JPH0814651B2 - Zoom lens barrel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a zoom lens barrel, and more particularly to a zoom lens barrel having a means for correcting aberration according to the object distance.

(Prior Art) An optical system of a taking lens barrel is designed based on a certain point (usually infinity) that is generally focused, and the aberration increases as the distance of an object point changes from the reference. Have a tendency. Therefore, in a normal single-focus lens barrel, a part of the lens system is moved based on a focusing operation to correct aberration according to the object point distance.

In a zoom lens barrel, the aberration is conventionally corrected according to the object point distance because of the relatively small aperture of the zoom lens barrel and the complicated frame structure itself for zooming. However, in order to provide a high-performance zoom lens barrel with a large aperture and little aberration, the deterioration of optical characteristics due to an increase in aberration has been accepted.
The applicant has previously corrected the aberration according to the object point distance by moving a part of the lens system other than the focusing lens system in conjunction with the operation of the focusing lens system during the focusing operation. We proposed a zoom lens barrel (Japanese Patent Application No. 58-11).
No. 6490).

That is, the zoom lens barrel previously proposed by the applicant is
As shown in FIG. 2, a cylindrical fixed frame 111 attached to the camera body at the rear end mount portion, and the fixed frame 1
A zoom ring 112 rotatably fitted to the outer periphery of 11, a front group holding frame 113 fitted in the tip of the fixed frame 111, and a helicoid coupling to the front group holding frame 113, A rear group holding frame 115, which is fitted in the middle of the fixed frame 111 and supports the rear ring lens composed of the second group lens II and the third group lens III, is fitted to the focus ring 114 supporting the lens I.
And a third group holding frame 116 fitted in the rear part of the rear group holding frame 115 and supporting the third group lens III, and rotating between the focus ring 114 and the third group holding frame 116. The main body is configured by the interlocking mechanism 117 that is integrally connected in the direction.

The zoom ring 112 is fitted on the outer periphery of the fixed frame 111 so as to be rotatable but not movable back and forth in the optical axis direction. 2 long cam holes 112 that form a “C” when viewed in a flat plane
A and 112b are drilled. In the cam elongated holes 112a and 112b, guide long light 111a, which is formed in the fixed frame 111 in the optical axis direction,
The cam pins 118 and 119 which are planted in the front group holding frame 113 and the rear group holding frame 115 are fitted through 111b, respectively.
The focus ring 114 is formed of a double cylinder body in which a large-diameter cylindrical portion and a small-diameter cylindrical portion are concentrically integrated by a front wall, and a helicoid screw engraved on the outer peripheral surface of the small-diameter cylindrical portion. Is arranged by being screwed into a helicoid screw engraved on the inner peripheral surface of the front group holding frame 113. The large-diameter cylindrical portion covers the front portion of the zoom ring 112 from the outer periphery to form an operating portion for focusing, and the inner peripheral surface of the small-diameter cylindrical portion has the front group lens I fitted and held. Has been done.

Further, on the rear end surface of the small-diameter cylindrical portion of the focus ring 114, a driving hook connecting member 117a forming the interlocking mechanism 117 is formed.
One end of is fixed by means not shown. As shown in FIG. 4, the drive hook connecting member 117a is formed of a strip-shaped plate body having the other end formed into a fork shape, and the driven wire is inserted in the middle long groove of the fork-shaped portion. Connecting member 117b
A connecting pin 117c, which is caulked, is fitted into one end of the. The driven row connecting member 117b is also formed of a strip-shaped plate body, and the other end thereof penetrates an arc-shaped play elongated hole 115a formed in the intermediate wall of the rear group holding frame 115 to form the third group. Holding frame 116
And is fixed to the head of the cam pin 120 penetrating through the cam elongated hole 115b formed in the small diameter cylindrical portion of the rear group holding frame 115 by means not shown.

The rear group holding frame 115 is formed of a double tubular body in which a large diameter tubular portion and a small diameter tubular portion are integrated by an intermediate wall,
The cam pin 119 is erected in the middle of the outer peripheral surface of the large diameter cylindrical portion, and the second group lens II is fitted and held in the front part of the small diameter cylindrical portion. In addition, the rear part of the small-diameter tubular part is
A third group holding frame 116 for fitting and holding the group lens III is fitted. The cam elongated hole 115b of the rear group holding frame 115 into which the cam pin 120 that is planted on the outer peripheral surface of the third group holding frame 116 is fitted is
As shown in FIG. 5, it has a curved shape that is gently inclined with respect to the circumferential direction, and by moving the third lens group III along the cam elongated hole 115b, aberrations according to the object point distance are obtained. Plays the role of correcting.

