WO2017068710A1

WO2017068710A1 - Optical fiber scanner, lighting device, and observation device

Info

Publication number: WO2017068710A1
Application number: PCT/JP2015/079910
Authority: WO
Inventors: 博一横田; 靖明葛西; 博士鶴田
Original assignee: オリンパス株式会社
Priority date: 2015-10-23
Filing date: 2015-10-23
Publication date: 2017-04-27
Also published as: JPWO2017068924A1; WO2017068924A1

Abstract

To achieve the objective of efficiently transmitting vibrations of a piezoelectric element to an optical fiber and easily increasing vibrations at the tip of the optical fiber, an optical fiber scanner (10) according to the present invention is provided with: a long, narrow optical fiber (11) that conducts light and emits light from the tip; a coil spring (21) that comprises an elastic material that is closely adhered to the outer peripheral surface of the optical fiber (11) so as to cover the outer peripheral surface at a position that is spaced apart from the tip toward the base end side; a piezoelectric element (23A) that is fixed by being adhered to the outer peripheral surface of the coil spring (21), undergoes stretching vibration in the length direction of the optical fiber (11) due to the application of an alternating voltage of a prescribed frequency, and generates, in the optical fiber (11) via the coil spring (21), bending vibration in a direction that intersects with the length direction; and a fixed part that is fixed to the coil spring (21) further to the base end side than the piezoelectric element (23A).

Description

Optical fiber scanner, illumination device and observation device

The present invention relates to an optical fiber scanner, an illumination device, and an observation device.

2. Description of the Related Art An optical fiber scanner that scans light emitted from the tip of a cantilever optical fiber by bending and vibrating a cantilever optical fiber by a lead zirconate titanate (PZT) actuator (hereinafter referred to as a piezoelectric element) is known. (For example, refer to Patent Documents 1 and 2.)

In the optical fiber scanner of Patent Document 1, a cantilever optical fiber and a cylindrical piezoelectric element are held in a cantilever shape by a common base, and vibration generated by the piezoelectric element is transmitted through the base to the cantilever optical fiber. To communicate.
In the optical fiber scanner of Patent Document 2, an optical fiber is passed through and bonded to a through hole of a cylindrical ferrule fixed to a base, and a piezoelectric element is fixed to the outer surface of the ferrule.

Japanese Patent No. 5069105 International Publication No. 2013/069382

The optical fiber scanner of Patent Document 1 has a structure having a low rigidity as a whole because a gap exists between a cylindrical piezoelectric element and a cantilever optical fiber passing through the inside of the piezoelectric element. A low-rigidity optical fiber scanner tends to generate a low-order vibration mode having a low frequency when resonating, and a high-order vibration mode (a spurious mode) having a high frequency due to the low-order vibration mode. . When the higher-order vibration mode overlaps with the original vibration mode of the optical fiber, other parts resonate with the vibration of the cantilever optical fiber, and the optical fiber is stably vibrated in a single vibration mode. And light cannot be stably scanned along the desired trajectory.

In addition, since the optical fiber scanner of Patent Document 2 has a structure in which the inner peripheral surface of the through hole of the ferrule and the outer peripheral surface of the optical fiber are bonded over the entire length, vibration of the piezoelectric element can be directly transmitted to the optical fiber. On the other hand, it is difficult to increase the vibration of the tip of the optical fiber because the rigidity of the ferrule is dominant. *

The present invention has been made in view of the above-described circumstances, and efficiently transmits the vibration of the piezoelectric element to the optical fiber and can easily increase the vibration of the tip of the optical fiber. An object is to provide an apparatus and an observation apparatus.

One embodiment of the present invention is an elongated optical fiber that guides light and exits from a distal end, and is closely attached to the outer peripheral surface so as to cover the outer peripheral surface of the optical fiber at a position spaced from the distal end to the proximal end side. A coil spring made of an elastic material bonded in a state, and fixed by being bonded to the outer peripheral surface of the coil spring, and by applying an alternating voltage of a predetermined frequency, the optical fiber expands and contracts in the longitudinal direction, and An optical fiber scanner comprising: a piezoelectric element that generates bending vibration in a direction intersecting the longitudinal direction in the optical fiber via a coil spring; and a fixing portion fixed to the coil spring on a proximal end side of the piezoelectric element. is there.

