JP4686923B2 - Zoom lens barrel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens barrel.
[0002]
[Prior art]
Conventionally, there are several methods for focusing the zoom lens barrel as follows.
[0003]
The first is zoom focus. In other words, the cam groove for driving the lens is formed in a step shape so that the zoom area and the focus area are alternately continued so that the focus drive can be performed at a predetermined focal length. In this method, since the entire lens barrel is driven, the driving time becomes longer and the release time lag becomes larger. In addition, since a large number of parts are moved, errors due to backlash and distortion tend to increase. If a large amount of run-up is driven to stabilize this, the drive time becomes longer.
[0004]
Second, it is a ball frame drive type. In other words, the lens frame holding the lens group of each component is moved as a whole to perform zoom driving, and in a specific lens frame, only the lens group held by the lens frame is partially moved to drive the focus. I do. This type is easy to drive at high speed. However, since the lens group for focusing requires a double holding and driving mechanism for focusing and zooming, the configuration is complicated, it is difficult to reduce the size, the cost is increased, and the lens holding accuracy is secured. Difficult to do.
[0005]
The third is a feed screw type. That is, a feed screw is screwed into a lens frame that holds the lens group, and the lens group is moved in the axial direction by rotation of the feed screw. In order to prevent the ball frame from tilting, it is necessary to provide a guide shaft or lengthen the fitting portion with the guide shaft, and this type can be downsized while ensuring lens holding accuracy. Have difficulty.
[0006]
[Problems to be solved by the invention]
Therefore, the technical problem to be solved by the present invention is to provide a zoom lens barrel capable of increasing the speed and reducing the size of the focus drive while ensuring the lens holding accuracy.
[0007]
[Means for Solving the Problems]
In order to solve the above technical problem, the present invention provides a zoom lens barrel having the following configuration.
[0008]
The zoom lens barrel includes a zoom mechanism and a focus lens moving mechanism. The zoom mechanism integrally moves at least two of the plurality of lens components. The focus lens moving mechanism moves one of the at least two lens components with respect to the other. The focus lens moving mechanism includes a first tube , a second tube that is rotatable around the optical axis inside the first tube and is integrally disposed in the optical axis direction, and an interior of the second tube. It is provided with a lens frame that holds the focus lens component, and a guide that is held by the first cylinder and guides the lens frame in the optical axis direction . The ball frame is provided with a focus motor and an output portion that is rotated by the focus motor and engages with the second tube. The rotation of the output portion causes the second tube to be connected to the first tube. Can be rotated.
[0009]
In the above configuration, the plurality of lens components appropriately move in the optical axis direction, and the focal length changes. The zoom drive mechanism moves a plurality of lens components in the optical axis direction, but moves at least two of the plurality of lens components integrally, that is, by the same distance in the same direction. Therefore, the relative distance between the at least two lens components does not change. On the other hand, by driving the focus lens moving mechanism, the relative distance between the at least two lens components can be changed to adjust the focal point.
[0010]
According to the above configuration, only the focus lens component is driven at the time of focusing, and the focus driving can be speeded up. Since the focus lens moving mechanism is constituted by the second tube disposed inside the first tube and the guide, the focus lens component is held at a length approximately equal to the diameter of the tube, so that the tilt with respect to the optical axis is highly accurate. It is possible to reduce the size while holding. Further, according to the above configuration, the first cylinder and the second cylinder are relatively rotated by the rotation of the focus motor, and thereby the focus lens component can be driven. Since the focus motor moves together with the lens frame that holds the focus lens component, the configuration of the driving force transmission system can be simplified. If the focus lens component is arranged at a position where the optical path is narrowed down, the zoom motor can be reduced in size by arranging the focus motor in a space in the radial direction.
[0011]
Preferably, at the time of zooming, both the zoom mechanism and the focus lens moving mechanism are driven. At the time of focusing, only the focus lens moving mechanism is driven.
[0012]
According to the above configuration, by moving the focus lens component in advance during zooming, the distance for moving the focus lens component during focusing can be made as short as possible. As a result, the release time lag can be shortened and the focus drive can be speeded up.
[0013]
Preferably, the zoom mechanism integrally moves the focus lens component and the lens components arranged before and after the focus lens component. The guide extends in parallel with the optical axis between lens components arranged before and after the focus lens component.
[0014]
According to the above configuration, when the focus lens component moves in the optical axis direction by the tube and the guide of the focus drive mechanism, positional deviation in the direction perpendicular to the optical axis is prevented by the restriction of the guide. Therefore, it is possible to move the focus lens component while holding it with high accuracy.
