Most high performance active matrix liquid crystal displays, AMLCDs, are controlled by a matrix of thin film transistors (TFTs) at the pixel level. Today, the majority of the commercially available AMLCDs use TFTs built with amorphous (a-Si); however, there is a great interest in polysilicon (p-Si) TFTs (1) because of their ability to form circuits to drive the display''s address lines on the same substrate as the AMLCD. This paper will compare the capability of the two technologies to meet the AMLCD requirements for the foreseeable future.
In the near future, the self-scanned displays will be developed to increase functionalities and complexity. Due to the rapid advances in TFT fabrication technology, and more sophisticated design technique, advanced self-scanned displays will integrate more data storage and bandwidth decompression circuitry and eventually become a system on glass. The new displays will not only include dynamic scanning circuitry, digital gray scale generators, and clock generators, it will also add circuitry for reformatting the data and possibly signal processor. Furthermore, the self-scanned circuitry will be able to interface directly with program source with standard 5V signals, as TFT device characteristics improve. Despite an increase in the complexity of the display, the external lead count will continue to be reduced by increasing the data rate per data line. The temperature and process compensation circuitry will also be transferred to the display plate both to increase its effectiveness and to reduce cost. The select and data line scanner circuitry will be simplified to fit within a 1 mm boundary along all sides of the plate. The redundancy circuitry will be further improved to increase the yield of both the AMLCD array and the scanners.
CdSe was the semiconductor used in the pioneering active matrix work of the 70''s. Today''s active matrix industry has chosen to disregard this material and is concentrating almost exclusively on Si films. This paper shows the historical roots of this decision, which in the author''s opinion has put the industry on a false trail, hindered the full development of the original concept of a fully integrated display subsystem and has resulted in excessive manufacturing cost. Important recent contributions to CdSe TFT technology are reviewed in the paper, followed by a comparison of the critical physical and fabrication parameters of CdSe, (alpha) -Si and poly-Si. These sections present an incontrovertible argument for an industry-wide reconsideration of an unjustly neglected material.
Full color liquid crystal (LC) displays with 5 inch diagonals are readily available today, and manufacturers are ramping up production of 10 inch full color displays for laptop computers. These displays require an integrated thin film transistor (TFT) as well as a capacitor to capture and store analog data voltage for a sixtieth of a second at each display element. For large displays there can be a million or so of these switching and data storage elements that comprise, in effect, a megasample analog memory. Fabricating such arrays is proving to be a formidable task. The concept for replacing the array of integrated TFTs with functionally identical plasma switches to address LC displays was first disclosed in the May, 1990. These switches consist of a channel of ionized gas that can be turned on and off quickly and that are capacitively coupled to the storage elements of the display. To achieve rapid data capture as well as fast turn-off of the columns of ionized gas it appears that at least one component of the gas must have a low atomic weight. To ensure long term stability, nonreactive gases are needed. Helium is an obvious choice since it is light and nonreactive, and furthermore, only a low level of visible light is generated when it is ionized in the channels. Unfortunately helium permeates through the glass enveloped of a liquid crystal display faster than any other gas. Containing it for the five to ten year life of a display is a challenge, and progress toward meeting that challenge is discussed here after a brief review of the plasma addressing (PA) concept.
An innovative switch for Active Matrix Liquid Crystal Displays (AM-LCD) is presented. The switch, referred to as MAG-LCD, replaces thin film transistors (TFTs) for large flat panel display screens. The manufacturing process for MAG-LCD is less stringent than that for TFTs. MAG-LCD is manufactured from a nickel/iron magnetic alloy which can be deposited at temperatures less than 150 degree(s)C. The NiFe is deposited by ion assisted electron beam evaporation and etched by standard photolithographic means. The switch uses the properties of resonant LRC circuits to control the voltage across the plates of the liquid crystal capacitor. When the circuit is tuned to resonance, it has a Q in excess of 4. When the circuit is out of resonance the Q is less than 1, limiting the capacitor voltage to less than the liquid crystal threshold voltage.
Optimum concentrations of gel monomer and chiral material are explored to maximize the contrast and reduce the drive voltage of light shutter from cholesteric liquid crystal/polymer gel dispersion. The results indicate that these materials are excellent candidates for use with the active matrix. Their performance is superior in some regards to PDLC materials from isotropic polymers.
