JP2003337276A - Zoom lens barrel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deformation and the rupture of a driving pin when receiving an external force such as impact without making a zoom lens barrel larger nor causing cost rise. <P>SOLUTION: By energizing the driving pin 6 of a 1st group lens and the driving pin 7 of a 2nd group lens to the accuracy wall surfaces 50a and 51a of cam grooves 50 and 51 formed on a cam barrel 5, the cam barrel 5 is rotated while making the driving pins 6 and 7 rubbingly slide on the wall surfaces 50a and 51a, and a 1st group lens 2A and a 2nd group lens 3A are moved in a photographic optical axis direction, so that zoom variable power is performed in the zoom lens barrel. A tilt angle θ2 to a plane perpendicular to an optical axis on an opposed wall surface 50b opposed to the wall surface 50a of the cam groove 50 guiding the lens 2A in the optical axis direction is larger than the tilt angle θ1 of the wall surface 50a. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens barrel capable of preventing the drive pin from being deformed or destroyed when it receives a load such as an impact from the outside.

[0002]

2. Description of the Related Art Conventionally, a straight-moving barrel having a straight-moving guide groove extending along the optical axis of a lens unit constituting a photographing optical system so as to move straight in the optical-axis direction, and a mirror for fixing and holding the straight-moving barrel. There is known a zoom lens barrel including a rotatable cam barrel having a cam groove formed on its peripheral surface between the barrel base member and the barrel base member. The cam barrel is connected to the drive source by a spur gear.

Each lens group is provided with a lens barrel, and a drive pin is projected from the lens barrel. The drive pin enters the cam groove through the straight-ahead guide groove and is sandwiched between a pair of cam wall surfaces facing each other in the cam groove. The pair of cam wall surfaces are formed in parallel with each other, and a slight gap is provided between the drive pin and the pair of cam wall surfaces. One of the pair of cam wall surfaces, for example, the image surface side cam wall surface, is finished as a precision surface in order to accurately define the positional relationship of the lens group in the optical axis direction. It is urged by a spring so that it comes into sliding contact with the precision surface.

When the cam barrel is rotated by the drive source, each lens group is moved in the optical axis direction, whereby zoom magnification is performed.

By the way, in the case where the cam groove is formed along the focusing curve so that the amount of extension of the focusing lens changes depending on the photographing magnification and the distance to the subject, a load such as an impact is applied to the zoom lens barrel. When this happens, the cam barrel rotates, and as a result, the positional relationship between the lens groups changes, causing a problem that focus is lost.

[0006]

Therefore, in the conventional zoom lens barrel, a resistance plate is provided in association with the spur gear as a rotational position detecting device for detecting the rotation angle of the cam barrel, and the resistance plate during zooming is provided. When the resistance value is memorized and a load such as impact is applied to the zoom lens barrel when the resistance value changes, it is determined that the positional relationship between the lens groups has shifted, and the focus is reset by resetting the zoom or housing the zoom lens. Measures are taken to prevent the deviation.

By the way, a zoom having a cam cylinder having a cam groove whose displacement in the optical axis direction is small with respect to the rotation of the cam cylinder, in other words, a cam cylinder having a small inclination angle of the cam groove with respect to a plane perpendicular to the optical axis is zoomed. There is a lens barrel.

With this structure, when an external force in the optical axis direction is applied from the outside to the zoom lens barrel, the rotation amount of the cam barrel is small, but the positional relationship of the lens groups in the optical axis direction shifts, resulting in focus. The rotation position detection device determines that the resistance value of the resistance plate does not change and the positional relationship between the lenses does not change due to backlash between the spur gears. , It may cause out of focus.

Further, since noise is mixed in the detection output of the resistance value in the rotational position detecting device, a threshold value for removing this noise is provided, and if the amount of change in the resistance value does not exceed this threshold value, the cam cylinder Since it is not determined that the cam cylinder has rotated, even if the resistance plate reliably follows the rotation of the cam cylinder, if the rotation amount of the cam cylinder is minute, it cannot be determined that the cam cylinder has rotated and the lens It is determined that the positional relationship between the two has not changed, and this may cause out of focus.

In order to solve this problem, a structure in which the resistance plate is formed large and the rotation amount of the cam barrel is enlarged by a gear to increase the variation amount of the resistance value with respect to the rotation amount of the cam barrel can be considered. If such a structure is adopted, the zoom lens barrel becomes large.

