ELECTRONIC IMAGING 14.2 Download, Please Go to MAY 2004
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Some of the photos and figures here are available in color in the electronic version of the newsletter. To ELECTRONIC IMAGING 14.2 download, please go to http://spie.org/web/techgroups/ei/pdfs/ei14-2.pdf MAY 2004 MAY 2004 VOL. 14, NO. 2 ELECTRONIC IMAGING LCoS microdisplays SPIE International for projection television Technical Group Newsletter LCoS (liquid crystal on silicon) microdisplays are, mination system that generates white light, typically unlike the active-matrix liquid-crystal displays from a metal halide arc lamp. Next, the light is bro- (LCDs) found on notebooks, reflective. As shown ken up into red, green, and blue bands, pre-polar- in Figure 1, they are built on a Si backplane with a ized, after which the polarization beam splitters Special Issue on: near-standard CMOS process and include the driv- (PBSs) dump each into a separate color channel. ing circuitry that delivers the appropriate voltages The way the LC manipulates polarization de- Displays to the Al electrodes that define the pixels. There pends on the mode in which it is operating, as shown are also layers above the aluminium for in Figure 4. On the left is shown a vertically-aligned Guest Editor planarization, reflection enhancement, and liquid- nematic (VAN) mode. In the unpowered state, the Gabriel Marcu, Apple Computer crystal (LC) alignment. Above the backplane lies LC molecules stand up and the retardation of the the LC layer, followed by an anti-reflection coat- crystal is nearly zero. In this case, the polarization ing, then a common transparent electrode of indium state is unchanged. In the powered state, the LC tin oxide (ITO), both on a sheet of glass. (The de- molecules are forced into the plane of the display, tails of the electro-optical operation of the LCoS and the design is such that in this state the retarda- NEWSLETTER NOW display is beyond the scope of this article, but see tion is about 1/4 wave. This causes the polarization AVAILABLE ON-LINE Reference 1.) All of this is inserted into a package at the mirror to be circularly polarized. Upon re- Technical Group members are being for mechanical and electrical connection to the rest flection, the handedness of the circular state is re- offered the option of receiving the of the system (see Figure 2). versed (just as a clock face is reversed when seen Electronic Imaging Newsletter Figure 3 shows the architecture for a typical in a mirror). This has the effect that the outgoing electronically. An e-mail is being sent three-LCoS projection system. There are three polarization is rotated 90 with respect to the input to all group members with advice of ° the web location for this issue, and major components to this system. First is the illu- asking members to choose between Continues on page 8. the electronic and printed version for future issues. If you are a member and have not yet received this message, then SPIE does not have your correct e-mail address. To receive future issues electronically please send your e-mail address to: [email protected] with the word EI in the subject line of the message and the words electronic version in the body of the message. If you prefer to receive the newsletter in the printed format, but want to send your correct e-mail address for our database, include the words print version preferred Figure 1. Schematic of the basic structure of an LCoS microdisplay. in the body of your message. SPIE International Technical Group Newsletter 1 ELECTRONIC IMAGING 14.2 MAY 2004 ing market for HDTV receivers were the main Is the CRT’s obsolescence imminent? forces driving improvements in not only guns and deflection yokes, but also in screens, magnetic shielding, and glass technologies. Then, in the In the 1970s, when a young engineer, fresh out the screen, used parallax to make sure each beam early 1990s, TDK developed the RAC deflection of school, started work at a Toshiba CRT (cath- only struck its corresponding colored phosphors. yoke and tube system for Toshiba. RAC systems ode ray display tube) factory in Japan, his man- In the early 1970s, guns shifted from the delta have rectangular-shaped CRT necks and yokes, ager told him that he was making a big mistake. to the inline configuration, in which the three guns which results in an impressive 30% reduction in “This is a sunset industry,” his manager said. were side-by-side. This resulted in a reduction in deflection power. As with the COTY gun, RAC “Soon, CRTs will be obsolete.” Now, more than the number of adjustments needed to align the red, and RAC-like systems are becoming pervasive, 30 years later, LCD, plasma, Digital Light Pro- green, and blue images with respect to one-an- having since been adopted by Matshita, Philips, cessing™, and their variants are eroding CRT other, and eventually allowed the shipment of pre- LGE, and others. markets at a surprising pace, and it appears