Primary and secondary mirror shared combined full-color and hyperspectral imaging lens

Abstract

The application discloses a primary and secondary mirror shared combined full-color and hyperspectral imaging lens, which comprises a primary and secondary mirror telescope group, a field separation mirror and a three-reflection aberration correction mirror group. The primary and secondary mirror telescope group is used for receiving target light and converging to the vicinity of the field separation mirror. The field separation mirror is used for turning over the light converged by the primary and secondary mirror telescope group and separating the light into a full-color field and a hyperspectral field. The application constructs a front end light collecting telescope system by using a coaxial two-mirror structure similar to R-C, corrects aberration by using an off-axis three-reflection system, and realizes the design of an imaging system with a large field of view and a small F number. The light path is turned over near the back focal point of the coaxial primary and secondary mirror to separate the field of view, and the off-axis three-reflection design is sequentially carried out for the full-color channel and the hyperspectral channel of different fields of view to realize multifunctional imaging. A plurality of turning mirrors are added in the off-axis three-reflection systems of the full-color and the hyperspectral to fold the light path, compact design is realized, and the system volume is reduced.

Description

Technical Field

[0001] This invention belongs to the field of spaceborne remote sensing observation technology, specifically relating to a combined panchromatic and hyperspectral imaging lens that uses both primary and secondary mirrors. Background Technology

[0002] In the field of aerospace remote sensing, panchromatic cameras and hyperspectral cameras are two important payloads with complementary functions but vastly different principles and applications. Panchromatic cameras offer a wide spectral band and high signal-to-noise ratio, enabling high spatial resolution. Hyperspectral cameras disperse incident light across hundreds of channels to form a three-dimensional data cube containing spectral information. This results in very limited light energy received by each channel, necessitating larger pixel sizes to achieve a good signal-to-noise ratio, but this also leads to a decrease in spatial resolution. In practical aerospace applications, panchromatic and hyperspectral cameras are often carried on the same satellite, working collaboratively. The panchromatic camera acquires high spatial resolution black-and-white images, while the hyperspectral camera acquires lower spatial resolution images rich in spectral information. Finally, advanced algorithms fuse the two images, generating a final image that simultaneously possesses high-resolution spatial detail and rich spectral dimensional information. With the development of science and technology and the needs of aerospace engineering applications, more and more researchers are attempting to design panchromatic and hyperspectral cameras into the same optical system. This approach offers several advantages. First, the satellite can acquire both types of data simultaneously in a single overhead pass, eliminating the need to manage two separate cameras and increasing image acquisition efficiency. Secondly, since panchromatic and hyperspectral data originate from the same optical system at the same time, their spatial registration accuracy is extremely high, making them ideal for image fusion. Finally, the integrated design facilitates reduced size and weight, lower costs, and further enables efficient utilization of satellite payload space and resources.

[0003] In terms of optical path structure, spaceborne telescope systems that pursue ultimate performance generally adopt an off-axis five-mirror configuration, which can achieve a large field of view and an extremely high resolution flat image plane. However, such systems with long focal lengths and high F-numbers often require a large volume of space and a lot of satellite platform resources. Moreover, the design, processing, and assembly are difficult and time-consuming. If you want to achieve multi-functional imaging in the same optical system, it is even more difficult. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a combined panchromatic and hyperspectral imaging lens that uses both primary and secondary mirrors, thereby solving several technical problems introduced by space telescopes to achieve multi-functional imaging, such as large size, complex optical and mechanical design, and high difficulty in assembly and adjustment.

[0005] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0006] A combined panchromatic and hyperspectral imaging lens for primary and secondary mirrors includes a primary and secondary mirror telescope group, a field-of-view separator, and a three-mirror aberration correction lens group.

[0007] The primary and secondary telescope group is used to receive target light and converge it onto the field-of-view separator.

[0008] The field-of-view separator is used to deflect the converged optical path of the primary and secondary telescope groups and separate them into a panchromatic field of view and a hyperspectral field of view.

