laser-lovers@uw-beaver (02/20/85)
From: John G. Aspinall <JGA@MIT-MC> I don't believe this has ever been discussed on this list, but correct me if I'm wrong. Has anyone ever considered placing the pixels on the printing surface in a non-rectangular pattern? I'm thinking of a close-packing pattern, which you can regard as either hexagonal or triangular tiling; I don't believe there are any other reasonable possibilities. This would give three fundamental axes of symmetry at 60 degrees rather than two at 90 degrees. Laser scanning marking technology could deal with this easily - one would leave the rows (fast-scan direction) in the same orientation, but offset alternate rows by 1/2 a pixel and change the inter-row spacing. Fixed-head marking technologies might have a harder time, but one can see possibilities that they might use too. The disadvantages might be serious, and would include - incompatibility with existing software, fonts, crt-bitmaps, etc. - lines in the column (slow-scan direction) would have a half-pixel waver to them (perhaps not serious in itself, but getting horizontal and vertical lines to look the same might be hard) but the reduction of "interstitial" space from 21% to 9% (calculated for circular pixels just touching) might be a big advantage in terms of not having to deal with so much flow of toner into un-imaged areas. (Yes, I know that fonts and the like are designed with this flow in mind.) So I'm not saying it's a better idea, but just that it might be worth a look. Has anyone considered this possibility? John Aspinall. [[Editor's note---I may be wrong, but I believe that the Apple Imagewriter (impact printer) does this --Rick ]]
laser-lovers@uw-beaver (02/21/85)
From: Lynch.ES@XEROX.ARPA The Leitz TAS (Textur-Analyse-System) uses a hexagonal tiling, by shifting rows a half-pixel. This thing digitizes video images from a TV camera looking through a microscope (usually) and applies various image processing algorithms in firmware to them, so it can be programmed to make a silk purse look like a sow's ear, etc. Leitz has technical literature on the properties and advantages of the hexagonal scheme. Gene Lynch