Open Access
Fig. 1.

Download original image
is the difference between the Hx components measured in pixels P(i + 1, j) and P(i, j). It can be seen that the z coordinate is not the same for the two pixels for an observation out of disk center, which is in contradiction with the definition of the partial derivative along x.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.