Combined panchromatic and hyperspectral imaging lens shared by primary mirror and secondary mirror

Abstract

The invention discloses a combined panchromatic and hyperspectral imaging lens shared by primary and secondary mirrors. The combined panchromatic and hyperspectral imaging lens comprises a primary and secondary mirror telescope group, a field-of-view separation mirror and a three-mirror aberration correction mirror group. The primary and secondary mirror telescope group is used for receiving target light and converging the target light to the vicinity of the field-of-view separation mirror. And the view field separation mirror is used for turning the light converged by the primary and secondary mirror telescope group and separating the light into a panchromatic view field and a hyperspectral view field. According to the invention, a front-end light-collecting telescope system is constructed by two R-C coaxial reflectors, and an off-axis three-reflector system is connected to correct aberration, so that the design of an imaging system with a large field of view and a small F number is realized; field-of-view separation is carried out on a turning light path near a rear focus of the coaxial primary and secondary mirrors, and respective off-axis three-mirror design is carried out on panchromatic channels and hyperspectral channels of different fields of view in sequence to realize multifunctional imaging; a plurality of turning mirrors are added in respective off-axis three-mirror systems of panchromatic and hyperspectral for optical path folding, so that compact design is realized, and the size of the system 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: 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.

[0006] The primary and secondary mirror telescope group is used for receiving target light and converging it to the field separation mirror.

[0007] The field separation mirror is used for turning the light path converged by the primary and secondary mirror telescope group and separating it into a full-color field and a hyperspectral field.

[0008] The three-mirror aberration-corrected lens group includes a full-color three-mirror lens group and a hyperspectral three-mirror lens group. The hyperspectral three-mirror lens group is used for receiving light of the hyperspectral field and performing aberration correction, and finally refracting and guiding it to a hyperspectral image plane.

[0009] The full-color three-mirror lens group includes a full-color first mirror, a full-color second mirror, a full-color third mirror, a full-color first turning mirror, and a full-color second turning mirror.

[0010] The full-color first mirror, the full-color second mirror, and the full-color third mirror form an off-axis three-mirror aberration-corrected system, which is used for performing aberration correction on light of the full-color field reflected by the full-color first turning mirror and reflecting it to a full-color image plane through the full-color second turning mirror.

[0011] Further, the primary and secondary mirror telescope group includes a primary mirror and a secondary mirror. The primary mirror has a 10th-order even aspheric surface, and the secondary mirror has a hyperboloid surface. The primary mirror and the secondary mirror form a coaxial R-C telescope system.

[0012] Further, the field separation mirror adopts a double-plane mirror, and the double-plane mirror is provided with two reflection surfaces arranged at a fixed included angle.

[0013] Further, the hyperspectral three-mirror lens group includes a hyperspectral first mirror, a hyperspectral second mirror, a hyperspectral third mirror, and a hyperspectral turning mirror. The hyperspectral first mirror, the hyperspectral second mirror, and the hyperspectral third mirror form an off-axis three-mirror aberration-corrected system, which is used for performing aberration correction on light of the hyperspectral field and reflecting it to a hyperspectral image plane through the hyperspectral turning mirror.

[0014] Further, the full-color first mirror has an ellipsoidal surface, the full-color second mirror has an 8th-order even aspheric surface, and the third mirror has a hyperboloid surface.

[0015] Further, the hyperspectral first mirror has a hyperboloid surface, the hyperspectral second mirror has an 8th-order even aspheric surface, and the hyperspectral third mirror has an ellipsoidal surface; and the hyperspectral turning mirror is a plane mirror.

[0016] Further, the maximum available field angle of the lens formed by the primary and secondary mirror telescope group, the field separation mirror, and the three-mirror aberration-corrected lens group is 2.28°. The lens F number is 3.2-3.42. The lens focal length is 1.43m-1.55m.

