Design of a polarized head-mounted projection display using FLCOS microdisplays

Abstract

Head-mounted projection display (HMPD) technology, as an alternative to conventional head mounted displays (HMD), offers the potential of designing wide field-of-view (FOV) optical see-through HMDs. Due to multiple passes through a beamsplitter, however, existing HMPD designs suffer from low luminance efficiency and thus the displayed image is lack of brightness and contrast. The design of a polarized head-mounted projection display (p-HMPD) was recently proposed. The major departure of a p-HMPD design from other existing HMPD systems is the usage of polarization management to minimize light loss through beamsplitting. A p-HMPD consists of a pair of projections lenses, microdisplays, polarization control elements, and retroreflective sheeting material as a projection screen. In this paper, we explore the usage of a ferroelectric liquid-crystal-on-silicon (FLCOS) microdisplay as the image source and present a compact design of an illumination unit with double telecentric optics to achieve highly bright and uniform illumination on the FLCOS microdisplay. The key contribution of this design lies in the compactness which is a critical factor in HMD systems. The first-order optics and the transformation of polarization in the design will be described in detail. The simulation of the illumination unit will be shown and its luminous efficiency and uniformity will be discussed. Based on this illumination engine, we will further describe the design of a compact projection lens and discuss the overall performance of the optics.

A new class of bookshelf bistable siloxane modified ferroelectric LC materials with electrical repairability in an LCoS configuration

“…In these intensity modulation applications, the optimum tilt angle of the liquid crystal is 22.5°and the phase shift required in the liquid-crystal modulator is π. These requirements are compatible with high switching speeds, which may be measured in tens of microseconds 8 at the voltages that are available from silicon backplanes.…”

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“…Table 1 shows some characteristics of microdisplays. 20,21 Liquid-crystal technology makes it possible to form an image with fairly good resolution. However, as can be seen from Table 1, liquid-crystal microdisplays are mainly distinguished by a setup for organizing the lighting and response rate and for providing contrast.…”

“…Moreover, the operating time of such systems is short by comparison with other systems. 4,21 Active-matrix LCDs (AMLCDs) 22 and liquid crystal on silicon (LCOS) displays [19][20][21] are also used.…”

“…A feature of such systems is that they require a supplementary lighting system-i.e., such microdisplays are nonself-illuminating. 19,20 The lighting of such displays is usually organized around an illumination system that uses a supplementary prism-cube with a beamsplitter face. One more distinguishing feature of such systems is the fact that they operate with polarized radiation.…”

“…This makes it possible to increase the efficiency with which the light flux is used in the system by employing a rationally organized lighting and image-forming system. 20 The objectives of projection information-display systems are reproduction objectives of fairly complex design, which provide the necessary scale of the symbols in the space in front of the observer-for example, on the windshield.…”