Apple patent application US20140125852 "Optical demodulation using an image sensor" by Richard Baer, Michael Malone, Ting Chen, and David Amnon Silverstein proposes two-mode image sensor. The first mode is a regular image capture, while the second one is optimized for the lighting LED-based data communication (Li-Fi). In Li-Fi mode, "the integration interval for the image sensor is set to less than two row periods, preferably close to one row period, without regard to the exposure data if the data capture mode is selected.
An analog gain may be increased to as large a value as possible in data capture mode. All pixels in a row may be summed before analog to digital conversion in data capture mode. An image sensor frame period may be set according to a signaling frame period of an illumination modulation data transmission in data capture mode.
The controller may further causes data to be inverted from frame to frame and decoding of the difference of two successive frames if the data capture mode is selected. The controller may further causes defocusing of an optical system that forms an image on the image sensor if the data capture mode is selected."
An analog gain may be increased to as large a value as possible in data capture mode. All pixels in a row may be summed before analog to digital conversion in data capture mode. An image sensor frame period may be set according to a signaling frame period of an illumination modulation data transmission in data capture mode.
The controller may further causes data to be inverted from frame to frame and decoding of the difference of two successive frames if the data capture mode is selected. The controller may further causes defocusing of an optical system that forms an image on the image sensor if the data capture mode is selected."
