Method of controlling device for feeding sheet-like member in auxiliary scanning direction

A method of controlling a device for feeding a sheet-like member reciprocally with a belt engaging a rotary actuator and also feeding the sheet-like member in an auxiliary scanning direction as one direction when the sheet-like member is scanned with a light beam, comprising:

• rotating said rotary actuator in a first direction to rotate said belt to feed said sheet-like member in another direction which corresponds to rotation of the rotary actuator in said first direction;
• before said sheet-like member is scanned by the light beam, rotating said rotary actuator in a second direction which is opposite to said first direction to rotate said belt by a predetermined length;
• and
• after said belt is rotated by said predetermined length, rotating said rotary actuator in said second direction to rotate said belt to feed said sheet-like member in the auxiliary scanning direction while scanning the sheet-like member with the light beam.