DMD-Based Super-Resolution Zoom Optical Imaging System and Its Design Method

Abstract

DMD-based super-resolution zoom optical imaging system and its design method. It belongs to the field of super-resolution imaging technology, and specifically relates to the field of DMD-based super-resolution zoom optical imaging system and its design technology. The imaging system includes a continuous zoom telescopic system, a DMD, and a relay projection system. The continuous zoom telescopic system includes a front fixed lens, a zoom lens, a compensation lens, and a rear fixed lens. 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, the zoom lens, the compensation lens, and the rear fixed lens of the optical imaging system and is imaged on 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 on the infrared detection unit.

Description

Technical Field

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

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

[0003] In the infrared band, for the detection system of the super-resolution imaging technology based on compressive sensing, a low-resolution detector can be used to obtain high-resolution target information, effectively broadening the imaging field of view, improving the imaging resolution, reducing the cost of infrared detection, and thus realizing the miniaturization and light weight of the imaging system.

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

[0005] Domestic and foreign research scholars have conducted extensive research on the super-resolution imaging optical system based on the digital micromirror device array DMD. However, for such imaging systems, currently, they basically focus on fixed-focus systems. Since the zoom imaging system can clearly observe the target at different focal lengths and the local micro-details of the target, this will effectively reduce the processing difficulty of the super-resolution algorithm for the information source and improve the processing accuracy of the super-resolution algorithm for the information source.

[0006] For super-resolution imaging, scientific research scholars not only require it to have better imaging performance, but also pursue a larger entrance pupil diameter to increase the image plane illuminance. In addition, considering the particularity of the infrared imaging system, the number of lenses in the system should also be reduced to achieve the miniaturization and light weight of the entire system. Summary of the Invention

[0007] In order to solve the technical problems that the previous super-resolution imaging optical system based on the digital micromirror device array DMD basically focuses on fixed-focus systems and the number of lenses in the infrared imaging system is too large, the present invention proposes a super-resolution zoom optical imaging system based on DMD and its design method.

[0008] The imaging system includes a continuous zoom telescopic system, a DMD, and a relay projection system. The continuous zoom telescopic system includes a front fixed lens, a zoom lens, a compensation lens, and a rear fixed lens. The relay projection system includes a first lens, a second lens, a third lens, a fourth lens, and an infrared detection unit;

[0009] The light emitted by the target object passes through the front fixed lens, the zoom lens, the compensation lens and the rear fixed lens of the optical imaging system and is imaged on 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 images the encoded light on the DMD onto the infrared detection unit.

[0010] Furthermore, the front fixed lens and the fourth lens adopt lenses of the same material, the zoom lens and the third lens adopt lenses of the same material, the compensation lens and the second lens adopt lenses of the same material, and the rear fixed lens and the first lens adopt lenses of the same material.

[0011] Furthermore, the front fixed lens, the zoom lens and the compensation lens adopt even aspherical lenses, and the rear fixed lens, the first lens, the second lens, the third lens and the fourth lens adopt spherical lenses.

[0012] Furthermore, the surface of the front fixed lens facing the object side is convex, and the surface facing the image side is concave; the focal length of the front fixed lens is positive;

[0013] The surface of the zoom lens facing the object side is concave, and the surface facing the image side is concave; the focal length of the zoom lens is negative;

[0014] The surface of the compensation lens facing the object side is convex, and the surface facing the image side is convex; the focal length of the compensation lens is negative;

[0015] The surface of the rear fixed lens facing the object side is concave, and the surface facing the image side is convex; the focal length of the rear fixed lens is negative.

[0016] Furthermore, the surface of the first lens facing the object side is convex, and the surface facing the image side is concave; the focal length of the first lens is positive;

[0017] The surface of the second lens facing the object side is concave, and the surface facing the image side is convex; the focal length of the second lens is negative;

[0018] The surface of the third lens facing the object side is convex, and the surface facing the image side is concave; the focal length of the third lens is positive;

[0019] The surface of the fourth lens facing the object side is convex, and the surface facing the image side is concave; the focal length of the fourth lens is positive;

[0020] An aperture stop of the super-resolution zoom optical imaging system based on the DMD is arranged on the rear fixed lens;

[0021] The design method of the DMD-based super-resolution zoom optical imaging system is carried out in ZEMAX software, including the following steps:

