LED illuminant on the ambient light Anqing Liu * , Mishra Sandipan, and Michael Shur Smart Lighting Research Engineering Center, Rensselaer Polytechnic Institute, Troy, NY *liua4@rpi.edu ABSTRACT We develop an approach for combining illuminance and spectral power distribution of the LED and ambient light and apply our technique for developing an LED camera flashlight balancing the illuminance contrast between object and background. Our method uses the closed loop, multiobjective optimization comprising: (1) characterizing the lighting task by illuminance, correlated color temperature (CCT), and statistical color quality indices that include a set of Statistical Color Quality Metrics and the Color Rendition Index (CRI) implemented with indexes of S (saturation) or D (dulling); (2) measuring the illuminance and the spectrum of the ambient light on the target lighting surface, which might depend on all the sources proving illumination and on the reflected light; (3) determining the desired illuminance of the LED source on the target lighting surface; (4) calculating the desired luminous flux of the LED source according to the desired illuminance; (5) constituting the SPD of the LED source; (6) calculating the relative spectra counts of the LED source and the ambient light on the target lighting surface (7) calculating the CCT and statistical color quality indexes of the combined light; (8) repeating the above steps until the resulting SPD is close enough to the expectation. Using the above method, an LED camera flashlight has been designed, which works together with usual fluorescent ambient light and generates working lighting environment with high fidelity and high CCT (6000K). The spectrum and luminous flux of the LED lamp is automatically tunable with a change of the ambient light. Key words: Ambient light augmenting, multi-objective optimization, color rendition, statistical color quality metrics 1. INTRODUCTION Lighting sources using LEDs have unprecedented flexibility in controlling the spectral power distribution (SPD) of light. For multi-color channel LED illuminants, the intensity of each channel might be independently adjusted to constitute desired SPDs meeting various lighting needs in the color quality of lighting [1], [2] . In particular, SPDs of such illuminants can have very distinct ability to saturate or desaturate the colors of illuminated objects [3-6] . Implemented with intelligently controlled LED clusters that generate metamers of white light, the illuminants with continuously tunable color rendition properties have been developed [7] . Such intelligent light sources have been applied to many practical needs, including improving visual impression of art work [8-10] and restoring the original colors of aged paintings [11] . Also they can meet specific color-quality requirements of people with different subjective needs, including those depending on cultural backgrounds. Cross-culture research showed that different cultural groups could have different responses and preferences to colors [12] , color qualities [13], [14] , and color combinations [15], [16] . Conventional light source such as incandescent bulb, fluorescent bulb and tubes have served lighting market in various applications. Their advantages include high brightness, easy beam shaping, and low cost. With an increasing need for high color quality lighting, some of the conventional sources are modified in response of different requirements. To this end, the advanced phosphor technology is used to meet the requirements of the specific lighting applications. Warm-white fluorescents and cool-white fluorescents are usually used for residential and office lighting, respectively. While conventional light sources served mostly as ambient light in many applications, they still cannot meet the increasing lighting needs because Thirteenth International Conference on Solid State Lighting, edited by Matthew H. Kane, Jianzhong Jiao, Nikolaus Dietz, Jian-Jang Huang, Proc. of SPIE Vol. 9190, 919004 © 2014 SPIE · CCC code: 0277-786X/14/$18 · doi: 10.1117/12.2062270 Proc. of SPIE Vol. 9190 919004-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 11/10/2014 Terms of Use: http://spiedl.org/terms