The illumination system is mounted on a separate baseplate and has less stringent requirements in regard to alignment and thermal expansion. Misalignments along the long axis of the illumination system would primarily change the size of the rectangular beam of light projected onto the DMD. Since the DMD is over-illuminated by several hundred micrometers, there should be no observable effect. The extent to which the projected image of the exit of the homogenizer over illuminates the DMD is determined by the four blades of the field aperture located immediately in front of the homogenizer shown in Figure . These blades can be adjusted both for 1080p and XGA DMDs. The 365 nm LED and primary heatsink (Figure ) are designed to be removable to enable LED replacement, either with equivalent LED emitting at 405 nm, or with another 365 nm LED if its performance had degraded significantly. The usable lifetime of each LED is estimated at five to ten years under heavy use. Extensive information on LED use and control is found in the supplementary materials and in Hölz et al 2017 .