Patent ID: 7705897

Claim:
A solid-state image-pickup device having a plurality of pixels, each converting an incident-light quantity into a respective electrical signal, the image-pickup device further having a plurality of analog-to-digital converters that each converts an analog signal obtained from a respective one of the pixels into a digital signal, wherein each analog-to-digital converter includes: an output having a plurality of bits; a plurality of comparators, wherein each of the comparators compares a respective one of a plurality of reference voltages changing over time to the analog signal from the same one of the pixels, and wherein each of the reference voltages are different from each other, and at least first and second reference voltages are transmitted to respective ones of the comparators; and a plurality of counters, each associated with a respective comparator, each counter counts a time period required to finish the comparison made by the associated comparator, and stores information about a result of the counting, each counter has a different count number than each other counter for counting the time period of the comparison made by associated comparator such that each counter outputs the stored counting result information as a respective portion of the plurality of bits of the output of the respective analog-to-digital converter.