JPH063497B2 - Cryogenic fiber scope - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a cryogenic fiberscope, and in particular,
The present invention relates to a cryogenic fiberscope capable of preventing condensation and dew condensation on the surfaces of fibers, optical windows and objective lenses.

[Technical background of the invention and its problems]

When constructing cryogenic facilities that handle liquefied natural gas, liquefied propane gas, liquid nitrogen, liquid helium, etc., it is necessary to confirm the behavior of the materials constructing these facilities at cryogenic temperatures by experiments. In such an experiment,
It is also important to visually observe the state of the material kept at cryogenic temperatures. Generally, the method of immersing the material in the above-mentioned cryogenic liquid is the easiest way to keep the material at cryogenic temperature. When such a system is adopted, the sample cannot be directly observed with the naked eye. Therefore, it is conceivable to use a fiberscope for observation.

However, when a fiberscope for normal temperature is used, there is a problem that good observation cannot be performed due to condensation and dew condensation on the surfaces of the fiber, the optical window and the objective lens.

[Object of the Invention]

The present invention has been made in view of such circumstances, and an object of the present invention is to prevent condensation and dew condensation on the surfaces of the fiber, the optical window and the objective lens, and thus maintain the cryogenic temperature. An object of the present invention is to provide a fiberscope for cryogenic temperature, which enables good observation of the state of substances present therein.

[Outline of Invention]

According to the present invention, an optical lens barrel, an objective lens held in the optical lens barrel, an optical fiber bundle covered by a coating tube and having one end connected to the optical lens barrel, and the optical lens barrel There is provided a cryogenic fiberscope having an exhaust path capable of evacuating a closed space portion existing therein.

〔The invention's effect〕

According to the present invention, by exhausting using the exhaust passage,
The space in which the objective lens is located can be kept in a vacuum atmosphere. Therefore, even if air or water vapor is present in the above-mentioned space at the time of manufacturing, all of the air or water vapor is removed when the vacuum atmosphere is maintained. Condensation and dew condensation on the surface of the objective lens when the space where the objective lens is located are cooled to a cryogenic temperature are caused by air and water vapor present in the space where the objective lens is located. However,
In the present invention, since the air and water vapor existing in the space are removed, the above-mentioned condensation and dew condensation do not occur. Therefore, it can contribute to the realization of good observation.

Example of Invention

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram when observing a sample kept at a cryogenic temperature using a cryogenic fiberscope according to an embodiment of the present invention.

That is, in the figure, 1 indicates a cryostat containing liquid helium H, which is a cryogenic liquid, and 2 indicates a sample contained in the cryostat 1.

Then, the cryogenic fiberscope 11 according to the present invention is installed through the upper wall of the cryostat 1. This cryogenic fiberscope 11 is roughly divided into an illumination system 12 for irradiating the sample 2 with light and a sample 2
And an image transmission system 13 for transmitting the image.

The illumination system 12 guides the light emitted from the light source 14 to the filter 15, cuts infrared rays by the filter 15, and introduces the infrared-cut light into one end of the light guide 16. The other end of the light guide 16 extends to the vicinity of the sample 2 through the upper wall of the cryostat 1 and is arranged so as to irradiate the introduced light toward the upper surface of the sample 2. It should be noted that the light guide 16 is composed of a few sub-optical fibers and a covering material for covering them, but it is caused by the fine bending that occurs in the optical fibers due to the compressive force caused by the contraction of the covering material at extremely low temperatures. In order to prevent the loss from increasing, the thickness of the coating material made of epoxy or the like is set to 1/4 or less of the diameter of the optical fiber bundle. On the other hand, the image transmission system 13 is specifically configured as shown in FIG. That is, the optical lens barrel 19 is coaxially connected to one end of the image guide 18 including the optical fiber bundle 17 and the flexible coating tube 88 that covers the optical fiber bundle 17. The thickness of the covering tube 88 is also set to 1/4 or less of the diameter of the optical fiber bundle 17 as in the case of the light guide 16. In the optical lens barrel 19,
For example, the objective lenses 20 and 21 are arranged in a two-stage configuration, and the peripheral portions of these objective lenses 20 and 21 are the optical barrel 1
It is fixed to the inner peripheral surface of 9 by an adhesive agent or a mechanical means that does not deteriorate its function even at an extremely low temperature. Further, the image guide 18 is provided on the peripheral wall of the optical barrel 19.
Through holes 23 and 24 are provided in a portion located between the objective lens 20 and the objective lens 20 and a portion located between the objective lens 20 and the objective lens 21, respectively. An outer cylinder 26 is arranged so as to form an airtight space 25 between the lower end of the optical lens barrel 19 in FIG. A pipe 27 for connecting the space 25 to a vacuum pump (not shown) is connected to the cylinder 26. A valve 28 is provided in the middle of the pipe 27. An eyepiece lens 29 is attached to the other end of the image guide 18 as shown in FIG. Image transmission system 3 configured in this way
As shown in FIG. 1, the outer tube 26 side is inserted into the cryostat 1, and the objective lens 21 thereof is arranged so as to be close to the upper surface of the sample 2.

