Victor Company of Japan, Limited

Kazunori Tokiwa

Hiroshi Tabata

Yasuhiko Teranishi

Hideharu Eguchi

Toshiyuki Kato

Test signals are recorded on a prescribed area in an optical disc. The prescribed area is scanned by a laser beam while the power of the laser beam is changed among different DC erasing values. The different DC erasing values are assigned to the recorded test signals, respectively. The recorded test signals are reproduced from the prescribed area to obtain reproduced signals. Parameter values of the respective reproduced signals are detected. The detected parameter values correspond to the different DC erasing values, respectively. Among the detected parameter values, a detected parameter value is decided which matches a target. One corresponding to the decided parameter value is selected from the different DC erasing values. A prescribed coefficient and the selected DC erasing value are multiplied to calculate an optimum level of an erasing power of the laser beam.

Method and apparatus for recording and reproducing signal on and from optical information recording medium

Reflected light caused by reflection of a laser beam at a first layer of an optical disc is converted into a main signal. Reflected light caused by reflection of the laser beam at a second layer of the optical disc is converted into a sub signal. An address of a currently-accessed position in the first layer is detected from the main signal. A reference address in the first layer corresponds to a boundary between a signal recorded area and a signal unrecorded area in the second layer. A specified address in the first layer corresponds to a position radially separated from the position at the reference address by an allowable range. A misalignment between tracks on the first and second layers is concluded to be within the allowable range in cases where the sub signal substantially takes a reference level when the detected address reaches the specified address.

Growing community of inventors

Tokyo-to, Japan

Kazunori Tokiwa