Gain calibration in emccd cameras

Abstract

A CCD device of the type which provides gain by impact ionisation in a multiplication register includes an arrangement for production of a first output signal derived from a known input with multiplication applied and a second output signal derived from a different input with unit gain applied. Using the known ratios of the two signals, the gain of the multiplication register can be determined. The two signals can be derived from accumulating thermal charge in elements a CCD image device and by summing charge to produce a signal processed with unity gain and by averaging charge for use with the signal with gain applied. An alternative embodiment uses an extra light source for producing input signals of known ratio.