| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical element of which the substrate can be reused while holding the optimum surface characteristics, and a method for recovering the substrate. SOLUTION: In manufacturing the optical element, not only a planar substrate but also a spherical or aspheric substrate are used. The cost of these substrates exceeds twice or more higher than that of coating according to circumstances. Especially, in development and research, if the substrate can be used repeatedly, the saving of cost can be achieved. In order to recover the substrate, it is proposed that an intermediate layer including at least one chromium layer and at least one scandium layer is provided between the substrate and a functional layer. By dipping the optical element in a hydrochloric acid solution, the intermediate layer is dissolved and, as a result, the functional layer is also removed from the substrate to bring the substrate to a reusable state.
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