| 摘要 |
PROBLEM TO BE SOLVED: To efficiently reduce the influence of ghost light by coloring the base material of an optical member so that the transmissivity of luminous flux may be lowered. SOLUTION: The base material of the optical member is colored in order to lower the transmissivity of the luminous flux. In this device, the luminous flux from an inspection target on a target disk illuminated by an illumination lamp is reflected upward by a mirror and made incident on a beam splitter 8. Both surfaces of the plate-like beam splitter 8 are constituted of a half mirror surface 8a to which a half mirror film is applied and a back surface 8b to which a reflection preventing film is applied. The material whose inside is uniformly colored or whose surface (at least either the surface 8a or 8b) is colored so as to absorb a part of visible light is used as the base material of the beam splitter 8. The surface is colored by dispersing dystuff and vapor- depositing it. Thus, the light quantity of the generated ghost is reduced while maintaining the necessary quantity of the luminous flux.
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