GB2129639A - Detecting vehicles - Google Patents
Detecting vehicles Download PDFInfo
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- GB2129639A GB2129639A GB07936321A GB7936321A GB2129639A GB 2129639 A GB2129639 A GB 2129639A GB 07936321 A GB07936321 A GB 07936321A GB 7936321 A GB7936321 A GB 7936321A GB 2129639 A GB2129639 A GB 2129639A
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- 238000001514 detection method Methods 0.000 claims abstract description 29
- 230000003111 delayed effect Effects 0.000 claims abstract description 13
- 238000000862 absorption spectrum Methods 0.000 claims description 17
- 230000003595 spectral effect Effects 0.000 claims description 12
- 230000001419 dependent effect Effects 0.000 claims description 11
- 239000007789 gas Substances 0.000 claims description 11
- 238000010521 absorption reaction Methods 0.000 claims description 6
- 238000004458 analytical method Methods 0.000 claims description 5
- 238000007620 mathematical function Methods 0.000 claims description 4
- 230000003466 anti-cipated effect Effects 0.000 claims description 3
- 230000007257 malfunction Effects 0.000 claims description 3
- 230000004048 modification Effects 0.000 claims 1
- 238000012986 modification Methods 0.000 claims 1
- 230000005855 radiation Effects 0.000 claims 1
- 0 **1CCCC1 Chemical compound **1CCCC1 0.000 description 6
- 230000003287 optical effect Effects 0.000 description 4
- 230000005693 optoelectronics Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 2
- 239000003350 kerosene Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 230000003068 static effect Effects 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
-
- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/04—Detecting movement of traffic to be counted or controlled using optical or ultrasonic detectors
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- Physics & Mathematics (AREA)
- General 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)
- Immunology (AREA)
- Pathology (AREA)
- Photometry And Measurement Of Optical Pulse Characteristics (AREA)
Abstract
Apparatus for the detection of vehicles by infra-red detection of their exhaust comprises an infra-red detector (1) and processing means 6-18 for distinguishing a pulse (fig. 6a) in the detector output due to the presence of a vehicle from the varying background level. In one embodiment a low pass filter 8 provides a signal representing the background variations. This background signal is then boosted in level (10) and combined with a delayed version (6) of the detector output to provide a reference signal 13. The detector output will be greater than the reference only when a pulse occurs, the reference being such that the higher the background level on which the pulse is superimposed, the lower the pulse amplitude needs to be for it to exceed the reference. Another embodiment (fig. 8, not shown) multiplies the detector output by a function of the background level and then compares with a fixed threshold. <IMAGE>
Description
SPECIFICATION
Infra-red absorption detection of vehicles
This invention relates generally to apparatus for infra-red absorption detection of vehicles ofwhich the exhaust gases have an infra-red absorption spectrum which contrasts instantaneouslywith thatofthe ambient medium.
It is known that heavy armoured vehicles can be detected, by spectrometer, from the emissions of gas and, by opto-electronic sensors, from the presence of hot bodies.
Emissions of gas vertically of these vehicles are the centre on the energy plane of a source of electromagnetic rays which are situated in the infrared spectrum and ofwhich the luminance and energy intensity are essentially determined bythetype of fuel, by the power of the engine and by the speed of travel.
The gases concentrated near the engine exhaust outlet and then progressively diluted in the atmosphere emit rays of which the spatial energy distribution is characteristc.
The energy emitted is distributed in spectral bands or lines of which the spectral positions are characteristic ofthe constituent gases. The emission factor is of the order of 1 at the centre of these lines or bands. For example, the combustion of a heavy hydrocarbon in an excess of air gives 95% of CO2 and 4% of CO and the principle energy line of the CO2 is situated atthe centre of a spectral band of which the central wavelength is in the neighbourhood of 4.2 CL.
The intensity of these bands increases with temperature which varies according to the concentration of the gases.
Spectrometers used for detecting or analysing the gases are heavy and fragile laboratory apparatus which are difficult to handle. In addition, this detection is essentially locally confined and cannot be carried out over a distance.
