Sharp Uses Lenses for Efficient Use of LED Lamps

Mar 31, 2009 18:44 Shinichi Kato, Nikkei Microdevices

Sharp Corp announced 10 types of LED street lamps including one equipped with a solar battery.

The main feature of the new LED and security lamps is the lens unit mounted on each LED chip. The lens unit has a structure composed of convex lenses stacked on concave lenses and serves to illuminate a wider area of a street.

As a result, the new LED lamps can be installed at greater intervals than existing lamps. For example, the solar-powered LED lamp "LN-LX1" can be installed at an interval of 32m, whereas street lamps using a 40W mercury lamp, which have a luminance equivalent to the LN-LX1, have to be installed at an interval of 12m.

Compared with the case using 40W mercury lamps, the number of lamps per kilometer can be reduced by 62%, from 84 to 32. And the electricity cost can be cut by about ¥290,000 (approx US$2,952) per year, according to Sharp.

The lens unit adopted by the company has a structure in which concave and convex lenses are stacked in this order on the LED chips. The concave lens has a function to horizontally widen the light (in the direction parallel to the street) while the convex lens focuses the light so that it intensively illuminates a certain area.

With these features, the new lamps can intensively illuminate a wider area of a street. In contrast, light emitted from existing LED lamps is scattered around the spot directly under the lamp.

The design and the production technique of the lens unit were developed in the Sharp Group, which utilized its optical design technologies that have been accumulated in the development of optical pickups, etc, and the injection molding technology based on temperature control that heats and cools molds more rapidly than normal. Resin can be molded without wrinkles and with a high gloss by setting the temperature higher than normal during acrylic resin injection, Sharp said.

The injection molding technique was originally developed for the frame of the Aquos LCD TV and was applied to the lens unit, the company said. In the case of the Aquos frame, the technique was adopted to produce acrylic resin in a glossy black color dubbed "Piano Black," which resembles the color of a grand piano.

Furthermore, the luminous efficiency of the LEDs in the new lamps was improved by about 30%, compared with LEDs used in Sharp's existing street lamps. The company has not revealed the factors that enabled the higher luminous efficiency, except for the fact that it used a package with a high light extraction efficiency. Featuring a luminance of 1,800lm, the lamps are ones of the brightest products in the industry, the company said.

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