JPH04345117A - Variable focus lens barrel - Google Patents

Abstract

PURPOSE:To minimize eccentricity as the whole, without decentering lens moving frames in different directions, respectively, by decentering plural lens moving frames together with a part of housed moving frames. CONSTITUTION:Plural lens moving frames 11, 17, and 20 supporting plural lens groups L1-L5 respectively, are provided, and the focusing ranges of the lens groups L3-L5, driven for focusing are changed by interlocking to a change in the focal distance by a zooming operation. These plural lens moving frames 11, 17, and 20 are composed of, at least, a first lens moving frame 9, and plural lens moving frames housed inside the first lens moving frame 9, and all lens moving frames are independently moved in an optical axis direction, accompanying with a movement to the optical axis direction of the first lens moving frame 9, to execute the zooming operation. At least, a part of the lens moving frames 11, 17, and 20 is moved, to execute a focusing action. Therefore, when the lens group has the eccentricity, plural lens moving frames are decentered like the first moving frame.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens barrel, and more particularly to a varifocal type zoom lens barrel.

0002

[Prior Art] In general, zoom lenses are designed so that the imaging position does not shift even when zooming is performed, and the amount of movement of the focusing lens from close range to infinity remains constant throughout the zoom range. It is designed so that there is no need to adjust the focus every time you zoom.

However, the above-mentioned advantage in use that the amount of movement of the focusing lens from close range to infinity is constant over the entire zoom range also makes optical design difficult, making it difficult to make the zoom lens more compact. This made it difficult to achieve cost reductions.

Therefore, in order to solve these problems, a varifocal lens is used that does not use the above-mentioned advantages, that is, the amount of movement of the focusing lens from infinity to close range changes depending on the change in focal length. It has become.

However, even in the above-mentioned varifocal lens barrel, as the focal length range for zooming expands and the magnification becomes higher, the error sensitivity (the degree of influence that the parallelism or tilt eccentricity of the lens has on aberrations) becomes severe. As a result, even the slightest eccentricity of the lens group has caused a significant deterioration in performance on the film surface.

[0006] To address this problem, Japanese Patent Application Laid-Open No. 1-296
No. 209 discloses a zoom lens barrel that holds another lens moving frame within one lens moving frame and has a second cam ring that drives the other lens moving frame. It is shown.

[0007]

[Problem to be Solved by the Invention] However, in the conventional example as described above, it is impossible to prevent the overall performance from deteriorating due to the eccentricity of each lens moving frame in a different direction. If such a configuration is adopted, a problem arises in that focusing cannot be performed using some of the lens movement frames among the plurality of lens movement frames.

[0008] The present invention solves the above problems, and
It can cope with the increase in error sensitivity associated with higher magnification of varifocal lenses, and even in such lens barrels, focusing can be performed using some of the multiple lens movement frames. The purpose is to obtain a varifocal lens barrel.

[0009]

[Means for Solving the Problems] In order to solve the above problem, the present invention provides that even if a plurality of lens groups have eccentricity, if the eccentricities point in the same direction, the deterioration of the overall performance is minimized. The lens consists of a plurality of lens groups arranged on the same optical axis and a plurality of lens movement frames for supporting each of the plurality of lens groups, and is driven for focusing. In a varifocal lens barrel in which the focusing range of a group changes in conjunction with a change in focal length due to a zoom operation, the plurality of lens movement frames include at least a first lens movement frame;
It consists of a plurality of lens moving frames housed inside the first lens moving frame, and as the first lens moving frame moves in the optical axis direction, all the lens moving frames independently move in the optical axis direction. A zoom operation is performed by performing a zoom operation, and a focusing operation is performed by moving at least a part of the lens movement frame housed inside the first lens movement frame in the optical axis direction. A focal lens barrel is provided.

0010

[Operation] In the configuration of the present invention, even if decentering occurs in the lens group, the plurality of lens moving frames housed inside the first lens moving frame are decentered in the same direction as the first lens moving frame. .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a zoom lens barrel showing an embodiment of the present invention, and FIGS. 2 and 3 are partial sectional views of the same lens barrel. FIG. 4 is a perspective view of the main components. Identical members in the figures are designated by the same reference numerals. The states of this zoom lens barrel shown in FIGS. 1, 2, 3, and 4 are at wide angle and infinity. The optical system consists of 5 groups, L1
-L5 is a zoom lens group, and L3 to L5 are focus lens groups, forming a varifocal type zoom lens barrel.

