of the present application can realize all-weather ground reconnaissance and surveying and mapping;The main mirror of the visible light optical system and infrared optical system of the present application, secondary mirror can be multiplexed, and the focal length of double system is different, the field of view of visible light optical system and infrared optical system can be realized 20 above, and the form of total reflection guarantees the super high energy utilization rate of system, especially suitable as wide area detection, small volume, multi-spectral integrated micro-nano satellite high-resolution camera.

Description

Technical Field

[0001] This invention relates to the field of optical remote sensing technology, specifically to an ultra-large field-of-view dual-band aperture multiplex optical remote sensing camera. Background Technology

[0002] As people continue to explore the field of space remote sensing, there are increasingly higher requirements for the observation targets, such as higher spatial resolution, wider swath, and all-weather observation. The specifications and performance of space optical cameras are developing towards longer focal lengths, larger fields of view, and wider spectral ranges based on existing components. Visible light optical cameras can achieve high-resolution imaging, while infrared optical cameras can achieve all-weather observation and high-temperature early warning, among other multi-functional detection capabilities. Traditional integrated visible and infrared cameras can be divided into two types according to their structure: coaxial reflector with a common aperture and off-axis reflector with a common aperture. Commonly used band-splitting methods include dichroic mirror dichroism or field-of-view splitting, but neither can simultaneously achieve dual-band ultra-large field-of-view high-resolution imaging.

[0003] Currently, many scholars have conducted research and design on dual-band optical cameras. To achieve high resolution, the focal length of visible light systems is generally greater than 1000mm, and the field of view is also developing in the opposite direction to wider-area detection. At the same time, while ensuring high resolution and a large field of view, there are also strict limitations on the camera's envelope size. This requires achieving a compact layout or even reuse design of the optical or structural components of the visible and infrared systems within a limited space to meet the system envelope size requirements.

[0004] Traditional telephoto integrated cameras mainly come in two forms: coaxial reflection and off-axis reflection. Coaxial reflection limits the system's field of view, with the entire field of view not exceeding 2°. Most current off-axis reflection integrated camera systems use dichroism to achieve two different wavelength systems. Existing off-axis integrated camera system designs fall into the following categories: 1) Systems with identical visible and infrared imaging parameters: The primary and secondary mirrors share a single imaging process. After light is emitted through the secondary mirror, it is split by a dichroic mirror, and then two third-lens systems are used for a second imaging process. However, the system has the same focal length and resolution, making it unsuitable for systems with different performance indicators for visible and infrared systems; 2) Systems with different visible and infrared imaging parameters: The primary and secondary mirrors share a single imaging process. After light is emitted through the secondary mirror, it is split by a dichroic mirror. Then, visible light is reflected by off-axis three-lens systems to the visible focal plane, and infrared light is reflected by an infrared correction lens group (a combination of reflection and transmission or a transmission lens group) to the infrared focal plane. However, the field of view of these two types of off-axis reflection integrated camera systems currently does not exceed 10°.

[0005] In summary, ultra-wide field-of-view visible light optical cameras or ultra-wide field-of-view infrared optical cameras are quite common at present. However, ultra-wide field-of-view integrated imaging optical cameras in the visible light and infrared spectrum are relatively rare in research and application. Existing coaxial integrated camera systems can achieve a field of view of 2°, while off-axis reflective integrated camera systems can achieve a maximum field of view of 6°. First, dichroic mirrors are used to separate the visible and infrared spectrums, and then systems for different wavelength ranges are designed. The cost of this is that the optical components used in the design process include reflective and transmissive elements, resulting in a large number of optical components, which is not conducive to the stability and lightweight design of the system. Summary of the Invention

[0006] This invention aims to solve the technical problems of existing long-focal-length integrated cameras, such as small field of view, poor stability, and failure to meet the requirements of lightweight and miniaturized design, and provides an ultra-large field of view dual-band aperture multiplex optical remote sensing camera.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] A dual-band aperture multiplexed optical remote sensing camera with an ultra-large field of view adopts an off-axis reflection form and includes a visible light optical system and an infrared optical system;

