JP3240845B2 - Optical element position detecting device in lens device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens device used for a camera or the like, and more particularly to an optical element position detecting device in a lens device for detecting the position of an optical element constituting a lens.

[0002]

2. Description of the Related Art In a camera having an automatic focusing mechanism,
When the lens is pointed at the subject, the focus is automatically adjusted. There are various methods for adjusting the focus of a lens.
First, there is a lens device configured to move a part of an optical element constituting a lens, for example, a front lens group in an optical axis direction to focus on a lens based on focus detection information indicating a state of defocus with respect to a subject. .

In such a lens device, when the lens is focused on the subject by moving the optical element in the optical axis direction, the position of the optical element in the optical axis direction becomes information indicating the subject distance, so that Not only the position needs to be detected, but also the position information of the optical element is one of the necessary information in performing the focus adjustment.

On the other hand, as a drive mechanism for moving an optical element constituting a lens in the optical axis direction, an impact type actuator using an electro-mechanical conversion element is known.

FIG. 9 shows an example of a drive mechanism of an optical element to which such a known impact-type actuator is applied, and is a perspective view in which a part of the structure is cut away.

The configuration will be described with reference to FIG. A drive shaft 53 for driving the lens holding frame 52 in the optical axis direction is supported on the support frame 51 of the actuator so as to be movable in the optical axis direction by a receiver 51a at the distal end of the support frame 51 and a receiver 51b at an intermediate portion. Have been. The piezoelectric element 5 is provided at one end of the drive shaft 53.
4 is fixed, and the other end of the piezoelectric element 54 is fixed to the flange 51 c of the support frame 51. The support frame 51 is provided with a guide shaft 56 that allows the lens group holding frame 52 to move in the optical axis direction but prohibits rotation.

A contact member 52b penetrating the drive shaft 53 is provided on the flange portion 52a of the lens holding frame 52. The contact member 52b and the drive shaft 53 are pressed against each other by a pressure spring 52c, and friction is generated by an appropriate frictional force. Are combined. FIG.
FIG. 5 is a view showing a cross section near the contact member 52b, and the contact member 52b of the lens holding
The state of pressure contact is shown by c. A cutout 52d through which the guide shaft 56 passes is formed in the flange 52a of the lens holding frame 52.

In the above configuration, when a drive pulse having a waveform composed of a gentle rising portion and a rapid falling portion as shown in FIG. 11 is applied to the piezoelectric element 54, the gentle rising portion of the driving pulse has The piezoelectric element 54 gently causes elongation displacement in the thickness direction, and the drive shaft 53
Is displaced in the direction of arrow a in the axial direction. Therefore, the drive shaft 5
Since the contact member 52b of the lens holding frame 52 that has been pressed against and frictionally connected to the lens holder 3 by the pressing spring 52c also moves in the direction of arrow a, the lens holding frame 52 can be moved in the direction of arrow a.

At the rapid falling portion of the drive pulse, the piezoelectric element 54 rapidly contracts in the thickness direction, and the drive shaft 53 is also displaced in the axial direction in the direction opposite to the arrow a. At this time, the contact member 52b of the lens holding frame 52 pressed against the drive shaft 53 by the pressure contact spring 52c overcomes the frictional force between the drive shaft 53 and the drive member 53 due to its inertial force and substantially stays at that position. The holding frame 52 does not move.

By continuously applying the driving pulse having the above-described waveform to the piezoelectric element 54, the lens holding frame 52 is moved in the direction indicated by the arrow a.
Can be continuously moved in the direction indicated by.

The movement of the lens holding frame 52 in the direction opposite to the arrow a can be achieved by applying a drive pulse having a waveform consisting of a rapid rising portion and a gentle falling portion following the rising portion to the piezoelectric element 54.

An impact type actuator as described above.
Since the lens holding frame 52 moves along the drive shaft 53 in the drive mechanism of the optical element to which the motor is applied, the magnetizing rod 57 is arranged in parallel with the drive shaft 53, and the magnetoresistive element 58 is mounted on the lens holding frame. If a position sensor (MR sensor) for detecting the position by changing the mounting and the magnetic resistance is configured, the position of the lens holding frame, that is, the position of the moving lens can be detected.

