WO1989010037A1 - Procede et appareil compensant le courant d'obscurite et la tension offset provenant d'une unite ccd - Google Patents

Procede et appareil compensant le courant d'obscurite et la tension offset provenant d'une unite ccd Download PDF

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Publication number
WO1989010037A1
WO1989010037A1 PCT/DK1989/000076 DK8900076W WO8910037A1 WO 1989010037 A1 WO1989010037 A1 WO 1989010037A1 DK 8900076 W DK8900076 W DK 8900076W WO 8910037 A1 WO8910037 A1 WO 8910037A1
Authority
WO
WIPO (PCT)
Prior art keywords
dark current
ccd
unit
integrator
amplifier
Prior art date
Application number
PCT/DK1989/000076
Other languages
English (en)
Inventor
Bjarne Engmann Jensen
Original Assignee
Helioprint A/S
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 Helioprint A/S filed Critical Helioprint A/S
Publication of WO1989010037A1 publication Critical patent/WO1989010037A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
    • H04N25/63—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to dark current
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/70—SSIS architectures; Circuits associated therewith
    • H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors

Definitions

  • the invention relates to a circuit for compensating for the dark current and thermal drift in the output voltage from a CCD-unit.
  • This compensation is usually effected either by compensating directly in the analog signal from the CCD-unit or by converting the analog signal into digital representations which are processed in a digital processing unit for that purpose.
  • the purpose of the present invention is to provide a method and an apparatus by which it is possible to effect the desired dark current and offset voltage compensation in such a way that the A/D-converter is included in the compensation loop without basing the compensation on computations in a digital processing unit and without using a high resolution A/D-converter.
  • This purpose is achieved by the method specified in the characterizing portion of claim 1.
  • the use of this method allows for compensating for dark current variations in the CCD-unit and for compensating for all the temperature dependent variations of the output voltages and conditions of all elements in the circuit.
  • a quick tracking of the compensation circuit is obtained upon its activation.
  • Claims 4 and 5 indicate preferred embodiments of the invention, claim 5 particularly specifying how it is possible to use an A/D-converter for conversion and dark current compensation for line pulses from a CCD-unit with two outputs.
  • Claim 3 defines a particularly advantageous embodiment of the circuit, and it will be seen that only one single A/D-converter with a resolution corres-ponding to the wanted grey tone resolution is necessary.
  • FIG. 1 shows a circuit in accordance with the invention
  • Fig. 2 shows a preferred embodiment of the invention.
  • Fig. 1 shows a circuit according to the invention.
  • the purpose of the circuit is to convert analog signals from a CCD-unit 1 into digital representations.
  • the output signal from the CCD-unit 1 is fed to a first amplifier 2, from the output of which the signal is fed to another amplifier 3, the output signals of which is fed to an A/D-converter 4.
  • the A/D-converter is connected to a control logic circuit 5 and a digital comparator 6.
  • Control circuit 5 serves to control A/D-converter 4 and the comparator 6 and to supply, in dependence on the output 7 from comparator 6, control signals to an amplifier 8 and a switch 9 via lines 10 and 11.
  • CCD-unit 1 is of the type comprising a plurality of masked cells and the output voltage from these cells is used as a measure of the dark current in all of the cells of the CCD-unit.
  • the voltage level from the masked cells in CCD-unit 1 is read out, the signal voltage is amplified in amplifiers 2 and 3 and converted into digital representations in A/D-converter 2.
  • the comparator compares said digital representations to a predetermined digital number and supplies the result of the comparison to the control logic.
  • the working point of amplifier 2 is shifted in a negative direction by supplying a positively moving signal from amplifier 8 to its negative input, said amplifier 8 constituting together with the resistors 12, 13, 14 and capacitors 15 and 16 an integrator whose time constant can be changed by switch 9.
  • This integrator is arranged so that the direction of the voltage changes at the output is determined by the voltage level on line 10. If the output signal from the A/D-converter is far from the optimum, switch 9 is closed, thereby materially reducing the time constant of the integrator.
  • the time of activating switch 9 is controlled by control logic 5 controlling the switch via line 11. When the output signal from the A/D-converter approaches the optimum, switch 9 is reopened and the integrator operates at a high time constant. This provides for obtaining a faster tracking.
  • control logic 5 Inverting the voltage on line 10, following which the direction of the change of the output voltage from the integrator changes.
  • A/D-converter 4 Under this control the output voltage of A/D-converter 4 always oscillates around the optimum value.
  • the characteristic feature of the described control is that it includes almost all parts of the circuit whose drift may influence the output signal from A/D-converter 4.
  • the control loop thus includes amplifiers 2 and 3, A/D-converter 4 and integrator 8. This makes it possible to compensate for changes in the output voltages of said components, said changes being mainly due to thermal variations.
  • Fig. 2 shows a preferred embodiment of the invention making use of a CCD-unit with two outputs.
  • the circuit associated with said CCD-unit is structured as shown in Fig. 2.
  • the parts illustrated in Fig. 2 having the same function as in Fig. 1 are indicated by the same reference numerals.
  • the circuit illustrated in Fig. 2 consists substantially of two sets of circuit elements identical with those shown in Fig. 1.
  • An amplifier 2 or 2', an integrator 8 or 8' and a switch 9 or 9' are associated with each output from the CCD-unit.
  • the output signals from amplifiers 2 and 2' are fed to switches 17 and 18. These switches provide for multiplexing the signal from amplifiers 2 and 2' to the input of amplifier 3.
  • the control loop is in this case composed of the same components as shown in Fig. 1 , use being made, however, of a common A/D-converter 4 and a common comparator 6 for both outputs of the CCD-unit.
  • An optimum utilization of the most expensive components of the control loop is attained by the above structure of the control loop, i.e. A/D-converter 4 and comparator 6.
  • the CCD-unit is of the linear type, i.e. composed of a plurality of light-sensitive elements positioned along a straight line. In this way each read-put from the CCD-unit yields a representation of a line in the image to be scanned.
  • the integrators according to the invention are constructed to work at two time constants controlled by switches 9 and 91. In a first position of the switches the integrators work at a low time constant used for tracking the control loop when is is far from the optimum dark current compensation, that is for instance the situation upon the starting-up of the apparatus or in case of big fluctations in the surrounding temperatures. In the second position of the switches the integrators work at a high time constant, thereby attaining the desired stable regulation around the optimum dark current compensation.
  • the above specified structure of the integrator actually provides for obtaining a quick tracking to the optimum compensation and a stable regulation around this optimum compensation, thereby preventing the dark current compensation from changing during the read-out of one single line.
  • Control logic 5 is not discussed in detail here, this being a circuit of conventional type.
  • the control logic is constructed by means of a programmable logic network since it is then possible to implement the control logic in one single circuit.
  • the CCD-unit is regarded to be a separate unit capable of reading out its own signals.
  • this is incidentally not the fact and in a practical embodiment of the invention it is necessary to provide the control signals necessary for the CCD-unit.
  • a programmable logic network for the implementation of the control logic it is possible to implement the generation og said control signals in the control logic in a simple and economic manner.

