JPS63287919A - Zoom lens barrel - Google Patents

Abstract

PURPOSE:To enable rapid change to an exact magnification by providing plural ranges where a zoom lens group does not make zoom motion even if a zoom driving member moves to an interlock mechanism for the motion of the zoom driving member and the zoom motion in the optical axis direction of the zoom lens group. CONSTITUTION:This zoom lens barrel is constituted by loosely fitting a 1st lens group zoom frame 2 and a 2nd lens group holding frame 3 into the bore of a stationary barrel and loosely fitting a zoom cam barrel 4 onto the outside diameter of the barrel 1 turnably around the optical axis. Pins 2P, 3P embedded to the zoom frame 2 and the holding frame 3 respectively are engaged respectively slidably with guide grooves 1G2, 1G3 in the optical axis direction provided on the barrel 1 and cam grooves 4C2, 4C3 provided on the zoom cam barrel 4. The zoom frame 2 and the holding frame 3 are, therefore, moved in the optical axis direction by turning a pinion 5 intermeshed with the gear part on the outside diameter of the barrel 4 by a forward and backward running motor (not shown in the figure) or the like to turn the barrel 4 around the optical axis. Then, the 1st lens group L1 and the 2nd lens group L2 make the zoom motion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a zoom lens barrel particularly suitable for use in still photography cameras and video cameras.

[Background of the invention]

In a zoom lens barrel used in a camera for still photography, it is desired that the zoom movement be performed quickly so as not to lose the opportunity to take a photograph. However, in conventional zoom lens barrels, when the zoom drive member is moved, the zoom lens group zooms in the optical axis direction. Apart from the magnification, there is a problem in that it becomes difficult to accurately stop the zoom lens group at a desired magnification. On the other hand, as a practical matter, continuous changes in magnification are not so necessary for still cameras;
It is sufficient in most cases if the temperature can be varied in about 5 steps. Also, a zoom lens mirror in which the zoom drive member is a cam barrel that rotates around the optical axis, and the zoom lens group is zoomed as the cam pin that slidably engages with the cam groove of the cam barrel moves in the optical axis direction. In the case of the cylinder, if you try to form the entire cam cylinder or at least the cam groove with resin molding,
Since the core mold for forming the cam groove is inserted into and removed from the mold for forming the cam tube in a direction perpendicular to the plane containing the optical axis, the core mold for forming the helical cam groove is inserted and removed from the core die in the direction perpendicular to the plane containing the optical axis. Undercuts occur in areas away from the surface, and there is a problem in that there is play in the engagement between the cam groove and the cam pin. This is a major reason why the cam cylinder is not made of resin even though fixed cylinders and the like are made of resin. In order to solve this problem, the following methods were adopted: ■ Reduce the thickness of the cam cylinder to reduce undercut I, ■ Use a spherical cam pin, and ■ Change the core mold for forming the cam groove to the mold for forming the cam cylinder. The tapered cam groove is inserted into the inner space for installing the core mold, and the width of the groove narrows before the insertion, and the tapered cam groove is also used for the cam pin, and the cam pin is biased to protrude. Methods such as doing this have been proposed.

However, method (2) has the problem that undercuts occur even if the amount is small, and the line contact length between the cam groove and the cam pin decreases, reducing durability. Not only is it difficult to form the core of the cam groove that contacts the groove wall at a certain height of the cam groove and the fitting groove of the cam cylinder forming mold into which it is inserted and removed, but also the cam pin and the cam groove are difficult to form. There is a problem that durability is further reduced because the contact becomes a point contact, and method (2) has a problem that the structure of the mold for the cam cylinder and cam groove, the mounting structure of the Taber bottle, etc. are complicated.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned background, and has as its first object the provision of a zoom lens barrel that can accurately change the magnification step by step. A second object of the present invention is to provide a zoom lens barrel that can be used in various ways.

[Structure of the invention]

The present invention is characterized in that the interlocking mechanism between the movement of the zoom drive member and the zoom movement of the zoom lens group in the optical axis direction has a plurality of ranges in which the zoom lens group does not move even if the zoom drive member moves. With this configuration, the first objective is achieved, and the zoom drive member is used as a cam barrel that rotates about the optical axis, and the zoom movement of the zoom lens group is caused by the cam groove of the cam barrel. The cam groove of the cam cylinder is made up of a plurality of circumferential groove portions and a helical groove portion connecting the circumferential groove portions. The second objective is achieved.

〔Example〕

The present invention will be explained below using illustrated examples.

FIG. 1 is a schematic sectional view showing an example of a zoom lens barrel according to the present invention, and FIG. 2 is a partially exploded view showing the shape of a cam groove of a zoom cam barrel.

