Abstract: An afocal optical element adapted to reduce a beam diameter of a light beam is provided. The afocal optical element includes an object-side surface facing an object-side through which the light beam passes and an image-side surface facing an image-side through which the light beam passes. The object-side surface is convex, and the image-side surface is concave. The afocal optical element has only one lens element. In addition, a projection device is also provided.

Abstract: A filter assembly that includes a filter housing having a radio frequency identification reader and a blocker; and a filter cartridge insertable into the filter housing having a radio frequency identification tag that the radio frequency reader on the housing can read to determine if the filter cartridge is of the proper type. When the proper filter cartridge is inserted in the filter housing and the tag is matched by the radio frequency identification reader, the blocker will allow the cartridge to go in. When the radio frequency identification reader does not match the tag on the filter cartridge, the blocker will prevent the filter cartridge from being fully inserted into the housing.