Apparatus and method for determining refractive index, central tension or stress distribution

Abstract

Apparatus and methods for determining a refractive index, central tension, or stress distribution are provided. The apparatus may include a cavity defined at least in part by a first major surface of a reference block and configured to receive a sample. The apparatus may include a first polarization-switching light source configured to emit a first polarization-switching light beam toward the cavity; and a first detector configured to detect a corresponding signal. The apparatus may include a second polarization-switching light source configured to emit a second polarization-switching light beam toward the cavity; and a second detector configured to detect a corresponding signal. The first reference block may be located between the second detector and the second reference block. The method for determining an estimated stress distribution may include determining the central tension based on a measured retardation distribution of the sample. The method may include determining an initial stress distribution based on a refractive index distribution of the sample. The method may include scaling and adjusting the stress distribution.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority under 35 U.S.C. §119 to U.S. Provisional Application No. 62 / 941,167, filed on November 27, 2019, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates generally to apparatus and methods for determining stress characteristics, and more particularly, to apparatus and methods for determining refractive index, central tension, or stress distribution. Background Art

[0004] Light scattering polarimetry (LSP) uses scattered polarized light to determine stress-based properties of samples that are able to scatter light from within the sample material. The sample is illuminated with input light at a relatively shallow angle. An optical compensator is used to continuously change the polarization of the light between different polarization states. The scattered light is detected by an image sensor. The stress in the sample causes an optical delay along the light path, and the amount of stress is proportional to the derivative of the optical delay. The amount of optical delay can be determined based on the detected scattered light intensity distribution, which varies due to constructive and destructive interference of different effective path lengths of the detection light. Measurable stress-related properties include stress distribution, central tension (CT) and depth of compression (DOC). However, the measurement may be subject to noise, and measurements of areas under compression may be unreliable.

[0005] The refractive near-field (RNF) method measures the refractive index and birefringence distribution (and therefore stress) of a sample. The RNF method passes input light through the sample and a reference block in contact with the sample. A prism is also used to couple the light exiting the sample into the transverse electric (TE) and transverse magnetic (TM) mode spectra, which are measured by an image sensor. The TE and TM mode spectra are analyzed to obtain stress-related properties, including the stress distribution. However, the magnitude of the stress distribution can be unreliable and can drift across the thickness of the sample.

[0006] Therefore, there is a need for a method of measuring CT that is more reliable and subject to lower variability. There is also a need for an apparatus and method for more accurate measurement using the RNF method. Furthermore, there is a need for a combined apparatus that can use LSP and RNF to measure more accurate stress distribution, as well as a method for using the apparatus.

[0007] Overview

[0008] This article describes an apparatus and method for determining the refractive index, central tension, or stress distribution of a sample. A combined apparatus for measuring using LSP and RNF simplifies and accelerates the measurement process. Furthermore, the combined apparatus reduces the risk of sample breakage because less handling is required to load the sample into the combined apparatus compared to using two separate apparatuses. The combined apparatus also produces more reliable measurements of the overall stress distribution.

[0009] The combined device or LSP device can be used in a method for measuring central tension (CT). The disclosed method can produce more reliable CT measurements that exclude noisy portions (e.g., one or more ends) measured near the edges of the CT region (e.g., interfaces between layers in a laminate). By moving the sample during the measurement, the disclosed method can also produce more reliable CT measurements that can be processed to produce an average intensity distribution with lower noise.

[0010] The combination device or RNF device may include more than one reference block. Clamping the reference blocks in a cavity configured to hold the sample can provide a means of correcting for drift and other systematic errors present in the measurement. Providing at least one reference block having a first refractive index and a fluid comprising a third refractive index, and which spans the estimated refractive index of the sample (e.g., the estimated refractive index distribution range) can provide more accurate and reproducible measurements of the refractive index and / or stress distribution. In addition, having the minimum difference between the at least one reference block comprising the first refractive index and the estimated refractive index of the sample (e.g., the extreme value of the estimated refractive index distribution) be within the range of about 0.7% to about 10% of the refractive index of the sample and / or within the range of about 0.006 to about 0.10 can further improve the reliability and / or reproducibility of the refractive index and / or stress distribution measurements. In addition, ensuring that the minimum difference between the fluid comprising the third refractive index and the estimated refractive index of the sample (e.g., the extreme value of the estimated refractive index distribution) is within a range of about 0.7% to about 10% of the refractive index of the sample and / or within a range of about 0.006 to about 0.10 can further improve the reliability and / or reproducibility of the refractive index and / or stress distribution measurement. In some embodiments, after measuring the corrected refractive index (e.g., the refractive index distribution) of the sample, the at least one reference block and / or fluid can be replaced so that the at least one reference block and / or fluid meets the above conditions. In some embodiments, in the combined device, the first reference block can include a prism.

[0011] Some exemplary embodiments of the present disclosure are described below, while it should be understood that any features of the various embodiments can be used alone or in combination with each other.

[0012] In some embodiments, an apparatus for measuring the stress distribution of a sample may include a cavity at least partially defined by a first major surface of a first reference block comprising a first refractive index. The cavity may be configured to receive the sample. The apparatus may include a polarization-switching light source configured to emit a first polarization-switching light beam toward the cavity. The apparatus may include a second polarization-switching light source configured to emit a second polarization-switching light beam toward the cavity. The apparatus may include a first detector configured to detect a signal from the first polarization-switching light beam. The apparatus may include a second detector configured to detect a signal from the second polarization-switching light beam. The first reference block may be located between the second detector and the first reference block. The first reference block may be located between the second detector and the second reference block.

[0013] In another embodiment, the apparatus may further comprise a sample holder. The sample holder is translatable in a direction perpendicular to the first major surface.

[0014] In further embodiments, a sample holder may be located between the second polarization-switching light source and the cavity.

[0015] In further embodiments, a sample holder may be located between the first polarization-switching light source and the cavity.

[0016] In another embodiment, the second polarization-switched beam can be configured to travel along a second beam path. The sample holder can include a first major surface facing the cavity and a second major surface opposite the first major surface. The second beam path can impinge on the second major surface of the sample holder at an angle of about 10° to about 15° relative to a direction perpendicular to the second major surface of the sample holder.

[0017] In another embodiment, the apparatus further comprises a second reference block, which may comprise a second major surface. The cavity may be further defined by the second major surface. The first reference block may comprise a first refractive index. The second reference block may comprise a second refractive index.

[0018] In further embodiments, the second refractive index may be substantially equal to the first refractive index.

[0019] In further embodiments, the apparatus may include a liquid in contact with the first reference block. The liquid may include a third refractive index.

[0020] In other embodiments, the third refractive index may be greater than the first refractive index.

[0021] In further embodiments, the magnitude of the difference between the first refractive index and the third refractive index may be approximately 0.05 or greater.

[0022] In some embodiments, a method for determining an estimated stress distribution of a sample may include measuring a retardation profile of the sample. The method may include determining a central tension of the sample based on the measured retardation profile of the sample. The method may include measuring a refractive index profile of the sample. The method may include determining an initial stress distribution of the sample based on the measured refractive index profile. The method may include scaling the initial stress distribution based on the initial stress distribution and the central tension to obtain a scaled stress distribution of the sample. The method may include adjusting the scaled stress distribution to obtain an estimated stress distribution after force balancing.

[0023] In further embodiments, the sample may comprise a laminate comprising a core layer positioned between a first outer layer and a second outer layer. The core layer may comprise a central tension layer.

[0024] In further embodiments, the sample may comprise a glass-based sample.

[0025] In another embodiment, determining the central tension may include determining a width of a central region including the central tension. Determining the central tension may include determining a fitting range including a fitting width that is smaller than a width of a central portion excluding one or more end portions of the retardation profile. Determining the central tension may include fitting a polynomial to a portion of the retardation profile within the fitting range. Determining the central tension may include determining the central tension of the sample based on the fitted polynomial.

[0026] In further embodiments, the method may include contacting the first reference block with a liquid.

[0027] In further embodiments, the liquid may comprise a third refractive index that is less than the first refractive index.

[0028] In another embodiment, measuring the refractive index distribution may include positioning the sample between a first reference block and a second reference block. The first reference block may include a first refractive index. The second reference block may include a first refractive index. Measuring the refractive index distribution and determining the initial stress distribution may include emitting a second polarization-switching light beam from a second polarization-switching light source. Measuring the refractive index distribution and determining the initial stress distribution may also include transmitting the second polarization-switching light beam through the first reference block, the sample, and the second reference block. Measuring the refractive index distribution and determining the initial stress distribution may include detecting the transmitted second polarization-switching light beam to determine a detection signal. Measuring the refractive index distribution and determining the initial stress distribution may include adjusting the detection signal based on data in the detection signal corresponding to the first reference block and the second reference block to determine the refractive index distribution.

[0029] In other embodiments, the minimum difference between the estimated refractive index of the sample and the first predetermined refractive index may be in the range of about 0.7% to about 10% of the estimated refractive index. The minimum difference between the estimated refractive index and the second predetermined refractive index may be in the range of about 0.7% to about 10% of the estimated refractive index.

[0030] In another embodiment, measuring the refractive index distribution and determining the initial stress distribution includes positioning a first reference block, which may include a first predetermined refractive index, between the sample and a second polarization-switching light source. Measuring the refractive index distribution and determining the initial stress distribution may include contacting the first reference block with a liquid having a second predetermined refractive index. Measuring the refractive index distribution and determining the initial stress distribution may include emitting a second polarization-switched light beam from the second polarization-switching light source. Measuring the refractive index distribution and determining the initial stress distribution also includes transmitting the second polarization-switched light beam through the liquid, the first reference block, and the sample. Measuring the refractive index distribution and determining the initial stress distribution may include detecting the transmitted second polarization-switched light beam to determine a detection signal. Measuring the refractive index distribution and determining the initial stress distribution also includes determining an estimated stress distribution based on the transmitted signal and the corrected refractive index. The minimum difference between the estimated refractive index of the sample and the first predetermined refractive index may be in a range of approximately 0.7% to approximately 10% of the estimated refractive index. The minimum difference from the second predetermined refractive index may be in a range of approximately 0.7% to approximately 10% of the estimated refractive index.

[0031] In other embodiments, the minimum difference between the first predetermined refractive index and the estimated refractive index of the sample can be in the range of about 0.006 to about 0.10. The minimum difference between the second predetermined refractive index and the estimated refractive index of the sample can be in the range of about 0.006 to about 0.10.

[0032] In further embodiments, measuring the refractive index profile may include simultaneously measuring the refractive index profile using two detectors oriented at an angle of about 85° to about 95° relative to each other.

[0033] In some embodiments, a refractive near-field device can include a first reference block comprising a first refractive index and a first major surface. The device can include a second reference block comprising a second refractive index and comprising a second major surface facing the first major surface. The device can include a cavity defined between the first major surface and the second major surface and configured to receive a sample. The device can include a liquid comprising a third refractive index in contact with the first reference block and the second reference block.

[0034] In other embodiments, the third refractive index may be greater than the first refractive index.

[0035] In other embodiments, the third refractive index may be less than the first refractive index.

[0036] In further embodiments, the magnitude of the difference between the first refractive index and the third refractive index may be approximately 0.05 or greater.

[0037] In further embodiments, the second refractive index may be substantially equal to the first refractive index.

[0038] In further embodiments, the apparatus may further comprise a sample holder that is translatable in a direction perpendicular to the first major surface.

[0039] In further embodiments, a sample holder may be located between the second polarization-switching light source and the cavity.

[0040] In another embodiment, the second polarization-switched beam can be configured to travel along a second beam path. The sample holder can include a first major surface facing the cavity and a second major surface opposite the first major surface. The second beam path can impinge on the second major surface of the sample holder at an angle of about 10° to about 15° relative to a direction perpendicular to the second major surface of the sample holder.

[0041] In some embodiments, a method of determining a stress distribution of a sample comprising a refractive index of the sample may include positioning the sample between a first reference block comprising a first refractive index and a second reference block comprising the first refractive index. The method may include emitting a second polarization-switching light beam from a second polarization-switching light source. The method further includes transmitting the second polarization-switching light beam through the first reference block, the sample, and the second reference block. The method may include detecting the transmitted second polarization-switching light beam to determine a detection signal. The method further includes adjusting the detection signal based on data in the detection signal corresponding to the first reference block and the second reference block to determine a correction signal. The method may include determining an estimated stress distribution based on the correction signal.

[0042] In further embodiments, the magnitude of the minimum difference between the first refractive index and the sample refractive index can be in the range of about 0.7% to about 10% of the sample refractive index.

[0043] In further embodiments, the magnitude of the minimum difference between the first refractive index and the sample refractive index can be in the range of about 0.006 to about 0.10.

[0044] In other embodiments, the first refractive index may be less than the sample refractive index.

[0045] In further embodiments, the method may further include contacting the first reference block with a liquid comprising a second refractive index.

[0046] In other embodiments, the second refractive index may be greater than the first refractive index.

[0047] In other embodiments, the second refractive index may be greater than the sample refractive index.

[0048] In further embodiments, the magnitude of the minimum difference between the sample refractive index and the second refractive index can be in the range of about 0.7% to about 10% of the sample refractive index.

[0049] In further embodiments, the magnitude of the minimum difference from the second refractive index may be in a range from about 0.006 to about 0.10.

