JP2607866B2 - Zoom lens barrel - Google Patents

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 zoom lens barrel having means for correcting aberration according to an object point distance.

[0002]

2. Description of the Related Art In a photographing lens barrel, an optical system is designed on the basis of a certain point (usually infinity) which is generally focused, and aberration increases as the distance between object points changes from the reference. It has the tendency. For this reason, in a normal single focus lens barrel, a part of the lens system is moved based on a focusing operation to correct an aberration according to an object point distance.

Conventionally, in a zoom lens barrel, aberrations are corrected in accordance with an object point distance because of a relatively small aperture of the zoom lens barrel and a complicated frame structure itself for zooming. Has not been performed, and the deterioration of the optical characteristics due to the increase in aberration has been accepted. However, in order to provide a high-performance zoom lens barrel having a large aperture and a small aberration, the present applicant first performed focusing. In conjunction with the operation of the focusing lens system during operation, a zoom lens barrel that moves a part of the lens system other than the focusing lens system and corrects aberration according to the object distance It was proposed (Japanese Patent Application No. 58-116490).

That is, as shown in FIG. 11, a zoom lens barrel previously proposed by the present applicant has a cylindrical fixed frame 111 attached to a camera body at a rear end mount portion.
A zoom ring 112 rotatably fitted to the outer periphery of the fixed frame 111; a front group holding frame 113 fitted in the distal end of the fixed frame 111; A focus ring 114 for supporting the front lens group I, and a rear group for supporting the rear lens group consisting of the second lens group II and the third lens group III, which is fitted in the middle of the fixed frame 111. The holding frame 115 is fitted in the rear portion of the rear group holding frame 115, and the third group lens III
The third group holding frame 116 for supporting the lens and the focus ring 1
An interlocking mechanism 117 for integrally connecting the rotation unit 14 and the third group holding frame 116 in the rotation direction constitutes a main body.

The zoom ring 112 is fixed to the fixed frame 1.
11 is fitted so that it can rotate but cannot move back and forth in the direction of the optical axis. , Two cam elongated holes 112a and 112b are formed. The cam pins set in the front group holding frame 113 and the rear group holding frame 115 in the cam long holes 112a and 112b through the optical axis direction guide long holes 111a and 111b formed in the fixed frame 111. 118 and 119 are fitted respectively.

The focus ring 114 is formed of a double cylinder in which a large-diameter cylindrical portion and a small-diameter cylindrical portion are concentrically integrated by a front wall, and is engraved on the outer peripheral surface of the small-diameter cylindrical portion. The helicoid screw is screwed to a helicoid screw engraved on the inner peripheral surface of the front group holding frame 113 and disposed.

[0007] The large-diameter cylindrical portion is connected to the zoom ring 11.
The front portion 2 is covered from the outer peripheral side to form an operating section for focusing, and the front group lens I is fitted and held on the inner peripheral surface side of the small diameter cylindrical portion.

Further, one end of a drive-side connecting member 117a forming the interlocking mechanism 117 is fixed to a rear end surface of the small-diameter cylindrical portion of the focus ring 114 by means not shown. As shown in FIG. 13, the drive-side connecting member 117a is formed of a band-shaped plate having a fork-like end at the other end, and a driven-side connecting member 117b is provided in an intermediate long groove of the fork-like portion. A connection pin 117c crimped to one end of the connector is inserted. Driven side connecting member 117b
Is formed of a band-shaped plate, and the other end is formed in an arc-shaped play elongated hole 115 formed in an intermediate wall of the rear group holding frame 115.
a, and is fixed to the head of a cam pin 120 which is planted in the third group holding frame 116 and penetrates the long cam hole 115b formed in the small-diameter cylindrical portion of the rear group holding frame 115 by means not shown. ing.

The rear group holding frame 115 is formed of a double cylinder in which a large-diameter cylindrical portion and a small-diameter cylindrical portion are integrated by an intermediate wall, and the cam pin 119 is provided on the outer peripheral surface of the large-diameter cylindrical portion. It is planted in the middle of
The group lens II is fitted and held.

A third lens group II is provided on the rear side of the small-diameter cylindrical portion.
A third group holding frame 116 for fitting and holding I is fitted. The long cam hole 11 of the rear group holding frame 115 into which the cam pins 120 planted on the outer peripheral surface of the third group holding frame 116 fit.
As shown in FIG. 14, 5b has a curved shape that is gently inclined with respect to the circumferential direction, and moves the third lens group III along the same cam elongated hole 115b so as to correspond to the object point distance. It serves to correct the aberration.

