Photorefractometer I Extension of Sensitivity and Range

The fractional sensitivity and operational refractive index range of the rod photorefractometer have been extended by physical modifications of axially symmetric refracting elements and the mode of illumination. Optical systems using conical and cylindrical rod elements with flat or spherical entrance ends illuminated by an axial light cone or a hollow annular light cone have been studied. Expressions describing the sensitivity of these configurations are presented, and typical numerical cases are computed on an IBM 650 computer. Extension of range to specimen index close to 1.0 permits the photorefractometer to detect index changes of low refractive index media. Experimental verification of the theory is achieved.