Letter

Serial time-encoded amplified imaging for real-time observation of fast dynamic phenomena

  • Nature volume 458, pages 11451149 (30 April 2009)
  • doi:10.1038/nature07980
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Subjects

Abstract

Ultrafast real-time optical imaging is an indispensable tool for studying dynamical events such as shock waves1,2, chemical dynamics in living cells3,4, neural activity5,6, laser surgery7,8,9 and microfluidics10,11. However, conventional CCDs (charge-coupled devices) and their complementary metal–oxide–semiconductor (CMOS) counterparts are incapable of capturing fast dynamical processes with high sensitivity and resolution. This is due in part to a technological limitation—it takes time to read out the data from sensor arrays. Also, there is the fundamental compromise between sensitivity and frame rate; at high frame rates, fewer photons are collected during each frame—a problem that affects nearly all optical imaging systems. Here we report an imaging method that overcomes these limitations and offers frame rates that are at least 1,000 times faster than those of conventional CCDs. Our technique maps a two-dimensional (2D) image into a serial time-domain data stream and simultaneously amplifies the image in the optical domain. We capture an entire 2D image using a single-pixel photodetector and achieve a net image amplification of 25 dB (a factor of 316). This overcomes the compromise between sensitivity and frame rate without resorting to cooling and high-intensity illumination. As a proof of concept, we perform continuous real-time imaging at a frame speed of 163 ns (a frame rate of 6.1 MHz) and a shutter speed of 440 ps. We also demonstrate real-time imaging of microfluidic flow and phase-explosion effects that occur during laser ablation.

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Acknowledgements

This work was partially supported by the US Defense Advanced Research Projects Agency and the Center for Nanoscience Innovation for Defense. We are grateful to D. R. Solli, Y. Hoshino and T. Kodama for discussions. We also thank T. Lay for creating the animated film.

Author information

Author notes

    • K. Goda
    • , K. K. Tsia
    •  & B. Jalali

    These authors contributed equally to this work.

Affiliations

  1. Department of Electrical Engineering, University of California, Los Angeles, California 90095, USA

    • K. Goda
    • , K. K. Tsia
    •  & B. Jalali

Authors

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Corresponding author

Correspondence to K. Goda.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    This file contains Supplementary Legends for Movies 1 and 2, Supplementary Methods and Supplementary Data.

Videos

  1. 1.

    Supplementary Movie 1

    This animated movie illustrates the functionality of the STEAM camera.

  2. 2.

    Supplementary Movie 2

    This Real-time movie shows the ultrafast microfluidic flow captured by the STEAM camera.

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