Next, the operation of this zoom lens barrel will be described.

First, when the zoom ring 112 is rotated, the cam long hole 112a,
By the action of 112b, the cam pin 11
The guides 8 and 119 move toward each other in the optical axis direction while being guided by the guide slots 111a and 111b. As a result, the front lens group I and the rear lens groups II and III narrow the distance between them, and the focal length of the zoom lens barrel increases. Also, the zoom ring
When the 112 is turned left when viewed from the front, the cam slots 112a, 11
Due to the action of 2b, the cam pins 118 and 119 are engaged with the guide elongated holes 111a and 11a.
While being guided by 1b, they move away from each other in the optical axis direction. As a result, the front lens group I and the rear lens groups II and III widen the distance between them, and the focal length of the zoom lens barrel becomes small. Therefore, when the zoom ring 112 is rotated, zooming is performed.

On the other hand, when the focus ring 114 is rotationally operated, the helicoid screws 114a and 113a cause the focus ring 114 to rotate, for example, in the direction of the optical axis during clockwise rotation when viewed from the front. 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 drive ring connecting member 117a is rotated by the rotation of the focus ring 114, and the driven line connecting member 117b is also rotated via the connecting pin 117c. Therefore, the cam pin 120 moves in the cam elongated hole 115b, and the third lens group III rotates and retracts in the optical axis direction. 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 rotated counterclockwise when viewed from the front, the focus ring 114 rotates while advancing in the optical axis direction, for example. 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 driving gutter connecting member 117a, the connecting pin 117c, and the driven girder connecting member 117b to rotate together, and the cam pin 120 moves in the cam elongated hole 115b. The third lens group III rotates and advances in the optical axis direction. Therefore, the aberration caused by the extension of the front lens group I is corrected by the movement of the third lens group III.

However, in the case of the zoom lens barrel, the amount of aberration correction is uniform according to the rotation of the focus ring 114 regardless of whether the lens group is on the wide-angle side or the telephoto side due to zooming. Accurate aberration correction could not be performed. That is, since the degree of aberration varies depending on the focal length, it is necessary to change the floating amount according to the focal length to change the aberration correction amount. The amount of float could not be changed.

(Purpose) In view of the above points, an object of the present invention is to provide a zoom lens barrel in which the amount of float associated with focusing differs depending on the focal length, and aberration correction is accurately performed.

(Outline) In the zoom lens barrel of the present invention, the first float cam mechanism is provided between the zoom frame that moves forward and backward in the optical axis direction by zooming and the rotary frame that is given a rotational component by the cam mechanism by the movement in the optical axis direction. A second float cam mechanism is provided between the float frame and the float frame that transmits the rotational movement of the focus frame through a connecting member, and both float cam mechanisms are provided for each float lens at a plurality of focal lengths. It is formed by a combination of a float cam and a cam follower that forms an approximate cam curve in which movement amount curves are continuously connected.

(Example) Hereinafter, the present invention will be described based on illustrated examples. First, before describing a specific embodiment of the present invention, an outline of the operation of the zoom lens barrel of the present embodiment will be described.

The zoom lens barrel of this embodiment, which has the front lens group I and the second and third lens groups II and III constituting the rear lens group, is used in the telephoto state when focused on an object point at infinity. When zooming is performed from the side to the wide-angle side, the front lens group I advances and the second lens group II and the third lens group III recede integrally, as shown by the solid line in FIG. Focusing is performed by moving the front lens group I forward as shown by the broken line in FIG. 6, but at this time, the third lens group III moves forward as shown by the broken line for aberration correction. Be paid out. The amount by which the third lens group III is extended for aberration correction with respect to the amount of movement of the front lens group I, that is, the float amount 1 is small on the telephoto side and changes on the wide-angle side in accordance with the focal length. That is, the float amount l of the third lens group (float lens) III with respect to the moving-out amount L of the front lens group is as shown in FIG. ， Differs in each wide-angle state. For other focal lengths, the float amount l of the third lens group III may change along the float lens movement amount curve having the inclination according to each focal length among the float lens movement amount curves T, S, W. Of course.