In pursuing a high bright ZnS:Mn AC thin film EL device with low operating voltage, we find that improvement of the insulator material is an effective way to achieve this goal. The process is illustrated with the devices fabricated with three types of insulator materials: silicon oxynitride (SiON), barium tantalate (BTO) and aluminum/titanium oxide (ATO). The results show that the insulator material affects EL device performance not only via the well known effect of insulator capacitance but also through the modification of the ZnS:Mn/insulator interface properties. Using analytical techniques, such as current vs. field and charge vs. voltage measurements, the properties of the interfaces between ZnS:Mn and BTO, ATO and SiON are deduced. It was found that these interfacial properties varied greatly among the three types of insulator materials investigated. The interface states in BTO devices are deep levels and the concentration of trapped charge at these states is high. On the other hand, the interface states in ATO devices are shallow levels and trap very few charges. Because of the excellent interfacial properties, the BTO devices exhibit the highest brightness and luminous efficiency of the three kinds of EL devices investigated.
A cockpit revolution is in the making. Many of the much ballyhooed, much promised, but little delivered technologies of the 70''s and 80''s will finally come of age in the 90''s just in time to complement the data explosion coming from sensor and processing advances. Technologies such as helmet systems, large flat panel displays, speech recognition, color graphics, decision aiding and stereopsis, are simultaneously reaching technology maturities that promise big payoffs for the third generation cockpit and beyond. The first generation cockpit used round dials to help the pilot keep the airplane flying right side up. The second generation cockpit used Multifunction Displays and the HUD to interface the pilot with sensors and weapons. What might the third generation cockpit look like? How might it integrate many of these technologies to simplify the pilots life and most of all: what is the payoff? This paper will examine tactical cockpit problems, the technologies needed to solve them and recommend three generations of solutions.
As designers and innovators of aircraft cockpit displays and display systems, we find ourselves in the unique position of participating in the evolving revolution in aircraft cockpit architecture. This revolution will only be limited by the availability of new (or upgraded) aircraft platforms, the innovative creativity of the designers, and - the limits of technology growth. The drivers of this technology growth will be the requirements for the new aircraft to be developed; the "new breed" of flight crew; and the requirement to wring more performance out of man and machine. But, what we must be mindful of, are the limits. The limits of assimilation, and the limits of technology growth. We, the designers, must pace ourselves to what will provide the aircraft industry with the best solution for its challenges without risking program cost and schedule. It is too easy to get into the frame of mind from which we will "push" a technology before it is mature. We all want to create that next advance, be on the leading edge. But, if we get ahead of that leading edge, we may do a disservice to ourselves and the industry. A case in point is the "pushing" of the Active Matrix Liquid Crystal display technology that has occurred. We engineers "know" it can be done!. The users "want" the latest for their new aircraft! The pilots are "fascinated" by its possibilities! However, these drivers must be tempered by reality. We tend to lose sight of what reality is in our desire to accomplish new and better things. Reality is — meeting the real requirements and no more. Reality is - making sure that availability meets schedule. Reality is — making sure that we don't oversell. Reality is - having a true understanding of cost.
An evaluation is made of current trends in the introduction of increasingly high resolution display technologies into such military vehicles as tanks. These displays will be used to present maps, targeting images and information, and night-vision scenes. It is noted that higher resolution alone will not significantly contribute to military effectiveness; the acceptability of a given display system is strongly affected by the interactivity that it supports between its various operational modes and the user/operator.
Accounts are presented of the current and near-term development status of a major American commercial aircraft manufacturer''s integrated cockpit-display systems, as well as the character and anticipated improvements of prospective development trends. The state-of-the-art is illustrated by the cockpit displays of the MD-11 airliner, which employs both CRTs and liquid-crystal displays with a sensor suite that encompasses a dual digital air data system, three separate inertial reference units, X-band weather radar, and radar altimeter. Satellite-based communications and navigation systems are under development.
Developments in backlighting technologies for LCDs based upon fluorescent lamps have substantially reduced the display module thickness and power consumption over the last 4 years. The present state-of-the-art in fluorescent backlighting is reviewed. Currently, there are two major categories of backlighting system design used extensively in graphic type LCD modules. These are back-lamped backlights and edge-lit or light-pipe backlights. Much of the recent design effort has focused on edge-lit backlights because of their superior lighting uniformity and reduced thickness as compared to the back-lamped type of system. In the past, edge-lit backlights suffered reduced lighting efficiency when compared to the back-lamped type. Also, edge-lit backlights tended to produce a lower total luminous output than back- lamped designs. Therefore, back-lamped backlights are often found in LCD modules requiring high brightness such as avionics/military applications and especially in color LCD modules. Edge-lit backlights predominate in commercial monochrome applications such as present day laptop computers. However, recent improvements in the design of edge-lit backlights have opened the way for this approach to be used in commercial color applications as well.
