Photographic lens apparatus

Details Photographic lens apparatus Photographic lens apparatus

1996-03-25

1997-08-12

Epps, Georgia Y.

Optical: systems and elements

Lens

Multiple component lenses

359739, G02B 934, G02B 900

Patent

active

056571704

ABSTRACT:
A photographic lens apparatus secures a sufficiently large back focus while sufficiently distancing the exit pupil position from the image-forming surface. From the object side along an optical axis L, a stop, a first lens, a second lens, a third lens having a meniscus form, and a fourth lens group, in which a lens having a negative refractive power and a lens having a positive refractive power are cemented together to yield a positive refractive power, are successively disposed. Refractive index n.sub.1 and abbe number .nu..sub.1 of the first lens, abbe number .nu..sub.2 of the second lens, radius of curvature r.sub.7 of the surface facing the object and radius of curvature r.sub.8 of the surface facing the image in the third lens, abbe number .nu..sub.4 of the lens having the negative refractive power and abbe number .nu..sub.5 of the lens having the positive refractive power in the fourth lens group, focal length f.sub.45 of the fourth lens group, and entire focal length f of the whole lens system satisfy the conditions 1.7<n.sub.1, 40<.nu..sub.1 <50, .nu..sub.2 <30, 9<(r.sub.7 +r.sub.8)/(r.sub.7 -r.sub.8)<50, f.sub.45 /f<1.20, and 20<.nu..sub.5 -.nu..sub.4.

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