Miniaturized transmission-type laser and medium-wave infrared common-caliber composite optical system

Abstract

The utility model relates to a miniaturized transmission-type laser and medium-wave infrared common-caliber composite optical system, belongs to the technical field of detection imaging, and aims to solve the problem of center shielding of the conventional catadioptric laser and medium-wave infrared common-caliber composite optical system structure. Comprising a color separation and beam splitting system, the color separation and beam splitting system comprises a beam splitter prism, a narrow-band filter and a reflecting prism, a common-caliber receiving lens group is arranged on the incident end side of the beam splitter prism, an infrared branch lens group is arranged on the transmission end side of the beam splitter prism, and the common-caliber receiving lens group and the infrared branch lens group share the same optical axis. The narrow-band optical filter and the reflecting prism are sequentially arranged on the reflecting end side of the beam splitter prism, the reflecting prism reflects light at the reflecting end of the beam splitter prism to the laser zoom branch lens group, the composite optical system adopts a transmission-type scheme to realize laser and medium-wave infrared common-caliber composite, the problem of center shielding existing in catadioptric composite is avoided, and the composite optical system has the advantages that the laser and medium-wave infrared common-caliber composite is realized. And the miniaturized design is realized.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of detection imaging technology, especially to a kind of miniaturized transmission type laser and middle wave infrared common aperture composite optical system. BACKGROUND

[0002] With the increasing requirement of photoelectric intelligent equipment on the amount of information acquisition, information dimension, single waveband photoelectric detection means is limited to obtain target characteristics, target features, false alarm rate and misjudgment rate are higher, it is difficult to meet the needs of high-end target detection, detection, identification and other requirements, to improve target capture probability, multi-waveband composite detection technology gradually becomes mainstream technology.

[0003] Multi-waveband composite detection technology utilizes the difference of target characteristics of target and background / interference source in different wavebands, realizes the distinction between target and background / interference source, so as to improve the probability of identifying target and the accuracy of tracking target.

[0004] Laser and middle wave infrared dual-waveband composite is one of multi-waveband composite detection technology routes, and the technical route can realize the complementary advantages between laser imaging radar and infrared imaging system through near-infrared laser and middle wave infrared dual-waveband composite.

[0005] Laser imaging radar three-dimensional detection attribute can measure target distance, but it is limited by the hardware limitation of Gm-APD detector used, and the mainstream resolution of Gm-APD laser imaging radar is 64x64 pixels, the image resolution is low, and the pixel size is large.

[0006] The image resolution of middle wave infrared imaging system is high, and the resolution of mainstream middle wave infrared refrigeration detector is at least 640x512 pixels, and most targets have obvious target characteristics in infrared waveband, but infrared imaging system has problems such as being easily disturbed by thermal interference source and being difficult to distinguish when target and background temperature are the same, which makes photoelectric equipment fail to detect and track target, and infrared imaging system also has the shortcoming of being unable to obtain target distance information.

[0007] Optical composite design is carried out on the two, and high-resolution image containing target distance information can be obtained through subsequent fusion processing of laser image and infrared image, which can greatly improve the target recognition probability and tracking accuracy of photoelectric equipment.

[0008] Composite mode is divided into common aperture composite and split aperture composite, and the optical system of common aperture composite mode generally collects light through mirror group shared by different wavebands, and then separates each waveband light through light splitting device and conducts to corresponding optical branch and photoelectric detection device;The optical system of split aperture composite is independent for each waveband, and there is no overlapping part in the light path, and there is no common optical element except optical window or head cover, and each waveband optical system can be independently designed.

[0009] Gm-APD detector (full name is Geiger mode avalanche photodiode detector) is a solid-state laser imaging radar mainstream photoelectric conversion device. Gm-APD has single photon level detection capability, and its principle for detecting weak signals is that when a photon is incident on the photosensitive surface of the detector, it will excite photo-generated carriers to form electron-hole pairs. Under the action of an external electric field, photo-generated carriers collide with atoms in the semiconductor lattice to produce new electron-hole pairs. The newly generated carriers continue to collide to produce more carriers, forming an avalanche multiplication phenomenon, thereby realizing the amplification of optical signals. Gm-APD can measure the distance of the target based on the time-of-flight method. In practical application, it needs to be used in combination with a pulsed laser. The pulsed laser emits a pulse of laser light, which triggers the Gm-APD detector to start timing. Until the laser echo reflected by the target is received, the timing is stopped. The target distance can be calculated by combining the flight time of the laser and the speed of light.

