Device and method for optical measurement

A method and device for optical measuring of small particles for analysis of the quality of the particles. A sample-feeding carrier is adapted to take up particle samples in sample holders and transport the particle samples to a place for optical measurement. A mirror-supporting means follows the movement of the carrier and has mirrors matching the sample holders. A device illuminates a particle sample when positioned for optical measurement and a detector, which is sensitive to electromagnetic radiation, records a result of optical measurement of the illuminated particle sample. A mirror reflects the particle sample, so that a mirror image thereof stands essentially still seen from the detector, when a measurement is being recorded, owing to the fact that the mirror image of the particle sample falls on a center axis of the movement of the mirror-supporting means.