Long eye relief long wave infrared zoom projection optical system and infrared target simulator

Abstract

The present application relates to a kind of long pupil distance long-wave infrared zoom projection optical system and infrared target simulator, belong to optical device technical field, solve the short pupil distance of existing zoom projection system exists Problem.The working waveband of the system of the present application is 8~12, it adopts the inverted structure of diaphragm front, including the first fixed lens group, variable magnification lens group, compensation lens group, second fixed lens group being sequentially arranged along optical axis, optical power is respectively positive power, negative power, positive power, positive power;First fixed lens group and second fixed lens group are fixed in position on optical axis, variable magnification lens group, compensation lens group reciprocating moves along the direction of optical axis to realize the switching between short focus-86.67mm and long focus-260mm.The present application has long pupil distance, can realize the far field projection to long-wave infrared target while stabilizing zoom, avoid the interference between infrared target simulator and long-wave infrared system to be measured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical devices, in particular to a long-telecentric long-wave infrared zoom projection optical system and an infrared target simulator. BACKGROUND

[0002] The infrared target simulator, as a key component of infrared semi-physical simulation, is mainly composed of an infrared radiation source, a light splitting system, an illumination system, and a projection optical system. The main function of the infrared target simulator is to simulate the infrared radiation characteristics of a real scene and to realize performance testing of a detector in a laboratory environment. The infrared target simulator has the advantages of repeatability, high efficiency, and low cost, and effectively makes up for the shortcomings of field tests.

[0003] With the progress of infrared simulation technology, a continuous zoom structure is applied to the projection system of the infrared target simulator, which enables the system to adjust the field of view according to different testing requirements and output infrared images of different field of view ranges, thereby enhancing the testing adaptability of the simulator. However, the current simulators with zoom function generally have a short telecentric distance, which results in a lack of sufficient physical spacing between the simulator and the long-wave infrared system to be tested. This not only brings difficulties to mechanical installation and debugging, but also easily leads to noise in the long-wave infrared system due to thermal radiation interference between devices, thereby affecting the accuracy of the long-wave infrared system testing.

[0004] Therefore, it is necessary to provide a new type of projection optical system with a significantly increased telecentric distance while ensuring high imaging quality and continuous zoom capability, in view of the application characteristics of the long-wave infrared band target simulator. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a long-telecentric long-wave infrared zoom projection optical system and an infrared target simulator. By optimizing the optical path configuration and optical power distribution, the present application significantly extends the telecentric distance while achieving stable zooming and high-quality imaging. This provides necessary thermal isolation and structural buffer space between the infrared target simulator and the long-wave infrared system to be tested, which helps to suppress thermal interference between systems, improve the authenticity and testing reliability of the long-wave infrared target simulation, and enhance the adaptability and advantages of the infrared target simulator in complex testing environments.

[0006] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0007] The long-telephoto long-eyepoint long-wave infrared zoom projection optical system adopts an inverted structure with a light barrier in front, and the inverted structure comprises a first fixed lens group, a zoom lens group, a compensation lens group and a second fixed lens group which are coaxially arranged in sequence along the optical axis, and the first fixed lens group, the compensation lens group and the second fixed lens group all have positive refractive powers, and the zoom lens group has a negative refractive power;

[0008] The first fixed lens group and the second fixed lens group are fixed in position on the optical axis, the zoom lens group and the compensation lens group move reciprocally along the optical axis to realize switching between a short focus and a long focus, and in the zooming process, the zoom lens group is zoomed when moving along the optical axis, and the compensation lens group is focused when moving along the optical axis, wherein the short focus is -86.67 mm, the long focus is -260 mm, and the eyepoint distance is 300 mm.

[0009] The infrared light source emits a light beam with a working wavelength of 8 ~ 12 The light beam emitted by the infrared light source passes through the illumination optical system and the digital micromirror device, enters the second fixed lens group, is adjusted in focal length by the compensation lens group and the zoom lens group, and is emitted from the first fixed lens group, thereby completing far-field projection of an infrared image.

