Patent ID: 7113470

Claim:
In an optical recording and reproducing method for recording and reproducing an optical recording medium by an optical system using recording and reproducing light with a wavelength selected in a range of from 780 nm±10 nm and an objective lens with a numerical aperture NA selected in a range of from 0.45±0.01, an optical recording and reproducing method characterized in that first and second optical recording mediums with different recording capacities are recorded and reproduced, said first optical recording medium is constructed by using a substrate with a track pitch selected in a range of from 1.5 μm to 1.7 μm and a groove depth selected in a range of from 70 nm to 90 nm, said second optical recording medium is constructed by using a substrate with a track pitch selected in a range of from 1.2 μm to 1.3 μm and a groove depth selected in a range of from 150 nm to 180 nm and that said second optical recording medium records information of which shortest recording bit length is less than a bit length corresponding to a cut-off frequency of a modulation transmission function of said optical system.