Abstract: A receiver assembly (1) has a radiation guide (4) having an elongate form. The length is at least five times longer than all dimensions of the radiation guide perpendicular to the longitudinal axis (3). The guide receives radiation via an outer lateral surface (8), converts the radiation to longer wavelength radiation, and guides the converted radiation to a longitudinal end surface (2). A receiver unit (5) receives radiation output from the longitudinal end surface.

Abstract: An imaging system for an object such as human or animal tissue applies acoustic vibrations localized in two or three dimensions and simultaneously illuminates the object with an illuminating electromagnetic wave. A transmitter or receiver is provided that has an antenna with at least one coil that surrounds an axis along which at least a portion of the acoustic vibration is output.

Abstract: An imaging system for an object such as human or animal tissue applies acoustic vibrations localized in two or three dimensions and simultaneously illuminates the object with an illuminating electromagnetic wave. A transmitter or receiver is provided that has an antenna with at least one coil that surrounds an axis along which at least a portion of the acoustic vibration is output.

Abstract: An optical wireless local area network using line of sight optical links. The base station and terminal stations are provided with optical transceivers which include a transmitter array and detector array. The transmitter array consists of an array of resonant cavity light emitting diodes integrated using flip-chip technology with a CMOS driver circuit. The driver circuit includes constant bias, current peaking and charge extraction. The driver circuitry is compact and can be confined within a region underlying the corresponding light source. The detector array consists of an array of photo diodes, provided with sense circuitry consisting of a pre-amplifier and post-amplifier. The diodes and sense circuitry are also integrated using a flip-chip technique. The light emitter and the detector may include adaptive optical elements to steer and/or focus the light beams.

Abstract: An optical wireless local area network using line of sight optical links. The base station and terminal stations are provided with optical transceivers which include a transmitter array and detector array. The transmitter array consists of an array of resonant cavity light emitting diodes integrated using flip-chip technology with a CMOS driver circuit. The driver circuit includes constant bias, current peaking and charge extraction. The driver circuitry is compact and can be confined within a region underlying the corresponding light source. The detector array consists of an array of photo diodes, provided with sense circuitry consisting of a pre-amplifier and post-amplifier. The diodes and sense circuitry are also integrated using a flip-chip technique. The light emitter and the detector may include adaptive optical elements to steer and/or focus the light beams.

Abstract: An optical wireless local area network using line of sight optical links. The base station and terminal stations are provided with optical transceivers which include a transmitter array and detector array. The transmitter array consists of an array of resonant cavity light emitting diodes integrated using flip-chip technology with a CMOS driver circuit. The driver circuit includes constant bias, current peaking and charge extraction. The driver circuitry is compact and can be confined within a region underlying the corresponding light source. The detector array consists of an array of photo diodes, provided with sense circuitry consisting of a pre-amplifier and post-amplifier. The diodes and senses circuitry are also integrated using a flig-chip technique. The light emitter and the detector may include adaptive optical elements to steer and/or focus the light beams.

Abstract: An optical wireless local area network using line of sight optical links. The base station and terminal stations are provided with optical transceivers which include a transmitter array and detector array. The transmitter array consists of an array of resonant cavity light emitting diodes integrated using flip-chip technology with a CMOS driver circuit. The driver circuit includes constant bias, current peaking and charge extraction. The driver circuitry is compact and can be confined within a region underlying the corresponding light source. The detector array consists of an array of photo diodes, provided with sense circuitry consisting of a pre-amplifier and post-amplifier. The diodes and senses and the detector may include adaptive optical elements to steer and/or focus the light beams.

Abstract: A communications device such as a personal identity card is in the form of a badge or label worn on the outside of the wearer's clothing. The badge includes a first layer of a transparent material having an inner surface that is contoured with a retroreflecting repeating pattern. A second layer also of a transparent material has an inner surface with a reciprocating retroreflecting pattern. Sandwiched between the two layers is a layer of liquid crystal material the refractive index of which can be varied through the application of an electric field. When the refractive index of the layer is close to that of the first and second layers, incident radiation passes through the device with little scattering. However, as the refractive index of the layer is varied by application of an electric field, incident radiation is retroreflected from the contoured interface of the first layer with the layer.