How to achieve accurate optical surface topography measurement
For many years, vendors of surface topography measuring instruments have been specifying resolutions of the order of nanometres, even picometres in some cases.
But, they rarely make any statements about accuracy, arguably a far more important instrument specification. Putting the marketing spin aside, this issue arises because the interaction between the instrument and the surface being measured is complex and it is difficult to state quantitative accuracies.
NPL is now ;making a leap forward in this area, first by understanding why optical instruments often give highly spurious results, then trying to understand the measurement process, design appropriate calibration strategies, and finally to design correction methods for systematic errors. The talk will present this story.