[0009] The visible light optical system and the infrared optical system share the primary mirror and the secondary mirror;

[0010] A visible light optical system includes, in the direction of the optical path: a primary mirror, a secondary mirror, three visible light mirrors, a folding mirror, and a visible light focal plane;

[0011] Visible light rays are reflected sequentially by the upper half of the primary mirror and the secondary mirror, and then by the three visible light mirrors and the folding mirror before finally reaching the visible light focal plane, thus achieving visible light imaging.

[0012] An infrared optical system includes, in the direction of the optical path: a primary mirror, a secondary mirror, three infrared mirrors, and an infrared focal plane;

[0013] Infrared light is reflected sequentially by the lower half of the primary mirror and secondary mirror, and then by the infrared three mirrors before finally reaching the infrared focal plane, thus achieving infrared imaging.

[0014] In the above technical solution, the primary mirror, secondary mirror, visible light mirror, and infrared mirror are all aspherical mirrors.

[0015] In the above technical solution, the secondary mirror is the aperture of an optical remote sensing camera, and the primary mirror, the visible light mirror, and the infrared mirror are all elongated aspherical reflectors.

[0016] In the above technical solution, the radius of curvature of the primary mirror is -1819.53 mm, the radius of curvature of the secondary mirror is -599.3 mm, the radius of curvature of the visible light three mirrors is -1028.02 mm, the radius of curvature of the folding mirror is a plane reflecting mirror, and the radius of curvature of the infrared three mirrors is -635.44 mm.

[0017] In the above technical solution, the mirror spacing between the primary mirror and the secondary mirror is 491 mm, the mirror spacing between the secondary mirror and the visible light three mirrors is 499.7 mm, the mirror spacing between the visible light three mirrors and the folding mirror is 272.2 mm, the mirror spacing between the folding mirror and the visible light focal plane is 434.52 mm, the mirror spacing between the secondary mirror and the infrared three mirrors is 402.4 mm, and the mirror spacing between the infrared three mirrors and the infrared focal plane is 472.6 mm.

[0018] In the above technical solution, the reflective surfaces of the primary mirror, secondary mirror, visible light mirror, folding mirror, and infrared mirror are all coated with a reflective film with a reflectivity higher than 98%.

[0019] In the above technical solution, the reflective surfaces of the primary mirror, secondary mirror, visible light mirror, folding mirror, and infrared mirror are all coated with a silver reflective film with a reflectivity higher than 98%.

[0020] In the above technical solution, the field of view of the visible light optical system is 20° or more, and the field of view of the infrared optical system is 20° or more.

[0021] The beneficial effects of this invention are:

[0022] The ultra-large field-of-view dual-band aperture multiplexing optical remote sensing camera of the present invention is a long focal length optical system with ultra-large field of view, small size, long focal length, large visible focal plane, large infrared focal plane, multiplexing of primary and secondary mirrors, integration of visible light and infrared, and unobstructed operation. If a conventional separate design is adopted, the system consists of 2 primary mirrors, 2 secondary mirrors, and 2 tertiary mirrors, which is difficult to achieve a compact layout in terms of space. However, by adopting the aperture multiplexing design of the present invention, that is, the primary mirror element and the secondary mirror element are reused in the system, compared with the traditional two independent cameras, the integrated camera only contains one primary mirror element and one secondary mirror element, with only one additional tertiary mirror reflector element. The corresponding structural system can adopt 1 primary mirror support assembly, 1 secondary mirror support assembly, and 2 tertiary mirror support assemblies, which not only reduces the size of the system, but also achieves the purpose of lightweighting.

