  In this work we present a novel, compact, power efficient magnetic field
source design for magnetic field imaging microscopy. The device is based on a
pair of diametrically magnetized permanent magnet cylinders with
electro-mechanical rotation control and ferrite field concentrators. A Hall
probe and NV centers in diamond are used to demonstrate a proof of concept of a
proposed magnetic field setup and to characterise the homogeneity of the
produced magnetic field on a micrometer scale. Numerical simulation results are
compared with experimental results showing good agreement of the distribution
of the magnetic field in the setup. As a result, a magnetic field source with a
tunable field amplitude in the range from 1 mT to 222 mT is demonstrated,
achieving a magnetic field homogeneity of 2 ppm/$\mu$m or 0.5 $\mu$T/$\mu$m at
222 mT in a 25$\times$25 $\mu$m field of view.