This lens is a so-called in-body motor AF lens that has a motor inside the body and performs a focusing operation by transmitting a driving force to the lens side via a coupler. It also has a zoom motor inside the lens, and is configured to allow power zoom operations using the operating ring.

The fixed cylinder 5 is fixed to a mount 51 by a mount fixing screw 52, and the outer cylinder 2 is fixed to the outside thereof by an outer cylinder fixing screw (not shown). A light shielding member 51b is formed inside the mount 51 and extends toward the tip in the optical axis direction. A fixing member 53 is screwed onto the tip of the outer cylinder 2, and the operating ring 1 is fitted on the outside.
A helicoid 2a is provided on the inside, and a clutch mounting member 54 having a fitting groove for a clutch member 55 is fixed to the rear. The lens of this example normally receives power from the body by operating the operation ring 1, and power zooming is possible using the motor inside the lens barrel.Although the lens has the same mount, it has a contact point for power supply. Power zoom is not possible when used on a body that does not have this. At this time, in order to perform a manual zoom operation, it is necessary to disconnect the power zoom motor and the manual zoom operation member (the zoom cam ring 4 in this embodiment). The clutch member 55 is provided for this purpose,
It is connected to a clutch mechanism to be described later, and the connection can be broken by operating the clutch member 55 in the optical axis direction.

The zoom reduction system 32 for power focusing is connected to the zoom motor via a clutch mechanism to be described later, and is connected to a gear portion 4c provided inside the rear end of the zoom cam ring 4.
are meshed with each other. The zoom ring 4 is provided with a straight groove 4a, a claw 4b at the tip, and a partial rib 4d on the inside, and is fitted on the outside of the fixed barrel 5. The fixed cylinder 5 has a cam groove 5a and a circumferential groove 5b at its tip, and a third zoom gear base plate 3 forming a zoom reduction system 32 at its rear end.
6 is fixed, and one end of the focus drive ring 12 abuts on the inside, and a straight groove 5c is provided. The zoom cam ring 4 can only rotate and is prevented from being extended by fitting the partial rib 4d into the circumferential groove 5b.

The first group moving frame 3 has a linear rib 3 provided inside.
It fits on the outside of the zoom cam ring 4 through b, and the first
It holds the lens group L1 and has a helicoid 3a on the outside that engages with the helicoid 2a of the outer tube 2.

The zoom drive ring 6 is held inside the fixed barrel 5, and has a cam groove 6a, a fitting part 6b at the rear end, a partial rib 6c on the inside, and a third group guide pin 24 implanted therein. established,
This pin 24 is connected to the cam groove 5a of the fixed barrel 5, and the zoom cam ring 4.
It passes through the straight groove 4a.

The linear cylinder 7 is fitted inside the zoom drive ring 6, and has a linear escape hole 7b, a notch 7c at the tip, a partial rib 7d at the rear end, and a protrusion 7a and a helicoid 7e on the inside.
is provided. Since the partial ribs 7d of the linear cylinder 7 fit into the partial ribs 6c of the zoom drive ring 6, the linear cylinder 7 can only rotate with respect to the zoom drive ring 6, and moves integrally in the optical axis direction.

The focus rotation tube 8 is an outer helicoid 8.
a meshes with the helicoid 7e of the straight tube 7, and has a partial rib 8b on the inside, and a longitudinal portion 8c having a straight groove 8d facing toward the mount surface.

The third group moving frame 9 is fitted inside the linear cylinder 7, has linear grooves 9a and 9b, a groove 9c and a circumferential groove 9e on the outside, and has a fourth group drive ring retainer 14 screwed to the rear end. A threaded portion 9g is provided at the tip thereof, and a straight key 10 is screwed to the tip so as to pass through the notch 7c and fit into the straight groove 5c. The fitting portion 10a of the straight key 10 with the straight groove 5c remains in the straight groove 5c even when the attached third group moving frame 9 is extended by zooming or focusing operation.
It is long enough so that it does not fall out. Third
A third lens group L3 is held inside the group movement frame 9, a known aperture mechanism 56 (not shown) that operates in response to a shutter release operation is provided in the center, and a C-shaped plate spring 19 is provided around the circumference. It is held within the groove 9d. Since the groove 9c and the protrusion 7a of the linear tube 7 fit together, the groove 9 is in the optical axis direction.
It can move along c, but it moves integrally in the direction of rotation. The focus rotation tube 8 can only rotate with respect to the third group moving frame 9 by fitting the circumferential groove 9e and the partial rib 8b, and moves integrally in the optical axis direction.

