High data rate optical communication system

Claim 1

An optical communication transmitter for producing a collimated light beam modulated in accordance with the information contained in a strip of photographiC film, said transmitter comprising: a cylindrical film support having a narrow circumferential slit about which said film, with its emulsion side outward, makes one helical turn centered on said slit and in which the pitch of said helical turn of said film is such that a small space exists between adjacent edges of the film at the start and completion of the turn; a mirror tape in contact with the emulsion side of said film; means for longitudinally moving the film and the tape together at a constant rate; means for producing a high intensity collimated incident light beam; a converging lens concentric with the axis of said cylindrical support and offset from said slit for bringing said collimated incident beam to focus on said mirror tape through said slit and said film, and for collimating the light reflected from said mirror tape; a mirror set at an angle of 45* to said axis at a point lying in the central plane of said slit and rotating about said axis at a constant speed for continuously moving said focused incident beam circumferentially of said cylindrical support along said slit at a constant speed providing a scanning beam; a reflector positioned in said space in the same plane of said mirror tape for producing a synchronizing pulse of reflected light each time said reflector is intercepted by the scanning beam; and means for separating the collimated reflected light beam from the collimated incident light beam to form the transmitted output beam.