JPH11236223A - Method for inspecting burner for synthesizing optical fiber preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the end face at the front end of a burner for synthesizing an optical fiber perform with high accuracy without contact. SOLUTION: An illumination light is cast from an illumination body 16 to the base end side of the burner 5 for synthesizing the optical fiber preform placed in an inspection position and the illumination light past the thick part of a glass tube constituting the burner 5 from the end face at the front end of the glass tube is put into the state that this light is emitted in respective directions. A CCD camera 18 is installed in the position where the front end of the burner 5 may be photographed in the state of inclining the optical axis 18a of the CCD camera 18 with respect to the tube axis 5b of the burner 5. The front end of the burner 5 is photographed by this camera 18. The front end of the burner is inspected in accordance with the image of a front end 5a of the burner 5 obtd. by subjecting the image data obtd. from the camera 18 to image processing by an image processor 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a burner for synthesizing an optical fiber preform for synthesizing a porous optical fiber preform.

[0002]

2. Description of the Related Art A porous optical fiber preform is made by a VAD method. In this VAD method, as shown in FIG. 5, a seed rod 3 is suspended from a top part of a reaction chamber 2 in a reaction vessel 1 by a support rod 4 as a target, and the reaction chamber 2 is placed at a lower end of the seed rod 3. The end face of the end portion 5a of the burner 5 for synthesizing the optical fiber preform having a multi-tube structure is made to face the inside thereof, and the burner 5 for synthesizing the optical fiber preform 5 is inserted into the oxyhydrogen flame 6 formed ahead of the end portion 5a. A gas of silicon tetrachloride is introduced through the burner 5 for synthesizing the optical fiber preform, and a fine particle 7 of silicon dioxide is generated by a flame hydrolysis reaction.
Is deposited on the lower end of the seed rod 3 as a target to produce a porous optical fiber preform 8. Burner for optical fiber preform synthesis 5
Has a structure in which a plurality of quartz glass tubes having different outer diameters are arranged coaxially and concentrically with an air gap between adjacent ones. An exhaust pipe 9 is provided in the reaction chamber 2 on the side opposite to the side where the burner 5 for synthesizing the optical fiber preform 5 exists, and exhausts fine particles 7 and the like that have not been deposited on the target.

In such a manufacturing process, when a small amount of an additive such as germanium tetrachloride together with silicon tetrachloride is introduced into the oxyhydrogen flame 6 through the burner 5 for synthesizing the optical fiber preform, fine particles such as germanium dioxide are produced. At the same time, a distribution of germanium dioxide or the like can be formed in the radial direction of the porous optical fiber preform 8. The distribution of germanium dioxide or the like corresponds to the refractive index distribution of the core of the optical fiber when the porous optical fiber preform 8 is sintered, vitrified, and drawn to form an optical fiber.

In the above method, the quality of the optical fiber is determined by the refractive index distribution derived from the distribution of an additive such as germanium dioxide. In order to stabilize the quality of an optical fiber, it is important to manage the following points.

The flow rate of the raw material gas The flow rate of the combustion gas The attitude of the burner 5 for synthesizing the optical fiber preform 5 The dimensions at the end face of the tip 5a of the burner 5 for synthesizing the optical fiber preform 5 Can also be managed with an appropriate jig.

[0006]

However, regarding the dimensions (tube diameter, tube wall thickness, gap between adjacent tubes, etc.) at the end face of the end portion 5a of the burner 5 for synthesizing an optical fiber preform 5 having a multi-tube structure. Management was difficult because there was no suitable method to measure.

The reason is as follows.

(1) When a contact-type measuring instrument such as a caliper is used, the quartz glass tube constituting the burner 5 has a low rigidity, so that the quartz glass tube is deformed and the burner 5 is deformed. Cannot be measured accurately at the end face of the tip 5a.

(2) Since the burner 5 having a multi-tube structure is made of quartz glass as described above, even if a CCD camera is placed on the tip side of the burner 5 in the direction of the tube axis, an enlarged photograph can be taken. If the contrast is insufficient and the illumination light is applied to give the contrast, the light reflected on the surface of the tube will cause halation or the appearance will change depending on the surface roughness of the tip of the tube. Dimension measurement is difficult.

If the dimensions of the respective portions on the end face of the tip 5a of the burner 5 are out of order, the shape, thickness, length, etc. of the flame 6 are affected, and a normal porous optical fiber preform cannot be synthesized.

An object of the present invention is to provide a method for inspecting a burner for synthesizing an optical fiber preform, which can inspect the tip of the burner for synthesizing an optical fiber preform with high accuracy without contact.

[0012]

SUMMARY OF THE INVENTION The present invention is an improvement of a method for inspecting a burner for synthesizing an optical fiber preform for synthesizing a porous optical fiber preform.