[0010] Meanwhile, the application also provides an infrared target simulator, which comprises the long-telephoto long-eyepoint long-wave infrared zoom projection optical system described above, and further comprises an infrared light source, an illumination optical system, a light splitting module and a digital micromirror device, wherein the infrared light source has a working wavelength of 8 ~ 12 .

[0011] The light beam emitted by the infrared light source is incident on the light splitting module after passing through the illumination optical system, the light splitting module guides the light beam to the modulation surface of the digital micromirror device, the digital micromirror device spatially modulates the incident light according to a target image signal, the reflected light in the on state is selectively diverted by the light splitting module, and then enters the long-telephoto long-eyepoint long-wave infrared zoom projection optical system, thereby the long-telephoto long-eyepoint long-wave infrared zoom projection optical system projects infrared images of different fields of view in the far field.

[0012] Compared with the prior art, the application has the following beneficial effects:

[0013] (1) The application provides a zoom projection optical system with a long eyepoint and a working wavelength of 8 ~ 12 by reasonably distributing the refractive powers of the lens groups and systematically optimizing the optical parameters, the zoom projection optical system can realize continuous and smooth zooming, the picture transition is smooth, and high-quality imaging effects can be stably output.

[0014] (2) The zoom projection optical system has a long exit pupil distance, the exit pupil distance is extended to 300mm, far field projection of the infrared target can be realized while the zoom is stable, interference between the infrared target simulator and the long wave infrared system to be tested is avoided, and the test precision of the long wave infrared system to be tested is improved. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The structure diagram of the long exit pupil distance long wave infrared zoom projection optical system is shown in one of the embodiments of the present application;

[0016] Figure 2 The modulation transfer function diagram of the long exit pupil distance long wave infrared zoom projection optical system in a short focus is provided in the embodiment of the present application;

[0017] Figure 3 The modulation transfer function diagram of the long exit pupil distance long wave infrared zoom projection optical system in a medium focus is provided in the embodiment of the present application;

[0018] Figure 4 The modulation transfer function diagram of the long exit pupil distance long wave infrared zoom projection optical system in a long focus is provided in the embodiment of the present application.

[0019] The figure mark description: G1, first fixed lens group; G2, zoom lens group; G3, compensation lens group; G4, second fixed lens group; L1, first lens; L2, second lens; L3, third lens; L4, fourth lens; L5, fifth lens; L6, sixth lens; L7, seventh lens; L8, eighth lens; L9, ninth lens; L10, tenth lens; L11, eleventh lens; L12, twelfth lens; L13, thirteenth lens; L14, fourteenth lens; L15, fifteenth lens; L16, sixteenth lens; L17, seventeenth lens; L18, prism replaced flat glass. DETAILED DESCRIPTION

[0020] The technical solutions of the present application will be described in detail below in combination with the drawings and preferred embodiments.

[0021] As shown in Figure 1 , the present embodiment provides a long exit pupil distance long wave infrared zoom projection optical system for infrared target simulation, the working waveband of the system is 8 ~ 12 The system adopts an inverted structure with a front aperture, which specifically includes first fixed lens group G1, variable magnification lens group G2, compensation lens group G3 and second fixed lens group G4 coaxially arranged in sequence along the optical axis, and the first fixed lens group G1 has positive focal power, the variable magnification lens group G2 has negative focal power, the compensation lens group G3 has positive focal power, and the second fixed lens group G4 has positive focal power. Optionally, the first fixed lens group G1, the variable magnification lens group G2, the compensation lens group G3 and the second fixed lens group G4 can be separately arranged or arranged in the same lens barrel (not shown in the figure). The focal power distribution of the first fixed lens group G1, the variable magnification lens group G2, the compensation lens group G3 and the second fixed lens group G4 makes the exit pupil of the entire projection optical system be pushed far to the rear of the system, effectively extending the exit pupil distance to 300 mm, thereby leaving sufficient physical spacing between the target simulator and the long-wave infrared system to be tested.

