JPH0458570B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an optical probe for receiving and transmitting light from an object to be measured. BACKGROUND ART In recent years, technologies for optically measuring temperature and various other physical quantities have been developed. In order to measure optical power etc. with an optical power meter etc. in such measurements, an optical probe is required to receive the light from the object to be measured and transmit the received light to the optical power meter etc. It is. FIG. 4 shows a conventional example of an optical probe used in an optical thermometer. In this conventional example, light from an object to be measured is focused on the end face of an optical fiber 2 by a spherical lens 1, and this focused light is transmitted through the optical fiber 2 to an optical power meter 3. . The material of the optical fiber 2 is quartz glass, and the quartz glass optical fiber has a small numerical aperture of 0.25 to 0.27. For this purpose, the optical fiber 2 is a multi-core optical fiber in which a plurality of core wires are bundled and fixed with resin so that the necessary amount of light can be obtained. However, since such a resin is not heat resistant, an optical rod 4 as a heat shielding member is connected to the end face of the optical fiber 2 so that the resin is protected even when measuring particularly high temperatures. The ends of the lens 1, the optical rod 4, and the optical fiber 2 are housed in a housing (not shown), and the lens 1 faces the outside of this housing. A ventilation passage having an opening near the lens 1 is formed in this housing, and the airflow from this ventilation passage prevents dust from adhering to the lens 1. Problems to be Solved by the Invention However, since the spherical lens 1 and the end face of the optical fiber 2 cannot be brought into close contact with each other, the optical probe becomes large in this conventional example. Further, since the optical fiber 2 is a multi-core optical fiber, it is not possible to connect the optical fiber 2 to another optical fiber using a connector or the like. For this reason, the optical fiber 2 must have a length from the vicinity of the object to be measured to the optical power meter 3, which impairs the operability of the optical probe. Furthermore, since the optical fiber 2 is a multi-core optical fiber, the connection loss between the optical rod 4 and the optical fiber 2 is large, making it impossible to measure temperature with high sensitivity. Furthermore, when the spherical lens 1 is used, the airflow to prevent dust from adhering to the spherical lens 1 becomes turbulent. For this reason, this airflow causes a disturbance to the object to be measured or causes fluctuations in the atmosphere, making it impossible to measure the temperature with high accuracy. SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide an optical probe that is small, has good operability, and is capable of highly sensitive and highly accurate measurements. Means for Solving the Problems The optical probe according to the present invention includes a gradient index lens housed in a housing and having one end surface facing the outside of the housing, and a gradient index lens connected to the other end surface of the gradient index lens. a multi-component glass optical fiber formed in the housing, and an air passageway formed in the housing and having an opening near the one end surface so as to form an airflow across the one end surface. There is. Function The optical probe according to the present invention focuses light from an object to be measured using a gradient index lens, and transmits the focused light through a multicomponent glass optical fiber. Embodiment Hereinafter, an embodiment of the present invention applied to an optical thermometer will be described with reference to FIGS. 1 to 3. As shown in FIG. 1, in this embodiment, a gradient index lens 12 fixed within a ceramic sleeve 11 is housed within a substantially cylindrical housing 13. As shown in FIG. One end surface 12A of the lens 12 faces the outside of the housing 13, and the other end surface 12B
The end faces of the optical fibers 14 are in close contact with each other. Optical fiber 14 is a single-core optical fiber made of multicomponent glass. Since a multi-component glass optical fiber can have a large numerical aperture, even a single-core optical fiber can transmit a large amount of light, but for this purpose it is desirable that the numerical aperture is set to 0.4 or more. The housing 13 is a front half 13 made of ceramics.
A and a metal rear part 13B are joined together, and the lens 12 is a ceramic front part 13.
It is stored in A. A flange 13C is integrally formed on the outer peripheral surface of the metal rear half 13B, and a cap nut 15 is fitted therein. Further, a ventilation passage 16 is formed in the housing 13.
This ventilation passage 16 has an opening 16A near one end surface 12A of the lens 12. To measure the temperature in such an embodiment, as shown in FIG. Fixed at 15. Then, light from the object to be measured enters the lens 12,
This incident light is focused on the end face of the optical fiber 14 and transmitted to an optical power meter (not shown). At this time, air 18 is supplied to the ventilation path 16.
This air 18 is discharged from the opening 16A and becomes an airflow that crosses one end surface 12A of the lens 12.
Prevents dust from adhering to one end surface 12A. Table 1 shows the specifications of the optical element of this example. Furthermore, FIG. 2 shows the relationship between the distance L from one end surface 12A of the lens 12 to the object to be measured and the measurement spot diameter D when temperature is measured according to this embodiment, and FIG. indicates the relationship between the temperature of the object to be measured and the received light power at that time.

[Table] As described above, in this example, since the optical fiber 14 is made of multi-component glass, a large amount of light can be transmitted even with a single optical fiber, and a composite optical fiber made of optical fibers bound together with resin can transmit a large amount of light. There is no need to use Shinko fiber. Therefore, even when measuring the temperature of a high-temperature object, a heat shield member is not required, and the optical probe can be made smaller. Furthermore, in this embodiment, since the front half 13A of the housing 13 is made of ceramics, the temperature can be measured even in a magnetic field such as in an induction heating furnace without significantly affecting the magnetic field. In addition, although the above-mentioned embodiment applies the optical probe according to the present invention to an optical thermometer, the optical probe according to the present invention can also be applied to various optical devices other than thermometers. Effects of the Invention Since the optical probe according to the present invention uses a gradient index lens as a condenser lens, the gradient index lens and the optical fiber can be brought into close contact to make the optical probe as a whole smaller. can do. Moreover, since the multi-component glass optical fiber can have a large numerical aperture, a large amount of light can be transmitted even with a single-core optical fiber, and there is no need to use a multi-core optical fiber. For this reason, the optical probe can be connected to other optical fibers using a connector or the like and does not require a long optical fiber, so the optical probe has good operability. Furthermore, since it is not necessary to make the optical fiber double-core, there is little connection loss between the optical fiber and the gradient index lens, and high-sensitivity measurement is possible. Further, since the gradient index lens may have a flat end face, the airflow for preventing dust from adhering to the end face is less likely to become turbulent. Therefore, this airflow is less likely to cause disturbance to the object to be measured or cause fluctuations in the atmosphere, allowing highly accurate measurement.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing one embodiment of the present invention, and FIGS. 2 and 3 are graphs showing the conditions and results of temperature measurement according to the embodiment shown in FIG. 1, respectively. FIG. 4 is a schematic side view showing a conventional example of the present invention. In addition, in the symbols used in the drawings, 12...gradient index lens, 12A...one end surface, 12B...
...Other end surface, 13...housing, 14...optical fiber, 16...ventilation path, 16A...opening.

Claims (1)

[Claims] 1. A gradient index lens that is housed in a housing and has one end surface facing the outside of the housing;
A multi-component glass optical fiber is connected to the other end surface of the gradient index lens, and an opening is formed in the housing in the vicinity of the one end surface so as to form an airflow that crosses the one end surface. Optical probe equipped with air passages and air passages.