JPS6259918B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser device that uses an optical transmission fiber, and its purpose is to reliably detect breakage or melting of the optical transmission fiber and stop laser oscillation. The goal is to ensure safety.

An example of a laser device using an optical transmission fiber is a surgical laser scalpel device. wavelength
In a laser scalpel device that uses a 10.6 μm CO ₂ laser as a light source, there are two methods for guiding laser light to the surgical site.
There are different methods. One method is called the mirror-articulated method, which uses multiple mirrors to guide the laser beam to an arbitrary position and direction.The other method is to pass the laser beam through a thin and highly flexible optical fiber. This is a method that guides you to any position and direction.

Optical fibers mainly made of quartz, which are used in ordinary optical communications, are extremely flexible and can transmit light with low loss from visible light to near-infrared light of about 1 to 2 μm. However, almost no CO ₂ laser light with a wavelength of 10.6 μm, which is used as a light source for surgical laser scalpels, passes through. Therefore, as an optical fiber for a CO ₂ laser scalpel, a material having relatively good light transmission characteristics at a wavelength of 10.6 μm, such as thallium bromide iodide (generally referred to as KRS-5), is processed into a fiber shape. But this KRS
Since the -5 optical fiber has a polycrystalline structure, it is brittle and has the disadvantage that it will break if bent beyond a certain curvature. For example, in the case of a KRS-5 optical fiber with a diameter of 1 mm, the radius of curvature is approximately 12 cm, and if it is bent beyond this, it will break. For this reason, safety is ensured by covering the optical fiber with a curvature-limiting outer sheath so that it can be bent freely up to a certain curvature with almost no resistance, but not beyond a certain curvature. is the current situation. However, if the optical fiber breaks during use, the broken surface will not become smooth because it is polycrystalline, and the absorption of light at the broken surface will increase significantly, causing the temperature of the broken surface to rise. Eventually, the fracture surface will dissolve. KRS−
The melting temperature of No. 5 is approximately 350°C, and the temperature around the fractured surface also rises, and if left untreated, the outer covering will be affected, creating a dangerous situation. Furthermore, if the optical fiber breaks and the laser beam directly exits from the outer sheath of the optical fiber, the danger becomes even greater.

In order to avoid such a situation, it is conceivable to measure the temperature of the optical fiber and control the laser oscillation to immediately stop when a temperature rise is detected. As a specific example of detecting the temperature of an optical fiber, a method may be used in which a resin tape or film whose electrical resistance changes depending on the temperature is wrapped around the optical fiber. However, this method has the disadvantage that even if the optical fiber breaks for some reason during storage, the breakage cannot be detected until the optical fiber is passed through the laser beam. Also KRS-5
As mentioned above, the optical fiber is easily broken and brittle, so it is technically difficult to tightly wrap the resin tape or film whose electrical resistance changes depending on the temperature around the optical fiber. Even if the electrical resistance of a part of the resin tape or film wound in this way changes, the resistance seen from the end of the resin tape or film hardly changes, and the optical fiber may break or melt due to the change in electrical resistance. Detection is not easy.

Therefore, the present invention avoids the above drawback by directly detecting the presence or absence of a fracture surface using a second light having a wavelength different from that of the CO ₂ laser beam. The case of a device will be explained based on the drawings as an example. 1 is a laser oscillator as a first light source, which generates CO ₂ laser light. 2 is a first lens that condenses the light beam from the laser oscillator 1; the incident end surface 3a of the optical fiber 3 is installed at the position of the light beam condensed to a predetermined size by the first lens 2; Laser oscillator 1
effectively guides the light beam from the optical fiber 3 to the optical fiber 3. 4
is the second lens, and the output end face 3b of the optical fiber 3
Collects the light emitted from the In addition, the dashed line 5
represents the path of the light beam for convenience of explanation. Reference numeral 6 indicates a second light source, and reference numeral 7 indicates a third lens, through which the light from the second light source 6 enters the optical fiber 3. Reference numeral 8 denotes a beam splitter that transmits almost 100% of the light from the laser oscillator 1, and at the same time efficiently transmits the light from the second light source 6, which is reflected inside the optical fiber 3 and emitted again from the input end face 3a. reflect. A fourth lens 9 condenses the light reflected by the beam splitter 8. 10 is a photodetector that detects the light focused by the fourth lens 9; 11 is a signal processing circuit; 12 is a laser oscillator control circuit; and 13 is a display/alarm device.

