The projection display industry represents a multibillion- dollar market that includes four distinct technologies. High-volume consumer products and high-value business products drive the market, with different technologies being used in different application markets. The consumer market is dominated by rear CRT technology, especially in the projection TV segment. Rear LCD (liquid crystal display), MEMS/DLP (or Digital Light Processing TM) and LCOS (Liquid-crystal-on-silicon) TVs are slowly emerging as future competitors to rear CRT projectors. Front CRT projectors are also facing challenges from LCD and DLP technology for the home theater market while the business market is completely dominated by front LCD and DLP technology. Three-chip DLP projectors have replaced liquid crystal light valves in large venue applications where projectors have higher light output requirements. In recent years front LCD and LCOS projectors have been increasingly competing with 3-chip DLP projectors especially at the low end of the large venue application market. Within the next five years the projection market will experience very fast growth. Sales and presentation applications, which are the fastest growing applications in the business market, will continue to be the major driving force for the growth for front projectors, and the shift in the consumer market to digital and HDTV products will drive the rear projection market.
All of the components for the electronic cinema are now commercially available. Sony has a high definition progressively scanned 24 frame per second electronic cinema camera. This can be recorded digitally on tape or film on hard drives in RAID recorders. Much of the post production processing is now done digitally by scanning film, processing it digitally, and recording it on film for release. Fiber links and satellites can transmit cinema program material to theaters in real time. RAID or tape recorders can play programs for viewing at a much lower cost than storage on film. Two companies now have electronic cinema projectors on the market. Of all of the components, the electronic cinema projector is the most challenging. Achieving the resolution, light, output, contrast ratio, and color rendition all at the same time without visible artifacts is a difficult task. Film itself is, of course, a form of light-valve. However, electronically modulated light uses other techniques rather than changes in density to control the light. The optical techniques that have been the basis for many electronic light-valves have been under development for over 100 years. Many of these techniques are based on optical diffraction to modulate the light. This paper will trace the history of these techniques and show how they may be extended to produce electronic cinema projectors in the future.
Electronic cinema projectors are being developed that use a digital micromirror device (DMDTM) to produce the image. Photera Technologies has developed a new architecture that produces truly digital imagery using discrete pulse trains of red, green, and blue light in combination with a DMDTM where in the number of pulses that are delivered to the screen during a given frame can be defined in a purely digital fashion. To achieve this, a pulsed RGB laser technology pioneered by Q-Peak is combined with a novel projection architecture that we refer to as Laser Digital CameraTM. This architecture provides imagery wherein, during the time interval of each frame, individual pixels on the screen receive between zero and 255 discrete pulses of each color; a circumstance which yields 24-bit color. Greater color depth, or increased frame rate is achievable by increasing the pulse rate of the laser. Additionally, in the context of multi-screen theaters, a similar architecture permits our synchronously pulsed RGB source to simultaneously power three screens in a color sequential manner; thereby providing an efficient use of photons, together with the simplifications which derive from using a single DMDTM chip in each projector.
In this paper recent research on high-power laser displays for large display applications is reported. We discuss our compact high-power red-green-blue laser system for use as a light source based on a passively mode-locked solid-state laser with an optical parametric oscillator and sum- frequency mixing with very high efficiency and 19 W of white light. Concepts for power scaling to 35 W of white laser light are presented. A direct laser beam scanning technology is described which results in high resolution displays. Multi channel concepts as required in flight simulator applications are discussed. The laser light is modulated at 32 MHz using acousto-optic modulators with 75% diffraction efficiency. A high contrast ratio of 1:150,000 is achieved and has been successfully tested in novel planetarium applications. We also present performance and lifetime data of initial commercial laser display systems in the field.
Analysis of the process of up-conversion suggest scaling rules for up-conversion based optically written displays. These rules have been demonstrated experimentally and give us confidence in our designs of such displays.
DigiLens Inc. (Sunnyvale, California) has developed the Application Specific Optical Element (ASOE) based on Electrically Switchable Bragg Gratings (ESBGs) using an advanced Holographic Polymer Dispersed Liquid Crystal material system. One of the embodiments of this fundamental technology is a customizable white light color sequential filter system which aims to replace traditional color wheel assemblies in microdisplay-based display applications such as business projectors, HDTV and large computer monitors. ASOEs are essentially stacks or laminates of intrinsically thin ESBGs encapsulated using transparent substrates. ASOEs have no moving parts; they are completely solid state and silent in operation. They offer the benefits of holographic optical elements in terms of being able to compress conventional optical systems into compact and lightweight form factors. Their switching speed is fast enough for color sequential display applications. They will have a major impact on the complexity and cost of a broad gamut of microdisplay applications, including projection and near- eye. This paper reviews the role of reflective ASOE filters in projection systems, with reference to design concepts currently in development.
Liquid crystal panels, originally designed and fabricated for projection systems, are used as spatial light modulator in optical correlators or in fringe projection systems. An adapted driver electronics and measurements of the phase modulation behavior can lead to a dynamic phase modulating system with an almost linear modulation and a maximum phase shift of 2(pi) . The electronics of our Sony-LCD based system can directly address the graphics card signal or can picture various video standards. So, computer generated holograms can be addressed at video frame rates. We demonstrate examples of technical beam splitters, 2D holograms, reconstruction of digital holograms and animation of diffraction patterns. Here we will state to problems of light efficiency, intensity and wavelength dependent modulation. Furthermore, we will show first results of an FLC based system and derive boundary conditions for applications in holographic projection and micro- structuring.
