Patent ID: 8164078

Claim:
A beam irradiation device comprising: a laser light source for emitting laser light; an actuator for scanning a targeted area with the laser light; a servo optical system for emitting servo light, and changing a propagating direction of the servo light in accordance with driving of the actuator; a photodetector for receiving the servo light, and outputting a detection signal depending on a light receiving position of the servo light; a signal processing section for generating a position detection signal based on the detection signal; and a control section for controlling the laser light source and the actuator based on the position detection signal, wherein the signal processing section includes: a differential acquiring section for acquiring a difference between two sampling values obtained by sampling the detection signal at two consecutive sampling timings; a first A/D converting section for converting the difference into a digital signal; and a first computing section for computing the position detection signal, based on the difference which has been converted into the digital signal by the first A/D converting section.