JPH07111498B2 - Zoom lens barrel - Google Patents

Description

The present invention relates to a zoom lens barrel, and more particularly to a rear focus type zoom lens barrel.

[Prior Art] Various so-called rear focus type zoom lens barrels having a single variable power group and a single focus group on the image plane side of the variable power group are known. In such a type of zoom lens barrel, the movement amount of the focus group from infinity to the close distance and the position of the focus group at the same subject distance or each focal length are changed. In particular, since the difference in the amount of movement of the focus group is substantially equivalent to the square of the zoom magnification, the difference becomes more remarkable as the zoom lens barrel has a higher magnification.

[Problems to be Solved by the Invention] Therefore, since the operation angle of the focus ring changes at each focal length or the focus movement occurs due to zooming, focusing can be performed at any focal length with the same rotation angle. However, the operability was significantly worse than that of the so-called front focus type.

In view of such a problem, the present invention corrects the focus movement due to zooming and changes the use range of the cam groove for controlling the movement of the focus group by changing only the range without changing the use angle. It is an object of the present invention to provide a rear focus type zoom lens barrel which enables focusing at the same operating angle and has good operability.

[Means for Solving the Problems] In the zoom lens barrel of the present invention, a first cam groove is provided in a first cam ring that rotates in association with zooming.
The interlocking frame movable only in the optical axis direction is engaged with the cam groove of the second cam ring of the second cam ring which is integral with the interlocking frame in the optical axis direction and is integral with the first cam ring in the rotational direction. In the 2 cam groove,
A projection that is integral with a focus group that rotates in conjunction with focusing is engaged. The second cam groove is formed with a set angle equal to or more than the sum of the focusing operation angle and the zooming operation angle, the focusing operation angle is equal at any focal length, and both ends of the same operation angle are formed. The difference in the optical axis direction is substantially equal to the amount of movement of the focus group from the infinity to the closest shooting distance at the focal length.

[Operation] By rotating the projection body integrated with the focus group by focusing, the projection body moves in the optical axis direction according to the cam shape of the second cam groove, and the focus group moves.
Focus group from the infinity to the closest shooting distance at the focal length when the focusing operation angles of the projections moving on the second cam groove are the same at any focal length and the movement amount in the optical axis direction at both ends of the same operation angle is Since the amount of movement is equal to the movement amount of, the focusing from the infinity to the close-up shooting distance is performed at the same focusing operation angle at any focal length.

[Examples] FIG. 1 is a sectional view of a zoom lens barrel showing an example of the present invention. The state of this zoom lens barrel shown in FIG. 1 is a telephoto state at infinity. The optical system has a four-group configuration, L ₁ and L ₃ are a fixed group, L ₂ is a variable power group, and L ₄ is a focus group, thus forming a rear focus type zoom lens barrel.

The fixed group L ₁ is held by the first group frame 16 and is screwed and fixed to the front fixed frame 2. A cam ring 5 is rotatably fitted to the inner circumference of the front fixed frame 2, and a shaft 17 arranged in parallel with the optical axis direction is provided on the inner side of the cam ring 5 at one end and at the other end of the front fixed frame 2. It is supported by the shaft retainer 18. Here, the shaft retainer 18 is fixed by fixing the retainer frame 19 to the inner circumference of the end of the front fixing frame 2 with a screw, and the shaft retainer 18 simultaneously restricts the movement of the cam ring 5 in the optical axis direction. . The shaft 17
Although only one is shown in FIG. 1, two are actually present to prevent rotation. That is, FIG. 4 shows a perspective view of the correction frame 7. The correction frame 7 has a fitting portion 7d provided on the brooke 7c and a fitting portion 7e provided at a position 180 ° opposite to the fitting portion 7d. The shaft 17 is fitted. These two
The correction frame 7 can be moved in the optical axis direction without being rotated by fitting the shaft 17 at the location.

