Abstract: A push-pull output stage for electronic integrated circuits includes two NPN transistors (Q1, Q2) connected in series between two supply terminals. The output (S) is the junction point of the transistors. A third NPN transistor (Q3) has its base and its collector connected respectively to the base and to the collector of Q1. Two current flow arms (R1, Q4 and R2, Q5) are formed, one to establish a current depending on the potential of the emitter of Q3 and the other to establish a current depending on the potential of the emitter of Q1. The arms are mounted in a current mirror arrangement, the second arm tending to copy the current of the first arm; the current mirror generating a current output (S2) representing a difference between the current set up in the second arm and the current copied from the first arm. This current output is used to control the conduction of the second transistor (Q2).

Abstract: A laser includes a gas enclosure placed in an optical cavity and receiving a pump beam to generate at least one first-order and one second-order Stokes wave. One of the mirrors of the cavity is transparent to wavelengths which are higher than the first-order Stokes wave.

Abstract: The present invention concerns an arrangement for reading an optically readable carrier having a substrate with diffractive tracks with respective longitudinal axes and formed of a succession of irregularities with respect to a smooth reference surface. The irregularities have a width of at most two microns and a variable length equal to or greater than their width and these irregularities have closed contours in the reference surface. The closed contours are diffractive along the entire extent in order to provide for a diffraction of light of a particular light spot focused and centered on a single one of the tracks and substantially occupying the width of the single track. Each of the irregularities has a data element stored along the entire length of the contour and successive irregularities along a track are separated by clearance spaces at least as long as the width of the irregularities in the reference surface.

Abstract: A coherent light power source comprising an oscillator and an amplifying optical fiber, both optically excited by the same pumping source, the beam of wave length L.sub.S output by the oscillator being amplified in the optical fiber.

Abstract: The method of picture compression consists:in processing a current displaced pixel block in the picture to be compressed by using a network of N neurons, 1 to N, disposed in a single plane, each neuron having a number of inputs equal to the dimension of the blocks extracted from the picture, and such that, after a learning phase during which the network has auto-organised so that the neurons represent most probable input values, each neuron receives on its inputs, at the same instant, the pixels of the current block and outputs a signal, or potential, d.sub.j, which is positive and is all the lower the nearer is the state of the corresponding neuron j to the state of the inputs e.sub.i,in coding the current pixel block through a code associated with the neuron j whose potential d.sub.j is minimal.The invention applies, in particular, to the compression of television pictures.

Abstract: Disclosed is a system with at least two complementary transistors, having n and p channels but comprising a heterostructure of junctions between III-V group materials. In order to balance the threshold voltages in the two channels, namely the n (2DEG) and p (2DHG) channels, at least two p and n delta doped layers are included in two layers of the heterostructure, at levels included between the channels (2DEG, 2DHG) and the gate electrodes. The n delta doped layer is then removed by localized etching right above the p channel transistor. Application to fast logic circuits.

Abstract: A device for reading sensors in fiber optics which includes an integrated optics interferometer wherein the interference signal is slaved to a set-point value by means of a negative feedback signal. The measurement for reading the sensors is provided from the negative-feedback generated signal. In one of the disclosed embodiments generated delays of a value greater than an optical wavelength are measured by coupling the interferometer to a counting-up/counting-down system for interference fringe jumps.

Abstract: Devices for deflecting an optical beam under the action of an ultrasonic beam propagating in a block of active acousto-optical material and operating under Bragg tangential conditions, with the acousto-optical interaction being anisotropic. The devices also include entry and exit faces into this material blocks which are inclined at angles .alpha. and .beta. such that the incoming beam and the emerging beam after the interaction are significantly parallel, keeping operation under Bragg tangential conditions. The devices can also be used to make a spectrum analyzer with a very large number of points and very high dynamics.

Abstract: The disclosure relates to the field of monocrystalline thin layers deposited on a substrate having an identical or a different nature, from a vapor phase. On the substrate made of monocrystalline material A, a cavity is built, determined by one face of the substrate and one face of a layer made of a material D in such a way that there can be neither nucleation nor growth on the faces exposed to the vapor phase. The growth is done from a seed made of monocrystalline material B located between two faces of the substrate and of the layer. The seed made of monocrystalline material B may be of a nature different from that of the substrate (for example, substrate=silicon and material B=GaAs) and is made, for example, by MBE or MOCVD. The material C to be made to grow is different from the material B of the seed. The material C is, for example, InP and the growth is done by VPE.

Abstract: An electro-optical modulator system obtained by linking a modulator incorporating a Y-junction coupler having a length Ll(101-108) to a passive coupler (104,105) whose length L2 in relation to the coupling length LC2 is determined so as to cancel substantially the third order distortions of the modulator. The resulting modulator has all of its even distortions cancelled and its uneven distortion is substantially zero. Furthermore, the rate of decay can potentially be zero.

