Patent Document ID: 20080232665
Application ID: 12076179
Patent Flag: 0

Claim One:
1. A method for noise reduction in images with locally different and directional noise, comprising: providing two image data records of an identical object region that have mutually independent noise; decomposing the two image data records by a discrete wavelet transformation into a number of frequency bands for which wavelet coefficients are respectively obtained for at least a lowpass filtered approximation image, a detailed image having relatively high frequency structures in a first direction, and a detailed image having relatively high frequency structures in a second direction; calculating a difference image for each frequency band and each direction from the difference between the wavelet coefficients of the respective detailed images of the two image data records; calculating local standard deviations of the noise in the difference images for a prescribable size of image areas and multiplying them by a prescribable threshold value factor in order to obtain local threshold values for each frequency band and each direction; averaging the wavelet coefficients of the two image data records for each frequency band and each direction to obtain an averaged approximation image and averaged detailed images for each direction; at least one of obtaining, in the averaged detailed images, wavelet coefficients above the local threshold values and reducing wavelet coefficients by the amount of the respective threshold value, and setting wavelet coefficients below the threshold value to zero; and subjecting the resulting averaged detailed images and approximation images to an inverse wavelet transformation to obtain a noise reduced image of the object region.