| 摘要 |
PURPOSE:To easily and securely detect whether or not an erasing function is normal and to protect data against a failure in erasure by varying the power of an erasing laser by a power varying means and deciding whether or not erasing operation is normal by an erasing function confirming means. CONSTITUTION:The 1st data is erased after the erasing power is set, but a residual signal is small when the erasing function is normal as well as when optimum erasing power is obtained or increases abruptly when not normal. Then, the 2nd data is recorded as recording data (x) and a comparing circuit 122 stores the recording data (x) in a memory. A read check on the recording data is made by the comparing circuit 122, which compares the recording data (x) stored in the memory with reproduced data (y) to decide that there is no error and the erasing function is normal when they coincide with each other or decide that there is an error and generate a dissidence pulse when they are not coincident. When the dissidence pulse is outputted, it is decided that the erasing function is no normal, so that the erasing function is inhibited while a failure in erasure is displayed.
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