VAN LCOS microdisplays: a decade of technological evolution

Abstract—Microdisplays of the liquid crystals on silicon (LCOS) type have gone through a rapid evolution during the last decade. We present an overview of how vertically aligned nematic (VAN) LCOS have evolved from an attractive, but notoriously difficult and even infamous technology, to the mainstream microdisplay technology that it is today. At the same time, we highlight a number of remaining issues and concerns, and present some ideas of how to remedy them

A silicon backplane technology for microdisplays

A silicon backplane technology is described for the fabrication of high-resolution microdisplays. The technology is embedded in a 0.7 mum CMOS technology, and comprises DEMOS devices for enabling voltage spans of 12 V, and a special back-end processing module for planarizing the wafer and light shielding. This technology is used to develop a GXGA (2560times2048 pixels) microdisplay with 15 mum pixels on which the first results are reported

Measuring Thickness and Pretilt in Reflective Vertically Aligned Nematic Liquid Crystal Displays

Pretilt angle is a parameter of the utmost importance in the ultimate performance of vertically-aligned negative nematic LC displays. When these devices work in reflective mode, as is the LCOS microdisplays, accurate measurement of pretilt angles becomes a difficult problem, since usual experimental setups based on retardation of the polarization components of the impinging light are proportional to the product effective birefringence (neff - no) times thickness, and any attempt to separate these variables is cancelled out by symmetry. This work shows a relatively simple method capable of separating both variables. An experimental setup specifically aimed at vertically aligned reflective cells has been prepared. At the same time, a simulation model has been developed taking into account the properties of actual reflective displays. Comparison between experimental and theoretical results shows some discrepancies that can be explained assuming that the LC profile contains a residual twist. Including that twist in the model, an excellent agreement between theory and experiment has been achieved. Matching of simulations and measurements yields to the separate determination of pretilt angle and thickness and gives good estimates for the residual twist angle

Electronic compensation for fringe-field effects in VAN LCOS microdisplays

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Monocrystalline silicon active matrix reflective light valve

In September 1997, six European companies and research institutes started the Esprit project Mosarel (Monocrystalline Silicon Active Matrix Reflective Light Valve) for an initial period of 2 years. The aim was to show the feasibility of making microdisplays using an ASIC approach, combining standard CMOS technology with standard liquid crystal technology. The target demonstrators were a rear projector and a head-up display built around a 5-megapixel microdisplay with 15 µm pixels, which had to be developed first. During this ambitious project, the consortium has faced a great number of anticipated, but also many unexpected difficulties, both on the technological and on the logistic level. Despite these difficulties, which caused a considerable delay, it was eventually possible to show a working rear projection demonstrator, albeit with several visible defects. In this presentation, an overview will be given of the project, starting with the initial ideas, describing some of the most important difficulties that were encountered and the way they were solved or avoided and ending with the actual achievements and the still existing loose ends

OLED microdisplays control cell behavior through optogenetics

M.C. Gather acknowledges funding from Marie Curie Career Integration Grant (PCIG45-GA-2012-334407), from the Scottish Funding Council (via SUPA), and from the RS Macdonald Charitable Trust.OLED microdisplays are introduced as a microscopic illumination platform for cell biology. The μm-scale dimensions of each pixel and the μm-thin encapsulation enable controlled light exposure of individual live cells. This breakthrough is facilitated by recent progress in ultrathin metal electrodes and by quality control via high resolution hyperspectral imaging.PostprintPeer reviewe

A Compact raster lensless microscope based on a microdisplay

Lensless microscopy requires the simplest possible configuration, as it uses only a light source, the sample and an image sensor. The smallest practical microscope is demonstrated here. In contrast to standard lensless microscopy, the object is located near the lighting source. Raster optical microscopy is applied by using a single-pixel detector and a microdisplay. Maximum resolution relies on reduced LED size and the position of the sample respect the microdisplay. Contrarily to other sort of digital lensless holographic microscopes, light backpropagation is not required to reconstruct the images of the sample. In a mm-high microscope, resolutions down to 800 nm have been demonstrated even when measuring with detectors as large as 138 μm × 138 μm, with field of view given by the display size. Dedicated technology would shorten measuring time

Tiny Devices Project Sharp, Colorful Images

Displaytech Inc., based in Longmont, Colorado and recently acquired by Micron Technology Inc. of Boise, Idaho, first received a Small Business Innovation Research contract in 1993 from Johnson Space Center to develop tiny, electronic, color displays, called microdisplays. Displaytech has since sold over 20 million microdisplays and was ranked one of the fastest growing technology companies by Deloitte and Touche in 2005. Customers currently incorporate the microdisplays in tiny pico-projectors, which weigh only a few ounces and attach to media players, cell phones, and other devices. The projectors can convert a digital image from the typical postage stamp size into a bright, clear, four-foot projection. The company believes sales of this type of pico-projector may exceed $1.1 billion within 5 years