[0015]
Preferably, the focus lens moving mechanism is a helicoid mechanism.
[0016]
In this case, for example, the lens frame that holds the focus lens component and the cylinder are configured to be helicoidally coupled. When a helicoid mechanism is used, the number of engaging portions can be increased, which is excellent in terms of strength and inclination accuracy. It is also easy to shield the outer shape side of the focus lens component.
[0017]
Preferably, the focus lens moving mechanism is a cam mechanism.
[0018]
In this case, for example, cam pins provided on a lens frame that holds the focus lens component engage with cam grooves provided on the cylinder and the guide, respectively, and the focus lens component is cam-driven by the relative rotation of the cylinder and the guide. To. When the cam mechanism is used, it is possible to realize non-linear feed or drive the focus lens component with different resolutions according to the focal length.
[0019]
Preferably, there is provided a relative position detecting means for detecting a relative position with respect to the other lens component of the focus lens component (that is, the other lens component).
[0020]
According to the above configuration, when the focus lens component is moved relative to the other lens component that is integrally moved by the zoom mechanism, the relative position of the focus lens component relative to the other lens component is detected. It can be detected by means. Using this detection data, the focus lens component can be appropriately moved with respect to the other lens component during zoom driving, and the focus lens component can be moved according to an arbitrary zoom curve or focus extension. Accordingly, the degree of freedom of zoom driving and focus driving is expanded.
[0021]
Preferably, a photo reflector disposed on the ball frame , and a reflection pattern disposed on one of the second tube and the guide so as to face the photo reflector are provided. As the focus lens component moves, the photo reflector moves along the reflection pattern.
[0022]
According to the above configuration, since the photo reflector moves along the reflection pattern, it is possible to detect the relative position of the focus lens component by the focus lens moving mechanism. Further, since it is non-contact, it can be driven and detected with high accuracy without causing disturbance to the driving of the lens component.
[0023]
Preferably, the output unit is a gear, and the second cylinder includes a gear unit in which teeth that engage with the output unit are arranged in a spiral.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a zoom lens barrel 10 according to an embodiment of the present invention will be described with reference to FIGS.
[0026]
1 is a front end side sectional view of a zoom lens at a long focal length, FIG. 2 is a rear end side sectional view, and FIG. 3 is a sectional view at a short focal length.
[0027]
As shown in FIGS. 1 to 3, a drive ring 24 and a rectilinear helicoid cylinder 25, a rotary cylinder 26 and a rectilinear cylinder 27, a forward cylinder 28 and a helicoid ring 29 are arranged in the fixed cylinder 22 of the zoom lens barrel 10. As the long gear 20 rotates, the first lens group 11, the second lens group 12, and the third lens group 13 move in the optical axis direction. Yes.
[0028]
The drive ring 24 is disposed inside the fixed cylinder 22 and its rear end engages with a helicoid formed on the inner peripheral surface of the fixed cylinder 22. The drive ring 24 meshes with the long gear 20 and is moved in the axial direction by the helicoid when rotated by the long gear 20.
[0029]
The long gear 20 is driven by a zoom motor 40 via a speed reduction system 42 as schematically shown in FIG. While the rotation amount of the zoom motor 40 is detected by the photo interrupter 41, expansion / contraction of the zoom lens barrel 10 is controlled.
[0030]
The rectilinear helicoid cylinder 25 is disposed inside the drive ring 24, and the rear end portion of the rectilinear helicoid cylinder 25 is engaged with a rectilinear groove provided in the fixed cylinder 22 so that rotation is restricted. The drive ring 24 is engaged with the drive ring 24 so as to be relatively rotatable and not relatively movable in the axial direction.
[0031]
The rear end of the rotary cylinder 26 engages with a helicoid formed on the inner peripheral surface of the rectilinear helicoid cylinder 25. Further, the pin is engaged with the drive ring 24 so as to be axially movable by a pin, and rotates together with the drive ring 24.
[0032]
A rectilinear cylinder 27 is disposed inside the rotary cylinder 26, and is engaged with the rotary cylinder 26 so as to be relatively rotatable and not relatively movable in the axial direction. The rectilinear cylinder 27 has its rear end engaged with a rectilinear groove formed in the rectilinear helicoid cylinder 25 so that its rotation is restricted.
[0033]
The forward end cylinder 28 is configured such that the rear end thereof engages with a helicoid formed on the inner peripheral surface of the rotary cylinder 26. A first group lens frame 11a that holds the first lens group 11 is fixed to the front end side of the advance barrel 28, and a third group lens frame 13a that holds the third lens group 13 is fixed to the rear end side. . A rectilinear groove 13b is formed in the third group lens frame 13a, and the front end side of the rectilinear cylinder 27 is engaged. Thereby, the advance cylinder 28 is restricted from rotating.