Further, when the inclination angle of the cam groove is small, when an external force in the direction of pressing the zoom lens barrel from the optical axis direction is applied to the tip of the zoom lens barrel, a load due to this external force is directly applied to the drive pin. There is a problem that the drive pin is easily deformed or broken.

As a countermeasure against this, Japanese Patent Application Laid-Open No. 8-212172
As disclosed in Japanese Patent Laid-Open Publication No. 2004-242242, it has been proposed to provide an elastic material to the zoom lens barrel to absorb and absorb the impact applied to the zoom lens barrel.

However, this Japanese Patent Laid-Open No. 21127/1996
When the elastic material is provided on the zoom lens barrel as disclosed in Japanese Patent Publication No. 2 No. 2, the number of parts is increased and the installation space for installing the elastic material must be secured, which increases the cost. It is disadvantageous in terms of the prevention of the above and the miniaturization of the zoom lens.

The present invention has been made in view of the above circumstances, and an object of the present invention is not to increase the size and cost of the zoom lens barrel, and to receive an external force such as an impact. Another object is to provide a zoom lens barrel that can prevent the drive pin from being deformed or destroyed.

[0015]

The invention according to claim 1 is provided with at least a first group lens and a second group lens,
By biasing the drive pin of the first lens group and the drive pin of the second lens group against the precision wall surface of the cam groove formed in the cam barrel, the cam barrel is rotated while the drive pin slides on the precision wall surface. In a zoom lens barrel that performs zoom magnification by moving the first group lens and the second group lens along the photographing optical axis direction, on a precision wall surface of the cam groove that guides the first group lens. It is characterized in that an inclination angle when the cam barrel is flattened with respect to a plane perpendicular to the optical axis on the opposed wall surface is larger than an inclination angle on the precision wall surface opposed to the opposed wall surface.

According to a second aspect of the present invention, there is provided rotational position detection means for detecting the rotational angle of the cam barrel, and the detected value detected during the zoom operation by the rotational angle detection means and from the zoom operation to the photographing. The zoom operation is reset when the difference between the detected value and the detected value exceeds a preset threshold value, or the lens group is housed in the lens housing position.

According to a third aspect of the present invention, the rotational position determining means is a detecting means for detecting the rotational angle of the cam barrel as a change in the electric resistance value, and the electric resistance value detected during the zoom operation and the zoom operation. It is characterized in that the zoom operation is reset or the lens group is housed in the lens housing position when the difference from the electric resistance value detected between the later and the photographing exceeds a preset threshold value.

According to a fourth aspect of the present invention, in the area of the cam groove that defines the tele position from the wide position of the lens group, the inclination angle of the facing wall surface of the cam groove is larger than the inclination angle of the precision wall surface. It is characterized by being set large.

In the zoom lens barrel according to claim 1,
The inclination angle of the facing wall surface facing the precision wall surface of the cam groove is
The accuracy is set to be larger than the inclination angle of the wall surface, and an external force in the optical axis direction acts on the zoom lens barrel from the outside, and the drive pin of the first lens group is pressed toward the facing wall surface by this external force. At this time, the drive pin that engages with the cam groove causes the cam barrel to rotate largely according to the inclination angle of the facing wall surface, so that the impact acting on the drive pin is efficiently converted into the rotational force of the cam barrel. This reduces the impact of the drive pin. Therefore, it is possible to prevent the drive pin from being deformed or destroyed without incorporating a special elastic material into the zoom lens barrel to reduce the impact on the drive pin.

In the zoom lens barrel according to claim 2,
The rotational position detecting means for detecting the rotational angle of the cam barrel captures the rotational displacement of the cam barrel, and the difference between the detection value detected during the zoom operation and the detection value detected after the zoom operation until the photographing is the threshold value. When the value exceeds, the zoom operation is reset or the lens group is stored in the lens storage position. The rotation position detecting means surely detects the rotation of the cam cylinder due to a small impact or the like that causes a slight focus deviation because the cam cylinder largely rotates according to the inclination angle of the facing wall surface, and the focus displacement due to the impact or the like occurs. Shooting as it is is reliably prevented.

In the zoom lens barrel according to claim 3,
Since a means for detecting the rotation of the cam barrel as a change in the electric resistance value is used as the rotation position detecting means, a compact conventional rotation detecting means can be adopted without increasing the size of the zoom lens barrel. Shooting out of focus due to impact is prevented.

