JP5787062B2 - Laser therapy device - Google Patents

Description

  The present invention relates to a laser treatment apparatus that performs treatment by irradiating a patient's tissue with a therapeutic laser beam.

  2. Description of the Related Art Laser treatment apparatuses that perform treatment by irradiating a patient's tissue with a therapeutic laser beam are known. For example, in an ophthalmic laser treatment apparatus (photocoagulation apparatus) disclosed in Patent Document 1, treatment laser light is irradiated onto the fundus of a patient's eye and the irradiated part is thermally coagulated with the energy of the laser light. In this apparatus, a laser light source unit and a laser irradiation unit (laser delivery) are separated and optically connected by a multimode fiber. The laser irradiation unit includes an optical system in which the emission end face of the multimode fiber is conjugated with the fundus of the patient's eye. Laser light emitted from the laser light source unit is guided by a multimode fiber and irradiated to the fundus etc. through the irradiation unit. In recent years, a laser light source (fundamental laser light source) that uses a fiber laser light source has been proposed (see, for example, Patent Document 2).

JP 2003-310653 A JP 2007-117511 A

  As disclosed in Patent Document 1, laser light is guided through a multimode fiber, so that speckle noise is generated on the output end of the multimode fiber, and burn unevenness is generated on the fundus of the patient's eye. It tends to occur. Although the speckle noise can be reduced by the technique disclosed in Patent Document 1, it cannot be said that the effect is high for laser light having a high beam quality such as a fiber laser disclosed in Patent Document 2.

  An object of the present invention is to provide a laser treatment apparatus that can suitably perform treatment by suppressing speckle noise of laser light with high beam quality in view of the above-described problems of the prior art.

In order to solve the above problems, the present invention is characterized by having the following configuration.
(1) A laser light source that emits treatment laser light, a multimode fiber for guiding the laser light emitted from the laser light source, and a laser beam emitted from the multimode fiber is applied to a patient's tissue. In a laser treatment apparatus comprising an irradiation optical system,
A non-linear optical element disposed between the laser light source and the multimode fiber in order to make the beam profile of the laser light emitted from the multimode fiber substantially flat, and the laser incident on the multimode fiber A nonlinear optical element that expands the spectral width of light by a self-phase modulation effect;
It is characterized by comprising.
(2) In the laser treatment device of (1),
The laser light source emits laser light having a spectral width of less than ± 0.2 nm with respect to the center wavelength of the laser light,
The nonlinear optical element achieves the desired therapeutic effect of the wavelength of the laser light irradiated to the patient's eye, so that the wavelength of the laser light emitted from the laser light source is ± 0.5 nm or more and ± 10 nm or less. It is characterized by extending to the spectral width.
(3) In the laser treatment device of (1) or (2),
The nonlinear optical element is a single mode fiber in order to expand the spectral width of the laser light continuously emitted from the laser light source.
(4) In the laser treatment device of (3 ) ,
The exit end of the single mode fiber is fused to the entrance end of the multimode fiber.

  ADVANTAGE OF THE INVENTION According to this invention, the treatment can be performed suitably, suppressing the speckle noise of the laser beam with high beam quality.

  Embodiments of the present invention will be described with reference to the drawings. In the present embodiment, as an ophthalmic laser treatment apparatus, an ophthalmic laser treatment apparatus that performs photocoagulation treatment on the fundus of a patient's eye is taken as an example. FIG. 1 is a schematic configuration diagram of an optical system and a control system of an ophthalmic laser treatment apparatus.

  The ophthalmic laser treatment apparatus 100 is roughly divided into a main body 100A in which the laser light source unit 10 is arranged, and a delivery unit 100B (laser irradiation unit) in which an irradiation optical system 80 for irradiating the patient's eye with treatment laser light is arranged. In this case, a delivery part 100B attached to a slit lamp for observing the patient's eye, and a light guiding fiber for guiding the laser light from the laser light source unit 10 to the irradiation optical system 80 disposed in the delivery part 100B ( Multimode fiber) 50 and a light guiding optical system. The main body portion 100A and the delivery portion 100B are separate units and are used by being placed at separate positions. The fiber 50 has a role of optically connecting the main body portion 100A and the slit lamp delivery portion 100B placed at a distant position. The fiber 50 has a length of about several meters.

