Illumination – With implement or hand held holder therefor – Key holder
Reexamination Certificate
2002-12-02
2004-10-12
Sember, Thomas M. (Department: 2875)
Illumination
With implement or hand held holder therefor
Key holder
C362S109000, C362S800000, C362S310000, C362S200000, C362S196000, C362S311040, C024S003100
Reexamination Certificate
active
06802620
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to optical lens and housing assemblies for use in lighting devices such as commercial and residential lighting fixtures, flashlights and miniature flashlights and more particularly to flashlight housings for use with lighting devices of the type employing a high brightness light emitting diode to provide a smooth uniform spotlight beam having sharp edges.
Most commercial lighting devices are designed to provide an on-axis, high intensity peak in their beam distribution as is typically found in flashlights with smooth reflectors. Attempts to provide a more uniform beam distribution include the use of multi-faceted reflectors, however, the resulting beam pattern tends to be Gaussian with no sharp edge between the area illuminated by the beam and the surrounding non-illuminated area. In both the faceted and unfaceted cases, the reflector tends to be parabolic in shape and essentially smears the image taken from the far field of the light source and projects that smeared image in the far field of the flashlight beam.
Other prior art attempts to produce a focused light source include the provision of a standard convex lens with a relatively long convergence factor in front of a Light Emitting Diode (LED) package. These devices also produce an unacceptable result as they capture the far field image from a plane projected in front of the LED package and simply enlarge that image in a reversed pattern in the flashlight beam far field. If the beam pattern is carefully studied, an image of the emitter die and diode reflector cup can be seen in the beam image.
In addition, to compliment the portable nature of these flashlight devices, a means for retaining them in a desired location is typically required. Often, this retaining means allows the light either to be clipped onto the user's apparel, such as to their belt loop, or onto the user's key ring. Generally, these devices have a pivotable latching mechanism that is spring biased into an outer closed position and operates inwardly allowing a loop to enter the mechanism but preventing its unintentional removal. However, in these prior art devices, the latch can be accidentally opened by exerting inward pressure on the face of the latch. This could happen for example when a user has the flashlight clipped onto their belt loop and leans against a counter or railing. In this manner, the light may become disengaged from its storage location and unintentionally lost.
Therefore, there is a need for a lighting device that produces a smooth, evenly distributed beam of light. In addition, there is a need for a lighting device that provides a high intensity beam of light that has a homogeneous illumination pattern. There is also a need for a high intensity flashlight beam that provides a uniform field of illumination and that has a sharp edge between the illuminated field and the non-illuminated field. There is a further need for a flashlight that has a clipping mechanism that is integral to the flashlight housing for retaining the flashlight that provides improved reliability and operating characteristics over the lights in the prior art.
SUMMARY OF THE INVENTION
In this regard, the present invention provides an improved LED lighting device for producing a high intensity focused light beam that has a uniform appearance across the entire field of illumination and that has a sharp defined edge between the illuminated and non-illuminated areas. The present invention is an improvement over the prior art in that it provides a uniform illumination pattern without producing peak illumination along the axis of the light beam and without creating “hot-spots” in the illumination field. In addition, unlike existing products that use parabolic reflectors for focusing the light beam, the uniformity of the pattern of light distribution is not dependant on the distance of the illuminated surface from the flashlight nor does the beam require refocusing as the distance between the light source and the illuminated surface increases.
More specifically, several novel elements are combined to result in the unique appearance of a focused uniform beam of light. The first element is the use of a specialized light emitting diode (LED) component. The LED used in the present invention is customized to provide a concentrated, uniform light output flux across the entire emitter die and reflector cup assembly. This is achieved by providing an LED that has a scatter layer coating, such as a phosphor slurry, covering the reflector cup and emitter die. The uniform scatter layer diffuses the energy emitted from the emitter die thereby causing it to be uniformly distributed over the entire surface of the reflector cup. This scattered light provides a high intensity and uniform light source that is used to generate a smooth and uniform near field light image at a plane located within the LED package between the emitter die and reflector cup assembly and the front of the LED package. The present further invention employs an LED having a clear optical housing with a narrow beam angle that preserves the concentrated near field light image produced by the lighting structure thereby allowing the compact light image to be captured and further focused and imaged into the far field light beam image of the present invention.
FIGS. 4 and 4
a
, illustrate two types of LED packages available in the prior art. LED packages are produced in both narrow (
FIG. 4
) and wide (
FIG. 4
a
) beam angles. For purposes of the present invention and as generally understood in the field, the term narrow angle refers to an LED with a beam angle of less than 15° and wide angle indicates an LED with a beam angle of greater than 15°. Generally, the prior art LED packages have an emitter chip
70
, a reflector cup
72
and an optical housing
74
. As can be seen in the illustrations, the wide angle LED in
FIG. 4
a
provides a greater amount of available luminous flux (illustrated by the ray trace lines) in the LED far field adjacent to the outer optical housing
74
of the LED. While the wide angle LED allows a greater amount of light to be controlled and therefore transmitted by the curved surface of the optical housing
74
thereby producing a greater amount of light, the output pattern and projected image is scattered which results in a very large and unfocused image of the LED package (cup and die) being transmitted to the LED far field. The narrow angle LED shown in
FIG. 4
, while transmitting less of the total available luminous flux into the far field of the LED, presents a narrower more focused image of the LED package in the LED far field. The present invention employs a narrow angle LED. Although this represents a trade-off in efficiency, in that all of the available luminous flux from the LED is not captured and projected into the far field of the beam, as will be seen later in the description, a high quality focused LED near field image is critical to produce a level beam output.
The other element of the present invention is a unique optical lens that captures an image of the emitter die and reflector cup from the near field plane within the LED package and projects a uniform focused image of the LED near field in the far field of the light beam. This unique lens captures a clear near field image of the reflector cup and emitter die from inside the LED package without interference from the LED optical housing.
The use of the near field image of the LED as the imaging source is considered to be a significant improvement over the prior art. Until now, the prior art has only attempted to utilize the far field image created at a plane beyond the outer surface of the LED optical housing. In contrast, in the in the present invention, the image used to create the far field light image is actually a near field image as taken from a plane within the interior of the LED. This is achieved by the use of a spherical lens placed in close proximity to the LED package such that the convergence point of the lens falls behind the die and reflector
Barlow Josephs & Holmes, Ltd.
Sember Thomas M.
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