References
參考資料
Nakagawa, K., Iwasaki, A., Oishi, Y., Horisaki, R., Tsukamoto, A., Nakamura,
A., Sakuma, I. (2014). Sequentially timed all-optical mapping
photography (STAMP). Nature Photonics Nature Photon, 8(9), 695-700.
Further Reading
延伸閱讀
• Pump-probe technique,
• Sequentially Timed All-optical Mapping Photography,
Capturing the Breeze :
High-Speed
Photography
By Man Hing Wong
黃雯馨
History’s
earliest surviving photograph, circa 1826, was
little more than a rudimentary sketch, requiring
several days of exposure. By 1838, daguerreotype
photography had shor tened exposure time
signif icantly, to the length of around ten to
twelve minutes. Since then, the development of
photography and videography has taken off at
an exponential rate, with standard cameras being
able to capture motion more rapidly than can be
detected by the naked eye. Recent research has
taken this to an entirely new level with high-speed
photography.
According to the Society of Motion Picture
and Television Engineers (SMPTE), high-speed
photography is categor ised as photographs
that can be taken at a rate of over 128 frames
per second. To capture a photograph, the
came ra mus t rece i ve l i ght ref l ected f rom
the su r face of an obj ect. Obj ect s i n rapid
motion must be sequential ly recorded with
high precision, which is vi r tual ly impossible
for ordinary cameras due to the unavoidable
delay of the shutter. Pump-probe technology
and sequentially timed
al l -optical mapping
photography (STAMP) offer to fill the lag.
In pump-probe photography, the “probe”
and “pump” lasers are adopted to eliminate
time lapse due to a light shutter. To photograph
the response of an object such as a collection of
atoms, an initial beam of ‘pump’ laser radiates the
object to an excited state of heightened energy,
and a precisely delayed beam of ‘probe’ light
is applied to take an image of the object. An
issue associated with pump-probe photography,
however, is that it requires repetitive measurements
to compile the final movie.
Scientists from Keio University and University
of Tokyo have invented a means of capturing
single-shot images at a rate of 4.4 trillion frames
per second at a resolution of up to 450 x 450 pixels
using STAMP, also known as femto-photography.
To put this into perspective of what this means,
STAMP can potentially capture the conduction of
heat (which moves at a speed nearly a sixth of the
speed of light), vibrations of atoms in their crystal
states (lattice vibrations), and plasma dynamics.
The technique involves shooting an ultra-short
laser pulse at the photographed object. A set
up of mirrors and careful orientation of cameras
surround the object so that all angles are
