| 摘要 |
PROBLEM TO BE SOLVED: To shorten entire length, to realize miniaturization and the improvement of telecentricity, to improve the workability of a lens and to reduce the cost. SOLUTION: This system is constituted of a 1st group consisting of a negative lens whose concave surface faces to an image side, a positive 2nd group, a brightness diaphragm, a 3rd group including a lens which has positive refractive power and whose surface on the image side is plane and having the positive refractive power as a whole, and an image transmitting means; and satisfies conditions 0.9<f2/f<2.5, 0.4<|f1/f2|<1.1, 0.4<|f1/D|<0.7. Provided that (f) is the focal distance of an entire system, f1 and f2 are the focal distances of the 1st group and the 2nd group and D is length expressed in terms of air between the surface of the 1st group on the image side and the diaphragm.
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