[0022] The first fixed lens group G1 and the second fixed lens group G4 are fixedly arranged and have fixed positions on the optical axis, so that the first fixed lens group G1 and the second fixed lens group G4 are stationary relative to the image plane. The variable magnification lens group G2 and the compensation lens group G3 are arranged to move along the optical axis, and reciprocally move along the optical axis to realize switching between short focus and long focus. During zooming, the variable magnification lens group G2 is zoomed when moving along the optical axis, and the compensation lens group G3 is focused when moving along the optical axis. The focal length of the zoom projection optical system can be adjusted by adjusting the positions of the variable magnification lens group G2 and the compensation lens group G3 on the optical axis, and the adjustment range of the focal length is -86.67 mm (W) - -260 mm (T), where W represents short focus and T represents long focus.

[0023] At the short focus position, the ratio of the focal length of the first fixed lens group G1 to the focal length F of the entire projection optical system is -3.183, the ratio of the focal length of the variable magnification lens group G2 to the focal length F of the entire projection optical system is 3.203, the ratio of the focal length of the compensation lens group G3 to the focal length F of the entire projection optical system is -1.756, and the ratio of the focal length of the second fixed lens group G4 to the focal length F of the entire projection optical system is -1.377.

[0024] At the mid-focus position, the ratio of the focal length of the first fixed lens group G1 to the focal length F of the entire projection optical system is -2.122, the ratio of the focal length of the variable magnification lens group G2 to the focal length F of the entire projection optical system is 2.135, the ratio of the focal length of the compensation lens group G3 to the focal length F of the entire projection optical system is -1.170, and the ratio of the focal length of the second fixed lens group G4 to the focal length F of the entire projection optical system is -0.918.

[0025] The ratio of the focal length of the first fixed lens group G1 to the focal length F of the entire projection optical system is -1.061, the ratio of the focal length of the variable magnification lens group G2 to the focal length F of the entire projection optical system is 1.067, the ratio of the focal length of the compensation lens group G3 to the focal length F of the entire projection optical system is -0.585, and the ratio of the focal length of the second fixed lens group G4 to the focal length F of the entire projection optical system is -0.159 when the projection optical system is in the long-focus position.

[0026] By controlling the ratios of the focal lengths of the first fixed lens group G1, the variable magnification lens group G2, the compensation lens group G3 and the second fixed lens group G4 to the total focal length of the system within the ranges as described above, the image plane position is kept stable and the zooming is smoother when the projection optical system continuously zooms in the focal length range of -86.67mm to -260mm.

[0027] Since the zoom projection optical system adopts an inverted structure design, the light beam emitted by the infrared light source enters the second fixed lens group G4 after passing through the illumination optical system (not shown in the figure) and the digital micromirror device (DMD) (not shown in the figure), and then exits from the first fixed lens group G1 after the focal length is adjusted by the compensation lens group G3 and the variable magnification lens group G2, thereby completing the far-field projection of the infrared image. The working wavelength of the infrared light source in this embodiment is 8 ~12 .

[0028] This embodiment proposes a continuously zoomable projection optical system with a long exit pupil distance in view of the application characteristics of the long-wave infrared band target simulator. By optimizing the optical path configuration and power distribution, both long exit pupil distance and zooming are taken into account. On the premise of ensuring high imaging quality and multi-field switching capability, the exit pupil distance is significantly increased, which not only provides necessary space for equipment layout and heat dissipation, but also makes the infrared target simulator using the projection optical system more advantageous in complex test environments.