To observe the sample 2 contained in the cryostat 1 using the cryogenic fiberscope configured as described above, the following is performed. First, the sample 2 is placed in the cryostat 1, and subsequently, the illumination system 12 and the image transmission system 13 are placed as shown in FIG. Next, the pipe 27
Is connected to a vacuum pump, the valve 28 is opened, and the space 25 is sufficiently evacuated. Since the space 25 communicates with the inside of the optical barrel 19 through the through holes 23 and 24, when exhausted as described above, the air and water vapor existing in the optical barrel 19 and the space 25 will not flow into the exhaust flow. It is removed to the outside. Then, the valve 28 is "closed" when the gas is sufficiently exhausted. In other words, keep it in a closed state. In addition,
After the image transmission system 13 is manufactured, it may be evacuated and sealed up as described above, or may be evacuated while the valve 28 is kept "open" until the observation is completed.

In this way, liquid helium H is introduced into the cryostat 1 when the exhaust is completed or when the exhaust is sufficiently completed. Then, the light source 14 is turned on from the time when the introduction of the liquid helium H is started, and the sample 2 is observed through the eyepiece lens 29, whereby the behavior of the sample 2 at an extremely low temperature can be visually recognized.

In this case, inside the optical barrel 19, that is, the objective lenses 20 and 2
Since air and water vapor do not exist in the vicinity of 1, the end surface 17a of the optical fiber bundle 17 and the inner surface 19 of the optical barrel 19 which are likely to occur when they are cooled to an extremely low temperature.
a. No condensation or dew condensation occurs on the surfaces of the objective lenses 20 and 21. Therefore, the sample 2 can be satisfactorily observed, and in the end, the effects described above are exhibited. If the thickness of the covering material of the light guide 16 and the image guide 18 is set to a value exceeding 1/4 of the diameter of each fiber bundle, loss increases and good contrast cannot be obtained. Therefore, it is preferably set to 1/4 or less as in the embodiment.

FIG. 3 shows only essential parts of a cryogenic fiberscope according to another embodiment of the present invention.

In the above-mentioned embodiment, the outer tube is arranged on the outer circumference of the part from the tip of the optical lens barrel to the middle of the image guide, and the exhaust passage is constituted by this outer tube. The exhaust passage is formed by the space between the provided groove and the optical fiber bundle of the image guide and the flexible covering tube.

That is, the image transmission system 13a in this embodiment is constructed as follows. First, as the image guide 34, an optical fiber bundle 31 and a flexible coating tube 33 which covers the fiber bundle 31 with a small space 32 provided between the optical fiber bundle 31 is used. The cladding tube 33 of the image fiber 34 is
Portions located at both ends of the image fiber 34 are removed. Then, holders 35 and 36 each having a cylindrical shape are attached to the removed portions. The holders 35 and 36 are formed so that the inner diameter is substantially equal to the outer diameter of the optical fiber bundle 31, and the end portions located on the cladding tube 33 side are hermetically connected to the end surfaces of the cladding tube 33, respectively. In addition, two grooves 37 extending in the axial direction and communicating with the above-mentioned space 32 are formed at positions facing each other on the inner surfaces of the holders 35 and 36, as shown by the holder 36 as a representative in FIG. 4 (b). Has been done. An annular groove 38 is formed on the inner peripheral surface of the holder 35 so as to allow the two grooves 37 provided in the holder 35 to communicate with each other. Further, a pipe 39 is provided so as to communicate with the annular groove 38.
One end of is connected. The other end of the pipe 39 is selectively connected to a vacuum pump (not shown) via a valve 40.

