JP2005134588A - Lens barrel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens barrel capable of performing automatic focusing and manual focusing without switching using a clutch or the like and easily assembled. <P>SOLUTION: A planet gear 37 is rotatably pivotally supported at the rear end of a cam lens barrel 15 where a cam groove for moving focus lenses 2a and 2b in an optical axis direction with turning is formed, and is meshed with a gear part formed on the outer periphery of the front end of an AF driving lens barrel 13 turned by driving by a motor and fixed by stopping it, and a gear part formed on the inner periphery of the front end of an MF operation ring 19 for manual focusing. The ring 19 is locked with specified locking torque by a rod spring 41 and can be turned with larger torque than the specified locking torque. The barrel 15 is turned to be interlocked with the turning of the barrel 13 by the motor and/or turning by the manual operation of the ring 19 through the gear 37, whereby the focus lens is moved in the optical axis direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lens barrel that can perform automatic focus adjustment and manual focus adjustment without switching.

  2. Description of the Related Art Conventionally, a lens barrel attached to a camera having an AF (automatic focus adjustment) function has an automatic focus adjustment unit composed of a motor or the like in order to cope with an application where it is desired to focus on a desired position with respect to a subject. In addition to the above, there is one provided with a manual focus adjusting means capable of performing focus adjustment by manual operation. In such a lens barrel, the automatic focus adjustment unit and the manual focus adjustment unit need not be switched by a clutch or the like. For this reason, there has been proposed one in which the rotational force for transmission is transmitted to the feeding optical system through a differential mechanism composed of ball bearings. According to this, the focus lens can be moved without rotating the manual operation ring for manual focus adjustment during automatic focus adjustment, and the focus lens can be moved by rotating the manual operation ring during manual focus adjustment. Adjustment and manual focus adjustment can be performed without switching.

Furthermore, with such a configuration, in order to prevent the user from inadvertently moving and defocusing the manual focus adjustment means at the time of shooting in applications where no manual focus adjustment is required, Auto mode in which force is transmitted only from the auto focus adjustment system, manual mode in which force is transmitted only from the manual focus adjustment system, and auto manual in which force is transmitted from both the auto focus adjustment system and the manual focus adjustment system Japanese Patent Application Laid-Open No. H11-228707 proposes that the simultaneous mode can be switched.
Japanese Patent No. 2721408

  However, in the above configuration, since the rotational force from the manual focus adjustment system or the automatic focus adjustment system is transmitted to the moving lens system by the friction transmission of the ball bearings constituting the differential mechanism, it is important to balance the torque of each part. It has become. For this reason, when assembling the lens barrel, there is a problem in that it takes time to adjust the tightening of each member in the direction parallel to the optical axis or in the radial direction perpendicular to the optical axis in order to balance the torque of the respective parts.

  On the other hand, the front focus type lens that has a zoom lens barrel and the front lens group is a focus lens that adjusts the focus, once the focus is adjusted, the focus position does not change even if the zoom is moved (the focus does not shift). There are features. On the other hand, in the case of the inner focus type in which the focus adjustment is performed by the rear group lens, even if the focus is once adjusted, the focus position changes (out of focus) if the zoom is moved. It is necessary to control the focus lens in conjunction. Therefore, in AF control, the front focus method has an advantage that the focus lens can be controlled more easily than the inner focus method. However, since the focus lens adjustment drive range is wider in the front focus method than in the inner focus method, there is a problem that it takes time to reach the focus when performing automatic focus adjustment.

  The present invention has been made in order to solve the above-described problems, and a problem thereof is a lens barrel capable of performing automatic focus adjustment and manual focus adjustment without switching by a clutch or the like. It is an object of the present invention to provide a configuration of a lens barrel that can eliminate the need for torque adjustment of each part. It is another object of the present invention to provide a configuration capable of performing automatic focus adjustment in a short time even when the adjustment drive range (movement range) of the focus lens is wide, such as a front focus zoom lens barrel.

