Abstract: A method is described for controlled polymerization of a target zone in a photopolymerizable medium wherein the method comprises a processor connectable to an exposure system for illuminating a target zone in a photopolymerizable medium receiving a 3D data representation of a 3D model of an object and using the 3D model to determine a volume of the target zone, the volume being shaped according to the 3D model; the processor determining a target energy field E0 defining an energy for volume elements in the medium that is needed to achieve polymerization inside the target zone, the determining being based on a model of the polymerization process in the medium; the processor using the target energy field E0 and a light propagation model M to compute a solution I0 for the equation E0=t·M[I0] wherein I0 is a direction-dependent illumination field needed for achieving energy deposition in the medium according to the target energy field E0 and t is the exposure time; and, the processor controlling the exposure syst

Abstract: A multi-angle imager (10) comprises an imaging array (Mij) configured to receive light beams (Li) via one or more entrance pupils (A1) according to distinct fields of view (Vi) of an object (P0) along each of multiple entry angles (?i). The imaging array (Mij) comprises multiple imaging branches (M1j, M2j) configured to form respective optical paths for the light beams (L1, L2) through the imager (10) for imaging respective subsections (S1, S2) of the object (P0). Each imaging branch (M1j) comprises a distinct set of optical elements (M11, M21) configured to receive the respective light beam (L1) along the respective entry angle (?1) and redirect the respective light beam (L1) towards the imaging plane (P1). The light beams (L1, L2) from each of the multiple imaging branches (M1j, M2j) are redirected to travel in a common direction (y) between the imaging array (Mij) and the imaging plane (P1).

Abstract: A multi-angle imager (10) comprises an imaging array (Mij) configured to receive light beams (Li) via one or more entrance pupils (A1) according to distinct fields of view (Vi) of an object (P0) along each of multiple entry angles (?i). The imaging array (Mij) comprises multiple imaging branches (M1j, M2j) configured to form respective optical paths for the light beams (L1,L2) through the imager (10) for imaging respective subsections (S1,S2) of the object (P0). Each imaging branch (M1j) comprises a distinct set of optical elements (M11,M21) configured to receive the respective light beam (L1) along the respective entry angle (?1) and redirect the respective light beam (L1) towards the imaging plane (P1). The light beams (L 1,L2) from each of the multiple imaging branches (M1j ,M2j) are redirected to travel in a common direction (y) between the imaging array (Mij) and the imaging plane (P1).

Abstract: Methods and apparatus are disclosed for determining a characteristic of a structure. In one arrangement, the structure is illuminated with first illumination radiation to generate first scattered radiation. A first interference pattern is formed by interference between a portion of the first scattered radiation reaching a sensor and first reference radiation. The structure is also illuminated with second illumination radiation from a different direction. A second interference pattern is formed using second reference radiation. The first and second interference patterns are used to determine the characteristic of the structure. Azimuthal angles of the first and second reference radiations onto the sensor are different.

Abstract: Disclosed is a method and associated apparatus for measuring a characteristic of interest relating to a structure on a substrate. The method comprises calculating a value for the characteristic of interest directly from the effect of the characteristic of interest on at least the phase of illuminating radiation when scattered by the structure, subsequent to illuminating said structure with said illuminating radiation.

Abstract: Described is a metrology system for determining a characteristic of interest relating to at least one structure on a substrate, and associated method. The metrology system comprises a processor being configured to computationally determine phase and amplitude information from a detected characteristic of scattered radiation having been reflected or scattered by the at least one structure as a result of illumination of said at least one structure with illumination radiation in a measurement acquisition, and use the determined phase and amplitude to determine the characteristic of interest.

Abstract: A metrology apparatus (302) includes a higher harmonic generation (HHG) radiation source for generating (310) EUV radiation. Operation of the HHG source is monitored using a wavefront sensor (420) which comprises an aperture array (424, 702) and an image sensor (426). A grating (706) disperses the radiation passing through each aperture so that the image detector captures positions and intensities of higher diffraction orders for different spectral components and different locations across the beam. In this way, the wavefront sensor can be arranged to measure a wavefront tilt for multiple harmonics at each location in said array. In one embodiment, the apertures are divided into two subsets (A) and (B), the gratings (706) of each subset having a different direction of dispersion. The spectrally resolved wavefront information (430) is used in feedback control (432) to stabilize operation of the HGG source, and/or to improve accuracy of metrology results.