Lensless coded aperture imaging with separable doubly Toeplitz masks

Abstract

In certain imaging applications, conventional lens technology is constrained by the lack of materials which can effectively focus the radiation within a reasonable weight and volume. One solution is to use coded apertures-opaque plates perforated with multiple pinhole-like openings. If the openings are arranged in an appropriate pattern, then the images can be decoded and a clear image computed. Recently, computational imaging and the search for a means of producing programmable software-defined optics have revived interest in coded apertures. The former state-of-the-art masks, modified uniformly redundant arrays (MURAs), are effective for compact objects against uniform backgrounds, but have substantial drawbacks for extended scenes: (1) MURAs present an inherently ill-posed inversion problem that is unmanageable for large images, and (2) they are susceptible to diffraction: a diffracted MURA is no longer a MURA. We present a new class of coded apertures, separable Doubly-Toeplitz masks, which are efficiently decodable even for very large images-orders of magnitude faster than MURAs, and which remain decodable when diffracted. We implemented the masks using programmable spatial-light-modulators. Imaging experiments confirmed the effectiveness of separable Doubly-Toeplitz masks-images collected in natural light of extended outdoor scenes are rendered clearly.

Low open fraction coded masks for x-ray backscatter imaging

“…The purpose of this was to sum both exposures, intensifying the signal and reducing/canceling noise within the final image. 28 All masks were mosaicked by repeating the original unit or base pattern twice in the Xand Y-directions of the array so that a total of four patterns were present. The mosaic had one row and one column removed, so only one full unit pattern (full cycle) was present.…”

From modeling to hardware: an experimental evaluation of image plane and Fourier plane coded compressive optical imaging

“…Compressive Fourier ptychography can achieve approximately an order of magnitude reduction in acquisition time over traditional sequential techniques [30]. Researchers are also investigating lensless CS systems [31][32][33][34] (Fig. 1(f)).…”

Toward depth estimation using mask-based lensless cameras

“…Coded-aperture cameras have traditionally been used for imaging wavelengths beyond the visible spectrum (e.g., Xray and gamma-ray imaging), for which lenses or mirrors are expensive or infeasible [3], [2], [4], [5], [6], [7]. Maskbased lensless designs have been proposed for flexible field-ofview selection in [9], compressive single-pixel imaging using a transmissive LCD panel [10], and separable coded masks [11]. In recent years, coded masks and light modulators have been added to lens-based cameras in different configurations to build novel imaging devices that can capture image and depth [12] or 4D light field [13], [14] from a single coded image.…”