JP7437750B2 - Tempered glass surface refractive index measuring device and surface refractive index measuring method, tempered glass surface stress measuring device and surface stress measuring method - Google Patents

Description

The present invention relates to a surface refractive index measuring device and surface refractive index measuring method for tempered glass, and a surface stress measuring device and surface stress measuring method for tempered glass.

In electronic devices such as mobile phones and smartphones, glass is often used for the display part and the main body of the case.In order to increase the strength of the glass, a surface layer is formed on the glass surface by ion exchange. So-called chemically strengthened glass is used. The surface layer of tempered glass such as chemically strengthened glass includes at least a compressive stress layer that exists on the glass surface side and generates compressive stress due to ion exchange, and a compressive stress layer that exists adjacent to the compressive stress layer on the inner side of the glass and generates tensile stress. It may also include a tensile stress layer in which stress is generated. The strength of tempered glass is related to the stress value of the formed surface layer and the depth of the surface compressive stress layer. Therefore, in the development of tempered glass and quality control during production, it is important to measure the stress value of the surface layer, the depth of the compressive stress layer, or the stress distribution.

As a technique for measuring stress in the surface layer of tempered glass, for example, when the refractive index of the surface layer of the tempered glass is higher than the internal refractive index, the stress of the surface layer is measured using the optical waveguide effect and the photoelastic effect. Techniques for non-destructively measuring compressive stress (hereinafter referred to as non-destructive measurement techniques) can be mentioned. In this non-destructive measurement technology, monochromatic light is incident on the surface layer of tempered glass to generate multiple modes due to the optical waveguide effect, and each mode extracts light with a fixed ray trajectory. to form an image. Note that there are as many imaged bright lines as there are modes.

In addition, with this non-destructive measurement technique, it is possible to observe bright lines of two types of light components in which the vibration direction of the light is horizontal and perpendicular to the emission surface of the light extracted from the surface layer. Using the property that the light of mode 1, which has the lowest order, passes through the side closest to the surface of the surface layer, the light of each light component is determined from the position of the emission line corresponding to mode 1 of the two light components. The refractive index is calculated, and the stress near the surface of the tempered glass is determined from the difference between the two refractive indexes and the photoelastic constant of the glass (for example, see Patent Document 1).

On the other hand, based on the principle of the non-destructive measurement technology described above, the stress at the outermost surface of the glass (hereinafter referred to as surface stress value) is calculated by extrapolation from the positions of the emission lines corresponding to modes 1 and 2, and , a method has been proposed in which the depth of the compressive stress layer is determined 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).

Japanese Unexamined Patent Publication No. 53-136886

Yogyo-Kyokai-Shi (Ceramic Industry Association Magazine) 87 {3} 1979

By the way, in order to determine the refractive index of tempered glass based on bright lines, it is preferable that two or more bright lines can be observed for each of two types of light components whose vibration directions are horizontal and perpendicular to the exit surface. Furthermore, in order to improve the measurement accuracy of the refractive index, it is preferable that a larger number of bright lines can be observed. There is also tempered glass with a thin surface layer, and in this case, in order to improve the measurement accuracy of the refractive index, it is necessary to obtain information on a shallow region closer to the surface of the tempered glass.

However, conventional surface refractive index measuring devices cannot be said to have a sufficiently high accuracy in measuring refractive index, and it has been desired to improve the accuracy in measuring refractive index.

The present invention has been made in view of the above points, and an object of the present invention is to improve the refractive index measurement accuracy of a surface refractive index measuring device.

The present surface refractive index measuring device is a surface refractive index measuring device for tempered glass, in which at least a first region and a second region in contact with the first region are provided in a surface layer of the tempered glass having a compressive stress layer. The light from the light source is made incident through the regions in this order, and the light propagated within the surface layer is directed out of the tempered glass through at least the second region and the first region in this order. A light input/output member to be emitted, and two types of light components that are included in the light emitted through the light input/output member and vibrate parallel and perpendicular to the incident surface of the tempered glass, and two types of bright lines. a light conversion member for converting into a column, an imaging device for capturing images of the two types of bright line arrays, a position measuring means for measuring the positions of the bright lines of the two types of bright line arrays from images obtained by the image pickup device; Refractive index distribution calculating means for calculating the refractive index of the surface of the tempered glass corresponding to the two types of light components, or the refractive index distribution extending from the surface of the tempered glass in the depth direction, based on the measurement results of the position measuring means. and the second region is an inorganic film or a glass layer, and the distance between the interface between the first region and the second region and the incident surface of the tempered glass is 1 μm or more and 10 μm or less. It is.

According to one embodiment of the disclosure, it is possible to improve the measurement accuracy of the refractive index of the surface refractive index measuring device.

1 is a diagram illustrating a surface refractive index measuring device for tempered glass according to a first embodiment; FIG. FIG. 1 is a diagram (part 1) showing the trajectory of light rays inside the glass. It is a figure which illustrates the refractive index distribution of the surface layer of tempered glass. It is a figure explaining the light ray locus of each mode when a plurality of modes exist. FIG. 3 is a diagram illustrating a bright line array corresponding to a plurality of modes. FIG. 2 is a diagram (part 2) showing the trajectory of light rays inside the glass. FIG. 3 is a diagram (Part 3) showing the trajectory of light rays inside the glass. It is a figure which shows the calculation example of the light ray trajectory in each mode of the guided light which transmits the surface layer of tempered glass. FIG. 3 is a diagram illustrating that multi-beam interference occurs in the optical waveguide effect. FIG. 3 is a diagram illustrating multi-beam interference of a Fabry-Perot interferometer. FIG. 7 is a diagram showing an example of calculation of the relationship between the guided light intensity and the angle Θ that the guided light makes with the surface of the tempered glass. 3 is a flowchart illustrating a measurement method according to the present embodiment. It is a figure which illustrates the functional block of the calculation part of a surface refractive index measurement apparatus. FIG. 2 is a diagram (part 1) for explaining the reason why the number of bright lines increases. FIG. 2 is a diagram (part 2) explaining the reason why the number of bright lines increases. FIG. 7 is a diagram illustrating a surface refractive index measuring device for tempered glass according to a second embodiment. FIG. 7 is a diagram (part 1) illustrating a method of forming a light input/output member according to a second embodiment. FIG. 7 is a diagram (part 2) illustrating a method for forming the optical input/output member according to the second embodiment. FIG. 7 is a diagram illustrating a surface refractive index measuring device for tempered glass according to a third embodiment. These are examples of photographs of bright line arrays when the flatness of the tempered glass surface is good and when the flatness is bad. It is a figure which illustrates the surface refractive index measurement apparatus of tempered glass based on 4th Embodiment. It is a figure (part 1) explaining an example. It is a figure (part 2) explaining an example. It is a figure which illustrates the surface refractive index measuring device of the tempered glass based on 5th Embodiment. FIG. 3 is a top view showing an example of a structural member formed on the bottom surface of a prism. It is a figure (part 3) explaining an example.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same components are given the same reference numerals, and redundant explanations may be omitted.

<First embodiment>
FIG. 1 is a diagram illustrating a surface refractive index measuring device for tempered glass according to a first embodiment. As shown in FIG. 1, the surface refractive index measurement device 1 includes a light source 10, a light input/output member 20, a light conversion member 40, a polarizing member 50, an image sensor 60, and a calculation unit 70.

200 is a tempered glass serving as an object to be measured. The tempered glass 200 is glass that has been strengthened by, for example, a chemical strengthening method or an air-cooling strengthening method, and includes a surface layer having a refractive index distribution on the surface 210 side. The surface layer includes at least a compressive stress layer that exists on the glass surface side and generates compressive stress due to ion exchange, and a tensile stress layer that exists adjacent to the compressive stress layer on the inner side of the glass and generates tensile stress. It may include layers.

The light source 10 is arranged so that the light beam L is incident on the surface layer of the tempered glass 200 via the light input/output member 20. In order to utilize interference, it is preferable that the wavelength of the light source 10 is a single wavelength that provides a simple bright and dark display.

As the light source 10, for example, an Na lamp from which light with a single wavelength can be easily obtained can be used, and the wavelength in this case is 589.3 nm. Further, as the light source 10, a mercury lamp having a shorter wavelength than the Na lamp may be used, and the wavelength in this case is, for example, 365 nm, which is the mercury I line. However, since a mercury lamp has many bright lines, it is preferable to use it through a bandpass filter that transmits only the 365 nm line.

Further, 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 LEDs is 10 nm or more at half-value width, has poor single wavelength property, and the wavelength changes depending on temperature. Therefore, it is preferable to use it through a bandpass filter.

When the light source 10 has a configuration in which an LED is passed through a bandpass filter, it is not as monochromatic as a Na lamp or a mercury lamp, but it is preferable in that any wavelength from the ultraviolet region to the infrared region can be used. Note that, since the wavelength of the light source 10 does not affect the basic principle of measurement by the surface refractive index measuring device 1, a light source having wavelengths other than those exemplified above may be used.

The light input/output member 20 is arranged on the surface 210 of the tempered glass 200 that is the object to be measured. The light input/output member 20 includes a prism 21 and an inorganic film 22 formed on a bottom surface 21c of the prism 21. Inorganic film 22 is in contact with surface 210 of tempered glass 200. Note that the prism 21 is a typical example of the first region according to the present invention, and the inorganic film 22 is a typical example of the second region according to the present invention.

The light input/output member 20 has a function of allowing light from the light source 10 to enter the surface layer of the tempered glass 200 having the compressive stress layer via the prism 21 and the inorganic film 22 in this order. Further, the light input/output member 20 has a function of emitting the light propagated within the surface layer to the outside of the tempered glass 200 via the inorganic film 22 and the prism 21 in this order.

The prism 21 of the light input/output member 20 is, for example, a prism made of optical glass with a refractive index of 1.60 to 1.80. In this case, since light rays optically enter and exit the surface 210 of the tempered glass 200 via the prism 21, the refractive index of the prism 21 needs to be larger than the refractive index of the inorganic film 22 and the tempered glass 200. be. Further, it is necessary to select a refractive index at the inclined surfaces 21a and 21b of the prism 21 such that the incident light and the outgoing light pass approximately perpendicularly.

For example, when the inclination angle of the prism 21 is 60° and the refractive index of the surface layer of the tempered glass 200 is 1.52, the refractive index of the prism 21 is, for example, 1.72. Further, the optical glass that is the material of the prism 21 has a highly uniform refractive index, and the in-plane deviation of the refractive index is suppressed to, for example, 1×10 ⁻⁵ or less.

Note that in the light input/output member 20, other members having similar functions may be used in place of the prism 21. Even when another member is used in place of the prism 21, the in-plane deviation of the refractive index of the bottom surface of the other member in the image area obtained in the imaging process described later can be suppressed to 1×10 ⁻⁵ or less. It is desirable that Further, the flatness of the bottom surface of other members is desirably formed to be λ/4 or less, where λ is the wavelength of the light from the light source 10, and if it is formed to be λ/8 or less, More desirable.

