Abstract
A tactile 3D scanning probe based on differential detection of astigmatic focus error is developed using commercial DVD optical pick-ups as sensing elements, and proposed for measurement of small structures with aspect ratio up to 30:1. The conflict between resolution and lateral size of the probe is resolved by a design of parallel kinematic flexible suspension with vertical and orthogonal layout of sensing elements, and common mode interference is significantly suppressed by differential detection of astigmatic focus error signals. Experimental results show that the displacement resolution of the probe is up to 1nm with a ϕ3mm probing ball and a 150mm long stylus. It is therefore concluded that the probe proposed is a solution for measurement of structures with high aspect ratio with high precision and low cost.
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