CN108333720B - Medium wave infrared imaging system - Google Patents
Medium wave infrared imaging system Download PDFInfo
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- CN108333720B CN108333720B CN201810235770.2A CN201810235770A CN108333720B CN 108333720 B CN108333720 B CN 108333720B CN 201810235770 A CN201810235770 A CN 201810235770A CN 108333720 B CN108333720 B CN 108333720B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0055—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element
- G02B13/0065—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element having a beam-folding prism or mirror
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
- G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/50—Constructional details
- H04N23/55—Optical parts specially adapted for electronic image sensors; Mounting thereof
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- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
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- Mechanical Light Control Or Optical Switches (AREA)
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Abstract
The invention relates to an optical imaging system, in particular to a medium wave infrared imaging system. The system comprises a first optical lens group, a DMD digital micromirror, a second optical lens group and a detector which are sequentially arranged from an object side to an image side; the light incident end of the first optical lens group comprises an incident area and an emergent area, and incident light enters the first optical lens group from the incident area, enters the first optical lens group again after being reflected by the DMD digital micro-mirror, and enters the second optical lens group from the emergent area. The first optical lens group adopts a deflection pupil design, incident light rays are incident from an optical axis, and finally image at the position of the detector after being reflected by the DMD digital micro-mirror, so that the use of a TIR prism is avoided, and the light path structure is simplified.
Description
Technical Field
The invention relates to an optical imaging system, in particular to a medium wave infrared imaging system.
Background
In infrared detection imaging and other applications, in order to obtain better detection, identification and tracking effects, the requirements on infrared imaging quality are higher and higher, and the technology for directly improving the resolution of the detector is difficult and expensive due to the influence of factors such as manufacturing process, working conditions and the like.
A chinese patent application (application number 201510187916.7) entitled "a compressed sensing theory-based infrared image super-resolution reconstruction method" discloses a method for converting an original low-resolution image into a high-resolution image by using a compressed sensing theory. Since the compressed sensing needs to perform compression coding on each pixel of the original image, a DMD digital micromirror is needed in practical application, and a chinese patent application (application number 201410141203.2) entitled "an optical system for a DMD camera" discloses a DMD imaging system, which is sequentially provided with an imaging optical system, a TIR prism, a DMD, a relay optical system and a detector along the optical path advancing direction, wherein the TIR prism is formed by gluing two rectangular prisms, and since the light beam is totally reflected from the optically dense medium to the optically sparse medium, but not from the optically sparse medium to the optically dense medium, a certain width air gap is reserved between the two rectangular prisms, so that the DMD can control the light beam to enter and exit, and meanwhile, in order to ensure the imaging quality, the width of the air gap must be kept in the order of μm. Since the DMD is used for imaging and controlling the direction of the light beam, the light beam must be directed to the DMD surface at a vertical or near vertical angle, but the TIR prism arrangement is too demanding, so that the whole light path structure is too complex and the cost is high to ensure the imaging quality.
Disclosure of Invention
The invention aims to provide a medium wave infrared imaging system to solve the problem that the structure of the traditional DMD imaging system is complex.
The invention provides a scheme I for solving the technical problems: the invention relates to a medium wave infrared imaging system which comprises a first optical lens group, a DMD digital micro-lens, a second optical lens group and a detector, wherein the first optical lens group, the DMD digital micro-lens, the second optical lens group and the detector are sequentially arranged from an object space to an image space; the light incident end of the first optical lens group comprises an incident area and an emergent area, and incident light enters the first optical lens group from the incident area, enters the first optical lens group again after being reflected by the DMD digital micro-mirror, and enters the second optical lens group from the emergent area.
According to the technical scheme, the incident area and the emergent area are arranged at the light incident end of the first optical lens group, so that incident light enters the first optical lens group from the incident area, enters the first optical lens group again after being reflected by the DMD digital micro-mirror and leaves from the emergent area, and finally reaches the detector through the second optical lens group, and the DMD can control light beams through deflection micro-mirror angles under the condition that imaging requirements are met by coaxial or nearly coaxial arrangement of the DMD and the first optical lens group, meanwhile, the TIR prism is avoided, the light path structure is simplified, and the hardware cost is saved.
Scheme II: on the basis of the first scheme, the incident area is located in the central area of the light incident end of the first optical lens group, and the emergent area is located around the incident area.
The first scheme is characterized in that the positions of the incident area and the emergent area are further limited, so that incident light enters the first optical lens group in an off-axis manner, reflected light passes through the first optical lens group along the axis under the regulation and control of the DMD, and the reflected light can be better imaged at the detector.
Scheme III: on the basis of the second scheme, a reflecting mirror for reflecting the light beam emitted from the emitting area to the second optical lens group is arranged between the first optical lens group and the second optical lens group.
