| 摘要 |
PURPOSE:To prevent an overshoot of the scanning speed of an optical system by controlling the speed approximately to a desired function. CONSTITUTION:An optical scanning system 14 moves forth and back through a wire 18 driven by a servomotor 22. When feedback control is performed by pulses generated synchronously with a scan so that the scanning speed approximates to a desired value, an overshoot is generated and the wire 18 is loosened to oscillate, so that the control becomes unstable. For this purpose, a reference pulse for specifying the desired speed is ferquency-divided and a desired function which increases gradually according to a rise is set to control the speed so that the speed approximates to the function. Frequency division ratios (alpha1, alpha2, alpha3-) are switched according to the scanning distance integrated from the starting, and set to 1 finally. At this time, transition from a starting mode to a constant- speed control mode is performed. |
