a-Si:H optical speed detector based on the flying spot technique

The authors have previously developed a transient technique, called the flying spot technique, based on the lateral photoeffect. It allows determination of the ambipolar diffusion length and the effective lifetime of the photogenerated carriers, once the light spot velocity and geometry of the structure are known. They propose to apply this technique backwards in order to detect the path and velocity of an object that is moving toward a light source direction. The light back reflected is analyzed by a p-i-n structure measuring the transient transverse photovoltage which is dependent on the object movement (position and velocity). Details concerning material characterization and device geometry are also presented