JPH01240804A - Measuring method for shape of transparent body - Google Patents

Abstract

PURPOSE:To precisely determine the internal and external shapes of a transparent body, by measuring the external and internal shapes of the transparent body on the basis of the peak of a deflection angle of a light beam which is transmitted through the boundary part of water for adjustment of a refractive index and an axial core part and through the boundary part of the axial core part and a sheath part. CONSTITUTION:An irradiation light beam emitted from a laser light source 12 of a light irradiation system 11 is direct through a condenser lens 13 to a transparent body 51 in water 44 for adjustment of a refractive index. This light beam is deflected by a change in the refractive index inside the transparent body 51, and the light beam transmitted therethrough drops a spot light on a detector 23 through a condenser lens 22. An output signal being proportional to the position of incidence of this spot light is inputted from the detector 23 to a scanning device 31 through a signal processor 24, a computer 25 and a controller 26. A prescribed operation signal is inputted to a motor 34 so as to move a mounting surface 32 of a moving stage 33 in the direction of a Z-axis. Thus, the transparent body 51 is scanned in the direction of the Z-axis. Thereby the shape of the transparent body can be measured precisely by an optical non-destructive measuring means.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to a method for non-contact and non-destructive measurement of the shape of a transparent body in which the refractive index of the axial center portion and the outer portion are different from each other by optical means.

“Conventional technology” As is well known, in the communication and optical fields, the shaft center,
Transparent bodies in which the refractive index of the mantle portions are different from each other are widely used, and a typical example thereof is an optical fiber base material having a core and a cladding.

For optical fiber base material, external dimensions (cladding outer diameter)
In order to check the internal dimensions (outer diameter of the core), eccentricity between the core and cladding, etc., the shape of each of the above parts is measured during or after manufacturing the base material, but the measurement means used at this time are: Non-contact, non-destructive measurement methods using optical systems are common.

In the case of such non-contact, non-destructive measurement methods, there are many methods that measure only the outer shape of the optical fiber base material.

In such a measurement method, when the irradiation light is irradiated from the outside of the optical fiber base material toward the base material, and the internal shape (core) and core position of the optical fiber base material are also measured from the transmitted light beam. In this case, the light beam transmitted through the optical fiber base material is greatly deflected, and the required optical information cannot be obtained, resulting in a measurement problem.

As a countermeasure to this problem, the invention disclosed in JP-A-62-14008 discloses that an optical fiber base material is immersed in a refractive index adjustment liquid (silicon oil: refractive index 1.4570), and the base material is irradiated with irradiation light. We try to suppress the deflection of the light beam as much as possible.

rProblem to be solved by the invention J In the case of the above-mentioned known examples, it is assumed that the core refractive index of the optical fiber base material is an ideal SI type, and the optical fiber base material to be examined satisfies this. However, if the core refractive index is tilted even slightly, or if the core refractive index is GI type, the deflection angle of the transmitted light will change. This makes it insufficient to obtain accurate information about the core.

Moreover, since the refractive index adjustment liquid is made of silicone oil with low volatility, a cleaning operation is required to wash off the silicone oil from the base material after measurement, which requires additional labor.

However, if a highly volatile refractive index adjustment liquid is used, cleaning the base material is not necessary, but the volatile components contaminate the working environment and have a harmful effect on the human body, including workers.

In view of the above-mentioned problems, the present invention has been developed to improve the internal shape of the transparent body even when the refractive index specifications of the transparent body vary or differ.
It is an object of the present invention to provide a measuring method that allows the external shape to be determined with high precision, and also eliminates the need to clean the transparent body after measurement, thereby avoiding contamination of the working environment.

1. Means for Solving the Problems] In order to achieve the intended purpose, the method for measuring the shape of a transparent body according to the present invention adjusts the refractive index of a transparent body whose axial center portion and outer mantle portion have mutually different refractive indexes. After immersing the body in water, the transparent body is scanned by the irradiation light beam emitted from the light irradiation system in a direction intersecting its axis, and the transmitted light beam is received by the light reception measurement system, and the light reception measurement is performed. In the system, the external and internal shapes of the transparent body are measured based on the peak of the deflection angle of the light beam that passes through the boundary between the water for adjusting the refractive index and the shaft center, and the boundary between the shaft center and the mantle. It is characterized by

rExample J An example of the method for measuring the shape of a transparent body according to the present invention will be described with reference to the drawings.

In FIG. 1, the light irradiation system 11 includes a laser light source 12 and a condensing lens 13, and the light receiving measurement system 21 includes a condensing lens 22, a detector 23, a signal processor 24, a computer 25, and a controller 26. , the detector 23 consists of a position sensing element or a sensing element array.

The scanning device 31 illustrated in FIG. 1 includes a movable stage 33 whose height of a mounting surface (upper surface) 32 is adjustable and an electric motor a34 for driving the stage. It operates upon receiving a signal from the controller 26.

In FIG. 1, a container 41 for holding a subject made of transparent glass has light transmitting portions 42 and 43 on both sides thereof, and water 44 for adjusting the refractive index is stored inside the container.

