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A Kerr cell shutter is a type of photographic shutter used for very fast shutter speeds down to
A Kerr cell shutter is a type of photographic shutter used for very fast shutter speeds down to 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 ...
level.
The Kerr Cell consists of a transparent container (A) filled with nitrobenzene
Nitrobenzene is an organic compound with the chemical formula C6H5 NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals. It is produced on a large scale from benzene as a precursor ...
(B) with attached electrodes (C and D). A high voltage is passed through the electrodes which causes an electric field perpendicular to the transmitted light beam to be applied.
The cell makes use of the Kerr effect
The Kerr effect, also called the quadratic electro-optic (QEO) effect, is a change in the refractive index of a material in response to an applied electric field. The Kerr effect is distinct from the Pockels effect in that the induced index cha ...
, in which the nitrobenzene becomes birefringent
Birefringence is the optics, optical property of a material having a refractive index that depends on the Polarization (waves), polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent (or ...
under the influence of the electric field. This allows it to be used as a shutter that can be opened for a very brief amount of time, around 10ns.
Its primary disadvantage was the use of toxic and flammable substances such as nitrobenzene
Nitrobenzene is an organic compound with the chemical formula C6H5 NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals. It is produced on a large scale from benzene as a precursor ...
and o-nitrotoluene. These have now largely been replaced by KTN (potassium tantalate niobate) and barium titanate
Barium titanate (BTO) is an inorganic compound with chemical formula BaTiO3. Barium titanate appears white as a powder and is transparent when prepared as large crystals. It is a ferroelectric, pyroelectric, and piezoelectric ceramic material th ...
(BaTiO3).
Speed of Light measurement
The Kerr Cell shutter was used in the 1920-40s to measure the speed of light. A beam of light is timed between an emitter and receiver while passing through a Kerr Cell. When the cell is activated the light beam is diverted and takes a different path to the receiver, this time difference is measured and the speed of light is calculated based on knowledge of the expected return time.See also
*Kerr effect
The Kerr effect, also called the quadratic electro-optic (QEO) effect, is a change in the refractive index of a material in response to an applied electric field. The Kerr effect is distinct from the Pockels effect in that the induced index cha ...
*Rapatronic camera
The rapatronic camera (a portmanteau of ''rap''id ''a''ction elec''tronic'') is a high-speed camera capable of recording a still image with an exposure time as brief as 10 nanoseconds.
The camera was developed by Harold Edgerton in the 1940s ...
References
External links
* Photographic shutters {{optics-stub