  Magnetic imaging based on ensembles of diamond nitrogen-vacancy quantum
sensors has emerged as a useful technique for the spatial characterisation of
magnetic materials and current distributions. However, demonstrations have so
far been restricted to laboratory-based experiments using relatively bulky
apparatus and requiring manual handling of the diamond sensing element,
hampering broader adoption of the technique. Here we present a simple, compact
device that can be deployed outside a laboratory environment and enables
robust, simplified operation. It relies on a specially designed sensor head
that directly integrates the diamond sensor while incorporating a microwave
antenna and all necessary optical components. This integrated sensor head is
complemented by a small control unit and a laptop computer that displays the
resulting magnetic image. We test the device by imaging a magnetic sample,
demonstrating a spatial resolution of 4 $\mu$m over a field of view exceeding 1
mm, and a best sensitivity of 45 $\mu$T/$\sqrt{\rm Hz}$ per ($5\,\mu$m)$^2$
pixel. Our portable magnetic imaging instrument may find use in situations
where taking the sample to be measured to a specialist lab is impractical or
undesirable.
