Laser and infrared common-caliber optical system

Abstract

The invention discloses a laser and infrared common-caliber optical system which is used for solving the technical problems that an existing composite optical system is difficult to achieve high-sensitivity detection, the optical axis pointing stability is prone to being affected by the environment, and an image stabilization function is not achieved. The optical system comprises an off-axis reflection optical unit, a color separation flat plate, an infrared imaging unit, a laser emitting unit and a laser receiving unit, and the color separation flat plate is located on a reflection light path of a seventh reflector in the off-axis reflection optical unit and used for transmitting infrared light and reflecting laser; the laser emission unit, the laser splitting flat plate, the color separation flat plate and the off-axis reflection optical unit form a laser emission optical system; the off-axis reflection optical unit, the color separation flat plate and the infrared imaging unit form an infrared imaging optical system; the off-axis reflection optical unit, the color separation flat plate, the laser splitting flat plate and the laser receiving unit form a laser receiving optical system. The optical system is high in integration level, and the consistency of the optical axis directions of all optical paths is greatly improved.

Description

Technical Field

[0001] The present invention relates to a compound optical system, and more particularly to an off-axis compound optical system with a common aperture for laser emission, laser reception, and cooling infrared imaging, which has a high detection sensitivity, a high optical axis stability, and an image stabilization function. Background Art

[0002] With the progress of laser technology, the development of laser and optical imaging compound detection systems has been rapid, making the integration of optical systems (i.e., compound optical systems) a trend. A compound optical system can achieve the fusion of multiple bands within a limited space, obtaining more target information, and has obvious advantages compared with traditional single-mode optical systems. The fusion methods of compound optical systems are divided into two types: split aperture and common aperture. Among them, in the split-aperture compound optical system, since the optical systems of each band are independent of each other, the external dimensions of the compound optical system are large, the structure is not compact enough, and the optical axis pointing consistency of each band is easily affected by factors such as the environment, resulting in a deviation between the laser irradiation point and the imaging tracking and aiming point, and even causing the optical system to malfunction. The common-aperture compound optical system has a high degree of integration and a compact structure. However, in traditional common-aperture compound optical systems, only some optical elements such as the primary and secondary mirrors are shared, and the optical path is divided into multiple paths by a rear-end beam splitter element. The optical paths after splitting are still relatively independent, and the optical axis pointing of each band may still change due to environmental influences. Especially when the divergence angle of laser emission and the resolution of the imaging optical path angle are small, the consistency of the optical axis pointing of each band is still an issue that needs to be focused on.

[0003] Currently, the laser and imaging common-aperture reflective optical system, as a commonly used common-aperture compound optical system, mostly combines the imaging optical path with the laser emission / reception optical path and has a coaxial common optical path structure. However, due to the existence of central obstruction, the imaging energy and the energy loss of the laser emission optical path are relatively large. At the same time, since a large number of lens relays for imaging or laser collimation are used in each optical path after splitting, the self-thermal radiation of the infrared imaging optical path is relatively large, which cannot meet the high-sensitivity detection requirements. Moreover, when the aperture of the laser emission optical path is smaller than the diameter of the secondary mirror, the common-aperture design of the laser emission optical path cannot be achieved. In addition, the above optical system does not have a scanning or image stabilization function, and the image stabilization function is crucial for achieving high-precision tracking and aiming.

[0004] As another commonly used common-aperture compound optical system, the off-axis reflective optical system has been widely used in high-performance infrared imaging due to its advantages such as no chromatic aberration, good heat resistance, simple structure, and low self-thermal radiation. In the published literature, the off-axis common-aperture laser / imaging compound optical system mostly adopts an off-axis common optical path structure, which avoids energy loss. However, this method only considers the common optical path design problem of the laser and the imaging system, and lacks consideration of the pointing stability of the optical axis, high-sensitivity infrared detection, etc. Moreover, the infrared relay mirror group brings a large amount of self-thermal radiation, which seriously reduces the infrared detection performance of the optical system. In addition, the optical paths of each wavelength band are still relatively independent after beam splitting, resulting in difficulty in ensuring the pointing stability of the optical axis.