Next, the operation of the zoom lens barrel will be described below. First, when the zoom ring 112 is rotated, the cam pins 118 and 119 are guided by the guide elongated holes 111a and 111b so that the cam pins 118 and 119 move toward each other in the optical axis direction due to the action of the cam elongated holes 112a and 112b when the clockwise rotation is viewed from the front. Go to Thereby, the front lens group I
And the rear group lenses II and III reduce the distance between them, and the focal length of the zoom lens barrel increases.

When the zoom ring 112 is turned left when viewed from the front, the cam pins 118 and 119 are moved by the action of the cam slots 112a and 112b.
While being guided by 11b, they move away from each other in the optical axis direction. Thereby, the front lens group I and the rear lens group II, III
Increases the distance between the two, and the focal length of the zoom lens barrel decreases. Therefore, when the zoom ring 112 is rotated, zooming is performed.

On the other hand, when the focus ring 114 is rotated, the focus ring 114 is rotated by the helicoid screw 114a,
By the action of 113a, when turning clockwise when viewed from the front, for example, it rotates while retracting in the optical axis direction. For this reason, the front lens group I is retracted, and the object distance in the focused state gradually increases.

At the same time, the focus ring 114
, The driving-side connecting member 117a is rotated, and the driven-side connecting member 117b is also rotated via the connecting pin 117c. Therefore, the cam pin 120 is inserted into the long cam hole 115b.
And the third lens unit III moves backward in the optical axis direction while rotating. Due to the movement of the third lens group III, the aberration caused by the retraction of the front lens group I is corrected.

When the focus ring 114 is turned leftward when viewed from the front, the focus ring 114 rotates, for example, while moving forward in the optical axis direction. For this reason, the front lens group I is extended, and the object distance in the focused state gradually becomes short.

At the same time, the rotation of the focus ring 114 causes the drive side connecting member 117a, the connecting pin 117c,
The driven side connecting member 117b rotates together with the cam pin 1
20 moves in the cam long hole 115b and the third lens group II
I advances in the optical axis direction while rotating. Therefore, the aberration caused by the extension of the front lens group I is caused by the third lens group.
Corrected by III movement.

[0017]

However, in the case of the zoom lens barrel according to the means disclosed in the above-mentioned Japanese Patent Application No. 58-116490, even when the lens group is on the wide angle side due to zooming, it is not on the telephoto side. In some cases, the aberration correction amount is uniform according to the rotation of the focus ring 114, and thus there is a problem that accurate aberration correction cannot be performed.

That is, since the degree of aberration differs depending on the change in the focal length, it is necessary to change the amount of floating according to the focal length to change the amount of aberration correction. There is a problem that the float amount cannot be changed according to the distance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens barrel which solves the above-mentioned conventional problems, makes the amount of float accompanying focusing different according to the focal length, and can perform more accurate aberration correction. It is in.

[0020]

SUMMARY OF THE INVENTION A zoom lens barrel according to the present invention holds a lens group that contributes to a focusing operation, and a lens group holding frame that performs only an advancing / retreating operation in an optical axis direction at the time of a variable power operation. A rotating frame rotatably provided around the optical axis with respect to the frame, a cam groove and a cam follower for cam-connecting the lens group holding frame and the rotating frame, and the length of the cam groove is within the cam groove. The moving amount of the cam follower is set to be larger than the moving amount of the cam follower, and the moving area of the cam follower in the cam groove is changed in accordance with the zooming operation. A cam means for changing the amount of movement of the lens group holding frame around the optical axis, when changing the moving area of the cam follower in the cam groove by the variable power operation, the focus of the optical system is changed. Is infinitely distal When in is characterized in that it does not advance and retract the lens group holding frame in the optical axis direction by not changing the position of the optical axis direction of the cam follower.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. First, prior to description of a specific embodiment of the present invention, an outline of the operation of the zoom lens barrel according to the embodiment of the present invention will be described below.

The zoom lens barrel according to the embodiment of the present invention, which includes the front lens group I and the second and third lens groups II and III constituting the rear lens group, is suitable for an object point distance at infinity. When zooming is performed from the telephoto side to the wide-angle side in the focused state, as shown by a solid line in FIG.
Moves forward, and the second lens group II and the third lens group III integrally retract.

In the case of focusing, the front lens group I is moved forward as shown by a broken line in FIG. 5, but at this time, the third lens group III is drawn by a broken line for aberration correction. It is fed forward as shown.

With respect to the extension amount L of the front group lens I, the amount by which the third group lens III is extended for aberration correction, that is,
The float amount 1 changes according to the focal length so as to be small on the telephoto side and large on the wide angle side.