[0022] S1. Design a continuous zoom telescopic system. The continuous zoom telescopic system uses four lenses, namely a front fixed lens, a zoom lens, a compensating lens, and a rear fixed lens. Determine the focal lengths of the short focus, medium focus, and long focus positions of the continuous zoom telescopic system according to the target detection range and complete the selection of the structure of the continuous zoom telescopic system; the front fixed lens, the zoom lens, and the compensating lens use even aspherical lenses, and the rear fixed lens uses a spherical lens;

[0023] S2. Conduct a short-focus structure design for the continuous zoom telescopic system; after determining the zoom form, determine the zoom parameters and set the structure parameters; select positive-group compensation in mechanical compensation for design, distribute the optical power of each part of the continuous zoom telescopic system according to the zoom equation, limit the total length of the system and reserve a certain length of 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 compensating lens; the front fixed lens uses a positive IRG106 lens, the zoom lens uses a negative germanium lens, the compensating lens uses a positive silicon lens, and the rear fixed lens uses a negative germanium lens;

[0024] S3. Conduct a medium-focus structure design for the continuous zoom telescopic system; after determining the short-focus structure, change the air gaps between the front fixed lens and the zoom lens, between the zoom lens and the compensating lens, and between the compensating lens and the rear fixed lens to achieve focal length change, and at the same time limit the medium-focus focal length and the total length of the continuous zoom telescopic system. Adjust the change amount of the air gaps between each lens of the continuous zoom telescopic system within 10 mm. Perform image quality optimization each time it is adjusted. The optimization variables are the surface shape parameters of each lens. Realize the change of the focal length from short focus to medium focus by changing the air gaps between the front fixed lens and the zoom lens, between the zoom lens and the compensating lens, between the compensating lens and the rear fixed lens, and the surface shape parameters of each lens multiple times;

[0025] S4. Design the long - focal - length structure for the continuous zoom telescopic system; after determining the middle - focal - length structure, change the air gaps between the front fixed lens and the zoom lens, between the zoom lens and the compensating lens, and between the compensating lens and the rear fixed lens to achieve focal - length change. Among them, always ensure that the zoom lens and the compensating lens move in the converging direction, and the front fixed lens group and the zoom lens, the compensating lens and the rear fixed lens move in the separating direction. At the same time, limit the long - focal - length of the continuous zoom telescopic system and the total system length, control the change amount of the air gaps between each lens of the continuous zoom telescopic system within 10 mm for adjustment, and perform image - quality optimization each time of adjustment. The optimization variables are the surface - shape parameters of each lens. Through repeatedly changing the air gaps between the front fixed lens and the zoom lens, between the zoom lens and the compensating lens, between the compensating lens and the rear fixed lens, and the surface - shape parameters of each lens, achieve the change of focal length from the middle - focal - length to the long - focal - length;

[0026] S5. Use the MEMS surface to represent the discontinuous surface of the DMD, and simulate the pixel size, the number of pixels, and the light - deflection - angle parameters of the DMD. On this basis, optimize the imaging quality at each focal - length position of the continuous zoom telescopic system, and eliminate the aberrations caused by the lens combinations and the discontinuous surface of the DMD; correct the image plane after DMD reflection, set the tilt parameters in the +x and +y directions of this image plane, increase the tilt amount by 1 mm each time, and at the same time optimize and adjust the surface shapes of each lens of the continuous zoom telescopic system until the central ray of the reflected light on the pupil diagram coincides with the center of the image plane after DMD reflection;

[0027] S6. Design the 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 telescopic system are designed with a relatively symmetric structure; set the field of view of the relay projection system according to the DMD image - plane size, and repeatedly optimize the surface shapes of each lens surface in the relay projection system until the image quality meets the specific application requirements. During the optimization, control the magnification as ; where, is the DMD pixel size, is the pixel size of the infrared detection unit, is the super - resolution reconstruction multiple. During the optimization, avoid the interference between the first lens and the second lens of the relay projection system and the rear fixed lens of the continuous zoom telescopic system by controlling the air gap between the first lens and the DMD, the size of the first lens, and the size of the second lens; the first lens, the second lens, the third lens, and the fourth lens use spherical lenses. Thus, complete the design of the relay projection system;

[0028] S7. Assemble the continuous zoom telescopic system, the DMD, and the relay projection system together and perform overall optimization to obtain the designed DMD - based super - resolution zoom optical imaging system.

