Coherent light generators – Optical fiber laser
Reexamination Certificate
1999-09-07
2002-10-08
Scott, Jr., Leon (Department: 2828)
Coherent light generators
Optical fiber laser
Reexamination Certificate
active
06463083
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a laser radiation device, and in particular, to a laser radiation device which employs a fiber laser that is capable of emitting a laser beam including two or more wavelength components.
DESCRIPTION OF THE PRIOR ART
Laser radiation devices for radiating objects with laser beams have widely been brought to practical use today in the fields of metal processing, semiconductor processing, medical care, etc. In almost laser radiation devices, a laser capable of emitting a laser beam including only one wavelength component is employed. Interaction between a laser beam and an object (metal, a semiconductor, a living body, etc.) depends on the wavelength of the laser beam, therefore, the oscillation wavelength of a laser radiation device is determined and selected depending on which interaction is desired. The absorption coefficient of a living body varies depending on parts (protein, fat, bone, water, etc.) of the living body. For instance, a 2 &mgr;m band laser beam is known to be suitable for coagulation of soft tissue, a 9 &mgr;m band laser beam is known to be suitable for perforation of dentin, a 3 &mgr;m band laser beam is known to be suitable for precise incision, and a 10 &mgr;m band laser beam etc. are known to be suitable for normal incision. A surgical laser knife which is provided with a 10 &mgr;m band CO
2
laser oscillator is in practical use today. As described above, laser radiation devices which are capable of emitting a laser beam including only one wavelength component have been used in almost cases. However, in the field of surgical laser knives, for example, it is also possible to implement and use a laser radiation device that is capable of emitting a laser beam including two or more wavelength components so that two or more effects can be attained simultaneously.
FIG. 1
is a schematic diagram showing a conventional laser radiation device which can be employed for emitting a laser beam including two or more wavelength components. The laser radiation device
31
shown in
FIG. 1
includes a first laser device
21
, a first collimator lens
23
, a second laser device
24
, a second collimator lens
26
, a dichroic mirror
27
, a total reflection mirror
29
, and a focusing lens
30
.
The first laser device
21
and the second laser device
24
having different oscillation frequencies emit a first laser beam
22
and a second laser beam
25
respectively. The first laser beam
22
and the second laser beam
25
emitted by the laser device
21
and
24
respectively are shaped into collimated beams by the first collimator lens
23
and the second collimator lens
26
respectively so as to be propagated in fixed directions losslessly, coupled together by the dichroic mirror
27
, guided (reflected) by the total reflection mirror
29
, and applied to an object
11
through the focusing lens
30
. The characteristics of the two wavelength components (i.e. the first laser beam
22
and the second laser beam
25
), such as the intensity, can be varied by controlling the first laser device
21
and the second laser device
24
respectively. The dichroic mirror
27
has high transmission (transmissivity) for the first laser beam
22
and high reflectivity for the second laser beam
25
.
In the case where the above laser radiation device
31
is employed for a surgical laser knife, coupling of a 3 &mgr;m band laser beam (which is suitable for precise incision of a living body) with a 2 &mgr;m band laser beam (which is suitable for tissue coagulation and hemostasis by means of denaturalization of protein) is a desirable selection. In such a case, an Er (erbium)-doped YAG (yttrium aluminium garnet) crystal laser having an oscillation frequency of 2.94 &mgr;m which is pumped by a 970 nm laser diode can be employed as the first laser device
21
, and a Tm (thulium)-Ho(holmium)-co-doped YLF (yttrium lithium fluoride) crystal laser having an oscillation frequency of 2.06 &mgr;m which is pumped by a 790 nm laser diode can be employed as the second laser device
24
. If it is necessary to further couple a third laser beam (generated by another laser device having another oscillation frequency) to the coupled laser beam
28
, the coupling can be attained by adding a coupling means which is similar to the dichroic mirror
27
.
As described above, it is possible to exert two or more effects (each of which is characteristic of each wavelength component) on the object simultaneously, by employing the laser radiation device
31
employing the two laser devices
21
and
24
to the surgical laser knife. It is also possible to change characteristics of each wavelength component (such as the intensity) by controlling the two laser devices
21
and
24
depending on the characteristics of the object and desired effects, therefore, the intensity of each wavelength component in the coupled laser beam can be set optimally by controlling the two laser devices
21
and
24
respectively.
However, in the case where two or more different laser beams are coupled together and guided in the same direction, the optical axes of the laser beams having different wavelengths can have misalignment in the coupling. Further, the propagation characteristics of each wavelength component varies depending on the laser device that emitted the wavelength component, and thus misalignment and variations in the intensity can occur on the object especially when the laser beams are focused on the object. Furthermore, the laser beams generated and emitted by the laser radiation device are not necessarily visible, and thus it is not easy to check and adjust the positions of the focused laser beams (focused laser beam spots) on the object. Moreover, the above laser radiation device needs to be provided with two or more laser devices, therefore, the cost necessary for the laser beam sources (principle parts of the laser radiation device) becomes twice, the power consumption becomes large, and the size of the laser radiation device is necessitated to be large.
SUMMARY OF THE INVENTION
It is therefore the primary object of the present invention to provide a laser radiation device which is capable of generating and emitting a laser beam including two or more wavelength components and applying the two or more wavelength components to the object coaxially in uniform and stable irradiation conditions.
Another object of the present invention is to provide a laser radiation device which is capable of generating and emitting a laser beam including two or more wavelength components and applying the two or more wavelength components to the object, which can be realized with a low manufacturing cost, small running costs, and in a small size.
Another object of the present invention is to provide a laser radiation device which is capable of generating and emitting a laser beam including two or more wavelength components and applying the two or more wavelength components to the object, by which the user of the laser radiation device can easily see and recognize the irradiation point (i.e. a focused beam spot) of the laser beam on the object.
In accordance with a first aspect of the present invention, there is provided a laser radiation device comprising a pumping light emission means, a fiber laser means and a beam guiding means. The pumping light emission means generates and emits pumping light. In the fiber laser means, an optical fiber doped with laser ions is excited by the pumping light emitted by the pumping light emission means, and thereby a laser beam including two or more wavelength components is generated. The beam guiding means guides the laser beam generated by the fiber laser means into desired place and direction.
In accordance with a second aspect of the present invention, in the first aspect, the laser radiation device further comprises a beam shaping means for shaping the laser beam guided by the beam guiding means.
In accordance with a third aspect of the present invention, in the second aspect, the beam shaping means focuses the laser beam so that a focused
Sekita Hitoshi
Sumiyoshi Tetsumi
Jr. Leon Scott
McGinn & Gibb PLLC
NEC Corporation
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