1. A device for IR imaging with surface wave readout comprising: a pyroelectric stratum which is doped with an impurity to obtain a free carrier concentration in said stratum the free carriers being repelled from the surface of said stratum by a surface charge to form a depletion layer, the density of said surface charge being a function of the temperature of the incident radiation from an IR image; a piezoelectric substrate parallel to the pyroelectric stratum and separated from it by spacers; first means for propagating a first acoustic surface wave in the piezoelectric substrate, said wave transversing the substrate such that the electric field of the wave penetrates the pyroelectric stratum; second means for propagating a second acoustic surface wave in the piezoelectric substrate, said second means located at the opposite end of the substrate from the first means so that second acoustic surface wave travels in the opposite direction from the first acoustic surface wave so as to amplitude modulate the first wave; and output means for observing the amplitude modulated first wave after it has transversed the pyroelectric stratum located at the same end of the piezoelectric substrate as the second propagating means.