| 摘要 |
PURPOSE:To lead an irradiation flux to a light condensing lens system practically in a stigmatism state by leading a flux coming out of a laser light source to the light condensing lens system, instead of reflecting, and forming a light condensing system attaining a diffraction limit. CONSTITUTION:Equation I shows a wave surface aberration W1(alpha1, phi1) in which the astigmatism caused by a parallel flat optical element 13 gives to the flux 2 coming out of the laser light source 1, where t1, N1, alpha1 and phi1 denote the thickness of the parallel flat optical element 13, its refraction factor, the inclination of the element 13 with respect to an optical axis, and an angle made by a plane including rays of light and the optical axis and a meridional plane, respectively. Equation II shows a wave surface aberration W2(alpha2, phi2) due to the astigmatism caused by a parallel flat optical element 3 with one surface as a half prism, where t2, N2, alpha2 and theta2 denote the thickness of the element 3, a refraction factor, an inclination with respect to the optical axis, and an angle made by a meridional surface and a plane including the optical axis and rays of light, respectively. Here the meridional surface of the element 3 equals that of the element 13, and phi1-pi/2=phi2 can hold. |
