Tempered glass measuring method and tempered glass measuring device

Abstract

To provide a method for measuring tempered glass capable of accurately measuring refractive index distribution or the like of tempered glass having a thickness of 200 μm or less.SOLUTION: A method for measuring tempered glass includes: a light supply step in which light from a light source is made incident on the inside of a surface layer having a compressive stress layer and a part deeper than the inside of the surface layer via a light supply member; a light extraction step in which surface layer guided light and surface-to-surface guided light are emitted to the outside of the tempered glass via a light extraction member; a light conversion step in which two kinds of light components included in the light emitted to the outside of the tempered glass are converted into a first emission line sequence based on the surface-layer guided light and a second emission line sequence based on the surface-to-surface guided light; an imaging step in which two kinds of emission line sequences are imaged; a position measurement step in which positions of respective emission lines of the two kinds of emission line sequences are measured from the captured image; a separation step for separating the first and second emission line sequences; and a calculation step for calculating at least one of the refractive index of the surface of the tempered glass corresponding to the two kinds of light components, the refractive index of the center, and the refractive index distribution in the depth direction from the surface.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for measuring tempered glass. [Background technology]

[0002] Ultra-thin glass, with a thickness of 200 μm or less, is flexible glass. Such ultra-thin glass combines the properties of glass, such as transparency, insulation, chemical stability, temperature stability, and low gas permeability, and is used in many products that require these characteristics. Examples of products that use ultra-thin glass include touch panel sensors, substrates for thin-film batteries, portable electronic devices, semiconductor interposers, flexible displays, cover glass for fingerprint sensors, solar cells, and flexible electronic products for flexible printed circuit boards.

[0003] Increasing demand for new product functions and the development of diverse new applications have led to a demand for thinner and lighter glass substrates with new properties (e.g., flexibility). However, as glass substrates become thinner, their strength weakens. For this reason, thin glass substrates are often chemically strengthened to increase their strength.

[0004] For example, Patent Document 1 discloses flexible, ultra-thin chemically strengthened glass, which has a thickness of less than 500 μm, an ion-exchange layer depth DOL of less than 30 μm, a surface compressive stress CS of 100 MPa to 700 MPa, and a central tensile stress CT of less than 120 MPa, and the DOL, CS, and CT satisfy a specific relationship.

[0005] Furthermore, Patent Document 2 proposes an ultra-thin chemically strengthened glass having a glass thickness of 0.4 mm or less, a DOL of less than 30 μm, a CS of 100 MPa to 700 MPa, and a CT of less than 120 MPa, in which the DOL, CS, and CT satisfy a specific relationship.

[0006] Typically, the surface layer of these chemically strengthened glasses includes at least a compressive stress layer present on the glass surface side in which compressive stress due to ion exchange is generated, and may also include a tensile stress layer present on the interior side of the glass adjacent to the compressive stress layer in which tensile stress is generated.

[0007] Sodium-containing aluminosilicate glass is often used for chemically strengthened glass, as it is easy to exchange ions and can produce a high surface stress value and a deep stress layer in a short time during the chemical strengthening process.

[0008] This alumina silicate glass is immersed in high-temperature potassium nitrate molten salt to undergo chemical strengthening. Because the potassium ions are highly concentrated in the molten salt, sodium ions in the glass are exchanged with potassium ions in the molten salt. Because potassium ions are larger than sodium ions, large compressive stress is generated on the glass surface, increasing the strength of the glass. After chemical strengthening, the glass surface in contact with the potassium nitrate solution has the highest potassium ion concentration, and the concentration decreases from the glass surface toward the depth.

[0009] The refractive index of glass increases when sodium ions are exchanged for potassium ions. In other words, the refractive index is highest at the surface of the glass, and decreases with depth from the surface.

[0010] One example of a technique for measuring the stress in the surface layer of chemically strengthened glass is a technique (hereinafter referred to as a nondestructive measurement technique) that uses the optical waveguiding effect and the photoelastic effect to nondestructively measure the compressive stress in the surface layer when the refractive index of the surface layer of the chemically strengthened glass is higher than the refractive index of the interior of the glass. In this nondestructive measurement technique, monochromatic light is incident on the surface layer of the chemically strengthened glass, generating multiple modes through the optical waveguiding effect, and light with a fixed ray trajectory is extracted in each mode and imaged into emission lines corresponding to each mode using a convex lens. Note that there are as many imaged emission lines as there are modes.

[0011] Furthermore, this nondestructive measurement technique is configured so that the light extracted from the surface layer can be observed as bright lines for two types of light components whose vibration directions are horizontal and vertical to the exit surface. Utilizing the property that the light of the lowest order, mode 1, passes through the side of the surface layer closest to the surface, the refractive index for each of the two types of light components is calculated from the position of the bright line corresponding to mode 1, and the stress near the surface of the chemically strengthened glass is determined from the difference between the two refractive indices and the photoelastic constant of the glass (see, for example, Patent Document 3).

[0012] Furthermore, with regard to measuring the stress distribution in the surface layer of chemically strengthened glass, a method has been proposed in which, based on the principles of the above-mentioned nondestructive measurement technology, the refractive index distribution from the surface of the glass is determined based on the positions of emission lines corresponding to all modes, and further, the stress distribution is determined based on the photoelastic effect (see, for example, Patent Document 4).

[0013] On the other hand, based on the principles of the above-mentioned non-destructive measurement technology, a method has been proposed in which the stress at the outermost surface of the glass (hereinafter referred to as the surface stress value) is calculated by extrapolation from the positions of the emission lines corresponding to Mode 1 and Mode 2, and the depth of the compressive stress layer is calculated from the total number of emission lines, assuming that the refractive index distribution of the surface layer changes linearly (see, for example, Non-Patent Document 1).

[0014] Generally, if no external force is applied, the sum of stresses is zero. Therefore, the value obtained by integrating the stress generated by chemical strengthening in the depth direction balances out in the central portion that is not chemically strengthened, resulting in approximately uniform tensile stress. A method has been proposed in which the tensile stress CT inside the glass is defined based on the surface stress value and the depth of the compressive stress layer measured using the above-mentioned nondestructive measurement technology, and the strength of tempered glass is controlled using the CT value (see, for example, Patent Document 5). In this method, the tensile stress CT is calculated as follows: CT = (CS × DOL) / (t × 1000 - 2 × DOL). Here, CS is the surface stress value (MPa), DOL is the depth of the compressive stress layer (unit: μm), and t is the plate thickness (unit: mm). [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Special Publication No. 2017-429304 [Patent Document 2] Special Publication No. 2016-508954 [Patent Document 3] Japanese Patent Application Publication No. 53-136886 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-142600 [Patent Document 5] Special Publication No. 2011-530470 [Non-patent literature]

[0016] [Non-Patent Document 1] Yogyo-Kyokai-Shi (Ceramics Association Journal) 87{3}1979 Summary of the Invention [Problem to be solved by the invention]

[0017] Figure 1 is an image of the bright lines of tempered glass with a thickness of 0.8 mm, and Figure 2 is an image of the bright lines of tempered glass with a thickness of 0.04 mm. Both Figures 1 and 2 are images of bright lines taken with an Fsm6000 (manufactured by Orihara Manufacturing Co., Ltd.), a surface stress meter that uses guided light in the surface layer. The row of bright lines shown in Figures 1 and 2 (hereinafter referred to as the row of bright lines) is caused by the decrease in refractive index of tempered glass from the surface to the deeper parts. Because the ions exchanged during the tempering process diffuse from the surface, the concentration gradient is high near the surface and gradually decreases with depth, becoming almost flat at the center of the glass, where the depth from the glass surface is half the glass thickness.

[0018] In the image of tempered glass of normal thickness shown in Figure 1, the left side of the image of the emission line train is where the angle of incidence of the light is large and the emission lines are of a small order mode. The emission line train based on the surface layer waveguide light generated by a refractive index distribution where the refractive index is higher towards the surface has narrower intervals between the emission lines of the higher order mode that passes through the deeper parts than the emission lines of the lower order mode that passes near the surface on the left side of Figure 1.

