Terahertz Ptychography with Efficient FOV for Breast Cancer Tissue Imaging

Ptychography is a lensless coherent diffraction imaging method that retrieves both the amplitude and the phase from a set of diffraction patterns. The phase-contrast imaging capacity combined with the unique penetration ability of THz radiation offers potential for applications such as biomedical imaging and nondestructive testing. We present two optimization strategies that allow THz ptychography to achieve efficiently a large field of view (FOV) with high resolution. We show that using a larger probe beam paired with a proportionally enlarged scanning step increases the imaging FOV without causing the imaging quality degradation as long as the overlap ratio is respected. Thus, a centimeter-scale object can be imaged with reasonable numbers of scan positions. We create a structural illumination by simply inserting a porous polymer foam that acts as a diffuser. The presence of the diffuser offers a higher spatial resolution and a better reconstruction for pure-phase objects. We experimentally demonstrate the reconstruction improvement with both an amplitude-contrast USAF target sample and a phase-contrast sample. The proposed THz ptychographic setup successfully images the phase variation distribution of a sample consisting of paraffin-embedded human breast cancer tissue.