  We present a new analysis of the ISOCAM 14.3 micron deep survey in a 20x20
square arcmins area in the Lockman Hole. This survey is intermediate between
the ultra-deep surveys and the shallow surveys in the ELAIS fields. The data
have been analyzed with the method presented by Lari et al. (2001). We have
produced a catalogue of 283 sources detected above the 5-sigma threshold, with
fluxes in the interval 0.1-8 mJy. The catalogue is 90% complete at 1 mJy. The
positional accuracy, estimated from the cross-correlation of infrared and
optical sources, is around 1.5 arcsec. The search for the optical counterparts
of the sources in the survey is performed on a medium-deep r' band optical
image (5-sigma depth of r'=25), making use of the radio detections when
available. The photometry has been checked through simulations and by comparing
the data with those presented in a shallower and more extended ISOCAM survey in
the Lockman Hole, that we have presented in a companion paper. Only 15% of the
14.3 micron sources do not have an optical counterpart down to r'=25 mag. We
use the 6.7/14.3 micron colour as a star/galaxy separator, together with a
visual inspection of the optical image and an analysis of the observed Spectral
Energy Distribution of the ISOCAM sources. The stars in the sample turn out to
be only 6% of the sample. We discuss the 14.3 micron counts of extragalactic
sources, combining our catalogue with that obtained from the shallower ISOCAM
survey. The data in the two surveys are consistent, and our results fully
support the claims in previous works for the existence of an evolving
population of infrared galaxies, confirming the evident departure from
non-evolutionary model predictions.
