Photon-Counting Image Sensors

Papers presented at the 2015 International Image Sensor Workshop (IISW), in Vaals, the Netherlands, organized by the International Image Sensor Society (IISS), showed that photon-counting image sensors may represent the next step in the evolution of solid-state image sensors. In a photoncounting image sensor, it is possible to determine, with a high degree of accuracy, the number of photons that have struck a sensor photoelement during some interval of time. This is enabled by both high quantum efficiency and deep-sub-electron read noise. For some time, single-photon avalanche detectors (SPADs) have grown in performance and array size, with photoelement counts approaching 100,000 or more, today. Practical image capture at such array sizes can now be readily envisioned. SPADs also have an added advantage of allowing fine time resolution of photon arrival, enabling applications such as time-of-flight (TOF) range imaging and fluorescent lifetime imaging microscopy (FLIM). More recently, photoelements that do not require avalanche multiplication and instead use ultra-low capacitance to achieve voltage gain from captured photoelectrons, and/or use multiple sampling techniques to reduce read noise, have shown photon-counting capability. While not having the time resolution of SPADs, these devices offer the potential for large array formats and low power operation in a fabrication process consistent with modern backside-illuminated stacked CMOS image sensor manufacturing.

MDPI Sensors and the International Image Sensor Society (IISS) have joined together to create an all-invited special issue reviewing the status of photon-counting image sensors as well as recent developments. The issue includes papers on avalanche gain devices such as SPADs, CMOS image sensors with deep sub-electron read noise, and other devices offering photon-counting capability. Also included are papers on recent progress in image reconstruction, an important aspect in the practical application of photon-counting image sensors.
[Basel: 2017]

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