JPH0486714A - Lens barrel - Google Patents

Abstract

PURPOSE:To reduce the size and weight of the lens barrel by constituting a lens driving part of a stationary part provided in the lens barrel and a moving part which is a part of a lens holding frame, forming one thereof of a magnetic material and providing coils on the other. CONSTITUTION:The lens driving part consists of the stationary part 2 fixed to the lens barrel 1 and the moving part 3 sliding with the stationary part 2. The stationary part 2 has bobbins 4, 5, coils 6, 7, and a stator yoke 8. The coils 6, 7 are wound along the circumference of the bobbins 4, 5 and voltages are impressed from terminals 9, 10. The moving part 3 holds a lens 12 on the inner side of a magnetized optical system holding member 11. The optical system holding member 11 is formed of, for example, a plastic magnet. Then the relative thrust in the axial direction is generated between the stationary part 2 and the moving part 3 and the moving part 3 moves when the coils 6, 7 of the stationary part 2 are energized. Abnormal sounds, such as oscillations and noises are eliminated and the reduction in the size and weight is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a lens barrel having at least a lens driven in the optical axis direction, and more specifically to a cylindrical lens barrel;
A lens mirror that includes a lens holding frame that holds a lens that is driven in the optical axis direction within this lens barrel, a lens drive device that drives this lens holding frame, and a position pressure detection device that detects the position of the lens. It concerns the torso.

[Conventional technology]

Conventionally, in optical devices having lenses that move at least in the optical axis direction, DC motors, step motors, voice coil motors, etc. have been adopted as means for driving all or part of the optical system for autofocus and zooming. The driving force is transmitted by a transmission mechanism such as a screw mechanism. However, there are problems such as large noise and vibration, large loss torque and backlash, and unsuitability for downsizing and weight reduction.In order to solve these problems, JP-A No. 511
No. 16208 provides a lens barrel mechanism equipped with an electromagnetic induction mechanism for moving an optical system holding member along the optical axis.

(Problems to be Solved by the Invention) The lens barrel equipped with the above-mentioned magnetic induction mechanism has the advantage that the driving part is magnetic induction, so there is no need for a DC motor, etc., and there is less noise, vibration, etc. The induction mechanism is large,
Another disadvantage is that the manufacturing cost is also high.

Therefore, it is an object of the present invention to provide a lens barrel that does not require a power transmission means such as a feed screw mechanism, has no abnormal sounds such as vibration or noise, can be made smaller and lighter, and can be manufactured at low cost. It is an object.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a cylindrical lens barrel,
A lens holding frame that holds a lens driven in the optical axis direction within the lens barrel, a lens driving device that drives the lens holding frame, and a position detection device that detects the position of the lens, the lens The driving device is composed of a fixed part provided in the lens barrel and a movable part which is a part of the lens holding frame, one of which is at least partially made of a magnetic material, and the other is made of a magnetic material. is configured to include at least one coil.

Further, in the invention as claimed in claim 2, the position detection device includes:
It consists of a magnetic sensor provided on a fixed part and a magnetic recording part provided on a movable part and working together with the sensor.

(Function) Since the present invention is configured as described above, it is assumed that the coil is formed in the fixed part within the lens barrel, and the movable part that is part of the lens holding frame is made of magnetic material. do. In this case, magnetic flux is constantly generated from the movable part made of magnetic material.

Therefore, when the coil in the fixed part is energized, the coil also generates magnetic flux, or the direction of the magnetic flux generated from the coil changes depending on the direction of the current, and the magnetic flux combined with the magnetic flux generated from the magnetic material also changes. Therefore, a relative thrust in the axial direction is generated between the fixed part and the movable part, and the movable part moves. That is, the lens holding frame is appropriately driven in the optical axis direction to perform operations such as focusing and zooming.

At this time, the position of the lens is detected by the position detection device and focusing is performed.

(Example) Below, using Fig. 1 (a), (b) and Fig. 2,
A first embodiment of the present invention will be described.

The lens drive section has a hollow cylindrical shape, and the lens barrel 1
It consists of a fixed part 2 fixed to and a movable part 3 that slides on the fixed part 2. The fixing part 2 has a bobbin 4.5.
It has a coil 67 and a stator yoke 8. The bobbin 4.5 is provided on both sides of the center pole of the stator yoke 8, and a coil 67 is wound around the bobbin 4, 5 along the circumferential surface thereof, and a voltage is applied from the terminal 9.1o. It is now possible to do so. The movable part 3 has a magnetized optical system holding member 11 and a lens 12 inside thereof. The magnetized optical system holding member 11 is, for example, a plastic magnet, and only a part of the optical system holding member 11 may be magnetized. Alternatively, an iron piece may be bonded to the outer peripheral surface of the optical system holding member 11, and the surface may be treated with Teflon to facilitate sliding. The lens 12 is held by the optical system holding member 11. Note that the fixed part 2. And the movable part 3 does not have to be provided all around.

The operating principle of the lens driving section of the first embodiment is similar to that of the iron core motor. The magnet 11 always generates a constant magnetic flux BM1.8M2, and constitutes a magnetic circuit so as to surround each coil 6.7.

Also, when a DC voltage is applied to the terminals 9 and 10, the coil 6
．． 7, a magnetic flux aC is generated by the coil 6.7. By changing the direction of the current, the direction of the magnetic flux Bc can be changed. The magnetic flux BMl+ 8M2 and the magnetic flux Bc weaken or strengthen each other to generate thrust in one direction, and this thrust causes the movable portion 3, that is, the lens 12 to slide along the optical axis.