[0013]

In a known lens device having a configuration in which a part of an optical element is moved by, for example, rotating a movable lens barrel disposed inside a fixed lens barrel along a helicoid screw, a fixed lens is used. The position of the optical element could be known from the relative movement angle between the lens barrel and the movable lens barrel. However, when the above-described impact-type actuator is driven based on the focus detection information for the subject and a part of the optical element constituting the lens is moved in the optical axis direction, as in the case of the conventional lens. Since no movable lens barrel is provided, the position of the optical element cannot be known from the relative movement angle between the fixed lens barrel and the movable lens barrel.

Therefore, as described above, the position of the lens holding frame, that is, the position of the moving lens is determined by mounting the magnetizing rod in parallel with the drive shaft and attaching the magnetoresistive element to the lens holding frame to form a position sensor. Means for detecting is proposed, but in this case, if there is a variation in the distance between the magnetizing rod and the magnetoresistive element, a detection error occurs, so that the considerably long optical element travels over the entire moving distance range. Variations in the distance between the magnetic rod and the magnetoresistive element must be kept within a predetermined tolerance. For this purpose, it is necessary to arrange the magnetizing rod parallel to the drive shaft and to prevent the lens holding frame from swinging during the movement, which makes assembly of the lens device extremely difficult. An object of the present invention is to solve the above problems.

[0015]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and the invention according to claim 1 is provided with an optical element constituting a lens device, an electro-mechanical conversion element, and an optical element. And coupled to the electro-mechanical conversion element,
A drive member that is displaced together with the mechanical conversion element, a drive mechanism that is fixedly connected to the optical element and that is a driven member that is frictionally connected to the drive member, and is disposed in the optical axis direction and magnetized at a predetermined interval. An optical element position detecting device in a lens device including a magnetized rod and a position sensor fixed to the driven member and disposed close to the magnetized rod, wherein the magnetized rod is
An optical element position detecting device for a lens device, wherein the position sensor detects a position of an optical element moved by the driving mechanism , the member also serving as a driving member .

According to a second aspect of the present invention, there is provided an optical element, an electro-mechanical conversion element, and an electro-mechanical conversion element arranged in an optical axis direction and coupled to the electro-mechanical conversion element. A driving member that is displaced together with the element, a driving mechanism that is fixedly coupled to the optical element and that is a driven member that is frictionally coupled to the driving member, and magnetized that is arranged in the optical axis direction and magnetized at a predetermined interval. An optical element position detecting device in a lens device including a rod and a position sensor including a magnetoresistive element fixed to the driven member and disposed close to the magnetized rod, wherein the magnetized rod is
Also serves as a guide member for guiding the driven member in the optical axis direction.
A member, an optical element position detecting device in the lens apparatus characterized by detecting the position of the optical element is moved by the driving mechanism by the position sensor.

[0017]

The optical element constituting the lens device moves in the optical axis direction via the driven member by the driving mechanism driven based on the focus detection information. At this time, the position of the optical element is detected by detecting the resistance value of the magnetoresistive element by moving the driven member over the magnetized rod arranged in the optical axis direction. By using the magnetized rod as a driving member or the magnetized rod as a guide member, the distance between the magnetized rod and the magnetoresistive element is kept constant, and no detection error occurs.

[0018]

Embodiments of the present invention will be described below.
1 and 2 show an embodiment of an optical element position detecting device in a lens device according to the present invention. FIG. 1 is a sectional view taken along the optical axis direction of the lens device 1, and FIG. FIG. In FIGS. 1 and 2, reference numeral 11 denotes a lens outer cylinder, and a holding frame 12 for the first lens L1 is fixedly attached to the left end thereof, and a right end 11a thereof forms a holding frame for the third lens L3. The second inside of the lens barrel 11
A holding frame 13 for the lens L2 is disposed so as to be movable in the optical axis direction as described later. The lens holding frame 13 is provided with a magnetoresistive element 18 of a ferromagnetic thin film magnetoresistive element type position sensor (hereinafter referred to as MR sensor) for detecting the moving distance of the lens holding frame 13.