[0050] In further embodiments, the sample may comprise a glass-based sample.

[0051] In further embodiments, the sample may comprise a laminate.

[0052] In some embodiments, a method of determining a stress distribution of a sample may include positioning a first reference block comprising a first predetermined refractive index between the sample and a second polarization-switching light source. The method may include contacting the first reference block with a liquid comprising a second predetermined refractive index. The method may include emitting a second polarization-switching light beam from the second polarization-switching light source. The method also includes transmitting the second polarization-switching light beam through the liquid, the first reference block, and the sample. The method may include detecting the transmitted second polarization-switching light beam to determine a detection signal. The method also includes determining the stress distribution based on the transmitted signal and the corrected refractive index. The magnitude of the minimum difference between the estimated refractive index of the sample and the first predetermined refractive index may be in the range of approximately 0.7% to approximately 10% of the estimated refractive index. The magnitude of the minimum difference from the second predetermined refractive index may be in the range of approximately 0.7% to approximately 10% of the estimated refractive index.

[0053] In other embodiments, the minimum difference between the first predetermined refractive index and the estimated refractive index of the sample is in the range of about 0.006 to about 0.10. The minimum difference between the second predetermined refractive index and the estimated refractive index of the sample is in the range of about 0.006 to about 0.10.

[0054] In some embodiments, a method for determining a corrected refractive index of a sample may include positioning a first reference block having a first predetermined refractive index between the sample and a second polarization-switching light source. The method may include contacting the first reference block with a liquid having a second predetermined refractive index. The method may include emitting a second polarization-switching light beam from the second polarization-switching light source. The method may include transmitting the second polarization-switching light beam through the liquid, the first reference block, and the sample. The method may include detecting the transmitted second polarization-switching light beam. The method may include estimating an estimated refractive index of the sample based on the detection signal. The method may include replacing the first reference block with another reference block having the first corrected refractive index. The method may include replacing the liquid with another liquid having the second corrected refractive index. The method may include transmitting the second polarization-switching light beam through the liquid, the first reference block, and the sample. The method may include detecting the transmitted second polarization-switching light beam to determine a detection signal. The method may include estimating the corrected refractive index of the sample based on the detection signal. The method may include determining a stress distribution based on the transmitted signal and the corrected refractive index. The minimum difference between the estimated refractive index of the sample and the first corrected refractive index may be in the range of about 0.7% to about 10% of the estimated refractive index. The minimum difference between the estimated refractive index and the second corrected refractive index may be in the range of about 0.7% to about 10% of the estimated refractive index.

[0055] In other embodiments, the minimum difference between the estimated refractive index of the sample and the first corrected refractive index can be in the range of about 0.006 to 0.10. The minimum difference between the estimated refractive index of the sample and the second corrected refractive index can be in the range of about 0.006 to about 0.10.

[0056] In some embodiments, a method for determining the central tension of a sample may include measuring a retardation profile of the sample. The method may include determining a width of a central region containing the central tension. The method may include determining a fitting range that includes a fitting width that is smaller than a width of a central portion excluding one or more ends of the retardation profile. The method may include fitting a polynomial to a portion of the retardation profile within the fitting range. The method may include determining the central tension of the sample based on the fitted polynomial.

[0057] In further embodiments, the sample may comprise a glass-based sample.

[0058] In further embodiments, the sample may include a laminate comprising a core layer positioned between a first outer layer and a second outer layer, the core layer comprising a central tension member.

[0059] In other embodiments, the fitted polynomial may include a straight line. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The above features and advantages and other features and advantages of the embodiments of the present disclosure may be better understood by reading the following detailed description with reference to the accompanying drawings, in which:

[0061] Figure 1 is a schematic diagram of an exemplary combined device according to some embodiments;

[0062] Figure 2 is a schematic diagram of an exemplary combined device according to some embodiments;

[0063] Figure 3 is a schematic diagram of an exemplary light scattering polarization measurement device according to some embodiments;

[0064] Figure 4 is a schematic diagram of an exemplary light scattering polarization measurement device according to some embodiments;

[0065] Figure 5 is a schematic diagram of an exemplary light scattering polarization measurement device according to some embodiments;

[0066] Figure 6 is a cross-sectional view of a sample comprising a laminate according to some embodiments;

[0067] Figure 7 is a schematic diagram of an exemplary refractive near-field device according to some embodiments;

[0068] Figure 8 is a graphical representation of intensity distribution measured using light scattering polarimetry according to an embodiment of the present disclosure;

[0069] Figure 9 is a diagram illustrating an optical retardation distribution measured using light scattering polarimetry according to an embodiment of the present disclosure;

[0070] Figure 10 is an exemplary optical retardation profile measured using light scattering polarimetry according to an embodiment of the present disclosure;

[0071] Figure 11 is a series of stress distributions measured on the same sample;

[0072] Figure 12 is a series of stress distributions measured on the same sample according to an embodiment of the present disclosure;

[0073] Figure 13 is a flow chart illustrating an exemplary method of measuring stress distribution according to an embodiment of the present disclosure;

[0074] Figure 14is a flow chart illustrating an exemplary method of measuring central tension according to an embodiment of the present disclosure;

[0075] Figure 15 is a flow chart illustrating an exemplary method of measuring refractive index and / or stress distribution according to an embodiment of the present disclosure.

[0076] In the present disclosure, the accompanying drawings are used to emphasize certain aspects. Therefore, unless otherwise explicitly stated, the relative sizes of different regions, parts, and substrates shown in the drawings should not be considered to be proportional to their actual relative sizes. DETAILED DESCRIPTION

[0077] Various embodiments will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments are shown. Whenever possible, the same reference numerals will be used throughout the drawings to represent the same or similar parts. However, the claims may encompass many different aspects of various embodiments and should not be construed as limited to the embodiments set forth herein.

[0078] Figure 1-5 7 illustrate views of devices according to embodiments of the present disclosure. Unless otherwise noted, a discussion of features of one embodiment of a foldable device may be equally applicable to corresponding features of any embodiment of the present disclosure. For example, in the present disclosure, identical part numbers may indicate that, in some embodiments, the identified features are identical to one another, and a discussion of an identified feature of one embodiment may be equally applicable to an identified feature of any other embodiment of the present disclosure, unless otherwise noted.

[0079] Figure 1-5 7 schematically illustrate exemplary embodiments of devices according to embodiments of the present disclosure. Figure 1-2 As shown, the device may be a combined device 101 comprising a light scattering polarimeter (LSP) device 131 and a refractive near field (RNF) device 121. In some embodiments, as Figure 3-5 As shown, embodiments of the device may include LSP devices 131, 131' as standalone devices. In some embodiments, such as Figure 7 As shown, embodiments of the device may include the RNF device 121 as a standalone device. Therefore, it should be understood that, unless otherwise noted, discussions regarding the LSP device 131 in the combination device 101 may apply to corresponding features of the standalone LSP devices 131, 131', and vice versa. Similarly, it should be understood that, unless otherwise noted, discussions regarding the RNF device 121 in the combination device 101 may apply to the standalone RNF device 121, and vice versa.

[0080] Figure 1-2A combined device 101 is schematically illustrated and may include a housing 107 enclosing an LSP device 131 and an RNF device 121. In some embodiments, the housing 107 or other area of ​​the combined device 101 may include a first dimension L1 and a second dimension L2, wherein the components of the combined device 101 are confined within the area defined by the first dimension L1 and the second dimension L2. In some embodiments, L1 and / or L2 may be within the following ranges: approximately 200 mm to 1 meter, approximately 200 mm to approximately 500 mm, approximately 200 mm to approximately 300 mm, or any range or sub-range therebetween. In some embodiments, although not shown, the controller 141 may be located outside of the housing 107.

[0081] like Figure 1-5 As shown, the LSP device 131, 131' may include a first polarization switching light source 133. In some embodiments, as Figure 2As shown, the first polarization-switching light source 133 may include a first light source 201 and a first optical compensator 203. The first light source 201 may include a laser, a light-emitting diode (LED), and / or an organic light-emitting diode. In further embodiments, the laser may include a gas laser, an excimer laser, a dye laser, or a solid-state laser. Exemplary embodiments of gas lasers include helium, neon, argon, krypton, xenon, helium-neon (HeNe), xenon-neon (XeNe), carbon dioxide (CO2), carbon monoxide (CO), copper (Cu) vapor, gold (Au) vapor, cadmium (Cd) vapor, ammonia, hydrogen fluoride (HF), and deuterium fluoride (DF). Exemplary embodiments of excimer lasers include chlorine, fluorine, iodine, or nitrous oxide (N2O) in an inert environment, wherein the inert environment includes argon (Ar), krypton (Kr), xenon (Xe), or a combination thereof. Exemplary embodiments of dye lasers include those using organic dyes, for example, rhodamine, fluorescein, coumarin, stilbene, umbelliferone, tetracene, or malachite green dissolved in a liquid solvent. Exemplary embodiments of solid-state lasers include crystal lasers, fiber lasers, and laser diodes. Crystal-based lasers include a host crystal doped with a lanthanide or transition metal. Exemplary embodiments of the host crystal include yttrium aluminum garnet (YAG), yttrium lithium fluoride (YLF), yttrium othoaluminate (YAL), yttrium scandium gallium garnet (YSSG), lithium aluminum hexafluoride (LiSAF), lithium aluminum calcium hexafluoride (LiCAF), zinc selenide (ZnSe), zinc sulfide (ZnS), ruby, forsterite, and sapphire. Exemplary embodiments of dopants include neodymium (Nd), titanium (Ti), chromium (Cr), cobalt (Co), iron (Fe), erbium (Er), holmium (Ho), thulium (Tm), ytterbium (Yb), dysprosium (Dy), cerium (Ce), gadolinium (Gd), samarium (Sm), and terbium (Tb). Exemplary embodiments of solid crystals include ruby, alexandrite, chromium fluoride, forsterite, lithium fluoride (LiF), sodium chloride (NaCl), potassium chloride (KCl), and rubidium chloride (RbCl). The laser diode may include a heterojunction diode or a PIN diode having three or more materials for the respective p-type, intrinsic, and n-type semiconductor layers. Exemplary embodiments of the laser diode include AlGaInP, AlGaAs, InGaN, InGaAs, InGaAsP, InGaAsN, InGaAsNSb, GaInP, GaAlAs, GaInAsSb, and lead (Pb) salts. Certain laser diodes may represent exemplary embodiments due to their size, tunable output power, and ability to operate at room temperature (ie, about 20° C. to about 25° C.).

[0082] In some embodiments, the first light source 201 can be configured to emit a first light beam comprising a first optical wavelength. In further embodiments, the first optical wavelength can be in the range of about 300 nanometers (nm) to about 1,000 nm, about 350 nm to about 900 nm, about 400 nm to about 800 nm, about 500 nm to about 700 nm, or any range or sub-range therebetween. In further embodiments, the first wavelength can be about 365 nm, about 415 nm, or about 590 nm. In some embodiments, as Figure 2-4 As shown, the first polarization-switching light source 133 is configured to emit a first polarization-switched light beam along a first path 205 , 205F, 205S, 205U.

[0083] like Figure 2 As shown, the first optical compensator 203 may include a polarization beam splitter. In other embodiments, the first optical compensator 203 may include a half-wave plate and a quarter-wave plate. In other embodiments, one of the half-wave plate or the quarter-wave plate may be rotated relative to the other, which may change the polarization of the light beam passing therethrough. In other embodiments, the first optical compensator 203 may include an electrically controlled polarization modulator, such as a liquid crystal-based modulator or a ferroelectric liquid crystal-based modulator. In other embodiments, the first optical compensator 203 may be controlled by a controller 141 (discussed below).

[0084] As used herein, the first polarization-switching light source 133 (e.g., including the first optical compensator 203) is configured to cycle between two or more polarization states (polarizations). In some embodiments, the first polarization-switching light source 133 can be configured to switch (e.g., cycle through) up to eight different polarizations that combine linear polarization, elliptical polarization, and / or circular polarization. In other embodiments, the first polarization-switching light source 133 can be configured to undergo a complete polarization cycle (i.e., change between two or more polarizations) in a range from less than 1 second to about 10 seconds.

[0085] In some embodiments, as Figure 2-3As shown, the LSP device 131, 131' may include a first focusing lens 135. As shown, the first focusing lens 135 may be positioned along the first path 205 of the first polarization-switched light beam. After passing through the first focusing lens 135, the first polarization-switched light beam may be focused along a portion 205F of the first path. The first focusing lens 135 may include a convex lens and / or an adjustable focus lens. In some embodiments, the first focusing lens 135 may be configured to collimate the first polarization-switched light beam along the portion 205F of the first path. In some embodiments, although not shown, a bandpass filter, additional focusing lens, light diffuser, beam splitter, and / or attenuator may be positioned along the portions 205, 205F, and / or 205S of the first path. In other embodiments, one or more of these additional elements may be controlled by the controller 141.

[0086] In some embodiments, as Figure 1 and 3 -5, the LSP device 131, 131' may include a prism 113. In another embodiment, as Figure 4 As shown, the prism 113 may optionally include an input surface 209 and a first output surface 213. In another embodiment, as shown in FIG. Figure 3 As shown, the prism 113 may include a second output surface 211. In another embodiment, as shown in FIG. Figure 3 As shown, the prism 113 can include a sample coupling surface 307. In further embodiments, the sample coupling surface 307 of the prism 113 can at least partially define a cavity 301 configured to receive the sample 103. In further embodiments, the sample coupling surface 307 of the prism 113 can face the index matching fluid 215. In further embodiments, the sample coupling surface 307 of the prism 113 can contact the index matching fluid 215.

