JP3881618B2 - Zoom lens barrel having a lens interval variable mechanism - Google Patents

Description

[0001]
【Technical field】
The present invention relates to a zoom lens barrel having a lens interval variable mechanism.
[0002]
[Prior art and its problems]
The present applicant has proposed a zoom lens system that switches the distance between two of the constituent lens groups at an intermediate focal length. Specifically, having a plurality of movable variable-power lens groups that change the focal length; at least one variable-power lens group has two sub-groups, one of which is the other sub-group A switching group that is a movable sub group that is selected and positioned at either one of both moving ends in the optical axis direction; a short focal length side zooming area from the short focal length end to the intermediate focal length; The movable sub group in the switching group is located at one of the different moving ends in the zooming area on the long focal length side from the intermediate focal length to the long focal length end; and the switching group and the other variable power lens group The zoom lens system is characterized in that the zooming basic trajectory is discontinuous at the intermediate focal length and is defined to form an image on a predetermined image plane in accordance with the position of the movable sub group. Open 2000-275518 ).
[0003]
In order to realize this zoom lens system, it is necessary to change the interval between the two sub-groups (lens groups) at the intermediate focal length.
[0004]
[Patent Literature]
JP 2000-275518 A
[0005]
OBJECT OF THE INVENTION
An object of the present invention is to obtain a zoom lens barrel having a lens interval variable mechanism that can be used in, for example, the zoom lens system described above. In particular, an object of the present invention is to obtain a zoom lens barrel in which a lens interval can be changed by a rotational movement of a rotating member around an optical axis such as a cam ring.
[0006]
SUMMARY OF THE INVENTION
According to the present invention, two lens groups in a lens group constituting a zoom lens system have two intervals between a region extending from the short focal length end to the intermediate focal length and a region extending from the intermediate focal length to the long focal length end. In a zoom lens barrel that changes in stages, two lens group blocks that support two lens groups that change the interval and are guided in a straight line in the direction of the optical axis; and rotational drive that controls the movement position of the two lens group blocks A switching ring supported on the circumferential surface of a linear guide ring that can freely rotate relative to the cam ring and move together in the direction of the optical axis; A switching frame moving mechanism that reciprocally moves the frame at the intermediate focal length in conjunction with rotation of the cam ring; and two lens groups in the two lens group block at the reciprocal rotation end in conjunction with the reciprocating rotation of the switching frame. In two steps It is characterized by having; a gap switching mechanism is of.
[0007]
According to this zoom lens barrel, the interval of the variable interval lens group can be changed at the intermediate focal length only by the rotational movement of the cam ring.
[0008]
The switching piece moving mechanism can be constituted by, for example, a switching ring that rotates together with the cam ring, a switching groove formed on the inner peripheral surface of the switching ring, and an interlocking pin that fits into the switching groove that protrudes from the switching piece. .
[0009]
The interval switching mechanism is, for example, a differential ring that rotates together with the switching piece, and a variable interval 2 that receives the rotation of the differential ring and rotates without changing the position in the optical axis direction. A rotating lens frame that supports one lens group of the two lens groups and a rectilinear lens frame that supports the other of the two lens groups that move forward and backward in the optical axis direction by the rotation of the rotating lens frame.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
First, a zoom lens optical system to which the zoom lens barrel of the present embodiment is applied will be described with reference to FIG. The zoom lens system includes, in order from the object side, a first lens unit L1 having a positive power, a second lens unit L2 having a negative power, a third lens unit L3 having a positive power, and a fourth lens unit having a negative power. It consists of L4. The second lens unit L2 and the third lens unit L3 change the interval in the intermediate focal length range (mode switching interval) (the long interval in the wide range (wide mode) is changed to the short interval in the tele range (tele mode)). The distance change group (referred to as L23) moves together in the wide area and the tele area. The first lens group L1 and the fourth lens group L4 always move together. The first lens unit L1, the interval changing unit L23, and the fourth lens unit L4 are arranged from the image side to the subject side in the entire zoom range from the short focal length end (wide end, W) to the long focal length end (tele end, T). Move monotonously. The zoom lens barrel of this embodiment is a step zoom lens barrel having focal lengths set to a plurality of stages (six stages), and the interval change group L23 functions as a focus group in the step zoom lens barrel. That is, the solid line in FIG. 1 is a cam trajectory including a focus operation, and the zooming basic trajectory at the time of photographing an object at infinity of the interval change group (focus lens group) L23 is indicated by a one-dot chain line.
