26 August 2005 Measurement advances for micro-refractive fabrication
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Micro-refractive lenses are an important example of components and subsystems that are being used increasingly in optical sensors, communications, data storage, and other diverse applications. These lenses have a continuous relief surface such that details of their dimensional shape, refractive index, and homogeneity all influence performance. Measurement capabilities for micro-refractives fall short of current and future needs and are complicated by the need to fabricate non-spherical refractive surfaces. To control the fabrication process, the target measurement uncertainties are approximately 3 parts in 10-4 for radius and on the nanometer scale for figure measurements. Carrying out metrology at this level is very challenging and especially so for micro-scale components. Micro-interferometry is the most promising tool and can be used to measure radius of curvature, focal length, dimensional surface errors, and transmitted wavefront. Common practice is to calibrate with a single high quality artifact for measurements of a range of different radii, and we see that this is only approximately valid. Figure measurement calibration, for example, will be improved if the radius of the calibration artifact closely matches the radii of the test lenses, but acquiring such a range of artifacts is not practical. We have demonstrated the application of a self-calibration procedure for figure measurement and transmitted wavefront measurement calibration, called the random ball test. Radius measurements on the micro-scale are also challenging. Our research focuses on measurement advances for refractive components and new data analysis strategies to optimize the impact of measurement results.
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Neil Gardner, Neil Gardner, Angela Davies, Angela Davies, Brent Bergner, Brent Bergner, } "Measurement advances for micro-refractive fabrication", Proc. SPIE 5858, Nano- and Micro-Metrology, 58580P (26 August 2005); doi: 10.1117/12.622753; https://doi.org/10.1117/12.622753

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