Optical: systems and elements – Optical modulator – Light wave temporal modulation
Patent
1998-05-22
2000-02-22
Ben, Loha
Optical: systems and elements
Optical modulator
Light wave temporal modulation
362119, 362109, 345 60, 349 25, 315246, G02F 103
Patent
active
060286946
ABSTRACT:
An illumination device utilizing a pulse modulation technique of a solid state light source to provide increased light output for a given heat load. In a preferred embodiment, power is supplied in pulses to periodically activate a short wavelength (i.e., blue) emitting LED, which in turn stimulates a phosphor-based color conversion system to produce sustained white light. In response to a pulse of power, the LED emits an intense burst of short wavelength light. The burst of light from the LED briefly excites the phosphor system, producing a bright illumination. During the interval while power is dissipated in the LED, the LED warms. After the pulse ends and before the next pulse begins, the LED cools because no more power is dissipated in the LED. However, the phosphorescent behavior of the phosphor system causes it to continue to glow for a period of time after being excited. The intensity of the illumination produced by the phosphor gradually decays during this period. The average illumination produced by the preferred embodiment over the entire period from the beginning of one pulse to the beginning of the next is higher than a conventional LED illumination device using constant power dissipation for a given heat load.
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