An improved real image projection system comprises, in the primary configuration, a tilted mirror to eliminate ghost reflections, and a unique arrangement allowing the introduction of a second background image without a 50%/50% beamsplitter, while providing system transmission of approximately 50%. A...http://www.google.com.hk/patents/US6935747?utm_source=gb-gplus-share專利 US6935747 - Image enhancement and aberration corrections in a small real image projection system