[0029] Since the projection optical system adopts an inverted structure design, the digital micromirror device can be regarded as an image plane when designed. As a specific implementation, the first fixed lens group G1 includes a first lens L1, a second lens L2 and a third lens L3 arranged in sequence from the stop to the image plane. The first lens L1 has positive refractive power, the second lens L2 has negative refractive power, and the third lens L3 has positive refractive power. The first lens L1, the second lens L2 and the third lens L3 are all spherical glass, and the glass grades are ZNSE, ZNS_BROAD and ZNSE respectively. The parameters of the first fixed lens group G1 are shown in Table 1. ZNSE is an infrared transmission material commonly used in infrared optical systems, with a transmission band of 0.55-18 , and a refractive index of about 2.4332 at 4 , and a refractive index of about 2.4332 at 4 about 2.4064; Abbe number in the range of 3-5 about 176.9 in the range of 8-12 about 57.4; thermal expansion coefficient of 7.7 x 10 -6 / °C; absorption coefficient less than 0.001 cm -1 ZNSE has good mechanical properties and chemical stability, and is often used in optical components such as thermal imaging, laser transmission and infrared windows. ZNS_BROAD is an infrared material with good transmittance in the visible to far infrared band, suitable for a wide spectral range of 0.42-18.2 ; refractive index in the range of 4 about 2.2525 in the range of 10 about 2.1999; Abbe number in the range of 3-5 about 109.87 in the range of 8-12 about 22.8; thermal expansion coefficient of 7.0 x 10 -6 / °C; absorption coefficient of 0.2 cm -1 ZNS_BROAD has a high refractive index and moderate dispersion characteristics, and is often used in multispectral infrared optical systems, window sheets and lenses.

[0030] Table 1 Detailed parameters of the first fixed lens group G1

[0031]

[0032] As a specific embodiment, the variable magnification lens group G2 includes, in order from the stop to the image plane, a fourth lens L4 and a fifth lens L5. The fourth lens L4 has a negative refractive power, and the fifth lens L5 has a positive refractive power. The fourth lens L4 and the fifth lens L5 are both spherical glasses, and the glass grades are GERMANIUM and GERMANIUM, respectively. The parameters of the variable magnification lens group G2 are shown in Table 2. GERMANIUM is an infrared optical material with high refractive index and low dispersion characteristics in the mid-to-far infrared band (2-12 ); refractive index in the range of 4 about 4.0250 in the range of 10 about 4.0043; Abbe number in the range of 3-5 about 107.27 in the range of 8-12 about 770.4; thermal expansion coefficient of 6.1 x 10 -6 / °C; absorption coefficient less than 0.03 cm -1 GERMANIUM has a light transmission band covering the typical infrared atmospheric window, has high hardness and stability, and is often used in the manufacture of high-precision infrared lenses and windows.

[0033] Table 2 Detailed parameters of the variable magnification lens group G2

[0034]

[0035] As a specific embodiment, the compensation lens group G3 includes, in order from the stop to the image plane, a sixth lens L6, a seventh lens L7, and an eighth lens L8. The sixth lens L6 has positive refractive power, the seventh lens L7 has negative refractive power, and the eighth lens L8 has positive refractive power. The sixth lens L6, the seventh lens L7, and the eighth lens L8 are all spherical glasses, and the glass grades are ZNSE, ZNS_BROAD, and ZNSE, respectively. The parameters of the compensation lens group G3 are shown in Table 3.

[0036] Table 3 Detailed parameters of compensation lens group G3

[0037]

[0038] As a specific embodiment, the second fixed lens group G4 includes, in order from the stop to the image plane, a ninth lens L9, a tenth lens L10, an eleventh lens L11, a twelfth lens L12, a thirteenth lens L13, a fourteenth lens L14, a fifteenth lens L15, a sixteenth lens L16, a seventeenth lens L17, and a prism-replaced flat glass L18. The prism-replaced flat glass L18 mainly functions to fold the light path, and is used to fold the light beam reflected by the DMD into the projection optical system. The ninth lens L9 has positive refractive power, the tenth lens L10 has positive refractive power, the eleventh lens L11 has positive refractive power, the twelfth lens L12 has negative refractive power, the thirteenth lens L13 has positive refractive power, the fourteenth lens L14 has positive refractive power, the fifteenth lens L15 has negative refractive power, the sixteenth lens L16 has positive refractive power, the seventeenth lens L17 has positive refractive power, and the prism-replaced flat glass L18 is a flat glass that replaces an actual prism and has a refractive power of 0. The ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, the thirteenth lens L13, the fourteenth lens L14, the fifteenth lens L15, the sixteenth lens L16, and the seventeenth lens L17 are all spherical glasses, and the glass grades are GERMANIUM, GERMANIUM, GERMANIUM, ZNSE, ZNSE, ZNSE, GERMANIUM, ZNSE, and ZNS_BROAD, respectively. The prism-replaced flat glass L18 is a flat glass that replaces an actual prism, and the glass grade is ZNS_BROAD. The parameters of the second fixed lens group G4 are shown in Table 4.

