Abstract: An optical disc recording and reproducing apparatus are provided in which even if a focusing error signal fluctuates suddenly by surface deflection or an obstacle such as scratch or dust on the surface of an optical disc, an effective recording laser power does not decrease but proper recording, erasure, and reproduction can be executed. An ordinary laser power for recording and a laser power for defocus, that is, a laser power larger than the ordinary recording laser power by a predetermined magnification are preset into a laser driver. In the normal case where a focusing error lies within a predetermined range, the former laser power is used. When the focusing error exceeds the predetermined range and the effective laser power is decreased by the defocus, the latter laser power is used.

Abstract: An information recording method includes the steps of carrying out an experimental write on both inner-peripheral and outer-peripheral experimental writing areas, in the case of the outer-peripheral experimental writing, a constant recording power computed on the basis of the optimum recording power is used, which is estimated by the inner-peripheral experimental writing, in addition, an optical disk apparatus operates according to this information recording method, thereby removing the fluctuation factors of the disk.

Abstract: A specific write power control method used for an optical disk drive is provided. This method relates to how to measure the writing quality and how to set write power for the next zone while settling the linear velocity so that each zone of an optical disk is provided with different linear velocity. At the time of zone switching, writing performed by the head facing an optical disk is interrupted. The head is moved to seek to a given return point in a written area. At the return point, the head is moved toward the next zone, and also a motor for rotating the optical disk is accelerated so that the linear velocity of the motor becomes the linear velocity of the next zone. During the acceleration, the written area is read to measure the writing quality. From the measured writing quality, write power for the next zone is set. At a point of time when the motor reaches the linear velocity of the next zone and the head reaches the next zone, restarting the writing to the optical disk is restarted.

Abstract: The mark-length recording system whereby information is recorded by changing the lengths of a recorded portion and an unrecorded or erased portion has a problem that, when new information is recorded in an already recorded region, the newly recorded information may deteriorate in reliability because the length and width of the newly recorded mark are different from those of the previously recorded mark and a part may exist that is not completely erased at the time of overwriting. The invention widens a setting freedom of the recording power and controls the length and width of the recorded mark by making the effective recording pulse length (the length from a rise of a first pulse to a fall of a last pulse) satisfy a relation: (effective recording pulse length)<(recording code length, i.e., the length of data to be recorded)−2T(twice the reference clock cycle).