Selective material x-ray imaging using spatial frequency multiplexing

A method is presented of encoding the transmission at specific regions of the x-ray energy spectrum onto a radiograph. A grating structure is placed in the x-ray beam that consists of alternate strips of material having different x-ray transmission spectra. The average spectral transmission of the two strips produces an image comparable to a conventional radiograph. The difference between the two transmission spectra produces an amplitude modulation of the grating pattern on the radiograph. When this grating pattern is decoded, through optical or scanning methods, it represents the transmission at the specific x-ray difference spectrum.