For routine precision measurements of refractive index, many optical glass manufacturers, such as Chance-Pilkington are presently using the Hilger-Chance Vee block refractometer which was first marketed in 1947. With a need for a higher throughput of glass samples, greater accuracy in measurements and a reduction in operator fatigue, a new automatic instrument based on the same 'vee' block principle has been commissioned by Chance-Pilkingtons. The new instrument is capable of accuracies in refractive index of ± 1 x 10-5 over a range of 1.48 to 1.95 and many of the limitations of the original Hilger-Chance design have been overcome. An interferometric technique is being included to encode the deviation angle for electronic readout. The design of this new system is described and discussed.
R. M. Lee,
"New Approach To Precision Automatic Refractometry", Proc. SPIE 0163, Advances in Optical Production Technology II, (25 September 1979); doi: 10.1117/12.956907; https://doi.org/10.1117/12.956907