GEOMETRIC CALIBRATION APPARATUS FOR CORRECTING IMAGE DISTORTIONS ON CURVED SCREEN, AND CALIBRATION CONTROL SYSTEM AND METHOD USING THE SAME

• US 20080129894A1
• Filed: 11/30/2007
• Published: 06/05/2008
• Est. Priority Date: 12/02/2006
• Status: Abandoned Application

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: KANG, Hyun, SON, Wook Ho
• Application Number:
  US11/948,927
• Publication Number:
  US 20080129894A1
• Time in Patent Office: Days
• US Class Current: 348/758
• CPC Class Codes: H04N 9/3147 Multi-projection systems displays in general H04N9/12; video walls G06F3/1446, G09G2300/026
• CPC Class Codes: H04N 9/3185 Geometric adjustment, e.g. keystone or convergence optical or mechanical adjustment of convergence H04N9/317; using scanning means H04N3/22; optical or mechanical adjustments of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/14

Abstract

Provided are a geometric calibration apparatus for correcting image distortions of a curved screen, and a calibration control system and method using the same. In the calibration control system for correcting the image distortions of the curved screen, a high resolution camera including a pan-and-tilt controller is installed at a center portion of a front direction of a hemispherical screen in order to well correct the distortion of the images projected from multi-projectors to a hemispherical screen. The calibration control system compares a partially photographed image with a reference image to generate a new coordinate map. Therefore, an offset between unit images projected on the hemispherical screen is removed to efficiently display an extra large image.

Claims

1. A geometric calibration apparatus for correcting distortion of images projected from a plurality of projectors to a curved screen in a rear projection type multi-projection display, the apparatus comprising:

a high resolution camera photographing unit images provided from the plurality of projectors to a hemispherical screen;

a pan-and-tilt controller controlling the high resolution camera such that the unit images are photographed in a preset order; and

a geometric calibration software execution PC including a calibration control software for measuring the degree of image distortion between the unit images provided from the plurality of projectors to the hemispherical screen to correct the image distortion.

2. The apparatus of claim 1, wherein the high resolution camera partially photographs the unit images of the plurality of projectors from a reference screen in the preset order.

3. The apparatus of claim 1, wherein the pan-and-tilt controller is installed at a viewing point of a user in a center portion of a front direction of the hemispherical screen.

4. The apparatus of claim 1, wherein the calibration control software performs camera geometric calibration on the distorted image.

5. The apparatus of claim 4, wherein the calibration control software measures the degree of the image distortion of the photographed unit images, calculates a calibration value based on the measured degree of the image distortion such that the unit images are not overlapped, and applies the calculated calibration value to generate a new coordinate map of the unit images.

6. The apparatus of claim 5, wherein the calibration control software analyzes a relationship between a geometric calibration pattern image and a previously stored and photographed image.

7. The apparatus of claim 6, wherein the geometric calibration pattern image comprises a plurality of white lines regularly arranged on a black ground.

8. The apparatus of claim 6, wherein the calibration control software measures the degree of the image distortion between line vectors of geometric calibration patterns of each of projectors and a parameter of straight lines and curved lines of a quadratic function.

9. The apparatus of claim 1, wherein the multi-projection system comprises a rear projection type tiled display that sequentially connects the plurality of unit images on the hemispherical screen to achieve a single extra large image.

18. The apparatus of claim 1, wherein the calibration control software measures the degree of the image distortion of the photographed unit images, calculates a calibration value based on the measured degree of the image distortion such that the unit images are not overlapped, and applies the calculated calibration value to generate a new coordinate map of the unit images.

19. The apparatus of claim 18, wherein the calibration control software analyzes a relationship between a geometric calibration pattern image and a previously stored and photographed image.

10. A calibration control system comprising:

a plurality of projector units including a pair of image control PCs transmitting unit images and a pair of projectors providing the unit images;

a hemispherical screen displaying the unit images provided from the plurality of projector units; and

a geometric calibration apparatus correcting image distortions of a curved screen to generate a new coordinate map based on a photographing result of an image projected on the hemispherical screen.

11. The calibration control system of claim 10, wherein the image control PCs generate a geometric calibration pattern image to the projectors.

12. The calibration control system of claim 10, wherein the plurality of projector units further comprises positioners moving the projectors according to a new coordinate map transmitted form the geometric calibration apparatus.

13. The calibration control system of claim 10, wherein the geometric calibration apparatus comprises:

a camera partially photographing the image projected on the hemispherical screen;

a pan-and-tilt controller controlling a position of the high resolution camera such that unit image on the hemispherical screen are partially photographed in a preset order; and

a geometric calibration software execution PC comparing the geometric calibration pattern image with the partially photographed image, extracting straight lines and curved lines of a quadratic function, and measuring the degree of the image distortion to change a coordinate map of the partially photographed image.

14. The calibration control system of claim 13, wherein the geometric calibration software execution PC changes a coordinate map in real time according to a calibration value based on the degree of the image distortion of the unit images projected from each of projectors.

15. A calibration control method using a geometric calibration apparatus for correcting distortion of images projected from projectors in a multi-projection display having a rear projection type hemispherical screen, the calibration control method comprising:

setting a right upper surface of a front surface of the hemispherical screen as a reference screen, and an image projected on the reference screen as a reference image;

determining a calibration order of remaining images except the reference image;

partially photographing the remaining images using a high resolution camera in pre-determined order;

comparing the partially photographed images with the previously stored reference image to measure the degree of image distortion and calculate a calibration value based on the measured degree of the image distortion;

applying the calculated calibration value and recalculating coordinate maps of the partially photographed images to generate a new coordinate map; and

changing positions of the projectors using the new coordinate map to correct the image distortion.

16. The calibration control method of claim 15, wherein the partially photographing of the remaining images comprises photographing of adjacent images in the calibration order set from the reference image.

17. The calibration control method of claim 15, wherein the measuring of the degree of the image distortion comprises measuring an offset degree of lines that disagree by comparing geometric calibration pattern lines of the partially photographed image with geometric calibration pattern lines of the reference image.