3-D laser metrology for the assessment of curved surface

Measurement instruments are identified which are suitable for the assessment of curved samples typically used in the manufacture of lens technology. The advantages and limitations of each instrument are discussed, together with their suitability for measuring surfaces and producing data that can be analysed for sphericity information. A number of numerical sphere- fitting algorithms are suggested for radius of curvature analysis, and a Contour Analysis technique is developed for the assessment of errors of Form without the need to sphere-fit to the data. Contour Analysis is shown as a useful visualisation tool, allowing the user to clearly see surface distortions, such as astigmatism, without the need to interpret the deviation from sphere plots