Light emitting diodes (“LEDs”) have been used in various applications including illuminating watches, transmitting information from remote controls, and forming images on jumbo television screens. More recently, LEDs have been used in portable lighting devices, such as flashlights, because, among other things, LEDs can last longer and can be more durable than incandescent lamps commonly used in conventional flashlights.
Notwithstanding the desirable characteristics LEDs may have over incandescent lamps, improvements can be made over existing lighting devices that use an LED as its primary source of light. For example, current LED flashlights typically fail to produce a quality light beam that projects for any appreciable distance. A reason for this is that available LED lamps substantially radiate light in a pattern over an angle less than 180° relative to the position of the LED. FIG. 1 illustrates the brightness or radiation pattern of a typical LED lamp. A typical LED lamp includes an LED and a lens arranged over the LED. The light rays that emanate from the typical LED lamp is generally conical —the brightness (indicated in percentages) is generally concentrated about the center axis 11 and reduces non-linearly as the spherical angle θ increases. Existing LED flashlights have not provided a reflector/lamp combination that effectively captures the brighter light rays that are concentrated about the center axis. Accordingly, although available LED lighting devices may be suitable to illuminate the immediate surrounding area, the distance that the light beam is able to project has been limited.
To try to overcome this deficiency, some devices have used multiple LEDs or a combination of LED lamps and incandescent lamps. However, such devices involve greater complexity, consume more energy, and cost more to manufacture. Accordingly, the present invention provides an energy efficient LED lighting device that has improved optical performance and that projects a quality light beam.
Also, as improvements are made to light sources, such as LEDs, another problem challenging the operation of portable lighting devices is effectively dissipating the increased heat that is generated by the light source. Accordingly, the present invention provides a combination that effectively dissipates heat from the light source of a portable lighting device. The present invention also provides a means to reduce the amount of heat generated by the light source and to use less energy to illuminate the light source.