Method and apparatus for applying correction to a signal used to

Details Method and apparatus for applying correction to a signal used to Method and apparatus for applying correction to a signal used to

1991-09-10

1993-04-13

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358183, 358182, 358181, 358178, 358169, H04N 514

Patent

active

052027627

ABSTRACT:
An apparatus and method which control the gain of the key signal dynamically and thereby compensate for the effects of an unevenly lit backing or lens vignetting. This dynamic control occurs over a video frame and has the effect of modulating the key signal. In this connection, there are four possible gain controls as follows: a) a horizontal ramp to increase the level of either side (left or right) of the key signal; b) a vertical ramp to increase the level of the top or bottom of the key signal; c) a horizontal parabola to raise or lower the gain of both sides of the key signal simultaneously to nullify lens effects; and d) a vertical parabola to raise or lower the gain of both the top and bottom of the key signal simultaneously to nullify lens effects.

REFERENCES:
patent: 3588338 (1971-06-01), Dischert
patent: 4121253 (1978-10-01), McCoy
patent: 4731652 (1988-03-01), Yamanaka

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