Patent ID: 8717535

Claim:
A lithographic apparatus comprising: a device configured to produce a modulated beam of radiation based on control signals; an array controller configured to provide the control signals to the device; a projection system configured to project the modulated beam of radiation onto a substrate; a calibration unit, disposed between the device and the projection system, and configured to at least one of generate calibration data and update calibration data; and a calibration controller configured to instruct the array controller to provide the control signals based on the calibration data; wherein the calibration unit is further configured to switch between at least a first state and a second state, such that, in the first state, the modulated beam of radiation is directed towards the projection system without interaction with the calibration unit and, in the second state, at least a portion of the modulated beam of radiation is directed towards the calibration unit, and wherein the calibration unit comprises a radiation beam inspection device configured to inspect the portion of the modulated beam of radiation received by the calibration unit.