JP3631221B2 - Fiber spectroscopic detector and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spectroscopic detector by an ATR method (attenuated total reflection method) using an optical fiber and a method for manufacturing the same. The fiber spectroscopic detector is not particularly limited, but is useful for spectroscopic analysis in a high temperature range in which a molten salt, a molten metal, or the like is an object to be measured.
[0002]
[Prior art]
One method for measuring the infrared absorption spectrum is the ATR method using total reflection. In this method, an ATR prism having a high refractive index is closely attached to a sample, the sample is irradiated with infrared light through the ATR prism, and light emitted from the ATR prism is spectrally analyzed. Such an ATR method is used in place of the transmission method because the sample and the measuring device are easy to handle.
[0003]
However, the configuration using the ATR prism as the internal reflection element has a small number of internal reflections and the sensitivity is not so high. Therefore, recently, a technique using an optical fiber as an internal reflection element has been proposed. In this method, a part of the clad of the optical fiber is removed by chemical or physical means to provide a clad defect portion having only a core. By using an optical fiber, the number of internal reflections can be increased and the sensitivity can be improved, and there is an advantage that a separate centralized optical system is not required, so that the size can be reduced.
[0004]
[Problems to be solved by the invention]
However, since a conventional spectroscopic detector using an optical fiber is manufactured by removing the entire circumference of the optical fiber cladding, it is difficult to manufacture the optical fiber with a quartz cladding / quartz core structure. Therefore, in the prior art, the polymer cladding is mainly removed using heat or a blade using an optical fiber having a polymer cladding / quartz core structure. However, such a method has a problem that the core is easily broken, and the production yield of the detector is very poor.
[0005]
In addition, since the clad is a polymer material, the usable temperature of the spectroscopic detector is determined by the heat resistance of the polymer material, and cannot be used in a high temperature range. Furthermore, since the manufactured spectroscopic detector is composed of an ultrafine optical fiber core, it is physically fragile and difficult to handle, and is easily affected by vibrations, and has many problems in practical use.
[0006]
An object of the present invention is to provide a fiber spectroscopic detector that has a robust structure and is therefore easy to handle, can be inserted into a highly viscous sample, and enables stable measurement. Another object of the present invention is to provide a fiber spectroscopic detector that can be used in a poor environment such as a high temperature environment or a chemically active environment. Still another object of the present invention is to provide a method of manufacturing a fiber spectroscopic detector which can be made robust and can easily form a detection surface having a required size.
[0007]
[Means for Solving the Problems]
The present invention is a square parallel to the through hole in the groove with the longitudinal direction into the groove of the one main surface of the columnar support member is formed is formed, the are detection fibers accommodated in the groove in the fiber fixing filler The reference fiber is inserted and fixed in the through hole so that the detection fiber and the reference fiber are integrated with the support member, a part of the cladding of the detection fiber is removed, and a part of the core is removed. It is a fiber spectroscopic detector characterized in that a detection surface is formed by exposure. This fiber spectroscopic detector measures the absorbance due to the interaction between an evanescent wave generated by total reflection of light propagating through the core and the external medium by removing the cladding of the optical fiber.
[0008]
In particular, when both the support member and the fixed filler are made of a heat resistant material and an optical fiber having a quartz clad / quartz core structure is used as the detection fiber, a high-temperature compatible fiber spectroscopic detector can be obtained.
[0009]
For example, the detection fiber and the reference fiber, to return bent along the support member with rounded tip, the return portion is secured to the support member so as to be covered by the fiber fixing filler. In order to prevent displacement of the return portion of the fiber, it is also effective to provide a separate groove in the support member and accommodate the fiber in the groove.
[0010]
The present invention is also a method for manufacturing a fiber spectroscopic detector having the above structure. A V- groove is formed in a longitudinal direction on one elongated main surface of the support member having a rounded tip, and a through hole is formed in parallel to the V-groove, and a fiber fixing filler is applied to the surface of the support member. The detection fiber is pushed into the V- groove to be in a semi-embedded state and bent back at the tip of the support member , the reference fiber is inserted into the through hole and bent back at the tip of the support member, and a fiber is further placed on the detection fiber. After applying a fixed filler to cover the detection fiber and solidifying by heating, the fiber is planarly polished together with the fiber fixed filler to remove the cladding, and the core is exposed to form a detection surface.