According to the invention there is provided apparatus for infra-red absorption detection of vehicles, comprising a spectral filter detector arranged to provide infra-red absorption spectrum detection within a zone covered by the detector, and processing means responsive to the detector and arranged to provide an analysis ofafirstvalue, dependent upon the detected infra-red absorption spectrum within said zone, relative to a threshold value, the operation ofthe processing means being such that the analysis is modified in accordance with a third value dependent upon the instantaneous contrast between the infra-red absorption spectrum of any detected vehicle and that of the ambient medium so as to provide an indication in the presence of a vehicle within said zone.
Suitably, the processing means comprises a two input comparator and means, in series between said detector and said comparator, arranged to modify a signal, derived in use from said detector in accordance with the detected infra-red absorption spectrum, and/ora reference signal, represented by said refer encevalue, in dependence upon a correction signal generated in accordance with the instantaneous contrast between the infra-red absorption spectrum of any detected vehicle and thatofthe ambient medium, the respective inputs of the comparator being responsive to said reference signal and said detector output signal as modified by the said correction signal.The following different arrangements are then possible:- (1) the detector signal, reference signal and the correction signal are respective voltages and the means in series between said detector and said comparator is arranged to add the correction voltage to the reference voltage.The correction voltage adding means may comprise a delay circuit for the detector voltage arranged in parallel with
- a low-passfilterwhose frequency response characteristic is intended to eliminate pulses of the kind anticipated due to the presence of a vehicle, the low passfilter being in series with
- a variable multiplication circuit arranged to produce an outputvoltage related by a predetermined mathematical function to the input voltage thereto, the correction voltage adding means further comprising
- an adder arranged to establish the algebraic sum of the delayed voltage and the multiplied voltage to form the reference voltage, modified bythe addition thereto of said correction voltage, applied to the second input of the comparator.
The detection apparatus mayfurthercomprise means arranged to impart movement to the detector and means arranged to detect movement ofthe detector, said adder being additionally responsive to the movement detecting means so astocausethe processing means to produce the said indication in the event of a change in movement of the detector indicative of malfunction.
(2) the detector signal, the reference signal and the correction signal are respective voltages, and the means in series between said detector and said comparator is arranged to modify the detector voltage in accordance with the correction voltage. Then, the detector voltage modifying means may comprise
- a restoration circuit arranged to produce an output voltage related by a restoration law to the input voltage thereto
- an analog multiplier arranged to multiply the output voltage ofthe restoration circuit with the detector output voltage, said multiplier being in series with
- an a.c. amplifier arranged to recentrethe output voltage ofthe multiplier around zero, and to supply the recentred voltage to one ofthe inputs ofthe comparator of which the second input is arranged to receive the reference voltage.
(3) the arrangement in accordance with (2) can be modified such that the detection apparatus further comprises means arranged to add the amplified multiplier output voltage to the threshold voltage and to apply the resulting voltage to the appropriate input ofthe comparator. Suitably, the means for adding the multiplier outputvoltage to the reference voltage comprises
- a delaying circuit arranged to receive the amplified multiplier output voltage and
- a two-input adder of which one ofthe inputs is arranged to receive the reference voltage and the otherthe delayed voltage from the delaying circuit, the adder being arranged to deliverthe resulting voltage to the appropriate input of the comparator.
In all cases, the spectral range of the detector can be chosen to correspond to that of CO2.
