Transparent tube manufacturing method and transparent tube measuring device

Abstract

To accurately measure at least one of an inner diameter and a refractive index of a transparent tube.SOLUTION: A measuring process for measuring tube glass Gt as a transparent tube comprises the steps of: emitting a parallel beam L1 to cross a tube length direction of the tube glass Gt; and imaging, by an imaging part 9, a straight traveling light beam M0, traveling outside the tube glass Gt, and a transmitted light beam M1, transmitted in the tube glass Gt, of the parallel light beam L1. The transmitted light beam M1 includes a primary refracted light beam M11 having an optical axis parallel with the straight traveling light beam M0 after being reflected once from an inner peripheral surface Gb of the tube glass Gt and a secondary refracted light beam M12 having an optical axis parallel with the straight traveling light beam M0 after being reflected twice from the inner peripheral surface Gb of the tube glass Gt. In a measuring process, a peak position of the straight traveling light beam M0 in contact with an outer peripheral surface Ga of the tube glass Gt, a peak position of the primary refracted light beam M11, and a peak position of the secondary refracted light beam M12 are found from imaging data of the imaging part 9, respectively, and at least one of the inner diameter and refractive index of the tube glass Gt is calculated based upon those three peak positions.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a transparent tube and a measuring device for a transparent tube. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a redraw method has been used as a method for producing a glass tube, in which a tubular glass base material is drawn while being heated to obtain a glass tube.

[0003] The inner diameter of this type of glass tube is used to control the quality of the glass tube. For example, Patent Document 1 discloses a method for measuring the inner diameter of a transparent tube, such as a glass tube, by irradiating it with a specific light beam. Specifically, this document first determines the outer diameter of the transparent tube from a straight light beam passing through the outside of the transparent tube. Next, the peak position of one type of light beam reflected by the inner surface of the transparent tube (either refracted light reflected once, twice, or three times) is determined from the transmitted light beams passing through the transparent tube. The inner diameter of the transparent tube is then determined using this peak position, the outer diameter of the transparent tube, and the known refractive index of the transparent tube. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-84172 Summary of the Invention [Problem to be solved by the invention]

[0005] In the method disclosed in Patent Document 1, the refractive index of the transparent tube is essential to determine the inner diameter of the transparent tube. In this document, the refractive index of the transparent tube is set to a known constant value that is measured in advance using a different method.

[0006] However, for example, when continuously molding a long transparent tube, if the components of the transparent tube change, the refractive index of the transparent tube may also change. Therefore, if the inner diameter of the transparent tube is determined assuming the refractive index of the transparent tube to be a known constant value, there is a problem that the inner diameter of the transparent tube cannot be measured accurately.

[0007] In addition, in situations where the refractive index of the transparent tube fluctuates as described above, it may be desirable to accurately measure the refractive index of the transparent tube, as well as the inner diameter of the transparent tube, in order to control the quality of the transparent tube.

[0008] An object of the present invention is to accurately measure at least one of the inner diameter and refractive index of a transparent tube. [Means for solving the problem]

[0009] (1) The present invention, which was invented to solve the above-mentioned problems, is a method for manufacturing a transparent tube, comprising a preparation step for preparing a transparent tube and a measurement step for measuring the transparent tube. The measurement step comprises a step of irradiating parallel light rays across the transparent tube in the tube length direction, and a step of imaging, with an imaging unit, straight light rays that pass through the outside of the transparent tube and transmitted light rays that pass through the transparent tube, among the parallel light rays. The transmitted light rays include a first refracted light ray that has an optical axis parallel to the straight light ray after being reflected m times on the inner surface of the transparent tube, and a second refracted light ray that has an optical axis parallel to the straight light ray after being reflected n times on the inner surface of the transparent tube, where m and n are two different natural numbers. The measurement step is characterized in that the peak position of the straight light ray that contacts the outer surface of the transparent tube, the peak position of the first refracted light ray, and the peak position of the second refracted light ray are each determined from the imaging data from the imaging unit, and at least one of the inner diameter and refractive index of the transparent tube is calculated based on these three peak positions.

