Abstract: An array of lenses is provided for focusing thermal infrared radiation onto a detector from a set of arcuately displaced directions 7, 8, 9, 10, 11 to detect intruders. The lenses are formed as fresnel lenses, typically, in a sheet 17 of radiation transmissive material as two planar leaves 18, 19 transverse to one another, one horizontal, the other vertical. With the detector 6 set to receive focused radiation from both leaves, the radiation at each lens is more nearly normal to the lenses, greatly reducing transmission losses from directions almost under the array and from horizontal directions. Also, when moulded as a single sheet, the intersecting edge 20 of the two sheets greatly increases the mechanical rigidity of the array. Being flat, a lip 32 can be provided around the sheet edge for easy mounting and good dust sealing.

Abstract: A device and method for doubling the frequency of electromagnetic radiation of a given frequency are described. The device comprises a substrate (1) on which is provided a first layer (2) and a second layer (3). One of the first and second layers (2) has a plasma oscillation frequency equal to the given frequency for causing an electric field at twice the given frequency to be produced across the device in response to electromagentic radiation at the given frequency being incident on the device normally of the first and second layers (2and 3). A thus-produced electric field is converted to electromagnetic radiation at twice the given frequency by the said other of the first and second layers (3) which forms a waveguide for electromagnetic radiation at twice the given frequency. A further layer (2') similar to the said one layer (2) may be provided so that the said other layer (3) is sandwiched between the said one and further layers (2 and 2').

Abstract: In a CCD, especially in an image sensing device, the electrodes of the sensor part and the memory part can be switched between a reference level signal and clock pulse signals. As a result, the information density and hence in the image sensor device the number of image lines to be read out independently can be doubled. Thus, the resolution is improved and it is possible to record even and odd lines simultaneously (for example, for an electronic still camera).

Abstract: A charge transfer device (CTD) eliminating the background level of a detected signal provided with an input circuit comprising an injection source (12) and an electrode (16) controlling a storage potential well, which can be subdivided into an evacuation well (18) and an output well (19) separated by the separation potential produced by a separation electrode (27). This CTD is characterized in that its input circuit comprises a floating electrode (25) connected to the separation electrode (27) in order that the separation potential controls the background level and an insulation electrode (28) insulating the reference well (29) from the output well (19), during the measuring operations, the respective dopings under the floating electrode and under the separation electrode being obtained in order that the potential wells situated under each of these respective electrodes have different depths.

Abstract: The arrangement comprises a carrier (1) having fibre-guiding grooves (2), which carrier is made of glass-like carbon. In the manufacture of the carrier the fibre-guiding grooves are formed in a cured phenol-resin body preferably by means of an extrusion die whose shape corresponds to that of the fibre-guiding grooves to be formed. The phenol-resin body thus formed is converted into the glass-like carbon carrier by carbonization.

Abstract: Protective sheath for fusion or adhesive optical waveguide splice. The protective sheath comprises a fusion bonding sleeve surrounding the splice and a shrinkable sleeve surrounding the fusion bonding sleeve. An oblong support is arranged between the fusion bonding sleeve and the shrinkable sleeve to protect the splice. The support has an open channel in which the splice is arranged.

Abstract: The invention relates to a non-reciprocal optical element, particularly for use an an isolator or circulator, which is connected to at least two monomode optical waveguides and which has a magneto-optical waveguide structure which is subjected to a transversal magnetic field directed perpendicularly to the direction of propagation of the optical wave. This arrangement is simplified by combining the functions of the coupler and the phase shifter, which is achieved by means of the following features:the magneto-optical waveguide structure (1,11) is formed as a multimode waveguide which can propagate at least one fundamental mode (5) and the first-order mode (6),the optical waveguides (A,B,C,D,9,10) are off-centered with respect to the waveguide structure (1,11),the dimensions and/or the cross-sectional distribution of the refractive index of the optical waveguide structure (1,11) are chosen to be such that the two modes (5,6) have a reciprocal phase difference of (.pi.2)+pb 2n.pi.

Abstract: Between an image intensifier (II) having a circular radiation exit surface (II2) and an image sensor in the form of a solid state sensor (CTD) with a rectangular picture pick-up surface (PP) there is arranged an optical coupling system (OP) for producing an ellipsoidal picture (EL) of the circular radiation exit surface (II2) within or at least partly around the rectangular picture pick-up surface (PP). A signal correction device (GEN, CTD or PROC, respectively) is provided for compensating the adaptation of the optical coupling system, whilst the sensor may form part of said device (GEN, CTD), said compensation being effected by adapting the clock pulse frequency so that the corrected picture signal produces the image in a circular surface (DIS) on a screen (MIS) of a picture display device (MON).

Abstract: An optical system is described, for example a radiation source unit (10) supplying a collimated radiation beam (RB), comprising a tubular holder (30) a radiation source (33) arranged in the holder and an optical system having a collimator lens (37). The displacement of the focus of the optical system caused by the variation in length of the holder occurring at a varying temperature can be compensated by a suitable choice of notably the geometry (R.sub.1, D.sub.1) and the refractive index (n.sub.1) of the collimator lens.

Abstract: Infrared, mm-wave or other radiation (100) is detected with at least one detector element in the form of a temperature-sensitive resistor (1) having a high positive temperature coefficient, e.g. 100 micro-ohm.multidot.cm.multidot.K.sup.-1. A sufficiently high voltage V is applied across the resistor (1) by means of a circuit (Vb,T1) so that, in accordance with the invention, the resistor (1) passes a sufficient current (I) as to raise its temperature by Joule heating to a position at which a further increase in its temperature in response to incident radiation (100) reduces the Joule heating by reducing the current (I), thereby stabilizing the temperature of the resistor (1). This varying current (I) through the resistor (1) is measured (e.g. as a voltage V' by means of a transconductance amplifier A) to provide a signal indicative of the power of the incident radiation (100). The change in the Joule heating produced by a change in the temperature of the resistor (1) at this position is larger (e.g.

