JP4995477B2 - Method for manufacturing glass article and method for manufacturing optical element - Google Patents

Description

  The present invention relates to a glass article manufacturing method and an optical element manufacturing method for manufacturing various glass articles, optical element blanks, and optical elements such as lenses that require high internal quality.

  Conventionally, in order to manufacture various glass articles, optical element blanks, and optical elements such as lenses that require high internal quality, manufacturing that has an inspection process for inspecting the internal state and quality of various glass ingots used as these materials A method has been proposed.

  For example, in Patent Document 1, in a state where a glass lump to be inspected is immersed in a liquid, inspection light is incident on the glass lump and observation light transmitted through the glass lump is observed. A technique for optically inspecting the internal state of a glass block is described.

  In this inspection technology, the glass lump is immersed in the liquid, so that the reflection loss on the surface of the glass lump including the curved surface is reduced and the internal state of the glass lump is changed by changing the direction of the glass lump. We are trying to check all over.

Japanese Patent No. 3698424

  In the conventional inspection technique described above, it is important to immerse the glass block in a liquid having a refractive index close to the refractive index of the glass block in order to expand the range that can be inspected by the incidence of the inspection light from one direction. It is.

  By the way, in recent years, materials having a higher refractive index than conventional materials have been developed and used as glass, translucent ceramics, and crystal materials. In order to inspect the glass lump having such a high refractive index by the above-described inspection technique, the refractive index of the liquid in which the glass lump is immersed must also be increased.

  However, with the recent increase in the refractive index of transparent materials, it has become difficult to bring the refractive index of liquid close to the refractive index of these glass blocks. The refractive index of a liquid can be increased by dissolving arsenic bromide in a solvent called matching oil. However, since arsenic bromide is toxic, the soaked glass mass must be thoroughly cleaned after inspection, and a large amount of toxic waste liquid is generated each time, or the liquid itself is treated as toxic waste liquid. There is a problem that must be done. In addition, since the liquid in which arsenic bromide is dissolved exhibits a black color, increasing the concentration of arsenic bromide to increase the refractive index makes it difficult for the liquid to pass the inspection light, making it impossible to perform a good inspection. There is also.

  Therefore, in the inspection object whose surface is curved like the glass lump described in Patent Document 1, the critical angle of total reflection on the interface between the glass lump and the matching oil, that is, the surface of the glass lump is reduced. The non-transmission area of the inspection light is enlarged. In other words, all the inspection light that is emitted from the inside of the glass lump to the matching oil from a direction perpendicular to the surface of the glass lump is totally reflected on the surface of the glass lump. It will be lost.

  In this situation, in order to observe the inspection light transmitted through the glass lump, the direction of the glass lump must be changed, which is a very complicated operation. In addition, in the manufacturing process of the optical element and the glass material for press forming as the material of the optical element, a large amount of optical elements and glass material must be inspected, so that the burden on the inspection process becomes large.

  In addition, when a glass block is formed from molten glass, this glass block is face-to-face polished to form a plane parallel to each other, and inspection light is transmitted from this plane to inspect the internal quality of the glass block. Can be inspected all over the inside of the glass block without causing an opaque region due to total reflection. In this case, after confirming that there is no problem in internal quality by inspection, the glass block may be cut, ground, and polished to produce an optical element or a glass material for press molding. That is, in this case, since there is no step of reducing the internal quality after the inspection step, an optical element or a glass material for press molding with good internal quality can be obtained.

  However, when a glass article having a curved surface is produced from molten glass, or when a glass article is produced by forming glass that has been heated and softened, the glass article is formed by flow deformation or plastic deformation. The Therefore, in such a glass article, an optically inhomogeneous part is formed in the molding process, or the concentration of a specific component on the surface and inside of the glass lump by volatilization of the glass component from a high temperature surface. There is a risk that a distribution will occur and this distribution will give rise to optically inhomogeneous parts.

  Therefore, in such a glass article, it is necessary to inspect the internal quality after being formed into a shape having a curved surface.

  Therefore, the present invention has been made in view of the above circumstances, and the internal quality of a glass lump having a surface including a curved surface obtained by molding molten glass or glass that has been heated and softened is obtained. By having an inspection process that can be efficiently inspected, various glass articles that require high internal quality, optical element blanks, and glass article manufacturing methods that can manufacture optical elements such as lenses with high productivity And it aims at providing the manufacturing method of an optical element.

  The inventor has found that the above-mentioned problems can be solved if there is a method for efficiently inspecting a glass lump having a curved surface obtained by molding molten glass or heated and softened glass. As a result of earnest study and repeated studies, the present invention has been achieved.

  That is, the present invention has the following configuration.

[Configuration 1]
The present invention relates to a method for producing a glass article by molding molten glass or glass softened by heating, and has a surface having a curved surface and a refractive index of 1.85 or more at a wavelength of 587.56 nm. A molding step for forming a glass lump and an inspection step for inspecting at least the internal quality of the glass lump by transmitting inspection light into the glass lump, and the inspection step is performed on a surface including the curved surface of the glass lump. The surface of the light guide member that is a solid having a refractive index of 1.85 or more at a wavelength of 587.56 nm is brought close to or in contact with the glass lump and the light guide member in the container, and the light guide member of the liquid is interposed between the facing surface and the surface of the glass gob, through a light guide member guides the inspection light to the interior the glass gob through the surface of the surface and the glass gob of the light guide member, and / or , Glass An inspection light transmitted through the inside, with the total reflection is suppressed of the inspection light emitted from the surface of the glass gob by the refractive index between the glass gobs and the light guide member is approaching, the surface and the glass gob It is characterized in that it is carried out by inspecting the inspection light after being guided into the light guide member through the surface of the light guide member and transmitted through the glass block.

[Configuration 2]
The present invention is characterized in that, in the method for producing a glass article having the configuration 1, the glass lump is a glass material for press molding.

