Patent ID: 8172402

Claim:
A projection system for displaying at least one visual image based on three primary colours, said projection system comprising: a signal processing unit for converting said visual image into a visual image based on at least four primary colours, a frequency spectrum being associated to each primary colour; first display means for displaying three first primary colours of said converted visual image on a screen, said three first primary colours being respectively red, green and blue; second display means for displaying at least a fourth primary colour of said converted visual image on said screen; and optical filtering means that are located between said first and or second display means and said screen and that are adapted to enhance the separation between the frequency spectrum of the three first primary colours of the first display means and the frequency spectrum of the at least fourth primary colour of the second display means, wherein said optical filtering means comprises a notch filter located between said first display means and the screen to attenuate or block at least a portion of the frequencies of at least one of the three first primary colours in the frequency spectrum associated to the fourth primary colour.