JPH0248805Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a focus adjustment mechanism for a zoom lens, and more particularly, to a focus adjustment mechanism for performing focus adjustment (fc adjustment) on a film surface of a zoom lens.

(Prior Art) An example of a conventional focus adjustment mechanism of this type is constructed as shown in FIGS. 1 and 2. FIG. 1 is a sectional view of the upper half of a zoom lens having the focus adjustment mechanism, and FIG. 2 is an exploded perspective view of the main parts of the focus adjustment mechanism. In FIG. 1, this zoom lens 01 includes a front group lens frame 2 that holds a front group lens _L1 , a rear group lens frame 3 that holds a rear group lens _L2 , and these lens frames 2, 3.
a fixed frame 4 consisting of a double cylinder which is rotatably supported by an inner frame 4a; a zooming cam frame 5 rotatably supported on the outer peripheral surface of the inner frame 4a of this fixed frame 4; An operating ring 6 integral with the cam frame 5 is rotatably fitted to the outer peripheral surface of the outer frame 4b of the fixed frame 4,
Zoom ring 7 for positioning the cam frame 5
The main parts are made up of.

The front group lens frame 2 is composed of a double barrel integrally connected by a vertical wall 2c provided near the front, and its outer frame covers the front outer periphery of the fixed frame 4 to form the same lens frame. It forms the operation section 2a of 2,
Further, the inner frame 2b is located in the front part of the inner frame 4a of the fixed frame 4, and the inner frame 2b is provided with the front group lens on its inner peripheral surface.
L ₁ is held, and the above-mentioned fixed inner frame 4a is attached to its outer peripheral surface.
A helicoid screw 2d is provided to be screwed into a helicoid screw 11a provided on the inner circumferential surface of the helicoid frame 11, which is fitted into the helicoid frame 11 so as to be able to move forward and backward.

The fixed frame 4 consists of a double barrel whose rear ends are integrally connected to each other and fixed to the lens mount member 12, and the front ends of both the inner and outer frames 4a, 4b are connected to the front lens frame 2. The helicoid frame 11 is fitted into the inner frame 4a toward the front, and the rear group lens frame 3 is fitted into the inner frame 4a so as to move forward and backward. .

As shown in FIG. 2, the cam frame 5 is formed of a cylindrical body, and has a partially arcuate cam slot 5a extending in the circumferential direction near the front, and a partially arcuate cam slot 5a extending in the circumferential direction in the middle. As shown in FIG. 1, each of these cam slots 5a and 5b is provided with a cam slot 5b which is inclined at a slanting angle. Drive pins 3a fixedly planted on the outer peripheral surface of the group lens frame 3 are respectively fitted and rotated by an operating ring 6 on a zoom ring integrated with the cam frame 5, thereby driving the drive pins 11b and 3a. As a result, the helicoid frame 11 and the rear group lens frame 3 are moved in the optical axis direction. Note that the drive pins 11b and 3a pass through cam slots 14a and 14b provided in series in the optical axis direction at the front and rear of the fixed inner frame 4a, so that the helicoid frame 11 and the rear group lens frame 3 The rotation of is regulated. A cam frame pin 10 that integrally connects the cam frame 5 and the zoom ring 7 is fixedly planted on the outer peripheral surface of the cam frame 5 from the rear side, and this pin 10 is placed near the rear of the fixed outer frame 4b. It passes through a circumferential cam slot 4c and is fitted into a fitting hole 7c of the zoom ring 7. Note that the cam frame pins 10 are provided in pairs, upper and lower.

The zoom ring 7 has a mechanism for adjusting the focus (fc adjustment) of the front and rear lens groups L ₁ and L ₂ that have been zoomed with respect to the fixed frame 4, and is fitted into the fixed outer frame 4b and As shown in the figure, it is formed into a ring shape with flanges 7a that are higher at the front and rear. A pair of relatively wide cam slots 7b in the circumferential direction are provided at opposing positions in the diametrical direction at the center thereof, and eccentric rollers 8 are respectively fitted into the cam slots 7b. The eccentric roller 8 is fixed to the outer peripheral surface of the fixed outer frame 4b with mounting screws 9 after adjustment. The eccentric roller 8 is rotated as appropriate to move the zoom ring 7 and cam frame 5 in the optical axis direction, and when the front and rear lenses L ₁ and L ₂ are brought into focus at the same time, the roller 8 is screwed. It is fixed at 9,
This is what is called fc adjustment. When the zoom ring 7 is rotated after the fc adjustment is made in this way, the fitting hole 7c and the circumferential cam slot 4 provided on the upper and lower peripheral surfaces near the rear of the fixed outer frame 4b are adjusted.
The above pair of cam frame pins 1 screwed through c
0, the cam frame 5 and zoom ring 7 are fixed frame 4
The lens rotates as a unit against the lens to perform zooming operations. Further, the reference numeral 13 indicates an aperture blade, and the reference numeral 15 indicates an aperture ring. In addition,
In FIG. 1, the eccentric roller 8 is shown to have the same cross section as the cam frame pin 10, but in reality, as shown in FIG. 2, it is disposed at a position offset by 90 degrees in the circumferential direction.

