A medium / long-wave common aperture new spectroscopic mode imaging system and imaging method

Abstract

The medium / long-wave co-aperture new spectroscopic imaging system and imaging method provided in this application are based on infrared imaging theory and achieve medium-wave and long-wave co-aperture imaging. Compared to the design of traditional co-aperture multi-spectral imaging systems, the medium / long-wave co-aperture new spectroscopic imaging system designed in this invention does not have a multi-spectral co-collimation structure, which reduces system weight and improves space utilization. The invention also does not adopt the traditional spectroscopic mode, but instead uses an annular reflector and a quadratic curved reflective surface on the lens surface to achieve medium-wave and long-wave spectroscopic separation. This eliminates the astigmatism problem of the transmission channel caused by the spectroscopic mirror, reduces design difficulty, and allows the dual-band transfer function to be designed to the diffraction limit.

Description

Technical Field

[0001] The present application relates to the field of optical imaging technology, and in particular to a medium / long-wave common aperture new spectroscopic mode imaging system and imaging method. Background Art

[0002] In the field of aviation payloads, multi-spectral integrated lenses have become a standard feature of aviation payloads. They require not only better performance and more working spectrum bands, but also lighter weight. Therefore, one solution is to maximize the proportion of shared parts between different spectrum bands. Conventional multi-spectral payloads first require the design of a co-collimation structure for the multiple spectrum bands, and then use a spectrometer plate to split the light after the collimation structure. However, this increases the weight and space of the system and reduces the transmittance of the lens. For example, the design of patent number ZL202310160400.8 uses 7 mirrors to co-collimate the medium-wave and long-wave infrared. The collimation structure is complex and the system transmittance is not high.

[0003] Without a co-collimation structure, the beamsplitter plate is not in a parallel optical path, which will affect the design of the transmission channel after the beam splitter. The astigmatism introduced by the beamsplitter plate in the transmission channel is difficult to eliminate, making it difficult to achieve the diffraction limit. Although there is a solution to design the beamsplitter plate as a wedge-shaped prism to reduce the astigmatism in the transmission channel, it places high demands on the processing of the wedge-shaped prism and the structural components, making it difficult to ensure the yield rate. Excessive processing deviation will deviate from the design and affect the imaging effect. To reduce astigmatism, there is also a solution to add a compensating mirror orthogonal to the beamsplitter plate after the beamsplitter plate, but this also faces the problem of increased weight, volume, and processing costs.

[0004] Currently, for early warning aviation payloads that integrate medium-wave and long-wave imaging channels, spectral splitting is conventionally achieved through a beamsplitter plate. Spectroscopic splitting through a beamsplitter plate, however, requires a collimating structure that increases the system's size and weight. Wider spectral bands require more lenses, and materials are limited. Another approach involves individually collimating each imaging channel after the beamsplitter plate separates the light. This introduces astigmatism in the transmission channel because the beamsplitter plate is not in a parallel optical path. The thicker the beamsplitter plate, the greater the astigmatism introduced. While the beamsplitter plate can be designed as a wedge-shaped prism to eliminate astigmatism in the transmission channel, this places high demands on the processing of the wedge-shaped prism and structural components, making it difficult to guarantee a high yield. Excessive processing deviations can deviate from the design, affecting the imaging effect. Summary of the Invention

[0005] In view of this, it is necessary to provide a medium / long wave common aperture new spectroscopic mode imaging system and an imaging method that effectively improve the imaging quality to address the problem of low imaging effect in the current medium / long wave common aperture new spectroscopic mode imaging system.

