Transversal direct readout CMOS APS with variable shutter mode

A transversal direct readout (TDR) structure for CMOS active pixel image sensors (APSs) eliminates the vertically striped fixed pattern noise. This novel architecture has evolved to incorporate a variable shutter mode as well as simplifying the pixel structure. This paper describes a 320 x 240-pixel TDR APS that not only exhibits neither vertically nor horizontally striped fixed pattern noise, but can also take pictures at selected exposure times. The pixel consists of a photodiode, a row- and a column-reset transistor, a source-follower input transistor, and a column-select transistor instead of the row-select transistor found in conventional CMOS APSs. The column-select transistor is connected to a signal line, which runs horizontally instead of vertically. The column-reset and the column-select transistor are driven by the same pulse different from its predecessor. Thus the pixel is simplified by the reduction of the number of bus lines similar to conventional CMOS APSs.