JPH0353608B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a lens barrel suitable for a zoom lens used in a television camera.

[Prior art]

Conventionally, zoom lenses for television cameras have used lens barrels made of metal materials. However, in order to spread the use of television cameras in a wide range of fields and increase their mobility, television cameras have become smaller, lighter, and even cheaper. smaller and lighter,
There is also a great demand for lower prices.

Conventionally, the lens barrel that performs the focusing action is also made of metal material, and the multi-threaded helicoid part that connects the focus ring to the fixed barrel and changes the rotational movement of the focus ring into linear movement is machined. It is formed by lapping, etc. to achieve high precision, and since it is made of metal, it has excellent wear resistance. However, since it takes a lot of time and effort to process, it inevitably increases costs and also poses a problem in terms of weight.

On the other hand, with the recent trend of using synthetic resin for parts, the use of synthetic resin for lens barrels is attracting a lot of attention, and multi-striped helicoid parts can also be obtained in a large scale by molding.
The labor and time required for processing are significantly reduced, making it possible to cut costs and achieve significant weight reduction.

However, lens barrels made of synthetic resin,
There are problems with dimensional stability and strength. In order to solve this problem, synthetic resin materials containing fillers such as glass fibers are used. On the other hand, the multi-striped helicoid part of the lens barrel is a mechanism that applies rotational force to the focus ring, converts the rotational movement into linear movement, and moves the focus ring in a straight line, so there is a loss in force transmission. For this reason, it is necessary to apply a force greater than the force required to move the focus ring straight to the multi-striped helicoid section, and the multi-striped helicoid section may wear out with repeated use over a long period of time. It becomes more likely to occur.
When the multi-threaded helicoid portion wears out, it naturally causes wobbling, and therefore the focus ring also wobbles in the direction of linear movement and in the direction perpendicular to the direction of linear movement.

Incidentally, in a lens barrel that has a focusing function, a holding frame for a focusing lens group is attached in a fixed relationship to a focus ring, and the focus ring is in a direction perpendicular to the straight direction, that is, the optical axis. If the focusing lens group has wobble in the direction perpendicular to the optical axis, the focusing lens group will also have wobbling in the direction perpendicular to the optical axis. This has the disadvantage that the focal lens group is tilted with respect to the optical axis, which deteriorates the optical performance of the lens and shortens its lifespan.

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
To provide a lens barrel made of a synthetic resin that can prevent the influence of the wobbling of a focus ring due to wear of a multi-striped helicoid part on a focusing lens group.

[Summary of the invention]

In order to achieve this object, the present invention provides a highly wear-resistant structure in which the holding frame of the focusing lens group is slidably fitted into a fixed cylinder having a multi-striped helicoid section that meshes with the multi-striped helicoid section of the focus ring. The focus ring is fixed to a sliding member, and the sliding member is pressed against the focus ring by an elastic member, and is movable in the optical axis direction by linear movement of the focus ring.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a lens barrel according to the present invention, in which 1 is a fixed barrel, 2 is a focus ring, 3 is an index ring, 4 is a cam ring, 5 is a guide rod, and 6 is a presser foot. plate, 7 is a variable magnification lens group, 8 is a sliding member, 9 is an elastic member, 10 is a screw ring, 11 is a holding frame, 12 is a focusing lens group, 13 is a stepped portion, 14 is a retaining ring, 15 is a gap , 16 is a drop groove portion, and 17 is a step portion.

In the figure, a multi-thread helicoid section consisting of mutually meshed multi-thread helicoid threads is provided on the outer surface of the fixed barrel 1 and the inner surface of the focus ring 2. When the focus ring 2 is rotated, the multi-thread helicoid section rotates. The movement is converted into a rectilinear movement, and the focus ring 2 moves rectilinearly in the directions of arrows A and A' (optical axis direction). The sliding member 8 is pressed against the stepped portion 13 of the focus ring 2 by an elastic body 9 such as an annular wave plate spring, and one surface of the elastic member 9 is fixed by a screw ring 10. Moreover, the sliding member 8 has a sliding surface with the fixed cylinder 1 and is fitted into the fixed cylinder 1.
The focusing lens group 12 is attached to the holding frame 1 by a retaining ring 14.
1, and the holding frame 11 is fixed to a sliding plate.

In this configuration, when the focus ring 2 is rotated, the focus ring 2 moves in the directions of arrows A and A' as the focus ring 2 rotates. Now, if the sliding member 8 moves in the direction of the arrow A, the step portion 13 of the focus ring 2 moves the sliding member 8 in the direction of the arrow A against the elastic force of the elastic member 9, and the focusing lens group 12 similarly moves in the direction of arrow A. Conversely, if the focus ring 2 moves in the direction of arrow A', the sliding member 8 moves in the direction of arrow A' due to the pressure of the elastic member 9 so as to always come into contact with the stepped portion 13 of the focus ring 2. , the focusing lens group 12 also moves in the direction of arrow A'. Note that since the focus ring 2 moves straight in the directions of arrows A and A' while rotating, the sliding member 8 may also rotate due to the rotation of the focus ring 2. There is no need to provide a means for regulating the rotation of 8.