[Configuration 3]
In the method for manufacturing a glass article having the configuration 1, the present invention is characterized in that the manufactured glass article is an optical element or an optical element blank.

[Configuration 4]
The present invention is characterized in that, in the method for manufacturing a glass article having any one of Configurations 1 to 3, quality assurance of the manufactured glass article is performed based on the inspection result in the inspection step.

[Configuration 5]
The present invention is characterized in that, in the method for manufacturing a glass article having any one of configurations 1 to 3, the molding conditions in the molding step are set or adjusted based on the inspection result in the inspection step. .

[Configuration 6]
The method for producing an optical element according to the present invention is characterized in that a glass article produced by the method for producing a glass article having Configuration 2 is heated, softened, and press-molded.

[Configuration 7]
The method for producing an optical element according to the present invention is characterized in that an optical element blank produced by the method for producing a glass article having the configuration 3 is ground and polished.

In the method for producing a glass article according to the present invention having Configuration 1, the inspection step is a light guide that is a solid having a refractive index of 1.85 or more at least at a wavelength of 587.56 nm on a surface including a curved surface of a glass lump. is close to the surface of the member, or by contacting the glass body and the light guide member is accommodated in the container, the liquid is interposed between the facing surface and the surface of the glass gob of the light guide member, a light guide member The inspection light is guided to the inside of the glass lump through the surface of the light guide member and the surface of the glass lump and / or the inspection light transmitted through the inside of the glass lump has a refractive index between the glass lump and the light guide member. The glass lump is guided into the light guide member through the surface of the glass lump and the surface of the light guide member in a state where the total reflection of the inspection light emitted from the surface of the glass lump is suppressed due to the approach. Inspecting inspection light after passing through Therefore, the deflection angle due to the refraction of the inspection light on the surface of the glass block and the surface of the light guide member can be reduced, and inspection over a wide range inside the glass block by the incidence of the inspection light from one direction. Can do. It is also possible to inspect the quality of the glass lump surface, for example optical homogeneity.

  In the method for producing a glass article according to the present invention having the configuration 2, since the glass lump is a glass material for press molding, the glass article having an optically inhomogeneous portion before being subjected to press molding is used in the inspection process. It can be detected as a defective product. As a result, it is possible to eliminate the waste of press molding defective products.

  In the method for manufacturing a glass article according to the present invention having the configuration 3, since the manufactured glass article is an optical element or an optical element blank, an optical element having a high internal quality or an optical element blank is manufactured. be able to.

  In the method for manufacturing a glass article according to the present invention having the configuration 4, since the quality of the manufactured glass article is guaranteed based on the inspection result in the inspection step, a glass article with high internal quality can be manufactured.

  In the method for manufacturing a glass article according to the present invention having the configuration 5, since the molding conditions in the molding process are set or adjusted based on the inspection result in the inspection process, a glass article with high internal quality is efficiently manufactured. Can do.

  In the manufacturing method of the optical element according to the present invention having the configuration 6, the glass article manufactured by the manufacturing method of the glass article having the configuration 2 is heated, softened, and press-molded. An element can be manufactured.

  In the manufacturing method of the optical element according to the present invention having the configuration 7, the optical element blank manufactured by the manufacturing method of the glass article having the configuration 3 is ground and polished, so that an optical element having a high internal quality is manufactured. Can do.

  That is, the present invention has a high internal quality by having an inspection process capable of efficiently inspecting the internal quality of a glass lump having a curved surface obtained by molding molten glass or glass that has been heated and softened. Can provide various glass articles, optical element blanks, optical element blanks, and glass article manufacturing methods and optical element manufacturing methods capable of manufacturing optical elements such as lenses with high productivity. is there.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a glass article manufacturing method and an optical element manufacturing method according to the present invention will be described with reference to the drawings.

  A glass article manufacturing method according to the present invention is a glass article manufacturing method for manufacturing a glass article by molding molten glass or glass that has been heated and softened, and forming a glass lump having a curved surface. And a testing step for inspecting at least the internal quality of the glass lump by transmitting inspection light into the glass lump.

[About glass articles]
The glass article manufactured by the method for manufacturing a glass article according to the present invention can be roughly classified into a glass material for press molding, an optical element, and an optical element blank.

  The glass material for press molding is a glass lump made of glass for one press-molded product and preformed into a shape suitable for press molding. This glass material for press molding is also called a press molding preform (hereinafter referred to as a preform). Each method of the present invention is preferably applied to a glass article made of optical glass.

[About inspection process]
FIG. 1 is a cross-sectional view seen from the side showing an inspection process in the method for manufacturing a glass article according to the present invention.

  In the inspection step, as shown in FIG. 1, the surface on one side of at least one light guide member 1, that is, the facing surface 1 a is brought close to or in contact with the surface 101 a including the curved surface of the glass lump 101, Inspection light is guided to the inside of the glass lump 101 through the light guide member 1 and through the opposing surface 1a and the surface 101a of the glass lump 101, and / or inspection light transmitted through the inside of the glass lump 101 is transmitted to the glass lump 101. Inspection light after being guided into the light guide member 1 through the surface 101a and the opposing surface 1a and transmitted through the glass block 101 is inspected. According to this process, not only the internal quality of the glass block but also the surface quality, for example, whether the surface is optically homogeneous can be inspected.

[About light guide members]
In the inspection process of the method for manufacturing a glass article, at least one light guide member 1 is used as shown in FIG. One surface of the light guide member 1 is a facing surface 1a facing the surface 101a including the curved surface of the glass lump 101, and the other surface 1b is a flat surface. In the inspection process, the light guide member 1 is disposed such that the facing surface 1a is brought close to the surface 101a of the glass lump 101 or the facing surface 1a is in contact therewith.