[0011]
A zoom lens system having the interval change group at the intermediate focal length as described above was proposed by the present applicant in Japanese Patent Laid-Open No. 2000-275518. This zoom lens system has a plurality of variable magnification lens groups that change the focal length; at least one variable magnification lens group has two subgroups, one of which is the other subgroup. A switching group that is a movable sub group that is selected and positioned at either one of the two moving ends in the optical axis direction in relation to the group; a short focal length side zooming range from the short focal length end to the intermediate focal length; The movable sub-group in the switching group is located at one of the different moving ends in the long focal length-side zooming region from the intermediate focal length to the long focal length end; and the switching group and the other zoom lens The zooming basic trajectory of the group is discontinuous at the intermediate focal length, and is defined so as to form an image on a predetermined image plane in accordance with the position of the movable sub group. The zooming trajectory of the step zoom lens barrel shown in FIG. 1 eliminates the discontinuity of the zooming basic trajectory at the intermediate focal length. Further, in FIG. 1, the first lens unit L1 to the fourth lens unit L4 are illustrated as single lenses, but it is normal that they are composed of a plurality of lenses.
[0012]
1 to 19 show the overall structure of the zoom lens barrel of the present embodiment. As shown in FIGS. 2 to 5, the fixed cylinder 11 fixed to the camera body is formed with a female helicoid 11a and a rectilinear guide groove 11b in a direction parallel to the optical axis. A male helicoid 12 a formed at the rear end of the helicoid ring 12 is screwed into the female helicoid 11 a of the fixed cylinder 11. The second rectilinear guide ring 13 is fitted on the inner peripheral surface of the helicoid ring 12 so as to be relatively rotatable and move together with the helicoid ring 12 in the optical axis direction. That is, a circumferential groove 12c is formed on the inner circumferential surface of the helicoid ring 12, and a guide projection 13a formed on the outer circumferential surface of the second rectilinear guide ring 13 is fitted in the circumferential groove 12c so as to be relatively rotatable. ing. The circumferential groove 12c and the guide protrusion 13a maintain the engagement when the helicoid ring 12 and the second linear guide ring 13 are in use. A radial protrusion 13 b that fits in the rectilinear guide groove 11 b of the fixed cylinder 11 is formed at the rear end of the second rectilinear guide ring 13.
[0013]
A spur gear 12b is formed at the peak of the male helicoid 12a, and this spur gear 12b is always meshed with a drive pinion 14 that is positioned in the inner surface recess 11c (FIG. 2) of the fixed cylinder 11 and is rotatably supported. . Therefore, when the drive pinion 14 is driven to rotate in the forward and reverse directions, the helicoid ring 12 moves forward and backward in the optical axis direction while rotating, and the second rectilinear guide ring 13 moves linearly together with the helicoid ring 12.
[0014]
A cam ring 15 is fitted on the inner periphery of the second rectilinear guide ring 13. FIG. 6 shows the developed shape of the cam ring 15. A male helicoid 15a and a guide pin 15b projecting radially from a part of the male helicoid 15a are formed on the outer periphery of the rear end of the cam ring 15. The male helicoid 15a is screwed into a female helicoid 13c formed on the inner peripheral surface of the second rectilinear guide ring 13, and the guide pin 15b is formed by penetrating the second rectilinear guide ring 13, and the circumferential component and the optical axis direction It fits in the escape groove 13d having a component. The guide pin 15b is further fitted into a straight guide groove 12d (FIG. 2) extending through the escape groove 13d and formed in the inner peripheral surface of the helicoid ring 12 in a direction parallel to the optical axis. Therefore, when the helicoid ring 12 rotates, the cam ring 15 moves straight in the optical axis direction while rotating according to the screwed relationship between the female helicoid 13c and the male helicoid 15a. On the inner peripheral surface of the cam ring 15, a female helicoid 15c and a bottomed cam groove 15d (FIGS. 6 and 19) are formed.
[0015]
Inside the cam ring 15, a switching ring 16, a first group support ring 17 that supports the first lens group L1, and a first rectilinear guide ring 18 are fitted in order (see FIG. 9). FIG. 7 shows a developed shape of the switching ring 16 alone. The switching ring 16 and the first group support ring 17 are a pair of annular bodies that can freely rotate relative to each other and move together in the optical axis direction. A male helicoid 17a is formed on the outer periphery of the rear end of the first group support ring 17, and a circumferential groove 16a (FIG. 7) formed on the inner periphery of the rear end of the switching ring 16 immediately before the male helicoid 17a. A guide projection 17b is formed to fit in a relatively rotatable manner.
