Study of quadrifoliate tool-setting method for diamond milling of microlens array

Rotary milling was used in this study to fabricate a microlens array (MLA) with diamond ball-end milling tools. Tool-setting error determines the positional accuracy of each lenslet during rotary milling. The position error of a single lenslet overlaps with adjacent lenslets, creating an adjacency defect in the MLA; the tool-setting error can be directly evaluated according to the MLA adjacency defect. We developed a quadrifoliate tool-setting method for machining a specific MLA, where tool-setting error can be calculated and corrected according to the adjacency ridge. The effects of tool-setting error on the type, length, and direction of the ridge were investigated. The proposed method was found to reduce setting error of the diamond ball-end milling tool to less than 1 μm. An MLA with low position error can be fabricated by rotary milling after applying the proposed quadrifoliate tool-setting method.