[0010] In this way, a first relational expression showing the relationship between the inner diameter, outer diameter, and refractive index of the transparent tube can be derived based on the law of refraction from the peak positions of the straight ray of light tangent to the outer surface of the transparent tube and the first refractive index ray. Similarly, a second relational expression showing the relationship between the inner diameter, outer diameter, and refractive index of the transparent tube can be derived based on the law of refraction from the peak positions of the straight ray of light tangent to the outer surface of the transparent tube and the second refractive index ray. Here, the outer diameter of the transparent tube can be determined from the peak position of the straight ray of light tangent to the outer surface of the transparent tube. In other words, two equations (first relational expression and second relational expression) showing the relationship between the inner diameter and refractive index of the transparent tube can be obtained for two unknown quantities, the inner diameter and refractive index of the transparent tube, so that the unknown inner diameter and / or refractive index of the transparent tube can be calculated. Therefore, by determining the peak positions of the straight ray of light tangent to the outer surface of the transparent tube, the peak position of the first refracted ray, and the peak position of the second refracted ray, respectively, at least one of the inner diameter and refractive index of the transparent tube can be accurately calculated based on these three peak positions.

[0011] (2) In the configuration of (1) above, in the measurement process, the inner diameter and refractive index of the transparent tube may be calculated based on the peak position of the straight ray that contacts the outer surface of the transparent tube, the peak position of the first refracted ray, and the peak position of the second refracted ray.

[0012] In this way, the quality of the transparent tube can be evaluated using the inner diameter and refractive index of the transparent tube, thereby enabling the quality of the transparent tube to be evaluated more accurately.

[0013] (3) In the configuration of (1) or (2) above, it is preferable that the first refracted ray is a ray having an optical axis parallel to the straight ray after being reflected once on the inner surface of the transparent tube, and the second refracted ray is a ray having an optical axis parallel to the straight ray after being reflected twice on the inner surface of the transparent tube.

[0014] The peak intensity of the refracted light beam reflected on the inner surface of the transparent tube decreases as the number of reflections on the inner surface of the transparent tube increases. In other words, as described above, if the first refracted light beam is defined as a light beam (m=1) that has an optical axis parallel to the straight-traveling light beam after being reflected once on the inner surface of the transparent tube, and the second refracted light beam is defined as a light beam (n=2) that has an optical axis parallel to the straight-traveling light beam after being reflected twice on the inner surface of the transparent tube, the peak intensity of the refracted light beam becomes sufficiently large, improving the measurement accuracy of the peak position. As a result, the calculation accuracy of the inner diameter and / or refractive index of the transparent tube is improved.

[0015] (4) In any of the configurations (1) to (3), the transparent tube may be a glass tube.

[0016] In this way, it becomes possible to stably supply glass tubes that meet strict dimensional standards, even in fields where dimensional standards are strict, such as ferrules for optical communication connectors, capillaries for holding optical fibers, and glass tubes for optical communication devices.

[0017] (5) In the above configuration (4), the preparation step may include a forming step of forming the glass tube in a forming unit.

[0018] (6) In the above configuration (5), it is preferable that the measuring step measures the glass tube connected to the forming section on the production line.

[0019] In this way, the measurement of the glass tube can be carried out on the glass tube production line, that is, in an online manner.

[0020] (7) The present invention, which was invented to solve the above-mentioned problems, is a measuring device for transparent tubes, comprising an irradiation unit that irradiates parallel light rays across the length of the transparent tube, an imaging unit that images, among the parallel light rays, straight light rays that pass through the outside of the transparent tube and transmitted light rays that pass through the transparent tube, and a measurement unit that measures the transparent tube based on the imaging data of the imaging unit, wherein the transmitted light rays include a first refracted light ray that has an optical axis parallel to the straight light ray after being reflected m times on the inner surface of the transparent tube, and a second refracted light ray that has an optical axis parallel to the straight light ray after being reflected n times on the inner surface of the transparent tube, where m and n are two different natural numbers, and the measurement unit is configured to determine, from the imaging data, the peak position of the straight light ray that contacts the outer surface of the transparent tube, the peak position of the first refracted light ray, and the peak position of the second refracted light ray, and to calculate at least one of the inner diameter and refractive index of the transparent tube based on these three peak positions.

