Reproducing method and reproducing apparatus for optical recording medium

A reproducing method for an optical recording medium for reproducing information from an optical recording medium having a recording layer reacting in a photon mode, said method comprising the steps of:

• irradiating said recording layer with a recording beam of power being set within a range of P.sub.rep (W) appearing in the following expression (II):
• ##EQU21## here SNR represents an S-N power ratio (PP/rms) required for a system, e represents an elementary electric charge of 1.6.times.10.sup.-19 (C), B represents a bandwidth (Hz) of said system, .eta. represents sensitivity (A/W) of a photodetector with respect to a gain 1, .gamma. represents pickup efficiency, R.sub.ave represents an average reflectance of said optical recording medium, .DELTA.R represents a difference in reflectance between recorded and unrecorded portions of said optical recording medium, k represents the Boltzman constant 1.38.times.10.sup.-23 (J.multidot.K.sup.-1), T represents an absolute temperature (K), I.sub.amp represents an average noise current (A) of a reproducing preamplifier, and Z represents impedance (.OMEGA.) of said reproducing preamplifier;
• and
• detecting said reproducing beam passing through said recording layer for reproducing recorded and unrecorded states.

A reproducing method for an optical recording medium for reproducing information from an optical recording medium having a recording layer reacting in a photon mode, said method comprising the steps of:

• irradiating said recording layer with a reproducing beam of power being set within a range of P.sub.rep (W) appearing in the following expression (II):
• ##EQU22## where SNR represents an S-N power ratio (PP/rms) required for a system, e represents an elementary electric charge of 1.6.times.10.sup.-19 (C), B represents a bandwidth (Hz) of said system, .eta. represents sensitivity (A/W) of a photodetector with respect to a gain 1, .gamma. represents pickup efficiency, R.sub.ave represents an average reflectance of said optical recording medium, .DELTA.R represents a difference in reflectance between recorded and unrecorded portions of said optical recording medium, k represents the Boltzman constant 1.38.times.10.sup.-23 (J.multidot.K.sup.-1), T represents an absolute temperature (K), I.sub.amp represents an average noise current (A) of a reproducing preamplifier, and Z represents impedance (.OMEGA.) of said reproducing preamplifier;
• detecting said reproducing beam passing through said recording layer for reproducing recorded and unrecorded states;
• and
• irradiating said recording layer with light in a wavelength band allowing substantially no absorption by a photon mode material contained in said recording layer as a servo beam, thereby carrying out at least either focus servo control or tracking servo control.