A broadband, low F-number optical system for detector stitching

Abstract

An optical system with a wide spectral range and low F-number for detector stitching is disclosed, relating to the field of detector stitching technology. This invention addresses the problems of poor stitching performance in existing detector systems, and the relatively high F-number of optical systems resulting in dim brightness during stitching, which affects the accuracy of detector stitching. The invention includes a detector end to be stitched, an imaging end, and a lens group arranged along the optical axis between the two. The lens group, from left to right, consists of: a first positive lens, a first negative lens, a second positive lens, a second negative lens, a third positive lens, a third negative lens, a fourth positive lens, and a fifth positive lens. The optical system also includes an aperture stop located between the second negative lens and the third positive lens. The spectral range of this invention is wider than similar products, ranging from 400 nm to 900 nm. The F-number of this invention is lower than similar products, ranging from 2.0 to 2.2. The optical system of this invention also has the advantages of high resolution, low chromatic aberration, compact structure, and low cost.

Description

Technical Field

[0001] This invention relates to the field of detector stitching technology, and more specifically to a broadband low F-number optical system for detector stitching. Background Technology

[0002] The current development trend of satellite remote sensing optical payloads is wide-spectrum, wide-swath, and high-resolution imaging.

[0003] Currently, China's manufacturing capacity for large-size detectors is limited, and exports of large-size detectors from abroad are restricted. To meet the swath width requirements of satellite remote sensing optical payloads, multiple detectors are typically stitched together. There are three common detector stitching methods: mechanical stitching, optical stitching, and field-of-view stitching. Optical stitching uses a semi-reflective prism to stitch detectors in the transmission and reflection light paths to achieve the required swath width. However, this method introduces a refractive lens behind the prism, causing chromatic aberration, and also has low light energy utilization. Field-of-view stitching arranges detectors at intervals on the image plane and achieves the required swath width through subsequent image stitching processing. This method places high demands on image processing. Mechanical stitching uses multiple detectors to overlap end-to-end to achieve the required swath width. This method allows for very large detectors and has advantages such as system simplicity, high response consistency, and high image plane stitching accuracy.

[0004] Currently, most optical systems used for splicing wide-swath detectors, both domestically and internationally, are in the visible spectrum range. This results in poor splicing performance for wide-swath detectors. Furthermore, the large F-number of these optical systems leads to dim brightness during splicing, affecting the accuracy of detector splicing. Summary of the Invention

[0005] To address the problems of poor stitching effect and low brightness during stitching due to the large F-number of existing detectors, which affects the accuracy of detector stitching, this invention provides a broadband, low F-number optical system for detector stitching. By rationally selecting the structure and materials, the optical system meets the requirements of broadband, low F-number, and high resolution.

[0006] A broadband low F-number optical system for detector stitching includes a detector end to be stitched, an imaging end, and a lens group arranged along the optical axis between the two. The center of the detector end to be stitched, the imaging end, and each lens is located on the same optical axis. The arrangement order of the lens group from the imaging end to the detector end to be stitched is a first positive lens, a first negative lens, a second positive lens, a second negative lens, a third positive lens, a third negative lens, a fourth positive lens, and a fifth positive lens.

[0007] The focal length of the first positive lens is between 240mm and 260mm; the focal length of the first negative lens is between -110mm and -130mm; the focal length of the second positive lens is between 180mm and 200mm; the focal length of the second negative lens is between -290mm and -310mm; the focal length of the third positive lens is between 180mm and 200mm; the focal length of the third negative lens is between -100mm and -120mm; the focal length of the fourth positive lens is between 180mm and 200mm; and the focal length of the fifth positive lens is between 240mm and 260mm.

[0008] The thickness of the first positive lens is between 15mm and 20mm; the thickness of the first negative lens is between 10mm and 15mm; the thickness of the second positive lens is between 20mm and 25mm; the thickness of the second negative lens is between 10mm and 15mm; the thickness of the third positive lens is between 20mm and 25mm; the thickness of the third negative lens is between 10mm and 15mm; the thickness of the fourth positive lens is between 20mm and 25mm; and the thickness of the fifth positive lens is between 20mm and 25mm.