That is, the float amount l of the third lens unit (float lens) III with respect to the extension amount L of the front lens unit I
In FIG. 6, as shown by float lens movement amount curves T, S, W having different inclinations, respectively, telephoto, standard,
Different for each wide-angle condition. At other focal lengths, the float amount l of the third lens group III changes along the float lens movement amount curve having an inclination corresponding to each focal length between the float lens movement amount curves T, S, and W. Of course.

A float cam is used to change the float amount 1 of the third lens group III according to the focal length. This float cam is formed by an approximate cam curve that continuously connects the float lens movement amount curves T, S, and W. This approximate cam curve will be described with reference to FIG. 7. The float lens movement amount curves T, S, and W are such that the float amount l is 11, 11, 2, 13 (l1>) with respect to the entire extension amount L of the front lens group I. l2> l3). To form an approximate cam curve from these curves, first, the end point of the float lens movement amount curve W in the wide-angle state (the front group lens I is extended to the maximum). Draws a float movement amount curve S in a standard state from a position very close to the object point distance, or a float movement amount in a telephoto state from an end point of the curve S or near the end point of the curve S. Draw a quantity curve T. An approximate cam curve l 'indicated by a smooth two-dot chain line is created based on the curve having the inflection point thus formed. Here, the error Δl between the approximate cam curve l ′ and each of the float lens movement amount curves T, S, W becomes so small as to be negligible.

Further, as shown in FIG. 8, the approximate cam curve may be created based on each float lens movement amount curve T, S, W partially wrapped.

That is, the float lens movement curve S in the standard state is drawn from the middle of the float lens movement curve W in the wide-angle state, and the float lens movement curve T in the telephoto state is drawn from the middle of the curve S. The approximate cam curve l ″ is drawn such that the error Δl is negligibly small for each of the curves T, S, W. The approximate cam curve l ″ thus created is the approximate cam curve l ″ shown in FIG. The length can be shortened as compared with the curve l ′.

Next, specific embodiments of the present invention will be described below. FIG. 1 is a longitudinal sectional view of an upper half of a zoom lens barrel according to a first embodiment of the present invention.
FIG. 2 is an exploded perspective view of a main part of the zoom lens barrel.

The zoom lens barrel according to the first embodiment includes a mount ring 2 fixed to a lens mount 1 attached to a camera body, a cylindrical fixed frame 3 fixed to the mount ring 2, and an outer periphery. A diaphragm ring 5 near the rear end
Are rotatably fitted to each other, and a zoom support frame 4 fixed to the outer periphery of the fixed frame 3 is rotatably fitted to the middle of the outer periphery of the zoom support frame 4 in a state where movement in the optical axis direction is restricted. A zoom cam frame 7 fitted with a pin 8 connected rotatably to the inner periphery of the zoom support frame 4 and connected to the zoom ring 6, and an inner periphery of the zoom cam frame 7; A front group moving frame 9 fitted between the outer frame and the fixed frame 3;
A helicoid frame 10 which is helicoid-coupled at the front end of the outer periphery of the front group moving frame 9; and a focus ring fixed to the helicoid frame 10 and arranged from the middle to the front end of the outer periphery of the zoom support frame 4. And a front group holding frame 12 which is a lens group holding frame screwed to the front ends of the helicoid frame 10 and the focus ring 11 to support the front group lens I.
A rectilinear frame 13 rotatably fitted to the rear end of the outer periphery of the front group holding frame 12, a rotation conversion frame 14 rotatably fitted to the outer periphery of the rectilinear frame 13, A rear group holding frame 15 which is a lens group holding frame which is fitted in the middle of the inner periphery of the fixed frame 3 and supports a rear group lens including the second group lens II and the third group lens III; The third lens unit (float lens) II is fitted to the rear part of the outer periphery of the frame 15.
A float frame 18 supporting the holding frame 16 and the flare stop mechanism 17 of I, a rotating frame 19 rotatably fitted on the outer periphery of the float frame 18, and a position in sliding contact with the outer periphery of the rotating frame 19. A connecting member 21 for integrally connecting the fixed cam frame 20 fixed to the rear portion of the fixed frame 3 with the rotation conversion frame 14 and the float frame 18 in the rotation direction;
22 and the like constitute the subject.

The zoom cam frame 7 has a front group cam groove 7a.
And a rear group cam groove 7b are formed. A cam pin 23 implanted in the front group moving frame 9 is fitted in the front group cam groove 7a, and a rear group cam groove 7b is formed in the rear group cam groove 7b. A cam pin 24 implanted in the holding frame 15 is fitted.

The front group moving frame 9 is formed with a rectilinear groove 9b in which the pins 25 implanted in the fixed frame 3 are fitted in the optical axis direction. Therefore, when the zoom cam frame 7 is rotated by operating the zoom ring 6, the front group moving frame 9 moves in the optical axis direction according to the shape of the cam groove 7a in which the cam pin 23 is fitted.

