CA2125038A1 - Infrared chemical vapor detector and method - Google Patents
Infrared chemical vapor detector and methodInfo
- Publication number
- CA2125038A1 CA2125038A1 CA 2125038 CA2125038A CA2125038A1 CA 2125038 A1 CA2125038 A1 CA 2125038A1 CA 2125038 CA2125038 CA 2125038 CA 2125038 A CA2125038 A CA 2125038A CA 2125038 A1 CA2125038 A1 CA 2125038A1
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- Prior art keywords
- filter
- bandwidth
- output signal
- infrared
- wavelength
- Prior art date
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- Abandoned
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- 238000000034 method Methods 0.000 title claims abstract description 21
- 239000000126 substance Substances 0.000 title abstract description 17
- 238000001914 filtration Methods 0.000 claims abstract description 15
- 238000005070 sampling Methods 0.000 claims description 5
- 238000001514 detection method Methods 0.000 abstract description 19
- 238000012544 monitoring process Methods 0.000 abstract description 4
- 241001527902 Aratus Species 0.000 description 3
- 241000231739 Rutilus rutilus Species 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- IJJWOSAXNHWBPR-HUBLWGQQSA-N 5-[(3as,4s,6ar)-2-oxo-1,3,3a,4,6,6a-hexahydrothieno[3,4-d]imidazol-4-yl]-n-(6-hydrazinyl-6-oxohexyl)pentanamide Chemical compound N1C(=O)N[C@@H]2[C@H](CCCCC(=O)NCCCCCC(=O)NN)SC[C@@H]21 IJJWOSAXNHWBPR-HUBLWGQQSA-N 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 238000012937 correction Methods 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- BGRJTUBHPOOWDU-UHFFFAOYSA-N sulpiride Chemical compound CCN1CCCC1CNC(=O)C1=CC(S(N)(=O)=O)=CC=C1OC BGRJTUBHPOOWDU-UHFFFAOYSA-N 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 101150034533 ATIC gene Proteins 0.000 description 1
- 101100102173 Aspergillus flavus (strain ATCC 200026 / FGSC A1120 / IAM 13836 / NRRL 3357 / JCM 12722 / SRRC 167) ustQ gene Proteins 0.000 description 1
- 101150008122 Bcan gene Proteins 0.000 description 1
- 241000272470 Circus Species 0.000 description 1
- 101100536354 Drosophila melanogaster tant gene Proteins 0.000 description 1
- 101150087426 Gnal gene Proteins 0.000 description 1
- 102000016941 Rho Guanine Nucleotide Exchange Factors Human genes 0.000 description 1
- 108010053823 Rho Guanine Nucleotide Exchange Factors Proteins 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000013528 artificial neural network Methods 0.000 description 1
- 238000009924 canning Methods 0.000 description 1
- PBAYDYUZOSNJGU-UHFFFAOYSA-N chelidonic acid Natural products OC(=O)C1=CC(=O)C=C(C(O)=O)O1 PBAYDYUZOSNJGU-UHFFFAOYSA-N 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001506 fluorescence spectroscopy Methods 0.000 description 1
- KEBHLNDPKPIPLI-UHFFFAOYSA-N hydron;2-(3h-inden-4-yloxymethyl)morpholine;chloride Chemical compound Cl.C=1C=CC=2C=CCC=2C=1OCC1CNCCO1 KEBHLNDPKPIPLI-UHFFFAOYSA-N 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000000504 luminescence detection Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 208000006379 syphilis Diseases 0.000 description 1
- 238000001931 thermography Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
- G01N21/3518—Devices using gas filter correlation techniques; Devices using gas pressure modulation techniques
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/12—Generating the spectrum; Monochromators
- G01J2003/1226—Interference filters
- G01J2003/1234—Continuously variable IF [CVIF]; Wedge type
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
- G01N2021/3531—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis without instrumental source, i.e. radiometric
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/12—Circuits of general importance; Signal processing
- G01N2201/127—Calibration; base line adjustment; drift compensation
- G01N2201/12723—Self check capacity; automatic, periodic step of checking
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
2125038 9311424 PCTABS00022 The invention relates to the remote infrared radiometric detection of chemical vapors (20). Air quality and substance control concerns present a need for more efficient ways of detecting the presence of select chemical vapors (20) in the atmosphere. A method and apparatus for such a detector includes elements for filtering (26, 34) collected infrared energy over a filter bandwidth by bandpass filtering only a fractional bandwidth of the filter bandwidth at any one time and repeatedly scanning the filter bandwidth with the passed fractional bandwidth. Also included are elements for measuring infrared energy (32) passed by the bandpass filtering thereby producing an output signal and for repeatedly nulling (40) the output signal in relation to the repeated scanning of the filter bandwidth. The invention is applicable to air monitoring including pollution control, chemical detection and the detection of any substances which provide telltale chemical vapors (20).
Description
`VO g3/1 1424 PCl /USg2/10401 2l2~n3s
2 INFRARED CHEMICAI. VAPOR DETECTOR AND MI~THOD
3 Bac~ground of the Invention g Field of the In~ention The ~resent ln~entlon ~enerally relates to the 6 identificatlon of chemical ~a~ors by means of infrared 7 (IR) radlation emisslon an~ absor~tlon and ~articularly a to the ~erforman~e of such detection at a location 9 remote-fro~ tho ~a~ors detected.
o Statement of the Prior Art 1l Increaslng concern for various as~ect~ of our 12 environmental quality has ~enerated a need in our 13 technical ca~a~bility for the convenient and remote 14 detection of ~arlous ~ubstances whlch might take the I5 form of ~a~ors ~resent in air. var~ous existing 16 systems range in nature from laser ~hotoacoustic 17 detectlon to dlfferential absor~tion Lidar, to 18 fluorescence or luminescence spectroscopy, and to 19 thermal infrared emission imaging. ~nfortunately, all 20 of the~e method~ are very ex~en~ive high-technology 1 systems requiring com~lex o~eration and exteneive 22 signal ~roceB~ing. All, exce~t thermal imaging, 23 require active illumination which beacon their 24 Dresence. These factors tend to enforce substantial limits- on the nature and fre~uency of the use of the 26 res~ectlve methods. ~nderstandably, there is, 27 therefore, a need for such detectlon equl~ment and WO 93/1 1424 PCI /US92tlO401,-2125~38 1 methods which are less exp~nsi~e, easler to oDerate and 2 slmDler in nature to Drovlde faster detection results.
3 8~MMARY OF THE INVEN~ION
o Statement of the Prior Art 1l Increaslng concern for various as~ect~ of our 12 environmental quality has ~enerated a need in our 13 technical ca~a~bility for the convenient and remote 14 detection of ~arlous ~ubstances whlch might take the I5 form of ~a~ors ~resent in air. var~ous existing 16 systems range in nature from laser ~hotoacoustic 17 detectlon to dlfferential absor~tion Lidar, to 18 fluorescence or luminescence spectroscopy, and to 19 thermal infrared emission imaging. ~nfortunately, all 20 of the~e method~ are very ex~en~ive high-technology 1 systems requiring com~lex o~eration and exteneive 22 signal ~roceB~ing. All, exce~t thermal imaging, 23 require active illumination which beacon their 24 Dresence. These factors tend to enforce substantial limits- on the nature and fre~uency of the use of the 26 res~ectlve methods. ~nderstandably, there is, 27 therefore, a need for such detectlon equl~ment and WO 93/1 1424 PCI /US92tlO401,-2125~38 1 methods which are less exp~nsi~e, easler to oDerate and 2 slmDler in nature to Drovlde faster detection results.
