Apparatus for manufacturing glass base material, and method for manufacturing glass base material

Abstract

This apparatus for producing a glass base material pulls up a starting bar while depositing glass fine particles produced by a burner in an axial direction of the starting bar while the starting bar is rotated about an axis thereof. This apparatus for producing a glass base material is provided with: an imaging device that images a deposition surface of a fine glass particle deposits deposited on the starting bar, to obtain a deposition surface image; and an image-processing unit that detects an edge shape of the deposition surface from the deposition surface image obtained by the imaging device, and quantifies the degree of deformation of the edge shape, to determine whether or not the glass fine particle deposits are good.

Description

Technical Field

[0001] The present disclosure relates to an apparatus for manufacturing a glass preform and a method for manufacturing a glass preform. This application claims priority based on Japanese Application No. 2021-033641 filed on March 3, 2021, and incorporates by reference all the descriptions described in the above Japanese application.

Background Art

[0002] Patent Document 1 discloses a method of manufacturing an optical fiber preform by the VAD (Vapor-phase Axial Deposition) method, in which the deposition state of glass fine particles is imaged using a television camera to detect deformation of the tip shape of the glass fine particle deposit, and the movement of the burner is controlled.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

[0004] The present disclosure relates to an apparatus for manufacturing a glass preform that pulls up a starting rod while rotating the starting rod around its axis and depositing glass fine particles generated by a burner in the axial direction of the starting rod. The apparatus for manufacturing this glass preform includes an imaging device that images the deposition surface of the glass fine particle deposit deposited on the starting rod to obtain a deposition surface image, and an image processing unit that detects the edge shape of the deposition surface from the deposition surface image obtained by the imaging device, quantifies the degree of deformation of the edge shape, and determines the quality of the glass fine particle deposit.

[0005] This disclosure relates to a method for manufacturing a glass base material, wherein the starting rod is rotated around an axis, and glass microparticles generated by a burner are deposited in the axial direction of the starting rod while the starting rod is being pulled up. This method for manufacturing a glass base material comprises the steps of: acquiring a deposition surface image by imaging the deposition surface of the glass microparticle deposit deposited on the starting rod; detecting the edge shape of the deposition surface from the deposition surface image; and determining the quality of the glass microparticle deposit by quantifying the degree of deformation of the detected edge shape. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 shows an example of the configuration of an apparatus for manufacturing a glass base material according to one embodiment of the present disclosure. [Figure 2] Figure 2 shows an example of a depositional surface image of a glass microparticle deposit that has not undergone deformation. [Figure 3] Figure 3 shows examples of depositional surface images of glass microparticle deposits. (a) shows an example of a depositional surface image without deformation, (b) shows an example of a depositional surface image where the leading edge has been deformed to be flat, (c) shows an example of a depositional surface image where the leading edge has been deformed rotationally asymmetrically, and (d) shows an example of a depositional surface image where the side surface has been deformed. [Figure 4] Figure 4 shows the edge of the leading edge of a glass microparticle deposit (the left half as an example) with approximate values ​​(dotted line) and measured values ​​(solid line), illustrating the case where the leading edge is not deformed. [Figure 5] Figure 5 shows the edge of the leading edge of a glass microparticle deposit (the left half as an example) with approximate values ​​(dotted line) and measured values ​​(solid line), illustrating the case where the leading edge is deformed to be flat. [Figure 6] Figure 6 is an enlarged view of the region S shown in Figure 5, illustrating an example of the residual difference between the approximate value (dotted line) and the measured value (solid line). [Figure 7] Figure 7 schematically shows the inclination of the sloped portion of the glass microparticle deposit. [Figure 8] Figure 8 is a flowchart showing a method for manufacturing a glass base material using the apparatus for manufacturing glass base materials shown in Figure 1. [Modes for carrying out the invention]

[0007] [Issues this disclosure aims to address] In the method for manufacturing optical fiber preforms disclosed in Patent Document 1, deformation of the tip shape of the glass microparticle deposit (which ultimately constitutes a part of the optical fiber preform) is detected mainly by image analysis. However, this detection alone makes it difficult to respond quickly to various deformations of the glass microparticle deposit. Therefore, there is a need for a method that can respond quickly to deformation of the glass microparticle deposit when manufacturing optical fiber preforms.

[0008] [Effects of this disclosure] According to this disclosure, it is possible to respond quickly to the deformation of glass microparticle deposits.

[0009] [Description of Embodiments in this Disclosure] First, the contents of the embodiments of this disclosure will be listed and explained. An apparatus for manufacturing a glass base material according to one embodiment of this disclosure is an apparatus that rotates a starting rod around an axis and pulls up the starting rod while depositing glass microparticles generated by a burner in the axial direction of the starting rod. This apparatus includes an imaging device that images the deposition surface of the glass microparticle deposit deposited on the starting rod and acquires a deposition surface image, and an image processing unit that detects the edge shape of the deposition surface from the deposition surface image acquired by the imaging device, quantifies the degree of deformation of the edge shape and determines the quality of the glass microparticle deposit.

[0010] The apparatus for manufacturing this glass matrix material is equipped with an image processing unit that detects the edge shape of the deposition surface from the deposition surface image acquired by an imaging device, quantifies the degree of deformation of the edge shape, and determines the quality of the glass microparticle deposition. In this case, instead of simply comparing images, the quality of the glass microparticle deposition is determined by quantifying the degree of deformation of the edge shape of the deposition surface image, allowing for a more detailed judgment. As a result, this apparatus can respond quickly to deformation of the glass microparticle deposition. Furthermore, by quantifying (numerically representing) the degree of deformation of the deposition surface in the manufacturing of the glass matrix material in this way, a large amount of manufacturing data can be used for analysis, making it possible to predict deformation and automate or simplify the maintenance of the manufacturing equipment.

