Endoscope system using cmos image sensor having pixels without internal sample/hold circuit

Abstract

An endoscope system includes a host device and an endoscope including a very small area CMOS image sensor having only four pads (power, ground, digital in, analog out), and including an array of 4T pixels and associated control circuitry for performing correlated double sampling (CDS) to generate analog reset level and analog signal level values associated with light detected by photodiodes in each pixel. Instead of processing the analog values on-chip, the analog reset values and analog signal values are transmitted in separate sets one row at a time along with interleaved synchronization signals by way of a single analog contact pad to the host device of the endoscopic system, which uses the synchronization signals to reconstruct the sensor's internal clock in order to process the analog values. The endoscope housing thus requires only four wires and is made very small.