Optical: systems and elements – Lens – With light limiting or controlling means
Reexamination Certificate
1999-08-27
2001-05-29
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With light limiting or controlling means
C359S738000
Reexamination Certificate
active
06239923
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens barrel which is mounted onto a camera body, and, more particularly, the present invention relates to a lens barrel having an iris stop unit having a support ring, blades and a drive ring, wherein the blades and the drive ring are secured to the d support ring using a lens group holding frame.
2. Description of the Related Art
Various types of lens barrels which are mountable on a camera body are known. The known types of lens barrels which are mountable on a camera body include single-focal-length lenses and zoom lenses ranging from wide-angle lenses to telephoto lenses. A lens barrel having a plurality of lens groups, which comprise one or multiple optical lens elements, can obtain accurate focusing by varying the relative distance between each lens group. Moreover, a type of lens barrel is known which incorporates exposure and depth of focus control in the lens barrel, and includes an aperture stop device built into the lens barrel to control the volume of light flux. Presently, the most prevailing aperture stop device is an iris stop unit which consists of a plurality of blades arranged diametrally. The iris stop unit controls a numerical aperture by moving the plurality of blades.
The conventional iris stop unit includes several blades, a support ring which supports the blades in a freely pivotable manner, and a drive ring having a cam which makes the blades pivot. The blades are pivoted by rotating the drive ring. The drive ring may be rotated by manually rotating an aperture ring arranged in an external surface of the lens barrel. However, in autofocus lens barrels, the drive ring is rotated by the drive control system of a camera body through an aperture stop coupling lever.
The conventional iris stop unit is fixed to a lens group holding frame (fixed tube or moving tube) using a fixing ring having a male screw on its external surface, or using a fixing ring having a perforated hole. The support ring of the iris stop unit may either be separated from the supporting parts for the lens group holding frame, or built onto the supporting parts for the lens group holding frame.
The conventional lens barrel which uses a fixing ring to fix an iris stop unit results in the problems of increased process time and an increased number of parts. For example, when a fixing ring with a male screw cut on its external surface is used to secure the iris stop unit, a female screw must be cut on the internal surface of the supporting parts for the lens group holding frame. Further, a special tool is required to turn the fixing ring around. Furthermore, if the fixing ring with a perforated hole is used to secure the iris stop unit, it becomes necessary not only to bore a threaded hole, but also to fasten multiple (nonnally more than three) screws with a screw driver. Thus, the number of parts and the process time required to fix the iris stop unit increases.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a lens barrel including an iris stop unit which is easily secured in the lens barrel.
Objects and advantages of the present invention are achieved in accordance with embodiments of the present invention with a lens barrel having an iris stop unit comprising a support ring, a freely pivotable blade arranged behind or in front of the support ring, a drive ring arranged behind or in front of the blade to pivot the blade, and a lens group holding frame to secure the blade and the drive ring to the support ring in a manner to assure the intended movements.
In accordance with embodiments of the present invention, it is not necessary to cut a female screw and to bore a threaded hole in the supporting member for a lens group holding frame. Further, a fixing ring and screws become unnecessary, since the lens group holding frame performs the function of a fixing ring.
In accordance with embodiments of the present invention, the support ring and the drive ring may be coupled such that the support ring and drive ring cannot be removed from the lens barrel, except when arranged at a predetermined relative angle.
In accordance with embodiments of the present invention, the iris stop unit eliminates or reduces a possibility of detachment or drop off of the blades or the drive ring by placing the drive ring with respect to the support ring at a position deviated from the predetermined relative angle when assembling the iris stop unit to the supporting parts for the lens group holding frame.
In accordance with embodiments of the present invention, the lens barrel further comprises an impetus device to provide an impetus to the drive ring in a direction deviated from the determined relative angle.
In accordance with embodiments of the present invention, the iris stop unit eliminates or reduces the possibility of detachment or drop off of blades or the drive ring when inserting the iris stop unit into the supporting member for the lens group holding frame, since the drive ring is placed at the position deviated from the predetermined relative angle.
REFERENCES:
patent: 4199247 (1980-04-01), Schwarz
patent: 4504134 (1985-03-01), Schlapp et al.
patent: 4897682 (1990-01-01), Kuwana
patent: 5923913 (1999-07-01), O'Brien et al.
patent: 5993079 (1999-11-01), O'Brien et al.
patent: 5997187 (1999-12-01), Hamasaki
patent: 6161966 (2000-12-01), Chang et al.
Epps Georgia
Nikon Corporation
Seyrafi Saeed
LandOfFree
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