JP4785041B2 - Method for measuring the outer diameter of the linear object to be measured - Google Patents

Description

  The present invention relates to a method for measuring the outer diameter of a measured linear body such as an optical fiber using a television camera.

Various methods are used to connect optical fibers, and one of them is a fusion splicing method in which mutual ends of optical fibers are softened by heating.
FIG. 7 shows an example of the optical fiber fusion splicing device 1. In FIG. 7, 2 is an optical fiber connected to each other, 3 is a V-groove base, 4 is a clamp, 5 is an optical fiber gripping mechanism comprising a V-groove base 3 and a clamp 4, etc., 6 is a TV camera, and 7 is a TV signal monitor. 8 is an arithmetic processing unit comprising a CPU, 9 is a discharge electrode, and 10 is a projector.

  The left and right optical fibers 2 are respectively placed on the V-groove portion of the V-groove base 3 and are pressed by the clamp 4 and the V-groove base 3. The two television cameras 6 and 6 respectively image the butted portions 2 ′ of the two optical fibers 2 from two directions of the image observation optical axis XY that are perpendicular to each other. The signal obtained by the TV camera 6 is sent to the TV signal monitor device 7 for image display. The image signal obtained by the television camera 6 is sent to the arithmetic processing unit 8. The signal calculated by the arithmetic processing unit 8 is transmitted to left and right optical fiber moving mechanisms (not shown), and the optical fiber gripping mechanism 5 is moved in the X and Y directions so that the axes of the optical fibers coincide with each other. Thereby, it arrange | positions between the discharge electrodes 9 * 9 of the said butt | matching part 2 'in the state in which the axial center of both the optical fibers 2 corresponded. After that, both ends of the optical fibers 2 are cleaned by a cleaning discharge, and then are advanced in the direction of the axis Z of both optical fibers 2 and are fusion-bonded by a discharge arc generated in the discharge electrodes. The

  FIG. 8 shows the flow of each process in a general fusion splicer. The cleaning discharge is performed in step S6 in FIG. 8, and the discharge arc for fusion is performed in step S13.

Generally used optical fibers have a cladding outer diameter of about 80 μm to 300 μm, and these optical fibers are fusion spliced.
At this time, in order to satisfactorily perform the cleaning discharge and fusion splicing of the optical fibers 2 and 2, it is important to appropriately perform the amount of heat applied to the optical fibers 2 and 2. At this time, it is known that the optimum amount of heat for heating and melting the optical fibers 2 and 2 depends on the diameter of the optical fibers 2 and 2. (For example, Patent Document 1)

  That is, when the optical fiber 2 is thin, the discharge arc current is reduced, and when the optical fiber 2 is thick, the discharge arc current is increased. I must. For example, according to Patent Document 1, it is necessary to correct the discharge arc current (mA) by an optimum discharge arc discharge with a diameter of 125 μmφ + 2.154 × (diameter of optical fiber (μm) −125). ing.

For this reason, when correcting the discharge arc current, it is necessary to know in advance how much the diameter of the optical fiber 2 to be connected is.
Conventionally, in order to measure the diameter of the optical fiber, for example, prior to the fusion splicing, the one optical camera 2 is imaged by the one television camera 6 to obtain the outline of the optical fiber 2, and the diameter of the optical fiber 2 is measured Was.

JP 2002-277671 A

  However, in the conventional method for obtaining the outline of the optical fiber, the value changes due to the focus adjustment of the magnifying lens 6 ′, and the outer diameter of the optical fiber cannot be measured accurately.

