Patent ID: 7145854
Filing Date: 2006-12-05
Classification: G11B

Abstract:
1. A recording layer determination apparatus comprising: a light irradiator that irradiates light to a recording medium; a scanning controller that scans the recording medium using a focus of the light in a direction of thickness; a signal generator that generates at least a sum signal and a focus-error signal based on reflected light of the light obtained from the scanning; a first threshold value setter that sets a first threshold value with respect to the sum signal; a first pulse generator that generates a first pulse during a period of time in which a level of the sum signal becomes larger than the first threshold value; a second threshold value setter that sets a second threshold value with respect to the focus-error signal, a level of the focus-error signal becoming larger than the second threshold value and then becoming smaller than the second threshold value when the focus of the light traverses one recording layer; a second pulse generator that generates a second pulse during a period of time in which the level of the focus-error signal becomes larger than the second threshold value; a third threshold value setter that sets a third threshold value which is smaller than the second threshold value with respect to the focus-error signal, the level of the focus-error signal becoming smaller than the third threshold value and then becoming larger than the third threshold value when the focus of the light traverses said one recording layer; a third pulse generator that generates a third pulse during a period of time in which the level of the focus-error signal becomes smaller than the third threshold value; a period determinator that determines a detection period of a recording layer based on the first pulse; an interval determinator that in the detection period specifies an initial generated second pulse and a last generated third pulse, and determines an interval from a time at which the specified second pulse is formed until a time at which the specified third pulse is formed, or specifies an initial generated third pulse and a last generated second pulse, and determines an interval from a time at which the specified third pulse is formed until a time at which the specified second pulse is formed; and a recording layer determinator that determines that the recording medium is a single layer type having a single the single recording layer when a value of the interval is smaller than a predetermined value, while determining that the recording medium is a multiple layers type having a plurality of recording layers when the value of the interval is larger than the predetermined value.