Inner cercumference measurement with AF optical axis tilt method

Abstract

Inner cercumference measurement of small complex parts,such as barrels for small-lenses dedicated for smartphones, has been in a great demand lately. To meet this demand,a new inner contour measuring method was developed. This new method tilts the optical axis of the point autofocus probe (PAP) to measure inner contour by applying the high tracking ability of PAP. The new measuring method has effective measuring inclination angles and measures cross section and circumference contours of a workpiece having its inner diameter less than several millimeters in sub-micron accuracy without repositioning by setting the optimal measuring conditions. In this paper,measurement accuracy and repeatability of inner contour measurement were verified by using an objective lens that is capable of measuring diameter having less than 7mm with its depth up to 7mm. It is useful for inner contour measurement of small lens ballels.