A compact medium- and long-wave common-aperture optical system

Abstract

The present invention relates to the technical field of optical systems, and specifically to a compact medium- and long-wave common-aperture optical system, comprising: a primary reflector and a secondary reflector constituting a Cassegrain structure; further comprising: a beam splitter, a switching mirror, a medium-wave infrared collimation system, a medium-wave infrared imaging system, a medium-wave infrared short-focus lens group, a long-wave infrared collimation system, a long-wave infrared imaging system, a first reflector, a second reflector, a third reflector, and a fourth reflector; light incident on the Cassegrain structure is reflected by the secondary reflector and then incident on the beam splitter; the beam splitter and the secondary reflector are located on the same side of the primary reflector; the long-wave infrared beam transmitted by the beam splitter is used in a long-wave infrared optical path; the medium-wave infrared beam reflected by the beam splitter is used in a medium-wave infrared long-focus optical path; after the switching mirror cuts out the medium-wave infrared long-focus optical path, the medium-wave infrared short-focus lens group is connected to the optical path. The present invention has a medium- and long-wave dual-band optical system, and the medium-band system has two focal lengths, and focal length conversion is performed by the switching mirror.

Description

Technical Field

[0001] The present invention relates to the technical field of optical systems, and in particular to a compact medium- and long-wave common-aperture optical system. Background Art

[0002] In recent years, with advancements in camouflage technology and increasingly complex application environments, the performance requirements for optical systems have become increasingly stringent in order to accurately detect targets at long distances. Different fields of view and wavelengths can address different application scenarios and requirements. After selecting a detector, a short-focus system has a larger field of view, enabling a wider search area and helping to quickly locate a target; a long-focus system has a greater magnification, allowing for greater detail and precise target capture. Infrared imaging technology has a long detection and recognition range and can operate day or night. Image quality is not significantly affected by ambient lighting and weather conditions. Long-wave infrared lenses provide a clearer view of terrain contours, while medium-wave infrared lenses are more sensitive to heat sources during infrared alert. Therefore, an optical system that combines short and long focal lengths with medium and long wavelengths can quickly and accurately extract targets from complex backgrounds, thereby enhancing military combat capabilities.

[0003] Traditional dual-band detection usually uses two cameras with different wavelengths. If a long focal length is to be achieved, the structure will be complicated and difficult to integrate. However, due to the common aperture system sharing the primary and secondary mirror optical paths, it usually only has a long focal state and no short focal state, which is not conducive to rapid search and positioning. For example, the publication number is CN116068742B, and the name is medium-long wave common aperture reentrant optical system.

[0004] Therefore, those skilled in the art urgently need to provide a new medium- and long-wave common-aperture optical system that can have both long and short focal lengths to achieve adaptive rapid search and positioning. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects existing in the above-mentioned prior art, thereby providing a compact medium- and long-wave common-aperture optical system.

[0006] A compact medium- and long-wave common-aperture optical system, comprising: a primary reflector and a secondary reflector forming a Cassegrain structure; further comprising: a beam splitter, a switching mirror, a medium-wave infrared collimation system, a medium-wave infrared imaging system, a medium-wave infrared short-focus mirror group, a long-wave infrared collimation system, a long-wave infrared imaging system, a first reflector, a second reflector, a third reflector, and a fourth reflector;

[0007] The light incident on the Cassegrain structure is reflected by the secondary mirror and then incident on the beam splitter; the beam splitter and the secondary mirror are located on the same side of the primary reflector;

[0008] Long-wave infrared optical path: The long-wave infrared beam transmitted by the beam splitter passes through the central through-hole of the primary reflector and is incident on the second reflector after being refracted into the optical path. It then converges into a primary image plane and is further incident on the third reflector, the long-wave infrared collimation system, the fourth reflector, and the long-wave infrared imaging system in sequence.

[0009] Medium-wave infrared telephoto optical path: The medium-wave infrared beam reflected by the beam splitter is incident on the switching mirror, converges into a primary image plane, and further enters the medium-wave infrared collimation system, the first reflector, and the medium-wave infrared imaging system in sequence;

[0010] Medium-wave infrared short-focus optical path: After the switching mirror cuts out from the medium-wave infrared long-focus optical path, the medium-wave infrared beam is converged into a primary image plane through the medium-wave infrared short-focus mirror group, and further enters the medium-wave infrared collimation system, the first reflector and the medium-wave infrared imaging system in sequence.

