  With the advent of quantum technology, nitrogen vacancy ($NV$) centers in
diamond turn out to be a frontier which provides an efficient platform for
quantum computation, communication and sensing applications. Due to the coupled
spin-charge dynamics of the $NV$ system, knowledge about $NV$ charge state
dynamics can help to formulate efficient spin control sequences strategically.
Through this paper we report two spectroscopy-based deconvolution methods to
create charge state mapping images of ensembles of $NV$ centers in diamond.
First, relying on the fact that an off axis external magnetic field mixes the
electronic spins and selectively modifies the photoluminescence (PL) of $NV^-$,
we perform decomposition of the optical spectrum for an ensemble of $NV$s and
extract the spectra for $NV^-$ and $NV^0$ states. Next, we introduce an optical
filter based decomposition protocol and perform PL imaging for $NV^-$ and
$NV^0$. Earlier obtained spectra for $NV^-$ and $NV^0$ states are used to
calculate their transmissivities through a long pass optical filter. These
results help us to determine the spatial distribution of the $NV$ charge states
in a diamond sample.