Abstract: In an imaging device, photocurrent generated by detector elements (1), e.g. cadmium mercury telluride photodiodes, may be integrated in resettable capacitors (2), and an output signal (S) may be derived by reading the potential of the capacitor (2) at the end of its integration period, e.g. using a source-follower MOST (3). In accordance with the invention first and second capacitors (2a and 2b) are switchably coupled in alternate parallel arms between each detector element (1) and the voltage-reading means (3), by means of an arrangement of input gates (8a and 8b) and output gates (9a and 9b). Since one of the first and second capacitors (2a or 2b) can be coupled to the detector element (1) while the other (2b or 2a) is coupled to the voltage-reading means (3), each detector element (1) can be switched from one to the other so as to be operated the whole time for photodetection without its signal being lost (i.e. not integrated) when reading the previous output signal from that detector element (1).

Abstract: The invention relates to a method for the time-dependent, automatic measurement of the backscattered portions of light pulses coupled into an optical fiber under test, said portions being received by an optical detector and converted into electrical measurement signals, followed by amplification by a gain factor adapted to the measurement range, application to an electronic evaluation circuit and storage in a memory wherefrom they can be fetched for display on a display device. In the course of an automatic measurement operation at least two time-adjacent time domains (.DELTA.t1, .DELTA.t2) of measurement signals (6) are measured with different gain factors in order to be stored in memories (S1, S2) which are associated with the respective gain factors and which can be independently addressed.

Abstract: A fibre plate comprising a stack of rows of glass fibre bundles and with or without light absorptive fibres in interstices thereof. A number of auxiliary glass fibre bundles are located in predetermined positions in a peripheral area of the face of the plate, having a light transmission characteristic differing from the bundles in the image-forming area of the plate. The positions of the auxiliary bundles with respect to an axis of symmetry of the plate are set in accordance with a code identifying the plate, such as a date or a stack number.

Abstract: An optical switching element including two parallel optical guides G.sub.1 and G.sub.2 each constituted by a strip of a semiconductor material having a refractive index n.sub.1 formed on a semiconductor substrate having a lower refractive index n.sub.0, the switching operation being obtained by the effect of voltages applied to electrodes arranged in the switching zone, characterized in that the latter is constituted by a strip of the same semiconductor material as the guides, which extends between the latter over a coupling length D between the abscissae -D/2 and +D/2 indicated on the orientated longitudinal axis of symmetry, and in that the electrodes are at least three in number, of which a first electrode permits of applying a reference voltage to the substrate, a second electrode extends substantially at the surface of the second guide from the abscissa -D to the abscissa -.epsilon., .epsilon.

Abstract: In an imaging device, photocurrent generated by photovoltaic detector elements (1), e.g. cadmium mercury telluride photodiodes, is integrated in resettable capacitors (2), and an output signal (S) is derived by reading the potential of the capacitor (2) at the end of its integration period, e.g. using a source-follower MOST (3). In accordance with the invention, blooming-protection means (11,48,12) is coupled to each capacitor (2) to inhibit forward-biasing of the detector elements (1) and inversion of the capacitor potential when the capacitor (2) becomes fully discharged by excessive photocurrent. The blooming-protection means comprises a further gate (11) which has substantially the same threshold voltage as the injection gate (10) via which the photocurrent is injected into the capacitor (2).

Abstract: Method of manufacturing a semiconductor device and semiconductor device manufactured by the use of such a method.The invention describes a method of contacting narrow regions, such as narrow polysilicon gates of a CCD having a width of, for example, 4 .mu.m. Poly 2 and poly 3 layers, which are required already for the other CCD phases, are used as etching masks having two contact openings of 4 .mu.m which are displaced both with respect to each other and with respect to the region to be contacted, so that it is possible to define a contact opening which is smaller than 4 .mu.m and is aligned accurately above the gate to be contacted. FIG. 4.

Abstract: A device is described for optically coupling a radiation source unit to at least one optical monomode transmission fiber. The fiber core has a tapered end portion by which it can be connected to a known radiation source housing without very stringent requirements on the positional accuracy of the fiber relative to the optical components in the housing.

Abstract: Arrangement for cancelling spurious signals inherent to a multiplexed video signal, comprising an arrangement of random access memories ("1"), ("2"), and ("3") and adders (AD1, 2 and 3) and having for its object to obtain by a digital signal processing operation the average value (Y) of the previously stored data contained in a certain section of the picture element for subtracting it from the information (Y) supplied by the picture element being analyzed. The transfer function of said processing operation has for its expression: ##EQU1## where n=2, 4, 8, 16, 32, 64k.sub.0 =0, 1 or 2 for the actual arrangement.

Abstract: A monomode optical transmission fibre (1) is described, having a tapered end portion (5) on which a lens (10) is arranged. This lens is obtained by immersing the fibre end in a transparent liquid material (7) whose melting temperature is lower than that of the fibre materials and whose refractive index is substantially equal to that of the fibre core (2), and by allowing the drop which adheres to the fibre after withdrawal to solidify.

Abstract: A collimator lens has a small numerical aperture and a specific focal length. One of the surfaces of the lens is planar and the other surface is aspherical. The aspherical surface is defined by a series expansion with only a few even terms.