Matthew S. Brennesholtz
The projection business continues to be an industry full of vitality, with a variety of new projection systems ranging from ones capable of resting in the palm of your hand to complex, multi-projector systems with total pixel counts up to 100 Mpixels. A wide variety of components needed for these advanced systems are also under development, including new microdisplays and scanners, new light sources such as lamps, LEDs and lasers, and the more mundane but essential components such as lenses, polarizers, or filters.
Herbert De Smet
André Van Calster
Abstract — Some technology aspects of LCOS microdisplays that are important for their deployment in advanced projection applications are discussed. The selection of the liquid-crystal parameters of the vertically aligned system as a function of the requirements (response speed, contrast, etc.) is addressed; a three-dimensional simulation engine to evaluate fringe-field effects between pixels is described, allowing the fine-tuning of the LCOS design with respect to the optical output. Finally, some observations on the nature of the so-called Vcom drift inside the asymmetrical LCOS cells are presented.
Black pixels are normally not affected, again due to the nature of the vertically aligned nematic (VAN) mode. This is actually quite fortunate because it means the contrast ratio, one of the strong points of VAN, is maintained. The consequences of the fringe field in the bright pixels can, however, be prominent enough to warrant some deeper investigations into the phenomenon. Figure 7 shows a typical, although severe case, of what can happen if fringe fields get out of bound.
FIGURE 7 — Close-up of some pixels in an LCOS device exhibiting serious artifacts in the white pixels due to the electrical fringe fields existing between pixels. The black pixels in the lower right corner are unaffected, while the white pixels neighboring the black ones show deep incursions of black lines produced by the reverse tilt zones.
Invited Paper: UHP-lamp systems for projection applications
Holger Mönch, Johannes Baier,
Mark Carpaij, Carsten Deppe,
Günther Derra, Hermann Giese,
Achim Körber, Thomas Krücken,
Uwe Mackens, Ulrich Niemann,
Pavel Pekarski, Arnd Ritz,
Philips Technologies GmbH
Abstract — Projection systems have found widespread use in conference rooms and other professional applications during the last decade and are now entering the home-TV market with considerable pace. Projectors as small as about one liter are nowadays able to deliver a screen flux of several thousand lumens and are, with a system efficacy of more than 10 lm/W, the most-efficient display system realized today. Because such highly efficient projectors employ microdisplays as light valves, short-arc lamps are a key component in realizing these properties. The introduction of the UHP-lamp system by Philips in 1995 can be identified as one of the key enablers for the commercial success of projection systems. The ultra-high-performance (UHP) lamp concept features outstanding arc luminance, a well-suited spectrum, long life, and excellent flux maintenance. For the first time, it combines a very-high-pressure mercury-discharge lamp having an extremely short and stable arc length with a regenerative chemical cycle that keeps the discharge walls free from blackening, leading to lifetimes of over 10,000 hours. In this review, the most important aspects of the UHP concept that enabled its success in the projection market are described, followed by a discussion of some recent additions to the UHP-product portfolio.
Figure 4 shows spectra of a 120-W UHP lamp with 200-bar pressure and an arc length of 1.0 mm, and a 200-W UHP lamp with 300-bar pressure and an arc length of 0.8 mm. While the color efficiency of the first lamp is only 66%, the 300-bar lamp reaches 83%,i.e., 25% more light on the screen due to the improved color-balancing efficiency alone. In addition, of course, the 200-W lamp delivers a lot more light due to its higher power and shorter arc.
Abstract — A new optical scheme for a LCOS-based rear-projection system utilizing an LED illumination source is presented. The proposed optical module could conveniently replace conventional aircraft panel instrumentation not only because it achieves major standard avionics application requirements, such as the capability to withstand mechanical shocks, high reliability, and weight and power-consumption minimization, but also as a consequence of the fact that it allows the display image area to be properly matched to the shape of the instrument panel more easily than with conventional displays
As shown in Fig. 1, the proposed architecture is based on the use of a single LCOS microdisplay (17.4 x 13.9 mm2 active area, 1280 x 1024 pixels) handling the three primary colors independently provided by three different LED sources via a folded optical path geometry. The LCOS microdisplay (whose nominal switch time is less than 100 μsec) is used in the present application at a frame rate of 60 Hz, providing an 8-bit resolution for each primary color. To match the responsivity of the human eye, the three LEDs (whose chip area is approximately 3 mm2) have different luminous fluxes, i.e., 140 lm for the red LED, 160 lm for the green LED, and 48 lm for the blue LED.
