With the introduction of Digital Micromirror Device (DMD) and Liquid Crystal on Silicon (LCOS) technologies, imagers for projection displays become increasingly smaller, thus requiring more intense, focused light with lower etendue values. To illuminate these smaller imagers, a patented dual paraboloid reflector system has been developed to collect and focus light from an arc lamp onto the imager without loss of brightness. This powerful optical platform provides the control and etendue efficiency that has been missing in standard illumination sy stems. The dual paraboloid reflector system consists of two parabolic reflectors placed symmetrically facing each other. The first parabolic reflector collects and collimates it into a parallel beam. The second parabolic reflector intercepts the parallel beam and focuses the light with unity magnification, i.e. 1:1 imaging, into a tapered light pipe (TLP) with conserved brightness. The TLP transforms the focused light into an output with the needed area, shape, and numerical aperture (NA). It also acts as a homogenizer so that the intensity profile at the output surface is uniform and eventually provides a uniform intensity profile at the screen. The reflection of light twice in the dual paraboloid reflector system provides a high IR and UV rejection ratios, resulting in less degradation of the optical components. Polarization and color recycling systems are also designed taking advantage of this reflector configuration.
We present a thin fog screen, which is formed into laminar airflow. The screen is part of a the laminar airflow, which protects the fog screen. In this way it is possible to create a high-quality, flat projection surface from the fog. The fog screen suits, e.g., for the creation of physically walk-thru screens and for large-scale screens both indoors and outdoors.
Microdisplays are considered to be an enabling technology for ultra-high resolution displays. Pixels can indeed be made very small using CMOS technology. Nevertheless, in multimillion pixel microdisplays, the die size becomes a limiting issue, because the optical field size of present day lithographic steppers, and consequently the resulting chip size, is limited to about 20x20 mm2. This paper shows how this limitation can be overcome using stitching techniques and discusses the resulting challenges in design as well as lithography. The partitioning of the schematics and the layout in stitchable modules is reviewed, as well as the definition of boundary conditions for these modules. The difficulties concerning design verification, and a virtual stitching procedure that can be helpful, are presented. From a technological point of view, the stepper job creation and the scribe line definition is described, as well as the positioning accuracy that is achieved. It is also shown that careful partitioning of the design can lead to a single stitchable mask set that allows the creation of microdisplays with several different resolutions. The paper is illustrated with results from the European Esprit project Mosarel, a project that has shown the feasibility of a 2560x2048 pixel microdisplay.
The response time for each TFT-LCD display mode, such as twisted nematic (TN), multi-domain vertical align (MVA), and in-plane switching (IPS) mode, has been measured and analyzed especially in grayscale. The characterization of each display mode has clarified the panel design dependence, especially that of IPS mode LCD. Several display modes have also been subjectively evaluated in view of moving picture appearance by comparing each LCD display monitor to CRT monitor. For moving picture image, subjective evaluation performed by selecting three display test patterns with two moving speeds. Subjective evaluation result is related to the three response parameters, 1) bi-level response time between L255 (brightest) and L0 (darkest), which is conventional definition of response time, 2) sum of average and variance of all response times including gray-levels (calculated twenty response times), and 3) average response time between middle and gray-level and next levels (L127 (reversible reaction) L191 and L127 (reversible reaction) L63). Among above parameters, the average response time of middle grayscales (to and from L127) shows good relationship with subjective evaluation result. The perception speed of each LCD monitor has been also subjectively evaluated to verify the relation to each response parameter. The target for the appropriated response parameter will be discussed.
An optical configuration and measurement algorithm are outlined for producing semi-automated Near to Eye Display measurements of the Michelson Contrast versus varying spatial frequencies. The input patterns measured include line on-line off (LOLO) images from a single LOLO to eight LOLO, in both the horizontal and vertical direction. These measurements result in a Contrast Transfer Function of the display under test, revealing information on the image quality of the display system.