Next, the configuration will be explained in detail based on the operation.

The light beam emitted from the laser oscillator 1 is focused by the first lens 2 and is directed to the input end face 3 of the optical fiber 3.
incident on a. The light beam emitted from the output end face 3b of the optical fiber 3 is emitted at a divergence angle determined by the refractive index and structure of the optical fiber 3, the incident angle at the input end face 3a, etc., and the second lens 4 emits this light beam. The energy density required for a laser scalpel can be obtained by condensing the light into a predetermined spot size at focal point 0. In addition, in the drawing, the optical fiber 3 is drawn in a straight line for convenience of explanation, but the optical fiber 3, which transmits light energy of 10 to 50 watts, has a diameter of about 1 mm, which is sufficient for operation for surgery. It is flexible and therefore has an arbitrary curved shape.

The wavelength of the second light source 6 provided for the purpose of detecting a break in the optical fiber 3 is different from the wavelength of the laser oscillator 1 and matches the transmission spectrum characteristics of the optical fiber 3. The wavelength is chosen for which a corresponding photodetector is readily available. For example, a wavelength of around 1 μm is also used in optical communications, so the light source and photodetector are easy to use, and when KRS-5 is used as the material for the optical fiber 3, the transmittance is relatively good. If the light transmission characteristics of the optical fiber 3 extend to the visible light region, visible light can also be used as the second light source 6. Similarly, it is also possible to use light in the wavelength range of 1 μm to 10 μm.

The optical axis of the third lens 7 is arranged at a certain angle with respect to the optical axis of the optical fiber 3, and this angle is such that when the light from the second light source 6 is reflected,
The angle must be such that this reflected light does not pass through the first lens 2 → beam splitter 8 → fourth lens 9 and enter the photodetector 10. In other words, the optical axis of the third lens 7 is tilted so that the light from the second light source 6 reflected by the entrance end surface 3a of the optical fiber 3 does not enter the photodetector 10.
This angle varies depending on the size of the beam of the laser beam, the focal length of the first lens 2, etc., but needs to be approximately 10 degrees or more.

Optical fibers used in CO ₂ laser scalpels generally have a large refractive index, so even light that is obliquely incident on the input end face can propagate inside the optical fiber.The present invention effectively takes advantage of this property. We are using. For example, as a material for optical fiber 3
When KRS-5 is used, the refractive index for a wavelength of 1 μm exhibits a large value of about 2.6, and the numerical aperture of the optical fiber 3 is 1.0. That is, even light incident almost parallel to the input end face 3a is refracted and enters the optical fiber 3, and is transmitted to the output end face 3b while repeating total reflection within the optical fiber 3.

The light from the second light source 6 that enters the optical fiber 3 propagates within the optical fiber 3 and reaches the output end face 3b.
When it reaches this point, a part of the light is emitted from the output end face 3b to the outside of the optical fiber 3, and a part of it is reflected from the output end face 3a. The emission end face 3b is coated with an anti-reflection coating for a wavelength of 10.6 μm in order to efficiently guide the CO ₂ laser beam with low loss, but it has no anti-reflection effect for light with a wavelength different from 10.6 μm. The light from the second light source 6 is reflected at the output end face 3b with a reflectance determined by the difference in refractive index. This value is KRS
-5, it is about 17%, and this is why the wavelength of the second light source 6 was chosen to be different from the wavelength of the CO ₂ laser beam.

The light from the second light source 6 reflected by the output end face 3b of the optical fiber 3 travels inside the optical fiber 3 in the opposite direction toward the input end face 3a, and reaches the input end face 3.
a to the outside of the optical fiber 3, and the first
beam splitter 8 through lens 2 in the opposite direction.
incident on . Beam splitter 8 is made of Ge, ZnSe,
Alternatively, a plane-parallel plate made of a material such as CdTe with an anti-reflection coating for the CO ₂ laser beam may be used, or if the laser beam is polarized, a plane-parallel plate made of a similar material may be used. It is arranged to form a Brewster angle with respect to the laser beam.