The reflecting mirror is arranged between the two optical lens groups and used for reflecting the light beams emitted from the first optical lens group to the second optical lens group, so that the whole light path is compact, and the inconvenience of actual use caused by overlong whole structure is avoided.
Scheme IV: on the basis of the first, second or third scheme, the first optical lens group comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens, wherein the first lens is a positive meniscus lens, the second lens is a negative meniscus lens with negative focal power, the third lens is a plano-convex lens, the fourth lens is a negative meniscus lens with negative focal power, and the fifth lens is a positive meniscus lens.
Scheme five: on the basis of the fourth aspect, the second optical lens group includes a sixth lens, a seventh lens, an eighth lens and a ninth lens, wherein the sixth lens is a positive meniscus lens, the seventh lens is a negative meniscus lens with negative focal power, the eighth lens is a negative meniscus lens with negative focal power, and the ninth lens is a convex flat lens.
Scheme six: on the basis of the fourth scheme, the thickness of the first lens is 12mm, the thickness of the second lens is 15mm, the thickness of the third lens is 15mm, the thickness of the fourth lens is 11.3mm, and the thickness of the fifth lens is 14.8mm; the first lens and the second lens are spaced 17.9mm apart, the second lens and the third lens are spaced 53.9mm apart, the third lens and the fourth lens are spaced 18.4mm apart, and the fourth lens and the fifth lens are spaced 6.52mm apart.
Scheme seven: on the basis of the fifth aspect, the thickness of the sixth lens is 13.68mm, the thickness of the seventh lens is 3.2mm, the thickness of the eighth lens is 15mm, and the thickness of the ninth lens is 3mm; the sixth lens is spaced 3.17mm from the seventh lens, the seventh lens is spaced 2.5mm from the eighth lens, and the eighth lens is spaced 13.67mm from the ninth lens.
Scheme eight: on the basis of the seventh aspect, the first lens is a SILICON lens, the second lens is a german lens, the third lens is a SILICON lens, the fourth lens is a german lens, the fifth lens is a SILICON lens, the sixth lens is a SILICON lens, the seventh lens is a german lens, the eighth lens is a SILICON lens, and the ninth lens is a SILICON lens.
Drawings
FIG. 1 is a schematic diagram of a medium wave infrared imaging system according to an embodiment of the present invention;
wherein 1 is a first optical lens group, 2 is a DMD digital micro-mirror, 3 is a reflecting mirror, 4 is a second optical lens group, and 5 is a detector;
FIG. 2 is a flowchart of the operation of the mid-wave infrared imaging system of the present invention;
FIG. 3- (a) is a coded matrix diagram of a mid-wave infrared imaging system of the present invention;
FIG. 3- (b) is a schematic diagram of a pixel cell of the detector of the present invention;
fig. 3- (c) is a sub-matrix diagram of a coded matrix diagram of a mid-wave infrared imaging system of the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and examples of the specification.
Fig. 1 is a schematic diagram of an embodiment of a medium wave infrared imaging system according to the present invention, in which a first optical lens group, a DMD digital micromirror, a reflecting mirror, a second optical lens group and a detector are sequentially disposed from an object side to an image side; the light incident end (i.e. the outer surface of the first lens) of the first optical lens group is divided into an incident area and an emergent area, the emergent area is positioned around the incident area, and incident light is imaged at the DMD digital micromirror for the first time after entering from the polarized axis of the incident area and passing through the first optical lens group. The DMD digital micro-mirror array consists of millions of micro-mirrors with the size of mu m, each micro-mirror can be controlled to overturn by a control system controller, and the DMD is overturned to be respectively +12° (other angles +theta) and-12 ° (other angles-theta) in two states. The first optical lens group adopts a deflection pupil design, incident light rays are incident from an optical axis, and the included angle between the principal light rays incident to the DMD digital micro-mirror and the overturning normal line of the DMD digital micro-mirror is ensured to be 24 degrees (when the DMD is overturned to be in +theta and-theta states respectively, the included angle is 2 theta). When the DMD is turned over by +12°, light rays are reflected by the micromirrors and then enter the first optical lens group again at the angle of the horizontal optical axis, and are emitted out of the first optical lens group and then are reflected by the reflecting mirror to enter the second optical lens group. When the DMD is inverted to-12 degrees, light rays are not reflected again into the first optical lens group, and therefore an image of the DMD position is encoded through a DMD micro-mirror inversion method. And finally, acquiring an image through a medium wave infrared detector. The control system ensures that the DMD digital micromirror is synchronous with the acquisition of the detector, controls the acquisition and exposure of the detector, is synchronous with the overturning of the infrared light modulator, and the image processing system processes the acquired image to output and display.