[0011] In one embodiment, the image processing unit may quantify the degree of deformation of the edge shape according to the type of deformation and determine whether it is good or bad. In this case, the quality of the glass microparticle deposition can be determined in more detail, allowing for a quicker response to deformation of the glass microparticle deposition. In this embodiment, the types of deformation may include deformation of the leading edge of the glass microparticle deposition, rotationally asymmetric deformation at the leading edge of the glass microparticle deposition, and deformation of the sides of the glass microparticle deposition. Different responses (such as changes in manufacturing conditions) may be required even after deformation is determined to be present, and by pre-determining and responding to each type of deformation, subsequent responses can be made easier.

[0012] As one embodiment, the apparatus for manufacturing a glass base material may further include a data creation unit that creates manufacturing data linking deformation degree data quantified by an image processing unit with axial position data (pulling length) of the glass microparticle deposit corresponding to the deformation degree data. In this case, the parts of the glass microparticle deposit that are deemed defective in the quality judgment can be removed more accurately in a later process. That is, if the range of defects in the quality judgment is unclear, it may be necessary to discard the entire glass base material composed of the glass microparticle deposit, or in the case of partial discarding, it may be necessary to discard a larger amount as a precaution. However, by creating such manufacturing data, it becomes possible to remove only the defective parts more accurately.

[0013] A method for manufacturing a glass base material according to one embodiment of the present disclosure is a method for raising a starting rod while rotating the starting rod around an axis, and depositing glass microparticles generated by a burner in the axial direction of the starting rod. This method for manufacturing a glass base material includes the steps of: acquiring a deposition surface image by imaging the deposition surface of the glass microparticle deposit deposited on the starting rod; detecting the edge shape of the deposition surface from the deposition surface image; and determining the quality of the glass microparticle deposit by quantifying the degree of deformation of the detected edge shape.

[0014] In this method for manufacturing glass matrix materials, the edge shape of the deposition surface is detected from the deposition surface image, and the degree of deformation of the detected edge shape is quantified to determine the quality of the glass microparticle deposition. In this case, rather than simply comparing images, the degree of deformation of the edge shape of the deposition surface image is quantified to determine the quality of the glass microparticle deposition, allowing for more detailed judgment and enabling a rapid response to deformation of the glass microparticle deposition. Furthermore, by quantifying (numerizing) the degree of deformation of the deposition surface in the manufacturing of glass matrix materials in this way, a large amount of manufacturing data can be used for analysis, making it possible to predict deformation and automate or simplify the maintenance of manufacturing equipment.

[0015] In one embodiment, the process for determining whether the product is good or bad may involve quantifying the degree of deformation of the edge shape for each type of deformation to determine its quality. In this case, the quality of the glass microparticle deposit can be determined in more detail, allowing for a more rapid response to deformation of the glass microparticle deposit. In this embodiment, the types of deformation may include deformation of the leading edge of the glass microparticle deposit, rotationally asymmetric deformation at the leading edge of the glass microparticle deposit, and deformation of the sides of the glass microparticle deposit. The types of deformation may further include deformation due to cracking of the glass microparticle deposit, or deformation due to the adhesion of foreign matter to the glass microparticle deposit.

[0016] As one embodiment, the method for manufacturing the glass base material may further include a step of changing the manufacturing conditions of the glass microparticle deposit based on the degree of deformation and the type of deformation quantified in the step of determining the quality. In this case, the manufacturing conditions can be changed more quickly for the glass microparticle deposit in which deformation has occurred, and the defective portion of the glass microparticle deposit can be made shorter.

[0017] As one embodiment, in the step of acquiring an image, light having a wavelength of 300 nm or more and 600 nm or less may be irradiated from a light source onto the deposition surface of the glass microparticle deposit to acquire a deposition surface image. In the method for manufacturing an optical fiber preform, there is strong light emission from the flame of the burner. By irradiating light in such a wavelength range to a position where the edge is emphasized to acquire an image, the edge portion of the glass microparticle deposit can be made clearer and image processing can be facilitated. Thereby, the accuracy of determination based on the deposition surface image in the step of determining the quality can be enhanced.

[0018] As one embodiment, in the step of acquiring an image, the deposition surface image may be acquired through an optical filter having a transmission characteristic with respect to light in any wavelength range within the range of 350 nm or more and 510 nm or less. In the method for manufacturing an optical fiber preform, there is strong light emission from the flame of the burner. By blocking the light from the burner through an optical filter having such a transmission characteristic to acquire an image, the edge portion of the glass microparticle deposit can be made clearer and image processing can be facilitated. Thereby, the accuracy of determination based on the deposition surface image in the step of determining the quality can be enhanced.

[0019] As one embodiment, the method for manufacturing the glass base material may further include a step of performing a predetermined notification when the degree of deformation exceeds a predetermined value in the step of determining the quality. In this case, it becomes possible to take necessary measures at an early stage with respect to the deformation of the glass microparticle deposit determined in more detail.

[0020] As one embodiment, the above method for manufacturing a glass base material may further include a step of removing defective portions from the glass microparticle deposit based on manufacturing data that links the deformation degree data quantified in the quality determination step with the axial position data of the glass microparticle deposit corresponding to the deformation degree data. In this case, the portions of the glass microparticle deposit that were deemed defective in the quality determination can be removed more accurately in a later step (for example, after a dehydration sintering step and a stretching step). That is, if the range of defects determined in the quality determination is unclear, it may be necessary to discard the entire glass base material composed of the glass microparticle deposit, or in the case of partial discarding, it may be necessary to discard a larger amount as a precaution. However, by creating such manufacturing data, it becomes possible to remove only the defective portions more accurately.

