JPH1164705A - Focusing driving device and lens barrel for digital still camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To thin a lens barrel in an optical axis direction while securing lens performance and to improve assemblability by arranging the driving direction of a driving member equipped with a cam surface on which a moving frame holding a lens group abuts on and the turning shaft of a stepping motor driving the driving member in parallel with a plane orthognally crossed with an optical axis. SOLUTION: A guiding shaft fitting sliding hole 20a of the moving frame 20 moving a held lens group in the optical axis direction by sliding and fitting on a guiding shaft 40 disposed in parallel with the optical axis 3 of the lens group is fit to the guide shaft 40 so as to freely slide. The moving frame 20 is energized downward by an energizing spring 50, and the driving member abutting part 20g of the moving frame 20 abuts on the cam surface 60d of the driving member 60. Furthermore, the driving direction of the member 60 and a lead screw directly connected with the turning shaft of the stepping motor installed in a driving source for driving the member 60 are arranged in parallel with the plane orthogonally crossed with the optical axis 3. By driving the member 60 by the driving source, the moving frame 20 is moved in the optical axis direction so as to perform focusing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital still camera and, more particularly, to a focus driving device for a digital still camera and a lens barrel of a digital still camera having the focus driving device.

[0002]

2. Description of the Related Art In a digital still camera, a stepping motor having a lead screw as a rotation axis is used as a power source, a rotation axis is set in parallel with an optical axis of a lens group, and a nut screwed to the lead screw. The member is locked to a moving frame that holds the lens group, the lead screw rotates by pulse driving of a stepping motor, and the lens group moves according to the rotation angle to focus on the subject.

Alternatively, a moving frame for holding the lens group has a hollow disk provided with a cam surface on one end surface which is in contact with the moving frame, and a gear is installed on the inner or outer periphery of the hollow disk.
A stepping motor having a pinion as a rotation axis is used as a power source, the motor rotation axis is set in parallel with the optical axis of the lens group, the pinion meshes with the gear of the hollow disk, and the pinion is rotated by the pulse drive of the stepping motor. 2. Description of the Related Art There is known a focus drive device in which a hollow disk rotates according to a rotation angle, a cam surface moves with the rotation of the hollow disk, and a focusing lens group moves to focus.

[0004]

In such a conventional technique, since the motor rotation axis and the optical axis are installed in parallel, it is difficult to reduce the thickness of the lens barrel in the optical axis direction.

In the lead screw type, when the motor is used with two-phase excitation (generally, the number of divisions is two).
0) The amount of movement of the lens in one pulse is determined by the lead of the lead screw. If the lead is made smaller, the amount of movement / pulse can be made finer, but the number of threads is reduced, so it is necessary to engage with many threads. Therefore, the output torque of the motor is eaten by the nut portion, and the torque for driving the lens is reduced. For this reason, when the lens weight becomes heavy, the movement amount / pulse cannot be reduced, and a problem occurs in focusing accuracy.

Further, in the hollow disk end face cam type, since the output torque of the motor is reduced by the pinion and the gear disposed around the hollow disk, even if the focusing lens is heavier than the lead screw type, it can be driven. is there. However, if the size of the hollow disk is increased to increase the reduction ratio, the frictional force between the hollow disk and the hollow disk guide increases, resulting in a torque loss. Then, there is a problem that the diameter of the lens barrel itself becomes large.

The present invention has been made to solve the above problems. That is, it enables the lens barrel to be thinner in the optical axis direction, secures lens performance, reduces loss of motor output torque, improves assemblability, and detects the reference position of the lens group with high accuracy. It is an object of the present invention to provide a focusing drive device and a lens barrel of a digital still camera for performing the operation.

[0008]

The object of the present invention is achieved by adopting the following constitution.

That is, it has a guide shaft disposed in parallel with the optical axis of the lens group, and a fitting portion that fits with the guide shaft, and holds the lens group to move the lens group in the optical axis direction. A moving frame, and a driving member having a cam surface with which a contact portion of the moving frame that moves the moving frame in the optical axis direction comes into contact. The driving direction of the driving member and the driving member are driven. A focus driving device for a digital still camera, wherein a rotation axis of a stepping motor installed in a driving source is arranged in parallel with a plane orthogonal to an optical axis.