  In this inspection process, the light guide member 1 is made of a material that transmits inspection light, for example, glass, plastic, translucent ceramic, crystal, and the like. The light guide member 1 is made of a light guide member 1 that does not include striae and a light scattering source so as not to cause refraction or scattering of the inspection light. And the opposing surface 1a of the light guide member 1 is formed as a concave surface when the surface 101a of the glass lump 101 is convex, and is formed as a convex surface when the surface 101a of the glass lump 101 is concave.

  In this inspection step, the inspection light from the light source 2 is guided to the inside of the glass lump 101 through the light guide member 1 and the opposing surface 1a and the surface 101a of the glass lump 101, and / or inside the glass lump 101. The transmitted inspection light is guided into the light guide member 1 through the surface 101a of the glass lump 101 and the opposing surface 1a of the light guide member 1. In the embodiment shown in FIG. 1, the light guide members 1, 1 are disposed on both sides of the glass lump 101, and the glass lump 101 is sandwiched between the light guide members 1, 1.

  This glass article manufacturing method reduces or eliminates the inspection light opaque region due to total reflection on the surface 101a of the glass lump 101 by forming such an optical path.

  As an aspect of this inspection process, as an aspect 1, the case where it leads to the inside of the glass lump 101 through the opposing surface 1a and the surface 101a of the glass lump 101 through the light guide member 1, and as the aspect 2, the inside of the glass lump 101 is When the transmitted inspection light is guided into the light guide member 1 through the surface 101a of the glass lump 101 and the opposing surface 1a of the light guide member 1, and as the mode 3, the opposing surface 1a and the glass are passed through the light guide member 1. The light guide member 1 is guided to the inside of the glass lump 101 through the surface 101a of the lump 101 and the inspection light transmitted through the inside of the glass lump 101 is passed through the surface 101a of the glass lump 101 and the facing surface 1a of the light guide member 1. The case where it guides in is considered.

  First, Mode 1 will be described. When the opposing surface 1a of the light guide member 1 and the surface 101a including the curved surface of the glass lump 101 are used in contact with each other, the inspection light is refracted at the contact surface between the light guide member 1 and the glass lump 101 according to Snell's law. To do. The change in the traveling direction of the inspection light on the contact surface is smaller as the refractive index difference between the light guide member 1 and the glass block 101 is smaller if the incident angle on the surface where refraction occurs is constant. Since the light guide member 1 is formed of a solid, the refractive index can be increased while maintaining the transparency to the inspection light. Therefore, even when the refractive index of the glass block 101 is high, the inspection on the contact surface is performed. The change in the traveling direction of light can be reduced. As a result, the incident angle with respect to the surface 101 a when the inspection light that has passed through the inside of the glass lump 101 is emitted to the outside of the glass lump 101 can be reduced, and this inspection light is totally reflected on the surface 101 a of the glass lump 101. Without passing through the glass lump 101.

  When the facing surface 1 a of the light guide member 1 is opposed to the surface 101 a of the glass lump 101, a space (air layer) is formed between the light guide member 1 and the glass lump 101. In this case, the inspection light is refracted according to Snell's law on the opposing surface 1a of the light guide member 1 and the surface 101a of the glass lump 101, but the opposing surface 1a and the surface 101a are close to each other. If the refractive index difference between the optical member 1 and the glass lump 101 is small, the change in the traveling direction of the inspection light due to refraction is small. As a result, as in the case described above, the inspection light is transmitted through the glass block 101 without being totally reflected on the surface 101 a of the glass block 101.

  In this way, in this inspection process, the inspection light can be transmitted over a wide area inside the glass lump 101 or over the entire area inside the glass lump 101, and defects inside the glass lump 101 can be transmitted. The presence or absence can be inspected.

  And about the aspect 2, what is necessary is just to consider the light guide member 1 and the glass lump 101 in description of the above-mentioned aspect 1 reversely. In the aspect 3, the above-described aspects 1 and 2 are performed continuously.

  As will be described later, the defect inside the glass lump 101 is detected by focusing or imaging the inspection light after passing through the glass lump 101. However, if the inspection light is remarkably focused or diverged by the glass lump 101, the inspection light cannot be focused or imaged. In any of the above-described aspects 1, 2, and 3, the light guide member 1 also serves to prevent the inspection light from being significantly focused or diverged by the glass lump 101. Therefore, in a state where the light guide member 1 is opposed to the glass lump 101 (in the state at the time of inspection), a parallel light beam is incident as inspection light and transmitted through the configuration in which the light guide member 1 and the glass lump 101 are combined. It is desirable to set the shape of the light guide member 1 using a known optical design technique so that the light beam becomes a parallel light beam.

  In this inspection process, as described above, the opposing surface 1a is formed in a shape obtained by inverting the surface 101a (curvature portion) of the glass lump 101 (inverted unevenness), and the surface opposite to the facing surface 1a is a flat surface. It is preferable to use two optical members 1. The surface 1b opposite to the facing surface 1a is an incident surface when the inspection light transmitted through the inside of the light guide member 1 exits from the facing surface 1a, and the inspection light enters the light guide member 1 from the facing surface 1a. Is the exit surface. And it is preferable to set it as the structure which pinches | interposes the glass lump 101 with these two light guide members 1. FIG.

  If the light guide member 1 is made of a material having a refractive index that is the same as or close to that of the glass lump 101, the inspection light is incident as a parallel light beam from the plane portion 1b of one light guide member 1. In addition, the inspection light can be emitted from the flat surface portion 1b of the other light guide member 1 in a state of being close to a parallel light beam or a parallel light beam. Here, if the optical homogeneity of the light guide member 1 is low, it cannot be determined whether the detected optical inhomogeneity is derived from the glass block 101 or the light guide member 1. Therefore, it is necessary to make the light guide member 1 using an optically homogeneous material.

