Illuminated surround and method for operating same for video and other displays
In a video or other screen display apparatus, a surround to the actual screen is provided whose light output is variable in order to compensate for the effect of ambient (room) illumination on apparent contrast and chroma of the displayed image. The relationship between ambient light level and the surround illumination is an inverse power function. This provides the effect of making the viewer perceive that the entire room is brighter than it actually is, resulting in a desirable change in his perception of brightness. Thereby, the chromaticity of the surround is variable to allow a match to the calibrated white point of the video display. The apparatus includes an ambient light sensor whose output signal is provided to a control system driving the illuminated surround.
1. A display apparatus comprising:
a screen adapted to display an image;
an illuminated surround adjacent at least one edge of the screen and visible to a viewer of the screen wherein light from the surround is directed directly to the viewer;
an ambient light sensor located near the screen; and
a control coupled to the sensor and to the surround and which generates red, green, and blue signals to set an intensity and color of the surround, thereby to control a brightness and chromaticity of the surround responsive to the sensed ambient light level, wherein chromatic adaptation is countered and apparent contrast improved.
2. The apparatus of claim 1 , wherein the screen is one of an LCD, SED, OLED, plasma, rear projection, front projection, or cathode ray tube.
3. The apparatus of claim 1 , wherein the surround includes an illuminated panel.
4. The apparatus of claim 3 , wherein the panel includes a source of red, green, and blue illumination and a diffuser.
5. The apparatus of claim 1 , wherein a portion of the surround which is illuminated is spaced apart from the screen by a black area.
6. The apparatus of claim 1 , wherein the control responds to a change in the sensed ambient light level over a time of at least two seconds.
7. The apparatus of claim 1 , wherein the control responds to a change in the ambient light level in a time-averaged fashion.
8. The apparatus of claim 1 , wherein the surround includes at least three portions, each adjacent one edge of the screen and each portion subtends at least 1/14 of the viewer's field of view of the screen.
9. The apparatus of claim 1 , wherein illumination of the surround is also a function of a white point of the display.
10. The apparatus of claim 1 , wherein the sensor includes two spaced apart sensor elements, each located behind the screen relative to the viewer of the screen, and at or near a top of the screen.
11. The apparatus of claim 1 , wherein the control sets the brightness of the surround as an inverse relation to the sensed level of ambient light.
12. The apparatus of claim 11 , wherein the relation is a power function.
13. The apparatus of claim 1 , wherein the control is also responsive to a black point of the display.
14. A method comprising the acts of:
displaying an image on a screen;
providing an illuminated surround adjacent at least one edge of the screen and which is visible to a viewer of the screen wherein light from the illuminated surround is directed directly to the viewer;
sensing a level of ambient light near the screen; and
controlling a brightness and chromaticity of the illuminated surround by generating red, green, and blue signals to set an intensity and color of the surround, responsive to the sensed ambient light level, wherein chromatic adaptation is countered and apparent contrast improved.
15. The method of claim 14 , wherein the screen is an LCD, SED, OLED, plasma, rear projection, front projection, or cathode ray tube.
16. The method of claim 14 , wherein the illuminated area includes an illuminated panel.
17. The method of claim 14 , wherein the illuminated area is spaced apart from the screen by a black area.
18. The method of claim 14 , wherein the controlling responds to a change in the sensed ambient light level over a time of at least two seconds.
19. The method of claim 14 , wherein the controlling responds to a change in the ambient light level in a time-averaged fashion.
20. The method of claim 14 , wherein the illuminated area includes at least three portions, each adjacent one edge of the screen and each portion subtends at least 1/14 of the viewer's field of view of the screen.
21. The method of claim 14 , wherein the controlling is also a function of a white point of the screen.
22. The method of claim 14 , wherein the sensing includes providing two spaced apart sensor elements, each located behind the screen relative to the viewer of the screen, and at or near a top of the screen.
23. The method of claim 14 , wherein the controlling sets the brightness of the surround as an inverse relation to the sensed level of ambient light.
24. The method of claim 23 , wherein the relation is a power function.
25. The method of claim 23 , wherein the illuminated panel includes a source of red, green, and blue illumination and a diffuser.
26. The method of claim 14 , wherein the controlling is also responsive to a black point of the screen.