Privacy filter for a display device

• US 5,528,319 A
• Filed: 11/08/1994
• Issued: 06/18/1996
• Est. Priority Date: 10/13/1993
• Status: Expired due to Fees

• Current Assignee: Photran Corporation
• Original Assignee: Photran Corporation
• Inventors: Austin, R. Russel
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): Williams, Kimberly A.
• Application Number:
  US08/336,270
• Time in Patent Office: 588 Days
• Field of Search: 348/834, 348/835, 348/840, 348/841, 348/842, 348/818, 313/110, 313/474, 313/478
• US Class Current: 348/835
• CPC Class Codes: H04N 5/65 Holding-devices for protective discs or for picture masks
• CPC Class Codes: H04N 5/72 Modifying the appearance of television pictures by optical filters or diffusing screens

Abstract

A privacy filter (20) for a display device includes at least two spaced-apart, generally parallel grids (22 and 24). Each grid includes an array of strips (26 and 30) or blocking members having transparent space (28 and 32) therebetween. The strips or blocking members are formed aligned such that an image (37) displayed on the display device may be viewed through the filter at an angle of incidence within a predetermined range of angles but is not discernable at angles outside of the predetermined range.

Claims

1. A filter for a display unit, comprising:

at least first and second parallel spaced-apart planar grids each thereof having a grid plane;

said first and second grids including respectively first and second pluralities of parallel spaced-apart generally flat opaque strips having transparent spaces therebetween;

each of said strips in each of said grids having first and second opposite surfaces, generally in the plane of the grid;

said first and second pluralities of strips aligned in the same direction, with said first surfaces of said strips in said first plurality of strips in a face-to-face relationship with said first surfaces of strips in said second plurality of strips, such that, when the filter is placed in front of the display with said first grid closest a user of the display and viewed by the user at a first angle of incidence, said second grid is not visible to the user and the display is visible to the user through said spaces in said first and second grids; and

said first and second pluralities of strips sized, spaced, and arranged such that when viewed by an observer at a second angle of incidence, said strips in said second grid appear to close said spaces between said strips in said second grid, whereby the display is not visible to the observer.

2. The filter of claim 1 wherein said first surface of each of said strips of said second grid has reflectivity greater than about 50 percent, and said strips of said first and second grids are deposited on first surfaces of respectively first and second transparent substrates.

3. The filter of claim 2 wherein each of said strips in said second grid includes a reflection reducing coating on said second surface thereof and each of said strips in said first grid includes a reflection reducing coating on said first and second surfaces thereof.

4. The filter of claim 3 wherein said first substrate has a reflection reducing treatment on a second surface thereof.

5. The filter of claim 4 wherein said second substrate has a reflection reducing treatment on a second surface thereof.

6. The filter of claim 5 wherein said reflection reducing treatments are multilayer optical interference coatings.

7. The filter of claim 1 wherein said strips and said spaces have a width between about 10 and 200 micrometers, and said first and second grids are spaced-apart by between about 10 and 200 micrometers.

8. The filter of claim 7 wherein said first and second pluralities strips are arranged in parallel groups, said strip widths within each group being equal, and in any adjacent first and second of said groups strips in said first group have a first width and strips in said second group have a second width, said first and second strip widths being different.

9. The filter of claim 7 wherein said strip widths are varied according to a predetermined pattern, said pattern being the same in each of said first and second grids.

10. The filter of claim 1 wherein any of said strips of said first grid has a greater width than a corresponding strip in said second grid.

11. A filter for a display unit, comprising:

at least first and second parallel grids each thereof having a grid plane, said first grid formed on a first surface of a first substrate and said second grid formed on a first surface of a second transparent substrate and each of said first and second substrates having an antireflection treatment on a second surface thereof;

said first and second grids including respectively first and second pluralities of generally flat parallel spaced-apart opaque strips having transparent spaces therebetween, each of said strips arranged parallel a corresponding one of said grid planes;

each of said strips including a metal layer and having first and second opposite surfaces, said second surface adjacent a said substrate, and each of said strips and each of said spaces having a width between about fifty and one-hundred-fifty micrometers;

said first surface of each of said strips in said second grid being highly reflective for visible light, said first surface of each of said strips in said first grid and said second surface of each of said strips in said first and second grids having a low reflectivity for visible light;

said substrates having said first surfaces thereof in a face-to-face relationship and spaced-apart by and in optical contact with a sheet of a transparent material having a width between about fifty and one-hundred-fifty micrometers; and

said first and second pluralities of strips aligned in the same direction with corresponding strips in each of said grids in a face-to-face relationship and said strip widths selected such that when the filter is placed in front of the display with the first grid closest a user of the display and viewed by the user at a first angle of incidence, said second grid is not visible to the user and the display is visible to the user through said spaces in said first and second grids; and

said first and second pluralities of strips sized, spaced, and arranged such that when viewed by an observer at a second angle of incidence, said strips in said second grid appear to close said spaces between said strips in said second grid, whereby the display is not visible to the observer.

12. The filter of claim 11 wherein on at least one of said second surfaces of said substrates includes a multilayer interference anti-reflection coating.

13. The filter of claim 11 wherein said metal layer includes a metal selected from the group consisting of silver, magnesium, aluminum, nickel and chromium.

14. The filter of claim 13 wherein each of said strips in said first and second grids includes at least one layer of a transparent dielectric material located between said metal layer and said substrate.