CN102288297B - Uncooled far infrared thermal imaging system - Google Patents
Uncooled far infrared thermal imaging system Download PDFInfo
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- CN102288297B CN102288297B CN2011102409527A CN201110240952A CN102288297B CN 102288297 B CN102288297 B CN 102288297B CN 2011102409527 A CN2011102409527 A CN 2011102409527A CN 201110240952 A CN201110240952 A CN 201110240952A CN 102288297 B CN102288297 B CN 102288297B
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Abstract
The invention relates to an uncooled far infrared thermal imaging system, belonging to the technical field of infrared thermal imaging. The uncooled far infrared thermal imaging system comprises a chopper, a far infrared light lens, a light splitter, an infrared focal plane array, a near infrared light source, a near infrared light lens, a near infrared light filter, another near infrared light lens and a digital camera; and the core component is the infrared focal plane array, the array structure of the infrared focal plane array is a thin film filter in an F-P cavity structure and the material of the cavity is alpha polycrystalline silicon, and the two sides of the cavity are provided with multiple film layers which are alternately formed by alpha polycrystalline silicon thin films and Si3N4 thin films to form a mirror surface structure. In the invention, on the basis of thermo-optic effect principle of the F-P cavity thin film filter, a measuring method of integrated optics is adopted and converting, demodulating and imaging on the optical wave are carried out, so that an interior reading circuit is eliminated and Johnson noise is avoided; meanwhile, vanadium oxide or pyroelectricity material which is usually not matched with silicon can be avoided from being used, devices are highly integrated without influence on the performance thereof, volume is reduced, producing stepsand vacuum packaging cost are reduced, and cost can be greatly reduced; therefore, the uncooled far infrared thermal imaging system provided by the invention has certain application potential.
Description
Technical field
The invention belongs to the infrared thermal imaging technique field, relate to a kind of non-refrigeration far infrared thermal imaging system.
Background technology
The uncooled ir thermal imaging system in a lot of fields, for example there is increasing application safety, investigation, antagonism, automobile and traffic control aspect.Since the refrigeration mode thermal imaging system exist as material for detector cost an arm and a leg, shortcoming such as yield rate is low, system reliability is poor, volume is heavy, system power dissipation is big; Limited its popularization greatly in low-cost armament systems and industry and commerce field; Therefore development and producing has that price is low, volume is little, the uncooled ir thermal imaging system of low in energy consumption, dependable performance, advantage such as easy to operate becomes inevitable, especially rapider in development in recent years.
The uncooled ir thermal imaging system all adopts the gazing type focal plane arrays (FPA), mainly comprises non-refrigeration detectors such as micro-metering bolometer type, thermoelectric type, bi-material microcantilevel type and thermoelectric pile type at present.Principle of work all is to absorb infrared radiation through the detector pixel to cause the pixel temperature variation basically, causes material for detector to change with internal microstructure resistance, voltage or relevant polarization characteristic, and their common ground all is to adopt the electrical readout mode.Traditional focal-plane array (FPA) signal is read with the silicon technology integrated circuit usually; And these material for detector are common and silicon does not match; And the circuit on each FPA makes Vacuum Package become difficult, has caused cost to be difficult to control, becomes the obstruction of the low-cost marketization.
Summary of the invention
The invention discloses a kind of non-refrigeration far infrared thermal imaging system; Different with the non-refrigeration far infrared thermal imaging system of existing thermal resistance sensitlzing effect based on LONG WAVE INFRARED, the present invention is based on the non-refrigeration far infrared thermal imaging system of the temperature-sensitive optical effect of LONG WAVE INFRARED.
Technical scheme of the present invention is following:
A kind of non-refrigeration far infrared thermal imaging system; As shown in Figure 1, comprise chopper 1, far red light (LWIR) lens 2, optical splitter 3, infrared focal plane array (IRFPA) 4, near infrared light (NIR) light source 5, the first near infrared light lens 6, near infrared light wave filter 7, the second near infrared light lens 8 and digital camera 9.The far red light that the target visual field is sent behind chopper 1 sampling and far red light lens 2 collimations, gets into infrared focal plane array 4 through optical splitter 3 successively; By near infrared light wave filter 7 filtering becoming arrowband near infrared reference light, arrowband near infrared reference light is reflected into infrared focal plane array 4 through optical splitter 3 to the near infrared light that near infrared light light source 5 is sent behind the first near infrared light lens, 6 collimations; Project the imageing sensor of digital camera 9 from the arrowband near infrared reference light of infrared focal plane array 4 outgoing through the second near infrared light lens 8, finally image on the display of digital camera 9.Wherein said infrared focal plane array 4 comprises a two-dimensional infrared focal plane pixel array like Fig. 2, shown in 3, and each infrared focus plane pixel structure is supported on the transparency carrier 13 through a pixel support column 12; Said infrared focus plane pixel structure is the film filter of a kind of Fabry Perot chamber (F-P chamber) structure, comprises cavity 10 and the mirror surface structure 11 that is positioned at cavity 10 two sides; Wherein cavity 10 is made up of alpha polycrystal silicon, and mirror surface structure 11 is one by alpha polycrystal silicon film and Si
3N
4The multi-layer film structure that film alternately constitutes.