[0006] To solve the above problems, this application adopts the following technical solutions:

[0007] One of the purposes of this application is to provide a medium / long-wave common aperture new spectroscopic mode imaging system, comprising: a medium-wave infrared imaging channel and a long-wave infrared imaging channel;

[0008] The medium-wave infrared imaging channel includes a common lens group and a medium-wave secondary imaging group, the common lens group includes a first lens (1), a second lens (2) and a third lens (3) arranged in sequence, and the medium-wave secondary imaging group includes a fourth lens (4), a fifth lens (5) and a sixth lens (6) arranged in sequence;

[0009] The long-wave infrared imaging channel comprises the common lens group, the long-wave infrared focusing group, the long-wave tertiary imaging group and the reflector group, the long-wave infrared focusing group comprises a seventh lens (7) and an eighth lens (8) arranged in sequence, the long-wave tertiary imaging group comprises a ninth lens (9), a tenth lens (10), an eleventh lens (11) and a twelfth lens (12) arranged in sequence, the reflector group comprises a first reflector (REL-1) and a second reflector (REL-2), and the reflector (REL-1) is an annular reflector with a central opening;

[0010] The medium-wave infrared light sequentially passes through the first lens (1), the second lens (2) and the third lens (3) and is focused into a medium-wave primary image point. The medium-wave primary image point is located at the center of the opening of the first reflector (REL-1). The medium-wave primary image point then sequentially passes through the fourth lens (4), the fifth lens (5) and the sixth lens (6) and is imaged again onto the image plane of the medium-wave infrared detector.

[0011] The long-wave infrared light sequentially passes through the first lens (1), the second lens (2) and the third lens (3) and is focused into a long-wave primary image point. The long-wave primary image point is located near the opening center of the first reflector (REL-1). The long-wave primary image point is reflected by the fourth lens (4) to form collimated light. The collimated light is reflected by the annular reflection surface of the first reflector (REL-1) and enters the second reflector (REL-2) through the seventh lens (7) and the eighth lens (8). The second reflector (REL-2) flips the incident convergent light beam, and realizes long-wave infrared secondary imaging after flipping. The secondary image point is then sequentially passed through the ninth lens (9), the tenth lens (10), the eleventh lens (11) and the twelfth lens (12) for aberration correction, and finally forms an image on the image plane of the long-wave infrared detector.

[0012] In some embodiments, the incident surface (S4-1) of the fourth lens (4) is a quadratic surface, and the surface of the incident surface (S4-1) is coated with a film layer, and the film layer is highly reflective to long-wave infrared and highly transmissive to medium-wave infrared.

[0013] In some embodiments, the first reflector (REL-1) is disposed at 45 degrees from the medium wave primary image point.

[0014] In some embodiments, the second reflector (REL-2) is positioned at a 45 degree angle to the horizontal.

[0015] In some embodiments, the working spectrum of the medium-wave infrared detector is 3.7-4.8 μm, and the detector pixel size is 640×512@15 μm.

[0016] In some embodiments, the long-wave infrared detector has an operating spectrum of 7.7 to 9.5 μm, and a detector pixel size of 640×512@15 μm.

[0017] The second object of the present application is to provide an imaging method of the medium / long wavelength common aperture new spectroscopic mode imaging system, comprising the following steps:

[0018] The medium-wave infrared light sequentially passes through the first lens (1), the second lens (2) and the third lens (3) and is focused into a medium-wave primary image point. The medium-wave primary image point is located at the center of the opening of the first reflector (REL-1). The medium-wave primary image point then sequentially passes through the fourth lens (4), the fifth lens (5) and the sixth lens (6) and is imaged again onto the image plane of the medium-wave infrared detector.

[0019] The long-wave infrared light sequentially passes through the first lens (1), the second lens (2) and the third lens (3) and is focused into a long-wave primary image point. The long-wave primary image point is located near the opening center of the first reflector (REL-1). The long-wave primary image point is reflected by the fourth lens (4) to form collimated light. The collimated light is reflected by the annular reflection surface of the first reflector (REL-1) and enters the second reflector (REL-2) through the seventh lens (7) and the eighth lens (8). The second reflector (REL-2) flips the incident convergent light beam, and realizes long-wave infrared secondary imaging after flipping. The secondary image point is then sequentially passed through the ninth lens (9), the tenth lens (10), the eleventh lens (11) and the twelfth lens (12) for aberration correction, and finally forms an image on the image plane of the long-wave infrared detector.