  In this way, when the refractive index of the glass lump 101 is the same as or close to the refractive index of the glass lump 101, the glass lump can be obtained even when the curvature of the curved surface portion on the surface 101a of the glass lump 101 is large. The inspection light opaque region due to total reflection on the surface 101a of the 101 can be reduced or eliminated. As a result, the quality inside the glass lump 101, for example, the striae inside the glass lump 101 and the presence / absence of a light scattering source can be efficiently inspected over the entire area of the glass lump 101.

[Liquid or buffer material]
In any of the first aspect, the second aspect, and the third aspect, the inspection light cannot be guided when total reflection of the inspection light occurs on the surface 101a facing the facing surface 1a. In this case, the opposing surface 1a of the light guide member 1 and the surface 101a of the glass lump 101 are brought into contact with each other, or a liquid that transmits inspection light or a buffer material is interposed between the opposing surface 1a and the surface 101a. The critical angle of the inspection light on the surface 101a of the glass lump 101 is increased, and the inspection light is transmitted through the glass lump 101 without being totally reflected.

  By introducing such a liquid or a buffer material, the change in the traveling direction of the inspection light due to refraction at the surface 101a of the glass lump 101 is reduced, and the inside of the glass lump 101 is spread over a wide area or the entire area. Can be inspected.

  It is difficult to precisely match the shape of the facing surface 1a with the shape obtained by inverting the unevenness of the surface 101a between the facing surface 1a of the light guide member 1 and the surface 101a of the glass lump 101. It is effective in the case. Further, when inspecting a plurality of glass pieces 101 having the same specification using one kind of light guide member 1, if the shape accuracy of the surface 101a of the glass piece 101 is not sufficiently high, It is difficult to bring the facing surface 1a into contact with the surface 101a of each glass lump 101 over the entire area. Even in such a case, it is effective to introduce a liquid or a buffer material between the facing surface 1 a of the light guide member 1 and the surface 101 a of the glass lump 101.

  In this inspection process, since the light guide member 1 is used, the inside of the glass lump 101 is inspected over a wide range even if the refractive index of the liquid or the buffer material does not match the refractive index of the glass lump 101. It is possible.

  As the liquid introduced between the facing surface 1a of the light guide member 1 and the surface 101a of the glass lump 101, a liquid that transmits the inspection light is selected. As this liquid, a liquid which does not change the surface 101a of the glass lump 101 and does not corrode is used, for example, matching oil or grease is used. As the matching oil, oil that does not contain environmentally undesirable substances such as arsenic compounds is desirable.

  As a preferred embodiment in the case of introducing a liquid between the facing surface 1a of the light guide member 1 and the surface 101a of the glass lump 101, as shown in FIG. 1, the glass lump 101, the light guide member 1 and the liquid 3a are contained in a container. 4, and the liquid 3 a is interposed between the facing surface 1 a of the light guide member 1 and the surface 101 a of the glass lump 101. That is, the glass lump 101 and the light guide member 1 are placed in the container 4, the surface 101 a of the glass lump 101 is opposed to the facing surface 1 a of the light guide member 1, and the liquid 3 a is placed in the container 4. The liquid 3a can be easily interposed between the surface 101a and the light guide member 1.

  In addition, when using grease as the liquid 3a, the effect mentioned above can be acquired, without using the container for accommodating this liquid 3a.

  In the case where the container 4 is used, it is desirable that the container 4 is made of a material that transmits inspection light and has good optical homogeneity. If it is such a container, inspection light can be introduced into the glass lump 101 in the container 4 from the outside of the container 4 through the container 4, and the inspection light transmitted through the glass lump 101 is emitted to the outside through the container 4. You can also. For example, the inspection light is introduced from the side wall of the container 4 and the inspection light transmitted through the glass lump 101 is emitted from the other side wall of the container, or the inspection light is introduced from the bottom of the container 4 and transmitted through the glass lump 101. The inspection light is emitted from the liquid surface of the liquid 3 a in the container 4, or the inspection light is introduced from the liquid surface of the liquid 3 a in the container 4, and the inspection light transmitted through the glass block 101 is transmitted from the bottom of the container 4. Can be emitted.

  When the inspection light is transmitted through the liquid surface of the liquid 3a in the container 4, the window 5 is provided on a part or all of the liquid surface in order to eliminate the influence of the undulation of the liquid surface. May be. The window 5 is formed in a flat plate shape using an optically homogeneous material while transmitting inspection light. By injecting or emitting the inspection light through the window portion 5, it is possible to eliminate the influence of the undulation of the liquid surface.

  FIG. 2 is a cross-sectional view seen from the side showing another example of the inspection process in the method for manufacturing a glass article according to the present invention.

  Alternatively, as shown in FIG. 2, if the flat surface portion 1 b serving as the inspection light incident surface or the inspection light emission surface of the light guide member 1 is brought out of the liquid 3 a (above the liquid surface), the liquid surface undulations. The inspection light can be incident on the light guide member 1 or the inspection light can be emitted from the light guide member 1 without being affected by the above.

  FIG. 3 is a cross-sectional view seen from the side showing an example in which a cushioning material is introduced between the opposing surface of the light guide member and the surface of the glass lump in the inspection process.

  Further, as shown in FIG. 3, the buffer material 3b introduced between the opposing surface 1a of the light guide member 1 and the surface 101a of the glass lump 101 transmits inspection light and is an optically homogeneous material, It is desirable that the shape changes along each of these surfaces so as to fill the gap between the facing surface 1a and the surface 101a and is made of a material that enables optical close contact with these surfaces, such as silicon rubber. .

  In this case, the container 4 is not necessary, and the light guide member 1, the buffer material 3 b, the glass lump 101, the buffer material 3 b and the light guide member 1 are sequentially stacked on the moving stage or the moving stage, for example. It can be installed on a glass flat plate disposed on the surface of the glass plate to transmit inspection light.