An exposure control device using an aperture and a shutter;
In a lens barrel of a digital still camera having a focus driving device for moving a lens group held by the exposure control device in an optical axis direction to focus, the exposure control device is provided with a lens frame mechanism; A lens barrel of a digital still camera characterized by incorporating a lens directly into the mechanism.

Next, the operation of the present invention will be described.

According to the first aspect of the present invention, the occupancy of the stepping motor in the optical axis direction is only the diameter of the motor, and the lens barrel can be made thin.

According to a second aspect of the present invention, the output torque by the stepping motor arrangement, that is, the rotation axis of the lead screw directly connected to the rotation axis of the stepping motor is parallel to the plane orthogonal to the optical axis of the lens group. And the driving direction of the driving member is also arranged so as to be parallel to the surface,
Such an arrangement of the stepping motor enables the output torque to be used effectively.

According to the third aspect of the present invention, since the contact area can be reduced, the loss of the output torque of the motor can be suppressed low.

According to the fourth aspect of the invention, accurate focusing can be achieved without occurrence of backlash caused by urging applied to the moving frame.

According to the fifth aspect of the present invention, since the frictional force generated on the contact surface can be reduced, the loss of the output torque of the motor can be suppressed low.

In the invention according to claim 6, the straightness of the nut member and the torque loss due to the fitting can be easily managed by the unit, and the assembling property is improved.

According to the seventh aspect of the present invention, the position of the lens can be detected by a component having a large moving amount, and the position of the lens can be accurately detected.

In the invention according to claim 8, since the lens is directly incorporated in the exposure control device using the aperture / shutter, the accumulation of the optical axis shift that occurs when the lens frame incorporating the lens is further incorporated in the exposure control device is reduced. And lens performance can be easily ensured.

According to a ninth aspect of the present invention, the flexible printed circuit board is prevented from having a spring property as the moving frame moves, so that the driving force of the moving frame is not consumed by the spring property. That is, a flexible printed circuit board is generally
Although the flexible printed circuit board has a spring property with the movement of the moving frame, the driving force of the moving frame is consumed by the spring property, but this is prevented.

The invention according to claims 10 and 11 is also claim 9
This is almost the same as the invention according to the first aspect, whereby an unnecessary external force is prevented from being applied to the flexible printed circuit board, and the loss of the output torque of the motor can be suppressed low.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings and FIGS. 1 to 5, but the present invention is not limited to the embodiments described below.

FIG. 1 is an exploded perspective view of members constituting a focusing drive device and a lens barrel of a digital still camera according to the present invention as viewed from the front. FIG. 2 is a side view of a moving frame of the focusing drive device and a driving member that moves the moving frame. FIG.
Is a diagram illustrating a configuration of a drive source that drives the drive member,
(A) is a top view of a drive source, (b) is a front view of a drive source. 4A and 4B are diagrams illustrating the configuration of the lens barrel. FIG. 4A is a front view of the lens barrel, and FIG. 4B is a cross-sectional view taken along line XX of FIG. 5A and 5B are diagrams further explaining the lens barrel of FIG. 4, wherein FIG. 5A is a front view of the lens barrel, and FIG. 5B is a cross-sectional view taken along line XX of FIG.

The focus driving apparatus for a digital still camera according to the first aspect of the present invention has a guide shaft provided in parallel with the optical axis of the lens group, and a fitting portion fitted to the guide shaft. A moving frame that holds the lens group and moves the lens group in the optical axis direction, and a driving member that has a cam surface with which a contact portion of the moving frame moves the moving frame in the optical axis direction. A digital still camera, wherein a driving direction of the driving member and a rotation axis of a stepping motor installed in a driving source for driving the driving member are arranged in parallel with a plane orthogonal to the optical axis. It is a focusing drive.

That is, in FIG. 1 to FIG. 4, the focus driving device 1 of the present invention includes a movable frame 20, a lens fitting portion 20 e as a lens frame mechanism of the movable frame 20, a first lens holder 211,
The lens fitting ring 80, which is a lens frame mechanism of the exposure control device 80,
a, a lens spacing ring 213 and a fifth lens holder 214 are provided, and a first lens 201, a second lens 202, a bonded third lens 203, a fourth lens 204, and a fifth lens 205 are mounted on these lens frame mechanisms. It has been incorporated.

