Evaluation Method for Resin Mold Using Reflective Wavefront Sensor

TL;DR

This paper introduces a precise optical method to evaluate resin molds used in contact lens manufacturing, detecting shape changes caused by thermal deformation.

Contribution

A novel high-precision optical evaluation method using a reflective wavefront sensor and OCT for resin mold quality control in contact lens manufacturing.

Findings

The reflective wavefront sensor achieved measurement accuracy of ≈1/100λ and reproducibility of ≈1/200λ.

Zernike coefficients Z07 (coma aberration) strongly correlated with mold thickness asymmetry measured by OCT.

Z04 (astigmatism) showed significant variability after polymerization with no consistent trend.

Abstract

Recent advances in molding technology have enabled the fabrication of plastic molded components with complex geometries. In contact lens (CL) manufacturing, a double-sided molding process using resin molds is employed, in which the front and back surfaces of the lens are replicated through injection molding. However, thermal deformation during polymerization can alter the mold shape, thereby affecting the optical characteristics of the final lenses. This study proposes a high-precision optical evaluation method for resin molds used in contact lens (CL) manufacturing, utilizing a reflective wavefront sensor and optical coherence tomography (OCT). The wavefront sensor demonstrated high measurement accuracy (≈1/100λ) and reproducibility (≈1/200λ) as confirmed using reference samples, and yielded values of approximately 0.012–0.015 μm for the resin molds. Five mold designs with radii of curvature ranging from 6.500 to 8.500 mm were evaluated, revealing that Zernike coefficients varied depending on design and thermal treatment conditions. In particular, astigmatism (Z04) and coma aberrations (Z07) exhibited pronounced trends. A strong correlation was also observed between the Zernike coefficient Z07 and the mold thickness asymmetry measured by OCT. When the thickness difference increased by 2.3 times due to thermal treatment, Z07 increased to 1.9 times. In contrast, Z04 showed no consistent trend and exhibited significant variability (standard deviation > 0.5 μm) after polymerization. The proposed method enables precise detection of subtle shape variations and aberrations, providing valuable feedback for optimizing molding conditions and improving the quality of contact lens production. Furthermore, this method can also be applied to the quality evaluation of other optical components.

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