Optical: systems and elements – Lens – With support
Reexamination Certificate
2001-09-14
2002-12-03
Mack, Ricky (Department: 2873)
Optical: systems and elements
Lens
With support
C359S613000, C313S116000
Reexamination Certificate
active
06490104
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to the field of illuminators for small displays. More particularly, the invention relates to a compact light source using a film stack to illuminate a small display.
2. Description of the Related Art
Micro displays of various kinds provide compact high resolution displays for a variety of applications. Such displays are used, for example in helmet, windshield, and visor projection systems as well as in small portable headsets and handsets for private display viewing and for virtual reality systems. Some micro display technologies, such as polysilicon (P-Si) and silicon-on-insulator (SOI), provide a transmissive surface which requires a backlight for illumination. Other types, such as Nematic, Static Random Access Memory (SRAM), Digital Micromirror (DMD), Ferro-electric (FLC) and Liquid Crystal on Silicon (LCoS) are reflective and require a front light. In any such micro display system, there are significant challenges in making a system that is both compact and low powered. Both challenges are eased by reducing light loss. Reducing light loss in the illumination system, whether it is a backlight or front light, allows for a smaller, cooler, lower power illumination system.
One example of an illuminator for a micro display is shown in U.S. Pat. No. 5,684,354 to Gleckman. That patent shows an illuminator with either a bulb
12
or red, green and blue LEDs
12
′ disposed within a reflective cavity to illuminate the display. An opaque baffle
56
or a wall of the cavity keeps the light source out of the field of view of the display and the optical system to ensure that the light source is not imaged to the viewer. The illumination light comes out of the reflective cavity through an aperture
18
that is covered by a diffuser
20
, a film
22
and a corrective color filter
24
, if necessary. This illuminator provides an even, well diffused, color corrected source of light for the display. However, the cavity must be large in order to keep the light source out of the view of the display and imaging optics. In addition, the illuminator is inefficient due to the indirect path from the light source to the display.
BRIEF SUMMARY OF THE INVENTION
A compact and efficient illumination system is provided that is particularly suitable for illuminating a micro display and places the light source within the view of the display. In one embodiment, the illumination system comprises a light source, a package for the light source having a reflective surface on at least one side of the light source, and a diffuser opposite the reflective surface in direct view of the light source. The invention further comprises a film stack to receive light through the diffuser, the film stack transmitting light within a maximum exit angle and reflecting substantially all other light to the diffuser.
REFERENCES:
patent: 4864408 (1989-09-01), Bridges
patent: 5272518 (1993-12-01), Vincent
patent: 5440197 (1995-08-01), Gleckman
patent: 5467215 (1995-11-01), Lebby et al.
patent: 5596402 (1997-01-01), Markantes et al.
patent: 5684354 (1997-11-01), Gleckman
patent: 5892325 (1999-04-01), Gleckman
patent: 6043591 (2000-03-01), Gleckman
patent: 6144508 (2000-11-01), Bransome
patent: 6449439 (2002-09-01), Boyd et al.
3M Optical Systems, “How 3M brightness enhancement film works”, 1993, 1 pg.
3M Innovation, “Vikuiti Display Enhancement Films for Public Display Applications”, 2000, 4 pps.
Gleckman Philip Landon
Schuck Miller
Ingrassia Fisher & Lorenz P.C.
Mack Ricky
Three-Five Systems, Inc.
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