JP2931530B2 - Lighting method used for optical fiber structure measurement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination method used for measuring the structure of an optical fiber, for example, measuring the eccentricity of a core with respect to the cladding of the optical fiber.

[0002]

2. Description of the Related Art Conventionally, as a method of measuring the structure of an optical fiber, for example, measuring the eccentricity of the core with respect to the cladding of the optical fiber, one end face of the optical fiber is imaged with a CCD camera, and the image is processed. A technique for measuring the structure of an optical fiber is known. When the structure of the optical fiber is measured in this way, if the contour or the like of the optical fiber cannot be clearly imaged, the measurement accuracy at the time of the structure measurement deteriorates, and the illumination method is important.

FIG. 3 is a view for explaining an example of a conventional coaxial epi-illumination method. In FIG. 3, 2
1 is an optical fiber to be measured, 22 is an objective lens, 23 is a lens barrel, 24 is a CCD camera, 25 is an image processing device, 26
Denotes a monitor, 27 denotes a white light source, and 28 denotes a half mirror. In this example, one end surface of the optical fiber 21 is connected to the objective lens 2.
2, the image is magnified through the lens barrel 23 and the half mirror 28, imaged by the CCD camera 24, and the imaged image is processed to measure the desired structure of the optical fiber. An image captured by the CCD camera 24 can be observed on a monitor 26.

In FIG. 3, the coaxial epi-illumination method is performed by irradiating an end face of an optical fiber 21 with white light from a white light source 27 via a half mirror 28 and an objective lens 22. The image obtained by this coaxial epi-illumination is, as described on the monitor 26, an optical fiber 21
Is dark, the portion of the cladding 21a of the optical fiber 21 is bright, and the portion of the core 21b is bright.
It is displayed as an outline in the portion 1a. Here, an optical fiber including a central core and a clad around the core is taken as an example.

[0005]

As described above, in the optical fiber structure measurement using the conventional coaxial epi-illumination method, the image of the optical fiber 21 is bright and the background is dark. The light transmitted through the optical fiber 21 is diffused light. Therefore, chipping (chipping), dirt, and the like of the end face of the optical fiber greatly affect the boundary portion of the captured image, and the contour of the optical fiber 21 and the optical fiber 21
However, there has been a problem that the boundary between the clad and the core cannot be measured with high accuracy, and the measurement accuracy of the core eccentricity and the like obtained by calculation using the result is deteriorated.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide an illumination method used for optical fiber structure measurement that can improve measurement accuracy.

[0007]

According to the present invention, there is provided an illumination method used for measuring the structure of an optical fiber.
In the illumination method used when measuring the structure of the optical fiber, the light is emitted from the other end surface of the optical fiber, and the optical fiber is passed through the central opening. A transmission illumination for irradiating light to the CCD camera from behind the optical fiber at one end face of the optical fiber is performed by a ring light guide and a light source.

[0008]

In the above-described configuration, first, by performing transmission illumination for irradiating the CCD camera with light from behind the optical fiber, an image in which the optical fiber portion is dark and the background portion is bright can be captured. The effects of chipping and dirt on the end face of the fiber are all dark portions, and the outline of the optical fiber can be obtained with high accuracy. In addition, since the core is irradiated with light from the end face opposite to the end face of the optical fiber to be imaged, the clad part of the optical fiber can be displayed dark, the core part can be displayed brightly, and the boundary between the clad and the core can be displayed. The part can also be obtained with high accuracy. In addition, it is preferable to use a ring light guide as the transmitted illumination, because the light uniformly irradiates the periphery of the optical fiber, so that more accurate measurement can be performed.