The variable power group L ₂ is supported by a variable power frame (not shown), and this variable power frame has a fitting portion for _two shuts like the correction frame 7 described above, so that it can move in parallel to the optical axis direction. Has become. The correction frame 7 is provided with pins 22 and a zoom frame (not shown) is also provided with similar pins, which are fitted in the cam grooves 5b and 5a of the cam ring 5 shown in FIG. 2, respectively. Further, a zoom pin 21 is planted in the cam ring 5, and the zoom pin 21 is fitted in a groove portion 15a of a zoom ring 15 which is rotatably fitted to the outer periphery of the front fixed frame 2. Further, the zoom ring 15 is provided with a gear portion 15b which is an engagement portion with a zoom motor (not shown). Therefore, when the zoom ring 15 is rotated by the zoom motor or manually, the cam ring 5 rotates via the zoom pin 21, so that the zooming group L ₂ follows the shape of the cam groove 5, and the correction frame 7 has the cam groove 5b. According to the shape of, each moves only in the optical axis direction.

A focus ring 6 is rotatably held on the outer periphery of the rear portion of the front fixed frame 2. On the outer circumference of the front fixed frame 2, between the beam ring 15 and the focus ring 6, an index ring 14 for reading the zooming position and the focusing position is fixed to the front fixed frame 2 by an index presser 20. ing. The movement of the focus ring 6 in the optical axis direction is restricted by the intermediate frame 3, and the intermediate frame 3 is fixed to the front fixed frame 2 by screws (not shown).
It is fixed to. The focus ring 6 is also provided with a gear portion 6a which is an engagement portion with a motor (not shown) (see FIG. 3).

Further, in the center of the intermediate frame 3, there is a fixed group L ₃ corresponding to the third group.
Is fixed. Fixed frame 1 that supports the focus group L ₄
Is fixed to the intermediate frame 3 by screws (not shown). At this time, the iris 4 is held between the intermediate frame 3 and the fixed frame 1. The focus group L ₄ is supported by the fourth group frame 13, and the fourth group frame 13 is slidable on the inner circumference of the fixed frame 1. Fixed frame 1
An interlocking frame 9 is fitted on the outer periphery of the interlocking frame, and a focus frame (hereinafter, referred to as an F frame) that is a second cam ring on the outer periphery of the interlocking frame 9.
8 is rotatably held and the holding frame 10 is screwed to the threaded portion 9d (see FIG. 4) of the interlocking frame 9, and the F frame 8 is connected to the interlocking frame 9
Against the optical axis. As shown in FIG. 4, the movement frame 9 is fixed at the screw portions 9a, 9b by the screw portions 4f, 4g of the longitudinal portions 7a, 7b extending along the optical axis direction of the correction frame 7 and the screws 25, When the correction frame 7 moves in the optical axis direction according to the shape of the cam groove 5b, the interlocking frame 9 also receives the correction frame 7.
Move together with. As shown in FIG. 5, a pin 23 is planted in the F frame 8 with a screw portion 8b, and the pin 23 is formed in the end of the longitudinal portion 5d of the cam ring 5 (see FIG. 2). Has been inserted into. A focus pin (hereinafter referred to as an F pin) 12 is planted in the fourth group frame 13, and the F pin 12 is provided in a groove portion 1a provided in the fixed frame 1, a groove portion 9c provided in the interlocking frame 9, and an F frame 8. It penetrates through the provided cam groove 8a and is further fitted into a groove portion 11a of a focus lever (hereinafter, referred to as F lever) 11 fixed to the focus ring 6 by screws 24 as shown in FIG.

In the zoom lens barrel shown in FIG. 1 configured as described above, the focusing surface of the zoom lens barrel exists on the right side due to the focus group L ₄ , and is not shown at this position in actual use. An image sensor is provided.

Next, the operation of the zoom lens barrel having such a configuration will be described.

Like this zoom lens barrel, in a rear focus type zoom lens barrel in which a single lens unit L ₂ is moved to change the magnification and focusing is performed from the image plane side, a focus group for zooming is used. The amount of movement of L _{4 to} the infinity position and the closest shooting distance changes sequentially. FIG. 6 shows the movement state of the focus group L ₄ in the zoom lens barrel of this embodiment. Curve 10 in FIG.
1 indicates the movement of the focus unit L ₄ when zooming is performed at the infinity focusing position, and the curve 102 is
7 shows movement of the focus unit L ₄ when zooming is performed at a position close to 0.5 m. Zooming barrel of this embodiment is a 6-fold ratio zoom ratio of the amount of movement of the to the closest distance infinity 0.5m at wide and telephoto has a 6 ^2, that about 36.

