Two-Dimensional Kerr Electrooptic Measurement of Nonuniform Electric Fields by CT Method

Abstract

It is very difficult to measure nonuniform electric field distributions in insulators. The optical measurements of the electric field were investigated in nitrobenzene using the Kerr effect. A sphere-to-sphere electrode or a sphere-to-plane electrode system was used to produce the nonuniform electric field. A rectangular test cell was made of teflon with two glass windows. A He-Ne laser was used for a light source. The intensity of the light transmitted through the cell was measured with a photodiode. The two-dimensional electric field distribution expressed in absolute value was reconstructed by the computed tomography (CT) method. The measured electric fields were compared with the theoretical one and good agreement was obtained.

Improvement of accuracy of the measurement of electric field distributions using the Kerr electrooptic effect and computed tomography

“…In addition, medical tomographs (PET and PECT) have recently employed ML-EM (Maximum Likelihood Expectation Maximization), OS-EM (Ordered Subset Expectation Maximization), and MAP-EM (Maximum A Posteriori Expectation Maximization). Considering the appropriate and easy application of CT to measurement of electric field distributions, we have used algebraic reconstruction [3,4,10].…”

“…Thus, we developed an original method combining the Kerr effect with the CT method (iterative approximation method) to measure the electric field distribution on an arbitrary plane in a liquid, and evaluated the effectiveness of the method [3][4][5][6][7].…”

“…We assumed that the CT principle can be applied to electric measurements considering that the phase difference between ordinary light and extraordinary light produced by birefringence in an electric field is equal to the integration of the infinitely small difference along a light path. Thus, we developed an original method combining the Kerr effect with the CT method (iterative approximation method) to measure the electric field distribution on an arbitrary plane in a liquid, and evaluated the effectiveness of the method [3][4][5][6][7].…”

Progress in Japan of electrical field measurement technology for liquid dielectrics

“…Basic Equations for a New Measurement Technique [7,91 As described above, elliptically polarized light with optic phase shift a is used as incident light and an ac electric field EAC sin cot is superimposed on dc electric field EDC to modulate the light intensity Then, the optic phase shift becomes (14) The fundamental component W , whch is much larger than the other sinusoidal components, is given as AIJI, = ~$ A C EDC + 314 J EAC~ EDC + J EAC EDC~ (15) The Kerr constant of the &electric liquid is so small that the fust term in Eq. (15) is much larger than the other terms; then Eq.…”

“…Despite the complexity and the difficulty of the problems, recently some researchers in Japan endeavored to develop three-dimensional electric field measurement techniques by introducing a CT (computer tomography) technique as shown in Table I. For example, Arii is developing a measurement technique for a three-dimensional electric field without electric field modulation [15,16,171. Hikita is developing a technique to measure three-dimensional electric field distribution in transformer oil with a small Kerr constant by use of electric field modulation and elliptically polarized incident light [18].…”