Laser and infrared common aperture optical system

Abstract

The application discloses a kind of laser and infrared common-caliber optical systems, for solving the technical problems such as the difficulty of existing composite optical system to realize high sensitivity detection, optical axis pointing stability is susceptible to environmental influence and not having image stabilization function etc..The optical system includes off-axis reflective optical unit, dichroic flat plate, infrared imaging unit, laser emission unit and laser receiving unit, dichroic flat plate is located in the reflection light path of the seventh mirror in off-axis reflective optical unit, for transmitting infrared light, reflecting laser;Laser emission unit, laser light splitting flat plate, dichroic flat plate, off-axis reflective optical unit form laser emission optical system;Off-axis reflective optical unit, dichroic flat plate, infrared imaging unit form infrared imaging optical system;Off-axis reflective optical unit, dichroic flat plate, laser light splitting flat plate, laser receiving unit form laser receiving optical system.The optical system has high integration, greatly improves the consistency of each optical path optical axis pointing.

Description

Technical Field

[0001] The present invention relates to a composite optical system, in particular to a co-aperture off-axis composite optical system with high detection sensitivity, high optical axis stability, laser emission, laser reception and refrigeration infrared imaging, and image stabilization function. Background Art

[0002] With advances in laser technology, hybrid laser and optical imaging detection systems have developed rapidly, making optical system integration (i.e., composite optical systems) a trend. Composite optical systems can fuse multiple wavelength bands within a limited space, acquiring more target information and offering significant advantages over traditional single-mode optical systems. Composite optical system fusion methods can be divided into two types: split-aperture and common-aperture. Split-aperture composite optical systems, due to the independence of the optical systems for each wavelength band, result in bulky and less compact structures. The consistency of the optical axis pointing across the wavelength bands is easily affected by environmental factors, leading to deviations between the laser illumination point and the imaging and aiming points, and even causing the optical system to malfunction. Common-aperture composite optical systems offer a high degree of integration and a compact structure. However, traditional common-aperture composite optical systems often share only a few optical components, such as the primary and secondary mirrors. The optical path is split into multiple paths by a back-end beamsplitter. After splitting, the optical paths remain relatively independent, and the optical axis pointing of each wavelength band can still vary due to environmental influences. This is particularly important when the divergence angle of the laser emission and the resolution of the imaging optical path angle are low. Maintaining consistent optical axis pointing across the wavelength bands remains a key concern.

[0003] Currently, laser and imaging co-aperture reflective optical systems are a commonly used co-aperture composite optical system. Most systems combine the imaging optical path with the laser emission / receiving optical path, creating a coaxial co-path structure. However, due to central obstruction, this results in significant energy loss in both the imaging and laser emission optical paths. Furthermore, the extensive use of lens-relay imaging or laser collimation in each optical path after beam splitting results in significant thermal radiation from the infrared imaging optical path itself, making it unable to meet high-sensitivity detection requirements. Furthermore, when the aperture of the laser emission optical path is smaller than the diameter of the secondary mirror, a co-aperture design of the laser emission optical path is also impossible. Furthermore, these optical systems lack scanning or image stabilization capabilities, which are crucial for achieving high-precision tracking and aiming.

[0004] Off-axis reflective optical systems, another commonly used co-aperture composite optical system, are currently widely used in high-performance infrared imaging due to their lack of chromatic aberration, excellent heat resistance, simple structure, and low self-heat radiation. Published literature on off-axis co-aperture laser / imaging composite optical systems often utilize an off-axis co-optical path structure to avoid energy loss. However, this approach only considers the co-optical path design of the laser and imaging system, lacking consideration for optical axis pointing stability and high-sensitivity infrared detection. Furthermore, the infrared relay mirror assembly generates a significant amount of self-heat radiation, which severely degrades the optical system's infrared detection performance. Furthermore, after beam splitting, the optical paths of each wavelength band remain relatively independent, making it difficult to ensure optical axis pointing stability.