[0005] For example, Chinese Patent No. CN112526531A discloses a dual-field-of-view infrared imaging system with multi-target laser ranging function. 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 beam splitting, the infrared imaging is relatively independent of the laser emission and laser reception optical paths, making the pointing stability of the optical axis of each optical path vulnerable to the environment. Moreover, the infrared imaging optical path uses an uncooled detector and a lens group for relay imaging, making it difficult to achieve high-sensitivity detection and without scanning or image stabilization functions. Chinese Patent No. CN119002079A discloses an off-axis compound tracking and laser emission common-aperture Coudé optical system and its alignment method. However, this optical system adopts a common optical path structure for visible light imaging and laser emission, without infrared imaging ability, laser reception function, and image stabilization function, and the structure is not compact enough.

[0006] Another example is the "A Laser and Infrared Compound Optical System" published by Xiang Jiansheng et al. in the first issue of Volume 48 of the journal Laser & Infrared in January 2018. This paper introduces a semi-active laser and long-wave infrared common-aperture compound optical system, which is a coaxial common-aperture folded-back structure and uses an uncooled infrared detector, having infrared imaging and laser reception functions, but without a laser emission optical path and also without an image stabilization function.

[0007] In the paper "Design of an Active Laser and Infrared Common-Aperture Compound Imaging Optical System" published by Yin Na et al. in the first issue of Volume 38 of the journal Infrared Technology in January 2016, an active laser and infrared imaging common-aperture compound optical system is introduced. It adopts a coaxial optical path structure and can achieve scanning imaging, laser emission, laser reception, and cooled infrared imaging. However, the thermal radiation of the infrared relay mirror group is relatively large, and the laser emission optical path is relatively independent of 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, it is of great significance to design a common-aperture off-axis compound optical system that combines laser emission, laser reception, and refrigerated infrared imaging, with image stabilization function, high infrared detection sensitivity, and high optical axis pointing stability, for realizing the integration and high performance of the compound system. Summary of the Invention

[0009] The object of the present invention is to solve the technical problems that it is difficult for existing compound optical systems to achieve high-sensitivity detection, the optical axis pointing stability is easily affected by the environment, and they do not have an image stabilization function, etc., and to provide a laser and infrared common-aperture optical system.

[0010] To achieve the above object, the technical solution provided by the present invention is as follows: A laser and infrared common-aperture optical system, which is characterized in that: It includes an off-axis reflective optical unit, a dichroic plate, an infrared imaging unit, a laser emission unit, and a laser reception unit; The off-axis reflective optical unit includes a fourth mirror, a fifth mirror, a sixth mirror, and a seventh mirror that are sequentially arranged in an off-axis manner along the optical path; the dichroic plate is located on the reflected optical path of the seventh mirror 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 realize infrared imaging; the laser reception unit is located on the reflected optical path of the dichroic plate and is used to realize laser reception; A laser beam splitting plate is provided on the outgoing optical path of the laser emission unit. The laser beam splitting plate is located between the dichroic plate and the laser reception unit and is used to transmit the laser light reflected by the dichroic plate to the laser reception unit and reflect the laser light emitted by the laser emission unit to the dichroic plate; The laser emission unit, the laser beam splitting plate, the dichroic plate, the seventh mirror, the sixth mirror, the fifth mirror, and the fourth mirror together form a laser emission optical system; The fourth mirror, the fifth mirror, the sixth mirror, the seventh mirror, the dichroic plate, and the infrared imaging unit together form an infrared imaging optical system; The fourth mirror, the fifth mirror, the sixth mirror, the seventh mirror, the dichroic plate, the laser beam splitting plate, and the laser reception unit together form a laser reception optical system.

[0011] Furthermore, it also includes an off-axis afocal telescopic system, which includes a first mirror, a second mirror, and a third mirror that are sequentially arranged in an off-axis manner along the optical path; the fourth mirror is located on the reflected optical path of the third mirror; The exit pupil position of the off-axis afocal telescopic system coincides with the entrance pupil position of the off-axis reflective optical unit and is located between the third mirror and the fourth mirror.

[0012] Further, a scanning mirror is disposed between the third mirror and the fourth mirror for adjusting the optical axes of the laser emission optical system, the infrared imaging optical system, and the laser reception optical system.

[0013] Further, the laser emission unit includes a laser and a laser emission lens; The laser emission lens is located between the laser and the laser beam splitting flat plate; the laser emission lens is a biconvex positive lens with a positive optical power.

