The LED is the most significant innovation in portable lighting since
the advent of the incandescent lamp. It is more efficient, less
fragile, runs cooler, and has a 50-100 times improvement in life
expectancy. The quality of light is quite different from that of an
incandescent lamp. It appears much whiter and shines farther
underwater. Despite all of the positives there are also some
challenges. Red and purple objects do not appear as vibrant under white
LED light. Brightness decreases slightly as the LED heats up. Power is
limited to a few watts per LED. Large arrays of LEDs must be clustered
to reach the illumination of a high wattage incandescent lamp. Although
decreasing, the cost of an LED is still high, and can only be justified
by the knowledge that it may never need to be replaced.
UK LED Design Features
Constant Brightness
The unique electrical properties of the LED make it possible to attach
it to an electronic circuit which controls power from the batteries in
a flashlight in such a way that brightness and color of the beam remain
constant as the batteries drain. Contrast this to a conventional
flashlight with an incandescent bulb. With fresh batteries the light is
extremely bright. As the batteries are consumed the light grows dim and
the color turns more yellow. This feature is represented by the "e"
used in naming UK eLED lights.
Another unique feature of LEDs is that they continue to give
light when there is very little power left in the batteries. The
benefit is that even though the batteries are considered dead in any
other type of flashlight, the LED continues to give light for hours or
even days after the high brightness mode is past. For emergency
situations this could make the difference.
What is a LED?LED stands for Light Emiting Diode. It is a semiconductor device which converts electrical energy directly into light. Compare this to the incandescent lamp which converts energy into light by heating a thin wire filament until it glows and gives off light.LEDs are made from a semiconductor material that has impurities called "dopants" that are added to the crystal. Two types of dopants are added to create "N" and "P" regions. "N" regions are parts of the crystal that are electron rich (free electrons) and "P" regions that are deficient in electrons (free holes). When the "P" region is connected to a positive voltage and the "N" region is connected to a negative voltage a current flows. When an excited electron from the "N" region meets with a hole from the "P" region, they combine where the two regions meet. This liberates energy of a discrete amount (the sum of electron and hole energy) in the form of light of a particular color. White LEDs are formed by covering a blue LED with a yellow phosphor. This phosphor converts the blue light to a range of colors in the yellow part of the spectrum. This combination of blue and yellow light gives the appearance of white. Compare the color spectrums of white LEDs and incandescent lights. Up to now, LEDs were not very efficient. Today, they are approaching the efficiencies of our best incandescent bulbs. In the next few years they are predicted to surpass most other forms of illumination in terms of light output for a given amount of power. LEDs are mechanically robust and last substantially longer than incandescents. |
Heat Dissipation
For any light which uses LEDs it is extremely important to keep the LED from getting too hot (less than 130� C, 266� F.) Heat shortens the life of the LED and reduces the brightness. At UK we have developed circuitry which monitors the temperature of the LED and cuts back power when it gets too hot. We have also developed specialized metal heat sinks which carry heat away from the LED and into the surroundings. Underwater this affect allows our lights to burn even brighter as the water acts as a coolant for the LED.
Multiple LEDs
Unlike incandescent lamps, the maximum power
which a LED can handle is about 5 watts. The only way for a LED
flashlight to be brighter is to use more than one LED.
At UK we work to find innovative ways to cluster several LEDs
in such a way as to provide a uniform beam of light which appears like
it was made from central lamp and to remove the additional heat in
order to protect the LEDs.
Improved Efficiency
As LEDs are manufactured, some are brighter than others. They are then sorted into bins based on brightness. Brighter LEDs which are also more efficient at converting energy into light are more rare and expensive to light manufacturers such as UK. When selecting LEDs to include in our lights we work with the suppliers to get the brightest we can at a price which will meet the budget of our customers. In addition innovative means are used to remove heat from the LED for improved brightness and efficiency.