[0005] For example, Chinese patent publication number CN112526531A discloses a dual-field-of-view infrared imaging system with multi-target laser ranging capabilities. However, the laser emission, laser reception, and infrared imaging optical paths of this imaging system share a front-end off-axis two-mirror afocal system. After the spectrometer is split, the infrared imaging and laser emission and laser reception optical paths are relatively independent, making the pointing stability of the optical axes of each optical path susceptible to environmental influences. Furthermore, the infrared imaging optical path uses an uncooled detector and lens group for relay imaging, making it difficult to achieve high-sensitivity detection, and it lacks scanning or image stabilization capabilities. Chinese patent publication number CN119002079A discloses an off-axis composite tracking and aiming and laser emission co-aperture Kude optical system and its assembly method. However, this optical system uses a common optical path structure for visible light imaging and laser emission, lacks infrared imaging capabilities, laser reception functions, and image stabilization functions, and its structure is not compact enough.

[0006] For example, Xiang Jiansheng et al. introduced a semi-active laser and long-wave infrared co-aperture composite optical system in the article "A Laser and Infrared Composite Optical System" published in the journal "Laser & Infrared" in Volume 48, Issue 1 in January 2018. The optical system is a coaxial co-aperture fold-back structure and uses an infrared uncooled detector. It has infrared imaging and laser receiving functions, but has no laser emission optical path and does not have image stabilization function.

[0007] In the article "Design of Active Laser / Infrared Co-aperture Composite Imaging Optical System" published by Yin Na et al. in the journal "Infrared Technology" Vol. 38, No. 1 in January 2016, an active laser and infrared imaging co-aperture composite optical system was introduced. The system adopts a coaxial optical path structure and can realize scanning imaging, laser emission, laser reception and cooled infrared imaging. However, the infrared relay mirror group has large thermal radiation, and the laser emission optical path is relatively independent from the laser reception optical path and the infrared imaging optical path, making it difficult to ensure the pointing stability of each optical axis.

[0008] In summary, designing a co-aperture off-axis composite optical system that combines laser emission, laser reception and cooled infrared imaging with image stabilization, high infrared detection sensitivity and high optical axis pointing stability is of great significance for achieving the integration and high performance of the composite system. Summary of the Invention

[0009] The purpose of the present invention is to solve the technical problems of existing composite optical systems, such as difficulty in achieving high-sensitivity detection, susceptibility of optical axis pointing stability to environmental influences, and lack of image stabilization function, and to provide a laser and infrared co-aperture optical system.

[0010] To achieve the above objectives, the technical solutions provided by the present invention are:

[0011] A laser and infrared co-aperture optical system, which is special in that:

[0012] It includes an off-axis reflective optical unit, a color separation plate, an infrared imaging unit, a laser emitting unit and a laser receiving unit;

[0013] The off-axis reflective optical unit includes a fourth reflector, a fifth reflector, a sixth reflector, and a seventh reflector, which are sequentially arranged off-axis along the optical path. The dichroic plate is located on the reflective optical path of the seventh reflector and is used to transmit infrared light in the incident light beam and reflect laser light in the incident light beam. The infrared imaging unit is located on the transmitted optical path of the dichroic plate and is used to achieve infrared imaging. The laser receiving unit is located on the reflected optical path of the dichroic plate and is used to achieve laser reception.

[0014] A laser beam splitter plate is provided on the outgoing light path of the laser emitting unit. The laser beam splitter plate is located between the color separation plate and the laser receiving unit and is used to transmit the laser reflected by the color separation plate to the laser receiving unit and reflect the laser emitted by the laser emitting unit to the color separation plate.

[0015] The laser emitting unit, the laser beam splitting plate, the color separation plate, the seventh reflector, the sixth reflector, the fifth reflector, and the fourth reflector together constitute a laser emitting optical system;

[0016] The fourth reflector, the fifth reflector, the sixth reflector, the seventh reflector, the color separation plate, and the infrared imaging unit together constitute an infrared imaging optical system;

[0017] The fourth reflecting mirror, the fifth reflecting mirror, the sixth reflecting mirror, the seventh reflecting mirror, the color separation plate, the laser beam splitting plate, and the laser receiving unit together constitute a laser receiving optical system.

[0018] Furthermore, an off-axis afocal telescope system is included, which includes a first reflector, a second reflector, and a third reflector that are sequentially arranged off-axis along the optical path; the fourth reflector is located on the reflected optical path of the third reflector;

[0019] The exit pupil position of the off-axis afocal telescope system coincides with the entrance pupil position of the off-axis reflective optical unit and is located between the third reflector and the fourth reflector.

[0020] Furthermore, a scanning reflector is provided between the third reflector and the fourth reflector for adjusting the optical axes of the laser emitting optical system, the infrared imaging optical system and the laser receiving optical system.

