Method of manufacturing optical low-pass filter

摘要

A mother layer made of a thermoplastic resin is formed on the substrate. The mother layer is etched to make a grating layer. The etching process is stopped so that an offset layer remains under the grating layer. The grating layer and the offset layer are baked to be molten. The baking process is stopped when a phase grating defined by a surface having a sinusoidal shape is formed.