BEAM POSITION DETECTOR HAVING A PHOTODETECTION UNIT

摘要

A beam position detector, which comprises a photodetection unit for receiving a laser beam and issuing a signal corresponding to photodetection amount, wherein said photodetection unit has a first photoelectric conversion unit and a second photoelectric conversion unit and width of said first photoelectric conversion unit is gradually decreased in positive position detecting direction, and width of said second photoelectric conversion unit is gradually increased in positive position detecting direction, and scanning position of the laser beam is detected by comparing the output value of said first photoelectric conversion unit with the output value of said second photoelectric conversion unit.