[0011] Preferably, the second reflector, the third reflector, the long-wave infrared collimation system, the fourth reflector and the long-wave infrared imaging system in the long-wave infrared optical path are connected in sequence to form a U-shaped optical path.

[0012] Preferably, the entrance pupil diameter of the medium-wave infrared telephoto optical path is 250 mm; the focal length is 1000 mm; the field of view angle is 1.44°; the operating band is 3.7 μm to 4.8 μm, and the distortion is less than 1%.

[0013] Preferably, the entrance pupil diameter of the medium-wave infrared short-focus optical path is 20 mm; the focal length is 80 mm; the field of view angle is 17.5°; the operating band is 3.7 μm to 4.8 μm, and the distortion is less than 1%.

[0014] Preferably, the entrance pupil diameter of the long-wave infrared optical path is 250 mm; the focal length is 500 mm; the field of view angle is 1.44°; the operating band is 7.7 μm to 12 μm, and the distortion is less than 0.5%.

[0015] Preferably, the transmissive materials used for the lenses constituting the medium-wave infrared long-focus optical path and the medium-wave infrared short-focus optical path include silicon and germanium.

[0016] Preferably, the transmissive material used in each lens constituting the long-wave infrared light path is germanium.

[0017] Preferably, the beam splitter, switching mirror, first reflector, second reflector, third reflector and fourth reflector all form an angle of 45 degrees with the optical axis.

[0018] The technical solution of the present invention has the following advantages:

[0019] The present invention has a medium-wave and long-wave dual-band optical system, and the medium-wave system has two focal lengths. The focal length is converted by switching mirrors, and the two medium-wave focal lengths share the same detector. Multiple folding mirrors are used to fold the optical path, which greatly reduces the volume of the system. The medium-wave infrared long-focus focal length reaches 1000mm, the short-focus focal length is 80mm, and the long-wave infrared focal length is 500mm, which helps to achieve long-distance detection and identification of multiple scenes; the medium-wave infrared imaging of the present invention adopts secondary imaging, and the long-wave infrared imaging system adopts primary imaging, and the cooling efficiency reaches 100%, the optical path is simple, the number of lenses is small, and the energy is strong; the central field of view of the primary reflector and the secondary mirror of the present invention is perfect imaging, the image point is far away from the primary mirror and is located behind its optical path, the primary reflector and the secondary mirror can be separately adjusted and tested, which ensures imaging quality and reduces the difficulty of adjustment; in the medium-wave band two-focus optical path of the present invention, the transmission materials used are both silicon and germanium; in the long-wave band optical path, the transmission materials used are all germanium, with low material cost and strong environmental adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 Schematic diagram of the structure of the compact medium- and long-wave common-aperture optical system of the present invention;

[0022] Figure 2 This is a schematic structural diagram of a medium-wave infrared imaging system of a compact medium- and long-wave common-aperture optical system of the present invention;

[0023] Figure 3 This is a schematic structural diagram of the long-wave infrared collimation system and the long-wave infrared imaging system of the compact medium- and long-wave common-aperture optical system of the present invention;

[0024] Figure 4 This is the MTF diagram of the telephoto system in the 3.7μm~4.8μm band after the improvement of the medium-wave infrared telephoto optical path of the present invention;

[0025] Figure 5 This is the MTF diagram of the short-focus system in the 3.7μm~4.8μm band after the improvement of the medium-wave infrared short-focus optical path of the present invention;

[0026] Figure 6 This is the MTF diagram in the 7.7μm~12μm band after the long-wave infrared optical path of the present invention is improved.

