Abstract: Improved passive heat sinking of acoustic cameras having a microphone array and onboard processor is provided. The onboard processor is heat sunk using a heat sink member within a sealed enclosure to conduct heat to a heat dissipation surface of the enclosure. Preferably the heat sink member is mostly a spring member having the dual functions of providing mechanical force to ensure good thermal contact with the onboard processor and providing heat conduction to the heat dissipation surface. A single enclosure can enclose both the onboard processor and the microphone array. Alternatively, the enclosure can have two parts, a first part enclosing the microphone array, and a second part enclosing the onboard processor.

Abstract: Microphone array calibration that does not require a calibrated source or calibrated reference microphone is provided. We provide a statistical (Bayesian) algorithm that (under condition of reasonable environment noise during calibration) can determine gain and phase differences of a whole array at once, even when the gain and/or phase of the source is unknown. More specifically, a Bayesian regression with complex log-normal prior and complex normal likelihood is employed. The inherent phase-wrapping ambiguity in this regression is resolved by exploiting the similarity of likelihood between a lattice point and its Euclidean Voronoi region.

Abstract: Microphone array calibration that does not require a calibrated source or calibrated reference microphone is provided. We provide a statistical (Bayesian) algorithm that (under condition of reasonable environment noise during calibration) can determine gain and phase differences of a whole array at once, even when the gain and/or phase of the source is unknown. More specifically, a Bayesian regression with complex log-normal prior and complex normal likelihood is employed. The inherent phase-wrapping ambiguity in this regression is resolved by exploiting the similarity of likelihood between a lattice point and its Euclidean Voronoi region.

Abstract: Microphone array calibration that does not require a calibrated source or calibrated reference microphone is provided. We provide a statistical (Bayesian) algorithm that (under condition of reasonable environment noise during calibration) can determine gain and phase differences of a whole array at once, even when the gain and/or phase of the source is unknown. More specifically, a Bayesian regression with complex log-normal prior and complex normal likelihood is employed. The inherent phase-wrapping ambiguity in this regression is resolved by exploiting the similarity of likelihood between a lattice point and its Euclidean Voronoi region.

Abstract: A system for generating a control signal comprises a data propagator (9) for propagating acoustic sensor array data relating to a set of acoustic measurements at a set of sensor positions covering an aperture towards a set of propagated positions to obtain propagated data relating to the set of propagated positions. A control signal generator (2) is arranged for generating a control signal based on the propagated data. The control signal generator (2) comprises a data analyzer (1) for analyzing the propagated data in a spatial frequency domain. The data propagator (9) is arranged for propagating the sensor array data in real-time and the control signal generator (2) is arranged for generating the control signal in real-time.

Abstract: A lithographic apparatus includes a support constructed to support a patterning device, the patterning device being capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate; a sensor array positioned and arranged to detect an acoustic wave from a movable part of the lithographic apparatus, a controller, the controller having a controller input connected to the sensor array so as to receive a sensor array output signal, and a controller output connected to at least one actuator arranged to act on the movable part, the controller being arranged to: calculate a movement of the movable part from the sensor array output signal, and drive via the controller output the at least one actuator in response to the calculated movement.

Abstract: An acoustic transducer assembly is disclosed. It comprises a layer of support material. An electric circuit is integrated with the layer of support material. A plurality of transducers are mounted on the layer of support material to form at least part of an array of transducers A recess or aperture is provided between a pair of the transducers of the array of transducers. The recess or aperture can comprise a recess or aperture of the support material between a pair of transducers of the plurality of transducers mounted on the layer of support material. The layer of support material can be rigid or flexible. A rigid support can be used for supporting at least one transducer of the plurality of transducers.

Abstract: A method of performing near-field acoustic holography comprises the following steps. Establishing (102) acoustic data representing a set of near-field acoustic holography measurements at a first set of positions. Extrapolating (204) acoustic data using a model-based extrapolation to obtain extrapolated acoustic data relating to a plurality of positions outside the aperture. Applying (108) a spatial frequency transform to the padded acoustic data to obtain data in a spatial frequency domain. Propagating (110) the Fourier transformed acoustic data. Applying (112) a regularization in a wavenumber domain. Performing (114) an inverse spatial frequency transform.

Abstract: A lithographic apparatus includes a support constructed to support a patterning device, the patterning device being capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate; a sensor array positioned and arranged to detect an acoustic wave from a movable part of the lithographic apparatus, a controller, the controller having a controller input connected to the sensor array so as to receive a sensor array output signal, and a controller output connected to at least one actuator arranged to act on the movable part, the controller being arranged to: calculate a movement of the movable part from the sensor array output signal, and drive via the controller output the at least one actuator in response to the calculated movement.

Abstract: A system for generating a control signal comprises a data propagator (9) for propagating acoustic sensor array data relating to a set of acoustic measurements at a set of sensor positions covering an aperture towards a set of propagated positions to obtain propagated data relating to the set of propagated positions. A control signal generator (2) is arranged for generating a control signal based on the propagated data. The control signal generator (2) comprises a data analyzer (1) for analyzing the propagated data in a spatial frequency domain. The data propagator (9) is arranged for propagating the sensor array data in real-time and the control signal generator (2) is arranged for generating the control signal in real-time.

Abstract: An acoustic transducer assembly is disclosed. It comprises a layer of support material. An electric circuit is integrated with the layer of support material. A plurality of transducers are mounted on the layer of support material to form at least part of an array of transducers A recess or aperture is provided between a pair of the transducers of the array of transducers. The recess or aperture can comprise a recess or aperture of the support material between a pair of transducers of the plurality of transducers mounted on the layer of support material. The layer of support material can be rigid or flexible. A rigid support can be used for supporting at least one transducer of the plurality of transducers.

Abstract: A method of performing near- field acoustic holography comprises the following steps. Establishing (102) acoustic data representing a set of near-field acoustic holography measurements at a first set of positions. Extrapolating (204) acoustic data using a model-based extrapolation to obtain extrapolated acoustic data relating to a plurality of positions outside the aperture. Applying a spatial frequency transform to the padded acoustic data to obtain data in a spatial frequency domain. Propagating (110) the Fourier transformed acoustic data. Applying (112) a regularization in a wavenumber domain. Performing (114) an inverse spatial frequency transform.

Abstract: A panel-acoustic transducer comprises a plate-like actuator (4) and a panel (5). The panel (5) has two substantially perpendicular axes of symmetry (AS,Al). The plate-like actuator (4) is coupled to the panel in such a way that: —the actuator (4) is coupled to the panel substantially symmetrically with respect to both symmetry axes (AS,Al) of the panel (4); the plate-like actuator (4) is so arranged that, in operation, at least the first five odd excitation modes ((1,1), (3,1), (1,3), (3,3), (5,1)), in order of increasing frequency, are actuated with alternating signs. Cusps in the power spectrum of the transducer are thereby prevented.