US2255691A - Television signal-translating system - Google Patents

Television signal-translating system Download PDF

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Publication number
US2255691A
US2255691A US250914A US25091439A US2255691A US 2255691 A US2255691 A US 2255691A US 250914 A US250914 A US 250914A US 25091439 A US25091439 A US 25091439A US 2255691 A US2255691 A US 2255691A
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United States
Prior art keywords
signal
translating
tube
predetermined
accordance
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Expired - Lifetime
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US250914A
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English (en)
Inventor
John C Wilson
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.)
HAZEL TINE CORP
HAZEL-TINE Corp
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HAZEL TINE CORP
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
Priority to BE437358D priority Critical patent/BE437358A/xx
Application filed by HAZEL TINE CORP filed Critical HAZEL TINE CORP
Priority to US250914A priority patent/US2255691A/en
Priority to US253040A priority patent/US2255692A/en
Priority to GB32445/39A priority patent/GB538947A/en
Priority to FR862876D priority patent/FR862876A/fr
Application granted granted Critical
Publication of US2255691A publication Critical patent/US2255691A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/14—Picture signal circuitry for video frequency region
    • H04N5/16—Circuitry for reinsertion of DC and slowly varying components of signal; Circuitry for preservation of black or white level
    • H04N5/165—Circuitry for reinsertion of DC and slowly varying components of signal; Circuitry for preservation of black or white level to maintain the black level constant
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/14—Picture signal circuitry for video frequency region
    • H04N5/20—Circuitry for controlling amplitude response
    • H04N5/202—Gamma control

