1. Field of the Invention
The present invention relates to an LED unit, and more particularly to an LED unit having an optimized lens for improving a light emission from an LED.
2. Description of Related Art
A typical LED often emits its light energy in a nearly hemispherical beam pattern. So most LED applications require substantial modification of this output beam profile to provide useful energy. Conventionally, a method for achieving this is to use reflectors, lens, and a combination of these.
US patent publication No. 2002/0093820 A1 discloses an LED lamp, which comprises a heat sink housing, an array of LEDs arranged in the heat sink housing, a reflector positioned over the LEDs, and a lens connecting with the heat sink housing and covering the reflector and LEDs. Each of the LEDs comprises an LED chip and an enclosure packing the LED chip for fixing and protecting the LED chip. When the LEDs are activated, the light emitted from the LED chips is reflected by the reflector to concentrate in respective beams, which converge into an integral beam after passing through the lens. Therefore, most light emitted from the LEDs is able to be conveyed to the ambient, and a high bright light is thus obtained.
However, there is a big problem in said LED lamp: the enclosure is often made from a transparent material such as epoxy or silicone, which has a refractive index larger than that of air. That means when the light is conveyed from the enclosure to the air that is received between the enclosure of the LED and the lens of the LED lamp, a total internal reflection may occur at the interface between the air and the enclosure. A part of light will be reflected back to the inner of the LED and cannot emit through the lens of the LED lamp, which causes the brightness of the light to be lowered.
What is needed, therefore, is an LED unit which can overcome the above-mentioned disadvantages.
An LED unit includes an LED and a lens disposed on the LED. The lens includes a square body and a frustum-shaped body formed downwardly from the square body, wherein a tapered side face of the frustum-shaped body is coated with a reflective film. The LED includes a lens that has a planar top face directly contacting with a planar, circular bottom face of the frustum-shaped body of the lens, thus light emitted from an LED chip in the LED can pass through the lens of the LED and the lens without a total internal reflection occurring at an interface between the lens of the LED and the lens. Accordingly, a high bright light is obtained since nearly all of the light generated by the LED chip can be transmitted out of the LED unit via the lens of the LED and the lens, which are intimated contacted with each other.
Other advantages and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:
Many aspects of the present apparatus can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present apparatus. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Referring to
As shown in
Referring to
Since the lens 30 and the lens 26 of the LED 20 are made of the same material, difference of reflective index therebetween is eliminated; moreover, the direct contact between the top face 28 of the LED 20 and the planar, circular bottom face 340 of the lens 30 can prevent air from existing therebetween, whereby a light pathway having a uniform reflective index is formed in the lens 30 and the lens 26 of the LED 20. When the LED chip 23 is activated, nearly all of the light emitted by the LED chip 23 can travel through the lens 26 of the LED 20 and the lens 30 via the light pathway, without a total internal reflection occurring at an interface between the lens 30 and the lens 26. On the other hand, the light that has traveled through the interface is reflected by the reflective film of the frustum-shaped body 34, and then concentrated into a straight beam. The straight beam extends through the square body 32 of the lens 30 and is conveyed to an outside of the lens 30, thereby to irradiate ambient objects. Therefore, loss of the light during the transmission process through the LED unit 10 can be minimized, and a high bright light is obtained accordingly.
It is believed that the present invention and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.
Number | Date | Country | Kind |
---|---|---|---|
200710124673.8 | Nov 2007 | CN | national |