WO2020008589A1

WO2020008589A1 - Optical unit and endoscope

Info

Publication number: WO2020008589A1
Application number: PCT/JP2018/025502
Authority: WO
Inventors: 松本　和宏; 猛志齊藤
Original assignee: オリンパス株式会社
Priority date: 2018-07-05
Filing date: 2018-07-05
Publication date: 2020-01-09

Abstract

The present invention is provided with: a stationary section 2 having a cylindrical shape centered on an optical axis O; guide shafts 15a, 15b provided to the stationary section 2 and extending in the direction of the optical axis O; a movable section 3 for holding a movable lens 16 and movable inside the stationary section 2 in the direction of the optical axis O while being supported by the guide shafts 15a, 15b; a voice coil motor 4 capable of moving the movable section 3 relative to the stationary section 2 in the direction of the optical axis O by means of both a coil 4a which is wound on the stationary section 2 and a magnet 4b which is affixed to the movable section 3; shield plates 3l, 3m mounted between the magnet 4b and the guide shafts 15a, 15b facing the magnet 4b; and openings 3n, 3o formed in the shield plates 3l, 3m and allowing magnetic flux from the magnet 4b to leak toward the guide shafts 15a, 15b.

Description

Optical unit and endoscope

The present invention relates to an optical unit and an endoscope that use a voice coil motor to move a movable unit that holds a movable lens group in an axial direction.

2. Description of the Related Art Conventionally, an electromagnetically driven actuator using a coil and a magnet (permanent magnet) has been used as a zooming function of changing a photographing magnification by moving a cylindrical movable portion holding a movable lens group forward and backward and a focusing function of adjusting a focus, that is, An optical unit using a voice coil motor (VCM) is known.

Since the voice coil motor is small and lightweight, it is widely used as an actuator for moving a movable lens group provided at a small-diameter end portion of an endoscope or the like forward or backward. The movable section that holds the movable lens group is supported by the fixed section via a guide member so as to be able to advance and retreat. At this time, if a play (gap) is formed between the guide member and the movable part, a shift occurs in a direction orthogonal to the moving direction of the movable part.

As a countermeasure, for example, in Japanese Patent Application Laid-Open No. 2011-2729, a permanent magnet is provided in the support portion, and the movable portion is moved while being attracted in the direction of the support portion by the magnetic force, so that play is prevented. I try to suppress it. However, according to the technology disclosed in this publication, when the magnetic biasing force is too strong, not only does the driving unit come into contact with the supporting unit and hinders smooth operation, but also loss in driving force due to sliding resistance occurs. Will occur. In order to attenuate the magnetic biasing force, the movable portion may be separated from the magnet or the volume of the magnet may be reduced to weaken the magnetic biasing force itself.

However, in order to separate the movable part from the magnet, a space for securing the distance is required, and the entire device is correspondingly increased in size. On the other hand, when the volume of the magnet is reduced, the processing difficulty is increased correspondingly, and therefore, there is a disadvantage that manufacturing is apt to vary, and the magnetic biasing force is greatly changed.

Also, Japanese Patent Application Laid-Open No. 2010-249858 discloses a design in which two yokes (magnetic bodies) are opposed to each other with a magnet of a movable portion therebetween, and the magnetic biasing force of the magnets with respect to both yokes is adjusted. There is disclosed a technique in which an arbitrary magnetic biasing force is applied to move. However, the technique disclosed in this publication requires two yokes with the movable portion interposed therebetween, and accordingly, not only the size of the entire device is increased, but also the weight is increased.

Furthermore, when the magnet of the movable part approaches one yoke, it moves away from the other yoke, but since the magnetic biasing force changes with the square of the distance, the difference in the magnetic biasing force is larger than the difference in the distance between the two yokes. Change. As a result, in a structure in which the balance is maintained by the difference between the magnetic biasing forces of the two yokes, the manufacturing tolerance has to be strict and the manufacturing cost increases.

In view of the above circumstances, the present invention does not increase the size of the entire apparatus, can suppress an increase in weight, can easily adjust the magnetic biasing force between the movable section holding the movable lens group and the support section, and can slide the apparatus. It is an object of the present invention to provide an optical unit and an endoscope that can reduce a driving force loss due to resistance.

