LIGHT-DIFFUSING PANEL AND WINDOW SHADE USING SAME

Abstract: A light-diffusing panel (10) includes a sheet (12) of transparent material and a plurality of elongated members (14) on a surface of the sheet (12). The members (14) are circular or semicircular in cross section, and are arranged side-by-side such that their longitidunal axes (L) are parallel to one another. Light incident on a surface of the sheet (12) is diffused along the sheet in a direction (D) normal to the longitudinal axes (L). A median of diffusion (M) remains relatively constant despite changes in the angle of incidence of the light on the sheet (12). The light-diffusing panel (12) can be utilized in a window shade or shutter, or it can be adhered directly to a window.

Description: LIGHT-DIFFUSING PANEL AND WINDOW SHADE USING SAME FIELD OF THE INVENTION The present invention relates in general to optical transmission media and in particular to a structure for diffusing light. BACKGROUND OF THE INVENTION It is very desirable to have a room with a window. In an office, a window is a symbol of status. It also provides a link to the outside world. In a house, the window allows sunlight to enter and brighten a room. The window is not always desirable, however, especially when intense rays of sunlight are streaming into the room. Looking out a clear window, directly into the incoming rays, can hurt one's eyes. Looking out through a dirty window is no better, as particles of dust and dirt cause the light to scatter randomly and create a blinding light. Sitting directly in the path of the intense rays can be discomforting to the skin and can even result in sunburn. To combat these problems, windows are outfitted with blinds, curtains and shades made of opaque materials. When opened, the blinds, curtains and shades allow a clear view outside the window. When the blinds, curtains and shades are closed, however, the direct sunlight is blocked. Although the direct rays are no longer bothersome, the room looses the benefits of sunshine: good lighting and natural heating. It is an objective of the present invention to provide a panel that diffuses light. It is a further objective to apply such a panel to a window. SUMMARY OF THE INVENTION A panel for diffusing light comprises a plurality of elongated members. Each member has a longitudinal axis and a cross-sectional shape that is at least partially circular. The panel further comprises means for securing the members together such that the longitudinal axes of the members lie in a substantially single plane and are substantially parallel to one another. Light incident to a surface of the panel is -diffused along the plane in a direction normal to the longitudinal axes. The amount of diffusion can be controlled by varying the cross-sectional size and shape of the elongated members. Deeper cross-sections result in greater diffusion. The members can be semi-circular, circular or elliptical in cross-section. The panel can be adapted to transmit light or reflect light. The securing means can include a thin sheet, thread or bands. Window shades and blinds can be formed from a single panel or from a plurality of panels. If a plurality of panels is used, the shade could be provided with sections of differing diffusion. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a panel according to one embodiment of the present invention; Figure 2 is a schematic representation of light being diffused by a light-transmissive panel; Figure 3 is a schematic representation of light being diffused by a light-reflective panel; Figures 4-9 are perspective views of alternative embodiments of panels according to the present invention; Figure 10 is a schematic representation of a window shade made of the light-diffusing panels; Figure 11 is a schematic representation of a light being diffused by the window shade shown in Figure 10; Figure 12 is a schematic representation of a shutter using the light-diffusing panels; and Figure 13 is schematic representation of a thin film of the light-diffusing panel adhered to a window. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows a panel 10 including a sheet 12 and a plurality of elongated ribs 14 located on one surface of the sheet 12. Each rib 14 is semicircular in cross-section and has a substantially smooth outer surface. The ribs 14 are arranged side-by-side, in a single row with their longitudinal axes L being parallel to one another. Resulting from this arrangement is a series of parallel striations on the ribbed surface of the sheet 12. The sheet 12 and ribs 14 are made of a transparent or translucent material. The material can be a polymer, such as Polymethyl Meta Acrylate ("PMMA") , polyester, polyvinyl chloride, polyethylene, or polycarbonate. In the alternative, the material could be a glass or crystal. The sheet 12 and ribs 14 could be made either flexible or rigid. When light impinges the panel 10, it is diffused in a direction along the sheet 12 and normal to the longitudinal axes L of the ribs 14. This direction is hereinafter referred to as the "diffusion axis D." The light can impinge either the ribbed surface of the sheet 12 or the surface that is not ribbed. Either way, the impinging light will be diffused along the diffusion axis D. The only difference is that the ribbed surface of the sheet 12 will reflect less light than the surface that is not ribbed. Figure 2 shows a panel 10 adapted to transmit light. Looking down at the top of the panel 10, two chief rays II (in solid lines) and 12 (in dashed lines) are seen striking the sheet 12 at different angles of incidence. Both chief rays II and 12 are transmitted by the sheet 12 and diffused along the diffusion axis D. The transmitted rays Til and T12 corresponding to the incident chief ray II have a median of diffusion Ml, and the transmitted rays T21 and T22 corresponding to the incident chief ray 12 have a different median of diffusion M2. It can be seen that the medians Ml and M2 are nearly coincident, even though their chief rays II and 12 have different angles of incidence. Moreover, both medians Ml and M2 are substantially perpendicular to the diffusion axis D. The transmitted rays Til and T22 define an angle known as the "diffusion angle." The diffusion angle provides a measure of the ability of the panel 10 to disperse light. Figure 3 shows a panel 10 adapted to reflect light. The ribbed surface or the unribbed surface of -the sheet 12 can be coated with a reflective material such as aluminum, by evaporation, sputtering or any other suitable means. Chief rays II and 12 are reflected off the surface and diffused along the diffusion axis D. As can be seen, the medians of diffusion Ml and M2 for the chief rays II and 12 are both substantially coincident and normal to the surface of the sheet 12. The panel 10 can be made by an embossing process. For example, a panel 10 was made by placing a sheet 12 in a mold and pressing the sheet 12 until the ribs 14 were formed. The sheet 12 had a thickness T of 1.7 mm, and the ribs 14 had a uniformly semi-circular cross- section, with a radius of 0.3 mm. The panel 10 had a light transmissibility of greater than 80% and a diffusion angle of approximately 160 degrees. Figure 4 shows another embodiment of a panel 110 according to the present invention. The panel 110 is made by embossing elongated ribs 114a and 114b on both surfaces of a sheet 112. The longitudinal axes La and Lb of the ribs 114a and 114b on both sides of the sheet 112 are parallel to one another and extend in the same direction. The extra ribs 114b serve to increase the amount of diffusion provided by the panel 110. In the panel 210 shown in Figure 5, ribs 214a and 214b are embossed on both surfaces of the sheet 212, with their longitudinal axes La and Lb lying in the same plane. However, the longitudinal axes La of the ribs 214a on one surface are orthogonal to the longitudinal axes Lb of the ribs 214b on the other surface. Crossing the longitudinal axes La and Lb causes a further increase in the amount of diffusion, which should eliminate any glare produced by the other panels 10 and 110. Figure 6 shows yet another embodiment of a panel 310. The panel 310 includes a thin sheet 312 that is substantially planar and a single row of monofilament fibers 314 adhered to one surface of the sheet 312. The fibers 314 are substantially straight, with their longitudinal axes L lying in the same plane and being substantially parallel to one another. The monofilament fibers 314 can be made fishing line having a diameter of 0.14 mm. A panel 310 was made with monofilament fibers having a 0.14 and a sheet 312 having a thickness of 3 mm. The diffusion angle was approximately 160 degrees and transmissibility was over 80%. Figure 7 shows a panel 410, again with the monofilament fibers 414 in a single row, but without a sheet. Instead, cloth strips 412 are used to hold the ends of the fibers 414 together. A rectangular panel 410, ten centimeters long and five centimes wide, was made of fishing wire having a diameter of 0.14 mm. Figure 8 shows yet another embodiment of a panel 510. The panel 510 includes a bundle of monofilament fibers 