By the way, the means for rotating the pair of eccentric rollers 8 and moving the zoom ring 7 in the optical axis direction with respect to the fixed frame 4 is to simultaneously rotate the pair of eccentric rollers 8 by the same amount. It is extremely difficult to fix the zoom ring 7, and it is easy to twist the zoom ring 7 and cause uneven rotation, which increases the working time.Also, when a force in the thrust direction is applied to each lens frame 2, 3, the force is cam frame 5, cam frame pin 10,
There was a fear that the power would be transmitted to the zoom ring 7 and then the eccentric roller 8 in that order, causing the eccentric roller 8 to rotate, causing the fc adjustment position to shift.

(Objective) The object of the present invention is to provide a focus adjustment mechanism that eliminates the drawbacks of the conventional zoom lens focus adjustment mechanism as described above and guarantees a high level of performance after adjustment.

(Summary) In order to achieve the above object, the present invention abolishes the focus adjustment mechanism of the conventional zoom lens using the eccentric roller mentioned above, and provides a new focus position adjustment ring that fits into the zoom ring. It is characterized by the fact that the drilled cam slot allows extremely simple and stable focus adjustment.

(Example) The present invention will be explained below based on the illustrated example.

FIG. 3 is a cross-sectional view of the upper half of a zoom lens to which a focus adjustment mechanism according to an embodiment of the present invention is applied, and FIG. 4 shows the main components of the focus adjustment mechanism of the zoom lens shown in FIG. It is a partially exploded perspective view. Note that each component of the zoom lens in this example is constructed in exactly the same manner as each component of the zoom lens shown in FIGS. 1 and 2 above, except for related members such as a zoom ring and a focus position adjustment ring. Therefore, the same constituent members are simply given the same reference numerals, and their explanations will be omitted. The zoom ring 21 in the zoom lens 20 of this embodiment is as shown in FIG.
The external shape is almost the same as the zoom ring 7 shown in the figure, but straight slots 21a extending in the optical axis direction are provided at opposing positions on the upper and lower circumferential surfaces, and four slots 21a are provided at opposing positions in the radial direction on the left and right circumferential surfaces. Circumferential stepped cam slot 2
1b is provided. This stepped cam slot 21b
As shown in FIGS. 5 and 6, a headed fixing screw 23 is inserted through the lens and screwed into a screw hole 22b of a focus position adjustment ring 22, which will be described later.

The position adjustment ring 22 in the present invention is a ring-shaped ring that fits between the zoom ring 21 and the fixed outer frame 4b, and as shown in FIG. Cam slot holes 22a are provided respectively. And the above cam frame 5
The cam frame pin 10 fixed to the cam frame pin 10 is adapted to fit into both the rectilinear slot 21a of the zoom ring 21 and the cam slot 22a of the focus position adjustment ring 22 at the same time.

As shown in FIGS. 7A and 7B, the position adjustment ring 22 is provided with three thrust-direction movement stops at equal intervals on the fitting portion of the position adjustment ring 22 of the fixed outer frame 4b (see FIG. 3). These claws 4d are engaged with three engaging portions 22c provided at corresponding positions on the inner surface of the rear end of the position adjustment ring 22 in a so-called bayonet manner. In this way, the cam frame pin 10 can be attached to the cam slot 4 of the fixed outer frame 4b.
Since the rotation angle is regulated by c, the bayonet will never come out of engagement. That is, Figure 7B
, the rotation angle for bayonet engagement is θ ₁
(approximately 120° in this case), long hole 4c of fixed outer frame 4b
Assuming that the rotation angle of the zoom ring 21 via the cam frame pin 10 (see FIG. 2) is θ ₂ , and the rotation angle of the cam slot 22 a of the focus position adjustment ring 22 in the circumferential direction is θ ₃ , As shown in the figure, θ ₁ >θ ₂ +2θ ₃ .

