Abstract: A filter with surface acoustic wave resonators using an equivalent electrical bridge structure to obtain a good form relationship, i.e., a relationship between the filter rejection band and its pass band. Bridge arms advantageously include the paralleling of several resonators, thereby not requiring additional electrical elements as in the background art which provides for the use of series-connected resonators. Particular implantation methods for preparing equivalent structures to paralleling several resonators are also disclosed.

Abstract: A surface acoustic wave filter having three acoustic pathways. The first acoustic pathway is made up of a first transducer including a first and second bonding pad and is arranged between two reflectors to form a first resonator. The second acoustic pathway is made of a second transducer including a third and fourth bonding pad and is arranged between two reflectors to form a second resonator. A third acoustic pathway is made of a third transducer including a fifth and sixth bonding pad and is arranged between two reflectors to produce a third resonator. Each bonding pad of the transducers is linked to a specified potential.

Abstract: It consists of several channels (V1, V2) in parallel, which exhibit an inter-transducer gap difference (2.sub.1 -4.sub.1 ; 2.sub.2 -4.sub.2) equal to an even multiple of the half-wavelength (.lambda.) at the central frequency, from one channel to the next, so as to cancel the delay line transfer function which corresponds to the direct path between transducers.

Abstract: In a transducer for surface waves, an alternating succession of transmitter cells and reflector cells is used. The transmitter cells transmit surface waves in phase opposition, leftwards and rightwards. The reflector cells have a reflection coefficient that is in phase opposition between the left-hand side and the right-hand side. The waves transmitted by the transmitter cells interfere with the waves reflected by the reflector cells, destructively in one direction and constructively in the other direction. This enables the making of transducers with spacings equal to .lambda./4 and .lambda./6 only.

Abstract: A method for the correction of surface wave devices consists of measuring the transfer function of an entirely finished surface wave device and then designing a surface wave corrective filter, the transfer function of which enables the correction of the transfer function of the preceding device. The method makes it possible to correct, in particular, RAC type dispersive filters.

Abstract: The system permits the multiplex telecommunication through the medium of an optical carrier wave. The system comprises a source of coherent light whose optical spectrum is dispersed in an optical device comprising a pair of diffraction gratings. A plurality of light modulators are disposed in the path of the spread out beams and controlled by electric signals which carry items of information. Output optical means collect the modulated spectral components.

Abstract: A piezoelectric substrate is subjected to the continuous excitations produced by a high-frequency electric field of fixed radian frequency .alpha. applied between its two opposite faces; high-frequency electrical pulses of radian frequency .alpha..sub.p are applied to the periodic network of conductors illuminated by the image; the electrical conductivity at the surface of the substrate at each point is made a function of the illumination directed towards said point, for example by the application of a photoconducting semi-conductor covering the network or by a substrate whose conductivity is directly modulated by the incident light. The non-linear interaction between the two substrate excitations induces a surface wave whose intensity is modulated by the luminous intensity and which is picked up by the transducers. Application with fixed .alpha..sub.p, to the point by point read-out of a linear optical image and with .alpha..sub.p = .alpha..sub.p (t) to the analysis of its spatial frequencies.

Abstract: A device for reading two-dimensional optical images. It comprises a piezoelectric substrate on which two transducers transmit elastic waves in two separate directions, and a semiconductive and photoconductive layer arranged near the surface of the substrate, in which a nonlinear interaction occurs opposite the point where the two said directions converge. This point of convergence forms a reading point of the image which is projected onto the photoconductor, this point moving as a function of time along a straight line which forms an analysis line of said image.

Abstract: A system is provided for reading acoustic images such as those obtainable in an elastic medium as a result of the focusing of, or interference between, acoustic waves. The image analysing device comprises a substrate made of piezoelectric material which is provided on one face with an interdigital array and an electro-acoustic transducer.The system permits to read acoustic images formed at the free surface on the opposite face of the substrate or at a certain distance from its free surface in contact with an elastic propagation medium.