514 arranged in multiple rows. The fibers 514 can be held together by means such as thread or cloth (not shown) . Multiple rows of fibers 514 have been found to provide a more stable median of diffusion than single rows of fibers. That is, the median of diffusion of multiple rows of fibers tend to move less in response to changes in the incident angle. Figure 9 shows yet another embodiment of a panel 610. Sections of monofilament fibers 614 are interwoven with cross-threads 612 running in a cross direction. Each section contains a single row of between fifty and one hundred fibers 614. The monofilament fibers 614 can be made of fishing line. The cross-threads 612 can be made of fishing line or any other material. Since the cross-threads 612 occupy such a small area of the panel 610, they could even be made of an opaque material. In view of the different embodiments above, it can be appreciated that the amount of diffusion can be -controlled by changing the cross-sectional size and shape of the members, and adding extra rows of members. For example, the cross-section of the members 314 in panel 310 are larger than the cross-section of the members 14 in panel 10 (assuming that the radii of the members are equal) ; therefore, panel 10 has a shallower depth than panel 310 and provides less diffusion than the panel 310. Panel 210 contains a greater number of rows of members 214 than panel 10; therefore, panel 210 provides greater diffusion than panel 10. As another example, where the members have a cross-section defined by a sector of a circle, the amount of diffusion increases as a predetermined function of a central angle of the sector. The central angle is selected to provided the desired amount of diffusion. For example, a central angle of 270° will provide more diffusion than a central angle of 180°. Figures 10 and 11 show a shade 750 for a window 760. 'The shade 750 includes ten panels 710a-710j, each panel being of a construction similar to the panel 10 shown in Figure 1. The panels 710a-710j can be sewn together or adhered to a thin transparent backing. The shade 750 panel has three separate axes of diffusion Dl, D2 and D3. The bottom panels 710f-710j have a vertical axis of diffusion D3, two of the panels 710b and 710d have a positive-sloped axis of diffusion D2, and the remaining three panels 710a, 710c and 710e have a negative-slope axis of diffusion Dl. The axes Dl, D2 and D3 can be selected to handle different angles of incident light. For example, morning sunlight could be diffused along one axis D2 and afternoon sunlight could be diffused along another axis Dl, while all light would be diffused along axis D3. In the alternative, different panels 710a-710j could have different numbers of rows and members of different cross-section shapes. In this way, diffusion could be controlled such that light can be redirected by the different panels into different sections of a room 770. In alternative embodiments, the shade 750 could utilize panels that are similar construction to any of the other panels 110, 210, 310, 410, 510, and 610. If the reduction of glare is important, the shade could use a single panel 210 or a pair of any of the other panels 10, 110, 310, 410, 510 and 610. If a pair of panels is used, one panel would be mounted to one surface of the backing material, and the other panel would be mounted to the other surface of the backing material, but with the its ribs or fibers orthogonal to the ribs or fibers on the other side of the backing material. Instead of a using the panels to form a shade 750, the panels could be used to form Venetian blinds or shutters 850 as shown in Figure 12. The vertical or horizontal slats would be formed from the panels 10, 110, 210, 310, 410, 510 or 610. In the alternative, the light diffusing panel 10, 110, 210, 310, 410, 510 or 610 could be formed as a thin film 910 that is adhered directly to the front and/or back surface of a window 960. This is shown in Figure 13. While many illustrative embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art, without departing from the spirit and scope of the invention. For example, the ribs could be semi-elliptical in cross-section instead of semicircular, and the monofilament fibers could be elliptical in cross-section instead of circular. Accordingly, it is intended that the present invention not be limited solely to the specifically described illustrative embodiments. Various modifications are contemplated and can be made without departing from the spirit and scope of the invention as defined by the appended claims.