[0021] [Details of the embodiments of this disclosure] Specific examples of apparatus and methods for manufacturing glass preforms relating to this disclosure will be described below with reference to the drawings. The present invention is not limited to these examples, but is intended to be shown in the claims, and all modifications within the meaning and scope of equivalence to the claims are intended. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0022] Figure 1 shows an example of the configuration of an apparatus for manufacturing a glass preform according to one embodiment of the present disclosure. As shown in Figure 1, the glass preform manufacturing apparatus 10 is an apparatus for manufacturing a glass microparticle deposit 100 (which ultimately constitutes a part of the optical fiber preform) by rotating a starting rod 12 around its axis and raising the starting rod 12 while depositing glass microparticles generated by burners 15 and 16 in the axial direction of the starting rod 12. The glass preform manufacturing apparatus 10 includes a reaction vessel 11, a support rod 13 for supporting the starting rod 12, a lifting and rotating device 14, a core burner 15, a cladding burner 16, a gas supply system 17, stages 18 and 19, an imaging device 20, a light source 25, and a control device 30. Such a manufacturing apparatus 10 is used, for example, when manufacturing a glass preform by the VAD (Vapor phase axial deposition) method, and the following description will mainly explain the case where it is used by the VAD method as an example. However, it will be readily apparent to those skilled in the art that the configuration of the manufacturing apparatus 10 (mainly the imaging device 20 and the control device 30, etc.) can be applied to the OVD (Outside vapor deposition) method.

[0023] The reaction vessel 11 is a component for manufacturing the glass microparticle deposit 100, and is fitted with an exhaust duct 11a. Inside the reaction vessel 11, a core burner 15, a cladding burner 16, and a portion of a support rod 13, to which a starting glass rod 12 for depositing glass microparticles is attached at one end, are positioned. As an example, the starting glass rod is a glass rod made of quartz glass with a diameter of 25 mm and a length of 400 mm.

[0024] The other end of the support rod 13 is supported by a lifting and rotating device 14, which rotates the support rod 13 along arrow S1 in Figure 1 and raises and lowers the support rod 13 along the direction indicated by arrow S2. The operation of the lifting and rotating device 14 is controlled by a control device 30. The control device 30 individually controls the gas flow rate to the gas supply system 17, the position of the core burner stage 18 and the angle adjustment mechanism 18a provided on the stage 18, and the position of the cladding burner stage 19 and the angle adjustment mechanism 19a provided on the stage 19, according to control conditions input from an external source.

[0025] In the example shown in Figure 1, the core burner 15 has multiple pipes of different outer diameters (arranged concentrically). Glass raw material gases (SiCl4 and GeCl4) supplied from the gas supply system 17 are introduced into the pipe with the smallest diameter (the innermost pipe). Fuel gas (H2), combustion-supporting gas (O2), and burner seal gas (N2) are introduced separately into the remaining spaces. Within the flame of the core burner 15, glass particles (SiO2) and refractive index-adjusting dopant (GeO2) are generated by the hydrolysis and combustion reactions of the glass raw material gases, as described below. The glass particles generated in the flame are blown from the core burner 15 onto the glass particle deposit 100. The burner seal gas is introduced to prevent thermal degradation of the burner tip and the accumulation of glass particles on the burner tip, and functions to separate the glass raw material gas, fuel gas, and combustion-supporting gas near the pipe end of the core burner 15. SiCl4 + 2H2O ⇒ SiO2 + 4HCl GeCl4 + O2 ⇒ GeO2 + 2Cl2

[0026] The structure of the cladding burner 16 is almost the same as that of the core burner 15 described above, but the type of raw material for the refractive index adjusting dopant contained in the glass raw material gas supplied from the gas supply system 17 is different. For example, when fluorine (F) is added as a refractive index adjusting dopant to the cladding portion, the glass raw material gas contains CF4 along with SiCl4. However, if the refractive index of the cladding portion is not adjusted, the glass raw material gas does not need to contain the raw material for the refractive index adjusting dopant.

[0027] The imaging device 20 is a device that images the deposition surface 105 of the glass microparticle deposition 100 deposited on the starting rod 12 and acquires a deposition surface image. The imaging device 20 comprises a camera unit 21 that uses, for example, a CCD or CMOS as an image sensor, and an optical filter 22 provided on the input side of the camera unit 21. The optical filter 22 is an optical filter that has transmission characteristics for light in any wavelength range within the range of 350 nm to 510 nm (for example, a wavelength range of 420 nm to 510 nm). Here, transmission characteristics mean, for example, if the optical filter 22 has transmission characteristics for light in the wavelength range of 350 nm to 510 nm, it transmits 95% or more of the light in the wavelength range of 350 nm to 510 nm, while blocking light of wavelengths outside this range to 1% or less. In the manufacturing method of optical fiber preforms, there is strong light emission from at least the flame of the core burner 15. The light from the flame of the core burner 15 is blocked by the optical filter 22, and the light from the light source 25, which is irradiated to emphasize the edges of the glass microparticle deposit 100, is selected and an image is acquired by the camera unit 21. This makes the edges of the deposit surface 105 of the glass microparticle deposit 100 clearer and makes image processing easier.

[0028] When the imaging device 20 photographs the glass microparticle deposit 100, it continuously photographs the deposit surface 105 of the glass microparticle deposit 100, which is rotating in direction S1 by the lifting and rotating device 14, that is, it acquires video data. In order to photograph the glass microparticle deposit 100 as it rotates, the imaging device 20 may acquire a deposit surface image by photographing only one side of the deposit surface 105 on the axis of rotation. When photographing, the imaging device 20 may misrecognize the interface of the edge portion due to reflections of background elements such as soot flowing inside the reaction vessel 11. In such cases, the shutter speed of the camera unit 21 of the imaging device 20 may be slowed down to blur the reflected portion and make it easier to recognize the interface of the edge portion. In this case, for example, the shutter speed may be set to 0.1 seconds or more and 0.5 seconds or less.

[0029] The imaging device 20 is further equipped with a light source 25 that irradiates the glass microparticle deposition 100 with light to facilitate image processing. The wavelength of the light emitted from the light source 25 may be between 300 nm and 600 nm. Preferably, the light source 25 is positioned to irradiate at least the deposition surface 105 opposite to the deposition surface that is struck by the flame of the core burner 15. In the manufacturing method of the optical fiber base material, there is strong light emission from the burner flame, but the light from the core burner 15 is blocked via the optical filter 22, and the light from the light source 25 that is irradiated in a way that emphasizes the edges is selected and an image is acquired by the camera unit 21. This makes the edge portion of the deposition surface 105 of the glass microparticle deposition 100 clearer and facilitates image processing. In other words, with the above configuration, reflections of the flame from the core burner 15 can be suppressed at least, and the edge portion of the deposition surface 105 can be extracted more accurately.