The second group moving frame 11 is fitted inside the third group moving frame 9, holds the second lens group L2 inside, and has a second group guide pin 26 implanted outside. 26
passes through the straight groove 9a of the third group moving frame 9, the straight escape hole 7b of the straight cylinder 7, and the cam groove 6a of the zoom drive ring 6.

The fourth group drive ring 13 is located outside the rear end of the third group moving frame 9, and has a cam groove 13b and an adjustment member insertion groove 13c inside. A support portion 13a extending outward and having a forked tip is provided at the tip, and a fitting portion 6b of the zoom drive ring 6 fits into this support portion 13a.

The fourth group moving frame 17 is fitted inside the third group moving frame 9, has a plurality of jig engagement grooves at equal intervals along the circumference on the rear end surface, and has a fourth lens group inside. Two fourth group moving guides 18 are fitted in the outer circumferential groove 17a at symmetrical positions on the circumference. A fourth group guide pin 28 is installed on the outside of the guide, and this pin passes through the straight groove 9b of the third moving frame 9 and the cam groove 13b of the fourth group drive ring 13.

The fifth group lens frame 20 is fitted so as to come into contact with the C-shaped plate spring 19 inside the third group moving frame 9, and holds the fifth lens group L5 inside and is also used for penetrating the jig. It has a plurality of notches at equal intervals along the circumference, the rear end is inclined inward toward the outside of the circumference, and the C-shaped wire spring 21 is fitted into the gap between it and the third group moving frame 9. Fixed.

At the rear end of the fitting portion between the third group moving frame 9 and the fourth group drive ring 13, a third-fourth group spacing adjustment ring 16 and a third-fourth group spacing adjustment washer 15 are inserted into the adjustment member insertion groove 13c. is inserted, and the fourth group moving ring retainer 14 is screwed onto the threaded portion 9g at the rear end of the third group moving frame 9, thereby fixing both.

Further, in FIG. 2, the AF coupler 30 is fitted with the AF coupler on the camera side in the fitting hole 51a on the mount member 51 having the light shielding member 51b inside, thereby allowing the AF coupler 30 to cover the inside of the body (not shown). It becomes possible to transmit driving force from the motor. The driving force transmitted to the coupler 30 is transmitted to the focus drive ring 12 via electric focus reduction gears 33 , 34 , and 35 attached to the focus gear base plate 22 . Focus drive ring 12
is attached to the rear end of the fixed cylinder 5, and the gear part 1 is attached to the outside.
2b, which meshes with the electric focus reduction gear 35, and which goes around the rear ends of the zoom drive ring 6 and the linear movement barrel 7, and is fitted into the linear movement groove 8d of the focus rotation cylinder 8. There is. This straight groove 8d and the engaging arm 12
Each of the engagements a has a sufficient length so that it will not come off even if the focus rotation barrel 8 moves in the optical axis direction due to zooming and focusing operations.

Next, the arrangement of control members such as the motor, deceleration mechanism, and IC in the lens barrel of this embodiment will be explained using FIGS. 5 and 7.

FIG. 5 is a layout diagram showing the arrangement of members such as a reduction gear at the rear of the lens, and FIG. 7 is an enlarged view of the vicinity of the zoom gear base plate 23 viewed from the optical axis direction. Also, A-A in FIG.
FIG. 8 shows a power zoom state in which the gears 32d and 32e are engaged in cross-sectional view, and FIG. 9 shows a manual zoom state in which the gears 32d and 32e are disengaged by the clutch mechanism.

