Infrared laser compound optical system

Abstract

This invention relates to an infrared laser composite optical system, comprising: a laser lens group, a common mirror group, and an infrared mirror group, with the optical elements of the three mirror groups coaxially arranged sequentially. The common mirror group includes a positive optical power first reflecting mirror, a negative optical power second reflecting mirror, and a beam splitter. A composite beam of long-wave infrared light and laser light enters the common mirror group, is reflected sequentially by the first and second reflecting mirrors, and then the laser light is reflected at the front surface of the beam splitter, passing through the laser lens group to reach the image plane of the laser system. The long-wave infrared light beam is transmitted at the beam splitter and passes through the infrared mirror group III to reach the image plane of the infrared system. This invention features a compact structure, high efficiency, and eliminates the asymmetric astigmatism introduced by the tilted plate.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging technology and relates to a long-wave infrared and laser co-aperture composite optical system. Background Technology

[0002] With the continuous advancement of aerospace technology, single-band imaging systems are increasingly unable to meet the demands of advanced technologies in the new era. Infrared imaging systems detect targets by identifying their infrared radiation characteristics. For example, in a seeker's infrared imaging system, the infrared radiation characteristics of a target aircraft differ from those of its surrounding environment. Capturing this information allows for precise tracking and engagement of the target. Infrared imaging systems offer advantages such as high resolution and all-weather operation. However, due to their working principle and mode, infrared imaging systems can only acquire surface feature information of the target aircraft and cannot obtain distance information. Changes in the ambient temperature affect the accuracy of identification, and targeted infrared interference may lead to target loss. Lasers, with their strong monochromaticity, good directionality, and coherence, ensure that the beam is not affected by stray light interference. In a guidance imaging system, laser ranging can obtain distance information. Combined with infrared imaging, a three-dimensional data cube is constructed, achieving complementary advantages and significantly improving the accuracy of the guidance system.

[0003] Traditional detection systems consist of two independent optical systems: infrared imaging and laser detection. These systems are too bulky and do not meet the miniaturization requirements of aerospace or military applications. Patent CN112068311A discloses a multi-band co-aperture optical imaging system. This system uses a flat beam splitter tilted at 45 degrees to the optical axis for beam splitting. The infrared band propagates along the optical axis, while the laser is deflected downwards at 90 degrees. While this achieves beam splitting, it increases the size of the optical system. Furthermore, the tilted beam splitter introduces difficult-to-correct asymmetric astigmatism into the transmitted light path. Patent CN111045102A discloses a co-aperture composite detection system for infrared and laser receivers. This system uses a beam splitter that transmits the laser and reflects the infrared band. This beam splitting method significantly reduces the laser system's transmittance, leading to a decrease in laser ranging distance. Therefore, there is an urgent need to develop a miniaturized, co-aperture infrared-laser composite optical imaging system that maintains high imaging quality. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a miniaturized infrared laser composite optical system with a common aperture. Compared with the coaxial folding beam splitting structure, the system does not have the asymmetric astigmatism introduced by the tilted plate. Compared with the transmission laser and the reflection infrared wavelength method, the reflectivity and transmittance are both higher, which can further improve the efficiency of the subsystem.

[0005] To solve the above problems, the infrared laser composite optical system of the present invention includes: a laser lens group I, a common mirror group II, and an infrared mirror group III. The optical elements of the three mirror groups are coaxially distributed in sequence; the common mirror group II includes a first mirror 5 with positive optical power, a second mirror 3 with negative optical power, and a beam splitter lens 4; the composite beam of long-wave infrared and laser enters the common mirror group II, and after being reflected by the first mirror 5 and the second mirror 3 in sequence, the laser is reflected on the front surface of the beam splitter lens 4 and reaches the laser system image plane 11 through the laser lens group I; the long-wave infrared beam is transmitted through the beam splitter lens 4 and reaches the infrared system image plane 12 through the infrared mirror group III.

[0006] The radius of curvature of the reflecting surface of the first mirror 5 is -180 mm < r1 < -160 mm, the radius of curvature of the reflecting surface of the second mirror 3 is -105 mm < r2 < -65 mm, the distance between the first mirror 5 and the second mirror 3 is |-55| mm < t1 < |-65| mm, and the distance between the second mirror 3 and the beam splitter lens 4 is 30 mm < t2 < 50 mm.

[0007] The reflecting surfaces of the first mirror 5 and the second mirror 3 are even aspherical surfaces; the aspherical coefficient k and the high-order quadratic coefficient A of the reflecting surface of the first mirror are 0, and the high-order quartic coefficient B, high-order sextic coefficient C, high-order octic coefficient D, and high-order decic coefficient E are 1.565E-8 to 7.565E-8, 8.604E-14 to 3.604E-13, 1.277E-17 to 9.277E-17, 1.579E-22 to 5.579E-22 respectively; the aspherical coefficient k and the high-order quadratic coefficient A of the reflecting surface of the second mirror 3 are 0, and the high-order quartic coefficient B, high-order sextic coefficient C, high-order octic coefficient D, and high-order decic coefficient E are 9.556E-7 to 5.556E-6, -5.854E-10 to -1.854E-10, -7.31E-15 to -1.31E-15, 1.929E-17 to 7.929E-17 respectively.

