WO2019207781A1

WO2019207781A1 - Optical unit and endoscope

Info

Publication number: WO2019207781A1
Application number: PCT/JP2018/017249
Authority: WO
Inventors: 松本　和宏; 幸太小川
Original assignee: オリンパス株式会社
Priority date: 2018-04-27
Filing date: 2018-04-27
Publication date: 2019-10-31

Abstract

The present invention is provided with a cylindrical fixed part (13), a cylindrical movable part (14) which retains a movable lens group (16) and is disposed inside the fixed part (13) so as to be able to move in the axial direction, a voice coil motor (15) capable of moving the movable part (14) relative to the fixed part (13) in the axial direction through use of a magnet (23) disposed in the movable part (14) and a coil (22) disposed concentrically with the fixed part (13), and restricting parts (17a, 18a) for restricting movement of the movable part (14) on an object side and an image side so that the movable range of the movable part (14) is a predetermined range, the image-side end of the coil (22) being further toward the object side or in the same position as the image-side end of the magnet (23) when the movable part (14) is positioned furthest toward the object-side end, and the object-side end of the coil (22) being positioned further toward the image side or in the same position as the object-side end of the magnet (23) when the movable part (14) is positioned furthest toward the image-side end.

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 portion that holds a movable lens group in the axial direction.

Conventionally, an electromagnetically driven actuator using a coil and a magnet (permanent magnet) as a zoom function for changing a photographing magnification by moving a cylindrical movable part holding a movable lens group forward and backward, and a focusing function for adjusting a focus, that is, An optical unit using a voice coil motor (VCM) is known.

Since this voice coil motor is small and lightweight, it is often used as an actuator for moving a movable lens group provided at a thin tip of an endoscope or the like back and forth. Also, an optical unit using this voice coil motor is known which uses a plurality of coils and magnets in order to improve driving force and responsiveness.

As a voice coil motor that activates a movable lens group of an endoscope, for example, Japanese Unexamined Patent Publication No. 2118-199303 discloses a moving magnet (MM) type voice coil. In the voice coil motor disclosed in this publication, a pair of magnets are arranged in a reverse direction with a predetermined interval before and after a cylindrical movable part, and are arranged on the outer periphery of the movable part. Then, a pair of coils are arranged in a cylindrical fixed part fixed in the tip part so as to flow current in the reverse direction.

And, by setting the width in the optical axis direction of the coil to be longer than the moving range of the movable part, and by setting the pair of magnets not to protrude from the pair of coils when the moving part moves back and forth, The moving part is reliably moved forward and backward within the moving range by a driving force using Lorentz force (electromagnetic force according to Fleming's left hand rule).

By the way, as shown in FIG. 6, the relationship between the one magnet 101 fixed to the movable portion and the coil 102 facing the same and fixed to the fixed portion, disclosed in the above-mentioned publication, is as follows. The coil 102 is set longer than the moving range of the movable part, and the magnet 101 is set so as not to protrude from the moving range. In this case, since the magnetic field M of the magnet 101 flows from the N pole to the S pole, assuming that the current flows constantly, the magnetic field M output from the N pole is the coil 102 as indicated by arrows a and a ′. Lorentz force is generated when crossing the road, causing the movable part to slide.

However, since the width of the coil 102 is longer than the width of the magnet 101, the magnetic field M passes through the coil 102 and travels toward the south pole as indicated by arrows b and b '. Therefore, at this time, a reverse Lorentz force is generated, and this reverse Lorentz force works to counteract the Lorentz force that attempts to slide the movable part. Therefore, a loss occurs in the actual Lorentz force that attempts to drive the movable part by the amount of the reverse Lorentz force.

In the technique disclosed in the above-mentioned publication, since the pair of magnets are arranged in the opposite direction in the moving direction of the movable part, the magnetic field between the pair of magnets is strong, and the Lorentz force generated thereby is reversed. Since it is stronger than the Lorentz force, the loss is relatively small.

In this case, in order to reduce the diameter of the distal end of an endoscope or the like in which the optical unit is disposed, it is necessary to simplify the structure of the optical unit, to make it smaller and lighter, and to use a magnet and a coil. Is not a pair of configurations, but a configuration in which the movable portion and the fixed portion are arranged one by one is preferable. However, if one magnet and one coil are configured, the Lorentz force in the opposite direction becomes relatively strong as shown in FIG. is there.

