LED: New Light Sources Means New Ways of Lighting – An Overview

The emergence of a new source of artificial light requires rethinking how to light in the most effective built environment and human activities. Based on the characteristics of human perception and the photometric data of LEDs the aspects of quantity, quality and spatial distribution of luminous flux are discussed. QUANTITY: From the human factors point of view, the quantitative aspect of LED source is their class laser characteristics. Solutions can be achieved by the design of lenses and/or reflector that diffract and/or hide the LED chip. Refracted, or even diffracted, light beam can be of interest, not only because it breaks directionality of the flow, but also for spatial effects. QUALITY: In the case of a quasi-monochromatic light, such as LED, it is essential to attain a match between the spectrum of the light source and colorimetric characteristics of the secondary emissive surface. This help maximizing Lambertian reflection and minimizing material absorption of energy flow and increase the efficiency in terms of luminance and meet the challenges of sustainable development. SPATIALITY: In the case of a luminous flux made up of multiple LEDs, the light source behaves as a lighting fixture. For instance, by combining an asymmetrical elliptical reflector, that reduces glare, with a lenses, whose outer surface has a curved shape similar to the desired polar diagram to maximize light distribution, plus an appropriate direction of each LED chip can help to reach higher luminous efficiency.