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.