[0016]
The male helicoid 17 a of the first group support ring 17 is screwed into the female helicoid 15 c of the cam ring 15, and the rotation transmission protrusion 16 b that protrudes from the outer periphery of the rear end portion of the switching ring 16 is formed on the inner peripheral surface of the cam ring 15. It fits in a rotation transmission groove 15e parallel to the formed optical axis.
[0017]
On the other hand, a guide protrusion 18a formed on the outer periphery of the rear end portion of the first rectilinear guide ring 18 is fitted in a rectilinear guide groove 13e formed on the inner peripheral surface of the second rectilinear guide ring 13 and parallel to the optical axis. A rectilinear guide protrusion 17c (same as above) formed on the inner peripheral surface of the first group support ring 17 is formed in a rectilinear guide groove 18b (see FIG. 9) parallel to the optical axis formed on the outer peripheral surface of the first rectilinear guide ring 18. Fits slidably. That is, the second rectilinear guide ring 13, the first rectilinear guide ring 18, and the first group support ring 17 are members that move in the optical axis direction without rotating. Further, a flange 18f (FIG. 9) formed at the rear end portion of the first rectilinear guide ring 18 is rotatable relative to a circumferential groove 15f (FIG. 6) formed at the inner periphery of the rear end portion of the cam ring 15 in the optical axis direction. Are engaged to move together.
[0018]
Accordingly, when the rotation of the cam ring 15 is transmitted to the switching ring 16 via the rotation transmission groove 15e and the rotation transmission projection 16b, the rotation is restricted by the first straight guide ring 18 having the male helicoid 17a meshing with the female helicoid 15c. The first group support frame 17 is moved in the optical axis direction.
[0019]
A fourth group support ring 19 is supported on the first group support ring 17 so as to be freely movable in the optical axis direction. That is, three optical axis parallel arms 19 a are formed around the fourth group support ring 19 that supports the fourth lens group L 4, and these optical axis parallel arms 19 a are connected to the optical axis of the first group support ring 17. It fits in the parallel straight guide groove 17d.
[0020]
Further, around the 2-3 group block 20 supporting the second lens group L2 and the third lens group L3, there are formed three rectilinear guide arms 20a parallel to the optical axis. The arm 20a is fitted in a rectilinear guide groove 18c formed in the first rectilinear guide ring 18 in a direction parallel to the optical axis. Further, the cam follower 20 b fixed to the tip of the straight guide arm 20 a is fitted in the bottomed cam groove 15 d of the cam ring 15. 10 and 11 show an assembled state and a disassembled state of the 2-3 group block 20. As shown in FIGS. 6 and 19, the cam groove 15d performs photographing with a photographing region (wide mode, mode switching section, tele mode in FIG. 19) 15d1 where the 2-3 group block 20 is located at a photographing position. There is a storage area (storage position) 15d2 that is positioned at a storage position that is not, and a mode switching area 15d3 that is shifted from the shooting area 15d1 to the storage position 15d2. The entire area of the cam groove 15 except for the photographing area 15d1 and the end of the mode switching area 15d3 on the storage area 15d2 side is a narrow area in which the cam follower 20b fits with a minimum clearance. The storage area 15d2 and the mode switching area The end region on the storage position side of 15d3 is an open cam region whose rear is opened. Therefore, when the cam ring 15 rotates, the 2-3 group block 20 moves straight in the optical axis direction along the bottomed cam groove 15d. The flange 18f of the first rectilinear guide ring 18 fitted in the circumferential groove 15f of the cam ring 15 so as to be relatively rotatable is positioned behind the storage area 15d2 when the 2-3 group block 20 is positioned at the storage position. Thus, a notch 18f ′ (FIGS. 3, 9, and 18) for escaping the cam follower 20b is formed.
[0021]
And between this 2-3 group block 20 and the 4th group support ring 19, the biasing compression spring 31 which moves this 4th group support ring 19 back is inserted. On the optical axis parallel arm 19a of the fourth group support ring 19, a retaining projection 17e of the first group support ring 17 that restricts the retracted end of the fourth group support ring 19 against the force of the compression spring 31 (FIG. 8, An engagement protrusion 19b (FIG. 8) is formed to engage with FIG. 9), and the fourth group support ring 19 is normally located at the retracted end with respect to the first group support ring 17 (in the photographing state).
