Characterization of the PHOCI™ data integrated video sensor technology

In this article, we report the characterization results of two data integrated video sensors designed by Clifton Labs, Inc. A data integrated video sensor consists of an array of photodetectors that provide both an analog and digital output based on the amount of incident light on the detector. Two approaches can be used to capture the resulting response from the photodetector. A sample-and-hold circuit is used in both chips to capture video data. The sample-and-hold circuitry is also used in the second design to capture data values. The second approach is to use an externally supplied voltage to provide a threshold that is used to determine if a value is a ´1´ or ´0´. The threshold approach is used in the first chip tested to capture optical data. The first design is characterized for output response at a given sample frequency for the video portion. The maximum data rate and optical response at a given data threshold are defined for the digital circuitry. Next, the digital and analog output values of the second chip are correlated to the incident optical power and the sample time used to capture the data. The results of these tests provide insight into the operation of the two designs and confirm simulation results used in the design of the circuits.