The moving frame 20 is provided with a guide shaft 40 provided in parallel with the optical axis 3 of the lens group.
And a guide shaft fitting sliding hole 20a that fits and slides with the guide shaft. The guide shaft 40 is fitted and fixed to the guide shaft fitting holes 30b and 10a of the main body cover 30 and the main body 10 as shown by a one-dot chain line in the figure. The mating slide hole 20a is slidably fitted on the guide shaft 40, and the moving frame 20 is urged downward by the urging force of the urging spring 50 in the downward direction. The U-shaped groove 20b of the moving frame 20 fits and slides with the moving frame rotation restricting portion 10b provided on the main body 10, so that the moving frame 20 can go straight without rotating. I have.

Then, the lens group is held as described above,
A moving frame 20 for moving this lens group in the direction of the optical axis 3 includes:
A drive member contact portion 20g which is a contact portion of the moving frame 20
The drive member cam surface 60 of the drive member 60 having a cam surface
d is brought into contact with the urging force of the urging spring 50. When the driving member 60 is driven by a driving source 70, which will be described later, the moving frame 20 moves in the optical axis direction and focuses. The driving direction of the driving member 60 and the driving direction of the driving member 60 are determined. The lead screw 70a directly connected to the rotation axis of the stepping motor 70e installed in the driving source 70 to be driven is arranged in parallel with a plane orthogonal to the optical axis 3.

As described above, since the focusing drive device of the present invention is constituted, the occupation amount of the stepping motor in the optical axis direction is only the diameter of the stepping motor plus some margin, and the lead screw of the conventional stepping motor is used. The rotation axis directly connected to the optical axis is different from the axis parallel to the optical axis, and the lens barrel can be made thinner.

The angle of the driving member cam surface 60d with respect to a surface perpendicular to the optical axis 3 is preferably less than 45 degrees.

The driving member 60 is slidably inserted in a longitudinal direction into a driving member linear slide guide 10c which is a rectangular concave portion of the main body 10, and the driving member presser 70f is disposed from above.
, So that the lid is pressed down. The fitting slide portions 60a, 60b, 60c of the driving member 60
The drive member slides and is guided by being fitted into the slide guide 10c. Then, the drive source mounting portion 10e of the main body 10
, A drive source 70 is attached.

The drive source 70 is a lead screw 70a of a stepping motor 70e installed in the drive source 70.
And a nut member guide shaft 70b of a guide shaft disposed in parallel with the rotation shaft. The nut member guide shaft 70b is fitted to the nut member guide shaft 70b, and the lead screw 70
a and a nut member 70c that is screwed together. For this reason, the straightness of the nut member 70c and the torque loss due to the fitting can be easily managed by the unit, and a drive source with improved assemblability can be provided.

The driving member locking portion 70d of the driving source 70 is inserted into the driving source locking portion 60f of the driving member 60, and the driving member 60 is driven by the rotation of the stepping motor 70e. , Drive member cam surface 60d
Since the angle with respect to the plane orthogonal to the optical axis 3 is less than 45 degrees, the moving frame 20 can be easily moved by the driving force of the driving member 60 by the rotating power of the stepping motor 70e. That is, the output torque due to the stepping motor arrangement, and therefore, the rotation axis of the lead screw directly connected to the rotation axis of the stepping motor is arranged parallel to the plane orthogonal to the optical axis of the lens group, and the driving direction of the driving member is also the same. The output torque can be used effectively by arranging the stepping motor in such a manner as to be parallel to the surface.

The shape of the drive member contact portion 20g of the moving frame 20 that contacts the drive member cam surface 60d is preferably spherical or cylindrical. By adopting such a shape, the contact area can be reduced, so that the loss of the output torque of the motor can be suppressed low.

The driving member 60 and the moving frame 20 at the time of focusing
It is preferable that focusing is performed in one operating direction. In the focus driving device of the digital still camera according to the present invention, the number of pulses is calculated back from the reference position by calculating the number of pulses back from the non-focus signal of the CCD at a time when the focus slightly passes from the time of focusing. As the movement of the lens, the lens moves forward a little over the in-focus position, and after returning once, moves the lens forward by the number of focusing pulses. That is,
By always focusing in one operation direction, backlash caused by the biasing spring 50 or the like applied to the moving frame 20 does not occur, and accurate focusing is possible.

