The fabrication of complex aspheric and freeform surfaces are possible with accurate iterative metrology feedback
during correcting polishing process. The tool path of the machine is generated based on the measured surface data
for corrective material removal. The computer controlled polishing machines are compatible with various metrology
tools. This paper presents annular null based interferometric in- process metrology for deterministic corrective
polishing for aspheric surface of infrared optical material.
A method is presented to measure refractive index of a plane parallel plate of optical glass. We have applied focal
displacement method to measure refractive index of a plane parallel plate of an optical glass having thickness of the
order of millimeters. The best focus position is found by applying edge detection algorithm. We have measured LAF2
optical glass using focal displacement method and obtained the value 1.746, which is within 0.1% of the standard value
1.747 at 555 nm. In comparison to Abbe refractometer, this method is simple in terms of sample preparation,
experimental set up and for measuring high refractive index of Zinc Sulfide. Using this method, refractive indices of
other optical glasses are also measured.