By superimposing the real samples (d) and the reconstructed images (f), we can see that the location matches with an error of mm level (hole of holder is 5 mm) as shown in Fig. 3g.
The setup of a planar Frequency Mixing Magnetic Detection (p-FMMD) scanner for performing Magnetic Particles Imaging (MPI) of flat samples is presented. It consists of two magnetic measurement heads on both sides of the sample mounted on the legs of a u-shaped support. The sample is locally exposed to a magnetic excitation field consisting of two distinct frequencies, a stronger component at about 77 kHz and a weaker field at 61 Hz. The nonlinear magnetization characteristics of superparamagnetic particles give rise to the generation of intermodulation products. A selected sum-frequency component of the high and low frequency magnetic field incident on the magnetically nonlinear particles is recorded by a demodulation electronics. In contrast to a conventional MPI scanner, p-FMMD does not require the application of a strong magnetic field to the whole sample because mixing of the two frequencies occurs locally. Thus, the lateral dimensions of the sample are just limited by the scanning range and the supports. However, the sample height determines the spatial resolution. In the current setup it is limited to 2 mm. As examples, we present two 20 mm × 25 mm p-FMMD images acquired from samples with 1 µm diameter maghemite particles in silanol matrix and with 50 nm magnetite particles in aminosilane matrix. The results show that the novel MPI scanner can be applied for analysis of thin biological samples and for medical diagnostic purposes.
An accurate stereo matching method developed by exploiting the two techniques, discrete-coded structured-light projection and image-guided cost volume filtering, is proposed. The former increases the distinctiveness of pixels by projecting a discrete pattern to the scene, and the latter helps to recover accurate object boundaries. In addition, a previous fast cost volume filtering approach is extended to better preserve slanted surfaces, and a suitable post-processing algorithm is also suggested for the proposed method. The performance of the proposed method is experimentally verified by comparing the results with those of other algorithms qualitatively and quantitatively in an indoor environment.
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