The driving member 60 is preferably made of a material having high lubricity, for example, a resin material such as polycarbonate (natural) or polyacetal. By using such a material having high lubricity, the frictional force generated on the contact surface can be reduced, so that the loss of the output torque of the motor can be suppressed low.

The reference position of the lens group is detected by a detection sensor such as a photo interrupter 90, which is a reference position detection sensor, and the angle of the drive member cam surface 60d with respect to a surface orthogonal to the optical axis is less than 45 degrees. Is detected by the movement of the driving member 60, and the angle is 45 degrees.
If it is higher than the degree, it is preferable to detect it by the movement of the moving frame 20. By doing so, it is possible to detect the position of the lens with a component having a large moving amount, and it is possible to detect the position of the lens accurately.

In detecting the reference position, the light shielding portion 60e of the driving member 60 is connected to the reference position detection sensor installation portion 1 of the main body 10.
0f, the recess 90a of the photo interrupter 90
The reference position is detected by driving the driving member 60 for moving the moving frame 20 for focusing. This reference position is determined as a reference position of the moving frame 20 at the position ∞, the closest shooting position, and this reference position is a reference at the time of focusing. Therefore, the reference position is an important position as a reference for focusing, and accurate positioning is required. Therefore, it is preferable to detect the reference position using a component having a large moving amount.

Next, in the lens barrel of the digital still camera according to the second aspect of the invention, an exposure control device using an aperture and a shutter, and a lens group held by the exposure control device are moved in the optical axis direction to focus. In a lens barrel of a digital still camera having a focus drive device, the exposure control device is provided with a lens frame mechanism, and a lens is directly incorporated in the lens frame mechanism to provide a lens barrel of the digital still camera.

That is, in FIGS. 1 and 5, the lens barrel 2 of the present invention is an aperture / shutter having a sector 80e which also has an aperture function for controlling the brightness of the lens and a shutter function for controlling the exposure time. A control device 80 is a lens barrel of a digital still camera having a focusing drive device that moves a lens group held by the exposure control device 80 in the direction of the optical axis 3 to focus, and the exposure control device 80 and the The movable frame 20, which is a part of the exposure control device 80, is provided with lens fitting portions 20e, 80a, which are lens frame mechanisms, and a first lens holder 21.
1. Lens spacing rings 212 and 213, Fifth lens holder 2
14 and the first lens 20 is directly connected to the lens frame mechanism.
1, second lens 202, bonded third lens 20
Third, the lens barrel of the digital still camera is characterized by incorporating the fourth lens 204 and the fifth lens 205.

As described above, since the lens barrel 2 of the present invention is constituted and the lens is directly incorporated in the exposure control device 80 having the aperture / shutter function, the lens frame incorporating the lens is further incorporated in the exposure control device. Therefore, it is possible to reduce the accumulation of the optical axis shift occurring in the above, and it is possible to easily secure the lens performance.

A flexible printed circuit board 80b for transmitting an electric signal for operating the aperture / shutter of the exposure control device 80 is attached to the exposure control device 80.
The flexible printed circuit board 80b is a lens barrel of a digital still camera which is not bent in the thickness direction and is connected to a connector of the camera body. By doing so, the flexible printed circuit board 80b is prevented from having spring properties as the moving frame 20 moves, so that the driving force of the moving frame 20 is not consumed by the spring property. That is, in general, the flexible printed circuit board is used by being bent. In this case, the flexible printed circuit board 80b has a spring property as the moving frame 20 moves, and the driving force of the moving frame 20 is consumed by the spring property. However, this can be prevented.

The flexible printed circuit board 80b has a flexible printed circuit board locking hole 80c for locking the movement of the flexible printed circuit board 80b in accordance with the movement of the lens, and a main barrel 10 constituting the lens barrel. To lock the flexible printed board locking hole 80c.
A configuration is provided in which a flexible printed board locking boss 10d is provided.