[0010] The existing composite optical system generally adopts a coaxial reflective structure to realize laser / mid-wave infrared common-caliber compounding. For example, a Chinese invention patent with publication number CN111045102A discloses an infrared and laser receiving common-caliber composite detection system, which adopts a coaxial two-mirror structure as a common optical path part. The primary mirror collects light and reflects it to the secondary mirror, where the light of two wavebands is separated. Such a coaxial catadioptric structure is relatively complex, and the assembly and adjustment are difficult. Most importantly, the secondary mirror and the mechanical structure for fixing the secondary mirror will block the central field of view, resulting in a decrease in the energy utilization rate of the optical system. When the blockage is too large, a circular dark spot will be formed at the center of the image plane, affecting the imaging quality.

[0011] At the same time, the existing laser / mid-wave infrared common-caliber composite optical system has two fixed-focus optical systems. Due to the hardware limitations of the Gm-APD detector, it is difficult to meet the requirements of large field of view and high angular resolution for the laser branch. This problem can be solved by designing the laser branch as a zoom optical system. However, adding a zoom function to the optical system means a larger volume than a fixed-focus optical system, making it more difficult to miniaturize the optical system.

[0012] Therefore, based on technical requirements, the utility model patent adopts a transmissive scheme to realize laser and mid-wave infrared common-caliber compounding. This can solve the problem of central blockage of the catadioptric structure and the problem of miniaturization design of the optical system. At the same time, the laser branch is designed as a zoom optical system, thereby meeting the requirements of large field of view and high angular resolution. The size of the optical system is reasonably constrained during the design process, and the miniaturization design of the optical system is completed. Utility model content

[0013] The utility model discloses a miniaturized transmission type laser and middle wave infrared common caliber composite optical system, to solve the central obstruction problem existing in the structure of the current catadioptric laser and middle wave infrared common caliber composite optical system.

[0014] A miniaturized transmission type laser and middle wave infrared common caliber composite optical system, comprising a common caliber receiving lens group, a color separation and beam splitting system, an infrared branch lens group and a laser zoom branch lens group, the color separation and beam splitting system comprising a light splitting prism, a narrowband filter and a reflecting prism, the common caliber receiving lens group being arranged on the incident end side of the light splitting prism, the infrared branch lens group being arranged on the transmission end side of the light splitting prism, the common caliber receiving lens group and the infrared branch lens group being arranged on the same optical axis, the narrowband filter and the reflecting prism being arranged on the reflecting end side of the light splitting prism in sequence, the reflecting prism reflecting the light rays on the reflecting end of the light splitting prism towards the laser zoom branch lens group, the optical axis of the laser zoom branch lens group being parallel to the optical axis of the infrared branch lens group.

[0015] Further, the common caliber receiving lens group comprises a first meniscus positive lens, a second meniscus positive lens, a third meniscus positive lens and a first meniscus negative lens arranged coaxially in sequence along the light ray propagation direction.

[0016] Further, the infrared branch lens group comprises a fourth meniscus positive lens, a first biconcave negative lens, a first biconvex positive lens and a fifth meniscus positive lens arranged coaxially in sequence along the light ray propagation direction.

[0017] Further, the laser zoom branch lens group comprises a second biconvex positive lens, a second biconcave negative lens, a second meniscus negative lens, a third biconvex positive lens and a sixth meniscus positive lens arranged coaxially in sequence along the light ray propagation direction.

[0018] Further, the utility model also discloses a laser emitting lens group, which is arranged on the light emitting port of the laser, and comprises a fourth biconvex positive lens, a third meniscus negative lens and a seventh meniscus positive lens arranged coaxially in sequence along the laser emitting path.