Projection based on the scrolling color single panel reflective liquid crystal on silicon (LCoS) architecture developed within Philips is set to become a competitive technology for high definition rear projection television. The colorimetry of the scrolling color illumination light engine is examined in this paper including the design issues considered in specifying dichroic color filters for uniform color illumination. The scrolling action can be achieved with rotating glass prisms (one for each primary color), which combined with the requirement for compact illumination optics can lead to beamsteering at some of the dichroic filters in the light path. This beamsteering can cause unacceptable color changes of the illuminating stripes as they are scrolled from the top to the bottom of the LCoS panel unless special attention is made to the choice of filter cut-off wavelengths and their sensitivity to angle of incidence variations. One solution involves the design of new dichroic filters that are relatively insensitive to these beamsteering effects. Filters have been designed and fabricated with edge sensitivities < 0.9 nm/deg compared with typical sensitivities of ~ 1.4nm/deg from standard filters; the filter specifications and their system performance will be described. Further system solutions are given that utilize conventional angle-sensitive dichroic filters. The effect of color balancing upon the optical efficiency of the system will also be described.
The international standard sRGB has been established as the default RGB color space for multimedia, in which 'reference image display system characteristics' are specified. That is, a display device is required to have characteristics close to these characteristics in order to properly display color image data that is in conformity with sRGB. For this reason, the sRGB specification for front projectors has been defined. Our newly developed projectors achieve less than one tenth of the color difference for the sRGB specification. Today as more and more people use the Internet as a source of information and computer-aided visual presentations have become a key tool, accurate and reliable color reproduction is essential for everyone. With sRGB compliant projectors we can reproduce identical colors, ensuring that images shown on other sRGB compliant devices such as CRT display monitors remain the same.
Speckle arises when coherent light scattered from a rough surface is detected by an intensity detector that has a finite aperture, such as an observer. In a laser projection display, the presence of speckle tends to mask the image information and therefore its reduction is highly desirable. Speckle contrast reduction is based on averaging a number of speckle configurations within the spatio-temporal resolution of the detector through diversification of the light parameters - angle, polarization, and wavelength. The maximum speckle contrast reduction for a given system will be derived, and two novel approaches to achieve the maximum reduction will be introduced. Application to the Grating Light Valve (GLV TM) laser projection system using the Hadamard diffuser has resulted in a suppression to 8% residual speckle contrast.
The laser TV using blue, green diode-pumped solid state lasers and a red diode laser is developed. The wavelengths of the blue, green and red are 457 nm, 532 nm and 648 nm, and the output powers are 350 mW, 700 mW and 500 mW, respectively. The power levels of lasers are adjusted for white color balance. The polygon mirror and the galvanometer are used for horizontal scanning and vertical scanning, respectively. The image size of 80 inches with high-brightness and VGA resolution (640 X 480 Progressive scanning) is obtained. The acousto-optic modulator (AOM) is fabricated for laser beam modulation, for which the carrier frequency of 350 MHz for XGA resolution is applied. TeO2 crystal, which is cut at Brewster angle, is used as an optical medium and LiNbO3 is attached as a transducer. In order to get a compact size, low cost, low-power consumption and lightweight, a scanning mirror using MEMS technology is fabricated by the size of 1500 micrometers X 1200 micrometers . This scanning mirror can be used as a galvanometric vertical scanner for laser TV.
A new technology, developed at Jet Propulsion Laboratory (JPL), using low-absorption color filters with polarization and color recycle system, is able to enhance efficiency of a single panel liquid crystal display (LCD) projector to the same efficiency of a three panel LCD projector.
It has recently been shown that a tapered slab glass waveguide (wedge) can be used to make a flat panel display by projecting a video image into the thick edge of the wedge1. In this paper, we present the equations that relate the incident angle to the position where the ray emerges from the wedge. In the analysis, skew rays are also considered. We also present the design and experimental results of an anti-reflection coating that increases the brightness and reduces the blur of the wedge. With the coating, the transmittance of the interface rises from 0 (TIR) to 99% for a 0.35 degree change in incident angle for S-polarised monochromatic light. Without the coating, the transmittance falls below 50%. We also present a chromatic design intended to work with S-polarised rays from an arc lamp.
A new compact front UXGA projector is introduced with three one inch reflective LCD panels; It delivers 1000 lumens with the advantages of the compactness and high resolution. Three PBS cubes and one recombination cube are employed for separation and recombination of the three primary colors. A newly developed PBS cube is used not only as a polarization selector but also as a dichroic mirror, and a parallelogram prism array is plugged in front of the polarization converter to make the green light and the blue light orthogonally polarized each others. Compared to the old design, this new one gets the advantage of the space savings. The telecentric projection F/2.5 lens is characterized as a zoom range from 45 mm to 55 mm. Lateral colors are eliminated to be under 0.8 pixels. MTF is estimated as 60% on axis and 40% at 0.7 field. Distortion is around -1.7%.