The inorganic film 22 of the light input/output member 20 is a distance defining means that defines the distance between the bottom surface 21c of the prism 21 (boundary surface between the prism 21 and the inorganic film 22) and the surface 210 which is the incident surface of the tempered glass 200. Examples of the inorganic film 22 include an oxide film, a nitride film, or an oxynitride film containing at least one metal selected from Si, Al, Zr, Ti, Nb, and Ta. Although glass and resin can also function, they will be described as inorganic films for convenience.

The refractive index of the inorganic film 22 is approximately the same as the refractive index of the tempered glass 200. The inorganic film 22 preferably has a refractive index within a range of ±0.05 with respect to the refractive index of the surface 210 of the tempered glass 200. For example, if the refractive index of the surface 210 of the tempered glass 200 is 1.52, the refractive index of the inorganic film 22 is preferably 1.47 or more and 1.57 or less. When the refractive index of the inorganic film 22 is 1.47 or more and 1.57 or less, reflection at the boundary between the inorganic film 22 and the surface 210 of the tempered glass 200 is sufficiently reduced, and the bright line can be more clearly confirmed. The refractive index of the inorganic film 22 can be measured using, for example, an ellipsometer.

The thickness of the inorganic film 22 is 1 μm or more and 10 μm or less. By setting the thickness of the inorganic film 22 to 1 μm or more and 10 μm or less, the distance d between the interface between the prism 21 and the inorganic film 22 and the surface 210 of the tempered glass 200 can be defined in the range of 1 μm or more and 10 μm or less. By setting the distance d to 1 μm or more, the number of bright lines, which will be described later, can be increased, so that the measurement accuracy of the refractive index of the tempered glass 200 can be improved. As a result, the accuracy of measuring stress in the tempered glass 200 can also be improved. The thickness of the inorganic film 22 can be measured using, for example, an ellipsometer, an X-ray photoelectron spectrometer (XPS), or a field emission scanning electron microscope (FE-SEM).

The deviation in the thickness of the inorganic film 22 is preferably suppressed to 10% or less, more preferably 2% or less, even more preferably 1% or less, and even more preferably 0.5% or less. If the deviation in the thickness of the inorganic film 22 is 10% or less, the optical path length from the lower end of the prism 21 to the surface 210 of the tempered glass 200 will be uniform, the finesse value described below will improve, and the emission line can be more clearly confirmed. . The thickness deviation of the inorganic film 22 can be measured using, for example, an ellipsometer, an X-ray photoelectron spectrometer (XPS), or a field emission scanning electron microscope (FE-SEM).

Even if the surface roughness Ra of the inorganic film 22 on the side closer to the surface 210 of the tempered glass 200 is large, the effect of the present invention is exhibited, but the measurement accuracy is improved if it is 0.02 nm or more and 1.5 nm or less. preferred above. If the surface roughness Ra is 0.02 nm or more and 1.5 nm or less, there is an effect of suppressing scattering of light from the light source 10 on the surface of the inorganic film 22 and inside the inorganic film 22, and as a result, surface refraction The effect of improving the accuracy of the measured values of the rate measuring device 1 can be obtained. The surface roughness Ra can be measured using, for example, an atomic force microscope (AFM).

The parallelism between the interface between the prism 21 and the inorganic film 22 and the surface 210 of the tempered glass 200 is preferably 10% or less of the thickness of the inorganic film 22. Thereby, a sufficient finesse value F (described later) can be obtained. For example, the parallelism of the film thickness is set to 10% or less of the film thickness of the inorganic film 22 by measuring at multiple points using a microscopic spectroscopic film thickness meter or a reflection spectroscopic film thickness meter, and the inorganic film 22 and the tempered glass 200 are High accuracy can be achieved through close contact.

Note that even if the distance d is larger than 10 μm, it is possible to increase the number of emission lines and improve the measurement accuracy of the refractive index, but forming the inorganic film 22 thicker than 10 μm has poor productivity, and If d greatly exceeds 10 μm, the emission lines will be too dense and difficult to observe. Therefore, the upper limit of the distance d is set to 10 μm. Note that the reason why the number of bright lines can be increased will be described later.

An image sensor 60 is disposed in the direction of light emitted from the inclined surface 21b side of the prism 21 of the light input/output member 20, and a light conversion member 40 and A polarizing member 50 is inserted.

The light conversion member 40 has a function of converting the light rays emitted from the inclined surface 21b side of the prism 21 of the light input/output member 20 into a bright line array and condensing the light onto the image sensor 60. For example, a convex lens can be used as the light conversion member 40, but other members with similar functions may also be used.

The polarizing member 50 is a light separating means having a function of selectively transmitting one of two types of light components vibrating parallel and perpendicular to the interface between the tempered glass 200 and the inorganic film 22. As the polarizing member 50, for example, a polarizing plate arranged in a rotatable manner can be used, but other members having similar functions may also be used. Here, the light component that vibrates parallel to the interface between the tempered glass 200 and the inorganic film 22 is S-polarized light, and the light component that vibrates perpendicularly is P-polarized light.

Note that the boundary surface between the tempered glass 200 and the inorganic film 22 is perpendicular to the exit surface of the light emitted to the outside of the tempered glass 200 via the light input/output member 20. Therefore, the light component that vibrates perpendicularly to the exit surface of the light emitted to the outside of the tempered glass 200 via the light input/output member 20 is S-polarized light, and the light component that vibrates in parallel is P-polarized light. It's okay.

The image sensor 60 has a function of converting the light emitted from the light input/output member 20 and received via the light conversion member 40 and the polarizing member 50 into an electrical signal. More specifically, the image sensor 60 can, for example, convert the received light into an electrical signal and output the luminance value of each of the plurality of pixels forming an image to the calculation unit 70 as image data. As the image sensor 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 with similar functions may also be used.

The calculation unit 70 has a 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 of controlling the light amount and exposure time of the light source 10). The calculation unit 70 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a main memory, and the like.

In this case, various functions of the calculation unit 70 can be realized by reading a program recorded in a ROM or the like into the main memory and executing it by the CPU. The CPU of the calculation unit 70 can read and store data from the RAM as necessary. However, part or all of the calculation unit 70 may be realized only by hardware. Further, the calculation unit 70 may be physically formed by a plurality of devices. As the calculation unit 70, for example, a personal computer can be used.

In the surface refractive index measuring device 1, the light L that is incident from the light source 10 on the inclined surface 21a side of the prism 21 of the light input/output member 20 is incident on the surface layer of the tempered glass 200 via the inorganic film 22, and is reflected in the surface layer. becomes guided light that propagates. When the guided light propagates within the surface layer, a mode is generated due to the optical waveguide effect, and it travels along several fixed paths from the inclined surface 21b side of the prism 21 of the light input/output member 20 to the tempered glass 200. Emit outside.

Then, the light converting member 40 and the polarizing member 50 form images on the image sensor 60 as bright lines of P-polarized light and S-polarized light for each mode. Image data of bright lines of P-polarized light and S-polarized light of the number of modes generated on the image sensor 60 is sent to the calculation unit 70 . The calculation unit 70 calculates the positions of the bright lines of P-polarized light and S-polarized light on the image sensor 60 from the image data sent from the image sensor 60.

With such a configuration, the surface refractive index measuring device 1 measures the refraction of P-polarized light and S-polarized light in the surface layer of the tempered glass 200 in the depth direction from the surface, based on the positions of the emission lines of P-polarized light and S-polarized light. Rate distribution can be calculated.

Thereby, 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 between the refractive index distributions of the P-polarized light and the S-polarized light and the photoelastic constant of the tempered glass 200. .

Hereinafter, the measurement of the refractive index distribution, the measurement of the stress distribution, etc. in the surface refractive index measuring device 1 will be explained in more detail.

(mode and emission line)
With reference to FIGS. 2, 3, etc., the locus and mode of a light ray when the light ray is incident on the surface layer of the tempered glass 200 will be described.

In FIG. 2, tempered glass 200 has a refractive index distribution extending from the surface 210 to the depth direction. In FIG. 2, if the depth from the surface 210 is x and the refractive index distribution over the depth direction is n(x), then the refractive index distribution n(x) over the depth direction is, for example, like the curve shown in FIG. become. That is, in the tempered glass 200, the refractive index of the surface 210 is high due to chemical strengthening or the like, and decreases as the depth increases. The refractive index becomes the same as the original glass at the depth at which the chemically strengthened layer formed by chemical strengthening ends (the deepest part of the surface layer), and remains constant (the refractive index of the original glass) at deeper parts. Become. In this way, in the surface layer of the tempered glass 200, the refractive index decreases toward the inside.

At this time, compressive stress is generated on the surface side of the surface layer, and tensile stress acts inside the glass to balance this compression. The position where this compressive stress changes to tensile stress is expressed by the distance from the outermost layer as a DOL_Zero value (Depth of Layer_Zero value), and the depth at which the reinforcing layer ends is expressed as DOL_Tail (Depth of Layer_Tail value). The depth at which the reinforced layer ends is the depth at which the chemically strengthened layer formed by chemical strengthening ends, and is the depth at which the composition ratio becomes almost the same as the composition ratio of the original glass. Further, the tensile stress value inside the glass generated due to this balance is expressed as a CT value (Center Tension value).

In FIG. 2, the light beam L from the light source 10 is incident on the inorganic film 22 through the prism 21 of the light input/output member 20, and reaches the interface between the inorganic film 22 and the tempered glass 200. Since the refractive index of the inorganic film 22 and the surface 210 of the tempered glass 200 are the same, the light travels into the tempered glass 200 without substantially refraction or reflection.

The refractive index of the light ray L incident on the surface 210 at a shallow angle decreases as it progresses toward the inside of the tempered glass 200, so the ray locus gradually approaches parallel to the surface 210, and at the deepest point Flip towards surface 210. In the example of FIG. 2, the light ray L is incident through the light input/output member 20 having a larger refractive index than the tempered glass 200.

The light beam whose trajectory has been reversed then heads toward the surface 210 in a shape similar to the shape of the beam trajectory from the point of incidence to the point where it is reversed, and reaches the interface between the inorganic film 22 and the tempered glass 200. Since the refractive indexes of the surfaces of the inorganic film 22 and the tempered glass 200 are the same, the light travels to the inorganic film 22 and reaches the interface between the inorganic film 22 and the prism 21 without substantially causing refraction or reflection. Since the refractive index of the prism 21 is greater than the refractive index of the inorganic film 22, at least a portion of the light is reflected and travels through the inorganic film 22 into the tempered glass 200 again.

