Electro-optical modulator and filter, comprises spatial modulation of electric field inducing diffraction of incident light, and spatial filtration of diffraction pattern of transmitted light

摘要

The modulator and filter comprise an Electro-optical cell (1) with an electro-optical, in particular liquid-crystal, material (14) illuminated by a light beam (60) from a source (6), at least one device for spatial modulation (2) of electric field in contact with the liquid-crystal material inducing an effect of diffraction of incident light, one or more layers (4) allowing to focus the light transmitted by the cell, and at least one making device (3) associated with the lenses and situated in a proximity of the focal plane (42) of the lenses allowing the spatial filtration of the diffraction pattern of the transmitted beam. The device for spatial modulation (2) of electric field comprises a periodic structure whose step is substantially greater than the wavelength of the light beam (60), in particular with the step in the range 3-6 times the wavelength, and where the step is 1-3 times the thickness of electro-optical, that is the liquid-crystal material. The periodic structure (7) comprises elements (20) of material whose index of refraction is in the range of variation of the liquid crystal in one of the states: electrically excited, intermediate, and nonexcited. The elements (20) of periodic structure are linear in form and organized in two dimensions. The spatial modulation device comprises one or more pixels in the form of a network of microelectrodes, where different electrodes of a pixel are interconnected. The modulator and filter (claimed) comprise a set of lenses (4), the masking device comprises a mask associated with each lens, and the cell comprises a set of pixels where one lens is associated with each pixel. The set of lenses is situated in a plane (40) parallel to the cell, and the masking device is situated between the plane and the focal points of the lenses. The set of lenses is covered with a layer of transparent material (5), a flat surface (50) of the layer is parallel to the plane (40) of the lenses, and the thickness of the layer is such that the masking device is situated in the proximity of the focal plane. The electro-optical cell is with nematic or ferroelectric liquid crystal. In other embodiments, the spatial modulation device comprises a second diffraction network, each lens is designed to transmit at least two beams of different wavelengths, comprises a spatial light modulator with four times more pixels in cross-configuration, or both electrodes are in the form of grids.