In the zoom lens barrel according to claim 4,
In the area of the cam groove that defines the tele position from the wide position of the lens group, the inclination angle of the facing wall surface of the cam groove is set to be larger than the inclination angle of the precision wall surface,
Unnecessary increase of the groove width of the cam groove due to the increase of the inclination angle is prevented, and deterioration of the strength of the cam barrel due to the unnecessary increase of the groove width is prevented.

[0023]

1 is a sectional view of a zoom lens barrel according to the present invention. In FIG. 1, 1 is a lens barrel base member, 2 is a lens barrel that holds a first lens group 2A, 3 is a lens barrel that holds a second lens group 3A, 4 is a straight-moving barrel, and 5 is a cam barrel. is there. The first group lens 2A held by the lens barrel 2 is arranged closer to the object side, which is the tip side of the zoom lens barrel, than the second group lens 3A held by the lens barrel 3.

The rectilinear barrel 4 is fixed to the lens barrel base member 1. The cam barrel 5 is rotatably provided around the photographing optical axis O between the lens barrel base member 1 and the rectilinear barrel 5 while slidingly contacting the outer peripheral wall of the rectilinear barrel 4.

As shown in FIG. 2, the rectilinear barrel 4 has rectilinear guide grooves 4a and 4b formed on its outer peripheral wall and extending in parallel with the photographing optical axis O.
Are formed. A disk-shaped flange portion 4c is formed on the straight-moving cylinder 4, and the tip of the cam cylinder 5 contacts the disk-shaped flange portion 4c.

As shown in the enlarged view of FIG. 3, cam grooves 50 and 51 are formed in the cam barrel 5. Lens barrel 2
A drive pin 6 functioning as a cam follower is screwed to the lens barrel, and a similar drive pin 7 is screwed to the lens barrel 3.

The drive pin 6 provided on the lens barrel 2 enters the cam groove 50 through the straight guide groove 4a, and the drive pin 7 provided on the lens barrel 3 through the straight guide groove 4b. 51 into the cam groove 5
It is sandwiched between a pair of cam wall surfaces 0, 51 facing each other. A slight gap is provided between the pair of cam wall surfaces of each cam groove 50, 51 so as to receive the drive pins 6, 7 with play therebetween.

Of the pair of cam wall surfaces of the cam groove 50, the object-side cam wall surface 50a is finished as a precision surface for accurately defining the positional relationship of the first group lens 2A in the optical axis direction. Of the pair of cam wall surfaces of the cam groove 51, the cam wall surface 51a on the image side is finished as a precision surface for accurately defining the positional relationship of the second group lens 3A in the optical axis direction. A compression coil spring 8 is arranged between the lens barrels 2 and 3, and the elastic force of the spring 8 causes the drive pin 6 of the lens barrel 2 to move the precision wall surface 50a of the cam groove 50.
The drive pin 7 of the lens barrel 3 is biased so as to come into sliding contact with the precision wall surface 51a of the cam groove 51.

When the cam barrel 5 is rotated around the optical axis O, the rectilinear guide groove 4a cooperates with the cam groove 50 to regulate the rotation of the first lens group 2A, and the first lens group 2A. Is guided in the direction along the photographing optical axis O, and the linear guide groove 4b cooperates with the cam groove 51 to guide the second group lens 3A in the direction along the photographing optical axis O, whereby the first group lens 2A. And the second group lens 3A are moved in the photographing optical axis direction and the magnification is changed.

A spur gear 5a is provided on the outer periphery of the rear end of the cam barrel 5, as shown in FIG. A rotational driving force is transmitted to the spur gear 5a by a drive source. The drive source is roughly composed of a DC motor 10 and a rotation transmission gear mechanism 11. The rotation transmission gear mechanism 11 has a transmission gear 11a that meshes with the spur gear 5a.
The rotational torque of the DC motor 10 is transmitted to the cam barrel 5 via 1a, and the cam barrel 5 is decelerated and rotated. The drive source is the drive source cover 14 of the lens barrel base member 1 shown in FIG.
It is housed inside.

The spur gear 5a is meshed with a position detecting gear 13 which constitutes a part of the rotational position detecting device 12. As shown in FIG. 5, the position detecting gear 13 is integrally provided with a conductor section plate 15. Conductor section plate 15
Has a pair of contacts 15a and 15b. This contactor 1
5a and 15b are in sliding contact with a resistance plate 16 arranged so as to face the conductor section plate 15.

