Abstract: An acoustic dampener for a duct carrying an acoustic signal, the acoustic dampener comprising a plurality of laminar surfaces stacked on top of one another and separated from one another, thereby creating a stack, wherein the plurality of laminar surfaces include a front laminar surface and a back laminar surface, a hole arranged in each of the plurality of laminar surfaces, and in the front laminar surface wherein the hole has dimensions enabling a duct carrying an acoustic signal, to be connected to the acoustic dampener and clamping means for clamping together the front laminar surface, the stack of plurality of laminar surfaces and the back laminar surface to create an acoustic dampener.

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: 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: 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.