[0020] This application adopts the above technical solution, and its beneficial effects are as follows:

[0021] The medium / long-wave co-aperture new spectroscopic imaging system and imaging method provided in this application are based on infrared imaging theory and achieve medium-wave and long-wave co-aperture imaging. Compared to the design of traditional co-aperture multi-spectral imaging systems, the medium / long-wave co-aperture new spectroscopic imaging system designed in this invention does not have a multi-spectral co-collimation structure, which reduces system weight and improves space utilization. The invention also does not adopt the traditional spectroscopic mode, but instead uses an annular reflector and a quadratic curved reflective surface on the lens surface to achieve medium-wave and long-wave spectroscopic separation. This eliminates the astigmatism problem of the transmission channel caused by the spectroscopic mirror, reduces design difficulty, and allows the dual-band transfer function to be designed to the diffraction limit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0023] Figure 1 This is a schematic structural diagram of the new medium / long-wave common-aperture spectroscopic mode imaging system provided in an embodiment of the present application.

[0024] Figure 2 Provided in the embodiments of this application Figure 2 , which is a schematic diagram of the surface position relationship of the new medium / long-wave common-aperture spectral mode imaging system. DETAILED DESCRIPTION

[0025] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0026] In the description of this application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this application.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0028] In order to make the purpose, technical solutions and advantages of this application more clear, this application is further described in detail below with reference to the accompanying drawings and embodiments.

[0029] See also Figure 1 The schematic diagram of the structure of the new medium / long-wave common-aperture spectroscopic imaging system provided in the embodiment of the present application includes: a medium-wave infrared imaging channel and a long-wave infrared imaging channel. The specific structure and implementation of each channel are described in detail below.

[0030] The medium-wave infrared imaging channel comprises a common lens group and a medium-wave secondary imaging group, wherein the common lens group comprises a first lens (1), a second lens (2) and a third lens (3) arranged in sequence, and the medium-wave secondary imaging group comprises a fourth lens (4), a fifth lens (5) and a sixth lens (6) arranged in sequence.

[0031] The long-wave infrared imaging channel comprises the common lens group, the long-wave infrared focusing group, the long-wave tertiary imaging group and the reflector group, the long-wave infrared focusing group comprises a seventh lens (7) and an eighth lens (8) arranged in sequence, the long-wave tertiary imaging group comprises a ninth lens (9), a tenth lens (10), an eleventh lens (11) and a twelfth lens (12) arranged in sequence, the reflector group comprises a first reflector (REL-1) and a second reflector (REL-2), and the reflector (REL-1) is an annular reflector with a central opening.

[0032] See also Figure 2 , which is a schematic diagram of the surface position relationship of the medium / long wave common aperture new spectroscopic mode imaging system. Among them: the medium wave infrared channel is numbered from the object side to the image side for each lens surface: the first surface S1-1 and the second surface S1-2 of the first lens (1); the first surface S2-1 and the second surface S2-2 of the second lens (2); the first surface S3-1 and the second surface S3-2 of the third lens (3); the first surface S4-1 and the second surface S4-2 of the fourth lens (4); the first surface S5-1 and the second surface S5-2 of the fifth lens (5); the first surface S6-1 and the second surface S6-2 of the sixth lens (6).

[0033] The surfaces of each lens in the long-wave infrared channel are numbered from the object side to the image side: the first surface S1-1 and the second surface S1-2 of the first lens (1); the first surface S2-1 and the second surface S2-2 of the second lens (2); the first surface S3-1 and the second surface S3-2 of the third lens (3). The first surface S4-1 of the fourth lens (4) is a high-reflection surface for long-wave infrared, and the first reflector (REL-1) is a long-wave infrared reflector with a central opening, which turns the long-wave infrared light upward. The first surface S7-1 and the second surface S7-2 of the seventh lens (7); the first surface S8-1 and the second surface S8-2 of the eighth lens (8), and the second reflector (REL-2) is a long-wave infrared reflector, which turns the long-wave infrared light rightward. The first surface S9-1 and the second surface S9-2 of the ninth lens (9); the first surface S10-1 and the second surface S10-2 of the tenth lens (10). The eleventh lens (11) has a first surface S11-1 and a second surface S11-2. The twelfth lens (12) has a first surface S12-1 and a second surface S12-2.