[0039] The prism substitutes the flat glass L18 and specifically comprises a first total reflection prism, a first compensation prism and a second compensation prism which are closely adjacent, and the lower side of the first total reflection prism is parallel to the upper side of the first compensation prism. The first total reflection prism is responsible for turning the light path of the illumination optical system to the DMD, and the first compensation prism and the second compensation prism are compensation flats responsible for compensating the optical path difference, i.e. the lower side of the first total reflection prism is parallel to the upper side of the first compensation prism, wherein the second compensation prism is also responsible for turning off the light rays to make them away from the projection light path, so as to avoid the interference of stray light. The light emitted by the infrared light source is incident from the left side of the first total reflection prism through the illumination optical system, and after total reflection on the inclined plane of the first total reflection prism, the light is incident on the DMD through the lower side of the first total reflection prism. The on-state light reflected by the DMD passes through the lower side of the first total reflection prism again and sequentially passes through the first total reflection prism, the first compensation prism and the second compensation prism, and enters the projection system. The prism group is equivalent to be substituted by a flat glass in the system design.

[0040] Table 4 detailed parameters of the second fixed lens group G4

[0041]

[0042] The projection optical system for infrared target simulation provided by the application adopts a zoom structure design, which is sequentially composed of a first fixed lens group G1, a zoom lens group G2, a compensation lens group G3 and a second fixed lens group G4. By reasonably configuring the focal power distribution and lens surface parameters of each group, and by accurately controlling the motion trajectories of the zoom lens group G2 and the compensation lens group G3 through the existing mechanical structure such as a zoom cam mechanism (not shown in the figure), the system can continuously zoom smoothly within a field of view angle range of 1.97°-5.90°, wherein 5.90° is the field of view angle corresponding to the short focus position, 1.97° is the field of view angle corresponding to the long focus position, the maximum light aperture is 59.4309mm, and the image size is 8.9mm.

[0043] The projection optical system adopts an inverted structure with a diaphragm in front, and the diaphragm is arranged at the front end to ensure that the light beam from the infrared light source enters the projection optical system after being reflected by the DMD through the illumination optical system, and completes the far field projection of the infrared scene. In order to realize the requirements of telecentricity and long exit pupil distance, the projection optical system adopts a two-stage imaging structure: the first fixed lens group G1 and the zoom lens group G2 form a zoom front group to realize two times zoom; the second fixed lens group G4 is used as an imaging rear group with a magnification of 1, which is spliced with the front group to effectively realize the design of telecentricity in the image side and ensure that the exit pupil distance is 300mm.

[0044] The overall performance indicators of the long exit pupil distance long-wave infrared zoom projection optical system are as follows:

[0045] Working waveband: 8 ~ 12 ;

[0046] Focal length: -86.67mm in short-focus position (W) and -260mm in long-focus position (T);

[0047] Field of view: 5.90° in short-focus position (W) and 1.97° in long-focus position (T);

[0048] Maximum clear aperture: 59.4309mm;

[0049] Image surface size: 8.9mm;

[0050] Exit pupil distance: 300mm.

[0051] The long exit pupil long-wave infrared zoom projection optical system of the present application works in 8 ~ 12 Long-wave infrared waveband, can simulate different field of view of infrared target scene, provide matched field of view conditions for rear detection system. Each group works cooperatively, realizes zoom function, guarantees image surface stability and optical performance.

[0052] Figures 2-4 The modulation transfer function (MTF) diagrams of the long exit pupil long-wave infrared zoom projection optical system in short-focus, mid-focus and long-focus positions are shown in the figure. As can be seen from the figure, the MTF of the system at a spatial frequency of 17lp / mm is greater than 0.35 at on-axis, 0.7 field of view and full field of view positions, the MTF curve changes gently from on-axis to full field of view, the correction of off-axis aberrations such as astigmatism, coma and field curvature is sufficient, and the image quality uniformity is good.