As the refractive index adjusting water 44, core distilled water, pure water, etc. containing no impurities is used, and its refractive index is 1.333 at 20°C.

In the transparent body 51 held by the container 41, the refractive index of the axial center portion 52 and the outer mantle portion 53 are different from each other.

- For example, when the transparent body 51 is made of an optical fiber base material, the core of the base material corresponds to the axial center part 52, and the cladding of the base material corresponds to the mantle part 53, but the transparent body 51 is a cylindrical body. , the axial center portion 52 is hollow.

As shown in FIG. 1, the transparent body 51 penetrates the front and rear walls of the container 41 airtightly (watertightly), and its longitudinal middle portion is immersed in the refractive index adjusting water 44 inside the container 41.

The laser light source 12 of the light irradiation system 11 and the condenser lens 1 described above
3, the condensing lens 22 and the detector 23 of the light receiving measurement system 21 are arranged relative to each other so that their optical axes coincide, and a container 41 is interposed in the image condensing lens 13. The light transmitting part 42.43 faces the condensing lens 13.22.

Thus, when the container 41 is placed in a predetermined position, the axial center line (X-axis) of the transparent body 51 held through the container 41
and the optical axis (Y
The transparent body 51 is supported by a scanning device 31 so as to be movable in the vertical (two) directions.

In FIG. 1, when carrying out the method of the present invention, the irradiation light beam emitted from the laser light source 12 of the light irradiation system 11 passes through the condensing lens 13 to the transparent body 5 in the refractive index adjustment water 44.
1.

The light beam that has entered the transparent body 51 is deflected by the change in the refractive index inside the transparent body 51 and is transmitted through the transparent body 51, and the transmitted light beam passes through the condenser lens 22 and reaches the detector 23. Shine a spotlight on top.

The detector 23 sends an output signal proportional to the incident position of the spot light to the signal processor 24 , and the processed signal from the signal processor 24 is sequentially processed via the computer 25 and controller 26 and sent to the scanning device 31 . is input.

That is, the processed signal from the signal processor 24 is sent to the computer 25.
When the signal is input to the transparent body 51, the computer 25 electrically and electronically processes the signal to determine the deflection angle of the transmitted light beam in correspondence with the change in the refractive index inside the transparent body 51.

Furthermore, the controller 26 to which the signal from the computer 25 has been input inputs a predetermined operation signal to the electric motor 34 in order to move the head surface 32 of the moving stage 33 upward in the two-axis direction.

Thus, the transparent body 5 on the a lid surface 32 of the moving stage 33
1 is scanned in the Z-axis direction at a predetermined speed.

As described above, in the method of the present invention, one section of the transparent body 51 is optically scanned in the Z-axis direction in FIG. The outer shape and inner shape of the transparent body 51 are determined by measuring with a measuring means, and the light irradiation situation and measurement situation will be explained as follows.
It will look like Figures 2 and 3.

The transparent body 51 in FIG. 2 is made of an optical fiber base material as an example, and the refractive index of the axial center portion (core) 52 of the transparent body 51 is Ill, and the refractive index of the cladding portion 53 (
1,458) as n2 and the refractive index (1,333) of the refractive index adjustment water 44 as n3, these refractive indices are as follows.
nl>n2>113.

In FIG. 2, when the arrow Z direction is the light scanning direction and the irradiation light beam is irradiated from the light irradiation system 11 side to the light receiving measurement system 21 side, a part of the irradiation light beam passes through only the refractive index adjustment water 44,
The other part of the irradiation light is transmitted through the refractive index adjusting water 44 → the outer mantle 53
(Transparent body 51)→Transmits like the refractive index adjustment water 44,
Furthermore, some of the other irradiation light beams are transmitted as follows: water for adjusting the refractive index 44 → mantle part 53 (transparent body 51) → shaft center part 52 (transparent body 51) → mantle part 53 (transparent body 51) → water for refractive index adjustment 44 To Penetrate.

As is well known, refraction of light is caused by a change in the refractive index of a medium through which the light passes.

Therefore, in the case of FIG. 2, no refraction of light occurs in the light rays that pass through only the refractive index adjustment water 44, but refraction occurs in each of the other light rays that pass through media with different refractive indexes.

In this case, since the refractive index of the refractive index adjusting water 44 with respect to the outer mantle 53 is small, the light that passes through the vicinity of the outer periphery of the transparent body 51 undergoes a large refraction as shown in FIG.

However, since the vicinity of the outer periphery of the transparent body 51 is not an important shape in terms of its optical properties, the transparent body 51 has the following characteristics:
It is sufficient to obtain information (transmitted light) about 90% of the outer diameter.

As mentioned above, the n2 of the mantle 53 is 1.458 and the refractive index is 21g! When n3 of the water treatment water 44 is 1.333, and if light is incident at a position < 0.9X (D/2) as shown in Fig. 2, the deflection angle φo9 of the transmitted light is as follows (1) It becomes like the expression.

φo q =2X(sin-1(0,9)-sin-]
[(1,333/1.458)Xo,9]) ”(1)
If a focal length f = 120 mm is selected as the condensing lens 22 for effectively guiding such transmitted light to the detector 23, the necessary effective diameter LD of the condensing lens 22 is expressed as follows (2
) is as follows.