[0021] Furthermore, the laser emitting unit includes a laser and a laser emitting lens;

[0022] The laser emitting lens is located between the laser and the laser beam splitting plate; the laser emitting lens is a double convex positive lens with positive optical power.

[0023] Furthermore, the laser receiving unit includes a relay lens group and a laser receiving detector;

[0024] The relay lens assembly includes a first lens, a second lens, a filter, and a third lens arranged in sequence along the optical path; the first lens is arranged near the laser beam splitter plate and is a biconvex positive lens; the second lens is a negative lens convex toward the object side; the surface of the filter is coated with a laser narrowband filter film for filtering out stray light; the third lens is a meniscus positive lens convex toward the object side.

[0025] Furthermore, the infrared imaging unit is a cooled infrared detector, and the aperture stop of the infrared imaging optical system is located at the cold stop of the cooled infrared detector; the laser receiving detector is an APD detector; and the laser is a fiber laser.

[0026] Furthermore, the reflective surfaces of the first reflector, the second reflector and the third reflector are quadratic surfaces;

[0027] The reflective surface profiles of the fourth reflector, the fifth reflector, and the sixth reflector are expressed as XY polynomials, with even-order terms of X being taken;

[0028] The reflecting surface of the seventh reflecting mirror is an even-order aspherical surface.

[0029] Furthermore, the first reflector, the third reflector, the fourth reflector, the fifth reflector and the seventh reflector all have positive optical power; and the second reflector and the sixth reflector all have negative optical power.

[0030] Furthermore, the color separation plate is made of one of germanium, silicon, ZnSe, Zns, and chalcogenide glass, and a surface thereof close to the seventh reflector is coated with a spectrum splitting film for transmitting infrared light and reflecting laser light.

[0031] Furthermore, the laser beam splitting plate is made of optical quartz glass, and a laser beam splitting film is coated on a side close to the color separation plate, and the ratio of laser transmittance to reflectivity is 1:1.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention provides a co-aperture optical system for laser and infrared, wherein a laser emitting unit, a laser beam splitter plate, a color separation plate, and an off-axis reflective optical unit constitute a laser emitting optical system; an off-axis reflective optical unit, a color separation plate, and an infrared imaging unit constitute an infrared imaging optical system; and an off-axis reflective optical unit, a color separation plate, a laser beam splitter plate, and a laser receiving unit constitute a laser receiving optical system. Thus, a co-aperture off-axis composite optical system combining laser emission, laser reception, and infrared imaging is provided. The optical system has a high degree of integration and greatly improves the consistency and stability of the optical axis pointing of each optical path.

[0034] 2. The present invention also sets an off-axis afocal telescope system at the front end of the off-axis reflective optical unit. The setting of this system not only avoids the energy loss caused by central obstruction, but also realizes the common aperture design of the laser emission optical path with arbitrary aperture.

[0035] 3. The present invention can also provide a scanning reflector between the third reflector and the fourth reflector (i.e., the light output end of the off-axis afocal telescope system) to achieve functions such as image stabilization.

[0036] 4. The off-axis reflective optical units of the present invention can be used in combination or individually to achieve a modular design of a reflective off-axis optical system, thereby improving the integration and interchangeability of the optical system.

[0037] 5. In order to avoid the relative independence of each optical path after splitting, the present invention splits the light in front of the infrared imaging light path. Most of the components in the optical system are common components for the three optical paths. The relay lens group after splitting is also relatively simple, with a small number of optical elements and a rotationally symmetrical structure, which greatly improves the consistency of the pointing direction of the optical axes of each optical path.

[0038] 6. The infrared imaging unit of the present invention adopts a cooled infrared detector, which, combined with an off-axis total reflection optical system, not only greatly improves the detection sensitivity of the infrared system, but also does not produce ghost images, cold reflections, etc., and has low spontaneous radiation and excellent cold reflection suppression characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1is a schematic diagram of an optical system according to an embodiment of the present invention;

[0040] Figure 2 yes Figure 1 A partial enlarged view of

[0041] Figure 3 Schematic diagram of the optical structure of the relay mirror assembly in the laser receiving unit according to an embodiment of the present invention;

[0042] Figure 4 is a light path diagram of the infrared imaging optical system in an embodiment of the present invention;

[0043] Figure 5 is a light path diagram of the laser emission optical system in an embodiment of the present invention;

[0044] Figure 6 2 is a light path diagram of the laser receiving optical system in an embodiment of the present invention.