[0009] The aberration correction lens group includes a panchromatic three-mirror group and a hyperspectral three-mirror group. The hyperspectral three-mirror group is used to receive light from the hyperspectral field of view and perform aberration correction, ultimately refracting and guiding it onto the hyperspectral image plane.

[0010] The panchromatic three-mirror group includes a first panchromatic mirror, a second panchromatic mirror, a third panchromatic mirror, a first panchromatic folding mirror, and a second panchromatic folding mirror.

[0011] The panchromatic first mirror, panchromatic second mirror, and panchromatic third mirror together form an off-axis three-mirror aberration correction system, which is used to correct the aberrations of the panchromatic field of view reflected by the panchromatic first mirror and reflect it onto the panchromatic image plane through the panchromatic second mirror.

[0012] Furthermore, the primary and secondary mirror telescope assembly includes a primary mirror and a secondary mirror. The primary mirror has a 10th-order even-order aspherical surface, while the secondary mirror has a hyperboloid surface. The primary and secondary mirrors form a coaxial RC telescope system.

[0013] Furthermore, the field-of-view separation mirror is a dual-plane reflector, which has two reflective surfaces placed at a fixed angle.

[0014] Furthermore, the hyperspectral three-mirror assembly includes a hyperspectral first mirror, a hyperspectral second mirror, a hyperspectral third mirror, and a hyperspectral deflector. The hyperspectral first mirror, the hyperspectral second mirror, and the hyperspectral third mirror form an off-axis three-mirror aberration correction system, used to correct aberrations in the hyperspectral field of view and reflect the light from the hyperspectral field of view onto the hyperspectral image plane via the hyperspectral deflector.

[0015] Furthermore, the surface shape of the first panchromatic reflecting mirror is an ellipsoid, the surface shape of the second panchromatic reflecting mirror is an 8th-order even-order aspherical surface, and the surface shape of the third reflecting mirror is a hyperboloid.

[0016] Furthermore, the first hyperspectral reflecting mirror is a hyperboloid, the second hyperspectral reflecting mirror is an 8th-order even-order aspherical surface, the third hyperspectral reflecting mirror is an ellipsoid, and the hyperspectral deflector is a plane reflecting mirror.

[0017] Furthermore, the maximum usable field of view of the lens formed by the primary and secondary telescope group, the field-of-view separator, and the three-mirror aberration-correcting lens group is 2.28°. The lens F-number is 3.2-3.42. The lens focal length is 1.43m-1.55m.

[0018] Furthermore, the optical path direction from the primary and secondary telescope group to the field-of-view separator is defined as the Z direction, and the direction from the field-of-view separator to the three-mirror aberration correction mirror group is defined as the Y direction. The Y direction is perpendicular to the Z direction. The direction perpendicular to both the Y and Z directions is defined as the X direction. The panchromatic three-mirror group performs aberration correction for the field of view in the Y direction off-axis range of 0.835°-0.855°, and the hyperspectral three-mirror group performs aberration correction for the field of view in the Y direction off-axis range of 0.47°-0.76°.

[0019] Furthermore, in the panchromatic field of view, the usable field of view along the X direction is 56 mm, and at the Nyquist frequency of 71 lp / mm, the full-field MTF is greater than 0.53, and the optical transfer function is close to the diffraction limit; in the hyperspectral field of view, the usable field of view along the X direction is 62 mm, and at the Nyquist frequency of 17 lp / mm, the full-field MTF is greater than 0.78, and the optical transfer function is close to the diffraction limit.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This invention constructs a front-end light-gathering telescope system using two coaxial mirrors similar to RC mirrors, and connects to an off-axis three-mirror system to correct aberrations, achieving a large field of view and a small F-number imaging system design. The optical path is deflected near the back focus of the coaxial primary and secondary mirrors to separate the field of view, and off-axis three-mirror designs are carried out for the panchromatic and hyperspectral channels of different fields of view to achieve multi-functional imaging. Multiple deflecting mirrors are added to the off-axis three-mirror systems of the panchromatic and hyperspectral channels to fold the optical path, achieving a compact design and reducing the system size. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0023] Figure 2 This is a schematic diagram of the optical path structure of the present invention;

[0024] Figure 3 This is a schematic diagram of the optical modulation function curve of the panchromatic image plane in this invention;

[0025] Figure 4 This is a schematic diagram of the optical modulation function curve of the hyperspectral image plane in this invention.

