On the Interference Color of a Dielectric Layer on Metal Surface

概要

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In Section I to II, the author calculated the interference color of Al mirror covered with ZnS and plotted the results on the I. C. E. chromaticity diagram in order to study the interference color of a dielectric layer on metal surface. In Section III, when a very thin Al film was evaporated again upon the mirror Al (opaque)+ZnS, the interference color of this mirror became very vivid. The spectral reflectivity of the mirror : Al (opaque)+ZnS+Al (very thin), was mesured by G. E. spectrophtometer taking the optical thickness of ZnS as parameter and the results of calculation of the interference color were plotted on the I. C. E. chromaticity diagram. In Section IV, the results observed by the eye were discussed in comparison with the results in Section III and we observed when the thickness of Al film became thicker app. 40A, the interference color changed from the initial state and the change of color went in the opposite direction. On the basis of these results, the method of coating ZnS layer with the accurate thickness of λ/4 or MgF_2 layer with λ/2, was discussed. In this method by using the substratum of Al mirror, the observation of interference color change was very easy and no analyzer was necessary in the observation.