According to this aspect, when an alternating voltage is applied to the piezoelectric element in a state where the proximal end portion of the coil spring is fixed to the surrounding member via the fixing portion, the position of the fixing portion is a node, and the frequency equal to the frequency of the alternating voltage is set. Bending vibration is generated in the coil spring, and the bending vibration is transmitted to the optical fiber. The portion on the tip side of the coil spring of the optical fiber is supported by the coil spring in a cantilever shape with the tip being a free end, and therefore the direction in which the tip of the optical fiber intersects with the longitudinal direction by the bending vibration transmitted from the coil spring The light emitted from the tip of the optical fiber is scanned in a direction crossing the traveling direction of the light.

In this case, since a coil spring is provided between the piezoelectric element and the optical fiber, the optical fiber scanner has a structure that is higher in rigidity than the single optical fiber as a whole. It is hard to do. Further, since the coil spring has a natural frequency different from the frequency of the alternating voltage, the coil spring does not resonate with the bending vibration of the protruding portion of the optical fiber.

Therefore, generation of vibration modes having frequencies other than the predetermined frequency is prevented, and the protruding portion of the optical fiber continues to vibrate stably in the vibration mode having a single frequency. Accordingly, it is possible to stably obtain a desired scanning locus by stabilizing the vibration of the optical fiber.
In addition, since the coil spring has low bending rigidity, bending vibration due to the piezoelectric element is hardly hindered, and the amplitude of vibration at the tip of the optical fiber can be efficiently increased.

In the above aspect, the coil spring may be a close coil spring in which the wire members constituting the coil spring are substantially in close contact with each other.
By doing so, the contact area between the piezoelectric element and the coil spring and between the coil spring and the optical fiber can be increased, the vibration of the piezoelectric element can be transmitted more directly to the optical fiber, and the tip of the optical fiber can be transmitted. The amplitude of vibration can be increased efficiently.

Moreover, in the said aspect, the said coil spring may space apart the wire which comprises this coil spring.
By doing in this way, the rigidity of a coil spring can be reduced and the bendability of an optical fiber can be improved. Thereby, it is possible to easily increase the amplitude of vibration at the tip of the optical fiber.

Moreover, in the said aspect, the said coil spring may space apart the wire which comprises this coil spring with a fixed pitch space | interval.
By doing so, the contact state between the piezoelectric element of the coil spring and the optical fiber sandwiched between the piezoelectric element and the optical fiber can be made uniform, and the optical fiber can be stably held.

The coil spring may be a square spring having a rectangular cross section.
By doing so, the contact between the piezoelectric element and the coil spring and the contact between the coil spring and the optical fiber can be made a surface contact, increasing the contact area and transmitting vibration more effectively. The amplitude of the vibration at the tip can be increased efficiently.

Moreover, in the said aspect, it is preferable that the natural frequency of the said coil spring is larger than the natural frequency of the said optical fiber.
By doing in this way, the vibration of an optical fiber can be stabilized more.

Moreover, the other aspect of this invention is an illuminating device provided with the light source which generates illumination light, and one of the said optical fiber scanners which scan the illumination light from this light source.
According to another aspect of the present invention, the illumination device, a light detection unit that detects return light that returns from the subject when the subject is irradiated with illumination light from the illumination device, and the piezoelectric element includes the predetermined element. And a voltage supply unit that supplies an alternating voltage having a frequency of.

According to the present invention, it is possible to efficiently transmit the vibration of the piezoelectric element to the optical fiber and to easily increase the vibration of the tip of the optical fiber.

