JP2008147687A - Ophthalmic laser unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a desired laser beam, even when a high-gain wavelength exists near the desired wavelength. <P>SOLUTION: The ophthalmic laser unit for guiding the laser beam to a patient's eye is equipped with a laser resonator, comprising a pair of resonant mirrors for totally reflecting and resonating a second wavelength adjacent to a first wavelength of high-gain within a range of the oscillation wavelength of a solid laser medium, a wavelength-selecting element which selectively extracts the second wavelength; a wavelength conversion element which converts the second wavelength into second harmonics; and an output mirror which totally reflects the second wavelength, while transmits the second harmonics. At least two members of the pair of resonant mirrors and the output mirror are coated with a coating so that each member loses the first wavelength to be less than the threshold which does not generate resonance; while multiple transmission via the at least two members lose the first wavelength more than the threshold and makes the second wavelength reflect. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser apparatus used in the ophthalmic field or the like.

  A solid-state laser oscillator can be obtained by selectively oscillating only a desired wavelength from a plurality of oscillation wavelengths of a solid-state laser medium. For example, an Nd: YAG crystal has oscillation lines of 1123 nm and 1319 nm in addition to a typical wavelength of about 1064 nm. These second harmonics have wavelengths of about 532 nm (green), 561 nm (yellow), and 659 nm (red), respectively, and can be used for ophthalmic photocoagulation.

  By the way, when selectively oscillating a low gain wavelength, the loss of the high gain oscillation wavelength is increased. In this case, a mirror having an optical characteristic that normally reflects a wavelength to be selected and transmits another wavelength having a high gain is used as the total reflection mirror in the resonator.

  However, when an attempt is made to obtain laser light having a wavelength of 561 nm using the Nd: YAG crystal, a wavelength of 1064 nm having a high gain is close in wavelength to the fundamental wavelength of 1123 nm. For this reason, it is difficult to form a mirror having a characteristic of efficiently reflecting the wavelength 1123 nm while greatly losing the wavelength 1064 nm. Therefore, in such a case, there is often a problem that it is difficult to obtain a laser beam having a desired wavelength, or even if it is obtained, a sufficient output cannot be obtained. In particular, a laser apparatus that multi-oscillates both 532 nm (green) and 561 nm (yellow) has not been put into practical use.

  In view of the above-described problems of the conventional technology, the present invention provides a laser device capable of obtaining laser light having a desired wavelength even when there is a high gain wavelength in the vicinity of the desired wavelength. Let it be an issue.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) A pair of resonant mirrors that totally reflect and resonate a second wavelength that is close to the first wavelength with a high gain among the oscillation wavelengths of the solid-state laser medium, and a wavelength that selectively extracts the second wavelength A laser oscillator comprising: a selection element; a wavelength conversion element that converts the second wavelength into a second harmonic thereof; and an output mirror that totally reflects the second wavelength and transmits the second harmonic. An ophthalmic laser device for guiding laser light emitted from the output mirror to a patient's eye, wherein at least two of the pair of resonant mirrors and the output mirror disposed in the laser oscillator In addition to these, or at least two members of the reflecting mirrors arranged in the optical path for changing the reflection direction, the loss of the first wavelength alone is not less than a threshold value that does not cause oscillation. However, the first wavelength loss is not less than a threshold value that does not lead to oscillation by passing through a plurality of stages of transmission by the at least two members, and a coating having a characteristic of totally reflecting the second wavelength is applied. It is characterized by being.
(2) A pair of resonant mirrors that totally reflect and resonate with a second wavelength that is close to the first wavelength with a high gain among the oscillation wavelengths of the solid-state laser medium, and a wavelength that selectively extracts the second wavelength. A laser oscillator comprising: a selection element; a wavelength conversion element that converts the second wavelength into a second harmonic thereof; and an output mirror that totally reflects the second wavelength and transmits the second harmonic. An ophthalmic laser device that guides laser light emitted from the output mirror to a patient's eye, wherein both end faces of the wavelength conversion element disposed in the laser oscillator are each only on one side. Although the loss of the first wavelength cannot be greater than or equal to the threshold value that does not lead to oscillation, the loss of the first wavelength is made to be greater than or equal to the threshold value that does not lead to oscillation by passing through the two-stage transmission of both end faces. And the second It is characterized by being provided with a coating having a characteristic of totally transmitting harmonics.

