Abstract: A system for the reduction of a laser equivalent surface area and for the optical protection of an optical device including a first polarizer and a first multiple wavelength quarter-wave plate placed in series in the path of a multiple wavelength light beam between the polarizer and the optical device. This system brings into play polarized light, and associates a liquid crystal shutter with it, providing for protection against optical aggression. The entire unit may take the form of a detachable optical attachment.

Abstract: A dynamic and decentralized self-adaptive method and system including allocation of all time/frequency resources available at a given moment to as many requesting mobile units as are necessary. Transmission between stations is performed by allocation of frequencies. For each frequency allocated, the transmissions are grouped in slots forming frames in a time/frequency space. Each frame includes n slots of a same duration and a same width. The method includes using the allocated transmission frequencies and the frames for each transmission from a station by occupancy of one and the same number of slots according to a modulo p operation. A search is made, during a monitoring procedure, for free slots to determine parameters of occupation of a transmission as a function of the state of occupancy of the frames of the time/frequency space existing before the transmission.

Abstract: An electromagnetic wave detector having a first detector element including an active photoconducting material capable of detecting a band of wavelength and a second detector element including an active photoconducting material capable of detecting the same band of wavelength. A common layer is positioned between the first and second detector elements. A first and second connectors are configured to connect to the first and second detector elements, respectively. A third connector is configured to connect in common to the first and second detector elements. The detector further includes contact mechanisms configured to apply control voltages where the voltage applied to the third connector has a value between the values applied to the first and second connectors. A reading circuit connected to the third connector reads a photoconduction current difference between the first and the second detector elements.

Abstract: The invention relates to a charge-coupled device. Such devices comprise at least one insulated conducting gate (3) connecting two semiconductor zones. According to the invention, each insulated conducting gate (3) has a width progressively increasing from the first semiconductor zone (1) to the second semiconductor zone (2). The width of each gate (3) is sufficiently narrow for the potential well created by the application of a voltage V to the gate to have a depth increasing progressively from the first zone (1) to the second zone (2), thus enabling the charges to be driven away. The invention applies to any type of charge-coupled device and particularly to photodiodes.

Abstract: Optical information recording/reading medium including at least one transparent layer (2) for recording or reading information in various strata (S1 to S3) distributed through the thickness of the medium. The medium includes, recorded in a principal plane at least the transparent layer with one or more information items (5) for carrying out either tracking, focusing, synchronization or addressing or any combination. Also included in each stratum is one more guidance information items (4).

Abstract: A unipolar multiple-wavelength quantum well laser comprises at least two stacks of layers of semiconductor materials. Each stack forms a quantum well laser working by intra-band transition and emitting a specified wavelength. The two stacks of layers are separated by a stack of layers of semiconductor materials constituting a quantum well transfer lattice which, under an electrical field, enables a transfer of electrons from the low level of the (conduction or valence) band of a quantum well of a first laser to the high level of the (conduction or valence) band of the quantum well of a second laser. FIG. 2b.

Abstract: The present invention relates to radars and sonars, and more particularly to a synthetic-band technique of pulse compression making it possible to reach a very high distance resolution. Synthetic band consists in transmitting a waveform pattern consisting of a string of N coherent elementary pulses, linearly frequency-modulated, following one another at a recurrence frequency F.sub.r, of rectangular frequency spectra of elementary band B and of stepped carrier frequencies such that their frequency spectra will link up exactly one ahead of another to form a global spectrum of width N.times.B. On reception, the frequency spectra of the signals received in return for the N elementary pulses of a pattern are extracted by calculation, translated and juxtaposed so as to reconstruct a global frequency spectrum of width N.times.B and then compressed. Pulse compression is thus obtained which is equivalent to that which would result from the transmission of a waveform having a single pulse of frequency band N.times.

Abstract: The disclosed motion device comprises a triangular platform supporting a load, for example a simulator cabin. This platform is supported at all three corners by hinged arms driven by cranks that are moved by an actuator. There is provided a load compensation device facilitating the work of the actuators. Thus the load can be moved in pitch and roll as well as vertically.

Abstract: A device for the generation of analog signals by means of analog-digital converters comprises a block for the generation of words encoded on N bits and an analog-digital converter whose input is encoded on M bits, M being smaller than N. The device furthermore comprises a sigma-delta modulator, at the output of the first block, the bus being separated into M most significant bits reserved for the input of the analog-digital converter and N-M least significant bits that enter the sigma-delta modulator, the output of this modulator being an M-bit bus that is added to the M output bits of the word generation block by digital addition means, M being smaller than N.

Abstract: A programmable acoustooptic device including an elastooptic medium configured to receive an input optical pulse and an acoustic wave; an acoustic transducer configured to generate the acoustic wave in the elastooptic medium along a defined direction; and a programmable circuit coupled to the acoustic transducer and configured to program at least one of a frequency modulation and phase modulation of the acoustic wave, whereby the acoustic transducer generates a modulated acoustic wave, wherein an output optical pulse is generated and is a convolution of the input optical pulse with the modulated acoustic signal.