[0053] Another embodiment of the present application provides an infrared target simulator, which comprises the long exit pupil long-wave infrared zoom projection optical system of the above embodiment, and further comprises an infrared light source, an illumination optical system, a light splitting module and a digital micromirror device.

[0054] Specifically, the light beam emitted by the infrared light source is incident to the light splitting module at a preset specific angle after passing through the illumination optical system. The light splitting module guides the light beam to the modulation surface of the digital micromirror device. The digital micromirror device spatially modulates the incident light according to the target image signal, and the reflected light in the open state is selectively diverted after passing through the light splitting module, and then enters the long exit pupil long-wave infrared zoom projection optical system. In the long exit pupil long-wave infrared zoom projection optical system, the focal length is continuously adjusted through the zoom structure, and finally the infrared image of different field of view is projected in the far field.

[0055] The working wavelength of the infrared target simulator proposed in the embodiment is 8 ~ 12 The long-wave infrared waveband can simulate infrared target scenes with different fields of view, provide matched field of view conditions for a rear detection system, has a continuous zoom function, and has higher image plane stability and optical performance.

[0056] The technical features of the above-described embodiments can be combined in any manner, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not exist, they should be considered as falling within the scope of the description.

[0057] The above-described embodiments only express several implementation manners of the present application, the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A long-wavelength infrared zoom projection optical system with a long exit pupil distance, characterized in that, The system employs an inverted structure with the aperture stop positioned in front. This inverted structure includes a first fixed lens group (G1), a zoom lens group (G2), a compensating lens group (G3), and a second fixed lens group (G4) arranged coaxially along the optical axis. The first fixed lens group (G1), the compensating lens group (G3), and the second fixed lens group (G4) all have positive optical power, while the zoom lens group (G2) has negative optical power. The first fixed lens group G1 and the zoom lens group G2 form the front zoom group, achieving a 2x zoom. The second fixed lens group G4 serves as the magnification factor. The image of the rear group is stitched together with the image of the front group; The first fixed lens group (G1) and the second fixed lens group (G4) are fixed in position on the optical axis. The zoom lens group (G2) and the compensating lens group (G3) reciprocate along the optical axis to achieve switching between short focal length and long focal length. During zooming, the zoom lens group (G2) zooms while moving along the optical axis, and the compensating lens group (G3) focuses while moving along the optical axis. The short focal length is -86.67mm, the long focal length is -260mm, and the exit pupil distance is 300mm. The operating wavelength is 8 ~12 The beam emitted by the infrared light source passes through the illumination optical system and digital micromirror device, then enters the second fixed lens group (G4). After the focal length is adjusted by the compensation lens group (G3) and the zoom lens group (G2), it exits from the first fixed lens group (G1) to complete the far-field projection of the infrared image. The second fixed lens group (G4) includes, from the aperture stop to the image plane, the ninth lens (L9), tenth lens (L10), eleventh lens (L11), twelfth lens (L12), thirteenth lens (L13), fourteenth lens (L14), fifteenth lens (L15), sixteenth lens (L16), seventeenth lens (L17), and a prism replacing the flat glass (L18); the twelfth lens (L12) and fifteenth lens (L15) both have negative optical power, and the ninth lens (L9), tenth lens (L10), eleventh lens (L11), thirteenth lens (L12), and eleventh lens (L13) are arranged sequentially. Lens (L13), the fourteenth lens (L14), the sixteenth lens (L16), and the seventeenth lens (L17) all have positive optical power, while the optical power of the prism replacing the flat glass (L18) is 0; the ninth lens (L9) to the seventeenth lens (L17) are all spherical glass, with glass grades of GERMANIUM, GERMANIUM, GERMANIUM, ZNSE, ZNSE, ZNSE, GERMANIUM, ZNSE, and ZNS_BROAD, respectively; the glass grade of the prism replacing the flat glass (L18) is ZNS_BROAD.

