Electric lamp and discharge devices – Cathode ray tube – Screen
Reexamination Certificate
1999-05-25
2001-12-04
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Screen
C313S462000, C313S471000, C359S290000, C359S291000, C359S614000, C359S609000, C359S015000
Reexamination Certificate
active
06326723
ABSTRACT:
BACKGROUND
This invention relates generally to screens for displays including screens over direct view displays and screens upon which an image is projected in projection displays.
Displays are commonly used to show an image which has been electronically generated. Displays are found in televisions receivers, computer monitors and projection display systems, processor-based appliances, toys and games and in a variety of hand-held devices including personal digital assistants, telephones, and the like. These displays may generally be divided into direct view displays, in which an image is viewed directly by the user, and projection displays, in which the image may be projected onto a larger surface so that a larger image results which is more readily viewable by one or more viewers. Projection displays may include those that use reflective techniques and those that use transmissive techniques for generating the projected image. In each case, a screen ultimately provides the image for view by the user.
Display screens are subject to a number of shortcomings. Commonly, the display screen may produce glare as a result of the reflection of ambient light from flare and ghosting. In addition, displays may be subject to graininess wherein the particles forming the display screen or the imaging device itself create pixel boundaries which are readily viewable by the user. Some displays are subject to a defect called pixellation where the graininess of the imaging device is visible to the user.
In addition, some displays, including those that are using coherent light sources, may be more susceptible to interference effects resulting in speckle. Speckle is a plurality of point light images which come from the display and may move when the user moves with respect to the display. To some degree, speckle artifacts may be enhanced by the graininess of the imaging device or the display screen.
Some displays may have limited fields of view so that the viewing angle may be restricted. If the user moves beyond the viewing angle of the display, contrast reversal may result.
It is known to use a diffuser over display screens to improve the viewing angle and to overcome the graininess of the image that is viewed. For example, some display screens use a diffuser in combination with a Fresnel lens to overcome these effects. However, such systems do little to overcome the effects of ambient light on the display and the glare that may result. In addition, many of the techniques for overcoming graininess and speckle are less than completely effective.
More recently, rear projection television screens have been based on a laminate structure combining lenticular and Fresnel optical elements that may achieve increased brightness uniformity, increased image brightness in a preferred viewing cone and reduced glare. A Fresnel lens forms an image of the projection lens aperture in the middle of the viewing area which is typically a small region. This small region is enlarged by adding a weak diffuser which expands the viewing area along the vertical direction. A lenticular array stretches the viewing area along the horizontal dimension. A holographic diffuser can replace a conventional diffuser and a lenticular array.
While existing designs may provide adequate gain, brightness and contrast, they may not provide adequate ambient light rejection due to back reflection from the screen. In some cases, speckle may be a problem due to the finite grain size on the diffusing screen, which may be a particularly severe problem under coherent illumination.
Thus, there is a continuing need for techniques which provide adequate gain, brightness and contrast while improving the ambient light rejection and, in some applications, reducing speckle.
SUMMARY
In accordance with one aspect of the present invention, a display screen includes a support structure. A moth-eye pattern of light absorbing elements is formed on the support structure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic depiction of one embodiment in accordance with the present invention;
FIG. 2
is a schematic depiction of a projection display in accordance with one embodiment of the present invention;
FIG. 3
is a schematic depiction of a direct view display in accordance with one embodiment of the present invention;
FIG. 4
is a perspective view of the embodiment shown in
FIG. 1
;
FIG. 5
is an enlarged perspective view of a portion of the display screen shown in
FIG. 2
showing how ambient light is rejected by the display screen in one embodiment of the present invention; and
FIG. 6
is an enlarged perspective view of moth-eye like element useful in another embodiment of the present invention.
REFERENCES:
patent: 4252865 (1981-02-01), Gilbert et al.
patent: 4634223 (1987-01-01), Ishii
patent: 4802737 (1989-02-01), Denton
patent: 4944986 (1990-07-01), Zuel
patent: 5142385 (1992-08-01), Anderson et al.
patent: 5212596 (1993-05-01), Andrus
patent: 5817396 (1998-10-01), Perlo et al.
patent: 5861990 (1999-01-01), Tedesco
Booth, Jr. Lawrence A.
Raj Kannan
Intel Corporation
Patel Ashok
Trop Pruner & Hu P.C.
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