[0027] Description of reference numerals:

[0028] 1-primary reflector; 2-secondary mirror; 3-beam splitter; 4-switching mirror;

[0029] 5-medium-wave infrared collimation system; 501-fourth lens; 502-fifth lens;

[0030] 6- first reflector;

[0031] 7-medium-wave infrared imaging system; 701-sixth lens; 702-seventh lens; 703-eighth lens; 704-ninth lens; 705-tenth lens; 706-eleventh lens; 707-twelfth lens; 708-thirteenth lens; 709-fourteenth lens;

[0032] 8-medium-wave infrared short-focus lens group; 801-first lens; 802-second lens; 803-third lens;

[0033] 9- second reflecting mirror;

[0034] 10- third reflecting mirror;

[0035] 11-long-wave infrared collimation system; 1101-fifteenth lens; 1102-sixteenth lens;

[0036] 12- fourth reflector;

[0037] 13-long-wave infrared imaging system; 1301-the seventeenth lens; 1302-the eighteenth lens; 1303-the nineteenth lens; 1304-the twentieth lens and 1305-the twenty-first lens. DETAILED DESCRIPTION

[0038] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0041] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] Example 1

[0043] like Figure 1 This embodiment discloses a compact medium- and long-wave common-aperture optical system, comprising: a primary reflector 1 and a secondary reflector 2 forming a Cassegrain structure, a beam splitter 3, a switching mirror 4, a medium-wave infrared collimation system 5, a medium-wave infrared imaging system 7, a medium-wave infrared short-focus lens group 8, a long-wave infrared collimation system 11, a long-wave infrared imaging system 13, a first reflector 6, a second reflector 9, a third reflector 10, and a fourth reflector 12;

[0044] The light incident on the Cassegrain structure is reflected by the secondary mirror 2 and then incident on the beam splitter 3; the beam splitter 3 and the secondary mirror 2 are located on the same side of the primary reflector 1;

[0045] Long-wave infrared optical path: The long-wave infrared beam transmitted by the beam splitter 3 passes through the central through-hole of the primary reflector 1 and is incident on the second reflector 9 after being folded. It then converges into a primary image plane and is further incident on the third reflector 10, the long-wave infrared collimation system 11, the fourth reflector 12 and the long-wave infrared imaging system 13 in sequence.

[0046] Medium-wave infrared long-focus optical path: After the medium-wave infrared light beam reflected by the beam splitter 3 is incident on the switching mirror 4, it is converged into a primary image plane and further incident on the medium-wave infrared collimation system 5, the first reflector 6 and the medium-wave infrared imaging system 7 in sequence. In actual application, it is converged and imaged on the long-wave detector.

[0047] Medium-wave infrared short-focus optical path: After the switching mirror cuts off the medium-wave infrared long-focus optical path, the medium-wave infrared beam passes through the medium-wave infrared short-focus lens group 8 and converges into a primary image plane. It is then incident on the medium-wave infrared collimation system 5, the first reflector 6, and the medium-wave infrared imaging system 7 in sequence. In actual applications, the medium-wavelength long-focus and short-focus optical paths share the same detector and are both converged and imaged on the medium-wave detector.

[0048] Specifically:

[0049] It should be noted that when the switching mirror 4 cuts into the medium-wave infrared long-focus optical path, the medium-wave infrared short-focus optical path is blocked and the medium-wave infrared long-focus optical path is connected;

[0050] When the switching mirror 4 cuts out the medium-wave infrared long-focus optical path, the medium-wave infrared long-focus optical path is disconnected, and the medium-wave infrared short-focus optical path is connected;

[0051] In the long-wave infrared optical path, the second reflector 9, the third reflector 10, the long-wave infrared collimating system 11, the fourth reflector 12 and the long-wave infrared imaging system 13 are sequentially connected to form a U-shaped optical path.

[0052] The beam splitter 3 , the switching mirror 4 , the first reflector 6 , the second reflector 9 , the third reflector 10 and the fourth reflector 12 all form an angle of 45 degrees with the optical axis.

[0053] like Figure 1 As shown, the medium-wave infrared short-focus lens group 8 includes a first lens 801, a second lens 802 and a third lens 803 optically connected in sequence; the medium-wave infrared collimation system 5 includes a fourth lens 501 and a fifth lens 502 optically connected in sequence.

[0054] like Figure 1 and 2 As shown, the medium-wave infrared imaging system 7 includes a sixth lens 701, a seventh lens 702, an eighth lens 703, a ninth lens 704, a tenth lens 705, an eleventh lens 706, a twelfth lens 707, a thirteenth lens 708 and a fourteenth lens 709 which are optically connected in sequence.