[0019] Further, the common caliber composite near-infrared laser wavelength is 1064nm, and the middle wave infrared wavelength is 3.7-4.8 microns.

[0020] Further, the volume of the composite optical system is 234.9mm*157.5mm*110mm.

[0021] The laser and middle wave infrared common caliber composite optical system is designed in combination with the actual application, the rationality of the design is considered, the feasibility of the development is implemented, and better imaging quality is achieved.

[0022] 1. This novel composite optical system employs a transmission-type scheme to achieve co-aperture fusion of laser and mid-wave infrared light, avoiding the central obstruction problem inherent in catadioptric fusion. To reduce the size of the optical system, a Galilean telescope system is used as the initial mechanism. The most basic Galilean telescope system contains one positive and one negative lens. During the design process, considering the burden of correcting aberrations in the laser zoom branch and the infrared branch, a split lens method is used to separate one positive lens into three meniscus positive lenses, reducing spherical aberration. Simultaneously, different grades of chalcogenide glass are used to correct chromatic aberration through a combination of positive and negative lenses. The co-aperture receiving lens group, using a combination of four lenses with positive, positive, positive, and negative optical powers, corrects some aberrations while simultaneously reversing the optical path and compressing the beam aperture to reduce the size of the subsequent dichroic beam splitting system, facilitating the miniaturization of the optical system.

[0023] 2. A magnesium fluoride prism beam splitting scheme is employed, using high-transmittance mid-wave infrared high-reflectivity laser for color separation and beam splitting. This method has the following characteristics:

[0024] a) Imaging: Compared with the beam-splitter type beam splitting scheme, it avoids problems such as astigmatism, optical axis shift, and ghosting introduced by the beam splitter;

[0025] b) Materials: Based on the characteristics of this system, and considering factors such as the material's transmission band, environmental adaptability, and refractive index matching with the optical adhesive, magnesium fluoride was selected as the beam splitter prism. Magnesium fluoride has a transmission band covering 0.2μm to 7.04μm, exhibiting high transmittance for near-infrared lasers and mid-infrared light. The refractive index of magnesium fluoride is close to that of the optical adhesive, reducing reflection loss at the bonding surface. Magnesium fluoride also possesses high mechanical strength, good environmental adaptability, and is not prone to deliquescence.

[0026] c) Assembly and adjustment: Considering that the reflection branch requires adjustment of the beam splitter prism and the reflection prism, and the laser branch has a large Gm-APD pixel, the prism uses the method of transmitting mid-wave infrared reflection laser for beam splitting, which can reduce the difficulty of assembling and adjusting the optical system.

[0027] 3. The laser branch employs a zoom design, using a zoom lens group to change the focal length of the optical system while the focusing lens group maintains the image plane position. In short-focal-length mode, it can search for targets within a large field of view; in long-focal-length mode, it can track targets with high angular resolution, thereby improving tracking accuracy. This addresses, to some extent, the problem of current Gm-APD detectors' low image resolution and large pixel size, which prevent the optical system from simultaneously achieving a large field of view and high angular resolution.

[0028] 4. The optical system is miniaturized, with a volume of 234.9 mm × 157.5 mm × 110 mm and an overall weight of 1646 g for the optical lenses. The optical system can be used in optoelectronic pods or other optoelectronic detection equipment, which is beneficial for the miniaturization of optoelectronic equipment.

[0029] 5. The optical system is designed to be thermal in the range of -55℃ to 70℃, and can operate in a wide temperature range while ensuring that the imaging quality remains unchanged. Attached Figure Description

[0030] Figure 1 This is a block diagram of the components of this utility model;

[0031] Figure 2 This is a schematic diagram of the composite transmission of laser and mid-wave infrared light with the laser branch in long focal length mode, sharing the same aperture.

[0032] Figure 3 This is a schematic diagram of the composite transmission of laser and mid-wave infrared light with the laser branch in a short focal length state and sharing the same aperture.

[0033] Figure 4 This is the MTF plot of the laser branch at 10 lp / mm in the long focal length state at 20℃;

[0034] Figure 5 This is the MTF plot of the long focal length laser branch at -55℃ with a resolution of 10 lp / mm.