[0011]
【Example】
FIG. 1 is an explanatory view showing an embodiment of a fiber spectral detector according to the present invention, in which A represents a longitudinal section, B represents a front surface, and C represents a bottom surface. FIG. 2 is a sectional view taken along line xx. The fiber spectroscopic detector 10 includes a detection fiber 16 accommodated in a V-groove 14 formed in a longitudinal direction on one elongated main surface of a square columnar support member 12 and fixed by a fiber fixing filler 18. A detection surface 24 is formed by removing a part of the clad 20 of the detection fiber 18 and exposing a part of the core 22. The front end of the support member 12 is rounded, and the return portion 16a of the detection fiber bent back along the support member 12 is fixed to the fiber on the main surface (back surface) opposite to the detection surface 24 of the support member 12. It is embedded and fixed in the material 26. The removal of the clad is performed by polishing the surface of the fiber together with the fiber fixing filler. As a result, a part of the core is also polished.
[0012]
Here the reference fiber 30, Ru is juxtaposed with detection fibers 16. Therefore, a through hole 32 is formed in the longitudinal direction of the support member 12 in parallel with the V groove 14, and the reference fiber 30 is inserted into the through hole 32 and fixed with a fiber fixing filler 34. The return portion 30a of the reference fiber bent back at the tip of the support member 12 is arranged in parallel with the return portion 16a of the detection fiber, and is embedded and fixed in the fiber fixing filler 26. By accommodating the reference fiber 30 in the through hole 32, the reference fiber is prevented from being polished when the detection fiber is polished. In this way, the fiber spectroscopic detector 10 integrated with the support member 12 is obtained through the detection fiber 16 and the reference fiber 30 through the same position as much as possible. In order to facilitate the positioning of the return portions 16a and 30a of the detection fiber and the reference fiber, although not shown, two parallel grooves are formed on the back surface of the support member, and the detection fiber and the reference fiber are respectively provided. The return part may be accommodated.
[0013]
When used in a high temperature environment, a chemically stable and highly heat-resistant alumina ceramic is used as the support member 12, and a high temperature alumina adhesive is used for the fiber fixing fillers 18, 26, and 34. As the detection fiber 16 and the reference fiber 30, an optical fiber having a quartz clad / quartz core structure is used. With this configuration, a fiber spectroscopic detector that can be used in a high temperature range of 1000 ° C. or higher can be manufactured. In addition, this configuration provides a fiber spectroscopic detector that can be used stably even in a strong acid strong base environment other than hydrofluoric acid that attacks quartz. Since the wavelength of the used light is a wavelength that can be efficiently transmitted through the optical fiber, a quartz fiber changes from near infrared light having a wavelength of several μm to ultraviolet light having a wavelength of several hundred nm.
[0014]
Since the fragile fiber detector is fixed to the support member 12, the fiber spectroscopic detector 10 of the present invention is not easily affected by a loss change due to disturbance such as bending, and can perform stable measurement. Further, in the fiber spectroscopic detector 10 manufactured in this way, since the clad / core structure remains in the light propagation part other than the detection surface, the input / output light propagates with low loss and without being affected by the disturbance. The object to be measured (sample) is mainly a liquid or gas around the fiber spectral detector. However, since the fiber detector is supported by the support member and has high mechanical strength, the solid surface can be measured by a method in which the detection surface is pressed against the sample.
[0015]
The fragile fiber detector is firmly attached to the support member and has a robust structure, so it is easy to handle and is used in a high temperature environment (for example, molten salt or molten metal) or a chemically active environment (for example, a strong acid or strong base). It is easy to perform remote control with the necessary robot arm. Moreover, since the present fiber spectroscopic detector can be easily inserted even in a sample having a high viscosity or a sample having a large number of particles, the object to be measured is widened. Furthermore, in the fiber spectroscopic detector according to the present invention, since the physical contact with the detection surface is easy, the detection surface can be easily cleaned. Therefore, it can be used for repeated measurement, and in this case, contamination of the sample can be kept low.
