Optical data reader with focussing appts. - has combined detector for track alignment and data reading

摘要

An optical system for reading information recorded on a tape or disc in the form of surface ridges or irregularities which react differently to a light beam focussed on the track. The beam is split by a semi-silvered mirror and part passes to lens to be focussed at a point on the record, where the light is modulated by the data to be read, where the light is modulated by the data to mirror and reflected to the system which may be a cylindrical lens that extends the light spot into a line if the alignment of the system is not correct and permits visual focussing, or automatic focussing by the provision of a set of photodetectors.