Super-resolution zoom optical imaging system based on DMD and design method thereof

Abstract

The invention discloses a DMD-based super-resolution zoom optical imaging system and a design method thereof. Belongs to the technical field of super-resolution imaging, and particularly relates to a super-resolution zoom optical imaging system based on a DMD and the technical field of design thereof. The imaging system comprises a continuous zoom telescope system, a DMD and a relay projection system, the continuous zoom telescope system comprises a front fixed lens, a zoom lens, a compensation lens and a rear fixed lens, and the relay projection system comprises a first lens, a second lens, a third lens, a fourth lens and an infrared detection unit. Light emitted by a target object passes through a front fixed lens, a zoom lens, a compensation lens and a rear fixed lens of the optical imaging system and then is imaged on a primary image plane where the DMD is located, the DMD encodes the light, and reflected light from the DMD sequentially passes through a first lens, a second lens, a third lens and a fourth lens. And the coded light on the DMD is imaged on the infrared detection unit.

Description

Technical Field

[0001] The invention belongs to the technical field of super-resolution imaging, and in particular relates to the technical field of a super-resolution zoom optical imaging system based on a DMD and its design. Background Art

[0002] Infrared detection technology has the characteristics of high sensitivity, fast response speed and strong anti-interference ability. It is widely used in many fields such as military, industry, medical care, and environmental monitoring.

[0003] In the infrared band, the detection system based on compressed sensing super-resolution imaging technology can obtain high-resolution target information using low-resolution detectors, effectively widening the imaging field of view, improving imaging resolution, and reducing infrared detection costs, thereby achieving miniaturization and lightweighting of the imaging system.

[0004] Super-resolution imaging optical system is currently one of the research hotspots of super-resolution imaging technology. The introduction of DMD in super-resolution imaging optical system enables researchers to design system structure flexibly according to actual needs, thereby continuously improving and improving the system's response speed, spectral resolution, imaging quality and other working parameters. Therefore, DMD has broad development prospects in the field of super-resolution imaging.

[0005] Domestic and foreign researchers have conducted extensive research on super-resolution imaging optical systems based on digital microlens arrays (DMDs), but for such imaging systems, most of them are currently focused on fixed-focal-length systems. Since variable-focal-length imaging systems can clearly observe targets at different focal lengths and local minute details of targets, this will effectively reduce the difficulty of super-resolution algorithms in processing information sources and improve the accuracy of super-resolution algorithms in processing information sources.

[0006] For super-resolution imaging, researchers not only require better imaging performance, but also pursue a larger entrance pupil diameter to improve the image surface illumination. In addition, due to the particularity of infrared imaging systems, they should also consider reducing the number of lenses in the system to achieve miniaturization and lightweight of the system. Summary of the invention

[0007] In order to solve the technical problem that previous super-resolution imaging optical systems based on digital microlens arrays (DMDs) basically focus on fixed focal length systems and infrared imaging systems with too many lenses, the present invention proposes a super-resolution variable focal length optical imaging system based on DMD and a design method thereof.

[0008] The imaging system includes a continuous zoom telescope system, a DMD and a relay projection system, wherein the continuous zoom telescope system includes a front fixed lens, a magnification lens, a compensation lens and a rear fixed lens, and the relay projection system includes a first lens, a second lens, a third lens, a fourth lens and an infrared detection unit; The light emitted by the target object passes through the front fixed lens, zoom lens, compensation lens and rear fixed lens of the optical imaging system and is imaged onto the primary image plane where the DMD is located. The DMD encodes the light, and the reflected light from the DMD passes through the first lens, the second lens, the third lens and the fourth lens in sequence, and the encoded light on the DMD is imaged onto the infrared detection unit.

[0009] Furthermore, the front fixed lens and the fourth lens are made of the same material, the variable power lens and the third lens are made of the same material, the compensation lens and the second lens are made of the same material, and the rear fixed lens and the first lens are made of the same material.

[0010] Furthermore, the front fixed lens, the variable power lens and the compensation lens are made of even-order aspherical lenses, and the rear fixed lens, the first lens, the second lens, the third lens and the fourth lens are made of spherical lenses.

[0011] Furthermore, the front fixed lens has a convex surface facing the object side and a concave surface facing the image side; the focal length of the front fixed lens is positive; The side of the variator lens facing the object side is concave, and the side facing the image side is concave; the focal length of the variator lens is negative; The side of the compensating lens facing the object side is convex, and the side facing the image side is convex; the focal length of the compensating lens is negative; The side of the rear fixed lens facing the object side is a concave surface, and the side facing the image side is a convex surface; the focal length of the rear fixed lens is negative.