[0034] The medium / long wavelength common aperture new spectroscopic imaging system provided in the above embodiment of the present application works as follows:

[0035] The medium-wave infrared light is sequentially passed through the first lens (1), the second lens (2) and the third lens (3) and is focused into a medium-wave primary image point. The medium-wave primary image point is located at the center of the opening of the first reflector (REL-1). The medium-wave primary image point is then sequentially passed through the fourth lens (4), the fifth lens (5) and the sixth lens (6) and is imaged again onto the image plane of the medium-wave infrared detector.

[0036] It can be understood that the first lens (1), the second lens (2) and the third lens (3) form a medium-wave infrared and long-wave infrared shared lens group. This lens group focuses the medium-wave infrared light into a primary image point. The primary image point is located at the center of the opening of the first reflector (REL-1). The first reflector (REL-1) is a ring reflector with a central opening. The primary image point is re-imaged to the image plane of the medium-wave infrared detector through the medium-wave secondary imaging group. The shared lens group can be used as a focusing group for the medium-wave infrared.

[0037] The long-wave infrared light sequentially passes through the first lens (1), the second lens (2) and the third lens (3) and is focused into a long-wave primary image point. The long-wave primary image point is located near the opening center of the first reflector (REL-1). The long-wave primary image point is reflected by the fourth lens (4) to form collimated light. The collimated light is reflected by the annular reflection surface of the first reflector (REL-1) and enters the second reflector (REL-2) through the seventh lens (7) and the eighth lens (8). The second reflector (REL-2) flips the incident convergent light beam, and realizes long-wave infrared secondary imaging after flipping. The secondary image point is then sequentially passed through the ninth lens (9), the tenth lens (10), the eleventh lens (11) and the twelfth lens (12) for aberration correction, and finally forms an image on the image plane of the long-wave infrared detector.

[0038] It can be understood that the first lens (1), the second lens (2) and the third lens (3) form a lens group shared by the medium-wave infrared and the long-wave infrared. This lens group focuses the long-wave infrared light into a long-wave primary image point. The long-wave primary image point is located near the center of the opening of the first reflector (REL-1). The light from the long-wave primary image point is incident on the surface S4-1 of the first reflector (REL-1). The surface S4-1 is a quadratic surface with a quadratic radius of -111.56 and a quadratic coefficient of -0.683. The surface S4-1 is coated with a film that is highly reflective for the long-wave infrared and highly transmissive for the medium-wave infrared. The long-wave infrared light reflected from the surface S4-1 is perfectly collimated light. The long-wave infrared light is incident on the annular reflective surface of the first reflector (REL-1) and is reflected, leaving the medium-wave infrared transmission channel to form an independent long-wave infrared channel. Lenses 7 and 8 form a focusing group for the long-wave infrared channel. The second reflector (REL-2) flips the convergent light beam emitted by the long-wave infrared focusing group again, realizing long-wave infrared secondary imaging after flipping. The secondary image point enters the long-wave tertiary imaging group for aberration correction, and finally forms an image on the image plane of the long-wave infrared detector.

[0039] The following is a table of optical system parameters:

[0040] Table 1 System parameters of the medium-wave infrared channel of the new medium / long-wave common aperture spectroscopic imaging system

[0041]

[0042] Table 2 System parameters of the long-wave infrared channel of the new medium / long-wave common aperture spectroscopic imaging system

[0043]

[0044] The system has a total of 6 aspheric surfaces, namely S4-1, S5-1, S6-2, S8-1, S9-1, and S12-2.

