1. A method for detecting a similarity between images, comprising the steps of: (a) creating a standard pattern matrix having a feature quantity of a standard image as an element and an input pattern matrix having a feature quantity of an input image as an element; (b) creating an arbitrary reference shape such as a normal distribution and a rectangle, the reference shape having a different value of variance for each specified element of the pattern matrices, creating a reference pattern vector having a value of the reference shape as an element, and creating a weighting vector having a value of a change rate of a kurtosis of the reference pattern vector as an element; (c) obtaining a length between the specified element and each element of the standard pattern matrix to calculate a weighting vector element number proximate to a position apart from a center of the weighting vector by the length, and obtaining a value of a product of an element value of the element number of the weighting vector and an element value of each element of the standard pattern matrix to calculate a product-sum value obtained by adding the value of the product to each element of the standard pattern matrix; (d) when calculating the product-sum value, obtaining the product-sum value while moving the specified element of the standard pattern matrix to a position of each element thereof, and creating a weighted standard pattern matrix having the product-sum value as an element value of the specified element; (e) obtaining a length between the specified element and each element of the input pattern matrix to calculate a weighting vector element number proximate to a position apart from a center of the weighting vector by the length, and obtaining a value of a product of an element value of the element number of the weighting vector and an element value of each element of the input pattern matrix to calculate a product-sum value obtained by adding the value of the product to each element of the input pattern matrix; (f) when calculating the product-sum value, obtaining the product-sum value while moving the specified element of the input pattern matrix to a position of each element thereof, and creating a weighted input pattern matrix having the product-sum value as an element value of the specified element; and (g) defining any of a square sum and a square root of the square sum of a value of a difference between the weighted standard pattern matrix and the weighted input pattern matrix for each element as a geometric distance value between the standard pattern matrix and the input pattern matrix.