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Photography optics in the time dimension


Ultrafast sensors and depth cameras are key enablers for imaging through complex geometries, through scattering, and beyond the line of sight. However, despite accelerating advances in imaging electronics and imaging applications, the optics of such cameras have been inherited from conventional low-speed photography cameras. This has limited ultrafast cameras and their applications to the design constraints of conventional optics. Here, we exploit time as an extra dimension in the optical design and demonstrate that by folding large spaces in time using time-resolved cavities, one can enable new camera capabilities without losing the targeted information. We demonstrate lens tube compression by an order of magnitude, together with ultrafast multi-zoom imaging and ultrafast multispectral imaging by time-folding the optical path at different regions of the imaging optics. Considering the vast variety of designs that could emerge by time-folding conventional imaging optics, we expect this technique to have a broad impact on time-resolved imaging and depth-sensing optics.

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Fig. 1: Experimental set-up and time-folded imaging overview.
Fig. 2: Spatial compression of imaging optics by time-folding the focal length.
Fig. 3: Multi-zoom ultrafast camera by time-folding the entrance lens.
Fig. 4: Multispectral ultrafast camera by wavelength-dependent time-folding.

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We thank M. Bawendi and his team members D. Franke and J. J. Yoo at the MIT Department of Chemistry for their help with preparation of fluorescent samples. We also thank A. Bhandari and K. Pulli for discussion of matrix representations and for reading the manuscript.

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Authors and Affiliations



B.H. proposed the idea, performed some of the experiments, analysed the data and supervised the project. M.T. performed some of the experiments and analysed the data. G.S. analysed the data and helped with the theoretical expressions. R.R. co-supervised the project. All authors contributed equally to manuscript preparation.

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Correspondence to Barmak Heshmat.

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The authors declare no competing interests.

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Supplementary information

Supplementary Information

This file contains additional information on the modelling and sampling of the approach, discussion and Supplementary Figures.

Supplementary Video 1

Imaging with time-folded compressed lens tube.

Supplementary Video 2

Time-folding enables capturing the evolution of the wavefront in the optical system.

Supplementary Video 3

Turning a streak camera into a multispectral infrared imaging camera using time-folding.

Supplementary Video 4

Turning a streak camera into a multispectral fluorescence lifetime imaging (FLIM) camera using time-folding.

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Heshmat, B., Tancik, M., Satat, G. et al. Photography optics in the time dimension. Nature Photon 12, 560–566 (2018).

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