In view of the above circumstances, the present invention eliminates the generation of a reverse Lorentz force and realizes the Loren force to drive a movable part when realizing miniaturization and weight reduction using one coil and one magnet. An object of the present invention is to provide an optical unit capable of relatively improving the above.

One aspect of the present invention has a cylindrical fixed portion centered on a predetermined axis, and the shaft disposed inside the fixed portion so as to be movable in the axial direction while holding a movable lens group. The movable part is moved relative to the fixed part in the axial direction by a cylindrical movable part, a coil arranged concentrically around the axis in the fixed part, and a magnet arranged in the movable part. A voice coil motor that can be moved, and a regulating unit that regulates the movement of the movable unit on the object side and the image side so that the movable range of the movable unit is a predetermined range in the axial direction, When the movable part is positioned at the most object-side end in the movable range, the image-side end of the coil is at the object side or at the same position as the image-side end of the magnet, and the movable part Is positioned at the end closest to the image in the movable range. End of the object side of the coil is set so that the image side or the same position than the edge of the object side of the magnet.

It is an external view of an endoscope provided with an optical unit at the tip. It is an optical unit arrange | positioned in the front-end | tip part of an endoscope, and is a cross-sectional side view which shows the state which the movable part moved to the front end. It is a cross-sectional side view equivalent to FIG. 2 which shows the state which the movable part moved to the rear end. It is IV-IV sectional drawing of FIG. It is a schematic diagram which shows the relationship between the coil provided in the optical unit in the state which the movable part moved to the front end, and a magnet. It is a schematic diagram which shows the relationship between the coil provided in the optical unit in the state which the movable part moved to the rear end, and a magnet. It is a schematic diagram which shows the relationship between the coil and magnet provided in the conventional optical unit.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the case where the optical unit is attached to the distal end portion of the endoscope will be described as an example. However, the optical unit is not applied only to the endoscope.

It should be noted that the drawings are schematic, and the relationship between the thickness and width of each member, the ratio of the thickness of each member, and the like are different from the actual ones. Of course, there are included portions where the dimensional relationships and ratios are different.

First, the configuration of the endoscope 1 will be briefly described with reference to FIG. The endoscope 1 is inserted into a subject, and an insertion portion 2 for observing the inside of the endoscope 1, an operation portion 3 connected to the proximal end side of the insertion portion 2, and an extension from the operation portion 3. The universal cord 4 and a connector 5 provided at the extended end of the universal cord 4 are provided. The connector 5 is electrically connected to an external device such as a control device or a lighting device.

The insertion portion 2 is composed of a hard distal end portion 2a, a curved portion 2b, and a flexible tube portion 2c whose rear end is connected to the operation portion 3 in order from the distal end side, and an optical unit 11 is provided in the distal end portion 2a. An imaging element 12 that forms an image of light collected by the optical unit and converts it into an electrical signal is disposed behind the imaging element 12. The operation unit 3 is provided with a bending operation knob 6, a zoom operation knob 7 and the like in a predetermined manner. The bending operation knob 6 bends the bending portion 2b provided in the insertion portion 2 in the up / down / left / right directions. The zoom operation knob 7 is a switch that drives the optical unit 11 built in the distal end portion 2 a to vary the zoom magnification of the subject image formed on the image sensor 12.

As shown in FIGS. 2 to 4, the optical unit 11 generates a fixed portion 13, a movable portion 14 movable with respect to the fixed portion 13, and a driving force for moving the movable portion 14 with respect to the fixed portion 13. The voice coil motor 15 is provided. In addition, a movable lens group 16 is held on the movable portion 14. The movable lens group 16 constitutes a zoom optical system.

The fixed portion 13 includes a fixed portion main body 17, a front frame portion 18 fixed to the distal end side of the fixed portion main body 17, and a rear frame portion 19 fixed to the proximal end side of the fixed portion main body 17. Yes. In addition, the movable portion 14 is internally provided in the fixed portion main body 17. A front flange 14a and a rear flange 14b are formed at the front end and rear end of the movable portion 14, and the outer circumferences of the

flanges

14a and 14b are guided by the inner circumference of the fixed portion main body 17 so as to be movable in the axial direction. Has been.

The fixed portion 13 and the movable portion 14 are formed in a cylindrical shape centered on a common axis, the object side fixed lens group 20 is held on the front frame portion 18, and the image side fixed lens is positioned on the rear frame portion 19. Group 21 is held. The

lens groups

16, 20, and 21 are well known and have no characteristics, and are therefore simplified in FIGS.

