A b s t r a c t. A principle of measurement of geometry of irregularly formed objects is presented. The ring-shaped sensor is based on the principle of a one-way light barrier. Sections of formed chords describe the contours of the objects. By movement of the object a spiral is formed which envelope the object. Simple calculating algorithms allow the precise determination of volume, axis measurements and shape of the object to be measured in real-time. The results show a high accuracy of the sensor principle.