For a better understanding ofthe invention, and to show howthe same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:
Figure 1 shows, by way of example, the spectrum of the emission curve of a kerosene flame and the optical characteristics of an optical filter used in the detection of vehicles, the wavelengths being recorded on the abscissa and the relative amplitude on the ordinate, Figure 2 showsthe appearance of signalsto be processed at the output of an infra-red detector
a) without a signal characteristic of a target,
b) with a target characteristic signal to be detected, Figure3 is a blockdiagramofoneformofapparatus used for processing the signal in accordance with a first mode of detection,
Figures 4a and 4b show the response of a filter circuit, included in the detection apparatus, according to the Bessel function,
Figures 5a and 5b show the mode of operation of a
variable multiplication circuit, included in the detec
tion apparatus, indexed to the amplitude of an input
voltage,
Figures 6a to 6fshowthe appearance of signals at
the characteristic points of the detection apparatus,
Figure 7 shows one possible circuit arrangementfor
the detection apparatus operating in accordance with
a first mode of detection,
Figure 8 is a block diagram ofanotherform of
apparatus used for processing the detected signal in
accordance with a second mode of operation, Figure 9 is a chronogram ofthe voltages at the characteristic points ofthe detection apparatus having the second mode of operation,
Figure 10 illustrates purely by way of example the
restoration law which determines the gain of an
analog multiplication circuit used in accordance with the second mode of operation, Figure 11 shows shows the showstheappearanceofthevalueofthe amplification factor of the analog multiplication circuit
used in accordance with the second mode of opera
tion,
Figure 12shows one example of circuit arrange
ment which will operate according to the second
mode of operation, and
Figure 13 is a block diagram of one form of detection
apparatus operating in accordancewith a third mode
of operation.
The first mode of operation is as follows (see Figure
3): the entry aperture of an infra-red detector 1 is
provided with a spectral filter 2 having an optical
response characteristictypically as indicated in Figure 1 (dotted characteristic) relative to the spectrum (continuous line) of a kerosene flame. The detector delivers an electrical signal 3 processed in known manner by a d.c. amplifier4which delivers an output signal at 5 (Figure 6a). The circuit 6 exhibits the characteristic of having a constant propagation time for a signal within an adapted frequency band. This property is better known as one of the properties of the BESSELfunction.
Thus, the characteristic pulse to be processed, which has a form comparable with a triangularwave equal in width to T (ms), will issue from this circuit at 7 (Figure 6b) with a delay equal to T2 (ms) for example.
This is also illustrated in Figures 4a and 4b. The circuit 8 is a low-passfilterwhich, through the choice of its cut-offfrequency, delivers at 9 a signal from which the pulse to be detected is exluded. This mode of operation is illustrated in Figure 6c.
The circuit 10 is a linearor non-linearcircuitwhich, at 11 (Figure 6d), delivers a voltage Vs obeying a mathematical law selected in dependence upon the input voltage Ve present at 9. Thus, Vs = f (t) x Ve, wheref (t) is a mathematical function: linear or logarithmic or exponential, etc. The mode of operation is also illustrated in Figures 5a and Sb.
The circuit 12 delivers at 13 (Figure 6e) the algebraic sum ofthe voltages present at its inputs 7,11,14: it is an adder.
The signal present at 14 comes from the circuit 15 which delivers a voltage indicative of the correct physical operation (for example rotation) of an opto-electronic detection system. When the infra-red detector is mounted so asto scan for vehicles, the opto-electronic detection system can be static and servetomonitorthemovement(e.g. rotating scan) of the infra-red detector, thereby delivering a voltage only so long asthedetectorcontinuesto move.
The comparator 16 compares the signals 5 and 13 in known manner and, at 17, delivers an "all or nothing" signal indicative ofthe presence of a vehicle which lasts for as long as the signal 5 remains above the signal 13.
The circuit 18 power-amplifiesthesignal 17 and, at 19 (Figure 61), delivers a signal capable of controlling one or more display, warning orsimilarsub-assemblies.
The detailed circuitry of one embodiment operating in accordance with the first mode is shown in Figure 7.
The second mode of operation (see Figure 8) is as follows:
The detector 1 delivers at2 a positive or negative pseudo-continuous voltage upon which the significant pulse to be processed will be superposed in the presence of a vehicle to be detected. These signals are amplified by the d.c. amplifier 3. From the signal presentat4,the circuit5 produces at 6 a proportional signal according to the restoration lawadopted [linear (Figure 10), exponential, polynominal, homographic . .
.].