Both the input end face 3a and the output end face 3b of the optical fiber 3
Similarly, an anti-reflection film for wavelength 10.6 μm is applied, but some CO ₂ laser light
The beam is reflected by the beam, travels the optical path in the opposite direction, and enters the beam splitter 8, but in the beam splitter 8,
Since the anti-reflection film or the Brewster angle effectively acts on this light, almost 100% of the light is transmitted and is not reflected. Therefore, some of the light reflected by the beam splitter 8
Almost no CO ₂ laser light is included, and only light from the second light source 6 is reflected within the optical fiber 3 and emitted from the incident end face 3a. Said second
This is another reason why the wavelength of the light source 6 was chosen to be different from the wavelength of the CO ₂ laser beam. However, it is preferable to insert a filter (not shown) in front of the photodetector 10 to cut off the CO ₂ laser beam.

The light from the second light source 6 reflected by the beam splitter 8 is focused on a photodetector 10 by a fourth lens 9, and the output signal of the photodetector 10 is inputted to a signal processing circuit 11 to perform necessary processing. Signal processing is performed, and the result is used to drive the laser oscillator control circuit 12 to control the output of the laser oscillator 1.

If a part of the optical fiber 3 is cracked or broken for some reason, the crack or broken surface becomes a diffusely reflecting surface instead of a mirror surface, so light absorption increases at the broken surface. Most of the light from the second light source 6 is also absorbed by this fracture surface, and the amount of reflected light becomes extremely small. the result,
Since the amount of light incident on the photodetector 10 decreases, the signal processing circuit 11 detects this change in the output of the photodetector 10, controls the laser oscillator control circuit 12 to stop the laser oscillator 1, and displays the information at the same time. The alarm device 13 is activated to immediately notify the operator and surrounding people that the optical fiber 3 has broken.

When breakage or melting occurs in the optical fiber 3, the signal processing circuit 11 immediately detects this via the photodetector 10, and the laser oscillator control circuit 12
Since the display/warning device 13 is operated, safety can be sufficiently ensured.

Furthermore, when performing surgery using a laser scalpel, the cylindrical handpiece (not shown) that holds the second lens 4 is held, so this handpiece is as light as possible and has a diameter of approximately 20 mm or less. However, in the present invention, a second light source 6, a third lens 7, a beam splitter 8, a fourth lens 9, and a photodetector 10 are used to detect the breakage of the optical fiber 3.
Since all of the signal processing circuit 11 can be disposed on the incident end face 3a side of the optical fiber 3, the handpiece can be lightweight and have a diameter of about 20 mm or less.

In the above embodiment, the detection of breakage of the optical fiber 3 while using a laser scalpel was explained, but even when the laser scalpel is not used, the second light source 6, photodetector 10, signal processing circuit 11, and display/alarm device Breakage detection can be performed by operating only 13.

As explained above, according to the laser device of the present invention, breakage and melting of the optical fiber, which serves as an optical transmission path for laser beams, can be reliably detected by the device disposed on the incident end face side of the optical fiber. By this detection, the laser oscillation is stopped, so the safety of the operator and the surrounding people can be sufficiently ensured.

[Brief explanation of the drawing]

The drawing shows a configuration diagram of a laser scalpel that is an embodiment of the laser device of the present invention. DESCRIPTION OF SYMBOLS 1... Laser oscillator [first light source], 2... First lens, 3... Optical fiber, 3a... Incident end face, 3b... Outgoing end face, 6... Second light source, 7...
...Third lens, 8...Beam splitter, 10
...Photodetector, 11...Signal processing circuit, 12...
Laser oscillator control circuit, 13...display alarm device.

Claims (1)

[Scope of Claims] 1. A first light source that generates a laser beam, a lens that focuses the laser beam, a flexible optical fiber that transmits the laser beam, and a first light source that generates light having a different wavelength from the laser beam. a second light source; a lens that focuses the light from the second light source on the input end face of the optical fiber; and a lens that focuses the light from the second light source on the input end face of the optical fiber; A beam splitter that splits the light from the second light source, a photodetector that detects the light split by the beam splitter, a signal processing circuit that processes the signal of this photodetector, and an output of the signal processing circuit. A laser device comprising: a control circuit for controlling the output of the first light source; and a display/warning device operated by a signal from the signal processing circuit. 2. A patent claim configured such that the laser light from the first light source enters from a direction that coincides with the optical axis of the optical fiber, and the light from the second light source enters from a direction tilted with respect to the optical axis of the optical fiber. The laser device according to item 1. 3. The laser device according to claim 1, wherein the beam splitter is arranged to form a Brewster angle with respect to the wavelength of the laser light when the laser light from the first light source is polarized.