Fig. 2. Timing of phosphorescence image acquisition. The curve shows the exponential decay of phosphorescence intensity I_t after an excitation flash at time t=0. The image intensifier is turned on at delay time t_d for the gate period T. The grey-shaded area indicates that portion of phosphorescence light (Z) that is integrated on the CCD array during T. I₀, initial phosphorescence intensity immediately after the excitation flash.