Optical: systems and elements – Glare or unwanted light reduction – With absorption means
Reexamination Certificate
1999-10-22
2003-01-21
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Glare or unwanted light reduction
With absorption means
C359S608000, C359S613000, C359S603000, C359S884000
Reexamination Certificate
active
06510005
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention disclosure relates to an improvement of an illusion apparatus of the type which utilizes a curved screen in the nature of a partially reflective partially transparent convex mirror, in front of a television set. Such illusion apparatus is the subject of U.S. Pat. Nos. 4,971,312 and 5,681,223.
2. Discussion of Problems To Be Solved and Prior Art
The patented devices allow a television image or any optical monitor to be viewed simultaneously with the reflected image of a person viewing the television. The devices may utilize a curved screen which consists of a thin metal layer and a clear supporting layer. The thin metal layer can either be deposited directly on the supporting layer or can consist of a thin metal layer deposited on a thin plastic web which is laminated to the supporting layer. The metal layer is made thin enough so that it is partially transparent and, therefore both a transmitted image from the television screen and a reflected image of the viewer are produced simultaneously. The amount of transmission in the metal layer (determined by its thickness) allows the relative brightness of the transmitted image and the reflected image to be adjusted. The curvature of the screen allows the relative size of the reflected image to be adjusted by moving the viewer closer or farther from the screen (larger or smaller reflected image, respectively). Typically, the reflected image is thus adjusted so that its size is equal to apparent size of the transmitted television image to the viewer. The overall situation is shown in FIG.
1
.
T
0
and T
1
are the intensities of the original and transmitted television image, respectively and U
0
and R
1
are the intensities of the original and reflected viewer image, respectively. The television image is typically a person whom the viewer is attempting to visually emulate.
This original patented device has two potential difficulties which the current invention helps to eliminate or minimize. The first of these difficulties (the ghost effect) is that there is a ghost image produced of the original television image. It is due to multiple reflections of the original television image, T
0
, between the concave side of the metal layer of the curved screen and the front surface of the television tube (and possibly between the concave side of the metal layer and the concave side of the supporting layer). This ghost image is shown schematically in the diagram of FIG.
2
and is represented by T
2
. Although this image is less intense than the transmitted image, T
1
, it is still noticeable since it has a slight geometric offset from T
1
and is distorted by the curvature of the screen. At best, the net effect will be an apparent blurring of the transmitted image.
According to U.S. Pat. No. 4,971,312, the screen (mirror) should be thin to minimize secondary reflections. However, the absorbing layer will also minimize these secondary reflections so that thicker and therefore sturdier screens are possible.
The second difficulty (the heating effect) occurs when the screen is separated from the television set or monitor and the concave side of the screen is exposed to a strong (at least partially collimated) source, S
0
, of optical radiation (such as the sun). Under these conditions the screen acts as a concentrator and can produce a high intensity reduced image of the strong source which could heat an item on which it impinges (hot enough to ignite the item). This concentrated image is shown as S
1
on
FIG. 2
(it can only form in the absence of the TV set or monitor). This concentrated image will always form when the concave side of the screen is exposed to a strong collimated light source.
SUMMARY OF THE INVENTION
The present invention addresses both of these difficulties by fabricating the supporting layer with some optical absorption. The invention is applicable to all embodiments (e.g., thin metal layer deposited on the supporting layer; thin plastic web laminated to the supporting layer) of the mirrors described in the aforementioned U.S. Pat. Nos. 4,971,312 and 5,681,223, in which the ghosting or heating effects appear. For example, in the case where the reflectivity is integral to the surface of the screen, rather than due to a metal coating, the ghosting effect is still a problem which may be caused by the geometry of the screen, and thus may be solved or ameliorated by the present invention. The disclosures of these patents are incorporated herein in their entireties, by reference thereto.
The invention will now be described in greater detail and by way of specific embodiments and with the assistance of the accompanying drawings in which:
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