[0023] Compared with traditional telephoto integrated cameras, the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of this invention has the ability to image with an ultra-large field of view. The visible light optical system and the infrared optical system have different focal lengths. The system does not use transmission components. All reflective surfaces of each mirror are coated with high-reflectivity films. The optical system does not introduce chromatic aberration. The number of optical components in the optical system is extremely small, thereby reducing the difficulty of system assembly and adjustment, and effectively improving the high reflectivity and signal-to-noise ratio of the imaging system. It is especially suitable as a high-resolution optical camera for small-volume, large-field-of-view, multi-spectral visible-infrared integrated micro-nano satellites.

[0024] The ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of this invention can realize all-weather earth reconnaissance and mapping. The primary and secondary mirrors of the visible light optical system and the infrared optical system can be reused, and the focal lengths of the two systems are different. The field of view of both the visible light optical system and the infrared optical system can reach more than 20°. The total internal reflection form ensures the ultra-high energy utilization rate of the system, making it particularly suitable as a high-resolution camera for wide-area detection, small size, multi-spectral integrated micro-nano satellites. Attached Figure Description

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1 This is a schematic diagram of the structure of the ultra-large field-of-view dual-band aperture multiplex optical remote sensing camera of the present invention.

[0027] Figure 2 This is a schematic diagram of the visible light optical system structure in the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of the present invention.

[0028] Figure 3 for Figure 2 The transfer function curve of a visible light optical system.

[0029] Figure 4 for Figure 2 Field curvature and distortion curves of a visible light optical system.

[0030] Figure 5 for Figure 2 A dot diagram of a visible light optical system.

[0031] Figure 6 This is a schematic diagram of the mid-infrared optical system structure of the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of the present invention.

[0032] Figure 7 for Figure 6 The transfer function curve of the infrared optical system.

[0033] Figure 8 for Figure 6Field curvature and distortion curves of an infrared optical system.

[0034] Figure 9 for Figure 6 A dot diagram of an infrared optical system.

[0035] Figure 10 This is a basic layout diagram of a coaxial three-reflector system.

[0036] The reference numerals in the figure are:

[0037] 1-Primary lens, 2-Secondary lens;

[0038] 3-Visible light three-lens system, 4-Folding mirror, 5-Visible light focal plane;

[0039] 6-Infrared three-lens, 7-Infrared focal plane. Detailed Implementation

[0040] The inventive concept of this invention is based on the urgent need for miniaturization of aerospace optical remote sensors. The purpose of this invention is to provide a large field-of-view, compact, visible-infrared integrated optical remote sensing camera, which, compared to traditional visible-infrared optical cameras, combines a large field of view, high spatial resolution, and miniaturization. This invention's ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera includes a visible light optical system (i.e., a visible light camera) and an infrared optical system (i.e., an infrared camera). Both the visible light and infrared cameras have a field of view of 20°. To achieve the large field of view requirement, the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera adopts off-axis reflection. The primary and secondary mirrors of the visible light and infrared optical systems are shared. Infrared light uses the lower half of the secondary mirror during imaging, while visible light uses the upper half. The light is reflected by the secondary mirror onto the infrared and visible light mirrors, respectively, and finally reaches the image plane (visible light focal plane and infrared focal plane) through the three mirrors, simultaneously achieving ideal visible and infrared imaging.

[0041] The primary, secondary, and tertiary mirrors (visible and infrared) of the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera are all aspherical. First, a coaxial system is selected as the initial structure for calculation, along with its structural parameters. The curvature radius and inter-mirror spacing of each mirror are calculated. The curvature radius and inter-mirror spacing of the primary mirrors for both the visible and infrared cameras are calculated using the same solution. These calculated parameters are then input into the system as its initial coaxial structure. The off-axis angles of the incident rays for the visible and infrared optical systems are set separately. The system consists of two off-axis optical systems identical to the primary mirror. Finally, the system's optimal layout is achieved by adjusting the off-axis eccentricity along the Y-axis. Specifically:

[0042] The ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of the present invention is a visible and infrared integrated optical camera system. The field of view of the visible light optical system can reach more than 20°, and the field of view of the infrared optical system can reach more than 20°.