[0021] In this way, the same effects as those of the corresponding configurations already described can be obtained. [Effects of the Invention]

[0022] According to the present invention, at least one of the inner diameter and the refractive index of a transparent tube can be accurately measured. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a diagram showing a manufacturing apparatus used in a method for manufacturing a transparent tube according to the present embodiment. FIG. [Figure 2] 2 is a cross-sectional view taken along the line AA in FIG. 1, showing a measuring device for a transparent tube according to the present embodiment. FIG. [Figure 3] FIG. 2 is a diagram illustrating an example of photographed data. [Figure 4] FIG. 1 is a diagram showing the geometric relationship between a glass tube and a straight ray of light that contacts the outer peripheral surface of the glass tube. [Figure 5] FIG. 1 is a diagram illustrating the geometric relationship between a glass tube and a primary refracted ray. [Figure 6] FIG. 1 is a diagram illustrating the geometric relationship between a glass tube and secondary refracted light rays. [Figure 7] FIG. 1 is a diagram illustrating the geometric relationship between a glass tube and third-order refracted light rays. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, a transparent tube manufacturing method and a transparent tube measuring device according to an embodiment of the present invention will be described with reference to the drawings. Note that XYZ in the drawings represent a Cartesian coordinate system. The X and Y directions are horizontal, and the Z direction is vertical.

[0025] As shown in FIG. 1, a manufacturing apparatus 1 used in the method for manufacturing a transparent tube according to this embodiment is an apparatus for manufacturing a glass tube G as a transparent tube by using a redraw method.

[0026] The manufacturing apparatus 1 includes a feed mechanism 2, a heating furnace 3, a tension roller 4, and a cutter 5, in this order from above.

[0027] The feeding mechanism 2 is a device that supports the tubular glass base material Gm and feeds the glass base material Gm downward at a predetermined speed.

[0028] The heating furnace 3 is a device that uses a heater 3a below the feeding mechanism 2 to heat and soften the glass base material Gm that is fed as the feeding mechanism 2 descends, and functions as a forming section that forms a glass tube.

[0029] The pulling roller 4 is a device that pulls the long tube glass Gt, which is continuous with the glass preform Gm softened in the heating furnace 3, below the heating furnace 3. This allows the softened glass preform Gm to be drawn and efficiently thinned into a thin tube. The drawing speed of the glass preform Gm is adjusted, for example, by the feed mechanism 2 and / or the pulling roller 4.

[0030] The cutter 5 is a device that cuts the long glass tube Gt to a predetermined length below the tension roller 4. In this way, short glass tubes G are successively obtained from the long glass tube Gt.

[0031] The manufacturing apparatus 1 further includes a measuring device 6 that measures the glass tube Gt between the heating furnace 3 and the tension rollers 4. In this embodiment, an online measurement method in which the measuring device 6 is used on the glass tube Gt manufacturing line is exemplified, but the measuring device 6 can also be applied to an offline measurement method used outside the glass tube Gt manufacturing line.

[0032] As shown in Figure 2, the measuring device 6 includes an irradiation unit 7 that irradiates parallel light rays L1 across the tube length direction of the tube glass Gt, a telecentric optical system 8 that receives, of the parallel light rays L1, straight light rays M0 that pass through the outside of the tube glass Gt and transmitted light rays M1 that pass through the tube glass Gt, an imaging unit 9 that outputs photographic data by inputting the straight light rays M0 and transmitted light rays M1 focused by the telecentric optical system 8, and a measuring unit 10 that measures the outer diameter, inner diameter, and refractive index of the tube glass Gt based on the photographic data.

[0033] In this embodiment, the irradiation unit 7 and the telecentric optical system 8 are arranged to face each other on the same straight line extending in the X direction, with a glass tube Gt placed in the atmosphere therebetween.

