| 摘要 |
PURPOSE:To compensate the aberration, and to make the titled lens small in size and light in weight by forming a shape of the surfaces to a general aspherical surface, respectively, forming the reference shape of the first surface and the reference shape of the second surface to an elliptical surface and a hyperbolic surface, respectively, and also setting a coefficient of development of an aspherical compensation term so as to satisfy a specified condition. CONSTITUTION:The titled lens is constituted of a single element lens consisting of the first surface 3a and the second surface 3b of an axially symmetric general aspherical shape. A curvature c1 of an inscribed spherical surface in an apex 3c of the first surface 3a, a curvature c2 of an inscribed spherical surface in an apex 3d of the second surface 3b, and a lens thickness (d) are set to values which are determined by a paraxial image forming relation by a focal distance (f), a lateral power beta, a refractive index (ne) of a lens medium, a conversion surface internal between a point light source 1 and the first surface 3a, and a conversion surface interval (w) between the second surface 3b and an image point. Also, a cone constant K1 of the first surface 3a and a cone constant K2 of the second surface 3b are selected as -1<K1<0, and K2<-1, respectively, and a biquadratic coefficient of development A1 of the first surface 3a and a biquadratic coefficient of development A2 of the second surface 3b are selected as inequalities, respectively. In this way, an operation of a collimator lens and an objective lens can be executed by the single element lens, and a small and light condensing lens which compensates an aberration generated in a paraxial area is obtained.
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