3 8~MMARY OF THE INVEN~ION
4 In one form, the Dresent invention Drovides an s lnfrared radiometer, com~rl~ing me~ns for collecting 6 i~frare~ onergy, means for flltering the collected 7 energy o~r a fllter bandwidth including filter means 8 for band~a~slng only a fractiona~ bandwidth of the g filter bandwidth at any one time and means for r~eatedly scanning the filter bandwidth with the 11 ~a~ed: fractlonal bandwidth, means for measuring 12 lnfrared energy ~assed by the filter means and for 13 ~roduclng an out~ut B ignal in rQsponse thereto, and 14 mQans for re~eatedly nulling the output signal in 15 relation to the repeated scanning of the filter 16 bandwldth.
17 In anot~er form, the ~resent invention prov~de~
18 an aDDaratus for d~tecting the ~resence of substance vaDors havlng ~nown infrared sDectral characteristics ~o aga~nst a bac~ground having contra~tlng infrared 21 s~ectral charactQristics relative to the known infrared 22 characterl~tlcs of the substance ~aDors, comprising 23 _ans for collectlng lnfrared energy Qmissions from the 24 backgroun~ and any ~a~ors prQsQnt between the bac~ground and the mean~ for coll~ctlng, means for 26 ~eaBur~g thQ 1nrar~ en~rgy 1eVQ1B coll~cted both in ~7 ~ flr~t ~lur~l~ty of wavelength bands known to contain ,~' wo 93/1 1424 PCI /US92/10401 1 infrared characterlstics of the sub~tance ~apors and in 2 a secona ~lurality of wa~length bands known to contain 3 infrared characteri~tics of the background, and means 4 for com~arin~ the infrared energy levels measured in the fir~t and second ~lurallty of bands for determining 6 the ~re~ence of substance va~ors ba~ed u~on the-7~: relative infrar~ ~ne~gy level~ measured in the first 8 and second ~lurality of bands.
g In one form, the method of the ~resent invention lo ~roviaes for collecting infrared energy, filtering the .
11 collectea energy over a filter bandwidth including 12 band~as~ filtering only a fractional bandwidth of the 13 filter bandwidth at any one time and repeatedly 14 ~canning the filter bandwidth with the ~assed fractional bandwidth, measuring infrared energy passed 16 by the band~aes filterlng ~roducing an output signal in 17 reB~onBe thereto, and re~eatedly nullin~ the output 18 Bignal in relation to the re~eated scanning of the Is filter bandwidth.
In another fonm, the ~resent ~nvention covers a 21 method for detecting the ~resence of sub~tance vapors 22 havin~ kn~wm infrared s~ectral charactQristics aga~nst 23 a background havln~ ~ontra~ting infrared s~ectral 24 charactQrlstics r~latlve to the known infrared 2s characteristic~ of the ~ubstance va~ors, com~rising the 26 step~ of collectlng infrared energy emlssions from the 27 bac~groun~ and any ~a~ors ~re~ent against the . :
WO93/11424 PCT/~JS92tl0401-21~038 1 bac~ground, measurlng the infrared energy levels 2 collected both in a first ~lurality of wavelength bands 3 ~nown to contain characterlstic~ of th- substance 4 va~ors and in a second ~lurality of wavelength bands S bnown to contaln characteristics of the background, and 6 co~aring the infrared energy levels ~easured in the 7 first an~ CQCOn~ ~lurality of b~na~ for deter~ining the 8 ~ro~ence of sub~tance va~ors based'u~on the relative~
g infrared energy level~ measured in the first and second Dlurallty of bands.
12 The ~resent inv~ntion iB illuBtratiVQly 13 described in refèrence to the accom~anying drawing~ in 14 which:
Fig. 1 is a re~resQntat$onal diagram of a remote 16 detQction environment in which the ~resent invention iB
7 intended to o~erate;
18 Fig. 2 i~ a ~chematic block diagram of a vapor ~9 detection a~paratu~ con~tructed in accordance with one embodiment of the ~resent invention;
21 Fig. 3 iB an infrared s~Qctral diagram of an 22 infrared filter de~igned to function in accordance with 23 the emb~diment of Fig. 2t and 24 Flg. 4 1B a flow chart of signal ~roces~ing Derfor~ed by the ap~aratus of F$g. 2.
~lUO 93/11424 PCr/lJS92/10401 2125~38 1 D~TAI~D D~SCRIPTION OF THE DRAWINGS
2 Fi~. 1 shows a tyDical lnfrared (IR) detection 3 en~ironment 10 in which the a~paratu~ and method of the 4 Dresent in~ention are intended to o~erate. The environ ent 10 generally lncludes a back~round 14 6 havin~ ~easurable i~frared emission/absor~tion/
7 reflectlon characterl~tlcs, and a non-lmagin~ infrared 8 . ~etector 16. Detector 16 i~ aimed in the direction of g arrow 18 toward the back~round 14 to detect for the ~os~ible ~resence of selectable chemical vapor~ 20 as 11 may Dass ln the area 12 between the background 14 and 12 the deteotor 16. Area 12 may also include normal 13 atmosDheric air 12 ca~able of sustaining human and 14 other forms of life. ~ore s~ecif~cally, the background 15 14 iB BeleCted ~O that lt ha~ a dlfferent tem~erature 16 from the ~apors being detected. ThiB contrast may 17 alternatlvely include the detection of warm vapors 18 again~t a cool background or the detection of cool 1~ va~ors against a warm background. The contra~t 20 ~rovld~e the basls for a detectable infrared 21 difference. The background 14 either may be man-made 22 ~uch as a surface or wall, or may be op~ortuni~tically 23 selectedr~uch as a hill~lde or sky. Background 14 does 24 not have to ha-e a stable tem~erature, BO long a~ it~
2s tem~eratur~ g*nerally contrasts t~at of ~a~ors 2Q.
26 Fl~. 2 sho~B a ~che~atic block aiagram of an 27 a~ar~tus 19 con~tructed ln aocordance wlth one ' WO 93/11424 PCI /US92/10401 -`
212~038 1 Qmbod~Qnt of the ~reeent inventlon and ca~able of 2 ~erformlng the ~etect~on of selectable chemical ~apors 3 such as 20 in the envlronment 10 of Fig. 1. A~paratus 4 19 genQrally includee the detector 16 of Fig. 1 and a
17 In anot~er form, the ~resent invention prov~de~
18 an aDDaratus for d~tecting the ~resence of substance vaDors havlng ~nown infrared sDectral characteristics ~o aga~nst a bac~ground having contra~tlng infrared 21 s~ectral charactQristics relative to the known infrared 22 characterl~tlcs of the substance ~aDors, comprising 23 _ans for collectlng lnfrared energy Qmissions from the 24 backgroun~ and any ~a~ors prQsQnt between the bac~ground and the mean~ for coll~ctlng, means for 26 ~eaBur~g thQ 1nrar~ en~rgy 1eVQ1B coll~cted both in ~7 ~ flr~t ~lur~l~ty of wavelength bands known to contain ,~' wo 93/1 1424 PCI /US92/10401 1 infrared characterlstics of the sub~tance ~apors and in 2 a secona ~lurality of wa~length bands known to contain 3 infrared characteri~tics of the background, and means 4 for com~arin~ the infrared energy levels measured in the fir~t and second ~lurallty of bands for determining 6 the ~re~ence of substance va~ors ba~ed u~on the-7~: relative infrar~ ~ne~gy level~ measured in the first 8 and second ~lurality of bands.
g In one form, the method of the ~resent invention lo ~roviaes for collecting infrared energy, filtering the .
