As a widely used lensless coherent diffraction imaging approach, ptychography has recently been implemented in Terahertz range. Combining with the unique penetration property of THz radiation, THz ptychography allows inspecting visually opaque samples and retrieving both amplitude and phase information. Here, we demonstrate for the first time to our knowledge, THz ptychography in reflective configuration. Due to the large wavelength (96.5 μm), THz ptychography requires small recording distance. Particular care has been taken in the experimental setup to minimize the recording distance. Extended ptychographic iterative engine (ePIE) is applied to reconstruct quantitatively the amplitude and phase information of the object wavefront. A lateral resolution of 180 μm and a depth resolution of 1.1μm are achieved.
Ptychography is a widely used lensless coherent diffraction imaging approach, in which the complex transmittance function of the object is retrieved from a set of diffraction patterns originating from overlapping sample illumination area. In this paper, we propose a normal-incidence reflection ptychographic system. The sample and detector are located on each side of the beam splitter similarly to Michelson interferometer without reference beam. This system can reveal the topographic structure of reflective samples. Compared with Michelson interferometer based off-axis digital holography, the field-of-view of the proposed reflective ptychography is unlimited by the aperture of the detector.