[0012] Furthermore, the first lens has a convex surface facing the object side and a concave surface facing the image side; the focal length of the first lens is positive; The second lens has a concave surface facing the object side and a convex surface facing the image side; the focal length of the second lens is negative; The third lens has a convex surface facing the object side and a concave surface facing the image side; the focal length of the third lens is positive; The fourth lens has a convex surface facing the object side and a concave surface facing the image side; the focal length of the fourth lens is positive; An aperture stop of a DMD-based super-resolution zoom optical imaging system is arranged on a rear fixed lens; The design method of the DMD-based super-resolution zoom optical imaging system is carried out in ZEMAX software, and comprises the following steps: S1. Design a continuous zoom telescope system. The continuous zoom telescope system uses four lenses, namely a front fixed lens, a variable magnification lens, a compensation lens and a rear fixed lens. Determine the focal lengths of the short-focus, medium-focus and long-focus positions of the continuous zoom telescope system according to the target detection range and complete the structure selection of the continuous zoom telescope system; the front fixed lens, the variable magnification lens and the compensation lens use even-order aspherical lenses, and the rear fixed lens uses a spherical lens; S2. Design the short-focus structure of the continuous zoom telescope system; after determining the zoom form, determine the zoom parameters and set the structural parameters; select the positive group compensation in the mechanical compensation for design, distribute the optical focal length of each part of the continuous zoom telescope system according to the zoom equation, limit the total length of the system and retain a certain length of the back intercept, realize the change of the system focal length through the linear movement of the zoom lens, and compensate for the image plane displacement caused by the linear movement of the zoom lens and temperature change through the curved trajectory movement of the compensation lens; the front fixed lens adopts a positive IRG106 lens, the zoom lens adopts a negative germanium lens, the compensation lens adopts a positive silicon lens, and the rear fixed lens adopts a negative germanium lens; S3, designing a medium focal length structure for the continuous zoom telescope system; after determining the short focal length structure, changing the air interval between the front fixed lens and the zoom lens, the air interval between the zoom lens and the compensation lens, and the air interval between the compensation lens and the rear fixed lens to achieve focal length change, while limiting the mid-focus focal length and the total length of the continuous zoom telescope system, controlling the change in the air interval between each lens of the continuous zoom telescope system to be adjusted within 10 mm, performing image quality optimization once each adjustment, and optimizing the surface parameters of each lens, and achieving focal length change from short focal length to medium focal length by repeatedly changing the air interval between the front fixed lens and the zoom lens, the air interval between the zoom lens and the compensation lens, the air interval between the compensation lens and the rear fixed lens, and the surface parameters of each lens; S4, designing a telephoto structure for the continuous zoom telescope system; after determining the mid-focus structure, changing the air interval between the front fixed lens and the zoom lens, the air interval between the zoom lens and the compensating lens, and the air interval between the compensating lens and the rear fixed lens to achieve focal length change, wherein the zoom lens and the compensating lens are always ensured to move in a converging direction, and the front fixed lens group and the zoom lens, the compensating lens and the rear fixed lens are moved in a moving away direction, while limiting the telephoto focal length of the continuous zoom telescope system and the total length of the system, controlling the change in the air interval between each lens of the continuous zoom telescope system to be adjusted within 10 mm, performing image quality optimization once each adjustment, and optimizing the surface parameters of each lens, and achieving focal length change from mid-focus to telephoto by repeatedly changing the air interval between the front fixed lens and the zoom lens, the air interval between the zoom lens and the compensating lens, the air interval between the compensating lens and the rear fixed lens, and the surface parameters of each lens; S5. Use MEMS surface to represent the discontinuous surface of DMD, and simulate the pixel size, number of pixels and light deflection angle parameters of DMD. On this basis, optimize the imaging quality of the continuous zoom telescope system at each focal length position, and eliminate the aberration caused by the lens combination and the discontinuous surface of DMD; correct the image plane after DMD reflection, set the tilt parameters in the +x and +y directions of the image plane, and increase the tilt amount by 1mm each time. At the same time, optimize and adjust the surface shape of each lens of the continuous zoom telescope system until the center light of the reflected light on the pupil diagram coincides with the center of the image plane after DMD reflection; S6. Design a relay projection system. The relay projection system uses four lenses, namely the first lens, the second lens, the third lens and the fourth lens. The relay projection system and the continuous zoom telescope system are designed with relatively symmetrical structures. Set the field of view of the relay projection system according to the DMD image plane size, and repeatedly optimize the surface shape of each lens in the relay projection system until the image quality meets the specific application requirements. The magnification is controlled during the optimization. ;in, is the DMD pixel size, is the pixel size of the infrared detection unit, In order to achieve super-resolution reconstruction multiples, the air gap between the first lens and DMD and the size of the first lens and the size of the second lens are controlled during optimization to avoid interference between the first lens and the second lens of the relay projection system and the rear fixed lens of the continuous zoom telescope system; the first lens, the second lens, the third lens and the fourth lens use spherical lenses, thus completing the design of the relay projection system; S7. The continuous zoom telescope system, DMD and relay projection system are spliced ​​together and optimized as a whole to obtain a designed DMD-based super-resolution zoom optical imaging system.

[0013] Furthermore, the relatively symmetrical structure is specifically: the lenses with relatively symmetrical structures in the relay projection system and the continuous zoom telephoto system are made of the same material, specifically: the front fixed lens and the fourth lens are made of the same material, the variable magnification lens and the third lens are made of the same material, the compensation lens and the second lens are made of the same material, and the rear fixed lens and the first lens are made of the same material.

