Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rutgers!ames!ucbcad!ucbvax!sdcsvax!sdcc6!calmasd!jpm From: jpm@calmasd.CALMA.UUCP (John McNally) Newsgroups: comp.graphics Subject: Re: CRT technology? Message-ID: <2138@calmasd.CALMA.UUCP> Date: Wed, 14-Jan-87 19:50:29 EST Article-I.D.: calmasd.2138 Posted: Wed Jan 14 19:50:29 1987 Date-Received: Fri, 16-Jan-87 01:25:00 EST References: <1219@ucbcad.berkeley.edu> Organization: G.E. CALMA R&D, San Diego, CA Lines: 53 Summary: LCD Displays - color, high resolution, and update speed In article <1219@ucbcad.berkeley.edu>, faustus@ucbcad.berkeley.edu (Wayne A. Christopher) writes: > Maybe somebody who knows a lot about CRT technology can answer a few > questions I've been wondering about... > How about LCD displays? Is > there any theoretical reason for LCD's to be more or less suitable than > CRT's for such high-resolution displays? (Is it even possible to make > multiple-color LCD's?) Thanks in advance for the enlightenment, Liquid Crystal Displays are just one of many forms of flat panel displays - others include plasma and electroluminesence. Each has advantages and disadvantages. For example, plasma screens are capable of high resolution and fast update speeds but require high voltage and are limited (currently) to an orange color. LCD displays have very low power requirements but (currently) have poor contrast, viewing angles, and update speeds. All flat panels obviously have the advantage of reduced space and simpler packaging than CRTs. However, there are even prototypes of "flat" CRTs (the electron gun is parallel to the tube and the deflection subsystem is radically different). The "winner" in this competition is yet to be determined... Currently LCDs appear to be the most promising flat panel technology and I expect that ultimately they will capture a major share of the display market. However, there are significant technical problems to be overcome (the Japanese are very active in this area). To me the most critical problem is the speed of update. Currently commercially available LCDs of any reasonable size do not have "pixel addressing" Writing to one pixel on a line or all pixels on a line requires the same amount of time - about 15 milliseconds. There are a lot of related problems in this area, but what it bolis down to is that LCDs are very slow in updating. Thin film transistor technology will solve this problem, but the technology has not yet reached the stage of mass manufacturing (several companies, mostly japanese are close). I refer you to an article that appeared in High Technology (May 1984, pp. 55 - 69), "LIQUID CRYSTALS BIG, BRIGHT, EVEN COLORFUL DISPLAYS". This is a good survey article on LCD technology. It discusses thin film transistor for active matrix addressing, the various methods used to make liquid crystals "turn on and off", and how color is introduced (using organic dyes). It also discussed futures and applications, and the inherent problems I have touched upon in much greater clarity. I think that it is premature to consider the use of LCD displays for CAD, especially areas requiring extremely good image quality (like solids modeling). We are still many years away from providing a cheap, reliable alternative to the 1024 x 1024 color CRT! (and the CRT manufacturers are not sitting still). -- John McNally GE/Calma 9805 Scranton Rd. San Diego CA 92121 ...{ucbvax | decvax}!sdcsvax!calmasd!jpm (619)-587-3211