Abstract: This invention concerns chromatic light separators, and is particularly intended to reduce their dimensions. A chromatic separator in accordance with the invention contains at least two selective wave length mirrors. According to one characteristic of the invention, the two selective mirrors are nested holographic mirrors. The invention is particularly suitable for three-color rear-projection type picture projectors using liquid crystal screens.

Abstract: The magnetic recording head of the invention comprises an electrical conductor constituted by the poles themselves or by a magnetic shunt, which gets saturated when an electrical current is sent to it. It is thus possible to control the field at the gap and control the recording by this electrical current which acts by inhibition or validation of the writing, respectively.

Abstract: A method whereby a moving body searches for an unoccupied time slot in a time-division communications channel for the transmission of a message. The moving body participates with other moving bodies located in the same geographical zone in an anti-collision system with the time being conventionally divided into reproducible time periods T. Each period includes a number N of time slots reference 1, 2, 3 . . . i . . N with the access to a time slot for the transmission of a message from the moving body being accomplished by identifying an unoccupied time slot during at least one listening period T, followed by a random choice of one slot i from among the slots identified as being unoccupied. For at least one period after the moving body has occupied slot i, the time of this slot is divided randomly into reception sub-slots R and transmission sub-slots E.

Abstract: An analogue-digital voltage converter comprising 2.sup.n -1 comparators making it possible to generate 2.sup.n different voltage levels when the input voltage varies, and a binary coding circuit comprising means (2) for converting the 2.sup.n voltage levels into 2.sup.n binary codes each having n bits of resolution, characterized in that it comprises additional means (20) making it possible to code the voltage contained in at least one range of variation of the input voltage into an item of information having a number of bits of resolution greater than n. The converter applies more particularly to video signal processing devices (televisions, video recorders, cameras, etc.).

Abstract: A phase conjugation mirror including a non-linear medium (1) and a focusing lens (2), in which a beam to be reflected (F1) is displaced relative to a non-linear medium. The displacement is obtained through displacement of the focusing lens and has application in the stabilization of the reflectivity of a phase conjugation mirror.

Abstract: In an anticollision device, a moving object heading in a given direction along a movement vector and having a relative speed vector directed towards an obstacle is fitted out with at least two antennas sending out a microwave signal liable to be received by the obstacle. The device furthermore comprises reception means and means to analyze the echoes received from the obstacle, the analyzing means determining the variation with respect to time of the angle .theta. between the movement vector and the relative speed vector, a substantially zero variation of the angle .theta. indicating a risk of collision. Application to the equipment of motor vehicles to prevent collisions, notably in the event of poor visibility.

Abstract: The disclosure relates to the connection of a coaxial cable to a printed circuit. There is proposed a device having a U-shaped metal part that fits into the edge of the printed circuit; a hole drilled into the bottom of the part enables the introduction of the bared end of a coaxial cable, wherein a contact is provided between the external conductor of the cable and the part; the internal conductor of the cable extending within the U and, by use of an aperture in the U, it can be soldered to a conductor of the printed circuit. In addition, a lid is placed on the aperture to prevent parasitic radiation.

Abstract: A variable gain amplifier which has n parallel-connected elementary amplifiers, and components for selecting j-order (j=1, 2, . . . , n) elementary amplifier according to the desired gain. Each elementary amplifier is of a common base type. The variable gain amplifier includes components that are used to obtain a low value input impedance that is independent of the gain of the selected elementary amplifier. The variable gain amplifier will find particular application at the input stages of amplification lines of receiving circuits which require noise performance characteristics.

Abstract: A device and method for interconnection packages in a stack. Each package encapsulates, for example a semiconductor chip containing an integrated circuit, which for example may be a memory. The packages (2) which have connecting pins (21) are mounted on support grid (4) which preferably act as a heat shunt, and are stacked and linked to each other with a resin coating (5). A stack (3) is cut out so that the pins on the packages and one edge of the grids are flush with faces (31, 32) of the stack (3). Connections between the packages themselves, and between the packages and stack connecting pads, are made on the faces of the stack. The connecting pads are where necessary fitted with connecting pins.

Abstract: A three-color image projector, of the type using several colored light beams with primary colors, with improved luminous efficiency. The projector employs spatial rather than temporal beam modulation. The projector includes a generator producing light in the three spectral bands corresponding to the primary colors (red, green, blue). The generator has at least two light sources (S1, S2), one of which produces multi-spectral band light, and the other is a monochromatic source. By comparison with the prior art, where the white light is produced by a single source, this arrangement avoids, in particular, the elimination of a significant quantity of lumens in the excess primary color.