[0029] Furthermore, the relatively symmetric structure is specifically as follows: the lenses with relatively symmetric structures in the relay projection system and the continuous zoom telescopic system are made of the same material. Specifically, the front fixed lens and the fourth lens are made of lenses of the same material, the zoom lens and the third lens are made of lenses of the same material, the compensating lens and the second lens are made of lenses of the same material, and the rear fixed lens and the first lens are made of lenses of the same material.

[0030] The beneficial effects of the DMD-based super-resolution zoom optical imaging system of the present invention are as follows:

[0031] In the related technologies of the existing zoom optical imaging systems, 3 or 4 lens groups are used to achieve zoom. For example, the variable zoom technology involved in the Chinese invention patent "A Variable-Focal-Length Infrared Imaging Terminal" CN 108366185 A is achieved by 3 lens groups, namely a front fixed lens group, a zoom lens mechanism, and a rear fixed lens group, and several lenses are used in both the front fixed lens group and the rear fixed lens group. This design has the disadvantages that the number of lenses is large, so it is difficult to miniaturize and lighten the whole system. In order to overcome this technical problem, the DMD-based super-resolution zoom optical imaging system of the present invention starts from two aspects: lens selection and system structure design for improvement. First, as many aspheric lenses as possible are used. The expression of the even aspheric surface is simple and the calculation amount is small, which can effectively reduce the system aberration. At the same time, a symmetric design method of a continuous zoom telescopic system and a relay projection system is adopted in the design. The content of this symmetric design method is the first in the field, not only aiming at the symmetry of the structure, but also seeking symmetry from the lens material and the setting of the aperture to try to reduce the aberration. The present invention also gives the imaging quality comparison diagrams of the system when the lens materials of the continuous zoom telescopic system and the relay projection system are symmetric and asymmetric, as Figure 5 and Figure 14 shown, Figure 14 In [the figure], the system MTF curve does not approach the diffraction limit, the MTF curves of each field of view are not concentrated, the MTF of the central field of view is 0.5 at the cut-off frequency of 46.2 lp / mm, and the MTF of the edge field of view is 0.1 at the cut-off frequency of 46.2 lp / mm, and the imaging quality of the system is poor. The above technical solution enables the system of the present invention to avoid achieving zoom through several groups of lenses as in the prior art. After adopting the symmetric design method, the original zoom achieved by several groups of lenses is changed to only four lenses, that is, the front fixed lens group, the zoom lens group, the compensating lens group, and the rear fixed lens group required by the prior art are simplified to the front fixed lens, the zoom lens, the compensating lens, and the rear fixed lens, effectively reducing the number of lenses and facilitating the miniaturization and lightening of the whole system.

[0032] The beneficial effects of the design method of the DMD-based super-resolution zoom optical imaging system of the present invention are as follows:

[0033] It solves the technical problem that the previous super-resolution imaging optical systems based on digital micromirror device (DMD) basically focus on fixed-focus systems, and guides those skilled in the art to design and implement the focal length change in the super-resolution imaging optical system based on digital micromirror device (DMD). Description of the Drawings

[0034] Figure 1 It is the structure diagram of the DMD-based super-resolution zoom optical imaging system in the embodiment of the present invention;

[0035] Figure 2 It is the schematic diagram of the short focal length position when the DMD-based super-resolution zoom optical imaging system in the embodiment of the present invention is zooming;

[0036] Figure 3 It is the schematic diagram of the medium focal length position when the DMD-based super-resolution zoom optical imaging system in the embodiment of the present invention is zooming;

[0037] Figure 4 It is the schematic diagram of the long focal length position when the DMD-based super-resolution zoom optical imaging system in the embodiment of the present invention is zooming;

[0038] Figure 5 It is the modulation transfer function (MTF) curve diagram of the short focal length position of the DMD-based super-resolution zoom optical imaging system in the embodiment of the present invention;

[0039] Figure 6 It is the modulation transfer function (MTF) curve diagram of the medium focal length position of the DMD-based super-resolution zoom optical imaging system in the embodiment of the present invention;

[0040] Figure 7 It is the modulation transfer function (MTF) curve diagram of the long focal length position of the DMD-based super-resolution zoom optical imaging system in the embodiment of the present invention;

[0041] Figure 8 It is the spot diagram of the short focal length position of the DMD-based super-resolution zoom optical imaging system in the embodiment of the present invention;

[0042] Figure 9 It is the spot diagram of the medium focal length position of the DMD-based super-resolution zoom optical imaging system in the embodiment of the present invention;

