Abstract: An optical data storage medium with burn-film having changeable optical properties, for example, changeable reflective power as a result of sufficiently intense illumination, due to hole-burning in the film, is provided with optical structures close to the burn-film for focusing and positioning during recording and reading of individually interpretable data bits (spots). The optical structures are preferably monodisperse, transparent spheres with a diameter in the range of 1-100 .mu.m. Illumination is performed selectively from a number of predetermined angles (.THETA.i, .phi.j) during recording and reading, and the number of individual data spots under each sphere corresponds roughly to the number of angles.