Light Field Tomography
Cameras with extreme speeds are enabling technologies in both fundamental and applied sciences. However, existing ultrafast cameras are incapable of coping with extended three-dimensional scenes.
To address this long-standing challenge, we developed light field tomography (LIFT), an imaging method that is highly efficient in recording light fields and enables snapshot acquisition of large-scale 2D time-resolved data. This is achieved by transforming a one-dimensional (1D) sensor to a 2D light field camera, exploiting the fact conventional light field acquisition is highly redundant—the sub-aperture images are mostly the same except for disparity cues. The vastly faster frame rate of 1D sensors also benefits LIFT for high speed imaging. While prior state-of-the-art ultrafast cameras are severely limited in pixel resolution that prevents light field acquisition, LIFT offers an elegant way to break this restriction. Coupled with a streak camera, LIFT can capture the complete four-dimensional spatiotemporal space in a single snapshot and provide an image resolution over 120 × 120 with a sequence depth beyond 1000, enabling unprecedented ultrafast 3D imaging capabilities.
Fig. 1. LIFT camera and ultrafast 3D imaging of a laser pulse propagating in a fiber-optic bundle at light speed.
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In addition to its ultrafast 3D-imaging capabilities, a LIFT camera can also photograph fast-moving targets hidden behind other objects or around corners — known as non-line-of-sight imaging — at 30 frames per second. The camera first picks up light from a hidden object, which is projected onto a wall in the camera’s field of vision. Similar to using a mirror, but with less-reflective surface, the camera system then computationally reconstructs the obscured scene. The device uses trace amounts of light difference — otherwise undetectable by a human eye — to reconstruct the image into a more distinct 3D picture. LIFT cameras could be incorporated into autonomous vehicles, allowing them to detect fast-moving hidden objects and make critical decisions. In addition, the technology holds potential for application in medical procedures, enabling surgeons to see behind bones or soft tissues.
Video 1. Real-time none-line-of-sight imaging of dynamic hidden scenes