Illumination optics for indoor lighting, automotive and street lighting

In the 20th Century, illumination optics systems were developed based on the concepts of reflectors, prisms and Fresnel optics for incandescent tungsten and discharge lamps of relatively extensive geometrical dimensions. Luminous intensity distributions and spectral as well as color properties were generally constant over the time of use. Therefore, it was not possible to develop smart lighting systems with variable spectral, geometrical and colorimetric features depending on application context (e.g. school, hospital, office, small or main street in a city), on the time of the day and on weather conditions. In the last 12 years, LED technology has been developing at a very fast pace. In the period from 2004 until 2016, the focus of lighting technology and lighting companies was on the elaboration of stable and efficient luminaire systems. Several new concepts of free-form reflector optics, highly efficient lens systems with cost-optimized manufacturing steps and new optical materials (e.g. optically transparent plastic materials, coatings, silicone) arose. The resulting new indoor and outdoor lighting systems exhibited high luminous efficiencies in the order of 145–160 lm/W as well as increased mechanical and optical stability. In the last 3–4 years, the philosophy and the concepts of lighting design in the lighting industry have achieved a new quality level. The concepts of human centric lighting that represent a deep knowledge on the impact of light on human behavior (alertness, sleep quality, mood, activity, well-being) combined with the concepts of Internet-based lighting control and cloud-based data processing applying machine learning and neuronal network methods will help lighting technology (in general) and illumination optics (in particular) achieve a new development stage. Human centric lighting concepts can be efficiently implemented to achieve their strongest impact only in the context of “dynamic lighting”. “Dynamic lighting” means the use of variable light source spectra with more or less non-visually stimulating spectral content in the range between 400 nm and 550 nm, with variable luminous intensity distributions over the time of the day and with a dependence on weather conditions and lighting applications. Consequently, the following aspects of illumination optics design will become essential in the future: (a) Details of the spectral and colorimetric distributions of the light from the light source (LED component or LED module) over the entire emission angle range will be necessary in order to design the optics to achieve a uniform white light distribution at a selected color temperature; (b) A high-quality optics will be indispensable in order to mix the optical radiations from the different LED groups with different spectral distributions in order to obtain the desired polychromatic light beam with well-defined spectra and luminous intensity distributions. Colorimetric uniformity of the mixed light beam shall be ensured over the entire angular emission range and over the whole light emitting area; (c) Photobiologically negative effects of optical radiation (e.g. glare and blue light hazard) should be limited by the design of suitable illumination optics.