Information signal transmission system - uses elliptically polarised laser light with variations in ellipse axes ratios as information signal independent of light intensity

摘要

The information transmission system comprises a source of a beam (13) of monochromatic coherent light which is linearly polrised. The beam (13) pores through a quarter wavelength strip (9) oriented at 45 deg. to the direction of polorised light to circularly polorise the light beam. The beam is then passed through a birefractive cell (10) such as a KERR cell which elliptically polerises the light. The signal to be transmitted (5) is used to control the power supply (15) of the birefractive cell (10) to vary the ratio of the ellipse axes in the conformity with the signal (5). The beam is then transmitted by a projector comprising concave and converse mirrors (11, 12). In the receiver, the signal is recovered by detecting the ratio of the ellipse axes. The cell (10) may be one in which the direction and orientation of the field are independently variable to allow transmission of two independent signals such as t.v. sound and vision signals.