HIGH-PRECISION MEASUREMENT FOR REFRACTIVE-INDEX DISTRIBUTION AND DISPERSION USING AN IMPROVED SCANNING TOTAL REFLECTION METHOD

An improved scanning total reflection (STR) method is discussed to accurately measure the refractive index distribution and dispersion of the gradient index optical element. We also describe the measuring apparatus and experimental results. The accuracy of 1 x 10(-4) (rms) was attained in terms of the absolute measurement of refractive indices, and good reproducibility of the index and Abbe number were also confirmed, delta-n=1 x 10(-4) (rms) and delta-nu(d)=0.5 (rms), respectively. A very good agreement is also observed between the result obtained by our method and that by an interference method.