An apparatus is provided for reading an information track, on a writable disk with reference tracks, almost immediately after the information track has been written. Precise control of the positioning of the laser source, which provides the parallel beams for writing and reading, is accomplished by an analysis of the electrical signal produced by a reference beam reflected from an edge of a reference track on the disk/medium. Oscillatory movement of this beam across a track edge produces the desired electrical signal for precise position determination and, hence, for position control.