JPWO2016189627A1 - Optical fiber scanner, illumination device and observation device - Google Patents

Abstract

An optical fiber scanner (10) of the present invention is provided for preventing resonance of a cylindrical shape fixed to an outer peripheral surface of an optical fiber (11) at a position spaced from the optical fiber (11) to the proximal end side. An elastic part (21) and piezoelectric elements (23A, 23B) that are fixed to the outer peripheral surface of the elastic part (21) and generate bending vibration in the elastic part (21) when an alternating voltage of a predetermined frequency is applied. And a fixed portion (25) fixed to the elastic portion (21) on the base end side of the piezoelectric elements (23A, 23B), and the elastic portion (21) is different from the predetermined frequency of the alternating voltage. Has a frequency.

Description

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

  2. Description of the Related Art Conventionally, 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 is known (for example, a patent). Reference 1). In this optical fiber scanner, a cantilever optical fiber and a cylindrical PZT actuator are held in a cantilever shape by a common base, and vibration generated by the PZT actuator is transmitted to the cantilever optical fiber via the base. Yes.

Japanese Patent No. 5069105

  However, the optical fiber scanner of Patent Document 1 has a structure having low rigidity as a whole because a gap exists between the cylindrical PZT actuator and the cantilever optical fiber passing through the inside of the PZT actuator. 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. There is a problem that light cannot be stably scanned along a desired locus.

  In particular, when the miniaturization of the optical fiber scanner is promoted, the dimensions of the cantilever optical fiber and the dimensions of the PZT actuator and the base approximate each other, and their natural frequencies also approximate each other. Resonance is more likely to occur, making it more difficult to ensure light scanning stability.

  The present invention has been made in view of the above-described circumstances, and an optical fiber scanner, an illuminating device, and an observation device that can stabilize a vibration of an optical fiber and stably obtain a desired scanning locus even if the size is reduced. An object is to provide an apparatus.

In order to achieve the above object, the present invention provides the following means.
According to a first aspect of the present invention, there is provided an elongated optical fiber that guides light and emits it from a distal end, and the optical fiber so as to cover an outer peripheral surface of the optical fiber at a position spaced from the distal end to a proximal end side. A cylindrical elastic portion for preventing resonance, fixed to the outer peripheral surface of the elastic portion, and applied with an alternating voltage of a predetermined frequency to expand and contract in the longitudinal direction of the optical fiber, and A piezoelectric element that generates a bending vibration in a direction intersecting the longitudinal direction in the elastic part; and a fixed part fixed to the elastic part at a base end side of the piezoelectric element, wherein the elastic part includes the alternating voltage. An optical fiber scanner having a natural frequency different from the predetermined frequency.

  According to this aspect, when an alternating voltage is applied to the piezoelectric element in a state where the base end portion of the elastic portion is fixed to the surrounding member via the fixing portion, the frequency of the fixing portion is a node and the frequency is equal to the frequency of the alternating voltage. Bending vibration is generated in the elastic portion, and the bending vibration is transmitted to the optical fiber. The portion (projecting portion) on the tip side of the elastic portion of the optical fiber is supported by the elastic portion in a cantilever shape with the tip being a free end, so that the tip of the optical fiber is caused by the bending vibration transmitted from the elastic portion. Vibrates in a direction crossing the longitudinal direction, and 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 the elastic portion is provided between the piezoelectric element and the optical fiber, the optical fiber scanner has a highly rigid structure as a whole, so that low-order mode vibration hardly occurs. Further, since the elastic portion has a natural frequency different from the frequency of the alternating voltage, the elastic portion does not resonate with the bending vibration of the protruding portion of the optical fiber, and the elastic portion functions as a resonance prevention means. . 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 the first aspect, the natural frequency of the elastic portion may be smaller than a predetermined frequency of the alternating voltage.
The natural frequency of the elastic part becomes smaller as the outer diameter of the elastic part is smaller. Therefore, the diameter of the optical fiber scanner can be reduced by reducing the outer diameter of the elastic portion so that the natural frequency of the elastic portion is smaller than the natural frequency of the protruding portion of the optical fiber.