[0035] Figure 6 This is the MTF plot of the laser branch at 70℃ with long focal length at 10 lp / mm;

[0036] Figure 7 This is the MTF plot of the laser branch in short focal length at 20℃ with a resolution of 10 lp / mm;

[0037] Figure 8 This is the MTF plot of the laser branch in short focal length at -55℃ with a value of 10 lp / mm;

[0038] Figure 9 This is the MTF plot of the laser branch in short focal length at 70℃ with a resolution of 10 lp / mm;

[0039] Figure 10 This is the MTF plot of the infrared branch at 33 lp / mm at 20℃;

[0040] Figure 11 This is the MTF plot of the infrared branch at -55℃ with a resolution of 33 lp / mm;

[0041] Figure 12 This is the MTF plot of the infrared branch at 33 lp / mm at 70℃;

[0042] Figure 13 This is a schematic diagram showing the external dimensions of this utility model.

[0043] In the figure, 1. Common aperture receiving lens group, 11. First meniscus positive lens, 12. Second meniscus positive lens, 13. Third meniscus positive lens, 14. First meniscus negative lens, 2. Dichroic beam splitting system, 21. Beam splitter prism, 22. Narrowband filter, 23. Reflecting prism, 3. Infrared branch lens group, 31. Fourth meniscus positive lens, 32. First biconcave negative lens, 33. First biconvex positive lens, 34. Fifth meniscus positive lens, 35. Infrared detector window, 36. Germanium filter. 37. Infrared detector photosensitive surface; 4. Laser zoom branch mirror group; 41. Second biconvex positive lens; 42. Second biconcave negative lens; 43. Second meniscus negative lens; 44. Third biconvex positive lens; 45. Sixth meniscus positive lens; 46. Gm-APD detector window; 47. Gm-APD detector photosensitive surface; 5. Laser emitting mirror group; 51. Seventh meniscus positive lens; 52. Third meniscus negative lens; 53. Fourth biconvex positive lens; 54. Laser output port. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the present utility model. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the present utility model.

[0045] The connections mentioned in this utility model are divided into fixed connections and detachable connections. Fixed connections, also known as non-detachable connections, include but are not limited to conventional fixed connection methods such as folded connections, riveted connections, adhesive connections, and welded connections. Detachable connections include but are not limited to conventional disassembly methods such as bolt connections, snap-fit ​​connections, pin connections, and hinge connections. When a specific connection method is not explicitly defined, it is assumed that at least one existing connection method can be found to achieve this function, and those skilled in the art can choose according to their needs. For example, a welded connection can be chosen for a fixed connection, and a bolted connection can be chosen for a detachable connection.

[0046] The present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0047] Example: Figures 1-13As shown, a miniaturized transmissive laser and mid-wave infrared co-aperture composite optical system is characterized by comprising a co-aperture receiving mirror group 1, a dichroic beam splitting system 2, an infrared branch mirror group 3, and a laser zoom branch mirror group 4. The dichroic beam splitting system 2 includes a beam splitter 21, a narrowband filter 22, and a reflecting prism 23. The co-aperture receiving mirror group 1 is disposed on the incident end side of the beam splitter 21, and the infrared branch mirror group 3 is disposed on the transmission end side of the beam splitter 21. The co-aperture receiving mirror group 1 and the infrared branch mirror group 3 are arranged along the same optical axis. The narrowband filter 22 and the reflecting prism 23... 3 are arranged sequentially from near to far on the reflecting end side of the beam splitter 21. The optical path of the reflecting end of the beam splitter 21 and the normal of the reflecting slope of the reflecting prism 23 form the incident angle of the near-infrared laser. The principal optical axis of the laser zoom branch mirror group 4 and the normal of the reflecting slope of the reflecting prism 23 form the reflection angle of the near-infrared laser. The reflecting prism 23 reflects the light from the reflecting end of the beam splitter 21 toward the laser zoom branch mirror group 4. The narrowband filter 22 is set perpendicular to the optical path of the reflecting end of the beam splitter 21. The optical axis of the laser zoom branch mirror group 4 is parallel to the optical axis of the infrared branch mirror group 3. The infrared detector and the infrared tributary mirror group 3 are arranged on the same optical axis. The infrared detector includes an infrared detector window 35 and a germanium filter 36. The mid-wave infrared light modulated by the infrared tributary mirror group 3 passes through the infrared detector window 35 and the germanium filter 36 in sequence and is imaged on the photosensitive surface 37 of the infrared detector. The Gm-APD detector and the laser zoom tributary mirror group 4 are arranged on the same optical axis. The Gm-APD detector is provided with a Gm-APD detector window 46. The near-infrared laser modulated by the laser zoom tributary mirror group 4 passes through the Gm-APD detector window 46 and is imaged on the photosensitive surface 47 of the Gm-APD detector.