The cam pins 24 are fitted into the straight grooves 3a formed in the optical axis direction in the fixed frame 3 so as not to contact the front group moving frame 9, and therefore, the zoom cam frame 7 When rotated by the operation of the ring 6, the rear group holding frame 15 moves in the optical axis direction according to the shape of the cam groove 7b in which the cam pin 24 is fitted.

The helicoid screw 9 of the front group moving frame 9 screwed with the helicoid screw 10a of the helicoid frame 10 described above.
A notch 9c in the optical axis direction for inserting the rotation stopper 26 is formed at the front end portion of the front end portion where a is formed.

The front group holding frame 12 screwed at the front end to the helicoid frame 10 and the focus ring 11 has a middle space between the front group moving frame 9 and the inner wall of the fixed frame 3. A relatively small-diameter cylindrical portion is formed from the rear to the rear, and a rectilinear frame 13 is rotatably fitted to the cylindrical portion. The rectilinear frame 13 has an inner periphery formed with a small diameter at the rear end, and the small diameter portion is fitted to a step near the rear end of the front group holding frame 12 to restrict movement in the optical axis direction. I have. A stop ring 27 is screwed into the rear end of the front group holding frame 12 so that the straight frame 13 does not fall out of the front group holding frame 12.

The rectilinear frame 13 has a rectilinear groove 13 in the optical axis direction.
a (see FIG. 2), and the lower end of the inner claw 26b of the rotation stopper 26 is fitted into the rectilinear groove 13a. Rotation stop 2
Numeral 6 is a cutout of a part of an elastic metal ring, and an outer claw 26a and an inner claw 26b are formed at a portion facing the cutout at an angle of 180 ° (degree). Since the inner claw 26b is fitted in the rectilinear groove 13a, the rotation stop 26
And the rectilinear frame 13 are relatively movable in the optical axis direction, but are immovable in the rotational direction and are integrated. This rotation stop 2
The outer pawl 26a of No. 6 is fitted in the notch 9c of the front group moving frame 9, so that the rotation stopper 26 and the front group moving frame 9 are integrated in the rotation direction.

Further, the outer stopper 26a is inserted into a ring groove (not shown) formed on the inner wall of the front group moving frame 9 in a state where the outer claw 26a is fitted in the notch 9c. The front group moving frame 9 and the rotation stopper 26 are also integrated in the optical axis direction.

That is, the outer diameter of the rotation stopper 26 is reduced by applying a force to the ring portion from the outer periphery.
In this state, when the outer pawl 26a is aligned with the notch 9c and the rotation stopper 26 is inserted from the front end of the front group moving frame 9, the rotation stopper 26 reaches the position of the ring groove on the inner wall of the front group moving frame 9. At this time, the outer periphery is fitted into the ring groove by the restoring elastic force, and is thereby integrated with the front group moving frame 9 in the rotation direction and the optical axis direction.

The rotation conversion frame 14 has a front end portion projecting obliquely outward and an outer edge portion 14a having an inward projection formed on a part of the front group moving frame 9 and the rotation stopper 2.
6 is rotatably held between the first and second motors. The rotary conversion frame 14 is formed with a rotary cam groove 14b inclined with respect to the optical axis direction (see FIG. 2).
4b, a pin 28 planted on the outer periphery of the rear portion of the rectilinear frame 13 is provided.
Is inserted.

A strip-shaped connecting member 21 extending rearward in the optical axis direction is fixed to the outer periphery of the rotation conversion frame 14. The connecting member 21 is attached to a rising portion 18 a at the front end of the float frame 18. It is slidably engaged with the fork-shaped portion of the connecting member 22 which is fixed and extends forward in the optical axis direction.

The rear group holding frame 15 is composed of a large-diameter cylindrical portion and a small-diameter cylindrical portion. The large-diameter cylindrical portion is slidably fitted to the fixed frame 3, and the float frame 18 rotates on the small-diameter cylindrical portion. Fits freely. For this reason, the connecting member 22 integrated with the float frame 18 extends forward through the notch 15a formed in the large-diameter cylindrical portion so as not to be hindered by the rear group holding frame 15. A cam pin 29 is implanted in the small-diameter cylindrical portion of the rear group holding frame 15, and a cam pin 30 is mounted on the float frame 18.
And a notch window 18b for allowing the cam pin 29 to pass therethrough is provided.

