An active-pixel sensor (APS) is an image sensor where each pixel sensor unit cell has a photodetector and one or more active transistors. APS sensors are used in digital camera technologies such as cell phone cameras, web cameras, most modern digital pocket cameras, most digital single-lens reflex cameras (DSLRs), mirrorless interchangeable-lens cameras (MILCs), and lensless imaging for, e.g., blood cells.