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WO1997034374A1 - Convertisseur analogique/numerique a integration et dispositif capteur sensible aux rayonnements comportant un tel convertisseur - Google Patents

Convertisseur analogique/numerique a integration et dispositif capteur sensible aux rayonnements comportant un tel convertisseur Download PDF

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Publication number
WO1997034374A1
WO1997034374A1 PCT/SE1997/000442 SE9700442W WO9734374A1 WO 1997034374 A1 WO1997034374 A1 WO 1997034374A1 SE 9700442 W SE9700442 W SE 9700442W WO 9734374 A1 WO9734374 A1 WO 9734374A1
Authority
WO
WIPO (PCT)
Prior art keywords
value
converter
comparator
reference value
counter
Prior art date
Application number
PCT/SE1997/000442
Other languages
English (en)
Inventor
Torbjörn GUSTAFSSON
Stan Zyra
Original Assignee
Försvarets Forskningsanstalt
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Försvarets Forskningsanstalt filed Critical Försvarets Forskningsanstalt
Publication of WO1997034374A1 publication Critical patent/WO1997034374A1/fr

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
    • H03M1/12—Analogue/digital converters
    • H03M1/50—Analogue/digital converters with intermediate conversion to time interval

Definitions

  • Integrating A/D Converter and Radiation-Sensitive Sensor Device comprising such a Converter
  • the present invention relates to an integrating A/D converter and a radiation- sensitive sensor device comprising such a converter. More specifically it concerns converters of that sort which can determine the strength of a signal over a much greater interval than those which prior art such converters can manage.
  • the background of the invention are optical sensor devices, which under highly varying intensity conditions will be saturated in known designs.
  • the principle can also be used in other integrating A/D converters, which are thus also comprised by the invention. Nevertheless, the invention will be described in connection with optical sensors.
  • the dynamic range of a radiation-sensitive sensor is normally restricted upwards by the maximum intensity that can be detected without its maximum reading value being exceeded.
  • the range is besides restricted upwards by the greatest digital value that can be expressed with the given number of bits that are available.
  • An ordinary mode of function of a radiation-sensitive sensor is that a photodiode is illuminated and the thus generated current is integrated in an element, e.g. a capacitor, during the time of exposure. After the time of exposure, the value can be read and/or be A/D converted.
  • a counter In the A/D conversion, use is often made of a circuit solution, which means that after completion of the exposure, a counter emits a sequence of gradually increas ⁇ ing digital values, which are converted into analogue values and which are sub ⁇ sequently compared with the exposure value that was generated during the last exposure.
  • the digital value is stored as the value that corresponds to the analogue exposure value.
  • prior-art sensor devices as those mentioned above cannot measure over a sufficiently great intensity range.
  • An example of measuring tasks that cause problems is the watching, by means of an image-generating sensor, of objects having very different radiation intensity in various parts.
  • a missile with a trailing jet can be mentioned as an example. It may very well be the case that both the shape of the missile, which is given with low radiation intensity, and the struc ⁇ ture of the flame, which is given with high intensity, are important. It is not possible to measure these two matters at the same time while using prior-art detector matrices. It is necessary to measure periodically with different exposure time.
  • the invention can also be used in very rapid adaptation of exposure time to changed illumination since it is possible to immediately obtain a good measure of how much a sensor has suddenly been overexposed in the classic measuring range.
  • a sensor according to the invention is also extremely suited for anti sensor laser detection since the sensor registers amplitudes although the measured values should normally cause an indication that the sensor has been saturated.
  • Fig. 1 shows a prior-art A/D converter
  • Fig. 3 illustrates an embodiment of an inventive A/D converter
  • Fig. 5 shows an embodiment of a combined A/D converter according to the invention.
  • Fig. 1 shows a prior-art A/D converter.
  • the parts appearing in the box are repeated for each cell whereas the parts situated outside are common.
  • the A/D converter comprises a light-sensitive cell which is cleared and subjected to exposure. During exposure, the value corresponding to the intensity integrated during exposure increases. This value is stated in the Figure as "Analogue input".
  • a hold signal is emitted from the control electronics such that the analogue signal is sampled and held in the S/H circuit.
  • the counter is cleared and begins to count upwards.
  • the digital values of the counter are converted into analogue values in a D/A converter.
  • the two analogue values are compared in a comparator, and if the values are found to be equal or if the hold value is smaller than the value of the counter in analogue form, this counter value is stored in digital form as the digital value of the intensity.
  • This type of A/D conversion is below called "afterExpAD”.
  • Fig. 2 shows the ratio of the digital value from the A D conversion, DVAQ, to the exposure value of the time te X p, E(te X p).
  • the Figure illustrates the appearance of the graph when "afterExpAD'' is applied and the number of bits n equals 3. Usually, more bits are used, for instance 8.
  • This type of A/D converter can define, with n bits, an intensity value of at most 2 n -1. The value 2 n -1 will below be called “maximum reference value”.
  • An A/D converter that does not suffer from the above-mentioned drawback can function as follows, see also Fig. 3.
  • the parts appearing in the box are repeated for each cell whereas the parts situated outside are common.
  • the counter is cleared and begins to count upwards. It is of course conceiv ⁇ able to count downwards instead, starting from a fixed starting value.
  • This is also possible in connection with the prior-art A/D converter according to Fig. 1. It is obvious to imagine that the counter is supplied with a constant clock frequency, the period of which together with the maximum number of steps of the counter deter ⁇ mine the length of the exposure time. However, it is also conceivable to let the clock frequency vary during the counting procedure.
  • the rising value is supplied to the comparator from the integrating cell directly without any hold, i.e. tracking.
  • a refer ⁇ ence value is supplied to the second input of the comparator.
  • the maximum reference value it is possible to use the maximum reference value according to the above example.
  • a fraction of the maximum reference value for instance a fourth or an eighth of the maximum reference value. If the comparator finds equality before the end of the exposure time, the exposure time that has passed since the clearing is a measure of the intensity, and therefore the size of the counter value is a measure of the intensity. This mode of A/D conversion as described above is below called "duringExpAD".
  • Fig. 4 shows what the ratio of the digital value from the A D conversion, DV ⁇ D, to the exposure value of the time t ⁇ p E(t ex p) can look like when the A/D conver ⁇ sion process "duringExpAD" according to the present invention is combined with, for instance, "afterExpAD”. If the exposure value is smaller than or equals ⁇ ADmax ⁇ xp)- “afterExpAD” is applied. If the exposure value is greater than EADmaxttexp). "duringExpAD” is applied.
  • the digital value, DVAQ can in ordinary A/D conversion assume values between 0 and 2 n -1.
  • “duringExpAD” use is made of the same binary digit as in “afterExpAD”, but in this context they will have a different meaning.
  • DV ⁇ D assumes values from 2 n -1 to 0 with “duringExpAD”.
  • A/D converters in a number of dif ⁇ ferent ways. Three are here to be mentioned, called A, B and C, which use a fixed exposure time and one called D, which has a selectable exposure time.

