  Our main goal is to derive a new extinction map of the OMC-1, obtaining
information about the structure of the OMC-1 and the Orion Nebula Cluster. The
most recent near-infrared catalog of stars is used to study the distribution of
reddening across a ~0.3 deg^2 area covering the Orion Nebula Cluster. On the
basis of the observed (H,H-K_S) diagram, we establish a criterion for
disentangling contaminants from bona-fide cluster members. For contaminant
stars, interstellar reddenings are estimated by comparison with a synthetic
galactic model. A statistical analysis is then performed to consistently
account for local extinction, reddening and star-counts analysis. We derive the
extinction map of the OMC-1 with angular resolution <5'. We also assemble a
sample of candidate cluster members, for which we measure the extinction
provided by the nebular environment. These extinction measurements are analyzed
similarly to the contaminant sample, and an extinction map of the Orion Nebula
is derived. The extinction provided by the OMC-1 is variable on spatial scales
of a few arcminutes, while showing a general increase from the outskirts
(A_V~6) to the direction of the Trapezium asterism (A_V>30). The Orion Nebula
extinction map is more irregular and optically thinner, with A_V of the order
of a few magnitudes. Both maps are consistent with the optical morphology, in
particular the Dark Bay to the north-east of the Trapezium. Both maps also show
the presence of a north-south high-density ridge, which confirms the
filamentary structure of the Orion molecular complex inside which star
formation is still taking place.
