Digital cameras and optical imaging devices employ image sensors. Image sensors convert optical images to digital data that may be represented as digital images. An image sensor typically includes an array of pixel sensors, which are unit devices for the conversion of an optical image into electrical signals. Pixel sensors often manifest as charge-coupled devices (CCDs) or complementary metal oxide semiconductor (CMOS) devices. However, CMOS pixel sensors have recently received more attention. Relative to CCD pixel sensors, CMOS pixel sensors provide lower power consumption, smaller size, and faster data processing. Further, CMOS pixel sensors provide a direct digital output of data, and generally have a lower manufacturing cost compared with CCD pixel sensors.