Method and apparatus for increasing effective contrast ratio and brightness yields for digital light valve image projectors
View Patent ↗A method and apparatus for increasing the effective contrast ratio and brightness yields for digital light valve image projectors using a variable luminance control mechanism (VLCM), associated with the projector optics, for modifying the light output and provide a correction thereto; and an adaptive luminance control module (ALCM) for receiving signals from the video input board, the adaptive luminance control module producing a signal on a VLCM bus connecting the variable luminance control mechanism and the adaptive luminance control module, the signal causing the variable luminance control mechanism to change the luminance of the light output and provide a corrected video signal for the projector.
1. A video projector for projecting the image of a received video signal, the projector comprising:
an illumination source;
a projection lens adapted to receive and project light generated by said illumination source;
at least one imaging device configured to modulate incident light in response to a received video signal wherein the video signal comprises one or more individual frames;
a light engine providing a light path extending from the illumination source to and through the projection lens, the light path being incident on at least a portion of the imaging device whereby at least a portion of the light in the light path is modulated in accordance with the received video signal;
a luminance control mechanism at least partially disposed in the light path and adapted to at least partially control the transmission of light through the light path in response to an applied luminance control signal; and
an adaptive luminance control module configured to generate and output, in response to the luminance level of at least one individual frame within the received video signal, a luminance control signal for application to the luminance control mechanism to control the effective contrast of the projected image.
2. The video projector of claim 1 , wherein the luminance control mechanism comprises an electro-mechanical iris controlled by the luminance control signal.
3. The video projector of claim 2 wherein the iris is oval or cats-eye shaped.
4. The video projector of claim 2 , wherein the luminance control mechanism includes a sensor adapted to generate a feedback signal for application to the luminance control module in response to a position of the iris to assist the module in controlling the iris.
5. The video projector of claim 1 , wherein the adaptive luminance control module includes at least one look-up table, whereby the luminance control module is adapted to utilize the look-up table to generate the luminance control signal.
6. The video projector of claim 1 , wherein in response to an increasing luminance level in multiple individual frames of the received video signal the adaptive luminance control module varies the luminance control signal to cause a decrease in light throughput by the luminance control mechanism.
7. The video projector of claim 1 , further including a sensor for sensing ambient light, the sensor generating an ambient light indicative signal for application to the adaptive luminance control module, the adaptive luminance control module varying, at least in part in response to the ambient light indicative signal, the luminance control signal to cause the luminance control mechanism to vary the luminance level provided in the light path with changes in ambient light.
8. The video projector of claim 1 , further including a media-content input device adapted to generate a content signal for application to the adaptive luminance control module, the adaptive luminance control module varying, at least in part in response to the luminance content signal, the luminance control signal to cause the luminance control mechanism to vary the luminance level with changes in media content or user preference.