1. A peripheral sensing system displaying an overhead view of a region around a vehicle, for shooting a real scene around the vehicle and generating the overhead view for display to a driver of the vehicle so as to assist a driver when maneuvering the vehicle, the system comprising: a plurality of fisheye lenses, scattered on all sides of the vehicle, for shooting scene images; a trip computer, for reading the scene images, and executing a plurality of built-in image processing procedures to combine the scene images into the overhead view of a region around the vehicle, wherein the plurality of image processing procedures comprise: a distorted image correction procedure, for reading radially distorted scene images, calculating a central deformation ratio according to a plurality of pixels at central portions of the scene images, and correcting the scene images; a planar transition procedure, for setting a rotation amount according to positions of the fisheye lenses, and rotating the scene images into projection scene images according to the rotation amount; and an image combining procedure, retrieving trusted zones of the projection scene images according to the disposed positions of the fisheye lenses of the projection scene images, so as to combine the images to the overhead view; and a screen, for displaying the overhead view when the vehicle is maneuvered, and wherein the distorted image correction procedure comprises: reading the radially distorted scene images; calculating the central deformation ratio of the scene images by using a plane correcting function according to the plurality of central pixels at the central portions of the scene images; and correcting positions of all the pixels in the scene images according to the central deformation ratio by taking the central pixels of the scene images as a reference, so as to restore the distorted images to normal scene images.