POLARIZED PLANE CONTROLLER

PURPOSE:To control a polarized plane almost without exerting influence upon the quantity of incident information light by converting an optical elliptically polarized wave into an elliptically polarized wave whose main axis coincides with a reference rectangular coordinate axis by an optically active liquid crystal element and converting the converted elliptically polarized wave into a linearly polarized wave to be TE component light by a double refractive liquid crystal element. CONSTITUTION:An optical information signal is converted into parallel beams by a collimeter part 2, the parallel beams are made incident upon a polarized plane control part 3, a transmitted optical elliptically polarized wave is converted into an elliptically polarized wave coincident with the reference rectangular rectangular coordinate axis, and then the converted wave is converted into a linearly polarized wave oscillated along the reference rectangular coordinate axis. The optical wave whose polarized plane is controlled is made incident upon a polarized wave separating part 4 and separate into a TE mode component and a TM mode component and the TM mode component light is converted into an electric signal by a photoelectric conversion part 6. The converted electric signal is supplied to a processing circuit 7 to generate a control signal for controlling the drive of the optically active liquid crystal element and the double refractive liquid crystal element. Consequently, the polarized plane can be controlled almost without entering influence upon the quantity of inputted information light.