Abstract: A telemeter is used to measure the distances between a sequence of points on a target surface. The telemeter includes an emitting source provided with a pulsed laser sending out a pencil of light energy in a determined direction of sight, a contra-rotating wedge communicating, to the pencil, a deflection along an epicycloidal type of scanning pattern in a plane perpendicular to the axis of sight, and a receiver including the same contra-rotating wedge and a photodiode. The disclosed device can be applied more particularly to a system for the detection of obstacles of a wire-shaped type.

Abstract: Ultrahigh-frequency surface acoustic wave filter has a two-channel structure with, preferably, a symmetric pair of input transducers (2, 6) and an associated pair of weighted output transducers (8, 9), and an associated pair of reflectors (14, 15). These reflectors (14, 15) are offset by a distance (d) equal to a quarter of the acoustic-wave wavelength (.lambda.), within an integral number of half wavelengths. The weightings of the output transducers are chosen in order to provide the desired impulse response.

Abstract: A method according to which a layer of a semiconductor material is made on a substrate by growth in a confinement space defined by this substrate and by a confinement layer, this growth being achieved from a seed. The cross-section of the seed, substantially perpendicular to the general direction of growth, possesses a thick central part framed by two thinned lateral parts. The confinement space has the same cross-section as the seed.

Abstract: Disclosed is a method to obtain a film of composite material based on particles of conductive polymer, stabilized by a highly steric or highly ionic surfactant. The efficient stabilization of the particles makes it possible to control the progress of the dielectrical properties of the materials as a function of the conductive entity content, leading to the preparation of films with variable impedance. The method can be applied to the making of coatings that meet goals related to electromagnetic wide-band attenuation. FIG. 2 .

Abstract: Disclosed is a motor drive device with tacho-generator that can be configured as a back-up motor. This device is designed for the driving of a movable element. It comprises an electrical rotor motor with supply coil, associated with a tachometrical sensor inducing an electrical current in at least one electrical coil, a regulator circuit controlling the speed and the position of the electrical motor as a function of the servo signal delivered by said electrical coil and applied to the supply coil. This device further comprises means to continue the driving of the movable element in the event of the malfunctioning of the electrical motor or of its electrical supply. These means to continue the driving of the movable element are constituted by a failure detection circuit which, in the event of failure, activates switching means to connect the electrical coil of the tachometrical sensor to an electrical supply source. Application: improvement of the safety of a motor drive mechanism.

Abstract: An electromagnetic wave detector has several stacks of layers of semiconducting materials. Each stack constitutes an asymmetrical quantum well with stepped barrier and has two energy levels, one of which is located beneath the energy level of the intermediate barrier step while the other is located above it. Means are used to apply an electric field to the structure.

Abstract: Material made up of a thin layer between two surfaces, a first and a second, to be used as the third layer of a transparent goggles face, the first layer being a screen and the second layer being a thickness layer, remarkable in that the material consists of a formable transparent polymer matrix having a refractive index and containing micro-cavities in the form of lenses, the micro-cavities being made from a transparent material different from that of the matrix, the refractive index of the material of the micro-cavities changing under the influence of an electric field applied across it, for a first field value the refractive index being equal to that of the matrix, and for a second field value being greater than that of the matrix, a pair of electrodes being associated with each micro-cavity.

Abstract: The device according to the invention is a frequency doubler comprising an optical index network which can be electrically controlled by two continuous electrodes, the network being created by the presence of (+P) polarization domains periodically separated by (-P) polarization domains, the electrodes being used to electrooptically compensate for variations in the index between the (+P) domains and (-P) domains.

Abstract: An optical head incorporating a single opto-electronic component and a laser device for transmitting and receiving data on a single optical fiber. The use of a single laser device for both sending and receiving data is made possible by a switching circuit, controlled by two transistors which forward-bias the laser device for transmission and reverse-bias the laser device for reception. Such a device may find particular application to data transmission on an optical path, and particularly between 1 and 10 GHz.

Abstract: The disclosure relates to amplifiers using emitter follower type transistors and, more particularly, to means for the biasing of these emitter followers. The amplifier includes a follower transistor, a biasing circuit injecting a base biasing current into the base of the follower transistor, a current generator connecting the emitter of the follower transistor to a supply potential. According to one characteristic, the biasing circuit includes, firstly, a transistor called an image transistor, the emitter of which is connected to the emitter of the follower transistor and, secondly, a current injector for the injection, into the base of the follower transistor, of a current constituting a replica of the base current of the image transistor. One of the advantages of this arrangement is that it can be used to obtain the biasing circuit with transistors that are all of a same type, NPN or PNP, as the follower transistor.