One embodiment of the present invention is a cylindrical fixed portion centered on a predetermined axis, a guide shaft provided on the fixed portion and extending along the axial direction, and the guide shaft holding a movable lens group. A movable portion supported inside and movable inside the fixed portion along the axial direction, a coil concentrically wound around the axis on one of the fixed portion and the movable portion, and A voice coil motor capable of relatively moving the movable portion in the axial direction with respect to the fixed portion by a fixed magnet; and an optical unit including: the magnet and the guide shaft facing the magnet. A shield plate interposed therebetween, and an opening that is opened in the shield plate and leaks magnetic flux from the magnet toward the guide shaft.

It is a perspective view of an optical unit. It is II-II sectional drawing of FIG. FIG. 3 is a sectional view taken along the line III-III of FIG. 2. It is the perspective view seen from the right upper surface of a movable part. It is a top view of a movable part. It is the perspective view seen from the left upper surface of the movable part. It is the perspective view seen from the lower right surface of a movable part. FIG. 3 is an external view of an endoscope including an optical unit at a distal end portion.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. It should be noted that the drawings are schematic, and that the relationship between the thickness and width of each member, the ratio of the thickness of each member, and the like are different from actual ones. It goes without saying that some portions have different dimensional relationships and ratios.

Reference numeral 1 shown in FIGS. 1 to 3 denotes an optical unit, which is formed in a slightly elongated rectangular parallelepiped. The optical unit 1 includes a fixed part 2, a movable part 3 movable with respect to the fixed part 2, and a voice coil motor 4 for generating a driving force for moving the movable part 3 with respect to the fixed part 2. I have. By disposing the optical unit 1 in front of the image sensor, the subject image condensed by the optical unit 1 can be formed on the image sensor. In the following description, the left side of FIG. 2 is referred to as an object side, and the right side is referred to as an image side for convenience. Reference numeral O in the figure is the optical axis of the optical unit 1.

The fixing portion 2 has a fixing portion main body 6 and a front frame portion 7. The fixed portion main body 6 has a rear frame portion 6a at an end on the image side, and four support portions 6b extend in parallel from four corners of the rear frame portion 6a centered on the optical axis O to the object side. In addition, a fixed front frame 6c is integrally formed at the object side end of each support 6b. A coil 4a of the voice coil motor 4 is wound concentrically around the optical axis O around four support portions 6b connecting the rear frame portion 6a and the fixed front frame portion 6c. Have been. The outer periphery of the coil 4a is formed substantially on the same plane as the fixed front frame 6c, and the inner circumference of the coil 4a is formed substantially on the same plane as the rear frame 6a. Note that the voice coil motor 4 of the present embodiment is a moving magnet (MM) type, and a magnet (permanent magnet) 4b described later is fixed to the movable unit 3.

The above-described front frame 7 has a front frame main body 7a having substantially the same outer shape as the fixed front frame 6c, and the front frame main body 7a is mounted on the front surface of the fixed front frame 6c. Fixed. A cylindrical front lens holding frame 7b centered on the optical axis O projects from the rear surface of the front frame body 7a, and the object-side first fixed lens 11 is attached to the front frame body 7a and the front lens holding frame 7b. And the object-side second fixed lens 12 are held around the optical axis O.

A cylindrical rear lens holding frame 13 is mounted around the optical axis O on the rear surface of the rear frame 6a provided on the fixed portion main body 6, and the rear lens holding frame 13 has an image side. The fixed lens group 14 is held.

As shown in FIGS. 1 and 3, a pair of a main guide shaft 15 a and a sub guide shaft 15 b are arranged between a rear frame portion 6 a of the fixed portion main body 6 and a front frame portion main body 7 a of the front frame portion 7. Both ends are fixed to the opposing surfaces of the rear frame portion 6a and the front frame portion main body 7a. The two

guide shafts

15a and 15b are arranged at two corners on a diagonal centered on the optical axis O, and extend in parallel with each other along the optical axis O. The movable section 3 is movably supported along the optical axis O by both

guide shafts

15a and 15b. The

guide shafts

15a and 15b are made of a magnetic material made of a magnetic material such as iron. The guide shafts may be provided at four or three corners between the rear frame 6a and the front frame body 7a. In this case, a shield plate is interposed between the added guide shaft and the magnet 4b.