The light that has traveled into the tempered glass 200 is reversed at the deepest point xt of the surface layer of the tempered glass 200. Then, the light reaches the surface of the tempered glass 200 again, and then reaches the interface between the inorganic film 22 and the prism 21, and a part of it is reflected again. The light is transmitted as guided light between the point xt and the point xt.

The guided light propagating between the bottom surface 21c of the prism 21 and the deepest point xt of the surface layer of the tempered glass 200 is taken out from the tempered glass 200 from the inclined surface 21b side of the prism 21 of the light input/output member 20. Ru.

In this way, the light ray that has proceeded inside the tempered glass 200 passes through a trajectory having the same shape as the previous light ray trajectory, reverses itself at the depth xt, and returns to the interface between the bottom surface 21c of the prism 21 and the inorganic film 22. Repeating this, the light beam travels back and forth between the bottom surface 21c and the deepest point xt. Since the light travels in a limited space from the bottom surface 21c to the deepest point xt, the light can only propagate as a discrete mode with a finite value.

That is, only light rays along a plurality of predetermined paths can travel through the surface layer of the tempered glass 200. This phenomenon is called the optical waveguide effect, and is also the principle behind the propagation of light rays within an optical fiber. The mode of light that propagates through the surface 210 due to the optical waveguide effect and the ray trajectory of that mode are determined by the refractive index distribution extending from the surface 210 in the depth direction.

Here, even if the flatness of the surface 210 of the tempered glass 200 is poor, and even if the uniformity of the refractive index of the surface 210 is poor, reflection will not occur on the surface 210 of the tempered glass 200, and the refractive index is uniform and the flatness is poor. It is reflected at the interface between the well-formed bottom surface 21c of the prism 21 and the inorganic film 22. Therefore, the effect of multi-beam interference is high, and the generation of guided light modes becomes very clear.

FIG. 4 is a diagram illustrating the ray trajectory of each mode when a plurality of modes exist. In the example of FIG. 4, three modes, mode 1, mode 2, and mode 3, are shown, but higher-order modes may also be included. Mode 1, which has the lowest order, has the shallowest angle with the bottom surface 21c of the prism 21 when the ray trajectory is reflected by the bottom surface 21c (the complementary angle of exit is the smallest). Further, the deepest point of the ray trajectory differs depending on the mode, and the deepest point xt1 of mode 1 is the shallowest. As the order of the mode increases, the angle made with the bottom surface 21c when reflected by the bottom surface 21c increases (the complementary angle of emission increases). Further, 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 deeper than the deepest point xt2 of mode 2.

Here, the angle of incidence of the light ray with respect to the predetermined surface is the angle between the incident light ray and the normal to the predetermined surface. On the other hand, the complimentary angle of incidence of a light ray with respect to a predetermined surface is the angle between the incident light ray and the predetermined surface. That is, if the angle of incidence of the light ray with respect to the predetermined surface is θ, the complementary angle of incidence of the light ray with respect to the predetermined surface is π/2−θ. The same holds true for the relationship between the exit angle and the complementary exit angle of the light beam with respect to a predetermined surface.

Note that although the incident light is represented by a single ray in FIG. 4, the incident light has a certain spread. Even with the spread light, the complementary angle of the light emitted from the surface 210 is the same in the same mode. Since the light in modes other than those generated cancel each other out, light other than the light corresponding to each mode is not emitted from the surface 210. The same applies to FIG. 6, which will be described later.

As shown in FIG. 5, the light emitted from the inclined surface 21b of the prism 21 of the light input/output member 20 is condensed by the light conversion member 40, and is transmitted to the image sensor 60, which is the focal plane of the light conversion member 40, according to its mode. The light corresponding to the image is formed into an array of bright lines in the depth direction. The reason why the bright line array is imaged will be explained with reference to FIG. 6.

FIG. 6 is an enlarged view of the inclined surface 21b side (right portion) of the prism 21 of the light input/output member 20 in FIG. In FIG. 6, once the refractive index distribution of the surface layer of the tempered glass 200 and the wavelength of the incident light are determined, all modes due to the optical waveguide effect are determined. The angle between the ray trajectory and the bottom surface 21c of the prism 21 is determined for each mode, and the angle also differs depending on the mode.

The larger the order of the mode, the deeper the ray trajectory passes through the surface layer of the tempered glass 200, and the angle with the bottom surface 21c becomes larger. Accordingly, the angle that the extracted light of each mode makes with the bottom surface 21c when emitted from the surface 210 of the tempered glass 200 differs depending on the mode, and the angle becomes larger in order of lower modes.

Further, in FIGS. 1 and 6, the light input/output member 20 and the tempered glass 200 have the same shape in the depth direction. Therefore, the light condensed by the light conversion member 40 is imaged on the image sensor 60, which is the focal plane of the light conversion member 40, with light corresponding to the mode forming a bright line in the depth direction.

Since the complementary angle of emission differs for each mode, the bright lines are lined up in order for each mode, forming a bright line array, as shown in FIG. The bright line array is usually a bright line array, but direct light from the light source acts as a reference light on the emitted light, and it may become a dark line array. However, the position of each line is exactly the same whether it is a row of bright lines or a row of dark lines.

In other words, the bright line appears as a bright line or a dark line when the mode is established. Even if the brightness of the bright line changes depending on the brightness of the reference light, it does not affect the calculation of the refractive index distribution and stress distribution according to this embodiment at all. Therefore, in this application, both bright lines and dark lines are expressed as bright lines for convenience.

In this way, the light beam L (for example, a monochromatic light beam) from the light source 10 is incident on the surface 210 of the tempered glass 200 through the inorganic film 22 from the inclined surface 21a side (left portion) of the prism 21 of the light input/output member 20. Then, the light incident on the surface 210 of the tempered glass 200 draws ray trajectories of several modes on the surface layer of the tempered glass 200 due to the optical waveguide effect, and propagates in the right direction through the surface layer of the tempered glass 200.

This propagated light is taken out of the tempered glass 200 through the inorganic film 22 on the inclined surface 21b side (right part) of the prism 21 of the light input/output member 20. When the light is focused on the image sensor 60 by the light conversion member 40, images of a plurality of bright line arrays or dark line arrays corresponding to the respective modes are formed on the image sensor 60, as many as the number of modes.

By the way, the complementary angle of exit when a light ray transmitted within the surface layer is refracted and emitted to the outside of the tempered glass 200 is determined by the refractive index of the tempered glass 200 at the deepest point of the ray trajectory within the surface layer. That is, it is 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 input/output member 20. The deepest point in each mode can also be interpreted as the point at which the light ray in that mode is totally reflected.

Here, the relationship between the difference Δn in effective refractive index nn between certain modes and the distance ΔS between bright lines is as follows: focal length f of the light conversion member 40, refractive index np of the light input/output member 20, and refractive index of the tempered glass 200. When ng, the following equations 1 and 2 have the following relationships.

従って、撮像素子６０上である一点の実効屈折率の位置が分かれば、観測される輝線の位置から、その輝線に対応する各モードの実効屈折率、すなわち、強化ガラス２００の表面層内での光線軌跡の最深点での屈折率を求めることができる。

Therefore, if the position of the effective refractive index at one point on the image sensor 60 is known, the effective refractive index of each mode corresponding to that bright line, that is, within the surface layer of the tempered glass 200, can be determined from the position of the observed bright line. The refractive index at the deepest point of the ray trajectory can be determined.

(ray trajectory)
In this embodiment, the refractive index distribution is calculated using Equation 3 below. Equation 3 was derived by the inventors based on the technical information described in Non-Patent Document 1. In Non-Patent Document 1, it is assumed that the refractive index distribution changes linearly, and the path along which light travels is approximated to a circular arc. On the other hand, in this embodiment, the refractive index distribution is set to an arbitrary distribution n(x) in order to obtain the conditions for the mode to hold in an arbitrary refractive index distribution.

In Equation 3, θ is the complementary angle of exit of the ray that travels in a straight line over the minute distance dr, n0 is the refractive index of the surface of the tempered glass, Θ is the complementary angle of exit of the ray that is incident on the tempered glass, and λ is the complementary angle of the ray that is incident on the tempered glass. , N is the order of the mode (for example, N=1 for mode 1). Further, tc is the thickness of the inorganic film 22, and nc is the refractive index of the inorganic film 22. Further, G1 is the point at which the light ray enters the tempered glass, F2 is the deepest point (xt) where the light ray is reversed, and G2 is the point at which the light ray reversed at F2 reaches the tempered glass again, which differs depending on the mode. Note that the first term on the left side is a term related to light propagating within the surface layer, the second term on the left side is a term related to light propagating through the inorganic film 22, and the third term on the left side is a term related to light propagating on the surface 210. .

式３を用いて、次数が隣接するモードの最深点の間では、強化ガラス２００の屈折率変化率が一定であると仮定し、次数の最も低いモードから順に、夫々のモードの最深点の深さを計算し、全体の屈折率分布を求めることができる。

Using Equation 3, assuming that the rate of change in the refractive index of the tempered glass 200 is constant between the deepest points of modes with adjacent orders, the depth of the deepest point of each mode is calculated in order from the lowest order mode. The overall refractive index distribution can be determined by calculating the refractive index distribution.

For example, in FIG. 6, the refractive indexes of the surface layer at the depths of the deepest parts xt1, xt2, xt3, . . . of each mode, that is, the effective refractive index, are n1, n2, n3, . Further, it is assumed that the refractive index change rate between the bottom surface 21c and xt1 of the prism 21, between xt1 and xt2, between xt2 and xt3, etc. is a straight line, and the refractive index change rate is α1, α2, α3, etc. ....

Since the ray trajectory in a certain mode n passes through a portion shallower than the deepest point xtn of that mode, if the refractive index distribution from the surface to xtn is determined, the ray trajectory in that mode n is uniquely determined. If xt of all modes is known, the refractive index distribution is uniquely determined, but from Equation 3, it is difficult to directly obtain the refractive index distribution at once, not only analytically but also numerically. It is.

Therefore, first, using modes 1 and 2 that pass through the portion closest to the surface 210, α1, α2, and xt1, xt2 are determined. Then, in mode 3, xt1 and xt2 are known and the only unknown parameter is xt3, so xt3 can be easily found. Similarly, if xt4, xt5, etc. are obtained in order for modes 4, 5, and so on, xtn at the deepest point corresponding to all modes can be obtained. Then, the refractive index distribution extending from the surface 210 in the depth direction can be determined.

FIG. 7 is a diagram showing the trajectory of light rays inside the glass. A specific method for calculating the refractive index distribution will be described with reference to FIG. First, use the ray tracing method to find the left side of Equation 3. In FIG. 7, the x direction (vertical direction) is the depth direction of the tempered glass 200, and the y direction (horizontal direction) is the direction horizontal to the surface 210 of the tempered glass 200. Further, the refractive index at depth x is n(x). Note that H is the normal to the surface 210.

