Abstract: There is disclosed herein a transducer for acoustic communications through a series arrangement of fluid and solid media, the transducer comprising: —a signal processor configured to implement a communications scheme at and around a center frequency of at least 1 MHz; a piezoelectric element for activation in accord with the communications scheme; an electrode electrically connected to the signal processor, and being attached to the piezoelectric element; and a substrate, having the piezoelectric element mounted thereon, wherein an aspect of the electrode at the piezoelectric element is approximately equal to the acoustic wavelength of an acoustic wave in the substrate at the center frequency. There is further disclosed a remote monitoring device employing at least one of the transducers described, in concert with a further transducer. Still further, there is disclosed a method of communicating using the transducer described herein.

Abstract: In an arrangement for transmitting power or data through a solid rigid substrate without penetrating the substrate, acoustic transducer components are mounted on the substrate by means of strain isolator elements which are welded or otherwise bonded to the substrate and providing an attachment surface to which the attachment interface of the acoustic transducer may be attached. The strain isolator element is of the same or similar acoustic impedance as the rigid substrate and may indeed be formed of the same material. Various geometries of strain isolator are disclosed, including a plain spacer block, and one comprising a stalk attached to the solid rigid substrate and topped by a disc in a ‘mushroom’ configuration.

Abstract: In an arrangement for transmitting power or data through a solid rigid substrate without penetrating the substrate, acoustic transducer components are mounted on the substrate by means of strain isolator elements which are welded or otherwise bonded to the substrate and providing an attachment surface to which the attachment interface of the acoustic transducer may be attached. The strain isolator element is of the same or similar acoustic impedance as the rigid substrate and may indeed be formed of the same material. Various geometries of strain isolator are disclosed, including a plain spacer block, and one comprising a stalk attached to the solid rigid substrate and topped by a disc in a ‘mushroom’ configuration.

Abstract: In an arrangement for transmitting power or data through a solid rigid substrate without penetrating the substrate, acoustic transducer components are mounted on the substrate by means of strain isolator elements which are welded or otherwise bonded to the substrate and providing an attachment surface to which the attachment interface of the acoustic transducer may be attached. The strain isolator element is of the same or similar acoustic impedance as the rigid substrate and may indeed be formed of the same material. Various geometries of strain isolator are disclosed, including one comprising a stalk attached to the solid rigid substrate and topped by a disc in a ‘mushroom’ configuration.

Abstract: There is disclosed a transducer apparatus for acoustic communications through a substrate at a predetermined center frequency, the apparatus comprising:—an active piezoelectric element for generating an acoustic signal; an intermediate layer, having a surface for accommodating the piezoelectric element, and having a first array of protrusions on a surface opposite the surface for accommodating the piezoelectric element; and a second array of protrusions at the substrate, wherein the active piezoelectric element is mounted onto the intermediate layer, and the intermediate layer is secured in position relative to the substrate such that the first array of protrusions faces the second array of protrusions such that the acoustic signal may propagate through the first and second arrays. There are further disclosed a method of mounting such an apparatus and a plate suitable for use in the transducer apparatus.

Abstract: In apparatus for the acoustic transmission of power or data through a solid barrier such as a ships hull, assembly of an acoustic transducer to the hull is facilitated by bonding it first to an intermediate element by a thin layer of bonding adhesive and then bonding the intermediate element to the barrier using a second bonding layer. Acoustic matching of the transducer to the intermediate element is achieved by the thin layer, and the mechanically more robust base of the intermediate element can be rubbed on the barrier surface to displace or abrade away any unwanted debris or imperfections which might otherwise prevent the achievement of a thin second bonding layer. This makes the mounting and bonding process more tolerant of imperfections in the barrier surface due to either surface defects or particulate contamination. The transmit and receive transducers may be positioned relative to each other so as to suppress or attenuate multiple-transit signals.

Abstract: In apparatus for the acoustic transmission of power or data through a solid barrier such as a ships hull, assembly of an acoustic transducer to the hull is facilitated by bonding it first to an intermediate element by a thin layer of bonding adhesive and then bonding the intermediate element to the barrier using a second bonding layer. Acoustic matching of the transducer to the intermediate element is achieved by the thin layer, and the mechanically more robust base of the intermediate element can be rubbed on the barrier surface to displace or abrade away any unwanted debris or imperfections which might otherwise prevent the achievement of a thin second bonding layer. This makes the mounting and bonding process more tolerant of imperfections in the barrier surface due to either surface defects or particulate contamination. The transmit and receive transducers may be positioned relative to each other so as to suppress or attenuate multiple-transit signals.

Abstract: There is disclosed a transducer apparatus for acoustic communications through a substrate at a predetermined centre frequency, the apparatus comprising: —an active piezoelectric element for generating an acoustic signal; an intermediate layer, having a surface for accommodating the piezoelectric element, and having a first array of protrusions on a surface opposite the surface for accommodating the piezoelectric element; and a second array of protrusions at the substrate, wherein the active piezoelectric element is mounted onto the intermediate layer, and the intermediate layer is secured in position relative to the substrate such that the first array of protrusions faces the second array of protrusions such that the acoustic signal may propagate through the first and second arrays. There are further disclosed a method of mounting such an apparatus and a plate suitable for use in the transducer apparatus.