[0022]
Before describing the specific configuration of the 2-3 group block 20, the operation according to the above configuration will be described as follows. When the helicoid ring 12 is rotationally driven via the drive pinion 14, the helicoid ring 12 moves in the optical axis direction while rotating, and the second rectilinear guide ring 13 whose rotation is restricted together with the helicoid ring 12 in the optical axis direction Move forward and backward. The rotation of the helicoid ring 12 is transmitted to the cam ring 15, and the cam ring 15 advances and retreats in the direction of the optical axis while rotating along with the first linear guide ring 18 guided in a straight line. When the cam ring 15 rotates, the switching ring 16 advances and retreats in the optical axis direction with the first group support ring 17 guided in a straight line. When the first group support ring 17 moves forward from the storage position, the compression spring 31 gradually expands to position the fourth group support ring 19 at the retracted end with respect to the first group support ring 17. This backward end is the photographing position (wide end), and thereafter, the first group support ring 17 and the fourth group support ring 19 move together. Since the first group support ring 17 carries the first lens group L1, and the fourth group support ring 19 carries the fourth lens group L4, the first lens group L1 and the fourth lens group L4 are mounted as shown in FIG. Move together linearly (without changing the interval) with respect to the rotation angle of the helicoid ring 12 in the zoom range.
[0023]
In the storage position, as is apparent from FIG. 3, the front end face of the 2-3 group block 20 is very close to or in contact with the rear end face of the first group frame 29 to which the first lens group L1 is fixed. The first group frame 29 is a member fixed to the tip of the first group support ring 17. At this time, since the storage area 15d2 of the cam groove 15d is open at the rear, if the 2-3 group block 20 is pressed rearward against the force of the compression spring 31 via the first group frame 29, the cam follower 20b can retreat away from the front cam surface of the cam groove 15d, and the storage length of the lens barrel is shortened. At the same time, the fourth group frame 30 to which the fourth lens group L4 is fixed moves backward to a position where it comes into contact with the light shielding frame 35 by the force of the compression spring 31. The fourth group frame 30 is a member fixed to the fourth group support ring 19, and the light shielding frame 35 is a member fixed to the rear end surface of the helicoid ring 12.
[0024]
On the other hand, the moving position of the 2-3 group block 20 guided linearly by the first linear guide ring 18 is regulated (determined) by the bottomed cam groove 15 d formed on the inner peripheral surface of the cam ring 15. The 2-3 group block 20 supports the second lens group L2 and the third lens group L3, and the cam ring 15 and the switching ring 16 are continuously rotated to rotate the second lens group L2 and the third lens group L3. The movement trajectory shown in FIG. The related structure of the 2-3 group block 20, the cam ring 15, and the switching ring 16 will be described below with particular reference to FIGS.
[0025]
The rectilinear guide arm 20 a and the cam follower 20 b are provided on the 2-3 group moving ring 21. Between the 2-3 group moving ring 21 and the tip holding plate 22, in order from the front, a second group frame 23 supporting the second lens group L2, a third group frame 24 supporting the third lens group L3, A differential linkage ring 25, a differential ring 26, and a differential spring 27 are accommodated. The front end pressing plate 22 has a rectilinear guide pin 22a parallel to the optical axis, and the second group frame 23 has a guide boss 23a that is slidably fitted to the rectilinear guide pin 22a. A compression spring 22b that presses the second group frame 23 rearward is inserted into the rectilinear guide pin 22a.