[About light source]
Then, based on the inspection light after passing through the glass lump 101, the inspection light source 2 is a point light source in order to inspect for defects such as striae inside the glass lump 101 that impair optical homogeneity. It is desirable. Examples of the light source that can be regarded as a point light source include a light source unit that combines a lamp and a slit, or a lamp and a pinhole, and a laser light source. As a configuration example of such a light source unit, a lens system (a lens system in which a plurality of lenses are combined) for focusing lamp light between a lamp (for example, a halogen lamp) and a slit (or pinhole) may be used. ) To guide the lamp light focused on the slit opening. Also, when using a laser light source, an optical system that focuses or collimates the laser light may be combined as necessary.

  In this inspection step, the inspection light is preferably light having a wavelength or wavelength range of light used for the purpose of the inspection object. For example, in the case of an optical element used for an imaging optical system in the visible range or a glass material (preform) for press molding the element, it is preferable to use visible light as inspection light. If the inspection light is visible light, general-purpose elements and devices can be used as components such as lenses, mirrors, and image sensors that constitute each optical system.

[Inspection light detection]
As shown in FIG. 1, an imaging optical system 6 that forms an image of the inspection light is used to detect the inspection light after passing through the glass block 101. The image forming optical system 6 forms an image of the glass lump 101 on the light receiving surface of the image sensor (image sensor) 7 and captures the image as image information, or visually observes the image. Also good.

  A defect in the glass lump 101 is detected as a two-dimensional intensity distribution in the light beam cross section of the inspection light, that is, the density of the inspection light.

  When the size of the defect inside the glass lump 101 is small, it is desirable to inspect the presence or absence of the defect by introducing inspection light transmitted through the glass lump 101 into a magnifying optical system such as a microscope. In this case, it is preferable to have a function such as a stage that moves the glass block 101 in a plane orthogonal to the traveling direction (optical axis) of the inspection light. By using this function and moving the glass lump 101, different areas inside the glass lump 101 can be observed in detail. When the glass lump 101 and the light guide member 1 are accommodated in the container 4 containing the liquid 3a for inspection, it is desirable to provide a stage on which the container 4 can be placed.

  As a configuration for remarkably visualizing defects inside the glass lump 101, a configuration for inspecting the inside of the glass lump 101 by the Schlieren method can be cited. The schlieren method is an inspection method in which when there is a slightly different refractive index in the glass lump 101, the portion is recognized as being clearly recognizable by using a change in the traveling direction of the inspection light. Specifically, the inspection light from the point light source is collimated into a parallel light beam, is incident on the glass lump 101, and the inspection light transmitted through the glass lump 101 is focused. Then, a knife edge is arranged at the focus position 8 of the inspection light, and the visual field viewed from the detection side is narrowed down. Then, the inspection light refracted in the direction approaching the knife edge is blocked and darkened, and the inspection light refracted in the direction away from the knife edge is not blocked, so that a bright image is observed.

  In the schlieren method, the defects inside the glass lump 101 can be clearly recognized as the contrast of light and darkness of the inspection light, so that the presence or absence of defects can be clearly visualized and the burden on the operator can be reduced.

  In addition, the presence of a defect can be visualized by arranging a fine pitch grating called Ronchi at the focus position 8 of the inspection light instead of the knife edge. The Ronchi can be considered as a large number of small knife edges arranged in parallel in a plane perpendicular to the optical axis. If the interval (grating interval) between the knife edges forming the Ronchi is matched to the spot diameter on the focal point, there is no need to adjust the position where the Ronchi is arranged in the direction orthogonal to the optical axis. When the Ronchi and the focal position are displaced in the optical axis direction, the inspection light that has passed through the Ronchi forms a striped pattern corresponding to the shape of the Ronchi. In this case, the long key and the focus position 8 of the inspection light can be matched by moving and adjusting the long key in the optical axis direction so that no stripe pattern appears.

  As the Ronchi, it is preferable to prepare a plurality of types, for example, about two types, having different intervals (lattice intervals) between the knife edges forming the Ronchi.

  Further, a net-like member in which a number of small knife edges are arranged vertically and horizontally in a plane orthogonal to the optical axis may be used in place of the Ronchi. In this case, if the interval between the knife edges forming a mesh shape is adjusted to the spot diameter on the focal point, there is no need to adjust the direction perpendicular to the optical axis, and the optical axis direction is a mesh pattern in the inspection light. As in the case of Ronchi, it is only necessary to adjust so that the net pattern corresponding to the shape of the member does not appear.

  In the case where there is a linear striae in the glass lump 101, if this striae is perpendicular to the edge of the knife edge or the lattice direction of the Ronchi, this striae May not be detected. In such a case, the knife edge or Ronchi may be rotated around the optical axis. In this case, it is necessary to rotate the knife edge around the focus position 8 of the inspection light. However, when the Ronchi is used, there is no problem even if the rotation center is shifted from the focus position 8 of the inspection light. .

  Further, when a net-like member is used in place of the Ronchi, this striae is not rotated without rotating the net-like member, regardless of the direction of the linear striae in the glass lump 101. Can be detected.

[Inspection process when manufacturing preforms]
In the case of manufacturing a preform, in the inspection process described above, for the purpose of improving the efficiency of the inspection, at least a surface on which the inspection light is incident (incident surface) or a surface to be emitted (exit surface) is formed. For one surface, a light guide member having an opposing surface having an inverted shape of these surfaces is used. A preform is placed on the opposing surface of the light guide member and immersed in matching oil, and the internal quality such as the presence or absence of striae is observed and inspected.

  In the case of preforms having different curvature radii on the entrance surface and the exit surface, it is desirable to use a light guide member for the surface with the smaller curvature radius.

  In this way, when the light guide member is used for one side of the preform, the inspection light non-transmission area is wide, that is, when the width of the dark outline around the preform is wide and the field of view is narrow, It is desirable to use a light guide member for the opposite surface. As described above, it is preferable to observe and inspect the inside of the preform by using two light guide members and sandwiching the preform between the opposing surfaces.