As shown in the enlarged view of FIG. 6, the resistance plate 16 has an annular conductive pattern 16a made of a low resistance conductive layer.
And a resistance pattern 16b formed of a high resistance layer concentrically with the conductive pattern 16a is formed outside the conductive pattern 16a. When the cam cylinder 5 is rotated by the driving of the DC motor 10 and the position detection gear 13 is rotated by the rotation of the cam cylinder 5, one contact 15a of the conductor section plate 15 is integrated with the rotation of the position detection gear 13. It slides on the conductive pattern 16a, and at the same time, the other contact 15b slides on the resistance pattern 16b. This conductor section plate 15 is
The conductive pattern 16a and the resistance pattern 16b are short-circuited via the pair of contacts 15a and 15b at a position corresponding to the rotation of the position detection gear 13.

Conductive pattern 16a and resistance pattern 16b
A voltage is applied between and through the connection terminals 16c and 16d. Therefore, when the pair of contacts 15a and 15b of the conductor section plate 15 slide on the resistance plate 16 due to the rotation of the position detection gear 13, the resistance value change between both terminals 16d and 16c is small. It is detected as a change in current. In FIG. 6, the rotational position of the conductor section plate 15 corresponding to the retracted position, the wide position, and the tele position of the zoom lens, that is, the positions of the contacts 15a and 15b are respectively denoted by reference numeral 1.
6e, 16f, 16g.

Rotation amount and rotation position detection device 12 of cam barrel 5
As shown in FIG. 7, there is a linearly proportional relationship with the resistance value, and the resistance value is uniquely determined with respect to the rotation amount of the cam barrel 5.

A linear proportional relational expression shown in FIG. 7 is stored in a program inside the camera by a program. Immediately after the power is turned on and the zoom operation is performed, a microcomputer (not shown) sets the resistance value by the rotation angle detecting device 12. The data is read, the data is stored in a memory (not shown), and the current zoom position is detected based on the linear proportional relational expression. Also,
The microcomputer appropriately reads the resistance value by the rotational position detection device 12 immediately after the zoom operation until the photographing by pressing the shutter, and reads the resistance value and the data after the zoom operation stored in the memory. It is compared and it is determined whether the difference exceeds a predetermined threshold value.

Further, inside the camera, there is provided a calculating means for calculating the amount of extension of the focus lens from the zoom position and the result of distance measurement by the distance measuring means, whereby the first lens group 2A of the focus lens is operated. The amount of extension is calculated, and focusing is performed.

When the cam barrel 5 is in the wide rotation position,
As shown in FIG. 3, the drive pin 6 of the first group lens 2A that engages with the rectilinear guide groove 4a is held in the position indicated by reference numeral 6a in the cam groove 50, and also engages with the rectilinear guide groove 4b. Two
The drive pin 7 of the group lens 3A is held in the cam groove 51 at the position indicated by reference numeral 7a. When the cam barrel 5 is rotated toward the tele position, the drive pin 6 moves the precision wall surface 50 of the cam groove 50.
Along a, it moves toward the tele position shown by the code 6c through the intermediate position shown by the code 6b. At the same time, the drive pin 7 moves along the precision wall surface 51a of the cam groove 51 toward the tele position shown by the reference numeral 7c through the intermediate position shown by the reference numeral 7b.

When the cam barrel 5 in the wide rotation position is rotated toward the storage position, the drive pin 6 moves toward the storage position 6d, and at the same time, the drive pin 7 is displayed 7d. Move to storage position.

Since the lens barrel 3 of the second lens group 3A is not subjected to an external force such as a strong impact that the lens barrel 2 for the first lens group 2A located on the image side of the second lens group 3A receives, The drive pin 7 provided on the lens barrel 3 does not receive a shock as strong as the drive pin 6 of the lens barrel 2 located at the front end. The cam groove 51 for receiving the drive pin 7 provided in the lens barrel 3 has a precision wall surface in which the drive pin 7 is biased by the compression coil spring 8 over the entire region from one end (7d) to the other end (7c) thereof. The facing wall surface 51b facing 51a is the cam wall surface 5
It is formed parallel to 1a.