Abstract: A Deramp type radar used in synthetic aperture radar for radar imaging transmits coherently repeated linear frequency-modulated pulses and carries out a sort of pulse compression in reception by demodulation of the echo signals received by means of a frequency ramp that reproduces all or part of a transmitted pulse, and by a Fourier transform performed in range. The application to a Deramp type radar signal of a standard SAR processing is disturbed by the fact that, in this signal, the effectively demodulated part of an echo signal due to a target has a position with respect to this echo signal and a duration that are variable as a function of the distance from the target to the radar. The proposed method makes it possible to eliminate this disturbance by means of a particular choice of a common temporal support used for the demodulation of the signals of all the targets of the useful swath and a phase correction applied to the level of the pulse response of the image focusing filter of the SAR processing.

Abstract: The present invention relates to a detector of electromagnetic emissions, especially from radars, with reduced upstream bit rate. The detector comprises, between means (1) for the acquisition of the electromagnetic pulses received and extraction means (2) which group together the pulses relating to each emission, bit rate reduction means (4) comprising means (41) of characterization and compression of the trains with high recurrence frequency (HRF). Applications include detection, location and identification of surrounding radar electromagnetic emissions.

Abstract: Disclosed is a ferrite material having low magnetic losses at frequencies of about 1 megahertz to 100 megahertz, and having firing and sintering temperatures lower than about 1000.degree. C. The material is a nickel-zinc-copper material with cobalt substitution, particularly well suited to the making of magnetic cores and more specifically to the making of micro-inductors.

Abstract: A display device including an illuminating source which emits radiation and a spatial light modulator illuminated by the radiation. The modulator includes a matrix of N.times.M elementary pixels (X.sub.i,j) of dimensions d.sub.N .times.d.sub.M, the pixels X.sub.i,j and X.sub.1+i,j being separated by a spacing p.sub.N. The radiation is collimated in each pixel. The spacing p.sub.N is greater by at least an order of magnitude than the dimension d.sub.M. The display may be used as a flat television screen.

Abstract: Disclosed are a method for the control of an image display screen displaying half-tones and a display device implementing this method. The disclosed method is used to control an image display screen of the type having cells arranged in rows and columns and working either in a state known as an "OFF" state or in a state known as an "ON" state in which they are activated and produce light. The method consists in activating the cells of each row during sub-periods of different duration, with orders of distribution of the sub-periods that are different between two successive rows. This results in a reduction of the amplitude of the variations of a load constituted by the cells in the <<lit>> state of these two consecutive rows. Application inter alia to alternating plasma panels.

Abstract: The invention relates to annular acoustic transducers formed by a set of piezoelectric segments placed under prestress.It consists in grouping these segments (101) into a set of sectors (102) which are separated by tightening wedges (109). The set is placed in a shaper annulus (108). The keys are drawn towards the center by screws (111), thus thrusting the sectors against the shaper annulus and prestressing the segments. The strain gauges (107) make it possible to check the stress obtained in order to adjust it to the desired value while minimizing the scatter between the sectors.It makes it possible to manufacture dismantleable low-frequency high-power acoustic transducers.

Abstract: The present invention provides a method for distinguishing a boundary of an object, and the object itself, from its background. In the method electromagnetic radiation is detected from at least one field of view substantially spanning the boundary of the object and background adjacent to the boundary and superimposed or overlaid as images onto a detector. The method includes correlating spatial transitions in intensity of the overlaid images on the detector with a boundary of the object. When used for determining the attitude of a satellite with respect to the earth, the detector is a thermal infrared detector thereby providing a sharp contrast between the thermal emission of the earth and cold space. The invention provides a simple, effective method and device for determining satellite orientation and/or attitude with respect to a thermal infrared-emitting target body.

Abstract: A fingerprint-reading system including a sensor on which a finger, whose imprint is to be read, is pressed. The sensor has an active surface of elements sensitive to variations in temperature and integrated heating resistors that create a transient variation in the temperature of the sensitive elements thereby to generate temporary charges in each element when pressed by a finger. The charges are output in synchronism with creation of the transient variations in the temperature of the sensitive elements to provide stable images of the fingerprint which may be motionless. The output of the sensor enables real-time display of the fingerprint images and processing of authentication data. The heating resistor enables the sensor to produce stable images of a fingerprint by producing an internal excitation to offset the tendency of electrical charges, induced by variations of the physical temperature of the finger, from disappearing because the temperature of the finger has reached equilibrium.

Abstract: The disclosed method uses the ancillary antennas of a radar, and consists in determining the positions of the phase centers of these ancillary antennas, compensating for the difference in optical path between the reflection lobe of the processed channel and that of the ancillary channel, and generating a synthetic channel by an SLO type processing in performing a coherent subtraction between the processed channel and the ancillary channels used, on the desensitized zone of the doppler distance/frequency ambiguous domain of each of the processed channels.

Abstract: A method for determining precipitation rate including on the basis of the signals received on the two polarization channels H and V of the radar, in firstly determining an estimate of the precipitation rates R.sub..alpha. in each range gate i along the radar beam for a single polarization, then a first estimated value (I.sub.1) of the integral of the precipitation rates and, finally, on the basis of the attenuated reflectivity coefficient (Z.sub.H.alpha. (r)), an estimate of the unattenuated differential reflectivity coefficient (Z.sub.DRs (r)). Furthermore, the measured value of the attenuated differential reflectivity coefficient (Z.sub.DRs (r)) is determined, and the integral (I.sub.2) of the precipitation rates is deduced therefrom, then is compared with the first estimated value (I.sub.1) so as to iteratively adjust a parameter (.alpha.) of the method when applied to the polarization H alone. When .alpha.