High Speed Readout for Photodiode Focal Plane Arrays

Recent progress in the development of high energy laser pulse sources and advancements in detector array technology has enabled single LADAR systems that can generate range and image data based on the target reflection from a single pulse. Accuracy of the system depends on precise temporal data to be extracted from each pixel when the reflected pulse is received. Advanced photodiode arrays using InGaAs are able to accurately track the reflected light as a function of time by converting the light return from a laser pulse to a photocurrent pulse for each pixel. The Readout Integrated Circuit (ROIC) must be capable of accurately sampling and processing the return pulse at each pixel at intervals of 1 ns or less. A unique CMOS based architecture, called PASH ROIC, is presented, which permits sampling the photocurrent pulse of each pixel at 1-2 GHz frequencies and also includes high speed analog track and hold circuits for temporary storage of the sampled data at each pixel. The proposed PASH ROIC architecture also incorporates a high performance ADC that could be integrated as part of the ROIC to convert the analog data to digital data for real time digital processing applications.