Synthetic Apertures for Visible Imaging Using Fourier Ptychography
Veeraraghavan, Ashok N
Doctor of Philosophy
In long-range imaging, spatial resolution is predominantly limited by diffraction blur. Diffraction blur is a fundamental limit that is determined by the diameter of the lens used in the imaging system. In principle, the diameter of a lens can be increased to circumvent diffraction. In reality, cost and manufacturing limitations place a limit on the maximum diameter that can be achieved. Therefore, computational methods are required to super-resolve the observed, blurry image and recover spatial resolution lost to diffraction. Macroscopic Fourier ptychography is proposed as a practical means to create a synthetic aperture for visible imaging to achieve sub-diffraction limit spatial resolution. In this thesis, two principle barriers to implementing Fourier ptychography are addressed and resolved. First, a prototype imaging system is introduced to recover high-resolution long distance images in a reflection imaging geometry. Second, an image space regularization technique is developed to reconstruct optically rough surfaces that exhibit speckle. Experimental results demonstrate, for the first time, a macroscopic Fourier ptychography imaging system to achieve sub-diffraction resolution of optically rough objects in a reflection geometry. Spatial resolution is increased six-fold over any single captured image.
Fourier ptychography; synthetic aperture; synthetic apertures for visible imaging; SAVI