Abstract: In order to modify the characteristics of light which passes through a plate of electrooptical material such as PLZT ceramic, at least two conductive strips are arranged on each face in displaced relation to the strips on the other face and are connected on each face to different voltage sources. A diagonal electric field is produced between two opposite and relatively displaced strips, thus producing a considerable non-linear variation in transmitted light intensity according to the voltage applied.

Abstract: A liquid crystal film placed between plate electrodes and point electrodes can have a first optical state 1 if the electrical excitation applied between the plate and point electrodes is higher than a threshold value V.sub.s and a second optical state 0 of this excitation is lower than the threshold value. A set of P voltages is applied to the P point connections of the device and a second set of S voltages is applied simultaneously to the S sector connections. In a boundary sector, some points of the liquid crystal are thus in state 1 while other points are in state 0. In the case of each of the other sectors, the points of any one sector are all in one of the two states 1 or 0.

Abstract: An analog liquid crystal display apparatus comprising a liquid crystal film band inserted between a first conductive electrode and a second resistive electrode; a first voltage source is connected between said first and second electrodes; a second power supply is connected between the two ends of the resistive electrode; the liquid crystal presents a first optical state on a first part of the band and a second optical state on the remainder of the band. The liquid crystal is of the type having a critical relaxation frequency which is either a load relaxation frequency or a dielectric relaxation frequency, the first power supply supplying a voltage at a first frequency and the second power supply supplying a voltage at a second frequency, said two frequencies being on either side of said critical frequency; one of the voltage is then a display voltage and the other is a voltage which inhibits the display.

Abstract: A display cell comprises a liquid-crystal film interposed between two groups of electrodes to which is applied a set of low-frequency voltages in order to produce an optical state "0" at desired points and a set of high-frequency voltages in order to produce an optical state "1" at other predetermined points. In the composite excitation applied to each zone, the low-frequency fraction of excitation exceeds the high-frequency fraction in the "0" display zones and the high-frequency fraction exceeds the low-frequency fraction in the "1" display zones.

Abstract: The invention relates to a method of controlling an optical characteristic of a material and it is concerned also with devices and image-forming means for carrying out the method.The method of control is particularly advantageous in devices comprising a plurality of points distributed in the form of a matrix. The optical characteristic K of the material is controlled by an energization having a magnitude G for a duration t, the values G and t being so selected as a function of the time response K (G, t) of the characteristic K at an energization stage of magnitude G that K (G.sub.O, t.sub.O) is equal to K.sub.O.

Abstract: In a liquid crystal whose molecules have temperature-dependent dielectric anisotropy within a range such that the liquid crystal retains the same phase, the optical properties of a liquid crystal film are controlled by applying an electric field of predetermined frequency to the film and by bringing the temperature of the film to a value within the range mentioned. The dielectric anisotropy then assumes a predetermined value in respect of said frequency and the liquid crystal film assumes a predetermined optical state.

Abstract: A device for controlling, by means of a phase comparator which receives an nput signal, the phase or frequency output of a voltage controlled oscillator connected with the phase comparator in a phase locked loop, this loop being also provided with a branch circuit including a high pass filter or appropriate characteristics.

Abstract: A method for controlling an optical characteristic of a material which is intercalated between two electrodes driven by periodic excitation signals having a zero mean value consists in applying to the electrodes signals having the same time-duration and the same recurrence frequency but in which one signal has a phase shift .phi. with respect to the other, the phase shift being modified in order to adjust the optical characteristic.

Abstract: A liquid crystal cell is made by covering a wafer with an electrode system. A second insulating and transparent wafer is covered with a second system of semi-transparent electrodes. A wall of controlled thickness is deposited on a wafer around a periphery thereof. A metallic thread is deposited on a wafer with the same perimeter as the wall. The wafers are applied to each other and heated to fuse the thread on the top of the wall to join and seal the wafers with a liquid crystal between them within the wall.

Abstract: A method of collective orientation of the molecules of a mesomorphous liquid crystal, in which each of two oppositely-facing walls of a liquid-crystal cell is covered with a conductive deposit forming an electrode and with a thin film of a substance which exhibits properties of orientation of smectic crystals in solid phase; the mesomorphous liquid crystal is placed in contact with the two thin films and the molecules of said liquid crystal are aligned with those of the thin film.

Abstract: An electrooptical display device comprising a film of liquid crystals between two systems of electrodes. One system comprises a plurality of integrated circuits forming a supporting layer on a substrate and a plurality of flat metallic electrodes deposited on the supporting layer, each electrode being connected electrically to one circuit. The other system comprises a transparent insulating plate provided on one face with a uniform coating of electrically conductive and semi-transparent material.