| 摘要 |
PURPOSE:To obtain a spot diameter of a diffraction threshold in a transparent material having >=1 refractive index by selecting the radius of rings so as to satisfy the prescribed simultaneous equations wherein the incident angle and refractive angle to and from a transparent material having >=1 refractive index are used as variables. CONSTITUTION:The radius vk of rings is so selected that the difference between the optical distance from the point M on a Fresnel zone plate 1 through the point N on a boundary 7 up to a condensing point O and the optical difference from the point M through the point P on the boundary 7 to the point L in a material 6 is integer times of the half wavelength. In other words, the radius vk of rings satisfying the simultaneous equations 1, 2, 3 where the incident angle of a ray MN is designated as theta1 and refractive angle as theta2 is determined. Many concentrical circles vk of such diameter are drawn on a transparent glass plate or film, and the spacings between 0 and r1, between r2k and r2k+1(k=1,2...) are made transparent and the spacings between r2k=1 and r2k(k=1,2...) are made opaque. The spot diameter of the diffraction threshold is thus obtd. in the transparent material having >=1 refractive index. |
