Vehicle periphery monitoring device, vehicle periphery monitoring program and vehicle periphery monitoring method

A vehicle periphery monitoring method which monitors a periphery of a vehicle according to a computer provided with an accessing portion configured to access a captured image by an imaging unit which is mounted in the vehicle to image the periphery of the vehicle to monitor the periphery of the vehicle on the basis of the captured image by the imaging unit, comprising steps of:

• an object detecting step in which the computer detects a distance from the vehicle of an object located in an imaging area imaged by the imaging unit;
• an image processing target area setting step in which the computer sets an image processing target area which may include an image portion of a monitoring object in the captured image on the basis of the detected distance of the object from the vehicle by the object detecting step;
• a contour extracting step in which the computer extracts a contour of the image portion included in the image processing target area;
• and
• an object type discriminating step in which the computer discriminates a type of the monitoring object in a real space corresponding to the image portion from which the contour has been extracted by the contour extracting step on the basis of the extracted contour, wherein
• the contour extracting portion extracts the contour of the image portion by setting an initial eclipse circling the image portion in the image processing target area and performing a contour convergence processing on the initial ellipse according to Snakes algorithm,
• the contour convergence processing is performed according to the Snakes algorithm by using a computation expression in which a multiplication term of an internal energy of Snakes energy where the Snakes energy and a contour positional variation and an external energy variation and an internal energy variation are presumed to be of zero at the time when a contour of a Snakes model of a discrete system is converged is multiplied to a multiplication term of the external energy, and wherein
• the contour extracting portion uses the following mathematical expressions (1) and (2) as the computation expression:
• [Mathematical expression 1]
• xt=(I−gA){xt-1−gfx(xt-1,yt-1} (1)
• [Mathematical expression 2]
• yt=(I−gA){yt-1−gfy(xt-1,yt-1)} (2)
• Herein
• (xt, yt):
• coordinate of a contour dot at timing t;
• (xt-1, yt-1):
• a model expression of the contour at timing t−1;
• I:
• a unit matrix;
• A:
• a transform matrix of internal energy:
• γ:
• an iteration step (moving amount of the contour per step when converged inward);
• fx:
• a computation expression of x components of the external energy;
• and
• fy:
• a computation expression of y components of the external energy.