The rotary frame 19 is formed with two float cam grooves 19a and 19b having the same shape at the same position along the optical axis direction. The cam grooves 29a and 19b are respectively formed in the cam grooves 29a and 19b. 30 is inserted,
A first float cam mechanism as a cam means is formed by the cam pin 29 and the float cam groove 19a.
And the float cam groove 19b, a second float cam mechanism as a cam means is formed. The two float cam grooves 19a and 19b are inclined forward from one end in the clockwise direction to the other end in the counterclockwise direction, and are formed by the approximate cam curve l ″ shown in FIG. It is.

Then, in a state where the object point is focused at infinity, the position of the first cam pin 29 with respect to the first float cam groove 19a and the second cam pin 30 with respect to the second float cam groove 19b. Are relatively equal to each other (see FIG. 3).

A guide pin 31 as a guide member is implanted in the rotary frame 19.
Are fitted into the inclined cam grooves 20a of the fixed cam frame 20 slidably in contact with the upper outer periphery of the rotating frame 19, and constitute cam means.

The inclined cam groove 20a is a cam groove which is inclined at a relatively gentle angle with respect to the optical axis direction. Therefore, when the rotating frame 19 moves forward and backward by receiving a force in the optical axis direction, the guide pin 31 is moved. Although it also moves in the rotational direction due to the engagement with the inclined cam groove 20a, when receiving a force in the rotational direction, the rotation is prevented.

The operation of the thus configured zoom lens barrel according to the first embodiment will be described below.

The state shown in FIG. 1 is a state in which zooming is performed on the telephoto side and focusing is performed at an object point distance of infinity. In this state, the focus ring 11 is viewed from the front of the zoom lens barrel. When the front group moving frame 9 is rotated in the clockwise direction, the front group moving frame 9 is prevented from rotating by the pin 25 being fitted into the rectilinear groove 9b, so that the helicoid frame 10 and the front group holding frame 12 integrated with the focus ring 11 are formed. Is fed out in the optical axis direction while rotating by the action of the helicoid screws 9a and 10a.

Then, the rectilinear frame 13 fitted to the front group holding frame 12 is prevented from rotating by the rotation stopper 26 fixed to the front group moving frame 9, so that the rectilinear frame 13 rotates. No, that is, it relatively rotates with respect to the front group holding frame 12, but does not rotate with respect to the fixed frame 3,
It is moved straight forward in the optical axis direction together with the front group holding frame 12 and is fed out. When the rectilinear frame 13 is fed straight in the optical axis direction, the rotation conversion frame 14 rotates counterclockwise by the action of the pin 28 integrated with the rectilinear frame 13 and the rotating cam groove 14b on the rotation conversion frame 14. The angle at which the rotation conversion frame 14 rotates can be appropriately set according to the degree of the inclination angle of the rotary cam groove 14b.

That is, as shown in FIG. 4, when the pin 28 moves the entire extension amount L from the infinity position to the close position of the front lens group I in the optical axis direction along the rotary cam groove 14b, this rotation Since the conversion frame 14 and the connecting member 21 rotate by an angle θ1 equal to the component of the rotation direction of the rotary cam groove 14b, the rotation angle θ1 is set by appropriately setting the inclination angle of the rotary cam groove 14b. It can be set arbitrarily, for example, it can be set smaller than the rotation angle of the focus ring 11.

When the rotation conversion frame 14 rotates counterclockwise, the float frame 18 also rotates by the same angle in the same direction as the rotation direction of the rotation conversion frame 14 via the connecting members 21 and 22. At this time, since the rear group holding frame 15 is prevented from rotating by the pin 25 being fitted into the rectilinear groove 3 a of the fixed frame 3, the float frame 18 is moved to the rear group holding frame 15.
However, the notch window 18b of the float frame 18 and the notch portion 15a of the rear group holding frame 15 are formed in sufficiently large shapes so that the rotation is not restricted by the pin 29 and the connecting member 22, respectively. I have.

Since the guide pin 31 is fitted in the inclined cam groove 20a of the fixed cam frame 20, the rotation frame 19 is prevented from moving in the rotation direction unless it moves in the optical axis direction. Even if the frame 18 rotates, the rotating frame 19
Does not rotate.

That is, when the focus ring 11 is rotated, a rotation amount proportional to the amount of extension of the front group holding frame 12 is transmitted to the float frame 18 through the connecting members 21 and 22, and the float frame 18 rotates. At this time, the rear group holding frame 1
5 and the rotating frame 19 are stationary.

In the telephoto state, the rear group holding frame 15
Is extended most forward. At this time, the positional relationship of the rotary frame 19 with respect to the rear group holding frame 15 is substantially the center of the cam groove 19a of the rotary frame 19 as shown in FIG. The cam pins 29 on the frame 15 are located.