  In the case of a spherical preform, using two light guide members whose opposite surfaces have a spherical reversal shape, the preform is sandwiched from above and below by the opposite surfaces of these light guide members, soaked in matching oil, It is preferable to observe and inspect the inside of the preform.

  Matching oils are generally commercially available and readily available, and the refractive index (nd) is highest at 1.78. Therefore, when applied to a preform having a refractive index exceeding this, the present invention can obtain a more advantageous effect.

As described above, the light guide member is preferably made of an optically homogeneous material that transmits inspection light. In relation to the preform to be inspected, the difference in the refractive index of the light guide member with respect to the refractive index (nd) of the preform is preferably −5000 × 10 ^{−5 to} 20000 × 10 ^−5. . More preferably, the difference in refractive index of the light guide member with respect to the refractive index (nd) of the preform is −500 × 10 ^{−5 to} 15000 × 10 ⁻⁵ . When the light guide member is made of glass, it is desirable to use optical glass.

  In the matching oil that does not contain an arsenic compound and has no toxicity, the highest refractive index is 1.78. Therefore, when the refractive index of the preform is high and the refractive index difference from the matching oil is large, the light guide member It is desirable to use a material having a higher refractive index than the preform.

  As the shape of the light guide member, when immersed in the matching oil, the inspection light transmitted through the preform is converged just before the image sensor or the detector by combining the light guide member and the container containing the matching oil. Or it is necessary to make it the shape which arrives without diverging. Therefore, both the lid and bottom of the container are made of two parallel flat plates, and the surface of the light guide member that contacts the bottom of the container and the surface of the light guide member that faces the lid of the container (both are in contact with the preform). It is preferable that the surface not to be used is a flat surface.

  As described above, the shape of the facing surface of the light guide member in contact with the preform is the inverted shape of the surface shape of the preform, but the shape of this facing surface is a rotation in which the shape of the preform has one axis of symmetry. Symmetric shape, when the radius of curvature differs between the surface including the first intersection and the surface including the second intersection of the two intersections of the surface of the preform and the axis of symmetry The preform is bisected by a virtual plane orthogonal to the axis, and processed into a shape inverted with respect to each surface shape of the bisected surface.

  Moreover, it is preferable that the light guide member is provided with a step on the outer peripheral portion, and is shaped so that the light guide member can be lifted and tilted using the step.

  And the matching oil used in the inspection process is such that the preform, the light guide member and the inspection light transmitted through the matching oil can be detected by the image sensor and the detector, and the existence of the striae can be confirmed. It is preferable to have visible light transmittance.

The matching oil is preferably a liquid (organic or inorganic solution) having a refractive index (nd) of 1.495 or more, and the difference between the refractive index of the preform and the light guide member is 2000 × 10. It preferably has a refractive index of ⁻⁵ or less. As the matching oil, it is desired that the liquid satisfy the above specifications, and does not contain, for example, an arsenic compound and does not have a poison, and is a liquid that is inexpensive and easy to use.

[Significance of inspection process in the present invention]
The significance of the inspection process in the present invention is roughly divided into two. The first significance is to assure the quality of the glass article based on the result of the inspection process. The second significance is to set or adjust the molding conditions in the glass lump forming step based on the result of the inspection step.

  When quality assurance of a glass article is performed, the quality of the glass article can be guaranteed by inspecting the inside of the glass article in an inspection process and confirming that there are no defects such as striae. In addition, the surface of the glass article can be inspected to confirm that there are no defects.

  That is, a number of glass articles, for example, a glass article as a certain amount of inspection sample is extracted from the same lot of glass articles, and the inside is observed by the above-described inspection process to confirm that there are no defects such as striae. . The number of inspection samples to be extracted from a lot of glass articles depends on how often the method of producing the lot contains glass articles containing internal defects. Therefore, it is desirable to empirically determine the number of inspection samples according to each manufacturing method. In addition, it is desirable to randomly extract the inspection sample. In this way, the quality of the entire lot can be ensured if no internal defects are found in the glass article to be inspected.

  When setting and adjusting the molding conditions in the glass lump forming process, prior to the start of mass production, the molding conditions are provisionally set in the molding process and the glass lump is molded based on these conditions, or A glass lump as an inspection sample is extracted from a glass lump formed by starting mass production based on the conditions, an inspection process is performed on the glass lump, and molding conditions are adjusted based on the inspection result.

  This method is suitable for the case where molten glass is continuously flowed out to form a glass article such as a preform. As long as a glass lump with good internal quality is obtained, the molding conditions should be kept constant. However, if deterioration in internal quality is observed, the molding conditions are based on the internal quality inspection results in the inspection process. To adjust the molding conditions and improve the internal quality. By this method, glass articles with good internal quality can be stably mass-produced.

  The glass lump manufacturing conditions include the temperature of the outflow pipe, the temperature of the molten glass, such as the temperature of the working tank that stirs, homogenizes the molten glass and flows it to the outflow pipe, the temperature of the molding die, and the ejection from the molding die Examples include molding conditions such as gas amount and temperature. In particular, the quality of the glass lump is most sensitive to the temperature of the outflow pipe and the temperature of the working tank among the above conditions. If the temperature of the outflow pipe or work tank is low, the glass lump is devitrified, and the optical performance is greatly impaired. Further, when the temperature of the outflow pipe or the working tank is high, striae are generated in the glass lump, and the optical performance is greatly impaired. The proper temperature range for the outlet pipe is usually in the range of tens of degrees Celsius, although it depends on the glass and other conditions. The proper temperature range for the work tank is usually in the range of several tens of degrees Celsius. In the outflow of the molten glass, the temperature of the molten glass is approximately 1000 ° C to 1200 ° C. Unless the temperature of the molten glass is set to an appropriate value within a few tens of degrees with respect to 1000 ° C, it is difficult to stably obtain a glass lump free from devitrification and striae.

