Television – Cathode-ray tube display automatic black level bias control
Patent
1994-05-19
1996-01-30
Groody, James J.
Television
Cathode-ray tube display automatic black level bias control
315383, H04N 568
Patent
active
054884179
ABSTRACT:
A controllable current source in an AKB circuit applies a measurement current to a kinescope driver amplifier during selected lines of the vertical interval of a video input signal to induce a beam current in a kinescope coupled to the driver amplifier. A comparison circuit compares samples of the beam current obtained during the selected lines with a reference signal and applies a correction current to the driver amplifier for regulating a parameter (e.g., black level) of images displayed by the kinescope. A signal source, coupled to the measurement current source, inhibits production of the measurement current during retrace portions of the selected lines and enables production of the measurement current during trace portions of the selected lines. Advantageously, the signal source provides suppression of visual artifacts due to AKB operation when using direct view or projection kinescopes of a type in which pincushion correction is not applied during line retrace intervals.
REFERENCES:
patent: 4263622 (1981-04-01), Hinn
patent: 4484228 (1984-11-01), Parker
patent: 4536800 (1985-08-01), Parker
patent: 4633321 (1986-12-01), Tallant, II
patent: 4694350 (1987-09-01), Hinn
patent: 5036257 (1991-07-01), Norman et al.
Coalter Richard G.
Emanuel Peter M.
Groody James J.
Lee Michael H.
Thomson Consumer Electronics Inc.
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