[0034]
Inside the advance cylinder 28, a helicoid ring 29 is disposed between the first group ball frame 11a and the third group ball frame 13a such that the helicoid ring 29 is relatively rotatable and is not relatively movable in the axial direction. As shown in the development view of FIG. 7, a helicoid 29 b is formed on the inner peripheral surface of the helicoid ring 29 on the front end side. A part of the helicoid 29b is extended to the rear end side to form a gear portion 29a cut in a valley shape in the direction of the axis O and meshes with an output gear 18 described later. A reflection pattern 30 is attached along the helicoid 29b so as to face a photo reflector 17 described later. A plurality of bright and dark patterns 30a and 30b repeated at a predetermined pitch are arranged in the middle portion of the reflection pattern 30, and patterns 30c and 30d having a long pitch are arranged at both ends.
[0035]
Inside the helicoid ring 29, a two-group ball frame 14 that holds the second lens group 12 that is a focus lens component is disposed. In the second lens group frame 14, a focus motor 16 and a photo reflector 17 are arranged outside the second lens group 12 in the radial direction, and a shutter unit 15 is arranged behind the second lens group 12. Since the optical path of the second lens group 12 is narrowed, the space that is vacated outside is effectively used, and the focus motor 16 and the photo reflector 17 are arranged to reduce the size of the zoom lens barrel 10. Can do.
[0036]
A helicoid 14 a is formed on the outer peripheral surface of the second group frame 14 and is engaged with the helicoid 29 b of the helicoid ring 29. A space between the second group ball frame 14 and the helicoid ring 29 is shielded by the helicoid. That is, between the second group ball frame 14 and the helicoid ring 29, the helicoids are arranged so as to overlap when viewed from the optical axis direction, so that light cannot pass between the helicoids.
[0037]
As schematically shown in FIG. 1, the rotation of the focus motor 16 is transmitted to the helicoid ring 29 via the speed reduction system 19, so that the second group ball frame 14 moves in the helicoid ring 29. It has become. The rotation of the focus motor 16 is detected by the photo interrupter 35.
[0038]
As shown in the sectional view of FIG. 4 and the front view of FIG. 5, the speed reduction system 19 is a gear train that transmits the rotation of the focus motor 16 to the output gear 18 and the pulse gear 34 that are output units. The photo interrupter 35 is disposed to face the pulse gear 34 so that the rotation of the focus motor 16 can be detected with high resolution. The output gear 18 meshes with the gear portion 29 a of the helicoid ring 29.
[0039]
As shown in FIG. 5, a pair of through holes 14a and 14b are formed in the second group ball frame 14, and a pair of guide shafts 32 and 33 fixed between the first group ball frame 11a and the third group ball frame 13a. Is inserted and guided in the optical axis direction while preventing the rotation of the second group ball frame 14. One through hole 14a is circular, the entire circumference of the guide shaft 32 is in sliding contact, the other through hole 14b is oval, the guide shaft 33 is in sliding contact only in the circumferential direction, and a gap is formed in the radial direction. The rotation of the second group ball frame 14 with respect to the guide shaft 32 is restricted. The position of the second group ball frame 14 in the direction perpendicular to the optical axis and the rotation with respect to the optical axis are restricted by the engagement with the guide shafts 32 and 33.
[0040]
Walls 14r, 14s, and 14t are erected around the through holes 14a and 14b. A flocking cloth (not shown) is fixed to the inner peripheral surfaces of the wall portions 14r, 14s, and 14t, the guide shafts 32 and 33 are surrounded by the flocking cloth, and the through holes 14a and 14b and the guide shafts 32 and 33 are formed. The gap is shielded.
[0041]
Next, the operation will be described.
[0042]
Due to the rotation of the zoom motor 40, the long gear 20, the drive ring 24, and the rotary cylinder 26 rotate, and the zoom lens barrel 10 expands and contracts. As a result, the first, second, and third lens groups 11, 12, and 13 supported via the advance cylinder 28 move.
[0043]
When the focus motor 16 rotates, the output gear 18 and the helicoid ring 29 rotate, and the second group ball frame 14 moves relative to the helicoid ring 29. By detecting the reflection pattern 30 with the photo reflector 17, the position of the second group ball frame 14 with respect to the helicoid ring 29 can be detected.
[0044]
During zoom driving, the zoom motor 40 is rotated to move the first, second, and third lens groups 11, 12, and 13 in the optical axis direction.