[0008] The infrared mirror group III includes a fourth mirror 6 with positive optical power, a third mirror 7 with positive optical power, a detector window 8, a detector cold stop 9, and a detector filter 10; the long-wave infrared beam transmitted through the beam splitter lens 4 passes through the third mirror 7, the fourth mirror 6, the detector window 8, the detector cold stop 9, and the detector filter 10 in sequence and reaches the infrared system image plane 12.

[0009] The radius of curvature of the reflecting surface of the third mirror 7 is -470 mm < r3 < -420 mm, and the radius of curvature of the reflecting surface of the fourth mirror 6 is 210 mm < r4 < 300 mm. The central thickness of the beam splitter lens 4 is 2 mm < d4 < 5 mm, the distance between the beam splitter lens 4 and the third mirror 7 is 135 mm < t3 < 165 mm, and the distance between the third mirror 7 and the fourth mirror 6 is |-115| mm < t4 < |-125| mm; the distance between the fourth mirror 6 and the detector window 8 is 115 mm < t5 < 130 mm; the distance between the detector cold stop 9 and the protective glass 10 is 25 mm < t7 < 35 mm.

[0010] The reflecting surfaces of the third mirror 7 and the fourth mirror 6 and the rear surface of the beam splitter lens 4 are all even aspherical surfaces; the aspherical coefficient k and the high-order quadratic term coefficient A of the reflecting surface of the third mirror are 0, and the high-order quartic term coefficient B, the high-order sextic term coefficient C, the high-order octic term coefficient D, and the high-order decic term coefficient E are 3.778E-9 to 9.778E-9, -1.043E-12 to -4.432E-13, 5.233E-17 to 6.523E-16, -6.939E-20 to -9.394E-21 respectively; the aspherical coefficient k and the high-order quadratic term coefficient A of the reflecting surface of the fourth mirror are 0, and the high-order quartic term coefficient B, the high-order sextic term coefficient C, the high-order octic term coefficient D, and the high-order decic term coefficient E are -1.189E-8 to -5.890E-9, -4.607E-13 to 1.393E-13, 3.945E-17 to 9.945E-17, -8.044E-21 to -2.044E-21 respectively; the aspherical coefficient k and the high-order quadratic term coefficient A of the rear surface of the beam splitter lens 4 are 0, and the high-order quartic term coefficient B, the high-order sextic term coefficient C, the high-order octic term coefficient D, and the high-order decic term coefficient E are 8.570E-7 to 5.143E-6, 1.440E-9 to 7.440E-9, -1.051E-11 to -4.507E-12, 4.064E-15 to 6.406E-14 respectively.

[0011] The laser lens group I includes a second lens 2 and a first lens 1; the second lens 2 is a meniscus positive lens with a convex surface facing the image side, and the first lens 1 is a meniscus positive lens with a concave surface facing the image side; the radii of curvature of the right and left surfaces of the second lens 2 are 15 mm < R3 < 35 mm and 2 mm < R4 < 12 mm respectively, the central thickness is 3.000 mm, the radii of curvature of the right and left surfaces of the first lens 1 are -20 mm < R5 < -2 mm and -30 mm < R6 < -10 mm respectively, and the central thickness is D1 = 3.000 mm; the air gap between the beam-splitting lens 4 and the second lens 2 is |-40| mm < T3 < |-50| mm, and the air gap between the second lens 2 and the first lens 1 is |-3| mm < T4 < |-9| mm.

[0012] The left and right surfaces of the first lens 1 and the right surface of the second lens 2 are spherical surfaces, and the left surface of the second lens 2 is an even aspherical surface, and its aspherical coefficient k and higher-order quadratic coefficient A are 0, and the higher-order quartic coefficient B, higher-order sextic coefficient C, higher-order octic coefficient D, and higher-order decic coefficient E are -3.501E-4, -7.791E-6, -5.224E-8, and -3.608E-11 respectively.

[0013] As another solution, the laser lens group I includes a second lens 2, a first lens 1, and a third lens 13; the second lens 2 is a meniscus positive lens with a convex surface facing the image side, the first lens 1 is a meniscus positive lens with a concave surface facing the image side, and the third lens 13 is a meniscus positive lens with a concave surface facing the image side; the radii of curvature of the right and left surfaces of the second lens 2 are 15 mm < R3 < 25 mm and 2 mm < R4 < 12 mm respectively, the central thickness is D2 = 3.000 mm, the radii of curvature of the right and left surfaces of the first lens 1 are -10 mm < R5 < 0 mm and -20 mm < R6 < -10 mm respectively, and the central thickness is D1 = 3.000 mm; the radii of curvature of the right and left surfaces of the third lens 13 are -25 mm < R7 < -15 mm and -30 mm < R8 < -10 mm respectively, and the central thickness is D3 = 3.000 mm; the air gap between the beam-splitting lens 4 and the second lens 2 is |-40| mm < T3 < |-50| mm, and the air gap between the second lens 2 and the third lens 13 is T 23 = |-6.365| mm, and the air gap between the third lens 13 and the first lens 1 is T 31 = |-5.2| mm.

[0014] The left and right surfaces of the first lens 1 and the third lens, and the right surface of the second lens 2 are all spherical. The left surface of the second lens 2 is an even-order aspherical surface, with its aspherical coefficient k and higher-order quadratic coefficient A being 0. The higher-order quartic coefficient B, higher-order sixth-order coefficient C, higher-order octet coefficient D, and higher-order decimal-order coefficient E are -7.551E-4, -5.416E-6, 9.179E-8, and 8.171E-10, respectively.

