US Patent 11699567 X-ray detection apparatus and method

A mask member is provided at an entrance opening of a mirror unit. Of a first diffraction grating and a second diffraction grating, when the second diffraction grating is used, the mask member masks preceding mirrors. With this process, aberration caused by reflective X-ray is suppressed. When the first diffraction grating is used, the mask member does not function. Alternatively, the mask member and another mask member may be selectively used.