First, when the zoom ring 15 is rotated, the cam ring 5 is rotated by the zoom pin 21. At this time, the variable magnification frame (not shown) of the variable magnification group L ₂ is restricted by the cam groove 5a shown in FIG. By doing so, a predetermined movement is performed in the optical axis direction, and zooming is performed. Also, when the cam ring 5 rotates, the F
The frame 8 also rotates in the same direction. Furthermore, at this time, since the pin 22 implanted in the correction frame 7 is restricted by the cam groove 5b of the cam ring 5, when the cam ring 5 rotates, the correction frame 7 moves along the optical axis direction. To do. Since the interlocking frame 9 is integrally fixed to the correction frame 7, the interlocking frame 9 also slides the outer periphery of the fixed frame 1 in the optical axis direction while rotatably holding the F frame 8.
That is, when the cam ring 5 rotates due to zooming, the F frame 8 moves in the optical axis direction together with the interlocking frame 9 while rotating on the motion frame 9.

On the other hand, regarding focusing, the rotation of the focus ring 6 is transmitted to the F pin 12 by the F lever 11 and the fourth group frame 13 rotates. Since the F pin 12 is regulated by the cam groove 8a of the F frame 8, the fourth group frame 13 moves in the optical axis direction while rotating along the cam groove 8a by the rotation of the focus ring 5. In this embodiment, the zooming cam groove 5a of the cam ring 5 is linear, but the correction frame cam groove 5b and the focusing cam groove 8a of the F frame 8 are non-linear. The shapes of the cam groove 8a and the cam groove 5b are respectively a curve 103 shown in FIG. 7 and a curve 104 shown by a solid line in FIG. In this embodiment, it is assumed that the rotation angle for zooming is 90 ° and the rotation angle for focusing is 90 °. First, the cam groove of the F frame 8
Explaining the shape of 8a, on the curve 103 shown in FIG. 7, the wide infinity state is 0 °, 0 mm, the angle corresponds to the rotation angle of the zoom ring 15, and the flow corresponds to the amount of extension to the subject side. . Point C on this curve 103 corresponds to the position where the F frame has rotated 90 °, and the amount of extension here is the focus group from infinity at wide angle to the close position of 0.5 m in FIG.
It is the same as the movement amount δ _{W of} L ₄ .

Next, considering the case of telephoto, the range of use of the cam groove 8a at telephoto is C on the curve 103 due to the characteristics of the zoom lens barrel.
It is from point A to point A. Here, since the coordinates of the point C have already been determined, the coordinates of the point A are the values obtained by adding the movement amount δ _T of the focus group L ₄ from the point of infinity to the closest point of 0.5 m in FIG. 6 to the coordinates of the point C. Become. Similarly, in the standard position, the range of use is 90 ° from D point to B point, and the difference between the B point coordinate and the D point coordinate is the focus group at the standard time in FIG.
It is the movement amount δ _{S of} L ₄ .

Although the three focal length states have been described above, the shape of the cam groove 8a shown by the curve 103 in FIG. 7 is such that the movement amount when an arbitrary 90 ° range is selected over more points is the focus group of FIG. It is set so as not to conflict with the movement amount of. Although the shape of the cam groove 5b for the correction frame of the cam ring 5 is shown in FIG. 8, the curve 105 shown by a broken line here is the same as the curve 101 at infinity in FIG. 6, and the curve shown by a solid line. 104 is the shape of the gum groove 5b. The curve 104 is a value corrected in consideration of the movement amount at points E to C of the curve 103 in FIG. 7 of the curve 105.