  As described above, according to the present invention, it is possible to efficiently oscillate laser light having a desired wavelength.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Example 1>
The first embodiment will be described using an apparatus that oscillates a single wavelength laser beam. FIG. 1 is an external view of an ophthalmic laser photocoagulation apparatus using a slit lamp. FIG. 2 is a schematic diagram of the optical system and control system of the apparatus.

  Reference numeral 1 denotes a laser device main body, which stores a laser oscillator 10, which will be described later, a part of a light guide optical system for guiding and irradiating laser light to an affected part of a patient's eye, a control unit 20, and the like. A control unit 2 of the apparatus is provided with various switches for setting and inputting laser irradiation conditions. Reference numeral 3 denotes a foot switch for transmitting a trigger signal for laser irradiation.

  Reference numeral 4 denotes a slit lamp, which includes an observation optical system for observing a patient's eye and a part of a light guide optical system. Reference numeral 5 denotes a fiber for guiding laser light from the main body 1 to the slit lamp 4. Reference numeral 6 denotes a frame for moving the slit lamp 4 up and down.

  In FIG. 2, reference numeral 10 denotes a laser oscillator as a laser oscillation source. Inside, an Nd: YAG crystal (hereinafter also simply referred to as a rod) 11 which is a solid laser medium, a semiconductor laser which is an excitation light source (hereinafter simply referred to as an LD). (Also referred to as laser diode) 12, nonlinear crystal (hereinafter also simply referred to as NLC (non linear crystal)) 13 a that is a wavelength conversion element, total reflection mirror (hereinafter also simply referred to as HR (high reflector)) 14 a and 14 b, An output mirror 15 is provided. As the nonlinear crystal, a KTP crystal, an LBO crystal, a BBO crystal, or the like can be used. In this embodiment, a KTP crystal is used.

  The Nd: YAG crystal emits light having a plurality of oscillation lines (peak wavelengths) in the near-infrared region by excitation light from the excitation light source. In the apparatus of the present embodiment, a laser beam of about 561 nm (yellow) is emitted by generating a second harmonic in an oscillation line of about 1123 nm among a plurality of oscillation lines using a nonlinear crystal. is there.

  An HR 14a is provided at one end of the optical path of the optical axis L1 where the rod 11 is disposed, and an output mirror 15 is provided at an angle inclined by a predetermined angle at the other end. The HR 14a has a characteristic of total reflection (99.8% reflection in this embodiment) with respect to the wavelength of 1123 nm and transmission of about 55% with respect to the wavelength of 1064 nm as shown in FIG. The output mirror 15 has a characteristic of totally reflecting the wavelength of 1123 nm and transmitting 561 nm.

  The NLC 13 and the HR 14b are fixedly provided in the optical path of the optical axis L2 that is the reflection direction of the output mirror 15. The NLC 13a is arranged to generate a wavelength of 561 nm, which is the second harmonic of the wavelength of 1123 nm. Like the HR 14a, the HR 14b transmits about 10% of the wavelength of 1064 nm and has total reflection characteristics with respect to 1123 nm and 561 nm.