[0087] like Figure 1-5 As shown, the LSP device 131, 131' may include a first detector 137. In some embodiments, the first detector 137 may include a digital camera, a CCD and / or a photodetector array. In some embodiments, the first detector may include one or more focusing lenses, attenuators and / or beam splitters. In some embodiments, such as Figure 2 and 4 As shown, the first detector 137 may include an image sensor 217. In another embodiment, as shown in FIG. Figure 4-5As shown, image sensor 217 may include an array of imaging pixels 401. In further embodiments, the array of imaging pixels may include a two-dimensional array. In other embodiments, the maximum size of a pixel in the array of imaging pixels may be in the range of about 1 micrometer (μm) to about 15 μm, about 2 μm to about 10 μm, about 5 μm to about 8 μm, or any range or sub-range therebetween. In other embodiments, as Figure 3-5 As shown, the first detector 137 can face the first output surface 213 of the prism 113. In other embodiments, the first detector 137 can be positioned along the first path 205S to detect a signal from the scattered first polarization-switched light beam traveling through the prism 113. Figure 1-4 As shown, the first detector 137 may be connected to the controller 141 via a communication path configured to transmit a signal SB.

[0088] In some embodiments, as Figure 3 As shown, LSP devices 131, 131' including first detector 137 may include more than one first detector. In other embodiments, as shown, the first detector may include a first image detector 137A and a second image detector 137B, where the first image detector 137A is configured to detect scattered light traveling along path 205S and the second image detector 137B is configured to detect scattered light traveling along path 205U. In further embodiments, the first image detector 137A may face the first output surface 213 of the prism 113, and the second image detector 137B may face the second output surface 211 of the prism 113. In other embodiments, a first axis is defined between the prism 113 and the first image detector 137A, and a second axis is defined between the prism 113 and the second image detector 137B. The angle between the first axis and the second axis may be in the range of approximately 85° to approximately 95°, approximately 87° to approximately 93°, approximately 89° to approximately 91°, or any range or sub-range therebetween. Providing multiple detectors at substantially right angles (e.g., in the range of about 85° to about 95°) can capture multiple measurements in the same polarization, which can be combined (e.g., averaged) to reduce noise in the measurement and / or shorten the time required to make corresponding measurements.

[0089] In some embodiments, as Figure 1-2 As shown in FIG. 5 , the LSP device 131 , 131 ′ may include a sample holder 701. In another embodiment, as shown in FIG. Figure 5 As shown, the sample holder 701 can at least partially define a cavity 301 configured to receive the sample 103. In other embodiments, the sample holder 701 can translate in direction 305. In other embodiments, the sample holder 701 can translate in direction 711. In some embodiments, as Figure 4 As shown, the LSP device 131' may include a first gantry 405 to which at least a portion of the first polarization-switching light source 133 is connected. In other embodiments, as shown, the first light source 201 of the first polarization-switching light source 133 may be connected to the first gantry 405. In other embodiments, as shown, the first light source 201 of the first polarization-switching light source 133 may contact the first gantry 405. In other embodiments, as shown, the first gantry may be translated in at least a direction 407 parallel to the first portion 205F of the first path 205 of the first polarization-switching light beam. In some embodiments, as shown Figure 4 As shown, the LSP apparatus 131' may include a second stage 409 to which at least a portion of the first detector 137 is coupled. In other embodiments, as shown, the first detector 137 may contact the second stage 409. In other embodiments, as shown, the second stage 409 is translatable in at least a direction 411, which is perpendicular to the second portion 205S of the first path of the first polarization-switched light beam after being scattered by the sample 103. In other embodiments, although not shown, when the first detector 137 includes more than one detector, the second stage 409 may include a plurality of stages, with each stage in the plurality of stages corresponding to a detector (e.g., the first image detector 137A, the second image detector 137B). In other embodiments, each stage in the plurality of stages is translatable in at least the direction 411. It should be understood that the translatable stages discussed above are applicable to all embodiments of the LSP apparatuses 131, 131'.

[0090] In some embodiments, as Figure 3-5 As shown, the LSP device 131, 131' may include a second reference block 707. In another embodiment, as shown in FIG. Figure 5 As shown, the second reference block 707 may include a second major surface 721 that faces the sample coupling surface 307 of the first reference block 113. Figure 3-5 As shown, the LSP devices 131, 131' may include a platform 303. In another embodiment, as Figure 5 As shown, the platform 303 may include a platform surface 713 that faces the sample coupling surface 307 of the first reference block 113. In another embodiment, as shown in FIG. Figure 5 As shown, the second reference block 707 may be located between the platform 303 and the first reference block 113 .

[0091] In some embodiments, as Figure 4As shown, the LSP device 131' can be configured to cause the beam path 205 of the first polarization-switching light beam to impinge on the input surface 209 of the prism 113. In other embodiments, the prism 113 can be located between the first polarization-switching light source 133 and the cavity 301 configured to receive the sample 103. In other embodiments, the prism 113 can be located between the first polarization-switching light source 133 and the sample holder 701. In other embodiments, the beam path 205 can be configured to impinge on the input surface 209 of the prism 113 at a substantially perpendicular angle of incidence (e.g., in a range of about 85° to about 95° relative to the input surface 209). In other embodiments, as described above and as Figure 3 As shown, the beam path may first impinge on a cavity 301 configured to receive the sample 103 and then illuminate one or more first output surfaces 213 and / or second output surfaces 211 of the prism. In another embodiment, as shown, the LSP device 131' may include one or more detectors configured to detect a signal from the first polarization-switched beam.

[0092] In some embodiments, as Figure 5 As shown, the LSP device 131 can be configured such that the beam path 205 of the first polarization-switched beam impinges on the sample holder 701. In another embodiment, as shown in FIG. Figure 2 As shown, the first polarization-switching light source can be positioned at an angle 231 relative to a direction perpendicular to the second major surface 143 of the sample holder 701. In further embodiments, the angle 231 can be in the range of about 5° to about 25°, about 5° to about 20°, about 10° to about 20°, about 10° to about 15°, or any range or sub-range therebetween. In further embodiments, as Figure 1-2 As shown in FIG5 and FIG6 , the sample holder 701 may be located between the first polarization-switching light source 133 and the cavity 301 configured to receive the sample 103. Figure 5 As shown, the LSP device 131 may include a second reference block 707, wherein the sample holder 701 is located between the first polarization switching light source 133 and the second reference block 707. In some embodiments, the beam paths 205, 205S may impinge on the reference fluid 723. In other embodiments, as described above and as Figure 3 As shown, the beam path may first impinge on a cavity 301 configured to receive the sample 103 and then illuminate one or more first output surfaces 213 and / or second output surfaces 211 of the prism. In other embodiments, as shown, the LSP device 131' may include one or more detectors configured to detect a signal from the first polarization-switched beam. In some embodiments, as shown, Figure 1-27, the first polarization switching light source 133 may face the second major surface 143 of the sample holder 701, the second major surface 143 being opposite to the first major surface 313 of the sample holder 701. In another embodiment, as Figure 1-2 As shown, the first polarization switching light source 133 and the second polarization switching light source 123 can both face the second major surface 143 of the sample holder 701. In some embodiments, as shown in FIG. Figure 2 As shown, the second detector 127 can be located at an angle 233 Figure 2 In some embodiments, angle 233 can be in the range of about 30° to about 60°, about 40° to about 60°, about 40° to about 50°, about 42° to about 48°, about 44° to about 46°, or any range or sub-range therebetween.

[0093] like Figure 1-2 As shown, the RNF device 121 may include a second polarization switching light source 123. In some embodiments, as shown in FIG. Figure 2 As shown, the second polarization-switching light source 123 may include a second light source 221. In other embodiments, the second light source 221 may include one or more of the light sources described above with respect to the first light source 201. In other embodiments, the second polarization-switching light source 123 may be configured to emit a second polarization-switching light beam along a second path 207, 207R. In some embodiments, the second polarization-switching light source 123 may include a second optical compensator 223, which may include one or more of the optical compensators described above with respect to the first optical compensator 203. In some embodiments, as Figure 1-2 As shown in FIG. 7 , the RNF device 121 may include a converging lens 125. In another embodiment, as shown in FIG. Figure 7 As shown, the converging lens 125 can be configured to focus the second polarization-switched light beam passing through the converging lens 125 to form a focal point 709 at the interface between the first major surface 313 of the sample holder 701 and the cavity 301 and / or the sample 103. In some embodiments, although not shown, one or more of the optical elements described above with respect to the first focusing lens 135 (e.g., a bandpass filter, an additional focusing lens, a light diffuser, a beam splitter, an attenuator) can be positioned along the portion 207 of the second path. In other embodiments, one or more of these additional elements can be controlled by the controller 141. For example, in other embodiments, a mask can be used in combination with the converging lens 125 so that a portion of the light cone can be focused at the focal point 709 by passing through the mask. In other embodiments, the mask can be configured to allow a portion of a circular cross-section of the outer periphery of the second polarization-switched light beam to pass through the mask and be focused at the focal point 709. In other embodiments, the mask can be configured to allow some light rays (e.g., two light rays) to pass through the mask and be focused at the focal point 709.

[0094] In some embodiments, as Figure 1-2 As shown in FIG. 7 , the RNF device 121 may include a first reference block 113. In some embodiments, as shown in FIG. Figure 1-2 As shown, the first reference block 113 may include a prism 113. As described above with respect to the prism 113, the first reference block 113 may include a first output surface 213 and an optional second output surface 211. In another embodiment, as Figure 3 As shown, the first reference block 113 may include a sample coupling surface 307. In other embodiments, as shown, the sample coupling surface 307 of the first reference block 113 may at least partially define a cavity 301 configured to receive the sample 103. In other embodiments, the sample coupling surface 307 of the first reference block 113 may face the refractive index matching fluid 215. In other embodiments, the sample coupling surface 307 of the first reference block 113 may contact the refractive index matching fluid 215. In some embodiments, as shown Figure 1 As shown, the prism 113 and / or the first reference block 113 may define the measurement location ML. In some embodiments, although not shown, the first reference block may include a structure different from the prism, and the first reference block may be located between the prism and the cavity. In other embodiments, although not shown, the first major surface of the first reference block may face away from the prism. In other embodiments, although not shown, the first reference block may contact the prism. In other embodiments, although not shown, a refractive index matching fluid may be located between the first reference block and the prism.

[0095] In some embodiments, the first reference block 113 can include a first refractive index. The first refractive index can be a function of the wavelength of light passing through the optically clear adhesive. For light of the first wavelength, the refractive index of a material is defined as the ratio between the speed of light in a vacuum and the speed of light in the corresponding material. Without being bound by theory, the refractive index of the optically clear adhesive can be determined by the ratio of the sine of a first angle to the sine of a second angle, where light of the first wavelength is incident on the surface of the optically clear adhesive from air at the first angle and is refracted at the surface of the optically clear adhesive, causing the light to propagate within the optically clear adhesive at the second angle. Both the first angle and the second angle are measured relative to a normal to the surface of the optically clear adhesive. In some embodiments, the first refractive index of the first reference block 113 can be approximately 1 or greater, approximately 1.3 or greater, approximately 1.4 or greater, approximately 3 or less, approximately 2 or less, or approximately 1.7 or less. In some embodiments, the first refractive index of the first reference block 113 can be in the range of about 1 to about 3, about 1 to about 2, about 1 to about 1.7, about 1.3 to about 3, about 1.3 to about 2, about 1.3 to about 1.7, about 1.4 to about 2, about 1.4 to about 1.7, or any range or sub-range therebetween.

[0096] In some embodiments, as Figure 7 As shown, the RNF device 121 can include a second reference block 707, as shown in dashed lines. In other embodiments, the second reference block 707 can include a second major surface 721 that faces the sample coupling surface 307 of the first reference block 113. In other embodiments, the second major surface 721 of the second reference block 707 can at least partially define a cavity 301 configured to receive the sample 103.

[0097] In some embodiments, the second reference block 707 may include a second refractive index. In other embodiments, the second refractive index may be within the above range. In other embodiments, the second refractive index may be substantially equal to the first refractive index. In other embodiments, the first reference block and the second reference block may comprise the same material. In other embodiments, the first refractive index may be greater than the second refractive index. In other embodiments, the second refractive index may be greater than the first refractive index. In other embodiments, the difference between the first refractive index and the second refractive index in absolute value (e.g., magnitude) may be approximately 0.1 or less, approximately 0.07 or less, approximately 0.05 or less, approximately 0.001 or greater, approximately 0.006 or greater, approximately 0.01 or greater, or approximately 0.02 or greater. In some embodiments, the difference is in the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.001 to about 0.05, about 0.001 to about 0.1, about 0.006 to about 0.07, about 0.006 to about 0.05, about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.01 to about 0.05, about 0.02 to about 0.1, about 0.02 to about 0.07, about 0.02 to about 0.05, or any range or sub-range therebetween.