A float cam is used to change the float amount l of the third lens group III according to the focal length. This float cam has the above-mentioned float lens movement amount curves T, S, W
Is formed by an approximated cam curve that is connected continuously. This approximate cam curve will be described with reference to FIG. 8. Each float lens movement amount curve T, S, W is the total extension amount L of the front lens group I.
And the float amount l is l ₁ , l ₂ , l ₃ (l ₁ ＞ l ₂ ＞
is intended to indicate that changes to l _3), 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 (front lens group I is fed to the maximum Draw a float movement amount curve S in the standard state from a position in which the object is in focus at the closest object point distance) or very close to it, and then draw a float movement amount curve T in the telephoto state from the end point of this curve S or its vicinity. Draw. An approximate cam curve l'indicating a smooth two-dot chain line is created based on the curve having the inflection point thus formed. The error Δl between the approximate cam curve l ′ and each float lens movement amount curve T, S, W is small enough to be ignored.

Further, the approximate cam curve may be created based on the float lens movement amount curves T, S, W which are partially overlapped as shown in FIG. That is, the float lens movement amount curve S in the standard state is drawn from the middle of the float lens movement amount curve W in the wide angle state, and the float lens movement amount curve T in the telephoto state is drawn from the middle of this curve S,
An approximate cam curve l ″ is drawn for each of these curves T, S, W so that the error Δl becomes small enough to be ignored. The approximate cam curve l ″ thus created is the approximation shown in FIG. The length can be made shorter than the cam curve l '.

 Next, specific examples of the present invention will be described.

FIG. 1 is a vertical sectional view of an upper half of a zoom lens barrel showing an embodiment of the present invention, and FIG. 10 is an exploded perspective view of a main part of the zoom lens barrel. This zoom lens barrel 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 aperture ring 5 at a position near the rear end of the outer circumference. And a zoom support frame 4 fixed to the outer circumference of the fixed frame 3 and a zoom support frame 4 rotatably fitted in the middle of the outer circumference of the zoom support frame 4 with movement in the optical axis direction being restricted. A combined zoom ring 6, a zoom cam frame 7 rotatably fitted to the inner circumference of the zoom support frame 4 and in which a pin 8 connected to the zoom ring 6 is implanted, and an inner circumference of the zoom cam frame 7. Fixed to the helicoid frame 10, a front group moving frame 9 fitted between the fixed frame 3 and the outer periphery of the fixed frame 3, a helicoid frame 10 helicoidally coupled at the front end of the outer periphery of the front group moving frame 9. Cover the zoom support frame 4 from the middle to the front end. The focus ring 11 arranged in this manner, and the front group lens I screwed to the front ends of the helicoid frame 10 and the focus ring 11.
A front lens group holding frame 12 which is a focus lens frame supporting
The rectilinear frame 13 rotatably fitted to the rear end of the outer circumference of the front group holding frame 12, the rotation conversion frame 14 rotatably fitted to the outer circumference of the rectilinear frame 13, and the fixed frame. A rear group holding frame 15 that is a zoom frame that fits in the middle of the inner periphery of the third lens group and supports the rear group lens composed of the second group lens II and the third group lens III.
And a float frame 18 that is fitted to the rear part of the outer periphery of the rear group holding frame 15 and supports the holding frame 16 of the third group lens III and the flare diaphragm mechanism 17, and is freely rotatable on the outer periphery of the float frame 18. The rotary frame 19 fitted to the rotary frame 19, the fixed cam frame 20 fixed to the rear portion of the fixed frame 3 at the position where the rotary frame 19 is slidably contacted with the outer periphery of the rotary frame 19, the rotary conversion frame 14, and the float frame 18
The main body is constituted by the connecting members 21 and 22 that integrally connect and in the rotational direction.

A front group cam groove 7a and a rear group cam groove 7b are formed in the zoom cam frame 7, and a cam pin 23 planted in the front group moving frame 9 is fitted in the front group cam groove 7a. , Rear group cam groove 7b
A cam pin 24, which is planted in the rear group holding frame 15, is fitted into this.

The front group moving frame 9 is formed with a rectilinear groove 9b in the optical axis direction into which the pin 25 planted in the fixed frame 3 is fitted. 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 into which the cam pin 23 is fitted. Further, the cam pin 24 is fitted in the straight groove 3a formed in the fixed frame 3 in the optical axis direction so as not to come into contact with the front group moving frame 9, so that the zoom cam frame 7 operates the zoom ring 6. When rotated by, the rear group holding frame 15 moves in the optical axis direction according to the shape of the cam groove 7b into which the cam pin 24 is fitted.