An optical lens barrel 41 is coaxially and airtightly connected to the lower end side of the holder 36 in FIG. Inside the optical barrel 41, the objective lenses 42, 43,
44 is fixed, and the lower end opening of the optical barrel 41 in FIG. 3 is airtightly closed by a transparent plate 45. Further, as shown in FIG. 4A, two grooves 46 are formed on the inner surface of the optical lens barrel 41 so as to communicate with the groove 37 provided in the holder 36. These grooves 46 are provided up to a position between the objective lens 42 and the transparent plate 45. Reference numeral 47 in FIG. 3 denotes an eyepiece lens.

Even if the image transmission system 13a is configured as described above, the same effect as that of the above-described embodiment can be expected. That is, the pipe 39
Is connected to a vacuum pump, and the valve 40 is “opened” to evacuate, the air and water vapor existing in the optical lens barrel 41 are transferred to the exhaust flow, and the groove 46 formed in the inner surface of the optical lens barrel 41.
~ Groove 37 formed in holder 36 ~ Space 32 ~ Removed through groove 37 formed in holder 35. Therefore, the same effect as that of the above embodiment can be obtained. In this case, since it is possible to provide flexibility to a position sufficiently close to the optical barrel 41, it is possible to contribute to facilitating installation in the cryostat.

FIG. 5 shows only essential parts of a cryogenic fiberscope according to still another embodiment of the present invention.

This embodiment is an example in which the present invention is applied to an integrated illumination system and image transmission system.

That is, a part of the image guide 51 is used as the light guide 52. A columnar space 56 for holding the objective lenses 54, 55 and a plurality of holes 57 for holding the light guide portion 52 are formed in the optical barrel 53. A portion of the image guide 51 used for image transmission is fitted into one end of the columnar space 56, and a light guide portion 52 is fitted into each hole 57. The columnar spaces 56 and the openings at the lower ends of the holes 57 in the figure are hermetically closed by a transparent plate 58. A lens 59 for diffusing light is mounted between the tip of the light guide portion 52 and the transparent plate 58 in each hole 57. Through the wall located between the columnar space 56 and each hole 57, through holes 60 and 61 that connect the columnar space 56 and each hole 57 are formed on both sides of the lens 59 as a boundary. A groove 62 communicating with the exhaust system is provided on the inner surface of the wall forming the columnar space 56, as in the embodiment shown in FIG.

With such a configuration, the columnar space 56 and each hole 57 communicate with each other through the through holes 60 and 61. Therefore, when exhausting through the groove 62, the columnar space 56 and each hole 57, that is, the objective lens. The air and water vapor existing in the space where the lenses 55 and 56 are located and the space where the lens 59 is located are also exhausted, so that the same effects as those of the above-mentioned respective embodiments can be obtained.

The present invention is not limited to the above embodiment and can be modified in various ways. For example, the number of objective lenses is not limited to the number of embodiments. Also, only the inside of the optical lens barrel may be evacuated and sealed off after fabrication. Of course, other modifications can be made without departing from the scope of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic view of an actual installation of a cryogenic fiberscope according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of an essential portion of the cryogenic fiberscope, and FIG. 4 is a longitudinal cross-sectional view of a main part of a cryogenic fiberscope according to another embodiment of FIG. 4, FIG. 4 (a) is a sectional view taken along the line XX in FIG. 3, and FIG. 4 (b) is Y in FIG. -Y line cutting arrow view, the same figure (c) is the ZZ line cutting arrow view in FIG. 3, FIG. 5 is a principal part of the cryogenic fiberscope which concerns on another Example of this invention. It is a local longitudinal cross-sectional view. 1 ... Cryostat, 2 ... Sample, 12 ... Illumination system, 1
3, 13a ... Image transmission system, 14 ... Light source, 15 ... Filter, 16, 52 ... Light guide, 18, 34, 51 ... Image guide, 19, 41, 53 ... Optical lens barrel, 20, 2
1, 42, 43, 44, 54, 55 ... Objective lens, 26
... Outer tube, 29, 47, ... Eyepiece, 35, 36 ... Holder, 37, 46, 62 ... Groove, 27, 39 ... Piping, 2
8,40 ... Valve, H ... Liquid helium.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Sanada 1440 Rokuzaki, Sakura City, Chiba Prefecture, inside the Sakura Factory, Fujikura Electric Wire Co., Ltd.

Claims (1)

[Claims] 1. An optical lens barrel, an objective lens held in the optical lens barrel, an optical fiber bundle covered by a covering tube and having one end side connected to the optical lens barrel, and the inside of the optical lens barrel. A fiberscope for cryogenic use, comprising: an exhaust passage capable of evacuating a closed space portion existing in.