[0015] Compared with the prior art, the infrared laser composite optical system of the present invention has the following advantages:

[0016] 1. The infrared laser composite optical system of the present invention can realize infrared long-wave imaging in the band of 7 micrometers to 11 micrometers and laser imaging in the band of 1.064 micrometers. The infrared band has excellent imaging quality at the characteristic frequency and the laser band has uniform imaging. The system has a full field of view of 4.96° and excellent imaging quality in the full field of view.

[0017] 2. The optical system composed of the shared mirror group II and the infrared mirror group III in this invention is a total internal reflection structure and also possesses full-spectrum imaging capabilities for visible light, mid-wave infrared, long-wave infrared, or microwave. Only the beam-splitting lens 4 needs to be replaced with a material that transmits the corresponding wavelength.

[0018] 3. The infrared laser composite optical system of the present invention adopts an optical design with the infrared band and the laser band sharing the same aperture. Compared with the traditional separate design, it reduces the system size and meets the requirements of compactness.

[0019] 4. The infrared laser composite optical system of the present invention adopts an optical design with the infrared band and the laser band sharing the same aperture. Compared with the coaxial folding beam splitting structure, it does not have the asymmetric astigmatism introduced by the tilted plate.

[0020] 5. The infrared laser composite optical system of the present invention adopts an optical design with the infrared band and the laser band sharing the same aperture. The beam splitter 4 transmits the infrared long-wave band and reflects the laser band. Compared with the method of transmitting laser and reflecting infrared wavelength, the reflectivity and transmittance are both higher, which further improves the efficiency of the subsystem.

[0021] 6. The infrared laser composite optical system of the present invention uses a reflector in the shared mirror group, which solves the problem that the lens material cannot simultaneously meet the requirements of a wide wavelength range. Attached Figure Description

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0023] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0024] Figure 2 This is a schematic diagram of the optical path of the infrared optical system of the present invention.

[0025] Figure 3 The curve of the full field-of-view modulation transfer function of the infrared optical system in Embodiment 1-1 of the present invention is shown.

[0026] Figure 4 This is a schematic diagram of the optical path of the laser optical system in Example 4-1.

[0027] Figure 5 This is a schematic diagram showing the thickness and spacing of the reflectors.

[0028] Figure 6 This is a point diagram of the 0° field of view of the laser optical system in Example 4-1.

[0029] Figure 7 This is a schematic diagram of the optical path of the laser optical system in Example 7-1.

[0030] Figure 8 This is a point diagram of the 0° field of view of the laser optical system in Example 7-1.

[0031] 1. First lens; 2. Second lens; 3. Second mirror; 4. Beam splitter lens; 5. First mirror; 6. Fourth mirror; 7. Third mirror; 8. Detector window; 9. Detector cold stop; 10. Detector filter; 11. Laser system image plane; 12. Infrared system image plane; 13. Third lens. Detailed Implementation

[0032] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Numerous specific details are set forth in the following description to provide a thorough understanding of the invention; however, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0034] like Figure 1 As shown, the infrared laser composite optical system of the present invention includes three lens groups: a laser lens group I, a common lens group II, and an infrared lens group III. The common lens group II includes a second reflecting mirror 3, a beam splitter lens 4, and a first reflecting mirror 5; the infrared lens group III includes a fourth reflecting mirror 6, a third reflecting mirror 7, a detector window 8, a detector cold stop 9, and a detector filter 10. The optical elements of the laser lens group I, the common lens group II, and the infrared lens group III are coaxially distributed sequentially.

[0035] like Figure 2As shown, the composite beam of infrared and laser light enters the shared mirror group II. After being reflected by the surface of the first reflector 5, it is reflected and diverged by the convex surface of the second reflector 3, which amplifies the optical power of the first reflector 5. After passing through the beam splitter 4, the beam is split into two parts; as shown... Figure 4 As shown, the laser beam is reflected on the front surface of the beam splitter 4, i.e., towards the image plane 11 of the laser system, and passes through each lens of the laser lens group I in sequence to form a uniform circular spot that reaches the image plane 11 of the laser system. The long-wave infrared beam is transmitted through the beam splitter 4 and passes through the third reflecting mirror 7, the fourth reflecting mirror 6, the detector window 8, the detector cold stop 9, and the detector filter 10 in sequence to reach the image plane 12 of the infrared system.

[0036] The first reflector 5, the second reflector 3, the third reflector 7, and the fourth reflector 6 can be made of materials suitable for reflectors, such as aluminum, silicon carbide, beryllium, beryllium aluminum, or microcrystalline materials, and the reflective surfaces are coated with a full-band reflective film. The first reflector 5, the third reflector 7, and the fourth reflector 6 are all even-order aspherical concave reflectors, and the second reflector 3 is an even-order aspherical convex reflector.

[0037] The beam splitter 4 is a parallel plate and can be made of materials that transmit long-wave infrared, such as zinc selenide, zinc sulfide, or germanium. It transmits long-wave infrared light with a wavelength range of 7 to 11 micrometers. The front surface of the beam splitter 4 reflects laser light with a wavelength range of 1.064 micrometers. The rear surface of the beam splitter 4 can also be made of a spherical surface, an even-order aspherical surface, or a freeform surface with curvature.