11 collectea energy over a filter bandwidth including 12 band~as~ filtering only a fractional bandwidth of the 13 filter bandwidth at any one time and repeatedly 14 ~canning the filter bandwidth with the ~assed fractional bandwidth, measuring infrared energy passed 16 by the band~aes filterlng ~roducing an output signal in 17 reB~onBe thereto, and re~eatedly nullin~ the output 18 Bignal in relation to the re~eated scanning of the Is filter bandwidth.
In another fonm, the ~resent ~nvention covers a 21 method for detecting the ~resence of sub~tance vapors 22 havin~ kn~wm infrared s~ectral charactQristics aga~nst 23 a background havln~ ~ontra~ting infrared s~ectral 24 charactQrlstics r~latlve to the known infrared 2s characteristic~ of the ~ubstance va~ors, com~rising the 26 step~ of collectlng infrared energy emlssions from the 27 bac~groun~ and any ~a~ors ~re~ent against the . :
WO93/11424 PCT/~JS92tl0401-21~038 1 bac~ground, measurlng the infrared energy levels 2 collected both in a first ~lurality of wavelength bands 3 ~nown to contain characterlstic~ of th- substance 4 va~ors and in a second ~lurality of wavelength bands S bnown to contaln characteristics of the background, and 6 co~aring the infrared energy levels ~easured in the 7 first an~ CQCOn~ ~lurality of b~na~ for deter~ining the 8 ~ro~ence of sub~tance va~ors based'u~on the relative~
g infrared energy level~ measured in the first and second Dlurallty of bands.
12 The ~resent inv~ntion iB illuBtratiVQly 13 described in refèrence to the accom~anying drawing~ in 14 which:
Fig. 1 is a re~resQntat$onal diagram of a remote 16 detQction environment in which the ~resent invention iB
7 intended to o~erate;
18 Fig. 2 i~ a ~chematic block diagram of a vapor ~9 detection a~paratu~ con~tructed in accordance with one embodiment of the ~resent invention;
21 Fig. 3 iB an infrared s~Qctral diagram of an 22 infrared filter de~igned to function in accordance with 23 the emb~diment of Fig. 2t and 24 Flg. 4 1B a flow chart of signal ~roces~ing Derfor~ed by the ap~aratus of F$g. 2.
~lUO 93/11424 PCr/lJS92/10401 2125~38 1 D~TAI~D D~SCRIPTION OF THE DRAWINGS
2 Fi~. 1 shows a tyDical lnfrared (IR) detection 3 en~ironment 10 in which the a~paratu~ and method of the 4 Dresent in~ention are intended to o~erate. The environ ent 10 generally lncludes a back~round 14 6 havin~ ~easurable i~frared emission/absor~tion/
7 reflectlon characterl~tlcs, and a non-lmagin~ infrared 8 . ~etector 16. Detector 16 i~ aimed in the direction of g arrow 18 toward the back~round 14 to detect for the ~os~ible ~resence of selectable chemical vapor~ 20 as 11 may Dass ln the area 12 between the background 14 and 12 the deteotor 16. Area 12 may also include normal 13 atmosDheric air 12 ca~able of sustaining human and 14 other forms of life. ~ore s~ecif~cally, the background 15 14 iB BeleCted ~O that lt ha~ a dlfferent tem~erature 16 from the ~apors being detected. ThiB contrast may 17 alternatlvely include the detection of warm vapors 18 again~t a cool background or the detection of cool 1~ va~ors against a warm background. The contra~t 20 ~rovld~e the basls for a detectable infrared 21 difference. The background 14 either may be man-made 22 ~uch as a surface or wall, or may be op~ortuni~tically 23 selectedr~uch as a hill~lde or sky. Background 14 does 24 not have to ha-e a stable tem~erature, BO long a~ it~
2s tem~eratur~ g*nerally contrasts t~at of ~a~ors 2Q.
26 Fl~. 2 sho~B a ~che~atic block aiagram of an 27 a~ar~tus 19 con~tructed ln aocordance wlth one ' WO 93/11424 PCI /US92/10401 -`
212~038 1 Qmbod~Qnt of the ~reeent inventlon and ca~able of 2 ~erformlng the ~etect~on of selectable chemical ~apors 3 such as 20 in the envlronment 10 of Fig. 1. A~paratus 4 19 genQrally includee the detector 16 of Fig. 1 and a
5 ~rOCeB80r sectlon 21.
6 -- The detector 16 ie directed 80 that infrared
7 -~ e~ergy~manati~g from the bac~groun~ 14 traverses
8 through the chemlcal va~or~ 20 an~ is collected by the
9 a~erture of an ob~ective lens 24. The chemical vapors 1o 20 select1vely abeorb or raa~at~ I~ energy in 11 accordance with their own unique IR characteristics and 12 in re~onee to the relatlve ~ifferential tem~erature 13 between th background 14, the va~ore 20 and any air or 14 gasees ~resent in the testing environment. The IR
1S energy collected by the ob~ective lens 24 ~asses 16 through a rotating, continuously varying infrared 17 s~ectral band~ass filter 26, a slit 28 and a field lens 18 30. The field lens 30 collects the energy onto an IR
~9 detector 3a. The filter a6 ie rotated at a fixed rate 20 w~th motor 34 and causes the detector 32 to see 21 re~eated scans of infrared wavelengths. In other 22 worde, the functioning of tbe a~aratus descxibed thus 23 far ~rod~ce~ an IR s~ectral ra~iometer.
24 - Thl~ ~R s~ectral radiometer may be conetructed 25 to cover any Dartial bandwidth of the IR s~ectrum which 26 1~ of lntere~t. Thls ~esi~n a~ect ~e~en~e ~rimarily 27 uDon the rotatlng fllter ~6.
''~93/11424 PCT/US92/1~401 21~ 38 l Filter 26 ~s clrcular and allowe the Das~age 2 thQrQthrough of a continuously varying wavelength of IR
3 energy. The wavelength varie~ in accordance with the 4 rotational angle of the filter over a predetermined s fllter bandwi~th. In one embo~lment, the wavelength 6 varies contl~uously from (6~ to (ll.4) ~icrons, bot~
7 lncrea~ing ~D~ ~ecreaslng the ~assed w~velength BO that 8 the (6) to (11.4) ~lcron fllter bandwidth iB scanned a g total of four (4) times in one rotation of the filter.
Bach ~can of the bandwidth may also be thought of as a 11 frame.
12 Th- IR energy ~assed at any ~oint around the 13 filter i8 only a fractional bandwldth of the overall 14 filter bandwidth. In the above example, thi~
fractional ban~width is (0.2) mlcrons.
16 By selection of the filter 26, the filter 17 bandwidth of a detector may be tailored BO that the 18 detection a~aratu~ may be dedicated for the long term ~ monitoring of elther a single va~or or a group of va~or~ having sufficiently ~roximate IR
21 characteristics.
22 The IR energy level that im~inge~ on the 23 ~etector 32 is detecte~ or measured causing the 24 ~etector 32 to ~roduce an out~ut signal which i8 25 ~ amDllfle~ by a ~reampllflQr 36 and an am~lifier 38.
26 The ~ pl~fie~ out~ut BigD~I fro~ am~lifier 38 is then 27 cou~le~ to the ~roceBBor cect~on 2l which may be WO93/1l424 2 1 2 5 n ~ 8 PCT/US92/l0401~-1 constructed either integral with or ~eparate from 2 detector 16.