Non-refrigeration far infrared thermal imaging system provided by the invention, wherein core devices is an infrared focal plane array (IRFPA) 4.The pixel structure of this infrared focal plane array is with the film filter of Fabry Perot cavity (F-P chamber) structure.Wherein the principle of work in F-P chamber mainly is based on the multiple-beam interference theory; The F-P chamber that with the air is cavity medium is an example; After incident light gets into air chamber, because the high reflectance of both sides catoptron, light will repeatedly reflect in the chamber back and forth; Have fixing phase differential between the adjacent reflection ray, thereby the light after the outgoing of F-P chamber will obtain modulation (shown in Fig. 4 a) owing to the result who receives multiple-beam interference.
Shown in Fig. 4 b, the thickness of establishing beam incident angle and be α (α ≈ 0), F-P air chamber is that h, cavity medium refractive index are n, then cavity optical thickness d=n*h; If the reflectivity of catoptron is R, incident light wave amplitude is A
0By above-mentioned parameter can obtain incident light finally the amplitude of the transmitted light after second catoptron outgoing can be expressed as:
……
Phase differential through causing behind the air chamber can be expressed as:
Wherein, k=2 π/λ is the light wave wave vector.The electric field intensity expression formula that can obtain the light wave of the i time outgoing is:
E
i=(1-R)□R
i□A
0□cos[ωt+kx+(i-1)□δ]
Can obtain the outgoing light intensity at last is:
The integral multiple that δ equals 2 π is maximum condition, the cavity optical thickness d=n*h of seeing through.So its optical property is decided by parameters such as its specular reflectance R, cavity optical thickness d usually, its peak value that sees through depends on cavity optical thickness d.Therefore, can carry out it by following two aspects tuning, the one, change its cavity thickness h, the 2nd, change the cavity medium refractive index n.
The present invention adopts the method that changes refractive index; Utilization has the semiconductor material-alpha polycrystal silicon of high thermo-optical coeffecient and makes cavity; Its refractive index is bigger with temperature variation; F-P in the single pixel of IRFPA up and down minute surface all has good absorption to far red light, and whole F-P chamber sees through the near infrared reference light, is arranged in through the pixel with a plurality of structures like this just to constitute detection together and use infrared focal plane array.After infrared focal plane array absorbs the radiation heat of incident far red light; Because the thermo-optic effect of cavity medium material alpha polycrystal silicon causes its refractive index to change in the F-P chamber; Thereby cause the variation of filtering characteristic, cause that wave filter (F-P chamber) sees through the variation (as shown in Figure 5) at peak; Because the refractive index in F-P chamber changes with temperature variation; Causing the near infrared reference light of local incident to obtain modulating---its emergent light light intensity will change with the cavity variations in refractive index; And then change with the variation of F-P cavity temperature; Therefore, the present invention has realized the measurement to zones of different temperature in the target visual field indirectly through the measurement near infrared reference light output intensity, and is the reddest in digital camera realization infrared imaging.
In the non-refrigeration far infrared thermal imaging system provided by the invention, the acting as of partial function device:
1, chopper 1 is realized the signal sampling function.Chopper is equivalent to a photoswitch; In the chopper turn-on cycle; The far red light that the target visual field is sent can get into infrared focal plane array through relevant light paths; The F-P chamber that causes relevant pixel structure in the infrared focal plane array absorbs the variation of far red light radiation heat occurrence temperature and causes variations in refractive index, thereby makes the near infrared reference light obtain modulation through infrared focal plane array, and its output intensity is surveyed and imaging by digital camera; At chopper in off period, the far red light that the target visual field is sent can not get into infrared focal plane array through relevant light paths, thereby makes the F-P chamber of the relevant pixel structure in the infrared focal plane array return to the details in a play not acted out on stage, but told through dialogues temperature from the temperature of a last imaging cycle.Like this, chopper has not only been realized the signal employing, can avoid influencing each other between the sequential frame image simultaneously.
2, optical splitter 3 is realized the bundle that closes of orthogonal far red light and near infrared reference light.It is to far red light full impregnated and near infrared light almost is all-trans almost.
3, near infrared light wave filter 7 is a narrow band filter, and the near infrared light filtering that it is sent near infrared light light source 5 becomes the infrared reference light in arrowband.
