Optical system manufacture

A method of manufacturing a touch screen apparatus, the method comprising:

• manufacturing an optically transmissive sheet by moulding the optically transmissive sheet as a laminate, wherein the optically transmissive sheet is adapted for total internal reflection at a first face and a second face of the optically transmissive sheet, and by forming one or more light absorbing layer regions on either the first face, the second face, or both of the first and the second faces of the optically transmissive sheet, wherein the one or more light absorbing layer regions are formed in the moulding of the optically transmissive sheet;
• mounting a top plate in the touch screen apparatus with a plurality of light sources mounted in association such that light from the plurality of light sources is transmitted within the top plate with total internal reflection;
• mounting a base plate relative to the top plate such that if an external body touches a first surface of the top plate, then light is coupled from a second surface of the top plate into the base plate through a first surface of the base plate;
• and
• mounting one or more detectors in association with the base plate for detecting light transmitted within the base plate.

A touch screen apparatus comprising:

• an optically transmissive sheet moulded as a laminate, wherein the optically transmissive sheet is adapted for total internal reflection at first and second faces of the optically transmissive sheet, with one or more light absorbing layer regions formed on either the first face, the second face, or both of the first and the second faces of the optically transmissive sheet, wherein the one or more light absorbing layer regions are formed in the moulding of the optically transmissive sheet;
• a top plate in the touch screen apparatus with a plurality of light sources mounted in association such that light from the plurality of light sources is transmitted within the top plate with total internal reflection;
• and
• a base plate mounted relative to the top plate such that if an external body touches a first surface of the top plate, then light is coupled from a second surface of the top plate into the base plate through a first surface of the base plate, and one or more detectors mounted in association with the base plate for detecting light transmitted within the base plate.