[0045] The reference numerals are as follows:

[0046] 1-first reflector, 2-second reflector, 3-third reflector, 4-fourth reflector, 5-fifth reflector, 6-sixth reflector, 7-seventh reflector, 8-color separation plate, 9-cooled infrared detector window, 10-cooled infrared detector cold block, 11-cooled infrared detector target surface, 12-laser spectrometer plate, 13-laser emitting lens, 14-laser, 15-relay lens assembly, 151-first lens, 152-second lens, 153-filter, 154-third lens, 16-laser receiving detector. DETAILED DESCRIPTION

[0047] In order to make the purpose, advantages and features of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific examples. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention, and are not used to limit the scope of protection of the present invention.

[0048] like Figure 1 and Figure 2 As shown, this embodiment provides a laser and infrared co-aperture optical system, including an off-axis reflective optical unit, a color separation plate 8, an infrared imaging unit, a laser emitting unit and a laser receiving unit.

[0049] The off-axis reflective optical unit includes a fourth reflector 4, a fifth reflector 5, a sixth reflector 6, and a seventh reflector 7, which are sequentially arranged off-axis along the optical path. A dichroic plate 8 is located in the reflective optical path of the seventh reflector 7 and is used to transmit infrared light in the incident light beam and reflect laser light in the incident light beam. An infrared imaging unit is located in the transmitted optical path of the dichroic plate 8 and is used to achieve infrared imaging. A laser receiving unit is located in the reflected optical path of the dichroic plate 8 and is used to achieve laser reception. The dichroic plate 8 can be made of one of germanium, silicon, ZnSe, ZnS, or chalcogenide glass. The surface of the dichroic plate adjacent to the seventh reflector 7 is coated with a spectral spectroscopic coating to transmit infrared light and reflect laser light. In this embodiment, the dichroic plate 8 is made of 1.5 mm thick single crystal germanium.

[0050] A laser beam splitter plate 12 is provided in the outgoing optical path of the laser emitting unit. Located between the dichroic plate 8 and the laser receiving unit, the laser beam splitter plate 12 transmits laser light reflected by the dichroic plate 8 to the laser receiving unit and reflects laser light emitted by the laser emitting unit back to the dichroic plate 8. In this embodiment, the surface of the laser beam splitter plate 12 closest to the dichroic plate 8 is coated with a laser beam splitter film, achieving a 1:1 laser transmittance to reflectivity ratio.

[0051] The laser emitting unit, the laser beam splitting plate 12, the color separation plate 8, the seventh reflector 7, the sixth reflector 6, the fifth reflector 5 and the fourth reflector 4 constitute a laser emitting optical system (the optical path of which is as shown in FIG. Figure 5 shown).

[0052] The fourth reflector 4, the fifth reflector 5, the sixth reflector 6, the seventh reflector 7, the color separation plate 8 and the infrared imaging unit constitute an infrared imaging optical system (the optical path is as follows Figure 4 shown).

[0053] The fourth reflecting mirror 4, the fifth reflecting mirror 5, the sixth reflecting mirror 6, the seventh reflecting mirror 7, the color separation plate 8, the laser beam splitting plate 12 and the laser receiving unit constitute a laser receiving optical system (the optical path of which is as follows Figure 6 shown).

[0054] The present invention provides a co-aperture laser and infrared optical system with high optical axis pointing stability, avoiding the traditional co-aperture off-axis system. After the splitting, the infrared imaging and laser emission and laser reception optical paths are relatively independent. The consistency of the optical axis pointing is easily affected by environmental factors, resulting in deviations between the laser irradiation point and the imaging and aiming points, and even causing the system to malfunction. The present invention avoids the relative independence of the optical paths after the splitting as much as possible, and splits the infrared imaging optical path in front of the image plane. The vast majority of components in the optical system are shared by the three optical paths. The optical system after the splitting is also very simple, with a small number of optical components and a rotationally symmetrical structure, which greatly improves the consistency of the optical axis pointing of each optical path.