The zoom gear base plate 23 is fixed to the rear end of the fixed barrel 5, and has a shape that forms part of a substantially circular shape surrounding the optical axis of the lens. This zoom gear base plate 2
3, a zoom motor 31 is fixed in such a direction that its drive shaft 31a is perpendicular to the optical axis and along the substantially circular shape. A worm gear 41 is attached to the drive shaft 31a, and a spherical portion 31b is formed at the tip. Further, a thrust bearing 23a projects from above the zoom gear base plate 23 in the optical axis direction, and the spherical portion 31b is supported at one point on the thrust bearing 23a. zoom motor 3
The driving force of 1 is transmitted via the worm gear 41 to the helical gear 32a of the electric zoom reduction system 32, which is made up of a plurality of gears arranged on a substantially circular arc so as to surround the optical axis on the zoom gear base plate 23. At the same time, the driving direction is changed from a direction perpendicular to the optical axis to a direction parallel to the optical axis.

In such a thrust bearing, when the motor rotates in the normal direction (clockwise when viewed from arrow P), the spherical portion 31c provided at the other end of the drive shaft 31a is connected to the thrust bearing in the motor. 31d is supported at one point, so the thrust load that occurs on the contact surface between the radial bearing 31e and the collar 31f during reverse rotation (when rotating counterclockwise as seen from arrow P) is absorbed by the radial bearing 31e and the collar. 31
This is provided to prevent this by providing a clearance C between both f. This also makes it possible to adjust the thrust play of the motor, which also serves to reduce backlash in the lens barrel.

The driving force from the zoom motor is further transmitted to a gear portion 4c provided inside the rear end of the zoom cam ring 4 via gears 32b to 32f. These gears 3
2b to 2f are incorporated between the zoom gear base plate 23 and the second zoom gear base plate 61, which are connected by a plurality of supports, and only one end of the gear 32f that transmits the driving force to the gear portion 4C is connected to the second zoom gear base plate 61. It is fixed to a third zoom gear base plate 36 fixed to.

To be more specific, a bidirectional spring clutch 32g is interposed between the helical gear 32a and the gear 32b. This spring clutch 32g is a helical gear 32a.
When the load on the motor exceeds a predetermined value, for example when the end of the wide-angle or telephoto side is reached during zooming, the spring clutch 32g is rotated integrally with the gear 32b. Prevents excessive current from flowing through the motor due to idling. Gear 32b is transmitted to gear 32e via gears 32c and 32d. A spring clutch 32h as a one-way clutch is interposed between the gear 32e and the gear 32f. This is a member to prevent gear damage due to external force, and gear 32e
and the gear 32f are strongly tightened, and normally rotate as one unit, but only when an excessive external force is applied to the first group moving frame 3, both rotate idly. This can occur, for example, when the camera is dropped or is forcibly pushed in by hand while the first group moving frame 3 is in the extended telephoto state.

Further, a clutch for switching between power zoom and manual zoom is provided within this speed reduction mechanism. This clutch mechanism will be explained in detail. In FIG. 8, the outer cylinder 2
A clutch member 55 is provided, and a clutch interlocking lever 57 that is integrally fixed thereto extends toward the optical axis and engages with an engaging portion 58a provided at an end of the clutch lever 58. ing. A groove 32i is provided at the end of the gear 32d, and a U-shaped end 5 provided at the other end of the clutch lever 58 is inserted into the groove 32i.
8b is engaged. Clutch lever 58 and gear 32d
are movable integrally in the optical axis direction using the support column 59 as a guide shaft.

When the clutch member 55 is operated in the direction M in FIG. 1, the clutch interlock lever 57 integrally displaces the clutch lever 58 in the optical axis direction, disengages the gears 32d and 32e, and performs manual zoom. Make it possible (Fig. 9). By manually operating the first group moving frame 3 in the optical axis direction in this state, manual zooming operation becomes possible. Furthermore, when the clutch member 55 is returned in the direction of P in FIG.
Move in the direction of engagement with e. At this time, gear 32d is 3
2e, even if the motor 31
When rotates, both gears mesh, creating a power zoom state.

Further, in FIG. 5, the electric zoom electrical equipment block 37 includes a flexible substrate 39, ICs 37a to 37e disposed on both sides thereof used for various controls, a ROM 37f storing lens information, a transistor 37g,
It consists of a plurality of electronic components such as a resistor 37i and a resistor 37i. One end of the substrate is fixed to the fixed cylinder 5 by a flexible printed holding plate 38, and the other end is also fixed inside the lens barrel by a portion not shown, and the flexible substrate 39 itself is arranged along the substantially circular shape at right angles to the optical axis. has been done.

