  The numerous extragalactic and cosmological motivations of the DENIS and
2MASS near infrared surveys are outlined. The performance of the DENIS survey
is estimated from 50 deg^2 of high galactic latitude data (20 deg < |b| < 60
deg). Simple star/galaxy separation methods are presented and comparison with
300 visually classified objects as well as COSMOS and APM classifications. We
find that the peak intensity over isophotal area is an excellent star/galaxy
separation algorithm, fairly robust to variations of the PSF within the frames,
achieving 98.5% completeness and 92.5% reliability for I < 16.5, in comparison
with visual classification. A new estimate of the photometric accuracy for
galaxies is presented. The limiting factors for homogeneous galaxy extraction
at high galactic latitudes are completeness and photometric accuracy in K,
photometric accuracy in J and star/galaxy separation in I (also used for
classification in J and K). Galaxy counts are presented on 50 deg^2. The I
counts are in excellent agreement with a Euclidean extrapolation of the
published counts around I=16-17 (more so than in all previous studies), and
thus point to a high normalization at the bright end, in contrast with the
counts published from the APM and COSMOS plate scans. The J-band differential
galaxy counts follow the relation N(J) = 12 \pm 1 dex (0.6 [J-14]) deg^{-2}
mag^{-1}. Extrapolation of these high latitude counts suggest that DENIS will
produce highly homogeneous catalogs of roughly 6000 (K < 11), 700,000 (J <
14.8) and, 1,000,000 (I < 16.5) galaxies, respectively with photometric
accuracy of 0.08^m in I and 0.20^m in J and K. Larger highly homogeneous
samples are expected with improvements to the camera and the algorithms.