[0048] The common aperture receiving lens group 1 includes a first meniscus positive lens 11, a second meniscus positive lens 12, a third meniscus positive lens 13 and a first meniscus negative lens 14 arranged coaxially along the direction of light propagation.

[0049] The infrared branch lens group 3 includes a fourth meniscus lens 31, a first biconcave negative lens 32, a first biconvex positive lens 33, and a fifth meniscus lens 34 arranged coaxially along the direction of light propagation.

[0050] The laser zoom tributary lens group 4 includes a second biconvex positive lens 41, a second biconcave negative lens 42, a second meniscus negative lens 43, a third biconvex positive lens 44, and a sixth meniscus positive lens 45 arranged coaxially along the direction of light propagation.

[0051] It also includes a laser emitting lens group 5, which is set on the laser output port 54. The laser emitting lens group 5 includes a fourth biconvex positive lens 53, a third meniscus negative lens 52 and a seventh meniscus positive lens 51 arranged coaxially along the laser emission path.

[0052] The near-infrared laser with a common aperture composite has a wavelength of 1064 nm and a mid-infrared wavelength of 3.7 μm to 4.8 μm.

[0053] The dimensions of the composite optical system are 234.9mm × 157.5mm × 110mm.

[0054] The target is irradiated by a laser beam modulated by the laser emitting mirror group 5. The laser beam undergoes diffuse reflection on the target surface, generating a reflected echo. Simultaneously, the target itself continuously radiates mid-wave infrared light. The target laser echo and the target mid-wave infrared radiation are received by the optical system. After being modulated by the common aperture receiving mirror group 1 and separated by the dichroic beam splitting system 2 within the optical system, the laser echo light is modulated at an angle and corrected for aberrations by the laser zoom tributary mirror group 4 before reaching the Gm-APD detector. The Gm-APD detector calculates and generates a three-dimensional image containing target distance information by measuring the delay from laser emission to return. The mid-wave infrared light is corrected for aberrations by the infrared tributary mirror group 3 before reaching the infrared detector. The detector performs photoelectric conversion to generate an infrared thermal image of the target.

[0055] The common-aperture receiving mirror group 1, the beam splitter prism 21, and the infrared branch mirror group 3 form the infrared branch, and the three are placed coaxially along the propagation direction of mid-wave infrared light. The common-aperture receiving mirror group 1, the color-splitting and beam-splitting system 2, the laser zoom branch mirror group 4, and the laser emitting mirror group 5 together form the laser branch. The beam splitter prism 21 is used to split the near-infrared laser and the mid-wave infrared light, so that the mid-wave infrared light is directed from the transmission end of the beam splitter prism 21 to the infrared branch mirror group 3, and the near-infrared laser is directed from the reflection end of the beam splitter prism 21 to the reflection prism 23, and then directed to the laser zoom branch mirror group 4 through the total internal reflection of the reflection prism 23.

