A source of radiation is travelling in a circular path in front of a 37 element (1-D) mask (based on a quadratic residue design with n=19). The center of the "orbit" is at 30 units from the mask, and the radius of the "orbit" is 20 units (where the unit of distance is the mask element size).
The reconstructions are based on backprojection of the detector array image data. It is assumed that the detector array (i) has adequate spatial resolution and (ii) has adequate lateral extent. The area of reconstruction extends from just in front of the mask to 56 units, and laterally goes a bit out past the ends of the mask.
The six animations differ in assumed distance between the mask and the detector array. From left to right, top to bottom: 1X, 2X, 5x, 10x, 20x, 40x mask element size.
Note the spatially varying, anisotropic point-spread function. The "core" of the point-spread function is elliptical, with the mayor axis pointing back at the center of the mask. The radial spread appears to go up more rapidly than linearly with distance from the mask.
Note the tradeoff between resolution and artifacts controlled by the distance of the detector array from the mask. For this particular combination of parameters it appears that a distance of 5 units is about the best.