CHARACTERIZATION OF MULTI-EMITTER TUNEABLE LED SOURCE FOR ENDOSCOPIC APPLICATIONS

In this paper we describe our own construction of a tuneable light source based on a set of light emitting diodes covering the visible spectrum using a homogenizing rod instead commonly used low energy-efficient integrating spheres. The expected prime application of the source is a medical endoscopic system, however it is possible to use it also for other purposes requiring both multispectral operation and a tuneable white light source. We describe the construction of the source and include precise characterization of the output white light - distribution of CCT, Duv, Delta u'v' and colour rendering indexes (R-a, R-9, R-f, R-g) of light in several planes located at various distances. The obtained results prove that our source is characterized by very good colour rendition according to the R-a and R-f method for various correlated colour temperatures (2700 - 6500) K. As an example of application images of the Macbeth colour chart registered with an RGB camera included in the laboratory measurement stand are presented. The obtained results prove that, after whole system calibration, this source can be used in many applications, where evaluation of objects requires precise analysis of their colour and multispectral procedures.