| 摘要 |
A backlight (10) in a liquid crystal display (LCD) is arranged to provide adjustment of the light source (C1,C2,C3,C4) brightness according to the intensity of ambient Iight (L1) detected through the LC panel without the use of external light sensors.
At least one pair (P1) of photodetectors (13,14) is arranged so that the detectors are next to each other on the inner side of the backlight housing (11) near the light source(s). Each photodetector (13,14) of the pair is covered by a polariser (15,16), whose orientation is orthogonal to that of the other detector (16,15). The orientation of one of the two polarisers (16) is arranged to be parallel to that of the rear LCD polariser (3).
One photodetector (14) detects ambient light (L1) together with Iight reflected from the backlight (L2b). The other photodetector (13) detects only light reflected from the backlight (L2a, which has the orthogonal polarisation state to L2b). The (corrected) difference signal from the two photodetectors is proportional to local ambient light intensity only.
Several photodetector pairs (P1,P2,P3,P4,P5) may be employed either to provide a signal representing the average detected ambient light intensity over the detector pairs (which is used to drive all sources together) or to allow the adjustment of the brightness of individual sources according to the locally detected ambient light intensity (via a mean over two pairs near the respective source).
The advantages of the arrangement include a lower cost and a simpler panel structure, since there are no external sensors. Furthermore a more accurate (local) ambient light measurement is possible.
Additional keywords: LED source, CCFL, edge-type backlight, direct-type backlight.
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