The circuit7 is known among certain experts as a "monolithic multiplier". Byway of example, Figure 11 shows the variation in the gain ofthe circuit7 as a function ofthe input signal restored at 6. Accordingly, the signal 8 is amplified by an a.c. amplifier 9 of which the pass band is adapted acco rding to th e sig nal-to- noise ratio and the duration ofthecharacteristic pulses. An a.c. voltage centred on the electrical "0" is
recovered at 10. Thus, irrespective of its amplitude,
the initial d.c. signal will be developed at 10 very close
to the electrical "0".
By contrast, when a pulse is superimposed at 2 on the "basesignal", it will be amplified proportionally to
the contiuous level at which it is situated, see Figure 9.
Avoltageoffixed sign is applied to a comparator 12 at 11. Thus, aa all.or-nothing pulse is recovered at 13, acting on a power interface 14 each time the voltage
10 is above the voltage 11.
The detailedcf:rcuitry of an embodiment operating in accordance with: the second mode is shown in
Figure 12.
The third modeldoperation (see Figure 13) is largely identical wiir!thatofthesecond solution. The difference lies in the.factthat between the fixed threshold voltage and'the second input ofthe compa rator 12, there is an adder 17 which also receives the voltage 10 passing through a delay circuit 15 fulfilling the Bessel function and having a constant propagation timeequal toT/2for a signal Tforanadapted frequency band.
The reference voltage applied to thecomparator 12 isthus the sum of the fixed threshold voltage V and the delayed voltage 10.
Oneparticular dynamic mode of operation ofthe apparatus according to the first of the three examples will now be described by way of example. The detector is mounted in an opto-electronicassembly and a rotating movement is imparted. Thus, the optical field of the opto-electronic assembly periodi cally scans an area ofterrain of which the depth depends on the natural relief.
Therearethree cases to be considered forthe treatment ofthe collected signal:
- withoutatarget, - withatarget, - without a target and with a failure attributable to the mechanical rotation mechanism.
In the first case, the signal produced by the detector 2 is amplified and then appiedat5tothecomparator 16 where it is compared with a reference voltage 13 produced bythe cirnuits6-,8, ,10; 15.
Thus, taking the particular functions of these circuits into account, itfollowsthatthevoltage 13 will be (relativeto the signal appliedat5tothe comparator 16)
- delayed by thevalue ofthe propagation time imposed by the circuit6;
- higher in amplitude by avaiue defined by the mathematical law ofthe circuit 10.
Thus, a slightly higher voltage is recovered at 13 which exactlyfollowsthevoltage 15, but with a delay equal to halfthe voltage ofthe pulse to be processed.
The difference between the two voltages is weighted bythevalue ofthe d.c. voltage of 5 indicative of the possiblities of infra-red detection, taking the natural surrounding elements into account. Thus, the signal 5 can never exceed the voltage 13.
If a target is present in the field of the detector, the chronological sequence is the same as before, except that, when the pulse arrives at 5, its amplitude is such that it becomes higherthan 13 which will only begin to increase T ms later.
2 Thus, the excess has occurred and an "all-ornothing" signal appears at 17,acting on the power interface 18.
In the third case, it will beassumedforexamplethat the opto-electrnnicassemblystopsturningforthe reasonthatthe system responsible for rotating the detector is faulty. The chronological sequence is the same as in the first case, except that the circuit 15 delivers a permanent d.c. voltage at 14so that, atthe output ofthe adder circuit 12, the reference voltage 13 immediately becomes greaterthan Sand thus triggers offthe circuit 16 and, at the same time, a specific alert reflecting failure of rotation.
Summing up, it will be appreciated thatthe principle of operation is as follows: when the detected signal corresponding to the presence of a vehicle is characterised by a marked contrast, i.e. when the signal corresponding to the infra-red absorption spectrum of the ambient medium is weak, or even when the target gives off energy, the reference voltage -- under the law of correction dependent on the contrast- is fairly high in proportion to the detected signal so that it is only the high-contrast signal which is detected.
