Abstract: An electrostatic loudspeaker comprises a multi-layer panel (1) incorporating an electrically insulating middle layer (2) sandwiched between first and second electrically conducting outer layers (3, 4). A signal generator is provided for applying an alternating electrical voltage across the outer layers (3, 4) to initiate vibration due to variation of the electrostatic forces acting between the layers, thereby serving as a loudspeaker. Furthermore at least one of the outer layers (3, 4) is permeable to air displaced by such vibration. Such a loudspeaker can serve as a low cost audio loudspeaker which can be made lightweight and flexible or large-area so as to render it suitable for a wide range of applications, for example to provide sound reproduction in a home environment without requiring any bulky enclosure, public-address systems, or in a notebook computer or mobile telephone.

Abstract: An electrostatic loudspeaker comprises a multi-layer panel (1) incorporating an electrically insulating middle layer (2) sandwiched between first and second electrically conducting outer layers (3, 4). A signal generator is provided for applying an alternating electrical voltage across the outer layers (3, 4) to initiate vibration due to variation of the electrostatic forces acting between the layers, thereby serving as a loudspeaker. Furthermore at least one of the outer layers (3, 4) is permeable to air displaced by such vibration. Such a loudspeaker can serve as a low cost audio loudspeaker which can be made lightweight and flexible or large-area so as to render it suitable for a wide range of applications, for example to provide sound reproduction in a home environment without requiring any bulky enclosure, public-address systems, or in a notebook computer or mobile telephone.

Abstract: A system to perform measurements on liquids, meat, viscous sugar or starch-based materials, and other foodstuffs using air-coupled ultrasound is provided. The technique uses ultrasonic transducers (advantageously capacitive transducers with polymer membranes), to generate ultrasonic signals in air, and to receive these signals after they have passed through the material under test. An ultrasonic pulse-compression process is then applied to increase the sensitivity of signals transmitted through the materials.

Abstract: An electrostatic transducer, such as a loudspeaker or microphone, comprises a multi-layer panel (1) incorporating an electrically insulating middle layer (2) sandwiched between first and second electrically conducting outer layers (3, 4). At least one of the layers has a profiled surface (6) where it contacts the surface of another of the layers. Furthermore a signal generator is provided for applying an alternating electrical voltage across the first and second layers (3, 4) to initiate vibration due to variation of the electrostatic forces acting between the layers, thereby serving as a loudspeaker (or for detecting variation of such electrostatic forces due to received vibration in the case of a microphone).

Abstract: Digital photographic printing apparatus comprises a photographic paper carrier unit (1) for feeding a sheet of photographic paper past the writing head of an optical scanner unit (2). The writing head incorporates an array of light-emitting devices which are controlled by signals from a digital controller unit (3) holding successive sets of partial image data received from a digital image data unit (4). The writing head comprises a light pipe in the form of a solid fused bundle (10) of coherent optical fibers incorporating a tapered region (17) and having a light receiving face (13) and a light transmitting face (12) adjacent the sheet of photographic paper. An array of light-emitting or laser diodes (14) mounted on a printed circuit board (15) adjacent the light receiving face (13).

Abstract: An electrostatic transducer, such as a loudspeaker or microphone, comprises a multi-layer panel (1) incorporating an electrically insulating middle layer (2) sandwiched between first and second electrically conducting outer layers (3, 4). At least one of the layers has a profiled surface (6) where it contacts the surface of another of the layers. Furthermore a signal generator is provided for applying an alternating electrical voltage across the first and second layers (3, 4) to initiate vibration due to variation of the electrostatic forces acting between the layers, thereby serving as a loudspeaker (or for detecting variation of such electrostatic forces due to received vibration in the case of a microphone).