[0014] The DMD-based super-resolution zoom optical imaging system of the present invention has the following beneficial effects: The existing technologies related to zoom optical imaging systems all use three or four lens groups to achieve zoom, such as the Chinese invention patent "A variable focal length infrared imaging terminal" CN 108366185 The variable focus technology involved in A is realized by three lens groups, namely, a front fixed lens group, a variable magnification lens mechanism and a rear fixed lens group, and a plurality of lenses are used in both the front fixed lens group and the rear fixed lens group. This design has the disadvantage that the number of lenses is large, so it is difficult to achieve the overall miniaturization and lightweight of the system. In order to overcome this technical difficulty, the DMD-based super-resolution variable focus optical imaging system of the present invention is improved from two aspects: lens selection and system structure design. First, even-order aspheric lenses are used as much as possible. The expression of even-order aspheric lenses is simple, the amount of calculation is small, and the system aberration can be effectively reduced. At the same time, a symmetrical design method of a continuous zoom telescope system and a relay projection system is adopted in the design. The content of this symmetrical design method is the first in the field, and it is not only aimed at structural symmetry, but also seeks symmetry from the lens material and the setting of the aperture to try to reduce aberrations. The present invention also provides a comparison chart of the imaging quality of the continuous zoom telescope system and the relay projection system when the lens material is symmetrical and the lens material is asymmetrical, as shown in FIG. Figure 5 and Fig.14 As shown, Fig.14 The system MTF curve is not close to the diffraction limit, the distribution of each field MTF curve is not concentrated, the center field MTF is 0.5 at the cutoff frequency of 46.2lp / mm, and the edge field MTF is 0.1 at the cutoff frequency of 46.2lp / mm, and the system imaging quality is poor. The above technical scheme enables the system of the present invention to avoid the use of several groups of lenses to achieve zooming as in the prior art. After adopting a symmetrical design method, the original zooming that requires several groups of lenses is transformed into only four lenses, that is, the front fixed lens group, variable magnification lens group, compensation lens group and rear fixed lens group required by the prior art are simplified to front fixed lens, variable magnification lens, compensation lens and rear fixed lens, which effectively reduces the number of lenses and is conducive to the overall miniaturization and lightweight of the system.

[0015] The beneficial effects of the design method of the DMD-based super-resolution zoom optical imaging system of the present invention are: The invention solves the technical problem that previous super-resolution imaging optical systems based on digital microlens array DMD basically focus on fixed focal length systems, and guides technical personnel in this field to design and implement focal length changes in super-resolution imaging optical systems based on digital microlens array DMD. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 4 is a structural diagram of a super-resolution zoom optical imaging system based on DMD in an embodiment of the present invention; Figure 2Schematic diagram of the short focal length position of the DMD-based super-resolution zoom optical imaging system during zooming in an embodiment of the present invention; Figure 3 Schematic diagram of the mid-focal length position of a DMD-based super-resolution zoom optical imaging system during zooming in an embodiment of the present invention; Figure 4 Schematic diagram of the long focal length position of the DMD-based super-resolution zoom optical imaging system during zooming in an embodiment of the present invention; Figure 5 It is a modulation transfer function MTF curve diagram of a super-resolution zoom optical imaging system based on DMD at a short focal length position in an embodiment of the present invention; Figure 6 is a modulation transfer function MTF curve diagram of the focal length position in the DMD-based super-resolution variable focal length optical imaging system in an embodiment of the present invention; Figure 7 The modulation transfer function MTF curve diagram of the super-resolution zoom optical imaging system based on DMD at the long focal length position in the embodiment of the present invention; Figure 8 is a point diagram of a short focal length position of a DMD-based super-resolution zoom optical imaging system in an embodiment of the present invention; Fig. 9 is a point diagram of the focal position in the DMD-based super-resolution zoom optical imaging system in an embodiment of the present invention; Fig.10 is a point diagram of the long focal length position of the DMD-based super-resolution zoom optical imaging system in an embodiment of the present invention; Fig.11 This is a curve diagram of energy concentration at a short focal length position of a super-resolution zoom optical imaging system based on DMD in an embodiment of the present invention; Fig.12 is a graph showing the energy concentration at the focal position in the DMD-based super-resolution zoom optical imaging system according to an embodiment of the present invention; Fig.13 Graph showing energy concentration at the long focal length position of a DMD-based super-resolution zoom optical imaging system in an embodiment of the present invention.

[0017] Fig.14 This is a modulation transfer function (MTF) curve diagram of the short focal position of the system when the lens materials of the continuous zoom telephoto system and the relay projection system in the beneficial effects section of the present invention are asymmetric. DETAILED DESCRIPTION

[0018] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0019] Embodiment 1, This embodiment provides a DMD-based super-resolution zoom optical imaging system to achieve super-resolution imaging at different focal lengths while keeping the image plane position fixed.

[0020] like Figure 1 As shown, the imaging system includes a continuous zoom telescope system, a DMD5 and a relay projection system, the continuous zoom telescope system includes a front fixed lens 1, a variable magnification lens 2, a compensation lens 3 and a rear fixed lens 4, and the relay projection system includes a first lens 6, a second lens 7, a third lens 8, a fourth lens 9 and an infrared detection unit 10; The light emitted by the target object passes through the front fixed lens 1, the zoom lens 2, the compensation lens 3 and the rear fixed lens 4 of the optical imaging system and is imaged onto the primary image plane where the DMD5 is located. The DMD5 encodes the light, and the reflected light from the DMD5 passes through the first lens 6, the second lens 7, the third lens 8 and the fourth lens 9 in sequence, and the encoded light on the DMD5 is imaged onto the infrared detection unit 10.

