OPTICAL MEMBER, LIGHT ROUTING UNIT, AND EXPOSURE APPARATUS

摘要

Embodiment of the present invention is to provide an optical member composed of calcium fluoride (fluorite) and being capable of preventing deterioration and demonstrating a long life even in use under severe conditions. An optical member of a preferred embodiment has a base material having an entrance face into which light is incident, a total reflection face totally reflecting the incident light, and an exit face from which the totally reflected light emerges to the outside, and made of a calcium fluoride crystal; and a protecting layer to control deterioration of the total reflection face by the light, which is provided on a surface outside the total reflection face in this base material.