[0019] On the other hand, this is not the case with the ultra-thin tempered glass shown in Figure 2, where the spacing between the emission lines widens midway through. This is thought to be because interference occurs somewhere other than the emission line sequence based on the waveguided light in the surface layer, resulting in the generation of new emission lines. Therefore, even if the refractive index distribution and stress distribution are calculated using all of the emission line sequences in Figure 2, correct results will not be obtained. The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a method for measuring tempered glass that can accurately measure the refractive index distribution and the like of tempered glass having a thickness of 200 μm or less. [Means for solving the problem]

[0020] The method for measuring tempered glass includes a light supplying step of irradiating light from a light source via a light supplying member into a surface layer having at least a compressive stress layer of tempered glass, which is a measurement object, and into a portion deeper than the surface layer; a light extraction step of emitting, via a light extraction member, surface layer guided light that has propagated within the surface layer and front-to-back surface guided light that is light that has exited the surface layer and propagates between the front and back surfaces of the tempered glass, to the outside of the tempered glass; and a light extraction step of extracting, based on the surface layer guided light, two types of light components that vibrate parallel and perpendicular to the interface between the tempered glass and the light extraction member and that are contained in the light that has been emitted to the outside of the tempered glass. the refractive index of the surface of the tempered glass, the refractive index of the center of the tempered glass, and the refractive index distribution in the depth direction from the surface of the tempered glass, based on the measurement results obtained in the position measurement step and the separation step. [Effects of the Invention]

[0021] The disclosed technique can provide a method for measuring tempered glass that can accurately measure the refractive index distribution and the like of tempered glass having a thickness of 200 μm or less. [Brief explanation of the drawings]

[0022] [Figure 1] This is an image of the bright lines of 0.8mm thick tempered glass. [Figure 2] This is an image of the bright lines of tempered glass with a thickness of 0.04 mm. [Figure 3] FIG. 2 is a diagram illustrating an example of a measuring device for strengthened glass according to the first embodiment. [Figure 4] FIG. 10 is a diagram illustrating modes. [Figure 5] FIG. 2 is a diagram illustrating a refractive index distribution of strengthened glass. [Figure 6] FIG. 10 is a diagram illustrating the ray trajectories of each mode when multiple modes exist. [Figure 7] FIG. 10 is a diagram illustrating an example of an emission line sequence corresponding to a plurality of modes. [Figure 8] 10A and 10B are diagrams illustrating how guided light in the maximum mode of surface layer guided light and light incident at an angle smaller than that of the guided light travel. [Figure 9] This is a diagram for deriving the mode conditions when interference occurs between the front and back surfaces of a glass plate with a glass thickness d and a refractive index ng. [Figure 10] This is a diagram showing light passing through an optical prism, which is a light extraction member from tempered glass, and being extracted to the outside of the tempered glass. [Figure 11] This is a photograph of an array of bright lines on thick tempered glass. [Figure 12] 1 is a flowchart illustrating a measurement method according to the present embodiment. [Figure 13] 2 is a diagram illustrating an example of functional blocks of a calculation unit 70 of the measuring device 1 for strengthened glass. FIG. [Figure 14] FIG. 4 is a diagram illustrating a measuring device for tempered glass according to a second embodiment. [Figure 15] FIG. 10 is a diagram illustrating a measuring device for strengthened glass according to a modified example of the second embodiment. [Figure 16] FIG. 10 is a first diagram illustrating a measuring device for tempered glass according to a third embodiment. [Figure 17] FIG. 10 is a second view illustrating the measuring device for tempered glass according to the third embodiment. [Figure 18] FIG. 10 is a diagram illustrating a measuring device for tempered glass according to a fourth embodiment. [Figure 19] FIG. 10 is a diagram illustrating a measuring device for tempered glass according to a fifth embodiment. [Figure 20] FIG. 2 is a diagram illustrating a state in which a split polarizing plate is viewed from the incident side. [Figure 21] 10 is an example of an image of a series of bright lines obtained by a measuring device 7 for tempered glass. DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes the preferred embodiments of the present invention with reference to the accompanying drawings. In the drawings, the same components are designated by the same reference numerals, and redundant explanations may be omitted.

[0024] First Embodiment Fig. 3 is a diagram illustrating the tempered glass measuring device according to the first embodiment. As shown in Fig. 3, the tempered glass measuring device 1 includes a light source 10, a light supply member 20, a light extraction member 30, a light conversion member 40, a polarizing member 50, an image sensor 60, and a calculation unit 70.

[0025] The object to be measured is an ultra-thin tempered glass 200. The tempered glass 200 is, for example, an ultra-thin glass having a thickness of 200 μm or less that has been tempered by a chemical tempering method, and is provided with a surface layer having a refractive index distribution at least on the surface 210 side.

[0026] (light source) The light source 10 is arranged so that light beam L is incident from the light supply member 20 onto the surface layer of the tempered glass 200. In order to utilize interference, the wavelength of the light source 10 is preferably a single wavelength that results in a simple bright / dark display.

[0027] As the light source 10, for example, a Na lamp, which can easily produce light of a single wavelength, can be used, and in this case the wavelength is 589.3 nm. Alternatively, a mercury lamp, which has a shorter wavelength than a Na lamp, can be used as the light source 10, and in this case the wavelength is, for example, 365 nm, which is the mercury I line. However, since a mercury lamp has many emission lines, it is preferable to use it through a bandpass filter that transmits only the 365 nm line. As other light sources with a high degree of single wavelength, laser light sources such as semiconductor lasers and DPSS (Diode Pumped Solid State) lasers can also be used.

[0028] Alternatively, an LED (Light Emitting Diode) may be used as the light source 10. In recent years, LEDs with many wavelengths have been developed, but the spectral width of an LED is 10 nm or more at half maximum, they have poor single-wavelength characteristics, and their wavelength changes with temperature. For this reason, it is preferable to use an LED through a bandpass filter.

[0029] When light source 10 is configured as an LED passed through a bandpass filter, it does not have the same single wavelength as a sodium lamp or mercury lamp, but is preferable in that any wavelength from the ultraviolet region to the infrared region can be used. Note that the wavelength of light source 10 does not affect the basic principle of measurement by tempered glass measuring device 1, so light sources with wavelengths other than those exemplified above may also be used.

[0030] However, measurement resolution can be improved by using a light source that irradiates ultraviolet light as light source 10. That is, since the surface layer of ultra-thin tempered glass 200 to be measured has a thickness of about several μm to several tens of μm, a large number of interference fringes can be obtained by using a light source that irradiates ultraviolet light as light source 10, and resolution is improved. On the other hand, if a light source that irradiates light with a wavelength longer than ultraviolet light is used as light source 10, the number of interference fringes decreases, and resolution is reduced.

[0031] In addition, in the case of tempered glass that transmits only specific wavelengths, it is desirable to select a light source that transmits only those wavelengths.

[0032] Furthermore, a diffusion plate may be provided between the light source 10 and the light supply member 20 to improve the uniformity of the light from the light source 10, or a lens may be used to condense the light and increase the effective light intensity.

[0033] (Light extraction and emission line imaging) The tempered glass 200 to be measured is placed with its surface 210 in optical contact with the light supply member 20 and the light extraction member 30. The light supply member 20 has a function of making light from the light source 10 incident on the tempered glass 200. The light extraction member 30 has a function of making light that has propagated through the surface layer of the tempered glass 200 and between the front and back surfaces of the tempered glass 200 exit the tempered glass 200.

[0034] For example, prisms made of optical glass can be used as the light supply member 20 and the light extraction member 30. In this case, since light rays optically enter and exit the surface 210 of the tempered glass 200 through these prisms, the refractive index of these prisms must be greater than the refractive index of the tempered glass 200. It is also desirable to select a refractive index such that the incident light and the outgoing light pass through the inclined surface of each prism approximately perpendicularly.

[0035] For example, if the inclination angle of the prism is 60° and the refractive index of the tempered glass 200 is 1.52, the refractive index of the prism can be 1.72. Note that instead of prisms, other members having similar functions may be used as the light supply member 20 and the light extraction member 30. Furthermore, the light supply member 20 and the light extraction member 30 may be integrally formed.

[0036] An imaging element 60 is disposed in the direction of the light emitted from the light extraction member 30, and a light conversion member 40 and a polarizing member 50 are inserted between the light extraction member 30 and the imaging element 60.

[0037] The light converting member 40 has the function of converting the light rays emitted from the light extracting member 30 into a row of bright lines and focusing the light on the imaging element 60. As the light converting member 40, for example, a convex lens can be used, but other members having a similar function may also be used.

[0038] The polarizing member 50 has a function of selectively transmitting one of two types of light components vibrating parallel and perpendicular to the boundary surface between the tempered glass 200 and the light extraction member 30. As the polarizing member 50, for example, a polarizing plate arranged in a rotatable state can be used, but other members having a similar function may also be used.

