Stitching Cutting Fabrication by Tool Replacement for Ultraprecision Microlens Arrays Based on In-Situ Optical Ranging Method

Single-point diamond turning (SPDT) is an ultraprecision technique for manufacturing high-precision microlens arrays (MLAs). This method achieves optical surface machining with excellent accuracy, thereby eliminating the need for secondary processing techniques. However, the application of SPDT for fabricating large-area MLAs is significantly limited by tool wear, which indirectly affects surface roughness due to the declined accuracy of the cutting edge. Severe tool wear can lead to failure during microstructure machining. In theory, SPDT stitching fabrication through tool replacement enables the management of cutting tool wear, facilitating MLAs production with high-precision and large-area. Nevertheless, maintaining the repositioning accuracy of the new tool relative to the worn tool remains a significant challenge. This study introduces an in-situ optical ranging (ISOR) method to measure and compensate for the tool replacement positioning error between the new and worn tools in accordance with the different feed directions during MLAs production. An in-situ measurement system comprising an optical microscope and a linear variable displacement transducer (LVDT) was developed. The positional relationship between the new and worn tools was determined using the measurement results from the optical microscope and LVDT in their respective directions. MLAs stitching fabrication experiment was conducted using the proposed method and system. The results confirmed the effectiveness and feasibility of the proposed method for the stitching fabrication of MLAs. The measurement and compensation processes were completed within 20 min, achieving an accuracy of 0.1 μm. This study provides an effective strategy for manufacturing large-area optical surfaces with high precision and efficiency.