In case a gap between a bisecting line BL12 which bisects the pinhole SS12 along the longitudinal direction of the focused tracks and the center line CL11 is identical to that between a bisecting line BL13 which bisects the pinhole SS13 and the center line CL11 along the longitudinal direction of the focused tracks, {HEAD ~ the first portion} of the focused laser beam containing the data read from the target track entirely passes through {TAIL ~ the pinhole SS11} 
In case a gap between a bisecting line BL12 which bisects the pinhole SS12 along the longitudinal direction of the focused tracks and the center line CL11 is identical to that between a bisecting line BL13 which bisects the pinhole SS13 and the center line CL11 along the longitudinal direction of the focused tracks , { HEAD ~ the first portion } of the focused laser beam containing the data read from the target track entirely passes through { TAIL ~ the pinhole SS11 }
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