[0039] A polarizing member with different polarization axes may be used immediately before the image sensor 60 so that bright line images of different light components can be captured depending on the imaging area of ​​the image sensor 60. The area may be divided into two areas, or each area may be for each pixel of the image sensor. Here, the light component vibrating parallel to the boundary surface between the tempered glass 200 and the light extraction member 30 is S-polarized light, and the light component vibrating perpendicularly to the boundary surface is P-polarized light.

[0040] The boundary surface between the strengthened glass 200 and the light extraction member 30 is perpendicular to the exit surface of the light emitted to the outside of the strengthened glass 200 via the light extraction member 30. In other words, the light component that vibrates perpendicular to the exit surface of the light that has been emitted to the outside of the strengthened glass 200 via the light extraction member 30 is S-polarized light, and the light component that vibrates parallel to the exit surface is P-polarized light.

[0041] The imaging element 60 has a function of converting light that is emitted from the light extraction member 30 and received via the light conversion member 40 and the polarization member 50 into an electrical signal. More specifically, the imaging element 60 can, for example, convert the received light into an electrical signal and output the luminance values ​​of each of a plurality of pixels that make up an image as image data to the calculation unit 70. As the imaging element 60, for example, an element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) can be used, but other elements having similar functions may also be used.

[0042] (Calculation function) The calculation unit 70 has the function of taking in image data from the image sensor 60 and performing image processing and numerical calculations. The calculation unit 70 may be configured to have other functions (for example, a function to control the light intensity and exposure time of the light source 10). The calculation unit 70 can be configured to include, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), main memory, etc.

[0043] In this case, the various functions of the calculation unit 70 can be realized by reading a program recorded in a ROM or the like into main memory and executing it with a CPU. The CPU of the calculation unit 70 can read and store data from RAM as needed. However, part or all of the calculation unit 70 may be realized solely by hardware. Furthermore, the calculation unit 70 may be physically configured with multiple devices, etc. A personal computer, for example, can be used as the calculation unit 70.

[0044] (Feature Overview) In the tempered glass measuring device 1, light ray L is emitted from a light source 10 and passes through a light supply member 20 to enter the surface layer of an ultra-thin tempered glass 200 having a thickness of 200 μm or less. The light ray L then propagates within the surface layer or between the front and back surfaces of the tempered glass 200. When the light ray L propagates within the surface layer or between the front and back surfaces, modes are generated due to the optical waveguiding effect, and the light ray L travels along several predetermined paths before being extracted to the outside of the tempered glass 200 by a light extraction member 30.

[0045] Then, the light converting member 40 and the polarizing member 50 form images of P-polarized and S-polarized bright lines for each mode on the image sensor 60 for the guided light within the surface layer and the guided light between the front and rear surfaces. Image data of the P-polarized and S-polarized bright lines generated on the image sensor 60 for each mode is sent to the calculation unit 70. The calculation unit 70 calculates the positions of the P-polarized and S-polarized bright lines on the image sensor 60 from the image data sent from the image sensor 60.

[0046] With this configuration, the strengthened glass measuring device 1 can calculate, based on the positions of the bright lines of P-polarized light and S-polarized light, the refractive index distribution of each of P-polarized light and S-polarized light in the depth direction from the surface in the surface layer of the strengthened glass 200. Furthermore, based on the calculated difference between the refractive index distributions of each of P-polarized light and S-polarized light and the photoelastic constant of the strengthened glass 200, the stress distribution of each of the surface layer of the strengthened glass 200 in the depth direction from the surface can be calculated.

[0047] Hereinafter, the measurement of the refractive index distribution and the measurement of the stress distribution in the measurement device 1 for strengthened glass will be described in more detail.

[0048] (Surface layer guided light modes and emission lines) The trajectory and mode of a light ray when the light ray is incident on the surface layer of the tempered glass 200 will be described with reference to FIGS.

[0049] In FIG. 4, tempered glass 200 has a refractive index distribution in the depth direction from the surface 210. In FIG. 4, if the depth from the surface 210 is x and the refractive index distribution in the depth direction is n(x), the refractive index distribution n(x) in the depth direction will be, for example, as shown in the curve in FIG. 5. That is, in tempered glass 200, both the front and back surfaces are typically chemically strengthened under the same conditions. The refractive index is high at the surface 210 and decreases with depth. The refractive index gradually decreases deeper than the depth where the compressive stress layer ends (the deepest part of the compressive stress layer), reaching its lowest point at the center of the glass, which is half the glass thickness. Deeper than the center, the refractive index increases again due to chemical strengthening on the back surface, and the refractive index at the back surface is the same as that of the surface. The shape of the refractive index curve is symmetrical with respect to the center of the glass. Furthermore, if the compression layer is sufficiently shallow compared to the glass thickness, the refractive index would theoretically be lowest at the center of the glass. However, in reality, the refractive index near the center of the glass is approximately the same as that of the original glass.

[0050] As described above, the refractive index of the surface layer of the tempered glass 200 decreases as it travels toward the interior. Therefore, in Fig. 4, the light ray L incident at a shallow angle with respect to the surface 210 (in the example of Fig. 4, the light ray L is incident via the light supply member 20, which has a refractive index higher than that of the tempered glass 200) gradually approaches parallel to the surface 210, and at the deepest point xt, the light ray reverses direction from the depth direction to the surface 210. Then, the light ray whose ray trajectory has reversed travels toward the surface 210 in a shape similar to the shape of the ray trajectory from the point of incidence to the point of reversal, is at least partially reflected by the surface 210, and travels again into the tempered glass 200.

[0051] The light ray that has traveled back into the tempered glass 200 follows a trajectory of the same shape as the previous trajectory, turns around at depth xt, and returns to the surface 210, repeating this process as the light ray travels back and forth between the surface 210 and the deepest point xt. Since the light travels from the surface 210 through a limited space with a width xt, the light can only propagate as a discrete mode with finite values.

[0052] In other words, only a number of light rays along certain fixed paths can propagate through the surface layer of the tempered glass 200. This phenomenon is called the optical waveguiding effect, and is also the principle by which light rays travel within optical fibers. The mode of light propagating through the surface 210 due to the optical waveguiding effect and the trajectory of the light rays in that mode are determined by the refractive index distribution in the depth direction from the surface 210.

[0053] FIG. 6 is a diagram illustrating the ray trajectories of each mode when multiple modes exist. In the example of FIG. 6, three modes, mode 1, mode 2, and mode 3, are shown, but higher-order modes may also be included. In mode 1, which has the lowest order, the angle between the ray trajectory and surface 210 when the ray trajectory is reflected from surface 210 is the shallowest (the complementary angle to the angle of emergence is smallest). The deepest point of the ray trajectory differs for each mode, with the deepest point xt1 of mode 1 being the shallowest. As the order of the mode increases, the angle between the ray trajectory and surface 210 when the ray trajectory is reflected from surface 210 increases (the complementary angle to the angle of emergence increases). The deepest point xt2 of mode 2 is deeper than the deepest point xt1 of mode 1, and the deepest point xt3 of mode 3 is even deeper than the deepest point xt2 of mode 2.

[0054] Here, the incident angle of a light ray to a given surface is the angle between the incident light ray and the normal to the given surface. In contrast, the complement of the incident angle of a light ray to a given surface is the angle between the incident light ray and the given surface. In other words, if the incident angle of a light ray to a given surface is θ, then the complement of the incident angle of the light ray to the given surface is π / 2-θ. The same applies to the relationship between the exit angle of a light ray to a given surface and the complement of the exit angle.

[0055] 6, the incident light is represented by a single ray, but the incident light has a certain degree of spread. Even with this spread, the complementary angle of the light emitted from surface 210 in the same mode is the same. Furthermore, since light other than the generated mode cancels out, only light corresponding to each mode is emitted from surface 210.

[0056] 3, the light supply member 20, the light extraction member 30, and the tempered glass 200 have the same shape in the depth direction. Therefore, the light condensed by the light conversion member 40 is focused on the imaging element 60, which is the focal plane of the light conversion member 40, and the light corresponding to the mode forms an image as a bright line in the depth direction.

[0057] Since the complementary angle of the emission angle differs for each mode, the emission lines are arranged in order for each mode, forming an emission line array, as shown in Fig. 7. Note that the emission line array is usually a row of bright lines, but when the light supply member 20 and the light extraction member 30 in Fig. 3 are in contact and integrated, direct light from the light source acts as reference light on the emitted light, and this may result in a row of dark lines. However, whether the emission line array is a row of bright lines or a row of dark lines, the positions of the lines are exactly the same.

[0058] In this way, bright lines appear as bright or dark lines when a mode is established. Even if the interference color of a bright line changes depending on the brightness of the reference light, this has no effect on the calculation of the refractive index distribution and stress distribution according to this embodiment. Therefore, in this application, for convenience, both bright and dark lines are referred to as bright lines.