[0021] The front fixed lens 1 and the fourth lens 9 use lenses of the same material, the variable power lens 2 and the third lens 8 use lenses of the same material, the compensation lens 3 and the second lens 7 use lenses of the same material, and the rear fixed lens 4 and the first lens 6 use lenses of the same material.

[0022] The front fixed lens 1, the variable power lens 2 and the compensation lens 3 are even-order aspherical lenses, and the rear fixed lens 4, the first lens 6, the second lens 7, the third lens 8 and the fourth lens 9 are spherical lenses.

[0023] The front fixed lens 1 has a convex surface facing the object side and a concave surface facing the image side; the focal length of the front fixed lens 1 is positive; The side of the variator lens 2 facing the object side is concave, and the side facing the image side is concave; the focal length of the variator lens 2 is negative; The side of the compensating lens 3 facing the object side is convex, and the side facing the image side is convex; the focal length of the compensating lens 3 is negative; The side of the rear fixed lens 4 facing the object side is a concave surface, and the side facing the image side is a convex surface; the focal length of the rear fixed lens 4 is negative.

[0024] The first lens 6 has a convex surface facing the object side and a concave surface facing the image side; the focal length of the first lens 6 is positive; The second lens 7 has a concave surface facing the object side and a convex surface facing the image side; the focal length of the second lens 7 is negative; The third lens 8 has a convex surface facing the object side and a concave surface facing the image side; the focal length of the third lens 8 is positive; The fourth lens 9 has a convex surface facing the object side and a concave surface facing the image side; the focal length of the fourth lens 9 is positive.

[0025] An aperture stop of the continuous zoom telephoto system is arranged on the rear fixed lens 4 , and an aperture stop of the relay projection system is arranged on the first lens 6 .

[0026] The DMD-based super-resolution zoom optical imaging system provided in this embodiment can realize super-resolution imaging of targets at different focal lengths. First, the image information of each focal length scene is projected onto the DMD5 through the continuous zoom telescope system, and then the deflection angle of the micromirror array in the DMD5 device is controlled by a computer device to realize the sampling encoding and modulation of the scene. Finally, the scene encoded by the DMD5 is projected to the image sensor CMOS in the infrared detection unit 10 for imaging through the relay projection system. By adjusting the exposure times of the CMOS detector, compressed data with different sampling rates can be obtained, thereby realizing effective compression and collection of data. The measurement value can be obtained through the M measurement process of the above optical system. According to the principle of compressed sensing It can be seen that choosing a suitable sparse basis , combined with the measurement matrix generated by DMD5 and the corresponding measured values , using a specific reconstruction algorithm to solve the sparse basis of the signal , using the sparse basis obtained , substitute into the formula The reconstructed signal is calculated to achieve accurate inversion and reconstruction of the original image.