[0045]
At this time, the focus motor 16 may be driven in conjunction with the rotation of the zoom motor 40 to move the second group lens 12 to an appropriate position with respect to the first and third lens groups 11 and 13. Accordingly, the first, second, and third lens groups 11, 12, and 13 can be moved according to an arbitrary zoom curve, and the degree of freedom of zoom driving is expanded.
[0046]
At the time of focus driving, only the focus motor 16 is driven. The position of the second group lens frame 14 is determined by the rotation of the focus motor 16 detected by the photo interrupter 35 with reference to the reflection pattern detected by the photo reflector 17 described above, and the position of the second group lens frame 14, that is, the second lens group 12. Can be finely adjusted. At the time of focus driving, only the second group ball frame 14 is driven, so that the focus driving can be speeded up and the release time lag can be shortened.
[0047]
As described above, the zoom lens barrel 10 can increase the speed and size of the focus drive while ensuring the lens holding accuracy.
[0048]
In addition, this invention is not limited to the said embodiment, It can implement in another various aspect.
[0049]
For example, instead of driving the second group ball frame 14 with a helicoid mechanism, a cam pin provided on the ball frame (for example, a member of reference numeral 14) is replaced with a cylinder (for example, a member of reference numeral 28 (or 29)) and a guide (for example, The lens frame may be engaged with cam grooves provided in the reference numeral 29 (or 28), and the lens frame may be cam-driven by the relative rotation of the tube and the guide. When the cam mechanism is used, it is possible to realize non-linear feed or drive with different resolutions according to the focal length.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a zoom lens barrel according to an embodiment of the present invention. Indicates the front end side when it is pushed out.
FIG. 2 is a cross-sectional view of the rear end side of the zoom lens barrel of FIG. 1;
FIG. 3 is a cross-sectional view of the zoom lens barrel of FIG. 1 when retracted.
FIG. 4 is a cross-sectional view of a main part of a second group ball frame.
FIG. 5 is a front view of a second group ball frame.
FIG. 6 is a perspective view of a second group ball frame.
FIG. 7 is a development view of a helicoid ring.
[Explanation of symbols]
11 First lens group (the other lens component)
12 Second lens group (focus lens component)
13 Third lens group (the other lens component)
14 2 group ball frame 14a helicoid 16 focus motor 17 photo reflector (relative position detecting means)
18 Output gear (output unit)
20 Long gear (zoom mechanism)
22 Fixed cylinder (zoom mechanism)
24 Drive ring (zoom mechanism)
25 Straight traveling helicoid cylinder (zoom mechanism)
26 Rotating cylinder (zoom mechanism)
27 Straight cylinder (zoom mechanism)
28 Advance cylinder (zoom mechanism)
29 Helicoid ring (focus lens moving mechanism, cylinder)
30 Reflection pattern (relative position detection means)
32, 33 Guide shaft (focus lens moving mechanism, guide)

Claims (5)

A zoom mechanism for integrally moving at least two of the plurality of lens components;
A focus lens moving mechanism that moves one focus lens component relative to the other of the at least two lens components;
The focus lens moving mechanism includes a first tube , a second tube that is rotatable around the optical axis inside the first tube and is integrally disposed in the optical axis direction, and an interior of the second tube. And a lens frame that holds the focus lens component, and a guide that guides the lens frame in the optical axis direction while restricting the rotation of the lens frame with respect to the optical axis .
The ball frame is provided with a focus motor and an output unit that is rotated by the focus motor and engages with the second cylinder,
A zoom lens barrel, wherein the second tube can be rotated with respect to the first tube by rotation of the output unit . 2. The zoom lens barrel according to claim 1, wherein the output unit is a gear, and the second cylinder includes a gear unit in which teeth engaging with the output unit are arranged in a spiral shape. 3. . During zooming, both the zoom mechanism and the focus lens moving mechanism are driven,
3. The zoom lens barrel according to claim 1, wherein only the focus lens moving mechanism is driven during focusing. The zoom mechanism integrally moves the focus lens component and the lens components arranged before and after the focus lens component,
The guide is characterized in that extending parallel to the optical axis between the lens components which are disposed before and behind the focus lens components, according to claim 1, 2 or 3 zoom lens barrel according. A photo reflector disposed on the ball frame ,
One of the second tube and the guide is provided with a reflection pattern arranged to face the photo reflector,
With the movement of the focus lens component, the photo reflector is thus being moved along the reflection pattern, according to claim 1, 2, 3 or 4 zoom lens barrel according.

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