[0059] The complement angle of the exit angle when a light ray that has propagated within the surface layer is refracted and emitted to the outside of the tempered glass 200 is equal to the refractive index of the tempered glass 200 at the deepest point of the ray's trajectory within the surface layer, i.e., equal to that of the critically refracted light when a medium having a refractive index equal to the effective refractive index nn is in contact with the light extraction member 30. The deepest point in each mode can also be interpreted as the point at which the light ray in that mode is totally reflected.

[0060] The ray trajectories of each mode of the surface layer guided light and the positions of the generated bright lines are determined by the refractive index distribution of the tempered glass, the refractive index and shape of the optical prism, and the wavelength of the light source. For example, Equation (1) satisfies the ray trajectories of each mode. Equation (1) is shown as Equation 4 in Patent Document 4.

[0061]

number

[0062] n(x) in Equation (1) is the refractive index distribution in the depth direction of the tempered glass shown in Figure 5 of the present application. Once the refractive index distribution is determined, the ray trajectories of each mode and the positions of the emission lines are also determined. In other words, in principle, if the positions of the emission lines of each mode are known, the refractive index distribution of that mode can be calculated by back-calculation. While it is difficult to obtain a complete analytical solution, approximate and numerical analyses can be used to calculate the refractive index distribution, albeit discrete, as the depth and refractive index corresponding to each mode from the positions of the emission lines based on the surface layer waveguide light. Furthermore, the overall refractive index distribution can be obtained by interpolation or function approximation. Furthermore, the computing power of commonly used PCs (personal computers) is high, allowing such calculations to be performed in a short time.

[0063] Based on these principles and methods, the tempered glass measuring device 1 can calculate the refractive index distribution of each of the P-polarized light and the S-polarized light from the surface to the depth direction in the surface layer of the tempered glass 200 from the positions of the bright lines of the P-polarized light and the S-polarized light in the surface layer.

[0064] This makes it possible to calculate the stress distribution in the surface layer of the strengthened glass 200 from the surface to the depth direction based on the calculated difference in the refractive index distribution of each of the P-polarized light and the S-polarized light and the photoelastic constant of the strengthened glass 200.

[0065] However, in the case of ultra-thin tempered glass, which is the object to be measured in this embodiment, in addition to the bright line array based on the surface layer guided light, a bright line array based on guided light other than the surface layer guided light also occurs. The bright line array based on guided light other than the surface layer guided light cannot be used to calculate the refractive index distribution or stress distribution. Therefore, it is necessary to separate the bright line array based on the surface layer guided light from which the refractive index distribution or stress distribution can be calculated from the total bright line array that occurs. Next, we will explain the bright line array based on the guided light other than the surface layer guided light.

[0066] (Wave-guided light between the front and back surfaces of glass) The mode of the guided light propagating within the surface layer described above is established, and light passing through the deepest part, that is, light incident at an angle smaller than the highest-order guided light, is considered.

[0067] 8 is a diagram illustrating the propagation of light guided in the maximum mode of the surface layer guided light and light incident at a smaller angle than the maximum mode of the surface layer guided light. As the angle of incidence decreases, the number of modes of the surface layer guided light increases and it passes through a deeper point.

[0068] In Figure 8, trajectory 1 is the trajectory of light that passes through the deepest point in the tempered layer, which is the trajectory of the maximum mode of the guided light in the surface layer. Trajectory 3 is the light that, at a smaller angle of incidence, passes through the center of the glass, which is half the thickness of the tempered glass, and travels to the back surface. In this trajectory, the light incident from the front surface (P_F1) gradually becomes closer to parallel to the glass surface, but even when it reaches the center of the glass, which has the lowest refractive index, it does not become parallel to the glass surface, but passes through the center of the glass and enters the tempered layer on the back surface. Then, within the tempered layer on the back surface, it traces a trajectory that is symmetrical to the one within the tempered layer on the front surface, reflects off the back surface (P_B1), traces a similar trajectory, and returns to the front surface (P_F2).

[0069] The light returning to the surface (P_F2) interferes with the light incident on the surface (P_F2), and only the light whose trajectory satisfies the conditions for interference can exist within the glass. Similar to the guided light in the surface layer, this becomes guided light between the front and back surfaces of the glass, and multiple modes exist.

[0070] That is, when the incident angle to the glass is large, the light is guided in the surface layer, i.e., the reinforced layer, and when the incident angle is small, the light is guided between the front and back surfaces of the glass. Hereinafter, the guided light when the incident angle is small may be referred to as front-to-back surface guided light.

[0071] On the other hand, trajectory 2 shows light at an incident angle that traces a trajectory in which the light travels parallel to the front and back surfaces of the glass at the center of the glass, which is half the depth of the tempered glass. This is the trajectory of light in virtual mode 0 of the light guided between the front and back surfaces. As will be described later, the position of mode 0 is also the boundary between the light guided through the surface layer and the light guided between the front and back surfaces.

[0072] 2, for example, when the larger incident angle is on the left, an emission line train based on light guided through the surface layer appears on the left side where the incident angle is larger, and an emission line train based on light guided through the surface and back surface appears on the right side where the incident angle is smaller, sandwiching the position of mode 0 of light guided between the surface and back surface. Hereinafter, the former will be referred to as the first emission line train based on light guided through the surface layer (or simply the first emission line train), and the latter will be referred to as the second emission line train based on light guided between the surface and back surface (or simply the second emission line train).

[0073] In this way, the second bright line sequence based on the front-to-back guided light generated in the ultrathin tempered glass does not overlap with the first bright line sequence based on the front-to-back guided light. That is, with the position of mode 0 of the front-to-back guided light as the boundary position, the first bright line sequence is aligned on one side of the boundary position, and the second bright line sequence is aligned on the other side. Therefore, by grasping the boundary position and determining that the side with a larger angle of incidence of the incident light than the boundary position is the first bright line sequence, it is possible to separate the first bright line sequence from the entire bright line sequence. Then, it is possible to calculate the refractive index distribution and stress distribution based on the separated first bright line sequence.

[0074] The boundary position is a position corresponding to a critical angle determined by the refractive index at a depth of half the thickness of the tempered glass 200 or the refractive index of the tempered glass 200 before being tempered, and the refractive indexes of the light supply member 20 and the light extraction member 30. Furthermore, if the order of the mode of a specific emission line of the light guided between the front and back surfaces can be identified, the boundary position, which is the position of mode 0, can also be determined, making it possible to separate the first and second emission line rows.

[0075] In other words, if the boundary position between the first bright line row based on the surface layer guided light and the second bright line row based on the front and back surface guided light can be determined in some way, it is possible to determine that the first bright line row based on the surface layer guided light is the one with a larger incident angle of light than the boundary position, and to separate the first bright line row based on the surface layer guided light from the entire bright line row.

[0076] In principle, the second line train based on the waveguided light should also occur in thick tempered glass, but it does not actually occur as the glass thickness increases because the coherence deteriorates. In other words, the second line train based on the waveguided light is a phenomenon unique to ultra-thin tempered glass.

[0077] (Second emission line sequence based on waveguided light between the front and back surfaces) As shown in Figure 5, the refractive index of tempered glass changes in the depth direction, but the amount of change is small, at a maximum of about 0.01 for ordinary tempered glass, compared to the refractive index of glass, which is 1.4 to 2.0. Therefore, when considering the mode of light guided between the front and back surfaces, it is safe to consider the refractive index of the glass in the depth direction to be constant.

[0078] Figure 9 shows the relationship between the glass thickness d and the refractive index n g This is a diagram for deriving the mode conditions when interference occurs between the front and rear surfaces of tempered glass. Also, the light incident on the tempered glass has a refractive index n p The light is incident from an optical prism, which is a light supplying member.

[0079] Refractive index n p Light Lp1 incident on point g1 of the tempered glass from the optical prism at an incident angle Ψ has a refractive index n p and refractive index n gThe light is refracted due to the difference in angle of incidence, enters the tempered glass at an angle of incidence ρ, reaches point g2 on the back surface, is reflected at point g2 on the back surface, and returns to point g3 on the front surface. The light that returns to point g3 on the front surface is further reflected, and this reflected light interferes with light Lp2 that has entered from the optical prism, and only light that meets the conditions for being in phase travels as guided light between the front and back surfaces.

[0080] The condition for a mode to exist is a phenomenon synonymous with the commonly known interference that occurs between the front and back surfaces, and if the wavelength of the incident light is λ and the complementary angle of the incident angle inside the tempered glass is Θ, then equation (2) is obtained. In equation (2), k is the number of modes and is a positive integer.