  The main body 100A controls the laser light source unit 10 that emits the treatment laser beam, the treatment laser beam output, the irradiation condition such as the irradiation time, the operation unit 20 that sets and operates the device, and the entire device. And a control unit 30. The slit lamp in the delivery unit 100B includes an illumination unit 60 that illuminates a patient's eye and a binocular microscope unit 70 as an observation optical system.

  The laser light source unit 10 disposed in the main body 100A is a combination of a fiber laser 11 serving as a laser light source and a wavelength conversion element 13, and laser light having a wavelength of the second harmonic of the fundamental laser light (second harmonic laser). A configuration of an SHG (Second Harmonic Generation) laser that obtains (emits) light. In the present embodiment, the fundamental wave of near-infrared light is wavelength-converted into visible light (medium wavelength to long wavelength region) laser light suitable for treatment. The fiber laser 11 includes an excitation light source 11a and a fiber 11b connected to the excitation light source 11a and serving as a resonator (oscillates excitation light). The fiber laser 11 emits a continuous wave (CW) fundamental wave laser beam.

  The laser light source unit 10 includes a lens 12 as a condensing optical system that makes the fundamental laser light emitted from the fiber laser 11 incident on the wavelength conversion element 13, and converts the incident laser light into its second harmonic (laser light). A wavelength conversion element 13 that performs the conversion, a dichroic mirror 14a that divides the laser light transmitted through the wavelength conversion element 13 according to the wavelength, a damper 14b that absorbs the laser light that has not been wavelength-converted, and a part of the second harmonic laser light. A beam splitter 15 for reflecting to the power monitor 42, a safety shutter 16 for blocking the second harmonic laser light, and a dichroic for making the optical axis of the aiming light emitted from the aiming light source 43 coaxial with the optical axis of the laser light. Lens 1 as an imaging optical system that forms an image of the laser beam on the incident surface of the mirror 17 and the photonic crystal fiber 19 Comprising the photonic crystal fiber is a nonlinear optical element for expanding the spectrum of the laser beam (second harmonic) (hereinafter referred to as crystal fiber) and 19, the. The wavelength conversion element 13 includes a temperature adjustment unit 41 that adjusts the temperature of the wavelength conversion element in order to keep the wavelength conversion efficiency constant. The temperature adjustment unit 41 includes a Peltier element that can be heated and absorbed by a contact object (wavelength conversion element 13) and a drive circuit for the Peltier element.

  The excitation light source 11a is a laser diode, and the fiber 11b is a single mode fiber doped with a specific element such as earth metal. The fiber laser 11 emits near-infrared laser light, for example, infrared laser light (fundamental laser light) having a wavelength of 1064 nm. The wavelength conversion element 13 is a quasi-phase matching element made from a nonlinear crystal, and the polarization inversion period is determined in accordance with the wavelength of the fundamental laser beam. Here, the wavelength conversion element 13 is configured to obtain laser light (treatment laser light) having a wavelength of 532 nm, which is the second harmonic of the laser light having a wavelength of 1064 nm. As the treatment laser light, it is preferable to use a medium-long wavelength region (green to red) in the visible light region. The excitation light source 11 a emits excitation light based on the drive signal (applied current) of the control unit 30. The control unit 30 drives the excitation light source 11a so that the laser light emitted from the fiber laser 11 has a set pulse width (duration duration). In this embodiment, the pulse width is about 0.01 ms to 3 s. In this way, the fiber laser 11, the lens 12, and the wavelength conversion element 13 serve as a laser light source for treatment laser light.

