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...lculations that the evolution of the populations of excited atomic states – thus the intensity of the spontaneous emission – follows well the flux surfaces. As a consequence if the lines of sight are not tangential to the flux surfaces (like in Fig. 2), then the measured light profile, I(x) will be smoothed in comparison 34th EPS Conference on Plasma Phys. Warsaw, 2 - 6 July 2007 ECA Vol.31F, P-2.137 (2007) with an ideal, hypothetical case of a 1D beam measurement (see Fig. 3). The 1/ ( ) ( ) /I x dI x dx© logarithmic derivative playing important role in the density reconstruction calculation [4] will be decreased because of the effect of such a distortion, which leads to the underestimation of ne, in a static density profie measurement. The systematic error of the recontructed ne distribution is about 30%, in the example represented on Fig. 1- 3, showing a calculation with typical plasma (COMPASS-D #30866) and beam parameters (40 keV, width: 2 cm). Distorsion can be even more severe in case of: 1. wider beam, 2. lines of sight less tangential to the flux surfaces, 3. higher electron density gradient along the beamline. Light profile correction A new algorithm has been developed, whic...