[0055] This embodiment also includes an off-axis afocal telescope system, which includes a first reflector 1, a second reflector 2, and a third reflector 3 arranged in an off-axis manner along the optical path; wherein the third reflector 3 is arranged close to the fourth reflector 4, and the fourth reflector 4 is located on the reflection optical path of the third reflector 3.

[0056] The exit pupil of the off-axis afocal telescope coincides with the entrance pupil of the off-axis reflective optical unit and is located between the third reflector 3 and the fourth reflector 4. The off-axis afocal telescope is used to compress the incident light beam. In this embodiment, the off-axis afocal telescope is an independent, modular optical system that can be used in conjunction with a back-end optical system to achieve functions such as focal length extension and laser divergence compression, or the back-end optical system alone can be used for infrared imaging, laser transmission, and reception.

[0057] In addition, since the off-axis afocal telescope system has excellent imaging quality, a fast scanning mirror can be set in the parallel optical path between the third reflector 3 and the fourth reflector 4 to accurately adjust the optical axes of the laser emitting optical system, the infrared imaging optical system and the laser receiving optical system to achieve image stabilization, image motion compensation, beam scanning, etc.

[0058] In this embodiment, the maximum aperture of the light beam incident on the off-axis afocal telescope system is 150 mm, and the magnification is 4 times.

[0059] The laser emitting unit includes a laser 14 and a laser emitting lens 13 ; the laser emitting lens 13 is located between the laser 14 and the laser beam splitting plate 12 .

[0060] After being reflected by the laser emitting lens 13, the laser beam splitter plate 12, and the color separation plate 8, the laser beam is collimated and emitted onto the object through the seventh reflector 7, the sixth reflector 6, the fifth reflector 5, the fourth reflector 4, the third reflector 3, the second reflector 2, and the first reflector 1, forming the laser emission optical path. In this embodiment, the laser 14 is a fiber laser with an emission wavelength of 1064 nm, but a specific wavelength can be selected based on actual needs. The laser emitting lens 13 uses a single biconvex positive focal length with a magnification of 1.167. The laser emission aperture of the laser emission optical path is 29 mm. The optical design parameters of the laser beam splitter plate 12 and the laser emitting lens 13 are shown in Table 1.

[0061] Table 1 Laser emission lens parameters (unit: mm)

[0062]

[0063] The laser receiving unit includes a relay mirror group 15 and a laser receiving detector 16; the fourth reflector 4, the fifth reflector 5, and the sixth reflector 6 further focus the outgoing light beam of the off-axis afocal telescope system. The light beam passes through the color separation plate 8, the laser beam splitting plate 12, and then passes through the relay mirror group 15 and is focused on the laser receiving detector 16, thus forming a laser receiving optical path.

[0064] In this embodiment, the laser receiving detector 16 is an APD detector, and the laser receiving wavelength band is 1064 nm. The magnification of the relay lens group 15 is 0.87, and the laser receiving aperture is 100 mm.

[0065] like Figure 3 As shown, the relay lens assembly 15 includes a first lens 151, a second lens 152, a filter 153, and a third lens 154, which are arranged in sequence along the optical path. The first lens 151 is arranged near the laser beam splitter plate 12 and is a biconvex positive lens; the second lens 152 is a negative lens convex toward the object; the surface of the filter 153 is coated with a laser narrowband filter film for filtering out stray light; the third lens 154 is a meniscus positive lens convex toward the object. The optical design parameters of each lens are shown in Table 2.

[0066] Table 2 Optical design parameters of each lens in the relay lens group

[0067]

[0068] The infrared imaging unit is a cooled infrared detector, which includes a cooled infrared detector window 9, a cooled infrared detector cold stop 10 and a cooled infrared detector target surface 11. The fourth reflector 4, the fifth reflector 5 and the sixth reflector 6 further image the outgoing light beam of the off-axis afocal telescope system. The light beam is sequentially transmitted through the color separation plate 8, the cooled infrared detector window 9 and the cooled infrared detector cold stop 10, and is imaged on the cooled infrared detector target surface 11, forming an infrared imaging optical path, and the aperture stop of the infrared imaging optical path is located at the cooled infrared detector cold stop 10.

[0069] In this embodiment, the reflecting surfaces of the first reflector 1, the second reflector 2, and the third reflector 3 are quadratic surfaces; the first reflector 1 and the third reflector 3 both have positive optical power, the second reflector 2 has negative optical power, and the optical path structure is "positive-negative-positive". The specific optical design parameters of each reflector are shown in Table 3.