Abstract

L'invention concerne un circuit de compensation de courant d'obscurité pour une unité CCD (à couplage de charge). Ce circuit de compensation de courant d'obscurité se caractérise en ce que l'on procède à la compensation de courant d'obscurité directement sur le signal de sortie analogique provenant de l'unité CCD, la boucle de commande comprenant des parties de traitement de signaux numériques pour les signaux provenant de l'unité CCD de manière à compenser davantage la dérive de température desdites parties.
PCT/DK1989/000076 1988-04-06 1989-04-06 Procede et appareil compensant le courant d'obscurite et la tension offset provenant d'une unite ccd WO1989010037A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DK185188A DK159235C (da) 1988-04-06 1988-04-06 Moerkestroemskompensering for ccd-enhed
DK1851/88 1988-04-06

Publications (1)

Publication Number Publication Date
WO1989010037A1 true WO1989010037A1 (fr) 1989-10-19

Family

ID=8108537

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DK1989/000076 WO1989010037A1 (fr) 1988-04-06 1989-04-06 Procede et appareil compensant le courant d'obscurite et la tension offset provenant d'une unite ccd

Country Status (4)

Country Link
EP (1) EP0400092A1 (fr)
JP (1) JPH03503703A (fr)
DK (1) DK159235C (fr)
WO (1) WO1989010037A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2682779A1 (fr) * 1990-11-30 1993-04-23 Lcia Insar Dispositif de prise d'images lineaires d'une surface.
DE4309724A1 (de) * 1993-03-25 1994-09-29 Kodak Ag Verfahren zur temperaturabhängigen Dunkelstromkompensation bei CCD-Bildsensoren
US5471244A (en) * 1994-05-31 1995-11-28 3M Company Automatic dark level zeroing for an analog video signal
USH1616H (en) * 1994-05-31 1996-12-03 Minnesota Mining And Manufacturing Company Web inspection system having enhanced video signal preprocessing
WO1999008440A1 (fr) * 1997-08-11 1999-02-18 Sirona Dental Systems Gmbh Procede pour la compensation du courant d'obscurite d'un detecteur electronique presentant plusieurs pixels
WO2000040009A2 (fr) * 1998-12-30 2000-07-06 Intel Corporation Circuit de compensation du courant d'obscurite
US6977364B2 (en) 2003-07-28 2005-12-20 Asml Holding N.V. System and method for compensating for dark current in photosensitive devices
EP1803400A1 (fr) * 2003-11-21 2007-07-04 Eastman Kodak Company Appareil de radiologie dentaire et procédé de traitement de signal utilisé correspondant
US9407843B2 (en) 2013-10-23 2016-08-02 General Electric Company Detector system and module for compensating dark current