Next, the operation of the focus adjustment mechanism of the present invention configured as described above will be explained. When performing fc adjustment, first attach the fixing screw 23 to the zoom ring 21.
The focus position adjustment ring 2 is inserted through the stepped cam slot 21b of the
Loosely screw it into the screw hole 22b of No.2. In this state, the lower surface of the head of the fixing screw 23 is not in pressure contact with the step of the stepped cam slot 21b, so the zoom ring 21 and the focus position adjustment ring 22 are rotatable with respect to each other. Therefore, in this state, by rotating the zoom ring 21 with respect to the focus position adjustment ring 22, the cam frame pin 10, which is fitted into the zoom ring 21 and the adjustment ring 22 at the same time, is moved into the straight slot 21a. fc adjustment can be performed by appropriately moving the optical axis along the optical axis direction. After this fc adjustment, the fixing screw 23 is fully tightened to integrate the zoom ring 21 and the focus position adjustment ring 22, and the fc adjustment is completed. Note that in reality, the fixing screw 23 is not completely screwed into the focus position adjustment ring 22, the rotation of the zoom ring 21 is controlled by hand, and a Phillips screwdriver is placed in the cross groove of the fixing screw 23. Therefore, we adopted a method of adjusting the adjustment ring 22 by shifting it in the rotational direction and then screwing it in completely to fix it. However, compared to conventional focus adjustment means, this method is extremely easy to work with and does not shift against vibration shock. It was stable without causing any problems.

(Effects) As explained above, according to the present invention, (1) In the conventional eccentric roller method, there is almost no fear that the focus position adjustment will be incorrect due to loosening of the eccentric roller. (2) Even if there are a plurality of adjusting cam slots, all the adjusting cam slots rotate at the same angle at the same time, so the adjustment work is extremely easy and there is almost no need for adjustment. (3) Since the cam slots of the zoom ring and focus position adjustment ring are generally short, they can be molded from synthetic resin, which has the great advantage of reducing costs. (4) Even if the focus position adjustment ring is a simple bayonet fitting method, since the rotation range is restricted after assembly, there is no risk of it coming off, and the thrust receiving member can be omitted. (Five)
In the case of the conventional eccentric roller system, a cam slot consisting of a large elongated hole was required to fit the eccentric roller in a movable manner, making the zoom ring weak and easily deformed. In the proposed system, the cam slot can be made small, so there is no possibility of this happening. (6) The structure is simple, the assembly work is easy, and there are almost no errors after assembly. It is possible to provide a focus adjustment mechanism for a zoom lens that has many remarkable effects such as.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the upper half of an example of a zoom lens equipped with a conventional focus adjustment mechanism, FIG. 2 is an exploded perspective view of the main parts of the focus adjustment mechanism in FIG. 1, and FIG. The figure is a sectional view of the upper half of a zoom lens equipped with a focus adjustment mechanism showing an embodiment of the present invention. 5 is a plan view of the zoom ring in FIGS. 3 and 4 above, FIG. 6 is a sectional view taken along the line X-X in FIG. 5, and FIGS. 7A and B
3A and 3B are enlarged cross-sectional views of essential parts of the zoom lens shown in FIG. 3, each showing an engaged state of the fixed frame and the focus position adjustment ring. 01 , 20 ...Zoom lens, 4...Fixed frame,
5...Cam frame, 7, 21...Zoom ring, 10
...Cam frame pin, 21a...straight groove, 21b...
...Long hole for positioning, 22...Focus position adjustment ring, 2
2a...Cam slot, 23...Fixing screw (fixing means).

Claims (1)

[Claims for Utility Model Registration] A focal point that is fitted into a fixed frame so as to be immovable in the direction of the optical axis and rotatable around the optical axis, and has a cam groove hole that is inclined with respect to the optical axis. A position adjustment ring, a zoom ring that is integrally fitted to the focus position adjustment ring in the optical axis direction and has a straight slot extending in the optical axis direction, and is rotatably fitted to the fixed frame. However, the cam frame pin that fits into the cam slot of the focus position adjustment ring and the linear slot of the zoom ring is fixed on the outer circumferential surface, and when changing the magnification, movement in the optical axis direction is restricted and only rotation is possible. A cam frame for moving the lens frame, and a fixing means for integrating the focus position adjustment ring and the zoom ring around the optical axis, and a cam frame for moving the lens frame, and a fixing means for integrating the focus position adjustment ring and the zoom ring around the optical axis. The focus position is adjusted by rotating the zoom ring around the optical axis and moving the cam frame forward and backward in the optical axis direction.Then, the focus position adjustment ring and the zoom ring are moved along the optical axis by the fixing means. A zoom ring focus adjustment mechanism that is integrated into the surrounding area.