Optical information recording method

DETAILED DESCRIPTION A first object of this invention is to provide a method of realizing a high erasability when a signal is to be overwritten on a recording medium using a single laser beam.
A second object of this invention is to provide a recording method which makes it possible to provide a reproduced signal with less waveform distortion.
In one aspect of the present invention, a light beam for forming record marks on a recording medium is applied also, after having been modified to have a reduced energy, to an area between the record marks to cause the recording medium at the area to melt but not change to a record mark forming state.
That is, in a method of recording an information signal on a recording medium which is changeable between a first state (written or recorded state) and a second state (non-recorded or erased state) which are optically distinguishable (or which are different in optical properties) from each other by application of a reading light beam, record marks are formed each by application of a writing light beam to the recording medium for a predetermined duration to cause the recording medium to melt at a portion applied with the writing light beam and become, after cooled, the first state.
To an area between the record marks is applied a light beam which is the writing light beam having been modified to have a reduced energy to cause the area to melt and become a state which is substantially identical to the second state.
As the result, the area of the recording medium beside the record mark formed portions becomes uniformly the state identical to the erased state.
This ensures the reliability of the information signal recorded on the recording medium.
The light beam applied to the area between the record marks may preferably consist of a train of auxiliary light pulses each having a pulse width smaller than the predetermined duration of the writing laser beam.
However, the modification of the light beam may be such that the peak power level is reduced.
It is the only requirement for the light beam applied to the area between the record marks to have an energy which does not cause the recording medium to change its state to the first state