Anordnung zur Phasenverschiebung von Lichtwellen, mit einem Fluessigkristall-Phasenschieber

The invention relates to an arrangement for shifting the phases of light waves by means of a liquid crystal phase shifter placed in the ray path of a light source, said phase shifter consisting of a liquid-crystal layer arranged between two transparent plates and electrodes and to which an electric voltage varied by means of a contoller to change the refractive index of this layer and thus the optical path length of the light transmitted through the layer and the plates is applied. A highly precise control of the phase is ensured by the invention by the fact that the liquid-crystalline layer (5) is arranged in the ray path of the light source (1) in such a way that the former also acts as a Shearing interferometer by coupling out part of the light at the boundary (9) facing the light source (1) and part of the light at the boundary (10) of the liquid-crystalline layer (5) facing the light source (2) by reflection and brings it to interference, and that a photodetector (12) is provided to detect the intensity of the coupled-out light waves interfering with each other, and that furthermore a reference/actual comparator (13) is provided whose reference value input (14) receives a predetermined reference value and whose actual value input (15) receives the output signal, both being from the photodetector (12), and that an output signal is formed by the reference/actual value comparator (13), said output signal ... the controller (6) as ...