[0030] The imaging device 20 may be a thermographic camera. As the thermographic camera, a flame-through imaging camera with an imaging wavelength of 3.7 μm to 4.1 μm may be used. The flame-through imaging camera comprises, for example, a camera unit that uses a microborometer as an image sensor, and an optical filter provided on the input side of the camera unit that has transmission characteristics for infrared light having a wavelength of 3.7 μm to 4.1 μm. The glass microparticle deposition 100 is heated to several hundred degrees Celsius by flames from the core burner 15 and the cladding burner 16, so infrared light having a wavelength of 1 μm to 10 μm is widely emitted from the glass microparticle deposition 100. Strong infrared light is also emitted from the flame of the core burner 15, but there is little infrared light with a wavelength of 3.7 μm to 4.1 μm. In the camera for shooting through flames, infrared light from the core burner 15 is blocked via an optical filter, and infrared light emitted from the glass microparticle deposit 100 is selected and captured as an image by the camera unit. This allows for more accurate extraction of the edges of the deposit surface 105, similar to the above, without the need for a separate light source.

[0031] An imaging device 20 with this configuration can acquire images of the deposition surface 105 of the glass microparticle deposit 100, such as the image shown in Figure 2, by continuous shooting. Figure 2 is a diagram showing an example of an image of the deposition surface 105 of the glass microparticle deposit 100. The imaging device 20 continuously acquires images of the deposition surface while the glass microparticle deposit 100 is being manufactured, and in addition to the undeformed image shown in part (a) of Figure 3, it may also acquire images shown in parts (b), (c), and (d) of Figure 3. Figure 3 is a diagram showing examples of images of the deposition surface of a glass microparticle deposit, where part (a) shows an example of an image of the deposition surface 105a in which no deformation has occurred, including the tip H, part (b) shows an example of an image of the deposition surface 105b in which the tip H1 has been deformed to be flat, part (c) shows an example of an image of the deposition surface 105c in which the tip H2 has been deformed rotationally asymmetrically, and part (d) shows an example of an image of the deposition surface 105d in which the side surface H3 has been deformed. The imaging device 20 transmits the acquired deposition surface image (video data) to the control device 30 (image processing unit 32). The deposition surface 105 (105a to 105d) is the deposition surface of the portion where glass nanoparticles were deposited with the core burner 15, and not the deposition surface of the portion where glass nanoparticles were deposited with the cladding burner 16. The deformation described above is the deformation of the deposition surface of the portion where glass nanoparticles were deposited with the core burner 15.

[0032] Returning to Figure 1, let's continue the explanation. As shown in Figure 1, the control device 30 controls the rotational movement S1 and lifting movement S2 of the lifting and rotating device 14, adjusts the flow rate of the gas supplied from the gas supply system 17, adjusts the movement (including angle adjustment) of the core burner 15 and cladding burner 16 by the stages 18 and 19, and processes the deposition surface image acquired by the imaging device 20. Functionally, the control device 30 comprises a device control unit 31, an image processing unit 32, a data creation unit 33, and an input / output unit 34. Such a control device 30 is composed of, for example, a computer and includes a CPU (Central Processing Unit), a storage medium such as memory, and an input / output interface. The control device 30 performs the various operations such as control, adjustment, and processing described above by having the CPU execute various programs or data stored in the storage medium. The control device 30 also receives signals from the outside (e.g., video signals) and transmits signals to the outside (e.g., control signals) via the input / output interface. Each processing function performed in each functional block of the control device 30 can be implemented, in whole or in any part thereof, by various programs executed by the CPU.

[0033] The device control unit 31 controls the rotational movement S1 and lifting movement S2 of the lifting and rotating device 14, adjusts the flow rate of the gas supplied from the gas supply system 17, and adjusts the movement (including angle adjustment) of the stage 18 of the core burner 15 and the stage 19 of the cladding burner 16. Since many of these controls are conventional, a detailed explanation will be omitted.

[0034] The image processing unit 32 detects the edge shape of the deposition surface 105 from the deposition surface image of the glass microparticle deposition 100 acquired by the imaging device 20, quantifies (digitizes) the degree of deformation of this edge shape, and determines the quality of the glass microparticle deposition 100. When the image processing unit 32 acquires video data from the imaging device 20, it divides the video data into two-dimensional images (still images) and extracts the edge shape of the deposition surface 105 from the obtained two-dimensional images (still images). Then, the image processing unit 32 determines from the extracted edge shape whether deformation has occurred on each deposition surface 105 for each type of deformation. This determination can be made by comparing the digitized data of images without deformation (a threshold is set for each type of deformation) with the digitized data obtained by converting the acquired images into still images. If the image processing unit 32 determines that no deformation has occurred on the deposition surface 105 (if it is below the threshold), it terminates processing for that deposition surface 105, determining that there is no deformation.

[0035] On the other hand, the image processing unit 32 calculates the amount of deformation (degree of deformation) for each type of deformation if it determines that deformation has occurred on the deposition surface 105 according to each type of deformation, that is, if any threshold is exceeded. The calculation of this amount of deformation and the determination of whether or not deformation is present may be processed simultaneously. Here, the types of deformation of the deposition surface 105 of the glass microparticle deposition 100 will be explained. In the above deformation determination and deformation amount calculation, for example as shown in Figure 3, the deformation is classified into three types: 1) deformation of the tip H1 of the glass microparticle deposition 100 (flat / protruding tip), 2) rotationally asymmetric deformation at the tip H2 of the glass microparticle deposition 100, and 3) deformation of the side surface H3 of the glass microparticle deposition 100, and the determination process and deformation amount calculation process are performed. Then, the deformation amount is calculated quantitatively for each type of deformation.

