Markus Duelli

64.2: Design and Characterization of a Compensator for High Contrast LCoS Projection Systems

We describe the design and contrast measurement results of a high performance contrast enhancer for an LCoS-based projection display that has these attributes: complete a/c-plate compensation, accurate retardance targeting, excellent retardance magnitude and axis uniformity and environmentally durable. An overall system contrast of more than 4500:1 under f/2.4 cone illumination has been obtained.

Thermal stress birefringence in LCOS projection displays

Thermal stress birefringence affects the contrast uniformity of LCOS projection displays since they employ polarization-based image recovery. System architecture, material selection, lumen levels, and component mounting arrangements can all affect a systems susceptibility to image degradation resulting from thermal stress birefringence. Theoretical analyses can provide some insight into the origins and magnitude of the problem, but can be difficult to carry out except for idealized systems. This article presents an empirical approach to understanding thermal stress birefringence, and includes quantitative results of a specific material study. The results help the system designer select glasses with appropriate material properties to insure that stress birefringence effects are kept to a tolerable level for a given LCOS projection display system and application. A qualitative discussion of the system factors mentioned above is also included.

Polarization recovery system based on light pipes

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.

P‐155: High Performance Contrast Enhancing Films for VAN‐Mode LCoS Panels

Vertically aligned nematic mode liquid crystal on silicon micro displays exhibit a residual birefringence in the dark or off-state. This retardance has to be compensated in order to achieve high contrast projection systems. A birefringent film compensator with individually controllable on- and off-axis retardance and high uniformity is presented. Sequential contrast of 4500:1 has been demonstrated in a wire grid polarizer based light engine for a rear projection television.

Birefringent films for contrast enhancement of liquid crystal on silicon projection systems

High-performance projection displays based on liquid crystal on silicon (LCoS) panel technology have the potential to deliver very high contrast and performance at an attractive price. These systems use polarization-based light engines that utilize wire grid polarizers (WGP) and vertical-aligned nematic LCoS panels. To achieve high contrast, the linear polarization state created by the WGP must be maintained in the dark state to prevent light leakage to the screen. However, the LCoS panel has a residual retardance, and without compensation, this leakage degrades the system contrast. We describe the design and contrast measurement results of a birefringent contrast enhancing component that compensates this residual retardance and improves the overall system contrast ratio to 6000:1. The component is comprised of birefringent films with individually controllable A-plate and C-plate compensation, accurate retardance targeting, and excellent uniformity for both retardance magnitude and orientation. The compon...

16.3: Novel Polarization Conversion and Integration System for Projection Displays

A novel polarization conversion and integration system based on an integrator rod and wide acceptance angle polarizing beam splitter cubes is presented. This system shows similar performance compared to the common polarization conversion system arrangement consisting of two lenslet integrators and a flat polarization conversion system. The proposed system offers low cost, high reliability and a compact illumination path for certain light engine architectures.

36.2: Integrator Rod with Polarization Recycling Functionality

intensity discharge lamps with small arc sizes facilitate the design of a new polarization recovery system that doubles as a beam homogenizer. As much as 70% of the rejected polarized light can be recovered and re-emitted in the desired polarization state while eliminating the need for a separate integrator assembly. In this paper we discuss the design and performance of two implementations of this system. 1. Introduction crystal based projection displays require polarized light to operate. Current light engines use either polarizing components, like polarizing beam splitters, and thus lose at least half of the available light or polarization conversion systems to achieve polarized light at the light valve. 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 homogenization with polarization recovery in the integrator rod leads to cost reduction and smaller light engines. A similar recovery scheme for colors has recently been reported by DeWald et.al. (1). A schematic of the proposed polarization recovery light pipe is shown in Figure 1. The system consists of a hollow or solid integrator rod, a mirrored input aperture, a reflective polarizer and a quarter wave plate for polarization rotation.

Increased collection efficiency of LIFI high intensity electrodeless light source

Recently, RF driven electrodeless high intensity light sources have been implemented successfully in the projection display systems for HDTV and videowall applications. This paper presents advances made in the RF waveguide and electric field concentrator structures with the purpose of reducing effective arc size and increasing light collection. In addition, new optical designs are described that further improve system efficiency. The results of this work demonstrate that projection system light throughput is increased relative to previous implementations and performance is optimized for home theater and other front projector applications that maintain multi-year lifetime without re-lamping, complete spectral range, fast start times and high levels of dynamic contrast due to dimming flexibility in the light source system.