[0038] The detector window 8 and the protective glass 10 are made of germanium.

[0039] The equation for even-order aspherical surfaces is expressed as follows:

[0040]

[0041] Where z is the rotational symmetry axis of the aspherical surface, c is the radius of curvature of the rotationally symmetric even-order aspherical surface, h is the radial coordinate, k is the coefficient of the conic quadratic curve (aspherical coefficient), and A, B, C, ... are successively the coefficients of higher-order quadratic terms, higher-order quartic terms, ... and so on.

[0042] The parameters of the infrared long-wave optical system in Embodiment 1 are shown in Table 1-1.

[0043] Table 1-1

[0044] surface Radius of curvature (mm) Thickness (mm) Material illustrate 1 —— —— —— —— —— 2 even aspherical surface <![CDATA[r1=-172.49]]> <![CDATA[t1=-61.1]]> reflection First reflecting mirror 5 3 even aspherical surface <![CDATA[r2=-98.123]]> <![CDATA[t2=44.33]]> reflection Second reflecting mirror 3 4 flat —— <![CDATA[d4=3.5]]> ZNSE Beam splitter 4 5 even aspherical surface —— <![CDATA[t3=150.47]]> —— —— 6 even aspherical surface <![CDATA[r3=-440.84]]> <![CDATA[t4=-120.2]]> reflection Third reflecting mirror 7 7 even aspherical surface <![CDATA[r4=283.59]]> <![CDATA[t5=122.4]]> reflection Fourth reflecting mirror 6 8 flat —— <![CDATA[d8=2.500]]> SCGERML Detector window 8 9 flat —— <![CDATA[t6=3.000]]> —— —— aperture flat —— <![CDATA[t7=29.200]]> —— —— 11 flat —— <![CDATA[d 10 =0.500]]> SCGERML Detector filter 10 12 —— —— <![CDATA[t8=0.300]]> —— ——

[0045] Where r1 is the radius of curvature of the left surface of the first reflecting mirror 5, r2 is the radius of curvature of the right surface of the second reflecting mirror 3, r3 is the radius of curvature of the left surface of the third reflecting mirror 7, and r4 is the radius of curvature of the right surface of the fourth reflecting mirror 6; t1 is the distance between the first reflecting mirror 5 and the second reflecting mirror 3 (i.e., the distance between the vertex of the reflecting surface of the first reflecting mirror 5 and the vertex of the reflecting surface of the second reflecting mirror 3), t2 is the distance between the second reflecting mirror 3 and the beam-splitting lens 4 (i.e., the distance between the vertex of the reflecting surface of the second reflecting mirror 3 and the center point of the front surface of the beam-splitting lens 4), and d4 is the beam splitter... The center thickness of lens 4; t3 is the distance between beam-splitting lens 4 and third reflector 7 (the distance between the center point of the rear surface of beam-splitting lens 4 and the vertex of the reflecting surface of third reflector 7); t4 is the distance between third reflector 7 and fourth reflector 6 (i.e., the distance between the vertex of the reflecting surface of third reflector 7 and the vertex of the reflecting surface of fourth reflector 6); t5 is the distance between fourth reflector 6 and detector window 8 (i.e., the distance between the vertex of the reflecting surface of fourth reflector 6 and the front surface of detector window 8); t7 is the distance between detector cold stop 9 and protective glass 10. The specific parameters represent the following distances: Figure 5 As shown. The beam splitter 4 is made of zinc selenide, and the optical path diagram of the infrared optical system is as follows. Figure 2 As shown.

[0046] The even-order aspherical coefficients of the infrared long-wave system are shown in Table 1-2. In Table 2, surfaces 2, 3, 5, 6, and 7 are the left surface of the first reflecting mirror 5, the right surface of the second reflecting mirror 3, the right surface of the beam splitter 4, the left surface of the third reflecting mirror 7, and the right surface of the fourth reflecting mirror, respectively.

[0047] Table 1-2

[0048] In the above embodiment, the full-field modulation transfer function is greater than 0.2 at the Nyquist frequency of 30 lp / mm.

[0049] The parameters of the infrared long-wave optical system in Embodiment 2 are shown in Table 2-1.

[0050] Table 2-1

[0051] surface Radius of curvature (mm) Thickness (mm) Material illustrate 1 —— —— —— —— —— 2 even aspherical surface <![CDATA[r1=-179.352]]> <![CDATA[t1=-64.264]]> reflection First reflecting mirror 5 3 even aspherical surface <![CDATA[r2=-105]]> <![CDATA[t2=30]]> reflection Second reflecting mirror 3 4 flat —— <![CDATA[d4=2.000]]> ZNSE Beam splitter 4 5 even aspherical surface —— <![CDATA[t3=135.970]]> —— —— 6 even aspherical surface <![CDATA[r3=-469.486]]> <![CDATA[t4=-124.58]]> reflection Third reflecting mirror 7 7 even aspherical surface <![CDATA[r4=210.137]]> <![CDATA[t5=115.032]]> reflection Fourth reflecting mirror 6 8 flat —— <![CDATA[d8=2.500]]> SCGERML Detector window 8 9 flat —— <![CDATA[t6=3.000]]> —— —— aperture flat —— <![CDATA[t7=25.000]]> —— —— 11 flat —— <![CDATA[d 10 =0.500]]> SCGERML Detector filter 10 12 —— —— <![CDATA[t8=0.300]]> —— ——

[0052] The even-order aspherical coefficients of the infrared long-wave system are shown in Table 2-2.