The first optical lens group 1 is characterized in that the front objective lens is operative to image the infrared scene at the DMD micromirror position. The field of view is 10 degrees, the F number is greater than 2.5, the included angle of the principal ray relative to the turning plane of the DMD is 24 degrees, the optical resolution requirement is less than or equal to the dimension of the DMD pixel, and the image detail cannot be lost when a scene is imaged on the DMD. The imaging objective lens requires MTF to be matched with the micro-mirror spacing size of the DMD digital micro-mirror to be more than 0.3@46mm/lp, the distortion of the imaging objective lens is required to be less than or equal to 1%, and specific design parameters of the first optical lens group are shown in table 1.
TABLE 1
The DMD digital micromirror consists of millions of tiny mirrors with dimensions on the order of μm, each mirror angle independently controlling two stable micromirror states (+12° and-12 °). The number of DMD micromirror arrays is 1280×1024, and the micromirror pitch is > 10 μm. The DMD window requires sapphire material with a transmission band in the range of 3.7 μm-4.8 μm.
The inclined angle of the reflector is required to be 45 degrees with the optical axis, and the surface of the reflector is plated with a medium wave reflecting film.
The second optical lens group requires that the second optical lens group object side NA (numerical aperture) number matches the first optical lens group image side NA number. The second optical lens set is used for being combined with the first optical lens set to project information on the DMD onto the infrared detector. Because the whole area of the group of 4×4 DMD pixels is larger than the area of a single pixel of the detector, the image on the DMD is reduced by corresponding times and then imaged on the detector through the second optical lens group, and the second optical lens group plays a role in matching the size of the image reflected by the DMD with the size of the target surface of the detector. The second optical lens set design parameters are shown in table 2.
TABLE 2
The mid-wave infrared detector requires a spectral range of 3.7 μm to 4.8 μm, a resolution of 320×256, and a pixel size of 30 μm.
The image processing system is used for reconstructing the acquired image and correcting non-uniformity, distortion and blurring.
FIG. 2 is a flow chart of the mid-wave infrared imaging system of the present invention, wherein after the system is powered on, the system is initialized, including sampling matrix, detector non-uniformity correction, etc.; and then the control module controls the parallel sampling module to carry out coding sampling and imaging, and imaging data is output, displayed and stored after being reconstructed by an image reconstruction algorithm.
The first optical lens group system images an infinite far field scene with a 10 ° diagonal field of view to an infrared modulator location. The infrared modulator is a DMD micro-mirror, the micro-mirror can be controlled to overturn to achieve the effect of modulating imaging, when the DMD micro-mirror is overturned by 12 degrees, light rays are re-incident into the first optical mirror group at the level of 0 degrees, and finally the light rays are formed into a medium wave detector of an imaging system through the second optical mirror. When the DMD micromirror is turned by-12 degrees, the subsequent system is not accessed.
The DMD coding matrix is designed according to the compressed sensing principle to control the DMD micro-mirror to rotate, namely, the reflection mirror on the DMD is divided into 4 multiplied by 4 small blocks (320 multiplied by 256 small blocks in total), each block corresponds to one pixel on the CCD, the blocks are mutually independent, and the whole matrix arrangement accords with Bernoulli distribution. When the imaging system works, the same scene is shot M times (namely, M times of sampling are carried out), and the DMD presents different codes when shooting each time. Fig. 3- (a) shows a coding matrix diagram corresponding to the detector pixel units shown in fig. 3- (b), and fig. 3- (c) shows a sub-matrix of the coding matrix, i.e. the 4×4 micro mirror small block, and the samples shown in the figure are coded as 1101000011011010.
And carrying out non-uniformity, distortion and blurring correction before reconstructing an image, and eliminating inherent non-uniformity of an infrared imaging system and distortion and blurring caused by an optical system. The correction process is as follows: the ideal infrared parallel light is first placed in front of the optical system, then only one DMD micromirror is placed "on" at a time (+12°) and the light intensity on the detector is recorded, and so on repeatedly, recording the light reflected by each DMD micromirror in turn. The detector pixels are 320×256= 81920, so the response of the light reflected by each DMD micromirror on the detector can be seen as a vector of length 81920. There are 1280×1024= 1310720 such vectors in total. Each vector acts as a column of the matrix, and a matrix C of 81920 × 1310720, called the correction matrix, can be formed. The rows of the correction matrix represent the light energy contributed by each DMD micromirror for a certain detector pixel, which can be used to correct the values of the sampling matrix. The non-uniformity correction process is as follows: the scene-based adaptive correction algorithm utilizes the relation between the detector response model and the image frames, dynamically updates correction parameters according to scene information by processing a plurality of frames of images, effectively solves parameter drift caused by time accumulation or working environment, and realizes dynamic real-time non-uniformity correction. The non-uniformity correction is by the following formula:
Y＝K·(X-B)+B Offset +B avr
wherein Y is the corrected output; k is a correction coefficient (the K value is a calibrated coefficient when the shutter is in operation mode, and the K value is fixed when the shutter is not in operation mode); x is the original output of the detector; the value B is a constant when a shutter algorithm is adopted, and is a calculated value when a shutter-free algorithm is adopted; b (B) Offset The value is calculated (the average value of the accumulated multi-frame images is calculated, and then the original output of the detector and the average value of the multi-frame images are used for making a difference to obtain B corresponding to the pixel position Offset A value); b (B) avr The value is the average value of the calculated B value of each frame of image.
