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.
Mechanical typesEdit
Mechanical streak cameras use a rotating mirror or moving slit system to deflect the light beam. They are limited in their maximum scan speed and thus temporal resolution.<ref>Template:Cite book</ref>
Optoelectronic typeEdit
Optoelectronic streak cameras work by directing the light onto a photocathode, which when hit by photons produces electrons via the photoelectric effect. The electrons are accelerated in a cathode-ray tube and pass through an electric field produced by a pair of plates, which deflects the electrons sideways. By modulating the electric potential between the plates, the electric field is quickly changed to give a time-varying deflection of the electrons, sweeping the electrons across a phosphor screen at the end of the tube.<ref>Template:Cite book</ref> A linear detector, such as a charge-coupled device (CCD) array is used to measure the streak pattern on the screen, and thus the temporal profile of the light pulse.<ref> {{#invoke:citation/CS1|citation |CitationClass=web }} </ref>
The time-resolution of the best optoelectronic streak cameras is around 180 femtoseconds.<ref> Akira Takahashi et al.: "New femtosecond streak camera with temporal resolution of 180 fs" Proc. SPIE 2116, Generation, Amplification, and Measurement of Ultrashort Laser Pulses, 275 (May 16, 1994); {{#invoke:doi|main}} </ref> Measurement of pulses shorter than this duration requires other techniques such as optical autocorrelation and frequency-resolved optical gating (FROG).<ref>Template:Cite book</ref>
In December 2011, a team at MIT released images combining the use of a streak camera with repeated laser pulses to simulate a movie with a frame rate of one trillion frames per second.<ref> {{#invoke:citation/CS1|citation |CitationClass=web }} </ref> This was surpassed in 2020 by a team from Caltech that achieved frame rates of 70 trillion fps.<ref>Template:Cite journal</ref>
See alsoEdit
- Photo finish, which uses a much slower but 2-dimensional version of a camera mapping time into a spatial dimension
- Femto-photography
ReferencesEdit
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