The behavior during focusing by these will be described in more detail. First, at wide infinity, the F pin 12 is located at the E point and the pin 22 is located at the F point. In this state, when the focus ring is rotated from infinity to the closest point, the F lever 11 is rotated and the F pin 12 is moved along the cam 8a, whereby the focus group L ₄ moves from the point E to the point C. Moving. At this time, the F frame 8 does not rotate or move in the optical axis direction. When zooming from a wide infinity position, the cam ring 5 rotates, but the F pin 12 does not rotate.
Since the rotation direction is restricted by the lever 11, the focus group L ₄ moves along the cam groove 8a only for the rotation of the cam ring 5. At this time, the correction frame 7 also moves due to the cam groove 5b,
The cam form of the cam groove 5b is as shown in FIG.
Since the points F to H in consideration of the cam shapes of the points E to C of 8a are provided, the position of the focus group L _{4 associated} with zooming in the infinite state is the curve at infinity shown in FIG. Same as 101. That is, at this time, the F frame 8 is rotated by the pin 23 around the outer periphery of the interlocking frame 9 that moves back and forth.

By zooming, the standard infinity position, that is,
When the F pin 12 is present at the D point and the pin 22 is present at the G point, the focusing ring 6 always has a rotation angle of 90 ° when the focusing is performed, so the F pin from the D point to the B point.
The reference numeral 12 moves within the cam groove 8a of the non-rotating F frame 8 while being restricted by the F lever 11. Here, since the difference between points B and D is set equal to the difference δ _S between infinity and the close distance at the standard position in FIG. 6, focusing from infinity to the close distance is possible.

In the tele state, pin 22 is located at point H and F pin 12 is at point C ~
Focusing is also possible by moving between points A as well.

With the above operation, focusing can be arbitrarily performed at any focal length.

[Effects of the Invention] As described above, according to the present invention, the focus cam groove is provided in the frame that rotates in association with zooming, and the use range of the cam groove is sequentially changed in association with zooming.
Moreover, since the infinity position is corrected by moving the frame in the optical axis direction, it is possible to perform focusing from infinity to the close distance with a single operating angle at any focal length.

[Brief description of drawings]

1 is a vertical sectional side view of a zoom lens barrel showing an embodiment of the present invention, FIG. 2 is a perspective view of a cam ring in FIG. 1, and FIG. 3 is a focus ring in FIG. FIG. 4 is a perspective view of the correction frame and the interlocking frame in FIG. 1, FIG. 5 is a perspective view of the F frame in FIG. 1, and FIG. FIG. 7 is a characteristic curve diagram showing the relationship between the movement amount and the focal length, FIG. 7 is a characteristic curve diagram showing the shape of the cam groove formed in the F frame, and FIG. 8 is a characteristic curve diagram showing the shape of the cam groove formed in the cam ring. It is a characteristic curve figure to show. 5 ... Cam ring (first cam ring) 5b ... Cam groove (first cam groove) 6 ... Focus ring 8 ... F frame (second cam ring) 8a ... Cam groove (second cam ring) Cam groove 9 …… Interlocking frame 12 …… F pin (projection body) 15 …… Zoom ring L ₂・ ・ ・ Variable group L ₄ …… Focus group

Claims (3)

[Claims] 1. In a rear focus type zoom lens barrel in which a moving range and a moving amount of a focus group with respect to the same shooting distance range change according to a focal length, the first cam rotates in association with zooming. A first cam ring having a groove, an interlocking frame that is restricted by the first cam groove and moves only in the optical axis direction when the first cam ring rotates, and the interlocking frame in the optical axis direction. And a second cam ring that has a second cam groove and that rotates integrally with the first cam ring in the rotation direction and is engaged with the second cam groove. A zoom lens barrel comprising: a projection that is integrally provided in the focus group in a combined state and that rotates in conjunction with focusing. 2. The second cam groove is formed at a set angle equal to or greater than the sum of the focusing operation angle and the zooming operation angle. The described zoom lens barrel. 3. In the second cam groove, when the focusing operation angle is set to an arbitrary focal length position, the same operation angle is the same, and the difference in the position in the optical axis direction at both ends of the same operation angle is: The zoom lens barrel according to claim 1, wherein the amount of movement of the focus group from infinity to the closest shooting distance at any focal length is approximately equal.