  The dichroic mirror 14a has a characteristic of transmitting visible light and reflecting infrared light, and has a function of separating wavelength-converted visible laser light and wavelength-converted infrared laser light. The beam splitter 15 has a characteristic of slightly reflecting (for example, 5%) the laser light on the optical axis. The power monitor 42 detects (monitors) the output of the treatment laser beam and sends it to the control unit 30. For the power monitor 42, a light receiving element such as a photodiode or an imaging element such as an image sensor is used. The dichroic mirror 17 has a characteristic of reflecting the aiming light (wavelength) and transmitting the treatment laser light (wavelength), and has a role of making the aiming light and the treatment laser light coaxial. The aiming light source 43 is a laser diode that emits laser light having a wavelength suitable as aiming light so that the operator can confirm the irradiation position of the treatment laser light. The aiming light source 43 is configured to emit visible laser light. The laser light obtained by combining the aiming light and the treatment laser light by the dichroic mirror 17 is incident on the crystal fiber 19 through the lens 18. The exit end of the crystal fiber 19 and the entrance end of the optical fiber 50 are fused, and the laser light incident on the crystal fiber 19 undergoes self-phase modulation due to a non-linear effect, and the fiber 50 has high efficiency (high coupling efficiency). It is guided to. The crystal fiber 19 and the fiber 50 are connected so that their optical axes coincide. The infrared laser light reflected by the dichroic mirror 14a is guided to the damper 14b and absorbed. A safety shutter 16 is placed between the beam splitter 15 and the mirror 17. By inserting the safety shutter 16 into the optical path, the emission of the treatment laser light from the laser light source unit 10 is blocked.

  The crystal fiber 19 is a single mode fiber having a core part and a porous part (cladding) formed along the core part. The crystal fiber of this embodiment has a sufficient length in order to cause a sufficient non-linear effect (for example, a self-phase modulation effect described later) to the treatment laser beam that is a continuous wave. Due to such a non-linear effect, the spectral width of the laser light is expanded (the half-value width is increased). The non-linear effect due to the photonic crystal significantly acts on the pulsed laser beam, but the effect on the continuous wave laser beam is not great. For this reason, in order to cause a sufficient nonlinear effect to act on the treatment laser beam that is a continuous wave as in this embodiment, the length of the nonlinear optical element (crystal fiber 19) in the optical axis direction is required to be greater than a predetermined length. . For example, the spectral width of the laser light incident on the crystal fiber 19 is 0.2 nm (± 0.1 nm with respect to the center wavelength), and the spectrum width is expanded to about 20 nm (± 10 nm with respect to the center wavelength). The crystal fiber 19 has a length of at least several meters, preferably from about 10 m to about several tens of meters. The treatment laser light incident on the crystal fiber 19 is less affected by a surge pulse or the like, and is a laser light having an output of about several tens mW to several W. The technique of crystal fiber is disclosed in Japanese Patent Application Laid-Open No. 2004-4320.

  The operation unit 20 includes a foot switch 21 for inputting a trigger signal for irradiating treatment laser light, and a touch panel type monitor 22 as input / output means. By operating the monitor 22, the surgeon can graphically set and confirm irradiation conditions and the like. The monitor 22 includes a pulse width setting unit 23 that sets the pulse width (irradiation time) of the treatment laser beam and an output setting unit 24 that sets the output of the treatment laser beam. The pulse width setting unit 23 includes a display unit 23a for displaying the currently set (selected) pulse width, a switch 23b for inputting a setting signal for shortening the pulse width, and a switch for inputting a setting signal for increasing the pulse width. 23c. Similarly, the output setting unit 24 includes a display unit 24a for displaying the currently set (selected) output (the output of the treatment laser beam), a switch 24b for inputting a setting signal for lowering the output, and for increasing the output. A switch 24c for inputting a setting signal;

  The control unit 30 is a unit that performs integration, control, determination, and the like of the device, and includes an excitation light source 11a, a safety shutter 16, a temperature adjustment unit 41, a power monitor 42, an aiming light source 43, a foot switch 21, a monitor 22, and a memory 31. Connected.

  Next, the configuration of the delivery unit 100B will be described. The illumination unit 60 that projects slit light includes an illumination light source that emits visible light, a condenser lens, a slit plate for obtaining slit light for illumination, a light projection lens, and a split mirror. In the illumination unit 60, an illumination optical system is configured by each optical element. The slit light emitted from the illumination unit 60 is projected onto the fundus of the patient's eye via the contact lens CL.

