Optical: systems and elements – Projection screen – Unitary sheet comprising plural refracting areas
Patent
1998-05-18
1999-08-03
Metjahic, Safet
Optical: systems and elements
Projection screen
Unitary sheet comprising plural refracting areas
G03B 2160
Patent
active
059332760
ABSTRACT:
There is disclosed a partially transparent, directional viewing sheet formed of plastic material with convex and concave lenses of elliptical cross-section, preferably lenticular lenses, formed respectively on the front and back surfaces of the sheet, there being intervening spaces with convex surfaces between the concave lenses which spaces are not transparent to images and may be imprinted with an image that is viewable through the sheet from some directions. Preferably the concave lens focal length is typically about one-half of the focal length of the convex lens. Elliptical cross-section of the lenses minimizes spherical aberration and sharpens the focus. The thickness of the sheet causes focal points of the lenses to substantially coincide producing the effect of a tiny Galilean telescope. The view through such a sheet in a direction substantially aligned with the optical axis of the tiny telescope is a minimally distorted view of objects distant from or near to the opposite side of the sheet while off-axis viewing will present the image imprinted on the intervening convex surfaces between the concave lenses on the back surface of the sheet. Such convex surfaces are preferred over flat surfaces for high speed printing in offset printing presses.
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Board of Trustees, University of Arkansas, N.A.
Keegan Robert R.
Mahoney Christopher E.
Metjahic Safet
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