| 摘要 |
PROBLEM TO BE SOLVED: To enable a reproduction apparatus to perform focus closing operation with an optimum S-character signal by time-measuring an interval of error signal obtained by moving an objective lens and then comparing the interval with a specified time. SOLUTION: A specified period time Td of ordinary reproduction and specified allowable valueαare stored previously in a ROM 39. When a total period time A of actual metering is within the range, Td-α<=A<=Td+α, each period time t1, t2,... stored in the ROM 42 are called. After the time t1 is converted to a half by CPU 40, the other time t2... is added to obtain the setting period time B and it is then stored in a RAM 42. Next, a lens is moved downward to measure the moving time and when it becomes equal to the time B stored in RAM 42 and operation of zero-cross circuit is continued until the zero-cross signal of S-character signal is detected. PWM 29 is controlled with FGA 27 to output a focus servo coil drive signal and the focus servo is started to make zero the focus error signal by closing the focus loop with a servo controller 38.
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