OBJECT DETECTOR

PROBLEM TO BE SOLVED: To accurately detect an object in a monitoring area even in the case where monitoring areas widely spread from the vicinity of a laser radar to a long distance.SOLUTION: In a monitoring area where a distance from a laser radar head 5 is long in the main scanning direction X of scanning light LB1, the degree of diffusion of reflected light LB2 is high and the intensity of the reflected light LB2 decreases. Therefore, a polygon mirror 11 and a light receiving unit 2 are arranged so that the reflected light LB2 of the scanning light LB1 emitted to the monitoring area far from the laser radar head 5 in the main scanning direction X has a wider luminous flux after reflected toward the light receiving unit 2 by the polygon mirror 11, compared to the reflected light LB2 of the scanning light LB1 emitted to a monitoring area close to the laser radar head 5. Thus, even in the case where the intensity of the reflected light LB2 of the scanning light LB1 emitted to the monitoring area far from the laser radar head 5 in the main scanning direction X is made high, the intensity of the reflected light LB2 of the scanning light LB1 emitted to the monitoring area close to the laser radar head 5 is prevented from being excessively increased.