[0014] Further, the laser reception unit includes a relay lens group and a laser reception detector; The relay lens group includes a first lens, a second lens, a filter, and a third lens arranged in sequence along the optical path; the first lens is disposed close to the laser beam splitting flat plate and is a biconvex positive lens; the second lens is a negative lens convex towards the object side; the surface of the filter is coated with a laser narrowband filter film for filtering stray light; the third lens is a meniscus positive lens convex towards the object side.

[0015] Further, 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 reception detector uses an APD detector; the laser uses a fiber laser.

[0016] Further, the reflecting surfaces of the first mirror, the second mirror, and the third mirror are aspherical surfaces of the second order; The expression of the reflecting surface of the fourth mirror, the fifth mirror, and the sixth mirror is an XY polynomial, and the even terms of X are taken; The reflecting surface of the seventh mirror is an even aspherical surface.

[0017] Further, the first mirror, the third mirror, the fourth mirror, the fifth mirror, and the seventh mirror all have positive optical powers; the second mirror and the sixth mirror both have negative optical powers.

[0018] Further, the dichroic flat plate is selected from one of germanium, silicon, Znse, Zns, and chalcogenide glass, and a spectral beam splitting film is coated on the side close to the seventh mirror for transmitting infrared light and reflecting laser light.

[0019] Further, the laser beam splitting flat plate is selected from optical quartz glass, and a laser beam splitting film is coated on the side close to the dichroic flat plate, and the ratio of the laser transmittance to the reflectance is 1:1.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention provides a laser and infrared co-aperture optical system. Among them, the laser emission unit, the laser beam splitting flat plate, the dichroic flat plate, and the off-axis reflective optical unit form the laser emission optical system; the off-axis reflective optical unit, the dichroic flat plate, and the infrared imaging unit form the infrared imaging optical system; the off-axis reflective optical unit, the dichroic flat plate, the laser beam splitting flat plate, and the laser receiving unit form the laser receiving optical system, thereby providing a co-aperture off-axis composite optical system that combines laser emission, laser reception, and infrared imaging. This optical system has a high degree of integration and greatly improves the consistency and stability of the optical axis pointing of each optical path.

[0021] 2. The present invention also provides an off-axis afocal telescopic 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 co-aperture design for any-aperture laser emission optical paths.

[0022] 3. The present invention can also set a scanning mirror between the third mirror and the fourth mirror (i.e., the light output end of the off-axis afocal telescopic system), which can realize functions such as image stabilization.

[0023] 4. The off-axis reflective optical unit of the present invention can be combined or used alone to realize the modular design of the reflective off-axis optical system, improving the integration and interchangeability of the optical system.

[0024] 5. To avoid the relative independence of each optical path after beam splitting, the present invention splits the light in front of the image plane of the infrared imaging optical path. Most of the components in the optical system are common components for the three optical paths. The relay mirror group after beam splitting is also relatively simple, with a small number of optical elements and a rotationally symmetric structure, greatly improving the consistency of the optical axis pointing of each optical path.

[0025] 6. The infrared imaging unit of the present invention uses a cooled infrared detector. Combining with the off-axis all-reflective optical system not only greatly improves the detection sensitivity of the infrared system but also does not generate ghost images, cold reflections, etc., and has low spontaneous emission and excellent cold reflection suppression characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the optical system according to an embodiment of the present invention; Figure 2 is Figure 1 a partial enlarged view of Figure 3 is a schematic diagram of the optical structure of the relay mirror group in the laser receiving unit according to an embodiment of the present invention; Figure 4 is the optical path diagram of the infrared imaging optical system according to an embodiment of the present invention; Figure 5 is the optical path diagram of the laser emission optical system according to an embodiment of the present invention; Figure 6 This is the optical path diagram of the laser receiving optical system in the embodiment of the present invention.

[0027] The reference signs are as follows: 1 - First reflector, 2 - Second reflector, 3 - Third reflector, 4 - Fourth reflector, 5 - Fifth reflector, 6 - Sixth reflector, 7 - Seventh reflector, 8 - Dichroic flat plate, 9 - Window of cooled infrared detector, 10 - Cold stop of cooled infrared detector, 11 - Target surface of cooled infrared detector, 12 - Laser beam splitting flat plate, 13 - Laser emitting lens, 14 - Laser, 15 - Relay lens group, 151 - First lens, 152 - Second lens, 153 - Filter, 154 - Third lens, 16 - Laser receiving detector. Detailed implementation manners

[0028] To make the objectives, advantages and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these implementation manners are only used to explain the technical principle of the present invention, rather than to limit the protection scope of the present invention.