[0034] The irradiation unit 7 includes a light source 11 such as an LED, and a collimator lens 12 that generates parallel light beams L1 that propagate along a plane that crosses the tube glass Gt from light beams (diffused light beams) L0 emitted from the light source 11. The optical axis of the parallel light beams L1 is parallel to the X direction. In this embodiment, the light source 11 and the collimator lens 12 are housed in a housing 13.

[0035] The irradiation unit 7 generates a group of parallel light beams L1 that are simultaneously present across the entire transverse plane including the glass tube Gt. In other words, the irradiation unit 7 does not include a scanning mirror such as a polygon mirror for scanning the light beams. The plane that crosses the glass tube Gt and through which the parallel light beams L1 propagate is preferably a plane that is perpendicular to the tube axis of the glass tube Gt.

[0036] The telecentric optical system 8 includes an object-side lens 14, an image-side lens 15, and an aperture 16 disposed at a focal position F of both the object-side lens 14 and the image-side lens 15. That is, in this embodiment, the telecentric optical system 8 is a so-called double-telecentric optical system. As a result, even if the distance WD between the tube glass Gt and the telecentric optical system 8 (strictly speaking, the distance WD between the center position of the tube glass Gt and the center position of the object-side lens 14) changes, the size of the image of the tube glass Gt does not substantially change. In this embodiment, the telecentric optical system 8 is housed in a housing 17.

[0037] 2, the lens configuration (number of lenses, lens shape, etc.) of each of the lenses 14 and 15 is shown in a simplified manner. The telecentric optical system 8 includes an object-side lens 14 and a diaphragm 16 arranged at a focal position F of the object-side lens 14, and may be a so-called object-side telecentric optical system in which the image-side lens does not have telecentric performance.

[0038] The imaging unit 9 is an imaging element that measures the luminance (light intensity level) at the pixel position when the straight light beam M0 and the transmitted light beam M1 collected by the telecentric optical system 8 are input. The imaging unit 9 outputs imaging data having multiple peaks (signal peaks) P0, P10 to P13 corresponding to the luminance of the measured light beams, as shown in FIG. 3, for example. The number of pixels of the imaging unit 9 and the performance such as the lens magnification of the lenses 14 and 15 included in the telecentric optical system 8 are selected according to the dimensions of the tube glass Gt and the required accuracy.

[0039] The measurement unit 10 determines the peak positions of peaks P0, P11 to P13 included in the imaging data, and measures (calculates) the outer diameter, inner diameter, and refractive index of the glass tube Gt based on these peak positions. Here, in this embodiment, the outer diameter and inner diameter of the glass tube Gt refer to diameters, but they may also refer to radii. The measurement unit 10 is configured by a computing device such as a personal computer or tablet terminal, and is connected to the imaging unit 9 by wire or wirelessly.

[0040] Next, a method for manufacturing a transparent tube using the manufacturing apparatus 1 configured as above will be described.

[0041] The manufacturing method according to this embodiment includes a preparation step of preparing a glass tube Gt as a transparent tube, and a measurement step of measuring the glass tube Gt.

[0042] The preparation process includes a forming process of forming a glass tube Gt from a glass preform Gm by a redraw method. Specifically, the glass preform Gm is heated and softened in a heating furnace 3 while being fed downward at a predetermined speed by a feeding mechanism 2. Thereafter, the softened glass preform Gm is drawn downward by a tension roller 4 to form a glass tube Gt. The glass tube Gt is cut into predetermined lengths by a cutter 5, and glass tubes G that become products are sequentially obtained.

[0043] The glass tube G is used, for example, as a ferrule for an optical communication connector, a capillary for holding an optical fiber, a glass tube for an optical communication device, and the like.

[0044] The outer diameter (diameter) of the glass tube Gt is preferably 0.1 to 10.0 mm, more preferably 0.2 to 7.0 mm, and even more preferably 0.3 to 5.0 mm. Meanwhile, the inner diameter (diameter) of the glass tube Gt is preferably 0.01 to 8.0 mm, more preferably 0.015 to 5.0 mm, and even more preferably 0.02 to 3.5 mm. The outer and inner diameters of the glass tube Gt before cutting are substantially the same as the outer and inner diameters of the glass tube Gt after cutting.