The sliding member 8 slides on the inner surface of the fixed cylinder 1 as it moves in the directions of arrows A and A'. This fixed tube 1
Due to the sliding fit, the sliding member 8 is fixed in position in the direction perpendicular to the optical axis (not shown). Therefore, the fixed barrel 1 and the focus ring 2 are made of synthetic resin, and the multi-striped helicoid part is also made of synthetic resin. This will cause wobbling in the direction perpendicular to the optical axis. However, the sliding member 8 is not fixed to the focus ring 2 and is in contact with the stepped portion 13, and the sliding member 8 is Since the position is regulated in the direction perpendicular to the optical axis by fitting, any looseness in the direction perpendicular to the optical axis of the multi-threaded helicoid part can be avoided by sliding member 8.
It doesn't get across. Therefore, the rattling of the multi-helicoid portion does not affect the focusing operation of the focusing lens group 12.

Of course, wear occurs on the sliding surfaces of the fixed cylinder 1 and the sliding member 8, and this wear causes the sliding member 8 to
This will cause wobbling in the direction perpendicular to the optical axis direction, but this wear will occur because the sliding member 8 receives only the force that causes the focusing lens group 12 to move straight.
This is sufficiently small compared to the wear rate of the multi-helicoid portion.

Note that the stepped portion 1 between the focus ring 2 and the sliding member 8
A gap 15 is provided in the opposing part below the opposing part in 3, and this gap 15 is made sufficiently large to prevent the focus ring 2 from coming into direct contact with the sliding member 8 at the opposing part due to rattling caused by the multi-thread helicoid part, To prevent an adverse effect on the focusing lens group 12.

In this embodiment, additives such as fluorine resin fine powder are added to the molding material of the fixed tube 1 in order to improve the wear resistance of the fixed tube 1 and the sliding member 8 and to withstand long-term use. It is also possible to take measures such as adding In this case, the fixed tube 1, which is molded with a fine powder of fluororesin added as an additive, is difficult to paint, so the lens barrel groove is formed so that it is not exposed to the exterior. That is, the index ring 3 is provided with a drop groove portion 16 so that the focus ring 2 can fit therein, and the focus ring 2 is provided with a stepped portion 17 so that the fixed barrel 1 is not exposed even if the focus ring 2 moves. In this way, there is no need to consider painting the fixed tube 1, and the range of materials for molding the fixed tube 1 can be widened. Furthermore, a grease groove is provided on the sliding surface of the sliding member 8 with respect to the fixed cylinder 1, thereby further increasing wear resistance.

The holding frame of the variable magnification lens group 7 is slidably attached to the guide rod, and a pin (not shown) provided on the holding frame is engaged with a cam groove (not shown) of the cam groove 4. By rotating the cam groove 4, the holding frame of the variable magnification lens group 7 slides on the guide rod, and a predetermined zoom magnification is set.

As described above, according to this embodiment, the position of the focusing lens group 12 in the direction perpendicular to the optical axis is controlled by the fitting between the sliding member 8 and the fixed tube 1, and by the focusing tube 2. Therefore, even if the focus cylinder 2 becomes loose due to wear of the multi-helicoid portion, the position setting of the focusing lens group 12 in the direction perpendicular to the optical axis will be affected by such looseness. There is no deterioration in optical performance even after repeated use over a long period of time. Therefore, a lightweight, inexpensive, and long-life zoom lens can be obtained.

FIG. 2 is a cross-sectional view showing another embodiment of the lens barrel according to the present invention, in which 18 is a ring, and parts corresponding to those in FIG. 1 are given the same reference numerals and their explanation will be omitted.

In this embodiment, a ring 18 that slides smoothly on the sliding member 8 and has excellent wear resistance is inserted into the sliding portion of the fixed cylinder 1 that contacts the sliding member 8. With such a ring 18, the abrasion resistance between the fixed barrel 1 and the sliding member 8 is significantly reduced, and a lens barrel with a longer life can be obtained.

[Effects of the present invention]

As explained above, according to the present invention, due to the rattling of the focus ring due to wear of the multi-threaded helicoid part, which can be formed of synthetic resin and converts the rotational movement of the focus ring into linear movement,
The position perpendicular to the optical axis of the focusing lens group is not affected, and high optical performance can be maintained even during repeated use over long periods of time, making it possible to be lightweight and have a long service life. , it is possible to provide a lens barrel with excellent functions at a low cost without the drawbacks of the prior art.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the lens barrel according to the present invention, and FIG. 2 is a cross-sectional view showing another embodiment of the lens barrel according to the present invention. DESCRIPTION OF SYMBOLS 1... Fixed cylinder, 2... Focus ring, 8... Sliding member, 9... Elastic member, 10... Screw ring, 11
...Holding frame, 12...Focusing lens group, 13...Stepped portion.

Claims (1)

[Claims] 1 By rotating a synthetic resin focus ring having a multi-threaded helicoid threaded part that engages with a multi-threaded helicoid threaded part of a synthetic resin fixed tube, the focusing lens group is moved in the optical axis direction and the focusing is performed. A lens barrel for positioning a lens group for use in a lens system, comprising: a sliding member to which a holding frame for the focusing lens group is fixed; and an elastic member for pressing the sliding member against the focus ring; The sliding member is configured to be able to prevent wobbling in a direction perpendicular to the optical axis of the focusing lens group due to wear of the multi-threaded helicoid thread portion by slidingly fitting into the fixed cylinder. A lens barrel characterized by: