CN103024299B - Gazing type numeral TDI short-wave infrared low-light level imaging instrument and formation method - Google Patents
Gazing type numeral TDI short-wave infrared low-light level imaging instrument and formation method Download PDFInfo
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- CN103024299B CN103024299B CN201210506236.3A CN201210506236A CN103024299B CN 103024299 B CN103024299 B CN 103024299B CN 201210506236 A CN201210506236 A CN 201210506236A CN 103024299 B CN103024299 B CN 103024299B
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Abstract
The invention discloses a kind of gazing type numeral TDI short-wave infrared low-light level imaging instrument and formation method.This instrument comprises short-wave infrared camera lens, short-wave infrared LED, and detector assembly and driving Acquisition Circuit, image data buffer, with master control system and the Storage & Display device of digital whole-frame TDI module.The view data that detector exports by digital whole-frame TDI module carries out whole frame timing delay integral and calculating at numeric field in real time.The night monitoring of foundation platform is mostly simple and reliable staring imaging, and alignment in the past therefore can not be adopted to scan TDI technology to improve signal to noise ratio.The digital whole-frame TDI technology that the present invention proposes is suitable for staring imaging, and it can realize very high TDI progression, significantly improves low-light level imaging quality, and can adjust dynamic range of images flexibly.The present invention is applicable to need safety monitoring at certain concealed night, and the vehicle-mounted or hand-hold type night patrol application of deathtrap.
Description
Technical field:
The present invention relates to a kind of infrared thermoviewer, be specifically related to a kind of gazing type numeral TDI short-wave infrared low-light level imaging instrument and formation method, it is applied to short-wave infrared imaging in photoelectronic imaging field and low-light level imaging field.
Background technology:
Low-light level imaging technology has a wide range of applications in fields such as safety, industry, scientific researches demand.Low-light level imaging instrument utilizes the night-glow of the sky such as moonlight, starlight, and instrument self light filling, gathers, imaging to the reflected light signal of target.
The service band of short-wave infrared imager is generally at 0.9 μm ~ 2.5 μm, its image-forming principle is identical with human eye visual light imaging, be all captured target reverberation, the thermal infrared imager therefore comparing captured target thermal radiation imaging, closer to visual imaging effect, is easy to target identification when monitoring in real time.In night-glow of the sky, the energy of this wave band is obviously better than its all band; And short-wave infrared light is not by human eye finding, instrument carries light aid to carry out throwing light on and still can keep hidden, and therefore this wave band is applicable to carrying out low-light safety monitoring very much night.
Under poor light condition, incident optical signal is very weak, and the signal to noise ratio therefore improving instrument is the technological difficulties of low-light level imaging instrument.Except the energy being mapped to detector surface except taking the method such as light filling, preposition booster to be added to, be that the photo-translating system of core also needs special high sensitivity design with detector.The means in the past improving short-wave infrared imaging system signal to noise ratio have be Optimization Design of Electronic Circuits at three: one, reduce the noise of detector reading circuit and electronics; Two is select large charge gain detection device; Three is extend the time of integration.At present, the noise of reading circuit and electronics has obtained good suppression in the middle of all multi-products, and the circuit noise of a lot of camera reaches photonoise limit, close to design limit.Signal to noise ratio under utilizing the detector of large charge gain also effectively can promote poor light condition, but this measure can sacrifice certain dynamic range, and therefore the amplification of charge gain restricts by it, can not infinitely expand.Extend while the time of integration obtains useful signal, the background emission of system configuration is also captured more by short-wave infrared detector, occupies certain dynamic range, also brings background emission noise, especially, in infant laser signal detection, background emission even can flood useful signal.Therefore, by increasing the signal to noise ratio increasing short-wave infrared imaging system the time of integration, its effect is also very limited under poor light condition.