[0056] The first meniscus positive lens 11, the second meniscus positive lens 12, the third meniscus positive lens 13, and the first meniscus negative lens 14 are all made of different grades of chalcogenide glass with high transmittance for both near-infrared and mid-infrared laser light, and are coated with optical films that have high transmittance for both wavelengths, enabling them to simultaneously receive the laser echo and mid-infrared radiation from the target. The first meniscus positive lens 11, the second meniscus positive lens 12, and the third meniscus positive lens 13 are mainly used to bend light rays and compress the beam diameter, thereby reducing the volume of the beam splitter prism 21 and facilitating the miniaturization of the optical system. The three meniscus positive lenses (first meniscus positive lens 11, second meniscus positive lens 12, and third meniscus positive lens 13) are designed using a split lens method. This lens arrangement can reduce spherical aberration introduced by the lenses while significantly compressing the beam diameter. The first meniscus negative lens 14 can collimate the beam compressed by the first meniscus positive lens 11, the second meniscus positive lens 12, and the third meniscus positive lens 13 to a certain extent, making the common-aperture receiving lens group 1 approximately a focusless telescope system. This can reduce the mutual influence between the laser zoom branch and the infrared branch to a certain extent, allowing the laser zoom branch and the infrared branch to be designed independently after the common-aperture receiving lens group 1 is designed. At the same time, using a combination of positive and negative lenses made of different materials can reduce the chromatic aberration introduced by the common-aperture receiving lens group 1, thereby reducing the pressure on subsequent lens group aberration correction. After modulating the angle of the light and compressing the beam aperture, the common-aperture receiving lens group 1 transmits the light to the dichroic beam splitting system.

[0057] The color-splitting and beam-splitting system 2 consists of three parts: a beam-splitting prism 21, a narrow-band filter 22, and a reflecting prism 23. The beam-splitting prism 21 is made of magnesium fluoride material. The beam-splitting slope of the beam-splitting prism 21 is coated with a color-splitting film that transmits high-wave infrared light and reflects high-wave near-infrared laser light. The color-splitting film enables the function of splitting light by wavelength, thereby distributing the light of the corresponding wavelength band to the corresponding optical path.

[0058] Near-infrared laser and mid-wave infrared light are separated into colors and beams at the beam splitting slope of beam splitter 21. Beam splitter 21 transmits the mid-wave infrared light of the target to the infrared branch by transmission and reflects the laser echo of the target to the laser branch by reflection. The laser echo first passes through narrowband filter 22 for physical filtering and noise reduction before being directed to reflector 23.

[0059] The narrowband filter 22 is coated with a narrowband filter film. Based on the interference effect of light, the narrowband filter film filters out stray light in other bands other than the laser wavelength through interference cancellation, thereby improving the signal-to-noise ratio and imaging quality of the laser branch.

[0060] The reflecting prism 23 uses an external reflection method to reflect the laser echo into the laser zoom branch mirror group 4, making the optical axes of the laser branch and the infrared branch parallel, which helps to reduce the size of the optical system. The reflecting slope of the reflecting prism 23 is coated with a dielectric reflective film, which has a higher reflectivity than ordinary metal reflective films, and the reflectivity for near-infrared lasers can reach 99%.

[0061] The fourth meniscus positive lens 31 and the first biconcave negative lens 32 can correct the residual chromatic aberration of the target-co-aperture receiving lens group 1; the first biconvex positive lens 33 generates positive spherical aberration, which is corrected by positive and negative cancellation to correct the residual spherical aberration of the preceding lenses; the fifth meniscus positive lens 34 is mainly used to correct field curvature aberration. The infrared branch adopts a single-imaging method, which, compared with the double-imaging method, is advantageous in reducing the length of the optical system. The cold stop of the mid-wave cooled detector is used as the aperture stop to ensure 100% cold stop efficiency. The infrared branch can perform high-quality optical modulation of the thermal radiation of distant targets and focus it on the focal plane of the optical system for detection by the mid-wave cooled detector.

