Stylus Measurement and Error Analysis of Large Slope Angle Lens

Abstract

Contact stylus instrument has difficulties in tracing large slope angle (LSA) lens for surface profile measurement due to the dilation of measured profile image by the shape of stylus tip. This research is to develop a surface profile reconstruction method for tip profile with LSA lens and then verified the result by estimating the form error. Experimental set-up is configured of a surface profile and roughness analyzer, Panasonic Ultra Accuracy 3-D Profilometer (UA3P), and the feasibility of the developed program is compared with the results of a commercial operation software, UA3P software. The figure form error (FFE) is used to evaluate the developed method. Experiments have been performed by measuring the LSA lens of a s55ml spherical gage with measuring ranges increasing from ±30°, ±45° to ±60° and measuring an aspheric lens with range ±50°. Experimental results showed that the FFE of the developed method has smaller FFE values than those obtained by the UA3P software as the measuring range of ±30° and ±45. Similar result of FFE is obtained as 0.891 μm for the aspheric lens by the developed method than FFE 0.896 μm by the UA3P software. Therefore, the developed method has been verified for estimating the FFE of LSA lens with variant measuring ranges. Future work is to develop related compensation methodology of FFE for LSA lens measurement and also to find appreciated tip profiles for measuring LSA lens of higher order nonlinear terms.