This paper presents a method of enhancing resolution in scanning laser display systems by manipulating the video signal. Spot size (of the laser beam on the projection screen) and system bandwidth typically defines image resolution. By applying a particular gain profile to the video signal, which derives from the spot profile, the resolution can be increased.
Light distribution curve from projection lamp is a key factor to design the illumination system. Realistically simulating the real light emitting behavior will let designer improve the system collection efficiency and uniformity. It is an advantage information to optimize the system performance.
In this paper we discuss our red, green, and blue (RGB) optical parametric oscillator (OPO) light source for projection display applications. Our source consists of a diode-pumped pump laser and a LBO-based OPO. Based on our Nd:YLF gain-module design, the pump laser is frequency doubled to serve as the pump source for the OPO. The unconverted pump power is recycled as the green light for projection. The singly resonant, non-critically phase- matched OPO has, to date, generated 13 W of 898-nm signal power and an estimated 9.3 W of intra-cavity idler power at 1256 nm. With approximately 76% of pump depletion, the power of the residual green light for projection is about 5.8 W. We have extra-cavity doubled the signal to produce approximately 3.5 W of 449-nm blue light and intra-cavity doubled the idler to produce approximately 6 W of 628-nm red light. The OPO-based RGB source generates about 4000 lumens of D65-balanced white light. The overall electrical power luminous efficiency (diodes only) is about 14.6 lumens/Watt.
A theoretical analysis of liquid crystal (LC) beam steering structures based on Sub-Wavelength Diffractive Optical Elements was performed. Rigorous Diffraction Analysis shows a significant diffraction efficiency gain of up to 40% in using Sub-Wavelength LC structures, compared to regular DOE structures. However, due to Fringe-Field Effects, the formation of a high Diffraction Efficiency Index Grating Structure inside a liquid crystal layer is possible, only if the grating pixel's aspect ratio (height to width) is much smaller than unity (approx. 0.1). This in turn, requires the use of a small aspect ratio LC cell. However, simulations of LC director behavior show, that such ultra-thin LC Cells will fall short of providing the 2(pi) phase modulation necessary for an effective beam steering. One possible solution for this issue is the generation of a Blazed Phase Grating inside a Non-Symmetrical Reflective Fabry-Perot Resonator. Such configuration essentially allows an increased phase modulation magnitude at the expense of a very high sensitivity of such structure to liquid crystal thickness variations--as was verified by computer simulations. A second possible solution is the formation of a Cascaded Diffractive Gratings Stack based on ultra-thin LC layers. These gratings are identically reproduced in each of due to the Talbot Effect. We have studied a Cascaded system, consisting of four Ultra-thin liquid crystal layers separated by glass plates. The results show, that the thickness of each layer in the cascade decreases proportionally to number of layers, followed by an increased absorption. An interesting feature of the cascaded structure is the discrete set of possible beam steering directions, which are determined by constraints of the Talbot Effect.
Control of the seal edge of LC cells with super narrow periphery is very important for the application to compact AM-LCD designs. Several thermal cure epoxy resins have been studied as candidates for LC panel seal materials, with emphasis on characterizing the seal edge. The factors affecting material selection are its effect on LC alignment, the seal edge waviness or straightness, the formation of the seal edge boundary during lamination and cure and finally, its compatibility with standard cell processing techniques. Optimal seal material selection is discussed in view of its application to the design and fabrication of super narrow periphery LC cells. Cell design of seal edge control is also discussed in view of application of seal characterization and structural contribution, including material and process matching.
In this study, the characterization method for a typical desktop LCD color projector is reviewed. Measurements were made with a spectroradiometer to establish the additivity of the primaries, inter-channel dependence, color gamut, tone scale, contrast, spatial non-uniformity, temporal stability and viewing angle variation. In the case of tone characterization, LCD projectors show S-shaped curve between input digital values and output luminance unlike the conventional CRT monitor represented by a power function. Mathematical models to predict the S-shaped electro-optical transfer function have been empirically derive.d Four mathematical models including PLCC, GOG, S-Curve Model I and II were compared for their accuracy in predicting the colors generated by the display for arbitrary signal inputs. It is proven that the newly derived S-Curve Model I and II work successfully for an LCD projector.
A seamlessly tiled projection system is composed of multiple projectors, a front or rear projection screen, feedback elements, and tiled image processors. Its seamlessness is achieved through the optical and electronic calibrations. The optical calibration in the components of projectors improves the contrast ratio, brightness, and the overall image quality. The electronic calibration aligns the tiled images, and blends the color between adjacent tiles using a camera feedback system. A front projection system with a 2 X 2 array of SXGA (1280 X 1024) projectors is set up to describe the fundamentals of achieving a scalable, high- resolution, seamlessly tiled projection display.
Polymer Dispersed Liquid Crystal (PDLC) is commonly used as active diffuser and optical switches. In this work we propose an optical active pupil by using the PDLC. The aperture size of this device is electronic controlled with highly accuracy and is determined by the diffused region. This device is made of similar way commercial PDLCs, but changes in the thickness of one glass plate, change a flat surface by concave surface. Some experimental results are shown.
Projection display industry in Taiwan is constructed into three tiers: the upstream, the midstream and downstream. The associated companies and products involves cover a very wide range, from key components, to sub-assemblies, to final system products. In the past, the growth of midstream and down stream segments is limited by the supply shortage of key components. Till recently, some companies started to produce the imagers and light sources, the tension of component shortage is relieved. Very soon, the projection display industry in Taiwan will become next rising star industry after personal computer industry.