| 摘要 |
PURPOSE:To increase the amount of information per recording medium by forming the mark of width in the radius direction of the recording medium and by controlling rotation of the recording medium so that the linear speed of the recording medium will be constant in accordance with the amount of detection in the width direction of the groove by an optical-type head. CONSTITUTION:The total sum of an optical feeding current, which is detected by a quarter-divided optical sensor 22, is inputted to a counter 27 through an adder 25, etc. For the input signal, the recording information signal by turning on/off of a semiconductor laser 12 and a CLV signal by a groove 2 which is formed on the surface of a recording medium 1 are mixed. The recording information signal which executes recording on the recording medium 1 has a very short period than that of the CLV signal. The fundamental clock pulse which is given by a control circuit 30 counts every width of the signal by the counter 27, when the counted pulse width has the satisfactorily longer pulse width than the period of the recording information signal, the control circuit 30 judges the signal as the CLV signal, and the circuit extracts the counting value. The counting value at the time of the extracted CLV signal is transmitted to a D/A converter 28 of the next step, and is converted to an analogue voltage. |
