System and method for detecting obstacle

A method for detecting an obstacle by using two cameras, the obstacle being on a reference plane in a field of view common to the two cameras, the method comprising:

• inputting a first image and a second image from the two cameras, respectively;
• transforming the first image to a transformed image on a basis of image transform which is introduced from a geometrical relationship between a reference plane and the two cameras for transforming any given pixel in a reference plane region in the first image to a corresponding pixel in the second image;
• obtaining a degree of similarity D indicating a similarity between an image in a processing region established in the second image and an image in a corresponding processing region established in the first image and being a function of position in the vertical direction of the image;
• establishing, when any given image line in a specified region in the second image is a contact line of the obstacle with the reference plane, the processing region for an inter-image arithmetic operation between the first image and the second image, and a plurality of the processing regions being established with the image line being shifted in the vertical direction;
• obtaining a degree of similarity P indicating a similarity between an image in the processing region established in the second image and an image in a corresponding processing region established in the transformed image and being a function of position in the vertical direction of the image;
• establishing the processing region for an inter-image arithmetic operation between the second image and the transformed image, and a plurality of the processing regions being established with the image line being shifted in the vertical direction;
• detecting the obstacle on a basis of the degree of similarity D and the degree of similarity P on a reference plane region;
• obtaining a difference K between the degree of similarity D and the degree of similarity P both obtained as being on the reference plane region;
• judging that the obstacle is at a position where the difference K is large;
• judging that there is no obstacle when there is no difference K of degree of similarity equal to or greater than a threshold value set beforehand about the vertical directions of all of the images;
• and
• detecting that there is the obstacle when there is the difference K of degree of similarity equal to or more than the threshold value in the vertical direction of the image.