The electric focus reduction block 40 consists of a focus gear base plate 22 and electric focus reduction gears 33, 34, and 35 mounted thereon, and transmits driving force to the focus drive ring 12. It is fixed to the fixed cylinder 5 at the illustrated portion. The driving force is transmitted from the camera body into the lens barrel through the autofocus coupler, and then to the focus rotation barrel 8 via the electric focus deceleration block 40 and the focus drive ring 12.

As mentioned above, the zoom gear base plate 23,
The zoom motor 31, the flexible substrate 38, and the focus gear base plate 22 are arranged so as to surround the optical axis on a substantially same plane perpendicular to the optical axis and substantially on the circumference.

Next, the operation of the entire zoom lens barrel configured as described above will be explained. This lens is an AF lens that has a zoom motor inside its body, and power focusing is also possible by switching the power zoom operation ring 1.

Here, a method of power zooming and power focusing operations using the operating ring 1 will be described. An I-shaped groove as shown in FIG. 10 is provided on the outer periphery of the outer cylinder 2, and when the operation ring 1 is operated, a switch 80 installed inside the ring moves within this groove and changes its position accordingly. Outputs the operation signal to the lens control IC. The switch 80 is always energized at the initial position a, so that even if an operation such as zooming is performed, the switch 80 returns to the initial position a. The power zoom operation is performed by turning the operating ring 1 from the initial position a in the circumferential direction.Turning it clockwise brings the telephoto state, and turning it counterclockwise brings it to the wide state. At this time, the switch 80 is provided with a known encoder configuration including a brush and a pattern contact in the groove, and the output signal changes depending on the rotation angle from the initial position a, and the zoom speed becomes variable accordingly. ing. Furthermore, when the operating ring 1 is pulled toward the user, the switch reaches position d. At this position, a signal is output and no AF operation is performed through the coupler. Power focusing is performed by turning the operating ring 1 in the circumferential direction from this position; turning it to the right moves it closer, and turning it to the left moves it closer to infinity. At this time as well, the aforementioned encoder configuration allows the focus speed to be made variable depending on the rotation angle from the focus lock position d.

First, the zooming operation will be explained. When a zooming operation is performed in which the operation ring 1 is rotated in the circumferential direction from the initial position a, the zoom motor 3 disposed inside the lens barrel
1 is driven, and its driving force is transmitted to the zoom cam ring 4 via the zoom reduction system 32. The zoom cam ring 4 has a claw 4d
The movement in the optical axis direction is restricted by the rib 5b of the fixed barrel 5, and only rotation is possible, so when the zoom cam ring 4 rotates, the first group moving frame 3 is moved by the engagement between the claw 4b and the linear rib 3b.
rotates and is extended by the engagement of the helicoids 3a and 2a. Therefore, the first lens group L1 supported by the first group moving frame 3 is extended in the optical axis direction.

On the other hand, due to the rotation of the zoom cam ring 4, the zoom drive ring 6 is moved to the third position passing through the straight groove 4a and the cam groove 5a.
Due to the action of the group guide pin 24, it is rotated and extended in the optical axis direction.

The rotation of the zoom drive ring 6 is controlled by the rotation of the second group moving frame 1.
For 1, the cam groove 6a, the straight escape hole 7b, the straight groove 9
Due to the action of the second group guide pin 26 passing through a, the movement is transmitted in a straight line to the optical axis. The amount of movement of the second group moving frame 11 in the optical axis direction at this time is the cam grooves 5a and 6a.
This will be the synthetic lead amount. Therefore, the second lens group L2 supported by the second group moving frame 11 is extended in the optical axis direction.

On the other hand, the linear cylinder 7 can only rotate with respect to the zoom drive ring 6 by the action of partial ribs 6c and 7d, and can move integrally in the optical axis direction. Further, the linear movement cylinder 7 can move in the optical axis direction by fitting the protrusion 7a with the groove 9c of the third group moving frame 9 to which the linear movement key 10 is attached, but movement in the rotational direction is restricted. has been done. The focus rotating barrel 8 includes the straight moving barrel 7 and the helicoid 7e,
They are helicoidally coupled at 8a, and can only rotate with the third moving group 9 through partial ribs 8b and circumferential grooves 9e, and move together in the optical axis direction.