4, the infrared reference light full impregnated in modulated arrowband of 8 pairs of infrared focal plane array 4 outgoing of the second near infrared light lens, and the remaining far red light of infrared focal plane array 4 outgoing is absorbed, imaging precision influenced to avoid remaining far red light to get into digital camera.
The invention has the beneficial effects as follows:
The non-refrigerating infrared focal plane imaging system that the present invention proposes; Thermo-optic effect principle based on F-P chamber film filter; Measuring method through integrated optics and the conversion of light wave is modulated into picture; Compare based on the non-refrigerating infrared focal plane imaging system of thermal resistance effect, micro-bridge structure with existing, saved the inner sensing circuit of non-refrigerating infrared focal plane, the Johnson noise of having avoided the micrometering kampometer to bring; Common and unmatched vanadium oxide of silicon or pyroelectricity material have been avoided using simultaneously; Under the situation that does not influence device performance, make element height integrated, reduced volume greatly, reduced making step and Vacuum Package cost; Can significantly reduce the cost, have certain application potential.
Description of drawings
Fig. 1 is the light channel structure synoptic diagram of the non-refrigeration far infrared thermal imaging system of the present invention's proposition.Wherein: 1 is chopper, and 2 is the far red light lens, and 3 is optical splitter, and 4 is infrared focal plane array, and 5 is near-infrared light source, and 6 is the first near infrared light lens, and 7 is the near infrared light wave filter, and 8 is the second near infrared light lens, and 9 is digital camera.
Fig. 2 is the cross-sectional view of infrared focal plane array in the non-refrigeration far infrared thermal imaging system of the present invention's proposition.Only provided two pixel structures among the figure, wherein 10 is the cavity of the film filter of F-P cavity configuration, and 11 is the mirror surface structure on cavity two sides, and 12 is the pixel support column, and 13 is transparency carrier.
Fig. 3 is infrared focal plane array planar structure synoptic diagram in the non-refrigeration far infrared thermal imaging system of the present invention's proposition.
Fig. 4 is a F-P chamber schematic diagram.
Fig. 5 is the optical modulation principle schematic of the non-refrigeration far infrared thermal imaging system of the present invention's proposition.
Embodiment
A kind of non-refrigeration far infrared thermal imaging system; As shown in Figure 1, comprise chopper 1, far red light (LWIR) lens 2, optical splitter 3, infrared focal plane array (IRFPA) 4, near infrared light (NIR) light source 5, the first near infrared light lens 6, near infrared light wave filter 7, the second near infrared light lens 8 and digital camera 9.The far red light that the target visual field is sent behind chopper 1 sampling and far red light lens 2 collimations, gets into infrared focal plane array 4 through optical splitter 3 successively; By near infrared light wave filter 7 filtering becoming arrowband near infrared reference light, arrowband near infrared reference light is reflected into infrared focal plane array 4 through optical splitter 3 to the near infrared light that near infrared light light source 5 is sent behind the first near infrared light lens, 6 collimations; Project the imageing sensor of digital camera 9 from the arrowband near infrared reference light of infrared focal plane array 4 outgoing through the second near infrared light lens 8, finally image on the display of digital camera 9.Wherein said infrared focal plane array 4 comprises a two-dimensional infrared focal plane pixel array like Fig. 2, shown in 3, and each infrared focus plane pixel structure is supported on the transparency carrier 13 through a pixel support column 12; Said infrared focus plane pixel structure is the film filter of a kind of Fabry Perot chamber (F-P chamber) structure, comprises cavity 10 and the mirror surface structure 11 that is positioned at cavity 10 two sides; Wherein cavity 10 is made up of alpha polycrystal silicon, and mirror surface structure 11 is one by alpha polycrystal silicon film and Si
3N
4The multi-layer film structure that film alternately constitutes.
Add a chopper 1 foremost in optical system, to adapt to the response of infrared focal plane array, promptly when the edge of chopper during through a pixel to temperature variation; Pixel is exposed under the object radiation, and its temperature begins to change accordingly, and temperature continues to change up to making object crested again; Through in a flash, signal is sampled at blade edge, and leading edge is during through a pixel; The pixel temperature returns to the details in a play not acted out on stage, but told through dialogues temperature, and in the moment that object reappears, signal is by sampling once more.
The light that said near infrared light light source is sent should be near the response wave band of digital camera, and away from the far red light wave band.As adopt gallium arsenide light emitting diode, its center wavelength of light of sending between 550 to 900 nanometers, with the response wave band of conventional CCD digital camera or CMOS digital camera near and away from the far red light wave band.