Reference numeral 14 denotes a drive shaft for driving the lens holding frame 13 in the optical axis direction. N and S magnetic poles are magnetized at predetermined intervals, and the lens holding is carried out in cooperation with the magnetoresistive element 18 of the MR sensor. It is also used as a magnetizing rod for detecting the moving distance of the frame 13.

The drive shaft 14 includes a first flange portion 11b of the lens barrel 11 and a flange portion 12b of the lens holding frame 12.
And one end thereof is adhesively fixed to one surface of the piezoelectric element 15.

The piezoelectric element 15 is displaced in the thickness direction to displace the drive shaft 14 in the axial direction. One end surface of the piezoelectric element 15 is fixedly bonded to the drive shaft 14, and the other end surface is the second end of the lens barrel 11.
Is adhesively fixed to the flange portion 11c.

Lens holding frame 1 for holding the second lens L2
3 includes a contact member 13b extending downward.
The drive shaft 14 passes through the contact member 13b. Also,
A cutout groove is formed on the lower surface of the contact member 13b. The contact member 13b and the drive shaft 14 have a press-contact spring 13c fitted between the notch groove and the upper surface of the contact member 13b.
, And are frictionally coupled with an appropriate frictional force. FIG.
Indicates a state in which the drive shaft 14 and the contact member 13b are pressed against each other by the pressing spring 13c.

The flange portion 13 of the lens holding frame 13
A notch 13d is also formed in the upper part of b, and engages with the guide shaft 19 to prevent the lens holding frame 13 from rotating.

Here, the MR sensor will be described. M
The R sensor is a non-contact type position sensor used for detecting a relatively long moving distance and position.
4 and a magnetoresistive element 18. Hereinafter, in the description related to the MR sensor, the drive shaft 14 that also serves as the magnetization rod may be referred to as the magnetization rod 14.

The principle will be described with reference to FIG. The magnetoresistive element 18 is placed on the magnetized rod 14 on which N and S magnetic poles are magnetized at predetermined intervals along the moving direction so that the current axis is perpendicular to the direction of the magnetic pole arrangement. The plane is placed close to and parallel to the pole face. As shown in FIG. 3, a leakage magnetic flux is emitted from each magnetic pole, and acts on the magnetoresistive element 18 to cause a magnetoresistive effect described below.

That is, the magnetoresistive element 18 is connected to the magnetized rod 14.
When there is between the magnetic poles, the resistance value decreases due to the magnetoresistance effect due to the horizontal component of the leakage magnetic flux, and there is no horizontal component of the leakage magnetic flux above the magnetic pole. It is not different from the time. When the magnetoresistive element 18 and the magnetized rod 14 move relatively, the magnetoresistive element 1
Since the resistance value of 8 periodically changes, the moving distance, that is, the position can be known by counting the number of changes.

FIG. 4 is a view for explaining the magnetic pole spacing of the magnetized rods constituting the MR sensor, the specific arrangement of the magnetoresistive elements, and the output signals thereof. As shown in FIGS. 4A and 4B, the magnetic poles N and S of the magnetized rod 14 are magnetized at a constant interval λ, and the resolution is determined by the dimension of the interval λ between the magnetic poles N and S.

As shown in FIG. 4 (c), the magnetoresistive element 18 is composed of a pair of folded patterns having a λ /
A group of magnetoresistive elements MRa1 arranged at intervals of 2
And MRa2, and b-group magnetoresistive elements MRb1 and MRb similarly arranged in pairs at an interval of λ / 2.
2 are arranged at a distance d (d = λ / 4).
When the outputs of these magnetoresistive elements are processed by an output signal processing circuit whose example is shown in FIG. 5, as shown in FIG. 4D, the output signals Va of the a-group magnetoresistive elements MRa1 and MRa2. Since the waveforms of the output signals Vb of the magnetoresistive elements MRb1 and MRb2 of the b group and the b group are output with a phase shift of d, the moving direction can be known from the phase difference.