[0026]
The third group frame 24, the differential linkage ring 25, and the differential ring 26 are rotating members centered on the optical axis. The second group frame 23 and the third group frame 24 have cylindrical portions that are in a fitting relationship with each other, and an inclined cam surface 23 b is formed on the outer peripheral surface of the cylindrical portion of the second group frame 23. A follower protrusion 24a that engages with the inclined cam surface 23b is formed on the inner peripheral surface of the cylindrical portion. The inclined cam surface 23b is a linear cam surface that is inclined with respect to both the circumferential direction and the axial direction. A rotation transmission protrusion 24 b is formed on the outer peripheral surface of the third group frame 24. A rotation transmission groove 25 a is formed on the inner peripheral surface of the differential linkage ring 25, and a rotation transmission projection 24 b of the third group frame 24 is fitted into the rotation transmission groove 25 a, The third group frame 24 always rotates together. The third group frame 24 is pushed rearward by the urging force of the compression spring 22b, and its optical axis direction position is determined by abutting against the 2-3 group moving ring 21. Further, a forced rotation transmission projection 25b is formed on the outer peripheral surface of the differential linkage ring 25, and this forced rotation transmission projection 25b is fitted into a forced rotation transmission groove 26a formed on the inner peripheral surface of the differential ring 26. ing. There is circumferential play between the forced rotation transmission protrusion 25b and the forced rotation transmission groove 26a (see FIGS. 16 and 17).
[0027]
The differential spring 27 is a torsion spring, and the coil portion 27a at the center of the optical axis is housed on the inner surface of the differential linkage ring 25 and frictionally engaged, and a pair of leg portions protruded from the coil portion 27a. 27 b protrudes radially outward from a spring hole 25 c formed in the differential linkage ring 25. 25 d (FIG. 11) is a protrusion that prevents the differential spring 27 from falling off the differential linkage ring 25. The pair of leg portions 27b of the differential spring 27 is torsioned so as to abut against both circumferential side surfaces of the rotation transmitting projection 26b. When the differential ring 26 rotates, the differential spring 27 usually passes through the differential spring 27. Thus, the differential linkage ring 25 is rotated. On the other hand, when the differential linkage ring 25 reaches the turning end (the differential linkage ring 25 has a turning resistance of a certain level or more), the differential spring 27 is elastically deformed so that the pair of leg portions 27b are opened, The differential ring 26 rotates relative to the differential linkage ring 25.
[0028]
A radial interlocking pin 26 c is fixed to the rotation transmitting protrusion 26 b of the differential ring 26, and the interlocking pin 26 c is fitted into a rotation transmitting groove 28 a in a direction parallel to the optical axis formed on the inner surface of the switching piece 28. waiting. As shown in FIG. 9, the switching piece 28 is supported by a receiving groove 18d formed in the first rectilinear guide ring 18 so as to be movable in the circumferential direction by a certain angle. A follower protrusion 28 b formed on the outer surface of the switch ring 16 is fitted in a bottomed switching groove 16 c formed on the inner surface of the switching ring 16.
[0029]
The bottomed switching groove 16c includes a tele section 16cT, a switching section 16cK, and a wide section 16cW, as shown in FIGS. The tele section 16cT and the wide section 16cW are reversely inclined with the same lead as the female helicoid 15c of the cam ring 15, and the switching section 16cK is parallel to the optical axis. Therefore, when the cam ring 15 and the switching ring 16 rotate together, the first rectilinear guide ring 18 and the switching piece 28 are maintained while the follower projection 28b of the switching piece 28 is positioned in the tele section 16cT and the wide section 16cW. There is no relative rotation. On the other hand, when the follower protrusion 28b is engaged with the switching section 16cK, relative rotation of the switching piece 28 with respect to the first rectilinear guide ring 18 occurs. Due to this relative rotation, the second lens group L2 and the third lens group L3 are held at the separated positions in the wide range of FIG. 1, and the second lens group L2 and the third lens group L3 are moved to the approach positions in the mode switching section. In the tele area, the second lens unit L2 and the third lens unit L3 are held at the approach positions.
[0030]
As shown in FIGS. 14 and 15, the third group frame 24 and the 2-3 group moving ring 21 are configured to restrict the rotation angle of the third group frame 24 to an angle necessary and sufficient for switching between the wide position and the tele position. A movement range regulating groove 24c and a stopper projection 21a are formed. On the other hand, the rotation angle of the switching piece 28 and the differential ring 26 is set to rotate larger than the rotation angle of the third group frame 24, and the difference is absorbed by the differential spring 27.
