Sub-Rayleigh dark-field imaging via speckle illumination

We demonstrate sub-Rayleigh dark-field imaging via speckle illumination. Imaging is achieved with second-order autocorrelated measurement by illuminating objects with hollow conical pseudothermal light. Our scheme can work well for highly transparent amplitude objects, pure phase objects, and even more complex transparent objects. The autocorrelated dark-field images show better resolution than intensity-averaged images and an ability in filtering out low-frequency noises.