Ambient light sensor with internal light cancellation

摘要

An electronic device includes a transparent surface, a light emitting device that emits light through the transparent surface, and a light sensor for receiving ambient light and providing an ambient light value. A retarder and a linear polarizer are placed between the transparent surface and the light emitting device. The retarder and linear polarizer may attenuate internal reflections from the transparent surface. The light sensor may have two channels and a second linear polarizer may attenuate the ambient light directed toward a second channel. A second retarder may be used with the second linear polarizer to attenuate the ambient light directed toward the second channel. A light detection circuit may use the difference between the two channels of the light sensor to provide the ambient light value.

主权项

1. An electronic device comprising:
a transparent surface; a light sensor; a light emitting device between the transparent surface and the light sensor, the light emitting device to emit light through the transparent surface; a first retarder between the transparent surface and the light emitting device; a first linear polarizer between the first retarder and the light emitting device; wherein the light sensor is for receiving ambient light that passes through the transparent surface, then the first retarder, and then the first linear polarizer, the light sensor including
a first channel for receiving both light from the light emitting device and ambient light, and to provide a first light level value, anda second channel with a second linear polarizer oriented to attenuate ambient light that has been polarized by the first linear polarizer, the second channel for receiving light from the light emitting device, and to provide a second light level value.