JP3402791B2 - Optical fiber core measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for observing the core of an optical fiber, and more particularly to an apparatus for measuring the core of an optical fiber so that the focal length can be adjusted in a short time.

[0002]

2. Description of the Related Art A system (autofocus system) for automatically adjusting a focus in a device for observing an optical fiber core will be described.

First, an optical fiber is photographed by a camera, a certain line in a direction substantially perpendicular to the longitudinal direction of the obtained fiber image is extracted, and a luminance distribution as shown in FIG. 4 is obtained. In FIG. 4, the horizontal axis represents the fiber radial direction and the vertical axis represents the brightness. The fiber-camera distance is changed by a small amount, and the luminance distributions are taken for each case and compared to find an inflection point or a singular point. That point (or a point that has moved a certain distance from that point) becomes the focusing position, and the camera is moved to this position for focusing.

Next, a specific example of the conventional method will be shown.

The brightness difference Db between the peak value Vp and the bottom value Vb of the brightness in the cladding portion of the brightness distribution of the fiber image (FIG. 4) is obtained. Then, the distance between the fiber and the camera is changed by a small amount, and the brightness difference Db at several places is changed by the same procedure.
(Dcl indicates the clad diameter, and Dcr indicates the core diameter). FIG. 5 is a graph showing this relationship. The focus is finally adjusted by moving the camera to a position (focusing position) where the maximum brightness difference is obtained in FIG. In FIG. 5, the horizontal axis represents the camera-fiber distance and the vertical axis represents the brightness difference.

[0006]

However, in the conventional method, in order to focus the camera on the core of the fiber, the camera is moved in small steps in the vertical (Z-axis) direction and the peak value P is searched for. Therefore, several measurements are required. There is a need to.

Therefore, since the same work is repeated while changing the observation point, it takes time to focus.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide an optical fiber core measuring apparatus having a short focusing time.

[0009]

In order to achieve the above object, the present invention provides an optical fiber core measurement for capturing an image of an optical fiber from a camera and performing image processing to measure the structure, dimensions and fiber twist angle. In the device, a light irradiation unit that irradiates parallel transmitted light in a direction substantially perpendicular to the optical axis in the longitudinal direction of the optical fiber to be observed, and a light emission unit of the light irradiation unit facing the light emission port so as to sandwich the optical fiber. The center of the optical fiber and the camera are provided with the arranged camera, a camera drive unit that moves the camera in the vertical and horizontal directions, a control device that controls the movement of the camera drive unit, and an image processing device that processes an image. The distance between the center position of the optical fiber and the camera is calculated using image data that has a proportional relationship with the distance between the camera and the camera. The one in which automatically adjust.

Further, according to the present invention, in an optical fiber core measuring device for measuring an optical fiber image from a camera and performing image processing to measure a structure, a dimension and a fiber twist angle, a longitudinal direction of an optical fiber to be observed. Light emitting means for irradiating parallel transmitted light in a direction substantially perpendicular to the optical axis of, the camera arranged to face the light emitting opening of the light emitting means so as to sandwich the optical fiber, and the camera for vertical and horizontal directions. An image having a camera drive unit that moves in a direction, a control device that controls the movement of the camera drive unit, and an image processing device that processes an image, and that has a proportional relationship with the distance between the center of the optical fiber and the camera. Calculate the distance between the center position of the optical fiber and the camera using the data, calculate the shift between the in-focus position, move the camera, and automatically adjust the focus. Compared by taking the luminance distribution of near, and requests that the luminance is maximized.

[0011]

According to the above construction, the parallel transmission light having a constant optical power is used, and the distance between the optical fiber and the camera and the data having a proportional relationship within a certain fixed range are subjected to the image processing from the fiber image. By calculating by the method and using this proportional relationship, the movement of the camera from the reference position where the proportional relationship is established is near the position obtained by one time, and the camera can be focused in a short time.

After focusing by the above-mentioned method,
If the conventional autofocus method is used, the focus can be obtained with higher accuracy.

[0013]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram of an optical fiber core measuring apparatus according to the present invention.

