KERR CELL, 1930's

This is not a Baird grid cell but a similar type. A Kerr cell is a device for the electrical modulation of light. The cell consists of a transparent container filled with nitro-benzene. Polarized light is passed through the liquid and between two banks of metal plates resembling the plates of a variable capacitor. As the potential across the two banks of plates is varied, so the polarised light beam is more or less rotated, away from the axis of rotation. Baird used these in experiments for television and one is present in his 'Televisor'. Further research was done to try and produce high definition television but this was unsuccessful due to the internal capacitance of the cell. A further drawback not directly connected with the Kerr cell, is the fact that light-modulation of this type is of use only with mechanical methods of scanning, and these, in themselves, are clumsy and unsatisfactory for high definition. Rev. John Kerr (1824 - 1907) was a Scottish physicist who inaugurated the field of electro-optics.

Your comments:

• These were also used in the Rapatronic camera during the early nuclear tests.
  as light is blocked by two polarizing filters at 90 degree angles, a kerr cell between the filters will rotate the light when activated, allowing light to move through both filters and expose the film.
  Kerr cells allowed early high speed photographs with shutter speeds as fast as 1 nanosecond.
  .......... Cole Paquette, Nevada City, CA, USA, 30th of March 2011
  
  

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