| 摘要 |
A focusing unit can be inserted into and removed from an illumination light path by rotating around a supporting portion. An index light source, a green LED, is attached to the bottom of a base. A transparent acrylic-resin disk is fixed to the base. A deflection prism is attached to the bottom of the disk. A beam from the light source enters the deflection prism. A focus index forming portion is provided on the top of the disk. In the center of a light-shielding portion is formed a slit-like opening, under which split prisms are provided. Deflected by the prisms, the beam from the light source is split into two, right-half and left-half, directional beams, and combined with an illumination optical system, in the form of two slit images, at the opening.
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