[0027] Embodiment 2, This embodiment provides a design method for a super-resolution zoom optical imaging system based on a DMD. The design method is performed in ZEMAX software and comprises the following steps: S1. Design a continuous zoom telescope system. The continuous zoom telescope system uses four lenses, namely a front fixed lens 1, a variable magnification lens 2, a compensation lens 3 and a rear fixed lens 4. Determine the focal lengths of the short-focus, medium-focus and long-focus positions of the continuous zoom telescope system according to the target detection range and complete the structure selection of the continuous zoom telescope system; the front fixed lens 1, the variable magnification lens 2 and the compensation lens 3 use even-order aspherical lenses, and the rear fixed lens 4 uses a spherical lens; S2. Design the short-focus structure of the continuous zoom telescope system; after determining the zoom form, determine the zoom parameters and set the structural parameters; select the positive group compensation in the mechanical compensation for design, distribute the optical focal length of each part of the continuous zoom telescope system according to the zoom equation, limit the total length of the system and retain a certain length of back intercept to avoid interference between the first part of the continuous zoom telescope system and the second part of the relay projection system; realize the change of the focal length of the system through the linear movement of the zoom lens 2, and compensate for the image plane displacement caused by the linear movement of the zoom lens 2 and the temperature change through the curved trajectory movement of the compensation lens 3; the front fixed lens 1 adopts a positive IRG106 lens, the zoom lens 2 adopts a negative germanium lens, the compensation lens 3 adopts a positive silicon lens, and the rear fixed lens 4 adopts a negative germanium lens; such as Figure 2 The figure shows the short focal length position when the system is zooming; S3, designing a medium focal length structure for the continuous zoom telescope system; after determining the short focal length structure, changing the air interval between the front fixed lens 1 and the zoom lens 2, the air interval between the zoom lens 2 and the compensation lens 3, and the air interval between the compensation lens 3 and the rear fixed lens 4 to achieve focal length change, while limiting the mid-focus focal length and the total length of the continuous zoom telescope system, controlling the change in the air interval between each lens of the continuous zoom telescope system to be adjusted within 10 mm, optimizing the image quality each time the adjustment is made, and the optimization variables are the surface parameters of each lens, and the focal length change from short focal length to medium focal length is achieved by repeatedly changing the air interval between the front fixed lens 1 and the zoom lens 2, the air interval between the zoom lens 2 and the compensation lens 3, the air interval between the compensation lens 3 and the rear fixed lens 4, and the surface parameters of each lens; Figure 3 Shown is a schematic diagram of the mid-focus position when the system is zooming; S4, designing a telephoto structure for the continuous zoom telescope system; after determining the mid-focus structure, changing the air interval between the front fixed lens 1 and the zoom lens 2, the air interval between the zoom lens 2 and the compensation lens 3, and the air interval between the compensation lens 3 and the rear fixed lens 4 to achieve focal length change, while limiting the mid-focus focal length and the total length of the continuous zoom telescope system, controlling the change in the air interval between each lens of the continuous zoom telescope system to be adjusted within 10 mm, optimizing the image quality each time the adjustment is made, and the optimization variables are the surface parameters of each lens, and the focal length change from mid-focus to telephoto is achieved by repeatedly changing the air interval between the front fixed lens 1 and the zoom lens 2, the air interval between the zoom lens 2 and the compensation lens 3, the air interval between the compensation lens 3 and the rear fixed lens 4, and the surface parameters of each lens; Figure 4 Shown is a schematic diagram of the long focal length position when the system is zooming; S5. Use MEMS surface type to represent the discontinuous surface of DMD5, and simulate the pixel size, number of pixels and light deflection angle parameters of DMD5. On this basis, optimize the imaging quality of the continuous zoom telescope system at each focal length position, and eliminate the aberration caused by the lens combination and the discontinuous surface of DMD5; correct the image plane after DMD5 reflection, set the tilt parameters in the +x and +y directions of the image plane, and increase the tilt amount by 1mm each time. At the same time, optimize and adjust the surface shape of each lens of the continuous zoom telescope system until the center light of the reflected light on the pupil diagram coincides with the center of the image plane after DMD5 reflection; S6. Design a relay projection system. The relay projection system uses four lenses, namely the first lens 6, the second lens 7, the third lens 8 and the fourth lens 9. The relay projection system and the continuous zoom telescope system are designed with relatively symmetrical structures. Set the field of view of the relay projection system according to the image plane size of DMD5, and repeatedly optimize the surface shape of each lens in the relay projection system until the image quality meets the specific application requirements. The magnification is controlled to be ;in, is the DMD5 pixel size, is the pixel size of the infrared detection unit, In order to achieve super-resolution reconstruction multiples, the air gap between the first lens 6 and the DMD 5 and the size of the first lens 6 and the size of the second lens 7 are controlled during optimization to avoid interference between the first lens 6 and the second lens 7 of the relay projection system and the rear fixed lens 4 of the continuous zoom telescope system; the first lens 6, the second lens 7, the third lens 8 and the fourth lens 9 are spherical lenses, thus completing the design of the relay projection system; S7, splicing the continuous zoom telescope system, DMD5 and relay projection system together and optimizing them as a whole, to obtain a designed DMD-based super-resolution zoom optical imaging system.

[0028] The relatively symmetrical structure is specifically: the lenses with relatively symmetrical structures in the relay projection system and the continuous zoom telephoto system are made of the same material, specifically: the front fixed lens 1 and the fourth lens 9 are made of the same material, the variable magnification lens 2 and the third lens 8 are made of the same material, the compensation lens 3 and the second lens 7 are made of the same material, and the rear fixed lens 4 and the first lens 6 are made of the same material.

[0029] In addition, when the systems are designed separately, for the continuous zoom telescope system, its aperture diaphragm is set on the rear fixed lens 1, and for the relay projection system, its aperture diaphragm is set on the first lens 6 which is relatively symmetrical with the rear fixed lens of the continuous zoom telescope system. When the continuous zoom telescope system, DMD5 and relay projection system are spliced ​​together and optimized as a whole, the aperture diaphragm on the first lens 6 is cancelled and only the aperture diaphragm on the rear fixed lens 1 is retained.

[0030] Embodiment 3, This embodiment further limits the embodiment 2, provides a specific scheme designed by the method described in the embodiment, and further introduces the beneficial effects of the present invention.

[0031] The method described in Example 2 is used to design a DMD-based super-resolution zoom optical imaging system: The DMD5 used in this embodiment has 1280×1024 pixels and a pixel size of 7.6 μm, and the imaging device in the infrared detection unit 10 uses a medium-wave infrared detector array with 640×512 pixels and a pixel size of 15 μm. The design parameters of the imaging optical system are calculated accordingly.

[0032] S1. Design a continuous zoom telescope system. The continuous zoom telescope system uses four lenses, namely front fixed lens 1, variable magnification lens 2, compensation lens 3 and rear fixed lens 4. Determine the focal lengths of the short-focus, medium-focus and long-focus positions of the continuous zoom telescope system according to the target detection range and complete the structural selection of the continuous zoom telescope system. Specifically: the F / # of the continuous zoom telescope system is 3.8, the length and width of DMD5 are 9.73mm and 7.79mm respectively, the length and width of the image plane of the overall system are 9.6mm and 7.7mm respectively, the focal lengths of the continuous zoom telescope system are 50mm, 150mm and 250mm respectively, and the field of view of the system is designed according to the target size of the medium-wave infrared detector array. The horizontal field of view at the short-focus position is planned to be ±2.8°, and the vertical field of view is ±2.2°; the horizontal field of view at the long-focus position is ±0.6°, and the vertical field of view is ±0.5° The front fixed lens 1, the variable power lens 2 and the compensation lens 3 are made of even-order aspherical lenses, and the rear fixed lens 4 is made of spherical lenses; The zoom telescope system lens group uses an even-order aspheric surface for design optimization. By introducing an even-order aspheric surface, the optimization variables are increased and the number of lenses in the zoom telescope objective group is reduced. At the same time, high-transmittance materials are given priority in material selection and material matching is performed, using a silicon-germanium combination of materials. Furthermore, each component of the zoom telescope objective group uses a lens to ensure that the system has a high transmittance and improves the utilization rate of light energy. The definition of the even-order aspheric surface shape description parameter z is as follows:

