JPH0216324Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a zoom lens barrel having a cam ring that controls the movement position of a variable magnification optical system and a correction optical system in the optical axis direction, and a fixed lens barrel that holds this cam ring. It is.

A conventional zoom lens barrel of this type has a configuration including a focusing lens L1, a variable power lens L2, a correction lens X3, and an imaging lens L4, as shown in FIG. 1, this focusing lens holder 1 is connected to a lens fixed lens barrel 2 by a helicoid coupling, and by rotating the focusing lens holder 1, the focusing lens L1 is extended in the optical axis direction. There is.

Further, the variable magnification lens L2 and the correction lens L3 are held by a lens holder 3 and a lens holder 4, respectively, and these lens holders 3 and 4 are guided by a guide bar 5 or the like using a well-known three-bar system and light is It is designed to be able to move in the axial direction.
The amount of movement of the variable magnification lens L2 and the correction lens L3 in the optical axis direction is determined by cam lifts 6a, 6 provided on a cam ring 6 rotatably held in the fixed lens barrel 2.
b. The cam ring 6 is adapted to rotate in conjunction with an interlocking shaft 8 implanted in the cam ring 6 in response to the rotation of a zoom operation ring 7 fitted to the outer periphery of the lens fixed barrel 2. Further, the imaging lens L4 is connected to the imaging lens holder 10 via the aperture 9.
It is held in the rear fixed cylinder 11 by the screws 12, and is fixed by screws 12.

The cam ring 6 is sandwiched between a front mask plate 13 and a rear mask plate 14, which serve as holding members for holding the three guide bars 5, inside the lens fixed barrel 2. Therefore, in order to minimize the amount of focus movement caused by zooming, it is necessary to manage the dimensions of the fixed lens barrel 2 and the cam ring 6 so that they are completely free of play and can be rotated. It is necessary to Furthermore, if the lens fixed lens barrel 2 is made of a synthetic resin material such as polycarbonate and the cam ring 6 is made of a metal such as aluminum, as has been the case recently, due to the difference in linear expansion coefficient specific to each material,
Temperature changes tend to cause backlash in the thrust direction, and shrinkage can cause the lens fixed lens barrel 2 and cam ring 6 to
There are also problems such as the thrust dimension becomes smaller and it becomes difficult to operate.

The purpose of this invention is to solve the above-mentioned problems, stabilize component dimensions, improve workability, and provide a zoom lens barrel that guarantees clearance in the thrust direction under temperature conditions and prevents malfunctions. The gist of the invention is to provide a cam ring for displacing a variable power lens and a correction lens in the optical axis direction, which are movably supported by a guide bar, by rotating within a fixed lens barrel. As a means for positioning with respect to the lens barrel, a flange portion is provided around one end surface of the cam ring, a step portion is formed on the fixed lens barrel, and the flange portion is positioned in the step portion, By sandwiching the flange portion between the end face of the stepped portion and the holding member of the guide bar,
positioning the cam ring with respect to the fixed lens barrel;
Further, in the held state, a gap in the optical axis direction is formed at the other end surface position of the cam ring.

The present invention will be explained in detail below based on the embodiment shown in FIG. In Figure 2, the same symbols as in Figure 1 represent the same members, and
Descriptions that overlap with the figures will be omitted.

In the embodiment shown in FIG. 2, the total length of the cam ring 6 is d2 with respect to the total length d1 of the fixed lens barrel 2.
It is shortened so that there is a clearance on the focusing lens L1 side. Further, a flange portion 6 having a thickness d3 that is extremely small compared to the overall length d1 of the lens fixed barrel 2 is provided at the rear end of the cam ring 6.
c is provided all around. Correspondingly, the lens fixed lens barrel 2 is also provided with a stepped portion 2a having a width dimension d3, and a flange portion 6c is provided between the stepped portion 2a and the rear mask plate 14 disposed on the end surface of the stepped portion 2a.
The cam ring 6 is held rotatably by being sandwiched therebetween.

In this embodiment, the dimensions in the thrust direction of the fixed lens barrel 2 and the cam ring 6 only need to be controlled by the short dimension d3. There will be no need to manage it. Further, because the front end surface of the cam ring 6 does not come into contact with the front mask plate 13 due to the existence of the clearance of the dimension d2, flatness management of the front mask plate 13 is not necessary.

Next, let's consider the dimensional changes of each part due to temperature changes. The linear expansion coefficient of the fixed lens barrel 2 is α1,
The wall expansion coefficient of the cam ring 6 is α2, the temperature change from room temperature is t1, and the ratio of the dimensions d1 and d3 mentioned above is d1=
40・d3, the state of change in the case of Figure 1 and Figure 2 is {(α1−α2)・t1・d3} /{(α1−α2)t1×d1}=1/40. Become.

That is, in the case of Fig. 2, the difference in thrust direction dimensions between the cam ring 6 and the lens fixed lens barrel 2 due to temperature changes is 1/40 of that in Fig. 1, and almost no play occurs due to temperature changes. It disappears. Therefore, even if the lens fixed lens barrel 2 is made of a plastic material such as polycarbonate, and the cam ring 6 is made of a metal material such as aluminum, no problem will occur under normal operating temperature conditions.

Note that the flange portion 6c of the cam ring 6 can also be provided on the front end side.

As explained above, the zoom lens barrel according to the present invention has a flange provided around one end face of the cam ring, and the flange is supported by the end face of the stepped part of the fixed lens barrel and the holding member of the guide bar. By sandwiching the cam ring, the cam ring is positioned relative to the fixed lens barrel, and by forming a gap at the other end surface position of the cam ring in the held state, the positional accuracy of the cam ring in the thrust direction is improved by the flange. This is extremely advantageous in terms of assembly and parts processing. Further, since the holding member of the guide bar does not tilt during assembly or thereafter, smooth movement of the lens supported by the guide bar can always be guaranteed. Furthermore, even when materials with significantly different coefficients of linear expansion are used, such as when the fixed lens barrel is made of synthetic resin, it is possible to minimize backlash and clearance fluctuations due to temperature changes, making zoom lenses can ensure smooth operation and improve reliability.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view illustrating a conventional zoom lens barrel, and FIG. 2 is a longitudinal sectional view illustrating an embodiment of the zoom lens barrel according to the present invention. Symbols 1, 3, 4, 10 are lens holders, 2 is a lens fixed lens barrel, 2a is a stepped portion, 6 is a cam ring, 6
c is a flange, 7 is a zoom operation ring, 13 is a front mask plate, 14 is a rear mask plate, L1 is a focusing lens, L2 is a variable magnification lens, L3 is a correction lens, L4
is an imaging lens.

Claims (1)

[Scope of utility model registration request] As means for positioning, relative to the fixed lens barrel, a cam ring that displaces the variable power lens and the correction lens in the optical axis direction, which are movably supported by a guide bar, by rotating within the fixed lens barrel; A flange portion is provided around one end surface of the cam ring, and a stepped portion is formed on the fixed lens barrel, and the flange portion is positioned at the stepped portion so that the end surface of the stepped portion and the guide bar are connected. The cam ring is positioned with respect to the fixed lens barrel by sandwiching the flange portion with a holding member, and a gap in the optical axis direction is formed at the other end surface position of the cam ring in the held state. A zoom lens barrel.