Output signal Va of group a magnetoresistive element
When the waveform Vb of the output signal of the b-group magnetoresistive element is converted into a pulse by the pulse signal converter and synthesized, a pulse signal of λ / 4 pitch is obtained as shown in FIG. By counting the pulse signals, the moving distance can be known with an accuracy of １ ／ of the magnetic pole interval λ.

FIG. 6 is a block diagram of a control circuit for displaying the focus adjustment of the lens and the subject distance.
1 and an MR sensor output signal processing circuit 4 connected via a pulse signal conversion circuit 43 connected to its input port.
2. It comprises a piezoelectric element driving circuit 44, a display section driving circuit 45, and a display section 46 connected to the output port.

Next, the control operation will be described. Focus detection information for a subject output from a focus detection circuit provided on a camera (not shown) is input to the CPU 41. C
The PU 41 determines the focus detection information, and determines the arrow a of the lens L2.
When movement in the direction is required, the piezoelectric element drive circuit 44 outputs a drive pulse output having a waveform consisting of a gentle rising portion as shown in FIG. To the piezoelectric element 15
Drive.

At the gentle rising portion of the drive pulse,
The piezoelectric element 15 gradually expands in the thickness direction, and the drive shaft 14 is axially displaced in the direction of arrow a. For this reason,
The contact member 132b of the lens holding frame 13, which is in pressure contact with the drive shaft 14 by the pressing spring 13c and is frictionally connected, also moves in the direction of arrow a, so that the lens holding frame 13 can be moved in the direction of arrow a.

At the rapid falling portion of the drive pulse, the piezoelectric element 15 rapidly shrinks in the thickness direction, and the drive shaft 14 is also displaced in the axial direction in the direction opposite to the arrow a. At this time, the contact member 13b of the lens holding frame 13 pressed against the drive shaft 14 by the pressure contact spring 13c overcomes the frictional force with the drive shaft 14 due to its inertia force and substantially stays at that position. The holding frame 13 does not move.

The term “substantially” as used herein means that the lens holding frame 1 is located in both the direction of arrow a and the direction opposite thereto.
This means that the third contact member 13b and the drive shaft 14 follow while causing a slip, and move in the direction of the arrow a as a whole due to a difference in drive time. The type of movement is determined according to a given friction condition.

By continuously applying the driving pulse having the above-mentioned waveform to the piezoelectric element 15, the lens holding frame 13
Can be continuously moved in the direction indicated by.

The movement of the lens holding frame 13 in the direction opposite to the arrow a can be achieved by applying to the piezoelectric element 15 a drive pulse having a waveform consisting of a rapid rising portion followed by a gentle falling portion.

When a focus detection circuit on the camera side (not shown) detects the in-focus state, the signal is input to the CPU 41,
The CPU 41 instructs the piezoelectric element drive circuit 44 to stop outputting the drive pulse to the piezoelectric element 15, and the lens holding frame 13 stops moving.

When the lens holding frame 13 moves, the magnetoresistive element 18 of the MR sensor attached to the lens holding frame 13 detects a magnetic pole magnetized at a predetermined interval on the magnetizing rod 14 which also serves as a drive shaft. I do. The detection signal is processed by an MR sensor output signal processing circuit 42, further converted into a pulse signal by a pulse signal conversion circuit 43, and input to the CPU 41. The CPU 41 counts the pulse signal,
Information on the position of the lens holding frame 13 in the focused state, that is, information on the lens position can be obtained.

The information on the lens position is calculated and converted into object distance information, and the object distance information is displayed on the display unit 46 via the display unit driving circuit 45. As the display unit 46, a display device using a liquid crystal and other known display devices can be used.

Next, a second embodiment of the present invention will be described. In the first embodiment, the drive shaft and the magnetizing rod are used in common. However, in the second embodiment, the guide shaft and the magnetizing rod are used in common.

FIG. 7 is a sectional view taken along the optical axis direction of the lens device 2 of the second embodiment, and FIG. 8 is a sectional view taken along line XX of FIG. Since the configuration is similar to that of the first embodiment, the same portions as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. However, N and S magnetic poles are attached to the guide shaft 19 at predetermined intervals. Magnetized, the magnetoresistive element 18 of the MR sensor described above.
In cooperation with the magnetizing rod for detecting the moving distance of the lens holding frame 13.

