We present results of an optical and near-infrared ( IR ) 1.8 deg ^ { 2 } survey in the Pleiades open cluster to search for substellar objects .
From optical I -band images from the CFHT and J -band images from the 3.5 m CAHA Telescope , we identify 18 faint and very red L brown dwarf candidates , with I > 20.9 and I - J > 3.2 .
The follow-up observations of nine objects in the H - and K _ { \mathrm { s } } -bands confirm that eight belong to the IR sequence of the cluster and the proper motion measurements of seven candidates confirm that they are Pleiades members .
A preliminary estimation of the substellar mass spectrum d N / d M in the form of a power law M ^ { - \alpha } provides \alpha = + 0.57 \pm 0.14 .
We extrapolate this function to estimate the number of very low-mass brown dwarfs and planetary mass objects that could be present in the cluster down to 1 M _ { \mathrm { J } up } .
Sensitive searches combining far red and near infrared observations may unveal these objects in a near future .