  The eclipses of certain types of binary millisecond pulsars (i.e. `black
widows' and `redbacks') are often studied using high-time-resolution,
`beamformed' radio observations. However, they may also be detected in images
generated from interferometric data. As part of a larger imaging project to
characterize the variable and transient sky at radio frequencies <200 MHz, we
have blindly detected the redback system PSR J2215+5135 as a variable source of
interest with the Low-Frequency Array (LOFAR). Using observations with cadences
of 2 weeks - 6 months, we find preliminary evidence that the eclipse duration
is frequency dependent ($\propto \nu^{-0.4}$), such that the pulsar is eclipsed
for longer at lower frequencies, in broad agreement with beamformed studies of
other similar sources. Furthermore, the detection of the eclipses in imaging
data suggests an eclipsing medium that absorbs the pulsed emission, rather than
scattering it. Our study is also a demonstration of the prospects of finding
pulsars in wide-field imaging surveys with the current generation of
low-frequency radio telescopes.
