Illumination – Revolving
Reexamination Certificate
1998-09-25
2001-10-23
Husar, Stephen (Department: 2875)
Illumination
Revolving
C362S026000, C362S330000, C362S331000, C362S019000, C362S268000, C349S065000, C385S146000
Reexamination Certificate
active
06305811
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to illumination systems, and more particularly, to an illumination system having an array of linear prisms located on a side of a solid waveguide opposite to which light emerges from the waveguide for controlling the light output distribution of the illumination system.
2. Description of the Prior Art
For home and office applications, it is desirable to control the angular light output distribution of illumination systems to prevent flooding areas with high angle light and to also eliminate light hot-spots (i.e., concentrations of light) when looking at the illumination system. Control of the angular output distribution has been accomplished by pre-limiting or pre-collimating the light input to the illumination system (see, e.g. U.S. Pat. Nos. 5,359,691 and 5,390,276 to Tai et al.). Such illumination systems require additional devices and structures to ensure the collimation of input light. In addition, the illumination systems disclosed in these patents are directed to backlighting of liquid crystal displays (LCDs), which require a highly collimated light output. e.g., output angles no greater than ±20°, where output angles are measured from a direction perpendicular to the plane of the output surface of the waveguide.
It is thus desirable to provide an illumination system that can accept an unrestricted light input (i.e. un-collimated or full hemisphere) and that can control the light output distribution and intensity. Such illumination systems must be inexpensive to manufactures durable and reliable.
SUMMARY OF THE INVENTION
The present invention provides an illumination system that advantageously provides a light output distribution that is ideally suited for home and office applications. The illumination system generally comprises a solid waveguide and a light directing structure located on a side opposite of the waveguide's light output side for controlling the light output distribution from the illumination system. The light directing structure may be unitarily formed with the waveguide or it may be secured thereto by an interface which provides approximately 100% contact between the waveguide and light directing structure. The light directing structure includes an array of light directing features configured as generally lenticular prisms that extend in a direction substantially perpendicular (i.e., not parallel) to the average direction at which light rays enter and propagate through the waveguide. Each light directing feature defines an included angle that controls the distribution of light output from the illumination system in a first direction. The interface when provided, controls the distribution of light output from the illumination system in a second direction that is generally orthogonal with respect to the first direction.
In a first embodiment, the present invention provides an illumination system for distributing light rays from a light source comprising a solid waveguide for propagating light rays from the light source. The solid waveguide has a light output side through which light rays emerge and a light directing structure unitarily formed with the waveguide and located on a side thereof opposite to the light output side. The light directing structure includes a light directing feature array defined thereon and comprising a plurality of generally lenticular prisms oriented substantially not parallel to the direction at which light rays enter and propagate through the solid waveguide. Each of the prisms has a first and a second light directing surface disposed with respect to each other so as to define an included angle therebetween. The included angle defines an output cut-off angle of greater than approximately ±25° for controlling the light output from said illumination system.
In a second embodiment, the present invention provides an illumination system for distributing light rays from a light source comprising a solid waveguide for propagating light rays from the light source. The waveguide has a light output side through which light rays emerge and a first refractive index that is greater than 1. A light directing structure is located on a side of the waveguide opposite to the light output side and has a light directing feature array defined thereon comprising a plurality of generally lenticular prisms oriented substantially not parallel to the average direction at which light rays enter and propagate through the solid waveguide. Each of the prisms has a first and a second light directing surface disposed with respect to each other so as to define an included angle therebetween. The included angle defines an output cut-off angle of greater than approximately ±25° for controlling the light output from the illumination system in a first direction. The illumination system of this embodiment also includes an interface for coupling the light directing structure with approximately 100% contact to the solid waveguide and having a second refractive index that is less than the first refractive index of the solid waveguide. The interface controls the light output distribution from the illumination system in a second direction that is generally orthogonal with respect to the first direction.
Advantageously, the present illumination system provides an illumination system with a controllable output light distribution and an ideal light output intensity that is especially well-suited for home and office applications.
REFERENCES:
patent: 5359691 (1994-10-01), Tai et al.
patent: 5390276 (1995-02-01), Tai et al.
patent: 5428468 (1995-06-01), Zimmerman et al.
patent: 5845035 (1998-12-01), Wimberger-Friedl
patent: 5887964 (1999-03-01), Higushi et al.
patent: 6036340 (2000-03-01), Fohl et al.
patent: 6106128 (2000-08-01), Zou et al.
patent: 6172809 (2001-01-01), Koike et al.
patent: 6185357 (2001-02-01), Zou et al.
patent: 6243150 (2001-06-01), Watanabe et al.
Beeson Karl W.
Zou Han
Honeywell International , Inc.
Husar Stephen
Shudy, Jr. John G.
Ton Anabel
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