Gradation distortion compensation by FET pre-emphasis circuit op

Details Gradation distortion compensation by FET pre-emphasis circuit op Gradation distortion compensation by FET pre-emphasis circuit op

1984-11-09

1987-08-25

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358 33, H04N 520

Patent

active

046896783

ABSTRACT:
A video signal as it comes from a camera is inverted and clamped to an adjustable voltage for the black level and then proceeds at an amplified level to a differential amplifier that applies a signal to the gate of an N-channel FET. The voltage source provides a positive voltage through a load resistor and the drain-source path of the FET in series, while the drain electrodes is fed back through the differential amplifier in phase opposition to the incoming video, causing the drain current to vary in the same way as the video signal voltage. The applied voltage and the load resistor are such as to operate the FET in its saturation region, with the result that the gate voltage which is the voltage at the output of the differential amplifier, has the desired square root curve characteristic for correcting the gradation distortion of the picture tube. If a P-channel FET is used, the polarity of the voltage supply is reversed and the video is applied to the differential amplifier non-invertedly and clamped low rather than high. A potentiometer adjusts the clamping level to obtain the desired value of the gradation slope (gamma).

REFERENCES:
patent: 3845326 (1974-10-01), Godden
patent: 4393406 (1983-07-01), Lehmann
R. G. Nelson, "Automatic Thresholding and Shading Circuit for Solid-State Cameras and Scanners" IBM Tech. Disclosure, vol. 17, #2, pp. 519-520, 7/74.

Affiliated with

Also associated with

Rating

Gradation distortion compensation by FET pre-emphasis circuit op does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Gradation distortion compensation by FET pre-emphasis circuit op, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gradation distortion compensation by FET pre-emphasis circuit op will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1926843