| 摘要 |
PURPOSE:To satisfactorily compensate respective aberrations with low-cost glass materials in a compact constitution by arranging a diaphragm a short length behind positive meniscus, negative double concave, and positive double convex lenses and setting specific conditional inequalities between focal lengths and intervals of lens surfaces. CONSTITUTION:The positive meniscus lens whose convex is directed to the object side, the negative double concave lens, and the positive double convex lens are arranged with slight air gaps among them, and the diaphragm is arranged a short length behind these lenses. Six conditional inequalities are set among a focal length (f), a surface interval (d), and an overall lens length SIGMAd. The occurrence of spherical aberration is suppressed and the lens diameter is reduced by the inequality I, and curvature of field and vignetting are reduced by the inequality II, and the occurrence of coma flare is suppressed and the back focus is shortened by the inequality III. The eccentricity error is reduced by the inequality IV, and the same effect as inequalities I and II is obtained by the inequality V, and the thickness of a first lens to the overall lens length is controlled by the inequality VI. Consequently, aberrations are proportionately compensated with low-cost glass materials in a compact constitution.
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