Measuring light emission from LEDs

LEDs are used in many applications, and new applications are found every day. To address this market, LEDs often come in vastly different varieties, shapes, sizes, packages and modules. Measurement of these LEDs is required so that they can be compared and selected within a global market. This paper presents the different types of optical quantity that can be measured for these LEDs together with guidelines for measurement. In particular, the protocols for measuring Averac,ed LED Intensity, Partial LED Flux, luminance and illuminance are presented. Some of these quantities are new, and the reader may be unfamiliar with them. Definitions are provided where appropriate. Many LED measurements have associated standard measurement conditions, which apply to LEDs and not other sources. Other measurements depend critically on setup conditions but lack standardization and hence details of methods used must accompany results. Where standard conditions exist these are detailed and where they do not advice is provided on the best methodologies. Work in establishing standard conditions is on-going, especially in Commission Internationale de Eclairage (CIE) technical committees, and information on this work is provided.