Further, the main barrel cover 30 constituting the lens barrel, which is also a cover of the exposure control device 80, and the main barrel 10 constituting the lens barrel,
The flexible printed circuit board 80b,
Flexible printed circuit board guards 30a and 10g, which are protective members for protection, are provided with at least a gap 11 in which a lens can be moved. This void 11
In the above, at least the interval between the reference position of the moving frame 20 and the closest photographing position is necessary. By doing so, unnecessary external force is prevented from being applied to the flexible printed circuit board 80b, and the stepping motor 70b is prevented.
e, the loss of the output torque can be kept low.

[0044]

According to the present invention, the lens barrel can be made thinner in the optical axis direction, the lens performance can be secured, the loss of the motor output torque can be reduced, the assemblability can be improved, and the lens group can be improved. A focus driving device and a lens barrel of a digital still camera that perform reference position detection with high accuracy have been provided.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of members constituting a focusing drive device and a lens barrel, as viewed from the front.

FIG. 2 is a side view of a moving frame of the focus driving device and a driving member that moves the moving frame.

FIG. 3 is a diagram illustrating a configuration of a drive source that drives a drive member.

FIG. 4 is a diagram illustrating a configuration of a lens barrel.

FIG. 5 is a diagram further illustrating the lens barrel of FIG. 4;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 focusing drive device 2 lens barrel 3 optical axis 10 main body 20 moving frame 30 main body lid 40 guide shaft 50 biasing spring 60 drive member 70 drive source 80 exposure control device 90 photo interrupter

Claims (11)

[Claims] A guide shaft disposed in parallel with an optical axis of the lens group; and a fitting portion fitted to the guide shaft. The lens group is held in the optical axis direction while holding the lens group. A moving frame, and a driving member having a cam surface with which a contact portion of the moving frame that moves the moving frame in the optical axis direction comes into contact. The driving direction of the driving member and the driving member are driven. A focus driving device for a digital still camera, wherein a rotation axis of a stepping motor installed in a driving source is arranged in parallel with a plane orthogonal to an optical axis. 2. The focus driving device of a digital still camera according to claim 1, wherein an angle of the driving member cam surface with respect to a surface orthogonal to the optical axis is less than 45 degrees. 3. The focus driving device for a digital still camera according to claim 1, wherein the shape of the moving frame contact portion that contacts the driving member cam surface is a spherical surface or a cylindrical surface. . 4. The focus driving device for a digital still camera according to claim 1, wherein the driving member and the moving frame at the time of focusing are operated in one direction. 5. The focus driving device for a digital still camera according to claim 1, wherein the driving member is made of a material having high lubricity. 6. The driving source has a rotating shaft forming a lead screw of a stepping motor installed in the driving source, and a guide shaft disposed in parallel with the rotating shaft. The focus driving device for a digital still camera according to claim 1, comprising a nut member fitted and screwed with the lead screw. 7. The reference position of the lens group is detected by a reference position detection sensor, and the angle of the drive member cam surface with respect to a surface orthogonal to the optical axis is less than 45 degrees. 2. The focus driving device for a digital still camera according to claim 1, wherein the detection is performed by a movement of the driving member, and when the angle is 45 degrees or more, the detection is performed by a movement of the moving frame. 3. 8. A lens barrel of a digital still camera having an exposure control device using an aperture and a shutter, and a focusing drive device that moves a lens group held by the exposure control device in an optical axis direction to focus. A lens barrel of a digital still camera, wherein a lens frame mechanism is provided in the control device, and a lens is directly incorporated in the lens frame mechanism. 9. A flexible printed circuit board for transmitting an electric signal for operating an aperture and a shutter of the exposure control apparatus is attached to the exposure control apparatus. 9. The lens barrel of a digital still camera according to claim 8, wherein the lens barrel is connected to the digital still camera. 10. The flexible printed circuit board includes:
10. The device according to claim 8, wherein a hole for locking the flexible printed circuit board in accordance with the movement of the lens is provided, and a locking boss for locking the hole is provided in the lens barrel. The lens barrel of the digital still camera described. 11. The cover of the exposure control device and the lens barrel are provided with a protection member for protecting the flexible printed circuit board by sandwiching at least a gap through which a lens can be moved. Item 11. A lens barrel of the digital still camera according to any one of items 8 to 10.