Thin high efficiency illumination system for display devices

• US 5,396,406 A
• Filed: 02/01/1993
• Issued: 03/07/1995
• Est. Priority Date: 02/01/1993
• Status: Expired due to Fees

• Current Assignee: Technocraft Group Services Limited
• Original Assignee: Display Technology, Inc. (Japan)
• Inventors: Ketchpel, Richard D.
• Primary Examiner(s): Husar, Stephen F.
• Application Number:
  US08/012,336
• Time in Patent Office: 764 Days
• Field of Search: 362/26, 362/27, 362/30, 362/31, 362/224, 362/231, 362/260, 362/84, 359/50, 359/48, 359/54
• US Class Current: 362/27
• CPC Class Codes: G02B 6/0003 the light guides being doped with fluorescent agents
• CPC Class Codes: G02B 6/003 Lens or lenticular sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 1/133617 Illumination with ultraviolet light; Luminescent elements or materials associated to the cell

Abstract

An illumination system for a display device includes an array of cylindrical lenslets for imaging an adjacent array of different color monochromatic emitting phosphor stripes onto the display device. Also included is a microcollimator reflector for each stripe which partially collimates emitted light from each phosphor stripe with respect to at least one axis of the display. An edge-irradiated energy distributor plate efficiently distributes ultra-violet energy by total internal reflection to the phosphor stripes that act as scattering and absorbing centers for the ultra-violet energy.

Claims

1. An illumination system for a display screen device having a screen composed of multicelled pixels for selectively controlling the intensity of light wherein said illumination system comprises:

means for remotely energizing a plurality of parallel luminescent stripe areas; and

reflective means for concentrating the emitted light from said stripe areas in a vertical plane which is perpendicular to said stripe areas and also perpendicular to said display screen while maintaining a non-directive emission pattern of said light in a horizontal plane which is also perpendicular to said display screen whereby a wide horizontal viewing angle is preserved for ease of viewing by a group of side-by-side observers.

2. The illumination system of claim 1 wherein said means for energizing said stripe areas comprise:

a transparent sheet of material containing luminescent sites disposed in a stripe pattern and

at least one linear radiation source aligned with said stripe pattern and in close proximity to one edge of said transparent sheet; and

wherein the reflective means comprises

a two sided collimator reflector for each said stripe positioned such that the plane of said stripe is contained within said collimator reflector.

3. The illumination system of claim 2 wherein said luminescent sites are disposed in a segmented stripe pattern such that segments of length "Y" are uniformly spread on a constant pitch along every stripe and the length "Y" of each said segment is a function of the distance from said linear radiation line source wherein length "Y" increases in proportion to Xⁿ for said constant width stripe and "X" is the distance of said stripe from said linear radiation source while "n" is a number from 1.7 to 3.

4. The illumination system of claim 2 wherein said luminescent sites comprise ultra-violet excited, visible light emitting phosphor segmented stripes;

and

said radiation source comprises at least one ultra-violet emitting linear radiation source.

5. The illumination system of claim 4 wherein said phosphor stripes are arranged in repeating parallel triads aligned with pixel control lines in said display device in which each triad consists of one red emitting stripe, one green emitting stripe, and one blue emitting stripe;

and

emitted light from each stripe is concentrated by a separate collimator reflector for each stripe which confines said red, green and blue emitted light to corresponding red, green and blue pixel control lines in said display device.

6. The illumination system of claim 5 wherein emitted light from each color emitting stripe is imaged by means of a cylindrical lens array onto remotely located pixel control lines whereby vertical concentration of said emitted light provides increased brightness and a wide horizontal viewing angle is preserved for ease of viewing by a group of side-by-side observers.

7. The illumination system of claim 4 wherein said reflective concentrating means comprise solid transparent prisms containing reflecting sidewalls which are located in optical contact with and centered in register with each stripe such that emitted light is re-directed in a vertical direction normal to the plane of said display device while maintaining a non-directive emission pattern in the horizontal plane whereby the reflector structure is simplified for manufacture.

8. An illumination system for a display device having a screen composed of multicelled pixels for intensity modulating the primary colors of light, and a light source for illuminating said screen, said illumination system comprising:

means for energizing different color phosphor stripes in alignment with multicelled pixel control elements; and

reflective means for concentrating the emitted light from said phosphor stripe toward said screen in one dimension in a vertical plane while maintaining a non-directional emission pattern in the orthogonal horizontal plane whereby a wide horizontal viewing angle is preserved for ease of viewing by a group of side-by-side observers.

9. The illumination system of claim 8 wherein said means for energizing said color phosphor stripes comprise:

a sheet of material transparent to ultra-violet radiation containing ultra-violet scattering sites on one side of said sheet; and

at least one ultra-violet extended line source aligned parallel with said phosphor stripes and in close proximity to one edge of said sheet.

10. The illumination system of claim 8 wherein said color phosphor stripes are disposed in a segmented stripe pattern such that segments of length "Y" are uniformly spread on a constant pitch along every stripe and the length "Y" of each said segment is a function of the distance from said ultra violet extended line source wherein length "Y" increases in proportion to Xⁿ for said constant width stripe and "X" is the distance of said stripe from said ultra violet extended line source while "n" is a number from 1.7 to 3.

11. The illumination system of claim 10 wherein said stripe patterns comprise sequential groups of red, green and blue emitting phosphors in which each stripe is a single color emitting phosphor.

12. The illumination system of claim 8 wherein emitted light from each color emitting stripe is imaged by means of a cylindrical lens array onto remotely located pixel control lines whereby vertical concentration of said emitted light provides increased brightness and a wide horizontal viewing angle is preserved for ease of viewing by a group of side-by-side observers.

13. The illumination system of claim 8 wherein said reflective concentrating means comprise solid transparent prisms containing reflecting sidewalls which are located in optical contact with and centered in register with each stripe such that emitted light is re-directed in a vertical direction normal to the plane of said display device while maintaining a non-directive emission pattern in the horizontal plane whereby the reflector structure is simplified for manufacture.