Lithographic apparatus and device manufacturing method

A device manufacturing method comprising transferring a pattern from a patterning device onto a substrate, the method including:

• projecting a patterned radiation beam onto a target portion of the substrate, the patterned radiation beam having first first-order radiation and second first-order radiation to form an image of at least part of a pattern of the patterned radiation beam;
• adjusting an optical phase of radiation of the patterned radiation beam using a phase adjuster to alter an image characteristic of the image, the adjusting comprising controlling the phase adjuster to selectively apply an optical phase difference between the first first-order radiation and the second first-order radiation traversing the phase adjuster.

A non-transitory computer readable storage medium having a computer program stored therein to cause a computing device to perform a method of processing a patterned radiation beam having first first-order radiation and second first-order radiation to form an image of at least part of a pattern of the patterned radiation beam on a substrate, the method comprising:

• identifying an area where the first first-order and/or the second first-order radiation traverses, in use, an optical element of an optical phase adjuster;
• and
• instructing the optical phase adjuster to adjust an optical phase of radiation of the patterned radiation beam to alter an image characteristic of the image, the adjusting comprising controlling the phase adjuster to selectively apply an optical phase difference between the first first-order radiation and the second first-order radiation traversing the phase adjuster.