Here, assume that the refractive index of the light input/output member 20 is 1.72, and consider a light ray L that enters the surface 210 from the light input/output member 20 at a complementary angle of incidence Ψ. Further, the coordinates of the point of incidence on the inorganic film 22 are (xc, yc), and the coordinates of the point of incidence on the tempered glass 200 are (x0, y0). Note that xc=0. At this time, the light ray L that has entered the inside of the tempered glass 200 is refracted at the complementary exit angle θ1 and proceeds. At this time, Snell's equation holds true for Ψ and θ1. Furthermore, since the refractive index of the inorganic film 22 is almost the same as the refractive index of the tempered glass 200, it can be assumed that the refractive index at the interface between the inorganic film 22 and the tempered glass 200 can be ignored.

Next, it is assumed that although the trajectory of the light ray L is a curve inside the tempered glass 200, it travels in a straight line over a certain minute distance dr (the distance dr is preferably about 1/10 to 1/100 of the wavelength). In other words, it is assumed that the light ray travels in a straight line by dr in the direction of the complementary angle θ1. At this time, the amount of movement in the x direction dx1=dr·sin θ1, and the amount of movement in the y direction dy1=dr·cos θ1. Also, the coordinates of the moved point (x1, y1)=(dr·sin θ1, y0+dr·cos θ1).

The refractive index at the starting point coordinates (x0, y0) of this partial ray trajectory is n(0), and the refractive index at the end point coordinates (x1, y1) is n(x1), but within this ray trajectory Assume that the refractive index at the starting point is constant, and the refractive index changes to n(x1) at the ending point. Then, the next ray trajectory changes its angle to the complementary exit angle θ2 and proceeds according to Snell's law. The light that travels at a complementary exit angle θ2 travels in a straight line by dr, and further changes direction and travels at a complementary exit angle θ3 (not shown). This is repeated to trace the ray trajectory to obtain the entire ray trajectory.

At this time, the first term on the left side of Equation 3 is calculated every time dr advances. For example, in the part from coordinates (x0, y0) to coordinates (x1, y1), the first term is dr·cosθ1·n(0), which can be easily calculated. Other drs can be calculated in the same way. Then, by adding the first term determined for each dr until the ray trajectory returns to the bottom surface 21c of the prism 21, the first term on the left side of Equation 3 is all determined. Also, at this time, the distance Σdy that this ray trajectory travels in the y direction is known. In Equation 3, since d _G1G2 =Σdy and Θ=θ1, the third term on the left side of Equation 3 can be found, and these two terms correspond to the optical path difference within the tempered glass 200. On the other hand, since the second term indicating the optical path difference within the inorganic film 22 is all known, the entire left side of Equation 3 can be found.

FIG. 8 shows the calculated ray trajectories in each mode of guided light that propagates through the surface layer of a typical tempered glass using the above method. Note that, for simplicity, FIG. 8 shows the case where tc=0, that is, there is no inorganic film. This typical tempered glass has a refractive index of the original glass ngb = 1.51, a refractive index distribution of the surface changed by the chemical strengthening process, a refractive index of the outermost surface ngs = 1.52, a depth of 50 μm, and a refractive index distribution of the surface changed by the chemical strengthening process. The rate distribution shape is a straight line. Further, the wavelength of the light source is 596 nm, the refractive index of the prism is np = 1.72, and the refractive index of the liquid sandwiched between the prism and the tempered glass is nf = 1.64.

At this time, according to the calculation results, there are 19 modes, and the angle θ1 of the lowest mode 1 with the glass surface, that is, Θ in equation 3, is 2.0°, and the deepest point is 4.3 μm. Furthermore, when the reflectance R of light energy at the interface between the surface of the tempered glass and the liquid is calculated from Fresnel's equation based on the ray trajectory of mode 1, R=0.7.

Although the guided light in FIG. 1 is drawn as a single straight line, the optical waveguide effect is multi-beam interference. FIG. 9 is a diagram illustrating that multi-beam interference occurs in the optical waveguide effect. In FIG. 9, the light ray L ₁ from the light source enters the surface 210 of the tempered glass 200 at the point P ₁ , and the light ray L ₁ that returns within the surface layer of the tempered glass 200 reaches the point P ₂ , and the same at the point P ₂ . Interference occurs with the light beam _L2 incident from the light source.

Then, the light ray L ₁ reflected at the point P ₂ and the incident ray L ₂ travel along the same path and reach the point P ₃ . At point _P3 , the light ray _L1 and light ray _L2 interfere with the light ray _L3 incident from the same light source, and furthermore, the light ray _L1 , light ray _L2 , and light ray _L3 travel to point _P4 on the same path. As the light progresses, it interferes with even more light rays, resulting in multi-beam interference.

In general, in the case of multi-beam interference, the interference conditions are narrow, so the guided light that propagates through the surface layer of the tempered glass is under very narrow conditions, that is, the light that only meets the narrow condition of Θ in Equation 3 is the guided light that passes through the tempered glass. transmitted through the surface layer. Therefore, the line width of the emission line is also very narrow and steep. This phenomenon is important in order to be able to accurately measure the position of the bright line.

However, in order for the width of the bright line to be narrowed by multi-beam interference, the glass surface serving as the interference surface needs to be optically flat and uniform.

(Fabry-Perot interference equation)
Multi-beam interference of a Fabry-Perot interferometer will be briefly explained. FIG. 10 is a diagram illustrating multi-beam interference of a Fabry-Perot interferometer. As shown in Fig. 10, light incident at an angle φ on a film with a refractive index n and a thickness L, in which two reflective surfaces with a reflectance R and a transmittance T are arranged vertically in parallel, Repeatedly reflect the pauses. Then, multi-beam interference occurs, and only the wavelengths that cause interference pass through the two reflective surfaces, and only light in a narrow range of wavelengths is transmitted. Therefore, this principle is used in spectrometers and narrowband interference filters. A finesse value F is defined as a measure of the wavelength range that is transmitted.

When the round-trip optical path length between the two reflective surfaces is an integral multiple of the wavelength of the incident light, the brightness reaches its maximum, which is a condition for interference, but since there are multiple wavelengths that satisfy this condition, The finesse value F is defined as the ratio of the width of wavelengths of transmitted light to the interval of matching wavelengths. The finesse value F is determined by the reflectance R, as shown in Equation 4.

ファブリペロー干渉計への入射する角度（図１０でのφ）に対しても、選択制があり、フィネス値Ｆは入射角でも同様な意味を持つパラメータである。又、フィネス値Ｆは反射面の平坦度や平行度が良いことが必要であり、反射率Ｒが高くても、反射面の平坦度、平行度の値が大きければ、十分なフィネス値Ｆが得られない。例えば、現在、実用化され、市販されているファブリペロー干渉計では、フィネス値Ｆが高く５０～１００程度であるが、それを得るための反射面の平坦度はλ／１００～λ／２００である。

There is also a selection system for the angle of incidence on the Fabry-Perot interferometer (φ in FIG. 10), and the finesse value F is a parameter that has the same meaning for the angle of incidence. In addition, the finesse value F requires that the flatness and parallelism of the reflective surface are good, and even if the reflectance R is high, if the flatness and parallelism of the reflective surface are large, the finesse value F will be sufficient. I can't get it. For example, Fabry-Perot interferometers currently in practical use and commercially available have a high finesse value F of about 50 to 100, but the flatness of the reflecting surface to obtain this is λ/100 to λ/200. be.

The multi-beam interference in the guided light of the surface layer of the tempered glass in this embodiment is also the same in principle as the Fabry-Perot interferometer. The Fabry-Perot interferometer uses two reflective surfaces with a reflectance R and a transmittance T, but the only difference is that the guided light in the surface refractive index measuring device 1 is totally reflected on one side, and the principle that causes multi-beam interference is It's the same. Although the values of the relational expression for the finesse value F and the necessary flatness of the reflective surface are slightly different, the tendency is the same. Therefore, the width and steepness of the bright line of the surface refractive index measuring device 1 are also related to the reflectance and transmittance of the surface of the tempered glass, and the flatness of the surface.

In the case of the surface refractive index measuring device 1, the finesse value F is total reflection on one side and the reflectance is 100%, so the reflectance R of the Fabry-Perot finesse value F in Equation 4 is Just substitute the square root. In addition, the minimum flatness required to obtain the finesse value F is q> because if the flatness is = λ/q, in the case of a Fabry-Perot interferometer, there are two reflecting surfaces for one round trip of the light beam. 2×F, and in the case of the surface refractive index measuring device 1, there is only one reflecting surface, so q>F.

As mentioned above, in the case of typical tempered glass, the reflectance of the tempered glass surface is approximately R=0.7. For example, in the case of R=0.7, the square root is 0.837, and the finesse value F is approximately 18, and a sufficient finesse value F can be obtained from the reflectance, but the flatness required for this is λ/18 Therefore, extremely high flatness is required. However, in the case of the surface refractive index measuring device 1, it is not necessary to have high resolution like a spectrometer, but it is sufficient to secure a finesse value F that is sufficient as long as the measurement accuracy of the position of the bright line can be obtained.

FIG. 11 shows the results of calculating the relationship between the guided light intensity and the angle Θ that the guided light makes with the surface of the tempered glass at each finesse value using the typical tempered glass example shown above.

In FIG. 11, the results when the finesse value F was 1, 5, and 18 were compared. The finesse value F=18 obtained from the reflectance is very sharp. on the other hand. When the finesse value F=1, the brightness is wide and the contrast is reduced to 1/5 or less, and it is expected that the bright line position measurement accuracy will be reduced.

However, even when the finesse value F is around 5, the contrast is reduced by about 10%, the peak is sharp, and the shape allows for sufficient emission line position measurement.In other words, a finesse value F of around 5 to 10 is sufficient. Position measurement is possible. The flatness required at this time is λ/10 to λ/5.

(Calculation of refractive index distribution)
Next, a method of calculating the refractive index distribution will be explained. First, as shown in Non-Patent Document 1, the refractive index of the surface 210 and the deepest point of mode 2 are determined from the positions of the emission lines of mode 1 and mode 2. As a result, the values of three points, the surface 210 (x=0), the deepest point of mode 1 (xt1), and the deepest point of mode 2 (xt2), and the refractive indexes n0, n1, and n2 of the points can be found. However, since the surface is an extrapolation of mode 1 and mode 2, these three points are straight lines.

Next, assuming that the deepest point xt3 in mode 3 is an appropriate value, the refractive index distribution up to xt3 can be defined, and the left side of equation 3 for this distribution can be calculated using the above calculation method. That is, the left side of equation 3 can be calculated using xt3 as the only parameter, and the right side is determined by the order of the mode, and in mode 3 it is 2.75λ.

