| 摘要 |
PURPOSE:To move quickly a pickup to a desired address by obtaining the difference between a demodulated address signal and a desired address, converting this address difference into the difference of track number and moving the pickup in response to the difference of track number. CONSTITUTION:The most inner circumference of a disk is set at gamma1mm. together with the most outer circumference set at gamma2mm., the linear speed set at vm/s and the track pitch set at pmum respectively. The address calculation is started at the inner circumference to obtain the time information (t) which is calculated every second. Then n={-2gamma1/ p+[(2gamma1/p)<2>+vt/pip]1/2}X10<3> is satisfied, where gamma is the position of the pickup and (n) is the number of tracks within a range from the inner circumference to the position gamma. Therefore a track number converter 30 receives the information on time difference (t) from an address difference calculator 26 and calculates the above-mentioned equation to obtain the track number (n). Then a desired address TX is designated and the present position Tr of a pickup 14 is confirmed, and the difference DELTAT=TX-TY is calculated. The shifting direction of the pickup is decided by the plus or minus value of the difference DELTAT. At the same time, the difference DELTAT is converted into the track number to decide the movement degree of the pickup. This operation is continued until DELTAT=0 is satisfied. |