[0033] In the formula, r is the surface light radius; c refers to the curvature radius closest to the spherical surface; k is the cone coefficient; - are the polynomial coefficients of an even-order aspheric surface.

[0034] At this point, the structure selection of the continuous zoom telescope system for the super-resolution imaging system has been completed.

[0035] The aspheric surface parameter values ​​of the continuous zoom telescope system are shown in Table 1, where the first, third and sixth surfaces are determined by taking the first incident surface of the light beam as the first surface and counting them in sequence along the incident direction of the light path.

[0036] Table 1

[0037] S2. Design a short-focus structure for the continuous zoom telescope system; after determining the zoom form, determine the zoom parameters and set the structural parameters; select the positive group compensation in the mechanical compensation for design, distribute the optical focal length of each part of the continuous zoom telescope system according to the zoom equation, limit the total length of the system and retain a certain length of the back intercept, realize the change of the system focal length through the linear movement of the zoom lens 2, and compensate for the image plane displacement caused by the linear movement of the zoom lens 2 and the temperature change through the curved trajectory movement of the compensation lens 3; the front fixed lens 1 adopts a positive IRG106 lens, the zoom lens 2 adopts a negative germanium lens, the compensation lens 3 adopts a positive silicon lens, and the rear fixed lens 4 adopts a negative germanium lens; S3, designing a medium focal length structure for the continuous zoom telescope system; after determining the short focal length structure, changing the air interval between the front fixed lens 1 and the zoom lens 2, the air interval between the zoom lens 2 and the compensation lens 3, and the air interval between the compensation lens 3 and the rear fixed lens 4 to achieve focal length change, while limiting the mid-focus focal length and the total length of the continuous zoom telescope system, controlling the change in the air interval between each lens of the continuous zoom telescope system to be adjusted within 10 mm, performing image quality optimization once each adjustment, and optimizing the surface parameters of each lens, and achieving focal length change from short focal length to medium focal length by repeatedly changing the air interval between the front fixed lens 1 and the zoom lens 2, the air interval between the zoom lens 2 and the compensation lens 3, the air interval between the compensation lens 3 and the rear fixed lens 4, and the surface parameters of each lens; S4, designing a telephoto structure for the continuous zoom telescope system; after determining the mid-focus structure, changing the air interval between the front fixed lens 1 and the zoom lens 2, the air interval between the zoom lens 2 and the compensation lens 3, and the air interval between the compensation lens 3 and the rear fixed lens 4 to achieve focal length change, while limiting the mid-focus focal length and the total length of the continuous zoom telescope system, controlling the change in the air interval between each lens of the continuous zoom telescope system to be adjusted within 10 mm, performing image quality optimization once each adjustment, and optimizing the surface parameters of each lens, and achieving focal length change from mid-focus to telephoto by repeatedly changing the air interval between the front fixed lens 1 and the zoom lens 2, the air interval between the zoom lens 2 and the compensation lens 3, the air interval between the compensation lens 3 and the rear fixed lens 4, and the surface parameters of each lens; The optical system design results of the continuous zoom telephoto system are shown in Table 2: Table 2

[0038] S5. Use MEMS surface to represent the discontinuous surface of DMD5, and simulate the target size of DMD 9.73mm×7.79mm, the number of pixels 1280×1024, and the light deflection angle parameters of +12°, 0°, and -12°. On this basis, optimize the imaging quality of the continuous zoom telescope system at each focal length position, and eliminate the aberration caused by the lens combination and the discontinuous surface of DMD5; correct the image plane after DMD5 reflection, set the tilt parameters in the +x and +y directions of the image plane, and increase the tilt by 1mm each time. At the same time, optimize and adjust the surface shape of each lens of the continuous zoom telescope system until the center light of the reflected light on the pupil diagram coincides with the center of the image plane after DMD5 reflection; S6. Design a relay projection system. The relay projection system uses four lenses, namely the first lens 6, the second lens 7, the third lens 8 and the fourth lens 9. The relay projection system and the continuous zoom telescope system are designed with relatively symmetrical structures. Set the field of view of the relay projection system according to the image plane size of DMD5, and repeatedly optimize the surface shape of each lens in the relay projection system until the image quality meets the specific application requirements. The magnification is controlled to be ;in, is the DMD5 pixel size, is the pixel size of the infrared detection unit, In order to achieve super-resolution reconstruction multiples, the air gap between the first lens 6 and the DMD 5 and the size of the first lens 6 and the second lens 7 are controlled during optimization to avoid interference between the first lens 6 and the second lens 7 of the relay projection system and the rear fixed lens 4 of the continuous zoom telephoto system; the first lens 6, the second lens 7, the third lens 8 and the fourth lens 9 use spherical lenses, and the design of the relay projection system is completed.

