A High Dynamic Range CMOS Image Sensor for Scientific Imaging Applications

This paper presents a high dynamic range CMOS image sensor that utilizes a combined linear-logarithmic readout scheme with built-in linear-logarithmic switching point detection for scientific imaging applications. The proposed readout architecture adjusts each individual pixel to operate in either linear or logarithmic readout mode according to the input illumination level. This realizes direct high-throughput image reconstruction enabling a hybrid combination of linear and logarithmic pixel outputs in the same image frame without introducing complicated post-signal processing. A novel feature of fine-tuning the overall dynamic range and contrast of the output image is also achieved using this readout method. An image sensor chip consisting of a 16times16 7-T pixel array with n-well/p-sub photodiodes and the proposed readout architecture has been implemented in 0.5 mum CMOS technology. The sensor chip has been evaluated through both electrical and optical characterizations, demonstrating an overall dynamic range of 121 dB. As a proof of concept, scientific imaging results on clusters of nano particles (CoF_e2O₄) and optical fiber sensor are presented and discussed.