GB1108283A - Improvements to television circuits - Google Patents

Improvements to television circuits

Info

Publication number
GB1108283A
GB1108283A GB20333/65A GB2033365A GB1108283A GB 1108283 A GB1108283 A GB 1108283A GB 20333/65 A GB20333/65 A GB 20333/65A GB 2033365 A GB2033365 A GB 2033365A GB 1108283 A GB1108283 A GB 1108283A
Authority
GB
United Kingdom
Prior art keywords
signal
gain
values
resistor
level
Prior art date
Legal status (The legal status 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 status listed.)
Expired
Application number
GB20333/65A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Compagnie Generale de Radiologie SA
Original Assignee
Compagnie Generale de Radiologie SA
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 Compagnie Generale de Radiologie SA filed Critical Compagnie Generale de Radiologie SA
Publication of GB1108283A publication Critical patent/GB1108283A/en
Expired legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00Details of television systems
    • H04N5/14Picture signal circuitry for video frequency region
    • H04N5/20Circuitry for controlling amplitude response
    • H04N5/205Circuitry for controlling amplitude response for correcting amplitude versus frequency characteristic
    • H04N5/208Circuitry for controlling amplitude response for correcting amplitude versus frequency characteristic for compensating for attenuation of high frequency components, e.g. crispening, aperture distortion correction
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06GANALOGUE COMPUTERS
    • G06G7/00Devices in which the computing operation is performed by varying electric or magnetic quantities
    • G06G7/12Arrangements for performing computing operations, e.g. operational amplifiers
    • G06G7/26Arbitrary function generators
    • G06G7/28Arbitrary function generators for synthesising functions by piecewise approximation
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/30Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from X-rays
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70Circuitry for compensating brightness variation in the scene
    • H04N23/76Circuitry for compensating brightness variation in the scene by influencing the image signals

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Theoretical Computer Science (AREA)
  • Software Systems (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Apparatus For Radiation Diagnosis (AREA)
  • Closed-Circuit Television Systems (AREA)
  • Television Receiver Circuits (AREA)

Abstract

1,108,283. Electric analogue calculating. COMPAGNIE GENERALE DE RADIOLOGIE. 13 May, 1965 [13 May, 1964; 16 Feb., 1965], No. 20333/65. Heading G4G. [Also in Division H4] The invention relates to an automatic gain control device which retains for the video frequency amplifier of a television camera, e.g. a radiological television camera, a normal gain for signal values corresponding to brightnesses of the subject televized which are between a zero and a mean value, and then abruptly reduces this gain for signals corresponding to brightnesses between the mean and maximum value. As shown, Fig. 1, the load resistor of the last amplification stage T 1 preceding the output stage T 2 feeding the television receivers comprises a fixed resistor R 1 determining the normal gain and a second resistor R 2 which is connected in parallel with resistor R 1 and in series with a diode D which becomes conductive only when the input signal S 1 exceeds the potential Vbl, thus reducing the effective load resistance and thereby reducing the gain. The inflection point of the curve of the output signal S 2 of the stage T 1 against the input signal S 1 of the same stage, Fig. 2 (not shown), is determined by the value of the direct current potential Vbl which can be regulated by potentiometer P1. The mean luminosity of the image may be controlled by varying with potentiometer P 2 the level of the back level signal S 3 to which the video signal is added and as before for signal values corresponding to the sum of signals S 3 and S 1 higher than Vbl the gain of the amplifier stage T 1 is reduced. The device may be put out of the circuit by application to the diode D potential Vb2 which blocks diode D whatever the value of signal S 1 . In simultaneous cinematography and radiological television the power supplied by the X-ray generator is proportional to and increases with the rate at which the cinematographic pictures are taken and the device described above is arranged as before to reduce in a certain ratio the gain of the signal which exceeds half the maximum standardized level feeding the television receiver so that the image remains readable without dazzling, the standardized level being the level of the video signal which gives the maximum white to the image. In a second embodiment, Fig. 11 (not shown), the device described in Fig. 1 is duplicated, i.e. two resistors (R 2 and R 3 ) are connected in parallel to load resistor (R 1 ) and in series with Two diodes (D 1 and D 2 ) which become conductive when the signals reach two values. Thus the device of Fig. 11 has two gain values for higher signal values, one for mean values of signals received (mean greys) and the other for maximum values of signals received (whites), Fig. 12 (not shown). In order that the device has only one gain when no signal exceeding the standardized level is presented at the output of the camera a diode amplitude selector device (SA), Fig. 13 (not shown), is included in the circuit which operates to unblock the two diodes (D 1 and D 2 ) when the signal exceeds the standardized level. The diodes are unblocked more quickly the higher the value of the signal at the output of the camera resulting in a variation of the inflection points, Fig. 15 (not shown). In a modification, Fig. 16 (not shown), in which the inflection joints are fixed and the slope of one or the other top portion of the curve, or both, are varied, Fig. 17 (not shown), one or more photodiodes, photoresistors or thermistors are associated with the amplitude selector and connected in parallel with the resistor (R 2 ) or resistors (R 2 and R 3 ).
GB20333/65A 1964-05-13 1965-05-13 Improvements to television circuits Expired GB1108283A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR974279A FR1403790A (en) 1964-05-13 1964-05-13 Improvements to television circuits
FR5744A FR87394E (en) 1964-05-13 1965-02-16 Improvements to television circuits

Publications (1)

Publication Number Publication Date
GB1108283A true GB1108283A (en) 1968-04-03

Family

ID=26162079

Family Applications (1)

Application Number Title Priority Date Filing Date
GB20333/65A Expired GB1108283A (en) 1964-05-13 1965-05-13 Improvements to television circuits

Country Status (4)

Country Link
DE (1) DE1462735A1 (en)
FR (2) FR1403790A (en)
GB (1) GB1108283A (en)
NL (1) NL6506018A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4821100A (en) * 1984-08-10 1989-04-11 Sony Corporation Image signal compressor
GB2273626A (en) * 1992-12-21 1994-06-22 Hitachi Ltd White Balance Correction Circuit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05153496A (en) * 1991-11-29 1993-06-18 Hitachi Medical Corp X-ray image pickup device, x-ray perspective device and x-ray television camera device used for them

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4821100A (en) * 1984-08-10 1989-04-11 Sony Corporation Image signal compressor
GB2273626A (en) * 1992-12-21 1994-06-22 Hitachi Ltd White Balance Correction Circuit
US5493342A (en) * 1992-12-21 1996-02-20 Naito; Yasushi White balance correction circuit
GB2273626B (en) * 1992-12-21 1997-04-30 Hitachi Ltd White balance correction circuit

Also Published As

Publication number Publication date
DE1462735A1 (en) 1969-09-04
FR87394E (en) 1966-07-29
NL6506018A (en) 1965-11-15
FR1403790A (en) 1965-06-25

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