[0026] Figure reference numerals: 1. Primary mirror; 2. Secondary mirror; 3. Field separation mirror; 4-0. First panchromatic conversion mirror; 4-1. First panchromatic reflecting mirror; 4-2. Second panchromatic reflecting mirror; 4-3. Third panchromatic reflecting mirror; 4-4. Second panchromatic conversion mirror; 5-1. First hyperspectral reflecting mirror; 5-2. Second hyperspectral reflecting mirror; 5-3. Third hyperspectral reflecting mirror; 5-4. Hyperspectral conversion mirror. Detailed Implementation

[0027] In the description of this invention, it should be understood that the terms "one end", "the other end", "outer side", "upper side", "inner side", "horizontal", "coaxial", "center", "end", "length", "outer end", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0028] The invention will now be further described with reference to the accompanying drawings.

[0029] like Figure 1 and 2 As shown, a combined panchromatic and hyperspectral imaging lens, using both primary and secondary mirrors, is employed for panchromatic imaging, visible spectrum imaging, and short-wave infrared spectrum imaging. From the object plane to the image plane, it comprises a primary / secondary mirror 2 telescope group, a field-of-view separator 3, and a three-mirror aberration correction mirror group. The optical path from the primary / secondary mirror 2 telescope group to the field-of-view separator 3 is defined as the Z-direction, and the path from the field-of-view separator 3 to the three-mirror aberration correction mirror group is defined as the Y-direction. The Y-direction is perpendicular to the Z-direction. The direction perpendicular to both the Y and Z directions is defined as the X-direction.

[0030] The primary and secondary telescope group 2 receives light rays from different fields of view of the target and converges them near the field-of-view separator 3. The field-of-view separator 3 deflects the converged light path of the primary and secondary telescope group 2, separating it into a panchromatic field of view and a hyperspectral field of view. The three-reflector aberration correction mirror group is divided into a panchromatic imaging channel and a hyperspectral channel. The panchromatic and hyperspectral fields of view pass through the panchromatic imaging channel and the hyperspectral channel, respectively, and are ultimately imaged on the panchromatic image plane and the hyperspectral image plane, respectively.

[0031] Specifically, such as Figure 1 As shown, the primary and secondary mirror 2 telescope assembly includes a primary mirror 1 and a secondary mirror 2. The primary mirror 1 has a 10th-order even-order aspherical surface, while the secondary mirror 2 has a hyperboloid surface. The primary mirror 1 and secondary mirror 2 together form a coaxial RC telescope system capable of receiving target light rays and converging them to form an intermediate image plane.

[0032] The field-separating mirror 3 is a double-plane mirror, which has two planar reflecting surfaces with a fixed angle between them. The two reflecting surfaces are used to deflect the light path converged by the secondary mirror 2 and separate it into a panchromatic field of view and a hyperspectral field of view along the positive Y direction and the negative Y direction, respectively.

[0033] The three-mirror lens assembly includes a panchromatic mirror group and a hyperspectral mirror group. The panchromatic mirror group and the hyperspectral mirror group are used to receive light from the panchromatic field of view and the hyperspectral field of view, respectively, and to perform aberration correction processing, enabling the lens to acquire high spatial resolution panchromatic images and high spectral resolution spectral data images within a large field of view.

[0034] The panchromatic three-mirror assembly includes a first panchromatic mirror 4-1, a second panchromatic mirror 4-2, a third panchromatic mirror 4-3, a first panchromatic deflector 4-0, and a second panchromatic deflector 4-4. The first panchromatic mirror 4-1 has an ellipsoidal surface, the second panchromatic mirror 4-2 has an 8th-order even-order aspherical surface, and the third mirror has a hyperboloidal surface. Light rays from the panchromatic field of view are reflected by the first panchromatic deflector 4-0, the first panchromatic mirror 4-1, the second panchromatic mirror 4-2, the third panchromatic mirror 4-3, and the second panchromatic deflector 4-4 before reaching the panchromatic image plane.