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

The front group holding frame 12, which is screwed to the helicoid frame 10 and the focus ring 11 at the front end, has a considerable distance between the front group moving frame 9 and the inner wall of the fixed frame 3 from the middle to the rear. Is a relatively small-diameter cylindrical part, and a straight frame
13 is rotatably fitted. The rectilinear frame 13 has a rear end portion having a small inner diameter at its rear end, and this small diameter portion has a front group holding frame.
The movement in the optical axis direction is restricted by fitting the stepped portion near the rear end of 12. Then, a stop ring 27 is screwed onto the rear end of the front group holding frame 12 so that the rectilinear frame 13 is moved to the front group holding frame 12
It doesn't fall out.

The rectilinear frame 13 has a rectilinear groove 13a (see FIG. 10) formed in the optical axis direction, and the inner claw 2 of the rotation stopper 26 is formed in the rectilinear groove 13a.
The lower end of 6b is fitted. The rotation stopper 26 is formed by notching a part of an elastic metal ring and forming an outer claw 26a and an inner claw 26b at a portion facing the notched portion by 180 °. The inner claw 26b is fitted in the straight groove 13a to prevent rotation.
26 and the rectilinear frame 13 are relatively movable in the direction of the optical axis but immobile in the direction of rotation and are integrated.

The outer claw 26a of the rotation stopper 26 is provided with the notch 9c of the front group moving frame 9 described above.
Therefore, the rotation stopper 26 and the front group moving frame 9 are integrated in the rotation direction. Further, the rotation stopper 26 is fitted with a ring groove (not shown) formed in the inner wall of the front group moving frame 9 at the outer peripheral portion of the ring portion of the rotation stopper 26 with the outer claw 26a fitted in the notch 9c. The front group moving frame 9 and the rotation stop 26 are integrated in the optical axis direction. That is,
Since the outer diameter of this rotation stop 26 is deformed small by applying a force to the ring portion from the outer circumference, the outer claw 26a is aligned with the position of the notch 9c in this state to prevent the rotation stop 26 from the front group moving frame 9 and the front end. When inserted, the rotation stopper 26 is fitted into the ring groove by its restoring elastic force when it reaches the position of the ring groove of the inner wall of the front group moving frame 9, whereby the rotation direction and the front group moving frame 9 are rotated. It is integrated in the optical axis direction.

A front end portion of the rotation conversion frame 14 is inclined outward and protrudes, and an outer edge portion 14a is provided between an inward projection formed in a part of the front group moving frame 9 and the rotation stop 26. It is held in a freely rotatable state. A rotation cam groove 14b inclined with respect to the optical axis direction is formed in the rotation conversion frame 14 (see FIG. 10). The rotation cam groove 14b has a pin planted on the outer periphery of the rear portion of the rectilinear frame 13. 28 is inserted. Further, a band-plate-shaped connecting member 21 extending backward in the optical axis direction is fixed to the outer periphery of the rotation conversion frame 14, and the connecting member 21 is fixed to the rising portion 18a at the front end of the float frame 18. The fork-shaped portions of the connecting member 22 extending forward in the optical axis direction are slidably engaged with each other.

The rear group holding frame 15 is composed of a large-diameter tubular portion and a small-diameter tubular portion. The large-diameter tubular portion is slidably fitted to the fixed frame 3, and the float frame 18 is rotatably fitted to the small-diameter tubular portion. are doing. For this reason,
The connecting member 22 integrated with the float frame 18 is provided in the rear group holding frame 15
Notch formed in the large-diameter cylindrical part so that it is not blocked by
It extends forward through 15a. A cam pin 29 is planted in the small-diameter cylinder part of the rear group holding frame 15, and the float frame
A cam pin 30 is planted in 18 and the cam pin
A cutout window 18b for penetrating 29 is provided.

