Considerable interest is growing around self homodyne techniques. Such techniques allow to avoid nonunitary detection efficiencies due to inefficient mode matching of the local oscillator. As proposed by Galatola et al. [1991], one possible scheme of self homodyne detection of a field with a strong coherent component involves the use of a Fabry-Perot cavity with a high reflecting rear mirror. Using this setup we are able to perform a tomographic measure of the Wigner function of the field emitted by a laser diode.