The zoom lens barrel shown in FIG.
The 71st group zoom frame 2 and the second lens group holding frame 3 play together,
A zoom cam cylinder 4 is rotatably engaged with the outer diameter of the fixed barrel 1 for the optical axis, and bins 2P and 3P are installed in the 1171st group zoom frame 2 and the second lens group holding frame 3, respectively. Since they are slidably engaged with the straight grooves IG2 and IG3 provided in the fixed barrel 1 in the optical axis direction and the cams 14C2 and 4C3 provided in the zoom cam barrel 4, they engage with the outer diameter gear portion of the zoom cam barrel 4. The 1171st group zoom frame 2 and the 2nd
The lens group holding frame 3 moves in the optical axis direction, and the lens group L1
and the second lens group L2 moves to zoom. Also, the 117th
The first group zoom frame 2 supports a focusing motor 7 that rotates forward and backward, and a focusing cam barrel 8 that is rotated about the optical axis by the motor 7, and a first lens group holding frame 9 is freely attached to the inner diameter thereof. The bottle 9P installed in the Luns group holding frame 9 is the 1171st bottle.
Since it is slidably engaged with the optical axis guide groove 2G9 of the group zoom frame 2 and the cam groove 8C9 of the focusing cam barrel 8, by rotating the focusing cam barrel 8 with the focusing motor 7, The 1st lens group holding frame 9 moves in the optical axis direction and brings the 1st lens group Ll to the in-focus position.

Note that 6 is a protection tube that is engaged with and held at the tip of the fixed barrel 1.

As shown in FIG. 2, the cam grooves 4C2 and 4C3 of the zoom cam barrel 4 are composed of a plurality of circumferential groove portions R1, R2, R3 and a helical groove portion 82 connecting them.

By forming the cam grooves 4C2 and 4C3 of the zoom cam barrel 4 in this way, the pin 2P of the 1171st group zoom frame 2
and the pin 3P of the second lens group holding frame 3 is in the circumferential groove portion R1.
, R2, and R3, even if the zoom cam barrel 4 rotates, the 1171st group zoom frame 2 and the second lens group holding frame 3 do not move in the optical axis direction, and the focal length, i.e. The magnification is kept constant for each. therefore,
If you decide to use this magnification for photography, the magnification will change with pin 2P.
This is done by changing the state where 3P is located within any one of the circumferential groove portions R1, R2, and R3 to the state where it is located within any other one, so there is a permissible width at the rotation stop position of the zoom cam barrel 4. Even if the rotational speed of the zoom cam barrel 4 is increased, it is easy to stop the zoom cam barrel 4 within the allowable range, and accurate photographing magnification can be achieved. Also, the zoom cam cylinder 4 is connected to the cam groove 4C2,
If molded with resin together with 4C3,
The core mold for forming the cam grooves 4C2 and 4C3 is the zoom cam cylinder 4.
Since the east direction when inserted into and removed from the mold is perpendicular to the paper surface of FIG. 2, the circumferential groove portions R1, R2, R3
No undercut occurs in the groove width, and undercuts occur in the helical groove portions 81 and 112. Therefore, the right cylindrical pins 2P and 3P can be easily engaged with the circumferential groove portions R1, 1112, and R3 without play, so that the stepwise magnifications used can be kept accurately constant. And helical groove portion H1,)1
Even if there is some play between pins 2P and 3P due to undercuts, etc., it will not adversely affect photography. Although FIG. 2 shows the cam grooves 4C2 and 4C3 at the same position in the circumferential direction for convenience, it goes without saying that the cam grooves 4C2 and 4C3 may be out of phase.

The present invention is not limited to the two-group zoom configuration shown in the illustrated example, but can also be applied to a zoom lens barrel using three or more lens groups, and the zoom drive member may be a drive member other than a cam barrel. Furthermore, it goes without saying that the zoom drive member and the focusing lens may be moved manually.

〔Effect of the invention〕

The zoom lens barrel of the present invention has a mechanism for interlocking the movement of the zoom drive member and the zoom movement of the zoom lens group in the optical axis direction, and has a plurality of ranges in which the zoom lens group does not zoom even if the zoom drive member moves. With this configuration, it is possible to change the magnification accurately even if the movement speed of the zoom drive member is increased to quickly change the magnification.
In addition, the zoom drive member is a cam tube that rotates around the optical axis, and the cam groove of the cam tube that moves the zoom lens group for zooming is composed of a plurality of circumferential groove portions and a helical groove portion that connects these groove portions. This makes it possible to easily mold the cam cylinder with resin, and has the advantage of being able to obtain a plurality of accurate magnifications.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of the zoom lens barrel of the present invention, and FIG. 2 is a partially developed view showing the groove shape of the zoom cam barrel. 1...Fixed cylinder, 1G2.1G3...Guide groove, 2...Zoom group zoom frame, 3...Holding frame for lune group, 2P, 2P...Pin, 4--Zoom cam barrel , 4C2, 4C3... cam groove, R1, R2, R3... circumferential groove portion, Hl, [2...
・Helical direction groove part, 5... Binion,
6...Protective tube, 7...Focusing motor, 8...
・Focusing cam tube, 9... No. 1 lens holding frame.

Claims (3)

[Claims] (1) The interlocking mechanism between the movement of the zoom drive member and the zoom movement of the zoom lens group in the optical axis direction has a plurality of ranges in which the zoom lens group does not move even if the zoom drive member moves. A zoom lens barrel. (2) A cam tube in which the zoom drive member rotates around the optical axis,
The zoom movement of the zoom lens group is performed together with the movement of a cam pin slidably engaged with a cam groove of a cam barrel in the optical axis direction,
2. The zoom lens barrel according to claim 1, wherein the cam groove of the cam barrel comprises a plurality of circumferential groove portions and a helical groove portion connecting the circumferential groove portions. (3) The zoom lens barrel according to claim 2, wherein the cam groove of the cam barrel is formed by resin molding.