[0016]
FIG. 3 is an explanatory diagram showing an example of a fiber spectroscopic measurement system. The fiber spectroscopic detector 10 is immersed in the sample 40. Here, the sample 40 is a high-temperature melt placed in a container 42 and heated by a heater 44. The light from the light source 46 is converted into parallel light by the collimator lens 48 and divided into two by the beam splitter 50. Then, the signal light guide fiber 52 and the reference light guide fiber 54 guide the detection light to the detection fiber 16 of the fiber spectral detector 10 and the reference light to the reference fiber 30, respectively, and collect the output light by the lenses 56 and 57. And each is detected by the detection parts 58 and 59, is converted into an electric signal, and is transmitted to a signal processing system. The signal (the ratio between the incident light intensity and the emitted light intensity) thus obtained becomes the absorbance. Since the measurement principle is the same as that of absorption spectrometry, the obtained information is the same as in the case of absorption spectrometry. The main measurement is the concentration of the object to be measured, ion state change, and the like. Further, since it is configured to provide references fiber, it is possible to correct the deterioration of the output fluctuation and fiber sources, thus improving the measurement accuracy. As signal processing, if the signal change becomes weak, the S / N can be improved by lock-in measurement in which incident light is modulated.
[0017]
FIG. 4 shows an example of the usage state. The fiber spectroscopic detector 10 is inserted into an object to be measured (sample) 40 accommodated in the container 42. If the length of the linear fiber detector is changed here (if it is shortened as A or B as required), the integration in the insertion direction according to the length of the fiber spectral detector Information can be obtained.
[0018]
FIG. 5 shows another example of the usage state. A is an example in which a plurality of fiber spectral detectors 10 are inserted in parallel into the DUT 40. If the fiber spectral detectors are two-dimensionally distributed in this way, it is possible to grasp the measured value distribution in the object to be measured. B is an example in which a plurality of fiber spectroscopic detectors 10 are connected in series into the DUT 40. If the fiber spectroscopic detectors are arranged in this way, the length of the fiber detection part (absorption length) can be easily extended, so that it is possible to easily cope with the measurement of a low absorption material such as a diluted material.
[0019]
An example of the support member is shown in FIG. 6, and an example of a manufacturing procedure of a fiber spectral detector using the support member is shown in FIG. Here, only the manufacturing process of the detection surface is shown, and the description of the bent-back structure of the optical fiber, the through hole for inserting the reference fiber, or the attachment to the reference fiber will be omitted. First, as shown in FIG. 6, the support member 12 is assumed to have a V-groove 14 for attaching a fiber formed on one main surface (one surface of an elongated surface) of a quadrangular prism. The V-groove 14 is formed on the surface of the support member 12 with the same cross-sectional shape from one end to the other end.
[0020]
The V groove 14 is shown in FIG. The maximum width of the V groove 14 is slightly larger than the diameter of the optical fiber (cladding outer diameter), and the depth of the V groove 14 is slightly deeper than the radius of the optical fiber. That is, when the optical fiber is accommodated in the V-groove, it is preferable that the core center position is the same as or slightly lower than the support member surface level (in the groove).
[0021]
As shown in B, a fiber fixing filler 50 is applied in advance to the inner and outer portions of the V groove 14 of the support member 12. Next, as shown in C, a detection fiber (an optical fiber from which the coating has been removed, that is, a core / cladding state) 52 is pushed into the V-groove 14 to make it a semi-embedded state. And as shown to D, the fiber fixing filler 54 is further apply | coated on this detection fiber 52, and the said detection fiber 52 is covered. Solidify by heating in that state. Thereafter, as shown in E, the fiber is polished together with the fiber fixing filler to remove the clad, and the core 22 is exposed to form the detection surface 24.