Even if the guide shaft 19 and the magnetizing rod are used,
The gap between the magnetoresistive element 28 on the lens holding frame 13 and the magnetized rod 29 also serving as a guide shaft does not change.

[0043]

As described above, according to the present invention, the driven element in which the optical element constituting the lens device is fixedly connected to the driving member and the optical element arranged in the optical axis direction and frictionally connected to the driving member. It is driven by a drive mechanism composed of members. At this time, the position of the optical element is detected by the driven member moving over the magnetized rod arranged in the optical axis direction and detecting the resistance value of the magnetoresistive element. By using the magnetized rod also as a drive member or as a guide rod, the distance between the magnetized rod and the magnetoresistive element is kept constant, and no detection error occurs.

Further, the number of components can be reduced by also using the magnetized rod as a driving member or the magnetized rod as a guide member, and the space inside the lens device can be effectively used.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a first embodiment of a lens device to which an optical element position detecting device according to the present invention is applied.

FIG. 2 is a cross-sectional view of the lens device shown in FIG. 1, taken along line XX.

FIG. 3 shows a ferromagnetic thin film magnetoresistive element type position sensor (MR)
FIG.

FIG. 4 is a view for explaining a specific arrangement of magnetic pole intervals and magnetic resistance elements of magnetized rods constituting an MR sensor and an output signal thereof.

FIG. 5 is a diagram illustrating an output signal processing circuit of an MR sensor.

FIG. 6 is a block diagram of a control circuit according to the first embodiment.

FIG. 7 is a sectional view showing a configuration of a second embodiment of a lens device to which the optical element position detecting device of the present invention is applied.

8 is a cross-sectional view of the lens device shown in FIG. 7, taken along line XX.

FIG. 9 is a cross-sectional view illustrating a configuration of a conventional lens device.

FIG. 10 is a sectional view of the vicinity of a contact member of the lens device shown in FIG. 9;

FIG. 11 is a diagram showing an example of the waveform of a drive pulse applied to an electro-mechanical conversion element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Lens outer cylinder 12 1st lens L1 holding frame 13 2nd lens L2 holding frame 13b Contact member 13c Pressure contact spring 14 Drive shaft and magnetizing rod 15 Piezoelectric element 18 Magnetic resistance element 19 Guide shaft 41 CPU 42 MR sensor output signal processing circuit 43 pulse signal conversion circuit 44 piezoelectric element drive circuit 45 display section drive circuit 46 display section

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yoshihiro Tasaka 2-13-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside the Osaka International Building Minolta Camera Co., Ltd. (56) References JP-A-8-29657 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B ^7/ 02-7/10

Claims (2)

(57) [Claims] An optical element constituting a lens device; an electro-mechanical conversion element; a driving member disposed in an optical axis direction and coupled to the electro-mechanical conversion element and displaced together with the electro-mechanical conversion element; A driving mechanism fixedly connected to the optical element and comprising a driven member frictionally connected to the driving member; a magnetized rod arranged in the optical axis direction and magnetized at a predetermined interval; and fixed to the driven member. And a position sensor comprising a magnetoresistive element disposed in close proximity to the magnetized rod, wherein the magnetized rod is a member that also serves as the driving member, An optical element position detecting device in a lens device, wherein a position of an optical element moved by a mechanism is detected by the position sensor. 2. An optical element constituting a lens device, an electro-mechanical conversion element, a drive member arranged in the optical axis direction and coupled to the electro-mechanical conversion element and displaced together with the electro-mechanical conversion element, A driving mechanism fixedly connected to the optical element and comprising a driven member frictionally connected to the driving member; a magnetized rod arranged in the optical axis direction and magnetized at a predetermined interval; and fixed to the driven member. And a position sensor comprising a magnetoresistive element disposed close to the magnetized rod, wherein the magnetized rod guides the driven member in the optical axis direction.
An optical element position detecting device in a lens device, wherein the position sensor detects a position of an optical element moved by the driving mechanism , the member being also used as a guide member .