  In the manufacturing method of the present invention, by feeding back to the temperature of the outflow pipe, the temperature of the working tank, or the temperature of the outflow pipe and the working tank according to the result of the inspection process, a high-quality glass lump free from devitrification and striae is obtained. It can be produced stably.

  As mentioned above, before initiating molding continuously, the glass ingot for inspection is molded and the internal quality inspection is performed, the molding conditions are set based on the inspection result, and continuous molding is started, and then the molding is performed. A glass lump can be sampled and subjected to internal inspection, and the results can be fed back to adjust the molding conditions.

  When internal quality inspection is performed prior to the production of glass lump, if striae, etc. are found in the glass lump for internal quality inspection, after adjusting either or both of the outflow conditions and molding conditions Molding is started, or the glass block for internal quality inspection is manufactured again under the adjusted condition, and the molding is started after the internal quality is inspected. If striae or the like is still found by the re-examination, molding is started after further adjusting one or both of the outflow condition and the molding condition.

  In addition, when sampling an actually manufactured glass lump (hot sample) and inspecting the internal quality, if striae is found in the hot sample, either the outflow condition or the molding condition or Give feedback to both to eliminate the source of striae.

  Thus, by adjusting and controlling the temperature of the outflow pipe, it is possible to prevent the occurrence of devitrification and to prevent the occurrence of striae. Alternatively, the occurrence of striae can be eliminated by adjusting other molding conditions described above.

  The internal inspection of the glass lump is preferably performed periodically. The inspection may be performed by sampling an end sample. However, in order to quickly feed back the internal inspection result to the molding conditions, it is preferable to feed back the inspection result of the hot sample.

  Also, in direct press molding, it is a press mold that includes the upper mold that directly receives the molten glass with the lower mold or receives the molten glass with the mold and then moves to the lower mold and the softened glass on the lower mold is opposed to the lower mold. Press molding. In direct press molding, the molded product before annealing is called a hot sample, and the annealed molded product is called an end sample. At least one of the hot sample and the end sample is sampled, and the presence of internal defects such as striae is confirmed by the internal inspection.

  If striae or the like is observed, as explained in the formation of the glass lump, feedback for suppressing the occurrence of striae is applied by adjusting the molding conditions such as the temperature of the outflow pipe that supplies the molten glass. In this way, a press-formed product having no defects such as striae and devitrification is produced. For feedback to molding conditions, it is desirable to quickly inspect the inside of the molded product and sample and inspect a hot sample in order to quickly feed back the result to the molding conditions. In this case as well, in order to set the molding conditions at the start of molding, first press-mold the glass molded product for inspection, inspect the internal quality of the molded product as described above, and set the molding conditions based on the result. You may do it.

[Method of manufacturing optical element]
Next, a method for manufacturing an optical element according to the present invention will be described.

  In this optical element manufacturing method, the glass material for press molding produced as a glass article as described above is heated, softened, and press molded. In this optical element manufacturing method, an optical element may be manufactured by precision press molding using a press molding glass material as a precision press molding preform, or the glass material may be heated and softened to perform press molding. Then, after producing an optical element blank having a shape similar to the optical element, the optical element blank may be annealed and then ground and polished to produce the optical element.

  Furthermore, using the optical element blank produced as a glass article as described above, this optical element blank may be ground and polished to produce an optical element. Also in this case, the optical element blank is annealed, and then ground and polished to produce an optical element.

  The optical element manufactured in this manner is confirmed to have excellent internal quality in the state of the glass article before processing, or quality is guaranteed, so that it is not necessary to inspect the internal quality again.

[Example 1 (related to preform)]
A molten glass from which an optical glass for press molding having a B ₂ O ₃ —La ₂ O ₃ system composition is obtained is continuously discharged from an outflow pipe, received by a porous floating mold, and a molten glass having a predetermined weight is obtained by a descending cutting method. A lump was obtained and formed into a preform for press molding.

  The refractive index of the press-molding preform was 1.85, and the refractive index of the light guide member for striae observation was also 1.85. An oil having a refractive index of 1.78 was used as the matching oil. Here, the refractive indexes of the glass block, the light guide member, and the matching oil are all values at a wavelength of 587.56 nm.

  As an inspection process, matching oil was put into a container (glass cell) made of white plate glass of a bottom plate and a cover plate having two parallel surfaces, and a light guide member was put therein. The light guide member faced the plane side downward, the facing surface having the inverted shape of the preform faced upward, and the preform was placed thereon. And the inspection light of the white light source was entered from the vertically lower side of the glass cell. Inspection light was detected by an imaging device arranged vertically above the preform, light guide member, matching oil, and glass cell, and the image was displayed on a monitor to observe and inspect for striae.

  Since the surface striae were seen at the end of the preform thus examined, the occurrence of surface striae was suppressed by blowing nitrogen gas to the molten glass flow that had come out of the outflow pipe and cooling it, It was confirmed by inspection that the striae was resolved, and preforms were mass-produced.

[Example 2]
The molten glass from which the optical glass for press molding having a B ₂ O ₃ —La ₂ O ₃ —TiO ₂ composition is obtained is continuously discharged from the outflow pipe, and this is received by a porous floating mold, and a predetermined weight is obtained by a descending cutting method. A molten glass lump was obtained and molded into a preform for press molding.

  The refractive index of the preform for press molding was 1.90, and the refractive index of the light guide member for striae observation was 2.00. The light guide member was made of glass. An oil having a refractive index of 1.78 was used as the matching oil. Also here, the refractive indexes of the glass block, the light guide member, and the matching oil are all values at a wavelength of 587.56 nm.

