Using X-ray grazing incidence diffraction ͑GID͒ it is possible to perform a nondestructive analysis of the heterogeneous stress field for different volumes below the surface of the sample. The stress can be measured at very small depths, of the order of a few m. The penetration depth of radiation is almost constant in a wide 2 range for a given incidence angle ␣. It can be easily changed by an appropriate selection of ␣ angle ͑or also by using a different type of radiation͒. There are, however, some factors which have to be corrected in this technique. The most important is the refraction of X-ray wave: it changes the wavelength and direction of the beam. Both effects modify a pick position. A corresponding correction was calculated and tested on ferrite powder and on 316L austenite stainless steel sample.

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