| 摘要 |
PURPOSE:To obtain the titled image forming lens having aberrations compensated excellently by allowing an optical system provided with two lenses made of a medium which varies in refractive index continuously with the distance from an optical axis to meet specific requirements. CONSTITUTION:The 1st lens provided at an object field side has a refractive index distribution which decreases in refractive index according to the distance from the optical axis, and is in such a meniscus shape that the thinnest is largest on the optical axis and the concave surface faces the image field side. The 2nd lens at the image field side has a refractive index distribution which decreases in refractive index according to the distance from the optical axis and is in such a meniscus shape that the thickness is thinnest on the optical axis and the concave surface faces the object image side. This lens system meets requirements shown by expressions I and II, where r1 is the radius of curvature of the object-side surface of the 1st lens, r2 is the radius of curvature of the image field side surface of the 1st lens, and (f) is the focal length of the whole system. |
