C.J. Oliver and E.R. Pike:Appl. Opt. 1975, 8 (1969) 6) J.K. Nakamura and S.E. Schmarz:Appl. Opt., 1073, 7, 6 (1968) 7) J.K. Nakamura and S. E. Schwarz:Appl. Opt., 7, 6 (1968) 8) R.R.Alfano and N. Ockman: Journal of the Optical Society ofAmerica, 58, 1 (1968) 9) T.Yoshimura, K. Hara and N. Wakabayashi