In [Simoni et al. 95b, Simoni et al. 95a] Simoni et al. describe an analog memory with some peripheral circuitry for difference detection. Each pixel comprises a photodiode and a storage capacitance. When a particular pixel is selected, first the previous pixel value which is stored in the capacitor is read out, and then the present value is read from the photodiode. A circuit computes the difference between these two values. The architecture and the circuits are based on the switched-capacitor technique. The schematic of a cell is shown in Figure 3.35. It should be noted that the change detection capability of this chip is not based on any algorithms or models.
Figure 3.35: Schematic of a cell of Simoni et al.'s motion detection
chip.