The light intensity of the LED units was measured by a silicon photo cell (Model 0560.0500, Testoterm GmbH & Co., Germany). The light intensities of a high-intensity LED unit were about 3 and 12 mW/cm2 when powered at 1.7 and 2.1 V, respectively.
The light intensity of the LED units was measured by asilicon photo cell (Model 0560.0500, Testoterm GmbH &Co., Germany). The light intensities of a high-intensityLED unit were about 3 and 12 mW/cm2 when powered at1.7 and 2.1 V, respectively.