JP4719894B2 - Method and apparatus for detecting loss or clogging of optical fiber - Google Patents

Description

  The present invention relates to a method and an apparatus for detecting an optical fiber defect or clogging.

In order to perform laser treatment, a laser treatment apparatus using a carbon dioxide laser (CO ₂ laser) having a wavelength in the infrared region is known. In such a laser treatment apparatus, light is guided from a laser light source to a handpiece via a light guide optical system.

  The hollow optical fiber has a small beam divergence angle, is excellent in condensing characteristics, and can transmit a laser in the infrared wavelength region, and is excellent as a medical laser transmission system, for example. This is because of the advantages such as surgery, dermatology or dentistry with less bleeding, faster healing, shorter operation time, and wider range of applicable patients. A carbon dioxide laser surgical apparatus is known.

  In a conventional carbon dioxide laser treatment device, light is transmitted by reflection using an articulated arm having a plurality of optical mirrors attached thereto. This method has a problem of high cost due to an optical mirror, a precise articulated arm, etc., and an operator's handleability due to the presence of the arm.

In order to solve these problems, an optical fiber soundness inspection device, an optical fiber breakage detection method, and a method of transmitting a carbon dioxide laser in a hollow optical fiber whose inner surface is a mirror like a medical optical cable (for example, are known) Patent Documents 1 to 3).
JP 2000-221108 A JP-A-6-300664 JP-A-7-284539

  In the case where the hollow optical fiber is used for a light guide optical system, if a defect occurs on the mirror surface of the hollow optical fiber, there is a risk that the carbon dioxide laser melts the glass and opens a hole to burn an unexpected part. is there. This danger also exists when the hollow optical fiber is broken.

  As a means for solving such problems, a method of monitoring the laser output by installing an optical system at the exit of the hollow optical fiber can be considered. However, in such a method, handling ability which is the greatest advantage of using the hollow optical fiber is considered. That is, there is a problem that the degree of freedom of operation is impaired, and there is a possibility that a cost increase due to an increase in optical system parts may also be a problem.

  Further, even if the hollow optical fiber does not have a hole, the hollow optical fiber becomes unhealthy when melted and clogged at the melting stage of the fiber.

  The problem to be solved is to detect defects in hollow optical fiber used to detect hollow optical fiber perforation, breakage, or clogging in a carbon dioxide laser treatment device that transmits carbon dioxide laser light using a hollow optical fiber. In the method and the apparatus therefor, it is a point to detect a defect or clogging of the hollow optical fiber without impairing the degree of freedom of the hollow optical fiber.

According to the first aspect of the present invention , the sound wave is incident on the hollow portion of the hollow optical fiber from the primary side of the hollow optical fiber and the sound wave that has passed through the hollow portion is detected from the secondary side. This is a method for detecting clogging.

According to a second aspect of the present invention , a sound wave is caused to enter the hollow portion of the hollow optical fiber from the primary side of the hollow optical fiber, and a sound wave that has passed through the hollow portion is detected from the secondary side. In this method, the secondary side acoustic wave is compared to detect a hollow optical fiber defect or clogging.

  According to a third aspect of the present invention, an optical fiber according to any one of claims 1 to 2, wherein the primary side sound wave and the secondary side sound wave signal are electrically detected. This is a method for detecting defects.

  According to a fourth aspect of the present invention, the sound wave is generated by a speaker, and the secondary side sound wave is detected by a microphone, and the optical fiber is broken or clogged according to any one of claims 1 to 3. It is a method of detecting.

  According to a fifth aspect of the present invention, in the method for detecting a defect or clogging of an optical fiber according to any one of the first to fourth aspects, the primary side sound wave is set to a low frequency of 1 kHz or less. is there.

  According to a sixth aspect of the present invention, there is provided a method for detecting a defect or clogging of an optical fiber according to any one of the first to fifth aspects, wherein the primary side sound wave has a plurality of frequencies.

According to a seventh aspect of the present invention, there is provided a sound source for allowing sound waves to be incident on the hollow portion of the hollow optical fiber from the primary side of the hollow optical fiber, and detecting means for detecting the sound wave that has passed through the hollow portion on the secondary side. A hollow optical fiber defect or clogging detection device characterized by being provided.