[0036] First, in calculating the amount of deformation (flat / protruding tip) of the tip H1 of the glass microparticle deposit 100, as shown in Figures 4 and 5, the image processing unit 32 pre-stores an equation (dotted line) that approximates the normal shape of the tip H1 of the glass microparticle deposit 100. Such an equation can be approximated by, for example, a polynomial. Figure 4 shows the edge of the tip (mainly the left half) of the glass microparticle deposit with approximate values ​​(dotted line) and measured values ​​(solid line), where the two are in close agreement, indicating that the tip is not deformed. The measured values ​​are created based on the deposit surface image acquired by the imaging device 20. On the other hand, Figure 5 shows the edge of the tip (mainly the left half) of the glass microparticle deposit with approximate values ​​(dotted line) and measured values ​​(solid line), where there is a discrepancy between the two, indicating that the tip is deformed.

[0037] In the image processing unit 32, if the measured value deviates from the formula approximating the normal shape, the residual yi-Yi between the measured value and the approximate value is calculated in the deviated region S, as shown in Figure 6. Next, the sum of squares of the residuals is calculated, and the unbiased variance is calculated from this. Similar calculations are performed in other deviated regions. These are then defined as 1) the deformation amount of the tip H1 of the glass microparticle deposit 100 (flat tip / protruding tip). Based on this deformation amount, the image processing unit 32 determines whether the data of the deposit surface image acquired by the imaging device 20 exceeds a predetermined threshold for deformations such as the tip becoming flat or conversely protruding, and determines the quality of the glass microparticle deposit 100, and stores the deformation amount as manufacturing data. If the glass microparticle deposit 100 is determined to be defective, the data creation unit 33 links the deformation amount data (or data indicating defect) with the corresponding axial position data (pulling length) of the glass microparticle deposit 100 and stores it in memory or the like.

[0038] Next, in the case of rotationally asymmetric deformation at the tip H2 of the glass microparticle deposit 100, as shown in Figure 7, the inclination of the edge is calculated by numerically differentiating (center difference) the core outer diameter coordinate points extracted from the image. The image processing unit 32 then determines the amount of change in inclination data over a first predetermined time (several seconds). Subsequently, the image processing unit 32 calculates the amount of variation in inclination change within a specified range for each range in which the inclination is analyzed. This is defined as the deformation amount for rotationally asymmetric deformation at the tip H2 of the glass microparticle deposit 100. Based on this deformation amount, the image processing unit 32 determines whether the data of the deposit surface image acquired by the imaging device 20 exceeds a predetermined threshold for rotationally asymmetric deformation at the tip, and determines the quality of the glass microparticle deposit 100, while also storing the deformation amount as manufacturing data. If the glass microparticle deposition 100 is determined to be defective, the data creation unit 33 stores the deformation amount data (or data indicating defect) and the corresponding axial position information of the glass microparticle deposition 100 in memory or the like.

[0039] Next, regarding 3) the deformation of the side surface 103 of the glass microparticle deposit 100, although it is different from the measurement location for the rotationally asymmetric deformation at the leading edge H2 of the glass microparticle deposit 100 (2), the amount of deformation of the side surface can be defined using a similar method. Based on this amount of deformation, the image processing unit 32 determines whether the data of the deposit surface image acquired by the imaging device 20 exceeds a predetermined threshold with respect to the deformation of the side surface, and determines whether the glass microparticle deposit 100 is good or bad, and stores the amount of deformation as manufacturing data. If the glass microparticle deposit 100 is determined to be defective, the data creation unit 33 links the deformation amount data (or data indicating defect) with the corresponding axial position information of the glass microparticle deposit 100 and stores it in memory or the like.

[0040] Returning to Figure 1, let's continue the explanation. The data creation unit 33 is the part that creates manufacturing data by linking the data of each deformation amount (degree of deformation) quantified (digitized) by the image processing unit 32 with the position data of the glass microparticle deposition 100 in the axial direction that corresponds to this deformation amount data. When the data creation unit 33 obtains the deformation amount data quantified by the image processing unit 32, for example, data indicating that a part of the glass microparticle deposition 100 is defective, from the image processing unit 32, it calculates the position data of the defective part in the axial direction from the amount of movement of the support rod 13 in the lifting and rotating device 14, performs a process to link the two, and creates the above-mentioned manufacturing data. The data creation unit 33 stores the created manufacturing data in the memory (not shown) of the control device 30, and may also output it to an external device from the input / output unit 34. The external device may use the acquired manufacturing data for quality control of the glass base material, or it may use it to discard the defective part after the dehydration and sintering process.

[0041] The input / output unit 34 outputs the manufacturing data created by the data creation unit 33 to an external device. Furthermore, the input / output unit 34 provides a predetermined notification, such as an alarm, when the image processing unit 32 detects a defect in the glass microparticle deposition 100 due to deformation. Alternatively, this notification may be transmitted wirelessly to an information terminal held by the manufacturing manager, along with the identification number of the target manufacturing device, indicating that a defect due to deformation of the glass microparticle deposition 100 has occurred. Especially when a small number of people are managing a large number of glass base material manufacturing devices 10, such notification allows for early identification of which device has a defect and the type of defect (type of deformation), enabling adjustments such as changes to manufacturing conditions to reduce the amount of glass microparticle deposition 100 that needs to be removed.

[0042] Next, a method for manufacturing a glass base material using the glass base material manufacturing apparatus 10 described above will be explained with reference to Figure 8. Figure 8 is a flowchart showing a method for manufacturing a glass base material using the glass base material manufacturing apparatus 10.

[0043] First, the control device 30 drives the lifting and rotating device 14 to rotate the starting rod 12 around its axis, while the glass microparticles generated by the burners 15 and 16 are deposited in the axial direction of the starting rod 12. Then, during the process of manufacturing the glass microparticle deposit 100, the imaging device 20 continuously acquires images of the deposition surface 105 of the glass microparticle deposit 100 (step S1). During this imaging, the deposition surface image may be acquired by irradiating the deposition surface 105 of the glass microparticle deposit 100 with light from the light source 25 with a wavelength of 300 nm to 600 nm. Alternatively, during this imaging, the deposition surface image may be acquired by passing the optical filter 22, which has transmission characteristics for light in any wavelength range within the range of 350 nm to 510 nm, through the optical filter 22.

