JPH0453287B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a cryogenic fiberscope, and more particularly, to a cryogenic fiberscope capable of preventing condensation or dew condensation on the end face of a fiber bundle, the surface of an objective lens, etc. Regarding fiberscopes.

[Technical background of the invention and its problems]

liquefied natural gas, liquefied propane gas, liquid nitrogen,
When constructing cryogenic facilities that handle liquid helium, etc., it is necessary to confirm through experiments the behavior of the materials used to construct these facilities at cryogenic temperatures. During such experiments, it is also important to visually observe the state of materials kept at extremely low temperatures.
Generally, the easiest way to maintain a material at a cryogenic temperature is to immerse the material in the cryogenic liquid described above. If such a method is adopted,
The sample cannot be observed directly with the naked eye. Therefore, it may be possible to observe using a fiberscope.

However, when a normal temperature fiberscope is used, condensation or dew condensation occurs on the end face of the fiber bundle, the optical window, and the surface of the objective lens, making it difficult to observe well.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and its purpose is to prevent condensation and dew condensation on the end face of the fiber bundle, the surface of the objective lens, etc., and to maintain the fiber bundle at an extremely low temperature. An object of the present invention is to provide a fiberscope for cryogenic temperatures that allows good observation of the state of a substance being heated.

[Summary of the invention]

According to the present invention, there is provided a cryogenic fiberscope in which an optical barrel supporting an objective lens is provided with means for communicating the inside and outside of the optical barrel. More specifically, the above-mentioned means are realized by holes formed in the optical barrel.

〔Effect of the invention〕

According to the invention, the space in which the objective lens is located communicates with the outside. Therefore, even if air or water vapor exists in the above space, when the objective lens is inserted into the cryogenic liquid, all of the air and water vapor will be absorbed by the cryogenic liquid that has flowed into the optical barrel. pushed outside. Condensation or dew condensation on the surface of the objective lens is usually caused by air or water vapor existing 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 realizing good observation.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram when a sample kept at a cryogenic temperature is observed 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 accommodated within the cryostat 1.

A cryogenic fiberscope 11 according to the present invention is installed through the upper wall of the cryostat 1. The cryogenic fiberscope 11 is broadly divided into an illumination system 12 that irradiates light toward the sample 2, and an image transmission system 13 that transmits an image of the sample 2.

The illumination system 12 guides light emitted from a light source 14 to a filter 15, which cuts off infrared rays, and introduces the cut off infrared light into one end of a light guide 16. light guide 1
The other end of the cryostat 6 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. On the other hand, the image transmission system 13 is specifically constructed as shown in FIG. That is, an optical lens barrel 20 is attached to one end of an image guide 19 consisting of an optical fiber bundle 17 and a flexible cladding tube 18 that covers the optical fiber bundle 17.
are connected coaxially. Inside the optical lens barrel 20,
For example, the objective lenses 21 and 22 are arranged in a two-stage configuration, and the peripheral edges of these objective lenses 21 and 22 are coated with adhesive or mechanical adhesive that does not deteriorate in function even at extremely low temperatures to the inner peripheral surface of the optical barrel 20. It is fixed by physical means etc.

The optical lens barrel 20 is formed into a simple cylindrical shape, and has a peripheral wall located between the end surface of the image guide 19 and the objective lens 21, and a portion of the peripheral wall of the optical barrel 20 that is located between the end surface of the image guide 19 and the objective lens 21.
A plurality of through holes 23, 24, 25, and 26 are provided in a portion located between 1 and the objective lens 22 and a portion located below the objective lens 22 in the figure, respectively, in the circumferential direction. Further, an eyepiece lens 27 is attached to the other end of the image guide 19, as shown in FIG. The image transmission system 13 configured in this way has its optical barrel 20 side inserted into the cryostat 1 as shown in FIG.
The objective lens 22 is arranged close to the upper surface of the sample 2.

The following procedure is used to observe the sample 2 housed in the cryostat 1 using the cryogenic fiberscope configured as described above. Further, the sample 2 is placed inside the cryostat 1, and then the illumination system 12 and image transmission system 13 are placed as shown in FIG. Next, the pipe 28 is connected to a vacuum pump to evacuate the inside of the cryostat 1. When the evacuation is completed, helium gas is first introduced through the pipe 29, and then liquid helium H is introduced into the cryostat 1 to a predetermined level.
In this way, when liquid helium H is introduced into the cryostat 1, a portion of the liquid helium flows through the through holes 23, 24, 2 provided in the wall of the optical barrel 20.
5 and 26 into the optical lens barrel 20, and finally the inside becomes full. Therefore, air and water vapor existing within the optical barrel 20 are forced out of the optical barrel 20. Then, when the liquid helium H reaches a predetermined level, the supply of liquid helium is stopped, and then the pressure inside the cryostat 1 is reduced to a certain value through the pipe 28. This reduced pressure removes air bubbles adhering to the surfaces of the objective lenses 21, 22, etc. After removing the bubbles, helium gas is introduced to return the pressure to 1 atmosphere.

When such operations are completed, the behavior of the sample 2 at extremely low temperatures can be visually confirmed by turning on the light source 14 and observing the sample 2 through the eyepiece 27.

In this case, since there is no air or water vapor inside the optical barrel 20, that is, around the objective lenses 21 and 22, the end face 17 of the optical fiber bundle 17 is likely to be affected when these are cooled to extremely low temperatures.
a. No condensation or dew condensation occurs on the surfaces of the objective lenses 21 and 22. Therefore, the sample 2 can be observed well, and the above-mentioned effects can be achieved after all. As is clear from the above description, when this cryogenic fiberscope is actually used, there are This means that a layer of liquid helium is present. Therefore, it goes without saying that the dimensions of each part must be set taking into account the refractive index of the liquid helium layer interposed between the parts.

Note that the present invention is not limited to the above embodiments. For example, the number of objective lenses is not limited to the number in the embodiment. It goes without saying that other modifications may be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram when a cryogenic fiberscope according to an embodiment of the present invention is actually installed;
FIG. 2 is a longitudinal cross-sectional view of the main part of the cryogenic fiberscope. 1...cryostat, 2...sample, 12...
...Illumination system, 13... Image transmission system, 14... Light source, 1
5...Filter, 16...Light guide, 19
...Image guide, 20...Optical lens barrel, 21,
22...Objective lens, 23, 24, 25, 26...
...hole, 27...eyepiece, H...liquid helium.

Claims (1)

[Scope of Claims] 1. A fiberscope for cryogenic use, characterized in that an optical barrel supporting an objective lens is provided with means for communicating the inside and outside of the optical barrel. 2. The cryogenic fiberscope according to claim 1, wherein the means for communicating the inside and the outside is a hole formed in the optical lens barrel.