[0081]

number

[0082] Generally, when a sine function is expanded by Taylor expansion, it becomes as shown in equation (3).

[0083]

number

[0084] Since the wavelength λ is usually much smaller than the thickness d, if we use the Taylor expansion of the sine function (Equation (3)) up to the first order in the low order of the mode and turn Equation (1) into an equation for Θ, we obtain a simple equation such as Equation (4).

[0085]

number

[0086] On the other hand, we will investigate the relationship between the interval between the bright lines imaged on the camera and the complementary angle Θ of the angle of incidence. Figure 10 is a diagram showing how light Lg passes through an optical prism, which is a light extraction member from tempered glass, and is extracted to the outside of the tempered glass. First, we consider the ratio between the change dψ* in the angle of emergence ψ* from the optical prism and the change dsinψ in the tangent of the angle of incidence ψ inside the optical prism, and since Ψ* and Ψ' are Snell's equation and Ψ' and Ψ are linearly related, we can obtain equation (5). In Figure 10, n air is the refractive index of air, which is usually 1.

[0087]

number

[0088] From this, the difference in ψ* between mode k and virtual mode 0 (Θ=0) is given by equation (6).

[0089]

number

[0090] The relationship between ψ and Θ can be derived from Snell's equation by using the second order of the Taylor expansion of the cos function, equation (7), to obtain equation (8).

[0091]

number

[0092]

number

[0093] On the other hand, Θ k Using equation (8), the change in the tangent of ψ at Θ0, Δsinψ, is given by equation (9).

[0094]

number

[0095] When an image is formed using a lens with focal length f, which is a light conversion member, the position of the emission line on the image plane from the virtual mode 0 can be expressed by equation (10), and therefore equation (11) is obtained.

[0096]

number

[0097]

number

[0098] Furthermore, if we use equation (4) for Θ and collectively define the coefficients related to (k-0.5) as B, we get equations (12) and (13), which are simple equations for the square of the degree k.

[0099]

number

[0100]

number

[0101] Here, equation (13) itself is an equation that holds when k=1 or more, but in equation (12), in the case of virtual mode 0, D 0-0 =0.

[0102] From equations (12) and (13), the spacing between the emission lines gradually increases as the order increases. Using this relationship, we can identify the second emission line train based on the waveguided light between the front and back surfaces among the entire emission line train.

[0103] (Specific method for separating the second emission line train based on waveguided light between the front and back surfaces) From equation (13), the distance D between an emission line of a certain order and the emission line of the order one lower than that is k-(k-1)is expressed as equation (14). In other words, the line spacing of the second line row based on the light guided between the front and back surfaces can be approximately expressed as a linear function of mode k. However, since k in equation (12) is 1 or more, equation (14) itself holds when k is 2 or more. However, when k is 1, D 0-0 =0, D 1-0 =0.25.

[0104]

number

[0105] Furthermore, the ratio of the spacing between adjacent emission lines, RM k becomes as shown in equation (15), B is eliminated, and the value becomes only the value of degree k.

[0106]

number

[0107] However, equation (15) holds when k is 3 or more, and when k is 2, RM3 = 8. Table 1 shows the values ​​actually calculated.

[0108] [Table 1]

[0109] Next, Figure 2 shows an example of an emission line train of ultrathin tempered glass. This emission line train includes a first emission line train based on light guided through the surface layer and a second emission line train based on light guided between the front and back surfaces, and these two lines are aligned. We will explain how to separate the emission line train of light guided between the front and back surfaces using the ratio of the intervals between the emission lines in the emission line train mentioned above.

[0110] First, all the bright lines in the bright line row in Figure 2 are numbered in order from left to right. Then, the measured bright line positions, which are the distances on the image sensor from the leftmost position in this image, and the intervals between the bright lines D k-(k-1) , the ratio of the emission line spacing RM k was calculated and is shown in Table 2.

[0111] [Table 2]

[0112] As mentioned above, the ratio of the spacing between emission lines of the light guided between the front and back surfaces is determined by the order, as shown in Table 1. Comparing this theoretical ratio of the spacing between emission lines with the actual measured values ​​in Table 2, we can see that emission line number 6 is mode 3 of the light guided between the front and back surfaces.

[0113] A more objective method is, for example, to assume that a certain emission line number is mode 1 of the light guided between the front and back surfaces, and to average the squared difference between the measured RM and the theoretical value of RM in Table 1 for all emission line numbers of assumed mode 1 from mode 3 onwards. This is calculated assuming that all emission line numbers are mode 1 of the light guided between the front and back surfaces, and the emission line number with the smallest average squared difference can be determined to be mode 1. Once the position of mode 1 of the light guided between the front and back surfaces is determined, it can be determined that the emission line row to the left of it is the first emission line row based on light guided between the front and back surfaces.

[0114] Also, the distance D between mode 0 and mode 1 1-0 is the distance D between mode 1 and mode 2 2-1 Taking advantage of the fact that it is 1 / 8 of 2-1 The position of mode 0 can be identified from

[0115] For example, in the case of Table 2, emission line number 4 is mode 1, and emission line number 5 is mode 2. Also, according to Table 2, the distance between mode 1 of emission line number 4 and mode 2 of emission line number 5 is 0.076 mm, so the point 4.3255 mm, which is shifted from emission line number 4 by 0.076 ÷ 8 = 0.0095 mm, becomes virtual mode 0.

[0116] In this way, the property of the second emission line train based on the light guided between the front and back surfaces can be used to determine the position of mode 0, which is the boundary position. The property of the second emission line train based on the light guided between the front and back surfaces here is that the emission line spacing of the second emission line train is approximately a linear function of mode k. Then, if the position of mode 0, which is the boundary position, can be determined, the side of the boundary position where the incident angle of the incident light is larger can be determined to be the first emission line train, and the first emission line train can be separated from all the emission line trains.

[0117] (Calculation of boundary position and CT value) Fig. 11 is a photograph of an array of bright lines in thick tempered glass. In Fig. 11, the boundary positions indicated by the arrows are positions where the brightness changes suddenly, and this occurs at a critical angle determined by the refractive index at a depth of half the thickness of the tempered glass 200 shown in Fig. 3 and the refractive indexes of the light supply member 20 and the light extraction member 30.

[0118] When the refractive index changes with depth, such as in tempered glass, the boundary position is determined by the lowest refractive index, which is usually the center of the glass, which is half the depth of the tempered glass's thickness. Conversely, the boundary position reflects the refractive index of the center of the glass. Usually, the lowest refractive index in tempered glass is also the refractive index of the original bulk of the tempered glass before it is tempered. In other words, the refractive index at the boundary position of tempered glass is the refractive index of the tempered glass (untempered glass) before it is tempered.

[0119] Therefore, it is possible to grasp the boundary position that depends on the refractive index of unstrengthened glass by measuring unstrengthened glass using the tempered glass measuring device 1. That is, since unstrengthened glass does not have a refractive index distribution, no bright line row appears when measured using the tempered glass measuring device 1, but the boundary position that depends on the refractive index of unstrengthened glass can be grasped as the position where the brightness changes suddenly.

[0120] By storing the boundary position, which depends on the refractive index of unstrengthened glass, as information, the pre-stored information on the boundary position can be used when measuring tempered glass. That is, when measuring tempered glass, it can be determined that the side where the incident angle of the incident light is larger than the pre-stored boundary position is the first emission line row based on the surface layer guided light. In this case, it is necessary to measure the unstrengthened glass and the tempered glass without changing the optical positional relationship in the tempered glass measuring device 1.

[0121] On the other hand, in Fig. 8, the ray trajectory corresponding to the boundary position in Fig. 11 is trajectory 2 shown by the dashed line. The ray trajectory at this boundary position is imaginary and does not actually exist, but it is light that travels through the center of the glass parallel to the glass surface, and it also coincides with the imaginary ray trajectory of mode 0 of light guided between the front and back surfaces.

[0122] In ultra-thin tempered glass, the boundary position does not appear clearly among all the bright line trains because a second bright line train is generated based on the light guided between the front and back surfaces. However, as mentioned above, the second bright line train based on the light guided between the front and back surfaces makes it possible to identify the position of the virtual mode 0, which is the boundary position.