Further, since the lens barrel 2 does not stand still from the retracted position to the initial position near the wide position, and the front end thereof is less likely to be impacted, the cam groove 50 for receiving the drive pin 6 of the lens barrel 2. In the region from the storage position (6d) to the initial position, the facing wall surface 50b facing the accuracy wall surface 50a is formed parallel to the accuracy wall surface 50a. However, in the region from the wide position (6a) to the tele position (6c), the facing wall surface 50b facing the accuracy wall surface 50a is formed non-parallel to the accuracy wall surface 50a.

FIG. 8 is an expanded view showing a part of the cam groove 50 according to the present invention in an enlarged manner.

The accuracy of the cam groove 50 is the cam groove surface located on the object side, and in the region from the wide position (6a) to the tele position (6c), the facing wall surface 50 located on the image side.
b is formed in a dogleg shape so as to gradually increase the width of the cam groove toward the center of the region. Therefore, the opposing wall surface 50b of the cam groove 50 has a large inclination as compared with the inclination angle θ1 with respect to the plane orthogonal to the optical axis O when the opposing wall surface 50b ′ parallel to the precision surface 50a virtually shown by a dashed line in FIG. The angle is set to θ2.

When an external force F is applied from the optical axis direction to the lens barrel 2 of the first group lens 2A, the drive pin 6 located at the reference numeral 6a, 6b or 6c is indicated at 6d, 6e or 6f in FIG.
As shown in FIG. 5, the sheet is pressed against the opposing wall surface 50b on the image surface side. At this time, a component force fx in the direction of rotating the cam barrel 5 is generated. If this component force fx is larger than the frictional force N of the cam barrel and the torque for rotating the DC motor in the non-energized state, the cam barrel 5 rotates.

The external force F and the component force fx have the following relationship.

Fx = Fcos θ2 · sin θ2 (1) The component force fx becomes zero when the inclination angle θ2 is 0 degree, increases with the increase of the inclination angle, and then exceeds the peak value, and then the inclination angle becomes 90 degrees. However, the inclination angle θ2 of the facing wall surface 50b is smaller than that of the facing wall surface 50b ′ which is parallel to the accuracy wall surface 50a.
To be larger than the component force obtained at the tilt angle θ1 of
The inclination angle θ2 is set to a value larger than the inclination angle θ1.

The angle of the cam groove is as small as the angle θ1,
When the component force fx is smaller than the torque for rotating the DC motor, the cam cylinder slightly rotates by an angle corresponding to the backlash of the position detection gear. At this time,
Although the cam barrel is rotating, the position detecting gear does not rotate, or even if it rotates, the amount of rotation thereof is very small, so the rotational position detecting device cannot detect the rotation of the cam barrel. Therefore, when the external force F disappears and the drive pin comes into contact with the precision wall surface again, before and after the external force F is applied.
After the addition of, the resistance value of the position detecting device does not change despite the positional relationship between the first group lens and the second group lens changing, or there is a change in the resistance value. Even if so, the amount of change is so small that the microcomputer cannot detect that the positional relationship between the first lens group and the second lens group has deviated, and if the focusing is continued as it is, there is a possibility of defocusing. There is. Further, the drive pin may be deformed or destroyed by the external force F.

On the other hand, according to the present invention, the external force F is applied to the lens barrel 2 of the first group lens 2A from the optical axis direction,
When the drive pin 6 comes into contact with the opposing wall surface 50b on the image side, a large component force fx corresponding to the increase in the inclination angle (θ2) is generated.
Rotate at a large rotation angle. Further, the cam barrel 5 can be reliably rotated by the relatively small external force F. Therefore, by setting the inclination angle to a large value, when the impact force F acts on the lens, the impact force causes the cam barrel 5 to rotate largely, and the rotation position detecting device 12 causes the rotation position detection device 12 to change the resistance value. Reliably detect changes.

If the change in the resistance value detected by the rotational position detecting device 12 exceeds a predetermined threshold value immediately after the zoom operation and before the photographing by pressing the shutter, the microcomputer shifts to the lens position. Is determined to have occurred. Based on this determination, the zoom lens barrel is reset to the zoom position or each lens 2
A and 3A are stored in the storage position. As a result, it is possible to reliably prevent shooting of out-of-focus images due to impact.