In the first aspect, the natural frequency of the elastic portion may be larger than a predetermined frequency of the alternating voltage.
By doing so, it is possible to prevent the resonance of the elastic part in the process of increasing the frequency of the alternating voltage from a frequency smaller than the predetermined frequency to a predetermined frequency at the start of application of the alternating voltage. Further, the natural frequency of the elastic part increases as the size of the elastic part in the longitudinal direction decreases. Therefore, by shortening the length of the elastic portion so that the natural frequency of the elastic portion is larger than the natural frequency of the protruding portion of the optical fiber, the hard portion on the tip side of the fixed portion can be shortened. it can.

In the first aspect, the elastic portion may be cylindrical or rectangular.
A second aspect of the present invention is an illumination device including a light source that generates illumination light and the optical fiber scanner according to any one of the above that scans illumination light from the light source.
According to a third aspect of the present invention, the illumination device described above, a light detection unit that detects return light returning from the subject when the illumination light from the illumination device is irradiated on the subject, and the piezoelectric element are provided. And a voltage supply unit that supplies an alternating voltage having the predetermined frequency.

  According to the present invention, there is an effect that a desired scanning locus can be stably obtained by stabilizing the vibration of the optical fiber even if the size is reduced.

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 the side view which looked at the optical fiber scanner in the observation apparatus of FIG. 1 from the direction orthogonal to a longitudinal axis. It is the front view which looked at the optical fiber scanner of Drawing 2A from the tip side in the direction of a longitudinal axis. It is a side view which shows the modification of the optical fiber scanner of FIG. 2A. It is a front view which shows another modification of the optical fiber scanner of FIG. 2A. It is a front view which shows another modification of the optical fiber scanner of FIG. 2A.

An optical fiber scanner, an illumination device, and an observation device according to an embodiment of the present invention will be described below with reference to the drawings.
An observation apparatus 100 according to this embodiment is an endoscope apparatus, and as illustrated in FIG. 1, a light source 1 that generates illumination light, an illumination apparatus 3 that irradiates a subject (not shown), and illumination light. A photodetector (photodetector) 5 such as a photodiode that detects return light that returns from the subject when illuminated with illumination light, and a drive control device (voltage supply) that drives and controls the illumination device 3 and the photodetector 5. Part) 7.

  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 15 that houses the optical fiber scanner 10 and the condensing lens 13, and a circumferential direction on the outer peripheral surface of the frame 15 And a plurality of optical fibers for detection 17 for guiding return light (for example, reflected light or fluorescent light of illumination light) 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 FIG. 2A, the optical fiber scanner 10 has an illumination optical fiber (optical fiber) 11 such as a multimode fiber or a single mode fiber, and a distance from the distal end to the proximal end side of the illumination optical fiber 11. An elastic portion 21 made of an elastic material provided at a certain position, four piezoelectric elements 23A and 23B fixed to the elastic portion 21, and a fixing portion 25 for fixing the base end portion of the elastic portion 21 to the frame body 15. And lead wires 27A and 27B for supplying an alternating voltage to the piezoelectric elements 23A and 23B.

  The illumination optical fiber 11 is made of an elongated glass material and is disposed 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 elastic part 21 is a cylindrical member made of a metal having elasticity, such as nickel or copper, and has a fitting hole 21a penetrating along the longitudinal axis. The illumination optical fiber 11 is inserted into the fitting hole 21a, and the inner surface of the fitting hole 21a 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 protruding from the distal end surface of the elastic portion 21 to the distal end side is referred to as a protruding portion 11a. In addition, the elastic part 21 does not necessarily need to be comprised only from an elastic material, if the resonance prevention function mentioned later can be exhibited effectively.

