Based on the self-imaging phenomenon a digital Talbot interferometer is pro
posed. This arrangement allows the detection of phase changes introduced by
a phase object. The output of the interferometer displays the fringe patte
rn obtained through the digital subtraction between two stored intensity di
stributions corresponding to a self-image plane where the phase-object is p
laced before the second image is captured. Due to the nature of the method
a relative rotation of the grating is avoided. The fringe pattern results f
rom the spatial beating between the self-image and its modified version int
roduced by the phase object. The frequency of the beating is related to the
quantitative change introduced by the phase object. To test the performanc
e of the interferometer, experimental results where the phase objects are l
enses are presented. The experiment gives a good characterization of the te
sted objects. A quantitative analysis is conducted through a straight forwa
rd model. which is based on the beating between the self-image and its defo
rmed version.