Patent ID: 7733747
Filing Date: 2010-06-08
Classification: G11B

Abstract:
1. An information recording apparatus comprising: a mounting means on which a removable disk-shaped optical recording medium is set in place; a rotation driving means for rotating the disk-shaped optical recording medium set on the mounting means at a predetermined velocity; a pulse signal generating means for generating N (N is a natural number) pulse signals in a predetermined cycle while the disk-shaped optical recording medium is being rotated one full turn by the rotation driving means; a counting means for counting the N pulse signals generated by the pulse generating means; a storage means for storing an axial-runout amount detected in a predetermined radial position on the disk-shaped optical recording medium in timing of generation of the pulse signals by the pulse signal generating means in correspondence with the count value in the counting means; a light source to emit a light beam of a predetermined wavelength modulated with information to be written to the information recording surface of the disk-shaped optical recording medium; a near-field light projecting means for condensing a light beam emitted from the light source and projecting the condensed light beam as near-field light to the information recording surface when it is located in a field near the information recording surface of the disk-shaped optical recording medium; a radial-position information detecting means for detecting radial-position information indicative of a radial position on the information recording surface of the disk-shaped optical recording medium being irradiated with the light beam from the near-field light projecting means; a gain generating means for generating a predetermined gain corresponding to radial-position information detected by the radial-position information detecting means; an axial-runout amount reading means for reading an axial-runout amount stored in the storage means correspondingly to the count of pulse signals counted by the counting means; a first controlling means for generating a control signal by multiplying the axial-runout amount read by the axial-runout amount reading means by the predetermined gain generated by the gain generating means to control the near-field light projecting means to follow the axial-runout amount; a return-light amount detecting means for detecting a return-light amount of the near-field light projected to the information recording surface; and a second controlling means for controlling the near-field light projecting means on the basis of the linear characteristic of the return light amount of the near-field light detected by the return-light amount detecting means to keep a predetermined distance within the near field from the information recording surface.