The rotating frame 19 has two float cam grooves 19 of the same shape.
a and 19b are formed at the same position along the optical axis,
The cam pins 29, 19b are provided in the cam grooves 19a, 19b, respectively.
The cam pin 29 and the float cam groove 19a form a first float cam mechanism, and the cam pin 30 and the float cam groove 19b form a second float cam mechanism. The two float cam grooves 19a, 19b have a shape inclined forward from one end on the clockwise side to the other end on the counterclockwise side, and the cam grooves formed by the approximate cam curve l ″ shown in FIG. The position of the first cam pin 29 with respect to the first float cam groove 19a and the position of the second cam pin 30 with respect to the second float cam groove 19b are in a state of being focused on the object point distance at infinity. The position is relatively equal (see Fig. 11), and the guide pin 31 is planted in the rotary frame 19.
Reference numeral 31 is fitted into the inclined cam groove 20a of the fixed cam frame 20 which is in sliding contact with the upper outer periphery of the rotary frame 19. The inclined cam groove 20a is a cam groove inclined at a relatively gentle angle with respect to the optical axis direction. Therefore, when the rotary frame 19 receives a force in the optical axis direction and moves forward and backward, the guide pin 31 and the inclined cam groove 20a. The groove 20a is adapted to move in the rotation direction as well, but is prevented from rotating when receiving a force in the rotation direction.

As described above, the smooth lens barrel of this embodiment is constructed.

Next, the operation of this zoom lens barrel will be described.

The state shown in FIG. 1 is a state in which the object is zoomed to the telephoto side and focused on the object point distance at infinity. In this state, the focus ring 11 is seen in the counterclockwise direction when viewed from the front of the zoom lens mirror. When the front group moving frame 9 is rotated, the rotation of the front group moving frame 9 is blocked because the pin 25 is fitted in the rectilinear groove 9b. Therefore, the helicoid frame 10 and the front group holding frame 12 integrated with the focus ring 11 are By the action of the screws 9a and 10a, it is extended in the optical axis direction while rotating. Then, since the rectilinear frame 13 fitted to the front group holding frame 12 is prevented from rotating by the rotation stop 26 fixed to the front group moving frame 9,
The rectilinear frame 13 does not rotate, that is, relatively rotates with respect to the front group holding frame 12, but does not rotate with respect to the fixed frame 3, and goes straight along with the front group holding frame 12 in the optical axis direction. It moves and is paid out. When the rectilinear frame 13 is straightly extended in the optical axis direction, the rotation conversion frame 14 rotates counterclockwise by the action of the pin 28 integral with the rectilinear frame 13 and the rotation cam groove 14b on the rotation conversion frame 14. The rotation angle of the rotation conversion frame 14 can be appropriately set depending on the degree of inclination of the rotation cam groove 14b. That is, as shown in FIG. 12, the pin 28 is attached to the rotary cam groove 14
When moving the entire amount L of extension of the front lens group I from the infinity position to the closest position along the optical axis along b, the rotation conversion frame 14 and the connecting member 21 become components in the rotation direction of the rotary cam groove 14b. equal because the angle theta ₁ will rotate, it can be arbitrarily set the rotation angle theta ₁ by setting the inclination angle of the rotating cam groove 14b appropriately, for example, focus ring 11
It can be set smaller than the rotation angle of.

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 due to the pin 25 being fitted into the rectilinear groove 3a of the fixed frame 3, the float frame 18 should rotate with respect to the rear group holding frame 15. But
Notch window 18b of float frame 18 and notch 1 of rear group holding frame 15
5a is formed in a sufficiently large shape so that its rotation is not restricted by the pin 29 and the connecting member 22, respectively.
Further, since the guide pin 31 of the rotary frame 19 is fitted in the inclined cam groove 20a of the fixed cam frame 20, the movement in the rotational direction is blocked unless the guide frame 31 moves in the optical axis direction. The rotating frame 19 does not rotate even when rotated.

That is, when the focus ring 11 is rotationally operated, the rotation amount proportional to the feeding amount of the front group holding frame 12 causes the connecting members 21 and 22 to rotate.
Is transmitted to the float frame 18, and the float frame 18 rotates. At this time, the rear group holding frame 15 and the rotary frame 19 are stationary.

By the way, in the telephoto state, the rear group holding frame 15 is extended to the frontmost position. At this time, the positional relationship between the rear group holding frame 15 and the rotary frame 19 is as shown in FIG. 11 (A).
The cam pin 29 on the rear group holding frame 15 is approximately in the center of the cam groove 19a of 19
Is located. Then, in the telephoto state, when the in-focus object point is in focus, the positional relationship of the float frame 18 with respect to the rotary frame 19 is as shown in FIG. 11 (A). The cam pin 30 on the float frame 18 is located substantially at the center of the cam groove 19b of the frame 19. That is, the float cam groove 19a
The position of the cam pin 29 with respect to and the position of the cam pin 30 with respect to the float cam groove 19b are in a matched relationship.