In FIG. 1, an optical fiber 10 is held horizontally by a fiber chuck 20, and the optical fiber 1
A lens 30 for a parallel light source that has an optical axis in a direction (Z-axis direction) substantially perpendicular to the longitudinal direction of 0 (X-axis direction) and illuminates upward parallel transmitted light with a constant optical power; A light guide 40 having one end connected to the lens 30 and a light source 50 connected to the other end of the light guide 40 are provided. These lens 30, light guide 40, and light source 5
The light irradiation means 60 is formed with 0.

On the other hand, the optical fiber 10 is opposed to the light emitting port 60a of the light irradiation means 60 so as to sandwich the optical fiber 10.
A camera 70 for observing is observed. An objective lens 80 is attached to the tip of the camera 70.
The camera 70 is attached to a camera driving unit 90 that moves vertically (Z axis) and horizontally (Y axis) with respect to the optical fiber 10. The camera driving unit 90 is controlled by the control device 100. There is.

A camera 70, an image processing device 110 for processing a fiber image from the camera 70, and a control device 100.
And are connected by signal transmission cables 120, 130 and 140, respectively.

Next, the operation of the embodiment will be described.

When a parallel transmitted light is applied to the optical fiber 10, a certain line in a direction substantially perpendicular to the longitudinal direction of the fiber image obtained by the camera 70 is extracted, and its luminance distribution is taken by the image processing device 110, which is given. Binarization is performed according to the slice level. Among the binarized dark areas, the number of pixels in the dark area of only the cladding area is calculated, and the average of the two areas is calculated, and this is defined as the "dark area width of the cladding" as image data.

FIG. 2 shows the width of the dark part when 80% is the slice level with respect to the background brightness level. Within a certain range, there is a proportional relationship between the width of the dark portion of the clad and the distance between the fiber and the camera. Coarse movement is performed by the camera driving unit 90 to a reference position where the distance between the optical fiber 10 to be observed and the camera 70 has a proportional relationship. The dark space width at this reference position is calculated by the image processing device 110, and the control device 100 is set so as to be in the vicinity of the peak position obtained using the proportional relationship.
The coarse movement amount is obtained by, and positioning is performed by the camera driving unit 90.

In this way, focusing near the position to be obtained can be performed by a method in which a proportional relationship is obtained from the conventional peak search method, and simple focusing can be performed by one movement from the reference position.

The results of experiments conducted under the following conditions are shown below.

It is obtained by the camera 70 under the measurement conditions of the parallel transmitted light having a constant optical power and the objective lens (40 times). When the luminance distribution of the fiber image is observed according to the change in the distance between the camera and the fiber, FIG. 2 (a), (b),
A waveform as shown in (c) is obtained. Camera 7 as shown
In the luminance distribution of the fiber image by 0, the width of the dark part occupies the majority (a), the central part (core part) of the optical fiber 10 looks bright (b), and the central part appears dark and the dark part occupies the majority (c). ), The waveform changes according to the distance between the camera and the fiber.

As shown in FIG. 2, about 80% of the background average luminance level was binarized as a slice level in the luminance distribution of the fiber image. At this time, the average of two dark area widths (A ₁ and B ₁ , A ₂ and B ₂ , A ₃ and B ₃ ) of only the inner fiber clad of the dark area binarized as shown in Equations ₁ , ₂ , and ₃ ( The average of the width of the dark part (left, right, W ₁ , W ₂ , W ₃ ) is taken.

[0025]

[Formula 1] W ₁ = (A ₁ + B ₁ ) / 2

[0026]

[Formula 2] W ₂ = (A ₂ + B ₂ ) / 2

[0027]

## EQU3 ## W ₃ = (A ₃ + B ₃ ) / 2 However, in FIGS. 2A, 2B, and 2C, the number 1 is
Equations 2 and 3 satisfy the relationship of Equation 4.

[0028]

Equation 4] W _1> W _2> W ₃ then camera - data cladding dark area width lateral average of the relative distance between the fiber and graphed as shown in FIG. In the figure, the horizontal axis represents the relative distance between the camera and the fiber,
The vertical axis shows the average width of the clad dark part on the left and right. L ₁ corresponds to the waveform shown in FIG. 2A, L ₂ corresponds to the waveform shown in FIG. 2B, and L ₃ corresponds to the waveform shown in FIG. 2C.

From the figure, a proportional relationship can be seen in a certain range of the distance between the camera and the fiber. Therefore, when linear approximation is applied, a linear function with an inclination of 44.5 pixels / 50 μm is obtained.
The maximum error between this linear function and the measured data was 2.5 pixels, and focusing was possible within an error of ± 3 μm.