1 is an overall configuration diagram of an observation apparatus including an optical fiber scanner and an illumination device according to an embodiment of the present invention. It is a longitudinal cross-sectional view along the longitudinal axis which shows the internal structure of the insertion part front-end | tip of the endoscope of the observation apparatus of FIG. It is the front view which looked at the observation apparatus of FIG. 1 from the front end side in the longitudinal axis direction. It is a longitudinal cross-sectional view which shows the modification of the observation apparatus of FIG. It is a side view which shows the modification of the optical fiber scanner of FIG.

An optical fiber scanner 10, an illumination device 3, and an observation device 100 according to an embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the observation device 100 according to the present embodiment includes an endoscope 20, a control device main body 30, and a display 40, and is emitted from the distal end of an insertion portion 20a of the endoscope 20. This is an optical scanning endoscope apparatus that scans a laser beam L along a spiral scanning locus B on a subject A to acquire an image of the subject A.

As shown in FIG. 2, the observation device 100 according to the present embodiment includes a light source 1 that generates illumination light, an illumination device 3 that irradiates the subject A with illumination light, and a subject A that is irradiated with the illumination light. A photodetector (photodetector) 5 such as a photodiode that detects return light returning from the light source, and a drive control device (voltage supply unit) 7 that drives and controls the illumination device 3 and the photodetector 5 are provided.

The illuminating device 3 includes an optical fiber scanner 10 having an illuminating optical fiber 11 that guides the illuminating light emitted from the light source 1 and emits the illuminating light from the distal end, and is disposed closer to the distal end than the illuminating optical fiber 11. A condensing lens 13 that condenses the illumination light emitted from the optical fiber 11, an elongated cylindrical frame (outer cylinder) 15 that houses the optical fiber scanner 10 and the condensing lens 13, and an outer peripheral surface of the frame 15 A plurality of optical fibers for detection 17 are provided which are arranged in the circumferential direction on the top and guide return light (for example, reflected light or fluorescent light of illumination light) from the subject A to the photodetector 5.

The light source 1 and the photodetector 5 are disposed on the proximal end side of the optical fiber scanner 10.
As shown in FIGS. 2 and 3, the optical fiber scanner 10 includes an illumination optical fiber (optical fiber) 11 such as a multimode fiber or a single mode fiber, and a distal end to a proximal end side of the illumination optical fiber 11. A coil spring 21 disposed in close contact with the outer peripheral surface so as to surround the outer peripheral surface of the illumination optical fiber 11 at an interval, and four

piezoelectric elements

23A and 23B fixed to the outer surface of the coil spring 21; A fixing portion 25 for fixing the proximal end portion of the coil spring 21 to the frame body 15 and

lead wires

27A and 27B for supplying an alternating voltage to the

piezoelectric elements

23A and 23B are provided.

The illumination optical fiber 11 is made of an elongated glass material and is arranged along the longitudinal direction of the frame 15. The tip of the illumination optical fiber 11 is disposed near the tip of the inside of the frame 15. The base end of the illumination optical fiber 11 extends from the base end of the frame 15 to the outside and is connected to the light source 1. Hereinafter, the longitudinal direction of the illumination optical fiber 11 is defined as a Z direction, and two radial directions of the illumination optical fiber 11 that are orthogonal to each other are defined as an X direction and a Y direction.

The coil spring 21 is a close-contact coil spring having an inner diameter dimension substantially equal to or smaller than the outer diameter dimension of the illumination optical fiber 11 in a free state, and having the adjacent wire rods in close contact with each other, and allows the illumination optical fiber 11 to penetrate inside. Thus, the inner surface of the illumination optical fiber 11 is disposed in close contact with the outer peripheral surface. The inner surface of the coil spring 21 and the outer peripheral surface of the illumination optical fiber 11 are bonded and fixed to each other with an epoxy adhesive. Hereinafter, the distal end portion of the illumination optical fiber 11 projecting from the distal end surface of the coil spring 21 to the distal end side is referred to as a projecting portion 11a.

The coil spring 21 is made of a material having high rigidity, for example, a material selected from metal (iron, aluminum alloy, titanium, etc.), synthetic resin (hard plastic), glass, and carbon. As will be described later, when the coil spring 21 is used as a common GND, the coil spring 21 needs to be made of a conductive metal material or coated with a conductive metal material. .

