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(a) Schematics of the conventional CT scanner (left) and the multiplexing imaging system using a nine-pixel x-ray source and a digital area detector (right). (b) Each individual x-ray pixel of the multipixel x-ray source is comprised of a CNT based field emission cathode, a thick dielectric spacer, an extraction gate, and a focusing electrode. The cathode was a thin CNT composite film deposited on a metal substrate by electrophoresis.
The flow chart for the OFDM imaging process. (a) Two incident x-ray beams with the respective pulsing frequencies of and transmitted through the phantom and formed a multiplexed x-ray signal including both frequency components. (b) The multiplexed images were recorded by a single flat panel x-ray detector which collected the transmitted x-ray intensity as a function of time over a certain period . (c) DFT algorithm was used to demultiplex the composite x-ray signals recorded by a detector pixel. The orthogonal nature of the signals was a result of the peak of each subcarrier corresponding to the nulls of other subcarriers. (d) The demultiplexed images were achieved by repeating the demultiplexing procedure for all the detector pixels.
(a) A schematic showing the wave forms used for the nine x-ray beams in this experiment. The pulsing frequencies ranged from with frequency separation. (b) In frequency domain, the simulation demonstrated that, at the central frequency of each subcarrier, there was no cross-talk from the other subcarriers due to the orthogonality of the signals. (c) The transmitted x-ray intensity vs time data recorded on one detector pixel. (d) One frame of a typical multiplexed x-ray image of the computer board.
(a) The DFT based algorithm was applied to demultiplex the multiplexing x-ray signal showed in Fig. 3(d). (b) Nine demultiplexed images corresponding to nine frequency channels were obtained by the OFDM scheme showing the circuit board from different viewing angles. (c) One of the demultiplexed images of the circuit board from the x-ray pixel . (d) A projection image taken using only the x-ray pixel with the same dose and geometry as in (c). The difference between the two images is visually negligible.
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