From this state, when the float frame 18 rotates counterclockwise by focusing, the cam pin
The reference numeral 30 moves counterclockwise in the float cam groove 19b toward the closest position 30a indicated by a two-dot chain line in FIG. 11 (A). Cam pin 3
When 0 moves in the float cam groove 19b toward the closest position 30A in the counterclockwise direction, the float frame 18 is fed forward while rotating in the counterclockwise direction. That is, the focus ring
The front group lens I is extended forward by the rotation operation of 11, and the third group lens III integrated with the float frame 18 rotates while the optical axis of the third lens group III integrated with the float frame 18 rotates as the object point distance in the focused state gradually decreases. Move forward in the direction. In this telephoto state, when the float frame 18 makes an angle θ ₁ rotation from the infinity position to the closest position, the float frame 18 advances by the float amount l ₁ . 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 cam grooves 7a and 7b cause the front group moving frame 9 and the cam pin 24 to move toward each other in the optical axis direction. It moves in the direction of facing or the direction of separating. For example, when focusing on the object point distance of infinity shown in FIG. 1 and rotating the zoom ring 6 to the side of the wide angle state in the telephoto state, the front group moving frame 9 advances in the optical axis direction, The cam pin 24 and the rear group holding frame 15 integrated with the cam pin 24 are retracted. 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 stop 26, the rotation converting frame 14 and the connecting member 21 are integrated with the front group moving frame 9. Advance. Further, when the rear group holding frame 15 is retracted, the cam pin 29 integrated with the rear group holding frame 15 pushes the rotary frame 19 rearward in the optical axis direction via the cam groove 19a. Then, the float frame 18 also moves rearward via the cam groove 19b and the cam pin 30. By the way, the guide pin 31 on the rotary frame 19 is provided with the inclined cam groove 20a of the fixed cam frame 20.
When the rotary frame 19 is pushed backward, the guide pin 31 is guided in the cam groove 20a, so that the rotary frame 19 rotates counterclockwise while moving rearward. When the rotary frame 19 rotates in the counterclockwise direction, the cam groove 19a is guided along the pin 29 that does not move in the rotational direction, so that the rotary frame 19 is rotated relative to the rear group holding frame 15 during the counterclockwise rotation. Move slightly forward. Then, the cam grooves 19a and 19b
Since and have the same shape, the cam pin 30 has the same positional relationship as the position of the cam pin 29 with respect to the float cam groove 19a as the rotary frame 19 rotates in the counterclockwise direction unless the float frame 18 rotates. It moves on the float cam groove 19b while keeping it. This will be described with reference to FIGS. 11A to 11C. When the focus ring 11 is at the infinite position, the cam pin 29 is substantially aligned with the float cam groove 19a in the telephoto state as shown in FIG. 11A. The cam pin 30 is located at the center, and therefore the cam pin 30 is also located at the center of the float cam groove 19b. The frame 19 rotates counterclockwise by an angle θ _{a in the} standard state shown in FIG. 11 (B) and an angle θ _{b in the} wide angle state shown in FIG. 11 (C). That is, when zooming 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 the respective float lens movement amount curves T on the approximate cam curve l ″. , S, W reaches the position with the position at infinity on the area corresponding to W as the base point.
Rotation angle θ of the rotating frame 19 from the telephoto state to the wide-angle state
_b is the angle θ between the ends of the float cam grooves 19a and 19b, which is 1/2 the angle θ
_It is equal to ₁ and is also equal to the rotation angle θ ₁ of the rotation conversion frame 14 and the float frame 18 which rotate by performing focusing from infinity to the closest distance.