3 The outDut slgna1 from am~llfier 38, which 4 corre~onds to the IR energy detected iB then cho~ped S or nulled by a null clrcuit 40. Null circuit 40 causes 6-~ the s1gD~1 from am~lifi-r 38;to be ~horted to ground 7~ ~between each b~ndwl~th ~can of filter a 6 . This 8 ~rQventB ~can to can ~ro~agat~on of l/f no~se by g ~roducing a deeD signal null between successive ~cans.
1o In the exam~le de~crlbed abo~e, where the filter 11 bnndw1dth 1~ ~cannea a total of four times durin~ each ; 12 rotatlon of the fllter 26, lt iB Dos~ible to use one or 13 ~ore of the filter bandwidth scans Droduced per 14 rotation and to null the slgnal during the unused scans or between ad~acent scans. It may also be said that 16 the out~ut ~lgnal iB nulled at the same rate that the 17 filter bandwidth is scanned. Nulling the signal just s ~rior to the scan enables a stable starting point for ~19 the out~ut signal, and nulling the signal after the end of the scan reduces the un~redictable res~onse caused 21 by l/f noise. Synchronization of this nulling is ~22 `described below.
2~ Thl~ reduction of l~f nolse Qnables improved 24 ~erformance for the entire detection a~aratus. Where conventional a~roach~s mi~ht UBe a lower scan rate and 6 ~ ~e~r~t- hl~h fr-quency ~odulator to limit the l/f 27 ~oise eff-ct, thls ~ri~tion of the ~resent in~ntion .~093~11424 PCT/US92/~01 21`2S038 g 1 allows a hi~her scan rate, ~roviding more data for more 2 ~ccur~t~ ~i~n~l ~rocess~ng.
3 The re~ultant ~lgnal out of null circuit 40 is . 4 buffered by a buffer am~li'fier 42 and filtered by a low ~ass filter 44. The flltered analog signal i8 Bamplea 6 by a sa~le an~ hold circu~t 46 and con~erted to a 7 ~igital for at by an analog to digital (A/D) con~erter 48. A d'lgltal slgnal ~rocessor 50 ~rocQss.e~ the g digitally formatted data using an algorithm described 1o below'and out~uts the re~ults to a dis~lay 52.
11 : The sam~le and hold circuit 46 and null clrcuit 12 40 are synchronized to the circular filter 26 by means 13 of a ~hase-locked loo~ 54. Th~ synchronization 14 enablQs effectlve nulling and identlfica~ion, for ~rocessing ~ur~o~Qs of the filter ~o~ition and 16 therefore the IR wavelength of each sam~le taken. Any 17 other suitable means may alternati~ely be used for 18 synchronizing the nulling and/or the sampling to the ~9 wavelQngth ~osltion of filter 26. An example, in the 20 form of a reflecting detector 55, i~ o~tionally shown.
21 Such a detector may be made to re~pona either directly 22 to thQ filter or otherwise to the metor 24 drive shaft.
23 The analo~ d~ta iB o~er ~am~lea, by sam~le and 24 hold circuit 46, at a rate which iB nomlnally ten time~
the rate of cha~e of filter 26. In the ex~mple gi~en, 26 the fllter b~n~w~th extend~ from (6.0) to (11.4) 27 ~icro~s for ~ total of (5.4) ~icrons, and the .
WO 93/11424 2 1 2 ~ 0 3 8 PCI/IJS92/104(~
1 fractional bandwidth Dassed by filter 26 at any ~oint - 2 in ti~e is (0.2) microns. The sam~ling is controlled 3 to Droduce a sample every (0.02) micron of wavelength 4 change and therefore produces a total of (270) sam~les 5- Der Bcan of-the bandwldth. It is these (270) samples 6 Droduce~ by e~ery scan of the bandwldth that are 7 digltl~Qd-and u~ed by the ~rocessor 50.
8 - Ths system thus far descrlbed re~Qatealy scans~
g the IR sDectrum of interQst to enable detection of lo ~dlfferences in the mQasured IR enQrgy at selected 11 wa~elengths, caused by the ~resence of ~arious 12 substancQ ~Dors contra~ted against the backgrouna.
13 This aetection of differencQs i8 performed with the `14 . s~gnal proces~ing dQscribQd below.
proceBsor 50 processes the digitized samples in 16 accordance wlth the flow chart 60 of Fig. 3.
17 Generally, Filter Calculation ste~ 62 uses the ~ample~
18 to calculate ~54) separate filter ~alues evenly spaced 9 acros~ the scanned filter bandwidth. The~e filter 20 ~alueB are taken by the Filter Correction step 64 and 21 i~di~ldually corrected for the tran~fer function of the 22 detector 16. The ~usted filter values are then 23 ad~ustQ~ by subtraction of an e~tlmated background 24 te~er~ture by the Back~round Subtraction ste~ 66.
Wlth the background tem~erature ~ubtracted, the filter 26 ~1UeB ~re then lnte~r~te~ for ~ multl~licity of filter 27 ban~ldth Bc~nB by Inte~ration ~tQ~ 68 for the purpose .
~093/11424 . PCT/US92/10401 l of remov~ng ~olee. Onc~ data for a sufflcient number 2 of ecans iB accumulated, the lntegrated flltQr value~
3 are thon testQd for the known IR s~ectral 4 charactQrietics of the com~ounds of interest by Detectlon ste~ 70. The indlvidual ete~s of flow chart 6 60 are ~iBCUBBe~ bolow in greater detail.
7 For oach rotatlon of filter 26, Filter 8- Calculation ete~ 62 ta~e the (270) ~amples and forms 9 (54) overla~ing s~ectral band~ass filters that are the averagQ of ten sam~lQs and are seDarated by five ll samDlo~. The over~amDlin~ rate of l0 le nom~nal, and 12 generally the number of samplee may be any ~uitable 13 multl~le of the filter bandwldth (5.4j divided by the 14 fractlonal ~aes bandwidth (0.2) for pur~oses of computatlonal eaee. Fl~ 4 ehows an exam~le of sample 16 grou~lng which may be used to calculate a set of narrow 17 band filter value~. Each of the ~oints in the left 18 hand column re~resents a sam~le value from A/D
ls converter 48. Bach of the actual wavelength values a~pearlng ~n the rlght hand column re~resents the 21 center wavelength of a narrow band fllter value. The 22 wavelength of each of t,he eam~le~ ln the left hand 23 column ~ay be read or lnter~olated from the values 24 a~earing ln the rlght han~ column.
~ch of the narrow band fllter values is 26 calculate~ by sum~lng (or averaglng) the ten (l0) 27 ~eare~t ~a~le ~alue~. This means ehat the (6.l) WO g3/11424 2 1 2 ~ 0 3 8 PCT/US92/1040~
1 .micron filter value is calculated by summ~ng the ~alues 2 for samples ~6.0) through (6.2); the ~6.a) filter value 3 18 summed from samples ~6.1) through (6.3) t and 80 on.
Thl~ method ~roduces (54) narrow band filter value~ over the bandwldth of fllter ~6. ~ach narrow - - 6 - ban~ fllter le ~O.a) ~lcrons wlde, which corres~onds to . 7 the ban~ass characeeristics of filter 26, and each 8 narrow band filter is ~e~aratea from ad~acent filters g by (0.1) microns. Because of this relationship, the lo s~m~les included in the com~utation of:each filter 11 value reDresent ~otentlal infrared energy passed by the :: 12 fllt!r with the wa-elength of the respective filter - 13 value.
14 . The ~ilter Correction s~ep 62 next corrects each ~ 15 calculate~ filter value for the system transfer : 16 function at each.wavelength by multi~lying each filter }7 value by a unique coefficient determlned by system 18 calibration.
