| 摘要 |
PURPOSE:To attain stable degree of collation by using a density taking a maximum frequency on a density histogram of a registered image as a threshold value so as to adjust the density of the registered image thereby suppressing the variance in the local density of the registered image. CONSTITUTION:A threshold value calculation circuit 8 reads a density histogram of a density histogram memory 4 via a data line (c), caluculates a threshold value TH and gives an output via data lines (d,e). a density adjusting circuit 9 reads the threshold value TH and a registered image 1, makes a density value of an image element having larger density in the registered image than the TH as a registered image replaced by the TH and outputs the result to a picture memory 10 via a data line (g). A density histogram normalizing circuit 5 reads the density histogram and collated picture via data lines (j,k) and outputs the density histogram of the collated image similar to the density histogram to the collation image memory 6. A collation degree calculation circuit 7 calculates the degree of collation between both the images. |
