Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2002-02-06
2004-06-08
Ben, Loha (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S695000, C359S700000, C359S701000, C396S072000, C396S079000
Reexamination Certificate
active
06747807
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens barrel which can be used as an interchangeable lens for SLR cameras.
2. Description of the Related Art
In a lens barrel in which two or more lens groups move in an optical axis direction, it is generally the case that a rotation of a rotating ring causes lens support rings, which respectively support the lens groups, to move in the optical axis direction. For instance, a lens drive mechanism having a structure wherein a set of cam grooves or lead grooves (hereinafter referred to as “a set of extending guide grooves”) are formed on an inner peripheral surface of a rotating ring and a set of follower pins formed on a linearly-guided lens support ring are respectively engaged in the extending guide grooves, is known in the art. However, since there is a maximum length to such a rotating ring to keep the lens barrel compact, the number of lens support rings that the single rotating ring can guide directly is a maximum of two in conventional lens barrels. If it is desired to guide more than two lens support rings, it has been conventional practice to provide an additional rotating ring, which increases the number of elements of the lens barrel and complicates the internal structure thereof. This generally increases the size of the lens barrel and also the cost of production; moreover, the increase of the number of elements of the lens barrel and the complicated structure thereof tend to become the cause of backlash and play, which deteriorate the accuracy in position of lens elements of the zoom lens. Accordingly, it is desirable to develop a compact and low-cost lens drive mechanism for moving more than two lens groups in the optical axis direction while ensuring a sufficient degree of accuracy in position of the lens groups in a lens barrel.
A typical extending guide mechanism using a rotating ring in a conventional lens barrel has a structure such that a linear guide ring is positioned inside the rotating ring and a lens support ring is positioned inside the linear guide ring. The rotating ring is provided on an inner peripheral surface thereof with the aforementioned set of extending guide grooves, and the linear guide ring is provided with a set of radial through slots for guiding the lens support ring linearly in the optical axis direction. The lens support ring is provided, along a circumference thereof at the same positions on the lens support ring, with a set of linear guide projections and a set of follower pins, so that the set of linear guide projections are respectively engaged in the radial through slots of the linear guide ring and so that the set of follower pins respectively pass through the set of radial through slots of the linear guide ring to be engaged in the set of extending guide grooves of the rotating ring. With this structure, a rotation of the rotating ring causes the lens support ring, which is guided linearly in the optical axis direction without rotating about the optical axis, to move in the optical axis direction along the set of radial through slots of the linear guide ring due to the engagement of the set of extending guide grooves of the rotating ring with the set of follower pins of the lens support ring.
If it is desired to increase in performance of a lens barrel, it is preferable that no radial holes or slots be provided on any components of the lens barrel. Namely, if radial through slots serving as linear guide slots such as those described above are formed on a ring member, the radial through slots have an adverse effect on the accuracy in dimensions of the ring member when the ring member is molded, which may cause one or more lens groups that are supported by the molded ring member to tilt and/or decenter, and/or to deviate in the optical axis direction. A solution to this problem is to make each fundamental component of the lens barrel, such as the aforementioned ring member, out of metal. However, this generally increases the cost of production. To make matters worse, if such radial through slots are formed, harmful rays and foreign particles enter inside the lens barrel through the radial through slots to thereby deteriorate the optical performance.
If the rotating ring on which the extending guide grooves are formed is molded of synthetic resin, each extending guide groove is generally formed to have a tapered cross section so that an associated mold can be easily removed, and so that each extending guide groove generally has a trapezoidal cross section. In this case, each of the two opposite surfaces of each extending guide groove which guide the associated follower pin along the groove is inclined with respect to the axial direction of the follower pin. Therefore, each follower pin cannot be easily positioned to the corresponding extending guide groove with precision. This may cause backlash and play in the optical axis direction and/or radial directions, and may cause harmful rays and foreign particles to pass through the engaging portions between the extending guide grooves and the follower pins. A solution to this problem is to make the rotating ring out of metal, not synthetic resin, to achieve a high degree of accuracy. Another solution is to improve the shape and the structure of the follower pins. However, these solutions are generally costly. In addition, the follower pins are formerly provided as independent elements separate from the lens support ring; the follower pins are fixed to the lens support ring after the lens support ring has been molded. This structure is a leading cause of an increase in the cost of production.
In the case of having two lens groups move relative to each other in the optical axis direction with the use of the above described rotating ring, usually the amount of relative movement between the two lens groups cannot be greater than the length of the rotating ring in conventional zoom lenses. When a greater amount of relative movement between the two lens groups is necessary, it is often necessary to increase the number of movable barrels by providing, e.g., another rotating ring. However, this increases the size of the lens barrel, makes it difficult to insure accuracy of some of the components of the lens barrel, and increases the cost of production, and accordingly, is unpreferable. Conventionally, when two lens groups are made to move relative to each other in the optical axis direction, the linear guide mechanism for guiding each movable lens group in the optical axis and also the driving force transfer mechanism for transferring rotation from one rotating ring another rotating ring tend to become complicated, so that such a mechanism has been desired to be simplified.
A lens barrel which is provided with a hand-operated ring which is turned to move the whole zoom lens optical system or a focusing lens group in the optical axis direction, and an additional electric drive mechanism for driving the zoom lens optical system or the focusing lens group in the optical axis direction is known in the art. In this advanced type of lens barrel, the hand-operated ring is engaged with a lens support member in a manner such that rotation of the hand-operated ring can be transferred to the lens support member, while the lens barrel is also provided with a drive gear which receives a driving force from the electric drive mechanism. Conventionally, the driving force received by the drive gear is transferred to the lens support member via the hand-operated ring. More specifically, the hand-operated ring is provided with a gear portion, and a relay gear (or a relay gear train) is positioned so that one end and the other end of the relay gear are respectively engaged with this gear portion and the drive gear. The space for the relay gear and the gear portion formed on the hand-operated ring interfere with inner moving parts of the lens barrel to therefore limit the range of movement thereof, and become leading causes to the increase in size of the lens barrel. For instance, the relay gear is preferably made of syntheti
Hamasaki Takuji
Iikawa Makoto
Ben Loha
Greenblum & Bernstein P.L.C.
PENTAX Corporation
LandOfFree
Lens barrel does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lens barrel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lens barrel will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3362048