In the opposite case, however, the reference voltage is fairly weak in proportion to the detected signal so that the characteristic pulse signal is more easily detected.
Thevarious forms of detection apparatus disclosed herein are essentially intended forsurveillance.
It should be noted thatthe detection apparatus is passive, i.e. discrete, difficult to decoy, can operate under a wide range of climatic conditions, detect a visible, partly concealed target with a decreasing or latent degree of probabilityand,finally, can detect a mobile or immobile target.
Finally, the spectral range ofthe infra-red detector can suitably correspond to that of CO2.
Claims (10)
1. Apparatusforinfra-red absorption detection of vehicles, comprising a spectral filterdetector arrangedto provide infra-red absorption spectrum detectionwithin a zone covered by the detector, and processing means responsivetothe detector and arranged'to provide an analysis of a first value, dependent upon the detected infra-red absorption spectrum within said zone, relative to a threshold value, the operation ofthe processing means being such thatthe analysis is modified in accordance with a third value dependent upon the instantaneous contrast between the infra-red absorption spectrum of any detected vehicle and that ofthe ambient medium so as to provide an indication in the presence of a vehicle within said zone.
2. Apparatus according to claim 1, wherein the processing means comprises a two input comparator and means in series between said-detectorand said comparator, arranged to modify a signal, derived in use from said detector in accordance with the detected infra-red absorption spectrum, and/or a reference signal, represented by said reference value, in de
pendence upon a correction signal generated in accordance with the instantaneous contrast between the infra-red absorption spectrum of any detected vehicle and that of the ambient medium,the respective inputs of the comparator being responsiveto said reference signal and said detector output signal as modified bythe said correction signal.
3. Apparatus as claimed in claim 2, wherein the detector signal, the reference signal and the correction signal are respective voltages and the means in series between said detector and said comparator is arranged to add the correction voltage to the reference voltage.
4. Apparatus as claimed in claim 3, wherein the correction voltage adding means comprises: - a delay circuitforthe detector voltage arranged in parallel with
- a low-pass filterwhose frequency response characteristic is intended to eliminate pulses of the kind anticipated due to the presence of a vehicle, the low pass filter being in series with
- a variable multiplication circuit arranged to produce an outputvotage related by a predetermined mathematical function to the input voltage thereto, the correction voltage adding means further comprising
- an adder arranged to establish the algebraic sum of the delayed voltage and the multiplied voltage to form the reference voltage, modified by the addition thereto of said correction voltage, applied to the second input of the comparator.
5. Apparatus as claimed in claim 4,further com- prising means arranged to impart movement to the detector and means arranged to detect movement of the detector, said adder being additionally responsive to the movement detecting meanssoastocausethe processing meansto producethesaid indication in the event of a change in movementofthedetector indicative of malfunction.
6. Apparatus as claimed in claim 2, wherein the
detector signal, the reference signal and the correction
signal are respective voltages, and the means in series
between said detector and said comparator is
arranged to modifythe detectorvoltage in accordance with the correction voltage.
7. Apparatus as claimed in claim 6, wherein the detectorvoltage modifying means comprises: - a restoration circuit arranged to produce an output voltage related by a restoration law to the input voltage thereto
- an analog multiplier arranged to multiply the output voltage ofthe restoration circuit with the detectoroutputvoltage, said multiplier being in series with
- an a.c. amplifier arranged to recentre the output voltage ofthe multiplier around zero, and to supply the recentred voltage to one ofthe inputs ofthe comparator of which the second input is arranged to receive the reference voltage.
8. Apparatus as claimed in claim 6 or7, further comprising means arranged to add the amplified multiplier output voltage to the threshold voltage and to applythe resulting voltage to the appropriate input ofthe comparator.
9. Apparatus as claimed in claim 8, wherein the means for adding the multiplier output voltage to the reference voltage comprises:
- a delaying circuit arranged to receive the amplified multiplier output voltage and
- a two-input adder of which one of the inputs is arranged to receive the reference voltage and the otherthe delayed voltage from the delaying circuit, the adder being arranged to deliverthe resulting voltage to the appropriate input ofthe comparator.