[0009]

FIG. 1 is a diagram for explaining an example of an illumination method used for optical fiber structure measurement according to the present invention. In FIG. 1, 1 is an optical fiber to be measured, 2 is an objective lens, 3 is a lens barrel, 4 is a CCD camera, 5 is an image processing device, and 6 is a monitor. In this example, one end surface of the optical fiber 1 is magnified through the objective lens 2 and the lens barrel 3 and imaged by the CCD camera 4, and the image is processed to measure the desired structure of the optical fiber. I have. The image captured by the CCD camera 4 can be observed on the monitor 6. The configuration of the above-described optical fiber structure measuring apparatus is the same as the conventional configuration.

According to the illumination method of the present invention, light is emitted from the light source 7 from the other end face of the optical fiber 1 opposite to the observation side, and the optical fiber 1 is irradiated with light from the one end face of the optical fiber 1 on the observation side. This is achieved by performing so-called transmission illumination in which the illumination device 8 irradiates light to the CCD camera 4 from behind. Therefore, in the image projected on the monitor 6, the background portion 1a of the optical fiber 1 is bright, the cladding portion 1b of the optical fiber 1 is dark, and the core portion 1c of the optical fiber 1 is bright.

As a result, the profile of the optical fiber 1, that is, the outer diameter of the clad, and the boundary between the clad and the core can be measured more accurately than the image obtained by the conventional illumination method. As a result, the structure of the optical fiber such as the clad diameter, clad non-circularity, core diameter, core non-circularity, and core eccentricity can be measured with high accuracy. In addition, a conventionally known method can be used for the image processing method and the like,
As the image processing device, for example, an optical fiber structure parameter measuring device C3030 manufactured by Hamamatsu Photonics KK can be used.

FIG. 2 is a view showing an example of a ring light guide used for transmitted illumination in the illumination method of the present invention.
In FIG. 2, reference numeral 11 denotes a light guide unit, and 12 denotes a ring illumination unit.
2 constitutes the ring light guide 13. Reference numeral 14 denotes a light source for irradiating the light guide unit 11 with light. When transmission illumination is performed using the ring light guide 13 and the light source 14 having the above-described configuration, when light from the light source 14 is irradiated while the optical fiber 1 passes through the central opening of the ring illumination unit 12, the optical fiber 1 CCD over 360 degrees from behind
This is preferable because light can be uniformly emitted to the camera.

When the above-described illumination method used for measuring the optical fiber structure according to the present invention is used, in addition to the improvement of the accuracy, the CC method can be used.
The requirement for the depth of field of the D camera 4 can be reduced. That is, when the illumination method of the present invention is used, instead of observing the one end surface of the optical fiber 1 itself, as in the case of using the conventional illumination method, the user observes the intensity signal of light. The depth of field can be made deep, and the lens system can be easily focused.

[0014]

As is apparent from the above description, according to the present invention, since the transmission illumination for irradiating the CCD camera with light from behind the optical fiber is performed, chipping and dirt on the end face of the optical fiber are performed. The effect can be eliminated, and the contour of the optical fiber can be determined with high accuracy.In addition, since the core is irradiated with light from the end face opposite to the end face where the optical fiber is imaged, the boundary between the clad and the core is also removed. It can be obtained with high accuracy. Therefore, the measurement accuracy of the optical fiber structure can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an example of an illumination method used for measuring an optical fiber structure according to the present invention.

FIG. 2 is a diagram showing an example of a ring light guide used for transmitted illumination in the illumination method of the present invention.

FIG. 3 is a diagram illustrating an example of a conventionally used side lighting method.

[Explanation of symbols]

1 optical fiber, 2 objective lens, 3 lens barrel, 4 CC
D camera, 5 image processing device, 6 monitor, 7 light source,
8 Lighting equipment

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01M 11/00

Claims (1)

(57) [Claims] An illumination method used for measuring one end face of an optical fiber with a CCD camera, processing the taken image and measuring the structure of the optical fiber, and irradiating light from the other end face of the optical fiber. A transmission light for irradiating a CCD camera with light from behind the optical fiber at one end face of the optical fiber using a ring light guide and a light source through an optical fiber in a central opening. Lighting method used for