Optical position-sensitive detectors are a useful class of sensor with a wide range of applications in machine control systems, industrial alignment, and robotic vision. They have distinct advantages over most arrayed discrete optical devices in that they can produce continuous optical signals, and versions based on thin-film amorphous silicon are Plot restricted by crystal growth limits and so have the potential to be fabricated in large area format, Sputter-deposited hydrogenated a-Si also has features such as excellent adhesion to glass substrates, precise film thickness, and hydrogen content control which are of some interest in device design and fabrication.