The present invention relates to a lens barrel,
A driving barrel that is rotated by driving a motor that is a driving source of the automatic focus adjustment mechanism, and is fixed by stopping the motor;
An operating ring for manual focus adjustment that is loosely fitted on the outside of the drive lens barrel, is locked with a predetermined locking torque, and is rotatable with a torque larger than the locking torque;
A cam groove is formed to move the focus lens along the optical axis along with the rotation, and has a cam barrel that is pivotably provided adjacent to the drive barrel and the front side of the operation ring. ,
A planetary gear rotatably supported at the rear end of the cam barrel is meshed with each of a gear portion formed on the outer periphery of the front end portion of the drive barrel and the inner periphery of the front end portion of the operation ring,
When the cam barrel rotates in conjunction with the planetary gear in response to the rotation of the drive barrel by driving the motor and / or the rotation of the operation ring by manual operation, the focus lens becomes light. It is characterized by being moved along the axial direction.

  Further, due to the shape of the cam groove of the cam barrel, in the range from the position of the shortest distance to the position of the predetermined distance that is frequently used, the cam barrel is longer than the range from the position of the predetermined distance to the position of infinity. The amount of movement of the focus lens in accordance with the amount of rotation is increased.

  According to the lens barrel of the present invention, at the time of automatic focus adjustment, the focus lens is moved by rotating the drive barrel by driving the motor without rotating the operation ring locked with a predetermined locking torque. In addition, during control of automatic focus adjustment, the focus lens can be moved by rotating the operating ring at a torque greater than the above-mentioned locking torque regardless of after the control, and the automatic focus adjustment and manual focus adjustment are clutched. It can be done without switching, etc., and it is easy to use. In addition, since the rotational power is transmitted via the planetary gear, it is not necessary to adjust the torque of each part as in the conventional example during assembly. Note that the locking torque of the operating ring can be set as desired as long as the locking member is configured as designed, so that adjustment thereof is also unnecessary. Therefore, assembly can be performed easily. Furthermore, automatic focus adjustment is possible even when the focus lens adjustment drive range is wide due to the relationship between the focus position range due to the cam groove shape of the cam barrel and the amount of movement of the focus lens according to the rotation amount of the cam barrel. It can be done in a short time.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Here, an embodiment of a zoom lens barrel of a front focus type of a terrestrial telescope with a digital camera is shown.

  FIG. 1 is a sectional view showing the structure of a zoom lens barrel according to an embodiment of the present invention. This zoom lens barrel is a digital camera of a terrestrial telescope with a digital camera (not shown) by a mount 44 provided at the rear end thereof. Connected to the part.

  Reference numeral 1 denotes a fixed main lens barrel, and a focus lens barrel 2 holding a focus lens 2a is fitted to the front part of the inner circumference so as to be slidable in the axial direction of the main lens barrel 1, that is, in the optical axis direction. ing. A zoom cam barrel 10 is fitted on the inner circumference of the main barrel 1 behind the focus lens barrel 2, and a zoom lens holding the zoom lenses 4a and 4b on the front side of the inner circumference. On the rear side of the holding barrel 4, a correction lens holding barrel 7 holding a correction lens 7a is fitted so as to be slidable in the optical axis direction. Further, a master lens holding barrel 8 holding a master lens 8a and a master lens holding barrel 9 holding a master lens 9a are fixed to the rear end of the main barrel 1. Light that has passed through the focus lens 2a, the variable magnification lenses 4a and 4b, the correction lens 7a, and the master lenses 8a and 9a from the outside is divided into two by a quick return half mirror (not shown), and one of the light passes through and is not shown. The other is reflected, re-imaged by a relay optical system (not shown), and observed by the user through an eyepiece (not shown).

  A focus cam barrel 15 for moving the focus lens 2a in the optical axis direction is provided at the front of the outer periphery of the main barrel 1, and a stepping motor (not shown) that is a driving source of the automatic focus adjustment mechanism is provided behind the focus cam barrel 15. AF driving lens barrels 13 that are rotated by an AF driving motor) are fitted so as to be rotatable about the optical axis. The rotational force of the AF drive motor (not shown) is transmitted to the gear portion 13b formed on the outer periphery of the rear end portion of the AF drive lens barrel 13 through a gear box (not shown). It is designed to rotate.

