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Hemispherical Display Uses Single Lens and Digital Projector

Photonics Spectra
Nov 2003
Brent D. Johnson

Delivering realistic graphical information to the retina has been a challenge for information display technology. Elumens Corp. of Durham, N.C., hopes that its immersive hemispherical digital projection system addresses this challenge and offers a display solution for a variety of fields, from corporate design and military simulation to education and entertainment.

appsDisplay1.jpg
VisionStation, an immersive hemispherical digital projection system, uses a patented single-lens design to produce images suitable for applications in a variety of fields, such as military simulation (top) and commercial training (bottom).

Display manufacturers have adopted various strategies to simulate the visual sensation of an authentic environment, but each approach has had its limitations as well as benefits. Wearable displays, for example, block extraneous information and have high contrast levels, but users may suffer from vertigo or motion sickness as a result of the discontinuity between their visual and vestibular systems. As a result, large immersive displays continue to be relevant despite their own problems.

Many such dome projection systems employ multiple projectors to generate a realistic visual environment. These systems, however, can lack uniformity across the image, and the pixels may stretch at the outer edge of the display. Immersing the subject in the image requires a very large image with uniformly good resolution.

Elumens' new system, the VisionStation, uses one digital projector and a patented single-lens design that resolves the problem of pixel stretching by projecting constant angular separation of the projected pixels from the lens with respect to the dome surface. This enables a more realistic viewing experience. For example, while a flat screen allows a field of view of only 60° to 90°, VisionStation puts the face of the viewer into the hemispherical viewing screen, enabling a 180° field of view. The field-deployable system was used by the US military in Operation Iraqi Freedom for strategic mission rehearsal.

The company's lens for digital projectors is the key to VisionStation, which is available with liquid crystal display, digital-micromirror-device or liquid-crystal-on-silicon projector options and with resolutions ranging from 1024 to 1280 pixels across the projected diameter. Ray Idaszak, chief technology officer at Elumens, said that when the company began the project in 1992, no one was making projection systems dedicated to digital technology. There were a number of iterations of the lens, and it took several years to develop a commercially viable product.

Kenneth J. Barber Jr. of Edmund Industrial Optics in Barrington, N.J., explained that making Elumens' prototype into a cost-efficient projector lens involved reducing the lens design's sensitivity to close tolerances and changing the mechanical interface between the lens and the projector from InFocus Corp. of Wilsonville, Ore. By adjusting these criteria, inexpensive glass could be used in the final design without sacrificing performance.


GLOSSARY
retina
1. The photosensitive membrane on the inside of the human eye. 2. A scanning mechanism in optical character generation.
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