Thereafter, by using xt3 as a parameter and using a nonlinear equation calculation method such as the bisection method or Newton's method, xt3 can be easily obtained. Once xt3 is obtained, xt4 is obtained from the position of the next mode 4 emission line, and by repeating the same calculation for all emission lines, the entire refractive index distribution can be calculated.

(Calculation of stress distribution)
Since tempered glass has strong in-plane compressive stress, the refractive index of P-polarized light and the refractive index of S-polarized light differ by the amount of stress due to the photoelastic effect. That is, if in-plane stress exists on the surface 210 of the tempered glass 200, the refractive index distribution will be different for P-polarized light and S-polarized light, the mode generation will be different, and the positions of emission lines will also be different.

Therefore, if the positions of the emission lines for P-polarized light and S-polarized light are known, the refractive index distributions for P-polarized light and S-polarized light can be calculated inversely. Therefore, the stress distribution σ(x) extending from the surface 210 of the tempered glass 200 in the depth direction can be calculated based on the difference between the refractive index distributions of the P-polarized light and the S-polarized light and the photoelastic constant of the tempered glass 200.

Specifically, the stress distribution can be calculated using Equation 5 below. In Equation 5, kc is a photoelastic constant, and Δn _PS (x) is the difference in refractive index distribution between P-polarized light and S-polarized light. Since the refractive index distribution n _P (x) for P-polarized light and the refractive index distribution n _S (x) for S-polarized light are obtained discretely, they can be approximated by a straight line between each point or by using multiple points. Stress distribution can be obtained at any position by calculating a curve.

なお、化学強化ガラスが測定された応力分布において、応力０となる点がＤＯＬ＿Ｚｅｒｏ値、計算された一番深い点での応力値がＣＴ値である。

In addition, in the stress distribution measured in chemically strengthened glass, the point at which stress is 0 is the DOL_Zero value, and the calculated stress value at the deepest point is the CT value.

However, since the CT value and DOL_Zero value are calculated from the minute refractive index difference between P-polarized light and S-polarized light, in areas where the change in refractive index is small (near the zero cross where the slope of the refractive index distribution becomes gentle), P-polarized light The refractive index difference between the S-polarized light and the S-polarized light becomes small, and the measurement error becomes large. Therefore, the CT value is calculated using Equation 6 (Equation 6) so that the value obtained by integrating the calculated stress distribution of the compressive stress layer in the depth direction of the tempered glass 200 balances the tensile stress inside the tempered glass 200. It's okay. Here, CS(x) is a compressive stress value at a position x in the depth direction of the tempered glass 200 shown in FIG. Hereinafter, when the CT value calculated based on Equation 0 and the CT value calculated based on Equation 5 are explained separately, they will be referred to as CT ₀ value and CT ₅ value, respectively. For example, the _CT5 value can be determined such that the integral range is from the surface 210 to the center of the tempered glass 200 and the integral result is zero. At this time, the depth at which the stress is zero may be calculated as the DOL_Zero value.

（測定のフロー）
図１２は、本実施形態に係る測定方法を例示するフローチャートである。図１３は、表面屈折率測定装置１の演算部７０の機能ブロックを例示する図である。

(Measurement flow)
FIG. 12 is a flowchart illustrating the measurement method according to this embodiment. FIG. 13 is a diagram illustrating functional blocks of the calculation unit 70 of the surface refractive index measuring device 1.

First, in step S501, light from the light source 10 is made to enter the surface layer of the tempered glass 200 (light supply step). Next, in step S502, the light propagated within the surface layer of the tempered glass 200 is emitted to the outside of the tempered glass 200 (light extraction step).

Next, in step S503, the light converting member 40 and the polarizing member 50 convert at least two types of light components (P-polarized light and S-polarized light) of the emitted light that vibrate parallel and perpendicular to the exit surface. It is converted into two types of bright line arrays having two or more bright lines (light conversion step).

Next, in step S504, the image sensor 60 images the two types of bright line arrays converted by the light conversion process (imaging process). Next, in step S505, the position measuring means 71 of the calculation unit 70 measures the position of each bright line of the two types of bright line arrays from the image obtained in the imaging process (position measuring process).

Next, in step S506, the refractive index distribution calculation means 72 of the calculation unit 70 calculates the surface 210 of the tempered glass 200 corresponding to the two types of light components from the positions of at least two or more bright lines in each of the two types of bright line arrays. A refractive index distribution over the depth direction is calculated from (refractive index distribution calculation step). Note that in order to calculate the refractive index distribution, it is sufficient to have two or more emission lines, and if there are three or more emission lines, approximation using a function of quadratic or higher order is possible, and more detailed distribution information can be obtained. .

Next, in step S507, the stress distribution calculation means 73 of the calculation unit 70 calculates the stress distribution in the depth direction from the surface 210 of the tempered glass 200 based on the difference in the refractive index distribution of the two types of light components and the photoelastic constant of the glass. (stress distribution calculation step). Note that if the purpose is to calculate only the refractive index distribution, the step S507 is not necessary.

Note that the profile of the refractive index distribution and the profile of the stress distribution are similar. Therefore, in step S507, the stress distribution calculating means 73 calculates, among the refractive index distributions corresponding to P-polarized light and S-polarized light, a refractive index distribution corresponding to P-polarized light, a refractive index distribution corresponding to S-polarized light, and a refractive index distribution corresponding to P-polarized light. Either the refractive index distribution or the refractive index distribution of the average value of the refractive index distribution corresponding to S-polarized light may be calculated as the stress distribution.

Further, in addition to the configuration shown in FIG. 13, the calculation unit 70 may include a CT value calculation means for calculating a CT value, a DOL_Zero value calculation means for calculating a DOL_Zero value, and the like. In this case, the CT value and DOL_Zero value can be calculated based on the stress distribution calculated by the stress distribution calculating means 73.

As described above, according to the surface refractive index measuring device and the surface refractive index measuring method according to the present embodiment, from the positions of at least two or more bright lines in each of the two types of bright line arrays, two types of light components are detected corresponding to the two types of light components. It is possible to calculate the refractive index distribution from the surface of tempered glass to the depth direction.

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 distribution of the two types of light components and the photoelastic constant of the glass. That is, the refractive index distribution and stress distribution of the surface layer of tempered glass can be measured non-destructively.

As a result, it becomes possible to calculate highly accurate CT values and DOL_Zero values based on the measured stress distribution, and it is possible to obtain optimal strengthening conditions in the development of tempered glass. Furthermore, in the manufacturing process of tempered glass, it becomes possible to manage the strength of glass with high reliability and precision, and it is possible to develop and manufacture stronger tempered glass.

Furthermore, by providing the inorganic film 22 on the tempered glass 200 side of the prism 21 and setting the distance d between the interface between the prism 21 and the inorganic film 22 and the surface 210 of the tempered glass 200 to be 1 μm or more, the number of bright lines can be increased. , the measurement accuracy of the refractive index of the tempered glass 200 can be improved. As a result, the accuracy of measuring stress in the tempered glass 200 can also be improved.

Here, the reason why the number of bright lines increases will be explained.

According to the measurement principle of the present invention, a bright line is generated according to the mode in which guided light is generated in the chemically strengthened layer of tempered glass, and from the bright line, the depth and refractive index of the deepest point of the ray trajectory of that mode can be determined. The resulting depth is only discrete and discrete.

Furthermore, the lower order mode, that is, the mode closer to the surface, the larger the interval between them. For example, in the example shown in FIG. 8, mode 1 is 4.3 μm, mode 2 is 9.2 μm, and there are only two points below 10 μm. . Therefore, it is difficult to obtain a refractive index distribution with high accuracy in a region close to the surface of 10 μm or less.

In particular, in a region shallower than mode 1, the refractive index can only be predicted by extrapolation from mode 1 and mode 2. Therefore, it is difficult to obtain a refractive index distribution with sufficient accuracy in a strengthening method that causes rapid changes in a shallow region of 10 μm or less.

However, in the present invention, by providing a layer on the surface of the tempered glass with the same refractive index as glass with a thickness close to the depth of normal mode 1, the deepest point of mode 1 is brought closer to the surface of the tempered glass, It becomes possible to measure the refractive index in a region closer to the surface of the tempered glass.

The principle will be explained with reference to FIG. FIG. 14(a) shows a conventional case in which the tempered glass 200 is in close contact with the prism 21, and a light ray A of a certain wavelength λ passes through the prism 21 and enters the tempered glass 200 from the surface 210 of the tempered glass 200. It is reversed at depth and returns to the surface 210 of the tempered glass 200. Let this point be p1, and the depth from the surface 210 of the tempered glass 200 to the deepest point be d1. Then, the light ray A passing through this point p1 and the parallel light ray B cause interference, and a bright line is generated at the incident angle of the light rays A and B such that the optical path difference between the light ray A and the light ray B is an integral multiple of the wavelength.

On the other hand, FIG. 14(b) shows one embodiment of the present invention, in which a layer (here, an inorganic A membrane 22) is provided.

The light ray C passes through the prism 21 and the inorganic film 22, enters the tempered glass 200 from the surface 210 of the tempered glass 200, is reversed at a certain depth, and returns to the surface 210 of the tempered glass 200. In this example, the refractive index of the inorganic film 22 and the surface 210 of the tempered glass 200 are almost the same, and there is no reflection or refraction at the interface, so the light ray C travels further and reaches the interface between the prism 21 and the inorganic film 22. Let this point be p2, and let the depth from this interface to the deepest point be d2.

Since the refractive index differs greatly at the interface between the prism 21 and the inorganic film 22, interference occurs between the ray C passing through this point p2 and the parallel ray D at this interface. Similarly, bright lines are generated at the incident angles of the rays C and D such that the optical path difference between the rays C and D becomes an integral multiple of the wavelength.

A light ray trajectory from the interface between the prism 21 and the surface 210 of the tempered glass 200 to the deepest point at depth d1 in the conventional example shown in FIG. 14(a), and the prism 21 shown in FIG. The ray trajectories from the interface between the inorganic film 22 and the inorganic film 22 to the deepest point at depth d2 are slightly different. That is, in FIG. 14(b), it is a straight line, but in the conventional case of FIG. 14(a), it draws a slightly circular arc.

However, in a short region, even if the arc is considered to be almost a straight line, the optical path difference due to the difference in the path is so small that it can be ignored. Therefore, the depth d2 in FIG. 14(b) can be considered to be approximately the same as the depth d1 in FIG. 14(a).

However, in FIG. 14(b), the depth d3 from the surface 210 of the tempered glass 200 to the deepest point becomes shallower by subtracting the thickness ds of the inorganic film 22 from d2. For example, if the depth d1 in FIG. 14(a) is 5 μm and the thickness of the inorganic film 22 in FIG. 14(b) is 4 μm, the depth d3 in FIG. 14(b) is 1 μm. Also, in mode 2 and later, the depth from the surface 210 of each tempered glass 200 to the deepest point becomes shallower by the thickness ds of the inorganic film 22.

