PURPOSE: To increase the accuracy of angle of beams without any high-precision assembly work, by sticking a parallel plate of glass to the outgoing surface of a beam splitting prism form two splitted beams are output.
CONSTITUTION: When torsion is present in two output surface of a triangular prism 2 and rhombus prism 1, angular errors are brought about in the two beams. Therefore, the triangular prism 2 and the rhombus prism 1 are bonded to each other, and besides, a parallel plate of glass 27 is bonded to the output surface with a bonding agent 28 of the same refractive index as that of glass. Then the torsion of the output surface is eliminated, so that the angular errors of beams caused thereby are reduced. Thereby, the accuracy of angle for parallelism, orthogonality and the like of the beams of a measuring optical system in which a beam is splitted into plural beams for use can be increased.
FUNATSU RYUICHI
FUJII KEN
NAKAYAMA YASUHIKO
