Symmetrical type four-component lens system
AssigneeNippon Kogaku K.K.
InventorTadashi Kawakami
Life of this patent
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Abstract
A symmetrical type four-component lens system comprises, in the direction of incidence of light, a first lens component, a second lens component, a stop, a third lens component and a fourth lens component. Each lens component is a combination of a positive and a negative lens element, the concave surface of each element facing the stop. The surfaces of the first and fourth components facing the stop have shorter radii of curvature than the surfaces of the second and third components facing away from the stop. The first and fourth components have greater focal lengths than the second and third components. The second and third components satisfy certain conditions relating to the materials forming them.
Claims6
A symmetrical type four-component lens system comprising, in the direction of incidence of light, a first positive meniscus lens component (L1), a second positive meniscus lens component (L2), a stop (S), a third positive meniscus lens component (L3) and a fourth positive meniscus lens component (L4), each of the lens components being a combination of a positive lens element and a negative lens element, the concave surfaces of each of the lens components facing the stop, the radii of curvature (R3 and R10) of the surfaces of the first and fourth components facing the stop being less than the radii of curvature (R4 and R9) of the surfaces of the second and third components facing away from the stop, the focal lengths of the first and fourth components being greater than the focal lengths of the second and third components, and the second and third components satisfying the following conditions:
- K.sub.p - K.sub.n is in the range of approximately -0.00392 to -0.00394, and .nu..sub.p - .nu..sub.n is in the range of approximately 34.6 to 55.4, where, if n.sub.E, n.sub.G and n.sub.C are the refractive indices of the lens-forming materials for light rays of wavelengths E (546.1m.mu.), G (435.8m.mu.) and C (656.3m.mu.), respectively, and if K is the value represented by (n.sub.E - n.sub.C)/(n.sub.G - n.sub.C), then K.sub.p is the sum of the K values of the materials forming the positive elements in the second and third components, .nu..sub.p is the sum of the Abbe numbers of the materials forming the positive elements in the second and third components, K.sub.n is the sum of the K values of the materials forming the negative elements in the second and third components, and .nu..sub. n is the sum of the Abbe numbers of the materials forming the negative elements in the second and third components.
A symmetrical type four-component lens system comprising in the direction of incidence of light, a first positive meniscus lens component (L1), a secoond positive meniscus lens component (L2), a stop (S), a third positive meniscus lens component (L3) and a fourth positive meniscus lens component (L4), each of the lens components being a combination of a positive and a negative lens element, the concave surfaces of each of the lens components facing the stop, the radii of curvature (R3 and R10) of the surfaces of the first and fourth components facing the stop being less than the radii of curvature (R4 and R9) of the surfaces of the second and third components facing away from the stop, the focal lengths of the first and fourth components being greater than the focal lengths of the second and third components, one component of said second and third components satisfying the following conditions:
- K.sub.p - K.sub.n is in the range of approximately -0.00392 to -0.00394, and .nu..sub.p - .nu..sub.n is in the range of approximately 34.6 to 55.4, where, if n.sub.E, n.sub.G and n.sub.C are the refractive indices of the lens-forming materials for light rays of wavelengths E(546.1m.mu.), G (435.8m.mu.) and C (656.3m.mu.), respectively, and if K is the value represented by (n.sub.E - n.sub.C)/(n.sub.G - n.sub.C), then K.sub.p is the K value of the material forming the positive element of said one component, .nu..sub.p is the Abbe number of the material forming the positive element of said one component, K.sub.n is the K value of the material forming the negative element of said one component, and .nu..sub.n is the Abbe number of the material forming the negative element of said one component.
Dependencies are inferred from the claim text.