Patent ID: 6906304

Claim:
An image sensor, comprising: a pixel array located on a first portion of an integrated circuit and having a plurality of pixels, each pixel having: a photosensor having an electrical property which varies in response to intensity of illumination, a first circuit switchable between operation as a comparator and as an op amp, the first circuit having first and second input nodes and an output node, and being configurable to generate a comparison signal at the output node in response to signals applied to the first and second input nodes, and a feedback loop for selectively connecting the first input node and the output node so as to switch the first circuit between operation as an op amp and as a comparator; a plurality of multi-bit storage elements displaced from the first portion of the integrated circuit, each of the storage elements connected to a respective one of the plurality of pixels, such that a separate storage element in the plurality is connected to each pixel; a counter signal generator configurable to provide a time-varying, multi-bit counter signal; and a reference signal generator configurable to provide a reference signal maintainable at a first value, and further configurable to vary the reference signal over time from the first value to a second value, wherein each storage element receives the counter signal, the first input node of the first circuit within each pixel is connected to the photosensor in the same pixel, the second input node of the first circuit within each pixel receives the reference signal, and each storage element is configured to latch the value of the multi-bit signal at the time that a comparison signal generated at the storage element's respective pixel transitions from a first value to a second value.