In the method of inspecting a burner for synthesizing an optical fiber preform according to the present invention, a glass tube constituting the burner is irradiated with illumination light at a base end side of the burner for synthesizing an optical fiber preform positioned at an inspection position. The illumination light passing through the thick portion of the glass tube is emitted in each direction from the end surface of the tip of the burner, and the tip of the burner is tilted with the optical axis of the camera inclined with respect to the tube axis of the burner. The tip of the burner is photographed by the camera installed at a position where the image can be photographed. The tip of the burner is inspected based on the image of the tip of the burner obtained by performing image processing on the obtained image data. The inclination angle at which the optical axis of the camera is inclined with respect to the tube axis of the burner is set to an angle at which the image of the tip of the burner captured by the camera is easily seen.

With this configuration, light passing through the thick portion of the glass tube travels through the thick portion of the glass tube constituting the burner and the space between the adjacent glass tubes, and the tip end of the burner. When emitted from the part, the end face of the tip of the glass tube is emitted to a wide range, but only light substantially parallel to the tube axis of the burner is emitted from the end of the space between adjacent glass tubes. You. Therefore, when the tip of the burner is photographed by a camera arranged at a position where the tip of the burner can be photographed in a state where the optical axis of the camera is inclined with respect to the tube axis of the burner, only the tip of the glass tube shines. Images can be obtained. Since this image has a strong contrast, the tip of the burner can be inspected with high accuracy by image processing such as binarization.

In the present invention, the illumination light is preferably monochromatic light, and the camera preferably has a monochromatic filter attached to the front surface of the lens for photographing. By doing so, it is possible to take an image while reducing the influence of ambient light.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 3 show a first example of an embodiment of an inspection apparatus for implementing a method for inspecting a burner for synthesizing an optical fiber preform according to the present invention. FIG. 2 is a side view showing the inspection apparatus for the burner for synthesizing an optical fiber preform of the present embodiment, FIG. 2 is an explanatory view showing the principle of measurement by the inspection apparatus of the present embodiment, and FIG. 2 is an example of an image photographed by the inspection apparatus of the present embodiment. It is an inspection object image figure which shows.

The inspection apparatus for a burner for synthesizing an optical fiber preform includes a mount mechanism 10 as shown in FIG. The mount mechanism 10 is configured such that one side of a mount table 12 is pivotally supported by a pivot portion 13 with respect to a base table 11, and the other side is connected by an air cylinder 14. Can be changed. At the center of the surface of the mount table 12, a burner 5 for synthesizing an optical fiber preform to be inspected is mounted.
Burner holder 1 supported in a direction parallel to the surface of the burner
5 are erected in an orthogonal direction. Mount stand 12
An illumination body holder 17 that supports the illumination body 16 is provided upright on one side of the surface of the illumination body 16 in an orthogonal direction. Mount stand 1
On the opposite side of the surface of 2, a camera holder 19 that supports the CCD camera 18 at a required angle is erected in an orthogonal direction. An image processing device 21 is connected to the CCD camera 18 via a cord 20.

As shown in FIG. 2, the burner 5 for synthesizing the optical fiber preform is coaxially fitted with quartz glass tubes 22, 23, 24 whose outer diameters are gradually reduced, as shown in FIG. A gas passage 25 is formed between the tubes 22 and 23, a gas passage 26 is formed between the quartz glass tubes 23 and 24, and a gas passage 27 is formed in the quartz glass tube 24.

Next, a method for inspecting a burner for synthesizing an optical fiber preform using such an apparatus for inspecting a burner for synthesizing an optical fiber preform will be described.

An illuminator 16 is provided on the base end side of the burner 5 for synthesizing the optical fiber preform placed at the inspection position by the burner holder 15.
And the illumination light 28a passing through the thick portions of the glass tubes 22, 23, 24 from the tips 22a, 23a, 24a of the quartz glass tubes 22, 23, 24 constituting the burner 5 in each direction. The tip 5a of the burner 5 is set in a state where the angle α formed by the optical axis 18a of the CCD camera 18 with respect to the tube axis 5b of the burner 5 is set to an appropriate angle (preferably 10 degrees or more). The tip 5a of the burner 5 is photographed by the CCD camera 18 installed at a position where photographing is possible. Image data obtained from the CCD camera 18 is input to an image processing device 21 via a code 20 to perform image processing. Thus, the tip 5 of the burner 5 as shown in FIG.
Image 22, 23 of quartz glass tubes 22, 23, 24 of a
', 24' are obtained. This image 22, '23', 24
'Each quartz glass tube 2 at the tip 5a of the burner 5
Measure 2, 23, 24 dimensions.