The Background Subtraction step 66 next uses the filter values to calculate the level of an estimated or 21 equlvalent background temperature across the filter i- 22 bandwidth and subtracts the calculated tem~erature 23 level from each of the fllter values. The background 24 temperature may be calculated by any sultable method.
I~ one ~iethod, ~clear~ fllter ~alues are determined 26 e1ther by ~ust loo~l~g at ~aveleDi~ths not affected by 27 th~ co~pou~d of i~tQr~st or by otherwlse examlning the 212~038 l filter values ~rom thQse ~clear~ filter values, a 2 tem~erature ~alue for all filters i~ e~timated by 3 minimizlng a mean square error criteria to find an 4 equlvalent blac~body tem~eraturQ whlch bQst fits the measur-~ ~alues in the ~clear filters The estimated 6 te~perature value in all filters is subtractQd from the 7 measure~ ~ignal in all filters to normalize the data 8 This normallzation, 1ncluding estimation, i~
9 ~erformed e~ery frame or scan of the filter bandwidth and iB the basis for det-cting the substance va~ors 20 11 against the contrastlng back~round 14 The equivalent 12 blac~bo~y tem~erature, whlch iB detQrminQd, i~ the 13 bac~ground t-m~erature agalnst which the vapors 20 are 14 contrast~ In the instance where cold va~or~ are lS d~tected a~alnst a warm background, subtracting the 16 background tem~erature result~ in a negat1ve number at 17 the wavQlengths of interest Other negative numbers 18 are al~o generated due to noise in the measurements The resulting values, both negative and ~ositive, are 20 then u~ed by the Integration ste~ 68 21 The Integration ~te~ 68 accumulates data for 22 successive frame~ or full filter bandwidth scans This 23 may be done for elther a fixea number of scans or in a4 res~onse to one or more accumulated filter value~
25 NoiBe s1gnals ln the mea~urement~ are eliminated by 26 thls l~tegratlon or ~ccu~ulat~on If there i~ an IR
27 ~lgn~l, oth-r th~n noi~e, ~resent at ~ny wavelength W093/11424 2 1 2 5 0 3 8 PCT/USs2/10401-1 wlthin the ~can bandwidth, the signal will integrate to 2 its final ~alu~.
3 The lnte~r~ted reeidual filter ~lues are then ~a~sed to Detection ste~ 70. Detection of com~ounas of s lntere~t ~y be a-cco~Dlished by any sultable means. In 6 o~e e_ns, a ~lcro~rocessor -ay be used to logically an~ ~ath -tlca-lly ~am~ne the fllter valueB~ co~aring 8 them a-~a-lnst known ~foot~rints~ or IR s~ectral g characterlstlcs of the com~ound of interest. This a roach afford~ ~rogr~aabillty of the system for the ll det-ctlon of one or more of a v~riety of substances ~12 thereby reducing ada~tatlon costs for each different 13 a~lication. ThiB ~rogrammability even extends to 14 BubBtance concentration and tem~erature. In an alternatlve detectlon a~roach, a neural network 16 de~ice/~roceesor can be u~ed to make the 17 ClaB8if ication/detection decision. Such an approach 18 would be used for detecting a large variety of 19 ~ub~tances.
~o Again thi~ detection ~roce~B iB intended to find 21 differences between the IR ener~y measured at 2 wa~elen~ths ha~lng known e~ectral characteristics for 23 the euSetancee of intereet. These detected differences 24 may be elther ~oeltive or negative de~ending u~on the 2s relatl~e te~er~ture differences between the background .
; 26 an~ the ~a~or~ to bQ detected.
; ~ . . .
`VO93/11424 PCT/US92/1~01 1 After detection, any deslr~ble information may 2 be ~a~sed to th~ di~lay 52. ~his might include the 3 substa~ce name, concentration, tem~erature, etc. or .4 somethlng as ~lm~le as an ln~lcator ~ignal that a ~eclflc sub~tance 18 ~re~ent or ha- exceeded a 6 ~eclflc concentratlon level. Thls data can also be ` 7 ~ trans~ltted for dl~.tant monltorlng, collect$on, 8 analysls,`etc.
9 CONCL~SION
The ~re~ent invention ~ro~ides a unique 11 a~uratus an~ mothod which iB readily ada~table for tho 12 d-tection of a wide ~arlety of ~ub~tanc-s in gaseous 13 form. The ~resent invention may be a~lied to any 14- situation in which a contrasting IR background i~
a~ailable and against which a gaseous ~olume may be monitored. The invention thereby ~rovidQs remote 17 monitoring which afforas an extremely wide range of 18 a~lications along with inex~en~ive, convenient and fast testing of an infinite number of ~otential sources of gasses or va~ors. Potential a~lications include 21 the monltoring of border cross~ngs for the detection of 22 ~ub~tance~ which must be declared or which may not be 23 legally ~Dorte~, methan~ monitoring in mining 24 o~eration~ an~ the outdoor ~onitoring of combustion ~ro~uct~, to name ~u~t ~ few. The re~dy 26 Dro~r~m~billty of~ the a~Daratus combines the low . 27 ~ro~uct~on co~t of unlformlty with the con~enient WO 93/11424 PCr/US92/104(~t ~12~038 1 modlflcatlon for moet a~llcations. Coet eaving~ and 2 ~imple o~eration enhance dietrlbution ~nd use. The 3 e~eclfic I~ radlometer and method ~rovided ehare theee 4 ad~antagee ~nd aleo re~resent an advancement in eyetem 5 ~erformance. ~rror ~ro~ucin~ eyetem noiee ie reduce~
6 ~n~ uDstable IR backgroun~ ener~y le tolerated~
7 Th e boaiment~ deecribed-above are intended to 8 be taken ln an ilIustrative and not a limiting ~en~e.
g Variou~ modifications and changes may be made to the o above embo~iments by ~ereone skilled in the art without 11 d~artln~ from the sco~e of the preeent invention a~
12 defined in the a~ended claime.
1S energy collected by the ob~ective lens 24 ~asses 16 through a rotating, continuously varying infrared 17 s~ectral band~ass filter 26, a slit 28 and a field lens 18 30. The field lens 30 collects the energy onto an IR
~9 detector 3a. The filter a6 ie rotated at a fixed rate 20 w~th motor 34 and causes the detector 32 to see 21 re~eated scans of infrared wavelengths. In other 22 worde, the functioning of tbe a~aratus descxibed thus 23 far ~rod~ce~ an IR s~ectral ra~iometer.
24 - Thl~ ~R s~ectral radiometer may be conetructed 25 to cover any Dartial bandwidth of the IR s~ectrum which 26 1~ of lntere~t. Thls ~esi~n a~ect ~e~en~e ~rimarily 27 uDon the rotatlng fllter ~6.
''~93/11424 PCT/US92/1~401 21~ 38 l Filter 26 ~s clrcular and allowe the Das~age 2 thQrQthrough of a continuously varying wavelength of IR
3 energy. The wavelength varie~ in accordance with the 4 rotational angle of the filter over a predetermined s fllter bandwi~th. In one embo~lment, the wavelength 6 varies contl~uously from (6~ to (ll.4) ~icrons, bot~
7 lncrea~ing ~D~ ~ecreaslng the ~assed w~velength BO that 8 the (6) to (11.4) ~lcron fllter bandwidth iB scanned a g total of four (4) times in one rotation of the filter.
Bach ~can of the bandwidth may also be thought of as a 11 frame.
12 Th- IR energy ~assed at any ~oint around the 13 filter i8 only a fractional bandwldth of the overall 14 filter bandwidth. In the above example, thi~
fractional ban~width is (0.2) mlcrons.