[0039] The relatively symmetrical structure is specifically: the lenses with relatively symmetrical structures in the relay projection system and the continuous zoom telephoto system are made of the same material, specifically: the front fixed lens 1 and the fourth lens 9 are made of the same material, the variable magnification lens 2 and the third lens 8 are made of the same material, the compensation lens 3 and the second lens 7 are made of the same material, and the rear fixed lens 4 and the first lens 6 are made of the same material.

[0040] The design results of the optical system of the relay projection system are shown in Table 3: Table 3:

[0041] S7, splicing the continuous zoom telescope system, DMD5 and relay projection system together and optimizing them as a whole, to obtain a designed DMD-based super-resolution zoom optical imaging system.

[0042] Since the continuous zoom telescope system and relay projection system are designed separately, the overall image quality of the system is poor after direct splicing, so a two-step optimization method is considered; the first step is to continue to optimize the surface parameters of each mirror of the relay projection system, and the second step is to repeatedly and slightly adjust the image plane tilt to ensure that the image plane is perpendicular to the optical axis, so as to obtain better image quality, thus completing the design of the super-resolution imaging zoom optical system based on DMD. Figure 5 , 6 7 and 8 respectively show the MTF curves of the continuous zoom telephoto system at the short focal length, medium focal length and long focal length positions. The results show that the MTF of the optical system at each zoom position is greater than 0.4 at the system cutoff frequency of 40lp / mm; Figure 8 ,9 Figures 10 and 11 respectively show that the optical system spot RMS radius of the continuous zoom telescope system at each zoom position of short focus, medium focus and long focus is smaller than the infrared detector pixel size of 15μm. Fig.11 , 12 Figures 1 and 13 show the energy concentration curves of the continuous zoom telephoto system at each zoom position of short focus, medium focus and long focus, respectively. It can be seen that the energy distribution of the system is uniform and the image quality is good.

Claims

1. A super-resolution zoom optical imaging system based on DMD, characterized in that: The imaging system comprises a continuous zoom telescope system, a DMD (5) and a relay projection system. The continuous zoom telescope system comprises a front fixed lens (1), a variable magnification lens (2), a compensation lens (3) and a rear fixed lens (4); the relay projection system comprises a first lens (6), a second lens (7), a third lens (8), a fourth lens (9) and an infrared detection unit (10); Light emitted by a target object passes through a front fixed lens (1), a zoom lens (2), a compensation lens (3) and a rear fixed lens (4) of an optical imaging system, and is imaged onto a primary image plane where a DMD (5) is located. The DMD (5) encodes the light, and reflected light from the DMD (5) passes through a first lens (6), a second lens (7), a third lens (8) and a fourth lens (9) in sequence, so that the encoded light on the DMD (5) is imaged onto an infrared detection unit (10).

2. The DMD-based super-resolution zoom optical imaging system according to claim 1, characterized in that: The front fixed lens (1) and the fourth lens (9) are made of the same material, the variable power lens (2) and the third lens (8) are made of the same material, the compensation lens (3) and the second lens (7) are made of the same material, and the rear fixed lens (4) and the first lens (6) are made of the same material.

3. The DMD-based super-resolution zoom optical imaging system according to claim 2, characterized in that: The front fixed lens (1), the variable power lens (2) and the compensation lens (3) are even-order aspherical lenses, and the rear fixed lens (4), the first lens (6), the second lens (7), the third lens (8) and the fourth lens (9) are spherical lenses.

4. The DMD-based super-resolution zoom optical imaging system according to claim 3, characterized in that: The front fixed lens (1) has a convex surface facing the object side and a concave surface facing the image side; the focal length of the front fixed lens (1) is positive; The variable power lens (2) has a concave surface on the side facing the object side and a concave surface on the side facing the image side; the focal length of the variable power lens (2) is negative; The side of the compensation lens (3) facing the object side is a convex surface, and the side facing the image side is a convex surface; the focal length of the compensation lens (3) is negative; The side of the rear fixed lens (4) facing the object side is a concave surface, and the side facing the image side is a convex surface; the focal length of the rear fixed lens (4) is negative.

5. The DMD-based super-resolution zoom optical imaging system according to claim 4, characterized in that: The first lens (6) has a convex surface facing the object side and a concave surface facing the image side; the focal length of the first lens (6) is positive; The second lens (7) has a concave surface facing the object side and a convex surface facing the image side; the focal length of the second lens (7) is negative; The third lens (8) has a convex surface facing the object side and a concave surface facing the image side; the focal length of the third lens (8) is positive; The surface of the fourth lens (9) facing the object side is a convex surface, and the surface of the fourth lens (9) facing the image side is a concave surface; the focal length of the fourth lens (9) is positive.

6. The DMD-based super-resolution zoom optical imaging system according to claim 5, characterized in that: An aperture stop of a DMD-based super-resolution zoom optical imaging system is arranged on a rear fixed lens (4).