In this telephoto state, when focusing on an object point distance of infinity, the positional relationship of the float frame 18 with respect to the rotating frame 19 is as shown in FIG. The float frame 1 is located substantially at the center of the cam groove 19b of the rotating frame 19.
The cam pin 30 on 8 is located. That is, the position of the cam pin 29 with respect to the float cam groove 19a and the position of the cam pin 30 with respect to the float cam groove 19b are in the same relationship.

Then, when the float frame 18 rotates counterclockwise by focusing from such a state, the cam pin 30 moves counterclockwise in the float cam groove 19b, and is indicated by a two-dot chain line in FIG. Closest position 30a shown
Head for. When the cam pin 30 moves counterclockwise in the float cam groove 19b toward the close position 30A, the float frame 18 is extended forward while rotating counterclockwise.

That is, the front lens group I is extended forward by the rotation operation of the focus ring 11, and as the object distance in the focused state becomes gradually shorter, the float frame 18 is moved.
The third lens unit III is advanced in the optical axis direction while rotating. In this telephoto state, when the float frame 18 rotates the angle θ1 from the infinity position to the close position, the float frame 18 advances by the float amount 11. In this way, the aberration caused by the extension of the front lens group I is corrected by the movement of the third lens group III.

On the other hand, when the zoom ring 6 is rotated, the zoom cam frame 7 integrated with the zoom ring 6 also rotates, and the front group moving frame 9 and the cam pins 24 move in the optical axis direction by the action of the cam grooves 7a and 7b. They move in directions that are close to each other or separated. For example, when the zoom ring 6 is rotated toward the wide-angle state while focusing on the object point distance at infinity shown in FIG. 1 and in the telephoto state, the front group moving frame 9 moves forward in the optical axis direction, and the cam pin The rear group holding frame 15 integrated with the cam pin 24 and the cam pin 24 retreats. When the front group moving frame 9 moves forward, the helicoid frame 10, the focus ring 11, the front group holding frame 12, the rectilinear frame 13, the rotation stopper 26, the rotation conversion frame 14, and the connecting member 21 are integrally formed with the front group moving frame 9. Advance.

When the rear group holding frame 15 retreats, the cam pin 29 integrated with the rear group holding frame 15 pushes the rotating frame 19 backward in the optical axis direction via the cam groove 19a. Then, the float frame 18 similarly moves rearward via the cam groove 19b and the cam pin 30.

The guide pins 31 on the rotating frame 19
Are fitted in the inclined cam grooves 20a of the fixed cam frame 20, so that when the rotating frame 19 is pushed rearward, the guide pins 3
1 is guided in the cam groove 20a, so that the rotating frame 19 rotates counterclockwise while moving backward.

When the rotating frame 19 rotates counterclockwise, the cam groove 19a is guided along the pin 29 which is immovable in the rotating direction. Advances slightly relative to 15. Then, since the cam grooves 19a and 19b have the same shape, as long as the float frame 18 does not rotate, the cam pin 30 moves with the rotation of the rotary frame 19 in the counterclockwise direction. It moves on the float cam groove 19b while maintaining the same positional relationship as the position.

This will be described with reference to FIGS. 3A to 3C. When the focus ring 11 is at the infinity position, in the telephoto state, as shown in FIG. At the approximate center of 19a,
The cam pin 30 is also located substantially at the center of the float cam groove 19b, but as zooming is performed on the wide angle side, the rotating frame 1 is moved relative to the cam pins 29, 30 that are stationary in the rotation direction.
3 rotates counterclockwise by an angle θa in the standard state shown in FIG. 3B, and rotates by an angle θ in the wide-angle state shown in FIG.
Rotate by b.

That is, when zooming is performed from the telephoto side to the wide-angle side, the cam pins 29 and 30 move clockwise with respect to the float cam grooves 19a and 19b, respectively, and each float lens on the approximate cam curve l " The movement amount curve T,
It reaches a position starting from a position at infinity on a region corresponding to S and W. In this case, the rotation angle θb of the rotating frame 19 from the telephoto state to the wide-angle state is equal to the floating cam groove 19.
The angle θ1 is equal to one-half the angle θ1 between the two ends of the a and 19b, and is equal to the rotation angle θ1 of the rotation conversion frame 14 and the float frame 18 that rotate by focusing from infinity to the closest.

As described above, even if zooming is performed from the telephoto state to the standard state, and further to the wide-angle state, the cam pin 30 with respect to the float cam groove 19b remains in focus at the infinite object distance. Is coincident with the position of the cam pin 29 with respect to the float cam groove 19a. Here, for example, when focusing is performed on the closest object point distance in the standard state, the float frame 18 is moved counterclockwise by the focusing operation described above. At this time, as shown in FIG. 3B, the cam pin 30 moves in the float cam groove 19b in the counterclockwise direction and also moves by the float amount l2 in the optical axis direction, as shown in FIG. 30B. The float cam groove 19b is formed by the approximate cam curve l ″ shown in FIG.
Is smaller than the float amount 11 in the telephoto state.

