13 September 2002 Characteristics of modulated white LED and their application to electrically controlled spectroscopy
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We have investigated characteristics of a commercially available one-chip white-LED based on indium-doped gallium nitride when modulating with an electrical pulse. The observation of a spectrum of the white-LED revealed that it contained four large peaks at wavelengths of 390nm (ultra-violet), 430nm (blue), 510nm (green), and 620nm (red), respectively. When the LED was modulated by use of a squared pulse signal with a 16kHz repetition frequency and an 85% duty cycle, each color exhibited different electric characteristics: ultra-violet and blue colors showed the similar electrical spectrum of the original input signal having three frequency bands (1st band: 16~108kHz, 2nd band: 108~208kHz, 3rd band: 208~320kHz), meanwhile a green color was presented in the two bands and a red component did not manifested in any bands. The measured result can be explained in terms of different response of the fluorescent materials responsible for the light emission. Use of electrical band filters enables to separate a white light into desired one.
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Yasuyuki Okamura, Tatsuo Shiina, Masafumi Ito, "Characteristics of modulated white LED and their application to electrically controlled spectroscopy", Proc. SPIE 4922, Color Science and Imaging Technologies, (13 September 2002); doi: 10.1117/12.483144; https://doi.org/10.1117/12.483144

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