2. The long-wavelength infrared zoom projection optical system with long exit pupil distance according to claim 1, characterized in that, The first fixed lens group (G1) includes a first lens (L1), a second lens (L2), and a third lens (L3) arranged sequentially from the aperture stop to the image plane; the first lens (L1) and the third lens (L3) both have positive optical power, and the second lens (L2) has negative optical power; the first lens (L1), the second lens (L2), and the third lens (L3) are all spherical glass, and the glass grades are ZNSE, ZNS_BROAD, and ZNSE, respectively.

3. The long-wavelength infrared zoom projection optical system with long exit pupil distance according to claim 1, characterized in that, The zoom lens group (G2) includes a fourth lens (L4) and a fifth lens (L5) arranged sequentially from the aperture stop to the image plane; the fourth lens (L4) has negative optical power and the fifth lens (L5) has positive optical power; both the fourth lens (L4) and the fifth lens (L5) are spherical glass, and the glass grade is GERMANIUM.

4. The long-wavelength infrared zoom projection optical system with long exit pupil distance according to claim 1, characterized in that, The compensating lens group (G3) includes the sixth lens (L6), the seventh lens (L7), and the eighth lens (L8) arranged sequentially from the aperture stop to the image plane; the sixth lens (L6) and the eighth lens (L8) both have positive optical power, and the seventh lens (L7) has negative optical power; the sixth lens (L6), the seventh lens (L7), and the eighth lens (L8) are all spherical glass, with glass grades ZNSE, ZNS_BROAD, and ZNSE, respectively.

5. The long-wavelength infrared zoom projection optical system with long exit pupil distance according to claim 1, characterized in that, At the short focal length position, the ratio of the focal length of the first fixed lens group (G1) to the focal length F of the entire projection optical system is -3.183, the ratio of the focal length of the zoom lens group (G2) to the focal length F is 3.203, the ratio of the focal length of the compensation lens group (G3) to the focal length F is -1.756, and the ratio of the focal length of the second fixed lens group (G4) to the focal length F is -1.

377.

6. The long-wavelength infrared zoom projection optical system with long exit pupil distance according to claim 1, characterized in that, At the mid-focal position, the ratio of focal length to focal length F of the first fixed lens group (G1) is -2.122, the ratio of focal length to focal length F of the zoom lens group (G2) is 2.135, the ratio of focal length to focal length F of the compensating lens group (G3) is -1.170, and the ratio of focal length to focal length F of the second fixed lens group (G4) is -0.

918.

7. The long-wavelength infrared zoom projection optical system with long exit pupil distance according to claim 1, characterized in that, At the telephoto position, the ratio of focal length to focal length F of the first fixed lens group (G1) is -1.061, the ratio of focal length to focal length F of the zoom lens group (G2) is 1.067, the ratio of focal length to focal length F of the compensation lens group (G3) is -0.585, and the ratio of focal length to focal length F of the second fixed lens group (G4) is -0.

459.

8. The long-wavelength infrared zoom projection optical system with long exit pupil distance according to claim 1, characterized in that, The first fixed lens group (G1), the zoom lens group (G2), the compensating lens group (G3), and the second fixed lens group (G4) are arranged in the same lens barrel.

9. An infrared target simulator, characterized in that, The system includes the long exit pupil distance long-wavelength infrared zoom projection optical system as described in any one of claims 1 to 8, and further includes an infrared light source, an illumination optical system, a beam splitting module, and a digital micromirror device, wherein the infrared light source operates at a wavelength of 8 nm. ~12 ; The light beam emitted by the infrared light source is incident on the beam splitting module after passing through the illumination optical system. The beam splitting module guides the light beam to the modulation surface of the digital micromirror device. The digital micromirror device spatially modulates the incident light according to the target image signal. Its open-state reflected light is then selectively redirected by the beam splitting module and enters the long exit pupil distance long-wave infrared zoom projection optical system. The long exit pupil distance long-wave infrared zoom projection optical system projects infrared images of different fields of view in the far field.

Images