[0009] The air gap between the first positive lens and the first negative lens is between 5 mm and 10 mm; the air gap between the first negative lens and the second positive lens is between 5 mm and 10 mm; the air gap between the second positive lens and the second negative lens is between 5 mm and 10 mm; the air gap between the second negative lens and the third positive lens is between 5 mm and 15 mm; the air gap between the third positive lens and the third negative lens is between 35 mm and 40 mm; the air gap between the third negative lens and the fourth positive lens is between 3 mm and 8 mm; and the air gap between the fourth positive lens and the fifth positive lens is between 3 mm and 8 mm.

[0010] Furthermore, the optical system includes an aperture plane located between the second negative lens and the third positive lens;

[0011] Furthermore, the first positive lens, the first negative lens, the second positive lens, the second negative lens, the third positive lens, the third negative lens, the fourth positive lens, and the fifth positive lens are all glass spherical lenses.

[0012] Furthermore, both the detector end and the imaging end to be stitched are placed perpendicular to the optical axis of the system.

[0013] Furthermore, the air gap between the aperture stop and the second negative lens is between 5 mm and 15 mm.

[0014] Preferably, the refractive index of the first positive lens is between 1.45 and 1.6; the refractive index of the first negative lens is between 1.6 and 1.75; the refractive index of the second positive lens is between 1.4 and 1.5; the refractive index of the second negative lens is between 1.55 and 1.7; the refractive index of the third positive lens is between 1.65 and 1.8; the refractive index of the third negative lens is between 1.8 and 1.9; the refractive index of the fourth positive lens is between 1.4 and 1.55; and the refractive index of the fifth positive lens is between 1.4 and 1.55.

[0015] Furthermore, the imaging spectral range of the optical system is between 400 nm and 900 nm, and the F-number of the optical system is between 2.0 and 2.2.

[0016] The beneficial effects of this invention are:

[0017] 1. The spectral band of this invention is between 400nm and 900nm, and can be used to stitch together wide-band detectors; this invention solves the problem of stitching together wide-band, small-pixel-size detectors.

[0018] 2. The F-number of this invention is relatively low, which can increase the amount of light entering the optical system and increase the image brightness.

[0019] 3. The present invention has a small number of lenses, a simple structure, and has undergone cost control and optimization, which can significantly save costs and space.

[0020] 4. Based on the basic imaging optics principle of this invention, the optical system has been repeatedly optimized for aberrations using optical design software, which can achieve high-quality image output and improve stitching accuracy. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of an optical system for detector splicing with a wide-band low F-number according to the present invention;

[0022] Figure 2 This is a schematic diagram of the lens assembly and the detector section to be spliced ​​together.

[0023] Figure 3 The modulation transfer function curve is shown.

[0024] Figure 4 A point-to-point graph;

[0025] Figure 5 This is a chromatic aberration diagram along the vertical axis.

[0026] Figure 6 This is a relative illumination map.

[0027] In the diagram: S, detector end to be stitched; M, lens group; L, imaging end; M1, first positive lens; M2, first negative lens; M3, second positive lens; M4, second negative lens; M5, third positive lens; M6, third negative lens; M7, fourth positive lens; M8, fifth positive lens; T, aperture plane. Detailed Implementation

[0028] Combination Figures 1 to 6 This embodiment describes a broadband, low-F-number optical system for detector stitching. The specific components of this system are as follows:

[0029] like Figure 1 and Figure 2 As shown, an optical system for detector stitching with a wide-band low F-number includes a detector end S to be stitched, an imaging end L, and a lens group M arranged along the optical axis between the two. The centers of each lens in the detector end S, imaging end L, and lens group M are located on the same optical axis. The arrangement order of the lens group from imaging end L to detector end S is: first positive lens M1, first negative lens M2, second positive lens M3, second negative lens M4, third positive lens M5, third negative lens M6, fourth positive lens M7, and fifth positive lens M8.

