Optical prism sensor for line detection - has prism formed by diagonal cutting of glass block and bonding after mirror finishing of side walls

摘要

The optical sensing system is for the reading of fine line markings e.g. microfilm, and uses a prism focus transmitted light to a small cross sectional area. The prism is produced by taking a small rectangular cross sectin block of optical quality glass and cutting along line diagonally such that a small area (2) at one end is formed. The small rectangular area forms the sensing aperture and is of a size compatible with the line width being sensed. After cutting the diagonal surface, the side (1) is mirror finished and the two halves are bonded together. Light emitted (11) from a fibre optic bundle is directed into the prism and is focussed through the sensing area to be transmitted (12) across the film. A similar unit may be used to detect light after transmission across the film.