Patent ID: 8094528

Claim:
A method of reading medium information on a recording medium, comprising: setting a plurality of successive radial positions including a first radial position, a second radial position, and a third radial position on the recording medium, wherein the plurality of radial positions are spaced apart from each other by a prescribed distance; detecting an index mark pattern at the first radial position; detecting an index mark pattern at the second radial position spaced apart from the first radial position by the prescribed distance; detecting an index mark pattern at the third radial position spaced apart from the second radial position by the prescribed distance, wherein the prescribed distance ranges from a first distance to a second distance, the first distance being a width affected by an eccentricity component and the second distance being (a width of a control feature outer ring area−the first distance)/2; selecting the second radial position between the first radial position and the third radial position, wherein the selected second radial position corresponds to a radial position located between an innermost radial position and an outermost radial position of the plurality of radial positions at which index mark patterns are detected; and obtaining medium information at the selected second radial position.