Colour compensation for LED technology enables colour-constant RGB luminaires

Deviations in luminous flux and hue occur during LED production, but colour compensation technology allows luminaire manufacturers to provide colour-constant products for demanding applications, writes Thomas Schielke of ERCO Leuchten.

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Lighting designers have always used coloured light to add emphasis or provide atmospheric effects. This was done using coloured lamps or luminaires with colour filters, but thanks to electronically controlled RGB colour mixing luminaires it is now possible to produce any colour of light with LEDs. Using colour compensation, the luminaire manufacturer is able to compensate for the deviations in luminous flux and hue due to the manufacturing tolerances of LEDs, and thus to satisfy the highest demands of designers for uniformity, e.g. for coloured wall-washing.

Manufacturing deviations
High colour saturation is one of the characteristic properties of LEDs. However, the actual colour of the individual LEDs is determined by two factors that are subject to certain manufacturing fluctuations: the luminous flux and the dominant wavelength. In practice this means that the colours of light from two identical LED luminaires can in fact deviate from one other. Semiconductor manufacturers classify every LED according to these two criteria, sorting them into different categories called "bins".

Some luminaire manufacturers demand that their suppliers provide bins that are particularly stringently selected with respect to the dominant wavelength. There is a good reason for this: the greater the accuracy with which an individual light source emits a certain wavelength from the outset, the more exact the match between light colours of several luminaires. But even with the most stringent selection, deviations in both the luminous flux and the dominant wavelength between individual LEDs of one colour still have to be accepted.

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This article was published in the April 2007 issue of LEDs Magazine.

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