  As an inspection process, matching oil was put into a container (glass cell) made of white plate glass of a bottom plate and a cover plate having two parallel surfaces, and a light guide member was put therein. The light guide member faced the plane side downward, the facing surface having the inverted shape of the preform faced upward, and the preform was placed thereon. And the inspection light of the white light source was entered from the vertically lower side of the glass cell. Inspection light was detected by an imaging device arranged vertically above the preform, light guide member, matching oil, and glass cell, and the image was displayed on a monitor to observe and inspect for striae.

  The preforms thus examined had no surface striae or internal striae, so the preforms were mass produced under the same conditions.

Example 3
From the preforms mass-produced in Example 1 and Example 2, a preform to be an internal quality inspection sample is randomly extracted, and the inside of the preform is observed by the same method as the inspection process performed in Example 1 and Example 2. did.

  None of the samples showed internal defects such as striae. From this result, it was possible to ensure that the internal quality of the preforms mass-produced in Example 1 and Example 2 had sufficient quality as a precision press molding preform.

Example 4
The preforms of Examples 1 to 3 were precision press-molded by a known precision press molding method, and optical elements such as aspherical lenses were mass-produced. When the internal quality of the obtained optical element was inspected by the same method as the inspection process performed in Example 1 and Example 2, it was confirmed that the optical element had sufficient internal quality.

  In this inspection, the optical element was sandwiched between light guide members having a surface obtained by inverting the surface shape of the optical element, and the apparatus used in the inspection process performed in Example 1 and Example 2 was used.

[Comparative Example 1]
When inspecting the inside of a press-molding preform made of glass having a refractive index of 1.90, this press-molding preform is immersed in oil having a refractive index of 1.78, and the above optical The system was tested.

  In this case, a wide black outline was generated in the peripheral portion of the press molding preform, and the field of view that could be observed and inspected was extremely narrow. This outline is an area through which the inspection light does not pass. For this reason, it is necessary to observe while changing the inclination of the press-molding preform and rotating the region where the inspection light is not transmitted, and it takes a long time for observation and inspection.

[Comparative Example 2]
When inspecting the inside of a glass preform made of glass having a refractive index of 1.90, the glass preform is immersed in oil having a refractive index of 1.90, and the optical system described above is used without using the light guide member 1. And inspected.

  In this case, the color of the oil itself was extremely dark and black, so that the location of the glass preform could not be specified. Further, the inspection light is almost absorbed by the oil, and it is difficult to obtain an image from the inspection light after passing through. In order to obtain an image from the inspection light after transmission, a powerful light source and a highly sensitive detector that detects weak inspection light are necessary.

  Furthermore, since oil with a refractive index of 1.90 contains toxic arsenic bromide, it must be handled with great care, and gloves and an apron must be worn to prevent contact with the oil. For example, a gas mask is attached so as not to suck the vapor, and it is necessary to inspect in a state in which safety is emphasized even at the expense of workability. Arsenic bromide was operated in a glove box because corrosive hydrogen bromide was generated by moisture in the air and corroded the observation device such as a microscope.

  In this way, when observing and inspecting glass preforms using high-refractive-index oil containing arsenic compounds, it is necessary to wear protective equipment and equipment that take into account its toxicity and corrosivity. Workability was greatly impaired and work efficiency was reduced. In addition, the oil itself is expensive, and the volatilization during the inspection and the oil adheres to the inspected glass preform and cannot be efficiently recovered, resulting in a loss and an increase in the cost required for the inspection.

It is sectional drawing seen from the side which shows the test | inspection process in the manufacturing method of the glass article which concerns on this invention. It is sectional drawing seen from the side which shows the other example of the test process in the manufacturing method of the glass article which concerns on this invention. It is sectional drawing seen from the side which shows the example which introduced the buffer material between the opposing surface of a light guide member, and the surface of a glass lump in the said test | inspection process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light guide member 1a Opposite surface 2 Light source 3a Liquid 3b Buffer material 4 Container 5 Window part 6 Imaging optical system 7 Imaging element 8 Focal position of inspection light 101 Glass lump 101a Surface

Claims (7)

In a method for producing a glass article by forming a glass article by molding molten glass or heated and softened glass,
A molding step of molding a glass block having a surface including a curved surface and having a refractive index of 1.85 or more at a wavelength of 587.56 nm;
An inspection step of inspecting at least the internal quality of the glass lump by transmitting inspection light into the glass lump,
In the inspection step, the surface of the light guide member which is a solid having a refractive index of 1.85 or more at a wavelength of 587.56 nm is brought close to or in contact with the surface including the curved surface of the glass lump, and the glass The lump and the light guide member are accommodated in a container, a liquid is interposed between the opposing surface of the light guide member and the surface of the glass lump, and the surface of the light guide member and the surface through the light guide member The inspection light is guided to the inside of the glass lump through the surface of the glass lump, and / or the refractive index of the inspection light transmitted through the inside of the glass lump is close to the glass lump and the light guide member. In a state where the total reflection of the inspection light emitted from the surface of the glass lump is suppressed, the glass lump is guided into the light guide member through the surface of the glass lump and the surface of the light guide member. Inspect the inspection light after passing through Method for producing a glass article which comprises carrying out the. The said glass lump is a glass raw material for press molding. The manufacturing method of the glass article of Claim 1 characterized by the above-mentioned. The method for producing a glass article according to claim 1, wherein the glass article to be produced is an optical element or an optical element blank. The method for manufacturing a glass article according to any one of claims 1 to 3, wherein the quality of the manufactured glass article is guaranteed based on an inspection result in the inspection step. The method for manufacturing a glass article according to any one of claims 1 to 3, wherein a molding condition in the molding step is set or adjusted based on an inspection result in the inspection step. A method for producing an optical element, wherein the glass article produced by the method for producing a glass article according to claim 2 is heated, softened, and press-molded. The optical element blank manufactured by the manufacturing method of the glass article of Claim 3 is ground and grind | polished. The manufacturing method of the optical element characterized by the above-mentioned.

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