Optical: systems and elements – Projection screen – Unitary sheet comprising plural refracting areas
Reexamination Certificate
2000-01-13
2003-01-07
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Projection screen
Unitary sheet comprising plural refracting areas
C359S464000, C359S619000, C348S059000
Reexamination Certificate
active
06504649
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to privacy screens and stereoscopic effects devices that use microprism sheets.
Each of the preferred embodiments of the invention has in common the transmission of light through a single microprism sheet made up of a transparent substrate in which are formed linear grooves having planar surfaces which intersect to form a v-shaped cross-section, the two sets of planar surfaces on respective sides of the grooves being selectively arranged to block or alter light transmitted through the sheet.
The microprism sheets used in the various preferred embodiments provide privacy screening and stereoscopic effects with an especially simple and low cost construction, and can easily be manufactured and/or assembled for use in a variety of applications.
The invention has three principal embodiments:
(i) The first principal embodiment relates to a privacy screen, and in particular to modification of a microprism sheet to emulate a privacy screen, to devices utilizing such privacy screen emulation arrangement, and to methods of making a privacy screen;
(ii) The second principal embodiment relates to stereoscopic image separation, and in particular to modification of a microprism sheet to separate interlaced images for the purpose of creating stereoscopic effects, to an arrangement utilizing such a stereoscopic microprism sheet, and to methods of making a stereoscopic microprism sheet;
(iii) The third principal embodiment relates to use of a microprism sheet to create interlaced images from separate sources such as a split screen, and which may be used in connection with the image separating arrangement of the second principal embodiment.
According to the first embodiment of the invention, a privacy screen is made up of a microprism transmission sheet. The microprism sheet of this embodiment is similar to the ones disclosed in U.S. Pat. No. 2,909,770 (Pugsley) and U.S. Pat. No. 4,756,603 (Ohtani) in that one of the two surfaces or facets of a microprism made up of v-shaped grooves is altered to attenuate or scatter light incident on the surface or facet, but instead of attenuating reflected light originating outside the image path, the modified microprism sheet of this embodiment of the invention attenuates or scatters light that would normally be within the optical path from the image source to a viewer situated in front of the microprism sheet, thereby providing a louvre or privacy screen effect.
According to the second embodiment of the invention, instead of preventing transmission of light through one of the surfaces or facets of an otherwise conventional microprism sheet, each of the two surfaces or facets of a microprism sheet made up of v-shaped grooves is modified to polarize light in an opposite direction. When the image source is an interlaced image, the oppositely polarized light may be recombined by corresponding polarized lenses to provide a stereoscopic effect. When a microprism sheet having a groove pitch corresponding to the pitch of the interlaced images is positioned over the interlaced images, the different sections of the interlaced image will be transmitted in different directions and oppositely polarized so that each lens will see a different channel for an enhanced three dimensional image.
According to the third embodiment of the invention, instead of altering the properties of light transmitted through the respective surfaces or facets of a microprism sheet made up of v-shaped grooves, the angles of the surfaces or facets on different portions of the microprism sheet are arranged so as to interlace separate images. This eliminates the need to interlace images during production, allowing the different portions of the image to be separately stored or transmitted and interlaced at the viewing end. Separation of the images for stereoscopic viewing can be in a conventional fashion using colored glasses or by means of the arrangement of the second principal embodiment of the invention.
2. Description of Related Art
Microprism sheets in the form of molded substrates with small prisms embedded within the material are well-known. The present invention involves various modifications or re-arrangements of a particular type of known microprism sheet in which a clear plastic material is formed with linear grooves, each having a v-shaped cross-section. Unlike prior devices involving multiple layers of microprism sheets, or microprism sheets combined with structures such as emicrolenses or light guides, each of the embodiments of the present invention utilizes a single microprism sheet, which may take the form of an overlay for a computer monitor or television, or which may be formed as an integral part of the monitor or television screen.
The prior art generally falls into one of two categories: (i) microprism sheets and devices using microprism sheets in which an image is uniformly transmitted through the microprism sheet, each facet of the microprism having identical light transmission properties and the facets being arranged in a uniform fashion across the sheet; and (ii) microprism sheets and devices utilizing microprism sheets in which one of the surfaces or facets of the microprisms in the sheet is altered in such a way as to reduce glare or reflections without affecting transmission of an image through the sheet.
The first category of prior art provides technical background concerning the materials and formation of microprism sheets and the manner in which light is transmitted through the sheets. Except as noted below, the materials and geometry of the sheets used in the preferred embodiments of the invention can easily be selected by those skilled in the art based on the principles disclosed in these patents, once the overall concepts of privacy screen emulation and image separation or interlacing are understood.
Examples of patents directed to microprism sheets in general, and to devices using microprism sheets, include the following: U.S. Pat. No. 5,836,096 (Brauer), U.S. Pat. No. 5,446,594 (Nelson et al.), U.S. Pat. No. 5,363,237 (Wakatake), U.S. Pat. No. 5,316,359 (Lansinger), U.S. Pat. No. 5,208,620 (Mitsutake et al.), U.S. Pat. No. 4,708,435 (Yata et al.) , U.S. Pat. No. 4,309,074 (Granieri), U.S. Pat. No. 4,309,073 (Nishimura et al.), U.S. Pat. No. 3,902,787 (Sherlock), and U.S. Pat. No. 4,206,969 (Cobb et al.) Each of these patents discloses transmission or projection devices that utilize microprism or Fresnel structures for the purpose of glare reduction or optimizing light transmission at all potential viewing angles. Also of general background interest is the transmission screen disclosed in U.S. Pat. No. 5,317,405, which uses Fresnel microprism structures to transmit an image from a television while at the same time reflecting an image of the viewer to a camera, and U.S. Pat. Nos. 5,835,661, 5,926, 601, and 5,359,691, all to Tai et al., which relate to light guide structures using microprisms. None of these patents discloses alteration of selected facets or surfaces in different intersecting planes to emulate a privacy screen or separate images according to the principles of the first and second embodiments of the present invention, or the arrangement of the planes to interlace images according to the principles of the third embodiment of the present invention.
U.S. Pat. No. 5,512,219 is of interest for its general disclosure of methods of making microprism sheets by casting, while U.S. Pat. No. 3,718,078 (Plummer) is of interest for its description of the use of acid etching for the purpose of creating light diffusing surfaces for non-glare glass and for focusing screens for cameras (“focusing screens” are reflective surfaces used in cameras as disclosed in U.S. Pat. No. 3,971,051 (Ruhle)). In addition, U.S. Pat. No. 5,837,346 is of interest for its description of methods of making “bulk diffusion screens,” which may configured for collimation “after the fashion of Fresnel lenses” and in which surface relief features may be formed by hot or cold embossing, by casting, or in any other w
Bacon & Thomas
Fineman Lee
Myers Kenneth J.
Spyrou Cassandra
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