A color facsimile system that prints out individual colors in separate traces does not require an achromatized lens. Focus corrections between individual single-color scan signals can maintain all colors in focus. Rearrangement of the video-signal color-scan sequence or high-speed incremental film transport may be employed instead of moving focus-correcting windows.
© 1984 Optical Society of America
James R. Jenness, Jr., "Focus correction for a CRT color facsimile system," Appl. Opt. 23, 529-536 (1984)