Patent ID: 8456410

Claim:
A system, comprising: a display; a light source to backlight the display; a controller to control the brightness of the light source; and a light sensor to generate a first photocurrent and a second photocurrent, the first photocurrent indicative of both the visible light and the IR light, and the second photocurrent indicative of the IR light; and wherein the controller controls the brightness of the light source based on a level of a differential photocurrent, produced by determining a difference between the first and second photocurrents; and wherein the differential photocurrent has a spectral response with a significant part of the IR light removed; wherein the light sensor includes: a layer of a first conductivity type; a first region of a second conductivity type in the layer of the first conductivity type and forming a first PN junction photodiode with the layer of the first conductivity type; a second region of the second conductivity type in the layer of the first conductivity type and forming a second PN junction photodiode with the layer of the first conductivity type; and at least one further layer intrinsic to CMOS technology that covers the second region of the second conductivity type, but not the first region of the second conductivity, the at least one further layer blocking visible light while allowing at least a portion of infrared (IR) light to pass therethrough; wherein carriers are produced in the layer of the first conductivity type when light, including both visible light and IR light, is incident on the light sensor; wherein a portion of the carriers produced due to the visible light and the IR light incident on the first region of the second conductivity type are captured by the first region of the second conductivity type and contribute to the first photocurrent that is indicative of both the visible light and the IR light; and wherein a further portion of the carriers, produced due to the IR light that passes through the at least one further layer, are captured by the second region of the second conductivity type and contribute to the second photocurrent that is indicative of the IR light.