Generating a matte signal from a retro reflective component of a front projection screen

• US 6,796,656 B1
• Filed: 06/14/2003
• Issued: 09/28/2004
• Est. Priority Date: 06/14/2003
• Status: Expired due to Fees

• Current Assignee: iMatte, Inc.
• Original Assignee: iMatte, Inc.
• Inventors: Dadourian, Arpag
• Primary Examiner(s): Fuller, Rodney
• Assistant Examiner(s): SEVER, ANDREW T
• Application Number:
  US10/601,299
• Time in Patent Office: 472 Days
• Field of Search: 353/97, 353/79, 353/80, 353/122, 353/121, 353/28, 353/21, 353/29, 356/51, 356/615, 356/621, 356/622, 348/586, 348/590, 359/452, 359/454, 359/459, 396/3
• US Class Current: 353/28
• CPC Class Codes: H04N 5/275 Generation of keying signals

Abstract

A white projection screen containing a small number of infrared retro reflective elements, uniformly distributed over the screen'"'"'s surface, is illuminated by an infrared source and observed by a coaxially located infrared camera. A matte signal is generated utilizing a high signal level from the infrared camera in all unobscured areas on the screen, and a very low signal level in screen areas obscured by a presenter between a projector and the projection screen.

Claims

1. A method for generating a matte signal identifying the silhouette area of a presenter in front of a projection screen onto which a projector displays images, said method comprising:

a) placing an infrared camera and an infrared illumination source in proximity to each other and to said projector;

b) illuminating said projection screen and said presenter with infrared illumination from an infrared source, said projection screen containing retro reflective elements;

c) observing said screen and said presenter with said infrared camera whose infrared signal levels constitute a linear matte signal defining the presenter'"'"'s silhouette area;

d) using said matte signal to inhibit visible light emitted from said image projector.

2. The method of claim 1 in which said infrared source is located coaxially with an axis of a lens of said infrared camera.

3. The method of claim 2 in which said infrared source is made coaxial with said infrared camera lens axis by using an infrared beam splitter before said camera lens.

4. The method of claim 2 in which said infrared source is made coaxial with said infrared camera lens axis by using a ring of infrared emitting diodes placed around a barrel of said infrared camera lens.

5. The method of claim 1 in which said infrared camera includes a filter to block passage of visible light.

6. The method of claim 1 in which said linear matte signal is assigned a signal level of 0.0 for those camera signal levels below a selected threshold, and assigned a signal level of 1.0 for signal levels above said selected threshold thereby generating a binary matte signal.

7. The method of claim 1 in which said projection screen provides an essentially uniform brightness distribution to a viewing audience, and said included retro reflective elements provide a very high gain as seen from the position of an infrared illumination source.

8. The method of claim 1 in which said retro reflective screen elements are of such a size as to be substantially invisible to a front row audience.

9. The method of claim 1 in which said projection screen containing retro reflective elements is created by silkscreen printing of a selected pattern with a white pigment onto a high gain retro reflective projection screen.

10. The method of claim 9 in which said selected pattern blocks the transfer of white pigment onto very small dot-like areas uniformly distributed over said screen area.

11. The method of claim 10 in which said dot-like areas occupy approximately 5% of the total screen area.

12. A system for selectively inhibiting light emitted from an image projector comprising:

a) an infrared camera disposed adjacent to an infrared illumination source and to said image projector,

b) means for generating a matte signal identifying a silhouette area of a presenter in front of a projection screen containing retro reflective elements utilizing infrared signals from said infrared illumination source reflected from said retro reflective elements.

13. The system defined by claim 12 wherein said generating means comprises said infrared camera operating to sense infrared illumination reflected by said retro reflective elements.