Optical: systems and elements – Projection screen – With reflector or additional screen
Reexamination Certificate
2001-03-23
2003-02-11
Mahoney, Christopher (Department: 2851)
Optical: systems and elements
Projection screen
With reflector or additional screen
C359S443000, C359S460000, C348S789000, C348S836000
Reexamination Certificate
active
06519085
ABSTRACT:
TECHNICAL FIELD
This invention relates to video display devices and more particularly to a screen assembly holding mechanism.
BACKGROUND OF THE INVENTION
There are previously known techniques for employing arrays of cathode-ray tube (“CRT”) displays in “video walls” and signage applications. Multiscreen displays employ an abutted array of substantially identical display devices that each display a subdivided portion of a total image such that together they display the total image. Each display device typically employs a removable screen assembly comprised of a front screen and rear Fresnel lens which, in some prior multiscreen displays, are attached to the screen frame by a single mullion or bracket having a channel into which the screen assembly is held in place. A portion of the mullion extends from one edge of the front screen across a portion of the surface of the front screen. This arrangement creates an unacceptable width for each mullion of about 3 mm. Since the display devices are arranged in an abutted array the adjacent mullions form a boundary of about 6 mm between the display devices. Because multiscreen displays require that each of the display devices be perceived as part of a whole large display device, it is important to make the boundaries between adjacent display devices appear as inconspicuous as possible. Unfortunately, the human eye is very sensitive to boundary discontinuities, making an acceptably “seamless” multiscreen display very difficult to produce.
One effort to reduce the boundaries between the display devices employs the use of a single mullion to which the screen assembly is attached by a double-sided adhesive strip having a width of about {fraction (1/16)} in. While this arrangement does reduce the boundary between display devices another problem becomes apparent. The screen and the Fresnel lens may be composed of different materials. For example, the screen may be glass and the Fresnel lens may be acrylic. The screen and the Fresnel lens may be composed of the same material but in either situation certain conditions such as, for example, heat and humidity may cause the screen, Fresnel lens, or both to expand and/or contract. A problem occurs when the screen and the Fresnel lens expand or contract at different rates causing an effect known as “pillowing” which causes poor focus, ghosting, and geometric disturbances. Furthermore, such expansion and contraction may cause one of the screen and the Fresnel lens to detach from the adhesive strip.
Additionally, some glass screens may have ragged outer edges that may cut or injure anyone handling or assembling the screen assembly to the display frame.
Therefore, it is desirable to provide a screen assembly holding mechanism that reduces the boundaries between the display devices while allowing for differing expansion and contraction rates for the screen and the Fresnel lens without becoming detached from the adhesive strip and that protects against injury.
SUMMARY OF THE INVENTION
An object of this invention is, therefore, to provide a screen assembly holding device for displays arranged in an array that provides a substantially seamless boundary between the display devices.
Another object of the invention is to provide a screen assembly holding device that allows for differing expansion and contraction rates for the screen and the Fresnel lens.
A further object of the invention is to provide a screen assembly holding device that minimizes the space between the screen and the Fresnel lens and is mechanically strong.
Still another object of the invention is to provide a screen assembly holding device that includes a safety lip that covers an outer edge of the screen to protect against injury.
The present invention provides a mechanism for holding a screen assembly on a display device used in a multiscreen display employing an abutted array of substantially identical display devices so that each display subdivides a portion of a total image such that together they display the total image. The screen assembly holding mechanism provides for a substantially seamless boundary between adjacent display devices so that the total image appears substantially uninterrupted and free of boundary lines.
A plurality of display devices are arranged in an abutting arrangement so that the screen assembly of each display device forms a substantially continuous projection screen onto which an image is projected. Each screen assembly includes a screen and a Fresnel lens closely adjacent thereto. A screen assembly holding device holds the screen assembly for connection to a screen frame. The screen assembly holding device includes a double mullion arrangement in which the screen and the Fresnel lens are connected to a separate mullion. The screen is attached to a first mullion by a first adhesive strip and the Fresnel lens is attached to a second mullion by a second adhesive strip having a width that is less than the width of the first adhesive strip. The screen and the Fresnel lens are separately attached to one end of the first and second mullions, respectively. The first and second mullions are connected to the display frame by a fastener at an opposite end. Attaching the screen to the first mullion and the Fresnel lens separately to the second mullion allow for differing rates of expansion and contraction of the screen and the Fresnel lens so that neither of them become unattached from their respective adhesive strips.
In another embodiment, the first mullion is the outermost mullion and is attached to the screen. The first mullion includes a safety lip that wraps around its associated adhesive strip and covers an outer edge of the screen at the point of attachment with the adhesive strip to prevent injury from exposure to the sharp outer edge of the screen. The safety lip also holds the screen in place should it become unattached from its associated adhesive strip.
Additional objects and advantages of this invention will be apparent from the following detailed description of preferred embodiments thereof which proceeds with reference to the accompanying drawings.
REFERENCES:
patent: 5548350 (1996-08-01), Yamada et al.
patent: 5604632 (1997-02-01), Sawai
patent: 5676441 (1997-10-01), Takahashi
patent: 5818639 (1998-10-01), Furuya
patent: 6081375 (2000-06-01), Furuya et al.
Clarity Visual Systems, Inc.
Cruz Magda
Mahoney Christopher
Stoel Rives LLP
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