  Since the peak wavelength of 1064 nm and the peak wavelength of 1123 nm are close to each other, if it is desired to resonate the wavelength of 1123 nm, the wavelength of 1064 nm is maintained at about 70% by a single path while maintaining the oscillation of the wavelength of 1123 nm (not resulting in oscillation) It is necessary to lose more than (threshold). In this case, it is very difficult to obtain an optical member having such a characteristic that only one of the total reflection mirrors transmits a wavelength of 1064 nm highly (transmittance of about 70%) and highly reflects a wavelength of 1123 nm. For this reason, in the present embodiment, an optical member is prepared that has a coating property that allows the wavelength of 1064 nm to pass to some extent (55% in the embodiment) while making the reflectance of the wavelength of 1123 nm as high as possible. . By using an optical member having such characteristics as a total reflection mirror at both ends of the resonator, a wavelength of 1064 nm is transmitted outside the resonator. As a result, in Example 1, the wavelength of 1064 nm is lost by about 70% in a single pass due to two-stage transmission.

  Reference numeral 40 denotes a wavelength selection element (here, an etalon is used) having a characteristic of selectively extracting a wavelength of 1123 nm. As described above, the wavelength of 1064 nm is gradually lost by the optical member and the wavelength selection element 40 selectively extracts 1123 nm, whereby the wavelength of 561 nm can be emitted using the peak wavelength of 1123 nm.

  In the case of the example in FIG. 2, either HR 14 a or HR 14 b and the output mirror 15 may be coated with a characteristic that allows 55% transmission of the 1064 nm wavelength. Further, a configuration may be adopted in which a plane mirror that changes the reflection direction is disposed in the optical path of the resonant optical system, and the plane mirror is coated with the coating.

  Further, it is preferable that the angle (reflection angle) formed by the optical axis L1 and the optical axis L2 is as narrow as possible in consideration of the influence of aberration.

The operation of the laser photocoagulation apparatus having the above configuration will be described.
The operator sets various conditions of the laser beam used for the operation by the control box 2. Laser beam emission control is performed by using the foot switch 3 to give an emission trigger signal to the control unit 20.

Upon receiving the trigger signal, the control unit 20 applies a current to the LD 12 and excites the rod 11 by the LD 12. When the rod 11 is excited, the light of 1123 nm is resonated between the HR 14a and the HR 14b, and further wavelength-converted by the NLC 13a disposed on the optical axis L2 to the light of 561 nm which is the second harmonic. The obtained 561 nm laser light is transmitted through the output mirror 15 and guided to the fiber 5. And it irradiates toward the patient's eyes from the irradiation port of the slit lamp 4.
<Example 2>
The second embodiment will be described using a laser device that selectively oscillates two-wavelength laser light. FIG. 4 is a schematic diagram of the optical system and control system of the apparatus. Here, components having the same functions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the laser apparatus shown in FIG. 4, two-color lasers of about 532 nm (green) and about 561 nm (yellow) are generated by generating second harmonics in two oscillation lines of about 1064 nm and about 1123 nm using a nonlinear crystal. Light is emitted.

  Here, the HR 14a 'has a characteristic of total reflection with respect to wavelengths of 1064 nm and 1123 nm, but is not limited thereto, and has a characteristic of widely reflecting wavelengths in the infrared region including wavelengths of 1064 nm and 1123 nm. You may have something. The output mirror 15 'has a characteristic of totally reflecting wavelengths of 1064 nm and 1123 nm and transmitting 532 nm and 561 nm.

  On the optical axis L2 in the reflection direction of the output mirror 15 ′, the NLC 13b and the HR 14c are fixed. The NLC 13b is arranged to generate a wavelength of 532 nm, which is the second harmonic of the wavelength of 1064 nm. The HR 14c has total reflection characteristics with respect to 1064 and 532 nm.

  With such an optical arrangement, a first resonant optical system having a pair of resonator structures in which the HR 14a 'on the optical axis L1 and the HR 14c on the optical axis L2 face each other with the rod 11 interposed therebetween is generated by the NLC 13b. The second harmonic 532 nm can be emitted from the output mirror 15 ′ without being blocked by the rod 11.