The

piezoelectric elements

23A and 23B are rectangular flat plates made of a piezoelectric ceramic material such as lead zirconate titanate (PZT), for example. The

piezoelectric elements

23A and 23B are subjected to + electrode processing on the front surface and − electrode processing on the back surface, and are thereby polarized in the thickness direction from the + pole toward the − pole. An arrow P in the figure indicates the polarization direction of the

piezoelectric elements

23A and 23B.

The four piezoelectric elements are composed of two A-phase piezoelectric elements 23A and two B-phase piezoelectric elements 23B. As shown in FIG. 3, the A-phase piezoelectric elements 23 </ b> A and the B-phase piezoelectric elements 23 </ b> B are alternately arranged at equal intervals in the circumferential direction of the coil spring 21, and are electrically conductive on the outer peripheral surface of the coil spring 21. It is fixed with adhesive. The two A-phase piezoelectric elements 23A facing each other in the X direction are arranged so that the polarization direction is the same in the X direction, and the two B-phase piezoelectric elements 23B facing each other in the Y direction are The polarization direction is arranged to face the same direction as the Y direction.

The fixing portion 25 is a cylindrical member having a through hole 26, and is electrically conductive in a state in which the base end portion of the coil spring 21 located on the base end side with respect to the

piezoelectric elements

23A and 23B is fitted into the through hole 26. It is fixed with an adhesive. The outer peripheral surface of the fixing portion 25 is fixed to the inner wall of the frame body 15. As a result, the coil spring 21 is supported by the fixed portion 25 in a cantilever shape with the tip as a free end, and the protruding portion 11a of the illumination optical fiber 11 is supported by the coil spring 21 in a cantilever shape with the tip as a free end. It is supported. The fixed portion 25 is electrically connected to the electrodes on the coil spring 21 side of the four

piezoelectric elements

23A and 23B via the coil spring 21 and functions as a common GND when driving the

piezoelectric elements

23A and 23B. It is like that.

A lead wire 27A for A phase is bonded to the two A phase piezoelectric elements 23A by a conductive adhesive. B-phase lead wires 27B are joined to the two B-phase piezoelectric elements 23B by a conductive adhesive. A GND lead wire (not shown) is joined to the fixing portion 25. In the fixing portion 25, grooves extending in the Z direction are formed at four locations spaced in the circumferential direction, and one

lead wire

27A, 27B is accommodated in each groove. The

lead wires

27A and 27B and the GND lead wire are connected to the drive control device 7.

As described above, the projecting portion 11a and the coil spring 21 of the illumination optical fiber 11 have a cantilever structure with each tip as a free end. Therefore, the natural frequencies F1 and F2 (Hz) of the protruding portion 11a of the illumination optical fiber 11 and the coil spring 21 are the Young's modulus E (N / m2), the cross-sectional secondary moment I (m4), and the break in the XY plane. Using the area A (m2), the length L (m) in the Z direction, and the density ρ (Kg / m3), each is represented by the following formula (1). λ is a dimensionless coefficient determined by the vibration mode.

The drive control device 7 applies an A-phase alternating voltage having a predetermined drive frequency to the A-phase piezoelectric element 23A via the lead wire 27A, and applies a predetermined voltage to the B-phase piezoelectric element 23B via the lead wire 27B. A B-phase alternating voltage having a driving frequency of 2 is applied. The predetermined drive frequency is set to a frequency equal to or close to the natural frequency F1 of the protruding portion 11a of the illumination optical fiber 11. The drive controller 7 supplies the

lead wires

27A and 27B with an A-phase alternating voltage and a B-phase alternating voltage whose phases are different from each other by π / 2 and whose amplitude changes in a sine wave shape over time.