FIG. 15 is an example of an arrangement of bright lines. FIG. 15(a) shows the bright line arrangement in the conventional case of FIG. 14(a), and FIG. 15(b) shows the bright line arrangement in the case of FIG. 14(b), which is an embodiment of the present invention. The mode 0 indicated by the dotted line in FIG. 15 is the position of the refractive index of the surface 210 of the tempered glass 200, and is assumed to be a virtual mode 0. In FIG. 15(b), the entire emission line arrangement approaches mode 0, which indicates the surface 210 of the tempered glass 200, and the depth at which the guided light effect occurs increases from d1 to d2, so new mode 5 and mode 6 emission lines are generated. appears, and the total number of bright lines increases.

Further, since the refractive index and thickness of the inorganic film 22 are both measured and known in advance, it is easy to calculate the optical path length in the inorganic film 22, and it is also possible to calculate the deepest point in each mode.

Note that the reason why the number of bright lines increases by providing a distance defining means such as the inorganic film 22 can also be explained from Equation 3. In Equation 3, the second term is a new part added due to the presence of distance defining means such as the inorganic film 22. That is, the left side of Equation 3 becomes larger by the second term in Equation 3. Therefore, for example, Ψ for which the equation 3 holds true when N=1 is smaller by the magnitude of the second term than in the case where the second term is not present. That is, emission lines begin to appear from shallow incident angles.

Furthermore, due to the presence of the second term sin θ1 in Equation 3, when Ψ is increased, θ1 also increases, so the second term gradually becomes larger. Therefore, Ψ at which the next N=2 mode holds is a smaller angle than in the case without the second term, and the distance from Ψ at which N=1 holds is also smaller than in the case without the second term. It gets narrower.

In this way, the angle Ψ at which Equation 3 holds true up to the critical angle becomes shallower and the interval becomes narrower compared to the case without the second term. As a result, the number of bright lines increases. That is, when a distance defining means such as the inorganic film 22 is provided between the prism 21 and the tempered glass 200, the number of bright lines increases.

In this way, when a distance regulating means such as the inorganic film 22 is provided between the prism 21 and the tempered glass 200, the light incident on the tempered glass 200 is directed toward the surface from the depth direction at a position closer to the surface 210 of the tempered glass 200. The direction is reversed and the number of emission lines increases. As a result, the measurement accuracy of the refractive index and the measurement accuracy of stress of the tempered glass 200 can be improved. In other words, the stress profile of the tempered glass 200 can be measured more accurately.

On the other hand, as the distance between the prism 21 and the tempered glass 200 increases, the interval between the bright lines becomes narrower. In order to measure more accurately, it is preferable to observe the bright line at a resolution of 3 pixels or more between the bright line of mode 1 of P-polarized light and the bright line of mode 1 of S-polarized light. Examples of methods for improving the resolution include a method of adjusting the light conversion member 40 to increase the optical magnification and photographing, and a method of using a high-resolution image sensor 60.

<Second embodiment>
In the second embodiment, an example of a surface refractive index measuring device having a light input/output member different from that in the first embodiment is shown. Note that in the second embodiment, descriptions of components that are the same as those in the already described embodiments may be omitted.

FIG. 16 is a diagram illustrating a surface refractive index measuring device for tempered glass according to the second embodiment. As shown in FIG. 16, the surface refractive index measuring device 2 differs from the surface refractive index measuring device 1 (see FIG. 1) in that the light input/output member 20 is replaced with a light input/output member 20A. The light input/output member 20A differs from the light input/output member 20 (see FIG. 1) in that the inorganic film 22 is replaced with a glass layer 23.

In FIG. 16, the glass layer 23 of the light input/output member 20A is a distance defining means for defining the distance between the bottom surface 21c of the prism 21 (the boundary between the prism 21 and the glass layer 23) and the surface 210 which is the incident surface of the tempered glass 200. It is. The material for the glass layer 23 is not particularly limited, and examples thereof include soda lime glass, aluminosilicate glass, borosilicate glass, and quartz glass.

The refractive index of the glass layer 23 is approximately the same as the refractive index of the tempered glass 200. The glass layer 23 preferably has a refractive index within a range of ±0.05 with respect to the refractive index of the surface 210 of the tempered glass 200. For example, if the refractive index of the surface 210 of the tempered glass 200 is 1.52, the refractive index of the glass layer 23 is preferably 1.47 or more and 1.57 or less. If the refractive index of the glass layer 23 is 1.47 or more and 1.57 or less, reflection at the boundary between the glass layer 23 and the surface 210 of the tempered glass 200 is sufficiently reduced, and the bright line can be more clearly confirmed. The refractive index of the glass layer 23 can be measured using, for example, an ellipsometer.

The thickness of the glass layer 23 is 1 μm or more and 10 μm or less. By setting the thickness of the glass layer 23 to 1 μm or more and 10 μm or less, the distance d between the boundary between the prism 21 and the glass layer 23 and the surface 210 of the tempered glass 200 can be defined in the range of 1 μm or more and 10 μm or less. By setting the distance d to 1 μm or more, the number of bright lines can be increased, so that the measurement accuracy of the refractive index of the tempered glass 200 can be improved. The thickness of the glass layer 23 can be measured, for example, by observing it from the side using a digital micrometer or a microscope.

The deviation in the thickness of the glass layer 23 is preferably suppressed to 10% or less, more preferably 2% or less, even more preferably 1% or less, and even more preferably 0.5% or less. If the deviation in the thickness of the glass layer 23 is 10% or less, the optical path length from the lower end of the prism 21 to the surface 210 of the tempered glass 200 will be uniform, the finesse value described below will improve, and the emission line can be more clearly confirmed. . The thickness deviation of the glass layer 23 can be measured using, for example, an ellipsometer, an X-ray photoelectron spectrometer (XPS), or a field emission scanning electron microscope (FE-SEM).

Even if the surface roughness Ra of the glass layer 23 on the side closer to the surface 210 of the tempered glass 200 is large, the effect of the present invention is exhibited, but the measurement accuracy is improved if it is 0.02 nm or more and 1.5 nm or less. preferred above. If the surface roughness Ra is 0.02 nm or more and 1.5 nm or less, there is an effect of suppressing scattering of light from the light source 10 on the surface of the glass layer 23 and inside the glass layer 23, and as a result, surface refraction The effect of improving the accuracy of the measured values of the rate measuring device 1 can be obtained. The surface roughness Ra can be measured using, for example, an atomic force microscope (AFM).

The parallelism between the interface between the prism 21 and the glass layer 23 and the surface 210 of the tempered glass 200 is preferably 10% or less of the thickness of the glass layer 23. Thereby, a sufficient finesse value F can be obtained. For example, the parallelism of the film thickness is set to 10% or less of the film thickness of the glass layer 23 by measuring at multiple points using a microscopic spectroscopic film thickness meter or a reflection spectroscopic film thickness meter, and the glass layer 23 and the tempered glass 200 are High accuracy can be achieved through close contact.

17 and 18 are diagrams illustrating a method of forming the optical input/output member according to the second embodiment. First, as shown in FIG. 17(a), a glass block 240 is prepared by processing a glass material into a rectangular parallelepiped, which will become the prism 21 of the light input/output member 20A. The surface 241 of the glass block 240 is processed to have a flatness of 1/4λ or less.

Next, as shown in FIG. 17(b), a thin glass plate 250 is prepared as a glass material that will become the glass layer 23 of the light input/output member 20A. The size of the surface 251 of the glass plate 250 is the same as the surface 241 of the glass block 240. The thickness of the glass plate 250 is, for example, 0.1 mm or more and 2 mm or less. At least the surface 251 of the glass plate 250 is processed to have a flatness of 1/4λ or less.

Next, as shown in FIG. 17C, the surface 241 of the glass block 240 and the surface 251 of the glass plate 250 are brought together and bonded together to produce a laminate 260. For adhesion, an optical glass adhesive having approximately the same refractive index as the glass plate 250 is used. Moreover, an optical contact may be used instead of the optical glass adhesive.

Next, as shown in FIG. 17(d), in the laminate 260, the surface 252 (the opposite surface to the surface 251) of the glass plate 250 is polished so that the thickness of the glass plate 250 is 1 μm or more and 10 μm or less. The surface 252 is finished as an optical surface. At this time, the parallelism of the surface 252 to the surface 251 of the glass plate 250 is preferably 10% or less of the thickness of the glass plate 250.

The thickness of the glass plate 250 during polishing can be measured with high accuracy in a small area with a resolution of 0.1 μm or less using, for example, an interferometric thickness meter (eg, spectral film thickness meter FE300 manufactured by Otsuka Electronics Co., Ltd.). By measuring, adjusting, and polishing a plurality of points within the surface 252 of the glass plate 250 using this thickness gauge, the parallelism of the surface 252 to the surface 251 is 10% or less of the thickness of the glass plate 250, and the glass plate The thickness of 250 can be controlled to 1 μm or more and 10 μm or less.

Next, as shown in FIG. 18A, the laminate 260 is cut vertically and horizontally to a size corresponding to one optical input/output member 20A, thereby producing a laminate 260A. Then, as shown in FIG. 18(b), surfaces 261 and 262 of the laminate 260A are obliquely polished and finished by optical polishing. Thereby, as shown in FIG. 18(c), a light input/output member 20A is obtained in which the glass layer 23 is adhered onto the prism 21.

In this way, the glass layer 23 may be provided as a distance defining means for defining the distance between the bottom surface 21c of the prism 21 and the surface 210 of the tempered glass 200. Also in this case, by setting the thickness of the glass layer 23 to 1 μm or more and 10 μm or less, the number of bright lines can be increased similarly to the first embodiment, so that the measurement accuracy of the refractive index of the tempered glass 200 can be improved. As a result, the accuracy of measuring stress in the tempered glass 200 can also be improved.

<Third embodiment>
In the third embodiment, an example is shown in which a light input/output member contacts tempered glass via a liquid. Note that in the third embodiment, descriptions of components that are the same as those in the already described embodiments may be omitted.

FIG. 19 is a diagram illustrating a surface refractive index measuring device for tempered glass according to the third embodiment. As shown in FIG. 19, in the surface refractive index measurement device 3, between the light input/output member 20 and the tempered glass 200, the bottom surface 22c of the inorganic film 22 of the light input/output member 20 and the surface 210 of the tempered glass 200 are connected. A liquid 30 is filled therein, which is an optical coupling liquid for optically coupling the two. That is, the bottom surface 22c of the inorganic film 22 is in contact with the surface 210 of the tempered glass 200 via the liquid 30. The thickness of the liquid 30 is preferably 1 μm or less.