[0043] Before optimizing the system design, the structural parameters of the system are first calculated. The known parameters are the focal length and entrance pupil diameter of the system. Appropriate magnifications for the primary, secondary, and tertiary lenses are then selected. And the obstruction ratios of the primary, secondary, and tertiary lenses of the system. As parameters of the constraint system, the constraint relationship is as follows:

[0044] For the basic layout of the coaxial three-reflector system, please refer to Figure 10 ( Figure 10 In the diagram, M1-M3 represent the primary mirror, secondary mirror, and tertiary mirror, respectively.

[0045] ;

[0046] ;

[0047] ;

[0048] There is also the relationship between objects and images:

[0049] ;

[0050] In the above formula, and These represent the image distance and object distance for different mirrors, respectively. The formula represents the focal length of different mirrors. - Indicates the pupil diameter of different mirrors. The time represents the main mirror. The time represents the secondary mirror, The time represents three mirrors;

[0051] Furthermore, when calculating the initial structural parameters of the visible light optical system and the infrared optical system, it is necessary to ensure that... ,Right now ( and These are the radii of curvature of the primary mirrors in visible light optical systems and infrared optical systems, respectively. Based on the above formula, the focal length of the primary mirror can be obtained. Secondary lens focal length Three-lens focal length Primary and secondary mirror interval Secondary and tertiary mirror intervals .

[0052] After obtaining the parameters, the visible light optical system and the infrared optical system share a common principal mirror and a common vertex secondary mirror. First, the aperture stops (secondary mirrors) of the visible light optical system and the infrared optical system are set off-axis. Then, different off-axis angles of the central rays are set for the two systems. By setting different off-axis angles, the visible light three mirrors of the visible light optical system and the infrared three mirrors of the infrared optical system avoid occlusion and interference, thus initially realizing the compactness and reasonable layout of the system.

[0053] Based on this, the system is optimized by changing the system's radius of curvature, non-curved surface coefficient, and the spacing between each mirror to eliminate aberrations. The system is a total reflection system and has no chromatic aberration. Both the visible light optical system and the infrared optical system are large field-of-view long-focal-length optical systems, and distortion is controlled and constrained during the optimization process.

[0054] Through system adjustments and optimizations, visible light rays are reflected by the primary mirror, secondary mirror, visible light mirror, and folding mirror before converging onto the visible light focal plane, while infrared light rays are reflected by the primary mirror, secondary mirror, and infrared mirror before converging onto the infrared focal plane. This results in good imaging quality for both visible and infrared channels.

[0055] The present invention will now be described in detail with reference to the accompanying drawings.

[0056] like Figure 1 As shown in Figures 2 and 6, the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of the present invention adopts an off-axis reflection form, including a visible light optical system and an infrared optical system; the visible light optical system and the infrared optical system share a primary mirror 1 and a secondary mirror 2; the visible light optical system includes, in the optical path direction: primary mirror 1, secondary mirror 2, visible light three mirrors 3, folding mirror 4, and visible light focal plane 5; the visible light rays pass sequentially through the upper part of the primary mirror 1 and secondary mirror 2, the visible light three mirrors 3 and the folding mirror 4, and finally reach the visible light focal plane 5 to achieve visible light imaging; the secondary mirror 2 is the aperture stop of the optical remote sensing camera optical system, and the primary mirror 1 and the visible light three mirrors 3 are both elongated aspherical mirrors; the reflective surfaces of the primary mirror 1, secondary mirror 2, visible light three mirrors 3 and folding mirror 4 are all coated with a high reflectivity film. In this embodiment, the primary mirror 1, secondary mirror 2, visible light three mirrors 3 and folding mirror 4 are all coated with a silver reflective film with a reflectivity higher than 98%, thereby effectively improving the high reflectivity and signal-to-noise ratio of the imaging system. The infrared optical system includes, in the optical path direction: a primary mirror 1, a secondary mirror 2, an infrared triple mirror 6, and an infrared focal plane 7. Infrared light passes sequentially through the primary mirror 1, the lower half of the secondary mirror 2, and is reflected by the infrared triple mirror 6 before finally reaching the infrared focal plane 7, thus achieving infrared imaging. The secondary mirror 2 is the aperture stop of the optical remote sensing camera system, and the infrared triple mirror 6 is a long strip-shaped aspherical reflector. The reflective surface of the infrared triple mirror 6 is coated with a high-reflectivity film. In this embodiment, the infrared triple mirror 6 is coated with a silver reflective film with a reflectivity higher than 98%, thereby effectively improving the high reflectivity and signal-to-noise ratio of the imaging system.