  An HR 14d, which is a plane mirror, is detachably disposed between the output mirror 15 'on the optical axis L2 and the NLC 13b. As shown in FIG. 3, the HR 14d has characteristics of total reflection (reflectance of about 99.8%) for 1123 nm and 561 nm, and transmittance of about 55.0% for 1064. An NLC 13a and an HR 14b are fixedly provided on the optical axis L3 in the reflection direction of the HR 14d.

  With such an optical arrangement, when the HR 14c is inserted on the optical axis L2, the HR 14a ', the rod 11, and the output mirror 15' of the first resonance optical system are shared, and the HR 14a and the HR 14b sandwich the rod 11. A second resonant optical system that constitutes a pair of resonators is configured. Further, the insertion / removal of the HR 14c onto / from the optical axis L2 is performed by the insertion / removal device 21.

  In Example 2, since two wavelengths are selected and emitted, the HR 14a ′ needs to totally reflect the wavelengths of 1064 nm and 1123 nm. In order to emit a wavelength of 561 nm in the second resonant optical system, it is difficult to lose most of the wavelength of 1064 nm due to the optical characteristics of the HR 14b. Therefore, in the second embodiment, an optical member having the same optical characteristics as that of the HR 14b is used for the HR 14d in order to switch the wavelength to be emitted and to sufficiently lose the wavelength of 1064 nm in the resonator. As a result, since the wavelength of 1064 nm can be greatly lost, the wavelength of 1123 nm can be efficiently resonated and the second harmonic wave of 561 nm can be emitted.

The operation of the laser photocoagulation apparatus having the above configuration will be described.
<Method of emitting laser beam of 532 nm>
The surgeon changes the color (wavelength) of the laser beam used for the operation to green (532 nm) by using the wavelength selection switch 2a provided in the control box 2. When green is selected, the HR 14d is in the position of the dotted line shown in FIG. 4 and is placed outside the optical axis L2. Laser beam emission control is performed by using the foot switch 3 to give an emission trigger signal to the control unit 20.

  Upon receiving the trigger signal, the control unit 20 applies a current to the LD 12 and excites the rod 11 by the LD 12. When the rod 11 is excited, the light of 1064 nm is resonated between the HR 14a 'and the HR 14c, and is further wavelength-converted by the NLC 13b disposed on the optical axis L2 to the light of 532 nm that is the second harmonic. The obtained laser beam of 532 nm passes through the output mirror 15 and is guided to the fiber 5 shown in FIG. And it irradiates toward the patient's eyes from the irradiation port of the slit lamp 4.

<Method of emitting laser beam of 561 nm>
The surgeon changes the color (wavelength) of the laser beam used for the operation to yellow (561 nm) by using the wavelength selective switch 2a. The controller 20 drives the insertion / removal device 21 to position the HR 14dc on the optical axis L2 (solid line position in FIG. 4). Further, the control unit 20 applies a current to the LD 12 by a trigger signal from the foot switch 3 to excite the rod 11.

  When the rod 11 is excited, the light of 1064 nm is lost by about 70% between the HR 14 a ′ and the HR 14 b and only the wavelength of 1123 nm is extracted by the wavelength selection element 40, so that the wavelength of 1123 nm resonates. Further, the NLC 13 a disposed on the optical axis L 3 is wavelength-converted to 561 nm light as the second harmonic, and the obtained 561 nm laser light is transmitted through the output mirror 15 and guided to the fiber 5. And it irradiates toward the patient's eyes from the irradiation port of the slit lamp 4.

  In the second embodiment, the HR 14d is inserted on the optical axis L2, and the HR 14b and the HR 14d lose 1064 nm by about 70%, so that the resonance of 1123 nm is performed. However, the present invention is not limited to this. For example, it is possible to resonate one of the adjacent peak wavelengths by selecting a wavelength by exchanging a nonlinear crystal and applying a coating that reflects / transmits a predetermined wavelength to both end faces of the nonlinear crystal.

