| 摘要 |
PURPOSE:To detect quickly the extension of data where the data is written by detecting the difference of optical characteristics on the disk surface between the part where the data is written and an unwritten part. CONSTITUTION:A counter 9 is cleared by the start signal Cs given from an image sensor driver 8 and then starts counting with the clock pulse Cp supplied from an image sensor 6. The counting of the counter 9 is stopped by the output signal that compares the variations of the video signal VD sent from the sensor 6 through a binary coding circuit 10. Thus the counted value of the counter 9 shows the written data area on a disk 1. In such a way, the written area of the disk 1 is roughly known from the count value of the counter 9. When the position of the written area is known, a ordinary record/reproduction head 3 is set at the cicinity of the detected area to read out the information. Then the termination of writing is detected for the disk 1. |
