A precision method for measuring large-diameter, high-gradient surface profiles using a chromatic confocal sensor and mirror assembly

Abstract High-gradient surfaces with large diameters are extensively utilized in various fields such as high-performance optical systems and aerospace engineering. Accurate measurement technologies are crucial to ensure that the machining precision of these surfaces meets application requirements. However, the need for sensor rotation axes and coupling devices imposes many limitations on current technologies and equipments when measuring these types of surfaces. To address this issue, this paper proposes an optical measurement method using a chromatic confocal sensor (CCS) and a mirror assembly that eliminates the need for rotation axes and coupling devices. This method deflects the optical path of the CCS by translating mirrors with different inclinations and achieves measurement of the entire surface using a four-axis system. This method lowers both the cost and complexity of the system, reduces potential error sources, and streamlines the measurement process. An experimental measurement of a hemispherical shell was conducted, resulting in a maximum deviation of 0.858 μm for the profiles reconstructed by the proposed system, compared to those obtained from the LUPHOScan260. The verification result demonstrates the feasibility and effectiveness of this method.