Time delay integration (TimeDelayIntegration) technology is the effective ways of signal to noise ratio under the little integral condition of enhancing, and it is applied to Visible-light CCD device the earliest, by the multiexposure, multiple exposure to same target, superposition, realizes signal and strengthens, improve signal to noise ratio.The structure of CCD device itself is easy to realize alignment scanning TDI function, and the principle of short-wave infrared detector difference to some extent with it, realize TDI function can only superpose at numeric field.
No matter various TDI modes are in the past that detector itself completes TDI or numeric field TDI, all belong to alignment scanning TDI, therefore can only be used for high speed ray machine scanning imagery, such as airborne, satellite borne sensor.And the present invention is applied to the area monitoring equipment of ground based observa tion platform, this kind equipment generally adopts the staring imaging that structure is simple, reliability is high, and therefore alignment scans TDI and is not suitable for this kind of instrument.
Summary of the invention:
The present invention aims to provide a kind of gazing type short-wave infrared low-light level imaging instrument utilizing digital whole-frame TDI technical limit spacing high signal-to-noise ratio image.
As shown in Figure 1, system comprises short-wave infrared camera lens, short-wave infrared LED, detector assembly and electronics, image data buffer, with master control system and the display unit of digital whole-frame TDI module.
Described detector assembly adopts large charge gain short-wave infrared detector.
Described electronics comprises detector drive circuit and Acquisition Circuit.
Described image data buffer can realize with high-speed high capacity RAM.It is divided into raw image data Pingpang Memory district, superimposed image data memory block and 3, final image data storage area partition holding.Its data bit width needs to calculate according to the highest TDI level time and A/D converter figure place, and guaranteed capacity can meet superimposed image data memory requirement.Suppose that A/D converter figure place is x, the highest TDI progression is n, then memory data width y demand fulfillment: y>=x+log
2n.The space that storing a frame image data needs is the product of memory bit wide and a frame pixel number.The size in raw image data Pingpang Memory district is equal to the size of two frame image datas, and the size of final image data storage area and superimposed image data memory block is equal to the size of a frame image data.
Described master control system is the main logic control section of this instrument, can be the logic control such as single-chip microcomputer, DSP, FPGA chip.Its Major Function comprises the switch controlling short-wave infrared LED, controls detector and electronics work, realizes image and stores the logic control with digital whole-frame TDI, complete image and export.
It is as follows that master control system controls each several part job order:
1, the LED light supplement lamp that master control system controls to open some carries out light filling illumination.
2, master control system configuration parameter, comprises detector running parameter and TDI progression n and dynamic range compression Coefficient m.If detector needs refrigeration, complete refrigeration in advance.
3, detector is started working, and the picture signal of acquisition sends into the raw image data Pingpang Memory district of image data buffer after A/D conversion.
4, according to digital whole-frame TDI algorithm hereinafter described, n level TDI superposition is completed.
5, according to the dynamic range compression Coefficient m arranged, complete dynamic range compression, obtain final image data in the final image data storage area of image data buffer.
6, master control system reads final image data, is forwarded to Storage & Display equipment, completes Polaroid.
The performing step of described whole frame of digital TDI function is as shown in Figure 2:
Step 1: it is n that master control system arranges TDI progression according to demand, penalty coefficient is m.
Step 2: be " 0 " by all data assignment in image data buffer.
Step 3: detector assembly and electronics obtain 1 two field picture, by the raw image data Pingpang Memory district of full frame image stored in image data buffer.
The data of corresponding pixel are added, the relevant position of superimposed image data memory block of restoring by step 4: the data in master control system reads image data buffer in raw image data Pingpang Memory district and superimposed image data memory block.Suppose that the gray value of each pixel in raw image storage district is A (i, j), the gray value of each pixel in superimposed image memory block before carrying out this step is B (i, j), completing the gray value after this step is C (i, j), wherein i and j represents the ranks number of planar array detector respectively.Then this step meets:
C(i,j)=A(i,j)+B(i,j)
Step 5: repeat the 3rd step and the 4th step, n time altogether, then now full frame image has carried out n superposition altogether, is stored in the superimposed image data memory block in image data buffer.
