Light-in-flight imaging — a set of techniques to visualize propagation of

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...

through different media.

History and techniques

Light was first captured in its flight by N. Abramson in 1978, who used a

holographic Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other Holography#Applications, applic ...

technique to record the

wavefront In physics, the wavefront of a time-varying ''wave field'' is the set (locus) of all points having the same ''phase''. The term is generally meaningful only for fields that, at each point, vary sinusoidally in time with a single temporal freque ...

of a pulse propagating and being

scattered Scattered may refer to: Music * ''Scattered'' (album), a 2010 album by The Handsome Family * "Scattered" (The Kinks song), 1993 * "Scattered", a song by Ace Young * "Scattered", a song by Lauren Jauregui * "Scattered", a song by Green Day from ' ...

by a white-painted screen placed in its path. This high-speed recording technique allowed the dynamic observation of light phenomena like

reflection Reflection or reflexion may refer to: Science and technology * Reflection (physics), a common wave phenomenon ** Specular reflection, reflection from a smooth surface *** Mirror image, a reflection in a mirror or in water ** Signal reflection, in ...

interference Interference is the act of interfering, invading, or poaching. Interference may also refer to: Communications * Interference (communication), anything which alters, modifies, or disrupts a message * Adjacent-channel interference, caused by extr ...

and focusing that are normally observed statically. More recently, light-in-flight holography has been performed in a scattering medium rather than using a reflective screen. Light can also be captured in motion in a scattering medium using a

streak camera A streak camera is an instrument for measuring the variation in a pulse of light's intensity with time. They are used to measure the pulse duration of some ultrafast laser systems and for applications such as time-resolved spectroscopy and LIDAR. ...

that has

picosecond A picosecond (abbreviated as ps) is a unit of time in the International System of Units (SI) equal to 10−12 or (one trillionth) of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 ...

temporal resolution Temporal resolution (TR) refers to the discrete resolution of a measurement with respect to time. Physics Often there is a trade-off between the temporal resolution of a measurement and its spatial resolution, due to Heisenberg's uncertainty pri ...

, thus removing the need for

interferometry Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...

and

coherent Coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a deri ...

illumination but requires additional hardware to raster scan the two-dimensional (2D) scene, which increases the acquisition time to hours. A few other techniques possess the temporal resolution to observe light in motion as it illuminates a scene, such as photonic mixer devices based on modulated illumination, albeit with a temporal resolution limited to a few

nanosecond A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or 10 seconds. The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit ( ...

s. Alternatively, time-encoded amplified imaging can record images at the repetition rate of a

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...

by exploiting wavelength-encoded illumination of a scene and amplified detection through a dispersive fibre, albeit with 160 ns temporal and spatial resolution. Recent studies based on computer tomography using data from multiple probe pulses enabled reconstruction of picosecond pulse propagation phenomena in condensed media. In 2015 a method to visualize events evolving on picosecond time scales based on single-photon detector arrays has been demonstrated.{{cite journal , last=Gariepy , first=Genevieve , last2=Krstajić , first2=Nikola , last3=Henderson , first3=Robert , last4=Li , first4=Chunyong , last5=Thomson , first5=Robert R. , last6=Buller , first6=Gerald S. , last7=Heshmat , first7=Barmak , last8=Raskar , first8=Ramesh , last9=Leach , first9=Jonathan , last10=Faccio , first10=Daniele , title=Single-photon sensitive light-in-fight imaging , journal=Nature Communications , publisher=Springer Science and Business Media LLC , volume=6 , issue=1 , date=2015-01-27 , issn=2041-1723 , doi=10.1038/ncomms7021 , page=6021, doi-access=free

References

Film and video technology Light Articles containing video clips

History and techniques

See also

References