An optical path adjusting device comprises a hollow cylindrical mount having a
center axis in alignment with an optical path of a light beam and an optical parallel
mounted on the hollow cylindrical barrel so as to intersect the optical path of
the light beam at a specified angle of intersection. The hollow cylindrical barrel
is supported so as to rotate about an original optical path of the light beam,
thereby causing a displacement of an optical path of said light beam coming out
of the optical parallel close to or away from the original optical path of the
light beam.
