Apparatus for providing contrast and/or brightness control of a video signal
AssigneeThomson Consumer Electronics, Inc.
InventorsAntoine Dupont, Bernard Hepp, Eric Benoit
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Abstract
The present invention is a video drive apparatus of the two ramp type which includes facility to selectively adjust the brightness and/or the contrast of an image reproduced on a display device. In this apparatus, at least one of the ramp signals is generated digitally by for example a counter. Provision is made to change the counting rate of such counter which effects a change in display contrast. Provision is also made to selectively change the phase of the ramp signal applied to the second stage relative to the start of respective pulses of the PWM signal thereby effecting brightness changes in the reproduced image.
Claims9
Apparatus for translating a video signal for reproduction of a video image on a display device comprising:
- a source of video signal;
- digital ramp generator for generating a ramp signal which increases at a controlled rate responsive to a control signal;
- an amplitude to pulse width converter having first and second input terminals coupled respectively to receive said video signal and said ramp signal, said pulse width converter providing pulses exhibiting a first state for the duration the amplitude of the video signal is greater than the ramp signal and exhibiting a second state when the ramp signal exceeds the video signal;
- control means for generating said control signal, said control signal conditioning said digital ramp generating means to increase or decrease said controlled rate and thereby control the contrast of the displayed image;
- and
- a pulse width to amplitude converter, responsive to said pulses for generating a sampled signal to drive the display device.
Apparatus for translating a video signal for reproduction of a video image on a display device comprising:
- a source of video signal;
- an amplitude to pulse width converter responsive to said video signal for providing pulses having pulse widths proportionally related to the amplitude of said video signal;
- digital ramp generator for generating a ramp signal;
- a pulse width to amplitude converter responsive to said pulses and said ramp signal for generating analog amplitude values to drive said display device;
- and
- means for controlling the phase of one of the transitions of respective said pulses relative to the start time of said ramp signal to control the brightness of images reproduced on said display device.
Dependencies are inferred from the claim text.