The present invention has been made in view of the above points, and by irradiating the optical fiber to be measured from the opposite side of the TV camera, the optical fiber to be measured is appropriately focused by the TV camera. by imaging without requiring to calculate the total value K1 of the luminance of each pixel that put on a specific line perpendicular to the axis of the optical fiber captured, are calculated in advance measured, not the optical fiber exist the difference between the luminance total value K2 for each pixel, obtains a difference between the total value K1 the calculated, and the luminance total value K2 and total value K1 the calculated prior Symbol particular line on time, the brightness by comparing the difference between the total luminance of the on a particular line which has been previously measured is calculated by the cladding each diameter of total value K2 and the optical fiber, based on the values approximating or matching, the said measurement target light And obtaining the outer diameter of Aiba.
According to another aspect of the present invention, a specific line perpendicular to the axis of the optical fiber is obtained by capturing an image of an optical fiber to be measured without requiring focus adjustment by a TV camera in which background luminance is set to be constant in advance. The brightness total value K1 of each pixel in the above is calculated, and the total value K1 is compared with the brightness sum of the specific line that is calculated in advance for each cladding diameter in the background brightness, and the total value K1 The outer diameter of the optical fiber to be measured is obtained from the luminance sum for each cladding diameter that approximates or coincides with.

  According to any of the above-described inventions, the present application has an effect that the outer diameter of the optical fiber can be accurately measured even if the focus adjustment is not appropriate.

  Hereinafter, the present invention will be described in more detail. FIG. 1 shows an example of an image of a TV signal monitor device at the time of fusion splicing. In the vicinity of the center of FIG. 1, an image from a television camera that images the optical fibers 2 and 2 from the image observation optical axis X direction is displayed. An image from a TV camera that captured the image is displayed. An arithmetic processing unit that processes an image signal from a television camera is adjusted in advance so that the background luminance of an image without the optical fiber 2 is in the vicinity of the middle. For example, the brightness and contrast are adjusted so that the darkest brightness is 0, the brightest brightness is 255, and the background brightness of a portion where no optical fiber is present is 110.

  When the optical fiber 2 is picked up by a television camera, the clad or cut surface of the optical fiber is displayed black (luminance value = 0). For this reason, on the specific line orthogonal to the axis of the optical fiber 2, a luminance difference is generated depending on the presence or absence of the optical fiber. If the background luminance is 110 and the luminance value of the clad of the optical fiber is 0, a luminance difference of 110 per pixel is produced at the location where the clad exists in the line where the optical fiber 2 exists.

  An arithmetic processing unit that processes an image signal from a television camera grasps and puts in advance a total value (integral value) of one line when no optical fiber is present. For example, in FIG. 1, if the background brightness is 110 and the number of pixels in the measurement range in the direction orthogonal to the optical fiber 2 is 400, the background brightness total value K2 is 44000 due to 110 × 400.

  In order for the arithmetic processing unit to measure the outer diameter of the optical fiber, the arithmetic processing unit drives the optical fiber moving mechanism to move the optical fiber gripping mechanism, and the end of the optical fiber 2 moves to the predetermined specific line. The total value K1 of the luminance on a specific line when the optical fiber is present is calculated. Therefore, the outer diameter of the optical fiber is obtained as follows based on the value of the total value K1 or the difference between the total value K2 and the total value K1.

2 to 4 are characteristic diagrams showing changes in luminance on the specific line when the outer diameter of the optical fiber is 125 μmφ when the focal length of the objective lens is a predetermined value. These characteristic diagrams show changes in luminance when imaging is performed by changing the focus adjustment of the objective lens of the television camera, and it is shown that the luminance pattern changes variously by adjusting the focus. Here, in the present invention, when the bright area near the center is the beam diameter, the dark area outside the outer diameter is the cladding outer diameter,
(Beam diameter / cladding outer diameter) × 100
Is defined as the focus width. That is, FIG. 2 shows that the focus width is 15%, FIG. 3 shows that the focus width is 30%, and FIG. 4 shows that it is 50%. Here, it is understood that when the focus width is small, the cladding outer diameter is smaller, the luminance in the cladding outer diameter region is smaller, and the luminance in the beam diameter region is larger than that with a larger value. . Note that the threshold value in the figure is determined by a discriminant analysis method. There are many other determination methods such as the p-tile method, the mode method, and the differential histogram method, but the results obtained by using any method are substantially the same.