The refractive index of the liquid 30 is adjusted to be equal to the refractive index of the outermost surface of the surface layer of the tempered glass 200. Here, equivalent means that no reflection or refraction occurs at the interface between the surface of the tempered glass 200 and the liquid 30, and the interface between the bottom surface 22c of the inorganic film 22 and the liquid 30 is used as one reflecting surface of the guided light. This refers to the relationship between the refractive index of the liquid 30 and the refractive index of the surface layer of the tempered glass 200 that enables this.

When ngb is the refractive index of the glass before the chemical strengthening process, ngs is the refractive index of the outermost surface of the tempered glass after the chemical strengthening process, and nf is the refractive index of the liquid 30, ngb<nf≦ngs+0.005. However, it is preferable because high contrast bright lines can be observed and accurate measurements can be made. It is more preferable that ngb+0.005≦nf≦ngs+0.005. Furthermore, it is particularly preferable that the absolute value of the difference between the refractive index nf of the liquid 30 and the refractive index ngs of the surface layer of the tempered glass 200 is 0.005 or less. A refractive index falling within this preferred refractive index range is referred to as an appropriate refractive index in the present invention, and a refractive liquid having this refractive index is referred to as an appropriate refractive liquid in the present invention.

The liquid 30 may be made by mixing two or more liquids made of different materials. By making the liquid 30 by mixing two or more types of liquids made of different materials, the viscosity of the liquid 30 can be adjusted. The lower the viscosity of the liquid 30, the more preferable it is because it is easier to bring the liquid 30 into close contact with the tempered glass 200 and the inorganic film 22. Specifically, the viscosity of the liquid 30 is preferably 5 cps (centipoise) or less, more preferably 3 cps or less, and even more preferably 1 cps or less.

Further, by making the liquid 30 by mixing two or more types of liquids made of different materials, the boiling point can be adjusted. It is preferable that the liquid 30 has a high boiling point because it is less likely to deteriorate during storage. Specifically, the boiling point of the liquid 30 is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher.

In this way, in the surface refractive index measuring device 3, the liquid 30, which is an optical coupling liquid, is filled between the light input/output member 20 and the tempered glass 200. The refractive index of the liquid 30 is adjusted to be equal to the refractive index of the surface layer of the tempered glass 200.

As a result, no reflection or refraction occurs at the interface between the surface of the tempered glass 200 and the liquid 30, and the interface between the bottom surface 22c of the inorganic film 22 of the light input/output member 20 and the liquid 30 is one reflection surface of the guided light. Therefore, strong guided light can be obtained. As a result, even with tempered glass whose surface has poor optical flatness or poor refractive index uniformity, it is possible to obtain strong guided light that does not depend on the surface condition of the tempered glass, and clear emission lines can be obtained. Therefore, the refractive index distribution of the surface layer of tempered glass can be measured non-destructively and with high precision.

Furthermore, depending on the refractive index of the liquid 30, it can be expected that the boundary between the area where emission lines appear and the area where no emission lines appear can be clearly seen, which can also improve the accuracy of measuring the refractive index and stress at the deepest part of the surface layer in FIG. Can be used. The boundary between the area where the bright line appears and the area where the bright line does not appear can be seen as a boundary line between a bright area and a dark area, or between a dark area and a bright area, and usually occurs near the critical angle due to the difference in refractive index between the tempered glass and the prism. .

For example, in the chemically strengthened glass formed through the chemically strengthened process where surface stress becomes strong in a short period of time after the glass forming process, ion exchange is not uniform and the refractive index locally changes. It may also be uneven. For example, in tempered glass in which metal ions are diffused into the surface layer, the slope of the refractive index sharply increases in the surface layer. The metal ions in this case are Sn, Ag, Ti, Ni, Co, Cu, In, etc.

With such a glass with poor optical flatness, the finesse value F due to multi-beam interference deteriorates, the width of the emission line becomes wide, and the contrast decreases, hindering highly accurate position measurement, and in extreme cases, In some cases, the mode may no longer occur, making measurement difficult. FIG. 20 shows photographs of bright line arrays when the flatness of the tempered glass surface is good and when the flatness is bad. FIG. 20(a) is an example where the flatness of the surface of the tempered glass is poor, and FIG. 20(b) is an example where the flatness of the surface of the tempered glass is good.

In this way, in chemically strengthened glass where the surface or the vicinity of the surface has large optical non-uniformity or the surface optical flatness is poor, the bright line imaged on the image sensor and the line width are They are wide, have low contrast, and are unclear, reducing the accuracy of bright line measurement. If the non-uniformity is extremely large or the flatness is poor, the guided light itself may disappear and no bright line may be generated. Therefore, the accuracy of measuring the surface refractive index of the tempered glass or the refractive index distribution of the surface layer may deteriorate, and furthermore, the measurement may become difficult.

In the surface refractive index measuring device 3, a liquid 30, which is an optical coupling liquid, is filled between the inorganic film 22 of the light input/output member 20 and the tempered glass 200, and the refractive index of the liquid 30 is equal to the surface of the tempered glass 200. The refractive index of the outermost surface of the layer is adjusted to be equal to or deeper than the surface layer of the tempered glass.

Therefore, even with tempered glass whose surface has poor optical flatness or poor refractive index uniformity, it is possible to obtain strong guided light that does not depend on the condition of the surface of the tempered glass. The refractive index distribution can be measured non-destructively and with high precision. For example, the surface refractive index measuring device 3 can measure the surface layer of a tempered glass 200 with a surface roughness Ra of 5 nm, 10 nm, or 50 nm, which is difficult to measure with a conventional device that reflects guided light on the surface of the tempered glass. The refractive index distribution of can be measured with high precision. Furthermore, even if the tempered glass 200 has a surface roughness Ra of 100 nm or more, the refractive index distribution of the surface layer can be measured with high accuracy.

Note that the liquid 30 may be applied to the bottom surface 22c of the inorganic film 22, or may be applied to the surface 210 of the tempered glass 200. When the liquid 30 is applied to the bottom surface 22c of the inorganic film 22, the liquid 30 may be considered as part of the optical input/output member 20.

In the above description, an example is shown in which the light input/output member 20 described in the first embodiment is used, but the glass layer 23 and the tempered glass 200 can also be used when the light input/output member 20A according to the second embodiment is used. By filling the liquid 30 between them, the same effect as above can be obtained.

<Fourth embodiment>
The fourth embodiment shows another example of a surface refractive index measuring device having a light input/output member different from that of the first embodiment. Note that in the fourth embodiment, descriptions of components that are the same as those in the already described embodiments may be omitted.

FIG. 21 is a diagram illustrating a surface refractive index measuring device for tempered glass according to the fourth embodiment. As shown in FIG. 21, the surface refractive index measuring device 4 differs from the surface refractive index measuring device 1 (see FIG. 1) in that the light input/output member 20 is replaced with a light input/output member 20B. The light input/output member 20B differs from the light input/output member 20 (see FIG. 1) in that the inorganic film 22 is replaced with a filler 24.

In FIG. 21, the filler 24 of the light input/output member 20B is a distance defining means that defines the distance between the bottom surface 21c of the prism 21 and the surface 210 which is the incident surface of the tempered glass 200. The particle size of the filler 24 is 1 μm or more and 10 μm or less. Here, the particle size means the average particle size. From the viewpoint of suppressing scratches on the tempered glass 200 and the prism 21, the material of the filler 24 is preferably a soft resin or the like. As the filler 24, polycarbonate, polyethylene, polystyrene, polypropylene, colloidal silica, silicone, etc. are preferably used. The particle size of the filler 24 can be measured, for example, by direct observation using an optical microscope or an electron microscope, or by an optical method such as a dynamic light scattering method or a laser diffraction method.

The periphery of the filler 24 between the prism 21 and the tempered glass 200 is filled with a liquid 30 that is an optical coupling liquid for optically coupling the bottom surface 21c of the prism 21 and the surface 210 of the tempered glass 200. There is. That is, the bottom surface 21c of the prism 21 is in contact with the surface 210 of the tempered glass 200 via the liquid 30. The liquid 30 is as described above.

In this way, the filler 24 may be provided as a distance defining means for defining the distance between the bottom surface 21c of the prism 21 and the surface 210 of the tempered glass 200. Also in this case, by setting the particle size of the filler 24 to 1 μm or more and 10 μm or less, the number of bright lines can be increased similarly to the first embodiment, so that the measurement accuracy of the refractive index of the tempered glass 200 can be improved. As a result, the accuracy of measuring stress in the tempered glass 200 can also be improved.

Note that a recessed portion for holding the filler 24 and the liquid 30 may be provided in the bottom surface 21c of the prism 21. In this case, the state in FIG. 1 is reversed upside down, the prism 21 is placed on the lower side, and the tempered glass 200 is placed on the outer peripheral surface of the recessed portion of the prism 21 (the portion that is not recessed), and the measurement is performed. Further, the distance between the bottom surface of the prism 21 (the bottom surface of the recess) and the surface 210 of the tempered glass 200 may be defined by the depth of the recess. In this case, only the liquid 30 may be used without using the filler 24.

<Fifth embodiment>
The fifth embodiment shows another example of a surface refractive index measuring device having a light input/output member different from that of the first embodiment. Note that in the fifth embodiment, descriptions of components that are the same as those in the already described embodiments may be omitted.

FIG. 24 is a diagram illustrating a surface refractive index measuring device for tempered glass according to the fifth embodiment. As shown in FIG. 24, the surface refractive index measuring device 5 differs from the surface refractive index measuring device 1 (see FIG. 1) in that the light input/output member 20 is replaced with a light input/output member 20C. The optical input/output member 20C has a structural member 25. In FIG. 24, the structural member 25 of the light input/output member 20C is a distance defining means for defining the distance between the bottom surface 21c of the prism 21 and the surface 210 which is the incident surface of the tempered glass 200.

In the space 26 formed by the structural member 25 between the bottom surface 21c of the prism 21 and the surface 210 which is the incident surface of the tempered glass 200, the bottom surface 21c of the prism 21 and the surface 210 of the tempered glass 200 are optically connected. A liquid 30 which is an optical coupling liquid for coupling is filled. That is, the bottom surface 21c of the prism 21 is in contact with the surface 210 of the tempered glass 200 via the liquid 30. The liquid 30 is as described above. Since the difference between the refractive index of the liquid 30 and the refractive index of the surface layer of the tempered glass 200 can be easily adjusted to be small, generation of bright lines due to factors other than the optical waveguide effect can be suppressed. Furthermore, since it is a liquid, no film stress is generated, so it does not adversely affect the measurement of stress generated within the glass. In this way, the structural member 25 is a distance defining means and is different from the inorganic film 22 of the light input/output member 20 in the first embodiment in that it forms the space 26.

The space 26 is formed, for example, when forming the structural member 25, by masking a part of the prism, that is, the part where no film is to be applied, forming a film, and then peeling off the masking.

