Abstract: An apparatus (10) includes a digital micromirror device (16) disposed within a housing (11), the housing having an opening (13) which is sealed by a lid (17). The lid includes a metal frame (21), a radiation transmissive window element (41) supported in an opening (23) provided through the frame, and a chrome layer (42) provided on one side of the window element. The chrome layer has an aperture (43) through it, and the edge portion (61) of the chrome layer adjacent the aperture forms with respect to the window element an acute angle (62) which is larger than in pre-existing devices. A technique for forming this acute angle involves the use of a positive photoresist material (101).