Current-Mode Temporal Difference CMOS Imager for Capsule Endoscopy

Abstract

A current-mode temporal difference imager for wireless capsule-endoscopy is introduced. The new imager generates low output data rate. Wide dynamic range image can be recovered from the low-rate data at the receiver side. To reduce the circuit charge injection error of the difference imager, a calibration technique for the pixel is developed, and introduced in the paper. The image restoration error is found to be bounded for our calibration scheme. With a designed estimation function, the restoration error is suppressed below 0.1 pA, which enables the imager with 95 dB dynamic range. The hardware cost of the decoder for the calibration scheme is moderate.