In such an inspection method, as shown in FIG. 2, the illuminating light 28 applied to the base end of the burner 5 is applied to the inside of the thick portions of the quartz glass tubes 22, 23, 24 constituting the burner 5. , And through gas passages 25, 26, 27 which are spaces between adjacent quartz glass tubes 22, 23, 24.

The quartz glass tubes 22 and 2 constituting the burner 5
The light 28a passing through the thick portions of the quartz glass tubes 22, 23, 24 has a higher refractive index than that of air, so that the quartz glass tubes 22, 23, 2 have an incident angle greater than the critical angle.
4 while repeating total internal reflection in the thick portion of the quartz glass tube 22, 23, 24.
The light is emitted from the end face 4a. Quartz glass tubes 22, 23,
The tips 22a, 23a, and 24a of the quartz glass tubes 22, 23, and 24 have chamfers or convex rounds.
The light is emitted to a wide range from the end face a. Moreover, the tip portions 22a, 23a, 24a of the quartz glass tubes 22, 23, 24
Even if the finish of the end face is slightly poor, the emitted light is hardly affected.

On the other hand, the quartz glass tube 2 adjacent to the burner 5
Gas passages 25, 26, which are spaces between 2, 23, 24
A part of the light 28b propagating through 27 enters the quartz glass tubes 22 and 23 while being repeatedly reflected on the surfaces of the adjacent quartz glass tubes 22 and 23 as shown by the lower gas passage 25 in FIG. It is attenuated by this. As shown by the upper gas passage 25 in FIG.
Of the light 28b that travels through the gas passage 25, which is a space between the burners 5, the light 28b with a small number of reflections, that is, light that is substantially parallel to the tube axis 5b of the burner 5, is emitted from the tip of the burner 5. Is hardly emitted in the direction deviating from the tube axis 5b.

Therefore, when viewed from the direction inclined with respect to the tube axis 5b of the burner 5, the quartz glass tubes 22, 23,
Since only the light emitted from the end faces of the tips 22a, 23a and 24a of the 24 is visible, the tip of the burner 5 is photographed with the optical axis 18a of the CCD camera 18 inclined with respect to the tube axis 5b of the burner 5. When the tip 5a of the burner 5 is photographed by the CCD camera 18 disposed at a position where it can be formed, the tips 22a of the quartz glass tubes 22, 23, and 24 as shown in FIG.
Images 22 ', 23', in which only 23a, 24a shine,
24 ′ can be obtained. Images 22 'and 23 of these
'And 24' have strong contrast, so that the dimensions at the end face of the tip 5a of the burner 5 can be automatically measured with high accuracy by image processing such as binarization.

It should be noted that the illumination light 38 may be monochromatic light, and the CCD camera 18 may be provided with a monochromatic filter to reduce the influence of ambient light.

In this example, the burner 5 has an outer diameter of 20 mm.
Was used. The posture of the burner 5 was set to a desired posture by changing the inclination angle θ of the mount table 12. When a CCD camera 18 having a size of 500 × 500 pixels was used and the field of view of the CCD camera 18 was set to be 10 mm square, the resolution was about 0.02 mm, which was sufficient for practical use. In an image processing device 21 that performs image processing on image data obtained from the CCD camera 18, binarization of image data, setting of a measurement area, and tips 22a, 23a, and 24a of quartz glass tubes 22, 23, and 24 are performed.
Of the required portions of the images 22 ′, 23 ′, and 24 ′ were automatically performed.

In this manner, the tip 5a of the burner 5 is
When an image was taken at an inclination angle α at which the image taken by the CD camera 18 was easy to see, and the inspection was carried out, it was possible to discriminate the burner 5 between good and bad dimensional accuracy.

The inclination angle α is the diameter of the burner 5, the burner 5
Since the preferred angle varies depending on the finished state of the tube surface, the gap between the tubes of the burner 5, etc., it is appropriately set according to the burner 5.

FIG. 4 is a vertical sectional view showing a main part of a second embodiment of the inspection apparatus for performing the method for inspecting a burner for synthesizing an optical fiber preform according to the present invention.

In this example, when inspecting the deterioration of the burner 5 for synthesizing the optical fiber preform at the time of changing the equipment in use,
This is an application of the present invention.

In this case, when the equipment being used is changed, the CCD camera 18 is placed in the reaction vessel 1 in the camera holder 1.
Arrange at 9. The CCD camera 18 appropriately selects an angle α formed by the optical axis 18a of the CCD camera 18 with respect to the tube axis 5b of the burner 5 (preferably 10) so that the tip 5a of the burner 5 can be photographed as described above. The burner 5 is placed at a position where the tip 5a of the burner 5 can be photographed while the image is being shot. C
A monochromatic filter 29 is attached to the tip of the CD camera 18. Outside the reaction vessel 1, an illuminator 16 for irradiating the monochromatic illumination light 28 to the base end side of the burner 5 for synthesizing the optical fiber preform is disposed so as to be supported by a burner holder (not shown).

