We report design, fabrication and characterization of molded chalcogenide microlens array for Infrared sensing applications. A master of desired microlens array with high sag value is prepared using ultraviolet lithography and thermal reflow method on a positive photoresist (ma–P1275HV). The negative replica of the master is created using polydimethylsiloxane which serves as a mold for micro-molding. Further, chalcogenide solution is prepared in ethanolamine solvent and spin coated on a substrate to get a uniform film; these films are characterized and are found to have the same optical properties as the parent bulk chalcogenide glass. Finally, the microlens array is fabricated by the micro-molding of chalcogenide film. Fabricated chalcogenide microlenses are characterized for geometrical parameters, which are used to estimate the optical parameters.
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.
Significant advances have been made in the field of fabrication of optical components over the years. While plano and
spherical surfaces are polished mostly by full aperture polishers made of pitch or polyurethane pads, no such approach is
possible for aspheric surfaces as polisher needs to conform to the changing local curvature of aspheric surface. For such
aspheric and freeform surfaces sub aperture polishing is a very attractive option as it forms a small polishing spot over
the surface of the optics and the path of this spot in multi axis configuration is precisely controlled by the computer. This
polishing process follows a deterministic approach and material removal information is very much necessary to control
surface form or surface accuracy of the optical component. Here we have carried out the polishing of several glass
substrates to find out the response of various glass types to this polishing process.
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.