  Claim 8 of the present invention is a hollow optical fiber defect or clogging detection device according to claim 7, wherein a speaker is connected to the gas laser generator, and a secondary microphone is connected to the hollow optical fiber. It is.

  The ninth aspect of the present invention is the hollow optical fiber defect or clogging detecting device according to the eighth aspect, wherein the hollow optical fiber 1 is provided with a primary microphone.

  The hollow optical fiber according to any one of claims 7 to 9, wherein the secondary side is a handpiece side where the secondary side is connected to the hollow optical fiber and emits laser light. It is a defect detection device.

  According to the first aspect of the present invention, in the method of detecting perforation or breakage of the hollow optical fiber using sound, a sound wave is incident from the primary side of the optical fiber and the sound wave is detected from the secondary side. If the hollow optical fiber is perforated, bent, or clogged, the sound wave propagation state in the hollow optical fiber changes, so that the hollow optical fiber is detected as perforated, broken, or clogged. Therefore, an expensive optical system on the secondary side of the hollow optical fiber becomes unnecessary, and the operator's handling performance is not impaired.

  According to the second aspect of the present invention, it is possible to detect the loss or clogging of the optical fiber by measuring the primary side sound wave and the secondary side sound wave and measuring the gain.

  According to the third aspect of the present invention, it is possible to detect defects or clogging with a voltmeter or the like.

  In a fourth aspect of the invention, the sound wave is generated by a speaker, and the secondary side sound wave is detected by a microphone, so that it can be manufactured at a relatively low cost.

  According to the fifth aspect of the present invention, even if the hollow optical fiber has a small inner diameter of the hollow portion, such a hollow portion surely transmits sound even if it functions as a low-pass filter for the sound frequency. Can do.

  In the invention of claim 6, the reliability of measurement can be increased by monitoring using not only one frequency but also a plurality of frequencies.

  In the invention of claim 7, a sound wave is incident from the primary side of the hollow optical fiber and the sound wave is detected from the secondary side, thereby detecting a change in the propagation state of the sound wave in the hollow optical fiber. It is possible to detect perforation, breakage, and clogging of a hollow optical fiber.

  In the invention of claim 8, a sound wave is incident from a primary side of the hollow optical fiber by a speaker, and the sound wave is detected from a secondary side by a secondary microphone.

  Thus, according to the ninth aspect of the present invention, the detection of the primary side microphone and the detection of the secondary side microphone can be compared to detect perforation, breakage or clogging of the hollow optical fiber.

  In the invention of claim 10, sound waves are emitted from the outlet of the handpiece 6 through the hollow portion of the optical fiber.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below do not limit the contents of the present invention described in the claims. In addition, all of the configurations described below are not necessarily essential requirements of the present invention.

  1 to 2 show Example 1, which is used for laser treatment. The advantages of laser treatment are less bleeding, faster healing, shorter surgical time, and wider patient coverage. A carbon dioxide laser surgical device is known as one of laser surgical devices.

  In the carbon dioxide laser, by using the hollow optical fiber 1 for the light guide portion, flexibility and handling properties can be improved. As shown in FIG. 1, a hollow optical fiber 1 is formed by forming a metallic mirror surface layer 3 on the inner surface of a hollow glass pipe 2 and forming an outer coating layer 4 on the outer surface. The carbon dioxide laser beam B travels while being reflected by the mirror surface layer 3.

  As shown in FIG. 2, the primary side that is the inlet of the hollow optical fiber 1 is connected to the carbon dioxide laser generator 5, and the secondary side that is the outlet is connected to the handpiece 6. A loudspeaker 7 as a speaker is connected to the carbon dioxide laser generator 5, and an oscillator 8 is connected to the loudspeaker 7. On the other hand, the secondary microphone 9 is connected directly or indirectly to the hollow optical fiber 1 to the handpiece 6 so that the sound of the hollow portion 1A can be captured. The secondary microphone 9 has a meaning of the secondary side downstream from the primary side, and the secondary microphone 9 that receives the sound incident on the primary side is not an outlet but a hollow optical fiber 1. An amplifier circuit 10, a filter circuit 11, and a voltmeter 12 are connected to the secondary microphone 9. In the figure, reference numeral 10A denotes an amplifier circuit connected to the loudspeaker 7.

