Method and apparatus for calibrating a tiled display

• US 6,525,772 B2
• Filed: 06/08/2001
• Issued: 02/25/2003
• Est. Priority Date: 09/23/1998
• Status: Expired due to Fees

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Johnson, Michael J., Chandrasekhar, Rajesh, Chen, Chung-Jen
• Primary Examiner(s): Kostak, Victor R.
• Application Number:
  US09/877,603
• Publication Number:
  US 20020027608A1
• Time in Patent Office: 627 Days
• Field of Search: 348/383, 348/744-747, 348/189, 348/190, 348/181, 348/36, 345/1.3, 345/20
• US Class Current: 348/383
• CPC Class Codes: H04N 17/04 for receivers
• CPC Class Codes: H04N 9/12 Picture reproducers H04N9/11 takes precedence
• CPC Class Codes: H04N 9/3147 Multi-projection systems displays in general H04N9/12; video walls G06F3/1446, G09G2300/026
• CPC Class Codes: H04N 9/3194 including sensor feedback

Abstract

A display system that can be calibrated and re-calibrated with a minimal amount of manual intervention. To accomplish this, one or more cameras are provided to capture an image of the display screen. The resulting captured image is processed to identify any non-desirable characteristics, including visible artifacts such as seams, bands, rings, etc. Once the non-desirable characteristics are identified, an appropriate transformation function is determined. The transformation function is used to pre-warp the input video signal that is provided to the display such that the non-desirable characteristics are reduced or eliminated from the display. The transformation function preferably compensates for spatial non-uniformity, color non-uniformity, luminance non-uniformity, and other visible artifacts.

Claims

1. A method for controlling a tiled display system that has two or more projectors, each projector manifesting one of a number of discrete images separately onto a viewing surface or screen in a tiled manner to form a tiled composite image, at least one of the discrete images overlapping an adjacent discrete image to form at least one overlapping region, the method comprising the steps of:

providing an input video stream to cause selected projectors to display a first test pattern;

capturing a capture image of at least a portion of the composite image, including at least a portion of at least one overlapping region;

examining the capture image to identify any undesirable artifacts in the capture image; and

determining a transformation function that can be applied to the input video stream to at least partially remove the undesirable artifacts found in the composite image including in the at least one overlapping region.

2. A method for controlling a display system that has two or more displays, each display manifesting one of a number of discrete images separately onto a viewing surface or screen to form a composite image related to an input video stream, the method comprising the steps of:

identifying a number of anchor points or regions in the input video stream;

capturing a capture image of at least a portion of the composite image;

identifying a spatial distortion in the capture image by comparing the location of selected anchor points or regions of the capture image with the location of the corresponding anchor points or regions in the input video stream; and

determining a transformation function that will at least partially remove the spatial distortion from the composite image.

3. The method of claim 2 wherein the step of identifying anchor points or regions includes the steps of:

saving a snapshot of the incoming video stream; and

extracting stochastically reliable anchor points from the saved snapshot of the incoming video stream.

4. A method for calibrating a tiled projection display, the tiled projection display having two or more projectors, each receiving an input signal and each projecting one of a number of discrete images separately onto a screen to form a composite image, at least one of the discrete images overlapping an adjacent discrete image to form at least one overlapping region, the method comprising the steps of:

sequentially inputting to selected projectors an input signal that corresponds to a flat field image of a first color for each of a number of luminance intensities;

capturing a capture image of selected flat field images, including at least a portion of at least one overlapping region;

saving the capture images to a memory;

determining a distortion in the composite image by examining the captured flat field images; and

identifying a transformation function that can be applied to the input signals to at least partially remove the distortion from the composite image including in the at least one overlapping region.

5. The method of claim 4 wherein the transformation function is dependent on luminance intensity.

6. The method of claim 5 wherein the transformation function is dependent on an X-Y location of the composite image.

7. The method of claim 4 wherein the capture images are saved into the memory as reduced resolution images.

8. The method of claim 4 wherein the capture image is captured from a side of the screen that is opposite to a viewing side.

9. The method of claim 4 wherein the capture image is captured from a viewing side of the screen.

10. A method for calibrating a tiled projection display, the tiled projection display having two or more projectors, each receiving an input signal and each projecting one of a number of discrete images separately onto a screen to form a composite image, the method comprising the steps of:

providing an input signal to selected projectors to project a number of discrete images for a predetermined period of time, each discrete image having a predetermined pattern with a number of features;

selecting a first image area that is part of the composite image;

aligning the camera to the first image area;

capturing the first capture image;

saving the first capture image;

selecting a second image area that is part of the composite image;

aligning the camera to the second image area;

capturing the second capture image;

saving the second capture image;

determining a distortion in the composite image by comparing the first and second capture images; and

identifying a transformation function that can be applied to the input signal of selected displays to at least partially remove the distortion from the composite image.

11. A method for calibrating a tiled projection display, the tiled projection display having two or more projectors, each receiving an input signal and each projecting one of a number of discrete images separately onto a screen to form a composite image, the method comprising the steps of:

selecting in sequence each of the projectors and, for each projector;

preventing all non-selected projectors from generating an image;

providing an input signal to the selected projector causing the selected projector to project a discrete image that has a predetermined pattern;

capturing the composite image;

determining a distortion in the composite image by examining the relative location of selected features of the predetermined pattern in the capture image;

identifying a transformation function that can be applied to the input signal of the selected projector to at least partially remove the distortion from the composite image; and

saving the identified transformation function.

12. The method of claim 11 further comprising the steps of:

inputting an input signal to each projector, the input signals collectively producing a discrete image that has a predetermined pattern;

applying the saved transformation functions to the corresponding input signals;

capturing a composite image;

determining a distortion in the composite image by examining the relative location of selected features in the capture image; and

identifying a transformation function that can be applied to the input signals to at least partially remove the distortion from the composite image.

13. A method for controlling a display system that has two or more displays, each display manifesting one of a number of discrete images separately onto a viewing surface or screen to form a composite image related to an input video stream, at least one of the discrete images overlapping an adjacent discrete image to form at least one overlapping region, the method comprising repeating the steps of:

capturing a first capture image of a first portion of the composite images, including at least a portion of at least one overlapping region;

determining if the first capture image has one or more non-desirable characteristics;

identifying a first transformation function that can be used to process the input video stream and provide a processed input video signal to selected displays to reduce the non-desirable characteristics in the first portion of the composite image, including at least a portion of at least one overlapping region;

capturing a second capture image of a second portion of the composite images; and

identifying a second transformation function that can be used to process the input video stream and provide a processed input video signal to selected displays to reduce the non-desirable characteristics in the second portion of the composite image.

14. The method according to claim 13 wherein at least one of the discrete images overlaps an adjacent discrete image to form at least one overlapping region.

15. The method according to claim 13 wherein the capture image is captured from a side of the viewing surface or screen that is opposite to a viewing side.

16. The method according to claim 13 wherein the capture image is captured from a viewing side of the viewing surface or screen.

17. A method for calibrating a tiled projection display, the tiled projection display having two or more projectors, each receiving an input signal and each projecting one of a number of discrete images separately onto a screen to form a composite image, the method comprising the steps of:

sequentially inputting to selected projectors an input signal that corresponds to a flat field image of a first color for each of a number of luminance intensities;

capturing a capture image of selected flat field images from a viewing side of the screen;

saving the capture images to a memory;

determining a distortion in the composite image by examining the captured flat field images; and

identifying a transformation function that can be applied to the input signals to at least partially remove the distortion from the composite image.