Photometric measurement for LED based sources

The utilization of SSL (Solid State Lighting), better known as LED, in internal and external application of lighting and displays is becoming nowadays more important. Their utilization is growing as an alternative to more traditional technologies due to their tangible features such as luminous efficacy comparable to the traditional compact fluorescent or HPS lamps, possibility to use CC forward current, wide opportunity to integrate renewable FV systems and operate in a way to ensure "smart" control and management operations to reduce energy consumption. In this paper is presented a simplified system set up at the Built Environment Control Lab of Department of Architecture and Industrial Design of Seconda Università di Napoli, for the photometric characterization of LED based sources. The facility is provided with photometric bench within a dark room equipped with both traditional luminance meter and videoluminancemeter (LMK) that acquires luminance map of a suitable target upon which falls the luminous flux emitted by the LED and LED & lens system under consideration. Starting from luminance map (ie. luminance of each pixel of CCD matrix), target reflectance and considering the application of cosine square law for a point source, it can be easy derived the luminous intensity distribution of the source considered. The methodology developed has been checked vs. a set of led and lens assembling system commercially available, giving useful information on the reliability and accuracy of results.