[0035] In this embodiment, the panchromatic first mirror 4-1, the panchromatic second mirror 4-2, and the panchromatic third mirror 4-3 form an off-axis three-mirror aberration correction system, which performs aberration correction on a field of view within a fixed angle range along the Y direction, expands the usable field of view, and ultimately forms a high-resolution image plane along the X direction.

[0036] The hyperspectral three-mirror assembly includes a first hyperspectral mirror 5-1, a second hyperspectral mirror 5-2, a third hyperspectral mirror 5-3, and a hyperspectral deflector 5-4. Among them, the first hyperspectral mirror 5-1 is a hyperboloid, the second hyperspectral mirror 5-2 is an 8th-order even-order aspherical surface, and the third hyperspectral mirror 5-3 is an ellipsoid.

[0037] The hyperspectral first reflector 5-1, the hyperspectral second reflector 5-2, and the hyperspectral third reflector 5-3 form an off-axis three-reflector aberration correction system. This system corrects aberrations in the field of view within a fixed angular range along the Y direction, expands the usable field of view, and ultimately forms a hyperspectral image plane along the X direction.

[0038] In this embodiment, the hyperspectral deflector 5-4 is a plane mirror used to deflect the light path and bring out the hyperspectral image plane to a suitable position.

[0039] The general expression for the 10th-order even-order aspherical surface in this embodiment is shown in Equation 1:

[0040]

[0041] In the formula, z is the surface vector height, c is the surface curvature, r is the radial distance from a point on the surface to the optical axis, k is the quadratic surface coefficient, and α... i It is the coefficient of the i-th term in the polynomial; for an 8th-order even-degree aspherical surface, α 10 It is 0.

[0042] In this embodiment, the surface shape of the primary mirror reflecting surface satisfies:

[0043] α4 = -2.412E -13 α6 = 5.987E -18 α8 = -1.516E -22 α 10 =1.234E -27 .

[0044] The panchromatic second reflecting mirror type in this embodiment satisfies:

[0045] α4 = 1.059E -7 α6 = 7.805E -12 α8 = 4.611E -15 .

[0046] The hyperspectral second reflecting mirror type in this embodiment satisfies:

[0047] α4 = -1.464E -7 α6 = 1.546E -10 α8 = -1.624E -13 .

[0048] For the surface shape, radius of curvature (the reciprocal of curvature c), and specific values ​​of the quadratic surface coefficient k for all surfaces in this embodiment, please refer to Table 1. It can be understood that the radius of curvature, quadratic surface coefficient k, and various higher-order coefficients α of each mirror surface in this invention are not explicitly defined. i

[0049] The value is not limited to the examples given, and those skilled in the art can adjust it according to actual needs.

[0050]

[0051] See Figure 3 and Figure 4As shown, both the panchromatic and hyperspectral three-mirror groups perform aberration correction on the off-axis fixed-angle field of view after reflection and convergence by the primary and secondary mirrors, expanding the usable field of view angle along the X direction to 2.28°. Specifically, in the panchromatic field of view, the usable field of view along the X direction is 56 mm long, and at the Nyquist frequency of 71 lp / mm, the full-field MTF is greater than 0.53, with the optical transfer function approaching the diffraction limit. In the hyperspectral field of view, the usable field of view along the X direction is 62 mm long, and at the Nyquist frequency of 17 lp / mm, the full-field MTF is greater than 0.78, with the optical transfer function approaching the diffraction limit. Figure 3 , Figure 4 The images are schematic diagrams of the optical modulation function curves for the panchromatic image plane and the hyperspectral image plane, respectively.