Landscapes

  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Analogue/Digital Conversion (AREA)
  • Measurement Of Radiation (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)

Abstract

Convertisseur analogique/numérique à intégration et dispositif capteur sensible aux rayonnements comportant un tel convertisseur. Ce convertisseur analogique/numérique comprend un élément intégrateur qui, pendant des intervalles de temps fixes, intègre un signal d'entrée, et en outre un comparateur à l'une des entrées duquel ladite valeur intégrée est continuellement appliquée et à l'autre entrée duquel une valeur de référence est appliquée, ainsi qu'un dispositif comprenant un générateur d'impulsions d'horloge qui alimente un compteur, lequel, pendant les intervalles de temps précités, comptent vers le haut ou vers le bas à partir d'une valeur de départ et qui, sur la base du signal de sortie du comparateur, déterminent si le signal intégré dans le décompte vers le haut dépasse ou égale la valeur de référence et, dans le décompte vers le bas, est inférieur ou égal à la valeur de référence et, dans l'affirmative, à quel instant de cet intervalle de temps, ce qui donne une mesure de l'importance du signal.
PCT/SE1997/000442 1996-03-14 1997-03-14 Convertisseur analogique/numerique a integration et dispositif capteur sensible aux rayonnements comportant un tel convertisseur WO1997034374A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9600971-7 1996-03-14
SE9600971A SE512332C2 (sv) 1996-03-14 1996-03-14 Integrerande A/D-omvandlare och strålningskänslig sensoranordning innefattande sådan

Publications (1)

Publication Number Publication Date
WO1997034374A1 true WO1997034374A1 (fr) 1997-09-18

Family

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Family Applications (1)

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PCT/SE1997/000442 WO1997034374A1 (fr) 1996-03-14 1997-03-14 Convertisseur analogique/numerique a integration et dispositif capteur sensible aux rayonnements comportant un tel convertisseur

Country Status (2)

Country Link
SE (1) SE512332C2 (fr)
WO (1) WO1997034374A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1227663A3 (fr) * 2001-01-30 2007-04-25 Nippon Telegraph and Telephone Corporation Appareil de conversion et de sortie de données

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0372548A2 (fr) * 1988-12-07 1990-06-13 Fujitsu Limited Dispositif de conversion analogique-numérique à approximation successive
US4940982A (en) * 1986-03-03 1990-07-10 Zdzislaw Gulczynski High speed integrating analog-to-digital converter
US5084704A (en) * 1990-02-02 1992-01-28 Grumman Aerospace Corporation Focal plane analog-to-digital converter
WO1996013903A1 (fr) * 1994-11-01 1996-05-09 Försvarets Forskningsanstalt Convertisseur analogique/numerique et capteur comprenant un tel convertisseur

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4940982A (en) * 1986-03-03 1990-07-10 Zdzislaw Gulczynski High speed integrating analog-to-digital converter
EP0372548A2 (fr) * 1988-12-07 1990-06-13 Fujitsu Limited Dispositif de conversion analogique-numérique à approximation successive
US5084704A (en) * 1990-02-02 1992-01-28 Grumman Aerospace Corporation Focal plane analog-to-digital converter
WO1996013903A1 (fr) * 1994-11-01 1996-05-09 Försvarets Forskningsanstalt Convertisseur analogique/numerique et capteur comprenant un tel convertisseur

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1227663A3 (fr) * 2001-01-30 2007-04-25 Nippon Telegraph and Telephone Corporation Appareil de conversion et de sortie de données
US7911520B2 (en) 2001-01-30 2011-03-22 Nippon Telegraph And Telephone Corporation Data conversion/output apparatus for digitalizing sensor data and outputting through a sensor array
US8432470B2 (en) 2001-01-30 2013-04-30 Nippon Telegraph And Telephone Corporation Data conversion/output apparatus for digitalizing sensor data and outputting through a sensor array

Also Published As

Publication number Publication date
SE9600971L (sv) 1997-09-15
SE512332C2 (sv) 2000-02-28

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