JPH0695397B2 - Optical disk defect location search method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for searching for a defective position on an optical disc.

(Prior Art) It is desired that the defect occurrence rate, which is one of the important performances of optical disks, be as low as possible. Therefore, in order to reduce the defect occurrence rate, it is necessary to know the cause of the defect occurrence, and observing the defective portion with a microscope (optical microscope, electron microscope, etc.) is one of the important means.

The defective portion of the optical disc is determined by processing a reproduced signal using a reproducing optical system and determining whether or not an error has occurred. Conventionally, the defect occurrence position at this time is observed as follows. When the track address information and the sector address information are already recorded on the optical disc, each address information is read at the time of observing a defect. If there is no address information on the optical disk, a read radius position reading mechanism of the read optical system and a rotation angle reading mechanism on the optical disk rotation axis are attached to read the read radius and the disk rotation angle when a defect is observed. When observing the defective portion of the disk whose defect generation position has been read as described above using a microscope, the defective portion is searched by observing the vicinity of the above-mentioned disk radial position and rotation angle position read at the time of defect observation.

In addition, as a method for easily searching for a defect position, which has been already proposed by the present inventors, a shape change region having a length of about 100 μm to 5 cm is provided in the vicinity of a defect position detected by a reproduction optical system of an optical disc. There is a method of recording an optical constant change area or an area having a different magnetization direction on an optical disk (hereinafter, these areas will be referred to as marking areas), and searching the marking area with a microscope to find a defect position.

(Problems to be Solved by the Invention) As described above, in the method of locating a defective portion by observing the vicinity of the disk radial position and the rotation angle position read at the time of defect observation, it is difficult to increase the positional accuracy to the recording density, so When there are several kinds of defects near the observation position, they cannot be distinguished. In addition, in the method of searching the marking area near the defect position, although the defect searching efficiency is good, many kinds of defects are detected in the same optical disc, and if the defect searching marking areas are recorded respectively, only the marking area is searched. Then, there was a drawback that it was not possible to determine which kind of defect it was.

(Means for Solving Problems) The gist of the present invention is to perform a search for a defect position by recording a shape change region, an optical constant change region or a region having a different magnetization direction in the vicinity of a defect portion of an optical disk. In the optical disc defect position searching method, the information on the type of the defective portion is included in the recording in the shape change area, the optical constant change area, or the area having a different magnetization direction in the vicinity of the defective portion.

(Operation) The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic view of the arrangement of the defective portion 1 and the marking area 2. The defect portion 1 of the optical disc is detected by the optical disc reproducing optical system to determine the type of the defect, and immediately after that, recording is performed for a certain period with the recording laser light modulated by the defect information to create the marking area 2. When searching for the defect position 1, first, the marking area 2 is searched, and the marking area 2 is traced in the opposite direction to the recording direction.
It is possible to find the defective portion 1 and to know what kind of defect the defective optical element and the signal processing system have determined to be the defective portion.

(Embodiment) FIGS. 2 and 3 are schematic diagrams of micrographs in which a defective portion of a recording bit missing portion and an extra defective portion are searched by using the defect position searching method of the present invention, respectively. The defect information of the recording bit omission shown in FIG. 2 was recorded in the marking area by lengthening the modulation pulse width, and the extra defect information in FIG. 3 was recorded in the marking area by shortening the modulation pulse width. As a result, it is possible to discriminate the type of the defect recorded in the marking area.

(Effects of the Invention) As described in detail above, by using the optical disk defect position searching method according to the present invention, it becomes possible to perform defect observation in which the type of defect is determined.

[Brief description of drawings]

FIG. 1 is a diagram showing the arrangement of defective portions and marking areas,
FIG. 2 and FIG. 3 are schematic diagrams showing micrographs in which a defective portion of the recording bit missing and an extra defective portion are searched. In the figure, 1 is a defective portion and 2 is a marking area.

Continuation of the front page (56) Reference JP-A 63-152039 (JP, A) JP-A 63-152041 (JP, A) JP-A 63-117245 (JP, A) JP-A 63-152040 (JP , A)

Claims (1)

[Claims] 1. A method for retrieving a defect position by recording a shape change region, an optical constant change region or a region having a different magnetization direction in the vicinity of a defective portion of an optical disk, wherein the shape change region and the optical constant change near the defective portion are recorded. A method for searching an optical disk defect position, wherein information on identification of the type of the defective portion is included in recording in the area or the area having different magnetization directions.