[0017] Further, the light path direction of the primary and secondary mirror telescope group to the field separation mirror is set as the Z direction, and the direction of the field separation mirror to the three-reflection aberration correction mirror group is set as the Y direction. The Y direction is perpendicular to the Z direction. The direction perpendicular to the Y direction and the Z direction is set as the X direction. The full-color three-reflection mirror group corrects aberration for the field of view in the range of 0.835°-0.855° outside the Y direction axis, and the hyperspectral three-reflection mirror group corrects aberration for the field of view in the range of 0.47°-0.76° outside the Y direction axis.

[0018] Further, the length of the available field of view in the full-color field of view along the X direction is 56 mm, the full-field MTF is greater than 0.53 at the Nyquist frequency of 71 lp / mm, and the optical transfer function is close to the diffraction limit; the length of the available field of view in the hyperspectral field of view along the X direction is 62 mm, the full-field MTF is greater than 0.78 at the Nyquist frequency of 17 lp / mm, and the optical transfer function is close to the diffraction limit.

[0019] Compared with the prior art, the present application has the following advantages: The present application realizes the design of a large-field-of-view and small-F-number imaging system by constructing a front-end light collecting telescope system with a coaxial two-mirror R-C structure and correcting aberration by an off-axis three-mirror system; the light path is turned around near the back focal point of the coaxial primary and secondary mirrors to separate the field of view, and then the off-axis three-mirror design is performed 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 to the off-axis three-mirror systems of the full-color and hyperspectral channels to fold the light path, so that compact design is realized and the system volume is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a schematic diagram of the overall structure of the present application; Figure 2 It is a schematic diagram of the light path structure of the present application; Figure 3 It is a schematic diagram of the optical modulation function curve of the full-color image surface in the present application; Figure 4 It is a schematic diagram of the optical modulation function curve of the hyperspectral image surface in the present application.

[0021] Reference signs: 1, primary mirror; 2, secondary mirror; 3, field separation mirror; 4-0, full-color first turning mirror; 4-1, full-color first reflecting mirror; 4-2, full-color second reflecting mirror; 4-3, full-color third reflecting mirror; 4-4, full-color second turning mirror; 5-1, hyperspectral first reflecting mirror; 5-2, hyperspectral second reflecting mirror; 5-3, hyperspectral third reflecting mirror; 5-4, hyperspectral turning mirror. DETAILED DESCRIPTION

[0022] In the description of the present application, it should be understood that the terms "one end", "the other end", "outer side", "upper", "inner side", "horizontal", "coaxial", "central", "end", "length", "outer end" and the like 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 the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0023] The present application will be further described below in conjunction with the drawings.

[0024] As shown in Figure 1 and 2 , a primary and secondary mirror shared combination type full-color and hyperspectral imaging lens is used for full-color imaging, visible spectrum imaging and short-wave infrared spectrum imaging. From the object plane to the image plane, it includes a primary and secondary mirror 2 telescope group, a field separation mirror 3 and a three-mirror aberration correction group in sequence. Among them, the light path direction from the primary and secondary mirror 2 telescope group to the field separation mirror 3 is set as the Z direction, and the direction from the field separation mirror 3 to the three-mirror aberration correction group is the Y direction. The Y direction is perpendicular to the Z direction. The direction perpendicular to the Y direction and the Z direction is set as the X direction.

[0025] The primary and secondary mirror 2 telescope group is used to receive light rays of different fields of view of the target and converge them near the field separation mirror 3. The field separation mirror 3 is used to bend the light path converged by the primary and secondary mirror 2 telescope group and separate it into a full-color field of view and a hyperspectral field of view. The three-mirror aberration correction group is divided into two parts, a full-color imaging channel and a hyperspectral channel. The full-color field of view and the hyperspectral field of view pass through the full-color imaging channel and the hyperspectral channel respectively, and finally form images on the full-color image plane and the hyperspectral image plane.

[0026] As shown in detail Figure 1 , the primary and secondary mirror 2 telescope group includes a primary mirror 1 and a secondary mirror 2. Among them, the surface type of the primary mirror 1 is a 10th order even aspheric surface; the surface type of the secondary mirror 2 is a hyperboloid. The primary mirror 1 and the secondary mirror 2 form a coaxial R-C telescope system, which can receive target light and converge to form an intermediate image plane.