16 By selection of the filter 26, the filter 17 bandwidth of a detector may be tailored BO that the 18 detection a~aratu~ may be dedicated for the long term ~ monitoring of elther a single va~or or a group of va~or~ having sufficiently ~roximate IR
21 characteristics.
22 The IR energy level that im~inge~ on the 23 ~etector 32 is detecte~ or measured causing the 24 ~etector 32 to ~roduce an out~ut signal which i8 25 ~ amDllfle~ by a ~reampllflQr 36 and an am~lifier 38.
26 The ~ pl~fie~ out~ut BigD~I fro~ am~lifier 38 is then 27 cou~le~ to the ~roceBBor cect~on 2l which may be WO93/1l424 2 1 2 5 n ~ 8 PCT/US92/l0401~-1 constructed either integral with or ~eparate from 2 detector 16.
3 The outDut slgna1 from am~llfier 38, which 4 corre~onds to the IR energy detected iB then cho~ped S or nulled by a null clrcuit 40. Null circuit 40 causes 6-~ the s1gD~1 from am~lifi-r 38;to be ~horted to ground 7~ ~between each b~ndwl~th ~can of filter a 6 . This 8 ~rQventB ~can to can ~ro~agat~on of l/f no~se by g ~roducing a deeD signal null between successive ~cans.
1o In the exam~le de~crlbed abo~e, where the filter 11 bnndw1dth 1~ ~cannea a total of four times durin~ each ; 12 rotatlon of the fllter 26, lt iB Dos~ible to use one or 13 ~ore of the filter bandwidth scans Droduced per 14 rotation and to null the slgnal during the unused scans or between ad~acent scans. It may also be said that 16 the out~ut ~lgnal iB nulled at the same rate that the 17 filter bandwidth is scanned. Nulling the signal just s ~rior to the scan enables a stable starting point for ~19 the out~ut signal, and nulling the signal after the end of the scan reduces the un~redictable res~onse caused 21 by l/f noise. Synchronization of this nulling is ~22 `described below.
2~ Thl~ reduction of l~f nolse Qnables improved 24 ~erformance for the entire detection a~aratus. Where conventional a~roach~s mi~ht UBe a lower scan rate and 6 ~ ~e~r~t- hl~h fr-quency ~odulator to limit the l/f 27 ~oise eff-ct, thls ~ri~tion of the ~resent in~ntion .~093~11424 PCT/US92/~01 21`2S038 g 1 allows a hi~her scan rate, ~roviding more data for more 2 ~ccur~t~ ~i~n~l ~rocess~ng.
3 The re~ultant ~lgnal out of null circuit 40 is . 4 buffered by a buffer am~li'fier 42 and filtered by a low ~ass filter 44. The flltered analog signal i8 Bamplea 6 by a sa~le an~ hold circu~t 46 and con~erted to a 7 ~igital for at by an analog to digital (A/D) con~erter 48. A d'lgltal slgnal ~rocessor 50 ~rocQss.e~ the g digitally formatted data using an algorithm described 1o below'and out~uts the re~ults to a dis~lay 52.
11 : The sam~le and hold circuit 46 and null clrcuit 12 40 are synchronized to the circular filter 26 by means 13 of a ~hase-locked loo~ 54. Th~ synchronization 14 enablQs effectlve nulling and identlfica~ion, for ~rocessing ~ur~o~Qs of the filter ~o~ition and 16 therefore the IR wavelength of each sam~le taken. Any 17 other suitable means may alternati~ely be used for 18 synchronizing the nulling and/or the sampling to the ~9 wavelQngth ~osltion of filter 26. An example, in the 20 form of a reflecting detector 55, i~ o~tionally shown.
21 Such a detector may be made to re~pona either directly 22 to thQ filter or otherwise to the metor 24 drive shaft.
23 The analo~ d~ta iB o~er ~am~lea, by sam~le and 24 hold circuit 46, at a rate which iB nomlnally ten time~
the rate of cha~e of filter 26. In the ex~mple gi~en, 26 the fllter b~n~w~th extend~ from (6.0) to (11.4) 27 ~icro~s for ~ total of (5.4) ~icrons, and the .
WO 93/11424 2 1 2 ~ 0 3 8 PCI/IJS92/104(~
1 fractional bandwidth Dassed by filter 26 at any ~oint - 2 in ti~e is (0.2) microns. The sam~ling is controlled 3 to Droduce a sample every (0.02) micron of wavelength 4 change and therefore produces a total of (270) sam~les 5- Der Bcan of-the bandwldth. It is these (270) samples 6 Droduce~ by e~ery scan of the bandwldth that are 7 digltl~Qd-and u~ed by the ~rocessor 50.
8 - Ths system thus far descrlbed re~Qatealy scans~
g the IR sDectrum of interQst to enable detection of lo ~dlfferences in the mQasured IR enQrgy at selected 11 wa~elengths, caused by the ~resence of ~arious 12 substancQ ~Dors contra~ted against the backgrouna.
13 This aetection of differencQs i8 performed with the `14 . s~gnal proces~ing dQscribQd below.
proceBsor 50 processes the digitized samples in 16 accordance wlth the flow chart 60 of Fig. 3.
17 Generally, Filter Calculation ste~ 62 uses the ~ample~
18 to calculate ~54) separate filter ~alues evenly spaced 9 acros~ the scanned filter bandwidth. The~e filter 20 ~alueB are taken by the Filter Correction step 64 and 21 i~di~ldually corrected for the tran~fer function of the 22 detector 16. The ~usted filter values are then 23 ad~ustQ~ by subtraction of an e~tlmated background 24 te~er~ture by the Back~round Subtraction ste~ 66.
Wlth the background tem~erature ~ubtracted, the filter 26 ~1UeB ~re then lnte~r~te~ for ~ multl~licity of filter 27 ban~ldth Bc~nB by Inte~ration ~tQ~ 68 for the purpose .
~093/11424 . PCT/US92/10401 l of remov~ng ~olee. Onc~ data for a sufflcient number 2 of ecans iB accumulated, the lntegrated flltQr value~
3 are thon testQd for the known IR s~ectral 4 charactQrietics of the com~ounds of interest by Detectlon ste~ 70. The indlvidual ete~s of flow chart 6 60 are ~iBCUBBe~ bolow in greater detail.
7 For oach rotatlon of filter 26, Filter 8- Calculation ete~ 62 ta~e the (270) ~amples and forms 9 (54) overla~ing s~ectral band~ass filters that are the averagQ of ten sam~lQs and are seDarated by five ll samDlo~. The over~amDlin~ rate of l0 le nom~nal, and 12 generally the number of samplee may be any ~uitable 13 multl~le of the filter bandwldth (5.4j divided by the 14 fractlonal ~aes bandwidth (0.2) for pur~oses of computatlonal eaee. Fl~ 4 ehows an exam~le of sample 16 grou~lng which may be used to calculate a set of narrow 17 band filter value~. Each of the ~oints in the left 18 hand column re~resents a sam~le value from A/D
ls converter 48. Bach of the actual wavelength values a~pearlng ~n the rlght hand column re~resents the 21 center wavelength of a narrow band fllter value. The 22 wavelength of each of t,he eam~le~ ln the left hand 23 column ~ay be read or lnter~olated from the values 24 a~earing ln the rlght han~ column.
~ch of the narrow band fllter values is 26 calculate~ by sum~lng (or averaglng) the ten (l0) 27 ~eare~t ~a~le ~alue~. This means ehat the (6.l) WO g3/11424 2 1 2 ~ 0 3 8 PCT/US92/1040~
1 .micron filter value is calculated by summ~ng the ~alues 2 for samples ~6.0) through (6.2); the ~6.a) filter value 3 18 summed from samples ~6.1) through (6.3) t and 80 on.
