| 摘要 |
PURPOSE:To reduce the maximum angular speed of a rotary polygon mirror so that the rotary polygon mirror does not shift during its rotation by providing a control means which smooths the rise of the angular speed of the rotary mirror. CONSTITUTION:A slow start control circuit 3 as the control means which controls the rotational acceleration of a scanner rotor 4 consists of a reference voltage generating transistor (TR) Q1, a current control FET Q4, time constant generating capacitor C1, fixed current generating TR Q2, fixed voltage follower TR Q3 and fixed resistors R1--R6. When a power switch 2 is turned on, a ramp increase type source voltage generated by the slow start control circuit 3 begins to rise. In a rotation startup area, a switching TR Q5 is turned on with a voltage determined by the resistances R5 and R6. The voltage with which the switching TR Q5 is turned on, is set to the voltage at which the ramp increase type source voltage nearly saturates. Thus, the angular speed of the rotary polygon mirror is made gentle when the rotary polygon mirror is started up. |