One position detection device is a magnetic encoder, and as shown in FIG. 2, a salient pole part 11b is provided at one end of the optical system holding member 11, and the sliding surface of the salient pole part 11b is multipole magnetized in the optical axis direction. There is a magnetic recording part 11b which is made of magnetic material, and the magnetic recording part 11 is made to face the magnetic recording part 11b as the movable part 3 slides in the optical axis direction.
A magnetic sensor 14 is provided within the stator yoke 8 at a distance capable of detecting the leakage magnetic field from the stator yoke 8. Here, the magnetic sensor 14 needs to detect a weak leakage magnetic field from the magnetic recording section 11b, so it is connected via a non-magnetic material 13 in order to prevent the influence of the leakage magnetic field from the magnet 11a of the lens driving section and the coil 6.7. The stator yoke 8 is provided in such a manner that it is surrounded by the stator yoke 8.

As mentioned above, the optical system holding member 11 serves as the optical system holding frame, the magnet of the lens drive device, and the magnetic recording section of the position detection device, thereby reducing the size, weight, and cost of the lens barrel. Something comes up. Furthermore, in implementation, by making the movable part 3 longer in the optical axis direction, eccentricity in the optical axis direction can be suppressed, and a stable structure with less fluctuation in the distance between the magnetic recording part 11b and the magnetic sensor 14 can be obtained. . As a result, a stable and highly accurate position pressure detection signal can be obtained.

Next, a second embodiment of the present invention will be described using FIGS. 3(a) and 3(b). According to this example, yes! ! ] Part 23
This embodiment differs from the first embodiment in that coils 27, 28 are provided at the ends, and the fixed portions are made of magnetic material.

In other words, lens drive! The part I] has a hollow cylindrical shape as in the first embodiment, and has a fixed part 22 fixed to the lens barrel 21 and a part 23 that slides against the fixed part 22.
It consists of. The fixed part 22 is formed from a piece of iron, and the inner peripheral surface is treated with Teflon, for example, so that the movable part 23 can easily slide. The movable portion 23 includes a bobbin 2526, a coil 2728, and a yoke 24. Bobbins 25.26 are provided on both sides of the central pole of the yoke 24, and coils 27 are attached to the bobbins 25.26.
．． 28 are respectively wound along the circumferential surface. Said coils 27.28 are connected in series and terminals 29.3
A voltage from 0 is applied. yoke 24
is a plastic magnet, for example, and also serves to hold the optical system. The yoke 24 is entirely or partially magnetized so as to constitute a magnetic circuit so as to surround the coils 27 and 28, respectively. For example, the center pole is the N pole, both end poles are the S pole, and the outer circumferential side of the center pole is the N pole.
It may be magnetized so that the inner peripheral side becomes 58i.

The operating principle of the second embodiment is the same as that of the first embodiment, and is also the same as that of the iron core motor.

One of the position detection devices is a magnetic encoder, and a salient pole portion 24b is provided at the end of the yoke 24, and a magnetic recording portion is provided on the sliding surface of the salient pole portion 24b with multipole magnetization in the optical axis direction.
A magnetic sensor 32 is provided on the fixed part 22 facing the magnetic recording part at a distance that allows detecting the leakage magnetic field from the magnetic recording part as the movable part 23 slides in the optical axis direction. . Here, the 6fl air sensor 32 has a non-6n material 33 in order to prevent the influence of the leakage magnetic field from the magnet 24a and the coils 27 and 28 of the lens drive section, since it is necessary to detect a weak leakage magnetic field from the magnetic recording section. It is provided in the fixed part 22 in a state where the periphery is surrounded by the fixing part 22.

As mentioned above, the yoke 24 serves as the optical system holding frame, the magnet of the lens drive device, and the three magnetic recording sections of the position detection device, making it possible to reduce the size, weight, and cost of the lens barrel. Furthermore, by making the movable portion 23 long in the optical axis direction, eccentricity in the optical axis direction can be suppressed, and a stable structure with less fluctuation in the distance between the magnetic recording II 24b and the magnetic sensor can be obtained. This makes it possible to obtain a stable and highly accurate position detection signal.

[Effects of the Invention] As described above, according to the present invention, the lens driving device has the following effects:
It consists of a fixed part provided in the lens barrel and a movable part which is a part of the lens holding frame, one of which is made of at least a magnetic material and the other is provided with a coil. Since the lens barrel and the lens holding frame are also used as part of the lens drive section, the lens barrel can be made small, lightweight, and inexpensive.

[Brief explanation of the drawing]

FIG. 1(a) is a sectional view of a lens barrel showing a first embodiment of the present invention, and FIG. 1(b) is a cross-sectional view of the lens barrel shown in FIG.
2 is a plan view showing the magnetized portion of the optical holding member, and FIG. 3(a) is a sectional view taken along the optical axis direction of a lens barrel showing a second embodiment of the present invention. Figure 3(b) is a sectional view taken along line )IX-Y-X' in Figure 3(a). 1.21 Lens barrel 2, 22 Fixed part 3.
23...Movable part 6.7, 27.28...Coil 11.24...Optical system holding member

Claims (1)

[Scope of Claims] 1. A cylindrical lens barrel, a lens holding frame that holds a lens driven in the optical axis direction within the lens barrel, a lens driving device that drives the lens holding frame, and the lens. and a position detection device for detecting the position of the lens, and the lens driving device includes a fixed part provided in the lens barrel and a movable part that is a part of the lens holding frame. 1. A lens barrel, characterized in that one is made at least in part of a magnetic material and the other is provided with at least one coil. 2. The position detection device according to claim 1 is a lens barrel comprising a magnetic sensor provided on a fixed part and a magnetic recording part provided on a movable part and working together with the sensor.