As described above, when the zoom drive ring 6 is rotated and extended, the amount of movement of the zoom drive ring 6, linear movement barrel 7, focus rotation barrel 8, and third group moving frame 9 in the optical axis direction is the same. As a result, the third group moving frame 9 is moved out in the optical axis direction according to the lead of the cam groove 5a. As a result, the third lens group L3 and the fifth lens group L5 attached to the fifth group lens frame 20 are extended in the optical axis direction. At this time, the rotational movement of the zoom drive ring 6 is caused by the linear movement cylinder 7 to cause the helicoids 7e, 8a to move into the focus rotation cylinder 8.
It is not transmitted as rotation due to the lead.

Further, the fourth group drive ring 13 rotates with respect to the rotation of the zoom drive ring 6 due to the engagement between the fitting portion 6b at the rear end and the support portion 13a, and also rotates with respect to the third group moving frame 9. It is possible to move integrally in the direction of the optical axis. Further, the fourth group guide 18 is extended in the optical axis direction via the fourth group guide pin 28 due to the action of the cam groove 13b and the straight groove 9b. Along with this extension, the fourth lens group L4 is extended together with the fourth group moving frame 17. The amount of movement of the fourth group moving frame 17 in the optical axis direction at this time is the combined lead of the cam grooves 5a and 13b.

Next, the focusing operation will be described. When an AF operation is performed by operating a switch on the camera body (not shown) or a manual focusing operation is performed by rotating the operation ring 1 in the circumferential direction from the focus lock position d, the driving force of the motor inside the body is transferred to the lens barrel through the coupler 30. will be communicated to. This driving force rotates the focus drive ring 12 via the electric focus reduction gears 33, 34, and 35. This rotation is transmitted to the focus rotating cylinder 8 by the engaging arm 12a via the straight groove 8d. Both straight grooves 8
d and the engaging arm 12a each have sufficient length,
Even if the focus rotary barrel 8 is extended in the optical axis direction integrally with the third group moving frame 9 due to a zooming operation, the engagement will not be disengaged.

As the focus rotation barrel 8 rotates, it is driven in the optical axis direction by the action of the helicoids 7e and 8a. The third group moving frame 9 can only rotate with respect to the focus rotating barrel 8, and is guided in the optical axis direction by the fitting between the fitting portion 10a and the straight groove 5c, and moves integrally therewith. As the third group moving frame 9 is extended, the third lens group L3 and the fifth lens group L5 are extended. At this time, the fourth lens group L4 supported by the fourth group moving frame 17 is extended integrally with the third group moving frame 9 because the fourth group driving ring 13 does not rotate. At this time, the second lens group L2 does not move due to the action of the rectilinear groove 9a.

Next, a description will be given of means for adjusting eccentricity, etc. of the lens group after lens assembly is completed in the lens barrel configured as described above.

Due to the optical design of the zoom lens of this embodiment, the deviation and eccentricity of each lens from the optical axis have a large effect on the performance of the entire lens. In particular, errors in the air spacing between the third and fourth groups and eccentricity of the optical axis of the fourth group, which includes an aspherical lens, have a large effect on the image plane, so these should be adjusted after lens assembly is completed. It has an adjustment mechanism for

First, the air gap between the third group and the fourth group is adjusted by changing the relative positions of the third group moving frame 9 and the fourth group moving frame 13 in the optical axis direction.

That is, when the lenses of the above embodiments have been assembled, the performance of each assembled lens is measured, and the third step is carried out to obtain the required lens performance.
Determine the amount of correction for the distance between the groups and the fourth group. Next, the fourth group drive ring holder 14 is removed from the third group moving ring 9, and the fourth group drive ring 13 is pulled out toward the film surface side. In this state, the 3rd-4th group interval adjustment washer 15 is replaced. By replacing this washer, the relative position of the fourth group moving ring 13 with respect to the third group moving frame 9 in the optical axis direction can be adjusted. This third
- The 4th group spacing adjustment washer 15 is available in several thicknesses, and the 3rd and 4th groups are adjusted according to the determined correction amount.
Select the one that optimizes the distance between lens groups. After replacing the washer, the fourth group moving ring 13 is returned to the position where it contacts the replaced third-fourth group spacing adjustment washer 15, and the fourth group moving ring retainer 14 is tightened again. At this time, the optical design is such that the distance between the fourth group and the fifth group, which changes in conjunction with the adjustment, does not have a large effect on lens performance.