  Note that the loudspeaker 7 and the secondary microphone 9 need to be provided in the hollow optical fiber 1 so as not to be affected by the laser beam B. For this purpose, the loudspeaker 7 and the secondary microphone 9 are installed in an optically shaded area. This is narrowed by a lens (not shown) when the laser beam B enters the hollow optical fiber 1 from the tube inlet 1I side or when it is output from the tube outlet 1O side. Therefore, sound is made incident by the loudspeaker 7 or received by the secondary microphone 9 from an optically shaded area. In the embodiment, the loudspeaker 7 is made to enter the hollow portion 1A on the side of the carbon dioxide laser generator 5 or the tube inlet 1I through the sound passage 7A, and the sound is incident on the secondary microphone 9 while the secondary side microphone 9 has the secondary side. The sound is received with the other end of the sound path 9A having one end connected to the receiving portion of the microphone 9 facing the hollow portion 1A. The hollow portion 1A side of the sound passage 9A is connected to the tube outlet 10 side.

  The effect | action is demonstrated about the said structure. The carbon dioxide laser beam B generated by the carbon dioxide laser generator 5 passes through the hollow portion 1A of the hollow optical fiber 1 and exits from the outlet of the handpiece 6. Further, the loudspeaker 7 is operated by an oscillator 8 to generate sound waves, and the sound waves are emitted from the exit of the handpiece 6 through the hollow portion 1A of the optical fiber 1. The sound wave is captured by the secondary microphone 9, and the sound wave signal input to the secondary microphone 9 is electrically converted and displayed by the voltmeter 12 via the amplifier circuit 10 and the filter circuit 11. . The sound wave is an elastic wave generated by the vibration of the generator (loud speaker 7) in the air or other sound medium, and includes not only the audible frequency region but also other frequency regions.

  If a hole P communicating from the hollow portion 1A to the outside is temporarily formed in the hollow optical fiber 1, the carbon dioxide laser B leaks through the hole P, and there is a risk of causing a human and material burnout accident. However, in such a case, a part of the sound wave leaks from the hole P, so that the lowered sound wave is captured by the secondary microphone 9, and the sound wave signal input to the secondary microphone 9 is electrically The voltmeter 12 is displayed with a voltage lower than normal by the voltmeter 12 through the amplifier circuit 10 and the filter circuit 11. Accordingly, when a voltage lower than normal is displayed, the carbon dioxide laser B may be leaked. For example, the control means (not shown) connected to the carbon dioxide laser generator 5 is operated to stop the laser. Appropriate action can be taken immediately.

  Thus, in the thin hollow optical fiber 1 whose inner diameter of the hollow portion 1A is less than 1 mm, the hollow portion 1A functions as a low-pass filter with respect to the frequency of sound, and therefore passes only a low frequency. Therefore, this method mainly employs a low frequency of 1 kHz or less. At these frequencies, the sound incident from the primary side of the hollow optical fiber 1 from the sound source can be confirmed with sufficient intensity by the secondary microphone 9 on the secondary side at normal times. Here, when the hole P is opened or broken in the middle of the hollow optical fiber 1, the acoustic power leaks from the hole P in the defective portion, so that the acoustic power transmitted to the secondary microphone 9 is extremely attenuated. The abnormality can be confirmed by the secondary microphone 9. Therefore, the laser may be stopped immediately.

  Although the hollow optical fiber 1 can be bent freely, the sound pressure may change in the bent state. However, even if there is an influence, the measurement is very small at such a very loose curvature. Less than error. If the hollow optical fiber 1 is bent at an acute angle, there is a considerable influence. However, the hollow optical fiber 1 has a curvature limit of 200 times or more of the inner diameter, and is a very loose bending method. There is nothing.

  Furthermore, when the hollow optical fiber 1 is melted by the laser B and the hollow optical fiber 1 is blocked by the melted laser, no sound reaches the exit side, and the sound pressure is lowered more than the sound pressure drop due to leakage. As with the leak, it can be detected as an abnormality. This is exactly the same as when no sound is incident in the hollow optical fiber 1.

  In particular, the above-mentioned acoustic detection in a laser surgical device can be used simultaneously with the laser surgical device, so that no disturbing device is attached to the hand, and it can be incorporated in a small handpiece without impairing handling properties. is there.

  In addition, since the leak can be detected at the moment when the hole P is opened in the middle of the hollow optical fiber 1 and the laser is immediately shut off, this is sufficiently effective as a method for preventing a leak accident.

  Further, for example, actual intraoperative noise may affect detection, but frequency discrimination is performed by applying a filter by the filter circuit 11 to the signal picked up by the secondary microphone 9, so noise at other frequencies is a problem. do not become. Furthermore, if the type of sound is detected using a plurality of frequencies such as “250 Hz and 400 Hz”, the possibility of malfunction can be almost eliminated.

  Since the gain waveform of the secondary microphone 9 changes depending on the leak position where the hole P is opened in the middle of the hollow optical fiber 1, the leak position can also be detected.

  FIG. 3 shows a second embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In addition to the secondary microphone 9 provided at the outlet of the hollow optical fiber 1, a primary microphone 13 is provided on the primary side which is the inlet of the hollow optical fiber 1. The primary microphone 13 is connected directly or indirectly to the hollow optical fiber 1 so that the sound of the hollow portion 1A can be captured. The transmitter 17 is connected to the loudspeaker 7, the primary microphone 13 is connected to the A channel 15 of the analyzer (FFT analyzer) 14, and the secondary side is connected to the B channel 16 of the analyzer (FFT analyzer) 14. A microphone 9 is connected. In the figure, 10A indicates an amplifier circuit between the loudspeaker 7 and the oscillator 17, and 10B indicates an amplifier circuit between the primary microphone 13 and the A channel 15.

  As in the first embodiment, the primary microphone 13 is placed in an optically shaded area so as not to be affected by the laser beam B. For example, a sound path (not shown) may be provided as in the secondary microphone 9.

  Accordingly, the carbon dioxide laser generated by the carbon dioxide laser generator 5 exits from the outlet of the handpiece 6 through the hollow portion 1A of the hollow optical fiber 1. Further, the loudspeaker 7 is actuated by the oscillator 17 to generate a sound wave, and this sound wave is also emitted from the outlet of the handpiece 6 through the hollow portion 1A.

  When a hole P communicating from the hollow portion 1A to the outside is temporarily formed in the hollow optical fiber 1, a part of the sound wave leaks from the hole P, so that the lowered sound wave is captured by the secondary microphone 9. The sound wave signal input to the secondary microphone 9 is electrically converted and input to the analyzer 14. On the other hand, the sound wave signal input to the primary microphone 13 is electrically converted and input to the analyzer 14. The analyzer 14 compares the input signal from the secondary microphone 9 and the input signal from the primary microphone 13 to analyze whether there is no hole or not.

  By doing in this way, the effect etc. similar to the said Example can be show | played.

  FIG. 4 shows a third embodiment, and the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  A primary microphone 13 is provided on the primary side which is the entrance of the hollow optical fiber 1, a transmitter 17 is connected to the loudspeaker 7, and a primary microphone 13 is connected to the A channel 15 of the analyzer (FFT analyzer) 14. It is a thing.

  Accordingly, the carbon dioxide laser generated by the carbon dioxide laser generator 5 exits from the outlet of the handpiece 6 through the hollow portion 1A of the hollow optical fiber 1. Furthermore, the loudspeaker 7 is actuated by the transmitter 7A to generate a sound wave, and this sound wave is also emitted from the outlet of the handpiece 6 through the hollow portion 1A.

  Then, when a hole communicating with the outside from the hollow portion 1A is temporarily formed in the hollow optical fiber 1, a part of the sound wave leaks from the hole, and the lowered sound wave is captured by the secondary microphone 9, The sound wave signal input to the secondary microphone 9 is electrically converted and input to the analyzer 14. By comparing the change in the input signal from the secondary microphone 9 with that in the normal state, it is possible to analyze the state where there is no hole P and the state where there is no hole P.

  By doing in this way, the effect etc. similar to the said Example can be show | played.

  FIG. 5 shows a fourth embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In Example 4, a loudspeaker 7 is connected to the tube inlet 1I of the hollow optical fiber 1 via a sound passage 7A, and a secondary microphone 9 is provided on the tube outlet 10 side via a sound passage 9A. Is.

  In the fourth embodiment as well, the same effects as in the first embodiment can be obtained.

  Next, experimental examples will be described. In the experimental example, the hollow optical fiber 1 was replaced with a stainless steel pipe. This is because the tube material is treated as a rigid boundary condition (sound does not propagate and is reflected), and both the glass pipe 2 and the stainless steel pipe have a large impedance of about 4 digits when viewed from the air, and acoustic when viewed from the air. This is because they are equivalent.

Experimental example 1

  Next, experimental examples will be described. In the experimental example, the hollow optical fiber 1 was replaced with a stainless steel pipe. This is because the tube material is treated as a rigid boundary condition (sound does not propagate and is reflected), and both the glass pipe 2 and the stainless steel pipe have a large impedance of about 4 digits when viewed from the air, and acoustic when viewed from the air. This is because they are equivalent.

  6 to 8 show Experimental Example 1, in which a loudspeaker 7 is connected to the inlet of a stainless steel pipe 21, a primary microphone 13 is provided at the inlet of the pipe 21, and a simulated leak hole is formed from the inlet of the pipe 21. FIG. 8 shows the spectrum from the primary microphone 13 formed with P.

Experimental example 2

  FIGS. 9 to 13 show Experimental Example 2, in which a loudspeaker 7 is connected to the inlet of a stainless steel pipe 21, and a secondary microphone 9 and a primary microphone 13 are provided at the outlet and inlet of the pipe 21. A simulated leak hole P is formed from the inlet of the pipe 21 and the gain using the secondary microphone 9 and the primary microphone 13 is shown in FIGS. 10 to 13.

Experimental example 3

  14 to 18 show Experimental Example 3, in which a loudspeaker 7 is connected to the inlet of the stainless steel pipe 21, a secondary microphone 9 is provided at the inlet of the pipe 21, and a simulated leak hole is provided from the inlet of the pipe 21. FIG. 15 to FIG. 18 show the spectrum formed from the secondary microphone 9 by forming P.

  From the above experiments, in the thin hollow optical fiber 1 in which the inner diameter of the hollow portion 1A is less than 1 mm, the hollow portion 1A functions as a low-pass filter with respect to the frequency of sound, and therefore passes only a low frequency. The reason that the method mainly employs a low frequency of 1 kHz or less appears over a wide frequency range from a very low frequency to about 1 kHz. Therefore, it is possible to monitor using not only one frequency but also a plurality of frequencies or frequency ranges. This can increase the reliability of the measurement. In the experiment, data using two microphones was collected, but one microphone is sufficient on the opposite side of the sound source.

Experimental Example 4

  Furthermore, another experimental example will be described. The same parts as those in the above-described examples and experimental examples will be described with the same reference numerals.

  19 to 24 show Experimental Example 4, and when the primary side microphone 13 is connected to the pipe 21, the tip of the primary side microphone 13, that is, the sound collecting portion 13A and the hole 21A formed in the pipe 21 are shown. In order to insulate vibration, a pipe-shaped vibration insulation relay member 22 such as silicon or rubber is interposed. Similarly, a pipe-like vibration insulation relay member 23 such as silicon or rubber is interposed between the loudspeaker 7 and the hole formed in the pipe 21 to insulate vibration, and the tip of the secondary microphone 9. In other words, a pipe-like vibration insulation relay member 24 such as silicon or rubber is interposed between the sound collecting portion 9A and the hole formed in the pipe 21 in order to provide vibration insulation.

  As a result of the experiment using the two microphones 9 and 13 as shown in FIG. 21, the sound pressure leaks from the leak hole, so that the sound pressure on the outlet side decreases and the transfer function (Gain) decreases. .

  22 and 23 show the air column of the pipe 21 by a transmission matrix using a wave equation. The sound pressure ratio G (gain) between the inlet side (primary side) and the outlet side (secondary side) is theoretically shown. Shows the derivation of the desired equation.

In the figure, P is the sound pressure, U is the volume velocity, Z is the impedance, L1 is the length of the pipe 21 from the loudspeaker 7 (or microphone 13) to the hole P,
L2 is the length from the hole P to the microphone 9 in the pipe 21, and A, B, C, and D are four-terminal constants.

  FIG. 24 shows the comparison between the theoretical value and the experimental result. The comparison between the theoretical value and the previous experimental value when the leak positions are 200 mm, 500 mm, and 1000 mm. The tendency of the theoretical value and the experimental value at each leak position agree in the frequency band of about 200-800Hz. In the frequency band in which the secondary microphone 9 at the exit picks up the sound incident on the pipe 21, the frequencies agree well.

The difference between the theoretical value and the measured value in the low frequency band enclosed by the left circle.
Originally, the experimental value is also considered to be greatly reduced (as in the theoretical value), but the signal of the exit microphone (secondary microphone 9) becomes smaller than the noise floor due to leakage, and the exit microphone (secondary) This is because the signal from the side microphone 9) is a noise floor.

About the difference in the right circle.
The results up to 1kHz are sufficient, but up to 2kHz is measured for reference. In the narrow tube (pipe 21), the higher the frequency, the harder the sound is transmitted. As a result, the S / N ratio decreases in the outlet microphone (secondary microphone 9). In this region, the reliability of the signal from the exit microphone (secondary microphone 9) is low. This indicates that the noise floor is being picked up from the fact that every leak position shows a tendency not to change in the circled portion.

Experimental Example 5

  FIGS. 25 to 26 show Experimental Example 5, which is a configuration diagram at the time of leak detection using only the outlet side microphone (secondary side microphone 9), and the outlet side microphone (secondary side microphone 9) is installed. In addition, a state in which a pipe-shaped vibration insulation relay member 23 such as silicon or rubber is interposed between the loudspeaker 7 and the hole formed in the pipe 21 in order to achieve vibration insulation is shown.

  In the spectrum experiment result using only the exit side microphone (secondary side microphone 9), the sound pressure decreases due to the leak. Therefore, when there is a leak, the spectrum (sound pressure level) is higher than when there is no leak. And the leak can be detected. Similar to the previous experiment, a similar decrease in sound pressure was confirmed at a leak position not shown in the graph.

  If there is a leak, it is thought that the sound pressure has fallen to “sound pressures like the red dashed lines at the left and right ends of the graph (this red dashed line is only a hypothetical model for explanation)” Because of the high sound pressure, the microphone (secondary microphone 9) picks up the noise floor and seems to have a spectrum similar to the experimental results. The noise floor was measured by measuring the sound pressure without driving the speaker to see the “bottom of the noise of the entire experimental device”.

  As described above, the leak can be detected by obtaining the gain of the transfer function in the pipe 21. Further, the amount of decrease in gain due to leakage can be predicted by theoretical analysis, and furthermore, leakage can be detected by spectrum measurement using the secondary microphone 9 or voltage change.

Experimental Example 6

  27 to 28 show Experimental Example 6, which is a configuration diagram of leak detection using only the outlet side microphone (secondary side microphone 9) (assumed in practical use), and the outlet side microphone (secondary side microphone 9). ) Can detect leaks, so that a simple and practical leak detection apparatus can be constructed. FIG. 27 is a configuration diagram thereof.

  Only a single frequency sound is entered into the stainless steel pipe (pipe 21), and the sound is picked up by the microphone on the outlet side (secondary microphone 9). The microphone (secondary microphone 9) converts the picked-up sound into an electric signal, and the voltage is monitored by the voltmeter 26 via the amplifier 10 and the filter 25. Therefore, an expensive measuring instrument is not required, and the microphone (secondary microphone 9) does not need to have a flat frequency characteristic. Leak detection is possible only with simple and inexpensive equipment.

  As shown in FIG. 28, a voltage measurement result when a 250 Hz sine wave (pure sound) is incident on the stainless steel pipe (pipe 21). As shown in the graph, when sound leaks, the voltage is greatly reduced at any leak position, so that leak detection is easy.

  As described above, the method and apparatus according to the present invention can be applied to various applications.