Precision display measurements often involve the integration of light measurements over many frames. Newer display technologies with high speed light modulators such as micromirrors are able to make sophisticated use of temporal modulation. This may result in measurement errors, and in situations where temporal modulation produces visible artifacts that affect display usability, but that conventional metrology techniques do not detect. There is a need for further development of new metrology techniques that collect information on the temporal behavior of high speed displays. The emergence of multiple technologies from multiple display manufacturers has created a need for generic, non-brand-specific or technology-independent tools. We are working on such a technique, using the triggered capture of display images with a sub-microsecond imager, with test images and image sequences designed to evoke particular display responses, triggers that can involve keying on features designed into the test images, and subsequent processing of captured images to reconstruct the behavior of the display. In principle, such measures can be calibrated with conventional full-screen measurements so that a determination of pixel sequences can lead to an accurate determination of the effective grayscale and luminance of each pixel. Complications include the finite time required for pixel switching (so that pixel duty cycles can not be computed in unit blocks of time), and the risk that the observation method used will introduce a bias in the temporal observations.
We propose a method for evaluating the image quality of color LCD monitors by using the polychromatic modulation transfer function (PMTF). The PMTF is calculated from the values of monochromatic MTFs weighted by the overall spectral response of the system. We also propose a method for simulating the PMTF of a color LCD monitor by using three bar targets with different amplitudes. To obtain the spectral response of the color LCD monitor, the chromaticity (x,y) and luminance are measured with a spectroradiometer. The PMTF measuring system with a 2-D cooled charge coupled- device camera, an objective lens and a translator is used to evaluate the color LCD monitor.
The accurate measurement of small area-black levels is important in projection display characterization. For example, techniques can be used to determine resolution of projection systems by measuring the contrast of alternating grille patterns or fully-modulated sine waves of various spatial frequencies. Unfortunately, the measurement of the contrast of these patterns may be influenced by stray light, either from ambient and reflected light in the environment, or from veiling glare scatter in the lens of the light-measuring device. Such stray-light corruption can lead to large errors in contrast determination, providing an inaccurate characterization of the projector. For large-area measurements, various techniques have been employed, including the use of frustums and masks, to minimize such unwanted effects and provide a more accurate measurement. With some modifications, these same tools may be used for small-area measurements with similar results. The design, construction, and implementation of these tools will be discussed. Results will be shown comparing small-area contrast measurements of projection systems, including resolution determination, with and without stray light compensation, for different measurement instrumentation.
With the availability of small arc size high intensity discharge lamps a new polarization recovery system using polarization recycling in a light pipe is made possible. Combining light integration/homogenization with polarization recovery in an integrator rod leads to cost reduction and smaller light engines. The polarization recovery light pipe utilizes a reflective polarizer that works at normal incidence at its exit face and a high-reflective mirror with a transparent circular aperture at the entrance face. The reflected linearly polarized light is recycled by rotating its polarization by 90 degree(s) during one round-trip in the integrator rod. Different possibilities for achieving this polarization rotation, including retarders and phase control coatings are investigated. As much as 70% of the rejected polarized light can be recaptured with this system.
The business presentation market has traditionally been the mainstay of the projection business, but as these users find the projectors work well at showing movies at home, interest in the home entertainment market is heating up. The idea of creating a theater environment in the home, complete with big screen projector and quality audio system, is not new. Wealthy patrons have been doing it for years. But can the concept be extended to ordinary living rooms? Many think so. Already pioneers like Sony, InFocus, Toshiba and Plus Vision are offering first generation products - and others will follow. But this market will require projectors that have different performance characteristics than those designed for data projection. In this paper, we will discuss how the requirements for a home theater projector differ from those of a data projector. We will provide updated information on who is doing what in this segment and give some insight into the growth potential.
The projection market is undergoing many dynamic changes. Front LCD and front-reflective (mainly DLP) technologies compete with each other for most projection applications. The front-projector market is still emerging, with new technologies (such as liquid-crystal-on-silicon, or LCOS), new product categories developing (like <EQ3-pound projectors), and new suppliers entering the market. In the rear-projection market, although rear CRT remains the dominant force in large TV applications, new products based on rear DLP, LCD, and LCOS will take more market share from rear-CRT technology. This paper analyzes changing scenarios in the projection market by examining the developments over last five years. Also, this paper touches on what to expect in the next five years.