[0098] In some embodiments, as Figure 7As shown schematically, the RNF device 121 may include a fluid 723. In other embodiments, as shown, the fluid 723 may contact the prism 113. In other embodiments, as shown, the fluid 723 may contact the first reference block 113. In some embodiments, the fluid 723 may include a third refractive index. In other embodiments, the third refractive index is greater than the first refractive index. In other embodiments, the first refractive index is greater than the second refractive index. In other embodiments, although not shown, the fluid 723 may be located between the first reference block 113 and the cavity 301 configured to receive the sample 103. In other embodiments, although not shown, the fluid 723 may be located between the second reference block 707 and the cavity 301 configured to receive the sample 103. In other embodiments, although not shown, the fluid 723 may be located between the first reference block 113 and the second reference block 707. In other embodiments, as shown, the fluid 723 may contact the sample holder 701. In further embodiments, a spacer (e.g., a glass strip) may be positioned between the cavity 301 configured to receive the sample 103 and one or both of the first reference block 113 and / or the second reference block 707, wherein the thickness of the spacer defines a region having a thickness within a range of about 10 μm to about 1 mm, about 25 μm to about 500 μm, about 50 μm to about 300 μm, about 100 μm to about 200 μm, or any range or sub-range therebetween. In some embodiments, although not shown, the fluid 723 may not extend past the first reference block 213 in the x-direction. In some embodiments, although not shown, the fluid 723 may not extend past the first reference block 213 in the z-direction. In some embodiments, although not shown, the fluid 723 may not extend past the first reference block 213 in the y-direction.

[0099] In other embodiments, the difference between the third refractive index and the first refractive index, which is equal to the absolute value, can be in the range of about 0.05 or greater, about 0.06 or greater, about 0.08 or greater, about 0.10 or greater, about 0.12 or greater, or about 0.14 or greater. In other embodiments, the difference between the third refractive index and the first refractive index, which is equal to the absolute value, can be in the range of about 0.05 to about 0.20, about 0.04 to about 0.18, about 0.06 to about 0.15, about 0.08 to about 0.10, or any range or sub-range therebetween.

[0100] like Figure 1-2As shown in FIG. 7 , the RNF device 121 may include a second detector 127. In some embodiments, the second detector 127 may include a digital camera, a CCD, and / or a photodetector array. In some embodiments, the second detector 127 may include one or more focusing lenses, attenuators, and / or beam splitters. In some embodiments, as shown in FIG. Figure 2 and 7 As shown, the second detector 127 may include an image sensor 219. In other embodiments, although not shown, the image sensor 219 may include similar or identical properties to the image sensor 217 described above. Figure 2 and 7 As shown, the second detector 127 can face the prism 113. In other embodiments, the second detector 127 can be positioned along the second path 207R to detect a signal from the refracted second polarization-switched light beam traveling through the prism 113. In other embodiments, as shown Figure 2 and 7 As shown, the second detector 127 can face the second reference block 707. In other embodiments, the second detector 127 can be positioned along the second path 207R to detect a signal from the refracted second polarization-switched light beam traveling through the second reference block 707. Figure 1-2 As shown in FIG. 7 , the second detector 127 may be connected to the controller 141 via a communication path configured to transmit a signal SA.

[0101] In some embodiments, as Figure 7 As shown, the RNF device 121 may include a sample holder 701. In other embodiments, as shown, the sample holder 701 may contact the fluid 723. In other embodiments, as shown, the sample holder 701 may contact the first reference block 113. In other embodiments, as shown, the sample holder 701 may at least partially define a cavity 301 configured to receive the sample 103. In other embodiments, the sample holder 701 may contact the second reference block 707. In other embodiments, the sample holder 701 may translate in a direction 305 that is perpendicular to the specimen coupling surface 307 of the first reference block 113. In other embodiments, the sample holder 701 may translate in a direction 711 (shown as away from the specimen coupling surface 307). Figure 7 In some embodiments, for example, in the combined device 101, the direction 711 is parallel to the sample coupling surface 307 of the first reference block 113. Figure 3-4 The sample holder 701 can be used with Figure 7 The sample holder 701 is the same as described above. In some embodiments, Figure 7As shown, the RNF device 121 may include a platform 303. In other embodiments, as shown, the platform 303 may include a platform surface 713 that faces the sample coupling surface 307 of the first reference block 113. In other embodiments, as shown, Figure 5 As shown, the second reference block 707 may be located between the platform 303 and the first reference block 113 .

[0102] In some embodiments, as Figure 7 As shown, the cavity 301 can be located between the first reference block 113 and the second reference block 707. In some embodiments, as shown, the sample holder 701 can be located between the second polarization-switching light source 123 and the cavity 301 configured to receive the sample 103. In some embodiments, as shown, the sample holder 701 can be located between the second polarization-switching light source 123 and the first reference block 113. In some embodiments, as shown, the sample holder 701 can be located between the second polarization-switching light source 123 and the fluid 723. In some embodiments, as shown, the sample holder 701 can be located between the second polarization-switching light source 123 and the second reference block 707. In some embodiments, as shown, the second path 207 of the second polarization-switching light beam emitted from the second polarization-switching light source 123 can illuminate the first reference block 113 and the second reference block 707.

[0103] As used herein, the term "controller" may encompass all devices, apparatuses, and machines for processing data, including, for example, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, the processor may also include a code for creating an execution environment for the computer program involved, such as a code constituting processor firmware, a protocol stack, a database management system, an operating system, or a combination thereof of one or more. In some embodiments, the controller may include a digital electronic circuit and / or be applied as a digital electronic circuit, or be applied as computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or a combination thereof of one or more. The controller embodiments described herein may be applied as one or more computer program products (e.g., one or more modules of computer program instructions encoded on a tangible program carrier, executed by a data processing device or used to control the operation of a data processing device). The tangible program carrier may be a computer-readable medium. The computer-readable medium may be a machine-readable storage device, a machine-readable storage substrate, a memory device, or a combination thereof of one or more. A computer program (also referred to as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that stores other programs or data (e.g., one or more scripts stored in a markup language file), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files storing one or more modules, subroutines, or partial codes). A computer program can be deployed and executed on one or more computers, which are located at one site or distributed across multiple sites and interconnected by a communication network. The programs described herein can be executed by one or more programmable processors that execute one or more computer programs to perform functions by operating input data and generating output information. Programs and logic flows can also be executed by dedicated logic circuits [e.g., FPGAs (field programmable gate arrays) or ASICs (application-specific integrated circuits), etc.], and devices can also be used as dedicated logic circuits. Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any type of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory, or both. The essential elements of a computer are a processor for executing instructions and one or more data storage devices for storing instructions and data.Generally speaking, a computer will also include or be operatively connected to one or more mass storage devices (e.g., magnetic, magneto-optical, or optical disks) for storing data, to receive data from or transfer data to, or both, the one or more mass storage devices. However, a computer need not have such devices. In addition, a computer may be embedded in another device, such as a mobile phone, a personal digital assistant (PDA), or the like. Computer-readable media suitable for storing computer program instructions and data include all forms of data storage, including non-volatile memory, media, and storage devices, including, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard drives or removable disks; magneto-optical disks; and CD ROM and DVD-ROM disks. The processor and memory may be supplemented by or incorporated into dedicated logic circuitry. To provide for user interaction, the embodiments described herein may be implemented on a computer having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, etc.) for displaying information to the user, as well as a keyboard and pointing device (e.g., a mouse or trackball or touch screen) for the user to provide input information to the computer. Other types of devices may also be used to provide interaction with the user; for example, input from the user may be received in any form, including sound, voice, or tactile input. The embodiments described herein may be implemented in a computing system that includes a back-end component (e.g., as a data server), or includes an intermediate device component (e.g., an application server), or includes a front-end component (e.g., a client computer with a graphical user interface or a web browser, through which a user can interact with the implementation process of the subject described herein), or any combination of one or more such back-end, intermediate device, or front-end components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Implementations of communication networks include local area networks ("LANs") and wide area networks ("WANs"), such as the Internet. A computing system may include a client and a server. The client and server are generally remote from each other and typically interact through a communication network. The relationship between the client and the server is established by computer programs running on their respective computers and having a client-server relationship.

[0104] In some embodiments, the combined device 101, the LSP device 131 and / or the RNF device 121 can be used to measure the refractive index, stress distribution and / or central tension of the sample 103. In some embodiments, the sample 103 may include a glass-based sample. As used herein, "glass-based" includes both glass and glass-ceramics, wherein the glass-ceramics have one or more crystalline phases and an amorphous residual glass phase. The glass-based material cools or has been cooled to become glass, glass-ceramics and / or becomes a glass-ceramic material after further processing. The glass-based material (e.g., a glass-based substrate) may include an amorphous material (e.g., glass) and optionally one or more crystalline materials (e.g., ceramics). The amorphous material and the glass-based material may be strengthened. As used herein, the term "strengthened" may refer to a material that has been chemically strengthened, for example, by ion-exchanging smaller ions in the substrate surface with larger ions, as described below. However, other strengthening methods known in the art may also be used to form a strengthened substrate, such as thermal tempering, or using a mismatch in the thermal expansion coefficients between parts of the substrate to produce a compressive stress region and a central tension region. Exemplary glass substrates containing or not containing lithium oxide include soda lime glass, alkali aluminosilicate glass, alkali-containing borosilicate glass, alkali-containing aluminoborosilicate glass, alkali-containing phosphosilicate glass, and alkali-containing aluminophosphosilicate glass. In one or more embodiments, the glass-based material may include, by mole percentage (mol%), about 40 mol% to about 80 mol% SiO2, about 10 mol% to about 30 mol% Al2O3, 0 mol% to about 10 mol% B2O3, 0 mol% to about 5 mol% ZrO2, 0 mol% to about 15 mol% P2O5, 0 mol% to about 2 mol% TiO2, 0 mol% to about 20 mol% RO, and 0 mol% to about 15 mol% RO. As used herein, RO may refer to alkali metal oxides, such as Li2O, Na2O, KO, Rb2O, and Cs2O. As used herein, RO may refer to MgO, CaO, SrO, BaO, and ZnO. In some embodiments, the glass-based substrate may optionally further include 0 mol% to about 2 mol% of each of the following: Na2SO4, NaCl, NaF, NaBr, K2SO4, KCl, KF, KBr, As2O3, Sb2O3, SnO2, Fe2O3, MnO, MnO2, MnO3, Mn2O3, Mn3O4, Mn2O7. "Glass-ceramics" include materials produced by controlled crystallization of glass. In some embodiments, the glass-ceramics have a crystallinity of about 1% to about 99%.Examples of suitable glass ceramics may include Li2O-Al2O3-SiO2 system (i.e., LAS system) glass ceramics, MgO-Al2O3-SiO2 system (i.e., MAS system) glass ceramics, ZnO×Al2O3×nSiO2 (i.e., ZAS system) and / or glass ceramics containing a main crystalline phase, wherein the main crystalline phase includes β-quartz solid solution, β-spodumene, cordierite, petalite and / or lithium disilicate. The glass ceramic substrate can be strengthened using the chemical strengthening process disclosed herein. In one or more embodiments, the glass ceramic substrate of the MAS system can be strengthened in a Li2SO4 molten salt, thereby generating 2Li. + Mg 2+ In some embodiments, the substrate comprising a glass-based substrate may be optically transparent. As used herein, "optically transparent" or "optically clear" means an average transmittance of 70% or greater through a 1.0 mm thick sheet of material in the wavelength range of 400 nm to 700 nm. In some embodiments, the average transmittance of an "optically transparent material" or "optically clear material" through a 1.0 mm thick sheet of material in the wavelength range of 400 nm to 700 nm may be 75% or greater, 80% or greater, 85% or greater, or 90% or greater, 92% or greater, 94% or greater, or 96% or greater. The average transmittance in the wavelength range of 400 nm to 700 nm is calculated by measuring the transmittance at all integer wavelengths from about 400 nm to about 700 nm and averaging the measured values.

[0105] like Figure 6 As shown, sample 103 may include a length 621 and a width perpendicular to the length. In some embodiments, the dimensions of the sample (e.g., length 621, width) may correspond to the dimensions of a consumer electronic product. In some embodiments, sample 103 may include a consumer electronic product. The consumer electronic product may include a glass-based portion and further include an electrical component at least partially within the housing. The electrical component may include a controller, a memory, and a display. The display may be at or adjacent to the front surface of the housing. The consumer electronic product may include a cover substrate disposed above the display.

[0106] In some embodiments, as Figure 6 As shown, sample 103 may include a laminate. As used herein, a laminate includes a core layer positioned between a first outer layer and a second outer layer. For example, referring to Figure 6, sample 103 may include a laminate comprising a core layer 601 positioned between a first outer layer 603 and a second outer layer 605. In further embodiments, the core layer 601 may comprise a central tension (e.g., comprising a region in tension). In further embodiments, the first outer layer 603 and / or the second outer layer 605 may comprise a compressive stress (e.g., comprising a region in compression). In further embodiments, the core layer 601 may comprise a core thickness 615 that may be greater than the sum of a first thickness 617 of the first outer layer 603 and a second thickness 619 of the second outer layer 605.

