Projection screen apparatus

Details Projection screen apparatus Projection screen apparatus

2002-04-12

2004-09-07

Mahoney, Christopher (Department: 2851)

Optical: systems and elements

Projection screen

Unitary sheet comprising plural refracting areas

C359S457000

Reexamination Certificate

active

06788460

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to projection systems and projection screens and more particularly to an improved screen apparatus that includes a double layered screen construction.
2. Background of the Related Art
Projected light may be used to display images on large surfaces, such as large computer displays or television screens. In a front projection system, an image beam is projected from an image source onto the front side of a reflection-type, angle transforming screen, which then reflects the light toward a viewer positioned in front of the screen. In a rear projection system, the image beam is projected onto the rear side of a transmission-type, angle transforming screen and transmitted toward a viewer located in front of the screen.
Referring to
FIG. 1
, wide angle projection systems that include a screen apparatus
10
are known to optimally use a conventional Fresnel lens
11
in combination with some diffusing element, such as a substrate covered with glass beads (e.g., a type of diffuser or diffusive screen)
12
. The combination forms an imaging screen that produces an image. The Fresnel lens
11
and the diffuser assembly
12
are held in relatively rigid or semi-rigid spaced apart relation to assure proper operation of the combination. Such screens, known generally in the art as “black matrix bead” or “BMB” screens, are commercially available from Minnesota Mining & Manufacturing Company and others. Fresnel lenses used in devices such as overhead projectors and projection television are commercially available from, for example, Fresnel Optics, Minnesota Mining & Manufacturing Company, and others. The Fresnel lens
11
element is constructed to provide the optical properties of a much thicker lens, however, with smaller thickness and weight. Concentric steps or discontinuities
11
A allow these optical and physical properties to be realized. Each of the steps has a curved profile, in cross-section, that exhibits optical power to redirect incident light
13
. The cut-out sections that define the steps reduce the overall size and weight.
In
FIG. 1
, the Fresnel lens
11
receives the incoming light
13
from a projection image engine or image projector
14
(e.g., a liquid crystal display imager, a light source, and a projection lens that produce image light in response to input video or other signals). The break in the light path of the light
13
shown in
FIG. 1
is included to recognize that the light
13
may be processed or filtered, for example, projected by the projection or other lens (not shown), and is generally indicated by numeral
13
A. The screen apparatus
10
and the image engine
14
are arranged such that a light beam exiting the Fresnel lens
11
is collimated, as shown by parallel rays of light
15
. The collimated rays
15
pass across an air gap
16
to a matrix of glass beads
17
-
21
in the diffuser assembly
12
. The glass beads
17
-
21
are mounted upon an adhesive black mask layer
22
that is on a first surface
23
of a substrate
24
of the diffuser assembly
12
. As the collimated light rays
15
strike any of the glass beads
17
-
21
, the rays
15
are refracted and focused to a point as shown in FIG.
1
. The substrate
24
is light transparent so that a viewer
27
can see an image from the light
25
that passes through a surface
26
(e.g., an acrylic, polystyrene, other polymer, or like surface) of the screen apparatus
10
. The exiting rays are now wide angle transformed for wide angle viewing. The screen apparatus
10
can be an “touch screen” television screen, having a large diagonal dimension, for example, substantially 60 inches, or a computer monitor screen.
Problems have been associated with BMB-type screens that affect their manufacturing quality control. Uniformity of bead diameter has been problematic with the BMB screens of the type having beads placed directly upon a substrate. In these screens the beads are, for example, attached to the substrate by an adhesive. Some adhesives used in BMB screens define a black matrix that can have holes. These holes may allow light to pass through at improper locations. Another problem with bead placement upon a matrix is associated with packing density. Often it is difficult to insure that the beads are densely packed enough to avoid light transmission non-uniformity or image non-uniformity. The beads themselves may also suffer from diameter variations, transparency differences, and surface glare, and may include relatively large inactive portions and therefore non-useful parts.
The present invention is directed to avoid or substantially avoid some or all of the problems set forth above, as well as other problems.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
SUMMARY OF THE INVENTION
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
In general, in one aspect, embodiments of the invention feature a screen apparatus that includes a first layer for substantially collimating light, a second continuous layer positioned proximate the first layer for receiving the substantially collimated light from the first layer and for converging the received substantially collimated light, and a third layer adjacent the second layer, having a plurality of openings for receiving and altering the converging light as image light. The second layer includes an array of bead-like members.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.


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