Definitions

  • This invention relates to television systems and particularly to the video-frequency signal-translating portion thereof.
  • the invention is especially concerned with controlling the characteristics of such systems relating to gradation and contrast of the illumination between the incremental areas of transmitted and reproduced images.
  • the 11- v lumination of the incremental areas of the rev produced image is proportional to the illumination'of the corresponding areas of the original image, that is, if the systemy has a linear over-all stimulus-response characteristic, the reproduced images may 'appear at or distorted to an observer. In such cases, therefore, it' is desirable to give the system. a predetermined non-linear over-all response characteristic.
  • a film In photography a film is said to have a gamma which deviates from. unity in accordance with differences in the relative detail or contrast for'the brighter detail or contrast for the brighter or darker portions of the scene represented thereby, compared to other portionsy thereof with respect 'to the corresponding contrasts of the original scene, This same concept is useful in television.
  • the gammaof any system may/ be definedy as the 'slope of the stimulus-response curve4 plotted on a logarithmic scale. Obviously, only where gamma is unity is there a linear relationship between the stimulus-and response over the entire response range of the system.
  • a television video-frequency signal-translating l system thus has a gamma4v greater or less than unitywhen its characteristic is such that it effects an expansion or contraction,respectively, of one portion of the amplitude range of the signal translated thereby relative to the portion of such amplituderange near its origin, and its gamma is unity only when its transmission characteristicI is linear over the entire signal amplitude range.
  • gamma control means be provided for television signaltranslating systems in order to compensate for various inherent non-linear response characteris-l tics of .such systems and the physiological phenomena referred to above.
  • gamma control means 4for television signal-translating systems that is, means-for effecting a predetermined distortion of a television video-frequency signal whereby improved contrast effects over a selected portion of the signal-amplitude range may be procured which distortion is automatically controlled in 'accordance with the illumination characteristics of the transmitted image.
  • a television signal-translating system comprises 'means for translating a television signal includf ing an input element and means for - ⁇ applying to' the input element the video-frequencyand background-illuminationl components of ⁇ the signal with predetermined amplitude values 'thereof corresponding substantially to ⁇ the black and white shade values of .the transmitted picture.
  • 'I 'he system includes means for adjusting the gamma of the signal-translating means and means responsive to a predetermined illumination characteristic of the signal for controlling the adjusting means in accordance therewith.
  • Fig. l is a schematic diagram of a complete television signal-receiving system including a video-frequency amplifier embodying the present invention
  • Figs. 2 yand 3 are graphs illustrating certain operating characteristics of the system of Fig. l, to aid in the understanding of the invention.
  • the system illustrated comprises a television receiver of the superheterodyne type including an antenna system I I, II connected to a radio-frequency ampliner I 2 to which there are connected in cascade, in the order named, an oscillatormodulator I3, an intermediate-frequency ampliner I4, a detector and A. V. C. supply Il, a videofrequency ampliner, I5, a second video-frequency amplifier I1 embodying the present invention, and an image-reproducing device Il. .A line-frequency scanning wave generator I3 and a neldfrequency scanning wave generator are also coupled to the output circuit oi the detector I5 and to the scanning elements of the signal-reproducing device.
  • 'I'he stages I2-2II, inclusive, excepting the video-frequency ampliiler I1 may all be of conventional well-"known construction so that detailed illustrations and descriptions thereof are unnecessary herein.
  • e television signal intcrceptedby the antenna I0, II is selected and amplified in the radio-frequency amplifier I 2 and supplied to the oscillator-modulator I3, wherein it is converted into an intermediatefrequency signal which, in'turn, is selectively ampliiled in the intermediate-frequency ampliner Il and delivered to the detector
  • the modulation components of the signal are-derived by the detector I5 and supplied to the video-frequency ampliier I6 wherein they are ampliiled and supplied to the further video-frequency ampliner I1 which translates the signal in accordance with the apparatus of the present invention as will be presently further described, and from which they areY applied to a scanning-beam control element of the image-reproducing device I8.
  • the intensity of the scanning beam of the device Il is thus' modulated or controlled in accordance with the video-frequency voltage impressed upon its control elemcnt in the usual manner.
  • the modulation signal is also applied to the generators I9 and 2l and the synchronizing components of the signal are utilized therein to synchronize the operations of these generators with the corresponding apparatus at the transmitter.
  • the video-frequency amplifier I.1 is designed in accordance with the present inventio'n and comprises signal-translating means, for example, a multigrid vacuum-tube ampliiler 2
  • -signal-input circuit for the amplifier I1 comprising a voltage-divider resistor 22 included in the output circuit of the video-frequency ampliner I3'.
  • the iirst grid or signalinput electrode ofthe tube 2l is coupled to the input circuit by means of a tap on the resistor 22, a vacuum-tube amplifier 23, and a diode reinserter 2l.
  • a suitable coupling condenser 25 andleak resistor 25 are included in the input y circuit of the tube 23 and a load resistor 23a is included in its output circuit.