Said infrared focal plane array 4 can adopt following technology to realize: select for use optical glass (like K9 glass) to make substrate; At first make the sacrifice layer of about 2 micron thick of one deck at substrate surface; Then according to infrared focal plane array etched portions sacrifice layer; Expose the dot matrix groove of making the required support column of pixel, next at dot matrix groove deposition SiO
2Or Si
3N
4Supporting medium layer utilizes plasma activated chemical vapour deposition (PECVD) technology to make by alpha polycrystal silicon film and Si again
3N
4The multi-layer film structure that film alternately constitutes is as first mirror surface structure, again at the first mirror surface structure surface deposition alpha polycrystal silicon film as the F-P chamber, again on the alpha polycrystal silicon thin layer deposition by alpha polycrystal silicon film and Si
3N
4The multi-layer film structure that film alternately constitutes removes sacrificial layer material at last as second mirror surface structure, obtains final infrared focal plane array.Wherein cavity layer thickness in F-P chamber is 1 micron, and the mirror surface structure on two sides is by the alpha polycrystal silicon film of 200 nanometer thickness and the Si of 100 nanometer thickness
3N
4Film alternately constitutes for four times.
Said digital camera 9 can be CCD digital camera or CMOS digital camera.
Non-refrigeration far infrared thermal imaging system according to the invention has low-power consumption, small size, and characteristics such as low cost make a large amount of popularizing become possibility, in medical treatment, industry, fields such as safety have broad prospects.
Claims (3)
1. a non-refrigeration far infrared thermal imaging system comprises chopper (1), far red light lens (2), optical splitter (3), infrared focal plane array (4), near infrared light light source (5), the first near infrared light lens (6), near infrared light wave filter (7), the second near infrared light lens (8) and digital camera (9); The far red light that the target visual field is sent behind chopper (1) sampling and far red light lens (2) collimation, gets into infrared focal plane array (4) through optical splitter (3) successively; By near infrared light wave filter (7) filtering becoming arrowband near infrared reference light, arrowband near infrared reference light is reflected into infrared focal plane array (4) through optical splitter (3) to the near infrared light that near infrared light light source (5) is sent behind first near infrared light lens (6) collimation; Project the imageing sensor of digital camera (9) from the arrowband near infrared reference light of infrared focal plane array (4) outgoing through the second near infrared light lens (8), finally image on the display of digital camera (9); Wherein said infrared focal plane array comprises a two-dimensional infrared focal plane pixel array, and each infrared focus plane pixel structure is supported on the transparency carrier (13) through a pixel support column (12); Said infrared focus plane pixel structure is a kind of film filter of F-P cavity configuration, comprises cavity (10) and is positioned at the mirror surface structure (11) on cavity (10) two sides; Wherein cavity (10) is made up of alpha polycrystal silicon, and mirror surface structure (11) is one by alpha polycrystal silicon film and Si
3N
4The multi-layer film structure that film alternately constitutes.
2. non-refrigeration far infrared thermal imaging system according to claim 1 is characterized in that the transparency carrier of said infrared focal plane array (13) material is an optical glass; Said pixel support column (12) material is SiO
2Or Si
3N
4Said cavity (10) thickness is 1 micron, and mirror surface structure (11) is by the alpha polycrystal silicon film of 200 nanometer thickness and the Si of 100 nanometer thickness
3N
4Film alternately constitutes for four times.
3. non-refrigeration far infrared thermal imaging system according to claim 1 is characterized in that said digital camera (9) is CCD digital camera or CMOS digital camera.
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| CN109632110A (en) * | 2018-12-21 | 2019-04-16 | 南京理工大学 | Eliminate the device and its removing method of micro-metering bolometer infrared image grid line |
| CN110307905B (en) * | 2019-07-15 | 2021-03-30 | 电子科技大学 | Infrared focal plane array and infrared thermal imaging system based on infrared focal plane array |
| CN111380829A (en) * | 2020-03-02 | 2020-07-07 | 南方科技大学 | Uncooled optical reading type infrared thermal imaging system |
| CN113660433B (en) * | 2021-08-16 | 2023-05-30 | 华中科技大学鄂州工业技术研究院 | Uncooled thermal infrared focal plane device and infrared imaging equipment |
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| CN101726365A (en) * | 2009-10-20 | 2010-06-09 | 西北工业大学 | Non-refrigeration type multiband far infrared thermal imager |
| CN101915924A (en) * | 2010-04-14 | 2010-12-15 | 清华大学 | Normal-temperature infrared inner satellite imaging detector |
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| CN101726365A (en) * | 2009-10-20 | 2010-06-09 | 西北工业大学 | Non-refrigeration type multiband far infrared thermal imager |
| CN101915924A (en) * | 2010-04-14 | 2010-12-15 | 清华大学 | Normal-temperature infrared inner satellite imaging detector |
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