[0030] The optical system includes an aperture plane T located between the second negative lens M4 and the third positive lens M5;

[0031] The first positive lens M1, the first negative lens M2, the second positive lens M3, the second negative lens M4, the third positive lens M5, the third negative lens M6, the fourth positive lens M7, and the fifth positive lens M8 are all glass spherical lenses.

[0032] The first positive lens M1, the first negative lens M2, the second positive lens M3, the second negative lens M4, the third positive lens M5, the third negative lens M6, the fourth positive lens M7, and the fifth positive lens M8 are all glass spherical lenses located on the same optical axis.

[0033] Both the detector end S and the imaging end L to be spliced ​​are placed perpendicular to the optical axis of the system.

[0034] The focal length of the first positive lens M1 is between 240mm and 260mm; the focal length of the first negative lens M2 is between -110mm and -130mm; the focal length of the second positive lens M3 is between 180mm and 200mm; the focal length of the second negative lens M4 is between -290mm and -310mm; the focal length of the third positive lens M5 is between 180mm and 200mm; the focal length of the third negative lens M6 is between -100mm and -120mm; the focal length of the fourth positive lens M7 is between 180mm and 200mm; and the focal length of the fifth positive lens M8 is between 240mm and 260mm.

[0035] The thickness of the first positive lens M1 is between 15mm and 20mm; the thickness of the first negative lens M2 is between 10mm and 15mm; the thickness of the second positive lens M3 is between 20mm and 25mm; the thickness of the second negative lens M4 is between 10mm and 15mm; the thickness of the third positive lens M5 is between 20mm and 25mm; the thickness of the third negative lens M6 is between 10mm and 15mm; the thickness of the fourth positive lens M7 is between 20mm and 25mm; and the thickness of the fifth positive lens M8 is between 20mm and 25mm.

[0036] The air gap between the first positive lens M1 and the first negative lens M2 is between 5mm and 10mm; the air gap between the first negative lens M2 and the second positive lens M3 is between 5mm and 10mm; the air gap between the second positive lens M3 and the second negative lens M4 is between 5mm and 10mm; the air gap between the second negative lens M4 and the third positive lens M5 is between 5mm and 15mm; the air gap between the third positive lens M5 and the third negative lens M6 is between 35mm and 40mm; the air gap between the third negative lens M6 and the fourth positive lens M7 is between 3mm and 8mm; and the air gap between the fourth positive lens M7 and the fifth positive lens M8 is between 3mm and 8mm.

[0037] The air gap between the aperture plane T and the second negative lens M4 is between 3mm and 8mm.

[0038] The first positive lens M1 has a refractive index between 1.45 and 1.6; the first negative lens M2 has a refractive index between 1.6 and 1.75; the second positive lens M3 has a refractive index between 1.4 and 1.5; the second negative lens M4 has a refractive index between 1.55 and 1.7; the third positive lens M5 has a refractive index between 1.65 and 1.8; the third negative lens M6 has a refractive index between 1.8 and 1.9; the fourth positive lens M7 has a refractive index between 1.4 and 1.55; and the fifth positive lens M8 has a refractive index between 1.4 and 1.55.

[0039] The imaging spectral range of the optical system is between 400 nm and 900 nm.

[0040] The F-number of the optical system is between 2.0 and 2.2.

[0041] In this embodiment, the following example uses a magnification of 20 times between the detector stitching end S and the imaging end L to illustrate the parameters of an optical system embodiment for detector stitching according to the present invention.

[0042]

[0043]

[0044] The imaging spectrum of this invention is from 400nm to 900nm, the focal length is 200mm, the F number is 2, the detector to be stitched is placed 200mm to the right of the fifth positive lens, and the imaging detector is placed 4000mm to the left of the first positive lens. Pixels with a pixel size of 2μm or larger can be magnified 20 times to the imaging end for clear imaging, ultimately achieving high-precision wide-spectrum detector stitching.

