Patent attributes
Apparatus for detecting proximity between a first object (target object) and a second object (reference object), comprising a light source and a light detector adapted to receive resulting back-scattered light from the reference object when illuminated from the light source, whereby the intensity of back-scattered light to the light detector is utilized as a measure of said proximity. The target object comprises an optical device having a focal plane and being adapted to be illuminated by the light source. The axes of the light rays from the light source and the back-scattering to the light detector have mutually closely adjacent and substantially parallel or coincident portions. Said proximity corresponds to a distance (relative position) between the target object and the reference object wherein the reference object is located substantially at the focal plane.