[0043] Figure 10 It is the spot diagram of the long focal length position of the DMD-based super-resolution zoom optical imaging system in the embodiment of the present invention;

[0044] Figure 11It is the energy concentration curve graph at the short focal length position of the super-resolution zoom optical imaging system based on DMD in the embodiment of the present invention;

[0045] Figure 12 It is the energy concentration curve graph at the medium focal length position of the super-resolution zoom optical imaging system based on DMD in the embodiment of the present invention;

[0046] Figure 13 It is the energy concentration curve graph at the long focal length position of the super-resolution zoom optical imaging system based on DMD in the embodiment of the present invention.

[0047] Figure 14 It is the modulation transfer function MTF curve graph at the short focal length position of the system when the lens materials of the continuous zoom telescopic system and the relay projection system are asymmetric in the beneficial effects part of the present invention. Specific Embodiments

[0048] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] Embodiment 1

[0050] This embodiment provides a super-resolution zoom optical imaging system based on DMD to achieve super-resolution imaging at different focal length positions while the image plane position remains fixed.

[0051] As Figure 1 shown, the imaging system includes a continuous zoom telescopic system, a DMD 5, and a relay projection system. The continuous zoom telescopic system includes a front fixed lens 1, a zoom lens 2, a compensation lens 3, and a rear fixed lens 4. 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;

[0052] 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 on the primary image plane where the DMD 5 is located. The DMD 5 encodes the light, and the reflected light from the DMD 5 passes through the first lens 6, the second lens 7, the third lens 8, and the fourth lens 9 in sequence, and images the encoded light on the DMD 5 onto the infrared detection unit 10.

[0053] The front fixed lens 1 and the fourth lens 9 are made of lenses of the same material, the varifocal lens 2 and the third lens 8 are made of lenses of the same material, the compensating lens 3 and the second lens 7 are made of lenses of the same material, and the rear fixed lens 4 and the first lens 6 are made of lenses of the same material.

[0054] The front fixed lens 1, the varifocal lens 2, and the compensating lens 3 are made of even 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 made of spherical lenses.

[0055] One side of the front fixed lens 1 facing the object side is convex, and the side facing the image side is concave; the focal length of the front fixed lens 1 is positive;

[0056] One side of the varifocal lens 2 facing the object side is concave, and the side facing the image side is concave; the focal length of the varifocal lens 2 is negative;

[0057] One 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;

[0058] One side of the rear fixed lens 4 facing the object side is concave, and the side facing the image side is convex; the focal length of the rear fixed lens 4 is negative.

[0059] One side of the first lens 6 facing the object side is convex, and the side facing the image side is concave; the focal length of the first lens 6 is positive;

[0060] One side of the second lens 7 facing the object side is concave, and the side facing the image side is convex; the focal length of the second lens 7 is negative;

[0061] One side of the third lens 8 facing the object side is convex, and the side facing the image side is concave; the focal length of the third lens 8 is positive;

[0062] One side of the fourth lens 9 facing the object side is convex, and the side facing the image side is concave; the focal length of the fourth lens 9 is positive.

[0063] An aperture stop of the continuous zoom telescopic system is provided on the rear fixed lens 4, and an aperture stop of the relay projection system is provided on the first lens 6.

[0064] Using the DMD-based super-resolution variable-focus optical imaging system provided in this embodiment, super-resolution imaging of targets at different focal lengths can be achieved. First, the image information of each focal length scene is projected onto the DMD 5 through a continuous zoom telescopic system, and then the deflection angle of the micromirror array in the DMD 5 device is controlled by a computer device to achieve sampling encoding and modulation of the scene. Finally, the scene encoded by the DMD 5 is projected onto the image sensor CMOS in the infrared detection unit 10 through a relay projection system for imaging. By adjusting the exposure times of the CMOS detector, compressed data with different sampling rates can be obtained, thereby achieving effective compression and collection of data. Through the above optical system M measurement processes, measurement values can be obtained. . According to the principle of compressive sensing , it is known that by selecting an appropriate sparse basis , combined with the measurement matrix generated by the DMD 5 and the corresponding measurement values , applying a specific reconstruction algorithm to solve for the sparse basis of the signal , using the obtained sparse basis , substituting it into the formula to calculate the reconstructed signal, thereby achieving precise inversion and reconstruction of the original image.

