Optical: systems and elements – Projection screen
Reexamination Certificate
1999-06-18
2001-11-13
Mahoney, Christopher E. (Department: 2851)
Optical: systems and elements
Projection screen
C359S460000
Reexamination Certificate
active
06317263
ABSTRACT:
BACKGROUND
This invention relates generally to transmissive screens, and more particularly to transmissive screens suitable for use in rear projection systems.
Rear projection screens are generally designed to transmit an image projected onto the rear of the screen into a viewing space. The viewing space of the projection system may be relatively large (e.g., rear projection televisions), or relatively small (e.g., rear projection data monitors). The performance of a rear projection screen can be described in terms of various characteristics of the screen, which typically include gain, viewing angle, resolution, contrast, the presence of undesirable artifacts such as color and speckle, and the like. It is generally desirable to have a rear projection screen that has high resolution, high contrast and a large gain. It is also desirable that the screen spread the light over a large viewing space. Unfortunately, as is described more fully below, as one screen characteristic is improved, one or more other screen characteristics often degrade. For example, in order to increase the screen gain using the same overall structure, one must decrease the viewing angle over which the screen is readily observable. As a result, certain tradeoffs are made in screen characteristics and performance in order to produce a screen that has overall acceptable performance for the particular rear projection display application.
Thus, there remains a need for screens that have improved overall performance while meeting the minimum performance criteria necessary for the rear projection display application in which the screen is used.
SUMMARY
Generally, the present invention relates to rear projection screens that include a film layer having a plurality of lenses for diverging light horizontally and vertically. The horizontal viewing angle created by the lenses may be different from the vertical viewing angle. Furthermore, the light may be directed by the lenses in a particular direction, so that the direction of the maximum intensity light does not lie parallel to an axis normal to the screen surface.
In one embodiment of the invention, a light dispersing screen includes a first film having a first surface, a portion of the first surface defining a plurality of non-lenticular lenses. Light passing through at least one of the non-lenticular lenses is formed into an image and is asymmetrically diverged.
In another embodiment of the invention, a rear projection screen assembly includes a first layer having a first surface, a portion of the first surface defining a plurality of non-lenticular lenses. The screen also includes a symmetric light disperser optically coupled to the first surface to disperse light transmitted by the first layer. Light passing through at least one of the non-lenticular lenses is formed into an image and is asymmetrically diverged.
In another embodiment of the invention, a light dispersing screen includes a first film having light imaging and diverging means thereon for forming an image and for asymmetrically diverging light passing through the first film.
In another embodiment of the invention, a light dispersing film, includes a first film having a first surface, a portion of the first surface defining a plurality of lenses, all of the lenses having dimensions less than one twentieth of a selected dimension of the first film. Light passing through at least one of the lenses is formed into an image and is asymmetrically diverged, and the selected dimension is selected from film length and film width.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and detailed description that follow more particularly exemplify these embodiments.
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“Optical and Energy Efficiency of Signal Lights” Lewin, et al.; pp. 17-18, 20-25, Jan. 1989.
Chou Hsin-hsin
Fleming Patrick R.
Hodapp Theodore W.
Moshrefzadeh Robert S.
Nelson John C.
3M Innovative Properties Company
Mahoney Christopher E.
Miller William D.
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