[0045] Aspheric coefficient formula

[0046] Where Z is the distance vector height from the aspheric surface vertex when the aspheric surface is at a height r along the optical axis, c represents the vertex curvature of the surface, k is the cone coefficient, a2, a3, a4, a5, a6 are the higher-order aspheric coefficients, and Table 3 shows the aspheric coefficients of the six surfaces.

[0047] Table 3 Aspheric coefficients of the new medium / long wavelength common aperture spectral imaging system

[0048]

[0049]

[0050] The new medium / long-wavelength common-aperture spectroscopic imaging system and method described in this invention consists of a medium-wave infrared channel and a long-wave infrared channel. The medium-wave infrared channel comprises six lenses, the first three of which are shared with the long-wave infrared channel. Light passes through the shared lens to form a primary image point, which is then imaged by a three-lens medium-wave infrared secondary imaging system. This system is then connected to an F4 medium-wave infrared detector, achieving 100% cold-stop matching. A reflector is positioned at a 45-degree angle to the primary image point of the medium-wave infrared channel, with an aperture in its center. The aperture size is designed to meet field of view requirements.

[0051] The long-wave infrared channel consists of nine lenses and two reflectors. The first three lenses are shared with the medium-wave infrared (MWIR) and focus the long-wave infrared light into a primary image point. This light is then reflected off the front surface of the first lens of the medium-wave infrared secondary imaging group to form a collimated optical path. This lens is coated on the front surface with an anti-reflection coating for the mid-infrared and a high-reflection coating for the long-wave infrared. The resulting collimated long-wave infrared light is reflected out of the medium-wave infrared imaging channel by the reflector positioned at a 45-degree angle. A two-mirror long-wave infrared focusing group forms a secondary image point. This secondary image point is then reimaged onto the image plane of the long-wave infrared detector by the final four lenses of the long-wave infrared detector. The long-wave infrared detector has an F-number of 2, achieving 100% cold stop matching.

[0052] The medium / long-wave co-aperture new spectroscopic imaging system and imaging method provided in this application are based on infrared imaging theory and achieve medium-wave and long-wave co-aperture imaging. Compared to the design of traditional co-aperture multi-spectral imaging systems, the medium / long-wave co-aperture new spectroscopic imaging system designed in this invention does not have a multi-spectral co-collimation structure, which reduces system weight and improves space utilization. The invention also does not adopt the traditional spectroscopic mode, but instead uses an annular reflector and a quadratic curved reflective surface on the lens surface to achieve medium-wave and long-wave spectroscopic separation. This eliminates the astigmatism problem of the transmission channel caused by the spectroscopic mirror, reduces design difficulty, and allows the dual-band transfer function to be designed to the diffraction limit.

[0053] It can be understood that the various technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above-mentioned 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.

[0054] The above are merely preferred embodiments of the present application and only specifically describe the technical principles of the present application. These descriptions are intended only to explain the principles of the present application and should not be construed in any way as limiting the scope of protection of the present application. Based on the explanations herein, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application, as well as other specific implementations of the present application that can be conceived by those skilled in the art without inventive effort, shall be included within the scope of protection of the present application.