FIG. 1A is a cross-sectional view of an optical fiber showing Embodiment 1 of the present invention, FIG. 1A is a normal cross-sectional view, FIG. 1B is a cross-sectional view when a laser beam leaks, and FIG. It is a partially cutaway perspective view at the time of leakage. It is explanatory drawing which shows Example 1 of this invention. It is explanatory drawing which shows Example 2 of this invention. It is explanatory drawing which shows Example 3 of this invention. It is explanatory drawing which shows Example 4 of this invention. It is explanatory drawing which shows Experimental example 1 of this invention. It is explanatory drawing of the position of the simulation leak hole which shows Experimental example 1 of this invention. It is a graph of the experiment by the primary side (inlet side) microphone which shows the experiment example 1 of this invention. It is explanatory drawing which shows Experimental example 2 of this invention. It is a graph of an experiment with a leak position of 100 to 500 mm using two microphones showing Experimental Example 2 of the present invention. It is a graph of an experiment with a leak position of 600 to 1000 mm using two microphones showing Experimental Example 2 of the present invention. It is a graph of an experiment with a leak position of 1100 to 1500 mm using two microphones showing Experimental Example 2 of the present invention. It is a graph of an experiment with a leak position of 1600-1900 mm using two microphones showing Experimental Example 2 of the present invention. It is explanatory drawing which shows Experimental example 3 of this invention. It is a graph of experiment whose leak position in the secondary side (exit side) microphone which shows Experimental example 3 of this invention is 100-500 mm. It is a graph of the experiment whose leak position in the secondary side (exit side) microphone which shows Experimental example 3 of this invention is 600-1000 mm. It is a graph of the experiment where the leak position in the secondary side (exit side) microphone which shows Experimental example 3 of this invention is 1100-1500 mm. It is a graph of the experiment whose leak position in the secondary side (exit side) microphone which shows Experimental example 3 of this invention is 1600-1900 mm. It is explanatory drawing of the experimental apparatus of the state which installed the microphone in the primary side and secondary side which show the example 4 of experiment of this invention. It is explanatory drawing which shows the measurement conditions which show Experimental example 4 of this invention. It is a graph of the gain using two microphones which show Experimental example 4 of this invention. FIG. 22A is a plan view of a pipe, FIG. 22B is an explanatory diagram of a transfer matrix, and FIG. 22C shows a mathematical formula of the transfer matrix. The numerical formula of the other transfer matrix which shows the experiment example 4 of this invention is shown. It is the graph which showed the theoretical analysis which shows Experimental example 4 of this invention, and the comparison of an experimental result. It is explanatory drawing of the experimental apparatus of the state which installed the microphone in the secondary side which shows Experimental example 5 of this invention. It is the graph which showed the spectrum in the secondary side microphone which shows Experimental example 5 of this invention. It is explanatory drawing of the experimental apparatus which shows Experimental example 6 of this invention. It is a graph of the leak detection by the measurement which shows Experimental example 6 of this invention.

DESCRIPTION OF SYMBOLS 1 Hollow optical fiber 5 Carbon dioxide laser generator 7 Loudspeaker 9 Secondary side microphone

Claims (10)

Method of detecting a hollow portion deficiency, the hollow optical fiber by detecting the sound wave that has passed through the hollow portion from the secondary side causes incident sound waves to clogging of the hollow fiber from the primary side of the middle empty optical fiber. Detecting the sound waves passed through the hollow portion from the secondary side with the primary side is made incident sound waves into the hollow portion of the hollow fiber of the middle empty optical fiber, comparing the secondary wave with the primary waves Then, the method of detecting the defect or clogging of the hollow optical fiber. The method for detecting a defect or clogging of an optical fiber according to any one of claims 1 to 2, wherein the primary side acoustic wave signal and the secondary side acoustic wave signal are electrically detected. The method for detecting an optical fiber defect or clogging according to any one of claims 1 to 3, wherein the sound wave is generated by a speaker and the secondary side sound wave is detected by a microphone. The method for detecting an optical fiber defect or clogging according to any one of claims 1 to 4, wherein the primary side acoustic wave has a low frequency of 1 kHz or less. The method for detecting an optical fiber defect or clogging according to any one of claims 1 to 5, wherein the primary side acoustic wave has a plurality of frequencies. A hollow characterized in that a sound source for allowing sound waves to enter the hollow portion of the hollow optical fiber from the primary side of the hollow optical fiber is provided, and a detecting means for detecting the sound wave that has passed through the hollow portion is provided on the secondary side. Optical fiber breakage and clogging detection device. 8. The hollow optical fiber defect or clogging detection device according to claim 7, wherein a speaker is connected to the gas laser generator side, and a secondary microphone is connected to the hollow optical fiber. 9. The hollow optical fiber defect / clogging detection device according to claim 8, wherein a primary microphone is provided in the hollow optical fiber. The hollow optical fiber defect or clogging detection device according to any one of claims 7 to 9, wherein the secondary side is a handpiece side that is connected to the hollow optical fiber and emits laser light.

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