  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 thus 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. 2B, 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 elastic portion 21. It is fixed. 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, and is fitted to the base end portion of the elastic portion 21 located on the base end side of the piezoelectric elements 23A and 23B and fixed to the outer peripheral surface of the base end portion of the elastic portion 21. Has been. The outer peripheral surface of the fixing portion 25 is fixed to the inner wall of the frame body 15. Thereby, the elastic part 21 is supported by the fixed part 25 in a cantilever shape having a free end as a distal end, and the protruding part 11a of the illumination optical fiber 11 is an elastic part in a cantilever shape having a free end as a free end. 21 is supported. The fixed portion 25 is electrically connected to the electrodes on the elastic portion 21 side of the four piezoelectric elements 23A and 23B, and functions as a common GND when driving the piezoelectric elements 23A and 23B. Yes.

  A lead wire 27A for A phase is joined 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 22B by a conductive adhesive. A GND lead wire 27G 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. Each lead wire 27 </ b> A, 27 </ b> B, 27 </ b> G is connected to the drive control device 7.

As described above, the projecting portion 11a and the elastic portion 21 of the illumination optical fiber 11 have a cantilever structure in which each tip is a free end. Therefore, the natural frequencies F1 and F2 (Hz) of the protruding portion 11a and the elastic portion 21 of the illumination optical fiber 11 are the Young's modulus E (N / m ² ), the secondary moment of inertia I (m ⁴ ), and XY, respectively. Using the cross-sectional area A (m ² ) in the plane, the length L (m) in the Z direction, and the density ρ (Kg / m ³ ), each is expressed by the following formula (1). λ is a dimensionless coefficient determined by the vibration mode.

  The cross-sectional secondary moment I1 and the cross-sectional area A1 of the protrusion 11a of the illumination optical fiber 11 are expressed by the following equations (2) and (3) using the diameter φ1 of the illumination optical fiber 11. The cross-sectional secondary moment I2 and the cross-sectional area A2 of the elastic part 21 are expressed by the following equations (4) and (5) using the outer diameter φout and the inner diameter φin of the elastic part 21. Therefore, the natural frequency F1 of the protruding portion 11a of the illumination optical fiber 11 can be obtained from the equations (1), (2), and (3), and the elastic portion can be obtained from the equations (1), (4), and (5). The natural frequency F2 of 21 can be obtained. As can be seen from the equations (1), (4), and (5), the natural frequency F2 of the elastic portion 21 depends on the material density ρ, the outer diameter φout, the inner diameter φin, and the length L.

  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 elastic portion 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 different from the natural frequency F1 of the protruding portion 11a of the illumination optical fiber 11. The material and dimensions φout, φin, L are designed to have

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 a subject 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. 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 contracts 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, whereby the elastic portion 21 is excited to bend in the X direction with the position of the fixed portion 25 as a node. Is done. Then, the bending vibration of the elastic part 21 is transmitted to the illumination optical fiber 11, so that the protrusion 11 a bends and vibrates in the X direction at a frequency equal to the drive frequency of the alternating voltage, and the tip of the optical fiber 11 moves in the X direction. The illumination light that vibrates and is 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 contracts in the Z direction orthogonal to the polarization direction. At this time, one of the two piezoelectric elements 23B is contracted in the Z direction and the other is expanded in the Z direction, so that the elastic portion 21 is excited to bend in the Y direction with the position of the fixed portion 25 as a node. The Then, the bending vibration of the elastic portion 21 is transmitted to the illumination optical fiber 11, so that the protruding portion 11 a 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 Y It is scanned linearly in the direction.

  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 trajectory, and the illumination light is scanned two-dimensionally along the spiral trajectory on the subject. 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 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 photodetector 5 to detect return light in synchronization with the scanning period of the illumination light, and generates an image of the subject by associating the detected intensity of the return light with the scanning position of the illumination light.

  In this case, according to the present embodiment, since the elastic portion 21 is provided between the piezoelectric elements 23A and 23B and the illumination optical fiber 11, the optical fiber scanner 10 has a highly rigid structure as a whole. Therefore, it is difficult for a low-order vibration mode having a frequency lower than the drive frequency to occur. Furthermore, since the natural frequency F2 of the elastic part 21 is different from the drive frequency of the alternating voltage, the elastic part 21 vibrates in resonance with the vibration at the drive frequency of the protruding part 11a of the illumination optical fiber 11. It 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.