[0065] Embodiment 2

[0066] This embodiment provides a design method for a DMD-based super-resolution variable-focus optical imaging system. The design method is carried out in ZEMAX software, and the method includes the following steps:

[0067] S1. Design a continuous zoom telescopic system. The continuous zoom telescopic system uses four lenses, namely the front fixed lens 1, the zoom lens 2, the compensating lens 3, and the rear fixed lens 4. Determine the focal lengths of the continuous zoom telescopic system at the short focal length, medium focal length, and long focal length positions according to the target detection range and complete the selection of the structure of the continuous zoom telescopic system; the front fixed lens 1, the zoom lens 2, and the compensating lens 3 use even aspherical lenses, and the rear fixed lens 4 uses a spherical lens;

[0068] S2. Design the short - focus structure of the continuous zoom telescopic system; after determining the zoom form, determine the zoom parameters and set the structural parameters; select positive - group compensation in mechanical compensation for design. According to the zoom equation, distribute the optical power of each part of the continuous zoom telescopic system, limit the total system length and reserve 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 system focal length through the linear movement of the variator lens 2, and compensate for the image - plane displacement caused by the linear movement of the variator lens 2 and temperature change through the curved - track movement of the compensator lens 3; the front fixed lens 1 uses a positive IRG106 lens, the variator lens 2 uses a negative germanium lens, the compensator lens 3 uses a positive silicon lens, and the rear fixed lens 4 uses a negative germanium lens; as Figure 2 shown is the schematic diagram of the short - focus position during system zoom;

[0069] S3. Design the medium - focus structure of the continuous zoom telescopic system; after determining the short - focus structure, change the air gaps between the front fixed lens 1 and the variator lens 2, between the variator lens 2 and the compensator lens 3, and between the compensator lens 3 and the rear fixed lens 4 to achieve the change of the focal length. At the same time, limit the medium - focus focal length and the total system length of the continuous zoom telescopic system. Adjust the change amount of the air gaps between each lens of the continuous zoom telescopic system within 10 mm. Perform image - quality optimization each time an adjustment is made, and the optimization variable is the surface - shape parameters of each lens. Realize the change of the focal length from short - focus to medium - focus by changing the air gaps between the front fixed lens 1 and the variator lens 2, between the variator lens 2 and the compensator lens 3, between the compensator lens 3 and the rear fixed lens 4, and the surface - shape parameters of each lens multiple times; as Figure 3 shown is the schematic diagram of the medium - focus position during system zoom;

[0070] S4. Design the long - focus structure of the continuous zoom telescopic system; after determining the medium - focus structure, change the air gaps between the front fixed lens 1 and the variator lens 2, between the variator lens 2 and the compensator lens 3, and between the compensator lens 3 and the rear fixed lens 4 to achieve the change of the focal length. At the same time, limit the medium - focus focal length and the total system length of the continuous zoom telescopic system. Adjust the change amount of the air gaps between each lens of the continuous zoom telescopic system within 10 mm. Perform image - quality optimization each time an adjustment is made, and the optimization variable is the surface - shape parameters of each lens. Realize the change of the focal length from medium - focus to long - focus by changing the air gaps between the front fixed lens 1 and the variator lens 2, between the variator lens 2 and the compensator lens 3, between the compensator lens 3 and the rear fixed lens 4, and the surface - shape parameters of each lens multiple times; as Figure 4 shown is the schematic diagram of the long - focus position during system zoom;

[0071] 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;

[0072] 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;

[0073] 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.

[0074] 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.

[0075] In addition, when designing the system separately, for the continuous zoom telescopic system, its aperture stop is set on the rear fixed lens 1. For the relay projection system, its aperture stop is set on the first lens 6 that is symmetrically opposite to the rear fixed lens of the continuous zoom telescopic system. When splicing the continuous zoom telescopic system, DMD 5, and the relay projection system together and optimizing them as a whole, the aperture stop on the first lens 6 is removed, and only the aperture stop on the rear fixed lens 1 is retained.

[0076] Embodiment 3

[0077] This embodiment further limits Embodiment 2, gives a specific solution designed by the method described in the embodiment, and further introduces the beneficial effects of the present invention.

[0078] Design the DMD-based super-resolution zoom optical imaging system by using the method described in Embodiment 2:

[0079] In this embodiment, the DMD 5 selected uses 1280×1024 pixels, and the pixel size is 7.6μm. The imaging device in the infrared detection unit 10 selects a mid-wave infrared detector array with 640×512 pixels and a pixel size of 15μm. Based on this, the design parameters of the imaging optical system are calculated.

