Lithographic apparatus and method

A patterning device comprising:

• first and second reflective portions, wherein:
• the second reflective portions have a first reflectivity smaller than a second reflectivity of at least sub-portions of the first reflective portions;
• each of the first reflective portions comprises a sub-grating having reflective lines and absorbing lines;
• the first reflectivity is greater than zero and substantially matches a mean reflectivity of the reflective lines and the absorbing lines;
• and
• each of the second reflective portions comprises an unpatterned area.

A support structure of a lithography apparatus comprising:

• first and second portions, wherein:
• the first portion is different from the second portion;
• the first portion is configured to support a patterning device;
• the second portion comprises a grating;
• the grating comprising first and second reflective portions;
• the first and second reflective portions are positioned in an alternating pattern;
• the second reflective portions have a first reflectivity smaller than a second reflectivity of at least sub-portions of the first reflective portions;
• and
• the first reflectivity is greater than zero.