[0053] Table 2-2

[0054] The infrared optical system of the above embodiment has a full-field modulation transfer function greater than 0.15 at the Nyquist frequency of 30 lp / mm.

[0055] The parameters of the infrared long-wave optical system in Embodiment 3 are shown in Table 3-1.

[0056] Table 3-1

[0057] surface Radius of curvature (mm) Thickness (mm) Material illustrate 1 —— —— —— —— —— 2 even aspherical surface <![CDATA[r1=-160.547]]> <![CDATA[t1=-55.510]]> reflection First reflecting mirror 5 3 even aspherical surface <![CDATA[r2=-65.391]]> <![CDATA[t2=49.461]]> reflection Second reflecting mirror 3 4 flat —— <![CDATA[d4=5]]> ZNSE Beam splitter 4 5 even aspherical surface —— <![CDATA[t3=164.458]]> —— —— 6 even aspherical surface <![CDATA[r3=-422.364]]> <![CDATA[t4=-115.000]]> reflection Third reflecting mirror 7 7 even aspherical surface <![CDATA[r4=300]]> <![CDATA[t5=129.457]]> reflection Fourth reflecting mirror 6 8 flat —— <![CDATA[d8=2.500]]> SCGERML Detector window 8 9 flat —— <![CDATA[t6=3.000]]> —— —— aperture flat —— <![CDATA[t7=34.453]]> —— —— 11 flat —— <![CDATA[d 10 =0.500]]> SCGERML Detector filter 10 12 —— —— <![CDATA[t8=0.300]]> —— ——

[0058] The even-order aspherical coefficients of the infrared long-wave system are shown in Table 3-2.

[0059] Table 3-2

[0060] The infrared optical system of the above embodiment has a full-field modulation transfer function greater than 0.16 at the Nyquist frequency of 30 lp / mm.

[0061] like Figure 4 As shown, the laser lens group I includes a first lens 1 and a second lens 2; the first lens 1 is a meniscus lens with its concave surface facing the image side, and the second lens 2 is a meniscus lens with its convex surface facing the image side. The materials of the first lens 1 and the second lens 2 are zinc sulfide and zinc selenide, respectively, but not limited to these. The two lenses may also be made of optical materials with higher refractive index and capable of transmitting laser wavelengths.

[0062] The optical parameters of the laser optical system in Example 4 are shown in Table 4-1.

[0063] Table 4-1

[0064] Serial Number Surface type Radius of curvature (mm) Thickness (mm) Material illustrate 1 —— —— —— —— —— aperture even aspherical surface <![CDATA[r1=-172.49]]> <![CDATA[t1=-61.1]]> reflection First reflecting mirror 5 3 even aspherical surface <![CDATA[r2=-98.123]]> <![CDATA[t2=44.33]]> reflection Second reflecting mirror 3 4 flat —— <![CDATA[T3=-46.248]]> reflection Beam splitter 4 5 spherical <![CDATA[R3=25.718]]> <![CDATA[D2=-3.000]]> ZNS Second lens 2 6 even aspherical surface <![CDATA[R4=7.580]]> <![CDATA[T4=-6.365mm]]> —— —— 7 spherical <![CDATA[R5=-8.779]]> <![CDATA[D1=-3.000]]> ZNS First lens 1 8 spherical <![CDATA[R6=-14.061]]> -3.161 —— ——

[0065] Wherein, r1 is the radius of curvature of the left surface of the first reflecting mirror 5, r2 is the radius of curvature of the right surface of the second reflecting mirror 3, R3 is the radius of curvature of the right surface of the second lens 2, R4 is the radius of curvature of the left surface of the second lens 2, R5 is the radius of curvature of the right surface of the first lens 1, and R6 is the radius of curvature of the left surface of the first lens 1; t1 is the distance between the first reflecting mirror 5 and the second reflecting mirror 3, t2 is the distance between the second reflecting mirror 3 and the beam splitter 4, T3 is the distance between the beam splitter 4 and the second lens 2, and T4 is the distance between the second lens 2 and the first lens 1.

[0066] The coefficients of the higher-order terms of the even-order aspherical surfaces in the laser optical system are shown in Table 4-2. In the table, surfaces 2, 3, and 6 are the left surface of the first reflecting mirror 5, the right surface of the second reflecting mirror, and the left surface of the second lens, respectively.

[0067] Table 4-2

[0068] Figure 6 The diagram shows the dot pattern at the 0 field of view of the laser band optical system in the above embodiment. It can be seen that the dispersion spot is uniform and circular.

[0069] The optical parameters of the laser optical system in Example 5 are shown in Table 5-1.

