Abstract: The invention relates to an apparatus for input of movements and/or registration of forces, comprising at least one light source, at least one position sensitive device (PSD) and at least one diaphragm, wherein at least one of these three elements is moveable with respect to the two other elements. The light source is arranged at a mounting so that light from the light source is emitted through an opening in the mounting and through the at least one diaphragm onto the at least one PSD.