[0044] Next, the image of the deposition surface (video data) acquired by the imaging device 20 is sent to the image processing unit 32, where the shape of the edge portion is detected (step S2) and the quality of the deposition surface is determined (step S3). In steps S2 and S3, still image data is extracted from the video data to form a deposition surface image, and the presence or absence of deformation of the deposition surface 105 of the glass microparticle deposition body 100 is determined for each type of deformation, for example, as shown below. 1) Deformation of the tip H1 of the glass microparticle deposit 100 (flat tip / protruding tip) 2) Rotationally asymmetric deformation at the tip H2 of the glass microparticle deposit 100, 3) Deformation of side surface H3 of glass microparticle deposit 100

[0045] As described above, the method for determining each type of deformation in the image processing unit 32 is as follows: The image processing unit 32 compares the amount of deformation for each type of deformation with a predetermined threshold to determine whether or not deformation has occurred on the deposition surface 105. This predetermined threshold is also set differently for each type of deformation. The threshold may be set by referring to some or all of the deformation amount data acquired in the past. If deformation is determined to exist, the amount of deformation for each type of deformation is quantitatively calculated and stored as described above (step S4). Furthermore, if any of the deformation amounts for each type of deformation significantly exceeds a predetermined threshold, the image processing unit 32 may determine that the deformation is due to cracking of the glass microparticle deposition or deformation due to the adhesion of foreign matter to the glass microparticle deposition. Deformation due to cracking of the glass microparticle deposition and deformation due to the adhesion of foreign matter to the glass microparticle deposition can be distinguished and determined by appropriately setting predetermined thresholds for each.

[0046] Next, if the image processing unit 32 determines that the deposition surface 105 of the glass microparticle deposition 100 is deformed, i.e., defective, the data creation unit 33 creates manufacturing data by linking the deformation amount data quantified by the image processing unit 32 with the axial position data of the glass microparticle deposition 100 corresponding to this deformation amount data, and stores it in memory or the like (step S4).

[0047] Furthermore, if the image processing unit 32 determines that the deposition surface 105 of the glass microparticle deposition 100 is deformed, i.e., defective, it may issue an alert via the input / output unit 34 (step S5) and / or change the manufacturing conditions (step S6).

[0048] In step S6, when the manufacturing conditions are changed, the device control unit 31 of the control device 30 changes the manufacturing conditions according to the type of deformation of the deposition surface 105 of the glass microparticle deposition 100. For example, 1) in the case of deformation of the tip H1 of the glass microparticle deposition 100 (flat tip / protruding tip), the device control unit 31 drives the stage 18, etc. to move the core burner 15 along the Y axis (a direction perpendicular to the rotation axis of the starting rod 12 and perpendicular to the burner's central axis) or along the X axis (a direction perpendicular to the Y axis and perpendicular to the burner's central axis), thereby adjusting the tip shape of the deposition surface 105. 2) In the case of rotationally asymmetric deformation of the tip H2 of the glass microparticle deposition 100, the device control unit 31 drives the stage 18, etc. to mainly perform the above-mentioned adjustment along the Y axis, thereby adjusting the rotationally asymmetric shape of the tip of the deposition surface 105. 3) In the event of deformation of the side surface H3 of the glass microparticle deposit 100, the device control unit 31 controls the gas supply system 17, etc., to adjust the gas flow rate of the core burner 15, thereby adjusting the side shape of the deposit surface 105. These changes in manufacturing conditions may be made manually by the manufacturing manager, or they may be made automatically by inputting predetermined data into the control device 30.

[0049] The information that a defect has occurred due to deformation of the glass microparticle deposition 100 may be wirelessly transmitted via the input / output unit 34 to an information terminal (smartphone, etc.) held by the manufacturing manager, along with the identification number of the manufacturing equipment in question. In this case, information such as the type of deformation and how to change the manufacturing conditions according to the type of deformation (the method described above) may also be transmitted to the information terminal held by the manufacturing manager. By transmitting such information, even manufacturing managers who manage a large number of glass substrate manufacturing equipment, or manufacturing managers with little experience, can respond quickly to deformation of the glass microparticle deposition and manufacture glass substrates more efficiently.

[0050] As described above, the glass base material manufacturing apparatus 10 according to this embodiment includes an image processing unit 32 that detects the edge shape of the deposition surface 105 from the deposition surface image acquired by the imaging device 20, quantifies the degree of deformation of the edge shape, and determines the quality of the glass microparticle deposition 100. In this case, instead of simply comparing images, the quality of the glass microparticle deposition 100 is determined by quantifying the degree of deformation of the edge shape of the deposition surface image, allowing for more detailed judgment and enabling a quick response to deformation of the glass microparticle deposition 100. Furthermore, by quantifying (numerizing) the degree of deformation of the deposition surface 105 in the manufacturing of the glass base material in this way, a large amount of manufacturing data can be used for analysis, making it possible to predict deformation and automate or simplify the maintenance of the manufacturing equipment.

[0051] In the glass substrate manufacturing apparatus 10, the image processing unit 32 quantifies the degree of deformation of the edge shape according to the type of deformation and determines whether it is good or bad. Therefore, by making it possible to determine the quality of the glass microparticle deposition 100 in more detail, it is possible to respond more quickly to deformation of the glass microparticle deposition 100.

[0052] The glass base material manufacturing apparatus 10 further includes a data creation unit 33 that creates manufacturing data by linking deformation degree data quantified by the image processing unit 32 with axial position data (pulling length) of the glass microparticle deposition 100 corresponding to the deformation degree data. Therefore, parts of the glass microparticle deposition 100 that are deemed defective in the quality judgment can be removed more accurately in subsequent processes (for example, in processes after the dehydration sintering process and the stretching process). In other words, if the range of defective parts in the quality judgment is unclear, it may be necessary to discard the entire glass base material composed of the glass microparticle deposition, or in the case of partial discarding, it may be necessary to discard a larger amount as a precaution. However, by creating such manufacturing data, it becomes possible to remove only the defective parts more accurately.