Claims: What is claimed is: 1. A panel for diffusing light, comprising: a plurality of elongated members, each member having a longitudinal axis and a cross-sectional shape that is at least partially circular; and means for securing the members together such that the longitudinal axes of the members lie in a substantially single plane and are substantially parallel to one another, whereby light incident to a surface of the panel is diffused along the plane in a direction normal to the longitudinal axes. 2. The panel of claim 1, wherein the members have a semi-circular shape in cross-section. 3. The panel of claim 1, wherein the members have a circular shape in cross-section. 4. The panel of claim 1, wherein the members have an elliptical shape in cross-section. 5. The panel of claim 1, wherein: the members have a cross-section defined by a sector of a circle; an amount of diffusion increases as a predetermined function of a central angle of said sector; and said central angle is selected to provide a desired amount of diffusion. 6. The panel of claim 1, wherein the members define a light-receiving surface, and wherein the light receiving surface is coated with a light-reflective material. 7. The panel of claim 1, wherein the securing means includes a sheet having a surface for carrying the plurality of members, each member of said plurality having a semi-circular shape in cross-section. 8. The panel of claim 7, wherein the panel includes second plurality of members on another surface of the sheet, each member of said plurality having a semi-circular shape in cross-section, the members of said second plurality having longitudinal axes that lie in a substantially single plane and that are substantially parallel to one another, the longitudinal axes of the first plurality being parallel to the longitudinal axes of the second plurality. 9. The panel of claim 7, wherein the panel includes a second plurality of members on another surface of the sheet, each member of said plurality having a semi-circular shape in cross-section, the members of said second plurality having longitudinal axes that lie in a substantially single plane and that are substantially parallel to one another, the longitudinal axes of the first plurality crossing the longitudinal axes of the second plurality. 10. The panel of claim 9, wherein the members of said plurality and said second plurality are woven together to form a textile. 11. The panel of claim 1, wherein the securing means includes a sheet having a first surface for carrying the plurality of members, and wherein each member of said plurality has a circular shape in cross- section. 12. The panel of claim 1, wherein each member of said plurality has a circular shape in cross-section, and wherein the securing means includes first and second bands for securing the fibers together at their first and second ends. 13. The panel of claim 1, wherein the plurality of members are stacked together to form a plurality of rows. 14. The panel of claim 1, wherein the securing means include a plurality of monofilament threads, wherein the plurality of members are organized into sections, and wherein the sections are woven together with the threads to form a textile. 15. A cover for a window, comprising: a sheet of light-transmissive material sized to cover the window; and a plurality of elongated members arranged side-by- side on at least one surface of the sheet, the members having longitudinal axes that are substantially parallel to one another and cross-sectional shapes that are at least partially circular, whereby light incident to a surface of the sheet is diffused along the sheet in a direction normal to the longitudinal axes. 16. The window cover of claim 15, wherein the sheet is divided into a plurality of panels, wherein the plurality of members are arranged on at least one of the panels to diffuse light along a first axis of diffusion and wherein the cover includes additional pluralities of members arranged on the other panels to diffuse light along at least one additional axis of diffusion. 17. The window cover of claim 16, wherein the pluralities of members are arranged to form three different axes of diffusion, morning sunlight being diffused along one of the axes, afternoon sunlight being diffused along another one of the axes. 18. The window cover of claim 16, wherein the panels are arranged in slats, and wherein the window cover includes means for opening and closing the slats, whereby the window cover functions as a shutter. 19. The window cover of claim 16, wherein panels are thin films adhered directly to the window. 20. The window cover of claim 15, further comprising a shade roller and brackets for hanging the sheet in front of the window, whereby the window cover functions as a window shade. 21. The window cover of claim 15, wherein the sheet is divided into a plurality of panels, wherein the plurality of members are arranged on at least one of the panels, wherein the cover includes additional pluralities of members arranged on other panels to diffuse light, and wherein at least two of the panels diffuse light in different amounts. 22. A window shade, comprising: a sheet of light-transmissive material sized to cover the window and divided into a plurality of sections; and a roller and brackets for hanging the sheet in front of the window; and a plurality of elongated members for each section on the sheet, wherein the members in each plurality have at least partially circular cross-sections, wherein the members in each plurality are arranged side-by-side on a surface of the sheet and are substantially parallel to the other members in the same plurality to diffuse light along an axis of diffusion, and wherein at least two pluralities of members " are arranged to diffuse light along at least two different axes of diffusion. 23. The window shade of claim 22, wherein the members are arranged to diffuse light along three different axes of diffusion, one of the axes being arranged to diffuse morning sunlight, another one of the axes being arranged to diffuse afternoon sunlight. 24. The window shade of claim 22, wherein the members of different pluralities have different cross- sectional sizes.

Inventors: OYAMA NOBUO, TAKAHASHI SUMIE, OYAMA, NOBUO, TAKAHASHI, SUMIE
Applicants: OYAMA NOBUO, TAKAHASHI SUMIE, OYAMA, NOBUO, TAKAHASHI, SUMIE
Application year: 1995
Main classification: G02B5
IPC codes: E06B9, F21S11, G02B5