LD/2=120Xtan (8,8deg)...
(2) In this case, the size of the detector 23 is 37.2 mm.
If this is the case, the transmitted light of 90% of the outer diameter DX of the transparent body 51 will be input to the detector 23, and the intended shape measurement will be possible.

Therefore, when the shape of the transparent body 51 described in FIG. 1 is measured while satisfying the above-mentioned conditions, results as shown in FIG. 3 are obtained.

In FIG. 3, the horizontal axis represents the cross-sectional position of the transparent body 51, and the vertical axis represents the magnitude (deflection angle) of the obtained signal.

In FIG. 3, the transparent body 5 is located between the beaks P1 to P6.
1, that is, the outer diameter of the transparent body 51, and the area between peaks 23 and P4 corresponds to the axial center portion 52 of the transparent body 51.

When the transparent body 51 is an optical fiber base material, each of the peaks P2 and P4 is a point of change in the refractive index that occurs when the base material is manufactured.

In addition, since the refractive index difference between the transparent body 51 and the refractive index adjusting water 44 is large, Pl, P2, P4, P6, etc. are quite close to both ends. Since both refractive indices are known, they can be easily corrected.

Therefore, in the light receiving measurement system 21, each of the above peaks P1
．． By determining P3, P4, and P6, the transparent body 51
The outer shape (outer diameter of the mantle 53) and the inner shape of the transparent body 51 (outer diameter of the shaft center part 52) are known, and the eccentricity between the shaft center part 52 and the mantle 53 and the transparent body 51 Each important peak P2.24 etc. in manufacturing can also be found.

In the case of the method of the present invention, the following measures can also be taken.

For example, when determining the inner shape and outer diameter of the transparent body 51, even if the laser beam of the light irradiation system 11 is narrowed down, the beam diameter is finite, so there will be a difference between the measured value and the true value. , this can be corrected since the cause is clear.

If the transparent body 51 has a problematic refractive index gradient in its axial center 52, this may affect the measured value, but at least the transparent body 5 manufactured by the same manufacturing method
1 can be corrected so that the measurement error range becomes sufficiently small.

In the light receiving measurement system 21, if the size of the detector 23 is limited, measurement may become impossible in general cases, but as described above, when the detector 23 is composed of a position detection element or a detection element array, Since all the light beams are received and the peaks P1, P3, P4, and P6 are used as criteria for judgment, it becomes possible to deal with various types of transparent bodies 51 without modifying the device configuration.

In the case of the method of the present invention, since the deflection angle of the transmitted light beam is accurately determined, the refractive index of each part of the transparent body can also be determined from the data obtained at that time.

Incidentally, according to the method of the present invention, the outer diameter of the outer part of the transparent body 51,
When determining the shaft center outer diameter, the measurement error can be suppressed to 1107p or less.

“Effects of the Invention” As explained above, the present invention provides the following effects in a predetermined measurement method:
The external and internal shapes of the transparent body are measured based on the peak of the deflection angle of the light rays that have passed through the boundary between parts with mutually different refractive indexes. It can be measured well and can be used as a reference for quality control of transparent objects.

Furthermore, since water is used for adjusting the refractive index, there is no need to wash the transparent body after measurement, and there is no contamination of the working environment or harmful effects on workers.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram schematically showing an embodiment of the transparent body of the present invention, Fig. 2 is an explanatory diagram showing the light transmission state of the transparent body in the method of the present invention, and Fig. 3 is the peak of the deflection angle of the transmitted light beam. FIG. 11... Light irradiation system 12... Laser light source 13 of the light irradiation system...
- Condensing lens 21 of the light irradiation system... Light receiving measurement system 22... Condensing lens 23 of the light receiving measurement system...
...Detector 24 of the light reception measurement system...Signal processor 25 of the light reception measurement system...
... Computer 26 of the light reception measurement system ... Controller 31 of the light reception measurement system ...
...Scanning device 32...Movement stage mounting surface 33...
- Moving stage 34 of the scanning device...Electric motor 41 of the scanning device...Container 42 for holding a subject...Light transmitting part 43 of the container...Container Light transmitting portion 44...Water 51 for refractive index adjustment...Transparent body 52...Transparent body mantle 53...Axis of the transparent body Department agent Patent attorney Yoshio Saifuji Figure 1 Figure 2
1・

Claims (1)

[Claims] After immersing a transparent body in which the refractive index of the axial center portion and the mantle portion are different from each other in water for adjusting the refractive index, the transparent body is irradiated with the irradiation light beam emitted from the light irradiation system in a direction that intersects the axial center line of the transparent body. At the same time, the transmitted light is received by a light receiving measurement system, and in the light receiving measurement system, the boundary between the water for adjusting the refractive index and the shaft center part, and the boundary between the shaft center part and the outer mantle part are measured. A method for measuring the shape of a transparent body, characterized by measuring the outer shape and inner shape of the transparent body based on the peak of the deflection angle of the transmitted light beam.