Optical disk technology today finds widespread application in VLP, CD and DS equipment. The required specifications of lenses for such systems are stated. Types of lenses which meet these requirements are discussed. Their image quality is given by RMS of wave aberration, by point spread function especially by encircled energy or by MTF. Due to the automatic servo focussing technique a certain amount of field curvature can be tolerated. Methods of measuring the image quality of such lenses are shown e.g. examination of point spread function, interferometric measurement of wave aberration and MTF measurement. The results are compared with theoretical values.