[0029] As Figure 1 and Figure 2 shown, this embodiment provides a laser and infrared co-aperture optical system, including an off-axis reflective optical unit, a dichroic flat plate 8, an infrared imaging unit, a laser emitting unit and a laser receiving unit.

[0030] 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 in an off-axis manner along the optical path; the dichroic flat plate 8 is located on the reflected optical path of the seventh reflector 7 and is used to transmit the infrared light in the incident light beam and reflect the laser in the incident light beam; the infrared imaging unit is located on the transmitted optical path of the dichroic flat plate 8 and is used to achieve infrared imaging; the laser receiving unit is located on the reflected optical path of the dichroic flat plate 8 and is used to achieve laser reception. The dichroic flat plate 8 can be selected from one of germanium, silicon, Znse, Zns, and chalcogenide glass, and a spectral beam splitting film is coated on the side close to the seventh reflector 7 for transmitting infrared light and reflecting laser. The dichroic flat plate 8 in this embodiment uses 1.5 mm thick single crystal germanium.

[0031] A laser beam splitting flat plate 12 is provided on the outgoing optical path of the laser emitting unit. The laser beam splitting flat plate 12 is located between the dichroic flat plate 8 and the laser receiving unit and is used to transmit the laser reflected by the dichroic flat plate 8 to the laser receiving unit and reflect the laser emitted by the laser emitting unit to the dichroic flat plate 8. A laser beam splitting film is coated on the side of the laser beam splitting flat plate 12 close to the dichroic flat plate 8, and the ratio of laser transmittance to reflectance is 1:1.

[0032] 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).

[0033] 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).

[0034] 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).

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] In this embodiment, the maximum aperture of the incident beam of the off-axis afocal telescopic system is 150 mm, and the magnification is 4 times.

[0040] The laser emission unit includes a laser 14 and a laser emission lens 13; the laser emission lens 13 is located between the laser 14 and the laser beam splitting flat plate 12.

[0041] The laser emitted by the laser 14 is reflected by the laser emission lens 13, the laser beam splitting flat plate 12, and the dichroic flat plate 8, and then the beam is collimated and emitted onto the object-side target through the seventh mirror 7, the sixth mirror 6, the fifth mirror 5, the fourth mirror 4, the third mirror 3, the second mirror 2, and the first mirror 1 in sequence, forming a laser emission optical path. In this embodiment, the laser 14 uses a fiber laser with an emission wavelength of 1064 nm, and specific selection can also be made according to actual requirements. The laser emission lens 13 only uses a single biconvex positive focal length lens with a magnification of 1.167, the laser emission aperture of the laser emission optical path is 29 mm, and the optical design parameters of the laser beam splitting flat plate 12 and the laser emission lens 13 are shown in Table 1.

[0042] Table 1 Laser Emission Lens Parameters (Unit: mm)

[0043] The laser reception unit includes a relay lens group 15 and a laser reception detector 16; the fourth mirror 4, the fifth mirror 5, and the sixth mirror 6 further focus the beam emitted from the off-axis afocal telescopic system. After the beam passes through the dichroic flat plate 8 and the laser beam splitting flat plate 12 in sequence, it passes through the relay lens group 15 and is focused on the laser reception detector 16, thus forming a laser reception optical path.

[0044] In this embodiment, the laser reception detector 16 uses an APD detector, and the laser reception band is 1064 nm. The magnification of the relay lens group 15 is 0.87, and the laser reception aperture is 100 mm.

[0045] As Figure 3 shown, the relay lens group 15 includes a first lens 151, a second lens 152, a filter 153, and a third lens 154 arranged in sequence along the optical path. Among them, the first lens 151 is arranged close to the laser beam splitting flat plate 12 and is a biconvex positive lens; the second lens 152 is a negative lens convex towards 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 meniscus positive lens convex towards the object side. The optical design parameters of each lens are shown in Table 2.