<Example 3>
FIG. 5 is a diagram showing an optical system in a case where a coating for reflecting / transmitting a predetermined wavelength is applied to a nonlinear crystal. Here, components having the same reference numerals as those in the second embodiment have the same functions, and thus description thereof is omitted.

  HR14b 'has a characteristic of total reflection with respect to wavelengths of 1064 nm and 1123 nm, like HR14a'. Further, both end faces (surfaces through which the light flux enters and exits) of the NLC 13a ′ that is detachably placed on the optical axis L2 in FIG. 5 are totally transmitted at wavelengths of 1123 nm and 561 nm as shown in FIG. Each of the coatings has an optical property of transmitting 45% of the wavelength. The coating is performed by a known method such as a vacuum evaporation method.

  When the NLC 13a 'is placed on the optical axis L2, the wavelength of 1064 nm can be transmitted only about 30% by the coating applied to both ends of the NLC 13a'. Accordingly, since the wavelength of 1064 nm is lost by about 70% in a single path, the resonance of 1123 nm can be performed as in the second embodiment, and the laser light of 561 nm can be emitted. Further, the driving means 30 removes the NLC 13a 'and the wavelength selection element 40 from the optical axis L2, and installs the NLC 13b on the optical axis L2, thereby emitting laser light of 532 nm, which is the second harmonic of 1064 nm. Can do.

It is the figure which showed the external appearance of the ophthalmic laser photocoagulation apparatus. FIG. 2 is a diagram illustrating an optical system and a control system in the apparatus according to the first embodiment. It is the figure which showed the optical characteristic by coating. FIG. 6 is a diagram illustrating an optical system and a control system in the apparatus of Example 2. FIG. 10 is a diagram illustrating an optical system and a control system in the apparatus of Example 3. It is the figure which showed the optical characteristic by coating.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser apparatus main body 2 Control part 10 Laser oscillator 11 Nd: YAG crystal 12 Semiconductor laser 13a Wavelength conversion element 14a, 14b Total reflection mirror 15 Output mirror 20 Control part

Claims (2)

A pair of resonant mirrors that totally resonate and resonate with a second wavelength that is close to the first wavelength of the high gain of the oscillation wavelengths of the solid-state laser medium; and a wavelength selection element that selectively extracts the second wavelength; A laser oscillator in which a wavelength conversion element that converts the second wavelength into the second harmonic and an output mirror that totally reflects the second wavelength and transmits the second harmonic are disposed; An ophthalmic laser device for guiding laser light emitted from the output mirror to a patient's eye,
At least two members of the pair of resonant mirrors and the output mirror disposed in the laser oscillator, or at least two of the reflecting mirrors disposed in the optical path for changing the reflection direction in addition to these members Each of the members alone cannot make the loss of the first wavelength equal to or higher than a threshold value that does not lead to oscillation, but the threshold value that does not cause the loss of the first wavelength to pass through a plurality of stages of transmission through the at least two members. In addition to the above, an ophthalmic laser device is provided with a coating having a characteristic of totally reflecting the second wavelength. A pair of resonant mirrors that totally resonate and resonate with a second wavelength that is close to the first wavelength of the high gain of the oscillation wavelengths of the solid-state laser medium; and a wavelength selection element that selectively extracts the second wavelength; A laser oscillator in which a wavelength conversion element that converts the second wavelength into the second harmonic and an output mirror that totally reflects the second wavelength and transmits the second harmonic are disposed; An ophthalmic laser device for guiding laser light emitted from the output mirror to a patient's eye,
On both end faces of the wavelength conversion element disposed in the laser oscillator, the loss of the first wavelength cannot be made to exceed the threshold value that does not lead to oscillation with only one of the faces, but the two end faces pass through two stages. Thus, the ophthalmic laser device is characterized in that the loss of the first wavelength is not less than a threshold value that does not lead to oscillation, and a coating having a characteristic of totally transmitting the second wavelength and the second harmonic is applied. .

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