Lensless imaging with a controllable aperture

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Lensless imaging with a controllable aperture (2006)

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by Assaf Zomet , Shree K. Nayar

Venue:	In CVPR
Citations:	37 - 2 self

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@INPROCEEDINGS{Zomet06lenslessimaging,
    author = {Assaf Zomet and Shree K. Nayar},
    title = {Lensless imaging with a controllable aperture},
    booktitle = {In CVPR},
    year = {2006},
    pages = {339--346}
}

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Abstract

In this paper we propose a novel, highly flexible camera. The camera consists of an image detector and a special aperture, but no lens. The aperture is a set of parallel light attenuating layers whose transmittances are controllable in space and time. By applying different transmittance patterns to this aperture, it is possible to modulate the incoming light in useful ways and capture images that are impossible to capture with conventional lens-based cameras. For example, the camera can pan and tilt its field of view without the use of any moving parts. It can also capture disjoint regions of interest in the scene without having to capture the regions in between them. In addition, the camera can be used as a computational sensor, where the detector measures the end result of computations performed by the attenuating layers on the scene radiance values. These and other imaging functionalities can be implemented with the same physical camera and the functionalities can be switched from one video frame to the next via software. We have built a prototype camera based on this approach using a bare image detector and a liquid crystal modulator for the aperture. We discuss in detail the merits and limitations of lensless imaging using controllable apertures. 1. Lensless Imaging with Apertures Virtually all cameras today have lenses. Lenses are useful as they focus the light from the scene on the image plane to form bright and sharp images. We are so accustomed to cameras with lenses that we often overlook their fundamental limitation; lenses severely constrain the geometric and radiometric mapping from the scene to the image. The goal of this paper is to develop a new approach to imaging that facilitates a new class of mappings from the scene to the image, thereby enabling the camera to perform a wide set of imaging functionalities. We propose in this paper a novel, flexible video camera that does not have a lens. The camera design is simple. It consists of two components, an image detector and a special aperture, that are placed at a small distance apart. Figure 1(a) shows the aperture in its simplest form- a flat light attenuator whose transmittances are controllable in space and in time.

Keyphrases

controllable aperture special aperture image detector flat light attenuator new class end result incoming light flexible camera new approach disjoint region video frame scene radiance value physical camera sharp image radiometric mapping conventional lens-based camera bare image detector fundamental limitation aperture virtually camera design wide set flexible video camera prototype camera image plane liquid crystal modulator different transmittance pattern computational sensor camera today capture image small distance useful way

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