ABSTRACT

The availability of quasi-monochromatic Light Emitting Diodes (LEDs) with peak wavelengths distributed over the visible spectrum has opened the way to the development of multichannel LED light sources generating tunable illumination spectra. As the color appearance of an object is strongly influenced by the spectral power distribution of the light source, these multichannel light sources are also commonly used as a research tool in color quality studies. In a number of studies, spectrum optimization algorithms are applied in order to generate a target spectrum directly. Other papers report on the calculation of an illumination spectrum with the aim to optimize one or a set of general quality metrics such as the luminous efficacy of radiation and the color rendering index R_a or R_f. The approach followed in this paper is to explore and visualize, for a given multichannel LED light source, the lighting quality parameters which can be reached within the chromaticity gamut for a selected object. For any predefined target white point chromaticity, the illumination metamers are calculated analytically within the constraints defined by the multichannel LED light source under consideration. The solution space is sampled with a brute force method and the values of any general or specific color quality index can be evaluated. For a predefined object spectral reflectance (or one typical spectral reflectance representative for a set of objects), the object chromaticity gamut is derived. Several object chromaticity targets within the gamut, such as the memory color of familiar objects, can be selected and the impact of “local” variations of the hue and chroma within this gamut on the general and special lighting quality indices and on the user preference can be checked. This can simplify the selection of an object-based optimum illumination spectrum. The approach is illustrated in practice using a five-channel LED light source which was developed in-house.

摘要

峰值波长分布在可见光谱上的准单色发光二极管 (LED) 的可用性为开发产生可调谐照明光谱的多通道 LED 光源开辟了道路。由于物体的颜色外观受光源光谱功率分布的强烈影响，这些多通道光源也常被用作颜色质量研究的研究工具。在许多研究中，为了直接生成目标频谱，应用了频谱优化算法。其他论文报告了照明光谱的计算，旨在优化一个或一组一般质量指标，例如辐射的发光效率和显色指数 R _a或 R _f. 本文采用的方法是探索和可视化对于给定的多通道 LED 光源，在选定对象的色度范围内可以达到的照明质量参数。对于任何预定义的目标白点色度，在所考虑的多通道 LED 光源定义的约束范围内分析计算照明同色异谱。解决方案空间使用蛮力法进行采样，并且可以评估任何一般或特定颜色质量指数的值。对于预定义的对象光谱反射率（或一组对象的一个​​典型光谱反射率代表），导出对象色度域。色域内的几个物体色度目标，例如熟悉物体的记忆色，可以选择，并且可以检查该色域内色调和色度的“局部”变化对一般和特殊照明质量指标以及用户偏好的影响。这可以简化基于对象的最佳照明光谱的选择。该方法在实践中使用内部开发的五通道 LED 光源进行说明。