the drivers may exist the headlights and the tail lights are generally mounted in positions lower than the positions of the drivers therefore the positions of the mask areas 801 and 802 are set above the detected light spot 601 of the headlight and light spot 602 of the tail light the sizes of the mask areas 801 and 802 are set so as not to be less than the sizes of the light spot 601 of the headlight and the light spot 602 of the tail light as shown in fig8 for achieving the object of not dazzling the drivers when the sizes of the light spot 601 of the headlight and the light spot 602 of the tail light are large the on coming vehicle 501 and the preceding vehicle 502 may be close to the own vehicle correspondingly and therefore the sizes of the mask areas 801 and 802 are also made large since the light spot 602 of the tail light is darker as compared with the light spot 601 of the headlight the color of the light spot is taken into consideration when determining the size and if it is the red light of the tail light the size of the mask area 802 needs to be changed specifically the mask area 802 is set to be large with respect to the light spot having the same size as compared with the case that the light spot is white headlight this is because as compared with the case of the headlight the preceding vehicle may be in a position near the own vehicle even if the light spot is small considering that the on coming vehicle 501 looks slant at.