10. Apparatus for infra-red absorption detection of vehicles, substantially as herein before described with reference to Figures 1 to 7, or Figures 8to 12, or Figure 13 ofthe accompanying drawings.
10. Apparatus as claimed in any preceding claim, wherein the spectral range ofthe detector corresponds to that of CO2.
11. Apparatus for infra-red absorption detection of vehicles, substantially as herein before described with referenceto Figures 1 to7,orFigures8to 12, or Figure 13 ofthe accompanying drawings.
12. An electronicapparatusforthe remotedetec- tion of vehicles equipped with an engine emitting exhaust gases having an infra-red absorption spectrum which contrasts instantaneously with that ofthe ambient medium, ofthetype comprising on the one hand a spectral filter detector supplying an optionally amplified electrical signal corresponding to the infrared absorption spectrum ofthe zone covered by the detector and, on the other hand, a two-input comparator ofwhich a first input receives a signal dependent on the signal issuing from the detector and of which the second input receives an electrical reference signal so asto supply a signal indicating the presence of a detected vehicle corresponding to a pulsed signal received by the detector, said apparatus further comprising, in series between the detector and the comparator, means for adding to the signal dependent on the signal issuing from the detector and/or to the reference signal an electrical correction signal depenedent on the instantaneous contrast between the infra-red absorption spectrum of the exhaust gases of the detected vehicle andthatofthe ambient medium.
13. An apparatus as claimed in claim 12 in which the signal issuing from the detector is a voltage which is compared with a reference voltage, characterised in that the electrical correction signal is a correction voltage added to the reference voltage.
14. An apparatus as claimed in claim 13, characterised in thatthe means for adding the correction voltage comprise:
- a delaycircuitforthevoltage issuing from the detector in parallel with
- a low-pass filterwhich eliminates the pulse to be detected from this voltage in series with
- a variable multiplication circuit which introduces a correction voltage dependent on the contrast, the delay and multiplication circuits being connected to the two inputs of
- an adderwhich establishesthe algebraic sum ofthe delayed voltage and the multiplied voltage to form the reference voltage applied to the second input ofthe comparator.
15. An apparatus as claimed in claim 14 in which a movement,for example a rotational movement, is imparted to the detector, characterised in thatthe adder comprises a third input which is connected to an optronic assembly supplying a voltage for detecting the movement ofthe detector.
16. An apparatus as claimed in claim 12 in which the signal issuing from the detector is a voltage which is compared with a predetermined reference voltage, characterised in thatthe electrical correction signal is a correction voltage added to the voltage issuing from
the detector.
17. An apparatus as claimd in claim 16, characte
rised in thatthe means for adding the correction
voltage comprise:
- a restoration circuit which supplies a voltage to
the input of
- an anolog multiplier which multiplies the pre
ceding voltage with the voltage issuing from the
detector, in series with
- an a.c. amplifierwhich recentresthevoltage aroundzero,thisvoltagebeingthatwhich issupplied to the first input of the comparator of which the second input receives the predetermined reference voltage.
18. An apparatus as claimed in claim 16or 17, characterised inthatthevoltageatthesecond input of the comparator is equal to the sum of the reference voltage and the voltagesdelivered bythe delayed analog multiplier.
19. An apparatus as claimed in claim 18, characterised in that the meansfor adding the voltage delivered bythe delayed analog multiplierto the reference voltage comprise:
- a delaying circuit which receives the voltage delivered bythe analog multiplier,
- a two-input adder of which one ofthe inputs receives the reference voltage and the other the voltage ofthe delayed analog multiplier, the sum voltage being delivered to the second input of the comparator.
20. An apparatus as claimed in claim 12, characterised inthatthe infra-red absorption spectrum of the gases of the vehicle detected is that of CO2.
