Abstract A wide angle photographing lens which has a brightness of F2, an angle of field greater than 74* and a long back focus of 1.2 times as great as the focal length, and which comprises a combination of a forward lens group which is an afocal reversed Galilean conversion, and a rearward lens group which is a master lens. The forward lens group comprises a negative meniscus lens convex to the object side, a positive lens, a negative meniscus lens convex to the object side, a positive lens and a negative lens cemented thereto. The rearward lens group comprises a biconvex lens, a biconcave lens, a positive meniscus lens concave to the object side, and a positive lens. All of these lenses are sequentially arranged in the named order in the direction away from the object so as to satisfy predetermined conditions. The spacing between the forward and rearward lens groups is variable.
Inventors
👤 Y Shimizu
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-11-04 19:50
CPC Classifications
G; G02; G02B; G02B13/00; G02B13/04
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
214 words
A wide angle photographing lens system having a large relative aperture, consisting of a first negative meniscus lens convex to the object side of the system, a second positive lens, a third negative meniscus lens convex to the object side, a fourth positive lens, a fifth negative lens cemented to said fourth positive lens, a sixth biconvex lens, a seventh biconcave lens, an eighth positive meniscus lens concave to the object side, and a ninth positive lens, said lenses being sequentially arranged in the named order in the direction away from the object, said first to fifth lenses together constituting a forward lens group and said sixth to ninth lenses together constituting a rearward lens group, said system satisfying the following conditions: fc > 3f 1/5f > (n5 - n4/r8) > 1/10f n4 n5 > 0.1 r10 > -r11 0.55f < -r12 < 0.73f 0.25f < d12 + d13 + d14 < 0.45f where r subscripts represent the radii of curvature of the successive lens surfaces; d subscripts the lens thicknesses or spacings between lenses, n subscripts the refractive indices of the lens glasses, fc the focal length of said forward lens group, and f the focal length of the entire system, the spacing d9 between said forward and rearward lens groups being variable.
Claim 2
Dependent Claim
214 words
A wide angle photographing lens system having a large relative aperture, consisting of a first negative meniscus lens convex to the object side of the system, a second positive lens, a third negative meniscus lens convex to the object side, a fourth positive lens, a fifth negative lens cemented to said fourth positive lens, a sixth biconvex lens, a seventh biconcave lens, an eighth positive meniscus lens concave to the object side, and a ninth positive lens, said lenses being sequentially arranged in the named order in the direction away from the object, said first to fifth lenses together constituting a forward lens group and said sixth to ninth lenses together constituting a rearward lens group, said system satisfying the following conditions: fc > 3f 1/5f > (n5 - n4/r8) > 1/10f n4 n5 > 0.1 r10 > -r11 0.55f < -r12 < 0.73f 0.25f < d12 + d13 + d14 < 0.45f where r subscripts represent the radii of curvature of the successive lens surfaces; d subscripts the lens thicknesses or spacings between lenses, n subscripts the refractive indices of the lens glasses, fc the focal length of said forward lens group, and f the focal length of the entire system, the spacing d9 between said forward and rearward lens groups being variable.