| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程系 === 103 === Projection extends much more display possibilities beyond what traditional monitors can offer. However, strict condition requiring the projector directly facing a plane screen needs be satisfied; otherwise, distortion will occur. Distortion occurs in incline plane projection where the projector is not facing in normal direction and more complicated in the cases when the screen is a curved surface. To compensate, a rectified pattern is needed as a pre-processing before an intended image is projected to ensure no distortion. Esisting solutions for the inclined planes involve warp perscpective operation; solutions for curved surfaces are by approximating the curve surface as a collection of small inclined planes or grids, rendering the rectification for curved surface a repetitive rectification process on each of these constituent inclined plane. Alternatively, this study proposes an auto-calibration approach based on the reversibility principle of projection image. To wit, the principle states that, if an image Im from point A is projected to a screen and observed as Im’by point B, then, by reversibility, when Im’is projected from B to the same projection screen, the original image Im will be observed at A. With the original image being a checkboard and A the point of observation and B the position for projection, we are able to calibrate rectification patterns for projections on both inclined planes and curved surfaces. In addition to mathematical support for this approach, this study also presents an auomatic calibration solution that together with projector and camera sertup calibrates rectification patterns for both inclined planes and curved surfaces. The auto-calibration process requires no repetitive matrix manipulations which are prone to numerical errors and ensures no overllaps or gaps among approximated grids. To demonstrate, rectified projections to inclined wall, corner of ceilings, and cylinderal surfaced buck are shown. The technique prsented in this paper can also be extended to applications in interactive virtual reality, as is shown by the demonstration of Wallscape, an interactive viewer dependent wall projection technique.
|
|---|
