A CMOS contact imager for locating individual cells

We describe the design of a contact imager for applications in lab-on-a-chip systems, such as sample preparation and manipulation and monitoring of cells. This is a challenging task because most cells are nearly transparent, so the contrast between the presence and absence of a cell is small. Thus additional image processing is necessary to locate cells. To enhance the image contrast and facilitate object recognition, the contact imager implements on-chip one bit quantization with a dynamic threshold that adapts to the background illumination. The imager is capable of locating dark objects in a bright background or bright objects in a dark background. The locations of recognized cells are generated as outputs to alleviate computational requirements for generating control signals in closed-loop systems.