[0045] like Figure 3 As shown, Figure 3 The figure shows the modulation transfer function curve of the present invention. 250 lp / mm is the cutoff frequency when the pixel size is 2 μm. At this frequency, the modulation transfer function of each field of view is better than 0.43, indicating that the lens can clearly image pixels larger than 2 μm and the optical system has strong resolution.

[0046] like Figure 4 As shown, Figure 4 The dot plots of this invention show that the average speckle radius of each field of view and at different wavelengths is smaller than the Airy disk size, resulting in excellent imaging quality.

[0047] like Figure 5 As shown, Figure 5 The chromatic aberration diagram of this invention shows that the separation of different colors of light during imaging on the image plane does not exceed 1.3 μm, demonstrating excellent chromatic aberration control and meeting the requirements for imaging quality.

[0048] like Figure 6 As shown, Figure 6 The relative illumination diagram of this invention shows that the relative illumination from zero field of view to the maximum field of view is at a large value and there is no obvious inflection point. The illumination is uniform and the imaging effect is excellent.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A broadband low F-number optical system for detector stitching, comprising a detector end to be stitched, an imaging end, and a lens group arranged along the optical axis between the two, characterized in that: The centers of the detector end to be stitched, the imaging end, and each lens in the lens group are located on the same optical axis. The arrangement of the lens group from the imaging end to the detector end to be stitched consists of a first positive lens, a first negative lens, a second positive lens, a second negative lens, a third positive lens, a third negative lens, a fourth positive lens, and a fifth positive lens. The thickness of the first positive lens is 16.7 mm; the thickness of the first negative lens is 8.6 mm; the thickness of the second positive lens is 22.5 mm; the thickness of the second negative lens is 14.3 mm; the thickness of the third positive lens is 21.3 mm; the thickness of the third negative lens is 13.6 mm; the thickness of the fourth positive lens is 22.4 mm; and the thickness of the fifth positive lens is 24.8 mm. The air gap between the first positive lens and the first negative lens is 6.7 mm; the air gap between the first negative lens and the second positive lens is 5.8 mm; the air gap between the second positive lens and the second negative lens is 8.9 mm; the air gap between the second negative lens and the third positive lens is 10.5 mm; the air gap between the third positive lens and the third negative lens is 37.8 mm; the air gap between the third negative lens and the fourth positive lens is 3.2 mm; and the air gap between the fourth positive lens and the fifth positive lens is 6.2 mm.

2. The broadband low F-number optical system for detector stitching according to claim 1, characterized in that: The first positive lens has a refractive index of 1.58; the first negative lens has a refractive index of 1.73; the second positive lens has a refractive index of 1.43; the second negative lens has a refractive index of 1.68; the third positive lens has a refractive index of 1.8; the third negative lens has a refractive index of 1.81; the fourth positive lens has a refractive index of 1.42; and the fifth positive lens has a refractive index of 1.

45.

3. The broadband low F-number optical system for detector stitching according to claim 1, characterized in that: The optical system includes an aperture plane located between the second negative lens and the third positive lens.

4. The broadband low F-number optical system for detector stitching according to claim 3, characterized in that: The air gap between the aperture plane and the second negative lens is 4.6 mm.

5. The broadband low F-number optical system for detector stitching according to claim 1, characterized in that: The first positive lens, the first negative lens, the second positive lens, the second negative lens, the third positive lens, the third negative lens, the fourth positive lens, and the fifth positive lens are all glass spherical lenses.

6. The broadband low F-number optical system for detector stitching according to claim 1, characterized in that: Both the detector end and the imaging end to be spliced ​​are placed perpendicular to the optical axis of the system.

7. The broadband low F-number optical system for detector stitching according to claim 1, characterized in that: The imaging spectral range of the optical system is between 400 nm and 900 nm.

8. The broadband low F-number optical system for detector stitching according to claim 1, characterized in that: The F-number of the optical system is between 2.0 and 2.2.

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