[0107] In some embodiments, the first outer layer 603 and / or the second outer layer 605 can be glass-based. In some embodiments, the core layer 601 can be glass-based. In some embodiments, the core thickness 615 of the core layer 601 can be about 100 μm or greater, about 200 μm or greater, about 400 μm or greater, about 10 millimeters (mm) or less, about 5 mm or less, about 2 mm or less, or about 1 mm or less. In some embodiments, the core thickness 615 of the core layer 601 can be in the range of about 100 μm to about 10 mm, about 200 μm to about 5 mm, about 400 μm to about 2 mm, about 400 μm to about 1 mm, or any range or sub-range therebetween. In some embodiments, the first thickness 617 of the first outer layer 603 and / or the second thickness 619 of the second outer layer 605 can be about 1 μm or more, about 10 μm or more, about 20 μm or more, about 200 μm or less, about 100 μm or less, or about 60 μm or less. In some embodiments, the first thickness 617 of the first outer layer 603 and / or the second thickness 619 of the second outer layer 605 can be in the range of about 1 μm to about 200 μm, about 10 μm to about 100 μm, about 20 μm to about 60 μm, or any range or sub-range therebetween.

[0108] In some embodiments, sample 103 can include a first outer major surface 105 and a second outer major surface 309 opposite first outer major surface 105. In further embodiments, sample 103 can include a laminate, and core layer 601 can include a first inner major surface 607 and a second inner major surface 609 opposite first inner major surface 607. In further embodiments, third inner major surface 611 of first outer layer 603 can face first inner major surface 607 of core layer 601. In further embodiments, third inner major surface 611 of first outer layer 603 can contact first inner major surface 607 of core layer 601. In further embodiments, fourth inner major surface 613 of second outer layer 605 can face second inner major surface 609 of core layer 601. In further embodiments, fourth inner major surface 613 of second outer layer 605 can contact second inner major surface 609.

[0109] In some embodiments, sample 103 can be positioned within cavity 301. In further embodiments, first outer major surface 105 of sample 103 can face first major surface 313 of sample holder 701. In further embodiments, second outer major surface 309 of sample 103 can face first major surface 313 of sample holder 701. In further embodiments, first outer major surface 105 of sample 103 can face specimen coupling surface 307 of prism 113 and / or first reference block 113. In further embodiments, second outer major surface 309 of sample 103 can face second major surface 721 of second reference block 707.

[0110] In some embodiments, the sample 103 may include a sample refractive index. In other embodiments, the sample refractive index may include a refractive index profile that varies in a direction 602 perpendicular to the first outer major surface 105. As used herein, the magnitude of the minimum difference between the first refractive index and the refractive index profile is the minimum absolute value of the difference between the first refractive index and each point in the refractive index profile. In practice, the magnitude of the minimum difference is equal to the lesser of (i) and (ii): (i) the absolute value of the difference between the first refractive index and the minimum refractive index in the refractive index profile; (ii) the absolute value of the difference between the first refractive index and the maximum refractive index in the refractive index profile. As used herein, the magnitude of the minimum difference expressed as a percentage is the magnitude of the minimum difference divided by the value of the refractive index profile used to produce the magnitude of the minimum difference.

[0111] In some embodiments, the magnitude of the minimum difference between the sample refractive index of the sample 103 and the first refractive index of the first reference block 113, expressed as a percentage of the sample refractive index, can be about 0.7% or greater, about 1% or greater, about 2% or greater, 3% or greater, about 5% or greater, about 10% or less, about 8% or less, or about 6% or less, or about 4% or less. In some embodiments, the magnitude of the minimum difference between the sample refractive index of the sample 103 and the first refractive index of the first reference block 113, expressed as a percentage of the sample refractive index, can be about 0.7% to about 10%, about 0.7% to about 8%, about 0.7% to about 6%, about 0.7% to about 4%, about 1% to about 10%, about 1% to about 8%, about 1% to about 6%, about 2% to about 10%, about 2% to about 8%, about 2% to about 6%, about 3% to about 8%, about 3% to about 6%, about 5% to about 10%, about 5% to about 8%, about 5% to about 6%, or any range or sub-range therebetween. In some embodiments, the magnitude of the minimum difference between the sample refractive index of sample 103 and the first refractive index of first reference block 113 can be about 0.006 or greater, about 0.01 or greater, 0.02 or greater, about 0.04 or greater, about 0.06 or greater, about 0.10 or less, about 0.08 or less, or about 0.06 or less. In some embodiments, the minimum difference between the sample refractive index of sample 103 and the first refractive index of first reference block 113 can be about 0.006 to about 0.10, about 0.006 to about 0.08, about 0.006 to about 0.06, about 0.02 to about 0.10, about 0.02 to about 0.08, about 0.02 to about 0.06, about 0.04 to about 0.10, about 0.04 to about 0.08, about 0.04 to about 0.06, about 0.06 to about 0.10, about 0.06 to about 0.08, or any range or sub-range therebetween. In some embodiments, the first refractive index of first reference block 113 can be greater than the sample refractive index of sample 103 (e.g., the first refractive index can be greater than substantially all points in the refractive index profile of the sample). In some embodiments, the first refractive index of first reference block 113 can be less than the sample refractive index of sample 103 (e.g., the first refractive index can be less than substantially all points in the refractive index profile of the sample). In some embodiments, the second refractive index of the second reference block 707 can be greater than the sample refractive index of the sample 103 (e.g., the second refractive index can be greater than substantially all points in the refractive index profile of the sample). In some embodiments, the second refractive index of the second reference block 707 can be less than the sample refractive index of the sample 103 (e.g., the second refractive index can be less than substantially all points in the refractive index profile of the sample).

[0112] In some embodiments, the magnitude of the minimum difference between the sample refractive index of the sample 103 and the third refractive index of the fluid 723 as a percentage of the sample refractive index can be about 0.7% or greater, about 1% or greater, about 2% or greater, about 3% or greater, about 5% or greater, about 10% or less, about 8% or less, or about 6% or less. In some embodiments, the magnitude of the minimum difference between the sample refractive index of the sample 103 and the third refractive index of the fluid 723 as a percentage of the sample refractive index can be about 0.7% to about 10%, about 0.7% to about 8%, about 0.7% to about 6%, about 0.7% to about 4%, about 1% to about 10%, about 1% to about 8%, about 1% to about 6%, about 2% to about 10%, about 2% to about 8%, about 2% to about 6%, about 3% to about 8%, about 3% to about 6%, about 5% to about 10%, about 5% to about 8%, about 5% to about 6%, or any range or sub-range therebetween. In some embodiments, the magnitude of the minimum difference between the sample refractive index of sample 103 and the third refractive index of fluid 723 can be about 0.006 or greater, about 0.01 or greater, about 0.02 or greater, about 0.04 or greater, about 0.06 or greater, about 0.10 or less, about 0.08 or less, or about 0.06 or less. In some embodiments, the magnitude of the minimum difference between the sample refractive index of sample 103 and the third refractive index of fluid 723 can be about 0.006 to about 0.10, about 0.006 to about 0.08, about 0.006 to about 0.06, about 0.02 to about 0.10, about 0.02 to about 0.08, about 0.02 to about 0.06, about 0.04 to about 0.10, about 0.04 to about 0.08, about 0.04 to about 0.06, about 0.06 to about 0.10, about 0.06 to about 0.08, or any range or sub-range therebetween.

[0113] Now refer to Figure 13-15 An embodiment of a method for determining the stress distribution of a sample according to an embodiment of the present disclosure is discussed with reference to the flowchart in FIG.

[0114] In a first step 1301 of a method for determining a stress distribution of a sample, the method may begin by providing a sample 103. In some embodiments, the sample 103 may be provided by purchasing or otherwise obtaining the sample, or by forming the sample using methods known in the art. In other embodiments, glass-based samples or layers of glass-based samples may be provided by forming them using various tape forming processes, such as slot drawing, down drawing, fusion down drawing, up drawing, press rollers, redrawing, or float drawing. In some embodiments, the sample 103 may include a glass-based sample. In some embodiments, the sample 103 may include a laminate comprising a core layer 601 positioned between a first outer layer 603 and a second outer layer 605, such as Figure 6In other embodiments, the core layer 601 may include a central tension member. In other embodiments, the sample 103 may include a first outer major surface 105 and a second outer major surface 309 opposite the first outer major surface 105 .

[0115] After step 1301, the method may proceed to step 1303, which includes positioning the sample 103 within the cavity 301 of the device (e.g., the combined device 101, the RNF device 121, the LSP device 131, 131'). Figure 3-4 As shown in FIG. 7 , the sample 103 may be secured by a sample holder 701. In some embodiments, as shown in FIG. Figure 7 As shown, the sample 103 can contact the sample coupling surface 307 of the first reference block 113 including a first refractive index. In other embodiments, the sample 103 can contact the second major surface 721 of the second reference block 707 including a second refractive index. In other embodiments, the second refractive index can be substantially equal to the first refractive index. In other embodiments, the sample 103 can be positioned within the cavity 301 by placing the sample 103 on the second major surface 721 of the second reference block 707 and then placing the sample coupling surface 307 of the first reference block 113 on the sample 103. In some embodiments, as Figure 7 As shown, the fluid 723 containing the third refractive index can contact the first reference block 113. In other embodiments, as shown, the fluid 723 can contact the second reference block 707. In other embodiments, as shown, the fluid 723 can contact the sample 103. In some embodiments, as shown Figure 7 As shown, cavity 301 can be at least partially defined by specimen coupling surface 307 of first reference block 113. In other embodiments, as shown, cavity 301 can be further defined by second major surface 721 of second reference block 707. In other embodiments, as shown, cavity 301 can be further defined by sample holder 701.

[0116] After step 1303, the method may proceed to step 1305, which includes measuring the retardation distribution of the sample and determining the central tension of the sample based on the measured retardation distribution of the sample. In some embodiments, step 1305 may include a series of steps, which will be referred to as Figure 14 In some embodiments, step 1305 may include steps 1403, 1405, 1407, 1409, and 1411. In some embodiments, step 1305 may follow arrow 1402 and omit step 1405, so that step 1305 includes steps 1403, 1407, 1409, and 1411.

[0117] In some embodiments, step 1305 may include step 1403, which includes measuring the retardation profile of the sample 103. In some embodiments, a first polarization-switched light beam may be emitted from a first polarization-switched light source 133, and the first polarization-switched light beam may be configured to travel along a first path 205, 205F, 205R. In some embodiments, as Figure 1-5 As shown, the first polarization-switched beam may impinge on (e.g., may be transmitted through) the first focusing lens 135 and / or other optical elements described above with respect to the first focusing lens and / or the first path 205, 205F. Figure 1-5 As shown, the first polarization-switched light beam may impinge on (eg, may be transmitted through) the prism 113. In other embodiments, as shown Figure 4 As shown, the first polarization-switched beam can be incident on the input surface 209 of the prism 113. In other embodiments, the first polarization-switched beam can be incident on the sample coupling surface 307 of the prism 113. In some embodiments, the first path can be incident on the input surface 209 of the prism 113 and the sample coupling surface 307 of the prism 113. In some embodiments, as Figure 5 As shown, the first polarization-switched beam can be incident on the sample holder 701. In some embodiments, the first polarization-switched beam can be incident on the index matching fluid 215. In some embodiments, the first path 205F and the first polarization-switched beam can be incident on the first outer major surface 105 of the sample. In other embodiments, as Figure 6 As shown, the sample 103 may include a laminate comprising a core layer 601 positioned between a first outer layer 603 and a second outer layer 605. In other embodiments, the core layer 601 may include a central tension. In other embodiments, as shown, the first path 205F and the first polarization-switched beam may impinge on the first outer layer 603. In other embodiments, the first path 205F and the first polarization-switched beam may impinge on the core layer 601. In other embodiments, the first path 205F and the first polarization-switched beam may impinge on the second outer layer 605. In some embodiments, the first path 205R, 205S and the scattered first polarization-switched beam that has been transmitted through the sample 103 may impinge on the prism 113 and the first output surface 213 and / or the second output surface 211 of the prism 113. In some embodiments, the first detector 137 may detect a signal from the first polarization-switched beam comprising the scattered first polarization-switched beam. In other embodiments, as Figure 3As shown, the first detector 137 may include a first image detector 137A and a second image detector 137B, each of which may detect a signal from the first polarization-switched light beam. In some embodiments, the detection signal may include one or more line graphs including an intensity distribution. In some embodiments, the detection signal may be converted into a signal SB that is sent to the controller 141. In other embodiments, the first image detector 137A may send the signal SB to the controller 141, and the second image detector 137B may send the second signal SB' to the controller. In some embodiments, the controller 141 may determine a delay profile based on the signal. As used herein, delay profile means the amount of optical delay of the signal, which is a function of the depth of the first polarization-switched light beam traveling into the sample 103 in the direction 602. As used herein, optical delay means the phase shift between two orthogonal light polarizations, which can be measured in radians (rad) or nanometers (nm). Without being limited by theory, the amount of optical delay can be determined based on the detection signal, which varies due to constructive and destructive interference of the detection signal through different effective path lengths of the sample. Without being bound by theory, stress in the sample can cause optical delay along the first path of the first polarization-switched beam, and the amount of stress encountered is proportional to the derivative of the optical delay. In some embodiments, one or more of the sample holder 701, the first stage 405, and the second stage 409 can be translated while the first polarization-switched beam is transmitted through the sample and / or while the transmitted first polarization-switched beam is detected. In some embodiments, multiple measurements corresponding to multiple detection signals can be combined (e.g., averaged) to produce a composite detection signal. In other embodiments, the sample holder 701 can be translated in the direction 305 while measuring the delay profile of the sample 103.