[0053] In the glass substrate manufacturing method according to this embodiment, the edge shape of the deposition surface 105 is detected from the deposition surface image, and the degree of deformation of the detected edge shape is quantified to determine the quality of the glass microparticle deposition 100. In this case, instead of simply comparing images, the degree of deformation of the edge shape of the deposition surface image is quantified to determine the quality of the glass microparticle deposition 100, allowing for more detailed judgment and enabling a quick response to deformation of the glass microparticle deposition 100. Furthermore, by quantifying (numerically representing) the degree of deformation of the deposition surface in the manufacturing of the glass substrate in this way, a large amount of manufacturing data can be used for analysis, making it possible to predict deformation and automate / simplify the maintenance of manufacturing equipment.

[0054] In the process of determining the quality of this manufacturing method, the degree of deformation of the edge shape is quantified separately for each type of deformation to determine its quality. Therefore, by making it possible to determine the quality of the glass microparticle deposition in more detail, it is possible to respond more quickly to deformation of the glass microparticle deposition 100.

[0055] This manufacturing method further includes a step of changing the manufacturing conditions of the glass microparticle deposition 100 based on the degree of deformation and the type of deformation quantified in the quality determination step. Therefore, the manufacturing conditions can be changed more quickly for glass microparticle deposition 100 that has undergone deformation, and the defective portion of the glass microparticle deposition 100 can be shortened.

[0056] In the process of acquiring an image of this manufacturing method, the deposition surface image may be acquired by irradiating the deposition surface of the glass microparticle deposition 100 with light of a wavelength between 300 nm and 600 nm from a light source. In the manufacturing method of optical fiber preforms, there is strong light emission from the burner flame, and by irradiating with such light to acquire an image, the edges of the glass microparticle deposition can be made clearer, making image processing easier. This can improve the accuracy of judgment based on the deposition surface image in the quality judgment process.

[0057] In the process of acquiring an image of this manufacturing method, the deposition surface image may be acquired through an optical filter 22 having transmission characteristics for light in any wavelength range within the range of 350 nm to 510 nm. In the manufacturing method of optical fiber preforms, there is strong light emission from the burner flame, but by acquiring an image through the optical filter 22, the edges of the glass microparticle deposition 100 can be made clearer, making image processing easier. This improves the accuracy of judgment based on the deposition surface image in the process of determining whether the product is good or bad.

[0058] The method for manufacturing this glass substrate may further include a step of providing a predetermined notification if the degree of deformation exceeds a predetermined value during the process of determining whether the material is good or bad. In this case, it becomes possible to take necessary measures earlier in response to the deformation of the glass microparticle deposition 100, which has been determined in more detail.

[0059] The manufacturing method for this glass substrate may further include a step of removing defective portions from the glass microparticle deposition 100 based on manufacturing data that links deformation degree data quantified by the image processing unit 32 with axial position data of the glass microparticle deposition 100 corresponding to the deformation degree data. In this case, the portions of the glass microparticle deposition 100 that are deemed defective in the quality judgment can be removed more accurately in a later step (for example, in a step after the dehydration sintering step and the stretching step). That is, if the range of defects in the quality judgment is unclear, it may be necessary to discard the entire glass substrate composed of the glass microparticle deposition, or in the case of partial discarding, it may be necessary to discard a larger amount as a precaution. However, by creating such manufacturing data, it becomes possible to remove only the defective portions more accurately.

[0060] Although embodiments of the present disclosure have been described in detail above, the present invention is not limited to the above embodiments and can be applied to various embodiments. For example, the control device 30 described above may be integrated into one unit for multiple glass base material manufacturing apparatuses 10.

[0061] Furthermore, embodiments of this disclosure may be applied to the OVD method as described above. The glass base material manufacturing apparatus used in this case is a manufacturing apparatus that rotates a starting rod around an axis and deposits glass microparticles generated by the burner onto the outer circumference of the starting rod while reciprocating a burner relative to the starting rod in the axial direction of the starting rod. This glass base material manufacturing apparatus includes an imaging device that images the deposition surface of the glass microparticle deposit deposited on the starting rod and acquires a deposition surface image, and an image processing unit that detects the edge shape of the deposition surface from the deposition surface image acquired by the imaging device, quantifies the degree of deformation of the edge shape, and determines whether the glass microparticle deposit is of good or bad quality.

[0062] Furthermore, in the method for manufacturing a glass base material when the above-described embodiment is applied to the OVD method, the starting rod is rotated around its axis, and the burner is moved back and forth relative to the starting rod in the axial direction of the starting rod, while the glass microparticles generated by the burner are deposited on the outer circumference of the starting rod. This method for manufacturing a glass base material includes the steps of: acquiring a deposition surface image by imaging the deposition surface of the glass microparticle deposit deposited on the starting rod; detecting the edge shape of the deposition surface from the deposition surface image; and determining the quality of the glass microparticle deposit by quantifying the degree of deformation of the detected edge shape.

[0063] When applying the above-described embodiment to the OVD method, the type of deformation detected by the image processing unit 32 may be set to deformation of the side surface of the glass microparticle deposit, and the image processing unit 32 may quantify the degree of deformation of the edge shape using this type of deformation and perform a quality judgment. In this case, the installation position of the imaging device 20 is preferably such that it is installed on the same side as the burner or on the opposite side of the burner from the deposit surface in order to reduce reflections of soot flow and other elements floating inside the reaction vessel.

[0064] The glass substrate manufacturing apparatus applicable to the OVD method may have one burner or multiple burners. If the manufacturing apparatus has multiple burners, and for example each burner reciprocates relative to the starting rod by a length equivalent to the distance between each burner, multiple imaging devices 20 may be installed. With such a glass substrate manufacturing apparatus, each imaging device 20 may image the shape of the deposition surface corresponding to each burner, quantify the amount of deformation of each deposition surface, and determine whether each is good or bad.