If the float frame 18 is rotated counterclockwise by an angle θ1 when focusing on an object point distance from infinity to a close object point in the wide angle state, the cam pin 30
Moves in the float cam groove 19b in a counterclockwise direction as shown in FIG.
It moves by 3 and reaches position 30C. This float amount 13
Is smaller than the float amount 12 in the standard state.

Even when the focus ring 11 is rotated, the positional relationship between the cam pin 29 and the float cam groove 19a does not change, and the positional relationship according to each focal length is changed as shown in FIGS. And, as described above, the cam pin 30
Only the position corresponding to the positional relationship between the cam pin 29 and the float cam groove 19a is used as a base point, and the float cam groove 19b
It moves up from infinity to the nearest. Therefore, in the state in which the object point is focused at infinity, the float frame 18 does not move in the optical axis direction even when zooming is performed. However, when focusing is performed, the float frame 18 corresponds to each focal length. The float frame 18 moves by the float amount, and the aberration is corrected accurately.

FIGS. 9 and 10 are views showing the main parts of a zoom lens barrel according to a second embodiment of the present invention.
FIG. 10 is a longitudinal sectional view of an upper half of a main part of the zoom lens barrel, and FIG. 10 is an exploded perspective view of a main part of the zoom lens barrel.

Note that in the second embodiment,
Since the configuration is basically the same as that of the above-described first embodiment, portions not shown in FIGS. 9 and 10 are described in the above-described first embodiment. Referring to FIGS. 1 and 2, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIGS. 9 and 10, a rear group holding frame 65 is slidably fitted on the inner periphery of the fixed frame 3, and the cam pins 24 are implanted in its large diameter cylindrical portion. Notch 6 so as not to obstruct the connecting member 22.
5a are formed, and a float cam groove 6 is formed in the small diameter cylindrical portion at the rear.
5b are formed and a cutout window 65c is formed. A holding frame 64 that supports the second group lens II is directly attached to the rear group holding frame 65 by screwing.

A rotating frame 69 is rotatably fitted to the inner periphery of the small-diameter cylindrical portion of the rear group holding frame 65, and a float frame 68 is rotatably fitted to the outer periphery. On the outer periphery of the rotary frame 69, two cam pins 79, 80 are implanted at the same position along the optical axis direction and separated by a fixed rotation angle, and these pins 79, 80 are respectively fitted to the float cam grooves 65b. ,
It is fitted in the cutout window 65c.

The float frame 68 has a front end rising portion 68a.
The floating frame 68 has a float cam groove 68b and a notch window 68c.
Are formed. And, this float cam groove 68b
A cam pin 80 penetrating through the cutout window 65c is fitted into the hole.

Further, a guide member 81 formed by bending a metal plate is fixed to the rotating frame 69, and a rising front end portion 81a of the guide member 81 penetrates the cutout window 68c to secure the fixed cam frame 70. Into the inclined cam groove 70a, and constitute cam means.

In the zoom lens barrel according to the second embodiment, a first float cam mechanism is formed by the cam pin 79 and the float cam groove 65b.
And the float cam groove 68b form a second float cam mechanism.

In the two float cam mechanisms, the relationship between the cam pin and the float cam groove is reversed as compared with the two float cam mechanisms in the first embodiment. Therefore, the float cam grooves 65b and 68b
The float cam groove 1 according to the first embodiment.
Similar to 9a and 19b, it is formed by the approximate cam curve l ″ shown in FIG. 8, but is formed by rotating the float cam grooves 19a and 19b by an angle of 180 ° (degrees) and reversing the vertical position. It has been.

Next, the operation of the zoom lens barrel according to the second embodiment will be described below.

First, when focusing is performed, as described in the first embodiment, the rotational movement is transmitted to the connecting member 22, and the float frame 68 rotates counterclockwise. Then, since the float cam groove 68b on the float frame 68 moves forward while moving in the counterclockwise direction along the cam pin 80 on the rotary frame 69, the third group lens III advances in the optical axis direction, Predetermined aberration correction is performed.