[0070] Table 3 Optical design parameters of each mirror in the off-axis afocal telescope system

[0071]

[0072] In Table 3, c represents the curvature, krepresents the quadratic surface coefficient.

[0073] The reflective surface profiles of the fourth reflector 4, the fifth reflector 5, and the sixth reflector 6 are expressed as XY polynomials; the reflective surface profile of the seventh reflector 7 is an even-order aspheric surface. To correct aberrations while maintaining reasonable machinability, minimize the number of free-form surfaces, and lower the order, the fourth reflector 4, the fifth reflector 5, and the sixth reflector 6 of this embodiment use only the even-order terms of X in the XY polynomial. The highest order of the XY polynomial for the fourth reflector 4 is 5th, the highest order of the XY polynomial for the fifth reflector 5 is 6th, and the highest order of the XY polynomial for the sixth reflector 6 is 6th; the highest order of the even-order aspheric surface of the seventh reflector 7 is 8th.

[0074] The XY polynomial free-form surface equation is:

[0075]

[0076]

[0077] in, z is the surface sag; c is the curvature, k is the quadratic surface coefficient, C j For the polynomial j The coefficient of the term, m and n are powers, respectively. m + n ≤10.

[0078] The fourth reflector 4, the fifth reflector 5 and the seventh reflector 7 have positive optical power, the sixth reflector 6 has negative optical power, and the optical path structure is "positive-positive-negative-positive". The specific optical design parameters of each reflector are shown in Table 4.

[0079] Table 4 Optical design parameters of each reflector in the off-axis reflective optical unit

[0080]

[0081] Note: Table 4 C 2. C 3.…… C 28 They respectively represent the polynomial coefficients of the reflecting surface shapes corresponding to the fourth reflecting mirror 4, the fifth reflecting mirror 5, and the sixth reflecting mirror 6; A4, A6, and A8 respectively represent the fourth-order, sixth-order, and eighth-order aspheric coefficients of the seventh reflecting mirror 7.

[0082] The optical path indicators of the laser and infrared co-aperture optical system of this embodiment are as follows. Of course, the corresponding parameters can also be adjusted according to actual needs.

[0083] Optical path of infrared imaging optical system: wavelength is 7.7-11μm, number of detector pixels is 640×512, 15μm×15μm, focal length is 300mm, and aperture is 150mm.

[0084] Laser emission optical system optical path: the emission laser wavelength is 1064nm, the emission collimation optical path focal length is 350mm, and the emission aperture is 29mm.

[0085] Laser receiving optical system optical path: the receiving laser wavelength is 1064nm, the focal length is 260mm, and the receiving aperture is 100mm.

[0086] The off-axis structure mentioned in this embodiment is described in detail below:

[0087] An exit pupil position of an off-axis afocal telescope system composed of a first reflector 1, a second reflector 2, and a third reflector 3 is used as a reference surface, and a first three-dimensional rectangular coordinate system (X1, Y1, Z1) is defined with the center of the reference surface as the origin; a second three-dimensional rectangular coordinate system (X2, Y2, Z2) is defined with the vertex of the first reflector 1 as the origin; a third three-dimensional rectangular coordinate system (X3, Y3, Z3) is defined with the vertex of the second reflector 2 as the origin; a fourth three-dimensional rectangular coordinate system (X4, Y4, Z4) is defined with the vertex of the third reflector 3 as the origin; a fifth three-dimensional rectangular coordinate system (X5, Y5, Z5) is defined with the vertex of the fourth reflector 4 as the origin; a sixth three-dimensional rectangular coordinate system (X6, Y6, Z6) is defined with the vertex of the fifth reflector 5 as the origin; a seventh three-dimensional rectangular coordinate system (X7, Y7, Z7) is defined with the vertex of the sixth reflector 6 as the origin; and an eighth three-dimensional rectangular coordinate system (X8, Y8, Z8) is defined with the vertex of the seventh reflector 7 as the origin. All the above three-dimensional rectangular coordinate systems are right-handed coordinate systems, and the coordinate units are all millimeters; rotation around the X-axis is counterclockwise as positive and clockwise as negative.

[0088] The rotation angle α1 of the second three-dimensional rectangular coordinate system around the X-axis relative to the first three-dimensional rectangular coordinate system is 0.74°, so the vertex coordinate position of the first reflector 1 is (0, 40.55, 233.8), and the first three-dimensional rectangular coordinate position is (0, 0, 0).