When the burner 5 deteriorates due to the use of the equipment,
Attachment is generated at the tip 5a of the burner 5, and the portion appears dark. In the case of this inspection, the illuminator 16 of monochromatic light is used.
By attaching a monochromatic filter 29 to the end of the CCD camera 18, the influence of surroundings is cut. Under such conditions, the tip 5a of the burner 5 is photographed by the CCD camera 18 in a state where the angle α formed by the optical axis 18a of the CCD camera 18 with respect to the tube axis 5b of the burner 5 is appropriately selected.

When the tip 5a of the burner 5 is photographed in this manner, the influence of the surroundings can be cut and photographed, and the deteriorated burner 5 can be easily found at an early stage.

[0034]

According to the method for inspecting a burner for synthesizing an optical fiber preform according to the present invention, the burner is constituted by applying illumination light to the base end side of the burner for synthesizing an optical fiber preform positioned at the inspection position. The illumination light passing through the thick portion of the glass tube is emitted in each direction from the end surface of the tip of the glass tube, and the burner is tilted with the optical axis of the camera inclined with respect to the tube axis of the burner. Since the tip of the burner is photographed by the camera installed at a position where the tip of the burner can be photographed, the light passing through the thick part of the glass tube emits light within the thick part of the glass tube constituting the burner and the adjacent glass tube. And through the space between,
When emitted from the tip of the burner, the end face of the tip of the glass tube is emitted in a wide range, but light from the tip of the space between adjacent glass tubes is substantially parallel to the tube axis of the burner. Therefore, the tip of the burner is photographed with a camera arranged at a position where the tip of the burner can be photographed with the optical axis of the camera inclined with respect to the tube axis of the burner. An image in which only the leading end shines can be obtained. Since the obtained image has a high contrast, by performing image processing such as binarization, the tip of the burner can be inspected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a side view showing a first example of an embodiment of an inspection apparatus for executing an optical fiber preform synthesis burner inspection method according to the present invention.

FIG. 2 is an explanatory diagram showing the principle of measurement by the inspection device of the present example.

FIG. 3 is an inspection target image diagram showing an example of an image captured by the inspection device of the present embodiment.

FIG. 4 is a vertical sectional view of a main part showing a second example of the embodiment of the inspection apparatus for performing the method for inspecting a burner for synthesizing an optical fiber preform according to the present invention.

FIG. 5 is a longitudinal sectional view of a conventional optical fiber preform manufacturing apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reaction vessel 2 reaction chamber 3 kind rod 4 support rod 5 burner for synthesizing optical fiber preform 5 a tip 5 b tube axis 6 hydrogen oxyflame 7 fine particles of silicon dioxide 8 porous optical fiber preform 9 exhaust pipe 10 mounting mechanism 11 base Table 12 Mount base 13 Pivot 14 Air cylinder 15 Burner holder 16 Illuminator 17 Illuminator holder 18 CCD camera 18a Optical axis 20 Code 21 Image processing device 22, 23, 24 Quartz glass tube 22a, 23a, 24a Tip 22, 22 ', 24' Image 25, 26, 27 Gas passage 28, 28a, 28b Illumination light 29 Monochromatic filter

Claims (2)

[Claims] 1. An inspection method for an optical fiber preform synthesis burner for inspecting an optical fiber preform synthesis burner for synthesizing a porous optical fiber preform, comprising the steps of: Irradiation light is applied, and the illumination light passing through the thick portion of the glass tube is emitted in each direction from the end surface of the tip portion of the glass tube constituting the burner, and a camera is provided with respect to the tube axis of the burner. The tip of the burner is obtained by taking an image of the tip of the burner by the camera installed at a position where the tip of the burner can be taken with the optical axis of the burner in an inclined state, and performing image processing on the obtained image data. A method for inspecting a burner for synthesizing an optical fiber preform, wherein an end of the burner is inspected based on the image of (1). 2. An inspection method for an optical fiber preform synthesis burner for inspecting an optical fiber preform synthesis burner for synthesizing a porous optical fiber preform, comprising the steps of: The illumination light of monochromatic light is applied, and the illumination light passing through the thick portion of the glass tube is emitted in each direction from the end surface of the tip portion of the glass tube constituting the burner. In contrast, an image of the tip of the burner is taken by the camera installed at a position where the tip of the burner can be taken in a state where the optical axis of the camera with the monochromatic filter is inclined, and the obtained image data is subjected to image processing. A method for inspecting a burner for synthesizing an optical fiber preform, comprising inspecting the end of the burner based on the image of the end of the burner obtained by the above method.