[0070] Table 5-1

[0071] Serial Number Surface type Radius of curvature (mm) Thickness (mm) Material illustrate 1 —— —— —— —— —— aperture even aspherical surface <![CDATA[r1=-179.741]]> <![CDATA[t1=-64.040]]> reflection First reflecting mirror 5 3 even aspherical surface <![CDATA[r2=-104.282]]> <![CDATA[t2=30.954]]> reflection Second reflecting mirror 3 4 flat —— <![CDATA[T3=-49.782]]> reflection Beam splitter 4 5 spherical <![CDATA[R3=15.019]]> <![CDATA[D2=-3.000]]> ZNS Second lens 2 6 even aspherical surface <![CDATA[R4=2.297]]> <![CDATA[T4=-9]]> —— —— 7 spherical <![CDATA[R5=-19.036]]> <![CDATA[D1=-3.000]]> ZNS First lens 1 8 spherical <![CDATA[R6=-29.171]]> -3.161 —— ——

[0072] The coefficients of the even-order aspherical higher-order terms of the laser optical system in Example 5 are shown in Table 5-2. In the table, surfaces 2, 3, and 6 are the left surface of the first reflecting mirror 5, the right surface of the second reflecting mirror, and the left surface of the second lens, respectively.

[0073] Table 5-2

[0074] The optical parameters of the laser optical system in Example 6 are shown in Table 6-1.

[0075] Table 6-1

[0076] Serial Number Surface type Radius of curvature (mm) Thickness (mm) Material illustrate 1 —— —— —— —— —— aperture even aspherical surface <![CDATA[r1=-160.341]]> <![CDATA[t1=-55.785]]> reflection First reflecting mirror 5 3 even aspherical surface <![CDATA[r2=-65.157]]> <![CDATA[t2=49.247]]> reflection Second reflecting mirror 3 4 flat —— <![CDATA[T3=-40.342]]> reflection Beam splitter 4 5 spherical <![CDATA[R3=34.221]]> <![CDATA[D2=-3.000]]> ZNS Second lens 2 6 even aspherical surface <![CDATA[R4=11.853]]> <![CDATA[T4=-4]]> —— —— 7 spherical <![CDATA[R5=-2.936]]> <![CDATA[D1=-3.000]]> ZNS First lens 1 8 spherical <![CDATA[R6=-11.085]]> -3.161 —— ——

[0077] The coefficients of the even-order aspherical higher-order terms of the laser optical system in Example 6 are shown in Table 6-2. In the table, surfaces 2, 3, and 6 are the left surface of the first reflecting mirror 5, the right surface of the second reflecting mirror, and the left surface of the second lens, respectively.

[0078] Table 6-2

[0079] like Figure 7 As shown, the laser lens group I includes, in addition to the first lens 1 and the second lens 2, a third lens 13, which is a meniscus lens with its concave surface facing the image side.

[0080] The optical parameters of the laser optical system in Example 7 are shown in Table 7-1.

[0081] Table 7-1

[0082] Surface type Radius of curvature (mm) Thickness (mm) Material illustrate 1 —— —— —— —— —— aperture even aspherical surface <![CDATA[r1=-172.49]]> <![CDATA[t1=-61.1]]> reflection First reflecting mirror 5 3 even aspherical surface <![CDATA[r2=-98.123]]> <![CDATA[t2=44.33]]> reflection Second reflecting mirror 3 4 flat —— <![CDATA[T3=-44.248]]> reflection Beam splitter 4 5 spherical <![CDATA[R3=23.2732]]> <![CDATA[D2=-3.000]]> ZNS Second lens 2 6 even aspherical surface <![CDATA[R3=8.4862]]> <![CDATA[T 23 =-6.365]]> —— —— 7 spherical <![CDATA[R7=-19.713]]> <![CDATA[D3=-3.000]]> ZNS Third lens 13 8 spherical <![CDATA[R8=-20.777]]> <![CDATA[T 31 =-5.2]]> —— —— 9 spherical <![CDATA[R5=-8.779]]> <![CDATA[D1=-3.000]]> ZNS First lens 1 10 spherical <![CDATA[R6=-14.061]]> -3.161 —— ——

[0083] The coefficients of even-order aspherical higher-order terms of the laser optical system in Example 7 are shown in Table 7-2.

[0084] Table 7-2

[0085] Figure 8 The diagram shows the dot pattern at the 0 field of view of the laser band optical system in the above embodiment. It can be seen that the dispersion spot is uniform and circular.

[0086] The optical parameters of the laser optical system in Example 8 are shown in Table 8-1.

[0087] Table 8-1

[0088] Surface type Radius of curvature (mm) Thickness (mm) Material illustrate 1 —— —— —— —— —— aperture even aspherical surface <![CDATA[r1=-179.372]]> <![CDATA[t1=-64.950]]> reflection First reflecting mirror 5 3 even aspherical surface <![CDATA[r2=-104.845]]> <![CDATA[t2=30.185]]> reflection Second reflecting mirror 3 4 flat —— <![CDATA[T3=-48.443]]> reflection Beam splitter 4 5 spherical <![CDATA[R3=15.904]]> <![CDATA[D2=-3.000]]> ZNS Second lens 2 6 even aspherical surface <![CDATA[R3=2.947]]> <![CDATA[T 23 =-6.365]]> —— —— 7 spherical <![CDATA[R7=-24.117]]> <![CDATA[D3=-3.000]]> Third lens 13 8 spherical <![CDATA[R8=-29.404]]> <![CDATA[T 31 =-5.2]]> 9 spherical <![CDATA[R5=-9.749]]> <![CDATA[D1=-3.000]]> ZNS First lens 1 10 spherical <![CDATA[R6=-19.061]]> -3.161 —— ——

[0089] The coefficients of even-order aspherical higher-order terms of the laser optical system in Example 8 are shown in Table 8-2.

[0090] Table 8-2

[0091] The optical parameters of the laser optical system in Example 9 are shown in Table 9-1.