  • a coupling condenser 21, leak resistor 28, and bias battery 29 are also included in the signal-input circuit of the tube 2l as shown, the leak resistor 28 serving as the load resistor of diode reinserter 24.
  • thus comprises an input element or first grid and means for applying to the input element the video-frequency and background-illumination components with predetermined amplitude values thereof corresponding substantially to the black and white shade values of the transmitted picture.
  • is similarly coupled to the input circuit by means of an adjustable tap on -the voltagedivider resistor 22, vacuum-tube amplifier 30, ,and diode reinserter 3
  • a coupling condenser 32 and leak resistor 33 are included in the input circuit of the tube 30 while a load resistor 30a is included in its output circuit.
  • a coupling condenser 34, leak resistor 35 and bias battery 36 are also provided in the input c'ircuit of the third grid of the tube 2
  • a load resistor 31 is included in the anode circuit of the tube 2
  • Operating potentials are applied .to the electrodes of the tubes 2
  • the video-frel quency signal is supplied to the'ampliier I1 froxn the output circuit of the-amplifier I6 and appears across the voltage-divider resistor 22 with such polarity that positively increasing signal v voltage corresponds to increased illumination in the image represented thereby.
  • the taps on resistor 22 are so adjusted that predetermined portions of the signal-input -voltage are applied to .the input circuits of the tubes 23 and 30, preferably in-a ⁇ ratio of approximately 1:3,
  • the tubes 30 ⁇ and 23 serve to amplify, and reverse the polarities of, the applied signal voltages, which are then applied by .way of the reinserter diodes 24v
  • function to derive from the signal input to the control electrodes ⁇ negative unidirectional-bias voltages equal to thepeak value ofJ the signal on the black side of the zero axis, which voltages appear across the resistorsl 28 and 35, respectively, andare thus applied to the i'lrst and third grids of the tube 2
  • the resultant signals applied to the control grids therefore, include the xed-bias voltages and the unidirectional background-illumination component as y well as thevideoor high-frequencypicture-signal components and they are so applied to their respective grids that a predetermined characteristic level thereof, preferably the level corresponding approximately to black, corresponds to zero signal voltage on each of'the control electrodes.
  • Thestage thus comprises means for developingin the output 4thereof video-frequency and illumination components of the translated signal with' predetermined amplitude values thereof corresponding substantially to the black and white shade values of the transmitted picture.
  • the rectier 38 operates, as explained above, to develop a unidirectional-bias voltage responsive to a predetermined illumination characteristic of the signal, specifically, to develop a bias voltage proportional to the average value of the video-frequency signal, and this Avoltage is applied negatively to the control electrode of the tube 30.
  • the amplication of the signal translated by thetube 30 is varied to control the gamma-adjusting means of stage l1 automatically in accordance therewith, thus to control the average amplitude of the signal applied to the third grid of the tube 2
  • Fig.. 1 The results obtained by the system of Fig.. 1 may. best be explained with referencev to the curves of Figs. 2 and 3.
  • the abscissae represent signal voltages applied to the rst or ⁇ signal-input grid of tube 2
  • the curves g3 represent the mutual conductance characteristics of the tube for different voltages aptrlling grid, the values given to g3 being in terms of anyV arbitrary unit rather than voltage values.
  • curves An, .A3, and A4 which is the same as 9s, illustrate the-effective mutual conductance characteristics of tube 2
  • this decrease is effected by successively increasing negatively bias voltage supplied by the rectier 38 resulting from receivedV signals of ,progressively decreasing average amplitudes, that is, representing images of decreasing average illumination.
  • the variation in the bias voltage, and hence the transition from one of the curves A1-A4 to another is, of course, continuous rather than in discrete steps, as illustrated.
  • the curves Bi-B4 of Fig. 3 represent curves A1-A4 of Fig. 2 plotted on logarithmic scales so that the parabolic curves of Fig. 2 are changed to the linear curves of Fig. 3, which latter indicate more clearly the gamma of the system which is measured by rthe slopes of the curves B1-B4 which, in the instances shown, are 2,-1.6, 1.3, and
  • the gamma of the system is thus varied over the range of. 1-2 in accordance with the average value of the signal translated by the system.
  • the contrast between the darker incremental areas of the re- 5 nal with predetermined amplitude values .thereproduced image is progressively increased relative to the contraest between the lighter areas of the image for progressively darker images.
  • a television signal-translating system comprising means for translating a television signalY including an input element and means for applying to said le ent the video-frequency and ba-ckground-illurnitrrila ⁇ tion components of said signal with predetermined amplitude values thereof corresponding substantially to the black and white shade values of the transmitted pictures, means for adjusting the gamma of said translating means, and means responsive to a predetermined illumination characteristic of said signal for controlling said adjusting means in accordance therewith.
  • a television signal-translating system comprising means for translating a video-frequency signal including an input element and means for applying to said element the video-frequency and background-illumination components of said signal with predetermined amplitude values thereof corresponding substantially to the black and white shade values of the transmitted pictures, means for adjusting the gamma of said translating means, means for ⁇ developing a controlling effect proportional to a predetermined illumina tion characteristic of said signal, and means for 4utilizing said. controlling effect to. control said adjusting means.