[0027] The field separation mirror 3 is a double-plane mirror, and two plane reflecting surfaces with a fixed included angle are arranged on the double-plane mirror. The two reflecting surfaces are used to bend the light path converged by the secondary mirror 2, and each of them is separated into a full-color field of view and a hyperspectral field of view along the Y positive direction and the Y negative direction.

[0028] The three-mirror aberration correction group includes a full-color three-mirror group and a hyperspectral three-mirror group. The full-color three-mirror group and the hyperspectral three-mirror group are respectively used to receive light rays of the full-color field of view and the hyperspectral field of view, and perform aberration correction processing, so that the lens can obtain a full-color image with high spatial resolution and a spectral data image with high spectral resolution in a large field of view.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] The general expression for the 10th-order even-order aspherical surface in this embodiment is shown in Equation 1:

[0035] 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.

[0036] In this embodiment, the surface shape of the primary mirror reflecting surface satisfies: α4 = -2.412E -13 α6 = 5.987E -18 α8 = -1.516E -22 α10 =1.234E -27 .

[0037] The panchromatic second mirror surface in the embodiment satisfies: α4=1.059E -7 , α6=7.805E -12 , α8=4.611E -15 .

[0038] The hyperspectral second mirror surface in the embodiment satisfies: α4=-1.464E -7 , α6=1.546E -10 , α8=-1.624E -13 .

[0039] The specific values of the surface type, the radius of curvature (the reciprocal of the curvature c), and the quadratic surface coefficient k of all the curved surfaces in the embodiment can be seen from Table 1. It can be understood that the values of the radius of curvature, the quadratic surface coefficient k, and the high-order coefficient α i in the present application are not limited to the embodiments, and can be adjusted according to actual needs by those skilled in the art.

[0040]

[0041] As shown in Figure 3 and Figure 4 , the panchromatic three-mirror group and the hyperspectral three-mirror group both correct the aberration of the field of view in the fixed angle range outside the axis after being reflected and converged by the primary mirror and the secondary mirror, and the usable field of view angle along the X direction can be enlarged to 2.28°. Among them, the usable field of view along the X direction in the panchromatic field of view is 56mm long, and at the Nyquist frequency of 71lp / mm, the full-field MTF is greater than 0.53, and the optical transfer function is close to the diffraction limit; the usable field of view along the X direction in the hyperspectral field of view is 62mm long, and at the Nyquist frequency of 17lp / mm, the full-field MTF is greater than 0.78, and the optical transfer function is close to the diffraction limit; Figure 3 、 Figure 4 are the optical modulation function curve diagrams of the panchromatic image surface and the hyperspectral image surface, respectively.

[0042] The results prove that the primary and secondary mirror shared combined panchromatic and hyperspectral imaging lens provided by the present application has a lens F number of 3.2-3.42. The lens focal length is 1.43m-1.55m. The panchromatic three-mirror group corrects the aberration of the field of view in the range of 0.835°-0.855° outside the Y direction axis, and the hyperspectral three-mirror group corrects the aberration of the field of view in the range of 0.47°-0.76° outside the Y direction axis.

[0043] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

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 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 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.

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. The combined panchromatic and hyperspectral imaging lens with primary and secondary lenses as described in claim 1, characterized in that: The field-of-view separation mirror is a double-plane reflector, which has two reflective surfaces placed at a fixed angle.

4. 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.

5. 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.

6. A combined panchromatic and hyperspectral imaging lens with shared primary and secondary lenses according to claim 4, 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.

7. A combined panchromatic and hyperspectral imaging lens with primary and secondary lenses as described in claim 1, characterized in that: 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.

8. A combined panchromatic and hyperspectral imaging lens with primary and secondary lenses as described in claim 1, characterized in that: 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°.

9. A combined panchromatic and hyperspectral imaging lens with primary and secondary lenses as described in claim 8, 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.

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