JP2549518B2 - Variable focal length lens barrel - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lens barrel of a variable focal length lens which is particularly preferably used for a still picture taking camera or video camera.

[Background of the Invention]

In a zoom lens barrel used for a still shooting camera, it is required that the zoom movement be performed swiftly in order not to lose time when shooting. However, in the conventional zoom lens barrel, when the zoom driving member is moved, the zoom lens group zooms in the optical axis direction accordingly. Therefore, if the driving speed of the zoom driving member is increased, both ends of the zoom range will be increased. Apart from the magnification, there is a problem that it becomes difficult to stop the zoom lens group accurately at a desired magnification on the way. On the other hand, as a practical matter, it is not necessary for the still camera to continuously change the magnification,
In most cases, it is sufficient if it can be changed in 3 to 5 steps.
Also, with the cam barrel in which the zoom drive member rotates around the optical axis,
In the case of a zoom lens barrel in which the zoom lens group is moved in the optical axis direction along with the movement of the cam pin that slidably engages with the cam groove of the cam barrel, the entire cam barrel or at least the cam groove is molded with resin. However, the core die for forming the cam groove will be inserted into and removed from the die for forming the cam cylinder in a direction perpendicular to the surface including the optical axis.
Undercut occurs in the portion of the helical cam groove that is away from the plane parallel to the core die insertion / removal direction including the optical axis, and there is a problem that there is rattling in the engagement between the cam groove and the cam pin. . This is a major reason why the cam barrel is not made of resin even though the fixed barrel and the like are made of resin. In order to solve this problem, the thickness of the cam cylinder is made as thin as possible to reduce the amount of undercut, a spherical cam pin is used, and the cam groove forming core mold is a cam core forming mold core. Inserting from the internal space for mold installation, forming a tapered cam groove whose groove width narrows just before the insertion, using a taper pin for the cam pin, and giving a biasing force to the cam pin, etc. The method of is proposed. However, the method (1) has a problem that undercut occurs even when the amount is small, and the line contact length between the cam groove and the cam pin is reduced, resulting in a decrease in durability. It is not only difficult to form a fitting groove, such as a cam groove core type that contacts the groove wall at a certain height position of the However, there is a problem that the durability is further deteriorated due to the point contact, and the method of (1) has a problem that the structure of the molding die for the cam barrel or the cam groove, the mounting structure of the taper pin, etc. are complicated.

[Object of the Invention]

The present invention has been made in view of the above background,
It is an object of the present invention to provide a lens barrel of a variable focal length lens in which the cam barrel is made of resin, in which the magnification can be changed accurately in steps.

[Structure of Invention]

According to the present invention, in a lens barrel of a variable focal length lens configured to control a position of a lens holding frame in an optical axis direction by a cam groove formed in a cam barrel which is rotated around an optical axis, It has at least three circumferential groove portions having different positions in the optical axis direction, and at least two helical groove portions that connect the circumferential groove portions that are adjacent to each other in the optical axis circumferential direction, and the circumferential groove portions are used when photographing. The positioning of the lens holding frame in the optical axis direction is configured so that the helical groove portion is used to control the movement of the lens holding frame in the optical axis direction at the time of non-photographing, and the cam barrel is molded of resin. It is in the lens barrel of a variable focal length lens characterized by being formed by molding, and achieves the object by this configuration.

〔Example〕

 Hereinafter, the present invention will be described with reference to illustrated examples.

FIG. 1 is a schematic sectional view showing an example of a lens barrel of a variable focal length lens of the present invention, and FIG. 2 is a partial development view showing a cam groove shape of a zoom cam barrel.

