Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
1999-11-18
2001-03-20
Mack, Ricky (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
C359S637000, C359S640000
Reexamination Certificate
active
06204975
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
FIELD OF THE INVENTION
The present invention relates to reflective display systems and more particularly to such systems having a reflective micro-display that requires light perpendicular to the surface of the display to generate an image.
BACKGROUND OF THE INVENTION
Miniature or micro-displays are known which are so small that they generate an image that the eye cannot resolve without the aid of magnification optics. These micro-displays have a sufficiently large number of pixels to generate an image of alpha-numeric information such as is capable of being generated on a standard size computer CRT display. One type of micro-display is shown in U.S. Pat. No. 5,771,124. This patent shows a reflective display system that is responsive to non-perpendicular light that impinges on the display at a particular angle in order to generate an image. A beam splitter, reflective magnifying lens and a second magnifying lens are used to direct light from the display to a user's eye so that an enlarged virtual image of the display generated image can be discerned.
Another known type of reflective micro-display requires on-axis light to generate an image. On-axis light as used herein is light that is generally or substantially perpendicular to the surface of the display. In this type of reflective micro-display, pixels in an in-active mode absorb light and pixels in an active mode reflect on-axis light so as to generate an image. In known reflective micro-displays of this type, multiple beam splitters having a partially reflective coating have been used to reflect light from an off-axis light source to the display surface. Multiple beam splitters of this type, however, greatly reduce the light throughput of the system and the resulting brightness of the image generated so that the image is difficult to discern.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, the disadvantages of prior reflective display systems requiring on-axis light have been overcome. The display system of the present invention has a miniature display and a minimal number of optics to provide a virtual image with enhanced brightness and a large field of view, heretofore not realized with such a small display system.
More particularly, the display system of the present invention includes a reflective display having a plurality of pixels, each of which in an active mode is responsive to on-axis light that is generally perpendicular to the surface of the display for reflecting the on-axis light to generate an image. A light source is positioned off-axis with respect to the display so as not to block any portion of the image generated by the reflective display. An illumination system with a single beam splitter is provided to direct the light from the light source to the display. The illumination system includes a prism with a first surface for reflecting light from the light source to the beam splitter surface. The beam splitter surface in turn reflects light from the first prism surface to the reflective display so that the light is generally perpendicular to the surface of the display to generate an image. The beam splitter passes therethrough light reflected from the display to an imaging optical system. The imaging optical system receives light passed through the beam splitter from the display for providing an enlarged virtual image, viewable by a user.
In one embodiment of the present invention, the prism uses total internal reflection for reflecting light from the first prism surface to the beam splitter surface and/or for reflecting light from the beam splitter surface to the reflective display. Because total internal reflection is used to form the beam splitter surface, little light is lost at this surface and the brightness of the image is greatly enhanced.
In another embodiment of the present invention, the illumination system includes a polarizer for polarizing the light from the light source that is directed to the first prism surface. The prism may use total internal reflection for reflecting light from the first prism surface to the beam splitter surface and/or for reflecting light from the beam splitter surface to the reflective display.
In a further embodiment of the present invention, the beam splitter surface is formed of a second polarizer that reflects light of a first polarization received from the first prism surface and that passes therethrough light of a second polarization received from the display. The first prism surface may use total internal reflection or a reflective coating to reflect the light from the light source to the beam splitter surface. The use of one or more polarizers allows greater light throughput than in prior systems to increase the brightness of the image.
The imaging optics of the present invention provide a virtual image with a large field of view that is 28° or greater and even on the order of 38° for a reflective, micro-display.
The display system of the present invention is extremely small having a height on the order of 25 mm but provides a bright image with a large field of view. The display system of the present invention is capable of displaying large amounts of alpha-numeric information such as typically displayed on a standard size computer CRT display. However, because of the display system's small size it is a suitable display for portable or hand-held computer and/or communication devices such as a pager or other messaging system. It is also suitable for use in a head mounted display system. The display system of the present invention substantially increases the amount of information that can be displayed to a user in an extremely small package with minimum optical elements.
These and other advantages and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings.
REFERENCES:
patent: 5696521 (1997-12-01), Robinson et al.
patent: 5771124 (1998-06-01), Kintz et al.
patent: 5886822 (1999-03-01), Spitzer
patent: 5892624 (1999-04-01), Kintz et al.
Heacock Gregory L.
Hudyma Russell M.
Watters Wayde
Mack Ricky
McAndrews Held & Malloy Ltd.
Virtual Vision, Inc.
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