Coded Aperture Imaging: Many Holes Make Light Work

Abstract

A coded aperture camera is similar to a pinhole camera in that no reflecting or refracting optics are used to form an image. However, it is different due to the fact that the single opening of the conventional pinhole camera has been replaced with a pattern of holes which may number in the hundreds or thousands. The resulting image is the superposition of many individual pinhole images and must be unscrambled to be meaningful. The advantage of the coded aperture is that many more photons are collected in a given period of time, and hence the resulting decoded image is of higher quality than if a conventional single pinhole camera were used. An additional advantage lies in the ability to obtain three-dimensional depth information from a single view. This paper presents an overview of past coded aperture imaging efforts which include the use of Fresnel zone plates, random arrays, and nonredundant pinhole arrays. The theory underlying their use is presented as well as a review of the digital and optical methods used in decoding. Recent important advances in the field, such as the use of uniformly redundant arrays, are presented. Typical results from some of the above-mentioned systems are shown and discussed.