  The binocular microscope unit 70 includes an objective lens, a zooming optical system that switches and arranges a zooming lens, a protective filter that protects the surgeon's eye OE from the reflected light of the treatment laser beam, an erecting prism group that bends the optical path, and the amount of light It has a field stop for adjustment and an eyepiece. The microscope unit 70 guides the reflected light from the fundus of the illuminated patient eye PE to the operator's eye OE. In the microscope unit 70, an observation optical system is constituted by each optical element.

  The irradiation optical system 80 includes a lens 81, a zoom lens (variable magnification optical system) 82 that can move along the optical axis in order to change the spot size of the laser light, an objective lens 83, and a reflection mirror 84. The irradiation optical system 80 forms an image of the exit end face of the fiber 50 on the target patient tissue (here, the fundus of the patient eye PE) with a predetermined spot size. Therefore, the irradiation optical system 80 is a perfocal optical system. In this embodiment, the core diameter of the fiber 50 is 50 μm, and the imaging magnification (spot size on the fundus) is changed between 1 and 20 times by the irradiation optical system 80.

  Next, the expansion of the spectrum width of the treatment laser beam and the flattening (homogenization and smoothing) of the beam profile will be described. FIG. 2 is a diagram illustrating the spectrum of laser light. FIG. 3 is a schematic diagram showing a beam profile (speckle pattern) when a laser beam having a narrow spectral width is passed through a multimode fiber. FIG. 4 is a diagram for explaining a beam profile when laser light of each wavelength is passed through a multimode fiber. 3 and 4 is a profile (intensity distribution) on a cross section passing through the optical axis at the exit end face position of the fiber 50 (multimode fiber). In addition, for convenience of explanation, it is assumed that the multimode fiber has a linear shape.

As shown in FIG. 2, the treatment laser beam (wavelength = 532 nm) B1 emitted from the fiber laser 11 and wavelength-converted has high beam quality. Specifically, M ² (beam quality factor) is close to 1.0. For this reason, the spectrum width is narrow, for example, the spectrum width with respect to the center wavelength is ± 0.2 nm or less, here, about ± 0.1 nm. Considering the conversion efficiency of the wavelength conversion element 13, even if the spectrum width is widened with respect to the set center wavelength, it is ± 0.2 nm. Although not shown, the beam profile of the laser beam B1 is Gaussian. Here, it is assumed that the laser beam B1 passes through the fiber 50. The laser beam B1 is interfered by repeating total reflection in the fiber 50, and shows the speckle pattern shown in FIG. This beam profile extends over the entire wavelength of the laser beam B1. Such a speckle pattern is imaged on the fundus of the patient's eye, and the heat diffusion is biased, which is likely to cause burn unevenness. FIG. 3 is a schematic diagram, and the actual fiber 50 is bent and held, and the beam profile of the laser beam B1 is often biased.

  On the other hand, in FIG. 2, the laser beam B <b> 2 shows a spectrum when the wavelength-converted therapeutic laser beam (B <b> 1) is transmitted through the crystal fiber 19. The spectrum of the laser beam B1 passing through the crystal fiber 19 is expanded by self phase modulation (SPM). In the present embodiment, it is assumed that the spectrum width is widened with a width of at least 1.0 nm (± 0.5 nm with respect to the center wavelength) around the wavelength (= 532 nm). At this time, the area of the laser beam B1 in FIG. 2 (which coincides with the product of the wavelength width and the intensity) and the area of the laser beam B2 substantially coincide. Therefore, the energy loss in the crystal fiber 19 is extremely small. For this reason, when the spectrum is expanded, the peak intensity of the laser light is lowered. In other words, in the intensity distribution of the laser light, the intensity diffuses according to the extension of the spectrum width.

  Regarding the extension of the spectrum width, it is preferable to make the spectrum width as wide as possible in order to reduce the speckle noise of the laser light emitted from the fiber 50 and flatten the beam profile. However, if the spectrum width is too wide, it affects the degree of penetration (advancement) of the treatment laser light into the tissue, the treatment effect, and the like. For this reason, the spectrum width is extended to ± 10 nm with respect to the center wavelength of the treatment laser beam (laser beam wavelength-converted by the wavelength conversion element 13). Preferably, it is up to ± 5 nm, more preferably up to ± 1 nm.

