The invention relates to an optical arrangement provided for a spectral fanning out of a light beam, preferably the detection beam path of a confocal microscope, especially for the subsequent splitting of the fanned out beam out of the dispersion plane thereof. The distances from its hard disk drive fixing parts to the substrate center are not the same. A tubular cylindrical rigid roller cover is open at one end and dimensioned to be positioned over the roller so that the cover entirely encloses the roller. The end portions and each contact the conductive film at least at its upper surface and end surface.