Abstract:
A first information recorder comprises a limit number−of−times of copying information setter for setting information on the limit number−of−times of copying electronic data, a first limit number−of times of copying information update unit for reading out the electronic data from a first information recording medium containing electronic data set with limit number of times of copying information by the limit number−of−times of copying information setter and updating the limit number−of−times of copying information set in the electronic data, and a first transmitter for transmitting electronic data whose limit number−of−times of copying information is updated by the first limit number of times of copying information update unit. A second information recorder comprises a second receiver for receiving electronic data transmitted from the first transmitter, a second limit number−of−times of copying information update unit for reading out the electronic data from a second information containing medium recording the electronic data and updating the limit number−of−times of copying information set in the electronic data, and a second transmitter for transmitting electronic data whose limit number−of−times of copying information is updated by the second limit number−of−times of copying information update unit.
Abstract:
An optical head comprising a light source, an object lens, a light splitting means, a light receiving element, a tracking error signal detecting means, and a spherical aberration detecting means, wherein the light splitting means has six regions divided by a first splitting line parallel to the longitudinal direction of information tracks and by second and third splitting lines perpendicular to the first splitting line, and the spherical aberration detecting means compares the deviation of a first focus point obtained from a light flux passed through two regions disposed between second and third splitting lines with the deviation of a second focus point obtained from a light flux passed through four regions disposed on the outer side of the second and third splitting lines to generate a spherical aberration error signal for detecting a spherical aberration generated at the object lens.