OPTICAL INPUT DEVICE BASED ON DOPPLER SHIFT AND LASER SELF-MIXING

摘要

In an optical input device based on movement of an object (15) and the device relative to each other and which comprising at least one optical sensor unit including a laser (3) having a laser cavity for generating a measuring beam (13), converging means (50) for converging the measuring beam in an action plane and for converging measuring beam radiation reflected by the object in the laser cavity to generate a self-mixing effect in the laser and measuring means for measuring the result of the self-mixing effect, which effect is determined by said movement, the converging means (50) is adapted to provide a self-mixing effect that is smaller than a possible maximum but larger than a detection threshold for an extended range of distances (AZ) between the object and the device. This allows obtaining the required self- mixing effect in an extended range of distances between the object and the device.