  As shown in FIG. 2, a substantially spiral cam groove 15a is formed in the focus cam barrel 15 in order to move the focus lens 2a along the optical axis direction. In addition, a straight groove (not shown) is formed along the optical axis direction at the front portion of the main barrel 1 that is in contact with the focus cam barrel 15, and the focus lens barrel 2 is formed with respect to the groove and the cam groove 15a. A focus cam pin 12 fixed to the outer periphery is engaged. Thus, when the focus cam barrel 15 rotates, the focus cam pin 12 is pressed in the optical axis direction through the cam groove 15a and the linear groove of the main barrel, and the focus lens barrel 2 moves along the optical axis direction. The focus lens 2a is moved.

  In FIG. 2, the length of the focus cam barrel 15 is enlarged about twice as much as the actual ratio in FIG. 1 in order to make the shape of the cam groove 15 a described later easier to understand.

  As shown in FIGS. 2 and 3, a flange 15b is formed at the rear end of the focus cam barrel 15, and planetary gears 37 are light-transmitted by a support shaft 37a at, for example, three places on the back surface of the flange 15b. It is pivotally supported so that it can rotate in the direction along the axis. As shown in FIGS. 3 and 4, the planetary gear 37 meshes with a gear portion 13 a formed on the outer periphery of the front end portion of the AF drive lens barrel 13, and is further rotatable to the outside of the AF drive lens tube 13. The loosely engaged manual focus adjusting MF operation ring 19 is engaged with a gear portion 19a formed on the inner periphery of the front end portion.

  The MF operation ring 19 has a rear end engaged with a front end portion of the first exterior lens barrel 20 that forms a fixing portion of the main body exterior of the zoom lens barrel together with the second exterior lens barrel 22. The portion is pressed by a bar spring 41 and locked with a predetermined locking torque, and can be rotated around the optical axis by applying a torque larger than the locking torque. The bar spring 41 is formed by thinning a leaf spring into a bar shape, and is formed into a crushed M-shape as shown in FIG. 5, and has an elastic force in the vertical direction of the M-shape. For example, the length of one side of the M character is 4 to 10 mm, the bending angle of each side is 145 °, and the height of the M character is about 3 mm. The bar spring 41 is sandwiched between, for example, three places in the circumferential direction between the front end portion of the first exterior lens barrel 20 and the engagement portion (for example, the concave portion and the convex portion) of the rear end portion of the MF operation ring 19. The MF operation ring 19 is pressed against the first exterior lens barrel 20 by the elastic force in the direction radiating from the optical axis and locked with a predetermined locking torque. The locking torque is set by the design of the bar spring 41 so that it becomes larger than the torque that the planetary gear 37 rotates to rotate the MF operation ring 19 as the AF drive barrel 13 rotates. The

  As shown in FIGS. 7A and 7B, the bar spring 41 may be curved in an arc shape as a whole and bent at one end in an L shape, and may have the dimensions as illustrated. In such a shape, the locking torque is weaker than in the case of the M-shape. What is necessary is just to use properly according to the use of the lens barrel, the weight of the MF operation ring 19, and the like.

  Further, a zoom operation ring 21 for zoom operation is fitted to the outer periphery of the rear portion side slightly recessed of the first exterior lens barrel 20 so as to be rotatable. A mounter 44 is fixed to the rear end of the second exterior barrel 22. Since the mechanism for performing the zoom operation by operating the zoom operation ring 21 is not related to the features of the present invention, the description thereof will be omitted and only the outline of the zoom operation will be described later.

  Next, the focus adjustment operation of this embodiment will be described. When focus adjustment is performed only by manual operation with the AF mode turned off at the time of shooting, the MF operation ring 19 is manually operated while the AF drive motor (not shown) that drives the AF drive lens barrel 13 is de-energized and stopped. Rotate. Note that, by applying a turning force larger than the locking torque by the bar spring 41 described above, the locking of the MF operation ring 19 can be released and rotated. By the rotation of the MF operation ring 19, the turning power is transmitted to the planetary gear 37 through the gear portion 19a, and the planetary gear 37 rotates. At this time, the AF drive lens barrel 13 is not held (fixed) in a predetermined rotational phase by energization because of the gear ratio of a gear train (not shown) that transmits the power of the AF drive motor to the AF drive lens barrel 13. However, since the planetary gear 37 is fixed so as not to rotate due to the rotation of the planetary gear 37, the planetary gear 37 revolves with the rotation. Then, the focus cam barrel 15 to which the support shaft 37a of the planetary gear 37 is fixed rotates, and the cam pin 12 is pressed in the optical axis direction through the cam groove 15a and the linear groove of the main barrel, thereby the focus lens mirror. The tube 2 moves along the optical axis direction together with the focus lens 2a. In this way, by rotating the MF operation ring 19 in both directions, the focus lens 2a can be moved back and forth along the optical axis direction to perform focus adjustment.