[0052] The results demonstrate that the combined panchromatic and hyperspectral imaging lens for primary and secondary mirrors provided by this invention has an F-number of 3.2-3.42 and a focal length of 1.43m-1.55m. The panchromatic three-mirror group performs aberration correction for the field of view in the Y-direction off-axis range of 0.835°-0.855°, while the hyperspectral three-mirror group performs aberration correction for the field of view in the Y-direction off-axis range of 0.47°-0.76°.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A combined panchromatic and hyperspectral imaging lens for primary and secondary mirrors, comprising a primary and secondary mirror telescope group, a field-of-view separator, and a three-mirror aberration-correcting lens group, characterized in that: The primary and secondary telescope group is used to receive target light and converge it onto the field-of-view separator. The field-of-view separator is used to deflect the converged light rays from the primary and secondary telescope groups and separate them into a panchromatic field of view and a hyperspectral field of view. The field-of-view separation mirror is a double-plane mirror, which has two reflecting surfaces placed at a fixed angle. The three-mirror correction lens group includes a panchromatic three-mirror group and a hyperspectral three-mirror group; the hyperspectral three-mirror group is used to receive light from the hyperspectral field of view and perform aberration correction, and finally refract and guide it to the hyperspectral image plane. The panchromatic three-mirror group includes a first panchromatic mirror, a second panchromatic mirror, a third panchromatic mirror, a first panchromatic folding mirror, and a second panchromatic folding mirror; The panchromatic first reflecting mirror, panchromatic second reflecting mirror, and panchromatic third reflecting mirror together form an off-axis three-reflection aberration correction system, which is used to correct the aberrations of the panchromatic field of view reflected by the panchromatic first convoluted mirror and reflect it onto the panchromatic image plane through the panchromatic second convoluted mirror. The optical path direction from the primary and secondary telescope group to the field-of-view separator is defined as the Z direction, and the direction from the field-of-view separator to the three-mirror aberration correction mirror group is defined as the Y direction; the Y direction is perpendicular to the Z direction; the direction perpendicular to both the Y and Z directions is defined as the X direction; the panchromatic three-mirror group performs aberration correction for the field of view in the Y direction off-axis range of 0.835°-0.855°, and the hyperspectral three-mirror group performs aberration correction for the field of view in the Y direction off-axis range of 0.47°-0.76°; The maximum usable field of view of the lens formed by the primary and secondary telescope group, the field-of-view separator, and the three-mirror aberration correction lens group is 2.28°; the lens F-number is 3.2-3.42; and the lens focal length is 1.43m-1.55m.

2. The combined panchromatic and hyperspectral imaging lens with primary and secondary lenses as described in claim 1, characterized in that: The primary and secondary mirror telescope assembly includes a primary mirror and a secondary mirror; the primary mirror has a 10th-order even-order aspherical surface; the secondary mirror has a hyperboloid surface; the primary mirror and the secondary mirror form a coaxial RC telescope system.

3. A combined panchromatic and hyperspectral imaging lens with primary and secondary lenses as described in claim 1, characterized in that: The hyperspectral three-mirror assembly includes a hyperspectral first mirror, a hyperspectral second mirror, a hyperspectral third mirror, and a hyperspectral deflector. The hyperspectral first mirror, the hyperspectral second mirror, and the hyperspectral third mirror together form an off-axis three-mirror aberration correction system, which is used to correct aberrations in the hyperspectral field of view and reflect the light to the hyperspectral image plane through the hyperspectral deflector.

4. A combined panchromatic and hyperspectral imaging lens with primary and secondary lenses as described in claim 1, characterized in that: The first panchromatic mirror has an ellipsoidal surface, the second panchromatic mirror has an 8th-order even-order aspherical surface, and the third mirror has a hyperboloidal surface.

5. A combined panchromatic and hyperspectral imaging lens with primary and secondary lenses as described in claim 3, characterized in that: The first hyperspectral mirror is a hyperboloid, the second hyperspectral mirror is an 8th-order even-order aspherical surface, and the third hyperspectral mirror is an ellipsoid; the hyperspectral deflector is a plane mirror.

6. A combined panchromatic and hyperspectral imaging lens with primary and secondary lenses as described in claim 1, characterized in that: The usable field of view in the panchromatic field of view has a length of 56 mm along the X direction, and the MTF of the entire field of view is greater than 0.53 at the Nyquist frequency of 71 lp / mm; the usable field of view in the hyperspectral field of view has a length of 62 mm along the X direction, and the MTF of the entire field of view is greater than 0.78 at the Nyquist frequency of 17 lp / mm.

Images