[0118] In some embodiments, the signal SB may be similar to Figure 8 In some embodiments, the optical delay profile may be similar to Figure 9 6, wherein the horizontal axis 901 is the distance in the direction 602 and the vertical axis 903 is the optical retardation in units of length (e.g., nm). In some embodiments, the optical retardation profile may include a reference region 905, a compression region 907, and a tension region 909.

[0119] After step 1403, step 1305 may include step 1405, which includes determining the width of the central region containing the central tension. In some embodiments, the width of the central region may be determined based on the location where the derivative of the measured delay profile is substantially zero. As used herein, the width of the central region is the minimum distance between two locations where the derivative of the delay profile is substantially zero, and the locations include a pair of relative extreme values ​​(e.g., a minimum and a maximum) of the measured delay profile. In some embodiments, the sample may include a laminate. In other embodiments, the width of the central region may be substantially equal to the core thickness 615 of the core layer 601 containing the central tension. In some embodiments, multiple measured delay profiles may be combined (e.g., averaged) and used to generate a delay profile and width of the central region with lower noise.

[0120] For example, Figure 10 An experimental optical delay profile 1017 is shown, where the horizontal axis 1001 is distance in the direction 602 and the vertical axis 1003 is optical delay in length units (e.g., nm). As shown, multiple measured delay profiles can be combined to reduce noise in the delay profile. Figure 10 , a central region has been demarcated by lines 1005. One line 1005 is located at the minimum of the delay profile, while the other line 1005 is located at the maximum of the delay profile. The width of the central region can be determined as the distance between the two lines 1005, which demarcates the central region containing the central tension.

[0121] After step 1405 or after step 1403 following arrow 1402, step 1305 may further include step 1407, which is to determine a fitting range that includes a fitting width. In some embodiments, the fitting width may be less than the width of the central portion. In other embodiments, the fitting width may exclude one or more end portions of the delay profile. In other embodiments, the excluded one or more end portions of the delay profile may include a portion of the central region. Without being bound by theory, portions of the delay profile near local minima in the delay profile may have greater noise than other portions of the delay profile. Without being bound by theory, portions of the delay profile corresponding to interfaces between layers in the laminated sample may have greater noise than other regions of the delay profile. In some embodiments, the one or more excluded end portions may include portions of the delay profile near one or more local minima in the delay profile and / or one or more portions corresponding to interfaces between layers in the laminated sample. Excluding the one or more end portions and excluding the noisy portion of the delay profile can produce more reliable central tension (CT) measurements.

[0122] Back to Figure 10, the fitted width may extend between a first position 1007 and a second position 1009 on the optical retardation profile. As shown, the fitted width excludes the first end portion, which includes a first portion 1011 located within the central region. The fitted width also excludes the second end portion, which includes a second portion 1013 located within the central region. Furthermore, first portion 1011 and second portion 1013 correspond to regions near the interface in the laminated sample, and both first portion 1011 and second portion 1013 have greater noise than fitted region 1015. As shown, the fitted width of the fitted region measured between first position 1007 and second position 1009 is smaller than the width of the central region demarcated by line 1005.

[0123] After step 1407, step 1305 may further include step 1409, which includes: fitting a polynomial to a portion of the delay distribution within the fitting range. In some embodiments, the portion may include the entire fitting range. In some embodiments, the polynomial may include a linear polynomial (e.g., a straight line). In some embodiments, the polynomial may include a quadratic polynomial (e.g., a parabola). In some embodiments, the polynomial may include a cubic polynomial. Without being limited by theory, if the laminated sample is substantially not chemically strengthened and / or thermally tempered, a linear polynomial may be used to fit the delay distribution of the laminated sample. Without being limited by theory, the delay distribution of the sample that has been chemically strengthened and / or thermally tempered may be fit with a cubic polynomial. Fitting the delay distribution with a low-order (e.g., linear, quadratic, cubic) polynomial reduces the noise in the measured central tension (CT). For example, referring to Figure 10 , the central region 1015 can be fitted with a linear polynomial.

[0124] After step 1409, step 1305 may further include step 1411, which includes: determining the central tension of the sample based on the fitted polynomial. In some embodiments, the central tension may include a central tension distribution. Without being limited by theory, the central tension (e.g., the central tension distribution) can be obtained by differentiating the fitted polynomial. In some embodiments, the fitted polynomial may include a linear polynomial, and the central tension distribution may include a substantially constant (e.g., constant) central tension distribution over the fitted width and / or the width of the central area. In some embodiments, the fitted polynomial may include a quadratic polynomial, and the central tension distribution may include a straight line. In some embodiments, the fitted polynomial may include a cubic polynomial, and the central tension distribution may include a parabola. In some embodiments, a single value of the central tension may be determined (e.g., reported), which may be an average (e.g., mean, median, mode) of the determined central tension distribution or an extreme value (e.g., maximum, minimum) of the determined central tension distribution. For example, referring to Figure 10, the central tension distribution of the fitted region will include a constant, which can be reported as a single value of the central tension.

[0125] After step 1305, return to Figure 13 The method may proceed to step 1307, which is to measure the refractive index distribution of the sample and determine the initial stress distribution of the sample based on the measured refractive index distribution. In some embodiments, step 1307 may include setting the reference Figure 15 In some embodiments, step 1307 may include steps 1503, 1505, 1507, 1509, and 1513. In other embodiments, arrow 1502 may be followed to step 1511, and then arrow 1504 may be followed back to steps 1503, 1505, 1507, and 1509, before following arrow 1502 again or proceeding to step 1513. For simplicity, step 1511 and the discussion following 1502 and 1504 are omitted from this discussion, but this will be discussed later with respect to subsequent steps. Figure 15 In some embodiments, arrow 1506 may be followed, thereby omitting step 1509 and proceeding directly from step 1507 to step 1513.

[0126] In some embodiments, as a result of step 1303 and as Figure 7 As shown, the sample 103 may be located between a first reference block 113 comprising a first refractive index and a second reference block 707 comprising a second refractive index, wherein the first refractive index may be substantially equal to the second refractive index (e.g., the second reference block 707 actually comprises the first refractive index). In further embodiments, as a result of step 1303 and as shown in FIG. Figure 7 As shown, the fluid 723 comprising the third refractive index may contact one or more of the first reference block 113 , the second reference block 707 , and / or the sample 103 .

[0127] In some embodiments, step 1307 may include step 1503, which includes emitting a second polarization-switched light beam from the second polarization-switching light source 123. In other embodiments, as shown, the second polarization-switched light beam may travel along a second path 207, 207R.

[0128] After step 1503, Figure 7 As shown, step 1307 may further include step 1505, which includes: transmitting the second polarization-switched light beam through the sample holder 701. In another embodiment, as shown in FIG. Figure 7As shown, the second polarization-switched beam can be focused by converging lens 125 to form focal point 709. In further embodiments, as shown, focal point 709 can include first major surface 313 of sample holder 701. In further embodiments, as shown, focal point 709 can include the location of sample 103 within chamber 301. In further embodiments, the method can include translating sample holder 701 in direction 711. In further embodiments, sample holder 701 can be translated in direction 711 to move the focal point from first reference block 113 to sample 103 and to second reference block 707. In further embodiments, sample holder 701 can be translated in direction 711 to move the focal point from second reference block 707 to sample 103 and to first reference block 113. In further embodiments, sample holder 701 can be translated in direction 305. In other embodiments, as shown, the second polarization-switched light beam can be transmitted through the sample holder 701 and then through the first reference block 113, the cavity 301 configured to receive the sample 103, and / or the second reference block 707. In other embodiments, the second polarization-switched light beam can be transmitted through the fluid 723.

[0129] After step 1505, step 1307 may further include step 1507, which includes: detecting the transmitted second polarization-switched light beam to determine a detection signal. In some embodiments, the transmitted second polarization-switched light beam may travel as a refracted second polarization-switched light beam along portion 207R of the second path 207 to the second detector 127. In some embodiments, the detection signal may be converted into a signal SA that is sent to the controller 141. In some embodiments, the detection signal may be measured in two polarizations that are orthogonal to each other. In other embodiments, the detection signal may be processed by the controller 141 to determine the initial refractive index distribution of the sample 103. In some embodiments, as described above, the sample holder 701 may be translated in the direction 711 while the second polarization-switched light beam is transmitted through the sample 103 and / or while the transmitted second polarization-switched light beam is detected. In some embodiments, multiple measurements corresponding to multiple detection signals may be combined (e.g., averaged) to produce a composite detection signal.

[0130] After step 1507, step 1307 may further include step 1509, which includes determining a refractive index (e.g., a refractive index distribution) based on the detection signal data corresponding to the first reference block 113 and the second reference block 707 for determining the refractive index distribution. In some embodiments, a first error between the initial measured refractive index of the first reference block 113 and a predetermined first refractive index of the first reference block 113 may be calculated. In other embodiments, the refractive index distribution may be determined by subtracting the first error from the detection signal (e.g., the measured refractive index distribution). In other embodiments, a second error between the initial measured refractive index of the second reference block 707 and a predetermined second refractive index of the second reference block 707 may be calculated. In further embodiments, an error distribution may be calculated using the first error and the second error. In other embodiments, the error distribution may include interpolation between the first error and the second error across the sample. In other embodiments, the refractive index distribution may be determined by subtracting the error distribution from the detection signal (e.g., the measured refractive index distribution).

[0131] After step 1509, in some embodiments, step 1307 may further include step 1513, which includes determining a stress profile (e.g., an initial stress profile) based on the measured refractive index profile. As described above, the measured refractive index profile may include two measured refractive index profiles, each based on a detection signal measured for mutually orthogonal polarization states (e.g., TE and TM). In some embodiments, the stress profile may be calculated by taking the difference between the two measured refractive index profiles. In other embodiments, the stress profile may include the difference between the two measured refractive index profiles divided by a stress-optical coefficient, which may be measured using any means known to those skilled in the art.

[0132] After step 1307, return to Figure 13 According to the flowchart of FIG. 1 , the method may proceed to step 1309, which includes scaling the initial stress distribution based on the initial stress distribution and the central tension to obtain a scaled stress distribution of the sample. In some embodiments, the entire stress distribution may be scaled based on a ratio of the central tension measured in step 1305 to an estimated central tension based on the initial stress distribution. In some embodiments, only a central region of the initial stress distribution, including the central tension, may be scaled based on a ratio of the central tension measured in step 1305 to an estimated central tension based on the initial stress distribution.

[0133] After step 1309, the method may proceed to step 1311, which includes adjusting the scaled stress distribution to obtain a force-balanced estimated stress distribution. As used herein, a stress distribution is stress-balanced if the integral of the stress distribution (e.g., estimated stress distribution, scaled stress distribution) from the first outer major surface 105 of the sample 103 to the mid-plane 623 of the sample 103 is substantially zero, and the integral of the stress distribution (e.g., estimated stress distribution, scaled stress distribution) from the second outer major surface 309 of the sample 103 to the mid-plane 623 of the sample 103 is substantially zero. As used herein and as Figure 6 As shown, the mid-plane is located midway between the first outer major surface 105 of the sample 103 and the second outer major surface 309 of the sample 103. In some embodiments, if the stress distribution (e.g., the estimated stress distribution, the scaled stress distribution) does not result in force balance by adjusting one or more of the following: adjusting the surface stress (e.g., the stress at the first outer major surface 105 of the sample 103, the stress at the second outer major surface 309 of the sample 103), adjusting the stress on the outside of the central region containing the central tension, and / or adjusting the stress at the interface between the central tension and the compressive stress, the stress distribution can be corrected.

[0134] After step 1311 , the method may be completed in step 1313 , where a stress distribution (eg, an estimated stress distribution, an adjusted stress distribution, a force-balanced stress distribution) has been determined.

[0135] In some embodiments, a method for determining a stress distribution of a sample according to embodiments of the present disclosure may proceed sequentially through steps 1301, 1303, 1305, 1307, 1309, 1311, and 1313, as described above. In some embodiments, the method may follow arrow 1302, thereby omitting step 1305 and instead proceeding directly from step 1303 to step 1307. In other embodiments, the method may follow arrow 1304, thereby omitting step 1309 and instead proceeding directly from step 1307 to step 1311, where the initial stress distribution may be adjusted to obtain an estimated stress distribution after force balance. In other embodiments, the method may follow arrow 1308, thereby omitting steps 1309 and 1311 and instead proceeding directly from step 1307 to step 1313, where the initial stress distribution may include the stress distribution determined by the method. In some embodiments, the method may follow arrow 1304, thereby omitting step 1309 and instead proceeding directly from step 1307 to step 1311, where the initial stress profile may be adjusted to obtain a force-balanced estimated stress profile. In some embodiments, the method may follow arrow 1308, thereby omitting steps 1309 and 1311 and instead proceeding directly from step 1307 to step 1313, where the initial stress profile may include the stress profile determined by the method. In some embodiments, the method may follow arrow 1306, thereby omitting step 1311 and instead proceeding directly from step 1309 to step 1313, where the scaled stress profile may include the stress profile determined by the method. In other embodiments, the scaled stress profile may be force-balanced without adjusting the scaled stress profile.

[0136] Now refer to Figure 14 An embodiment of a method for determining the central tension of a sample according to an embodiment of the present disclosure is discussed with reference to the flowchart in FIG.