[0089] The X-axis rotation angle α2 of the third three-dimensional rectangular coordinate system relative to the first three-dimensional rectangular coordinate system is 1.47°, and the vertex coordinate position of the second reflector 2 is (0, 38.27, 5).

[0090] The X-axis rotation angle α3 of the fourth three-dimensional rectangular coordinate system relative to the first three-dimensional rectangular coordinate system is 2.93°, and the vertex coordinate position of the third reflector 3 is (0, 48.46, 260).

[0091] The rotation angle α4 of the fifth three-dimensional rectangular coordinate system around the X-axis relative to the first three-dimensional rectangular coordinate system is -39.14°, and the vertex coordinate position of the fourth reflector 4 is (0, 187.94, -54.03).

[0092] The X-axis rotation angle α5 of the sixth three-dimensional rectangular coordinate system relative to the first three-dimensional rectangular coordinate system is 23.63°, and the vertex coordinate position of the fifth reflecting mirror 5 is (0, -23.72, -25.29).

[0093] The X-axis rotation angle α6 of the seventh three-dimensional rectangular coordinate system relative to the first three-dimensional rectangular coordinate system is 83.65°, and the vertex coordinate position of the sixth reflector 6 is (0, -53.48, -64.69).

[0094] The X-axis rotation angle α7 of the eighth three-dimensional rectangular coordinate system relative to the first three-dimensional rectangular coordinate system is 10.599°, and the vertex coordinate position of the seventh reflecting mirror 7 is (0, -72.28, 41.468).

[0095] In this embodiment, the dichroic plate 8 is located 8 mm in front of the cooled infrared detector window 9. It is 1.5 mm thick and made of single crystal germanium. The angle between the dichroic plate 8 and the optical axis of the infrared imaging light path is -27°. The distance between the dichroic plate 8 in the Z direction and the vertex of the seventh reflector 7 in the Z direction is 84.23 mm. After the light beam is reflected by the dichroic plate 8, the laser beam splitter plate 12 is positioned along the reflected light path, 42.07 mm away from the dichroic plate along the optical axis. Made of optical quartz glass, the laser beam splitter plate 12 forms a 16° angle with the optical axis.

[0096] It should be noted that the above parameters are only for illustrative purposes, and the specific parameters must be determined according to the design and size requirements of the optical system.

[0097] This embodiment provides a co-aperture off-axis composite optical system that combines laser emission, laser reception, and infrared imaging. The front-end off-axis afocal telescope system adopts a modular design and can be equipped with a fast scanning mirror to achieve image stabilization and other functions. Even when used alone, the back-end optical system still achieves a good co-optical path design, maintaining excellent performance such as good optical axis pointing stability and infrared imaging system detection sensitivity. This system avoids energy loss caused by central obstruction, achieves co-aperture design for laser emission optical paths of any aperture, and greatly improves the consistency of optical axis pointing across each optical path.

[0098] The infrared imaging optical system of this embodiment adopts an off-axis total reflection structure, which not only greatly improves the sensitivity of infrared detection, but also does not produce ghost images, cold reflections, etc., and has low spontaneous radiation and excellent cold reflection suppression characteristics.

[0099] In this embodiment, each reflector and its structural support material can be made of aluminum alloy, which is machined using a single-point lathe, resulting in excellent machinability. Furthermore, since each reflector and support material is made of aluminum alloy, the optical system has excellent temperature adaptability, achieving optical passive athermalization and making the optical system insensitive to ambient temperature changes.

