Abstract. Subsurface structural features of biological tissue are visualized using polarized light images. The technique of Pearson correlation coefficient analysis is used to reduce blurring of these features by unpolarized backscattered light and to visualize the regions of high statistical similarities within the noisy tissue images. It is shown that under certain conditions, such correlation coefficient maps are determined by the textural character of tissues and not by the chosen region of interest, providing information on tissue structure. As an example, the subsurface texture of a demineralized tooth sample is enhanced from a noisy polarized light image. Characterization of biological tissues from intrinsically noisy digital images is currently considered in the frames of several scientific approaches, i.e., pattern recognition, texture analysis, and image processing. [1][2][3][4] Many methods are suggested to increase the contrast, eliminate scattered bright or dark pixels, and filter out noise and certain artifacts. Among the most popular are gray-level run techniques, 5 fast Fourier transforms, 6 and wavelet analysis. 7 None is universal in application, but individual user preference is commonly based on features of the data. Texture analysis aims to characterize the image using a number of parameters that are sensitive to specific structural features of the object and especially to distinguish normal and abnormal biological tissues in the noisy images. For example, a few methods were developed for the detection of clustered microcalcifications from digital mammograms. [8][9][10] Texture enhancement is also required when imaging subsurface tissue structures with a diffusively backscattered polarized beam. Previously it was shown that imaging the degree of polarization can enhance the visibility of the hidden x-ray-induced early fibrosis of mouse skin.11 The analysis of Pearson correlation coefficients was also used to estimate local variations of the directionality and orientation of the structural elements. That work led us to visualize the hidden structures of biological tissues by imaging regions of statistical similarities using the correlation coefficient as the measure of comparison. The mathematical basis for this approach was established earlier by a mathematical proof that such a measure enabled one to reveal dependencies between random variables. 12,13 Biological tissues often exhibit characteristic regular features or ornamental patterns. Therefore, various regions of the tissue image can be statistically well correlated. By choosing a region of interest ͑ROI͒ and comparing it with other regions of the image through the correlation coefficient, it is possible to map the degree of statistical similarities. This mapping can carry valuable comparative information about the structural features of the tissue.Let us consider the main principles of image processing using correlation coefficients. To evaluate the spatial correlation in the raw image data, one has an intensity matrix G. Then two sim...