Aram Mooradian, Glen Carey,
Renata Carico, Rene Dato,
James Dudley, Giorgio Giaretta,
Sascha Hallstein, Jurgen Hofler,
Frank Hu, Mitch Jansen,
Joachim Krueger, Sui Lim,
Neil McKinnon, Greg Niven,
Yae Okuno, Ashish Tandon,
Abstract — High-power red, green, and blue laser light sources made from vertically emitting arrays of intracavity doubled IR lasers is reported. The emitted infrared light from a monolithic array of large-aperture vertical cavity lasers is converted into visible light using a PPLN doubling crystal in an external cavity. A volume Bragg grating provides simultaneous feedback for all emitters in the array and sets the laser wavelength. Increased diffraction losses for higher-order modes result in quasi-Gaussian beams with excellent conversion efficiency. Green 532-nm lasers with more than 5.8-Wvisible power have been demonstrated at a base temperature of 40°C. Blue 465-nm lasers with 4.4-Wpower at 40°C are unmatched in performance and wavelength when compared to competing GaN-based edge emitters. Typical wall-plug efficiencies are higher than 8%. We have measured single-emitter operating lifetimes to be more than 28,000 hours. Red lasers based on highly strained InGaAs achieve record laser powers of 2.0 Wat 618 nm in the same form factor as the green and blue lasers. Red single-emitter lifetimes of more than 10,000 hours have been attained. The technology described in this paper delivers on a full suite of cost efficient and reliable red, green, and blue lasers that meet the demands of the display markets.
In the present design, there is a forward and backward propagating second-harmonic beam. A dichroic element is inserted to extract the backward harmonic beam as shown in Fig. 2. The dichroic element also serves to polarize the fundamental wavelength. When periodically poled material such as lithium niobate is used, the second harmonic is also polarized in the same direction as the fundamental wavelength. To maintain simplicity of manufacture, flat optics are used.
Charles L. Bruzzone
Abstract — 3M polarization beam splitter (PBS) technology has been shown to be the most light-efficient solution currently available for use in LCOS projection. It also provides short back focal length, very high contrast, and extremely uniform dark states without the use of lead-glass prisms. Recent improvements in contrast performance, increased understanding of the effects of pupil shape and size on contrast, effects of temperature on optical performance, and improved photostability are reported. New light-engine architectures employing the 3M PBSs with associated light budget analyses are suggested.
As seen from the ray-trace in Fig. 11, no light is lost due to aberrations between the exit window of the light integrator and the imager. This result is achieved with a small number of glass optical elements and the front-surface aspherical mirrors. In other words, the geometrical collection efficiency of the system is equal to the thermodynamic limits imposed by the étendue properties of the light source. Another attractive feature of the optical layout of Fig. 11 is its small footprint. This layout uses 0.7-in.-diagonal LCOS panels with an effective system f/# of 2.0.
FIGURE 11 — Three-panel LCOS layout with MOF PBS and hollow light integrator.
Abstract — A GxL device is a one-dimensional light modulator suitable for laser projectors. A blazed GxL, which diffracts the incident laser beam in only one direction was developed, and a contrast ratio of 10,000:1 and a diffraction efficiency of 70% was achieved by nanometer-order control of ribbons based on the MEMS structural simulation and using common 0.25-μm CMOS-compatible fabrication processes. The 1.09-in.-long 1080-pixel blazed GxL was implemented in the 2005-in. Laser Dream Theater at the 2005 World Exposition in Aichi, Japan, and performed perfectly during that period. Recently, by optimizing the posts supporting the ribbon and flattening of the sacrificial layer using chemical mechanical polishing, an ultra high contrast ratio of 34,700:1 with a 0.72-in.-long GxL has been realized, and a smaller ceramic module with high reliability has also been realized. The blazed GxL will be a promising technology to further advance laser-projector performance.
FIGURE 1 — Internal view of the 2005-in. Laser Dream Theater at the 2005 World Exposition in Aichi, Japan.
FIGURE 16 — Latest GxL ceramic module. The length of the GxL modulation area is 0.72 in. The size of the module is 26 x 38 mm.
Abstract — A new technology has been developed for high-temperature-polysilicon (HTPS) TFT liquid-crystal panels employed in projection systems. It consists of vertically aligned nematic (VAN) liquid-crystal, inorganic alignment layers, and a new driving technique. Full-HD (1080 p) resolution was realized in a 0.7-in.-diagonal device with high contrast and low power consumption.
Figure 3 shows a comparison between (a) conventional and (b) D6 driving technologies. In the conventional technology, a controller IC, video-signal-conversion ICs, and level-shift ICs are mounted on the circuit board [Fig. 3(a)]. Digital video signals, generated from the controller IC, are converted to 48-ch analogue video signals and input to the horizontal drivers, which include shift resisters, on the LCD panel. The D6 series employs a new technology using internal and external drivers for driving the LCD. The LCD driver, which has video-signal-conversion ICs and shift-resister functions, and a level-shift IC are mounted on flexible printed circuits [Fig. 3(b)].
Mitsubishi Electric Corp.