Abstract: There is disclosed herein a transducer for acoustic communications through a series arrangement of fluid and solid media, the transducer comprising: a signal processor configured to implement a communications scheme at and around a centre frequency of at least 1 MHz; a piezoelectric element for activation in accord with the communications scheme; an electrode electrically connected to the signal processor, and being attached to the piezoelectric element; and a substrate, having the piezoelectric element mounted thereon, wherein an aspect of the electrode at the piezoelectric element is approximately equal to the acoustic wavelength of an acoustic wave in the substrate at the centre frequency. There is further disclosed a remote monitoring device employing at least one of the transducers described, in concert with a further transducer. Still further, there is disclosed a method of communicating using the transducer described herein.

Abstract: In an arrangement for transmitting power or data through a solid rigid substrate without penetrating the substrate, acoustic transducer components are mounted on the substrate by means of strain isolator elements which are welded or otherwise bonded to the substrate and providing an attachment surface to which the attachment interface of the acoustic transducer may be attached. The strain isolator element is of the same or similar acoustic impedance as the rigid substrate and may indeed be formed of the same material. Various geometries of strain isolator are disclosed, including one comprising a stalk attached to the solid rigid substrate and topped by a disc in a ‘mushroom’ configuration.

Abstract: In apparatus for the acoustic transmission of power or data through a solid barrier such as a ships hull, assembly of an acoustic transducer to the hull is facilitated by bonding it first to an intermediate element by a thin layer of bonding adhesive and then bonding the intermediate element to the barrier using a second bonding layer. Acoustic matching of the transducer to the intermediate element is achieved by the thin layer, and the mechanically more robust base of the intermediate element can be rubbed on the barrier surface to displace or abrade away any unwanted debris or imperfections which might otherwise prevent the achievement of a thin second bonding layer. This makes the mounting and bonding process more tolerant of imperfections in the barrier surface due to either surface defects or particulate contamination. The transmit and receive transducers may be positioned relative to each other so as to suppress or attenuate multiple-transit signals.

Abstract: In apparatus for the acoustic transmission of power or data through a solid barrier such as a ships hull, assembly of an acoustic transducer to the hull is facilitated by bonding it first to an intermediate element by a thin layer of bonding adhesive and then bonding the intermediate element to the barrier using a second bonding layer. Acoustic matching of the transducer to the intermediate element is achieved by the thin layer, and the mechanically more robust base of the intermediate element can be rubbed on the barrier surface to displace or abrade away any unwanted debris or imperfections which might otherwise prevent the achievement of a thin second bonding layer. This makes the mounting and bonding process more tolerant of imperfections in the barrier surface due to either surface defects or particulate contamination. The transmit and receive transducers may be positioned relative to each other so as to suppress or attenuate multiple-transit signals.

Abstract: A camouflage panel arranged to be attachable to an outer area of a submarine is disclosed. The panel comprises a light emitter operable such that light is emitted from a surface of the panel. The intensity and colour of the emitted light being controllable in response to a control signal received from a sensor arranged to sense the intensity and colour of light in the region of the submarine. Apparatus comprising a number of such panels is also disclosed.

Abstract: An apparatus and method are provided for transferring data through a submarine hull or other solid boundary using high frequency acoustic signals, so avoiding penetration of the hull or boundary. First and second transducers are mounted on opposed surfaces of the hull and aligned to communicate acoustic signals through the hull. The first transducer is driven by a continuous wave carrier signal modulated with data. A demodulator detects that data in the modulated acoustic signals received by the second transducer. Critically, the dimensions of the first and second transducers and the frequency of the carrier signal are selected so as to reduce the interference by triple transit signals through the hull to a level sufficiently low to enable continuous communication of data through the hull at a bit rate of at least 1 MHz. Carrier signals of the order of 40 MHz may be used to achieve data bit rates of the order of 15-18 MHz through the hull.

Abstract: A laser is provided, suitable for use in laser displays, having a laser cavity defined by at least first and second mirrors, a lasing material positioned in an optical path within the cavity with an associated pumping source and wherein one of the mirrors has a reflective surface that is moveable so as to alter the length of the cavity at a rate sufficiently high to ensure that effects due to a speckle pattern, as perceived by an observer or detector of light generated by the laser, are reduced while preserving the instantaneous coherence of the laser light. Sufficiently rapid movement of the mirror surface ensures that any speckle pattern changes at a faster rate than can be detected by the human eye or by a detector so that speckle is no longer visible, or is at least considerably reduced.

Abstract: An apparatus and method are provided for transferring data through a submarine hull or other solid boundary using high frequency acoustic signals, so avoiding penetration of the hull or boundary. First and second transducers are mounted on opposed surfaces of the hull and aligned to communicate acoustic signals through the hull. The first transducer is driven by a continuous wave carrier signal modulated with data. A demodulator detects that data in the modulated acoustic signals received by the second transducer. Critically, the dimensions of the first and second transducers and the frequency of the carrier signal are selected so as to reduce the interference by triple transit signals through the hull to a level sufficiently low to enable continuous communication of data through the hull at a bit rate of at least 1 MHz. Carrier signals of the order of 40 MHz may be used to achieve data bit rates of the order of 15-18 MHz through the hull.