Next, the eccentric adjustment with respect to the optical axis of the fourth group is as follows.
This is done by rotating the fourth lens group using a jig and searching for a position where the optical performance is balanced.

That is, after adjusting the air gap between the third and fourth groups, a jig with two claws is inserted from the rear of the lens barrel through a notch provided in the fifth group lens frame 20. Then, the jig is engaged with a groove provided at the rear end of the fourth group moving frame 17, and the jig is rotated. As this jig rotates, the fifth group lens frame 20 held by the fifth group lens frame holding spring 21 also rotates at the same time, but the optical design is such that the rotation of the fifth group lens does not affect lens performance. has been done. After determining the optimal position by rotating the jig, remove the jig from the rear end of the lens.

[0053] Furthermore, when configured as in this embodiment,
Due to the increase in the number of parts, the fourth group moving frame 17 and the fourth
Backlash occurs between the group movement frame guides 18. This backlash inevitably occurs depending on the processing precision of the parts, but depending on the amount of play, it can become so large that the adjustment of the lens frame described above is wasted. Therefore, this embodiment has a mechanism to remove this backlash. (Refer to FIGS. 1 and 6) First, the backlash in the optical axis direction between the fourth group moving frame 17 and the fourth group moving frame guide 18 is eliminated by a ring-shaped optical axis biasing spring 62 that is undulated in a waveform in the optical axis direction. It is biased by This optical axis direction biasing spring 62 is fitted on the front end side of the optical axis between the fourth group moving frame 17 and the fourth group moving frame guide 18 when assembling the lens.

Further, the radial backlash between the fourth group moving frame 17 and the fourth group moving frame guide 18 is offset in the radial direction by a U-shaped radial biasing spring 63. this,
The radial bias spring 63 is inclined at 90 degrees with respect to the optical axis between the fourth group moving frame guide 18 and the third group moving frame 9 so that the bulging portion faces radially outward. Two are inserted.

[0055]

Effects of the Invention In the above-described embodiment, since the plurality of lens movement frames housed inside the first lens movement frame are decentered together with the first lens movement frame, each lens movement frame moves in a different direction. There is no eccentricity, and the overall amount of eccentricity can be minimized, and the influence on the film surface can be minimized.

[0056]Also, despite having the above-mentioned configuration, the present invention has the effect that focusing can be performed using some of the plurality of lens movement frames.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a zoom lens barrel showing an embodiment of the present invention.

FIG. 2 is a partial sectional view of the zoom lens barrel.

FIG. 3 is a partial cross-sectional view of the zoom lens barrel.

FIG. 4 is a perspective view of the main components of the zoom lens barrel.

FIG. 5 is a diagram showing the arrangement of members at the rear of the zoom lens barrel.

FIG. 6 is a sectional view of the zoom lens barrel.

FIG. 7 is a partially enlarged view of FIG. 5;

8 is a diagram showing a power zoom state in the AA cross section of FIG. 5. FIG.

9 is a diagram showing a manual zoom state in the AA cross section of FIG. 5. FIG.

FIG. 10 is a diagram showing grooves provided on the outer periphery of the zoom lens barrel.

[Explanation of symbols]

L1 to L5: Zooming lens group L3 to L5: Focusing lens group 9: First lens moving frame

Claims (1)

[Claims] Claims: 1. A combination of lens groups, which comprises a plurality of lens groups disposed on the same optical axis and a plurality of lens movement frames for supporting each of the plurality of lens groups, and is driven for focusing. In a varifocal lens barrel whose focal range changes in conjunction with a change in focal length due to a zoom operation, the plurality of lens movement frames include at least a first
It consists of a lens moving frame and a plurality of lens moving frames housed inside the first lens moving frame, and as the first lens moving frame moves in the optical axis direction, all the lens moving frames move independently. A zoom operation is performed by moving in the optical axis direction, and a focusing operation is performed by moving at least a part of the lens movement frame housed inside the first lens movement frame in the optical axis direction. A varifocal lens barrel featuring