As described above, according to the present embodiment, the parallel transmitted light having a constant optical power is used, and the distance between the optical fiber and the camera and the data having a proportional relationship within a certain fixed range are obtained from the fiber image. By calculating by the image processing method and using this proportional relationship, the movement of the camera from the reference position where the proportional relationship is established becomes close to the position obtained by one time, and the focus can be adjusted in a short time.

After focusing by the above-mentioned method, if the conventional autofocus system is used, the focus can be obtained with higher accuracy.

[0032]

In summary, according to the present invention, the following excellent effects are exhibited.

The distance between the optical fiber and the camera and the data having a proportional relationship within a certain fixed range are calculated from the image of the fiber by an image processing method. Can be matched.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an optical fiber core measuring apparatus of the present invention.

FIG. 2 is a diagram showing a luminance distribution of a fiber image obtained by the device shown in FIG.

FIG. 3 is a view showing a clad dark portion width left-right average with respect to a relative distance between a camera and a fiber, which is obtained by the apparatus shown in FIG.

FIG. 4 is a diagram showing a luminance distribution of a fiber image obtained by a conventional method.

5 is a diagram showing a luminance difference distribution obtained from the luminance distribution shown in FIG.

[Explanation of symbols]

10 optical fibers 60 light irradiation means 60a Light exit port 70 cameras 90 camera drive 100 control device 110 image processing device

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Minako Morisato Minako Morisato 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside Hitachi, Ltd. Production Technology Laboratory (56) Reference JP-A-1-28533 (JP, A) Kaihei 1-91007 (JP, A) JP-A-63-68805 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01M 11/00-11/08 G01N 21/84- 21/958

Claims (3)

(57) [Claims] 1. An optical fiber core measuring device for measuring a structure, a dimension, and a fiber twist angle by capturing an image of an optical fiber from a camera and performing image processing on the image.
Light irradiation means for irradiating parallel transmitted light in a direction substantially perpendicular to the optical axis in the longitudinal direction of the optical fiber to be observed, and arranged so as to face the light emission port of the light irradiation means so as to sandwich the optical fiber. And a camera drive unit that moves the camera in the vertical and horizontal directions, a control device that controls the movement of the camera drive unit, and an image processing device that processes an image . Take that brightness distribution,
The intensity distribution is paired with the intensity level of the background without the optical fiber.
Binarization at a predetermined brightness level
In the binary data indicating the dark part of the bell, the
Calculate the number of pixels in the dark area only in the rad area, and calculate the number of pixels in the dark area.
The width of the dark part of the clad is calculated from the
Calculate the distance between the camera and the optical fiber from the section width,
The camera drive is used to focus the optical fiber.
An optical fiber core measuring device characterized by moving a camera . 2. An optical axis in the longitudinal direction of an optical fiber to be observed in an optical fiber core measuring device for measuring the structure, dimension and fiber twist angle by capturing an image of the optical fiber from a camera and performing image processing. A light irradiating means for irradiating parallel transmitted light in a direction substantially at right angles to the camera, a camera arranged to face the light irradiating means so as to sandwich the optical fiber, and the camera is moved vertically and horizontally. comprising a camera driver, a control device for controlling the movement of the camera driver, and an image processing apparatus for processing an image, the
The brightness distribution is taken by the image processing device, and the brightness distribution is calculated.
The predetermined level for the brightness level of the background without the optical fiber
Binarization at the brightness level and the dark part of the brightness level
In the binary data showing the
Calculate the number of pixels in the dark area, and calculate the pixel number from the number of pixels in the dark area.
Obtain the dark area width of the rud part,
Driving the camera by calculating the distance between the camera and the optical fiber
Part moves the camera so that the optical fiber is in focus.
After moving , compare the brightness distribution around the focus,
An optical fiber core measuring device characterized by finding a point at which the brightness is maximized. 3. The image data is obtained by extracting a certain line in a direction substantially perpendicular to the longitudinal direction of the image of the optical fiber, taking the luminance distribution of the line, and binarizing the dark part in the dark part of the optical fiber by a certain slice level. The optical fiber core measuring device according to claim 1 or 2, which is data obtained by calculating the number of pixels in the dark portion of only the clad portion and taking the average of the two portions.