In-process display analysis: fast testing using the spectroradiometer

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German article by Dr. Ðenan Konjhodžić

The brightness and color reproduction of a flat panel display is factory calibrated. For economic reasons this should take place in an automated process at the production stage. Spectroradiometers enable precise photometric and colorimetric measurements, and are fast enough for use in production.

The subjective brightness sensitivity of the human eye is not linear, but roughly proportional to the logarithm of the intensity of the physical stimulus. Thus the brightness reproduction of a display must be adjusted accordingly. This is possible with the aid of gamma correction – a corrective function frequently used in image processing. With gamma correction a linearly increasing variable is transformed into a non-linear course, so that the brightness of the display is perceived as uniform by the observer. Expressed mathematically...

published in Elektronik 17/18