The fixed portion 13 and the movable portion 14 are formed in a cylindrical shape centered on a common axis, and the optical axis O of each

lens group

16, 20, 21 held is fixed to the fixed portion 13 and the movable portion 14. Are consistent with the common central axis.

As shown in FIG. 2, the movable portion 14 is housed in a state of being supported so as to be movable along the direction of the optical axis O with respect to the fixed portion main body 17, and its front flange 14 a is the front frame portion 18. The position hooked on the rear end surface 18a becomes the foremost end of the movement toward the object side. Further, as shown in FIG. 3, a stopper portion 17 a having a convex section is formed on the inner periphery of the rear portion side of the fixing portion main body 17. The position where the rear flange 14b of the movable portion 14 is hooked to the front end of the stopper portion 17a is the final end of the movement toward the image side.

Therefore, the maximum movable range L1 of the movable portion 14 is a width obtained by subtracting the front-rear length of the movable portion 14 from the distance between the rear end surface 18a of the front frame portion 18 and the front end surface of the stopper portion 17a. Therefore, by setting the distance between the rear end surface 18a of the front frame portion 18 and the front end surface of the stopper portion 17a to a predetermined value, the maximum movable range L1 can be set to be a predetermined range. The rear end surface 18a of the front frame portion 18 and the front end surface of the stopper portion 17a correspond to a restricting portion that restricts the movement of the movable portion 14 of the present invention.

The voice coil motor 15 is of a moving magnet type, and a coil 22 is wound around the outer periphery of the fixed portion main body 17 in a concentric manner around the central axis of the fixed portion main body 17. On the other hand, the magnet (permanent magnet) 23 is fixed to the outer periphery of the movable portion 14 with the south pole facing the movable portion 14 side and the north pole facing the coil 22 side. One or a plurality of magnets 23 are arranged concentrically in the direction around the axis of the movable portion 14.

FIG. 4 shows an example of the arrangement of the magnets 23. The figure shows a mode in which the magnets 23 are arranged in a concentric cross shape in the direction around the axis of the movable portion 14. The magnet 23 is flat, and a portion of the coil 22 facing the magnet 23 is formed flat, and both are arranged in parallel at a predetermined interval. Note that the arrangement of the magnets 23 is not limited to a cross shape, and may be one, three in a Y shape, or may be arranged at equal intervals, and two at positions symmetrical with respect to the optical axis O. It may be arranged. Further, five or more magnets 23 may be arranged at equal intervals. Further, the magnets 23 may be arranged at unequal intervals around the optical axis O.

Each magnet 23 is mounted and positioned between front and

rear flanges

14a and 14b formed in the movable portion 14 in the front-rear direction. Therefore, the longitudinal length L3 of each magnet 23 is the width between the

flanges

14a and 14b.

On the other hand, the longitudinal length L2 of the coil 22 is uniquely determined by the maximum movable range L1 of the movable portion 14 and the longitudinal length L3 of each magnet 23. That is, as shown in FIG. 2, at the foremost end where the movable portion 14 moves to the object side and the front flange 14 a contacts the rear end surface 18 a of the front frame portion 18, the rear end that is the image side end of the coil 22. 22 a is set at the same position as the rear end of each magnet 23. On the other hand, as shown in FIG. 3, at the rearmost end where the movable portion 14 moves to the image side and the rear flange 14b comes into contact with the front end surface of the stopper portion 17a, the front end 22b which is the object side end of the coil 22 is It is set at the same position as the front end of the magnet 23. In addition, the same position here is not a completely same position but a position including an error.

Accordingly, the longitudinal length L2 of the coil 22 is set to a value obtained by subtracting the maximum movable range L1 from the longitudinal length L3 of each magnet 23, that is, a value shorter by the maximum movable range L1 than the longitudinal length L3 of each magnet 23 ( L2 = L3-L1). This front-rear length L2 is the maximum length derived from the front-rear length L3 of each magnet 23 and the maximum movable range L1 of the movable portion 14.

In the following description, the longitudinal length L2 of the coil 22 is described as the maximum length, but the longitudinal length L2 of the coil 22 only needs to have a relationship of L2 ≦ (L3-L1). Therefore, when the movable portion 14 is at the object side end, the rear end 22a of the coil 22 is set to the object side with respect to the rear end of each magnet 23, and when the movable portion 14 is at the image side end, the front end of the coil 22 is set. 22b may be located on the image side from the front end of each magnet 23.

