APPLICATION OF REAL-TIME PHASE-SHIFT INTERFEROMETER TO THE MEASUREMENT OF CONCENTRATION FIELD

A real time phase shift interferometer developed by Nakadate is applied to the measurement of the concentration distribution around a growing or dissolving crystal. Use of the polarized light interferometer allowed either a grey level picture depending on a two-dimensional phase distribution or a three-dimensional perspective profile of the concentration field to be displayed on a TV monitor in real time. The sensitivity of the interferometer is increased at least by a factor of 20 to 30 compared with the conventional two-beam interferometer. The time resolution was also improved so that succesive phase distribution could be obtained at the time resolution of 1/60 s. Using the Abel transformation method, a quasi-three-dimensional concentration profile of a sodium chlorate crystal was calculated, which made it possible to measure the actual surface concentration.