[0055] like Figure 1 and 3 As shown, the long-wave infrared collimation system 11 includes a fifteenth lens 1101 and a sixteenth lens 1102 optically connected in sequence; the long-wave infrared imaging system 13 includes a seventeenth lens 1301, an eighteenth lens 1302, a nineteenth lens 1303, a twentieth lens 1304 and a twenty-first lens 1305 optically connected in sequence.

[0056] Example 2

[0057] Based on Example 1, this example further discloses the following:

[0058] Keeping the parameters of the Cassegrain structure unchanged, this embodiment optimizes the medium-wave infrared long-focus optical path. The technical indicators of the medium-wave infrared long-focus optical path are as follows:

[0059] The entrance pupil diameter of the medium-wave infrared telephoto optical path is 250mm; the focal length is 1000mm; the field of view is 1.44°; the operating band is 3.7μm~4.8μm, and the distortion is less than 1%. Figure 4As shown, since the embodiment improves the medium-wave infrared telephoto optical path, the MTF at the Nyquist frequency of 33 lp / mm is close to the diffraction limit.

[0060] Example 3

[0061] Based on Example 2, this example further discloses the following:

[0062] like Figure 1 and 2 Keeping the parameters of the MWIR collimation system 5, all reflectors, and the MWIR imaging system 7 unchanged, the MWIR short-focus optical path is optimized. The technical specifications of the MWIR short-focus optical path are as follows:

[0063] The entrance pupil diameter of the medium-wave infrared short-focus optical path is 20mm; the focal length is 80mm; the field of view angle is 17.5°; the operating band is 3.7μm~4.8μm, and the distortion is less than 1%. Figure 5 As shown, in this embodiment, the MTF at the Nyquist frequency of 33 lp / mm is close to the diffraction limit because the medium-wave infrared short-focus optical path is improved in this embodiment.

[0064] Example 4

[0065] Based on Example 3, this example further discloses the following:

[0066] like Figure 1 and 3 Keeping the parameters of the Cassegrain structure unchanged, this embodiment optimizes the long-wave infrared imaging system 13. The technical indicators of the long-wave infrared imaging system 13 are as follows:

[0067] The entrance pupil diameter of the long-wave infrared optical path is 250mm; the focal length is 500mm; the field of view is 1.44°; the operating band is 7.7μm~12μm, and the distortion is less than 0.5%. Figure 6 As shown, in this embodiment, the MTF at the Nyquist frequency of 33 lp / mm is close to the diffraction limit because the medium-wave infrared short-focus optical path is improved in this embodiment.

[0068] Example 5

[0069] Based on Example 4, this example further discloses the following: the transmissive materials used for the lenses constituting the medium-wave infrared long-focus optical path and the medium-wave infrared short-focus optical path include silicon and germanium.

[0070] The transmissive material used in each lens that constitutes the long-wave infrared light path is germanium.

[0071] Specifically:

[0072] Table 1 lists the detailed data of the medium-wave infrared telephoto optical path, including the curvature radius, thickness and material of each lens. The incident surface is the incident surface of each lens, and the exit surface is the exit surface of each lens.

[0073] Table 1 Detailed data of the medium-wave infrared telephoto optical path

[0074]

[0075] Table 2 Detailed data of the long-wave infrared imaging optical path, including the curvature radius, thickness, and material of each lens. The incident surface is the light incident surface of each lens, and the exit surface is the light exit surface of each lens.

[0076] Table 2 Detailed data of the long-wave infrared imaging optical path

[0077]

[0078] Table 3 lists the detailed data of the medium-wave infrared short-focus lens set 8, including the curvature radius, thickness and material of each lens. The incident surface is the light incident surface of each lens, and the exit surface is the light exit surface of each lens.

[0079] Table 3 Detailed data of medium-wave infrared short-focus lens set 8

[0080]

[0081] In this embodiment, the aspheric surfaces all satisfy the equation:

[0082] ;

[0083] Where Z is the distance from the aspheric surface to the vertex of the aspheric surface at a height of r along the optical axis, c is the radius of curvature, k is the cone coefficient, 、 、 is the aspheric coefficient. Table 4 shows the aspheric parameters for medium-wave infrared and long-wave infrared imaging.

