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Ophthalmic Metrology
To manufacture ophthalmic products to the tight tolerances required is a challenge. Process set up and optimization has always been critical. Historically manufacturing equipment has been the limiting factor when tolerances have been reduced. Single point diamond turning equipment is now vastly improved. Lathes can be setup to tolerances of less than 1 um. To take advantage of this improved manufacturing capability process metrology equipment also has to be up-dated. Optical metrology can provide the accuracy and flexibility to help overcome this challenge.
Critical Ophthalmic Measurements
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The PTI 250 is Zygo’s latest optical metrology tool and is ideally suited for ophthalmic product production process control and optimization.
PTI 250 features include –
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Non Contact Radius of Curvature Measurement
The radius of curvature of a spherical surface is defined as the distance from the surface (or its best-fit spherical equivalent) to the center of curvature. These two locations are called the catseye and the confocal positions. To accurately determined these positions an interferometer is used, and the distance between them, R, is measured with the scale.The PTI250 uses a measurement scale that is linked to the system PC. The interferometer measures the part at both positions. The surface data and the “R” measurement from the scale are used to calculate the radius of curvature of the part.
Spherical Surface Measurement
A product of the radius of curvature measurement procedure is a complete 3 dimensional surface map of the part under test. This data can then be analyzed to provide a range of 3D plots and surface measurements.
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Plots include-
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