  • a television signal-translating system comprising means for translating a television signal including an input element andV means for applying to said element the video-frequency and background-illumination components of said signal with predetermined amplitude values thereof corresponding substantially to the black and white shade values of the transmitted' pictures, means for adjusting the gamma of said translating means, and means responsive to the average value 4of the illumination components of of corresponding substantially to the black and white shade values oi the transmitted pictures, means for adjusting the gamma of said translating means, rectifying means for developing a .control-bias voltage prUPOrtlonal to the average value of the illumination components of said sigl nal, and means for utilizing said bias voltage to Cal Cil
  • a television, signal-translating system comcontrol said adiusting means.' l
  • a television signal-translating system comprising means for translating a video-frequency signs! with s predetermined distortion of its wave form including an input element and means for applying to said element the video-frequency and background-illumination components of said signal with predetermined amplitude values thereof 4corresponding substantially to the black and white shade values of the transmitted pictures, means for adjusting said translating means to vary said predeterminedA distortion, yand means responsive to a predetermined illumination characteristic of 'said signal for controlling said adjusting means in accordance therewith.
  • a television vsignal-translating system comprising signal-translating means including a selfmodulating signal-translating device, means for applying to said device a television signal including video-frequency and unidirectional background-llumination components with predetermined input amplitude values corresponding substantially to black and white shade values of the transmitted pictures, thereby to effect a predetermined distortion of the wave form of the translated. signal in accordance with the instantaneous 'values thereof, means for adjusting said translating means to vary said predetermined distortion, and means responsive to a predetermined illumination characteristic of said signal for controlling said adjusting means in accordance therewth.
  • a television signal-translating system comprising signal-translating means, means for applying to said translating meansfor translation thereby a television signal including video-fre- 'quency and unidirectional background-illumination components with predetermined input amplitude values corresponding substantially to black and white shade values of the transmitted pictures, means for separately applying said signal to said translating means instantaneously to modify the signal-transfer ratio thereof in accordance with the instantaneous values of said signal, thereby to eiect a predetermined distortion-of the wave form of the translated signal, and means for controlling the amplitude-of said separately applied signal in accordance with a predetermined illumination characteristic of said signal, to adjust said distortion in accordance with said characteristic.
  • a television signal-translating system comprising a vacuum tube having a cathode, an output electrode. and a plurality of signal-input electIOdeS, meanslfor applying to a first of said input electrodes a television signal including videofrequency and unidirectional background-illumination components for translation by said tube, means for applying said signal to a second of said input electrodes instantaneously to vary the mutual conductance of said rst of said input electrodes with respect to said output electrode in accordance with the instantaneous values of tures, and lsimultaneously'adjusting the gamma said signal, thereby to effect a predetermined disy tortion of the wave form oi the translated signal, and means for controlling the amplitude of said i' signal applied to said second of said electrodes in accordance with a predeterminedl illumination characteristic of said signal, automatically to adjust said distortion in accordance with saidcharf acteristic.
  • a television signal-translating 'system comprising a vacuum tube having va cathode, an output electrode, and a plurality' oi control electrodes, means for applying to a rst one of said control electrodes a television signal including video-frequency and unidirectional background- .illumination components for translation by said tube, means including signal-repeating means for applying said signal to another of said control' electrodes instantaneously to vary the mutual conductance of said one of saidc'ontrol electrodes with respect to said output electrode in accordance with said signal, and means for controlling the repeating ratio of said signal-repeating means in accordance with the average predetermined' ⁇ illumination characteristic of said signal, auto-l matically to effect an adjustment of said predetermined distortion in accordance with said characteristic.
  • the method oi operating a television signal-translating system which comprises translating through said system an input television signal including videofrequency and unidirectional background-illumination components with predetermined amplitude values thereof corresponding substantially to the black and white shade values of the transmitted pictures, sepa-A rately utilizing said signal instantaneouslygto modify the signal-transfer ratio of said system in accordance with said signal, thereby to eiiect a predetermined distortion of the wave form of the J OHN C. WILSON.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Picture Signal Circuits (AREA)
  • Processing Of Color Television Signals (AREA)
US250914A 1939-01-14 1939-01-14 Television signal-translating system Expired - Lifetime US2255691A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
BE437358D BE437358A (en, 2012) 1939-01-14
US250914A US2255691A (en) 1939-01-14 1939-01-14 Television signal-translating system
US253040A US2255692A (en) 1939-01-14 1939-01-27 Television signal-translating system
GB32445/39A GB538947A (en) 1939-01-14 1939-12-18 Improvements in television signal-translating systems
FR862876D FR862876A (fr) 1939-01-14 1940-01-13 Système de transmission des signaux de télévision