[0080] S1. Design the continuous zoom telescopic system. The continuous zoom telescopic system uses four lenses, namely the front fixed lens 1, the zoom lens 2, the compensating lens 3, and the rear fixed lens 4. Determine the focal lengths of the short-focus, medium-focus, and long-focus positions of the continuous zoom telescopic system according to the target detection range and complete the selection of the structure of the continuous zoom telescopic system. Specifically: the F / # of the continuous zoom telescopic system is 3.8, the length and width of DMD 5 are 9.73mm and 7.79mm respectively, the length and width of the overall system image plane are 9.6mm and 7.7mm respectively, the focal lengths of the continuous zoom telescopic system are 50mm, 150mm, and 250mm respectively, and the system field of view is designed according to the target surface size of the mid-wave infrared detector array. It is planned that the horizontal field of view at the short-focus position is ±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°.

[0081] The front fixed lens 1, the zoom lens 2, and the compensating lens 3 use even aspherical lenses, and the rear fixed lens 4 uses a spherical lens;

[0082] The lens group of the zoom telescopic system is designed and optimized by using even aspheres. By introducing even aspheres, the number of lenses in the zoom telescopic objective lens group is reduced by increasing the optimization variables. At the same time, high transmittance materials are preferentially used in the material selection and material matching is carried out, and a silicon-germanium combination material is adopted. Furthermore, each component of the zoom telescopic objective lens group uses a single lens to ensure that the system has a high transmittance and improves the utilization rate of light energy. The definition of the even aspherical surface shape description parameter z is as follows:

[0083]

[0084] In the formula, r is the clear aperture radius of the surface; c refers to the radius of curvature closest to the spherical surface; k is the conic constant; - are the polynomial coefficients of the even aspherical surface.

[0085] Thus, the structure selection of the continuous zoom telescopic system for the super-resolution imaging system is completed.

[0086] The aspherical surface parameter values of the continuous zoom telescopic system mirror are shown in Table 1. The determination methods of the first surface, the third surface and the sixth surface are as follows: taking the first surface as the first surface of the initial light beam incidence, and sequentially counting along the light path injection direction.

[0087] Table 1

[0088]

[0089] S2. Design the short-focus structure of the continuous zoom telescopic system; after determining the zoom form, determine the zoom parameters and set the structural parameters; select positive group compensation in mechanical compensation for design, distribute the optical power of each part of the continuous zoom telescopic system according to the zoom equation, limit the total length of the system and reserve a certain length of back intercept, realize the change of the system focal length through the linear movement of the variable magnification lens 2, and compensate for the image plane displacement caused by the linear movement of the variable magnification lens 2 and temperature change through the curved track movement of the compensation lens 3; the front fixed lens 1 uses a positive IRG106 lens, the variable magnification lens 2 uses a negative germanium lens, the compensation lens 3 uses a positive silicon lens, and the rear fixed lens 4 uses a negative germanium lens;

[0090] S3. Conduct the design of the middle focal length structure for the continuous zoom telescopic system; after determining the short focal length structure, change the air gaps between the front fixed lens 1 and the varifocal lens 2, between the varifocal lens 2 and the compensating lens 3, and between the compensating lens 3 and the rear fixed lens 4 to achieve focal length changes. At the same time, limit the middle focal length of the continuous zoom telescopic system and the total system length. Adjust the change amount of the air gaps between the lenses of the continuous zoom telescopic system within 10 mm. Conduct image quality optimization each time an adjustment is made. The optimization variable is the surface shape parameters of each lens. Achieve the change of focal length from short focal length to middle focal length by changing the air gaps between the front fixed lens 1 and the varifocal lens 2, between the varifocal lens 2 and the compensating lens 3, between the compensating lens 3 and the rear fixed lens 4, and the surface shape parameters of each lens multiple times;

[0091] S4. Conduct the design of the long focal length structure for the continuous zoom telescopic system; after determining the middle focal length structure, change the air gaps between the front fixed lens 1 and the varifocal lens 2, between the varifocal lens 2 and the compensating lens 3, and between the compensating lens 3 and the rear fixed lens 4 to achieve focal length changes. At the same time, limit the middle focal length of the continuous zoom telescopic system and the total system length. Adjust the change amount of the air gaps between the lenses of the continuous zoom telescopic system within 10 mm. Conduct image quality optimization each time an adjustment is made. The optimization variable is the surface shape parameters of each lens. Achieve the change of focal length from middle focal length to long focal length by changing the air gaps between the front fixed lens 1 and the varifocal lens 2, between the varifocal lens 2 and the compensating lens 3, between the compensating lens 3 and the rear fixed lens 4, and the surface shape parameters of each lens multiple times;