Here, attention is focused on the five wavelengths (λ0, λ1, λ2, λ3, and λ4) of the laser beam B2. λ0 is the center wavelength of 532 nm, and the wavelengths λ1 and λ2 correspond to 531.5 nm and 531 nm in the wavelength extended to the short wavelength side. Similarly, the wavelengths λ3 and λ4 correspond to 532.5 nm and 533 nm in the wavelength extended to the long wavelength side. The beam profile (speckle pattern) of the laser beam at each wavelength (λ0 to λ4) is schematically shown on the left side of FIG. As in the case of FIG. 2, speckle patterns having different shapes appear at each wavelength. Between each wavelength, the coherence is low (the coherency of the longitudinal mode of the laser beam B2 is reduced). For this reason, in the fiber 50 in which the laser beam B2 is incident, the wavelengths (modes) are mixed, and speckle patterns are generated for each wavelength, but these speckle patterns overlap without interfering with each other. Therefore, the beam profile shown on the right side of FIG. 4 has a shape in which speckle patterns of wavelengths λ0 to λ4 are added. By adding the speckle patterns for different wavelengths, the peaks and valleys of the speckles cancel each other out and become almost flat. Thereby, the beam profile when the laser beam B1 passes through the fiber 50 has a top hat shape with a flat upper portion.

In the apparatus having the above-described configuration, the operation at the time of surgery will be described. Prior to the operation, the operator sets the irradiation conditions of the treatment laser light. When the apparatus 100 is turned on, the current irradiation conditions are displayed on the display unit 23 a of the pulse width setting unit 23 and the output setting unit 24 a of the monitor 22. The surgeon operates the switches 23b and 23c to set the desired pulse width. In addition, the surgeon operates the switches 24b and 24c to set the output value of the intended treatment laser beam. The set pulse width and output are stored in the memory 31. When the output is set, the control unit 30 drives the excitation light source 11a. The control unit 30 drives the temperature adjustment unit 41 and maintains the temperature of the wavelength conversion element 13 so as to have a constant conversion efficiency. Further, the control unit 30 inserts the shutter 16 into the optical path and performs test irradiation. The excitation light source 11a is driven based on the set output value, and a part of the treatment laser light subjected to wavelength conversion is received by the power monitor 42, and the output is confirmed.

  When the setting of the apparatus 100 is completed, the operator observes the patient's eye and aligns the spot. The illumination unit 60 is operated to illuminate the fundus with illumination light. The fundus is observed through the microscope unit 70. The surgeon turns on the aiming light source 43 with a switch (not shown) and adjusts the spot diameter to obtain a desired spot size. The fundus of the patient eye PE is irradiated through the irradiation optical system 80. The operator aligns the aiming light with the affected area, and then presses the foot switch 21 to irradiate the treatment laser light.

  At this time, the control unit 30 removes the safety shutter 16 from the optical path and drives the excitation light source 11a. Infrared fundamental laser light is emitted (oscillated) from the fiber 11 b on which the excitation light is incident. The fundamental laser light is converted into visible treatment laser light by the wavelength conversion element 13, and passes through the crystal fiber 19. The light enters the fiber 50. The treatment laser light whose spectral width has been expanded by the crystal fiber 19 passes through the fiber 50, whereby speckle noise is reduced as a whole. The treatment laser light emitted from the fiber 50 is irradiated to the fundus of the patient's eye PE through the lens 81, the zoom lens 82, the objective lens 83, the reflection mirror 84, and the contact lens CL. At this time, the beam profile of the treatment laser beam on the fundus is in a top hat shape.

  As described above, even if a laser with high beam quality is guided by a multimode fiber, the effect of speckle can be suppressed and a flattened top-hat beam profile suitable for treatment can be obtained. Can be treated.

  In the present embodiment described above, the emission end of the crystal fiber 19 and the incident end of the fiber 50 are fused so that their optical axes coincide with each other. It is good also as composition which makes a shaft eccentric. In such a case, there is a possibility that the speckle pattern of the laser light at each wavelength is diversified in the fiber 50 and the beam profile is flattened. Further, the crystal fiber 19 and the fiber 50 do not necessarily have to be fused. The laser light emitted from the crystal fiber 19 may be condensed on the incident end face of the fiber 50 using a lens.