The compressed perceived image reconstruction algorithm reconstructs a high resolution image (1280 x 1024) using the detected sampled M low resolution images (320 x 256) and M different encoding matrices. In order to shorten the reconstruction time, the high-speed reconstruction module reconstructs all sub-blocks in parallel in a block reconstruction mode, and finally splices the sub-blocks into a 1280 multiplied by 1024 high-resolution image.
In the above embodiment, 320×256 pixel detectors are used, and a 1280×1024 DMD micromirror array is used in combination, however, other pixel detectors may be used, and a corresponding DMD micromirror array may be used.
Specific embodiments are given above, but the invention is not limited to the described embodiments. The basic idea of the invention is that the above-described basic solution is that changes, modifications, substitutions and variations of the embodiments are possible without departing from the principle and spirit of the invention, which still fall within the scope of the invention.
Claims (3)
1. The medium wave infrared imaging system is characterized in that the system comprises two optical lens groups with refractive power, a first optical lens group, a DMD digital micromirror, a second optical lens group and a detector, wherein the first optical lens group, the DMD digital micromirror, the second optical lens group and the detector are sequentially arranged from an object space to an image space; the light incident end of the first optical lens group comprises an incident area and an emergent area, incident light enters the first optical lens group from the incident area, enters the first optical lens group again after being reflected by the DMD digital micro-mirror, and enters the second optical lens group from the emergent area;
the first optical lens group consists of a first lens, a second lens, a third lens, a fourth lens and a fifth lens, wherein the first lens is a positive meniscus lens, the second lens is a negative meniscus lens with negative focal power, the third lens is a plano-convex lens, the fourth lens is a negative meniscus lens with negative focal power, and the fifth lens is a positive meniscus lens;
the second optical lens group comprises a sixth lens, a seventh lens, an eighth lens and a ninth lens, wherein the sixth lens is a positive meniscus lens, the seventh lens is a negative meniscus lens with negative focal power, the eighth lens is a negative meniscus lens with negative focal power, and the ninth lens is a convex flat lens;
the thickness of the first lens is 12mm, the thickness of the second lens is 15mm, the thickness of the third lens is 15mm, the thickness of the fourth lens is 11.3mm, and the thickness of the fifth lens is 14.8mm; the interval between the first lens and the second lens is 17.9mm, the interval between the second lens and the third lens is 53.9mm, the interval between the third lens and the fourth lens is 18.4mm, the interval between the fourth lens and the fifth lens is 6.52mm, the thickness of the sixth lens is 13.68mm, the thickness of the seventh lens is 3.2mm, the thickness of the eighth lens is 15mm, and the thickness of the ninth lens is 3mm; the interval between the sixth lens and the seventh lens is 3.17mm, the interval between the seventh lens and the eighth lens is 2.5mm, and the interval between the eighth lens and the ninth lens is 13.67mm;
the first lens is a SILICON lens, the second lens is a GERMANIUM lens, the third lens is a SILICON lens, the fourth lens is a GERMANIUM lens, the fifth lens is a SILICON lens, the sixth lens is a SILICON lens, the seventh lens is a GERMANIUM lens, the eighth lens is a SILICON lens, and the ninth lens is a SILICON lens.
2. The mid-wave infrared imaging system of claim 1, wherein said entrance region is located in a central region of an entrance end of said first optical lens set and said exit region is located around said entrance region.
3. The medium wave infrared imaging system of claim 2, wherein a mirror for reflecting the light beam exiting from the exit region to the second optical lens group is provided between the first optical lens group and the second optical lens group.
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| CN1300624C (en) * | 2001-10-01 | 2007-02-14 | 松下电器产业株式会社 | Projection type display unit, rear projector and multi-vision system |
| CN102213906B (en) * | 2011-05-06 | 2013-05-29 | 中国科学院上海技术物理研究所 | Optical engine of infrared digital light processing (DLP) telecentric projection system |
| CN208044176U (en) * | 2018-03-21 | 2018-11-02 | 中国航空工业集团公司洛阳电光设备研究所 | Medium-wave infrared imaging system |
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