  We use a strong lensing inversion in the cluster of galaxies AC 114 to derive
constraints on the cosmological parameters Omega_M0 and Omega_Lambda. If it is
possible to measure spectroscopically the redshifts of many multiple images
then one can in principle constrain (Omega_M0,Omega_Lambda) through ratios of
angular diameter distances, independently of any external assumptions.
Numerical tests on simulated data show rather good constraints from this test.
We also use an analytic ``pseudo-elliptical'' NFW profile in the simulations,
following the general new formalism we present. An application to AC 114 favors
a flat Universe, an EdS model being marginally ruled out.
