Wide-field magnetometry can be realized by imaging the optically detected magnetic resonance of diamond nitrogen-vacancy (N-V) center ensembles. However, N-V ensemble inhomogeneities significantly limit the magnetic field sensitivity of these measurements. We demonstrate a double-double quantum (DDQ) driving technique to facilitate wide-field magnetic imaging of dynamic magnetic fields at a micron scale. DDQ imaging employs four-tone radio-frequency pulses to suppress inhomogeneity-induced variations of the N-V resonance response. As a proof of principle, we use the DDQ technique to image the dc magnetic field produced by individual magnetic nanoparticles tethered by single DNA molecules to a diamond-sensor surface. This demonstrates the efficacy of the diamond N-V ensemble system in high-frame-rate magnetic microscopy, as well as single-molecule biophysics applications.
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