Recent advances in SiC blue LED technology have led to the viability of Full-Color LED Displays. In this paper, a full-color LED backlight is constructed and tested. The results show that a full-color LED backlight is effective for a wide variety of avionics, automotive, commercial and industrial applications.
Flat panel display products could have an important effect on submarine design decisions. Beyond the obvious volume savings, flat panel displays offer improved flexibility during system design, and thus, create new opportunities for useful and innovative compartment and equipment arrangements. While suitable MIL-SPEC flat panel displays are still a number of years away, advanced flat panel-based submarine control room concepts, anticipating the technology, are already being explored.
A virtual display with 1120 X 900 pixel resolution has been constructed using a high density LED array and scanning optics. The display has a field of view of 25 degree(s) X 20 degree(s). The display is small, light weight, and suitable for hand-held or head-mounted use. Pixels appear red on a jet black background. Individual pixel size is 1.3 arc minutes, which is near the resolution limit of the human eye. Pixels appear crisp and sharply defined. Contrast ratio is over 500:1. The paper describes operation of the display in detail, and discusses design tradeoffs encountered in the development of high resolution virtual displays. Extension of this design to other resolutions and field of views is also explored.
We will discuss design image-optimization for helmet mounted displays (HMDs) in the context of a system engineering approach that includes a description of natural targets in the field, a description of perceptual characteristics of the human visual system, and device specifications that relate to these ecological and human-factors parameters that ultimately determine task performance. We will consider two HMD system as examples: the GEN III (AN/PVS-7A) night vision goggle (NVG) system and the SIPE helmet system (Soldier''s Integrated Protective Ensemble), both developed by S-TRON for use by the US Army.
Over the past five years we have been involved in the design of projection display products based on LCD panels. We have specialized in a particular application, where the panel is placed on the stage of a standard overhead projector and electrically connected to the video output of a personal computer. The LCD panel thus provides a low cost and portable method for projecting a computer screen large enough for group viewing. Our designs have been paced by the available LCD technology. As we refined our designs, we accumulated a ''wish list'' of LCD panel features. To our great satisfaction, most of our wish list desires have been met by the first generation of commercially available active matrix LCD panels. To set the stage for a discussion of active matrix technology, we first describe the technical characteristics of the predecessor technology, now known as ''passive matrix''. Then we explain the particular advantages of active matrix technology in our designs.
Electronic image projection systems generally suffer from dark grid (pixelation) or scan line structures which become more noticeable as the image is expanded. Since these structures represent a high spatial frequency error in the image, appropriate spatial filtering can be used to reduce this error and increase image fidelity. A new, transparent spatial filter is introduced and demonstrated to depixelize the image produced by a liquid crystal video projector. Various filter design and fabrication guidelines to achieve the best apparent image are also discussed.
Solutions for the problems associated with large screen video projection have been found resulting in the development of compact, lightweight, low-cost full-color projectors with good image quality. Problems addressed include: producing high contrast and good color fidelity with an LCD projector, heat management, cooling noise reduction, use of a single LCD and optical system, elimination of visible dots or lines in the image, and 3-D image projection.
A novel SLM based on a two dimensional array of Kerr cell shutters, the electrodes of which have been deposited on PLZT, has been proposed and initial measurements on such devices have been made. The cell or pixel density is 1000 per inch by 500 per inch and operating voltage for 30 light transmission is less than 50 volts. Extension of 1250 X 1250 per inch is the next step. The Kerr cells may be either photo-activated or may be electronically addressed. Pixel to pixel contrast ratios in excess of 750 to 1 have been measured, which implies that the device could have applications as an optical computer element.
In the past several years, the Display Systems Branch, Naval Ocean Systems Center (NOSC), has been involved in the development of laser based display systems with the goal of upgrading the image quality of shipboard displays. In this paper we report work on: (1) developing laser generated 3D volumetric images on a rotating double helix, (where the 3D displays are computer controlled for group viewing with the naked eye), and (2) system feasibility results along with the first and second generation component parameters.
Explained is a proposal for a structure and method of fabricating a Holographic Electro-optic Device (HED), a hologram whose image can be controlled by applying a voltage. Electrostriction switches a photo-elastically active polymer with a recorded holographic stress pattern.
