The theoretical aspects of the playback of an optical videodisk have been extensively investigated by Hopkins1 and others on the basis of scalar diffraction theory. In this paper we describe the results of similar theoretical calculations from the perspective of digital optical recording. It is shown that because of the interference between different diffraction orders in the laser beam readout process, the mapping between the length of the recorded hole on the disk and the pulse length of the recovered electrical signal is highly nonlinear.