[0062] The second biconvex positive lens 41 is a fixed front lens that corrects the residual aberrations of the common-aperture receiving lens group 1. The second biconcave negative lens 42 and the second meniscus negative lens 43 form a zoom lens group, which can adjust the focal length of the laser branch and change the field of view of the laser branch. The third biconvex positive lens 44 and the sixth meniscus positive lens 45 form a focusing lens group, which can compensate for the image plane shift caused by the zoom lens group, thereby ensuring that the laser zoom branch has good imaging quality and a stable image plane position when zooming. In practical applications, the zoom lens group and the focusing lens group are moved by a zoom motor and a cam structure to realize the zoom function of the laser branch, taking into account the requirements of a large field of view and high angular resolution. The laser branch modulates the beam emitted by the laser from the laser to the divergence angle required by the whole machine for emission. After the emitted light is diffusely scattered by the illuminated target, the echo carrying the target's information reaches the optical system. After being modulated by the optical system, it is imaged on the photosensitive surface 47 of the Gm-APD detector. The three-dimensional distance information of the target is obtained by laser pulse time-of-flight measurement (TOF). The detection sensitivity can reach the single-photon level, thus realizing active imaging of distant targets.

[0063] The laser zoom emitting lens group modulates the laser emitted by the laser and emits it at a certain angle to match the field of view of the laser receiving optical system. The laser emitting lens group 5 contains three lenses: a fourth biconvex positive lens 53, a third meniscus negative lens 52, and a seventh meniscus positive lens 51. During the receiving optical system operation, the laser emitting lens group 5 changes the laser emission field of view by moving the seventh meniscus positive lens 51 to match it with the laser receiving field of view in real time, ensuring that the laser illumination beam can cover the receiving field of view without wasting laser energy.

[0064] The system of this invention is designed to be athermalized within a temperature range of -55℃ to +70℃, ensuring good imaging quality within this temperature range. The imaging quality transfer function of the laser branch at long focal length is evaluated at different temperatures as follows: Figures 4-6 As shown, the imaging quality transfer function evaluation for the short-focal-length laser branch at different temperatures is as follows: Figures 7-9As shown, the imaging quality transfer function evaluation of the infrared branch at different temperatures is as follows: Figures 10-12 As shown.

[0065] The design and practical application of this novel laser and mid-wave infrared co-aperture composite optical system are closely integrated. It takes into account both the rationality of the design and the feasibility of the development, and achieves good imaging quality.

[0066] 1. This novel composite optical system employs a transmission-type scheme to achieve co-aperture composite laser and mid-wave infrared light, avoiding the central obstruction problem inherent in catadioptric composite systems. To reduce the size of the optical system, a Galilean telescope system is used as the initial mechanism. The most basic Galilean telescope system contains one positive and one negative lens. During the design process, considering the pressure on the laser zoom branch and infrared branch to correct aberrations, a split lens method is used to separate one positive lens into three meniscus positive lenses, reducing spherical aberration in the system. Simultaneously, different grades of chalcogenide glass are used to correct chromatic aberration through a combination of positive and negative lenses.

[0067] The common aperture receiving lens group 1 corrects some aberrations while turning the optical path by combining four lenses with positive, positive, positive and negative optical powers, and compresses the beam aperture to reduce the volume of the subsequent dichroic beam splitting system, which facilitates the miniaturization of the optical system.

[0068] 2. A magnesium fluoride prism beam splitting scheme is employed, using high-transmittance mid-wave infrared high-reflectivity laser for color separation and beam splitting. This method has the following characteristics:

[0069] In terms of imaging: Compared with the beam-splitter type beam splitting scheme, it avoids problems such as astigmatism, optical axis shift, and ghosting introduced by the beam splitter;

[0070] b. Regarding materials: Based on the characteristics of this system, and considering factors such as the material's transmission band, environmental adaptability, and refractive index matching with the optical adhesive, magnesium fluoride was selected for the beam splitter prism 21. Magnesium fluoride has a transmission band covering 0.2μm to 7.04μm, exhibiting high transmittance for near-infrared lasers and mid-infrared light. The refractive index of magnesium fluoride is 1.38, close to that of the optical adhesive, reducing reflection loss at the bonding surface. Magnesium fluoride also possesses high mechanical strength, good environmental adaptability, and is not prone to deliquescence.

[0071] c. Assembly and adjustment: Considering that the reflection branch requires adjustment of the beam splitter prism 21 and the reflection prism 23, and the laser branch has a large Gm-APD pixel, the prism adopts the method of transmitting mid-wave infrared reflection laser for beam splitting, which can reduce the difficulty of optical system assembly and adjustment.

