Patent Application
20070064420
This invention relates to light emitting devices and more particularly to light emitting diode (LED) devices with enhanced light output.
It has become standard practice to use light emitting diodes (LEDs) as flash modules in mobile applications that have camera functions. For example, mobile phones or PDAs are increasingly equipped with camera modules for image capture and a flash module serves as an illumination source in low ambient light situations. These flash modules must produce a large amount of light each time they are activated.
One prior art device employs multiple LEDs in a single housing to produce the proper light output. These devices are not efficient in light output because they are not located at optimum positions relative to the dome profile which acts as a lens and because there is cross absorption of the light between the LEDs.
In another prior solution, a single LED is used to replace multiple LEDs. The drawback for using a single LED is that it requires a higher current and while the light output is higher, the actual photo extraction is less efficient. Consequently, light output is not optimized for power consumption.
An enhanced light output light emitting diode (LED) is constructed using a plurality of single domed LEDs with each dome acting as a lens. By packaging multiple LEDs, each with its own dome (lens), greater-light output can be achieved. In one embodiment, each individually domed LED is a single color and the mixed colors from the group of LEDs within a device yields white light output. In another embodiment, the phosphors within each dome are mixed to produce white light. Reflectors can be added to enhance light output.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
As discussed above, prior art flash devices, such as device 50 is shown in
The individual domes can be fabricated using any known method such as transfer molding, injection molding, casting, spraying, ink-jet printing, vacuum printing, film printing, photolithography or any known mechanical or chemical methods.
The phosphor material is preferably embedded inside the dome. Diffusant or thixotropic agents can further be added both inside the individual domes and outside the domes to improve the uniformity of the light radiation.
Electrical terminals such as terminals 17-1, 17-2 connected by electrical traces 18 to LEDs 13-1, 13-2 and 13-3 (not shown), below the substrate, can be used to control the flash. In one embodiment, all the LEDs within a device would be used in common such that a single “pulse” of energy would cause them all to light in unison. However, if desired, the individual LEDs could be controlled independently, thereby allowing a user to adjust the intensity and perhaps the ultimate color of the light output.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