As shown in FIGS. 4 to 7, the movable portion 3 has a movable portion main body 3a at a rear end, and a movable lens 16 constituting a zoom optical system has the optical axis O aligned with the movable portion main body 3a. Is held in. Further, a cylindrical portion 3b extending toward the object side around the optical axis O is protrudingly provided on the front surface of the movable portion main body 3a. An inner periphery 3c of the cylindrical portion 3b is formed in a cylindrical shape, and both sides are opened in a rectangular shape, and a front end frame 3d is integrally formed on the front surface. The inner periphery 3c of the cylindrical portion 3b is externally mounted on the front lens holding frame 7b (see FIG. 2). Therefore, the inner periphery 3c of the cylindrical portion 3b is formed to have a slightly larger diameter than the outer periphery of the front lens holding frame 7b.

Further,

upper flange portions

3e and 3f are formed on one upper side (upper left of FIGS. 3 and 4) of the movable portion main body 3a and the front end frame portion 3d of the movable portion 3, and these

upper flange portions

3e and 3f are formed. The main guide shaft 15a is inserted through the drilled support hole 3g. The movable section 3 is supported by the main guide shaft 15a and is movable along the optical axis O. A lower flange portion 3h is formed on the other lower side (lower right in FIG. 3) of the movable portion main body 3a, and a sub guide shaft 15b is inserted into a support groove 3i formed in the lower flange portion 3h. The movement of the movable portion 3 in the rotation direction is regulated by the sub-guide shaft 15b.

上 In addition, an upper concave portion 3j and a lower concave portion 3k for mounting and fixing a magnet (permanent magnet) 4b are formed on the upper surface and the lower surface of the cylindrical portion 3b. Each magnet 4b is fixed to the upper concave portion 3j and the lower concave portion 3k with the S pole facing the inner periphery 3c of the cylindrical portion 3b and the N pole facing the coil 4a. When the magnet 4b moves together with the movable portion 3, the coil 4a is set to have a width (the front-rear width) covering the entire moving area of the magnet 4b. The position where the front surface of the front end frame portion 3d abuts the stepped portion 7c formed on the back surface of the front frame portion main body 7a provided on the front frame portion 7 is the foremost end. The position where the back surface abuts on the rear frame portion 6a of the fixed portion main body 6 is the rearmost portion. By moving the movable section 3 within this movement range, the zoom magnification of the subject image to be formed on the image sensor is changed.

As shown in FIGS. 3 to 6, the upper concave portion 3j is displaced slightly to the right with respect to the left and right central axis SL shown in FIG. 3 in order to avoid interference with the main guide shaft 15a. On the other hand, the lower recess 3k is displaced slightly to the left with respect to the left and right center axis SL shown in FIG. 3 in order to avoid interference with the sub guide shaft 15b.

シールド Further,

shield plates

31 and 3m are integrally formed on the side surface of the upper concave portion 3j on the side of the main guide shaft 15a and the side surface of the lower concave portion 3k on the side of the sub guide shaft 15b. The movable portion 3 is entirely made of a magnetic material formed of a magnetic material such as iron. Therefore, the

shield plates

31 and 3m have a function as a magnetic shield for each of the

guide shafts

15a and 15b. When the movable part 3 moves along the optical axis O, the movable part 3 is moved by the magnetic force of the magnet 4b. Is prevented from being inadvertently drawn toward the

guide shafts

15a and 15b.

Openings 3n and 3o are cut out in the shield plates 3l and 3m, respectively, and the magnetic biasing force F is applied to the

guide shafts

15a and 15b by the magnetic flux of the magnet 4b leaking from the openings 3n and 3o. Occurs. Thereby, the position of the movable part 3 with respect to each of the

guide shafts

15a and 15b is secured. The details will be described later.

Next, the operation of the optical unit 1 having such a configuration will be described. When a current flows through the coil 4a of the voice coil motor 4 provided in the optical unit 1 and the coil 4a crosses the magnetic field generated in the magnet 4b, the Lorentz force (Fleming's force) corresponding to the direction of the current flowing through the coil 4a is obtained. Electromagnetic force according to the left hand rule) is generated. Then, the movable portion 3 for fixing the magnet 4b is supported by the main guide shaft 15a, and moves along the optical axis O in a state where the rotation direction is regulated by the sub guide shaft 15b.

In the case where the image pickup device is provided on the image side of the optical unit 1, the subject image captured from the object side is formed on the image pickup device by changing the zoom magnification by moving the movable unit 3.