When zooming is performed from the telephoto side to the wide-angle side, the rear group holding frame 65 moves rearward in the optical axis direction, and moves the rotation frame 69 rearward via the cam pins 79 engaged with the float cam grooves 65b. Push. Then, since the guide member 81 integrated with the rotating frame 69 moves along the inclined cam groove 70a of the fixed cam frame 70, the rotating frame 69 rotates counterclockwise while moving backward. Then, at this time, the cam pin 79 of the rotary frame 69 moves with respect to the rear group holding frame 65 along the float cam groove 65b. This float cam groove 65b
And the shape of the float cam groove 68b are the same,
When the focus position is at infinity, the positional relationship between the cam pin 79 and the float cam groove 65b matches the positional relationship between the cam pin 80 and the float cam groove 68b. Therefore, when the rotating frame 69 rotates, the cam pin 80 moves along the float cam groove 68b, but the float frame 68 does not rotate. Therefore, when focusing on an infinity distance, the third group lens III does not move due to zooming.

After the focal length has been changed by zooming, when focusing is performed to the nearest side from a state in which the camera is focused on infinity, the float frame 68 rotates counterclockwise, and the float cam groove 68b is moved to the cam pin 80. At this time, the movement of the cam pin 80 with respect to the float cam groove 68b is a movement along the approximate cam curve l ″ with a position corresponding to the focal length as a base point.
In the same manner as in the embodiment, predetermined aberration correction is performed.

[0078]

As described above, according to the present invention, the float cam is formed by an approximate cam curve which continuously connects each float cam movement amount curve at a plurality of focal lengths. Even when the distance changes, the amount of float is always zero when focused on infinity, and when focusing on the closest distance position, the float amount corresponding to the focal length at that time is obtained, so aberration A zoom lens barrel with significantly improved correction accuracy can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an upper half portion of a zoom lens barrel according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of a main part of the zoom lens barrel of FIG. 1;

FIG. 3 is an essential part developed view showing the telephoto, standard, and wide-angle states of the float cam mechanism in the zoom lens barrel of FIG. 1, respectively.

FIG. 4 is an essential part developed view showing a rotation angle of a connecting member with respect to an extension amount of a focus lens in the zoom lens barrel of FIG. 1;

FIG. 5 is a diagram for explaining movement of each lens due to zooming of the zoom lens barrel according to the present invention.

FIG. 6 is a diagram showing the amount of movement of the float lens with respect to the amount of extension of the focus lens in the wide-angle, standard, and telephoto states in the zoom lens barrel according to the present invention.

FIG. 7 is an approximate cam curve diagram showing an example of the shape of a float cam in the zoom lens barrel according to the present invention.

FIG. 8 is an approximate cam curve diagram showing another example of the shape of the float cam in the zoom lens barrel of the present invention.

FIG. 9 is a longitudinal sectional view of an upper half of a main part of a zoom lens barrel according to a second embodiment of the present invention.

FIG. 10 is an exploded perspective view of a main part of the zoom lens barrel of FIG. 9;

FIG. 11 is a longitudinal sectional view of an upper half portion of a zoom lens barrel previously proposed by the present applicant.

FIG. 12 is an essential part developed view showing a zooming cam mechanism in the zoom lens barrel shown in FIG. 11;

FIG. 13 is an enlarged perspective view of a main part of a connection mechanism in the zoom lens barrel shown in FIG. 11;

FIG. 14 is an essential part developed view showing a float cam mechanism in the zoom lens barrel shown in FIG. 11;

[Explanation of symbols]

3 Fixed frame 12 Front group holding frame (lens group holding frame) 15 Rear group holding frame (lens group holding frame) 18, 68 Float frame 19, 69 Rotating frame 20a, 70a Inclined cam groove (cam means) 31, 81 Guide member (cam means) 21, 22 Connection member 19a, 65b ... Float cam groove (first float cam mechanism; cam means) 29, 79 ... cam pin (Cam follower; first float cam mechanism; cam means) 19b, 68b ... float cam groove (second float cam mechanism; cam means) 30, 80 ... cam pin (cam follower; second float cam mechanism; cam means) ) S, T, W ... Float lens movement amount curve l ', l "... Approximate cam curve

Claims (1)

(57) [Claims] 1. A lens group holding frame for holding a lens group contributing to a focusing operation and performing only an advancing / retreating operation in an optical axis direction at the time of a variable power operation, and provided rotatably around an optical axis with respect to a fixed frame. A rotating frame, a cam groove and a cam follower for cam-connecting the lens group holding frame and the rotating frame, and the length of the cam groove is set to be larger than the moving amount of the cam follower in the cam groove. By changing the moving area of the cam follower in the cam groove along with, the amount of advance / retreat of the lens group holding frame around the optical axis according to the relative rotation amount of the lens group holding frame and the rotating frame during the focusing operation is reduced. And a cam means for changing the moving range of the cam follower in the cam groove by the zooming operation, when the focal point of the optical system is at an infinity position, Optical axis direction A zoom lens barrel characterized in that the lens group holding frame is not moved back and forth in the optical axis direction by not changing its position.