[0031]
That is, as shown in FIG. 14, in the state where the second lens group L2 and the third lens group L3 are separated from each other, the switching piece 28 shown in FIG. 16 is provided via the bottomed switching groove 16c and the follower projection 28b. When the counterclockwise rotation is given, the differential ring 26 rotates, and the rotation is transmitted to the differential linkage ring 25 by the engagement relationship between the rotation transmission protrusion 26b and the pair of legs 27b of the differential spring 27, The third group frame 24 rotates in the same direction. When the rotation range restricting groove 24c of the third group frame 24 contacts the stopper projection 21a, the rotation of the differential linkage ring 25 that always rotates together with the third group frame 24 is also restricted. Even after the rotation of the differential linkage ring 25 is restricted, the differential ring 26 rotates in the same direction, and the differential spring 27 elastically deforms and absorbs the overcharge. When the third group frame 24 rotates, the second group frame 23 that is moved and urged rearward by the compression spring 22b moves rearward according to the relationship between the follower projection 24a and the inclined cam surface 23b, and the second lens group L2. The third lens unit L3 is moved closer (FIGS. 15 and 17). Note that the forced rotation transmission groove 26a of the differential ring 26 and the forced rotation transmission protrusion 25b of the differential linkage ring 25 have a large rotational resistance due to some reason in the differential linkage ring 25. When the pair of leg portions 27b of the differential spring 27 are opened, they contact each other and forcefully transmit the rotation of the differential ring 26 to the differential linkage ring 25.
[0032]
If the switching piece 28 rotates in the reverse direction (clockwise) from the state of FIG. 15 and FIG. 17, the second lens group L2 and the third lens group L3 are separated from each other. The overcharge absorbing action of the differential ring 25, the differential linkage ring 26, and the differential spring 27 is the same as that when rotating in the positive direction (counterclockwise direction) described above. Concave portions 23b1 and 23b2 for stably holding the follower projection 24a at the tele position and the wide position are formed at both ends of the inclined cam surface 23b. Further, four inclined cam surfaces 23b (and corresponding follower protrusions 24a) having the recesses 23b1 and 23b2 at both ends are provided at equal angular intervals in the circumferential direction of the second group frame 23 (third group frame 24). Combined with the fitting relationship between the second group frame 23 and the third group frame 24, the lens interval accuracy and concentricity of the lens groups L2 and L3 at the wide position and the tele position are ensured.
[0033]
In the zoom lens barrel described above, a shutter block 32 is fixed behind the 2-3 group moving frame 21 of the 2-3 group block 20, and the shutter block 32 provides a control circuit for the camera body. The connected FPC board 33 is exposed. Further, a light shielding bellows 34 is located between the inner surface of the front end surface of the first group frame 17 and the front end surface of the 2-3 group block 20.
[0034]
Next, the focusing operation of this step zoom lens barrel will be described with reference to FIG. In the present embodiment, focusing is also performed by the cam groove 15d of the cam ring 15 (by rotation of the cam ring 15). For this reason, there are a total of 6 focal length steps, 4 steps in the wide mode (steps 1, 2, 3, 4) and 2 steps on the telephoto side (steps 5 and 6). In order to move the 2-3 group block 20 (second lens group L2 and third lens group L3) between the far shooting position (∞ position) and the shortest shooting position (N position), the cam groove 15d shape Is set. More specifically, the cam grooves 15d are arranged in the order of rotation in the order of the ∞ position of Step 1, the N position, the N position of Step 2, the ∞ position, the ∞ position of Step 3, the N position, the N position of Step 4, and ∞. The positions are in order, and the ∞ position and N position in step 5 and the N position and ∞ position in step 6 are sequentially provided with the mode switching section in between. The rotation angle (position) of the cam ring 15 is controlled according to the set focal length and subject distance information.
[0035]
In this way, by making the N positions and ∞ positions of adjacent steps adjacent to each other, the shape of the cam groove 15d can be simplified and the overall length can be shortened.
[0036]
In the above embodiment, the first lens group L1, the second lens group L2, the third lens group L3, and the fourth lens group L4 constitute a zoom lens system, of which the second lens group L2 and the third lens group L3. Changes the interval in two steps between a region from the short focal length end to the intermediate focal length and a region from the intermediate focal length to the long focal length end (FIG. 1). The 2-3 group block (2 lens group block) 20 is a 2 lens group block that supports the second lens group L2 and the third lens group L3 with variable spacing. In the two-lens group block (2-3 group block 20), the straight guide arm 20a is fitted in the straight guide groove 18c of the first straight guide ring (straight guide ring) 18, and the straight movement in the optical axis direction is performed. It is only possible. The cam follower 20 b is fitted in the bottomed cam groove 15 d of the cam ring 15, and advances and retreats in the optical axis direction by the rotation of the cam ring 15.
