Lithographic apparatus and device manufacturing method

A lithography apparatus comprising:

• a projection system configured to project a beam of radiation onto a substrate as an array of sub-beams of radiation;
• an array of individually controllable elements configured to modulate said sub-beams of radiation so as substantially to form a requested dose pattern on said substrate, said requested dose pattern being built up over time from an array of localized exposures in which at least neighboring localized exposures are imaged at substantially different times and in which each localized exposure is produced by one of said sub-beams of radiation;
• a rasterizer device arranged to convert data defining said requested dose pattern to a sequence of data representing a requested dose at a corresponding sequence of points within a pattern;
• and
• a data manipulation device arranged to receive said sequence of data and constitute a control signal therefrom suitable for controlling said array of individually controllable elements, wherein said data manipulation device is configured to calculate a desired sub-beam intensity for each localized exposure so as to reproduce said requested dose pattern, said calculation being based for each localized exposure on context information comprising said requested dose pattern in a region on said substrate around said localized exposure, and wherein said data manipulation device includes
• a memory buffer arranged to store at least a portion of said context information, wherein said portion of said context information includes at least a portion of said sequence of data;
• and
• a desired sub-beam intensity calculation device configured to calculate said desired sub-beam intensity for the plurality of neighboring localized exposures based on said context information provided by said memory buffer.