| 摘要 |
The present invention provides an improved Gauss type lens system of a five unit six element construction which fulfills the following lens conditions: <IMAGE> (1) 0.52 f < SIGMA d < 0.65 f (2) <IMAGE> (3) <IMAGE> (4) <IMAGE> (5) wherein: f represents the focal length of the whole lens system; r8 represents the radius of curvature of the intermediate cemented surface of the doublet of the fourth unit; SIGMA d represents the total length of the whole lens system; f1 represents the focal length of the first unit; f45 represents the focal length of the fourth unit; and F23 represents the focal length of an air lens formed between the second and third units (F23=N3/ phi 23, if the refractive power of the air lens is phi 23).
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