[0100] The above descriptions are merely embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent structural transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied to other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A laser and infrared co-aperture optical system, characterized by: It includes an off-axis reflective optical unit, a color separation plate (8), an infrared imaging unit, a laser emitting unit, and a laser receiving unit; The off-axis reflective optical unit comprises a fourth reflector (4), a fifth reflector (5), a sixth reflector (6) and a seventh reflector (7) which are sequentially arranged off-axis along the optical path; the color separation plate (8) is located on the reflective optical path of the seventh reflector (7) and is used to transmit infrared light in the incident light beam and reflect laser light in the incident light beam; the infrared imaging unit is located on the transmitted optical path of the color separation plate (8) and is used to realize infrared imaging; the laser receiving unit is located on the reflected optical path of the color separation plate (8) and is used to realize laser reception; A laser beam splitter plate (12) is provided on the outgoing light path of the laser emitting unit. The laser beam splitter plate (12) is located between the color separation plate (8) and the laser receiving unit and is used to transmit the laser reflected by the color separation plate (8) to the laser receiving unit and reflect the laser emitted by the laser emitting unit to the color separation plate (8). The laser emitting unit, the laser beam splitting plate (12), the color separation plate (8), the seventh reflector (7), the sixth reflector (6), the fifth reflector (5) and the fourth reflector (4) constitute a laser emitting optical system; The fourth reflector (4), the fifth reflector (5), the sixth reflector (6), the seventh reflector (7), the color separation plate (8) and the infrared imaging unit constitute an infrared imaging optical system; The fourth reflector (4), the fifth reflector (5), the sixth reflector (6), the seventh reflector (7), the color separation plate (8), the laser beam splitting plate (12) and the laser receiving unit constitute a laser receiving optical system.

2. The laser and infrared co-aperture optical system according to claim 1, characterized in that: Also included is an off-axis afocal telescope system, comprising a first reflector (1), a second reflector (2), and a third reflector (3) which are sequentially arranged off-axis along an optical path; the fourth reflector (4) is located on the reflecting optical path of the third reflector (3); The exit pupil position of the off-axis afocal telescope system coincides with the entrance pupil position of the off-axis reflective optical unit and is located between the third reflector (3) and the fourth reflector (4).

3. The laser and infrared co-aperture optical system according to claim 2, characterized in that: A scanning reflector is provided between the third reflector (3) and the fourth reflector (4) and is used to adjust the optical axes of the laser emitting optical system, the infrared imaging optical system and the laser receiving optical system.

4. The laser and infrared co-aperture optical system according to claim 1, 2 or 3, characterized in that: The laser emitting unit comprises a laser (14) and a laser emitting lens (13); The laser emitting lens (13) is located between the laser (14) and the laser beam splitting plate (12); the laser emitting lens (13) is a double convex positive lens with positive optical power.

5. The laser and infrared co-aperture optical system according to claim 4, characterized in that: The laser receiving unit includes a relay mirror assembly (15) and a laser receiving detector (16); The relay lens assembly (15) comprises a first lens (151), a second lens (152), a filter (153), and a third lens (154) arranged in sequence along the optical path; The first lens (151) is arranged close to the laser beam splitting plate (12) and is a double convex positive lens; The second lens (152) is a negative lens convex toward the object side; The surface of the filter (153) is coated with a laser narrow-band filter film for filtering out stray light; The third lens (154) is a positive meniscus lens convex toward the object side.

6. The laser and infrared co-aperture optical system according to claim 5, characterized in that: The infrared imaging unit is a refrigerated infrared detector, and the aperture stop of the infrared imaging optical system is located at the cold stop of the refrigerated infrared detector; The laser receiving detector (16) adopts an APD detector; The laser (14) is a fiber laser.

7. The laser and infrared co-aperture optical system according to claim 2, characterized in that: The reflecting surfaces of the first reflecting mirror (1), the second reflecting mirror (2) and the third reflecting mirror (3) are quadratic surfaces; The reflection surface profile expressions of the fourth reflector (4), the fifth reflector (5), and the sixth reflector (6) are XY polynomials; The reflecting surface of the seventh reflecting mirror (7) is an even-order aspherical surface.

8. The laser and infrared co-aperture optical system according to claim 7, characterized in that: The first reflector (1), the third reflector (3), the fourth reflector (4), the fifth reflector (5) and the seventh reflector (7) all have positive optical focal lengths; and the second reflector (2) and the sixth reflector (6) all have negative optical focal lengths.

9. The laser and infrared co-aperture optical system according to claim 1, characterized in that: The color separation plate (8) is made of one of germanium, silicon, ZnSe, Zns, and sulfur-based glass, and a side thereof close to the seventh reflector (7) is coated with a spectral spectroscopic film for transmitting infrared light and reflecting laser light.

10. The laser and infrared co-aperture optical system according to claim 1, characterized in that: The laser beam splitting plate (12) is made of optical quartz glass, and a surface thereof close to the color separation plate (8) is coated with a laser beam splitting film, and the ratio of laser transmittance to reflectivity is 1:1.

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