  Context. The mass loss from massive stars is not understood well. Eta Car is
a unique object for studying the massive stellar wind during the LBV phase. It
is also an eccentric binary with a period of 5.54 yr. The nature of both stars
is uncertain, although we know from X-ray studies that there is a wind-wind
collision whose properties change with orbital phase.
  Methods. Observations of Eta Car were carried out with the ESO VLTI and the
AMBER instrument between approximately five and seven months before the August
2014 periastron passage. Velocity-resolved aperture-synthesis images were
reconstructed from the spectrally dispersed interferograms. Interferometric
studies can provide information on the binary orbit, the primary wind, and the
wind collision.
  Results. We present velocity-resolved aperture-synthesis images reconstructed
in more than 100 different spectral channels distributed across the Br Gamma
2.166 micrometer emission line. The intensity distribution of the images
strongly depends on wavelength. At wavelengths corresponding to radial
velocities of approximately -140 to -376 km/s measured relative to line center,
the intensity distribution has a fan-shaped structure. At the velocity of -277
km/s, the position angle of the symmetry axis of the fan is ~ 126 degree. The
fan-shaped structure extends approximately 8.0 mas (~ 18.8 au) to the southeast
and 5.8 mas (~ 13.6 au) to the northwest, measured along the symmetry axis at
the 16% intensity contour. The shape of the intensity distributions suggests
that the obtained images are the first direct images of the innermost wind-wind
collision zone. Therefore, the observations provide velocity-dependent image
structures that can be used to test three-dimensional hydrodynamical, radiative
transfer models of the massive interacting winds of Eta Car.