25(a) and 25(b) are top views showing an example of the structural member 25 formed on the bottom surface 21c of the prism 21. In the top view of FIG. 25, since the total area occupied by the structural member 25 is smaller than the area of the bottom surface 21c of the prism 21, a space 26 can be secured and the liquid 30 can be filled. The area occupied by the structural member 25 is, for example, half or less of the area of the bottom surface 21c of the prism 21, and may be one-third or less, or one-fourth or less. In order to accurately maintain the distance between the surface 210 of the tempered glass 200 and the bottom surface 21c of the prism 21, the area occupied by the structural member 25 is preferably 1/20 or more of the bottom surface 21c of the prism 21. Further, it is preferable that a plurality of structural members 25 be arranged in a small area at the end of the bottom surface 21c of the prism 21 or within the plane of the bottom surface 21c so as not to affect the propagation of the guided light.

In FIGS. 25(a) and 25(b), the spacing between the structural members 25 is preferably set so that the distance between the bottom surface 21c of the prism 21 and the surface 210 of the tempered glass 200 can be kept constant, for example, 10 mm or less. Yes, it may be 5 mm or less, or 3 mm or less. Further, it is preferable that the structural member 25 is installed so that the space 26 is continuous without dividing the space 26 on the bottom surface 21c, as shown in FIG. 25(a). If the space 26 is continuous, when the liquid 30 is filled, the liquid 30 moves within the space 26 and fills the gap. Furthermore, if the interval between the structural members 25 is, for example, 0.1 mm or more, or 0.5 mm or more, the liquid 30 can move between the structural members 25.

The thickness of the structural member 25 is 1 μm or more and 10 μm or less. By setting the film thickness of the structural member 25 to 1 μm or more and 10 μm or less, the number of bright lines can be increased similarly to the first embodiment, so that the measurement accuracy of the refractive index of the tempered glass 200 can be improved. As a result, the accuracy of measuring stress in the tempered glass 200 can also be improved.

The smaller the difference between the refractive index of the structural member 25 and the refractive index of the liquid 30 is, the more the influence on guided light propagation can be suppressed.

The material of the structural member 25 is not particularly limited, and is selected from inorganic films, glass, resins, etc., and preferably inorganic films. Examples of the inorganic film include an oxide film, a nitride film, or an oxynitride film containing at least one metal selected from Si, Al, Zr, Ti, Nb, and Ta.

[Examples, comparative examples]
In the surface refractive index measuring device, the number of bright lines was evaluated while changing the parameters shown in FIGS. 22 and 23, including the distance d between the interface between the prism 21 and the inorganic film 22 and the surface 210 of the tempered glass 200.

As the object to be measured, tempered glass 200 with a compressive stress layer depth of 5 μm was used in Examples 1 to 4, and tempered glass 200 with a compressive stress layer depth of 10 μm was used in Examples 5 to 8. In Examples 9 to 11, tempered glass 200 with a compressive stress layer depth of 7 μm was used.

Further, in Examples 1, 2, and 5 to 7, an inorganic film (silicon aluminum oxide) was used as the distance defining means. In Example 8, a filler serving as a spacer was used as the distance defining means. In Examples 1, 2, and 5 to 7, the distance d was the total thickness of the inorganic membrane and the liquid 30, and in Example 8, the distance d was the average particle size of the filler. In Examples 3 and 4, which are comparative examples, no distance defining means was provided, and the distance d (only the thickness of the liquid 30) was 1 μm or less.

In Examples 9 to 11, an inorganic film (silicon aluminum oxide) serving as a spacer is installed as the structural member 25 of the distance defining means so as to cross the prism, as shown in FIG. was filled with liquid 30. The spacing between the structural members 25 was 4.5 mm, and the width of the structural members 25 was 1 mm. In Examples 9 to 11, the distance d is the thickness of the inorganic film.

The parameter C shown in FIGS. 22 and 23 is ((nc×tc)/λ)×1000. Here, nc is the average refractive index of the inorganic film and the liquid 30. tc is the total thickness (μm) of the inorganic membrane and the liquid 30, or the particle size (μm) of the filler. λ is the wavelength (nm) of the light source.

The values of each parameter and the evaluation results (number and photographs) of bright lines are shown in FIGS. 22, 23, and 26. In addition, the judgment "OK" means that two or more bright lines can be confirmed for both P-polarized light and S-polarized light, and "NG" means that only one bright line or less can be seen for at least one of P-polarized light and S-polarized light. This shows the case where there was no such thing.

As shown in Examples 1 and 2 in FIG. 22, Examples 5 to 8 in FIG. 23, and Examples 9 to 11 in FIG. Two or more emission lines were confirmed for both S-polarized light. On the other hand, as in Examples 3 and 4 shown in FIG. 22, when the distance d was less than 1 μm, only one bright line was observed for both P-polarized light and S-polarized light.

In this way, it was confirmed that the number of bright lines could be increased by setting the distance d to 1 μm or more. By increasing the number of bright lines, the accuracy of measuring the refractive index of tempered glass can be improved, and as a result, the accuracy of measuring stress of tempered glass can also be improved.

Furthermore, by comparing Example 1 and Example 2 in FIG. 22 and comparing Example 5 and Example 7 in FIG. 23, it was confirmed that the larger the distance d, the more the number of bright lines increases. By increasing the number of bright lines, the measurement accuracy of the refractive index of the tempered glass can be further improved, and as a result, the measurement accuracy of the stress of the tempered glass can also be further improved.

Furthermore, from FIGS. 22, 23, and 26, the value of parameter C is preferably 5 or more. In particular, considering the case where the compressive stress layer has a relatively shallow depth of 5 μm as shown in FIG. 22, the value of the parameter C is more preferably 10 or more.

Furthermore, from the results of Example 8, it was confirmed that when a filler was used as the distance defining means, the same effect as when an inorganic film was used could be obtained.

Although the preferred embodiments and examples have been described in detail above, the embodiments and examples described above are not limited to the embodiments and examples described above, and without departing from the scope described in the claims. Various modifications and substitutions can be made to .

For example, in each of the above embodiments, the light source has been described as a component of the surface refractive index measuring device, but the surface refractive index measuring device may have a configuration that does not include a light source. In this case, the surface refractive index measurement device can be configured to include, for example, a light input/output member 20, a liquid 30, a light conversion member 40, a polarizing member 50, an image sensor 60, and a calculation unit 70. The user of the surface refractive index measuring device can prepare and use an appropriate light source.

1, 2, 3, 4 Surface refractive index measuring device 10 Light source 20, 20A, 20B, 20C Light input/output member 21 Prism 21a, 21b Inclined surface 21c, 22c Bottom surface 22 Inorganic film 23 Glass layer 24 Filler 25 Structural member 26 Space 30 Liquid 40 Light conversion member 50 Polarizing member 60 Image sensor 70 Arithmetic unit 71 Position measuring means 72 Refractive index distribution calculating means 73 Stress distribution calculating means 200 Tempered glass 210 Surface of tempered glass

Claims (10)

A surface refractive index measuring device for tempered glass,
Light from a light source is made to enter the surface layer of the tempered glass having the compressive stress layer through at least a first region and a second region in contact with the first region in this order, and a light input/output member that outputs the light that has propagated to the outside of the tempered glass through at least the second region and the first region in this order;
a light conversion member that converts two types of light components that are included in the light emitted through the light input/output member and vibrate parallel and perpendicular to the incident surface to the tempered glass into two types of bright line arrays; ,
an imaging element that images the two types of bright line arrays;
position measuring means for measuring the positions of the bright lines of the two types of bright line arrays from the image obtained by the image sensor;
refractive index distribution calculation for calculating the refractive index of the surface of the tempered glass corresponding to the two types of light components or the refractive index distribution extending from the surface of the tempered glass in the depth direction based on the measurement results of the position measuring means; having means;
The second region is an inorganic film or a glass layer,
A surface refractive index measuring device for tempered glass, wherein a distance between an interface between the first region and the second region and an incident surface of the tempered glass is 1 μm or more and 10 μm or less. The tempered glass according to claim 1, wherein the parallelism between the interface between the first region and the second region and the incident surface of the tempered glass is 10% or less of the thickness of the second region. surface refractive index measuring device. The tempered glass surface refractive index measuring device according to claim 1 or 2, wherein the second region has a refractive index within a range of ±0.05 with respect to the refractive index of the surface of the tempered glass. The second region is an inorganic film,
The inorganic film is an oxide film, a nitride film, or an oxynitride film containing at least one metal selected from Si, Al, Zr, Ti, Nb, and Ta, according to any one of claims 1 to 3. Tempered glass surface refractive index measuring device. The tempered glass surface refractive index measuring device according to any one of claims 1 to 4 , wherein the second region has a thickness of 1 μm or more and 10 μm or less. The tempered glass surface refractive index measuring device according to any one of claims 1 to 5 , wherein the thickness deviation of the second region is 10% or less. Surface refractive index measurement of tempered glass according to any one of claims 1 to 6 , wherein the surface roughness Ra of the second region near the surface of the tempered glass is 0.02 nm or more and 1.5 nm or less. Device. A tempered glass surface refractive index measuring device according to any one of claims 1 to 7 ,
Stress that calculates the stress on the surface of the tempered glass or the stress distribution in the depth direction from the surface of the tempered glass based on the difference in refractive index distribution corresponding to the two types of light components and the photoelastic constant of the glass. A surface stress measuring device for tempered glass having a distribution calculation means. A method for measuring the surface refractive index of tempered glass, the method comprising:
Light from a light source is made to enter the surface layer of the tempered glass having the compressive stress layer through at least a first region and a second region in contact with the first region in this order, and a light input/output step of emitting the light propagated to the outside of the tempered glass through at least the second region and the first region in this order;
a light conversion step of converting two types of light components contained in the light emitted from the tempered glass and vibrating parallel and perpendicular to the incident surface to the tempered glass into two types of bright line arrays;
an imaging step of imaging the two types of bright line arrays;
a position measuring step of measuring the positions of the bright lines of the two types of bright line arrays from the image obtained in the imaging step;
A refractive index distribution that calculates the refractive index of the surface of the tempered glass corresponding to the two types of light components, or the refractive index distribution extending from the surface of the tempered glass in the depth direction, based on the measurement results in the position measurement step. a calculation step;
The second region is an inorganic film or a glass layer,
In the light input/output step, the distance between the interface between the first region and the second region and the incident surface of the tempered glass is 1 μm or more and 10 μm or less. Stress on the surface of the tempered glass based on the difference in refractive index distribution corresponding to the two types of light components obtained by the method for measuring the surface refractive index of tempered glass according to claim 9 and the photoelastic constant of the glass, Or a method for measuring surface stress of tempered glass, comprising a stress distribution calculation step of calculating a stress distribution in the depth direction from the surface of the tempered glass.

Images