Method of controlling laser power of main beam by monitoring sub beam

Abstract

A method is designed for recording information on an optical disk in the form of a sequence of pits along a track of the optical disk. The method is carried out by the steps of generating a main optical beam and a sub optical beam while modulating a power of the main optical beam and the sub optical beam according to a recording signal representative of the information, the main optical beam having a power sufficient to form the pit, the sub optical beam having a power insufficient to form the pit, irradiating the main optical beam along the track to form the sequence of pits, irradiating the sub optical beam onto a vicinity area which is not irradiated by the main optical beam but which is adjacent to an area irradiated by the main optical beam, detecting a first return signal level of the sub optical beam reflected back from the vicinity area at a timing when the pit is formed by the main optical beam, detecting a second return signal level of the sub optical beam reflected back from the vicinity area at another timing when the pit is not formed, and controlling the power of the main optical beam in a real time basis during the recording of information based on both of the first return signal level and the second return signal level of the sub optical beam.