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US 8,553,339 B2Granted
Enhanced variable power zoom lens
AssigneesTamron Co., Ltd., Sony Corporation
InventorsHisayuki Yamanaka, Makoto Kanai, Masafumi Sueyoshi, Masaharu Hosoi
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AssigneesTamron Co., Ltd., Sony Corporation
InventorsHisayuki Yamanaka, Makoto Kanai, Masafumi Sueyoshi, Masaharu Hosoi
Estimating the term…
The present invention is directed to provide an enhanced variable power zoom lens that has focusing lens optics reduced in weight so as to relieve of a load on a focusing drive system, and that has its anti-vibration lens optics reduced in both diameter and weight so as to relieve of a load on an anti-vibration drive system and downsize the same. The enhanced variable power zoom lens is adapted to have the foremost or first lens group G1 of positive refractivity, the second lens group G2 of negative refractivity, the third lens group G3 of positive refractivity, the fourth lens group G4 of negative refractivity, and the fifth lens group G5 of positive or negative refractivity arranged in sequence from a position closer to the object where the fourth lens group G4 serves as a focusing lens, and the third lens group G3 and the fifth lens group G5 together move on and along the same cam structure during zooming.
An enhanced variable power zoom lens adapted to have the foremost or first lens group of positive refractivity, the second lens group of negative refractivity, the third lens group of positive refractivity, the fourth lens group of negative refractivity, and the fifth lens group of positive or negative refractivity arranged in sequence from a position closer to the object, the fourth lens group serving as a focusing lens, and the third lens group and the fifth lens group together moving on and along the same cam structure during zooming, being displaced by the same distance, and being integrated in a single unit.
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
The first group being positive: arranged +-+-+
Optical elements, systems or apparatus
About 4 years 11 months of term left · ends 12 Sep 2031 (estimated)
The present invention relates to a compact and enhanced variable power zoom lens having a zoom ratio of 10× or even greater and an angle of view of 75 degrees or even wider at the wide-angle end, which is suitable for use in 35 mm cameras, video cameras, electronic still cameras, and the like.
As one example of prior art focusing systems for a zoom lens, an upfront lens focusing system is well-known in the art where the foremost group of lens pieces positioned the closest to the object to photograph is displaced for focusing. When designed in an application of an auto-focusing zoom lens, the upfront lens focusing zoom lens must have its large and heavy foremost lens group moved along the optical axis, and this makes it difficult to achieve instantaneous focusing.
In order to overcome the aforementioned disadvantage, inner and rear focusing systems that force the second foremost lens group and/or the further succeeding one(s) are to be displaced instead have come to be known. Employing the inner or rear focusing system brings about a successful result in achieving an instantaneous auto focusing zoom lens of which focusing lens groups can be generally down-sized and reduced in weight so as to reduce the load on an actuating motor for an auto focusing mechanism.
FIG. 1 is a cross-sectional view showing a first embodiment of a zoom lens according to the present invention.
FIG. 2a illustrates graphs of various types of aberration when the zoom lens of the first embodiment at the wide-angle end for zooming is in infinity focus.
FIG. 2b illustrates graphs of the various types of aberration when the zoom lens of the first embodiment at the wide-angle end for zooming is in proximity focus.
The present invention will now be described in conjunction with embodiments, referring to the accompanying drawings.
In discussing each embodiment, the term ‘aspherical surface or aspheric’ means a surface or state as expressed by the following formula:
x = H 2 / r 1 + 1 - ( 1 + k ) ( H / r 2 ) + A 4 H 4 + A 6 H 6 + A 8 H 8 + A 10 H 10 ( 1 ) where x is the optical axis, H is a height from the optical axis in a direction orthogonal to the optical axis, r is a paraxial radius of curvature, k is a coefficient of the cone, and An is a factor of the aspherical surface raised to the n-th power.