Patent ID: 6845074

Claim:
An information readout apparatus for irradiating a recording medium having a recording layer and a readout layer with a light beam and reading recorded information of the recording layer by opening a detecting window smaller in size than an area irradiated with the light beam, said apparatus comprising: a resolution detecting means for detecting a resolution based upon sampled values of a readout waveform of an isolated mark recorded/formed on said recording medium, said resolution detecting means detects the resolution based upon a quotient obtained by dividing a difference X between a sample value Y near a peak of said isolated mark and a sample value adjacent to said sample value Y by said sample value Y near the peak, or X/Y; a reference value output means for outputting a reference value for said resolution; and, a readout control means for controlling the size of said detection window so as to make said detected resolution close to said reference value.