Even if the zoom is performed from the telephoto state to the standard state and further to the wide-angle state as described above, the position of the cam pin 30 with respect to the float cam groove 19b is floated when the object point distance at infinity is in focus. Although it matches the position of the cam pin 29 with respect to the cam groove 19a, here, for example, when focusing on the closest object point distance in the standard state, the float frame 18 moves counterclockwise by the angle θ ₁ by the focusing operation described above. Since the cam pin 30 rotates, at this time, the cam pin 30 moves counterclockwise in the float cam groove 19b and moves the float amount l _{2 in the} optical axis direction to reach the position 30B, as shown in FIG. 11 (B). . Since the float cam groove 19b is formed by the approximate cam curve l ″ shown in FIG.
l ₂ is less than the float amount l ₁ in the telephoto state. Also,
In the wide-angle state, when focusing on an object point distance from infinity to the closest point, when the float frame 18 rotates counterclockwise by an angle θ ₁ , the cam pin 30 moves as shown in FIG. 11 (C) at this time. While moving in the float cam groove 19b in the counterclockwise direction, the float amount l _{3 is} moved in the optical axis direction to reach the position 30C. This float amount l ₃ is smaller than the float amount l ₂ in the standard state.

Even if the focus ring 11 is rotated, the positional relationship between the cam pin 29 and the float cam groove 19a does not change, and FIG.
As shown in (C), the positional relationship according to each focal length is maintained, and as described above, only the cam pin 30 has the cam pin 29.
And a position corresponding to the positional relationship between the float cam groove 19a and the float cam groove 19a are used as base points to move on the float cam groove 19b from infinity to a close distance. Therefore, when focusing on an object point at infinity, the float frame 18 does not move in the optical axis direction even if zooming is performed, but when focusing is performed, the float corresponding to each focal length is floated. Float frame 18 in quantity
Moves to correct the aberration accurately.

 Next, another embodiment of the present invention will be described.

FIGS. 13 and 14 are main parts of a zoom lens barrel showing another embodiment, and the portions not shown have the same structure as the zoom lens barrel shown in FIG. The same reference numerals are allotted to those and description thereof will be omitted. A rear group holding frame 65 is slidably fitted to the inner circumference of the fixed frame 3, and the cam pin 24 is planted in the large-diameter cylindrical portion thereof so as not to interfere with the connecting member 22. Thus, the cutout portion 65a is formed, the float cam groove 65b is formed in the rear small diameter cylinder portion, and the 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. Then, the rotary frame 69 is provided on the inner circumference of the small-diameter tubular portion of the rear group holding frame 65.
Is rotatably fitted, and a float frame 68 is rotatably fitted on the outer circumference. Two cam pins 79, 80 are provided on the outer circumference of the rotary frame 69 at the same position along the optical axis and separated by a constant rotation angle.
And the pins 79 and 80 are fitted in the float cam groove 65b and the cutout window 65c, respectively. The float frame 68 fixedly supports the connecting member 22 at the rising portion 68a at the front end, and the float cam groove 68 is provided in the float frame 68.
b and a cutout window 68c are formed. The float cam groove 68b has a cam pin 80 penetrating the cutout window 65c.
Is inserted. Further, a guide member 81 formed by bending a metal plate is fixedly mounted on the rotary frame 69, and a rising front end portion 81a of the guide member 81 penetrates the cutout window 68c and an inclined cam groove of the fixed cam frame 70. It fits into 70a.

In this embodiment, the cam pin 79 and the float groove 65b
The first float cam mechanism is formed by and the cam pin
A second float cam mechanism is formed by 80 and the float cam groove 68b. Compared with the two float cam mechanisms in the above-described embodiment, the relationship between the cam pins and the float cam groove is reversed in these two float cam mechanisms. Therefore, although the float cam grooves 65b and 68b are formed by the approximate cam curve l ″ shown in FIG. 9 similarly to the float cam grooves 19a and 19b, the float cam grooves 19a and 19b are formed by 180 °. It is rotated so that the vertical position is reversed.

Next, the operation of the zoom lens barrel of this embodiment will be described.

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

Also, when zooming from the telephoto side to the wide-angle side, the rear group holding frame 65 moves rearward in the optical axis direction, and the float cam groove
The rotating frame 69 is pushed rearward through the cam pin 79 engaged with 65b. 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 backwards. And
At this time, the rotary frame 69 is cam pin 79 with respect to the rear group holding frame 65.
Performs an operation along the float cam groove 65b. If the shape of the float cam groove 65b is the same as that of the float cam groove 68b, and if the focus position is at infinity, the cam pin 79
The positional relationship between the cam pin 80 and the float cam groove 68b matches the positional relationship between the cam pin 80 and the float cam groove 65b. Therefore, when the rotary 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 changing the focal length by zooming and focusing from the state of focusing on infinity to the close side, the float frame 68 rotates counterclockwise and the float cam groove 68b moves along the cam pin 80. At this time, the movement of the cam pin 80 with respect to the float cam groove 68b is based on the position corresponding to the focal length as the base point, and the approximate cam curve l ″ is moved.
Then, the predetermined aberration correction is performed in the same manner as in the above embodiment.

