US Patent 7104623 Fluid ejection system with photosensor activation of ejection element

A fluid ejection system includes a fluid ejection assembly including a plurality of photosensors and a first array of fluid ejection elements. Each of the fluid ejection elements is configured to cause fluid to be ejected when the fluid ejection element is activated. Each one of the photosensors is coupled to a respective one of the fluid ejection elements for activating the fluid ejection element. A first light source emits a light beam. A control system scans the light beam across the fluid ejection assembly and selectively illuminates the photosensors, thereby activating the fluid ejection elements coupled to the illuminated photosensors.