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11 February 2010 Novel sensor for color control in solid state lighting applications
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LED wavelength and luminosity shifts due to temperature, dimming, aging, and binning uncertainty can cause large color errors in open-loop light-mixing illuminators. Multispectral color light sensors combined with feedback circuits can compensate for these LED shifts. Typical color light sensor design variables include the choice of light-sensing material, filter configuration, and read-out circuitry. Cypress Semiconductor has designed and prototyped a color sensor chip that consists of photodiode arrays connected to a I/F (Current to Frequency) converter. This architecture has been chosen to achieve high dynamic range (~100dB) and provide flexibility for tailoring sensor response. Several different optical filter configurations were evaluated in this prototype. The color-sensor chip was incorporated into an RGB light color mixing system with closed-loop optical feedback. Color mixing accuracy was determined by calculating the difference between (u',v') set point values and CIE coordinates measured with a reference colorimeter. A typical color precision ▵u'v' less than 0.0055 has been demonstrated over a wide range of colors, a temperature range of 50C, and light dimming up to 80%.
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Alex Gourevitch, Thomas Thurston, Rajiv Singh, Bartosz Banachowicz, Vladimir Korobov, and Cliff Drowley "Novel sensor for color control in solid state lighting applications", Proc. SPIE 7617, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XIV, 761711 (11 February 2010);

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