Step 6: the superimposed image that master control system obtains from the superimposed image data memory block read step 5 of image data buffer, by the gray value C (i of each pixel, j) all divided by penalty coefficient m, obtain final image data, stored in the final image data storage area in image data buffer.
Suppose that each pixel gray value of final image data is D (i, j), then this step meets:
D(i,j)=C(i,j)/m
Arranging of penalty coefficient can adjust flexibly according to the power of TDI progression and picture signal.Suppose that original image most strength gray value is saturation value
then desirable m value should meet:
the number of significant digit of such output image is consistent with A/D converter bit wide, and dynamic range is through linear stretch.
Because view data during imaging constantly enters image data buffer from A/D converter in a steady stream, therefore Pingpang Memory is set, as shown in Figure 3.When odd-numbered frame view data arrives, original image is stored in Pingpang Memory B district, and master control system reading A district image carries out TDI algorithm; When even frame view data arrives, original image is stored in Pingpang Memory A district, and master control system reading B district image carries out TDI algorithm.
After above-mentioned whole frame of digital TDI step, the effect the same with traditional wire column scan numeral TDI can be realized.It is the same with traditional TDI, is all to carry out n exposure, superposition to target, finally realizes the effect that signal to noise ratio promotes.
During without TDI, the computational methods of signal to noise ratio are:
its Middle molecule N
efor the signal electron number obtained after detector opto-electronic conversion, denominator
for photon noise
with reading noise N
readthe total equivalent noise electron number be formed by stacking (comprising Electronics noice).
During low-light level imaging, although projectile energy is weak, the short-wave infrared detector charge gain selected is general very large, according to the design level of present electronics and detector reading circuit, still can meet photon noise
much larger than reading noise N
readcondition, thus signal to noise ratio is close
after n level TDI, signal increases n doubly, and noise is approximate to be increased
doubly, so the approximate lifting of signal to noise ratio
doubly.
Alignment scanning TDI in the past superposes unit with behavior, and superposition realizes TDI line by line, is therefore applicable to scanning imagery, such as airborne, satellite borne sensor, obtains two dimensional image by high accuracy optical mechaical scanning system.And digital whole-frame TDI is in units of frame, superposition realizes TDI frame by frame, is applicable to staring imaging, the security monitoring of such as ground or vehicle platform.Particularly lll night vision needs the occasion utilizing TDI technology to improve signal to noise ratio like this badly, and just can complete by complicated heavy optical mechaical scanning and stare TDI imaging, lightly nimble, reliability is high.
Digital whole-frame TDI carries out multiple stacking full frame image in electronic system, and superposition level time does not limit by detector line number, as long as shooting time and memory capacity allow, can realize the TDI that infinite stages is secondary in theory, very great Cheng ground degree improves signal noise ratio (snr) of image.
In addition, digital whole-frame TDI is when superposing, in image data buffer, the data bank bit of superimposed image data memory block is wider than the bit wide (concrete bit wide value is calculated by the highest TDI progression) of A/D converter output image data, ensure that the value after superposition can not be overflowed, this also just improves dynamic range equivalently; Meanwhile, the method is with dynamic range compression function, and the storing value after superposition, divided by penalty coefficient m, ensures that output image data can not be saturated.Therefore, the whole frame of digital TDI in the present invention can meet multilevel superposition and final image can not be saturated.
The present invention is applicable to area monitoring at night.The energy of short-wave infrared light in night-glow of the sky, apparently higher than its all band, is the desirable wave band of nighttime imaging.This wave band image-forming principle is identical with human eye visual light imaging, is easy to target identification when monitoring in real time.The short-wave infrared light compensating lamp used carries out light filling, and light source is not human eye finding, watch-dog is not easily found, good concealment.