[0092] Table 9-1

[0093] Surface type Radius of curvature (mm) Thickness (mm) Material illustrate 1 —— —— —— —— —— aperture even aspherical surface <![CDATA[r1=-160.939]]> <![CDATA[t1=-576.721]]> reflection First reflecting mirror 5 3 even aspherical surface <![CDATA[r2=-66.973]]> <![CDATA[t2=49.003]]> reflection Second reflecting mirror 3 4 flat —— <![CDATA[T3=-40.100]]> reflection Beam splitter 4 5 spherical <![CDATA[R3=24.161]]> <![CDATA[D2=-3.000]]> ZNS Second lens 2 6 even aspherical surface <![CDATA[R3=11.370]]> <![CDATA[T 23 =-6.365]]> —— —— 7 spherical <![CDATA[R7=-15.663]]> <![CDATA[D3=-3.000]]> Third lens 13 8 spherical <![CDATA[R8=-11.107]]> <![CDATA[T 31 =-5.2]]> 9 spherical <![CDATA[R5=-2.454]]> <![CDATA[D1=-3.000]]> ZNS First lens 1 10 spherical <![CDATA[R6=-10.401]]> -3.161 —— ——

[0094] The coefficients of even-order aspherical higher-order terms of the laser optical system in Example 9 are shown in Table 9-2.

[0095] Table 9-2

[0096] In the above embodiments, the laser band dispersion spots are all uniformly distributed in a circular pattern.

[0097] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0098] The optical system in this invention, composed of shared lens group II and infrared lens group III, is a total internal reflection structure and also possesses full-spectrum imaging capabilities for visible light, mid-wave infrared, long-wave infrared, or microwave. When imaging other spectral wavelengths, it is only necessary to replace the beam-splitting lens 4 with a material that transmits the corresponding wavelength.

[0099] This invention is an infrared laser composite optical system that uses both laser and infrared long-wave bands. Under guidance conditions, the laser band optical system is responsible for long-range target aircraft identification and obtaining distance information; the infrared long-wave band optical system has the advantages of all-weather and high resolution, and obtains the contour characterization information of the target.

[0100] This invention solves the problems of large size, high energy loss, and complex structure in current infrared laser composite optical systems. In a coaxial optical system, a beam-splitting lens coated with a reflective film is used to split the composite light into two bands: laser and long-wave infrared. The laser band is reflected from the front surface of the beam-splitting lens and enters the laser lens group, while the long-wave infrared band is transmitted through the beam-splitting lens and enters the infrared lens group. Compared to beam-splitting methods using a beam-splitting lens coated with an infrared reflective film, energy loss is reduced. Compared to beam-splitting methods using tilted parallel plates, the entire system has no asymmetric aberrations, reducing system size and simplifying system structure. As shown in the embodiments, the infrared long-wave optical system exhibits excellent imaging quality, with the laser band dispersion spot showing a uniform circular distribution.

Claims

1. An infrared laser composite optical system, comprising a laser lens group (Ⅰ) and an infrared mirror group (Ⅲ), characterized in that... It also includes a common lens group (Ⅱ), and the optical elements of the three lens groups are coaxially distributed in sequence; the common lens group (Ⅱ) includes a first reflecting mirror (5) with positive optical power, a second reflecting mirror (3) with negative optical power, and a beam splitter lens (4); the composite beam of long-wave infrared and laser enters the common lens group (Ⅱ), and after being reflected by the first reflecting mirror (5) and the second reflecting mirror (3) in sequence, the laser is reflected on the front surface of the beam splitter lens (4) and reaches the laser system image plane (11) through the laser lens group (Ⅰ); the long-wave infrared beam is transmitted at the beam splitter lens (4) and reaches the infrared system image plane (12) after passing through the infrared lens group (Ⅲ); the radius of curvature of the reflecting surface of the first reflecting mirror is -180mm < r1 < -160mm, the radius of curvature of the reflecting surface of the second reflecting mirror is -105mm < r2 < -65mm, the distance between the first reflecting mirror and the second reflecting mirror is |-55|mm < t1 < |-65|mm, and the distance between the second reflecting mirror and the beam splitter lens is 30mm < t2 < 50mm; the infrared lens group (Ⅲ) includes a fourth reflecting mirror (6) with positive optical power, a third reflecting mirror (7) with positive optical power, a detector window (8), a detector cold stop (9), and a detector filter (10); the long-wave infrared beam transmitted by the beam splitter lens (4) passes through the third reflecting mirror (7), the fourth reflecting mirror (6), the detector window (8), the detector cold stop (9), and the detector filter (10) in sequence and reaches the infrared system image plane (12); the radius of curvature of the reflecting surface of the third reflecting mirror is -470mm < r3 < -420mm, the radius of curvature of the reflecting surface of the fourth reflecting mirror is 210mm < r4 < 300mm; the central thickness of the beam splitter lens is 2mm < d4 < 5mm, the distance between the beam splitter lens and the third reflecting mirror is 135mm < t3 < 165mm, the distance between the third reflecting mirror and the fourth reflecting mirror is |-115|mm < t4 < |-125|mm; the distance between the fourth reflecting mirror and the detector window is 115mm < t5 < 130mm; the distance between the detector cold stop and the protective glass is 25mm < t7 < 35mm.