[0045] In the measurement process, the glass tube Gt connected to the glass preform Gm located in the heating furnace 3 as a forming unit is measured on the production line. That is, the measurement process is performed online. In the measurement process, the glass tube Gt located between the heating furnace 3 and the pulling roller 4 is measured. This is because the glass tube Gt is measured at a position close to the heating furnace 3 and the measurement results are quickly fed back to adjust various parameters of the manufacturing conditions. Note that the measurement process may also be performed on the glass tube Gt located between the pulling roller 4 and the cutter 5.

[0046] 2, the measurement process includes the steps of using an irradiation unit 7 to irradiate the glass tube Gt with a parallel light beam L1 across the tube length direction, receiving, with a telecentric optical system 8, a straight light beam M0 that passes through the outside of the glass tube Gt and a transmitted light beam M1 that is transmitted through the glass tube Gt, inputting the straight light beam M0 and the transmitted light beam M1 that are collected by the telecentric optical system 8 into an imaging unit 9 and outputting photographed data, and measuring the outer diameter, inner diameter, and refractive index of the glass tube Gt from the photographed data using a measurement unit 10. The telecentric optical system 8 guides only light beams having optical axes parallel to the parallel light beam L1 to the imaging unit 9.

[0047] The straight light beam M0 is not affected by the tube glass Gt and therefore maintains an optical axis parallel to the parallel light beam L1. That is, the straight light beam M0 passes through the telecentric optical system 8 and is received by the imaging unit 9.

[0048] The transmitted light beam M1 travels straight through the hollow portion of the glass tube Gt without being refracted at the outer peripheral surface Ga or the inner peripheral surface Gb of the glass tube Gt, and includes a non-refracted light beam M10 having an optical axis parallel to the parallel light beam L1. In other words, the non-refracted light beam M10 is received by the imaging unit 9 via the telecentric optical system 8.

[0049] The transmitted light beam M1 enters the glass tube Gt, undergoes total reflection at the inner surface Gb, and exits, again including refracted light beams M11-M13 whose optical axes are parallel to the parallel light beam L1. Specifically, the refracted light beam M11 is a first-order refracted light beam that is reflected once at the inner surface Gb of the glass tube Gt. The refracted light beam M12 is a second-order refracted light beam that is reflected twice at the inner surface Gb of the glass tube Gt after being reflected once at the outer surface Ga of the glass tube Gt. The refracted light beam M13 is a third-order refracted light beam that is reflected three times at the inner surface Gb of the glass tube Gt after being reflected twice at the outer surface Ga of the glass tube Gt. These refracted light beams M11-M13 are received by the imaging unit 9 via the telecentric optical system 8.

[0050] The transmitted light beam M1 is refracted or reflected by the outer peripheral surface Ga or the inner peripheral surface Gb of the glass tube Gt and exits to the outside, but includes light beams that no longer have an optical axis parallel to the parallel light beam L1 before irradiating the glass tube Gt. However, these light beams are blocked by, for example, the aperture 16 of the telecentric optical system 8 and are not received by the imaging unit 9.

[0051] 3, the imaging data of the imaging unit 9 mainly includes a peak P0 of the straight ray M0, a peak P10 of the unrefracted ray M10, a peak P11 of the primary refracted ray M11, a peak P12 of the secondary refracted ray M12, and a peak P13 of the tertiary refracted ray M13. The straight ray M0, the primary refracted ray M11, the secondary refracted ray M12, and the tertiary refracted ray M13 occur in a first semi-cylindrical portion Gt1 (the upper half in the figure) and a second semi-cylindrical portion Gt2 (the lower half in the figure) of the glass tube Gt, which are divided into two by the unrefracted ray M10. Therefore, the peaks P0 and P11-P13 of the straight ray M0 and the refracted rays M11-M13 form pairs at positions that are approximately symmetrical with respect to the peak P10 of the unrefracted ray M10. The intensities of peaks P11 to P13 of the refracted rays M11 to M13 tend to decrease in the order of the primary refracted ray M11, the secondary refracted ray M12, and the tertiary refracted ray M13 (P11>P12>P13).