[0046] Table 2 Optical Design Parameters of Each Lens of the Relay Lens Group

[0047] 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 mirror 4, the fifth mirror 5, and the sixth mirror 6 further image the outgoing beam of the off-axis afocal telescopic system. The beam is transmitted through the dichroic plate 8 in sequence, passes through 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. The aperture stop of the infrared imaging optical path is located at the cooled infrared detector cold stop 10.

[0048] In this embodiment, the reflecting surface profiles of the first mirror 1, the second mirror 2, and the third mirror 3 are aspheric surfaces; the first mirror 1 and the third mirror 3 both have positive optical powers, the second mirror 2 has a negative optical power, and the optical path structure is "positive-negative-positive". The specific optical design parameters of each mirror are shown in Table 3.

[0049] Table 3 Optical design parameters of each mirror of the off-axis afocal telescopic system

[0050] In Table 3, c represents the curvature, k represents the aspheric coefficient.

[0051] The reflecting surface profile expressions of the fourth mirror 4, the fifth mirror 5, and the sixth mirror 6 are XY polynomials; the reflecting surface profile of the seventh mirror 7 is an even aspheric surface. In order to correct aberrations while maintaining reasonable processability, minimizing the number of free-form surfaces and reducing the order as much as possible, only the even terms of X in the XY polynomial are taken for the fourth mirror 4, the fifth mirror 5, and the sixth mirror 6 in this embodiment. The highest order of the XY polynomial of the fourth mirror 4 is 5, the highest order of the XY polynomial of the fifth mirror 5 is 6, and the highest order of the XY polynomial of the sixth mirror 6 is 6; the highest order of the even aspheric surface of the seventh mirror 7 is 8.

[0052] The XY polynomial free-form surface equation is:

[0053]

[0054] Where, z is the surface sag; c is the curvature, k is the aspheric coefficient, C j is the coefficient of the j th term in the polynomial, m and n are the exponents respectively. Generally, m +n ≤ 10.

[0055] The fourth mirror 4, the fifth mirror 5, and the seventh mirror 7 have positive optical power, the sixth mirror 6 has negative optical power, and the optical path structure is "positive - positive - negative - positive". The specific optical design parameters of each mirror are shown in Table 4.

[0056] Table 4 Optical design parameters of each mirror in the off - axis reflective optical unit

[0057] Note: In Table 4, C 2, C 3, ……, C 28 respectively represent the polynomial coefficients of the reflective surface profiles corresponding to the fourth mirror 4, the fifth mirror 5, and the sixth mirror 6; A4, A6, and A8 respectively represent the aspheric coefficients of the fourth - order, sixth - order, and eighth - order terms of the seventh mirror 7.

[0058] The optical path indicators of each optical path of the laser - infrared co - aperture optical system in this embodiment are as follows. Of course, the corresponding parameters can also be adjusted according to actual requirements.

[0059] Optical path of the infrared imaging optical system: The wavelength is 7.7 - 11 μm, the number of detector pixels is 640×512, 15 μm×15 μm, the focal length is 300 mm, and the aperture is 150 mm.

[0060] Optical path of the laser emission optical system: The emitted laser wavelength is 1064 nm, the focal length of the emission collimation optical path is 350 mm, and the emission aperture is 29 mm.

[0061] Optical path of the laser reception optical system: The received laser wavelength is 1064 nm, the focal length is 260 mm, and the reception aperture is 100 mm.

[0062] The following specifically describes the off - axis structure mentioned in this embodiment: Taking the exit pupil position of the off-axis afocal telescopic system composed of the first mirror 1, the second mirror 2, and the third mirror 3 as the reference plane, a first three-dimensional rectangular coordinate system (X1, Y1, Z1) is defined with the center of this reference plane as the origin; a second three-dimensional rectangular coordinate system (X2, Y2, Z2) is defined with the vertex of the first mirror 1 as the origin; a third three-dimensional rectangular coordinate system (X3, Y3, Z3) is defined with the vertex of the second mirror 2 as the origin; a fourth three-dimensional rectangular coordinate system (X4, Y4, Z4) is defined with the vertex of the third mirror 3 as the origin; a fifth three-dimensional rectangular coordinate system (X5, Y5, Z5) is defined with the vertex of the fourth mirror 4 as the origin; a sixth three-dimensional rectangular coordinate system (X6, Y6, Z6) is defined with the vertex of the fifth mirror 5 as the origin; a seventh three-dimensional rectangular coordinate system (X7, Y7, Z7) is defined with the vertex of the sixth mirror 6 as the origin; an eighth three-dimensional rectangular coordinate system (X8, Y8, Z8) is defined with the vertex of the seventh mirror 7 as the origin. All of the above three-dimensional rectangular coordinate systems are right-handed coordinate systems, and the coordinate unit is millimeter; the counterclockwise rotation around the X-axis is positive, and the clockwise rotation is negative.