Furthermore, even if an impact acts on the drive pin 6,
Since the load acting on the drive pin 6 is converted into the rotational force of the cam barrel 5, it is possible to prevent the drive pin 6 from being damaged without incorporating a special elastic member for protecting the drive pin 6.

In the above description, the description has been given along with the zoom lens of the camera that searches for the in-focus point while moving the focus lens. However, the present invention is a varifocal type zoom lens in which the focus position changes depending on each zoom position. Can be applied to.

[0051]

According to the invention described in claim 1, since the inclination angle of the opposing wall surface facing the precision wall surface of the cam groove engaging with the drive pin is set to be large, the impact acting on the drive pin is prevented. It is effectively converted into the rotational force of the cam barrel, which can prevent the drive pin from being deformed or destroyed.

According to the second aspect of the present invention, since the cam barrel largely rotates according to the inclination angle of the facing wall surface, the cam barrel due to a small impact or the like that causes the rotational position detecting device 12 to slightly defocus. It is possible to reliably detect the rotation of the image pickup, and it is possible to reliably prevent the image capturing that is out of focus due to the impact or the like.

According to the third aspect of the invention, since the means for detecting the rotation of the cam barrel as the change in the electric resistance value is used as the means for detecting the rotation of the cam barrel, it is possible to increase the size of the zoom lens barrel. It is possible to prevent shooting of out of focus due to impact or the like without inviting.

According to the fourth aspect of the present invention, the inclination angle of the facing wall surface of the cam groove is set to be large in the area of the cam groove that defines the tele position from the wide position where it is likely to receive an impact. It is possible to prevent the strength of the cam barrel from being lowered due to an increase in unnecessary groove width of the cam groove due to an increase in the inclination angle.

[Brief description of drawings]

FIG. 1 is a sectional view showing a zoom lens barrel according to the present invention.

FIG. 2 is an exploded perspective view of the zoom lens barrel shown in FIG.

3 is a plan view showing a developed cam groove shown in FIG. 2. FIG.

FIG. 4 is a perspective view schematically showing a drive mechanism and a rotational position detection device.

5 is an exploded perspective view showing the rotational position detecting device shown in FIG. 4. FIG.

FIG. 6 is a plan view of the resistance plate shown in FIG.

FIG. 7 is a graph showing the relationship between the resistance value of the rotational position detector and the zoom position.

FIG. 8 is an enlarged view showing a part of the cam groove shown in FIG.

[Explanation of symbols]

1 lens barrel base member 2, 3 lens barrel 2A first lens group 3A Second lens group 4 straight advancing barrel 5 cam barrel 6, 7 Drive pin 8 compression coil spring 50, 51 Cam groove 50a precision wall 50b facing wall

Claims (4)

[Claims] 1. A first group lens and a second group lens are provided at least, and the drive pin of the first group lens and the drive pin of the second group lens are urged against a precision wall surface of a cam groove formed in a cam barrel. By doing so, the cam barrel is rotated while slidingly contacting the drive pin with the precision wall surface, and the first group lens and the second group lens are moved along the photographing optical axis direction to perform zoom magnification / zoom. In the zoom lens barrel, an inclination angle when the cam barrel is flattened with respect to a plane perpendicular to the optical axis on the opposing wall surface facing the precision wall surface of the cam groove guiding the first group lens is equal to the opposing wall surface. A zoom lens barrel characterized in that it is larger than the inclination angle of the facing precision wall surface. 2. A rotation position detecting means for detecting a rotation angle of the cam barrel, wherein the rotation angle detecting means detects a detection value during a zoom operation and a detection value detected after the zoom operation and before photographing. The zoom lens barrel according to claim 1, wherein the zoom operation is reset or the lens group is housed in a lens housing position when the difference between the lens group and the lens group exceeds a preset threshold value. 3. The rotation position output means is a detection means for detecting the rotation angle of the cam barrel as a change in electrical resistance value,
When the difference between the electric resistance value detected during the zoom operation and the electric resistance value detected after the zoom operation until the photographing exceeds a preset threshold value, the zoom operation is reset or the lens group is moved to the lens storage position. The zoom lens barrel according to claim 2, wherein the zoom lens barrel is housed in. 4. An inclination angle of the facing wall surface of the cam groove is set to be larger than an inclination angle of the precision wall surface in a region of the cam groove that defines a tele position from a wide position of the lens group. The zoom lens barrel according to claim 1, wherein the zoom lens barrel is a zoom lens barrel.