We are developing an advanced black and white CRT monitor to meet the needs of critical users in government, medical and commercial applications. A CRT, deflection system and video amplifier are being developed, with attention to system integration and cost-effective design. The work is being carried out in cooperation with AVP/Megascan for transfer to a commercial product. The design parameters for this monitor have been established by analysis and simulations, taking into account limitations for a practical system. The studies show the need for both high brightness and uniform high resolution for the most demanding users, such as image analysts and radiologists. Our goal is 2 K X 2.5 K resolvable spots with 200 fL peak luminance and
While electronic technology has evolved enormously, there are no displays which are both very large and of high resolution. This paper describes our 6 K X 2 K, 60 inch by 20 inch, display prototype which consists of three 2 K X 2 K CRT displays connected seamlessly. Using a custom frame and a half-silvered mirror, the three images are joined by reflecting the center display image from above and transmitting the two side display images directly. Two problems must be solved to achieve a truly seamless effect. First, viewers can still see seams between regular screen images even if the displays are strictly aligned. Second, each physical display has a different geometrical space, and the center display image must be drawn in reverse because it will be reflected by the mirror. We developed a seamless window system to solve these problems. The window system displays overlapping images with translucent borders to enable better blending of the three display screens. Custom application software treats the system as a single 6 K X 2 K area. A concept named ''virtual framebuffer architecture'' enables us to implement the two kinds of seamlessness easily. To evaluate the visual effects, we developed some application systems which include video in a window, stereo sound and a high speed channel to the Connection Machine II for image processing.
High frequency interstitial point generation by Two Dimensional Convolute Integer Technology leads to enhanced resolution for large screen television, i.e., three gun display monitors. The high frequency interstitial points generate a high frequency interstitial image, which is interlaced with the real image, doubling the number of horizontal lines on the monitor. A side-by-side comparison of a number of images, interstitial and real will be presented. The interstitial image is 100 calculated data. The real data is from a video camera/frame grabber digitizer. The real and interstitial images are 512 pixels per row and 480 rows, allowing a resolution enhanced image of 960 rows with 512 pixels per row. The high frequency nature of the interstitial image is the result of applying a high frequency Two Dimensional Convolute Integer Operator, 8 X 8 mask 6 Dimensional Convolute Integer Operators with mask sized up to 14 X 14 and surface orders 12 and 13 have been developed. The larger mask size, higher surface order Operators have higher frequency response characteristics. The higher the frequency response of the Operator, the higher the resolution, or fine line detail, in the interstitial image.
Large size, full color ac plasma displays with high level gray scale have been demonstrated with live TV video images and computer generated graphics. These memory panels employ a double-substrate high resolution barrier structure and are capable of very high speed operation with high luminosity and high contrast at wide viewing angles. At high sustain frequencies, the memory function is superior to that of monochrome AC-PDPs. The display monitors offer full multimedia capability and can be formulated for stereoscopic viewing. A comparison of the leading direct-view high definition display system (HDS) technologies will be made including both single and double substrate AC-PDPs, DC-PDPs, CRTs and TFT-LCDs. The technologies will be compared on the basis of optical, electrical, physical, and cost characteristics. A summary of the status and challenges facing each technology will be presented. Special emphasis will be given to the various approaches being pursued in the development of color AC-PDPs. A status report on the DARPA/Photonics Imaging color AC- PDP HDS program will be presented.
Invented in 1964 at the University of Illinois, AC plasma is the most mature of all flat panel display technologies. Functional products have been delivered in high volume since 1971, many of which remain in active use today. Building on this proven foundation, several recent advances have given promise for this technology to provide exciting new products, especially where large area, high resolution, and full color are required.
The types of flaws susceptible to affect image quality in tiled displays are identified and psychophysical thresholds for their detectability are prescribed. Bright seams are not tolerable and completely dark seams have a threshold of 3. 5 arcsec. Tile luminosity variability threshold is less than 1 in some instances. Chromaticity variabilities must be kept well below 1 for one jnd discrimination in certain regions of the spectrum and vernier misalignments must be about 5 arcsec. Despite these stringent requirements tiling remains a viable way of making large displays.
We present a new method of tiling flat panel displays to a continuous large display. The method was tested for color Active Matrix Liquid Crystal Display (AMLCD) with backlight. Diverging glass fiber-optic faceplates configuration were used to show the principle however the method is applicable and was verified also with plastic faceplates and micro-channels (hollow pipes). The manufacturing of the displays and the faceplates are done separately and then assembled together. The method presented shows very little loss of resolution and very wide viewing angles. There are no limitations to the number of tiled displays in both horizontal and vertical directions.