(organic LED) structures include several thin organic layers sandwiched between electrodes. The thickness and optical constants of these layers need to be measured and controlled in R&D and production. system is perfectly suited for OLED thickness measurement. In case of the patterned sample, a small spot measurement (on a pixel), is done using . It offers non-contact, robust and inexpensive metrology for this application. Individual layers, complete OLED structure and/or thickness and dispersion of the organic layers can be measured. OLEDs are used in a variety of applications from TV screens to cell phones. This requires the use of different materials for implementation of the OLED. Typical implementation of the are displayed on the left. One of the interesting implementations uses NPD (hole transport material) and (electron transport material) materials. Both of these materials have a fairly comples dispersion, especially, in the UV range that depends on the deposition conditions. Alq3 is particularly sensitive to deposition conditions since it has several crystalline phases.