[0137] In a first step 1401 of a method for determining the central tension of a sample, the method may include providing a sample 103 and positioning the sample 103 within a cavity 301 of a device (e.g., a combination device 101, an LSP device 131, 131'). In some embodiments, as described above, the sample 103 may be provided by purchasing or otherwise obtaining the sample, or by forming the sample using methods known in the art. In some embodiments, as described above, Figure 3-4 As shown, the sample 103 can be secured by a sample holder 701. In further embodiments, the cavity 301 can be further defined by a sample holder 701 as shown.

[0138] After step 1401, the method may include step 1403, which includes measuring the retardation profile of the sample 103. In some embodiments, a first polarization-switched light beam may be emitted from a first polarization-switched light source 133, and the first polarization-switched light beam may be configured to travel along a first path 205, 205F, 205R. In some embodiments, as Figure 1-5 As shown, the first polarization-switched beam may impinge on (e.g., may be transmitted through) the first focusing lens 135 and / or other optical elements described above with respect to the first focusing lens and / or the first path 205, 205F. Figure 1-5 As shown, the first polarization-switched light beam may impinge on (eg, may be transmitted through) the prism 113. In other embodiments, as shown Figure 4 As shown, the first polarization-switched beam can be incident on the input surface 209 of the prism 113. In other embodiments, the first polarization-switched beam can be incident on the sample coupling surface 307 of the prism 113. In some embodiments, as Figure 5 As shown, the first polarization-switched beam can be incident on the sample holder 701. In some embodiments, the first polarization-switched beam can be incident on the index matching fluid 215. In some embodiments, the first path 205F and the first polarization-switched beam can be incident on the first outer major surface 105 of the sample. In other embodiments, as Figure 6 As shown, the sample 103 may include a laminate comprising a core layer 601 positioned between a first outer layer 603 and a second outer layer 605. In other embodiments, the core layer 601 may include a central tension. In other embodiments, as shown, the first path 205F and the first polarization-switched beam may impinge on the first outer layer 603. In other embodiments, the first path 205F and the first polarization-switched beam may impinge on the core layer 601. In other embodiments, the first path 205F and the first polarization-switched beam may impinge on the second outer layer 605. In some embodiments, the first path 205R, 205S and the scattered first polarization-switched beam that has been transmitted through the sample 103 may impinge on the prism 113 and the first output surface 213 and / or the second output surface 211 of the prism 113. In some embodiments, the first detector 137 may detect a signal from the first polarization-switched beam comprising the scattered first polarization-switched beam. In other embodiments, as Figure 3As shown, the first detector 137 may include a first image detector 137A and a second image detector 137B, each of which may detect a signal from the first polarization-switched light beam. In some embodiments, the detection signal may include one or more line graphs including an intensity distribution along a certain direction. In some embodiments, the detection signal may be converted into a signal SB sent to the controller 141. In other embodiments, the detection signal from the first image detector 137A may be converted into a signal SB, and at the same time, the detection signal from the second image detector 137B may be converted into a signal SB', and both signals SB and SB' may be sent to the controller 141. In some embodiments, the controller 141 may determine the delay profile based on the signal. As used herein, the delay profile means the optical delay amount of the signal, which is a function of the depth of the first polarization-switched light beam traveling into the sample 103 in the direction 602. As used herein, optical delay means the phase shift between two orthogonal light polarizations, which can be measured in radians (rad) or nanometers (nm). Without being limited by theory, the amount of optical delay can be determined based on the detection signal, which varies due to constructive and destructive interference of the detection signal through different effective path lengths of the sample. Without being limited by theory, stress in the sample can cause optical delay along the first path of the first polarization-switched beam, and the amount of stress encountered is proportional to the derivative of the optical delay. In some embodiments, one or more of the sample holder 701, the first stage 405 and the second stage 409 can be translated while the first polarization-switched beam is transmitted through the sample and / or while the transmitted first polarization-switched beam is detected. In some embodiments, multiple measurements corresponding to multiple detection signals can be combined (e.g., averaged) to produce a composite detection signal. In other embodiments, the sample holder 701 can be translated in the direction 305 while measuring the delay profile of the sample 103.

[0139] In some embodiments, the signal SB may be similar to Figure 8 Intensity distribution shown in FIG, wherein the horizontal axis 801 is the distance in a certain direction and the vertical axis 803 is the intensity of the detection signal. In some embodiments, the optical delay distribution can be similar to Figure 9 6, wherein the horizontal axis 901 is the distance in the direction 602 and the vertical axis 903 is the optical retardation in units of length (e.g., nm). In some embodiments, the optical retardation profile may include a reference region 905, a compression region 907, and a tension region 909.

[0140] After step 1403, the method may further include step 1405, which includes determining the width of the central region containing the central tension. In some embodiments, the width of the central region may be determined based on the location where the derivative of the measured delay profile is substantially zero. As used herein, the width of the central region is the minimum distance between two locations where the derivative of the delay profile is substantially zero, and the locations include a pair of relative extreme values ​​(e.g., a minimum and a maximum) of the measured delay profile. In some embodiments, the sample may include a laminate. In other embodiments, the width of the central region may be substantially equal to the core thickness 615 of the core layer 601 containing the central tension. In some embodiments, multiple measured delay profiles may be combined (e.g., averaged) and used to generate a delay profile and width of the central region with lower noise.

[0141] For example, Figure 10 An experimental optical delay profile 1017 is shown, where the horizontal axis 1001 is distance in the direction 602 and the vertical axis 1003 is optical delay in length units (e.g., nm). As shown, multiple measured delay profiles can be combined to reduce noise in the delay profile. Figure 10 , a central region has been demarcated by lines 1005. One line 1005 is located at the minimum of the delay profile, while the other line 1005 is located at the maximum of the delay profile. The width of the central region can be determined as the distance between the two lines 1005, which demarcates the central region containing the central tension.

[0142] After step 1405 or after step 1403 following arrow 1402, the method may further include step 1407, which is to determine a fitting range that includes a fitting width. In some embodiments, the fitting width may be less than the width of the central portion. In other embodiments, the fitting width may not include one or more end portions of the delay profile. In other embodiments, the excluded one or more end portions of the delay profile may include a portion of the central region. Without being limited by theory, portions of the delay profile near local minima in the delay profile may have greater noise than other portions of the delay profile. Without being limited by theory, portions of the delay profile corresponding to interfaces between layers in the laminated sample may have greater noise than other regions of the delay profile. In some embodiments, the one or more excluded end portions may include portions of the delay profile near one or more local minima in the delay profile and / or one or more portions corresponding to interfaces between layers in the laminated sample. Excluding the one or more end portions and excluding the noisy portion of the delay profile can produce more reliable central tension (CT) measurements.

[0143] Back to Figure 10, the fitted width may extend between a first position 1007 and a second position 1009 on the optical retardation profile. As shown, the fitted width excludes the first end portion, which includes a first portion 1011 located within the central region. The fitted width also excludes the second end portion, which includes a second portion 1013 located within the central region. Furthermore, first portion 1011 and second portion 1013 correspond to regions near the interface in the laminated sample, and both first portion 1011 and second portion 1013 have greater noise than fitted region 1015. As shown, the fitted width of the fitted region measured between first position 1007 and second position 1009 is smaller than the width of the central region demarcated by line 1005.

[0144] After step 1407, the method may further include step 1409, which includes fitting a polynomial to a portion of the delay distribution within a fitting range. In some embodiments, the portion may include the entire fitting range. In some embodiments, the polynomial may include a linear polynomial (e.g., a straight line). In some embodiments, the polynomial may include a quadratic polynomial (e.g., a parabola). In some embodiments, the polynomial may include a cubic polynomial. Without being limited by theory, if the laminated sample is substantially not chemically strengthened and / or thermally tempered, a linear polynomial may be used to fit the delay distribution of the laminated sample. Without being limited by theory, the delay distribution of the sample that has been chemically strengthened and / or thermally tempered may be fit with a cubic polynomial. Fitting the delay distribution with a low-order (e.g., linear, quadratic, cubic) polynomial reduces the noise in the measured central tension (CT). For example, referring to Figure 10 , the central region 1015 can be fitted with a linear polynomial.

[0145] After step 1409, the method may further include step 1411, which includes: determining the central tension of the sample based on the fitted polynomial. In some embodiments, the central tension may include a central tension distribution. Without being limited by theory, the central tension (e.g., the central tension distribution) can be obtained by differentiating the fitted polynomial. In some embodiments, the fitted polynomial may include a linear polynomial, and the central tension distribution may include a substantially constant (e.g., constant) central tension distribution over the fitted width and / or the width of the central area. In some embodiments, the fitted polynomial may include a quadratic polynomial, and the central tension distribution may include a straight line. In some embodiments, the fitted polynomial may include a cubic polynomial, and the central tension distribution may include a parabola. In some embodiments, a single value of the central tension may be determined (e.g., reported), which may be an average (e.g., mean, median, mode) of the determined central tension distribution or an extreme value (e.g., maximum, minimum) of the determined central tension distribution. For example, referring to Figure 10, the central tension distribution of the fitted region will include a constant, which can be reported as a single value of the central tension.

[0146] Now refer to Figure 15 Flowchart of the present disclosure is used to discuss embodiments of a method for determining the refractive index (e.g., refractive index profile, corrected refractive index, corrected refractive index profile) and / or stress distribution of a sample according to embodiments of the present disclosure.

[0147] In a first step 1501 of a method for determining a refractive index and / or stress distribution of a sample, the method may include providing a sample 103 and positioning the sample 103 within a cavity 301 of a device (e.g., a combined device 101, an RNF device 121). In some embodiments, as described above, the sample 103 may be provided by purchasing or otherwise obtaining the sample, or by forming the sample using methods known in the art. In some embodiments, as described above, Figure 7 As shown, the sample 103 can be positioned between a first reference block 113 comprising a first refractive index and a second reference block 707 comprising a second refractive index, wherein the first refractive index can be substantially equal to the second refractive index (e.g., the second reference block 707 actually comprises the first refractive index). In further embodiments, as shown, a fluid 723 comprising a third refractive index can contact one or more of the prism 113, the first reference block 113, the second reference block 707, and / or the sample 103.

[0148] In some embodiments, the sample 103 may include an estimated refractive index. In other embodiments, the first reference block 113 may include a first refractive index (e.g., a first predetermined refractive index), and the fluid 723 may include a third refractive index (e.g., a third predetermined refractive index), each of which satisfies one or more of the following conditions: the magnitude of the minimum difference compared to the estimated refractive index of the sample is (i) a percentage of the estimated refractive index of the sample and / or (ii) the absolute value of the minimum difference. In some embodiments, the magnitude of the minimum difference between the estimated refractive index of the sample 103 and the third refractive index of the fluid 723 as a percentage of the refractive index of the sample can be about 0.7% or greater, about 1% or greater, about 2% or greater, about 3% or greater, about 5% or greater, about 10% or less, about 8% or less, or about 6% or less. In some embodiments, the magnitude of the minimum difference between the estimated refractive index of the sample 103 and the third refractive index of the fluid 723 as a percentage of the sample's refractive index can be about 0.7% to about 10%, about 0.7% to about 8%, about 0.7% to about 6%, about 0.7% to about 4%, about 1% to about 10%, about 1% to about 8%, about 1% to about 6%, about 2% to about 10%, about 2% to about 8%, about 2% to about 6%, about 3% to about 8%, about 3% to about 6%, about 5% to about 10%, about 5% to about 8%, about 5% to about 6%, or any range or sub-range therebetween. In some embodiments, the magnitude of the minimum difference between the estimated refractive index of the sample 103 and the third refractive index of the fluid 723 can be about 0.006 or greater, about 0.01 or greater, 0.02 or greater, about 0.04 or greater, about 0.06 or greater, about 0.10 or less, about 0.08 or less, or about 0.06 or less. In some embodiments, the magnitude of the minimum difference between the estimated refractive index of the sample 103 and the third refractive index of the fluid 723 can be about 0.006 to about 0.10, about 0.006 to about 0.08, about 0.006 to about 0.06, about 0.02 to about 0.10, about 0.02 to about 0.08, about 0.02 to about 0.06, about 0.04 to about 0.10, about 0.04 to about 0.08, about 0.04 to about 0.06, about 0.06 to about 0.10, about 0.06 to about 0.08, or any range or sub-range therebetween. Providing a first reference block comprising a first refractive index and a fluid comprising a third refractive index, wherein the first and third refractive indices each fall within one of the ranges specified above, can enhance the reliability, precision, and / or accuracy of the measured refractive index and / or stress profile.

[0149] In some embodiments, the method may include step 1503, which includes emitting a second polarization-switched light beam from the second polarization-switching light source 123. In other embodiments, as shown, the second polarization-switched light beam may travel along a second path 207, 207R.