[0057] The primary mirror 1 has a radius of curvature of -1819.53 mm, the secondary mirror 2 has a radius of curvature of -599.3 mm, the visible light three-mirror 3 has a radius of curvature of -1028.02 mm, the folding mirror 4 is a plane mirror, and the infrared three-mirror 6 has a radius of curvature of -635.44 mm.

[0058] The mirror spacing between the primary mirror 1 and the secondary mirror 2 is 491 mm, the mirror spacing between the secondary mirror 2 and the visible light three-lens 3 is 499.7 mm, the mirror spacing between the visible light three-lens 3 and the folding mirror 4 is 272.2 mm, the mirror spacing between the folding mirror 4 and the visible light focal plane 5 is 434.52 mm, the mirror spacing between the secondary mirror 2 and the infrared three-lens 6 is 402.4 mm, and the mirror spacing between the infrared three-lens 6 and the infrared focal plane 7 is 472.6 mm.

[0059] Figure 3 This is a transfer function curve of the visible light optical system of the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of the present invention. In the figure, OTF on the vertical axis refers to the optical transfer function. As can be seen from the figure, each field of view includes the modulation transfer function curve of the meridional ray and the modulation transfer function curve of the sagittal ray. The unit is the field of view angle. The figure contains modulation transfer function curves under 9 field of view angles, and the average transfer function of each field of view is better than 0.35.

[0060] Figure 4 The figure shows the field curvature and distortion curves of the visible light optical system of the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of the present invention. As can be seen from the figure, the distortion of the visible light optical system is less than 0.7% across the entire field of view.

[0061] Figure 5 This is a dot plot of the visible light optical system of the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of the present invention. The dot plot shows the positions of the nine incident beam fields of view, and RMS represents the root mean square radius of the dot plot.

[0062] Figure 7 This is a transfer function curve of the infrared optical system of the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of the present invention. In the figure, OTF on the vertical axis refers to the optical transfer function. As can be seen from the figure, each field of view includes the modulation transfer function curve of the meridional ray and the modulation transfer function curve of the sagittal ray. The unit is the field of view angle. The figure contains modulation transfer function curves under 7 field of view angles. At line 33, the average transfer function of each field of view design is better than 0.5.

[0063] Figure 8 The figure shows the field curvature and distortion curves of the infrared optical system of the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of the present invention. As can be seen from the figure, the distortion of the infrared optical system is less than 0.5% across the entire field of view.

[0064] Figure 9 This is a dot plot of the infrared optical system of the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of the present invention. The dot plot shows the positions of the nine incident beam fields of view, and RMS represents the root mean square radius of the dot plot.

[0065] Simulation results show that the optical system of the ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera of the present invention is practical and effective.

[0066] In summary, this invention provides an ultra-large field-of-view dual-band aperture multiplexed optical remote sensing camera. It is a long-focal-length optical system with ultra-large field of view, long focal length, small size, integration of visible and infrared light, reuse of both primary and secondary mirrors, and unobstructed operation, enabling all-weather Earth reconnaissance and mapping. The visible light and infrared optical systems of this invention both have reusable primary and secondary mirrors, and the two systems have different focal lengths. Both the visible light and infrared optical systems have a 20° field of view, and the total internal reflection ensures extremely high energy efficiency, making it particularly suitable as a high-resolution camera for wide-area detection, small size, and multi-spectral integrated micro / nano satellites.

