PROJECTION SYSTEM BASED ON METAMERISM

• US 20100085491A1
• Filed: 02/20/2008
• Published: 04/08/2010
• Est. Priority Date: 03/05/2007
• Status: Active Grant

• Current Assignee: Magnolia Licensing LLC (IP Edge LLC)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Doyen, Didier, Thiebaud, Sylvain, Sacre, Jean-Jacques, Vigouroux, Jean-Ronan, Bourdon, Pascal, Morvan, Patrick
• Granted Patent: US 8,172,402 B2
• Time in Patent Office: Days
• US Class Current: 348/744
• CPC Class Codes: H04N 2005/9135 by superimposing the spectrally spread copy protection signal onto the video signal
• CPC Class Codes: H04N 2005/91392 using means for preventing making copies of projected video images
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection

Abstract

The invention relates to a projection system for displaying at least one visual image based on three primary colours, comprising a signal processing unit for converting said visual image into at least a visual image based on four primary colours, a frequency band being associated to each colour primary, first display means for displaying three first primary colours of said visual image on a screen and second display means for displaying at least the fourth primary colour of said visual image on said screen. According to the invention, the system further comprises optical filtering means that are adapted to enhance the separation between the frequency spectrum of the first three primary colours of the first display means and the frequency spectrum of the at least fourth primary colour of the second display means. Application to anti-camcorder systems.

Claims

1. A projection system for displaying at least one visual image based on three primary colours, 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 colour primary,

first display means for displaying three first primary colours of said converted visual image on a screen, these three first primary colours being respectively red, green and blue, and

second display means for displaying at least a fourth primary colour of said converted visual image on said screen, wherein it further comprises 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 first three primary colours of the first display means and the frequency spectrum of the at least fourth primary colour of the second display means.

2. The projection system according to claim 1 wherein, in the CIE xy chromaticity diagram and under a D65 or a C illuminant, if x_R, y_R are the coordinates of the red primary colour of the three first primary colours, if x_G, y_G are the coordinates of the green primary colour of the three first primary colours, if x_B, y_B are the coordinates of the blue primary colour of the three first primary colours, then, x_R≧

0.63 and y_R≦

0.34, x_G≦

0.31 and y_G≧

0.59, x_B≧

0.14 and y_B≦

0.08.

3. The projection system according to claim 1, wherein said fourth primary colour of the second display means has a red colour with a frequency spectrum developing more luminous power in the range of large wavelengths that the frequency spectrum of the red primary colour of the first display means.

4. The projection system according to claim 1, wherein, in the CIE xy chromaticity diagram and under a D65 or a C illuminant, if x_R0, y_R0 are the coordinates of the red primary colour of the three first primary colours, if x_Rn, y_Rn are the coordinates of the said fourth primary colour, then x_Rn≧

x_R0 and y_Rn≦

y_R0.

5. The projection system according to claim 1, 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.

6. The projection system according to claim 5, wherein, the notch filter blocks, in the frequency spectrum associated to the fourth primary colour, frequencies of two of the three first primary colours.

7. The projection system according to claim 5, wherein said optical filtering means further comprises a band-pass filter located between said second display means and the screen to reduce the frequency spectrum of the fourth primary colour.

8. Use of the projection system according to claim 1 to generate two different spectral power distributions for a given colour in a picture displayed by said projection system.