GB1205164A - Improvements in gamma correction circuits - Google Patents
Improvements in gamma correction circuitsInfo
- Publication number
- GB1205164A GB1205164A GB26592/68A GB2659268A GB1205164A GB 1205164 A GB1205164 A GB 1205164A GB 26592/68 A GB26592/68 A GB 26592/68A GB 2659268 A GB2659268 A GB 2659268A GB 1205164 A GB1205164 A GB 1205164A
- Authority
- GB
- United Kingdom
- Prior art keywords
- transistor
- signal
- output
- gamma correction
- fed
- 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
Links
- 239000004065 semiconductor Substances 0.000 abstract 2
- 230000000903 blocking effect Effects 0.000 abstract 1
- 230000003071 parasitic effect Effects 0.000 abstract 1
Classifications
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Picture Signal Circuits (AREA)
- Networks Using Active Elements (AREA)
Abstract
1,205,164. Gamma correction circuit. COMPAGNIE FRANCAISE THOMSON HOUSTON-HOTCHKISS BRANDT. 4 June, 1968 [1 June, 1967; 20 Dec., 1967], No. 26592/68. Heading H4F. An adjustable gamma correction circuit for a television transmitter-receiver assembly comprises a transistor current-generator 1, a gamma correction transistor 2, a differential amplifier 3, a phase reversal transistor 4 and a variable-gain amplifier and combining circuit 5. The video signal to be corrected is fed from input terminal E through the current generator 1 to the gamma correction transistor which produces two outputs, one being a first signal altered according to a fixed law of the form: (output) = = (input)γ from the use of the transistor 21 as a semiconductor junction, γ being a constant = 0À4, and the second being simply an unaltered signal whose amplitude is equal to the first due to the use of the transistor 21 as a linear amplifier. The first, altered, signal is fed via the differential amplifier 3 together with the second, unaltered, signal and an output proportional to their difference is fed to the combining circuit, and the second, unaltered, signal is via the phase reversing transistor 4 to the combining circuit 5, whence an output signal is fed to terminal S of the form: (output) = A[(input)<SP>0À4</SP>- (input)] + (input), where A is the gain of the combining circuit. The D.C. component of the video signal fed to the current generator 1 is clamped by a level blocking or clamping voltage applied at terminal 11, and the output from the current generator is blocked for signals corresponding to black and open to other signal values. The gain A of combining circuit 5 is adjustable between 0 and 1 by potentiometer 53 which may be distant from the circuit. To eliminate background noise and parasitic signals the collector of the current generator transistor 12 may be connected to a source of negative pulses fed in concomitance with the line blanking periods. Further to reduce noise a low-pass filter of lower bandwidth than the television assembly may be connected in series with the first output from the gamma correction transistor, compensation in the second output being provided by a delay line. A source of constant amplitude negative pulses may be connected to either the emitter or the base of the gamma correction transistor by means of diodes in series opposition, Figs. 6 and 7, not shown, to cause a shift in amplitude of the characteristic curve of the semi-conductor junction and match it more closely to the correction curve desired.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR108716A FR1534777A (en) | 1967-06-01 | 1967-06-01 | Improvements to gamma correction circuits |
FR133119A FR93720E (en) | 1967-06-01 | 1967-12-20 | Improvements to gamma correction circuits. |
Publications (1)
Publication Number | Publication Date |
---|---|
GB1205164A true GB1205164A (en) | 1970-09-16 |
Family
ID=26176962
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB26592/68A Expired GB1205164A (en) | 1967-06-01 | 1968-06-04 | Improvements in gamma correction circuits |
Country Status (5)
Country | Link |
---|---|
DE (1) | DE1762353B2 (en) |
FR (2) | FR1534777A (en) |
GB (1) | GB1205164A (en) |
NL (1) | NL160694C (en) |
SE (1) | SE330940B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4686562A (en) * | 1985-03-30 | 1987-08-11 | Kabushiki Kaisha Toshiba | Gamma correction circuit |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3970774A (en) * | 1975-03-31 | 1976-07-20 | Rca Corporation | Electronic signal mixer |
JPS58130676A (en) * | 1982-01-29 | 1983-08-04 | Toshiba Corp | Gamma compensating circuit |
DE19845187A1 (en) * | 1998-10-01 | 2000-04-13 | Loewe Opta Gmbh | Method for adjusting the brightness of a cell on a flat display |
-
1967
- 1967-06-01 FR FR108716A patent/FR1534777A/en not_active Expired
- 1967-12-20 FR FR133119A patent/FR93720E/en not_active Expired
-
1968
- 1968-05-28 NL NL6807530.A patent/NL160694C/en not_active IP Right Cessation
- 1968-05-31 DE DE19681762353 patent/DE1762353B2/en active Granted
- 1968-05-31 SE SE07391/68A patent/SE330940B/xx unknown
- 1968-06-04 GB GB26592/68A patent/GB1205164A/en not_active Expired
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4686562A (en) * | 1985-03-30 | 1987-08-11 | Kabushiki Kaisha Toshiba | Gamma correction circuit |
Also Published As
Publication number | Publication date |
---|---|
DE1762353B2 (en) | 1977-07-21 |
FR1534777A (en) | 1968-08-02 |
NL160694B (en) | 1979-06-15 |
NL160694C (en) | 1979-11-15 |
DE1762353C3 (en) | 1978-03-09 |
DE1762353A1 (en) | 1970-04-30 |
SE330940B (en) | 1970-12-07 |
NL6807530A (en) | 1968-12-02 |
FR93720E (en) | 1969-05-09 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PS | Patent sealed [section 19, patents act 1949] | ||
PCNP | Patent ceased through non-payment of renewal fee |