Imager selects the sensitive detection parts of high-gain, and the electronics of optimal design reduces equivalent noise, and imaging mode adopts simple and reliable staring imaging.But because short-wave infrared imager is subject to the impact of system configuration background emission, staring the time of integration can not be long, whole frame of digital TDI technology is therefore adopted to improve instrument signal to noise ratio.Particularly general LED light supplement lamp power is little, and energy is not concentrated, and illuminating effect increases decay rapidly with distance, utilizes this technology can extend effective observed range, improves the image quality of the not enough region of illumination and dark area.
The present invention also can be used as vehicle-mounted or hand-hold type night inspection instrument.
Accompanying drawing illustrates:
Accompanying drawing 1 is general diagram of the present invention.
Accompanying drawing 2 is digital whole-frame TDI workflow diagram of the present invention.
Accompanying drawing 3 is ping-pong buffer schematic diagram of the present invention.
Embodiment:
According to the system block diagram that accompanying drawing 1 of the present invention is shown, the present invention includes:
Short-wave infrared camera lens: select little F number camera lens to strengthen optically focused, other parameters are chosen according to required resolution and observed range.The present embodiment adopts the OB-SWIR200/2.4 of Italian OPTEC company, focal length 200mm, F number 2.4.
Short-wave infrared LED and drive circuit (2): some light filling illuminating LED lamps are placed in camera lens surrounding, luminous towards consistent with camera lens observed direction, LED number can increase and decrease flexibly according to observing environment.The wavelength of LED used can cover each wave band of short-wave infrared, and during observed object, information is relatively complete.Drive circuit selects constant voltage or constant-current source to drive as required.The present embodiment uses the short-wave infrared LED of each wavelength selecting IBSG company of Russia to produce.
Detector assembly and electronics (3): large charge gain planar array detector selected by short-wave infrared detector, observe performance under improving poor light condition.The present embodiment selects 500 × 256MCT detector of French Sofradir company.Electronics comprises bias voltage supply, detector driving, collection of simulant signal and A/D conversion.The A/D converter of the present embodiment adopts 10bit bit wide, and speed and amount of acquisition channels are determined according to detector.This example adopt 2 tunnels read, every road 8Mpixels/s, frame frequency 90Hz, the time of integration maximum 11ms.
Image data buffer: this memory adopts high-speed high capacity RAM, its data width the highest TDI progression as required and A/D converter figure place are tried to achieve.According to the algorithm in summary of the invention, suppose that A/D converter figure place is x, the highest TDI progression is n, then memory data width y demand fulfillment: y>=x+log
2n, to ensure that image can not be saturated in additive process.In the present embodiment, A/D converter is 10, if the highest TDI progression is 64, then needs to select 16 RAM as image data buffer.RAM capacity needs to be filled with 4 whole two field pictures, wherein the space of 2 frame image datas is as raw image data Pingpang Memory district, the space of 1 frame image data is as superimposed image data memory block, and the space of 1 frame image data is as final image data storage area.Storage speed will mate detector output speed.In this example, RAM capacity need be greater than 500 × 256 × 16bit × 4=8.2Mbit, and storing read-write speed is 8Mpixels/s × 2=16MHz(16bit bit wide).
Master control system: the present embodiment adopts the Spartan6 Series FPGA of Xilinx company.Master control system controls light compensating lamp switch, provides and drives and gather sequential, coordinate image buffer control figure whole frame TDI sequential, and complete to storage and display device transmit image data to detector and electronics.
Storage & Display equipment: PC, the industrial computer of being furnished with high speed interface can be selected; Portable occasion uses high speed flash memory and embedded system fluid,matching crystal display screen to complete.Under data communication rates need meet minimum TDI progression (1 grade of TDI, namely without TDI calculate, through image export, now output speed is the fastest) the requirement of image output speed.Suppose frame frequency 90Hz in this example, then the fastest data rate is: 500 × 256 × 16bit × 90Hz=185Mbit/s.This data rate high-speed PCI board or LVDS interface realize.
