Optical: systems and elements – Projection screen – Border – mask – shade – or curtain
Reexamination Certificate
1997-04-21
2001-04-17
Adams, Russell (Department: 2851)
Optical: systems and elements
Projection screen
Border, mask, shade, or curtain
C359S460000, C353S075000
Reexamination Certificate
active
06219183
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a rear projection display with variable image size, such as a liquid crystal projection display, and more particularly, to a compact rear projection display having an extendable telescopic screen and folding mirrors to reduce a dimension thereof.
2. Discussion of the Prior Art
Portable computers and high definition television sets require high quality displays, such as liquid crystal displays and projections displays. The main advantage of a projection display, besides its resolution, is that it can be lightweight and slim compared to a cathode ray tube (CRT) display.
In conventional compact projection displays, the size of the display monitor is reduced by folding the optical path from the projection lens to the screen using plane mirrors. In addition, a wide-angle projection lens is typically used to minimize the lens to screen distance.
Although conventional compact projection displays are of fixed image size and are useful for viewing by a limited audience, they are not suitable for viewing by a large audience in large rooms. Accordingly, there is a need for a versatile rear projection display that is compact, yet is suitable for large rooms and audiences.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a display that eliminates the problems of conventional displays.
Another object of the present invention is to provide a display that is compact, light weight, and easily transportable, yet is suitable for large audiences and large rooms.
Yet another object of the present invention is to provide a display that has a telescopic screen to change the image size.
A further object of the present invention is to provide a display that projects a small image suitable for a small room and limited audience, and projects a large image suitable for a large room and audience.
These and other objects of the present invention are achieved by a display comprising a projection device for projecting an image; a screen for displaying the image; and a screen moving device which moves the screen in relation to the projection device.
The screen moving device comprises a first frame attached to the screen and a second frame. The first and second frames telescopically move to extend and retract the screen.
The display further comprises a display box that contains the projection device. The screen is substantially flush with the display box in a retracted position, and is extended away from the display box in an extended position.
As the screen moves away from the projection device, the image increases in size. Conversely, as the screen moves towards the projection device, the image size decreases.
The projection device includes a projection lens for projecting the image. Illustratively, the projection lens is a fixed focal length lens. The projection device also has a first reflective surface for receiving the projected image and reflecting a first reflected image; and a second reflective surface for receiving the first reflected image and reflecting a second reflected image, having a central optical axis, onto the screen. The central optical axis is parallel to the screen moving device.
The first and second reflective surfaces provide a folded projection path to reduce a dimension of the display. Illustratively, the first and second reflective surfaces are folding mirrors, where the second mirror is larger than the first mirror.
The screen moving device has an opening to allow movement of the screen toward the projection device without interfering therewith. A flexible light blocking material covers the opening.
The inventive display has a variable screen image size capability, which variable image size function is nearly impossible to achieve for conventional rear CRT projectors. This is because of the difficulty in rear CRT projectors to converge three light sources (e.g., red, green and blue sources) on a movable screen.
The inventive display has a very compact retracted size, is easily transportable, and fits through narrow doorways. In addition to being suitable for a small room and limited audience in the retracted mode, where the viewing image is small, the inventive display screen extends to provide a large viewing image suitable for a large room and a large audience.
Providing a large image size by extending the telescoping screen allows use of folding mirrors that are smaller than those used in conventional fixed screen displays having the same image size. Furthermore, the inventive display is light weight as compared to a CRT rear projection display having a similar screen size.
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Adams Russell
International Business Machines - Corporation
Mahoney Christopher
Scully Scott Murphy & Presser
Underweiser, Esq. Marian
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