  On the other hand, when only the automatic focus adjustment is performed without performing the manual focus adjustment operation with the AF mode turned on, the AF drive motor is driven, and the rotational force of the AF drive barrel 13 is not shown through a gear train (not shown). The AF drive lens barrel 13 is rotated by being transmitted to the gear portion 13b at the rear end. The rotational force is transmitted to the planetary gear 37 via the gear portion 13a at the front end of the AF driving barrel 13, and the planetary gear 37 rotates. At this time, the MF operation ring 19 is locked by the bar spring 41, and as described above, the locking torque is adjusted to be stronger than the torque for the planetary gear 37 to rotate the MF operation ring 19 by rotation. Therefore, the MF operation ring 19 does not rotate. For this reason, the planetary gear 37 revolves as it rotates, the focus cam barrel 15 rotates as described above, and the focus lens barrel 2 moves along with the focus lens 2a along the optical axis direction.

  When the AF mode is started, the focus lens 2a is moved from the position closest to the focal position (shortest distance) to the position at infinity by the control of a control circuit (not shown). Scanning is performed aiming at a position with a high focus evaluation value. Here, as described above, since the zoom lens barrel of the front focus method has a wider adjustment driving range of the focus lens than the inner focus method, it takes time to reach the focus when performing automatic focus adjustment. End up.

  Therefore, in this embodiment, as shown in FIG. 2, the cam groove 15a of the focus cam barrel 15 is substantially spiral and is inclined with respect to the axial direction (optical axis direction) of the barrel 15. A non-linear shape in which the inclination changes depending on the range. That is, in this case, assuming that the focus position frequently used in normal use is a position of 20 m, the cam groove is in the range from the position of 5 m to the position of 20 m in the nearest position (shortest distance). By loosening the inclination of 15a with respect to the optical axis direction, the amount of movement of the focus lens 2a is increased in accordance with the amount of rotation of the focus cam barrel 15, and the focus lens is moved relatively quickly to adjust the coarse movement of the focus. In the range from the focal point position of 20 m to the infinity position, by making the inclination steep, the amount of movement corresponding to the amount of rotation is reduced, and the focus lens is moved relatively slowly to finely adjust the focus. I try to do it.

  That is, in this embodiment, the focus evaluation value is sampled over the entire moving range of the focus lens at the time of automatic focus adjustment, but as shown in FIG. 2, the light of the focus lens by the focus position and the cam groove 15a of the focus cam barrel 15 is obtained. The relationship with the length of the moving range in the axial direction is non-linear, and the length of the moving range from the nearest 5 m position to the 20 m position of the focal position is from the focal position of 20 m to the infinity position. It is considerably longer than the length of the moving range. On the other hand, by making the shape of the cam groove 15a as described above, it is assumed that the normally used focal position is 20m, and the focal position is focused to the nearest 5m or infinity. Even if there is a lens, it can be quickly returned to the position of 20 m from there. In this way, even when the adjustment driving range (movement range) of the focus lens is wide, it is possible to shorten the time until focusing is achieved when performing automatic focus adjustment.

  On the other hand, if the AF mode is turned on and the MF operation ring 19 is rotated to perform manual focus adjustment during the AF control, the rotation directions of the AF drive barrel 13 and the MF operation ring 19 coincide. Depending on whether or not, the revolution speed of the planetary gear 37 increases synergistically or cancels and slows down, but in any case, the focus lens 2a is moved in the optical axis direction by the revolution of the planetary gear 37 to adjust the focus. In this case, no extra load is applied to the MF operation ring 19 and the AF drive motor. Therefore, for example, even if the MF operation ring 19 is kept being touched, the focus lens can be driven by AF control without rotating it, and the AF mode is turned off after the focus position is determined by AF control. Thus, the user can easily operate the MF operation ring 19 to move it to the user's preferred focus position.