[0065] Thus, even in the OVD method, the degree of deformation of the edge shape of the deposition surface image can be quantified to determine the quality of the glass microparticle deposition, allowing for more detailed judgment. As a result, the glass substrate manufacturing apparatus and method for manufacturing glass substrates according to the embodiments of this disclosure can respond quickly to deformation of the glass microparticle deposition. Furthermore, by quantifying (numerically representing) the degree of deformation of the deposition surface in the manufacturing of glass substrates in this way, a large amount of manufacturing data can be used for analysis, making it possible to predict deformation and automate or simplify the maintenance of the manufacturing equipment. Moreover, even when applying the embodiments of this disclosure to the OVD method, in addition to the deformation of the glass microparticle deposition (deformation of the sides), it is also possible to detect cracks in the glass microparticle deposition surface or foreign matter adhesion to the glass microparticle deposition based on the calculated deformation amount. If cracks or foreign matter adhesion in the glass microparticle deposition surface can be detected quickly, the production of defective glass microparticle deposition can be stopped quickly. [Explanation of Symbols]

[0066] 10…Glass base material manufacturing equipment 11…Reaction vessel 11a... Exhaust duct 12... Departure stick 13...Support rod 14… Lifting and rotating device 15… Burner for core 16…Clad burner 17…Gas supply system Stages 18, 19… 18a,19a…Angle adjustment mechanism 20…Imaging device 21...Camera Club 22…Optical filters 25...Light source 30...Control device 31...Device Control Unit 32…Image Processing Unit 33...Data Creation Department 34…Input / output section 100... Glass microparticle deposits 105,105a,105b,105c,105d...Deposition surface H,H1,H2…Tip H3…side S...area S1... Rotational motion S2... Lifting and lowering operation

Claims

1. An apparatus for manufacturing a glass base material, comprising: rotating a starting rod around an axis while accumulating glass microparticles generated by a burner in the axial direction of the starting rod, and then pulling up the starting rod, An imaging device that captures an image of the deposition surface of the glass microparticle deposit accumulated on the starting rod, The system includes an image processing unit that detects the edge shape of the deposited surface from the image of the deposited surface acquired by the imaging device, quantifies the degree of deformation of the edge shape, and determines whether the glass microparticle deposit is of good or bad quality. The degree of deformation is calculated based on the difference between an approximate value of the normal shape on the depositional surface and an actual measured value, and at least one of the values ​​obtained by calculating the inclination of the edge shape and the amount of variation in the change of inclination data over a predetermined time. The image processing unit determines the quality of the glass microparticle deposit based on the degree of deformation. A device for manufacturing glass base materials.

2. The image processing unit quantifies the degree of deformation according to the type of deformation and determines whether it is good or bad. An apparatus for manufacturing a glass base material as described in claim 1.

3. The types of deformation include deformation of the leading edge of the glass microparticle deposit, rotationally asymmetric deformation at the leading edge of the glass microparticle deposit, and deformation of the sides of the glass microparticle deposit. An apparatus for manufacturing a glass base material as described in claim 2.

4. The system further includes a data creation unit that creates manufacturing data by linking the deformation degree data quantified by the image processing unit with the position data in the axial direction of the glass microparticle deposit corresponding to the deformation degree data. An apparatus for manufacturing a glass base material according to any one of claims 1 to 3.

5. A method for manufacturing a glass base material, comprising rotating a starting rod around an axis while raising the starting rod, thereby depositing glass microparticles generated by a burner in the axial direction of the starting rod, The process involves imaging the deposition surface of the glass microparticle deposits accumulated on the starting rod to obtain a deposition surface image, A step of detecting the edge shape of the deposition surface from the deposition surface image, The process includes a step of quantifying the degree of deformation of the detected edge shape to determine the quality of the glass microparticle deposit, The degree of deformation is calculated based on the difference between an approximate value of the normal shape on the depositional surface and an actual measured value, and at least one of the values ​​obtained by calculating the inclination of the edge shape and the amount of variation in the change of inclination data over a predetermined time. In the step of determining the quality, the quality of the glass microparticle deposit is determined based on the degree of deformation. A method for manufacturing glass substrates.

6. In the process of determining whether the product is good or bad, the degree of deformation is quantified separately for each type of deformation to determine whether the product is good or bad. A method for manufacturing the glass base material described in claim 5.

7. The types of deformation include deformation of the leading edge of the glass microparticle deposit, rotationally asymmetric deformation at the leading edge of the glass microparticle deposit, and deformation of the sides of the glass microparticle deposit. A method for manufacturing the glass base material described in claim 6.

8. The type of deformation further includes deformation due to cracking of the glass microparticle deposit, or deformation due to adhesion of foreign matter to the glass microparticle deposit. A method for manufacturing the glass base material described in claim 7.

9. The process further includes changing the manufacturing conditions of the glass microparticle deposit based on the degree of deformation and the type of deformation quantified in the process of determining whether the product is good or bad. A method for manufacturing a glass base material according to any one of claims 6 to 8.

10. If deformation can be predicted based on the degree of deformation and the type of deformation, the manufacturing conditions of the glass microparticle deposit are changed. A method for manufacturing the glass base material described in claim 9.

11. In the step of acquiring the image, the deposition surface of the glass microparticle deposit is irradiated with light from a light source with a wavelength of 300 nm to 600 nm to acquire an image of the deposition surface. A method for manufacturing a glass base material according to any one of claims 5 to 10.

12. In the process of acquiring the aforementioned image, the image of the deposition surface is acquired by passing it through an optical filter having transmission characteristics for light in any wavelength range within the range of 350 nm to 510 nm. A method for manufacturing a glass base material according to any one of claims 5 to 11.

13. The process of determining whether the product is good or bad further includes a step of providing a predetermined notification if the degree of deformation exceeds a predetermined value. A method for manufacturing a glass base material according to any one of claims 5 to 12.

14. The process further includes a step of removing defective portions from the glass microparticle deposit based on manufacturing data that links the deformation degree data quantified in the process of determining quality with the position data of the glass microparticle deposit in the axial direction corresponding to the deformation degree data. A method for manufacturing a glass base material according to any one of claims 5 to 13.

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