JPS6323063Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a laser scalpel, and an object thereof is to provide an optical fiber light guide type laser scalpel with improved optical characteristics of an emitted beam.

The optical fiber light guide type laser scalpel has new functions such as flexibility, operational stability, and endoscope operation compared to the mirror joint light guide type laser scalpel, and is expected to have a promising future. However, there are many technical issues that need to be solved in the future, such as deterioration of the optical characteristics of the emitted beam and high attenuation rate.
Future improvements in the attenuation rate can be expected through research into improved materials, but many of the optical characteristics of the former emitted beam are inherent shortcomings of optical fiber laser scalpels, and require improvements from the basic configuration. The optical characteristics of the emitted beam include the beam diameter and divergence angle, and the transmittance, shape, and
Affects light gathering characteristics, etc. The beam diameter is determined by the optical fiber diameter, but the divergence angle is determined by the various factors described below, and the current value is about 20 degrees full angle, which is much larger than the 0.5 degrees of the mirror joint type. It must be said that it has extremely low characteristics.

The spot diameter φ at the focal point when the emitted beam is focused by the optical system is the focal length of the optical system,
When the full angle of expansion is θ, φ=・θ ...(1), and φ is proportional to the expansion angle, so the increase in θ described above is a linear function of φ, and the energy density at the focal point is Characteristics deteriorate quadratically.

FIG. 1 shows a prior art method of coupling laser light to an optical fiber. A laser beam 5 from a laser oscillator 1 is focused by a coupling lens 2 and introduced into an optical fiber 3. 4 is the optical axis of the laser beam 5. This optical axis changes to 6 inside the optical fiber and 7 in the exit beam. The laser beam before the coupling lens 2 has a divergence angle θ ₁ , which is a low value of 1 to 2 mrad, which is characteristic of a laser resonator. The divergence angle after the coupling lens is θ ₂ , and if the focal length of the coupling lens is F and the diameter of the laser beam is φ, then θ ₂ = sin ^-1 φ/2F ...(2), and φ=14mmφ, F = 100 mm, the divergence angle θ ₄ of the emitted beam, which is θ ₂ ≒4°, is primarily due to this θ ₂
This is due to the fact that the light remains almost intact within the optical fiber, propagates through repeated multiple reflections on the side walls, and is eventually emitted. FIG. 2 shows θ ₄ caused by θ ₂ in a simplified diagram. In this case, it can be seen that θ ₂ = θ ₄ holds, but in reality, the optical fiber is curved, and other causes are superimposed, so such a simple relationship is not practical. do not have. The second cause is insufficient polishing precision of the entrance end face of the optical fiber. In Fig. 1, the orthogonal relationship between the incident end surface 9 of the fiber 3 and the fiber central axis 4 is slightly exaggerated, but for this reason, the laser beam central axis 4 is refracted by the incident surface and passes through the fiber 6. As the light evolves through continuous multiple reflections on the side walls, it generates a divergence angle that is approximately the same as this angle of refraction. The third cause is the spread of the emitted beam due to scattering within the optical fiber. In reality, these three types of causes exist simultaneously, and the above-mentioned expansion full-width
It forms the cause of 20°. The second of these,
While the third cause can be eliminated by improvements in optical fiber materials and construction, the first cause cannot be easily eliminated.

The present invention provides a laser scalpel that eliminates these conventional drawbacks, and FIG. 3 shows a diagram of the principle of the present invention. In the present invention, the diameter of the laser beam as it is emitted from the oscillator, thus keeping the divergence angle θ ₁ at a small value, is selected to be the same as or smaller than the diameter of the optical fiber, and the beam is focused by a coupling lens. The laser beam is directly coupled to the fiber without any interference. In FIG. 3, 11 is a waveguide laser tube, 12 is a total reflection mirror, and 13 is an output coupling mirror, and the laser excitation method is omitted because it is a conventional method. The inner diameter of the waveguide laser tube is 1 mmφ or less, and the diameter of the emitted laser beam is an even smaller value. In a normal laser, the fundamental mode is the TEM ₀₀ mode, and in this type of waveguide laser, the fundamental mode is the EH ₁₁ mode, but the intensity distribution is almost a Gaussian distribution and there is no problem. The divergence angle of the beam emitted from the waveguide laser tube 11 is normally
It is about 1.5° (full-width). As shown in Figure 3, the _optical fiber is approximately 1
Since the diameter is about mmφ, if the coupling to the fiber is performed sufficiently close to the output coupling mirror, the laser beam can be introduced into the fiber without using a coupling lens. Alternatively, as shown in FIG. 4, the end face 9' of the optical fiber 3 can be used instead of the output coupling mirror, and in this case, the efficiency of introducing the laser beam into the fiber end face when no coupling lens is present is increased. , reflection loss at the fiber entrance surface can be prevented. Thus, according to the present invention, θ ₂ is reduced to a value substantially equal to θ ₁ , so that if optical fiber materials and manufacturing techniques are further improved, the exit beam from the fiber will be reduced. The divergence angle can be reduced to 1.5° (full width), which is the divergence angle of a waveguide laser tube.

As mentioned above, the present invention is a laser scalpel that directly introduces the output beam from a waveguide laser tube, which has a diameter smaller than that of the optical fiber, into the optical fiber without using a coupling lens. This makes it possible to significantly reduce the beam divergence angle and improve light collection characteristics.

[Brief description of the drawings]

Figure 1 is a configuration diagram of main parts explaining a conventional example of an optical fiber light guide laser scalpel, Figure 2 is a principle diagram explaining the spread of the emitted beam from the tip of the laser knife due to the coupling lens, and Figure 3 is a diagram of the main part of the optical fiber guide laser scalpel. FIG. 4 is a block diagram showing one embodiment of the invention. FIG. 4 is a block diagram showing another embodiment of the invention. 3...Optical fiber light guide, 9'
...Incidence surface of optical fiber, 11...
... Waveguide laser tube, 12 ... Total reflection mirror, 13 ...
Output coupling mirror.

Claims (1)

[Scope of utility model registration request] A laser scalpel includes at least a laser oscillator and an optical fiber light guide path made of a transparent material for the laser beam, which guides the output laser beam from the laser oscillator to a predetermined point. A laser scalpel comprising a waveguide laser tube having an aperture smaller than the diameter of a light guide.