(Effects of the Invention) As described above, according to the present invention, the float cam is formed by an approximate cam curve in which the respective float cam movement amount curves at a plurality of focal lengths are continuously connected, and the focus can be obtained by zooming. Even if the distance changes, the amount of float is always zero when focusing on infinity, and when focusing on the close-up distance position, the amount of float according to the focal length at that time is obtained. The accuracy of correction is significantly improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of an upper half of a zoom lens barrel showing an embodiment of the present invention, and FIG. 2 is a zoom lens barrel previously proposed by the applicant. FIG. 3 is a longitudinal sectional view of the upper half of FIG. 3, FIG. 3 is an exploded view of a main part showing a zooming cam mechanism in the zoom lens barrel shown in FIG. 2, and FIG. 4 is a zoom shown in FIG. FIG. 5 is an enlarged perspective view of an essential part of a connecting mechanism in the lens barrel, FIG. 5 is an exploded view of an essential part of the float cam mechanism in the zoom lens barrel shown in FIG. 2, and FIG. 6 is a zoom lens mirror of the present invention. FIG. 7 is a diagram for explaining the movement of each lens due to the zooming of the cylinder, and FIG. 7 is a movement amount of the float lens with respect to the amount of extension of the focus lens in each state of wide angle, standard and telephoto in the zoom lens barrel of the present invention FIG. 8 shows a zoom lens of the present invention. FIG. 9 is an approximate cam curve diagram showing an example of the shape of the float cam in the lens barrel, FIG. 9 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, and FIG. 11 is an exploded perspective view of a main part of the zoom lens barrel shown in FIG. 1, and FIGS. 11A to 11C are telephoto, standard, and wide-angle views of the float cam mechanism in the zoom lens barrel shown in FIG. FIG. 12 is a developed view of the essential parts showing the respective states, FIG. 12 is a developed view of the essential parts showing the rotation angle of the connecting member with respect to the amount of extension of the focus lens in the zoom lens barrel shown in FIG. 1, and FIG. FIG. 14 is a longitudinal sectional view of an upper half part of a main part of a zoom lens barrel showing another embodiment, and FIG. 14 is an exploded perspective view of the main part of the zoom lens barrel shown in FIG. 3 …… Fixed frame 12 …… Front group holding frame (focus lens frame) 15 …… Rear group holding frame (zoom frame) 18,68 …… Float frame 19,69 …… Rotating frame 20a, 70a …… Inclined cam groove (Cam mechanism) 31,81 …… Guide member (Cam mechanism) 21,22 …… Coupling member 19a, 65b …… Float cam groove (first float cam mechanism) 29,79 …… Cam pin (cam follower) (No. 1 float cam mechanism) 19b, 68b …… Float cam groove (second float cam mechanism) 30,80 …… Cam pin (cam follower) (second float cam mechanism) S, T, W …… Float lens movement Quantity curve l ′, l ″ …… Approximate cam curve

Claims (1)

[Claims] 1. A focus lens frame which moves forward and backward in the optical axis direction by a focus operation, a zoom frame which moves forward and backward in the optical axis direction with respect to the focus lens frame by a zooming operation, and a light of the focus lens frame which supports a float lens. The float frame, which is transmitted and rotated via the connecting member according to the movement in the axial direction, and whose distance from the focus lens frame changes, and the float frame is connected to the fixed frame via the cam mechanism, and the optical axis of the zoom frame. By moving back and forth in the direction, movement in the optical axis direction,
A rotary frame provided with a rotation component around the optical axis, and a first frame which is formed between the rotary frame and the zoom frame and which transmits the forward / backward movement of the zoom frame in the optical axis direction to the rotary frame by a cam mechanism. Is formed between the throat cam mechanism and the rotary frame and the float frame,
Rotation of the rotating frame around the optical axis and movement in the optical axis direction,
A second float cam mechanism for determining the position of the float frame by rotating the focus lens frame around the optical axis in accordance with the movement of the focus lens frame in the optical axis direction; Float cam mechanism,
A zoom lens barrel characterized in that it is formed by a combination of a float cam and a cam follower that forms an approximate cam curve by continuously connecting respective float lens movement amount curves at a plurality of focal lengths.