Modeling and characterization of logarithmic complementary metal-oxide-semiconductor active pixel sensors

We present a detailed analysis of logarithmic active pixel sensors (log-APS ) to be used in complementary metal-oxide-semiconductor (CMOS) imagers for real-time on-chip motion detection. Based on an equivalent circuit model fo r CMOS-compatible photodiodes. an HSPICE simulation has been used to charac terize different configurations of these sensors under various conditions o f light intensities and switching speeds. These investigations are supporte d by the experimental results obtained from the chip fabricated with standa rd 0.5 mu m CMOS technology. It is concluded that more robust on-chip motio n detection in CMOS imagers can be achieved with careful design of its log- APS photocircuits that considers the issues discussed here. (C) 2000 Americ an Vacuum Society. [S0734-2101(00)01803-0].