Luminance coefficient

The luminance coefficient ( RL, q, q _t, etc.) in the case of retroreflection is the quotient of the luminance L of the reflective material in a specified direction and the illuminance E at the reflector perpendicular to the incidence of light .

${\displaystyle RL={\frac {L}{E}}}$

usually given in candela per square meter and lux ( ) ${\displaystyle \mathrm {\frac {cd}{m^{2}\,lx}} }$

It measures perpendicular to the direction of incidence, i.e. the reflection losses. It is used to assess the nighttime visibility of road markings and warning notices and the performance of retroreflective surfaces.

There is also a direction-dependent definition. This is used, for example, to evaluate facade systems and establishes a relationship between the luminance that can be perceived in the room and the illuminance on the facade from a certain direction. This quantifies the reaction of the system to solar radiation dependent on the position of the sun .

literature

• Susanne Köhler: Metrological determination of luminance coefficients for road surface courses at flat angles . Dissertation Technical University Berlin, Berlin, October 2011 ( pdf , opus.kobv.de)

proof

• Luminance coefficient techniklexikon.net,

1. ↑ SN 640 877 markings; Lighting requirements.
2. ↑ follows approximately DIN V 18599, Part 4: Useful and final energy requirements for lighting. See J. de Boer, B. Panhans, F. Stößel: New photometric evaluation of facade systems: The IBP photogoniometer. In: IBP Communication 37 (2010), New Research Results, in Brief , 499 ( Article , pdf, ibp.fraunhofer.de)