An optical information recording system in which the energy when transmitted to the recording layer is constant

An optical system for recording information on a photosensitive layer deposited on a substrate, comprising a coherent light source for emitting a radiation beam, said source having a control input, optical means for dividing said beam into a reference beam and a second beam, an optical device for focusing said second beam onto said photosensitive layer, a first part of said second beam being transmitted to said photosensitive layer and a second part being reflected by said photosensitive layer, first means for detecting said reference beam having a first output for delivering a first signal proportional to the energy E(t) of said second beam, second means having a second output for delivering a second signal proportional to the energy R(t) E(t) reflected by said photosensitive layer, storage means for storing signals characteristic of the energies E(t) and R(T) E(t) at an instant taken as reference, said energies being Eo and RoEo, said storage means having two outputs, and logic means having four inputs respectively connected to said first and second outputs of said storage means for forming an error signal, said logic means having an output for delivering said error signal, said output of said logic means being connected to said control input of said source, the energy when transmitted to said photosensitive layer being kept constant.