Patent ID: 7807952

Claim:
A CCD device of the type for providing charge gain by impact ionisation, comprising a store section, a readout register having a plurality of elements, and a multiplication register for producing charge gain having a plurality of elements, the multiplication register having an output arranged to provide: a first output signal based on a given input and provided from the multiplication register with gain applied, wherein the given input comprises charge from the plurality of elements of the readout register that occurs due to thermal electrons accumulated in the store section in a defined time period, and the first output signal is representative of the mean of the charge in the plurality of elements; and a second output signal based on a known multiple of the given input and provided from the multiplication register with substantially no gain applied, wherein the second output signal is the sum of the charge in the plurality of elements; whereby the gain of the multiplication register is derivable from the first and second signals and the known multiple.