Newslaims or amendmentsto claims filed on 8th June1983 Superseded claims 1-20
CLAIMS
1. An infra-red detection apparatus for use in the detection ofthe presence of a vehicle having an engine which emits exhaust gases having an infra-red absorption spectrum which contrasts with that ofthe ambient medium,the apparatus comprising an infrared detector preceded by a spectral filter and arranged to provide infra-red detection within a zone covered by the detector, and processing means responsive to the detector and arranged to provide an analysis of a first value, dependent upon the detected infra-red radiation within said zone, by comparison ofthe first value with a reference threshold value so asto provide an indication of the presence of a vehicle with in said zone when the reference threshold value is passed by the first value, the first value comprising a background component, dependent on the ambient medium, and a superimposed pulse which occurs when a vehicle is present and which pulse may be detected by said comparison, the processing means being such that at least one of said first value and said reference threshold value will be modified, priorto said comparison, in dependence upon a signal which is derived from saidfirstvalue and is indicative of the background component alone, the modification taking place to the effectthatwhen said background component is relatively low only a pulse having a relatively high contrast will be detected in said comparison, and when said background component is relatively high a
pulse above a relatively low contrast will be detected
in said comparison.
2. Apparatus as claimed in claim 1, wherein said
detected first value, said reference threshold value i and said derived modifying signal are respective
voltages and the processing means is arranged to
provide the derived modifying signal as a component partofthe reference threshold value.
3. Apparatus as claimed in claim 2, wherein the processing means comprises,forforming the refer ence threshold value; - a delay circuitforthe detected first value
arranged in parallel with
- a low-pass filter whose frequency response characteristic is intended to eliminate from the
detected first value pulses ofthe kind anticipated due
to the presence of a vehicle, the low pass filter being in
series with
- a variable multiplication circuit arranged to
produce an output voltage related by a predetermined
mathematical function to the input voltage thereto,
and
- an adderarrangedto providethe reference
threshold value as comprising the algebraic sum of t the delayed detected firstvalue and the output of the variable multiplication circuit.
4. Apparatus as claimed in claim 3, further com- prising means arranged to impartmovementtothe detector and means arranged to detect movement of
the detector, said adder being additionally responsive
to the movement detecting means so asto be able to
indicate malfunction of the movement imparting
means.
5. Apparatus as claimed in claim 1, wherein said
detected first value, said reference threshold value
and said derived modifying signal are respective voltages, and the processing means isarrangedto modifythe detected first value in dependence upon
said derived modifying signal.
6. Apparatus as claimed in claim 5, wherein the
processing means comprises, for modifying the
detected first value:
- a restoration circuit arranged to produce an
output voltage related by a restoration law to the input voltage thereto
- an analog multiplier arranged to multiply the output voltage ofthe restoration circuit with the
detected first value, said multiplier being in series with
- an a.c. amplifierarranged to recentretheoutput voltage ofthe multiplier around zero, and to supply the recentred voltage to be compared with the
reference threshold value.
7. Apparatus as claimed in claim 5Or6,further comprising means arranged to modifythe reference threshold value by incorporating in it a value depen
dent upon the amplified multiplier output voltage.
8. Apparatus as claimed in claim 7, wherein the
means for modifying the reference threshold value
comprises:
- a delaying circuit arranged to receive the
amplified multiplier output voltage; and
- a two-input adder of which one ofthe inputs is
arranged to receive a fixed reference voltage and the otherthe delayed voltagefrom the delaying circuit, the adder being arranged to deliverthe resulting voltage as the reference threshold value.
