An achromatic linear polarization switch (ALPS<sup>TM</sup>)is discussed that enables stereoscopic 3D projection systems using conventional linear polarizing eyewear. The ALPS resides at the output of the projection lens and functions as a switchable polarizer. Features include rapid switching, high contrast, and a color-balanced on-state. The ALPS forms a flexible platform for switching between any set of orthogonal polarizations or filter states.
Contrast limits are investigated for MacNeille PBS based LCOS projection systems that use retarder stack filters (RSF). The two contributing factors are considered separately; namely the color management system and the panel port. To enhance performance of the former, skew ray compensated RSFs are introduced. For the latter, a general methodology is presented to optimize contrast by compensating the LCOS panel. It is shown that the orientation of the LCOS panel and compensator, relative to the MacNeille PBS, is critical. The significant impact of AR coating performance on system contrast is also revealed. A high contrast architecture will be presented by way of example.
Military displays have been limited first by the availability of CRT and then AMLCD for color multifunctional displays. Projection display technology has been offered as an alternative. With the growth of the LCOS based consumer projection display industry, commercially off the shelf (COTS) components and technology are becoming readily available. A projection display system addresses the lessons learned from the CRT or AMLCD based attempts. This approach presents multiple vendors and user defined aspect ratio, resolution, brightness and color. This paper will present the latest work at ColorLink, Inc. on a two-panel LCOS based projection light engine developed for the consumer industry driven Rear Projection Television (RPTV) market. This engine demonstrates throughput, contrast and color performance that exceeds military requirements using COTS technology and components. We will introduce the core technology and philosophy followed by this industry in defining such a product.
The fabrication and characterization of thin film optical retarders using liquid crystal polymer (LCP) material is presented. The advantages of LCP are high optical birefringence, high optical clarity, good surface quality, the possibility for large aperture applications, flexibility in orienting the crystal and low cost. An additional advantage over conventional liquid crystals is the processing on a single substrate as opposed to confinement between two hermetically sealed substrates, thus the prospect for compact multilayer stacks. Experimental result for single layer LCP thin films and numerical modeling of multilayer stacks are presented for on- and off-axis incident light.
Several Cu-based alloys such as Cu-Co, Cu-Fe and Cu-Nb, which are of considerable technological importance, possess a flattened liquidus implying a thermodynamic tendency to immiscibility upon undercooling. In this paper, both container and containerless processing were used to study the undercooling behavior, metastable liquid separation and microstructural development in the Cu-based systems. For undercooling experiments in an oxide flux, the melt separation temperature could be measured and the metastable liquid miscibility gap has been directly determined; while containerless processing in the 105 m drop tube permits larger undercooling to be achieved prior to solidification. All phase-separated samples were found to exhibit droplet- shaped morphologies, however there were various droplet size distributions, dependent upon composition, undercooling, and cooling rate.
Containerless processing provides a high purity environment for the study of high-temperature, very reactive materials. It is an important method which provides access to the metastable state of an undercooled melt. In the absence of container walls, the nucleation rate is greatly reduced and undercooling up to (Tm-Tn)/Tm approximately 0.2 can be obtained, where Tm and Tn are the melting and nucleation temperatures, respectively. Electromagnetic levitation represents a method particularly well-suited for the study of metallic melts. The TEMPUS facility is a research instrument designed to perform electromagnetic levitation studies in reduced gravity. It provides temperatures up to 2600 degrees C, levitation of several grams of material and access to the undercooled state for an extended period of time (up to hours).
Presented are experimental results that demonstrate bipolar optical incremental update in an amorphous silicon/ferroelectric liquid crystal (PLC) optically addressed spatial light modulator. The results are understood in terms of charge compensation in the PLC producing a nonlinear capacitance behaviour. Describing the FLCin this way, the experimental results have been accurately modelled. Also, an optoelectronic neural network, in which this device is incorporated as an adaptable weight storage device, is described and experimentally demonstrated with parallel optical updating of the interconnection weights
Optical implementations of neural networks utilize the inherent parallelism of optics to form the large number of interconnections required by neural networks. By carrying out computations in parallel, the processing speed of such systems can be substantial, despite the relatively slow response times of the optical devices. In this paper, a single-layer neural network is presented, which uses ferroelectric liquid crystal (FLC) spatial light modulators (SLM) to represent input patterns and weighted interconnections. The learning example for the network is handwritten character recognition. The experiment shows that this network successfully recognizes 58 of the handwritten patterns from the training set, when the synaptic weights have five grey levels and a dynamic range from -1 to +1. Computer simulations of networks indicate that by increasing the grey levels to eleven, and the dynamic range from -12.5 to +12.5, this net easily learns to recognize all the handwritten patterns in the training set. It also correctly recognizes 60 of the test patterns.
We demonstrate both nematic and ferroelectric liquid crystal SLM's in two separate optical connectionist
machines on which two layer neural network algorithms are executed. An analysis of their system
performance with respect to non-ideal operation of the component parts is presented; the analysis being
carried out with the aid of a computer simulation. A direct comparison between the two machines is then
made demonstrating the improved performance of the compact ferroelectric liquid crystal based machine.