| 摘要 |
PURPOSE:To judge the correctness of recording, by providing a means to detect the change of the reflected light of a recording beam of light by the recording of information, and a means to compare a detected signal with an information signal. CONSTITUTION:When the information is recorded by the projection of a laser beam, a reflected laser beam at the time of recording a space part becomes a 0-th order diffracted light 300 and a first-order diffracted light 301. Meanwhile, the reflected light at the time of recording a mark part becomes a 0-th order diffracted light 304 and a first-order diffracted light 305. When those diffracted light are compared, it can be observed that no different point in directions of the 0-th order diffracted light 300 and 304 exists, however, as for the first- order diffracted light, the diffracted light of the mark part has broadening larger than that of the diffracted light of the space part. Therefore, by providing the means to detect the change of the first-order diffracted light at the time of recording and the means to compare the detected signal with the information signal, it is possible to judge the correctness of the recording.
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