[0037]
A switching piece 28 is supported on the first rectilinear guide ring 18 that can freely rotate relative to the cam ring 15 and move together in the optical axis direction so as to be able to reciprocate in the circumferential direction at a constant angle. 28 is reciprocated at the intermediate focal length in conjunction with the rotation of the cam ring 15. Specifically, the switching piece 28 reciprocates in the circumferential direction by the bottomed switching groove 16 c of the switching ring 16 that rotates together with the cam ring 15 and the follower protrusion 28 b of the switching piece 28. When the switching piece 28 reciprocates, the distance between the two lens groups L2 and L3 in the 2-3 group block 20 changes widely.
[0038]
That is, when the switching piece 28 reciprocates in the circumferential direction, the differential ring 26 moves in the same direction, and the rotation is transmitted to the differential linkage ring 25 via the differential spring 27, so that the third group frame 24 moves in the same direction. Rotate to. When the third group frame 24 rotates, the second group frame 23 that is urged rearward by the compression spring 22b moves in the optical axis direction according to the relationship between the follower projection 24a and the inclined cam 23b, and the second lens group L2 The three lens unit L3 changes in a wide and narrow manner.
[0039]
The interval changing mechanism changes the interval between the second lens unit L2 and the third lens unit L3 in the 2-3 group block 20 in two steps of wide and narrow at the reciprocal rotation end in conjunction with the reciprocal rotation of the switching piece 28. However, a third group frame (rotating lens frame) supporting the third lens group that rotates without changing the position in the optical axis direction in response to the rotation of the differential ring 26 described above. ) 24 and the second group frame (linear lens frame) 23 that supports the second lens group L2 that moves forward and backward in the optical axis direction by the rotation of the rotating lens frame, the distance changing mechanism is configured with a relatively simple configuration. it can.
[0040]
The switching piece moving mechanism may be any mechanism that can reciprocate the switching piece 28 at the intermediate focal length in conjunction with the rotation of the cam ring 15, and the switching ring 16 that rotates together with the cam ring 15. According to the switching groove 16 c formed on the inner peripheral surface of the switching ring 16 and the interlocking pin 28 b fitted into the switching groove protruding from the switching piece 28, the switching piece is surely secured by the rotational movement of the cam ring 15. It can be reciprocated.
[0041]
Although the above embodiment is applied to the zoom lens system of FIG. 1, the present invention can be generally used for a zoom lens system having two lens groups that change the interval in two steps at an intermediate focal length. .
[0042]
【The invention's effect】
According to the present invention, the two lens groups in the lens group constituting the zoom lens system are spaced from each other between a region extending from the short focal length end to the intermediate focal length and a region extending from the intermediate focal length to the long focal length end. In the zoom lens barrel that changes the distance between the two lens groups, a zoom lens barrel that can change the distance between the two lens groups is obtained only by the rotational movement of the rotating member around the optical axis including the cam ring.
[Brief description of the drawings]
FIG. 1 is a diagram showing a zooming basic locus of a step zoom lens system having a switching group to which a zoom lens barrel according to the present invention is applied.
FIG. 2 is an exploded perspective view showing an embodiment of a zoom lens barrel according to the present invention.
FIG. 3 is an upper half sectional view of the zoom lens barrel in a stored state.
FIG. 4 is an upper half cross-sectional view of the zoom lens barrel in a wide end infinity photographing state.
FIG. 5 is an upper half cross-sectional view of the zoom lens barrel in the tele end infinity photographing state.
FIG. 6 is a development view of an inner peripheral surface of a cam ring of the zoom lens barrel.
FIG. 7 is a development view of an inner peripheral surface of a switching ring of the zoom lens barrel.
FIG. 8 is an upper half sectional view showing a locking structure between the first group support ring and the fourth group frame of the zoom lens barrel;
FIG. 9 is an exploded perspective view of a switching ring, a first group support ring, and a first straight guide ring of the zoom lens barrel.
FIG. 10 is a perspective view of a 2-3 group block of the zoom lens barrel;
FIG. 11 is an exploded perspective view of the 2-3 group block.
FIG. 12 is an upper half sectional view of a switching mechanism portion including the 2-3 group block.
FIG. 13 is a perspective view showing an overcharge mechanism using a differential linkage ring, a differential ring and a differential spring in the 2-3 group block.
FIG. 14 is a development view showing a state of the 2-3 group block in the wide mode.
FIG. 15 is a development view showing a state of the 2-3 group block in the tele mode.