[0022]
The polishing of the fiber is performed by a planing polishing machine that performs crystal polishing. Naturally, it is finished with optical accuracy to eliminate loss due to scattered light. When manufacturing, if polishing is performed while the fiber light is conducted and the intensity of the output light is monitored, the detection state can be easily formed because the removal status of the clad can be grasped. As the cladding is removed, the loss of the evanescent wave increases and the output light decreases. The loss of the evanescent wave is almost proportional to the amount of light involved in the measurement, and the fact that the output light becomes zero means a disconnected state. Therefore, a reduction in output of 20 to 40% is a guideline for completion of polishing. .
[0023]
Thus, the detection surface is formed by polishing the entire surface of the support member. The size of the fiber spectroscopic detector is about 200 mm at the longest in consideration of polishing with optical accuracy. In the case of a dilute medium in which the absorbance cannot be measured sufficiently with a length of about 200 mm, it can be handled by connecting a plurality of fiber spectroscopic detectors in series as in the embodiment shown in FIG. 5B. . Therefore, considering the ease of handling and manufacturing, it is sufficient to prepare a fiber spectroscopic detector having a length of about 100 mm as a standard product.
[0024]
【The invention's effect】
In the present invention, as described above, the detection fiber is accommodated in the groove of the support member and fixed with the fiber fixing filler, and the detection surface is formed by removing a part of the cladding and exposing a part of the core. The fiber spectroscopic detector has a robust structure, so that it is easy to handle and can be inserted into a highly viscous object to be measured, thereby enabling stable measurement. In addition, according to the present invention, an optical fiber having a quartz clad / quartz core structure can be easily manufactured, so that it can be used in a poor environment such as a high temperature environment or a chemically active environment, and the measurable range is widened. . Furthermore, since the fiber spectroscopic detector can be handled in units, various arrangements (two-dimensional distribution measurement by parallel arrangement, change of optical path length by serial connection, etc.) can be easily performed.
[0025]
Further, the present invention is a method of forming a detection surface by fixing an optical fiber from which a protective coating has been removed to a groove of a support member with a fiber fixing filler, and polishing the optical fiber. Can be easily manufactured.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an embodiment of a fiber spectral detector according to the present invention.
FIG. 2 is a sectional view taken along line xx.
FIG. 3 is an explanatory diagram showing an example of a measurement system using a fiber spectral detector.
FIG. 4 is an explanatory diagram showing an example of a usage state of a fiber spectral detector.
FIG. 5 is an explanatory diagram showing another example of the usage state of the fiber spectral detector.
FIG. 6 is an explanatory view showing an example of a support member used in the present invention.
FIG. 7 is a process explanatory view showing an example of a manufacturing method according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Fiber spectroscopy detector 12 Support member 14 V groove 16 Detection fiber 18 Fiber fixing filler 20 Cladding 22 Core 24 Detection surface 26 Fiber fixing filler 30 Reference fiber 32 Through-hole 34 Fiber fixing filler

Claims (3)

Is parallel to the through hole in the groove with the longitudinal direction into the groove of the one main surface of the square cylindrical support member is formed is formed, detection fibers are housed is fixed in the fiber fixing filler in the groove, The reference fiber is inserted and fixed in the through hole, whereby the detection fiber and the reference fiber are integrated with the support member, and a part of the cladding of the detection fiber is removed and a part of the core is exposed. A fiber spectral detector, wherein a detection surface is formed. 2. The fiber spectroscopic detector according to claim 1, wherein both the support member and the fiber fixing filler are made of a heat-resistant material, and the detection fiber is a high-temperature compatible type using an optical fiber having a quartz clad / quartz core structure. 3. A method of manufacturing a fiber spectroscopic detector according to claim 1 , wherein a V-groove is formed in a longitudinal direction on one elongated main surface of a support member having a rounded tip and parallel to the V-groove. A through hole is formed , a fiber fixing filler is applied to the surface of the support member, the detection fiber is pushed into the V- groove to be in a semi-embedded state , bent back at the tip of the support member , and the reference fiber is inserted into the through hole And is bent back at the tip of the support member , further coated with a fiber fixing filler on the detection fiber, covered with the detection fiber, solidified by heating, and then flattened the fiber together with the fiber fixing filler to polish the cladding. A method for manufacturing a fiber spectroscopic detector that is removed and a core is exposed to form a detection surface.

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