In the lens barrel of the variable focal length lens shown in FIG. 1, the first lens group zoom frame 2 and the second lens group holding frame 3 are loosely fitted to the inner diameter of the fixed barrel 1, and the zoom cam barrel 4 is attached to the outer diameter of the fixed barrel 1. Are rotatably fitted around the optical axis, and the pins 2P and 3P implanted in the first lens group zoom frame 2 and the second lens group holding frame 3, respectively, are attached to the fixed barrel 1 in the optical axis direction. Since the guide grooves 1G2 and 1G3 and the cam grooves 4C2 and 4C3 provided on the zoom cam barrel 4 are slidably engaged with each other, the pinion 5 meshing with the external gear portion of the zoom cam barrel 4 is not shown. By rotating the zoom cam barrel 4 around the optical axis by rotating it with a forward / reverse rotation motor or the like, the first lens group zoom frame 2 and the second lens group holding frame 3 move in the optical axis direction, and the first lens group L1 And the second
The lens unit L2 zooms. Further, the first lens group zoom frame 2 supports a focusing motor 7 that rotates in the forward and reverse directions and a focusing cam barrel 8 that is rotated around the optical axis by the motor 7, and holds the first lens group in the inner diameter portion. The frame 9 is loosely engaged, and the pin 9P implanted in the first lens group holding frame 9 guides the optical axis direction guide groove 2G9 of the first lens group zoom frame 2 and the cam groove 8 of the focusing cam barrel 8.
Since it is slidably engaged with C9, when the focusing cam barrel 8 is rotated by the focusing motor 7, the first lens group holding frame 9 moves in the optical axis direction, and the first lens group L1 To the in-focus position. Reference numeral 6 is a protective cylinder that is engaged with and held by 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 helical groove portions H1, H2 connecting them. By forming the cam grooves 4C2 and 4C3 of the zoom cam barrel 4 in this way, the first
The zoom cam barrel 4 in which the pin 2P of the lens group zoom frame 2 and the pin 3P of the second lens group holding frame 3 are in the circumferential groove portions R1, R2, R3
In the rotation range of, the first lens group zoom frame 2 and the second lens group holding frame 3 do not move in the optical axis direction even if the zoom cam barrel 4 rotates, and the focal length, that is, the magnification is kept constant. . Therefore, if this magnification is used for shooting, variable magnification can be achieved by changing the state in which the pins 2P and 3P are in any one of the circumferential groove portions R1, R2, R3 to the state in any other. Therefore, the rotation stop position of the zoom cam barrel 4 has an allowable width, and even if the rotation speed of the zoom cam barrel 4 is increased, it is easy to stop the zoom cam barrel 4 within the allowable width, and an accurate photographing magnification can be obtained. . In addition, the zoom cam barrel 4 is provided with a cam groove 4C2,
When molding with resin together with 4C3, the direction in which the core mold for forming the cam grooves 4C2, 4C3 is inserted into and removed from the mold of the zoom cam barrel 4 is the direction perpendicular to the paper surface of FIG. No undercut occurs in the groove width of the circumferential groove portions R1, R2, R3, and the undercut occurs in the helical groove portions H1, H2. Therefore, the circumferential groove portions R1, R
Since it is easy to make the right cylindrical pins 2P and 3P engage with R2 and R3 without rattling, the stepwise magnifications to be used can be made exactly constant. And the helical groove part
Even if there is some play between H1 and H2 due to undercut and the like due to pins 2P and 3P, it will not adversely affect shooting. In FIG. 2, for convenience, the cam grooves 4C2 and 4C3 are shown at the same position in the circumferential direction, but it goes without saying that the phases may be shifted.

The present invention is not limited to the two-group zoom configuration of the illustrated example, but can be applied to a lens barrel of a variable focal length lens using three or more lens groups, and the zoom driving member is a driving member other than the cam barrel. Good. It goes without saying that the zoom driving member and the focusing lens may be manually moved.

〔The invention's effect〕

In the lens barrel of the variable focal length lens of the present invention, the cam groove includes at least three circumferential groove portions having different positions in the optical axis direction,
The helical groove portion has at least two helical groove portions that connect the circumferential groove portions that are adjacent to each other in the optical axis direction, and the helical groove portion is used for positioning of the lens holding frame at the optical axis direction position during photographing. It is configured to be used to control the movement of the lens holding frame in the optical axis direction when not shooting, and the cam barrel is formed by resin molding, so it is easy to form the cam barrel by resin molding. As a result, it is possible to reduce the weight of the lens barrel, and it is possible to obtain a plurality of accurate magnifications despite the fact that the cam barrel is formed by resin molding.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a lens barrel of a variable focal length lens of the present invention, and FIG. 2 is a partial development view showing a groove shape of a zoom cam barrel. 1 ... Fixed barrel, 1G2,1G3 ... Guide groove, 2 ... First lens group zoom frame, 3 ... First lens group holding frame, 2P, 2P ... pin, 4 ... Zoom cam barrel, 4C2,4C3 …… Cam groove, R1, R2, R3 …… Circular direction groove part, H1, H2 …… Helical direction groove part, 5 …… Pinion, 6 …… Protective cylinder, 7 …… Focusing motor, 8 …… Focusing Focusing cam barrel, 9 ... First lens holding frame.

Claims (1)

(57) [Claims] 1. A lens barrel of a variable focal length lens configured to control a position of a lens holding frame in an optical axis direction by a cam groove formed in a cam barrel which is rotated around an optical axis. , At least three circumferential groove portions having different positions in the optical axis direction, and at least two helical groove portions connecting the circumferential groove portions that are adjacent to each other in the optical axis circumferential direction, and the circumferential groove portions are used for photographing. In the positioning of the lens holding frame in the optical axis direction position, the helical groove portion is configured to be used for movement control of the lens holding frame in the optical axis direction at the time of non-shooting, and the cam barrel is made of resin. A variable focal length lens barrel characterized by being formed by molding.