Patent ID: 7801003
Filing Date: 2010-09-21
Classification: G11B

Abstract:
1. An optical disc type determining method of determining a mounted optical disc to be any one of the following types of selectively mountable optical discs: a first optical disc which has a first signal surface compliant with a first recording format located a first distance away from a beam entrance surface of a first optical disc substrate, a first laser beam being applied to the first signal surface to record or reproduce an information signal; a second optical disc which has a second signal surface compliant with a second recording format located a second distance away from a beam entrance surface of a second optical disc substrate, the value of the second distance being smaller than that of the first distance, a second laser beam at a wavelength shorter than that of the first laser beam being applied to the second signal surface to record or reproduce an information signal; and a third optical disc which has a third signal surface compliant with the first recording format located a third distance away from a beam entrance surface of a third optical disc substrate, the value of the third distance being between those of the first distance and the second distance, the first laser beam being applied to the third signal surface to record or reproduce an information signal, the method comprising: a focus error signal detecting step of selectively applying the first and second laser beams to the signal surface of the optical disc to carry out a focus search and, at the same time, detect first and second focus error signals; a focus error signal amplitude value detecting step of detecting first and second focus error signal amplitude values on the basis of the first and second focus error signals; a focus balance signal-value detecting step of finding a plus side level FEP and a minus side level FEM of each of the first and second focus error signals to detect first and second focus balance signal values by the calculation of 100×(FEP−FEM)/(|FEP|+|FEM|); and an optical disc type determining step of determining whether the optical disc is the first optical disc with reference to at least one of the first and second focus error signal amplitude values, and then, in the case where the optical disc is determined not to be the first optical disc, determining the optical disc to be the third optical disc when a sum value of the addition of the first focus balance signal value to the second focus balance signal value is equal to or more than a predetermined threshold value, while determining the optical disc to be the second optical disc when the sum value is smaller than the predetermined threshold value.