JPH08136397A - Illumination method used for optical fiber structure measurement - Google Patents

Abstract

PURPOSE: To provide an illumination method used for optical fiber structure measurement which can improve measurement accuracy. CONSTITUTION: In an illumination method used when one end face of an optical fiber 1 is photographed by a CCD camera 4, a photographed image is image- processed by an image processor 5 and structure of the optical fiber 1 is measured, the other end face of the optical fiber 1 is irradiated with light from a light source 7 and transparent illumination is performed by an illumination device 8 for irradiating the CCD camera 4 with light from rearward of the optical fiber 1 at one end face.

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 the 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 by a CCD camera and the imaged 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 manner, if the contour of the optical fiber or the like cannot be clearly imaged, the measurement accuracy at the time of the structure measurement will deteriorate, and thus the illumination method becomes important.

FIG. 3 is a diagram 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
Is a monitor, 27 is a white light source, and 28 is a half mirror. In this example, one end surface of the optical fiber 21 is attached to the objective lens 2
2 and the lens barrel 23 and the half mirror 28 are enlarged to pick up an image with the CCD camera 24, and the picked-up image is subjected to image processing to measure a desired structure of the optical fiber. The image captured by the CCD camera 24 can be observed on the monitor 26.

In FIG. 3, the coaxial epi-illumination method is performed by irradiating the end face of the 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, the optical fiber 21.
Is dark, the clad 21a of the optical fiber 21 is bright, and the core 21b is bright.
It is displayed as a contour in the portion 1a. Here, an optical fiber including a central core and a clad around it is taken as an example.

[0005]

As described above, in the optical fiber structure measurement using the conventional coaxial epi-illumination method, the portion of the optical fiber 21 is bright and the background portion is dark. The light transmitted through the optical fiber 21 is diffused light. Therefore, chipping of the end surface of the optical fiber, dirt, and the like have a great influence on the boundary portion of the captured image, and the contour of the optical fiber 21 and the optical fiber 21.
However, there was a problem that the boundary between the clad and the core could not be measured accurately, and the measurement accuracy of the core eccentricity and the like obtained by calculation using the result deteriorated.

The object of the present invention is to solve the above problems,
It is intended to provide an illumination method used for measuring an optical fiber structure, which can improve measurement accuracy.

[0007]

An illumination method used for measuring an optical fiber structure according to the present invention is a method in which one end surface of the optical fiber is a CCD.
In an illumination method used for measuring the structure of an optical fiber by imaging the captured image with a camera and irradiating light from the other end surface of the optical fiber, the optical fiber at one end surface of the optical fiber It is characterized in that the CCD camera is provided with transmissive illumination for irradiating light from behind.

[0008]

In the above-mentioned structure, first, by transmitting light to the CCD camera from behind the optical fiber, it is possible to take an image in which the optical fiber portion is dark and the background portion is bright. The effects of chipping, dirt, and the like on the end face of the fiber are all in the dark part, and the contour of the optical fiber can be accurately obtained. Also, since the core part is irradiated with light from the end face opposite to the end face of the optical fiber for imaging, the clad part of the optical fiber can be darkened and 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 accurately. Note that it is preferable to use a ring light guide as the transmitted illumination because the light uniformly illuminates the periphery of the optical fiber, and thus more accurate measurement can be performed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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. 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 imaged image is processed to measure a desired structure of the optical fiber. There is. The image captured by the CCD camera 4 can be observed on the monitor 6. The configuration of the optical fiber structure measuring device described above 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 surface of the optical fiber 1 which is opposite to the observation side, and at the one end surface of the optical fiber 1 on the observation side. This is achieved by performing so-called transmission illumination in which the CCD camera 4 is illuminated with light from the rear by the illumination device 8. Therefore, in the image displayed 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.

Therefore, the contour 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 with higher accuracy than an image obtained by the conventional illumination method. As a result, the structure of the optical fiber such as the clad diameter, the clad non-circularity, the core diameter, the core non-circularity, and the core eccentricity can be accurately measured. As the image processing method, a conventionally known method can be used,
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 diagram showing an example of a ring light guide used for transmitted illumination in the illumination method of the present invention.
In FIG. 2, 11 is a light guide part, 12 is a ring illumination part, and these light guide part 11 and ring illumination part 1
2 constitutes the ring light guide 13. Reference numeral 14 is a light source for irradiating the light guide portion 11 with light. When transmitted illumination is performed using the ring light guide 13 and the light source 14 having the above-described configuration, when the light from the light source 14 is radiated through the optical fiber 1 through the central opening of the ring illumination unit 12, the optical fiber 1 360 degrees from the rear of the CCD
It is preferable because light can be uniformly emitted to the camera.

When the illumination method used for measuring the optical fiber structure according to the present invention is used, in addition to improvement in accuracy, CC
The demand for the depth of field of the D camera 4 can be relaxed. That is, when the illumination method of the present invention is used, the intensity signal of light is observed instead of observing the one end surface itself of the optical fiber 1 here as in the case of using the conventional illumination method. , The depth of field can be deepened and the lens system can be easily focused.

[0014]

As is apparent from the above description, according to the present invention, since the transmissive illumination for irradiating the CCD camera with light from the rear of the optical fiber is performed, the end face of the optical fiber is prevented from being chipped or soiled. The effect is eliminated and the contour of the optical fiber can be obtained with high accuracy.Because the core part is irradiated with light from the end face opposite to the end face where the optical fiber is imaged, the boundary part between the clad and the core is also It can be calculated accurately. Therefore, the measurement accuracy of the optical fiber structure can be improved.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of an illumination method used for measuring an optical fiber structure of 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 for explaining an example of a conventionally used side illumination method.

[Explanation of symbols]

1 optical fiber, 2 objective lens, 3 lens barrel, 4 CC
D camera, 5 image processing devices, 6 monitors, 7 light sources,
8 lighting equipment

Claims (2)

[Claims] 1. An illumination method used for measuring the structure of an optical fiber by imaging one end of the optical fiber with a CCD camera, processing the captured image, and irradiating light from the other end of the optical fiber. In addition, the illumination method used for measuring the optical fiber structure is characterized in that the one end surface of the optical fiber is subjected to transillumination by irradiating the CCD camera with light from behind the optical fiber. 2. The transmission illumination is performed by a ring light guide and a light source having an optical fiber through a central opening.
An illumination method used for measuring the optical fiber structure described.