FIG. 16 is a front view showing a state of the 2-3 group block in a wide mode;
FIG. 17 is a front view showing a state of the 2-3 group block in the tele mode.
FIG. 18 is a development view showing a switching state between the wide mode and the tele mode of the 2-3 group block.
FIG. 19 is a development view of the cam shape of the cam ring.
[Explanation of symbols]
L1 first lens group
L2 Second lens group
L3 Third lens group
L4 4th lens group
L23 Interval change group
11 Fixed cylinder
11a Female helicoid
11b Straight guide groove
11c Inner surface recess
12 Helicoid ring
12a male helicoid
12b spur gear
12c circumferential groove
12d Straight guide groove
13 Second straight guide ring
13a Guide protrusion
13b Radial protrusion
13c female helicoid
13d escape groove
14 Drive pinion
15 Cam ring
15a male helicoid
15b Guide pin
15c female helicoid
15d bottomed cam groove
15e Rotation transmission groove
16 Switching ring (switching piece moving mechanism)
16a Circumferential groove
16b Rotation transmission protrusion
16c Bottomed switching groove (switching piece moving mechanism)
16cT tele section
16cK switching section
16cW wide section
17 Group 1 support ring
17a male helicoid
17b Guide protrusion
17c Straight guide protrusion
17e Retaining protrusion
18 First straight guide ring (straight guide ring)
18a Guide protrusion
18b Straight guide groove
18c Straight guide groove
18d receiving groove
18f flange
18f 'notch
19 Group 4 support ring
19a Optical axis parallel arm
19b engagement protrusion
20 2-3 group block (2 lens group block)
20a Straight guidance arm
20b Cam Follower
21 2-3 group moving ring
21a Stopper protrusion
22 Tip holding plate
22a Straight guide pin
22b Compression spring
23 Group 2 frame
23a Guide boss
23b Inclined cam surface
24 3 group frame (rotating lens frame) (interval switching mechanism)
24a Follower protrusion
24b Rotation transmission protrusion
24c Rotation range restriction groove
25 Differential linkage ring (straight-ahead lens frame) (interval switching mechanism)
25a Rotation transmission groove
25b Forced rotation transmission protrusion
25c Spring hole
26 Differential ring (interval switching mechanism)
26a Forced rotation transmission groove
26b Rotation transmission protrusion
26c Interlocking pin (switching piece moving mechanism)
27 Differential spring
27b Leg
28 switching pieces
28a Rotation transmission groove
28b Follower projection
29 Group 1 frame
30 4 groups
31 Compression spring
32 Shutter block
33 FPC board
34 Shading bellows
35 Shading plate

Claims (3)

Zoom in which two lens groups in a lens group constituting a zoom lens system change an interval in two steps between a region from the short focal length end to the intermediate focal length and a region from the intermediate focal length to the long focal length end. In the lens barrel,
A two-lens group block that supports the two lens groups that change the distance and is guided straight in the optical axis direction;
A rotationally driven cam ring for controlling the moving position of the two lens group blocks;
A switching piece supported on the peripheral surface of the linear guide ring that is freely rotatable relative to the cam ring and moves together in the optical axis direction so as to be capable of reciprocating rotation at a constant angle;
A switching piece moving mechanism for reciprocating the switching piece at the intermediate focal length in conjunction with rotation of the cam ring;
An interval switching mechanism that changes the interval between the two lens groups in the two lens group block at the two reciprocal rotation ends in conjunction with the reciprocal rotation of the switching piece;
A zoom lens barrel having a lens interval varying mechanism. The zoom lens barrel having the lens interval varying mechanism according to claim 1, wherein the switching piece moving mechanism includes a switching ring that rotates together with the cam ring, a switching groove formed on an inner peripheral surface of the switching ring, A zoom lens barrel having a lens interval varying mechanism including an interlocking pin that fits into the switching groove protruding from the switching piece. 3. The zoom lens barrel having the lens interval varying mechanism according to claim 1 or 2, wherein the interval switching mechanism includes a differential ring that rotates together with the switching piece, and a rotation of the differential ring to receive light. A rotating lens frame that supports one lens group of the two lens groups having a variable interval that rotates without changing the position in the axial direction, and advances and retreats in the optical axis direction by the rotation of the rotating lens frame. A zoom lens barrel having a lens interval variable mechanism including a linear lens frame that supports the other of the two lens groups.

Images