Thl~ method ~roduces (54) narrow band filter value~ over the bandwldth of fllter ~6. ~ach narrow - - 6 - ban~ fllter le ~O.a) ~lcrons wlde, which corres~onds to . 7 the ban~ass characeeristics of filter 26, and each 8 narrow band filter is ~e~aratea from ad~acent filters g by (0.1) microns. Because of this relationship, the lo s~m~les included in the com~utation of:each filter 11 value reDresent ~otentlal infrared energy passed by the :: 12 fllt!r with the wa-elength of the respective filter - 13 value.
14 . The ~ilter Correction s~ep 62 next corrects each ~ 15 calculate~ filter value for the system transfer : 16 function at each.wavelength by multi~lying each filter }7 value by a unique coefficient determlned by system 18 calibration.
The Background Subtraction step 66 next uses the filter values to calculate the level of an estimated or 21 equlvalent background temperature across the filter i- 22 bandwidth and subtracts the calculated tem~erature 23 level from each of the fllter values. The background 24 temperature may be calculated by any sultable method.
I~ one ~iethod, ~clear~ fllter ~alues are determined 26 e1ther by ~ust loo~l~g at ~aveleDi~ths not affected by 27 th~ co~pou~d of i~tQr~st or by otherwlse examlning the 212~038 l filter values ~rom thQse ~clear~ filter values, a 2 tem~erature ~alue for all filters i~ e~timated by 3 minimizlng a mean square error criteria to find an 4 equlvalent blac~body tem~eraturQ whlch bQst fits the measur-~ ~alues in the ~clear filters The estimated 6 te~perature value in all filters is subtractQd from the 7 measure~ ~ignal in all filters to normalize the data 8 This normallzation, 1ncluding estimation, i~
9 ~erformed e~ery frame or scan of the filter bandwidth and iB the basis for det-cting the substance va~ors 20 11 against the contrastlng back~round 14 The equivalent 12 blac~bo~y tem~erature, whlch iB detQrminQd, i~ the 13 bac~ground t-m~erature agalnst which the vapors 20 are 14 contrast~ In the instance where cold va~or~ are lS d~tected a~alnst a warm background, subtracting the 16 background tem~erature result~ in a negat1ve number at 17 the wavQlengths of interest Other negative numbers 18 are al~o generated due to noise in the measurements The resulting values, both negative and ~ositive, are 20 then u~ed by the Integration ste~ 68 21 The Integration ~te~ 68 accumulates data for 22 successive frame~ or full filter bandwidth scans This 23 may be done for elther a fixea number of scans or in a4 res~onse to one or more accumulated filter value~
25 NoiBe s1gnals ln the mea~urement~ are eliminated by 26 thls l~tegratlon or ~ccu~ulat~on If there i~ an IR
27 ~lgn~l, oth-r th~n noi~e, ~resent at ~ny wavelength W093/11424 2 1 2 5 0 3 8 PCT/USs2/10401-1 wlthin the ~can bandwidth, the signal will integrate to 2 its final ~alu~.
3 The lnte~r~ted reeidual filter ~lues are then ~a~sed to Detection ste~ 70. Detection of com~ounas of s lntere~t ~y be a-cco~Dlished by any sultable means. In 6 o~e e_ns, a ~lcro~rocessor -ay be used to logically an~ ~ath -tlca-lly ~am~ne the fllter valueB~ co~aring 8 them a-~a-lnst known ~foot~rints~ or IR s~ectral g characterlstlcs of the com~ound of interest. This a roach afford~ ~rogr~aabillty of the system for the ll det-ctlon of one or more of a v~riety of substances ~12 thereby reducing ada~tatlon costs for each different 13 a~lication. ThiB ~rogrammability even extends to 14 BubBtance concentration and tem~erature. In an alternatlve detectlon a~roach, a neural network 16 de~ice/~roceesor can be u~ed to make the 17 ClaB8if ication/detection decision. Such an approach 18 would be used for detecting a large variety of 19 ~ub~tances.
~o Again thi~ detection ~roce~B iB intended to find 21 differences between the IR ener~y measured at 2 wa~elen~ths ha~lng known e~ectral characteristics for 23 the euSetancee of intereet. These detected differences 24 may be elther ~oeltive or negative de~ending u~on the 2s relatl~e te~er~ture differences between the background .
; 26 an~ the ~a~or~ to bQ detected.
; ~ . . .
`VO93/11424 PCT/US92/1~01 1 After detection, any deslr~ble information may 2 be ~a~sed to th~ di~lay 52. ~his might include the 3 substa~ce name, concentration, tem~erature, etc. or .4 somethlng as ~lm~le as an ln~lcator ~ignal that a ~eclflc sub~tance 18 ~re~ent or ha- exceeded a 6 ~eclflc concentratlon level. Thls data can also be ` 7 ~ trans~ltted for dl~.tant monltorlng, collect$on, 8 analysls,`etc.
9 CONCL~SION
The ~re~ent invention ~ro~ides a unique 11 a~uratus an~ mothod which iB readily ada~table for tho 12 d-tection of a wide ~arlety of ~ub~tanc-s in gaseous 13 form. The ~resent invention may be a~lied to any 14- situation in which a contrasting IR background i~
a~ailable and against which a gaseous ~olume may be monitored. The invention thereby ~rovidQs remote 17 monitoring which afforas an extremely wide range of 18 a~lications along with inex~en~ive, convenient and fast testing of an infinite number of ~otential sources of gasses or va~ors. Potential a~lications include 21 the monltoring of border cross~ngs for the detection of 22 ~ub~tance~ which must be declared or which may not be 23 legally ~Dorte~, methan~ monitoring in mining 24 o~eration~ an~ the outdoor ~onitoring of combustion ~ro~uct~, to name ~u~t ~ few. The re~dy 26 Dro~r~m~billty of~ the a~Daratus combines the low . 27 ~ro~uct~on co~t of unlformlty with the con~enient WO 93/11424 PCr/US92/104(~t ~12~038 1 modlflcatlon for moet a~llcations. Coet eaving~ and 2 ~imple o~eration enhance dietrlbution ~nd use. The 3 e~eclfic I~ radlometer and method ~rovided ehare theee 4 ad~antagee ~nd aleo re~resent an advancement in eyetem 5 ~erformance. ~rror ~ro~ucin~ eyetem noiee ie reduce~
6 ~n~ uDstable IR backgroun~ ener~y le tolerated~
7 Th e boaiment~ deecribed-above are intended to 8 be taken ln an ilIustrative and not a limiting ~en~e.
g Variou~ modifications and changes may be made to the o above embo~iments by ~ereone skilled in the art without 11 d~artln~ from the sco~e of the preeent invention a~
12 defined in the a~ended claime.
Claims (20)
1. An infrared radiometer, comprising:
means for collecting infrared energy;
means for filtering the collected energy over a filter bandwidth including filter means for bandpassing only a fractional bandwidth of the filter bandwidth at any one time and means for repeatedly scanning the filter bandwidth with the passed fractional bandwidth;
means for measuring infrared energy passed by the filter means and for producing an output signal in response thereto; and means for repeatedly nulling the output signal in relation to the repeated scanning of the filter bandwidth.
means for collecting infrared energy;
means for filtering the collected energy over a filter bandwidth including filter means for bandpassing only a fractional bandwidth of the filter bandwidth at any one time and means for repeatedly scanning the filter bandwidth with the passed fractional bandwidth;
means for measuring infrared energy passed by the filter means and for producing an output signal in response thereto; and means for repeatedly nulling the output signal in relation to the repeated scanning of the filter bandwidth.
