A High Dynamic Range CMOS Image Sensor with Adaptive Integration Time Control

Abstract

The scope of this thesis encompasses the development and testing of a CMOS based image sensor. The imaging process consists of the integration of the photocurrent generated by incident light in each pixel. The implementation of a concept for adaptive regulation of the local integration time allows imaging of high dynamic range scenes without loss of information due to over- or underexposure. Depending on the size of the integrated memory, the proposed concept allows the specification of a freely movable image region within which the integration time is regulated. At a chosen maximum integration time of 33ms the dynamic range of the sensor amounts to 134dB and covers a range of intensities from 1mW/m^2 to 5kW/m^2. The prototype consists of 170x170 pixels with a high dynamic region of 85x85 pixels. The additionally implemented ability to average neighboring pixels allows an expansion of the high dynamic range region over the entire extent of the sensor. An on-chip double sampling circuitry reduces the fixed pattern noise caused by unavoidable device-to-device mismatch.