Lock-in Detection based Dynamic Widefield Magnetometry using Quantum Defects in Diamond

Wide field-of-view magnetic field microscopy has been realized by probing shifts in optically detected magnetic resonance (ODMR) spectrum of nitrogen-vacancy (NV) defect centers in diamond. However, these widefield diamond NV magnetometers require a few to several minutes of acquisition to get a single magnetic field image, rendering the technique as temporally static in its current form. This limitation prevents application of diamond NV magnetometers to novel imaging of dynamically varying microscale magnetic field processes. Here, we show that the magnetic field imaging frame rate can be significantly enhanced by performing lock-in detection of NV photo-luminescence (PL), simultaneously over multiple pixels of a lock-in camera. A detailed protocol for synchronization of frequency-modulated PL of NV centers with fast camera frame demodulation, at few kilohertz frequencies, has been experimentally demonstrated. This modified diamond NV imaging allows up to ten thousand pixels to simultaneously track an applied magnetic field waveform of sub-second temporal variation at imaging frame rates of 50-200 Hz. Our work demonstrates that widefield per-pixel lock-in detection, in combination with frequency-modulated NV ODMR, enables millisecond scale dynamic magnetic field microscopy.