[0084] Table 4 Aspheric parameters for medium-wave infrared and long-wave infrared imaging

[0085]

[0086] Furthermore, the present embodiment adopts a segmented aberration-correcting optimization design method, which realizes that the front group of reflective effect devices and the rear group of collimated imaging devices connected by the optical path can independently correct the aberrations, and the front group of reflective effect devices can be individually adjusted and tested, thereby ensuring the imaging quality. Figure 4-6 , which is a schematic diagram illustrating the optical imaging quality related to this embodiment.

[0087] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A compact medium- and long-wave common-aperture optical system, comprising: A primary reflector (1) and a secondary reflector (2) forming a Cassegrain structure, characterized in that the primary reflector (1) and the secondary reflector (2) further comprise: a beam splitter (3), a switching mirror (4), a medium-wave infrared collimation system (5), a medium-wave infrared imaging system (7), a medium-wave infrared short-focus mirror group (8), a long-wave infrared collimation system (11), a long-wave infrared imaging system (13), a first reflector (6), a second reflector (9), a third reflector (10), and a fourth reflector (12); The light incident on the Cassegrain structure is reflected by the secondary mirror (2) and then incident on the beam splitter (3); the beam splitter (3) and the secondary mirror (2) are located on the same side of the primary reflector (1); Long-wave infrared optical path: the long-wave infrared light beam transmitted by the beam splitter (3) passes through the central through hole of the main reflector (1) and is incident on the second reflector (9) to fold the optical path, converges to form a primary image plane, and further incident on the third reflector (10), the long-wave infrared collimation system (11), the fourth reflector (12) and the long-wave infrared imaging system (13) in sequence; Medium-wave infrared telephoto optical path: The medium-wave infrared light beam reflected by the beam splitter (3) is incident on the switching mirror (4), converges into a primary image plane, and further sequentially enters the medium-wave infrared collimation system (5), the first reflector (6), and the medium-wave infrared imaging system (7); Medium-wave infrared short-focus optical path: After the switching mirror (4) cuts out from the medium-wave infrared long-focus optical path, the medium-wave infrared light beam is converged into a primary image plane through the medium-wave infrared short-focus mirror group (8), and further incident on the medium-wave infrared collimation system (5), the first reflector (6) and the medium-wave infrared imaging system (7) in sequence.

2. A compact medium- and long-wavelength common-aperture optical system according to claim 1, characterized in that: In the long-wave infrared optical path, the second reflector (9), the third reflector (10), the long-wave infrared collimation system (11), the fourth reflector (12) and the long-wave infrared imaging system (13) are connected in sequence to form a U-shaped optical path.

3. The compact medium- and long-wavelength common-aperture optical system according to claim 1, characterized in that: The entrance pupil diameter of the medium-wave infrared telephoto optical path is 250mm; the focal length is 1000mm; the field of view angle is 1.44°; the operating band is 3.7μm~4.8μm, and the distortion is less than 1%.

4. The compact medium- and long-wavelength common-aperture optical system according to claim 1, characterized in that: The entrance pupil diameter of the medium-wave infrared short-focus optical path is 20mm; the focal length is 80mm; the field of view angle is 17.5°; the operating band is 3.7μm~4.8μm, and the distortion is less than 1%.

5. The compact medium- and long-wavelength common-aperture optical system according to claim 1, characterized in that: The entrance pupil diameter of the long-wave infrared optical path is 250mm; the focal length is 500mm; the field of view angle is 1.44°; the operating band is 7.7μm~12μm, and the distortion is less than 0.5%.

6. The compact medium- and long-wavelength common-aperture optical system according to claim 1, characterized in that: The transmission materials used in the lenses constituting the medium-wave infrared long-focus optical path and the medium-wave infrared short-focus optical path include silicon and germanium.

7. The compact medium- and long-wavelength common-aperture optical system according to claim 1, characterized in that: The transmissive material used in each lens that constitutes the long-wave infrared light path is germanium.

8. The compact medium- and long-wavelength common-aperture optical system according to claim 1, characterized in that: The beam splitter (3), the switching mirror (4), the first reflector (6), the second reflector (9), the third reflector (10) and the fourth reflector (12) all form an angle of 45 degrees with the optical axis.

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