Abstract — A new light-collection optics has been developed that enhances the luminance of projection TV which use lamps as the light source. The conventional optical system consists of an elliptical reflector and a flat-surface front glass, but these systems cannot sufficiently collect the beams coming from the light source, and they cause loss in the coupling with the light pipe. To solve this problem, we devised a new optical system through a structure of an aspherical reflector and an aspherical front glass. This new optical system concentrates thebeams coming from the light source to a smaller point which improves the coupling efficiency. Thus, we have successfully increased the luminance of the projection TV by approximately 10%. This paper reports the design principles of the new optical system and the results of a prototype experiment.
FIGURE 5 — Design principle for new collection optics. The front glass should have a convex shape around the optical axis and a concave shape in the area peripheral to the optical axis. This system gives a converging action on beams with a smaller emission angle and gives a diverging action on beams with a higher emission angle, and thus can adequately control the size of the arc image by emission angles. The reflector should also have an aspherical shape. These arrangements increase the design flexibility to improve the front glass more effectively.
NHK Science and Technical ResearchLaboratories
Abstract — For future broadcasting, NHK is studying new video services offering very-high-picture quality achieved through Super Hi-Vision. Toward that aim, a projection display that has a resolution equivalent to 7680 x 4320 pixels by using four 4096 x 2160 D-ILA™ panels has been developed. The display requires precise convergence adjustment because it consists of two projection units, so an automatic adjustment system was developed. Although the pixel number of the digital camera used is less than that of the display, a 0.2-pixel accuracy was obtained. This report introduces theaters that use this display as an example of applying the Super Hi-Vision video system.
NHK installed a Super Hi-Vision theater with a 600-in. screen in the Orange Hall of the Global House, the theme pavilion at Expo '05. To emphasize the distinctive feature of a "real-time" video system and to attract an audience, images of the people entering the Orange Hall were captured with a Super Hi-Vision camera while they were waiting. When they entered the theater, they saw themselves on the big screen. This Super Hi-Vision program was carried with 22.2-multichannel sound.
FIGURE 7 — Super Hi-Vision theater at Expo '05
National Cheng Kung University
Abstract — Two monodisperse polystyrene microspheres, 2.76 and 9.25 μm in diameter, were prepared by dispersion polymerization in an ethanol/iso-propanol/water media. 2,2¢-azobis(isobutyroni-trile) (AIBN) and poly(acrylic acid) (PAA) were utilized as the initiator and steric stabilizer, respectively. Optical properties including total transmittance (T%) and transmittance haze (H%) were determined when these two monodisperse polystyrene microspheres were applied as diffusive agents. This paper mainly discusses (1) different particle-size effects and its hybrid behavior, (2) different thicknesses for the diffusion-layer effect, and (3) the effects of diffusion-layer arrangement and direction of incident light on the total transmittance (T%) and transmittance haze (H%).
In general, the transmittance haze (H%) increases and the total transmittance (T%) decreases as the weight percentage of the diffusive agents increase; meanwhile, the small-diameter (2.76 μm) diffusive agent results in a better transmittance haze (H%) than the larger diameter agent (9.25 μm) for the same weight percentage of diffusive agent. It is interesting that the hybrid diffusive agent (9.25 + 2.76 μm) does not perform between these two component diameters, i.e., the hybrid diffusive agent (9.25 + 2.76 μm) performs more similar to the small-component diameter (2.76 μm) than the large-component diameter (9.25 μm).
FIGURE 1 — SEM photograph of (2.76 + 9.25 μm) blended microspheres.
Vladimir G. Chigrinov
Hong Kong University ofScience and Technology
Abstract — Results for a ferroelectric-liquid-crystal (FLC) display cell, aligned on inorganic SiO2 thin-film surfaces by using oblique ion-beam sputtering deposition on the substrates, is presented. A large deposition angle from 60° to 80° can be employed for the thin alignment layer, with thicknesses varying from 5 to 40 nm. Two types of uniform alignment, chevron (before electrical treatment) and quazi-bookshelf (after electrical treatment), were studied. High-quality alignment on large-sized substrates was also easily be achieved because of the linear design of the ion-beam sputtering source, which was previously a significant challenge for FLC on SiOxlayers.
The scheme of the sputtering source and deposition geometries is based on the anode-layer ion source with a racetrack shape of the discharge area, which is shown in Fig. 1. It generates two sheet-like fluxes of Ar+ ions, which focuses on the surface of a lengthy target with the dimensions of 60 x 500 mm2. The incidence angle of ions onto the vitreous quartz target, determined from the target's normal, is about 60°. This allows obtaining the maximal efficiency of sputtering at the same power consumption.
FIGURE 1 — Sputtering-source and sputtering-deposition geometries. 1) Parts of sputtering source; 2) diaphragm, 3) ion beam; 4) moving platform with substrates.