  In particular, when the miniaturization of the optical fiber scanner 10 is promoted, the dimensional difference between the protruding portion 11a and the elastic portion 21 is reduced, and the natural frequency F1 of the protruding portion 11a and the natural frequency F2 of the elastic portion 21 are Become close to each other. Therefore, in the small-sized optical fiber scanner 10, the elastic part 21 easily resonates with the vibration of the protrusion 11a, and a vibration mode with a frequency other than the driving frequency is likely to occur. According to the present embodiment, the natural frequency F1 of the protruding portion 11a of the illumination optical fiber 11 and the natural frequency F2 of the elastic portion 21 are selected by selecting the material of the elastic portion 21 and designing the dimensions L, φout, and φin. The difference can be secured and the resonance vibration of the elastic portion 21 can be surely prevented.

In the present embodiment, the natural frequency F2 of the elastic portion 21 may be smaller than the drive frequency of the alternating voltage.
When the supply of the alternating voltage from the drive control device 7 to the piezoelectric elements 23A and 23B is started, the frequency is swept from a frequency smaller than the drive frequency to the drive frequency so that the vibration amplitude of the protrusion 11a gradually increases. Therefore, by making the natural frequency F2 of the elastic part 21 larger than the drive frequency of the alternating voltage, it is possible to prevent the elastic part 21 from resonantly vibrating during the sweep of the frequency of the alternating voltage.

  In order to make the natural frequency F2 of the elastic part 21 smaller than the drive frequency of the alternating voltage, it is preferable to shorten the length L of the elastic part 21 as shown in FIG. By doing so, the length in the Z direction of the hard portion covered with the frame body 15 on the tip side of the fixed portion 25 can be shortened.

Or in this embodiment, the natural frequency F2 of the elastic part 21 may be larger than the drive frequency of an alternating voltage.
In order to make the natural frequency F2 of the elastic part 21 larger than the drive frequency of the alternating voltage, it is preferable to reduce the outer diameter φout ′ of the elastic part 21 as shown in FIG. By doing in this way, the optical fiber scanner 10 can be reduced in diameter.

Further, in the present embodiment, the elastic portion 21 is cylindrical, but instead of this, as shown in FIG. FIG. 5 shows an elastic portion 21 having a regular rectangular tube shape as an example. The cross-sectional secondary moment I ₂ ′ and the cross-sectional area A ₂ ′ of the regular rectangular cylindrical elastic part 21 are expressed by the following expressions (6) and (7), respectively, using the length d of one side.

DESCRIPTION OF SYMBOLS 1 Light source 3 Illumination device 5 Light detector (light detection part)
7 Drive control device (voltage supply unit)
10 Optical fiber scanner 11 Optical fiber for illumination (optical fiber)
13 condensing lens 15 frame 17 detection optical fiber 21 elastic part 21a fitting hole 23A, 23B piezoelectric element 25 fixing part 27A, 27B, 27G lead wire 100 observation device

Claims (6)

An elongated optical fiber that guides light and emits it from the tip;
A cylindrical elastic portion for preventing resonance that is fixed to the optical fiber 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 elastic portion is fixed to the outer peripheral surface of the elastic portion, and an alternating voltage having a predetermined frequency is applied to cause stretching vibration in the longitudinal direction of the optical fiber to generate bending vibration in the direction intersecting the longitudinal direction in the elastic portion. A piezoelectric element;
A fixed portion fixed to the elastic portion on the base end side of the piezoelectric element,
An optical fiber scanner in which the elastic portion has a natural frequency different from a predetermined frequency of the alternating voltage.   The optical fiber scanner according to claim 1, wherein a natural frequency of the elastic portion is smaller than a predetermined frequency of the alternating voltage.   The optical fiber scanner according to claim 1, wherein a natural frequency of the elastic portion is larger than a predetermined frequency of the alternating voltage.   The optical fiber scanner according to any one of claims 1 to 3, wherein the elastic portion has a cylindrical shape or a rectangular tube shape. A light source that generates illumination light;
An illuminating device comprising the optical fiber scanner according to any one of claims 1 to 4, wherein the illuminating light from the light source is scanned. A lighting device according to claim 5;
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.

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