  Next, an outline of the zoom operation will be described with reference to FIG. By rotating the zoom operation ring 21, the variable magnification lens holding barrel 4 and the correction lens holding barrel 7 are moved in the optical axis direction, and the variable magnification lenses 4a, 4b and the correction lens 7a are telephoto end in the optical axis direction. The focal length can be changed within a range of 75 mm to 225 mm, for example. The wide end is when the variable power lens 4a is at the position A and the correction lens 7a is at the position C, and the tele end is when the variable power lens 4a is at the position B and the correction lens 7a is at the position D. The variable magnification lenses 4a and 4b are moved in the optical axis direction while maintaining a constant interval by the variable magnification lens holding barrel 4, whereas the correction lens 7a is moved in an independent movement. This is because the correction lens 7a corrects the out-of-focus state due to the movement of the variable power lenses 4a and 4b at each position to keep the focused state.

  According to the zoom lens barrel of the present embodiment as described above, the focus lens 2a is moved without rotating the MF operation ring 19 during automatic focus adjustment, and the MF operation ring 19 is rotated during manual focus adjustment. The focus lens can be moved, and automatic focus adjustment and manual focus adjustment can be performed without switching by a clutch or the like. And since it is the structure which transmits rotational force via the planetary gear 37, the torque adjustment of each part like the prior art example of patent document 1 at the time of an assembly is unnecessary. The locking torque of the MF operation ring 19 can be set as desired as long as the bar spring 41 is configured as designed, so that adjustment thereof is also unnecessary. Therefore, assembly can be performed easily. Furthermore, by setting the shape of the cam groove 15a of the focus cam barrel 15 to the shape described with reference to FIG. 2, automatic focus adjustment can be performed in a short time even if the adjustment drive range of the focus lens is wide.

  Of course, the configuration of the present invention is not limited to the zoom lens barrel of the embodiment, but can be applied to other lens barrels.

It is sectional drawing which shows the structure of the zoom lens barrel in the Example of this invention. It is a perspective view showing the shape of a cam groove of a focus cam barrel of a zoom lens barrel. It is an expanded sectional view which shows the structure around the planetary gear of a zoom lens barrel. It is arrow sectional drawing of the arrow A in FIG. It is explanatory drawing which shows the shape and dimension of a bar spring. It is explanatory drawing explaining the zoom operation | movement of a zoom lens barrel. It is the front view (A) and top view (B) which show the other shape and dimension of a bar spring.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main barrel 2 Focus lens barrel 2a Focus lens 4 Variable magnification lens holding barrel 4a, 4b Variable magnification lens 7 Correction lens holding barrel 7a Correction lens 8, 9 Master lens holding barrel 8a, 9a Master lens 10 Zoom cam mirror Tube 12 Focus cam pin 13 AF drive barrels 13a, 13b Gear portion 15 Focus cam barrel 15a Cam groove 19 MF operation ring 19a Gear portion 20 First exterior barrel 21 Zoom operation ring 22 Second exterior barrel 37 Planetary gear 41 Rod Spring 44 mount

Claims (2)

A driving barrel that is rotated by driving a motor that is a driving source of the automatic focus adjustment mechanism, and is fixed by stopping the motor;
An operating ring for manual focus adjustment that is loosely fitted on the outside of the drive lens barrel, is locked with a predetermined locking torque, and is rotatable with a torque larger than the locking torque;
A cam groove is formed to move the focus lens along the optical axis along with the rotation, and has a cam barrel that is pivotably provided adjacent to the drive barrel and the front side of the operation ring. ,
A planetary gear rotatably supported at the rear end of the cam barrel is meshed with each of a gear portion formed on the outer periphery of the front end portion of the drive barrel and the inner periphery of the front end portion of the operation ring,
When the cam barrel rotates in conjunction with the planetary gear in response to the rotation of the drive barrel by driving the motor and / or the rotation of the operation ring by manual operation, the focus lens becomes light. A lens barrel that is moved along an axial direction.   Due to the shape of the cam groove of the cam barrel, the cam barrel rotates in the range from the position of the shortest distance to the position of the predetermined distance where the frequency of use is high and from the position of the predetermined distance to the position of infinity. 2. The lens barrel according to claim 1, wherein the amount of movement of the focus lens in accordance with the amount of movement is increased.

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