POSITION SENSING DEVICE HAVING A SINGLE PHOTOSENSING ELEMENT

A position sensing device having a single photosensing element is disclosed herein. The position sensing device determines the location of an object to which the position sensing device is attached relative to a surface. The position sensing device has a plurality of light paths that direct light from different area portions of the surface to the single photosensing element. Each area portion of the surface is associated with a light source wherein each light source may be activated individually. A processor illuminates these area portions individually. As the area portions are illuminated, the photosensing element creates image data representative of the image of the area portion being illuminated. The processor analyzes the image data and identifies distinct features in the area portions. As the object is moved relative to the surface, the locations of these distinct features relative to the photosensing element move. By measuring this movement, the processor is able to determine the velocity, direction of movement, and position of the object relative to the surface.