Here, the coil spring 21 has a natural frequency F2 that is different from a predetermined drive frequency of the alternating voltage, that is, a natural frequency F2 that is larger than the natural frequency F1 of the protruding portion 11a of the illumination optical fiber 11. Designed to be

Next, operations of the optical fiber scanner 10, the illumination device 3, and the observation device 100 configured as described above will be described.
In order to observe the subject A using the observation apparatus 100 according to the present embodiment, the drive control device 7 is operated to supply illumination light from the light source 1 to the illumination optical fiber 11 and through the

lead wires

27A and 27B. Thus, an alternating voltage having a predetermined drive frequency is applied to the

piezoelectric elements

23A and 23B.

The A-phase piezoelectric element 23A to which the A-phase alternating voltage is applied vibrates and expands in the Z direction orthogonal to the polarization direction. At this time, one of the two piezoelectric elements 23A is contracted in the Z direction and the other is expanded in the Z direction, so that the coil spring 21 is excited to bend in the X direction with the position of the fixing portion 25 as a node. The Then, when the bending vibration of the coil spring 21 is transmitted to the illumination optical fiber 11, the protrusion 11a bends and vibrates in the X direction at a frequency equal to the drive frequency of the alternating voltage, and the tip of the illumination optical fiber 11 is in the X direction. And the illumination light emitted from the tip is linearly scanned in the X direction.

The B-phase piezoelectric element 23B to which the B-phase alternating voltage is applied vibrates and expands in the Z direction orthogonal to the polarization direction. At this time, one of the two piezoelectric elements 23 </ b> B contracts in the Z direction and the other extends in the Z direction, so that the coil spring 21 is excited to bend in the Y direction with the position of the fixing portion 25 as a node. . Then, when the bending vibration of the coil spring 21 is transmitted to the illumination optical fiber 11, the protrusion 11a bends and vibrates in the Y direction at a frequency equal to the drive frequency of the alternating voltage, and the illumination light emitted from the tip is in the Y direction. Are scanned linearly.

Here, the phase of the A-phase alternating voltage and the phase of the B-phase alternating voltage are shifted from each other by π / 2, and the amplitudes of the A-phase alternating voltage and the B-phase alternating voltage change in a sine wave shape over time. As a result, the tip of the illumination optical fiber 11 vibrates along a spiral locus, and the illumination light is scanned two-dimensionally on the subject A along the spiral locus. Moreover, since the drive frequency is equal to or near the natural frequency F1 of the protrusion 11a, the protrusion 11a can be excited efficiently.

The return light from the subject A is received by a plurality of detection optical fibers 17 and the intensity thereof is detected by the photodetector 5. The drive control device 7 causes the light detector 5 to detect the return light in synchronization with the scanning period of the illumination light, and generates an image of the subject A by associating the detected intensity of the return light with the scanning position of the illumination light. .

In this case, according to this embodiment, since the coil spring 21 is provided between the

piezoelectric elements

23A and 23B and the illumination optical fiber 11, the optical fiber scanner 10 as a whole is more than the illumination optical fiber 11 alone. Since it has a highly rigid structure, it is difficult to generate a low-order vibration mode having a frequency lower than the drive frequency. Furthermore, since the natural frequency F2 of the coil spring 21 is set larger than the drive frequency of the alternating voltage, the coil spring 21 vibrates in resonance with the vibration at the drive frequency of the protruding portion 11a of the illumination optical fiber 11. Is prevented.

Therefore, a vibration mode having a frequency different from the drive frequency is not generated, and only a single vibration mode is generated in the illumination optical fiber 11. Thereby, the protrusion part 11a of the optical fiber 11 for illumination can be continuously vibrated with a predetermined drive frequency, and illumination light can be stably scanned along a desired spiral path.

Further, since the coil spring 21 is adhered between the

piezoelectric elements

23A and 23B and the illumination optical fiber 11, the vibration of the

piezoelectric elements

23A and 23B can be transmitted to the illumination optical fiber 11 more directly. And the coil spring 21 can suppress bending rigidity sufficiently low compared with the ferrule which consists of a cylindrical rigid body. Therefore, the vibration of the illumination optical fiber 11 is not hindered by the coil spring 21, and there is an advantage that the amplitude of the vibration of the protruding portion 11a can be easily increased.