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US250914A US2255691A (en) 1939-01-14 1939-01-14 Television signal-translating system

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US2255691A true US2255691A (en) 1941-09-09

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BE (1) BE437358A (en, 2012)
FR (1) FR862876A (en, 2012)
GB (1) GB538947A (en, 2012)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2519238A (en) * 1947-04-05 1950-08-15 Rca Corp Biased diode wave shaping circuit
US2548436A (en) * 1946-01-25 1951-04-10 Hazeltine Corp Television receiver background control circuit
US2552588A (en) * 1947-04-26 1951-05-15 Columbia Broadeasting System I Gamma control circuit
US2569297A (en) * 1948-12-16 1951-09-25 Rca Corp Direct-current restoring apparatus
US2594870A (en) * 1945-11-29 1952-04-29 Us Navy Indicator
US2692299A (en) * 1948-12-11 1954-10-19 Westinghouse Electric Corp Image contrast intensifier
US2740071A (en) * 1950-05-11 1956-03-27 Columbia Broadcasting Syst Inc Television
US2760008A (en) * 1950-08-30 1956-08-21 Rca Corp Amplifier having controllable signal expansion and compression characteristics
US3752905A (en) * 1970-12-16 1973-08-14 H Schneider Gamma control in the luminance channel of a color television transmitter
US4489349A (en) * 1980-01-31 1984-12-18 Sony Corporation Video brightness control circuit
US4866513A (en) * 1985-07-04 1989-09-12 Fuji Photo Film Co., Ltd. Color contrast correction system for video images obtained from color film

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL82594C (en, 2012) * 1952-05-07
GB8521019D0 (en) * 1985-08-22 1986-10-01 Rank Pullin Controls Ltd Imaging apparatus

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2594870A (en) * 1945-11-29 1952-04-29 Us Navy Indicator
US2548436A (en) * 1946-01-25 1951-04-10 Hazeltine Corp Television receiver background control circuit
US2519238A (en) * 1947-04-05 1950-08-15 Rca Corp Biased diode wave shaping circuit
US2552588A (en) * 1947-04-26 1951-05-15 Columbia Broadeasting System I Gamma control circuit
US2692299A (en) * 1948-12-11 1954-10-19 Westinghouse Electric Corp Image contrast intensifier
US2569297A (en) * 1948-12-16 1951-09-25 Rca Corp Direct-current restoring apparatus
US2740071A (en) * 1950-05-11 1956-03-27 Columbia Broadcasting Syst Inc Television
US2760008A (en) * 1950-08-30 1956-08-21 Rca Corp Amplifier having controllable signal expansion and compression characteristics
US3752905A (en) * 1970-12-16 1973-08-14 H Schneider Gamma control in the luminance channel of a color television transmitter
US4489349A (en) * 1980-01-31 1984-12-18 Sony Corporation Video brightness control circuit
US4866513A (en) * 1985-07-04 1989-09-12 Fuji Photo Film Co., Ltd. Color contrast correction system for video images obtained from color film

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Publication number Publication date
BE437358A (en, 2012)
GB538947A (en) 1941-08-22
FR862876A (fr) 1941-03-18

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