[0123] The position of the emission line of mode 0 of the light guided between the front and back surfaces, i.e., the boundary position of the light guided in the surface layer, indicates the refractive index of the glass center. When stress is present at the glass center, the photoelastic effect causes a difference in the positions of the virtual emission lines of mode 0 for P-polarized and S-polarized light. Therefore, the refractive index difference can be calculated from the difference in the positions of mode 0 of the light guided between the front and back surfaces for P-polarized and S-polarized light, and the photoelastic constant can be used to directly calculate CT, the stress at the glass center.

[0124] (Calculating glass thickness) The thickness d of the tempered glass 200 can be calculated based on the second bright line sequence based on the light guided between the front and rear surfaces. That is, when the order and the bright line interval are measured, the wavelength λ, the refractive index n p , n g (cosΨ is n p , n g) is known, it is possible to calculate the thickness d of the strengthened glass 200. The thickness d of the strengthened glass 200 calculated here may be used to calculate the refractive index distribution and the stress distribution.

[0125] (Method for calculating refractive index distribution and stress distribution from the first bright line array based on surface layer guided light) As already explained, if the first bright line row based on the surface layer waveguided light can be separated from the entire bright line row, the refractive index distribution can be calculated by performing approximate analysis or numerical analysis from the position of this first bright line row based on the surface layer waveguided light. Furthermore, the stress distribution in the surface layer of the tempered glass 200 from the surface to the depth direction can be calculated based on the calculated difference in the refractive index distribution between the P-polarized light and the S-polarized light and the photoelastic constant of the tempered glass 200.

[0126] Furthermore, by adding the stress value at the center of the glass obtained from the second bright line sequence based on the light guided between the front and back surfaces to this stress distribution, the stress distribution throughout the entire glass thickness can be calculated. However, the number of data points for the calculated refractive index distribution or stress distribution is discrete, equal to the number of bright lines. Therefore, the stress distribution at any position can be obtained by linear approximation between each point or by calculating an approximation curve using multiple points. The approximation curve can be a quadratic or cubic function, or an error function that represents the distribution due to diffusion phenomena.

[0127] (immersion liquid) In the tempered glass measuring device 1, accurate measurement of the bright line position is required to calculate the refractive index distribution and stress distribution. To achieve this, the light supply member 20 and the light extraction member 30 must be in stable optical contact with the tempered glass 200, and a liquid or gel may be filled between the light supply member 20 and the light extraction member 30 and the tempered glass 200.

[0128] In particular, the ultra-thin tempered glass 200 is highly flexible and therefore bends under its own weight, resulting in poor adhesion between the light supply member 20 and the light extraction member 30. However, by filling the gap between the light supply member 20 and the light extraction member 30 and the tempered glass 200 with a liquid or gel, the surface tension of the liquid or gel increases the adhesion between the light supply member 20 and the light extraction member 30 and the tempered glass 200, thereby enabling stable optical contact.

[0129] Furthermore, the refractive index of this liquid or gel is preferably between the refractive index of the light supply member 20 and the light extraction member 30 and the refractive index of the tempered glass 200, and is as close as possible to the refractive index of the light supply member 20 and the light extraction member 30, or is preferably approximately the same as the refractive index of the tempered glass 200. When the refractive index of the liquid or gel to be filled is approximately the same as the refractive index of the tempered glass 200, the refractive index of the liquid or gel to be filled is preferably within ±0.02 of the refractive index of the tempered glass 200, and more preferably within ±0.01 of the refractive index of the tempered glass 200.

[0130] When the light supplying member 20 and the light extracting member 30 are an optical prism with an integral structure and the refractive index of the liquid filled therein is approximately the same as that of the tempered glass 200, the reflecting surface on the optical prism side when guided light is generated within the tempered glass 200 will have approximately the same refractive index as that of the tempered glass 200 and the liquid. This eliminates the optical boundary, and the light is reflected not by the surface of the tempered glass 200 but by the surfaces of the integrally-constructed light supplying member 20 and light extracting member 30. As a result, even if the surface of the tempered glass 200 is somewhat rough, a sharp bright line image with high contrast can be obtained, and the bright line position can be accurately measured.

[0131] (Measurement flow) Next, a measurement flow will be described with reference to Fig. 12 and Fig. 13. Fig. 12 is a flowchart illustrating a measurement method according to this embodiment. Fig. 13 is a diagram illustrating functional blocks of a calculation unit 70 of the measuring device 1 for strengthened glass.

[0132] First, in step S401 (light supply step), light from the light source 10 is incident via the light supply member 20 onto at least the surface layer of the tempered glass 200 having the compressive stress layer and a portion deeper than the surface layer.

[0133] Next, in step S402 (light extraction process), the surface layer waveguide light that has propagated within the surface layer of the tempered glass 200, and the front-to-back surface waveguide light that is light that has escaped within the surface layer and propagates between the front and back surfaces of the tempered glass 200, are emitted to the outside of the tempered glass 200 via the light extraction member 30.

[0134] Next, in step S403 (light conversion process), the light conversion member 40 converts two types of light components (P-polarized light and S-polarized light) contained in the light emitted outside the tempered glass 200 and vibrating parallel and perpendicular to the boundary surface between the tempered glass 200 and the light extraction member 30 into two types of bright line series including a first bright line series based on the surface layer guided light and a second bright line series based on the front and back surface guided light.

[0135] Next, in step S404 (imaging step), the image sensor 60 captures images of the two types of bright line trains converted by the light conversion step.

[0136] Next, in step S405 (position measurement step), the position measurement unit 71 of the calculation unit 70 measures the positions of each of the two types of bright line trains from the image obtained in the imaging step.

[0137] Next, in step S406 (separation step), the separation unit 72 of the calculation unit 70 separates the entire bright line array obtained in the position measurement step into a first bright line array based on the front surface layer guided light and a second bright line array based on the front and back surface guided light.

[0138] Next, in step S407 (calculation process), the calculation unit 73 of the operation unit 70 calculates at least one of the refractive index of the surface of the tempered glass 200 corresponding to the two types of light components, the refractive index of the center of the tempered glass 200, and the refractive index distribution in the depth direction from the surface of the tempered glass 200, based on the measurement results obtained in the position measurement process and the separation process.

[0139] The calculation unit 73 of the operation unit 70 may further calculate the stress distribution in the depth direction from the surface of the tempered glass 200 based on the difference between the refractive index distributions corresponding to the two types of light components and the photoelastic constant of the tempered glass 200.

[0140] Furthermore, since the profile of the refractive index distribution and the profile of the stress distribution are similar, in step S407, the calculation unit 73 may calculate, as the stress distribution, any one of the refractive index distributions corresponding to P polarization and S polarization: the refractive index distribution corresponding to P polarization, the refractive index distribution corresponding to S polarization, or the refractive index distribution that is the average value of the refractive index distribution corresponding to P polarization and the refractive index distribution corresponding to S polarization.

[0141] Furthermore, in addition to the configuration of FIG. 13, the calculation unit 70 may include a CT value calculation unit that calculates a CT value from a second bright line row based on the guided light between the front and back surfaces, a DOL value calculation unit that calculates a DOL value from a refractive index distribution or a stress distribution, etc.

[0142] As described above, the tempered glass measuring device and tempered glass measuring method according to this embodiment separate the first bright line sequence based on the surface layer waveguide light and the second bright line sequence based on the front and back surface waveguide light from the entire bright line sequence. The refractive index distribution in the depth direction from the surface of the tempered glass can be calculated from the first bright line sequence based on the surface layer waveguide light corresponding to the two types of light components. Furthermore, the stress distribution in the depth direction from the surface of the tempered glass can be calculated based on the difference in the refractive index distributions of the two types of light components and the photoelastic constant of the glass. Furthermore, the stress value at the center of the glass can be calculated from the second bright line sequence based on the front and back surface waveguide light. In other words, the refractive index distribution of ultra-thin tempered glass with a thickness of 200 μm or less can be measured nondestructively and accurately.

[0143] Second Embodiment In the second embodiment, an example is shown in which tempered glass is provided with a light supply member and a light extraction member, which are members for stably adhering to the prism surface. Note that in the second embodiment, descriptions of components that are the same as those in the previously described embodiments may be omitted.

[0144] Fig. 14 is a diagram illustrating a strengthened glass measuring device according to a second embodiment. As shown in Fig. 14, the strengthened glass measuring device 2 has an optical prism 23, which is an integrally structured member that serves as both a light supply member and a light extraction member, and fixing members 25a and 25b. A strengthened glass 200 to be measured is in contact with one surface 23a of the optical prism 23. The fixing members 25a and 25b are provided around the optical prism 23 at positions spaced apart from the optical prism 23.