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4473839A (en) * 1981-11-13 1984-09-25 Hitachi, Ltd. Signal processing circuit for video camera
US4580168A (en) * 1982-05-27 1986-04-01 Rca Corporation Charge-storage-well dark current accumulator with CCD circuitry
US4589025A (en) * 1984-11-30 1986-05-13 Rca Corporation Dark current measurement and correction for video from field-transfer imagers
US4652927A (en) * 1982-11-30 1987-03-24 Canon Kabushiki Kaisha Image sensing device
DD245047A1 (de) * 1985-12-13 1987-04-22 Univ Schiller Jena Anordnung und verfahren zur korrektur der ausgangssignale einer halbleiterbildsensor-kamera

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4473839A (en) * 1981-11-13 1984-09-25 Hitachi, Ltd. Signal processing circuit for video camera
US4580168A (en) * 1982-05-27 1986-04-01 Rca Corporation Charge-storage-well dark current accumulator with CCD circuitry
US4652927A (en) * 1982-11-30 1987-03-24 Canon Kabushiki Kaisha Image sensing device
US4589025A (en) * 1984-11-30 1986-05-13 Rca Corporation Dark current measurement and correction for video from field-transfer imagers
DD245047A1 (de) * 1985-12-13 1987-04-22 Univ Schiller Jena Anordnung und verfahren zur korrektur der ausgangssignale einer halbleiterbildsensor-kamera

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2682779A1 (fr) * 1990-11-30 1993-04-23 Lcia Insar Dispositif de prise d'images lineaires d'une surface.
DE4309724A1 (de) * 1993-03-25 1994-09-29 Kodak Ag Verfahren zur temperaturabhängigen Dunkelstromkompensation bei CCD-Bildsensoren
US5471244A (en) * 1994-05-31 1995-11-28 3M Company Automatic dark level zeroing for an analog video signal
USH1616H (en) * 1994-05-31 1996-12-03 Minnesota Mining And Manufacturing Company Web inspection system having enhanced video signal preprocessing
US6351519B1 (en) 1997-08-11 2002-02-26 Sirona Dental Systems Gmbh Method for compensating the dark current of an electronic sensor having several pixels
WO1999008440A1 (fr) * 1997-08-11 1999-02-18 Sirona Dental Systems Gmbh Procede pour la compensation du courant d'obscurite d'un detecteur electronique presentant plusieurs pixels
US6525769B1 (en) 1998-12-30 2003-02-25 Intel Corporation Method and apparatus to compensate for dark current in an imaging device
WO2000040009A3 (fr) * 1998-12-30 2000-10-12 Intel Corp Circuit de compensation du courant d'obscurite
WO2000040009A2 (fr) * 1998-12-30 2000-07-06 Intel Corporation Circuit de compensation du courant d'obscurite
US6977364B2 (en) 2003-07-28 2005-12-20 Asml Holding N.V. System and method for compensating for dark current in photosensitive devices
US7081610B2 (en) 2003-07-28 2006-07-25 Asml Holding N.V. System for compensating for dark current in sensors
EP1803400A1 (fr) * 2003-11-21 2007-07-04 Eastman Kodak Company Appareil de radiologie dentaire et procédé de traitement de signal utilisé correspondant
US8008628B2 (en) 2003-11-21 2011-08-30 Carestream Health, Inc. Dental radiology apparatus and signal processing method used therewith
US8319190B2 (en) 2003-11-21 2012-11-27 Carestream Health, Inc. Dental radiology apparatus and signal processing method used therewith
US8481954B2 (en) 2003-11-21 2013-07-09 Carestream Health, Inc. Dental radiology apparatus and signal processing method used therewith
US8481955B2 (en) 2003-11-21 2013-07-09 Carestream Health, Inc. Dental radiology apparatus and signal processing method used therewith
US8481956B2 (en) 2003-11-21 2013-07-09 Carestream Health, Inc. Dental radiology apparatus and signal processing method used therewith
US9407843B2 (en) 2013-10-23 2016-08-02 General Electric Company Detector system and module for compensating dark current

Also Published As

Publication number Publication date
DK159235C (da) 1991-03-04
EP0400092A1 (fr) 1990-12-05
DK159235B (da) 1990-09-17
DK185188D0 (da) 1988-04-06
JPH03503703A (ja) 1991-08-15
DK185188A (da) 1989-10-07

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