that aligned tube-yoke combinations to receiver and LCDs will dominate most high-volume applica- monitor assembly factories. To the future tion areas. So we find ourselves wondering: is The ability to systematically model electron Modern-day CRTs can inexpensively provide that manager’s prediction finally about to come behavior in the electric and magnetic fields of a large, bright images with a large color gamut. true? color CRT has been the most powerful enabler Resolution has reached 0.125mm, new cathodes of the development of the technology. Early mod- deliver brighter pictures with lower-cost circuitry, CRT vs. LCD eling techniques were borrowed from early par- and bulbs have become wider and their depths Unlike LCDs, CRTs can directly generate images ticle accelerator work in the 1950s and 1960s and, shorter. Although those working in CRT research in a variety of formats, and do so without digital in 1975, a paper from Zenith articulated the prin- and development agree that there will not be any image scaling and the problems that go with it. ciples of CRT electron gun optimization. By the more big-budget projects on the scale seen in the They also currently enjoy superiority over LCDs early 1980s, computer-modeling tools had been past, innovation continues. A recent example is a in the areas of cost, viewing angle, and smooth developed—thus reducing the need for physical set of technologies for television, known collec- presentation of motion. prototypes—and the pace of innovation quick- tively as ‘slim’ CRTs, which are in pilot produc- Chief among the reasons the CRT is more cost ened. tion. One is Philips’ new 32" wide-screen effective than LCDs are the CRT’s ability to ad- Around 1982-1983, RCA started production on RealFlat™ tube for HDTV, with a depth of only dress millions of pixels sequentially with only the COTY (cost-optimized tube and yoke) gun. 35cm. three analog video signals, and the lower cost and The COTY made a tremendous improvement in The CRT will be still be around for a very long longer lives of CRT production lines. the tradeoff between deflection power and beam time because of its low cost compared to other distortion and was quickly adopted by CRT manu- technologies. Perhaps, as that manager in the Mature progression factures the world over. In the late 1980s, the dy- 1970s said, the CRT industry is a ‘sunset indus- Mass production of television receivers follow- namic quadrupole yoke was introduced. This al- try’: but it’s taking a very long time for that sun ing World War II established CRTs as mature dis- most completely compensates for deflection to slip below the horizon. play components. Advancements in the technol- defocusing of the beams from self-convergence The author wishes to acknowledge contribu- ogy came more slowly after the introduction of yokes used with inline guns. Though it took nearly tions to this article from: Roger Alig, Hsing- color tubes in 1950s. Those tubes used a ‘delta 10 years to perfect, it made 110° display tubes Yao Chen, Chris Curtin, Basab Dasgupta, gun’: three electron guns mounted in a triangular and, thus, thinner displays practical: it was the last Carlo Infante and Seyno Sluyterman. configuration in the neck of the CRT. The red, great breakthrough in gun design. green, and blue guns emited electron beams, which The emergence of a market for high-resolution Dick Cappels were scanned over the screen by a deflection yoke. personal computer displays in the late 1980s, a Mesa, AZ, USA A sheet of steel inside the tube, mounted close to sense of competition with LCDs, and the burgeon- E-mail: [email protected] C 2004 2005 A XVII International Conference on Optical Imaging IS&T/SPIE’s Electronic Imaging Photoelectronics and Night Vision Devices Optical Diagnostic Imaging from Bench 23 - 27 January 25-28May to Bedside at the National Institutes of Health San Jose, California USA L Moscow, Russia 20 - 22 September Call for Papers • Abstracts Due 5 July 2004 Sponsored by SPIE Russia Chapter. Washington, D.C. USA Exhibition http://electronicimaging.org/call/05/ E SPIE International Symposium Organized by NIH, managed by SPIE Optical Science and Technology http://spie.org/conferences/calls/04/nih/ SPIE International Symposium N SPIE’s 49th Annual Meeting Smart Imagers and Their Applications Medical Imaging 2-6August 6-8October 13-18February Denver, Colorado USA Moscow, Russia San Diego, California USA D Includes technology track on: Signal and Image Processing and Sensors • Algorithms, Architectures, and Devices A • Mathematical Methods For More Information Contact • Detectors and Imaging Devices SPIE • PO Box 10, Bellingham, WA 98227-0010 R http://spie.org/conferences/calls/04/am/ Tel: +1 360 676 3290 • Fax: +1 360 647 1445 • E-mail: [email protected] • Web: www.spie.org 2 SPIE International Technical Group Newsletter ELECTRONIC IMAGING 14.2 MAY 2004 LCDs get up to TV speed LCDs enabled the notebook computer mechanisms and rates are different.