Moreover, in this embodiment, since the coil spring 21 is a close coil spring in which the wire constituting the coil spring 21 is in close contact with the wire adjacent in the longitudinal direction, the inner diameter of the coil spring 21 and the wire diameter of the wire are used. Is made constant, the contact area between the

piezoelectric elements

23A and 23B and the coil spring 21 and the contact area between the coil spring 21 and the illumination optical fiber 11 can be maximized. Thereby, there exists an advantage that the vibration of

piezoelectric element

23A, 23B can be more efficiently transmitted to the optical fiber 11 for illumination.
In order to further increase the contact area, it is effective to reduce the wire diameter of the coil spring 21 and increase the number of turns.

In the present embodiment, a close-contact coil spring is employed as the coil spring 21. Alternatively, as shown in FIG. 4, a structure in which adjacent wires are separated from each other may be employed. By doing in this way, although a contact area reduces compared with a close_contact | adherence coil spring, the coil spring 21 becomes easy to bend and there exists an advantage that the amplitude of the vibration of the optical fiber 11 for illumination can be made easy to increase. In addition, since the wires are spaced apart from each other, unnecessary vibration from the fixed portion 25 side can be attenuated and can be made difficult to be transmitted to the tip of the illumination optical fiber 11.

In this case, it is preferable that the wire rods have a predetermined pitch interval. Thereby, the contact state between the

piezoelectric elements

23A and 23B and the coil spring 21, the coil spring 21 and the illumination optical fiber 11 can be made uniform, and the illumination optical fiber 11 can be stably held.

Further, as the coil spring 21, as shown in FIG. 5, a square spring having a rectangular cross section may be adopted. By doing so, the

piezoelectric elements

23A and 23B and the coil spring 21, and the coil spring 21 and the illumination optical fiber 11 are brought into surface contact, so that the contact area can be further increased, and the vibration of the

piezoelectric elements

23A and 23B can be increased. There is an advantage that it can be transmitted to the illumination optical fiber 11 more directly.

DESCRIPTION OF SYMBOLS 1 Light source 3 Illuminating device 5 Light detection part 7 Drive control apparatus (voltage supply part)
10 Optical fiber scanner 11 Illumination optical fiber (optical fiber)
21 Coil springs 23A, 23B Piezoelectric element 25 Fixed portion 100 Observation device A Subject

Claims

An elongated optical fiber that guides light and emits it from the tip;
A coil spring made of an elastic material adhered in close contact with the outer peripheral surface so as to cover the outer peripheral surface of the optical fiber at a position spaced from the distal end to the proximal end side;
The coil spring is fixed by being bonded to the outer peripheral surface, and when an alternating voltage having a predetermined frequency is applied, it expands and contracts in the longitudinal direction of the optical fiber, and the longitudinal direction of the optical fiber passes through the coil spring. A piezoelectric element that generates a bending vibration in a direction intersecting with
An optical fiber scanner comprising: a fixed portion fixed to the coil spring on a proximal end side with respect to the piezoelectric element.
2. The optical fiber scanner according to claim 1, wherein the coil spring is a close-contact coil spring in which the wire members constituting the coil spring are substantially in close contact with each other.
2. The optical fiber scanner according to claim 1, wherein the coil spring separates wire members constituting the coil spring.
4. The optical fiber scanner according to claim 3, wherein the coil spring separates the wires constituting the coil spring with a constant pitch interval.
The optical fiber scanner according to any one of claims 1 to 4, wherein the coil spring is a square spring having a rectangular cross section.
The optical fiber scanner according to any one of claims 1 to 5, wherein a natural frequency of the coil spring is larger than a natural frequency of the optical fiber.
A light source that generates illumination light;
An illumination device comprising: the optical fiber scanner according to claim 1, which scans illumination light from the light source.
A lighting device according to claim 7;
A light detection unit that detects return light returning from the subject by irradiating the subject with illumination light from the illumination device; and
An observation apparatus comprising: a voltage supply unit that supplies an alternating voltage having the predetermined frequency to the piezoelectric element.