Abstract: Disclosed is a novel type of composite electro-optical material based on liquid crystal dispersed in a polymer with reactive functional groups (Y). The originality of this material lies in the chemical modification of the interface between the polymer and the liquid crystal leading to the formation of a composite material comprising a porous network of polymer and liquid crystal molecules in the pores of the network. The polymer possesses reactive functional groups (Y) and functional groups (X) at the interface between the polymer and the liquid crystal. The totality constituted by the functional groups (Y) and the functional groups (X) enables the optimizing of the electro-optical performance characteristics obtained from this type of material. Also disclosed is a method to obtain this composite material as well as a device comprising a material such as this.

Abstract: This invention concerns conductive materials based on an encapsulated conductive polymer. Encapsulation in a shell of polymer stabilizes the conductivity of these materials, which can be encapsulated in a shell of film-generating polymer, to give the material formed very good mechanical properties, unlike conductive polymers which existed in the prior art, which, if not encapsulated, form brittle materials that are less stable in time.

Abstract: Disclosed are a device for the measurement of stresses exerted on a mechanical part and a method for the fastening of this device. The device comprises at least one plate and one strain gauge, the gauge being fixed to the plate which is connected to the mechanical part by linking and coupling means, the strain gauge generating an electrical signal representing the stresses exerted. Application to the measurement of stresses exerted on all types of mechanical parts, notably on brake calipers.

Abstract: A device for carrying out a pre-correction of audio signals before they are amplified in amplification systems of transmitters with amplitude modulation, the amplification systems each having a determined number of modules generating pulses of modulated width. This device includes:an analog-digital converter for converting the audio signal to be transmitted into digital samples;an interpolation circuit coupled to the output of the analog-digital converter to carry out the computation, by a linear interpolation, of the slope of variation and the computation, by a parabolic interpolation, of the value of the audio signal applied to the input of the analog-digital converter;and memory means coupled to the output of the interpolation circuit storing pre-correction values of the samples of the audio signal addressable by means of the interpolation values of the audio signal computed by the interpolation circuit.

Abstract: A quantization process proposes a low data rate for predictor filters of a vocoder with a speech signal broken down into packets having a predetermined number L of frames of constant duration and a weight allocated to each frame according to the average strength of the speech signal in the respective frame. The process involves allocating a predictor filter for each frame and determining the possible configurations for predictor filters having the same number of coefficients and the possible configuration for which the coefficients of a current frame predictor filter are interpolated from the predictor filter coefficients from neighboring frames. Subsequently, a deterministic error is calculated by measuring the distances between the filters in order to form a first stack with a predetermined number of configurations which give the lowest errors.

Abstract: A magnetic field sensor having a planar element made of a material formed by crystalline magnetoresistive thin layers with an anisotropy of resistivity in the planar element also having, in the planar element, two magnetization axes of different values. This sensor also has two electrical connections enabling, in the presence of an external magnetic field, the flow of a current in the element in a first direction that is not collinear with each of the axes of magnetization and two electrical connections enabling a measurement of voltage in a second direction transversal to the first direction. This sensor thus works by planar Hall effect.

Abstract: A phosphor material based on manganese-doped zinc silicate, in which the manganese doping level ranges from 3.5% to 25%, can be used to obtain a very short time of decay after excitation.

Abstract: An acoustic antenna includes at least one surface sensor formed by a stack of conducting materials and dielectric layers of piezo-electric material enclosed in a sheathing of flexible material. The assembly forms a flat panel 2 mounted against the hull 5 of a navel vessel and takes the shape of the hull. The mounting of the panel on the hull is achieved by two streamlined edging sections 3, 4 while leaving an intermediate water layer 6 remaining between the panel 2 and the hull 5. The sheathing includes an envelope of flexible material filled with a visco-elastic lining material and the piezo-electric material of the dielectric layers of the sensor is preferably a polyvinylidene fluoride film.

Abstract: The disclosure relates to broadcasting by means of rotary antennas using rigid dipoles. Each of two distinct channels passes through the joint between the fixed support of the mobile part of the antenna and rise vertically into the interior of the mast to respectively reach two distinct vertical groups of dipoles. It is thus possible to carry out two simultaneous transmissions from one and the same rotary antenna. Application to broadcasting in decameter waves.

Abstract: The system comprises a focusing optics in the focal plane of which a linear array of photodetectors is disposed. A double prism located opposite to said photodetectors with respect to said focusing optics, is servo controlled in rotation relative to a support about its longitudinal axis perpendicular to the axis of said optics, said support being itself servo controlled in rotation about said optical axis in order to scan a space of about 2 .pi. steradians. A derotating prism aligned with said optical axis rotates about said optical axis at a speed half of that of said double prism, in order to hold the image of the target in a single direction in said focal plane, whatever the rotations of said support.