As described above, the movable portion 3 is a main guide inserted into the

upper flange portions

3e and 3f formed on one upper side (upper left of FIGS. 3 and 4) of the movable portion main body 3a and the front end frame 3d. It moves while being supported by the shaft 15a. At this time, the rotation direction of the movable portion is controlled by a sub-guide shaft 15b inserted into a support groove 3i formed in a lower flange portion 3h provided on the other lower side (lower right in FIG. 3) of the movable portion main body 3a. Movement to is regulated.

As shown in FIGS. 3 and 4, a gap for securing the movement of the movable portion 3 is provided between the main guide shaft 15a and the support holes 3g of the

upper flange portions

3e and 3f that support the main guide shaft 15a. Is set to a predetermined value. As shown in FIG. 3, a gap is also set between the sub-guide shaft 15b and the support groove 3i that supports the same for the same reason.

Therefore, when the movable section 3 moves along the optical axis O while being supported by the main guide shaft 15a, between the main guide shaft 15a and the support hole 3g, and between the sub guide shaft 15b and the support groove 3i. Play in the direction perpendicular to the axis is likely to occur.

In the present embodiment, the play is suppressed by the magnetic flux of the magnet 4b leaking from the openings 3n and 3o. That is, since both guide

shafts

15a and 15b are made of a magnetic material, a magnetic biasing force F [mN] generated by the leaked magnetic flux acts on each of the

guide shafts

15a and 15b. By maintaining the position of the movable part 3 and each of the

guide shafts

15a and 15b by the magnetic urging force F, the backlash acting on the movable part 3 in the direction perpendicular to the axis is suppressed. Since the magnet 4b is a component of the voice coil motor 4, it is not necessary to add a new component, and it is possible to prevent a complicated structure, an increase in the size of the entire apparatus, and an increase in weight.

The above-mentioned play is not constant for each product due to dimensional tolerances in design and variations during manufacturing. Further, the magnetic flux density of the magnet 4b also varies from product to product. Similarly, the openings 3n and 3o also have design dimensional tolerances, and the distance between the magnet 4b and each of the

guide shafts

15a and 15b varies from product to product.

Therefore, even if the openings 3n and 3o are formed as designed at the time of manufacturing, the openings 3n and 3o are affected by variations due to the various factors described above, so that the positional balance between the movable portion 3 and each of the

guide shafts

15a and 15b is kept constant. It is difficult to obtain a desired magnetic biasing force F for maintaining the magnetic force.

Therefore, in the present embodiment, pre-processing such as slits and dents for forming the openings 3n and 3o is performed at the time of manufacturing, and the openings 3n and 3o are used when assembling the optical unit 1, that is, when the magnet 4b and the magnets 4b are used. After the positional relationship with the

guide shafts

15a and 15b is determined, the post-processing is performed.

When post-processing the openings 3n and 3o, first, the magnetic flux density of the magnet 4b and the shortest distance from the side surface of the magnet 4b in contact with the

shield plates

31 and 3m to the surfaces of the

guide shafts

15a and 15b are measured. Next, a magnetic urging force F [mN] capable of supporting the movable portion 3 with respect to each of the

guide shafts

15a and 15b in a well-balanced manner is obtained. Then, the required opening area S [mm ² ] is determined. Then, the openings 3n and 3o are processed so as to have the opening area S.

As described above, in the present embodiment, the magnetic biasing force F is adjusted by the opening area S of the openings 3n and 3o, so that the distance between the magnet 4b and each of the

guide shafts

15a and 15b is kept constant without changing. The optimum magnetic biasing force F can be obtained while maintaining the state described above. As a result, it is easy to design and adjust, and an optimal and stable magnetic biasing force F can be obtained, and the sliding between each of the

guide shafts

15a and 15b and the support holes 3g and the support grooves 3i supported by the

guide shafts

15a and 15b can be obtained. The loss of the driving force due to the resistance can be reduced.

In addition, since the magnet 4b of the voice coil motor 4 is used to generate the magnetic biasing force F on each of the

guide shafts

15a, 15b, it is possible to prevent an increase in the number of parts and a complicated structure. .

FIG. 8 illustrates an endoscope 21 on which the optical unit 1 is mounted in the present embodiment. The endoscope 21 is inserted into a subject, and an insertion section 22 for observing the inside thereof, an operation section 23 provided continuously on a base end side of the insertion section 22, and extending from the operation section 23 And a connector 25 provided at an extended end of the universal cord 24. The connector 25 is electrically connected to an external device such as a control device or a lighting device.