[0145] The surfaces of the fixing members 25a and 25b that come into contact with the tempered glass 200 are at the same height as and parallel to the surface 23a of the optical prism 23 that comes into contact with the tempered glass 200. The fixing members 25a and 25b are preferably made of metal, glass, resin, or the like.

[0146] Because the ultra-thin tempered glass 200 is highly flexible, if the tempered glass 200 is larger than the first surface 23a of the optical prism 23, the tempered glass 200 will warp due to its own weight. Therefore, unless some countermeasure is taken, the tempered glass 200 will not be able to fit parallel to the first surface 23a of the optical prism 23, and a gap will be created, which may prevent sufficient light from entering or extracting from the optical prism 23.

[0147] However, in the tempered glass measuring device 2, fixing members 25a and 25b are provided around the optical prism 23, with surfaces parallel to and at the same height as the surface 23a of the optical prism 23 that contacts the tempered glass 200. In other words, in the tempered glass measuring device 2, fixing members 25a and 25b are provided, and the fixing members 25a and 25b support an area of ​​the tempered glass 200 surrounding the area that contacts the optical prism 23. Therefore, the tempered glass 200 does not warp due to its own weight, and can be stably adhered to the surface 23a of the optical prism 23 and be in optical contact with it.

[0148] It is also possible to fill the space between the optical prism 23 and the tempered glass 200 with a liquid or gel. In this case, optical contact can be made even more stable.

[0149] <Modification of the second embodiment> Fig. 15 is a diagram illustrating a tempered glass measuring device according to a modified example of the second embodiment. As shown in Fig. 15, the tempered glass measuring device 3 has an optical prism 24, which is an integrally structured member that serves as both a light supply member and a light extraction member. A tempered glass 200 to be measured is in contact with one surface 24a of the optical prism 24.

[0150] The optical prism 24 is provided with fixing members 26a and 26b of width Q around an area of ​​width S through which light is supplied. In other words, one surface 24a of the optical prism 24 that comes into contact with the tempered glass 200 is wider than the area through which light is supplied or extracted. The fixing members 26a and 26b have the same function as the fixing members 25a and 25b in Fig. 14. This allows the tempered glass 200 to stably adhere to and optically contact the one surface 24a of the optical prism 24 without warping due to its own weight.

[0151] The optical prism 24 may be, for example, an integrally formed region of width S for supplying light and fixing members 26a and 26b. Alternatively, the optical prism 24 may be formed by attaching thin optical glass plates with the same refractive index as the fixing members 26a and 26b to a triangular optical prism such as the optical prism 23 shown in Fig. 14.

[0152] It is also possible to fill the space between the optical prism 24 and the tempered glass 200 with a liquid or gel. In this case, optical contact can be made even more stable.

[0153] Third Embodiment In the third embodiment, similar to the second embodiment, an example is shown in which tempered glass is provided with a member for stably adhering to one surface of an optical prism, which is a light supply member and a light extraction member. Note that in the third embodiment, descriptions of components that are the same as those in the previously described embodiments may be omitted.

[0154] 16 is a diagram (part 1) illustrating a strengthened glass measuring device according to the third embodiment. As shown in FIG. 16, the strengthened glass measuring device 4 includes an optical prism 23 that serves as both a light supply member and a light extraction member, and a fixing member 80.

[0155] The fixing member 80 has a flat lower surface 80a, and the ultra-thin tempered glass 200 is adhered to the lower surface 80a by suction or the like. Therefore, the tempered glass 200 does not warp due to its own weight, and can be stably adhered to one surface 23a of the optical prism 23 and can be in optical contact with it.

[0156] It is also possible to fill the space between the optical prism 23 and the tempered glass 200 with a liquid or gel. In this case, optical contact can be made even more stable.

[0157] 17, a fixing member 81 having a flat upper surface 81a may be used, and the tempered glass 200 may be placed on the upper surface 81a of the fixing member 81, and the optical prism 23 may be placed thereon. Even in this configuration, the tempered glass 200 will not warp due to its own weight, and can be stably adhered to and optically contacted with one surface 23a of the optical prism 23.

[0158] It is also possible to fill the space between the optical prism 23 and the tempered glass 200 with a liquid or gel. In this case, optical contact can be made even more stable.

[0159] Fourth Embodiment In the fourth embodiment, an example of a measuring device for tempered glass that can measure refractive index distribution, etc. with higher accuracy using light sources of multiple wavelengths will be described. Note that in the fourth embodiment, descriptions of the same components as those in the already described embodiments may be omitted.

[0160] 18 is a diagram illustrating a strengthened glass measuring device according to Embodiment 4. As shown in FIG. 18, the strengthened glass measuring device 6 includes light sources 10A and 10B and a light introducing member 15.

[0161] The light sources 10A and 10B are light sources capable of emitting light of multiple different wavelengths. Specifically, the light sources 10A and 10B have different wavelengths, and are arranged such that light from either the light source 10A or the light source 10B is incident as light ray L on the surface layer of the tempered glass 200 via the light supply member 20 through the light introducing member 15. To utilize interference, it is preferable that the wavelengths of the light sources 10A and 10B are each a single wavelength that results in a simple bright / dark display.

[0162] For example, a half mirror or a dichroic mirror can be used as the light introducing member 15. When a dichroic mirror is used as the light introducing member 15, the transmission efficiency or reflection efficiency can be increased.

[0163] The light sources 10A and 10B are electrically controlled so that only one of them is turned on. Alternatively, a mechanical shutter or the like may be used to transmit only one of the light sources 10A and 10B. As long as the light from the light sources 10A and 10B can be irradiated onto the light supply member 20 along the same optical axis and can be switched, other methods may be used, such as mechanically moving the positions of the light sources 10A and 10B.

[0164] By using light sources 10A and 10B to sequentially incident light of multiple different wavelengths onto the tempered glass 200, the calculation process can calculate at least one of the refractive index of the surface of the tempered glass 200, the refractive index of the center of the tempered glass 200, and the refractive index distribution in the depth direction from the surface of the tempered glass 200 based on the positions of the emission line rows at each wavelength.

[0165] The position and spacing of the bright lines depend on the wavelength of the light source, and different wavelengths result in different positions and spacing of the bright lines. The position of the bright lines reflects the refractive index and depth corresponding to that position. The more bright lines there are, the more data on depth and refractive index there is, and the more accurate the measurement of refractive index distribution and stress distribution becomes. However, with ultra-thin tempered glass, the depth of the tempered layer cannot be made very deep, and the number of bright lines produced is small. However, by using light sources with multiple wavelengths and measuring the bright line arrays at different wavelengths, the number of bright lines can be increased substantially, making it possible to measure refractive index distribution and stress distribution with high accuracy.

[0166] The wavelength of one of light sources 10A and 10B is preferably 1.5 to 2.5 times the wavelength of the other. For example, if light source 10A has a wavelength of 365 nm, which is the wavelength of an Hg lamp, light source 10B can have a wavelength of 589 nm, which is the wavelength of an Na lamp. By setting the wavelength of one of light sources 10A and 10B to 1.5 to 2.5 times the wavelength of the other, one of the emission line trains of the two wavelengths will fall somewhere between the other, allowing refractive index data to be obtained efficiently at many depths.

[0167] Fifth Embodiment In the fifth embodiment, an example of a measuring device for tempered glass equipped with a split polarizing plate will be described. Note that in the fifth embodiment, the description of the same components as those in the embodiments already described may be omitted in some cases.

[0168] Fig. 19 is a diagram illustrating a strengthened glass measuring device according to embodiment 5. As shown in Fig. 19, strengthened glass measuring device 7 differs from strengthened glass measuring device 1 (see Fig. 3) in that a split polarizing plate 90 is arranged in contact with the incident side of image sensor 60 instead of polarizing member 50.

[0169] Fig. 20 is a diagram illustrating a state of the split polarizing plate 90 as viewed from the incident side. As shown in Fig. 20, the split polarizing plate 90 splits the light from the light source 10 into two types of light components. The split polarizing plate 90 is, for example, a plate-like member having two regions, regions 91 and 92, which correspond to the imaging area of ​​the imaging element 60. Region 91 is a region that transmits one of the two types of light components (P-polarized light or S-polarized light), and region 92 is a region that transmits the other.

[0170] Fig. 21 shows an example of an image of a row of bright lines obtained by the tempered glass measuring device 7. The upper side of Fig. 21 is an image of P-polarized bright lines, and the lower side of Fig. 21 is an image of S-polarized bright lines. The positions of the P-polarized and S-polarized bright lines can be measured from the image shown in Fig. 21.

