1. Lamp Engineering Group, Toshiba Lighting & Technology Corporation, Funakoshi 1–201-1, Yokosuka, 237–8510, Japan
2. Research and Developing Center, Toshiba Lighting & Technology Corporation, Funakoshi 1–201-1, Yokosuka, 237–8510, Japan
3. Graduate School of Electronic Science and Technology, Shizuoka University, Johoku 3–5-1, Hamamatsu, 432–8011, Japan