Abstract: A triode type cathode structure including a cathode assembly composed of a cathode electrode at least one electron emitter and a resistive layer inserted between the cathode electrode and the at least one electron emitter to connect them together electrically. The triode cathode structure also includes a grid electrode separated from the cathode assembly by a layer of electrical insulation. The cathode electrode is arranged in a first plane and the at least one electron emitter is arranged in a second plane parallel to the first plane and the cathode electrode and each electron emitter are separated by a same distance measured in a third plane parallel to the first and second planes.

Abstract: A device produces an electric field between two electrodes, the electric field having a specified value in the vicinity of a first of the two electrodes. The device includes a means for applying a potential difference between the two electrodes, means forming modulation electrode located near to the first electrode in the vicinity of which the electric field must have specified value. The device also includes control means for applying a potential difference between the means forming modulation electrode and the first electrode located nearby in order to obtain, through the contribution of the potential differences, the specified value of electric field.

Abstract: The invention relates to a triode type cathode structure comprising a cathode assembly composed of a cathode electrode (33), a layer of electron emitting material (34) and a resistive layer (36) inserted between the cathode electrode (33) and the layer of electron emitting material (34) to connect them together electrically, the structure also comprising a grid electrode (35) separated from the said cathode assembly by a layer of electrical insulation (31). The cathode electrode (33) and the layer of electron emitting material (34) are arranged one at the side of the other.

Abstract: A microtip electron source including at least one electron emission zone composed of a plurality of microtips connected electrically to a cathode conductor. At least one gate electrode is positioned opposite the electron emission zone and pierced with apertures located opposite the microtips, to extract the electrons from the microtips. An emitted electron focusing gate is positioned opposite the gate electrode, and includes an aperture unit including at least one slit located opposite at least two successive microtips. A flat display screen can include such a microtip electron source. Further, a manufacturing process of such an electron source is disclosed.

Abstract: An apparatus for depositing a material by evaporation on a substrate having a large surface. The apparatus includes an enclosure in which are placed a number of material evaporation sources. It also includes a device for channeling or piping of vapors emitted by the sources toward the substrate during evaporation. This is formed by walls or covers which define compartments within the enclosure, each evaporation source being placed in a compartment. The apparatus can also utilize a device for moving the substrate in order to improve the uniformity of the deposit.

Abstract: The invention involves the making of a group of apertures spaced in a precise manner on a structure and including, for example, a first aperture made in a first layer and a second aperture made in a second layer which covers the first layer, the first aperture being located within the second aperture.

Abstract: A process for manufacturing a micropoint electron source with an extraction grid and a focusing grid. This process allows for precise alignment of the holes of the extraction grid with the apertures of the focusing grid by using a single photolithography step for making the holes in the extraction grid. Such a process may find particular application for making a micropoint electron source for a flat viewing screen.

Abstract: The invention relates to a method for collective manufacturing of spacers (35) for flat viewing screens with high voltage control and divided into picture elements or pixels (28), characterized in that it comprises the following steps:machining a substrate, of an adequate material for making spacers, in view of obtaining a profile structure (30) with a cross section (32, 42, 52) comprising a center core (33, 43, 53) and lateral stiffeners (34, 44, 54), the thickness of the center core and the lateral stiffeners as well as the distance separating the lateral stiffeners being such that said section can be inserted between the screen pixels without overlapping them, cutting the profile structure (30) obtained during the preceding interval in view of obtaining sections of a given length, designed to form said spacers (35).

Abstract: Self-alignment process usable in microelectronics to obtain alignment of at least one group of holes, one of said holes (or large diameter hole) being formed in an upper level and the other hole (or small diameter hole) being formed in a lower level of a stacked structure.

Abstract: The invention relates to a microwave antenna having at least one tubular portion with a central axis, and magnets which are located within the tubular portion along the central axis. The magnets generate a magnetic field in the vicinity of the antenna, with each end of each magnet facing an end having the same polarity of an immediately adjacent magnet. This type of antenna is used in the manufacture of microtips on large surfaces.

Abstract: Source evaporation machine for covering samples optionally by a mixture produced by several sources (3).Mobile covers (6) are placed between the sources (3) and the sample. The covers (6) are designed so as to ensure that the solid parts (23,24) and the openings (21,25) alternate and the sources (3) move relative to the covers in such a way that different circumferences of the covers pass in front of them. As the angular sectors surrounded by the openings differ for each circumference, the degree of hiding of the sources (3) can be regulated in a very accurate and reliable manner. It is possible to modify the flow of the source on the sample or, in the case of several sources, vary the composition of the deposited mixture.

Abstract: Ferroelectric liquid crystal screen with opacified electrodes in the non-switchable area of the screen and processes for obtaining spacers and treating said screen.On each part of each row or column electrode of the screen, facing a gap separating two column or row electrodes is arranged an element (40,50) preventing the passage through the screen of light reaching the latter in the direction of the element. The elements located on the row electrodes (32) or those located on the column electrodes (34) also permit the spacing, without electrical connection, of the screen plates and the localization of the zigzag defects which the liquid crystal may have, in or in the vicinity of the non-switchable area of the screen. The screen is appropriately heated and an alternating voltage is applied between the electrodes in order to localize the zigzag defects of the liquid crystal in the vicinity of the spacing elements.

Abstract: Apparatus and method for depositing on the flat surface (4) of a substrate (1) a layer of uniform thickness of particles emitted by a source (5). The substrate (1) is held at the extremity of a radial arm (2) which arm in turn is carried on a rotating axis (3). The substrate also rotates on the arm (2) and is carried on the arm so that the flat surface (4) is orientated such that a line drawn normal to the flat surface forms an angle (.theta.) with the axis (3). The apparatus is particularly suited for the production of optical parts.

Abstract: Cell with a double liquid crystal layer using the electrically controlled birefringence effect and process for producing a negative optical anisotropy uniaxial material usable in said cell.The cell can comprise two crossed rectilinear polarizers, three glass plates provided with transparent electrodes and placed between said polarizers, two liquid crystal layers between the plates and, between a plate and a polarizer, a sheet of the medium, whose extraordinary axis is perpendicular to the plates. This sheet can be obtained by heating a thermoplastic polymer up to the isotropic state, under a uniform pressure on the polarizers, cooling and eliminating the pressure. The cell is designed in such a way that the molecules of the respective layers tilt in two directions forming the same angle with the homeotropy direction, when an exciting voltage is applied between the electrodes, said directions, viewed in projection on a plate, also being opposite in the main observation plane.

Abstract: A matrix display device and control therefore applicable to liquid crystal displays incorporates two groups of row electrodes and two column electrodes per image element. Each row conductor is connected by k.times.m switches to m groups of k parallel electrodes of a first family and to m groups of k parallel electrodes of a second family which alternate with one another, in such a way that each switch is connected to an electrode of the first family, to an electrode of the second family and to the row conductor. An image element is defined by the overlap zone of two column conductors of a first and a second family with two groups respectively of k electrodes of a first and a second family connected by k switches to the corresponding row conductor.Application to liquid crystal display means.