Abstract
Light emitting diodes(LEDs) are expected to become as the new source of illumination light in place of electric bulbs and fluorescent lamps. LEDs has advantages such as long life, low electricity consumption, and are highly reliable. Mounting yellow phosphor on blue LED is the most popular type of white color LED and is widely used. However, the average color rendering index(Ra) of the LEDs are still low and improvements are necessary. This time, we developed four types of LEDs to be used as light source and measured the optical characteristics respectively. Next, we constructed four light sources using these four types of LEDs and evaluated the optical characteristics respectively.
