8 September 2005 Remote phosphor with recycling blue-pass mirror
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Phosphor-conversion (PC) LEDs are the leading type of white solid-state lighting (SSL), due to the high efficacy of the yellow wavelengths of blue-stimulated photoluminescence. Conventional phosphor-conversion LEDs have the photoluminescent phosphor in immediate contact with the blue LED. Major types are the thin conformal phosphor and the thick or in-cup phosphor. The first trades away efficiency for increased luminance, while the latter gains efficiency at reduced luminance. In both cases the phosphor suffers from the elevated temperature of the blue chip, particularly the thermal quenching that reduces phosphor quantum efficiency. Also, the inevitable 15% Stokes heat of the phosphor conversion of blue light to longer-wave yellow light adds to the chip's heat load, as does much of a conformal phosphor's back-emission into the chip. It would be preferable to relocate the phosphor away from the chip illuminating it. Although remote phosphors have recently been showcased, their phosphor is much larger than the chip, greatly reducing luminance. A new design is presented of a Dual-Optic-based remote phosphor configuration with minimal increase in phosphor etendue over that of the source, as well as greatly improved spatial uniformity. Moreover, the yellow phosphor back-emission is recycled with a blue-pass mirror that re-illuminates the phosphor to increase its luminance. The result is a new white-light source with superior luminance, efficacy, and uniformity.
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Bill Parkyn, Bill Parkyn, Julio Chaves, Julio Chaves, Waqidi Falicoff, Waqidi Falicoff, } "Remote phosphor with recycling blue-pass mirror", Proc. SPIE 5942, Nonimaging Optics and Efficient Illumination Systems II, 59420M (8 September 2005); doi: 10.1117/12.619155; https://doi.org/10.1117/12.619155

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