[0052] Then, two inter-peak distances selected from the inter-peak distance h1 between the pair of peaks P11 of the primary refracted light ray M11, the inter-peak distance h2 between the pair of peaks P12 of the secondary refracted light ray M12, and the inter-peak distance h3 between the pair of peaks P13 of the tertiary refracted light ray M13, and the inter-peak distance h0 between the peaks P0 of the straight ray M0 that contacts the outer surface of the glass tube Gt (strictly speaking, the rising portion of the peak P0) are calculated from the imaging data. Then, the outer diameter, inner diameter, and refractive index of the glass tube Gt are measured (calculated) based on the three inter-peak distances (e.g., h0, h1, h2). Here, the "inter-peak distance" refers to the distance between one peak position and the other peak position of a pair of peaks.

[0053] A specific measurement method will be described below, assuming that the outer diameter (diameter) of the glass tube Gt is D, the inner diameter (diameter) is r, and the refractive index is n.

[0054] 4, the peak-to-peak distance h0 of the straight light beam M0 that contacts the outer peripheral surface of the glass tube Gt is equal to the outer diameter D of the glass tube Gt. In other words, the outer diameter of the glass tube Gt can be calculated from the peak-to-peak distance h0.

[0055] On the other hand, as shown in FIG. 5, if the incident angle of the primary refracted ray M11 on the outer peripheral surface Ga of the tube glass Gt is θ11 and the refraction angle is θ12, the following relational expression is obtained from the geometrical relationship and the law of refraction. h1 / 2=D / 2×sin(θ11)…(1) sin(θ11)=nsin(θ12)…(2) r / 2×cos(α1)=D / 2×sin(θ12)…(3) α1=θ11-θ12…(4)

[0056] From these equations (1) to (4), the following equation (5) is obtained. r=h1 / [ncos{Arcsin(h1 / D) -Arcsin(h1 / (nD))}]…(5)

[0057] As shown in FIG. 6, when the incident angle of the secondary refracted ray M12 on the outer peripheral surface Ga of the glass tube Gt is θ21 and the refraction angle is θ22, the following relational expression is obtained from the geometrical relationship and the law of refraction. h2 / 2=D / 2×sin(θ21)…(6) sin(θ21)=nsin(θ22)…(7) r / 2×sin(α2)=D / 2×sin(θ22)…(8) 2(α2-θ22)+θ21=90°…(9)

[0058] From these equations (6) to (9), the following equation (10) is obtained. r=h2 / [nsin{π / 4-1 / 2×Arcsin(h2 / D) +Arcsin(h2 / (nD))}]…(10)

[0059] Furthermore, as shown in FIG. 7, for the third-order refracted light ray M13, if the incident angle on the outer peripheral surface Ga of the glass tube Gt is θ31 and the refraction angle is θ32, the following relational expression is obtained from the geometrical relationship and the law of refraction. h3 / 2=D / 2×sin(θ31)…(11) sin(θ31)=nsin(θ32)…(12) r / 2×sin(α3)=D / 2×sin(θ32)…(13) 3(α3-θ32)+θ31=90°…(14)

[0060] From these equations (11) to (14), the following equation (15) is obtained. r=h3 / [nsin{π / 6-1 / 3×Arcsin(h3 / D) +Arcsin(h3 / (nD))}]…(15)

[0061] Here, D (= h0), h1 to h3 are known values ​​obtained from the imaging data. Therefore, r and n can be calculated by solving any two equations selected from the above equations (5), (10), and (15) for the unknowns r and n. This allows the inner diameter and refractive index of the glass tube Gt to be determined in addition to the outer diameter. In other words, the inner diameter of the glass tube Gt can be measured with high accuracy without being affected by fluctuations in the refractive index. Furthermore, as long as the ambient air conditions are constant, the refractive index of the glass tube Gt can also be measured with high accuracy even if the components of the glass tube Gt fluctuate. The refractive index can be used to calculate the density of the glass tube Gt.

