Generating an inhibit signal by pattern displacement

• US 6,789,903 B2
• Filed: 02/18/2003
• Issued: 09/14/2004
• Est. Priority Date: 02/18/2003
• Status: Expired due to Fees

• Current Assignee: iMatte, Inc.
• Original Assignee: iMatte, Inc.
• Inventors: Vlahos, Paul, Parker, Joseph, Berman, Arie, Dadourian, Arpag
• Primary Examiner(s): Mahoney, Christopher E
• Application Number:
  US10/370,356
• Publication Number:
  US 20040160581A1
• Time in Patent Office: 574 Days
• Field of Search: 353/122, 353/28, 353/97, 348/586, 348/590, 348/607, 382/173
• US Class Current: 353/28
• CPC Class Codes: G03B 21/26 Projecting separately subsidiary matter simultaneously with main image
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor

Abstract

A pattern is projected onto a screen by a projector using an illumination having a non-visible wavelength. A camera, displaced several inches from the projector, observes the projected pattern whose signals are then stored to create a reference frame. The pattern is then projected onto the screen a second time with a presenter present. The camera observes the projected pattern whose signals are then stored to create a current frame, including the presenter, and signals obtained from the reference frame are compared to determine their difference. In unobscured screen areas, the pattern images match. The pattern on the presenter is displaced because of the displaced camera, and no longer matches the reference pattern, thereby identifying the presenter'"'"'s silhouette area.

Claims

1. A method for generating a binary matte signal that selectively inhibits data image signal levels of pixels within a silhouette area of a presenter in front of a projection screen comprising,

a) projecting a pattern upon said projection screen, with said presenter absent, using an illumination having a non-visible wavelength,

b) storing in a reference frame memory signal levels of said projected pattern as observed by a camera sensitive to said non-visible wavelength,

c) projecting said pattern upon said projection screen, with said presenter present, using an illumination having a non-visible wavelength,

d) storing in a current frame memory signal levels of said step c) projected pattern as observed by said camera,

e) comparing said reference frame signal levels with said current frame signal levels at corresponding pixel addresses and storing a measure of their difference in a memory,

f) identifying said presenter'"'"'s silhouette area as those pixels whose neighborhoods contain at least a predetermined number of pixels whose said measure of difference between current and reference frame signal levels is above a predetermined threshold,

g) assigning a matte signal first level for pixels in the identified presenter'"'"'s silhouette area and a matte signal second level to all other pixels, said first level being different than said second level, thereby generating a binary matte signal.

2. The method of claim 1 in which said stored measure of the difference between said reference frame signals and said current frame signals at corresponding pixel addresses is the absolute value of the difference of their differentials.

3. The method of claim 2 in which said reference frame signals and their differentials are acquired only once prior to a presentation.

4. The method of claim 2 in which said differentials of current frame signals are determined for each succeeding current frame.

5. The method of claim 1 in which said binary matte signal is blurred.

6. The method of claim 5 in which said blurred binary matte signal is applied to a second threshold in which all signals above said second threshold are assigned a third level, and all signals below said threshold are assigned a fourth level, said third level being different than said fourth level, to form a second binary matte signal.

7. The method of claim 6 in which said second binary matte is sized to substantially conform to a size and shape of the presenter.

8. The method of claim 7 in which said second binary matte signal is blurred to soften a matte edge.

9. The method of claim 1 in which the pattern is such that a displacement of the pattern has a low probability of matching the pattern.

10. The method of claim 1 in which said pattern includes simulated random noise of limited bandwidth.

11. The method of claim 1 in which said projecting utilizes an infrared bandwidth within the region of 700 to 1000 nanometers.

12. The method of claim 1 in which illumination, employed in both projection and imaging of said pattern is limited to infrared wavelengths.

13. The method of claim 1 in which said stored measure of the difference between said reference frame signals and said current frame signals at corresponding pixel addresses is the absolute value of their arithmetic difference.

14. The method of claim 1 in which said stored reference frame signal levels are updated at selected intervals with an offset correction in the amount of an average difference between the pixels having the reference frame signal levels and the pixels having the second signal level thereby compensating for uniform changes of spill light upon the screen and presenter.

15. An apparatus for generating a binary matte signal that selectively inhibits data image signal levels of pixels within a silhouette area of a presenter in front of a projection screen comprising:

a) a projector means for projecting a pattern upon said projection screen, with said presenter absent, using an illumination having a non-visible wavelength,

b) reference frame memory means for storing in a reference frame memory signal levels of said projected pattern as observed by a camera sensitive to said non-visible wavelength,

c) said projector means projecting said pattern upon said projection screen, with said presenter present, using an illumination having a non-visible wavelength,

d) current frame memory means for storing in a current frame memory the signal levels of said projected pattern as observed by said camera,

e) means for comparing said reference frame signal levels with said current frame signal levels at corresponding pixel addresses and storing a measure of their difference in a memory,

wherein said presenter'"'"'s silhouette area is defined as those pixels whose neighborhoods contain at least a predetermined number of pixels whose said measure of difference between current and reference frame signal levels is above a predetermined threshold, and

a matte signal first level is assigned to pixels in the presenter'"'"'s silhouette area and a matte signal second level is assigned to all other pixels, said first level being different than said second level.

16. The apparatus defined by claim 15, further comprising an inhibitor coupled to said projection means and said means for comparing.