[0063] The rotation angle α1 of the second three-dimensional rectangular coordinate system relative to the first three-dimensional rectangular coordinate system around the X-axis is 0.74°, then the vertex coordinate position of the first mirror 1 is (0, 40.55, 233.8), and the first three-dimensional rectangular coordinate position is (0, 0, 0).

[0064] The rotation angle α2 of the third three-dimensional rectangular coordinate system relative to the first three-dimensional rectangular coordinate system around the X-axis is 1.47°, and the vertex coordinate position of the second mirror 2 is (0, 38.27, 5).

[0065] The rotation angle α3 of the fourth three-dimensional rectangular coordinate system relative to the first three-dimensional rectangular coordinate system around the X-axis is 2.93°, and the vertex coordinate position of the third mirror 3 is (0, 48.46, 260).

[0066] The rotation angle α4 of the fifth three-dimensional rectangular coordinate system relative to the first three-dimensional rectangular coordinate system around the X-axis is -39.14°, and the vertex coordinate position of the fourth mirror 4 is (0, 187.94, -54.03).

[0067] The rotation angle α5 of the sixth three-dimensional rectangular coordinate system relative to the first three-dimensional rectangular coordinate system around the X-axis is 23.63°, and the vertex coordinate position of the fifth mirror 5 is (0, -23.72, -25.29).

[0068] The rotation angle α6 of the seventh three-dimensional rectangular coordinate system relative to the first three-dimensional rectangular coordinate system around the X-axis is 83.65°, and the vertex coordinate position of the sixth mirror 6 is (0, -53.48, -64.69).

[0069] The rotation angle α7 of the eighth three-dimensional rectangular coordinate system relative to the X-axis of the first three-dimensional rectangular coordinate system is 10.599°, and the vertex coordinate position of the seventh mirror 7 is (0, -72.28, 41.468).

[0070] In this embodiment, the dichroic plate 8 is located 8 mm in front of the window 9 of the cooled infrared detector, with a thickness of 1.5 mm. The material is germanium single crystal. The included angle between the dichroic plate 8 and the optical axis of the infrared imaging optical path is -27°. The distance between the Z direction of the dichroic plate 8 and the Z direction of the vertex of the seventh mirror 7 is 84.23 mm. After the light beam is reflected by the dichroic plate 8, the laser beam splitting plate 12 is arranged along the reflected optical path, 42.07 mm away from the dichroic plate along the optical axis. The material is optical quartz glass, and the included angle between the laser beam splitting plate 12 and the optical axis is 16°.

[0071] It should be noted that the above relevant parameters are only for exemplary illustration, and the specific parameters need to be determined according to the design requirements and size requirements of the optical system.

[0072] This embodiment provides a common-aperture off-axis compound optical system that combines laser emission, laser reception, and infrared imaging. The front-end off-axis afocal telescopic system adopts a modular design and can be equipped with a fast steering mirror to achieve functions such as image stabilization. Even when used alone, the rear-end optical system can still achieve a good common optical path design, and still has excellent performance such as good optical axis pointing stability and detection sensitivity of the infrared imaging system; it not only avoids the energy loss caused by central obstruction and realizes the common-aperture design for any-aperture laser emission optical path, but also greatly improves the consistency of the optical axis pointing of each optical path.

[0073] The infrared imaging optical system of this embodiment adopts an off-axis all-reflective structure, which not only greatly improves the sensitivity of infrared detection, but also does not generate ghost images, cold reflections, etc., and has low spontaneous emission and excellent cold reflection suppression characteristics.

[0074] In this embodiment, each mirror and its structural support material can be made of aluminum alloy, and processed by a single-point turning machine tool, which has good machinability. In addition, since each mirror and support material are aluminum alloy, the optical system has good temperature adaptability, can achieve optical passive athermalization, and the optical system is insensitive to environmental temperature changes.

