System and method for calibrating an image projection system
A method and system for calibrating and operating projection systems where one or more projectors are utilized to project an image. One or more projectors are oriented to project an image on a projection screen and one or more image sensors are oriented to acquire the projected image. Three-dimensional position coordinates of the respective image fiducials as projected on the screen are identified by applying three-dimensional mapping functions to represent the manner in which two-dimensional points in a projector frame map to three-dimensional points on the projection screen. Parametric functions are fit to a neighborhood of points representing the three-dimensional image fiducial position coordinates and corresponding parametric models are generated. The projectors are then operated in accordance with geometric calibration data generated from validation and correction of the fiducial coordinates.
1. A method of operating an image display system comprising one or more projectors oriented to project an image on a projection screen and one or more image sensors oriented to acquire an image projected on the projection screen, the method comprising:
operating the projector to project a calibration image comprising one or more image fiducials on the image projection screen;
operating the image sensor to acquire the projected calibration image including the image fiducials as projected on the projection screen;
identifying approximate three-dimensional position coordinates of the respective image fiducials as projected on the projection screen by applying one or more three-dimensional mapping functions, wherein the three-dimensional mapping functions represent the manner in which two-dimensional points in a projector frame map to three-dimensional points on a virtual approximation of the projection screen;
fitting one or more parametric functions to a neighborhood of points representing the approximate three-dimensional image fiducial position coordinates;
generating one or more parametric models from the parametric functions fit to the neighborhood of points;
validating the identified fiducial positions by applying the parametric model to compare approximations of the fiducial positions predicted by the parametric model with respective ones of the fiducial positions identified with the three-dimensional mapping functions; and
operating the projector in a manner that is at least partially dependent on the result of the validation of the identified fiducial positions.
2. A method as claimed in claim 1 wherein the projector is operated to project a calibration image comprising a three-dimensional pattern of image fiducials and the approximate three-dimensional position coordinates of the respective image fiducials within the pattern are identified.
3. A method as claimed in claim 1 wherein the method further comprises certifying validation errors and generating corrected fiducial positions when a result of one of the comparisons exceeds an error threshold.
4. A method as claimed in claim 3 wherein the method further comprises generating geometric calibration data for the projector using validated fiducial positions and corrected fiducial positions in place of fiducial positions for which errors are certified.
5. A method as claimed in claim 4 wherein the method further comprises utilizing the geometric calibration data to operate the projector in the calibrated projection mode.
6. A method as claimed in claim 3 wherein the error threshold at least partially accounts for error in fitting the parametric functions to the neighborhood of points representing the approximate three-dimensional image fiducial position coordinates.
7. A method as claimed in claim 3 wherein the corrected fiducial positions are determined with reference to a fixed or dynamic correction factor.
8. A method as claimed in claim 3 wherein the corrected fiducial positions are at least partially a function of the approximations of the identified fiducial positions.
9. A method as claimed in claim 3 wherein the approximations of the identified fiducial positions are used as the corrected fiducial positions.
10. A method as claimed in claim 3 wherein respective combinations of identified fiducial positions and approximations of the identified fiducial positions are used as the corrected fiducial positions.
11. A method as claimed in claim 1 wherein the approximation of the identified fiducial position used in validation is determined from a three-dimensional neighborhood of image fiducials in the calibration image.
12. A method as claimed in claim 1 wherein the projector is operated in a calibrated projection mode by utilizing data obtained from the validation of the identified fiducial positions.
13. An image display system comprising one or more projectors oriented to project an image on a projection screen, one or more image sensors oriented to acquire an image projected on the projection screen, and one or more controllers programmed to calibrate the projectors, wherein the controller is programmed to:
operate the projector to project a calibration image comprising one or more image fiducials on the image projection screen;
operate the image sensor to acquire the projected calibration image including the image fiducials as projected on the projection screen;
identify approximate three-dimensional position coordinates of the respective image fiducials as projected on the projection screen by applying one or more three-dimensional mapping functions, wherein the three-dimensional mapping functions represent the manner in which two-dimensional points in a projector frame map to three-dimensional points on a virtual approximation of the projection screen;
fit one or more parametric functions to a neighborhood of points representing the approximate three-dimensional image fiducial position coordinates;
generate one or more parametric models from the parametric functions fit to the neighborhood of points;
validate the identified fiducial positions by applying the parametric model to compare approximations of the fiducial positions predicted by the parametric model with respective ones of the fiducial positions identified with the three-dimensional mapping functions; and
operate the projector in a manner that is at least partially dependent on the result of the validation of the identified fiducial positions.
14. An image display system as claimed in claim 13 wherein the controller is further programmed to operate the projector in a calibrated projection mode by utilizing data obtained from the validation of the identified fiducial positions.
15. An image display system as claimed in claim 13 wherein the controller is further programmed to certify validation errors and generate corrected fiducial positions when a result of one of the comparisons exceeds an error threshold.
16. An image display system as claimed in claim 15 wherein the controller is further programmed to generate geometric calibration data for the projector using validated fiducial positions and corrected fiducial positions in place of fiducial positions for which errors are certified.
17. An image display system as claimed in claim 16 wherein the controller is further programmed to utilize the geometric calibration data to operate the projector in the calibrated projection mode.