[0062] From the viewpoint of measuring the inner diameter and refractive index of the glass tube Gt with high accuracy, it is preferable to calculate r and n using the primary refracted light beam M11 and the secondary refracted light beam M12, which have large peak intensities. In other words, it is preferable to calculate r and n by solving the above two equations (5) and (10) simultaneously.

[0063] When the measurement unit 10 automatically calculates the inner diameter r of the glass tube Gt, it uses a polynomial related to the inner diameter r, for example, by solving two simultaneous equations selected from (5), (10), and (15) and eliminating the refractive index n in advance. Similarly, when the measurement unit 10 automatically calculates the refractive index n of the glass tube Gt, it uses a polynomial related to the refractive index n, for example, by solving two simultaneous equations selected from (5), (10), and (15) and eliminating the inner diameter r in advance.

[0064] The outer diameter, inner diameter and refractive index of the glass tube Gt determined by the above method are fed back to the manufacturing conditions of the glass tube Gt, and various parameters of the manufacturing conditions (for example, drawing speed) are adjusted as necessary.

[0065] Although the manufacturing method of a glass article according to an embodiment of the present invention has been described, the embodiment of the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention.

[0066] In the above embodiment, the inner diameter and refractive index of a glass tube as a transparent tube are measured, but it is also possible to measure only one of the inner diameter and refractive index. However, since the inner diameter of a glass tube is an important parameter for controlling the quality of the glass tube, it is preferable to measure at least the inner diameter.

[0067] In the above embodiment, the transmitted light beam includes a first refracted light beam having an optical axis parallel to the straight light beam after being reflected once by the inner surface of the transparent tube, a second refracted light beam having an optical axis parallel to the straight light beam after being reflected twice by the inner surface of the transparent tube, and a third refracted light beam having an optical axis parallel to the straight light beam after being reflected three times by the inner surface of the transparent tube. However, the present invention is not limited to this. The transmitted light beam may include a first refracted light beam having an optical axis parallel to the straight light beam after being reflected m times by the inner surface of the transparent tube, and a second refracted light beam having an optical axis parallel to the straight light beam after being reflected n times by the inner surface of the transparent tube, where m and n are two different natural numbers. In this case, at least one of the unknowns, the inner diameter and the refractive index, can be calculated from a simultaneous equation consisting of a first relational expression derived from the law of refraction, including the refractive index of the transparent tube, which indicates the relationship between the inner diameter of the transparent tube, the peak-to-peak distance of a straight ray tangent to the outer surface of the transparent tube, and the peak-to-peak distance of the first refracted ray, and a second relational expression derived from the law of refraction, including the refractive index of the transparent tube, which indicates the relationship between the inner diameter of the transparent tube, the peak-to-peak distance of a straight ray tangent to the outer surface of the transparent tube, and the peak-to-peak distance of the second refracted ray. However, since the peak intensities included in the imaging data decrease when the values ​​of m and n become too large, it is preferable that m and n be 3 or less, and more preferably 2 or less. Furthermore, the "simultaneous equations of the first relational expression and the second relational expression" also includes the case where a first polynomial related to the inner diameter obtained from these simultaneous equations, from which the refractive index has been previously eliminated, and a second polynomial related to the refractive index obtained from which the inner diameter has been previously eliminated, are used.

[0068] In the above-described embodiment, the irradiation unit is not particularly limited as long as it can generate parallel light beams. For example, the irradiation unit may include a line light source in which a plurality of light sources such as LEDs are arranged in a line along the Y direction. Furthermore, the irradiation unit may scan laser light emitted from a laser emitting unit on a plane that crosses the transparent tube using a scanning mirror.

[0069] In the above embodiment, the optical system is not particularly limited as long as it can guide straight light rays and transmitted light rays to the imaging unit. However, from the viewpoint of measuring the outer diameter, inner diameter, and refractive index of the transparent tube with high accuracy, it is preferable to use a telecentric optical system.

[0070] In the above embodiment, the transparent tube is formed using the redraw method, but the present invention is not limited to this. In the transparent tube forming process, other known forming methods such as the Danner method, the downdraw method, and the updraw method can be applied.

