| 摘要 |
A method for manufacturing an externally circular precursor lens that is processed into a rim-shaped lens includes inputting processing data to specify the shape of the rim-shaped lens, and processing a material block based on the processing data so as to manufacture a precursor lens. An elliptical virtual rim surrounding the precursor lens manufactured at that time is imaginarily set, and is processed based on the processing data up to that range, and, outside the virtual rim, an amount of sag is changed to secure the edge thickness of the precursor lens. This method for manufacturing a precursor lens for a rim-shaped lens reduces an excessive load imposed on a processing tool during processing, allows the precursor lens to be processed into a rim-shaped lens while satisfactorily maintaining its edge thickness without the lack of the edge of the precursor lens, and results in a thin lens.
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