2. The infrared laser composite optical system according to claim 1, characterized in that... The reflecting surfaces of the first and second reflectors are even-order aspherical surfaces. The aspherical coefficient k and the higher-order quadratic coefficient A of the reflecting surface of the first reflector are 0, while the higher-order quartic coefficient B, higher-order sixth-order coefficient C, higher-order octagonal coefficient D, and higher-order decimal coefficient E are 1.565E-8~7.565E-8, 8.604E-14~3.604E-13, 1.277E-17~9.277E-17, and 1.579E-22, respectively. ~5.579E-22; The aspherical coefficient k and the higher-order quadratic coefficient A of the reflecting surface of the second reflecting mirror are 0, and the higher-order quartic coefficient B, higher-order sixth-order coefficient C, higher-order octet coefficient D, and higher-order decimal-order coefficient E are 9.556E-7~5.556E-6, -5.854E-10~-1.854E-10, -7.31E-15~-1.31E-15, and 1.929E-17~7.929E-17, respectively.

3. The infrared laser composite optical system according to claim 1, characterized in that... The reflecting surfaces of the third and fourth reflecting mirrors, as well as the rear surface of the beam-splitting lens, are all even-order aspherical surfaces. The aspherical coefficient k and the higher-order quadratic coefficient A of the reflecting surface of the third reflecting mirror are 0, while the higher-order quartic coefficient B, sixth-order coefficient C, octave coefficient D, and decimal-order coefficient E are 3.778E-9~. 9.778E-9, -1.043E-12~-4.432E-13, 5.233E-17~6.523E-16, -6.939E-20~-9.394E-21; the aspherical coefficient k and the higher-order quadratic coefficient A of the fourth reflecting surface are 0, while the higher-order quartic coefficient B, higher-order sixth-order coefficient C, higher-order octave coefficient D, and higher-order decimal-order coefficient E are -1.189E-8~-5.890E-9, -4.607E-13~1.393E-13, and 3.94 respectively. 5E-17~9.945E-17、-8.044E-21~-2.044E-21;The aspherical coefficient k and the higher-order quadratic coefficient A on the back surface of the beam splitter (4) are 0, and the higher-order quartic coefficient B, higher-order sixth-order coefficient C, higher-order octet coefficient D, and higher-order decimal-order coefficient E are 8.570E-7~5.143E-6、1.440E-9~7.440E-9、-1.051E-11~-4.507E-12、4.064E-15~6.406E-14.

4. The infrared laser composite optical system according to claim 1, characterized in that... The laser lens group includes a second lens and a first lens; the second lens is a meniscus positive lens with a convex surface facing the image side, and the first lens is a meniscus positive lens with a concave surface facing the image side; the curvature radii of the right and left surfaces of the second lens are 15 mm < R3 < 35 mm and 2 mm < R4 < 12 mm respectively, the central thickness is 3.000 mm, the curvature radii of the right and left surfaces of the first lens are -20 mm < R5 < -2 mm and -30 mm < R6 < -10 mm respectively, and the central thickness is D1 = 3.000 mm; the air gap between the beam splitter lens and the second lens is |-40| mm < T3 < |-50| mm, and the air gap between the second lens and the first lens is |-3| mm < T4 < |-9| mm.

5. The infrared laser composite optical system according to claim 4, characterized in that... The left and right surfaces of the first lens and the right surface of the second lens are all spherical surfaces, and the left surface of the second lens is an even aspherical surface, with its aspherical coefficient k and higher-order quadratic coefficient A being 0, and the higher-order quartic coefficient B, higher-order sextic coefficient C, higher-order octic coefficient D, and higher-order decic coefficient E being -3.501E-4, -7.791E-6, -5.224E-8, and -3.608E-11 respectively.

6. The infrared laser composite optical system according to claim 1, characterized in that... The laser lens group includes a second lens, a first lens, and a third lens; the second lens is a meniscus positive lens with a convex surface facing the image side, the first lens is a meniscus positive lens with a concave surface facing the image side, and the third lens is a meniscus positive lens with a concave surface facing the image side; the curvature radii of the right and left surfaces of the second lens are 15 mm < R3 < 25 mm and 2 mm < R4 < 12 mm respectively, and the central thickness is D2 = 3.000 mm. The curvature radii of the right and left surfaces of the first lens are -10 mm < R5 < 0 mm and -20 mm < R6 < -10 mm respectively, and the central thickness is D1 = 3.000 mm; the curvature radii of the right and left surfaces of the third lens are -25 mm < R7 < -15 mm and -30 mm < R8 < -10 mm respectively, and the central thickness is D3 = 3.000 mm; the air gap between the beam splitter lens and the second lens is |-40| mm < T3 < |-50| mm, and the air gap between the second lens and the third lens is T 23 = |-6.365| mm, and the air gap between the third lens and the first lens is T 31 = |-5.2| mm.

7. The infrared laser composite optical system according to claim 6, characterized in that... The left and right surfaces of the first lens and the third lens and the right surface of the second lens are all spherical surfaces, and the left surface of the second lens is an even aspherical surface, with its aspherical coefficient k and higher-order quadratic coefficient A being 0, and the higher-order quartic coefficient B, higher-order sextic coefficient C, higher-order octic coefficient D, and higher-order decic coefficient E being -7.551E-4, -5.416E-6, 9.179E-8, and 8.171E-10 respectively.

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