[0067] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A dual-band aperture multiplexing optical remote sensing camera with an ultra-large field of view, characterized in that, It employs off-axis reflection, including a visible light optical system and an infrared optical system; The visible light optical system and the infrared optical system share the primary mirror (1) and the secondary mirror (2); The visible light optical system includes, in the direction of the optical path: primary mirror (1), secondary mirror (2), visible light three mirrors (3), folding mirror (4), and visible light focal plane (5); Visible light rays are reflected sequentially by the upper half of the primary mirror (1) and secondary mirror (2), and then by the visible light three mirrors (3) and the folding mirror (4) before finally reaching the visible light focal plane (5), thus realizing visible light imaging. The infrared optical system includes, in the direction of the optical path: primary mirror (1), secondary mirror (2), infrared three mirrors (6) and infrared focal plane (7); Infrared light is reflected sequentially by the lower half of the primary mirror (1) and secondary mirror (2), and then by the infrared three-mirror (6) before finally reaching the infrared focal plane (7), thus achieving infrared imaging.

2. The ultra-large field-of-view dual-band aperture multiplexing optical remote sensing camera according to claim 1, characterized in that, The primary mirror (1), secondary mirror (2), visible light three mirrors (3) and infrared three mirrors (6) are all aspherical mirrors.

3. The ultra-large field-of-view dual-band aperture multiplexing optical remote sensing camera according to claim 1, characterized in that, The secondary mirror (2) is the aperture of the optical remote sensing camera, and the primary mirror (1), the visible light three mirrors (3) and the infrared three mirrors (6) are all elongated aspherical reflectors.

4. The ultra-large field-of-view dual-band aperture multiplexing optical remote sensing camera according to claim 1, characterized in that, The primary mirror (1) has a radius of curvature of -1819.53 mm, the secondary mirror (2) has a radius of curvature of -599.3 mm, the visible light three-mirror (3) has a radius of curvature of -1028.02 mm, the folding mirror (4) is a plane mirror, and the infrared three-mirror (6) has a radius of curvature of -635.44 mm.

5. The ultra-large field-of-view dual-band aperture multiplexing optical remote sensing camera according to claim 1, characterized in that, The mirror spacing between the primary mirror (1) and the secondary mirror (2) is 491 mm, the mirror spacing between the secondary mirror (2) and the visible light three-lens (3) is 499.7 mm, the mirror spacing between the visible light three-lens (3) and the folding mirror (4) is 272.2 mm, the mirror spacing between the folding mirror (4) and the visible light focal plane (5) is 434.52 mm, the mirror spacing between the secondary mirror (2) and the infrared three-lens (6) is 402.3 mm, and the mirror spacing between the infrared three-lens (6) and the infrared focal plane (7) is 472.6 mm.

6. The ultra-large field-of-view dual-band aperture multiplexing optical remote sensing camera according to claim 1, characterized in that, The reflective surfaces of the primary mirror (1), secondary mirror (2), visible light three mirrors (3), folding mirror (4) and infrared three mirrors (6) are all coated with a reflective film with a reflectivity higher than 98%.

7. The ultra-large field-of-view dual-band aperture multiplexing optical remote sensing camera according to claim 6, characterized in that, The reflective surfaces of the primary mirror (1), secondary mirror (2), visible light three mirrors (3), folding mirror (4) and infrared three mirrors (6) are all coated with a silver reflective film with a reflectivity higher than 98%.

8. The ultra-large field-of-view dual-band aperture multiplexing optical remote sensing camera according to claim 1, characterized in that, The visible light optical system has a field of view of 20° or more, and the infrared optical system has a field of view of 20° or more.

Images