|
The grouping of red, green and blue cathode ray tubes optically and electronically converged and projected upon a common screen surface has found wide usage for large screen projection of color video images. The majority of such projectors need only have sufficient convergence and geometry correction capability to "look good" with relatively low resolution broadcast and personal computer graphics video. These projectors typically use analog waveform correction techniques derived from standard broadcast technology which has evolved over many years. Colorimetry only needs to be good enough to give "good skin tones". There is another class of large screen color projectors which is gaining increased attention. These projectors are used with high resolution computer image generators in such demanding applications as flight simulators, image interpretation and military command and control systems. Often the images from multiple projectors are mosaicked to create a single very wide field of view-image. In these applications attention must be given to edge matching and blending between adjacent channels and matching the colorimetry of the multiple channels. Misconvergence and other errors between the three colors must be essentially zero. Until now the electrical waveforms used for convergence, blending, colorimetry and geometrical correction have been based on the use of second and third order power series and their cross products. The coefficients of the waveforms have been either adjusted by analog or digital techniques but the main waveform has had to be analog since subpixel correction as required when using fully digital techniques has been impractical from a size, cost and difficulty of calibration standpoint. This paper describes in detail the requirements for the various corrections mentioned above for single and multiple channel high resolution projectors and introduces a new and novel patent pending three dimensional digital waveform generation technique with two dimensional smoothing that functionally has subpixel bit mapping correction capability, yet is small in size, economical to construct and, best of all, easy to calibrate.
|