2. The infrared radiometer of claim 1, further comprising means for synchronizing the means for repeatedly scanning with the means for repeatedly nulling for causing the output signal to be nulled between repeated scans of the filter bandwidth.
3. The infrared radiometer of claim 1, further comprising means for synchronizing the means for repeatedly scanning with the means for repeatedly nulling for causing the output signal to be nulled and the filter bandwidth to be scanned at an identical rate.
4. The infrared radiometer of claim 1, wherein the filter means has a bandpass wavelength which varies over the filter bandwidth and further wherein the fractional bandwidth of the filter means is substantially constant over the filter bandwidth.
5. The infrared radiometer of claim 4, wherein the bandpass wavelength of the filter means varies in accordance with position on the filter means.
6. The infrared radiometer of claim 5, wherein the filter means is circular having a bandpass wavelength which varies with rotational position of the filter means and further wherein the means for filtering further includes means for rotating the filter means in relation to the means for nulling the output signal.
7. The infrared radiometer of claim 4, further comprising means for sampling the output signal a predetermined number of times for each scan of the filter bandwidth which predetermined number is a multiple of the filter bandwidth divided by the fractional bandwidth.
8. The infrared radiometer of claim 7, further comprising computational means for summing output signal samples from the means for sampling into a multiplicity of filter values each representing a separate wavelength within the filter bandwidth.
9. The infrared radiometer of claim 8, wherein each filter value has a bandwidth substantially equal to the fractional bandwidth of the filter means.
10. The infrared radiometer of claim 9, wherein the computational means includes means for grouping samples for summing for each filter valve around the separate wavelength represented by the respective filter value.
11. The infrared radiometer of claim 10, wherein the means for grouping is adapted to include in each filter value those samples representing potential infrared energy passed by the filter means with the wavelength of the respective filter value.
12. A method for measuring infrared energy, comprising the steps of:
collecting infrared energy;
filtering the collected energy over a filter bandwidth including bandpass filtering only a fractional bandwidth of the filter bandwidth at any one time and repeatedly scanning the filter bandwidth with the passed fractional bandwidth;
measuring infrared energy passed by the bandpass filtering producing an output signal in response thereto; and repeatedly nulling the output signal in relation to the repeated scanning of the filter bandwidth.
collecting infrared energy;
filtering the collected energy over a filter bandwidth including bandpass filtering only a fractional bandwidth of the filter bandwidth at any one time and repeatedly scanning the filter bandwidth with the passed fractional bandwidth;
measuring infrared energy passed by the bandpass filtering producing an output signal in response thereto; and repeatedly nulling the output signal in relation to the repeated scanning of the filter bandwidth.
13. The method of claim 12, further comprising the step of synchronizing the scanning of the filter bandwidth with the repeated nulling of the output signal for causing the output signal to be nulled between repeated scans of the filter bandwidth.
14. The method of claim 12, wherein the bandpass filtering has a bandpass wavelength which varies over the filter bandwidth and further wherein the fractional bandwidth of the bandpass filtering is substantially constant over the filter bandwidth.
15. The method of claim 14, wherein the bandpass filtering is performed with a circular filter having a bandpass wavelength which varies with rotational position of the filter and further wherein the step of bandpass filtering further includes rotating the filter in relation to the means for nulling the output signal.
16. The method of claim 14, further comprising sampling the output signal a predetermined number of times for each scan of the filter bandwidth which predetermined number is a multiple of the filter bandwidth divided by the fractional bandwidth.
17. The method of claim 16, further comprising summing output signal samples from the sampling step into a multiplicity of filter values each representing a separate wavelength within the filter bandwidth.
18. The method of claim 17, wherein each filter value has a bandwidth substantially equal to the fractional bandwidth used for the bandpass filtering.
19. The method of claim 18, wherein the step of summing includes grouping samples for summing for each filter value around the separate wavelength represented by the respective filter value.
20. The method of claim 19, wherein the step of grouping includes into each filter value those samples representing potential infrared energy passed by the filter means with the wavelength of the respective filter value.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US801,983 | 1985-11-26 | ||
| US80198391A | 1991-12-03 | 1991-12-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2125038A1 true CA2125038A1 (en) | 1993-06-10 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2125038 Abandoned CA2125038A1 (en) | 1991-12-03 | 1992-12-03 | Infrared chemical vapor detector and method |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0615613A1 (en) |
| CA (1) | CA2125038A1 (en) |
| WO (1) | WO1993011424A1 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20040259234A1 (en) * | 2003-06-06 | 2004-12-23 | Northrop Grumman Corporation | Detection and analysis of chemical and biological materials |
| US7023545B2 (en) | 2003-06-12 | 2006-04-04 | Textron Systems Corporation | Chemical identification by flash spectroscopy |
| US20050056785A1 (en) * | 2003-09-16 | 2005-03-17 | Northrop Grumman Corporation | Detection and analysis of chemical and biological materials by passive emission of terahertz wave against a cold background target |
| GB2447925B (en) * | 2007-03-28 | 2010-04-07 | Internat Moisture Analysers Ltd | Fluid detector |
| US9471969B2 (en) | 2014-06-23 | 2016-10-18 | Exxonmobil Upstream Research Company | Methods for differential image quality enhancement for a multiple detector system, systems and use thereof |
| EP3158321A1 (en) | 2014-06-23 | 2017-04-26 | Exxonmobil Upstream Research Company | Systems for detecting a chemical species and use thereof |
| US9501827B2 (en) | 2014-06-23 | 2016-11-22 | Exxonmobil Upstream Research Company | Methods and systems for detecting a chemical species |
| US9442011B2 (en) | 2014-06-23 | 2016-09-13 | Exxonmobil Upstream Research Company | Methods for calibrating a multiple detector system |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3409772A (en) * | 1965-09-09 | 1968-11-05 | Barnes Eng Co | Vertical air temperature gradient determination |
| JPS5014141B1 (en) * | 1969-05-28 | 1975-05-26 | ||
| US3843258A (en) * | 1971-08-25 | 1974-10-22 | Bendix Corp | Dual beam absorption type optical spectrometer |
| US4427306A (en) * | 1980-08-04 | 1984-01-24 | University Patents, Inc. | Radiometer apparatus for air disturbance detection |
| US4725733A (en) * | 1983-07-18 | 1988-02-16 | The United States Of America As Represented By The Secretary Of The Navy | Apparatus and method for remotely detecting the presence of chemical warfare nerve agents in an air-released thermal cloud |
| US4682291A (en) * | 1984-10-26 | 1987-07-21 | Elscint Ltd. | Noise artifacts reduction |
| JP3162708B2 (en) * | 1990-04-09 | 2001-05-08 | コモンウェルス・サイエンティフィック・アンド・インダストリアル・リサーチ・オーガニゼイション | Detection system for use in airplanes |
| US5075550A (en) * | 1990-07-12 | 1991-12-24 | Amoco Corporation | Infrared detector for hydrogen fluoride gas |
-
1992
- 1992-12-03 CA CA 2125038 patent/CA2125038A1/en not_active Abandoned
- 1992-12-03 WO PCT/US1992/010401 patent/WO1993011424A1/en not_active Application Discontinuation
- 1992-12-03 EP EP93900783A patent/EP0615613A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP0615613A4 (en) | 1994-07-21 |
| EP0615613A1 (en) | 1994-09-21 |
| WO1993011424A1 (en) | 1993-06-10 |
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