[0092] The optical system design results of the continuous zoom telescopic system are shown in Table 2:

[0093] Table 2

[0094]

[0095] S5. Use the MEMS surface shape to represent the discontinuous surface of the DMD5, and simulate the target surface size of the DMD as 9.73 mm × 7.79 mm, the number of pixels as 1280 × 1024, and the light ray deflection angle parameters as +12°, 0°, -12°. On this basis, optimize the imaging quality at each focal length position of the continuous zoom telescopic system to eliminate the aberrations caused by the lens combination and the discontinuous surface of the DMD5; correct the image surface after reflection by the DMD5, set the tilt parameters in the +x and +y directions of this image surface, increase the tilt amount by 1 mm each time, and at the same time optimize and adjust the surface shapes of the lenses of the continuous zoom telescopic system until the central light ray of the reflected light on the pupil diagram coincides with the center of the image surface after reflection by the DMD5;

[0096] 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 telescopic system are designed with a relatively symmetric structure. Set the field of view of the relay projection system according to the image plane size of the DMD5, and repeatedly optimize the surface shapes of the lenses in the relay projection system until the image quality meets the specific application requirements. During the optimization, control the magnification to be ; where is the pixel size of the DMD5, is the pixel size of the infrared detection unit, is the super-resolution reconstruction multiple. During the optimization, by controlling the air gap between the first lens 6 and the DMD5, the size of the first lens 6, and the size of the second lens 7, 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 telescopic system. The first lens 6, the second lens 7, the third lens 8, and the fourth lens 9 use spherical lenses. Thus, the design of the relay projection system is completed.

[0097] The specific form of the relatively symmetric structure is as follows: The lenses with relatively symmetric structures in the relay projection system and the continuous zoom telescopic system use the same material. Specifically, the front fixed lens 1 and the fourth lens 9 use lenses of the same material, the variable magnification 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.

[0098] The design results of the optical system of the relay projection system are shown in Table 3:

[0099] Table 3:

[0100]

[0101] S7. Assemble the continuous zoom telescopic system, the DMD5, and the relay projection system together and conduct overall optimization to obtain the designed DMD-based super-resolution zoom optical imaging system.

[0102] Since the continuous zoom telescopic system and the relay projection system are designed separately, the overall image quality of the system is poor after direct assembly. Therefore, consider using the two-step optimization method. First, continue to optimize the parameters as the surface shape parameters of each mirror surface of the relay projection system. Second, it is necessary to repeatedly and slightly adjust the image plane tilt amount to ensure that the image plane is perpendicular to the optical axis, so as to obtain better image quality. Thus, the design of the DMD-based super-resolution imaging zoom optical system is completed. As Figure 5 、 6Figs. 7 respectively show the MTF curves of the continuous zoom telescopic system at the short focus, medium focus, and long focus positions. The results show that the MTF of the optical system at each zoom position is greater than 0.4 at the system cut-off frequency of 40 lp / mm; Figure 8 and 9 Figs. 10 respectively show that the RMS root mean square radius of the optical system spot of the continuous zoom telescopic system at each zoom position of the short focus, medium focus, and long focus is less than the pixel size of the infrared detector, which is 15 μm. Figure 11 and 12 Figs. 13 respectively show the energy concentration curves of the continuous zoom telescopic system at each zoom position of the short focus, medium focus, and long focus. It can be seen that the system energy distribution 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 the target object passes through a front fixed lens (1), a zoom lens (2), a compensation lens (3) and a rear fixed lens (4) of the 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); 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.

2. The DMD-based super-resolution zoom optical imaging system according to claim 1, 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.

3. The DMD-based super-resolution zoom optical imaging system according to claim 2, 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 positive; 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.

4. The DMD-based super-resolution zoom optical imaging system according to claim 3, 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.

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

6. A method for designing a super-resolution zoom optical imaging system based on DMD as claimed in claim 5, wherein the 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.

7. The design method of the DMD-based super-resolution zoom optical imaging system according to claim 6, 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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