Weekly Patent Review

Magnachip's application US20080296630 talks about applying negative bias voltage to transfer gate transistor during the integration. It looks like today everybody uses negative bias to reduce dark current. One possible problem here is increase in blooming and everybody solves it in its own way. Magnachip proposes a special burried channel for blooming current. This complicates the doping scheme of the transfer gate area, so I doubt that this idea finds a big use.

Nokia camera team filed application US20080297816 on improved black level correction. They try to compensate black level gradients across the sensor array by measuring black level in many points on the periphery of the array and interpolating the results for all the pixels, doing it separately for each color. There is nothing unusual in the idea itself, other than it points out that the black level spatial variations is probably the real problem in the sensors that Nokia uses.