Claims

1. A new medium / long wavelength common aperture spectral imaging system, characterized in that: include: Medium-wave infrared imaging channel and long-wave infrared imaging channel; The medium-wave infrared imaging channel includes a common lens group and a medium-wave secondary imaging group, the common lens group includes a first lens (1), a second lens (2) and a third lens (3) arranged in sequence, and the medium-wave secondary imaging group includes a fourth lens (4), a fifth lens (5) and a sixth lens (6) arranged in sequence; The long-wave infrared imaging channel comprises the common lens group, the long-wave infrared focusing group, the long-wave tertiary imaging group and the reflector group, the long-wave infrared focusing group comprises a seventh lens (7) and an eighth lens (8) arranged in sequence, the long-wave tertiary imaging group comprises a ninth lens (9), a tenth lens (10), an eleventh lens (11) and a twelfth lens (12) arranged in sequence, the reflector group comprises a first reflector (REL-1) and a second reflector (REL-2), and the reflector (REL-1) is an annular reflector with a central opening; The medium-wave infrared light sequentially passes through the first lens (1), the second lens (2) and the third lens (3) and is focused into a medium-wave primary image point. The medium-wave primary image point is located at the center of the opening of the first reflector (REL-1). The medium-wave primary image point then sequentially passes through the fourth lens (4), the fifth lens (5) and the sixth lens (6) and is imaged again onto the image plane of the medium-wave infrared detector. The long-wave infrared light sequentially passes through the first lens (1), the second lens (2) and the third lens (3) and is focused into a long-wave primary image point. The long-wave primary image point is located near the opening center of the first reflector (REL-1). The long-wave primary image point is reflected by the fourth lens (4) to form collimated light. The collimated light is reflected by the annular reflection surface of the first reflector (REL-1) and enters the second reflector (REL-2) through the seventh lens (7) and the eighth lens (8). The second reflector (REL-2) flips the incident convergent light beam, and realizes long-wave infrared secondary imaging after flipping. The secondary image point is then sequentially passed through the ninth lens (9), the tenth lens (10), the eleventh lens (11) and the twelfth lens (12) for aberration correction, and finally forms an image on the image plane of the long-wave infrared detector.

2. The medium / long wavelength common aperture new spectroscopic imaging system according to claim 1, characterized in that: The incident surface (S4-1) of the fourth lens (4) is a quadratic curved surface, and the surface of the incident surface (S4-1) is coated with a film layer, which is highly reflective to long-wave infrared and highly transmissive to medium-wave infrared.

3. The medium / long wavelength common aperture new spectroscopic imaging system according to claim 1, characterized in that: The first reflector (REL-1) is arranged at 45 degrees to the medium wave primary image point.

4. The medium / long wavelength common aperture new spectroscopic imaging system according to claim 1, characterized in that: The second reflector (REL-2) is arranged at 45 degrees to the horizontal direction.

5. The medium / long wavelength common aperture new spectroscopic imaging system according to claim 1, characterized in that: The working spectrum of the medium-wave infrared detector is 3.7-4.8 μm, and the detector pixel size is 640×512@15 μm.

6. The medium / long wavelength common aperture new spectroscopic imaging system according to claim 1, characterized in that: The long-wave infrared detector has an operating spectrum of 7.7 to 9.5 μm, and a detector pixel size of 640×512@15 μm.

7. An imaging method for a medium / long wavelength common aperture new spectroscopic imaging system according to claim 1, characterized in that: The steps include: The medium-wave infrared light sequentially passes through the first lens (1), the second lens (2) and the third lens (3) and is focused into a medium-wave primary image point. The medium-wave primary image point is located at the center of the opening of the first reflector (REL-1). The medium-wave primary image point then sequentially passes through the fourth lens (4), the fifth lens (5) and the sixth lens (6) and is imaged again onto the image plane of the medium-wave infrared detector. The long-wave infrared light sequentially passes through the first lens (1), the second lens (2) and the third lens (3) and is focused into a long-wave primary image point. The long-wave primary image point is located near the opening center of the first reflector (REL-1). The long-wave primary image point is reflected by the fourth lens (4) to form collimated light. The collimated light is reflected by the annular reflection surface of the first reflector (REL-1) and enters the second reflector (REL-2) through the seventh lens (7) and the eighth lens (8). The second reflector (REL-2) flips the incident convergent light beam, and realizes long-wave infrared secondary imaging after flipping. The secondary image point is then sequentially passed through the ninth lens (9), the tenth lens (10), the eleventh lens (11) and the twelfth lens (12) for aberration correction, and finally forms an image on the image plane of the long-wave infrared detector.

Images