[0171] Unlike the tempered glass measuring device 1 (see FIG. 3), the tempered glass measuring device 7 does not have a mechanism for rotating the polarizing member 50, which simplifies the device structure. Furthermore, unlike the tempered glass measuring device 1 (see FIG. 3), there is no need to rotate the polarizing member 50 and capture images of the bright lines twice, which reduces the measurement time.

[0172] Although the preferred embodiments and modifications have been described in detail above, the present invention is not limited to the above-described embodiments and modifications, and various modifications and substitutions can be made to the above-described embodiments and modifications without departing from the scope of the claims.

[0173] For example, in each of the above embodiments, a light source has been described as a component of the tempered glass measuring device, but the tempered glass measuring device may be configured without a light source. In this case, the tempered glass measuring device may be configured to include, for example, a light supply member 20, a light extraction member 30, a light conversion member 40, a polarizing member 50, an image sensor 60, and a calculation unit 70. The user of the tempered glass measuring device may prepare and use an appropriate light source.

[0174] Furthermore, in the description of the present invention, the object to be measured, ultra-thin tempered glass, is assumed to have a thickness of 200 μm or less. However, the factors that cause the second emission line row based on the light guided between the front and back surfaces include, in addition to thickness, the refractive index of the glass, the flatness and parallelism of the front and back surfaces of the glass, and the second emission line row can occur even with a thickness of 200 μm or more, and the present invention is also effective for tempered glass of such thickness.

[0175] Furthermore, the above-described embodiments and modifications can be combined as appropriate. [Explanation of symbols]

[0176] 1,2,3,4,5,6,7 Tempered glass measuring device 10,10A,10B light source 15 Light introduction member 20 Light supply member 23,24 Optical Prism 23a,24a 1st page 25a, 25b, 26a, 26b, 80, 81 Fixing members 30 Light extraction member 40 Light conversion material 50 Polarizing element 60 image sensor 70 Arithmetic section 71 Position measurement section 72 Separation part 73 Calculation Unit 80a bottom side 81a Top side 90-segment polarizer 91, 92 area 200 tempered glass 210 Tempered Glass Surface

Claims

1. a light supplying step of irradiating light from a light source via a light supplying member into at least a surface layer having a compressive stress layer of the tempered glass as the measurement object, and into a portion deeper than the surface layer; a light extraction step of emitting, to the outside of the tempered glass via a light extraction member, surface-layer guided light that has propagated within the surface layer and front-to-back surface guided light that is light that has exited the surface layer and propagates between the front and back surfaces of the tempered glass; a light conversion step of converting two types of light components, which are included in the light emitted to the outside of the tempered glass and vibrate parallel and perpendicular to the boundary surface between the tempered glass and the light extraction member, into two types of bright line trains, including a first bright line train based on the surface layer waveguide light and a second bright line train based on the front and back surface waveguide light; an imaging step of imaging the two types of bright line sequences; a position measuring step of measuring the positions of each of the two types of bright line sequences from the image obtained in the imaging step; a separation step of separating the first bright line row and the second bright line row; and a calculating step of calculating at least one of a refractive index of the surface of the tempered glass, a refractive index of the center of the tempered glass, and a refractive index distribution in a depth direction from the surface of the tempered glass corresponding to the two types of light components, based on measurement results obtained in the position measuring step and the separating step.

2. In the separation step, A boundary position corresponding to a critical angle determined by the refractive index at a depth of half the thickness of the tempered glass or the refractive index of the tempered glass before being tempered and the refractive indexes of the light supply member and the light extraction member is grasped; The method for measuring strengthened glass according to claim 1 , wherein a side of the boundary position at which an incident angle of the incident light is larger is determined to be the first bright line row.

3. The strengthened glass measurement method according to claim 2 , wherein in the separating step, the boundary position is determined by utilizing a property of the second bright line row.

4. The method for measuring strengthened glass according to claim 3 , wherein a property of the second bright line train is that a bright line interval of the second bright line train is approximately a linear function.

5. In the separation step, The tempered glass before being tempered is measured to determine a boundary position depending on the refractive index of the tempered glass before being tempered; 2. The method for measuring tempered glass according to claim 1, wherein, when measuring the tempered glass after tempering, information on the boundary position is used to determine that a side of the boundary position at which an incident angle of light is larger is the first bright line row.

6. The method for measuring strengthened glass according to claim 1 , further comprising separating the light from the light source into the two light components prior to the imaging step.

7. 7. The method for measuring tempered glass according to claim 6, wherein the separation is performed using a plate-like member having a region that transmits a light component vibrating parallel to the boundary surface and a region that transmits a light component vibrating perpendicular to the boundary surface, out of the two types of light components.

8. 8. The method for measuring tempered glass according to claim 1, wherein the calculating step calculates a stress distribution in a depth direction from a surface of the tempered glass based on a difference in refractive index distributions corresponding to the two types of light components and a photoelastic constant of the tempered glass.

9. The method for measuring strengthened glass according to claim 8 , further comprising calculating a thickness of the strengthened glass based on the second bright line sequence.

10. The method for measuring tempered glass according to claim 9 , wherein the calculated thickness of the tempered glass is used to calculate the stress distribution.

11. Light beams of different wavelengths are sequentially incident on the tempered glass, 8. The method for measuring strengthened glass according to claim 1, wherein the calculating step calculates at least one of a refractive index of a surface of the strengthened glass, a refractive index of a center of the strengthened glass, and a refractive index distribution in a depth direction from the surface of the strengthened glass, based on positions of the bright line rows at each of the wavelengths.

12. the light providing member and the light extracting member are integrally formed members, 8. The method for measuring tempered glass according to claim 1, further comprising providing a fixing member around the integral structural member, the fixing member having a surface parallel to and at the same height as a surface of the integral structural member that contacts the tempered glass.

13. the light providing member and the light extracting member are integrally formed members, The method for measuring tempered glass according to claim 1 , wherein a surface of the integral structural member in contact with the tempered glass is larger than an area for supplying or extracting light.

14. The method for measuring tempered glass according to claim 1 , wherein a liquid or gel is filled between the tempered glass and the surfaces of the light supply member and the light extraction member that come into contact with the tempered glass.

15. The method for measuring tempered glass according to claim 14 , wherein the refractive index of the liquid or the gel is within ±0.01 of the refractive index of the tempered glass.

16. a light supplying member that causes light from a light source to enter at least a surface layer having a compressive stress layer of the tempered glass that is the object to be measured, and a portion deeper than the surface layer; a light extraction member that outputs, to the outside of the tempered glass, surface-layer guided light that has propagated within the surface layer and front-to-back surface guided light that is light that has exited the surface layer and propagates between the front and back surfaces of the tempered glass; a light conversion member that converts two types of light components, which are included in the light emitted to the outside of the tempered glass and vibrate parallel and perpendicular to the boundary surface between the tempered glass and the light extraction member, into two types of bright line trains, including a first bright line train based on the surface layer waveguide light and a second bright line train based on the front and back surface waveguide light; an imaging element for capturing the two types of bright line sequences; a position measurement unit that measures the position of each of the two types of bright line sequences from the image obtained by the image sensor; a separation unit that separates the first bright line array and the second bright line array; and a calculation unit that calculates at least one of a refractive index of the surface of the tempered glass corresponding to the two types of light components, a refractive index of the center of the tempered glass, and a refractive index distribution in a depth direction from the surface of the tempered glass, based on measurement results obtained by the position measurement unit and the separation unit.

17. The separation unit is A boundary position corresponding to a critical angle determined by the refractive index at a depth of half the thickness of the tempered glass or the refractive index of the tempered glass before being tempered and the refractive indexes of the light supply member and the light extraction member is grasped; The strengthened glass measuring device according to claim 16 , wherein the first bright line row is determined to be on a side where an incident angle of the incident light is larger than the boundary position.

18. The strengthened glass measuring device according to claim 17 , wherein the separating unit grasps the boundary position by utilizing a property of the second bright line row.

19. The strengthened glass measuring device according to claim 18 , wherein the second bright line train has a property in which an interval between bright lines in the second bright line train is approximately a linear function.

20. The separation unit is The tempered glass before being tempered is measured to determine a boundary position depending on the refractive index of the tempered glass before being tempered; 17. The tempered glass measuring device according to claim 16, wherein, when measuring the tempered glass after tempering, information on the boundary position is used to determine that a side of the boundary position where an incident angle of light is larger is the first bright line row.

21. 21. The strengthened glass measuring device according to claim 16, wherein the calculation unit calculates a stress distribution in a depth direction from a surface of the strengthened glass based on a difference in refractive index distributions corresponding to the two types of light components and a photoelastic constant of the strengthened glass.

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