| 摘要 |
<p>PURPOSE:To prevent a picture from splitting by canceling the circumferential-speed error of a drum by a correction signal obtained by detecting and processing information corresponding to the rotation of the drum. CONSTITUTION:To the lower end part of the rotation shaft of video head drum 1, magnetic member 4 which rotates synchronizing with rotary drum 1a is fitted being eccentric from the shaft, and magnetism sensing element 5 is provided corresponding to member 4. The speed of revolution of rotary drum 1a of drum 1 is detected by a speed detector, whose output signal controls motor 2 through trapezoidal-pulse generating circuit 13, sample holding circuit 14, adder 9, motor driver circuit 11, etc. Then, if unevenness of speed detection of drum 1 or torque variation of motor 2 occurs, an error signal is fed back to the adder. The sine-wave signal of magnetism sensing element 5, on the other hand, is amplified 6 and phase-shifted 7 to be equal in amplitude level to and out of phase with the error signal supplied to adder 9, and supplied as a correction signal to adder 9. Therefore, a corrected signal of the error signal appears at the output of adder 9 and is supplied to motor 2 after being amplified 10.</p> |