9. Apparatus as claimed in any preceding claim, wherein the spectral range ofthe detector corresponds to that of CO2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB07936321A GB2129639B (en) | 1979-10-19 | 1979-10-19 | Detecting vehicles |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB07936321A GB2129639B (en) | 1979-10-19 | 1979-10-19 | Detecting vehicles |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2129639A true GB2129639A (en) | 1984-05-16 |
| GB2129639B GB2129639B (en) | 1984-10-31 |
Family
ID=10508623
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB07936321A Expired GB2129639B (en) | 1979-10-19 | 1979-10-19 | Detecting vehicles |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2129639B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0286251A2 (en) * | 1987-03-18 | 1988-10-12 | Centre De Recherche Industrielle Du Quebec | Microwave size/speed vehicle detector |
| US4788428A (en) * | 1985-03-04 | 1988-11-29 | The United States Of America As Represented By The Secretary Of The Navy | Thermodynamics infrared imaging sensor |
| US5012099A (en) * | 1986-12-23 | 1991-04-30 | U.S. Philips Corp. | Intrusion detection and identification arrangement for land vehicles |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB766556A (en) * | 1953-12-23 | 1957-01-23 | British Thomson Houston Co Ltd | Improvements relating to radiation responsive apparatus |
| GB1088254A (en) * | 1965-06-04 | 1967-10-25 | Impulsphysik Gmbh | Receiver for optical radiation pulse signals of low repetition rates with automatic control for maintaining a constant noise level |
| GB1237546A (en) * | 1967-09-20 | 1971-06-30 | Barnes Eng Co | Gun-flash detector |
| GB1242563A (en) * | 1968-04-17 | 1971-08-11 | Nat Res Dev | Improvements relating to the retrieval of information from noisy channels |
| GB1263108A (en) * | 1969-08-13 | 1972-02-09 | Emi Ltd | Improvements in or relating to apparatus for detecting changes in a field of view |
| GB1338591A (en) * | 1969-12-24 | 1973-11-28 | Westinghouse Electric Corp | Adaptive signal detection system |
| GB1377683A (en) * | 1971-03-04 | 1974-12-18 | Cerberus Ag | Flame detectors |
| GB1381573A (en) * | 1973-05-18 | 1975-01-22 | Philips Electronic Associated | Device for the detection of moving objects |
| GB1509562A (en) * | 1975-03-26 | 1978-05-04 | Mettoy Co Ltd | Gun and target apparatus utilising a light signal |
-
1979
- 1979-10-19 GB GB07936321A patent/GB2129639B/en not_active Expired
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB766556A (en) * | 1953-12-23 | 1957-01-23 | British Thomson Houston Co Ltd | Improvements relating to radiation responsive apparatus |
| GB1088254A (en) * | 1965-06-04 | 1967-10-25 | Impulsphysik Gmbh | Receiver for optical radiation pulse signals of low repetition rates with automatic control for maintaining a constant noise level |
| GB1237546A (en) * | 1967-09-20 | 1971-06-30 | Barnes Eng Co | Gun-flash detector |
| GB1242563A (en) * | 1968-04-17 | 1971-08-11 | Nat Res Dev | Improvements relating to the retrieval of information from noisy channels |
| GB1263108A (en) * | 1969-08-13 | 1972-02-09 | Emi Ltd | Improvements in or relating to apparatus for detecting changes in a field of view |
| GB1338591A (en) * | 1969-12-24 | 1973-11-28 | Westinghouse Electric Corp | Adaptive signal detection system |
| GB1377683A (en) * | 1971-03-04 | 1974-12-18 | Cerberus Ag | Flame detectors |
| GB1381573A (en) * | 1973-05-18 | 1975-01-22 | Philips Electronic Associated | Device for the detection of moving objects |
| GB1509562A (en) * | 1975-03-26 | 1978-05-04 | Mettoy Co Ltd | Gun and target apparatus utilising a light signal |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4788428A (en) * | 1985-03-04 | 1988-11-29 | The United States Of America As Represented By The Secretary Of The Navy | Thermodynamics infrared imaging sensor |
| US5012099A (en) * | 1986-12-23 | 1991-04-30 | U.S. Philips Corp. | Intrusion detection and identification arrangement for land vehicles |
| EP0286251A2 (en) * | 1987-03-18 | 1988-10-12 | Centre De Recherche Industrielle Du Quebec | Microwave size/speed vehicle detector |
| EP0286251A3 (en) * | 1987-03-18 | 1990-07-11 | Centre De Recherche Industrielle Du Quebec | Microwave size/speed vehicle detector |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2129639B (en) | 1984-10-31 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19931019 |