[0071] In the above embodiment, a glass tube is used as the transparent tube, but the present invention is not limited to this. For example, the transparent tube may be a resin tube. Here, the transmittance of the transparent tube at a thickness of 1 mm is preferably 20% or more at any wavelength in the range of 150 nm to 20 μm, more preferably 30% or more at any wavelength in the range of 200 nm to 1800 nm, and even more preferably 40% or more at any wavelength in the range of 380 nm to 780 nm.

[0072] In the above embodiment, the step of preparing the transparent tube may be a step of preparing a transparent tube that has been cut to a predetermined length in advance. In this case, the step of measuring the transparent tube measures the transparent tube that has been cut to the predetermined length in advance. [Explanation of symbols]

[0073] 1 Manufacturing equipment 2. Feed mechanism 3 Heating furnace 4 tension roller 5 Cutter 6. Measuring equipment 7 Irradiation unit 8 Telecentric optical system 9. Imaging unit 10 Measuring part 11 Light source 12 Collimator lens 14 Object-side lens 15 Image side lens 16 apertures Gt Tube Glass (Transparent Tube) M0 straight ray M1 Transmitted ray M11 Primary refracted ray M12 Secondary refracted ray M13 Third-order refracted rays P0 Peak of straight light P11 Peak of the primary refracted ray P12 Peak of secondary refracted rays P13 Peak of third-order refracted rays

Claims

1. A method for manufacturing a transparent tube, comprising: a preparation step of preparing a transparent tube; and a measurement step of measuring the transparent tube, the measuring step includes a step of irradiating the transparent tube with parallel light rays so as to cross the tube length direction, and a step of capturing images of the parallel light rays, which are straight light rays passing through the outside of the transparent tube and transmitted light rays which are transmitted through the transparent tube, by an imaging unit; The transmitted light beam includes a first refracted light beam having an optical axis parallel to the straight light beam after being reflected m times by the inner peripheral surface of the transparent tube, and a second refracted light beam having an optical axis parallel to the straight light beam after being reflected n times by the inner peripheral surface of the transparent tube, where m and n are two different natural numbers, In the measurement process, the peak position of the straight light ray that contacts the outer surface of the transparent tube, the peak position of the first refracted light ray, and the peak position of the second refracted light ray are each determined from the imaging data of the imaging unit, and the outer diameter, inner diameter, and refractive index of the transparent tube are calculated based on these three peak positions.

2. 2. A method for manufacturing a transparent tube as described in claim 1, wherein the first refracted light ray is a light ray having an optical axis parallel to the straight light ray after being reflected once on the inner surface of the transparent tube, and the second refracted light ray is a light ray having an optical axis parallel to the straight light ray after being reflected twice on the inner surface of the transparent tube.

3. 3. The method for manufacturing a transparent tube according to claim 1, wherein the transparent tube is a glass tube.

4. The method for manufacturing a transparent tube according to claim 3 , wherein the preparation step includes a forming step of forming the glass tube in a forming section.

5. The method for manufacturing a transparent tube according to claim 4, wherein the measuring step measures the glass tube connected to the molding portion on a manufacturing line.

6. A transparent tube measuring device, comprising: an irradiation unit that irradiates parallel light beams across the transparent tube in a tube length direction; an imaging unit that images straight light rays that pass through the outside of the transparent tube and transmitted light rays that pass through the transparent tube, among the parallel light rays; a measuring unit that measures the transparent tube based on the imaging data of the imaging unit, The transmitted light beam includes a first refracted light beam having an optical axis parallel to the straight light beam after being reflected m times by the inner peripheral surface of the transparent tube, and a second refracted light beam having an optical axis parallel to the straight light beam after being reflected n times by the inner peripheral surface of the transparent tube, where m and n are two different natural numbers, The measuring unit is configured to determine the peak position of the straight light ray that contacts the outer surface of the transparent tube, the peak position of the first refracted light ray, and the peak position of the second refracted light ray from the imaging data, and to calculate the outer diameter, inner diameter, and refractive index of the transparent tube based on these three peak positions.

Images