| 摘要 |
PURPOSE:To obtain a good image forming performance by constituting a titled lens of a lens group G1 of a positive refractive power having a meniscus positive lens whose concave surface is turned to an object side, a lens group G2 having a positive refractive power, a lens group G3 which has a joint surface, is a composite one, has a negative refractive power and is movable, and a lens group G4 having a negative refractive power. CONSTITUTION:A titled lens consists of a lens group G1 of a positive refractive power having a meniscus positive lens whose concave surface is turned to an object side, a lens group G2 having a positive refractive power, a lens group G3 which has a joint surface, is a composite one, has a negative refractive power, and is movable, and a lens group G4 having a negative refractive power, in order from an object O side. An aberration is corrected by moving the lens group G3 in accordance with a variation of an optical characteristic of a transparent object placed between the lens and the surface of the object. In this state, in order to satisfy an aberration structure of each lens group, this lens is constituted so as to satisfy the conditions of 3F<¦f3¦<10F, 3F<-r1, 1.5F<f12<3F, and 0.2F<D2<0.4F, when a focal distance of the lens group G3, a radius of curvature of the surface of the lens being nearest to the object side in the lens group G1, a composite focal distance of the lens group G1 and the lens group G2, an interval of the lens group G2 and the lens group G3, and a composite focal distance of the lens are denoted as f3, r1, f12, D2, and F, respectively. In this way, even in case a thickness of a cover glass, etc. is varied, a good performance can be maintained.
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