This study was conducted to evaluate light intensity and uniformity of two SMD (surface-mount device) type LEDs for protected crop production. A low-power (0.1 W) and a high-power (1 W) LEDs were selected and the intensity and uniformity was evaluated at different vertical (height) and horizontal (distance) intervals. When the horizontal interval of the LED bar was fixed,the light intensity increased and the uniformity decreased as the height decreased. At the 30~40 cm heights, 20~30% of the area showed 200 ±20 μmolm-2s-1. As the horizontal distance of the LED bars increased, while the uniformity increased as well, the light intensity decreased. At the distances of 6~10 cm, 17~23% of the area showed 200 ±20 μmolm-2s-1. When the LED bars were added to the sides, the light intensity and uniformity were generally improved. Results showed that the light intensity and uniformity depended on the height and interval of the LED bulbs; therefore, optimum arrangement for the crops interested should be determined through experiments.

Abstract
 1 Introduction
 2 Literature Review
 3 Materials and Methods
  3.1 LED and Light Quantity Measurement Device
  3.2 Experimental Equipment and Methods
 4 Results and Discussion
  4.1 Light intensity and uniformity by the vertical height
  4.2 Light intensity and uniformity by the horizontal distance
 5 Summary and Conclusions
 References

• MunJung Kim(Dept. of Biosystems Machinery EngineeringChungnam National University)
• YounKug Choo(Dept. of Biosystems Machinery EngineeringChungnam National University)
• YongJoo Kim(Dept. of Biosystems Machinery EngineeringChungnam National University)
• SunOk Chung(Dept. of Biosystems Machinery EngineeringChungnam National University)