SAVI: Synthetic Apertures for High Resolution Visible Imaging

NU 2017-083

Inventors

Oliver S. Cossairt*

Manoj K. Sharma

Jason Holloway

Yicheng Wu

Ashok Veeraraghavan

Short Description

Using Fourier ptychography (FP), a computational imaging technique, to create a synthetic aperture for visible imaging (SAVI) with high resolution.

Background

Imaging objects from far distances is essential in many computer vision and imaging applications such as surveillance and remote sensing. In these scenarios, the imaging device is sufficiently far away from the object that imaging resolution is fundamentally limited not by magnification but rather by the diffraction of light of the imaging system's aperture. A lens with a larger aperture offers increased spatial resolution. However, physically increasing the aperture of the lens, by building a larger lens, results in expensive, heavy, and bulky optics and mechanics. A number of alternative techniques have been proposed to improve spatial resolution for various imaging systems, including refractive telescopes, holography, and incoherent super-resolution. One notable computational imaging technique called Fourier ptychography (FP) is capable of generating high resolution images by capturing and stitching together multiple low-resolution images.

Abstract

Researchers at Northwestern have developed a synthetic aperture based on FT. For the first time, they demonstrated long-range, high resolution imaging of diffuse objects, well beyond the diffraction limit imposed by the imaging optics, using synthetic aperture FP-based techniques. Moreover, they have developed the first working prototype that is capable of imaging optically rough objects, that typically produce speckle caused by light scattering. This achievement makes the system more conducive to imaging everyday objects, like people and buildings, that scatter light in random directions. In addition, the researchers developed an image space regularization technique that reduces the speckle visible in the final reconstructed images and results in improved perceptual image quality. This novel approach has been validated experimentally where the resolution of various diffuse objects is improved six-fold. This technology demonstrates the feasibility and success of using a synthetic aperature for visible imaging (SAVI) and provides proof-of-concept for building a full-scale imaging platform in the near future.

Applications