  We report on a near-infrared adaptive optics survey of a sample of 66
low-mass members of the pre-main sequence stellar cluster IC 348. We find 12
binary systems in the separation range 0.1-8.0 arcsec. An estimate of the
number of faint undetected companions is derived, before we evaluate the binary
frequency in this cluster. In the orbital period range log P=5.0-7.9 days, the
binary fraction in IC 348 is 19+/-5 %.This is similar to the values
correspondings to G- and M-dwarfs populations in the solar neigbourhood.
  Substellar companions are found to be rare, or even missing, as companions of
low-mass stars in the separation range we surveyed. Also, the mass ratio
distribution is not peaked at q=1.
  We do not find any evidence for an evolution of the binary frequency with age
within the age spread of the cluster of about 10 Myr. We conclude that there is
no temporal evolution of the binary fraction between a few Myrs after the
formation process, the zero-age main sequence and the field population. We find
instead a trend for the binary fraction to be inversely correlated with stellar
density, with only loose associations exhibiting an excess of binaries. Either
all star-forming regions initially host a large number of binaries, which is
subsequently reduced only in dense clusters on a timescale of less than 1 Myr
due to numerous gravitational encounters, or specific initial conditions in the
parental molecular clouds impact on the fragmentation process leading to
intrinsically different binary fractions.