The present invention complete imaging time is the detector frame frequency product with TDI progression reciprocal, and suppose that TDI progression is set to 8, frame frequency 90Hz, then the Polaroid time is 0.09s.
The present invention also comprises the links such as power management, COMPUTER PARAMETER configuration software, data transfer of computer and software for display.In the present embodiment, input power is direct current 28V, is divided for various piece, have master control system operational relay by DC-DC, controls the power on/off of various piece.Parameter configuration software realizes on PC, adopts VC6.0 to write, is connected to master control system by RS422 communication interface by PC, is responsible for the switch controlling detector, refrigeration machine, and configures progression and the dynamic range compression coefficient of digital whole-frame TDI.Acquisition software adopts LabView to write, and it is high-speed PCI interface that number passes interface.The power supply of portable occasion can be provided by storage battery, and software is directly write by embedded system.
Claims (1)
1. the formation method of a gazing type numeral TDI short-wave infrared low-light level imaging instrument, described gazing type numeral TDI short-wave infrared low-light level imaging instrument comprises: short-wave infrared camera lens, short-wave infrared LED, detector assembly and electronic installation, image data buffer, with master control system and the Storage & Display device of digital whole-frame TDI module, it is characterized in that the formation method of gazing type numeral TDI short-wave infrared low-light level imaging instrument comprises the following steps:
1): master control system arranges TDI progression n according to demand, penalty coefficient m;
2): be " 0 " by all data assignment in image data buffer;
3): detector assembly and electronic installation obtain 1 two field picture, by the raw image data Pingpang Memory district of full frame image stored in image data buffer;
4): the data in master control system reads image data buffer in raw image data Pingpang Memory district and superimposed image data memory block, the data of corresponding pixel are added, to restore the relevant position of superimposed image data memory block, suppose that the gray value of each pixel in raw image storage district is A (i, j), the gray value of each pixel in superimposed image memory block before carrying out this step is B (i, j), completing the gray value after this step is C (i, j), wherein i and j represents the ranks number of planar array detector respectively, and this step meets:
C(i,j)＝A(i,j)+B(i,j)；
5): repeat step 3) and step 4) n time altogether, then now full frame image has carried out n time altogether and has superposed, and is stored in the superimposed image data memory block in image data buffer;
6) superimposed image obtained: master control system is from the superimposed image data memory block read step 5 of image data buffer), by the gray value of each pixel divided by penalty coefficient m, obtain final image data, stored in the final image data storage area in image data buffer.
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| CN103776534B (en) * | 2014-03-05 | 2016-01-06 | 哈尔滨工业大学（威海） | A kind of area array CCD prism spectrometer and space-time cumulative data disposal route thereof |
| CN104750123B (en) * | 2015-03-31 | 2017-03-15 | 中国科学院上海技术物理研究所 | The airborne face battle array imager of the two-way IMC of big visual field sweeping |
| CN106101583B (en) * | 2016-07-29 | 2019-03-22 | 中国科学院长春光学精密机械与物理研究所 | Infrared imaging method based on numeric field TDI |
| CN107888849B (en) * | 2017-10-27 | 2020-07-28 | 天津津航技术物理研究所 | Method for realizing area array imaging mode of linear TDI (time delay integration) type infrared detector |
| CN107957296B (en) * | 2017-12-28 | 2020-05-12 | 中国科学院西安光学精密机械研究所 | Interference pattern sampling method for satellite-borne large-aperture static interference spectrum imager |
| CN108955890B (en) * | 2018-05-07 | 2019-12-10 | 上海海事大学 | Pixel arrangement design method of point target detection type infrared TDI detector |
| CN112261326B (en) * | 2020-09-01 | 2022-12-27 | 北京空间机电研究所 | Infrared remote sensor based on photon information digital accumulation overlong TDI |
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