Nick Miller

Optical sparse aperture imaging

The resolution of a conventional diffraction-limited imaging system is proportional to its pupil diameter. A primary goal of sparse aperture imaging is to enhance resolution while minimizing the total light collection area; the latter being desirable, in part, because of the cost of large, monolithic apertures. Performance metrics are defined and used to evaluate several sparse aperture arrays constructed from multiple, identical, circular subapertures. Subaperture piston and/or tilt effects on image quality are also considered. We selected arrays with compact nonredundant autocorrelations first described by Golay. We vary both the number of subapertures and their relative spacings to arrive at an optimized array. We report the results of an experiment in which we synthesized an image from multiple subaperture pupil fields by masking a large lens with a Golay array. For this experiment we imaged a slant edge feature of an ISO12233 resolution target in order to measure the modulation transfer function. We note the contrast reduction inherent in images formed through sparse aperture arrays and demonstrate the use of a Wiener-Helstrom filter to restore contrast in our experimental images. Finally, we describe a method to synthesize images from multiple subaperture focal plane intensity images using a phase retrieval algorithm to obtain estimates of subaperture pupil fields. Experimental results from synthesizing an image of a point object from multiple subaperture images are presented, and weaknesses of the phase retrieval method for this application are discussed.

Progress in flexible and drapable reflective cholesteric displays

— Recent results from encapsulation work on the development of flexible and drapable cholesteric liquid-crystal displays (LCDs) on substrates such as thin plastics, fabrics, and even paper will be presented. The approaches used to create flexible displays using single- and dual-substrate methods based on printable emulsions and polymerization-induced phase-separation (PIPS) techniques will be discussed.

6.1: Invited Paper: Recent Progress in Color Flexible Reflective Cholesteric Displays

We report on highly flexible layered full color cholesteric displays built using ultra thin substrates with encapsulation through the phase separation approach. Recent progress of the state of the art of the cholesteric display technology will be presented as well.

Reflective cholesteric displays: From rigid to flexible

— Bistable reflective cholesteric liquid-crystal displays are low-power displays that are suitable for a variety of applications ranging from signage to high-resolution electronic books. Recent advancements have included higher brightness, full color, black and white from a single layer, and lighting solutions. Cholesteric displays also lend themselves to simple integration into flexible materials since they may be coated and printed. We have developed reflective cholesteric displays on thin flexible plastic substrates, as well as other unconventional substrates such as paper and drapable fabrics. This paper serves as a review for recent advances in the cholesteric-display technology at Kent Displays.

P‐171: A Flexible Touch‐Sensitive Writing Tablet

We present a flexible touch-sensitive writing tablet utilizing a reflective bistable cholesteric liquid crystal laminated between two conductive-polymer coated polyethylene-terephthalate substrates. The device features a selective pressure response suitable for high-resolution lines to be drawn into the screen. The device is inexpensive, conformable, and laser-cut to any desired shape.

27.4: Super High Brightness Reflective Cholesteric Display

A unique way to dramatically enhance the brightness of single layer and stacked reflective cholesteric LCDs is shown. The LC aligning surfaces are treated to provide varying degrees of homogeneity while maintaining the bistability. The result is reflective displays with exceptionally high brightness approaching that of printed paper.

6.4: Single Substrate Coatable Multicolor Cholesteric Liquid Crystal Displays

This paper describes new ultra-thin multicolor cholesteric liquid crystal displays with all functional layers coated sequentially on a single flexible substrate. Shared electrode driving is implemented for the first time to drive a passive matrix multicolor emulsion based displays comprising of three stacked layers of cholesteric droplets embedded in a polymer matrix.

Camera phasing in multi-aperture coherent imaging.

The resolution of a diffraction-limited imaging system is inversely proportional to the aperture size. Instead of using a single large aperture, multiple small apertures are used to synthesize a large aperture. Such a multi-aperture system is modular, typically more reliable and less costly. On the other hand, a multi-aperture system requires phasing sub-apertures to within a fraction of a wavelength. So far in the literature, only the piston, tip, and tilt type of inter-aperture errors have been addressed. In this paper, we present an approach to correct for rotational and translational errors as well.

Multi-aperture coherent imaging

Aperture synthesis offers the potential for high resolution images in a relatively compact system. We describe our multiaperture IMAGE testbed which uses coherent detection to measure the complex field in spatially separated apertures. We describe a post-detection optimization algorithm which is used to synthesize a composite image whose angular resolution exceeds that of a single aperture. We present experimental results in which we image extended targets at a simulated range using a compact range developed for this purpose.

4.2: Flexible Electronic Skin Display

Reflex™ electronic skin displays can be conformed to cover the case of electronic consumer devices allowing the consumer to instantaneously switch the case color electronically. These displays have inherent reflective color and an ultra thin and flexible form factor. The optical performance, environmental ruggedness, and conformability of these displays are presented.