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.
A streak camera operates by transforming the time variations of a light pulse into a spatial profile on a detector, by causing a time-varying deflection of the light across the width of the detector. A light pulse enters the instrument through a narrow slit along one direction gets deflected in the perpendicular direction so that photons that arrive first hit the detector at a different position compared to photons that arrive later.
The resulting image forms a "streak" of light, from which the duration, and other temporal properties, of the light pulse can be inferred. Usually, in order to record periodic phenomena, a streak camera needs to be triggered accordingly, similarly to an oscilloscope.
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. 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.
The time-resolution of the best optoelectronic streak cameras is around 180 femtoseconds. Measurement of pulses shorter than this duration requires other techniques such as optical autocorrelation and frequency-resolved optical gating (FROG).
- Photo finish, which uses a much slower but 2-dimensional version of a camera mapping time into a spatial dimension
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