Carl@sri-unix (07/27/82)
In reply to Jeff La Coss' message concerning the resolutions of various displays, I would like to clarify a misunderstanding that he had. He claims that a BBN BitGraph is comparable to a D0 with a display resolution of about 80 dots/inch. In fact, the BitGraph resolution is almost identical to that of the PERQ and the Symbolics machine at around 100 points/inch. The BitGraph I am typing this on has a usable display area of 7.75"x10.75" and is 768 points x 1024 points, yielding a resolution of 99 points/inch horizontally and 95 points/inch vertically. Carl Howe
Hamilton.es@PARC-MAXC@sri-unix (08/02/82)
"The trouble with all of this is that the video bandwidth required to do any of this is cosmic. No problem generating it (well, maybe no problem) but displaying it is quite another matter. Building a monitor that can swing the beam fast enough to do 1000 lines/frame is a trick only a few vendors have managed. 300 lines/inch resolution will require 3000 lines/frame. Ouch. In addition, the beam is going to have to be modulated at about 250 MHz. The only way to do this will be to up voltages/currents in the amp circuit and increase the anode voltage- don't sit in front of this tube if you ever want to procreate." One answer seems to me to have multiple guns on one tube. Why not divide the screen into nine squares and drive one high-res gun for each? I realize adjusting all the edge convergences could be a slight problem, but I don't see why it shouldn't be within the state of the art. --Bruce
FISCHER@RUTGERS@sri-unix (08/02/82)
From: Ron <FISCHER at RUTGERS> Another way to build really high resolution displays is to keep from using a technology that requires refreshing the screen. One way might be with plasma panels, which are effectively their own memory. Each dot on the display is similar to a neon bulb, with an anode and a cathode and neon gas in the gap between. Dots are turned on with a short higher voltage pulse and then continue to glow because of a constant background voltage. The initial pulse ionizes the neon in the gap, which then stays lit using the lower "maintaining" voltage. I assume the problem with building a high resolution display with a plasma panel would be that as the cell size goes down it gets dimmer. I wonder what the practical limits are for the narrowness of the gap between the cathode/anode in a plasma panel and or the closest spacing between cells? (do existing panels isolate the display cells with walls of a dielectric?) Or we might be limited by the amount of energy to be dissapated in each cell (the glow of the glass panel cannot be brighter than the cells in it...) Or how about other technologies; liquid crystal and electroluminescent to name two? The Grid/Compass portable computer (or workstation if you prefer) has an electroluminescent display of low resolution. (ron) -------
G.Tech@MIT-EECS@sri-unix (08/03/82)
From: G.Tech at MIT-EECS at MIT-AI (The Tech) Sorry this is late (coming after the summary), but seeing all the references to "book quality" made me want to add my 2 cents: In the phototypesetting business, very few people will accept less than 1000 lines/inch for their originals. Two typesetters, the Alphatype CRS and the Compugraphic 8600, generate 5000 lpi. It's possible to generate 1000+ newspaper lines/minute at 1000lpi using a text window of 1 inch for $70,000. (The photographic paper moves past the window.) Somone with better contacts in the industry may be able to provide more info, but I'd say "book quality" is a long way off for workstations... -Rich$alz -------
grunwald (08/03/82)
#R:sri-unix:-229300:uiucdcs:13900001:000:1406 uiucdcs!grunwald Aug 3 12:44:00 1982 Having use plasma panels for 6 years (PLATO rears its ugly head), I'll toss in what little I know about it: The main problem with plasma panels is dot density, since when you increase the density of the dots too much, you get "accidental" firings of some dots. This also happens when the panels get older. At last report, the Army had a three foot by three foot panel constructed for high-altitude / high-resolution applications. I don't know how many pixals wide and high it was, but I imagine it was either 1024x1024 or 2048x2048. Additionally, several japenese companies (Nippon Bell is one, I think) are getting into the plasma panel market. They are trying to get color plasma panels to work, as well as develope other fast panels. The color panels work by putting posphores where the dots light up and using that energy to excite the phosphore (or so they said). The "fast" panels they were working on at the time they came and talked to us were called "shift panels" -- they were slightly different in design from the standard panel. They create an image at the far right on a 16 pixal tall space and then "shift" it over to where it should be. This causes some really strange effects and seems to only be very useful for alphanumerics or customized character sets. Their main advantage is that they are much flatter than normal plasma panels and it would be practical to make a plasma based TV.
Kosower@PARC-MAXC@sri-unix (08/05/82)
1400 lpi seems to be the point at which further increases in resolution are nearly impossible to detect (even for experts). Several photocomposers (Autologic, Compugraphic, and Mergenthaler) generate ~1400 lpi output. Although 1000 lpi might possibly be adequate for some applications, 1400 is probably the only adequate resolution for truly high-quality publications (e.g. books). 200 lpi (as mentioned by Bern Niamir) is completely inadequate, as anyone who has ever looked at XGP output will readily admit. Furthermore, while increasing the number of gray-scales improves the effective resolution for bit graphics (e.g. photos), it does little good where sharp outlines are required, as in typeset material or symbolic graphics. Making the outlines fuzzy is hardly a substitute for increasing the resolution. David.