The direction of energization and current to the coil 22 of the optical unit 11 is set by the operator operating the zoom operation knob 7 provided in the operation unit 3. When the movable unit 14 moves to the object side, the image to be captured becomes tele (telephoto), and when it moves to the image side, it becomes wide (wide angle). In this case, depending on the design of the optical unit 11 including the movable lens group 16, the movable lens group 16 can be wide (wide angle) on the object side and tele (telephoto) on the image side.

Next, the operation of this embodiment having such a configuration will be described. When the operator of the endoscope 1 operates the zoom operation knob 7 provided in the operation unit 3, the energization to the coil 22 of the optical unit 11 and the current direction are set according to the operation direction. As shown in FIGS. 5A and 5B, the magnetic field M emitted from the N pole of the magnet 23 crosses the coil 22 as shown by arrows a and a ′, and then goes to the S pole as shown by arrows b and b ′. Head. And when the magnetic field 23 crosses the coil 22, the Lorentz force (electromagnetic force by Fleming's left-hand rule) corresponding to the direction of the current flowing through the coil is generated.

Therefore, when the operator operates the zoom operation knob 7 in the tele direction, the movable portion 14 moves to the object side, and the front flange 14a of the movable portion 14 is placed on the rear end surface 18a of the front frame portion 18 as shown in FIG. The abutted position is the tele end. On the other hand, when the operator operates the zoom operation knob 7 in the wide direction, the movable portion 14 moves to the image side, and the rear flange 14b of the movable portion 14 is located on the rear side of the fixed portion main body 17 as shown in FIG. The position in contact with the front end surface of the stopper portion 17a formed on the circumference is the wide end.

The maximum movable range L1 of the movable portion 14 is a width obtained by subtracting the front-rear length of the movable portion 14 from the distance between the rear end surface 18a of the front frame portion 18 and the front end surface of the stopper portion 17a. Since the magnet 23 is fixed to the movable portion 14, the maximum movable range L <b> 1 naturally becomes the maximum movable range of the magnet 23. As shown in FIG. 2, when the movable portion 14 is at the tele end, the rear end of the magnet 23 fixed to the outer periphery of the movable portion 14 is fixed to the outer periphery of the fixed portion main body 17. It is in the same position as the rear end 22a. On the other hand, as shown in FIG. 3, the front end of the magnet 23 is in the same position as the front end 22 b of the coil 22 when the movable portion 14 is at the wide end.

Therefore, the front and rear ends of the magnet 23 do not always protrude beyond the error from the front and

rear ends

22 b and 22 a of the coil 22 in the maximum movable range L1 of the movable portion 14. Therefore, no matter where the movable part 14 is, the magnetic field M that crosses the coil 22 of the magnet 23 and moves in the direction of the arrows b and b ′ passes through the outward direction of the front and

rear ends

22b and 22a of the coil 22. Never cross.

As a result, when realizing a reduction in size and weight by using one coil 22 and one magnet 23, the reverse Lorentz force unlike the conventional case does not act on the movable portion 14, and the movable portion is moved accordingly. Loss of actual Lorentz force to drive the portion 14 can be reduced, and the movable portion 14 can be efficiently slid.

Claims

A cylindrical fixing part centered on a predetermined axis;
A cylindrical movable portion centered on the shaft, which is disposed inside the fixed portion so as to be movable in the axial direction while holding a movable lens group,
A voice coil capable of moving the movable part relative to the fixed part in the axial direction by a coil arranged concentrically around the axis in the fixed part and a magnet arranged in the movable part. A motor,
A regulation unit that regulates movement of the movable unit on the object side and the image side so that the movable range of the movable unit is a predetermined range in the axial direction,
When the movable part is positioned at the most object-side end in the movable range, the image-side end of the coil is at the object side or at the same position as the image-side end of the magnet, and the movable part Is set so that the object side end of the coil is located at the image side or the same position as the object side end of the magnet when the coil is positioned at the most image side end in the movable range. An optical unit.
2. The optical unit according to claim 1, wherein one or a plurality of the magnets are arranged in a direction around an axis centering on the axis of the movable part with respect to the movable part.
An endoscope that is inserted into a subject and observes the inside of the subject,
The optical unit according to claim 1 or 2,
An imaging device that forms an image of the light collected by the optical unit and converts it into an electrical signal;
An endoscope comprising: