Optical scanning unit sets distance from diffraction point in modulation medium to transducer depending on point on reflector from which sensor receives reflected laser beam

摘要

Distance from diffraction point in modulation medium to transducer is set depending on point on reflector from which sensor (122) receives reflected laser beam in relation to end region of reflection mirror on recording medium side, main scanning speed and ultrasonic wave propagation speed in modulation medium. The unit has an acousto-optical modulation element (60) and medium and a transducer producing ultrasonic waves. The modulation element diffracts a laser beam passing through the modulation medium depending on the ultrasonic waves. The diffracted waves are deflected (76) in a main scanning direction onto a recording medium (62) via a reflection mirror (120). The distance from the diffraction point in the modulation medium to the transducer is set depending on the point on the reflector from which a sensor (122) receives the reflected laser beam in relation to an end region of the reflection mirror on the recording medium side, the main scanning speed and the ultrasonic wave propagation speed in the modulation medium.