Patent ID: 7558167
Filing Date: 2009-07-07
Classification: G11B

Abstract:
1. A tilt detecting apparatus for performing tilt detection of an information recording medium, in which a plurality of recording layers are laminated and which has a disc shape, in an information reproducing apparatus, an information recording apparatus, or an information recording/reproducing apparatus, which can perform at least one of reproduction and recording of record information as for each of the recording layers, by irradiating the information recording medium with laser light, said tilt detecting apparatus comprising: a first changing device for changing a focus position of the laser light in a lamination direction of the recording layers; a second changing device for changing the focus position in a radial direction of the information recording medium; a tilt detecting device for detecting an amount of tilt of the information recording medium with respect to the laser light, on the basis of a photo-detection signal of light from the information recording medium caused by the laser light; and a controlling device for (i) controlling said first changing device to set the focus position onto one recording layer out of the recording layers, controlling said second changing device to displace the focus position to a j-th radial direction position (wherein j is a natural number) on the information recording medium, and controlling said tilt detecting device to detect the j-th amount of tilt for the one recording layer, then, (ii) controlling said first changing device to set the focus position onto another recording layer out of the recording layers while the focus position is fixed at the j-th radial direction position and controlling said tilt detecting device to detect the j-th amount of tilt for the other recording layer, then, (iii) controlling said second changing device to displace the focus position to a j+1-th radial direction position on the information recording medium while the focus position is fixed on the other recording layer and controlling said tilt detecting device to detect the j+1-th amount of tilt for the other recording layer, and then, (iv) controlling said first changing device to set the focus position onto the one recording layer while the focus position is fixed at the j+1-th radial direction position and controlling said tilt detecting device to detect the j+1-th amount of tilt for the one recording layer.