| 摘要 |
PURPOSE:To make an in-focus point unchangeable before and after a concave and convex cemented lens is mounted, by increasing only spherical aberration of high order by mounting the cemented lens on the object side of a general photographic lens. CONSTITUTION:A concave lens (refractivity: nB) and a convex lens (refractivity: nB) are cemented and in this case, the concave cemented surface (having radius rB of curvature and on-axis distance dB from cemented surface to diaphragm) faces the diaphragm (radius R when opened) provided on the object side of a main lens; and the whole cemented lens is a focal and has angular magnification 1, and conditional inequalities (1)-(3) hold. As a result, only spherical aberration of high order is generated and the in-focus point is unchangeable even when this attachment lens is mounted in front of the diaphragm provided on the object side of the main lens. |
