A fast global shutter image sensor based on the VOD mechanism

This paper presents a method to realize a fast and uniform global shutter for time resolved imaging in standard, commercially available image sensors. Fast toggling of the substrate voltage is used in image sensors with a Vertical Overflow Drain (VOD) shutter mechanism, a common building block of IT-CCDs. Special measurements and analysis techniques were developed in order to characterize the shutter performance. Results show very good performance, with various potential applications such as Time-of-Flight imaging, transient imaging, and Fluorescence Lifetime Imaging Microscopy. Using off-theshelf devices we were able to produce shutter rise and fall times of 1.5ns, and shutter contrast ratio of 1:50 or better. The global shutter temporal behavior is very uniform, with less than 200ps delay between the periphery and the center measured across 1/4" and 1/3" sensors. Moreover, neighboring pixels exhibit less than 50ps timing variation. The physical principles that allow this fast operation are discussed in detail and explained through measurement results supported by device simulations.