| 摘要 |
PROBLEM TO BE SOLVED: To improve reliability and set the respective apertures of an object lens for respective light beams from 1st and 2nd light source without switching an aperture diameter by a method wherein a 2nd aperture setting means which sets the aperture of the object lens for a light beam with the wavelength of the 2nd light source is provided on the same light axis as an aperture setting member. SOLUTION: In order to restrict a light beam from a 1st light source in an aperture setting member 9 which sets the aperture of an object lens for a light beam with the wavelength of the 1st light source, a diffraction lattice is used and the characteristics of the diffraction grating is so predetermined as not to diffract a light beam with the wavelength of a 2nd light source. With this constitution, the aperture setting member 9 does not have influence upon an aperture for the light beam with the wavelength of the 2nd light source and, by providing a 2nd aperture setting means 12 which sets the aperture of the object lens 10 for the light beam with the wavelength of the 2nd light source, the respective apertures of the object lens 10 for the respective light beams from the 1st and 2nd light source can be set. |