7. A design method for a DMD-based super-resolution zoom optical imaging system as claimed in claim 6, wherein the design method is performed in ZEMAX software, and is characterized in that: The method comprises the following steps: S1. Design a continuous zoom telescope system. The continuous zoom telescope system uses four lenses, namely a front fixed lens (1), a variable magnification lens (2), a compensation lens (3) and a rear fixed lens (4). The focal lengths of the short focal length, the middle focal length and the long focal length of the continuous zoom telescope system are determined according to the target detection range, and the structure of the continuous zoom telescope system is selected. The front fixed lens (1), the variable magnification lens (2) and the compensation lens (3) use even-order aspherical lenses, and the rear fixed lens (4) uses a spherical lens. S2. Design a short-focus structure for the continuous zoom telephoto system; After determining the zoom form, determine the zoom parameters and set the structural parameters; select the positive group compensation in the mechanical compensation for design, distribute the optical power of each part of the continuous zoom telescope system according to the zoom equation, limit the total length of the system and retain a certain length of back intercept, realize the focal length change of the system through the linear movement of the zoom lens (2), and compensate for the image plane displacement caused by the linear movement of the zoom lens (2) and temperature change through the curved trajectory movement of the compensation lens (3); the front fixed lens (1) adopts a positive IRG106 lens, the zoom lens (2) adopts a negative germanium lens, the compensation lens (3) adopts a positive silicon lens, and the rear fixed lens (4) adopts a negative germanium lens; S3. Design the mid-focus structure of the continuous zoom telephoto system; After the short focal length structure is determined, the air interval between the front fixed lens (1) and the variable magnification lens (2), the air interval between the variable magnification lens (2) and the compensation lens (3), and the air interval between the compensation lens (3) and the rear fixed lens (4) are changed to achieve focal length change, while limiting the mid-focus focal length and the total length of the continuous zoom telescope system, and controlling the change in the air interval between each lens of the continuous zoom telescope system to be adjusted within 10 mm. Image quality optimization is performed each time the adjustment is performed, and the optimization variables are the surface shape parameters of each lens. The focal length is changed from short focal length to medium focal length by repeatedly changing the air interval between the front fixed lens (1) and the variable magnification lens (2), the air interval between the variable magnification lens (2) and the compensation lens (3), the air interval between the compensation lens (3) and the rear fixed lens (4), and the surface shape parameters of each lens. S4. Design a telephoto structure for the continuous zoom telephoto system; After the mid-focus structure is determined, the air interval between the front fixed lens (1) and the variable-power lens (2), the air interval between the variable-power lens (2) and the compensating lens (3), and the air interval between the compensating lens (3) and the rear fixed lens (4) are changed to achieve focal length change, while limiting the telephoto focal length of the continuous zoom telescope system and the total length of the system, and controlling the change in the air interval between each lens of the continuous zoom telescope system to be within 10 mm for adjustment. Image quality optimization is performed each time the adjustment is performed, and the optimization variables are the surface parameters of each lens. The focal length change from mid-focus to telephoto is achieved by repeatedly changing the air interval between the front fixed lens (1) and the variable-power lens (2), the air interval between the variable-power lens (2) and the compensating lens (3), the air interval between the compensating lens (3) and the rear fixed lens (4), and the surface parameters of each lens. S5. Use MEMS surface to represent the discontinuous surface of DMD (5), and simulate the pixel size, number of pixels and light deflection angle parameters of DMD (5). On this basis, optimize the imaging quality of the continuous zoom telescope system at each focal length position, and eliminate the aberration caused by the lens combination and the discontinuous surface of DMD (5); correct the image plane after reflection of DMD (5), set the tilt parameters in the +x and +y directions of the image plane, and increase the tilt amount by 1 mm each time. At the same time, optimize and adjust the surface shape of each lens of the continuous zoom telescope system until the center ray of the reflected light on the pupil diagram coincides with the center of the image plane after reflection of DMD (5); S6. Design a relay projection system. The relay projection system uses four lenses, namely the first lens (6), the second lens (7), the third lens (8) and the fourth lens (9). The relay projection system and the continuous zoom telescope system are designed with relatively symmetrical structures. The field of view of the relay projection system is set according to the image plane size of the DMD (5). The surface shape of each lens in the relay projection system is repeatedly optimized until the image quality meets the specific application requirements. The magnification is controlled during the optimization. ;in, is the DMD (5) pixel size, is the pixel size of the infrared detection unit, In order to achieve super-resolution reconstruction magnification, the air space between the first lens (6) and the DMD (5) and the size of the first lens (6) and the size of the second lens (7) are controlled during optimization to avoid interference between the first lens (6) and the second lens (7) of the relay projection system and the rear fixed lens (4) of the continuous zoom telescope system; the first lens (6), the second lens (7), the third lens (8) and the fourth lens (9) are spherical lenses, thereby completing the design of the relay projection system; S7. The continuous zoom telescope system, DMD (5) and the relay projection system are spliced ​​together and optimized as a whole to obtain a designed DMD-based super-resolution zoom optical imaging system.

8. The design method of the DMD-based super-resolution zoom optical imaging system according to claim 7, characterized in that: The relatively symmetrical structure is specifically: the lenses with relatively symmetrical structures in the relay projection system and the continuous zoom telephoto system are made of the same material, specifically: the front fixed lens (1) and the fourth lens (9) are made of the same material, the variable magnification lens (2) and the third lens (8) are made of the same material, the compensation lens (3) and the second lens (7) are made of the same material, and the rear fixed lens (4) and the first lens (6) are made of the same material.

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