Separation of the threshed grain through the
concave grating can be increased two-fold (on average) using the experimental concave (Fig.
A meniscus lens is added before the
concave grating to correct the aberration brought by the separation at the same time, as is shown in Figure 6.
Baets, "Planar
concave grating demultiplexer fabricated on a nanophotonic silicon-on-insulator platform," IEEE Photon.
The investigation showed that there was no significant difference in the proportion of impurities that fell through the
concave grating (Table 1) regardless of the shape of the threshing cylinder's spaces between the rasp bars.
However, RCWA cannot be used to simulate the imaging of a
concave grating in the large free propagation region.
Previous studies have demonstrated that the variable radius concave improves the efficiency of corn grain separation through the
concave grating by 2.5 [9].