[0072] 3. The laser branch employs a zoom design, using a zoom lens group to change the focal length of the optical system while the focusing lens group maintains the image plane position. In short-focal-length mode, it can search for targets within a large field of view; in long-focal-length mode, it can track targets with high angular resolution, thereby improving tracking accuracy. This addresses, to some extent, the problem of current Gm-APD detectors' low image resolution and large pixel size, which prevent the optical system from simultaneously achieving a large field of view and high angular resolution.

[0073] 4. The optical system features a miniaturized design, with dimensions of 234.9mm × 157.5mm × 110mm and an overall lens weight of 1646g. Dimensions are as follows: Figure 13 As shown, the optical system can be applied to optoelectronic pods or other optoelectronic detection equipment, which is beneficial for the miniaturization of optoelectronic equipment.

[0074] 5. The optical system is calorimetric in the range of -55℃ to 70℃, and can operate in a wide temperature range while maintaining consistent image quality.

[0075] The above embodiments are merely illustrative examples of the present utility model and do not limit its scope of protection. Those skilled in the art can make partial changes to it, as long as they do not exceed the spirit and essence of the present utility model, they are all within the scope of protection of the present utility model.

Claims

1. A miniaturized transmissive laser and mid-wave infrared co-aperture composite optical system, characterized in that: The system includes a common-aperture receiving mirror group (1), a dichroic beam splitting system (2), an infrared branch mirror group (3), and a laser zoom branch mirror group (4). The dichroic beam splitting system (2) includes a beam splitter (21), a narrowband filter (22), and a reflecting prism (23). The common-aperture receiving mirror group (1) is located on the incident end side of the beam splitter (21), and the infrared branch mirror group (3) is located on the transmission end side of the beam splitter (21). The infrared branch mirror group (3) is set with the same optical axis. The narrow band filter (22) and the reflecting prism (23) are set sequentially on the reflecting end side of the beam splitter (21). The reflecting prism (23) reflects the light from the reflecting end of the beam splitter (21) to the laser zoom branch mirror group (4). The narrow band filter (22) is set perpendicular to the optical path of the reflecting end of the beam splitter (21). The optical axis of the laser zoom branch mirror group (4) is parallel to the optical axis of the infrared branch mirror group (3).

2. The miniaturized transmissive laser and mid-wave infrared co-aperture composite optical system according to claim 1, characterized in that: The common aperture receiving lens group (1) includes a first meniscus positive lens (11), a second meniscus positive lens (12), a third meniscus positive lens (13), and a first meniscus negative lens (14) arranged coaxially along the direction of light propagation.

3. The miniaturized transmissive laser and mid-wave infrared co-aperture composite optical system according to claim 1, characterized in that: The infrared branch lens group (3) includes a fourth meniscus positive lens (31), a first biconcave negative lens (32), a first biconvex positive lens (33) and a fifth meniscus positive lens (34) arranged coaxially along the direction of light propagation.

4. The miniaturized transmissive laser and mid-wave infrared co-aperture composite optical system according to claim 1, characterized in that: The laser zoom tributary lens group (4) includes a second biconvex positive lens (41), a second biconcave negative lens (42), a second meniscus negative lens (43), a third biconvex positive lens (44), and a sixth meniscus positive lens (45) arranged coaxially along the direction of light propagation.

5. The miniaturized transmissive laser and mid-wave infrared co-aperture composite optical system according to claim 1, characterized in that: It also includes a laser emitting lens group (5), which is set on the laser output port (54). The laser emitting lens group (5) includes a fourth biconvex positive lens (53), a third meniscus negative lens (52) and a seventh meniscus positive lens (51) arranged coaxially along the laser emission path.

6. The miniaturized transmissive laser and mid-wave infrared co-aperture composite optical system according to claim 1, characterized in that: The near-infrared laser with a common aperture composite has a wavelength of 1064 nm and a mid-infrared wavelength of 3.7 μm to 4.8 μm.

7. A miniaturized transmissive laser and mid-wave infrared co-aperture composite optical system according to any one of claims 1-6, characterized in that: The dimensions of the composite optical system are 234.9mm × 157.5mm × 110mm.

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