Molded optical lenses are widely used in various fields such as medical devices, mobile phone cameras, and optical systems that require high performance, miniaturization, and mass production. This is because molded lenses offer advantages including low manufacturing cost and the ability to form complex shapes without grinding or polishing processes. Since the molding process is performed under high-temperature and high-pressure conditions, changes in the thickness and refractive index of the lens material before and after molding are inevitable. Therefore, accurate measurement of thickness and refractive index before and after molding is essential for precise optical design using molded optical lenses.
In addition, applications in these fields demand compact, lightweight, and wide-angle optical systems, making high-refractive-index glass advantageous in lens design and manufacturing. In this study, we introduce a precision spectral interferometric technique capable of measuring changes in thickness and refractive index of molded optical lenses before and after the molding process. The proposed technique is based on a spectral interferometer incorporating a self-developed high-resolution spectrometer operating in the 1,550 nm wavelength band (s-Nova-1550-60). Because the technique enables simultaneous measurement of thickness and refractive index, it is well suited for applications in which material properties change, such as molded lens fabrication.
Furthermore, by employing a spectrometer with a high wavelength resolution of 0.06 nm, the proposed method can be applied to thickness measurements of high-refractive-index optical lenses with large optical thickness. For preliminary validation, thickness and refractive index measurements were performed on molded lens samples provided by the Korea Institute of Optical Technology. The results confirmed that both thickness and refractive index could be successfully measured for a lens material with a nominal thickness of 4 mm and a refractive index of 1.8.