The insertion portion 22 includes, in order from the distal end, a hard distal end portion 22a, a curved portion 22b, and a flexible tube portion 22c having a rear end connected to the operation portion 23, and the optical unit 1 is mounted on the distal end portion 22a. Have been. Further, behind the optical unit 1, there is provided an image pickup device 28 that forms light (subject image) condensed by the optical unit 1 and converts the light into an electric signal. In addition, a bending operation knob 26, a zoom operation knob 27, and the like are arranged in the operation unit 23 in a predetermined manner. The bending operation knob 26 is for bending the bending portion 22b provided on the insertion portion 22 in the up / down / left / right directions. The zoom operation knob 27 is a switch that drives the optical unit 1 provided inside the distal end portion 22a to change the zoom magnification of the subject image formed on the image sensor 28.

When the operator of the endoscope 21 operates the zoom operation knob 27 provided on the operation unit 23, the energization of the coil 4 a of the voice coil motor 4 provided on the optical unit 1 and the current The direction is set. Then, when the magnetic field of the magnet 4b fixed to the movable portion 3 crosses the coil 4a, a Lorentz force (an electromagnetic force according to Fleming's left-hand rule) corresponding to the direction of the current flowing through the coil 4a is generated.

すると When the operator operates the zoom operation knob 27 in the tele (telephoto) direction, the movable part 3 moves to the object side. Then, as shown in FIG. 2, the position where the front end frame 3 d of the movable portion main body 3 a provided on the movable portion 3 abuts on the step 7 c formed on the back surface of the front frame 7 provided on the fixed portion 2. Is the tele end. On the other hand, when the operator operates the zoom operation knob 27 in a wide (wide angle) direction, the movable unit 3 moves to the image sensor 28 side. The position where the rear surface of the movable portion main body 3a abuts on the rear frame 6a of the fixed portion main body 6 is the wide end. Some optical units 1 become wide when the movable unit 3 moves to the image side, and become tele when the movable unit 3 moves to the image sensor 28 side.

By the way, although the above-described embodiment has described the moving magnet (MM) type, this embodiment can also be applied to the moving coil (MC) type. That is, in the MC type voice coil motor, the magnet 4b is fixed to the fixed part 2, the coil 4a is wound around the movable part 3, the

guide shafts

15a and 15b are fixed to the movable part 3, and the support holes 3g and A support groove 3i is formed. Then, the

shield plates

31 and 3m are formed integrally with the fixed part 2, and the

shield plates

31 and 3m are interposed between the magnet 4b and each of the

guide shafts

15a and 15b. Thereafter, openings 3n and 3o for allowing the magnetic flux from the magnet 4b to leak toward the

respective guide shafts

15a and 15b are formed in the shield plates 3l and 3m when the optical unit 1 is assembled, and a desired magnetic biasing force is formed. Adjust to obtain F.

Claims

A cylindrical fixing portion centered on a predetermined axis,
A guide shaft disposed on the fixing portion and extending along the axial direction;
A movable portion that holds a movable lens group, is supported by the guide shaft, and is movable inside the fixed portion along the axial direction;
The movable portion is relatively moved in the axial direction with respect to the fixed portion by a coil concentrically wound around one of the fixed portion and the movable portion around the axis and a magnet fixed to the other. A voice coil motor capable of
An optical unit comprising:
A shield plate interposed between the magnet and the guide shaft facing the magnet,
An opening that is opened in the shield plate and leaks magnetic flux from the magnet in the guide shaft direction;
An optical unit, further comprising:
The optical unit according to claim 1, wherein the opening is formed by post-processing after a positional relationship between the guide shaft and the magnet is determined.
The coil is wound around the fixing portion,
The magnet is fixed to the movable part,
The optical unit according to claim 1, wherein the shield plate is formed integrally with the movable portion.
The coil is wound around the movable part,
The magnet is fixed to the fixing portion,
The optical unit according to claim 1, wherein the shield plate is formed integrally with the fixed portion.
The optical unit according to claim 1, wherein the guide shafts are arranged in a pair at least diagonally about the axis.
An endoscope that is inserted into the subject and observes the inside of the subject,
The optical unit according to claim 1,
An imaging element that forms an image of light condensed by the optical unit and converts the light into an electric signal;
An endoscope comprising: