Sub-wavelength Coherent Imaging of a Pure-Phase Object with Thermal Light

We report, for the first time, the observation of sub-wavelength coherent image of a pure phase object with thermal light. We demonstrate that ghost-imaging scheme (GI) recovers amplitude transmittance of objects rather than the transmitted intensities as the classical Coherence-Function Imaging (CFI) scheme does. Also, the understanding of whether the entanglement is a prerequisite for GI is sharpened:Only entangled two photon state contributes to the joint detection,whereas the entangled light beam source is not a prerequisite