  In the present embodiment described above, the photonic crystal fiber is used as the nonlinear optical element. However, the present invention is not limited to this. Any optical element that can expand the spectrum of the treatment laser light incident on the fiber 50 by a non-linear effect may be used. For example, a fiber doped with an element or compound that can increase the nonlinearity of the fiber by being doped into the fiber core, or a silica fiber may be used. Examples of the substance doped into the core include germanium, germanium oxide, fluoride, rare earth, and the like. In the case of a silica fiber, a non-linear effect is applied to the transmitted laser light by making it extremely long (for example, several km). Further, the nonlinear optical element is not limited to a fiber form. The treatment laser light may be transmitted through a bulk nonlinear crystal. In this case, the treatment laser light that is incident on the nonlinear crystal is substantially parallel light, and an optical system that collects the emitted treatment laser light on the incident end of the fiber 50 with a lens is used.

  In the above description, the fiber laser is exemplified as the laser light source that emits the fundamental laser beam. However, the present invention is not limited to this. The laser light source may be a laser light source having a relatively narrow spectral width, for example, a solid state laser. In the above description, the infrared laser light is converted into visible laser light. However, the present invention is not limited to this. The infrared light may be converted into infrared light (such as the second harmonic wave of the infrared light that becomes the fundamental wave).

  In the above description, the treatment laser beam is emitted with the set pulse width by driving the excitation light source 11a (current control). However, the present invention is not limited to this. The safety shutter may be controlled to be emitted by inserting / removing the safety shutter to / from the optical axis of the treatment laser light. In the above description, the treatment laser light is emitted as a continuous wave. However, the present invention is not limited to this. In the treatment in which the beam profile of the treatment laser light irradiated to the tissue is preferably flat, the treatment laser light may be appropriately pulsed. Note that. In such a case, it is preferable that the pulse is not a giant pulse having a mechanical destruction action.

  Further, in the above description, an apparatus that irradiates a treatment laser beam to the fundus of a patient's eye is taken as an example. Any device can be applied.

It is a schematic block diagram of the optical system and control system of an ophthalmic laser treatment apparatus. It is a figure explaining the spectrum of a laser beam. It is the schematic diagram which showed the beam profile (speckle pattern) when a laser beam with a narrow spectral width is allowed to pass through a multimode fiber. It is a figure explaining the beam profile when the laser beam of each wavelength is passed through a multimode fiber.

DESCRIPTION OF SYMBOLS 10 Laser light source unit 11 Fiber laser 19 Photonic crystal fiber 13 Wavelength conversion element 20 Operation unit 30 Control unit 31 Memory 50 Optical fiber

Claims (4)

Laser light source for emitting treatment laser light, multimode fiber for guiding laser light emitted from the laser light source, and irradiation optical system for irradiating a patient's tissue with laser light emitted from the multimode fiber In a laser treatment apparatus comprising:
A non-linear optical element disposed between the laser light source and the multimode fiber in order to make the beam profile of the laser light emitted from the multimode fiber substantially flat, and the laser incident on the multimode fiber A nonlinear optical element that expands the spectral width of light by a self-phase modulation effect;
A laser treatment apparatus comprising: The laser treatment apparatus of claim 1,
The laser light source emits laser light having a spectral width of less than ± 0.2 nm with respect to the center wavelength of the laser light,
The nonlinear optical element achieves the desired therapeutic effect of the wavelength of the laser light irradiated to the patient's eye, so that the wavelength of the laser light emitted from the laser light source is ± 0.5 nm or more and ± 10 nm or less. A laser treatment device, which extends to a spectral width. In the laser treatment apparatus of Claim 1 or 2,
The non-linear optical element is a single-mode fiber in order to expand the spectrum width of laser light continuously emitted from a laser light source. The laser treatment device of claim 3 ,
The laser treatment apparatus according to claim 1, wherein an exit end of the single mode fiber is fused to an entrance end of the multimode fiber.