Patent ID: 7808523

Claim:
A boundary detector comprising: a camera that is mounted on a vehicle and picks up an image of a road surface; a candidate line detecting unit that detects a candidate line of a lane boundary position drawn on the road surface based on image data of a predetermined detection time period acquired from the image supplied from the camera; a lane boundary position selecting unit that selects a lane boundary position based on the candidate line of the lane boundary position detected by the candidate line detecting unit; a branch lane boundary position selecting unit that selects a lane boundary position of a branch lane that diverts from a main lane based on the candidate line of the lane boundary position detected by the candidate line detecting unit; and a branch processing unit that sets a branch process mode in which the candidate line of the lane boundary position is detected based on image data of a detection time period that is shorter than the predetermined detection time period without adopting the selected lane boundary position of the branch lane when the branch lane boundary position selecting unit selects the lane boundary position of the branch lane.