Fourier Aperture (FA) consists of two sinusoidal gratings in contact with each other. One possible mode of operation, both gratings are rotated about the same axis through equal angles in opposite directions. A clear difference moire fringes is shown. The moire frequency depends on the angle between two gratings. This aperture of moire fringes is used as a variable frequency grating. It is able to scan the object spectrum in frequency domain. The summation filtered back projection alqorithm with three different apodizing functions were introduced in the reconstruction. 99mTc gamma ray source and 1" diameter NaI scintillation detector was used in the experiment. The thyroid phantom images show the spatial resolution of FA agree with the theoretical prediction. Three-D images capability is also discussed. The matrix inversion algorithm was used in the computer simulation of 3-D images. The depth resolution of FA is limited by the restricted view angle of the detector. Two plane objects with noise free in different depth were reconstructed.
"Fourier Coded Aperture Imaging In Nuclear Medicine", Proc. SPIE 0454, Application of Optical Instrumentation in Medicine XII, (15 June 1984); doi: 10.1117/12.939367; https://doi.org/10.1117/12.939367