Here, when the total value of the luminance within the measurement range in the specific line is calculated, the total value K1 is about 30000 in any focus width.
Further, when the above-described change in luminance was examined by changing the diameter of the optical fiber, the focus width with respect to the outer diameter of the clad variously changed according to the change of the optical fiber, as shown in FIG. The total luminance value is a substantially coincident point as indicated by a circle in FIG. 5 (the three points within the circle indicate the total value K1 when the focus widths are different). Therefore, the total luminance value K1 on the specific line is the same as long as the outer diameter of the optical fiber is the same.
Therefore, the diameter of the optical fiber can be obtained by obtaining the total value K1 by adjusting the background luminance to be constant in advance.
Further, the difference between the total brightness value K2 of each pixel on the specific line when the optical fiber measured in advance is not present and the measured total value K1 is obtained, and the total value K2 is also obtained from the difference value. Is constant, the diameter of the optical fiber can be obtained in the same manner.

  The above measurement shows the case where the focal length of the objective lens, that is, the magnification of the image formed on the television camera is a predetermined value. If this focal length is different, the subject (optical fiber) per pixel is different. Since the size changes, when using an objective lens with a changing focal length such as a zoom lens, the brightness change for each focal length is grasped.

  FIG. 6 shows the total luminance of each optical fiber having an optical fiber diameter of 60 μmφ, 80 μmφ, 125 μmφ, 160 μmφ, and 200 μmφ with a background luminance of 110. As is apparent from this figure, the clad diameter of the optical fiber can be measured by determining the difference between the luminance sum or background luminance sum and the luminance sum (Δn, n = integer). In addition, since this measurement can measure the cladding diameter of the optical fiber even if the focus adjustment of the objective lens is not constant, the measurement can be easily performed.

Explanatory drawing which shows the television image in the time of one Example of this invention. The image pattern of the optical fiber in one Embodiment of this invention. The image pattern of the optical fiber in other embodiment of this invention. The image pattern of the optical fiber in other embodiment of this invention. The characteristic view in embodiment of this invention. The characteristic view in other embodiment of this invention. The conceptual diagram of the fusion splicer in an example of the past. The process flowchart figure which shows the process of a general fusion splicer.

Explanation of symbols

2 Optical fiber K1 Aggregate value K2 Aggregate value

Claims (4)

By irradiating light from the opposite side of the TV camera to the optical fiber to be measured, the optical fiber to be measured is imaged without requiring proper focus adjustment by the TV camera , and the imaged optical fiber is captured. calculating a total value K1 of the luminance of each pixel that put on a particular line perpendicular to the axis,
Calculating a difference between the luminance total value K2 of each pixel on the specific line and the calculated total value K1 when the optical fiber is not present and calculated in advance;
The difference between the luminance total value K2 and the calculated total value K1 is compared with the difference between the luminance total value K2 and the luminance total of a specific line for each cladding diameter of the optical fiber calculated in advance. An outer diameter measurement method for an optical fiber , wherein the outer diameter of the optical fiber to be measured is obtained based on an approximate or coincident value . The optical fiber to be measured is irradiated from the opposite side of the TV camera, and the optical fiber to be measured is imaged without requiring proper focus adjustment by the TV camera in which the background luminance is set to be constant in advance. And calculating the total value K1 of the luminance of each pixel on a specific line orthogonal to the axis of the optical fiber,
The total value K1 is compared with the total luminance of the specific line that is measured and calculated in advance for each cladding diameter in the background luminance,
A method for measuring an outer diameter of an optical fiber, wherein the outer diameter of the optical fiber to be measured is obtained from the luminance sum for each cladding diameter that approximates or coincides with the total value K1 . 3. The outer diameter measurement method according to claim 1, wherein the background luminance is adjusted in advance so that a background luminance of an image in which no optical fiber is present is in the vicinity of an intermediate value in a luminance range. Advancing the optical fiber in the z-axis direction, arriving at the primary set line and stopping;
  A cleaning discharge step;
  Focusing, and
  Advancing the optical fiber in the z-axis direction, arriving at the secondary set line and stopping;
  Core alignment process,
  Discharging according to the diameter of the optical fiber measured by the method according to any one of claims 1 to 3,
  Measuring and displaying estimated losses;
An optical fiber fusion method including:

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