13 March 2014 Brightness increase using dual parabolic recycling collar and RGBW LEDs for pico-projector applications
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Proceedings Volume 9005, Advances in Display Technologies IV; 900502 (2014) https://doi.org/10.1117/12.2044625
Event: SPIE OPTO, 2014, San Francisco, California, United States
Abstract
Spherical reflector had been used to recycle light in LEDs so as to increase the brightness of the system. The LED is placed at the center of curvature of the spherical reflector and the emitted light is reflected back to the LED itself by the spherical reflector. For single color LED place at the center, this system will suffice. But for multiple LEDs of different colors, due to imaging property of the spherical reflector, the image of a chip is imaged diagonally to the opposite side of the center of curvature, and not onto itself. As a result, recycling can only occur on symmetrically placed LEDs with different colors. A parabolic reflector system with two reflections is described here such that the output from a LED is reflected back to itself. When it is placed at the proximity of the center of curvature, there will be minimum distortion with higher recycling efficiency. The single reflection from a spherical is analogous to a single lens producing inverted images. The two reflections from this parabolic reflector system is similar to imaging with two lenses where the image become upright. Such system will be very applicable to LED packages with multiple LEDs, for example, RGBW, RGGB, etc. used in entertainment lighting systems.
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Kenneth Li, "Brightness increase using dual parabolic recycling collar and RGBW LEDs for pico-projector applications", Proc. SPIE 9005, Advances in Display Technologies IV, 900502 (13 March 2014); doi: 10.1117/12.2044625; https://doi.org/10.1117/12.2044625
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