[0075] The above are only the embodiments of the present invention, and do not limit the protection scope of the present invention. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A laser and infrared co-aperture optical system, characterized in that: It includes an off-axis reflective optical unit, a dichroic plate (8), an infrared imaging unit, a laser emitting unit and a laser receiving unit; The off-axis reflective optical unit includes a fourth mirror (4), a fifth mirror (5), a sixth mirror (6) and a seventh mirror (7) arranged in an off-axis manner in sequence along the optical path; the dichroic plate (8) is located on the reflected optical path of the seventh mirror (7) and is used for transmitting infrared light in the incident light beam and reflecting laser light in the incident light beam; the infrared imaging unit is located on the transmitted optical path of the dichroic plate (8) and is used for realizing infrared imaging; the laser receiving unit is located on the reflected optical path of the dichroic plate (8) and is used for realizing laser reception; A laser beam splitting plate (12) is provided on the outgoing optical path of the laser emitting unit. The laser beam splitting plate (12) is located between the dichroic plate (8) and the laser receiving unit and is used for transmitting the laser light reflected by the dichroic plate (8) to the laser receiving unit and reflecting the laser light emitted by the laser emitting unit to the dichroic plate (8); The laser emitting unit, the laser beam splitting plate (12), the dichroic plate (8), the seventh mirror (7), the sixth mirror (6), the fifth mirror (5) and the fourth mirror (4) form a laser emitting optical system; The fourth mirror (4), the fifth mirror (5), the sixth mirror (6), the seventh mirror (7), the dichroic plate (8) and the infrared imaging unit form an infrared imaging optical system; The fourth mirror (4), the fifth mirror (5), the sixth mirror (6), the seventh mirror (7), the dichroic plate (8), the laser beam splitting plate (12) and the laser receiving unit form a laser receiving optical system.

2. The laser and infrared co-aperture optical system according to claim 1, characterized in that: It further includes an off-axis afocal telescopic system, which includes a first mirror (1), a second mirror (2), and a third mirror (3) arranged in an off-axis manner in sequence along the optical path; the fourth mirror (4) is located on the reflected optical path of the third mirror (3); The exit pupil position of the off-axis afocal telescopic system coincides with the entrance pupil position of the off-axis reflective optical unit and is located between the third mirror (3) and the fourth mirror (4).

3. The laser and infrared co-aperture optical system according to claim 2, characterized in that: A scanning mirror is provided between the third mirror (3) and the fourth mirror (4) and is used for adjusting 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 or 2 or 3, characterized in that: 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); the laser emitting lens (13) is a biconvex 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 group (15) and a laser receiving detector (16); The relay mirror group (15) includes 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 flat plate (12), and it is a biconvex positive lens; The second lens (152) is a negative lens convex towards the object side; The surface of the filter (153) is coated with a laser narrowband filter film for filtering stray light; The third lens (154) is a meniscus positive lens convex towards the object side.

6. The laser and infrared co-aperture optical system according to claim 5, wherein: 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 (16) uses an APD detector; The laser (14) uses a fiber laser.

7. The laser and infrared co-aperture optical system according to claim 2, wherein: The reflecting surface shapes of the first mirror (1), the second mirror (2), and the third mirror (3) are quadratic surfaces; The reflecting surface shape expression of the fourth mirror (4), the fifth mirror (5), and the sixth mirror (6) is an XY polynomial; The reflecting surface shape of the seventh mirror (7) is an even aspherical surface.

8. The laser and infrared co-aperture optical system according to claim 7, wherein: The first mirror (1), the third mirror (3), the fourth mirror (4), the fifth mirror (5), and the seventh mirror (7) all have positive optical powers; the second mirror (2) and the sixth mirror (6) both have negative optical powers.

9. The laser and infrared co-aperture optical system according to claim 1, wherein: The dichroic flat plate (8) is selected from one of germanium, silicon, ZnSe, ZnS, and chalcogenide glass. The side close to the seventh mirror (7) is coated with a spectral beam splitting film for transmitting infrared light and reflecting laser light.

10. The laser and infrared co-aperture optical system according to claim 1, wherein: The laser beam splitting flat plate (12) is selected from optical quartz glass. The side close to the dichroic flat plate (8) is coated with a laser beam splitting film, and the ratio of laser transmittance to reflectance is 1:1.

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