Illumination – Light source and modifier – Including reflector
Reexamination Certificate
2003-03-19
2004-07-06
Sember, Thomas M. (Department: 2875)
Illumination
Light source and modifier
Including reflector
C362S303000, C362S304000, C362S305000
Reexamination Certificate
active
06758582
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to an electrical lighting device, and more specifically, to an electrical lighting device utilizing light emitting diodes (LEDs).
2. Description of the Prior Art
Light emitting diodes (LEDs) are frequently selected for large-scale lighting applications, such as traffic lights and other indicator lights. LEDs provide high intensity light with substantially reduced heat generation when compared with incandescent light bulbs. LEDs also consume significantly less power than other sources of light, have a relatively long life and are easily incorporated into digital circuits.
One disadvantage of LEDs is their small size. Typically, LEDs are not readily scalable to larger sizes or higher brightness. In contrast, if greater intensity of light is required in an incandescent application, an incandescent light bulb can be easily exchanged for one having a higher power rating, and consequent physical characteristics, for delivering increased intensity of light. Power ratings and intensities of conventional light bulbs (incandescent, halogen, etc) range from 40W household bulbs to high power bulbs used in spotlights having millions of candlepower, where single LEDs are usually only suitable for smaller applications. To overcome this deficiency of LEDs, conventional practice has been to array a group of LEDs into a single lighting device to achieve increased brightness.
An example of a conventional lighting device incorporating LEDs is shown in
FIG. 1. A
lighting device
10
comprises a housing
12
, a substrate
16
, an LED array
18
, an optical lens set
22
, and a mask
14
. The substrate
16
is disposed inside the housing
12
. The LED array
18
includes a plurality of LEDs
24
disposed on the substrate
16
for generating red, green, yellow, blue, white or other colored light. A first reflector set
20
comprises a plurality of reflectors
26
installed on the substrate
16
in an array corresponding to the LED array
18
. The optical lens set
22
comprises a plurality of lenses
28
installed above the LED array
18
in a corresponding array for focusing light emitted by the LEDs
24
and reflected by the reflectors
26
. The light focused by the optical lens set
22
penetrates the mask
14
installed on the housing
12
.
Please refer to
FIG. 2
illustrating a schematic diagram of light rays emitted by the lighting device
10
. A light ray
30
generated by an LED
24
is focused directly by the corresponding lens
28
. Each of lenses
28
concentrates light emitted by a corresponding LED
24
and transmits light within a range of angle
34
. Finally, the light, focused by the optical lens set
22
, penetrates the mask
14
of the lighting device
10
.
Due to the structure of the lighting device
10
, most of the light focused by the optical lens set
22
penetrates the central part of the mask
14
. The remaining light focused by the optical lens set
22
is transmitted to the circumference of the mask
14
. Light intensity at the central part of the mask
14
higher than light intensity near the circumference of the mask. Consequently, light emitted by the lighting device
10
is non-uniform in intensity over the surface of the mask.
SUMMARY OF INVENTION
It is therefore a primary objective of the claimed invention to provide an uncomplicated and inexpensive LED lighting device for providing a more uniform light intensity profile.
Briefly summarized, the claimed invention includes a concave mirror and a convex mirror having a diameter less than a diameter of the concave mirror. The convex mirror is positioned to face the concave mirror and is fixed to the concave mirror. A light emitting diode (LED) array Is fixed to the concave mirror between the concave mirror and the convex mirror. The LED array faces the convex mirror such that light emitted by the LED array reflects off of the convex mirror and onto the concave mirror. A power supply is provided for powering the LED array. Light emitted by the LED array is reflected from the convex mirror onto the concave mirror, and then reflected by the concave mirror to exit the lighting device.
According to an embodiment of the claimed invention, the concave and convex mirrors are parabolic mirrors having metal or plastic bodies coated in metallic reflective material forming reflecting surfaces. The optical axes of the concave and convex mirrors and a central normal axis of the LED array are substantially collinear (or confocal). The LED array is a flat circular array fixed to the metallic reflecting surface of concave mirror. Each LED of the LED array can include a lens for concentrating light onto the convex mirror. Further provided are three stays for attaching the convex mirror to the concave mirror, and a translucent cover spanning the diameter of the concave mirror for protecting the reflecting surfaces of the concave and convex mirrors and the LED array.
It is an advantage of the claimed invention that the concave and convex mirrors can evenly distribute light emitted by the LED array.
It is a further advantage of the claimed invention that light can be delivered to a confined area from an LED array using few components.
These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
REFERENCES:
patent: 1050466 (1913-01-01), Jones, Jr.
patent: 3796886 (1974-03-01), Freeman
patent: 4463410 (1984-07-01), Mori
patent: 4587601 (1986-05-01), Collins
patent: 4755916 (1988-07-01), Collins
patent: 6558032 (2003-05-01), Kondo et al.
Hsiao Ya-Kuang
Shaw Ching-Chi
Elumina Technology Incorporation
Sember Thomas M.
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