[0150] After step 1503, Figure 7 As shown, the method may further include step 1505, which includes: transmitting the second polarization-switched light beam through the sample holder 701. In another embodiment, as Figure 7 As shown, the second polarization-switched beam can be focused by the converging lens 125 to form a focal point 709. In other embodiments, as shown, the focal point 709 can include the first major surface 313 of the sample holder 701. In other embodiments, as shown, the focal point 709 can include the location of the sample 103 in the cavity 301. In other embodiments, the method can include translating the sample holder 701 in a direction 711. In other embodiments, the sample holder 701 can be translated in the direction 711 to move the focal point from the first reference block 113 to the sample 103 and to the second reference block 707. In other embodiments, the sample holder 701 can be translated in the direction 711 to move the focal point from the second reference block 707 to the sample 103 and to the first reference block 113. In other embodiments, as shown, the second polarization-switched light beam can be transmitted through the sample holder 701 and then through the first reference block 113, the cavity 301 configured to receive the sample 103, and / or the second reference block 707. In other embodiments, the second polarization-switched light beam can be transmitted through the fluid 723.

[0151] After step 1505, the method may further include step 1507, which includes detecting the transmitted second polarization-switched light beam to determine a detection signal. In some embodiments, the transmitted second polarization-switched light beam may travel as a refracted second polarization-switched light beam along portion 207R of the second path 207 to the second detector 127. In some embodiments, the detection signal may be converted into a signal SA that is sent to the controller 141. In some embodiments, the detection signal may be measured in two polarizations (e.g., TE, TM) that are orthogonal to each other. In other embodiments, the detection signal may be processed by the controller 141 to determine the initial refractive index distribution of the sample 103. In some embodiments, the sample holder 701 may be translated in the direction 711 while the second polarization-switched light beam is transmitted through the sample and / or while the transmitted second polarization-switched light beam is detected. In some embodiments, multiple measurements corresponding to multiple detection signals may be combined (e.g., averaged) to produce a composite detection signal.

[0152] After step 1507, the method may further include step 1509, which includes determining a refractive index (e.g., a refractive index distribution) based on the detection signal data corresponding to the first reference block 113 and the second reference block 707 for determining the refractive index distribution. In some embodiments, a first error between the initial measured refractive index of the first reference block 113 and a predetermined first refractive index of the first reference block 113 may be calculated. In other embodiments, the refractive index distribution may be determined by subtracting the first error from the detection signal (e.g., the measured refractive index distribution). In other embodiments, a second error between the initial measured refractive index of the second reference block 707 and a predetermined second refractive index of the second reference block 707 may be calculated. In further embodiments, an error distribution may be calculated using the first error and the second error. In other embodiments, the error distribution may include interpolation between the first error and the second error across the sample. In other embodiments, the refractive index distribution may be determined by subtracting the error distribution from the detection signal (e.g., the measured refractive index distribution).

[0153] In other embodiments, the first refractive index of the first reference block 113 and / or the third refractive index of the fluid 723 can be compared to the refractive index (e.g., refractive index profile) measured for the sample 103 in step 1509. If the first refractive index of the first reference block 113 and / or the third refractive index of the fluid 723 relative to the measured refractive index (e.g., the measured refractive index profile) does not fall within one or more ranges described above for the magnitude of the minimum difference compared to the measured refractive index of the sample, then arrow 1502 can be followed to step 1511, where the magnitude of the minimum difference is (i) as a percentage of the estimated refractive index of the sample and / or (ii) as the absolute value of the minimum difference. In some embodiments, step 1511 can include replacing the first reference block with a new first reference block that includes a corrected first refractive index, wherein the magnitude of the minimum difference between the corrected first refractive index and the refractive index of the sample (e.g., the measured refractive index) falls within one or more ranges described above. In some embodiments, step 1511 may include replacing the fluid with a new fluid containing a corrected third refractive index, wherein the minimum difference between the corrected third refractive index and the refractive index of the sample (e.g., the measured refractive index) falls within one or more of the above ranges. In other embodiments, both the first reference block and the fluid may be replaced. In some embodiments, arrow 1504 may then be followed back to steps 1503, 1505, 1507, and 1509, and then arrow 1502 may be followed again until the first and third refractive indices used to measure the refractive index of the sample meet one or more of the above ranges before proceeding to step 1513. In some embodiments, arrow 1504 may then be followed back to steps 1503, 1505, 1507, and 1509 before proceeding to step 1513.

[0154] After step 1509, in some embodiments, the method may further include step 1513, which includes determining a stress profile (e.g., an initial stress profile) based on the measured refractive index profile. As described above, the measured refractive index profile may include two measured refractive index profiles, each based on a detection signal measured for mutually orthogonal polarization states (e.g., TE, TM). In some embodiments, the stress profile may be calculated by taking the difference between the two measured refractive index profiles. In other embodiments, the stress profile may include the difference between the two measured refractive index profiles divided by a stress profile coefficient, which may be measured using any means known to those skilled in the art.

[0155] After step 1513 , in some embodiments, the method may proceed to step 1515 , which includes adjusting the stress distribution to obtain an estimated stress distribution (if it is force balanced), as described above with respect to step 1311 .

[0156] Example

[0157] Various embodiments are further illustrated by the following examples. Figure 11-12 Table 1 will be used to demonstrate the effect of the choice of the first refractive index of the first reference block and the third refractive index of the fluid on the accuracy, precision, reliability and consistency of the measured refractive index and stress distribution using the method herein. Figure 6 A similar laminate wherein the core layer comprises a refractive index of 1.496 (core RI) and the first and second outer layers comprise a refractive index of 1.475 (outer RI).

[0158] Table 1 presents the measured refractive index (RI) of the core layer and the average measured RI of the outer layer of the sample. The reference block included a first refractive index of 1.4622 or 1.4847 (reference block RI). Based on the known refractive indices of the core and outer layer of the sample, the minimum difference between the reference block RI and the sample RI was 0.013 (0.9%) and 0.009 (0.7%), respectively. The fluid included a third refractive index (fluid RI) of 1.498, 1.517, or 1.5945. Based on the known refractive indices of the core and outer layer of the sample, the minimum difference between the fluid RI and the sample RI was 0.002 (0.1%) and 0.021 (1.4%) and 0.099 (6.6%), respectively.

[0159] Table 1: Refractive Index (RI) of Reference Blocks and Fluids of Examples AF

[0160]

[0161] Examples A and B included a reference block RI of 1.4622 and a fluid RI of 1.5945, which corresponded to minimum differences of 0.013 (0.9%) and 0.099 (6.6%). Examples A and B both underestimated the core RI by more than 2% and underestimated the outer layer RI. While Examples A and B demonstrated good precision (the two measurements differed by 0.4%), Examples A and B exhibited the worst accuracy of the examples presented.

[0162] Examples C and D include a reference block RI of 1.4847 and a fluid RI of 1.498, corresponding to minimum differences of 0.097 (0.7%) and 0.002 (0.1%). Example C underestimates the core RI by 0.80% and overestimates the outer layer RI by 1.91%, while Example D overestimates the core RI by 1.39% and underestimates the outer layer RI by 1.10%. In other words, Examples C and D exhibit opposite errors, suggesting poor precision in the measurements, as reinforced by the difference of over 2% between Examples C and D.

[0163] Examples E and F included a reference block RI of 1.4622 and a fluid RI of 1.517, corresponding to minimum differences of 0.013 (0.9%) and 0.021 (1.4%), respectively. Examples D and E overestimated the core RI and outer layer RI by only 0.1% to 0.2%, demonstrating excellent accuracy. The measurements of Examples D and E were the closest, demonstrating excellent precision and reliability. Thus, Examples E and F demonstrated the best accuracy, precision, and reliability.

[0164] Based on Examples AF, the magnitude of the minimum difference for embodiments with superior precision and reliability is about 0.099 (6.6%) or less, about 0.021 (1.4%) or less, about 0.009 (0.7%) or greater, about 0.013 (0.9%) or greater, or about 0.021 (1.4%) or greater. Thus, for a minimum difference within a range of about 0.009 to about 0.099, about 0.009 to about 0.021, about 0.013 to about 0.099, about 0.013 to about 0.021, about 0.021 to about 0.099, or any range or sub-range therebetween, improved accuracy, precision, and / or reliability can be expected. Improved accuracy, precision, and / or reliability can be expected for a minimum difference within the range of about 0.7% to about 6.6%, about 0.7% to about 1.4%, about 0.9% to about 6.6%, about 0.9% to about 1.4%, about 1.4% to about 6.6%, or any range or sub-range therebetween. Furthermore, further improvements in accuracy, precision, and / or reliability can be expected when both the reference block and the fluid comprise a minimum difference within one or more of the above-specified ranges.

[0165] Figure 11-12 Horizontal axis 1101 comprises the depth from first outer major surface 105 of the sample measured in direction 602. Vertical axis 1103 comprises stress. Figure 11-12 Include the same drawing range. In other words, Figure 11-12 Displayed at the same scale.

[0166] Figure 11 These correspond to three stress profiles experimentally measured using an RNF apparatus comprising a single reference block with a reference block RI of 1.4622 and a fluid with a fluid RI of 1.517. The average compressive stresses of the samples used for the measurements were 140 MPa, 250 MPa, and 400 MPa. The average central tensions of the samples used for the measurements were 48 MPa, 55 MPa, and 132 MPa. Figure 11 The measurements shown demonstrate wide variability, reflecting poor precision and reliability.

[0167] Figure 12 Corresponding to three stress profiles experimentally measured using a combined apparatus according to an embodiment of the present disclosure, the combined apparatus comprises a first reference block and a second reference block, each comprising a reference block RI of 1.4622, and a fluid comprising a fluid RI of 1.517. Superimposing all three measured stress profiles of the sample on one another, so that only one stress profile is visible, demonstrates a surprising level of accuracy and reliability. Figure 11 The variability of the measurements shown is in contrast to Figure 12 This represents a huge improvement in the measurement of stress distribution.

[0168] The above can be combined to provide an apparatus and method for determining the refractive index, central tension, or stress distribution of a sample. A combined apparatus for measuring using LSP and RNF can simplify and accelerate the measurement process. Furthermore, the combined apparatus reduces the risk of sample breakage because less handling is required to load the sample into the combined apparatus compared to two separate apparatuses. Methods using the combined apparatus can also produce more reliable measurements of the overall stress distribution.

[0169] The combined device or LSP device can be used in a method for measuring central tension (CT). The disclosed method can produce more reliable CT measurements that exclude noisy portions (e.g., ends) measured near the edges of the CT region (e.g., interfaces between layers in a laminate). By moving the sample during the measurement, the disclosed method can also produce more reliable CT measurements that can be processed to produce an average intensity distribution with lower noise.

[0170] The combination device or RNF device may include more than one reference block. Clamping the reference block in a cavity configured to receive the sample can provide a means of correcting for drift and other systematic errors present in the measurement. Providing at least one reference block having a first refractive index and a fluid comprising a third refractive index, and which spans the estimated refractive index of the sample (e.g., the range of the estimated refractive index distribution) can provide more accurate and reproducible measurements of the refractive index and / or stress distribution. In addition, having the minimum difference between the at least one reference block comprising the first refractive index and the estimated refractive index of the sample (e.g., the extreme value of the estimated refractive index distribution) be within the range of about 0.7% to about 10% of the refractive index of the sample and / or within the range of about 0.006 to about 0.10 can further improve the reliability and / or reproducibility of the refractive index and / or stress distribution measurements. In addition, ensuring that the minimum difference between the fluid comprising the third refractive index and the estimated refractive index of the sample (e.g., the extreme value of the estimated refractive index distribution) is within a range of about 0.7% to about 10% of the refractive index of the sample and / or within a range of about 0.006 to about 0.10 can further improve the reliability and / or reproducibility of the refractive index and / or stress distribution measurement. In some embodiments, after measuring the corrected refractive index (e.g., the refractive index distribution) of the sample, the at least one reference block and / or fluid can be replaced so that the at least one reference block and / or fluid meets the above conditions.

[0171] Directional terms used herein—such as up, down, right, left, front, back, top, and bottom—are used only with reference to the drawings in which they are drawn and are not intended to imply absolute orientations.

[0172] It should be understood that the various disclosed embodiments may relate to features, elements, or steps described in conjunction with the embodiments. It should also be understood that, although described in terms of one embodiment, features, elements, or steps may be interchanged or combined with alternative embodiments in various combinations or arrangements not illustrated.

[0173] It should also be understood that the terms "the," "a," or "an" as used herein mean "at least one" and should not be limited to "only one" unless expressly specified to the contrary. For example, reference to "a component" includes embodiments having two or more such components, unless the context clearly indicates otherwise. Similarly, "plurality" is intended to mean "more than one."

[0174] As used herein, the term "about" refers to amounts, dimensions, formulas, parameters, and other quantities and features that are not exact and need not be exact, but may be approximate and / or larger or smaller as required, such as reflection tolerances, conversion factors, rounding, measurement errors, etc., as well as other factors known to those skilled in the art. Herein, ranges can be expressed as starting from "about" one specific value and / or ending at "about" another specific value. When expressing such a range, embodiments include starting from a specific value and / or ending at another specific value. Similarly, when a numerical value is expressed as an approximation using the antecedent "about," it should be understood that the specific numerical value constitutes another embodiment. Regardless of whether the numerical values ​​or endpoints of a range in the specification are listed using "about," the numerical values ​​or endpoints of the range are intended to include two embodiments: one modified with "about" and the other not modified with "about." It should also be understood that the endpoints of each range are important both in relation to and independently of the other endpoint.

[0175] As used herein, the terms "substantially," "substantially," and variations thereof are intended to indicate that the feature being described is equal to or approximately equal to a value or description. For example, a "substantially flat" surface is intended to indicate a flat or approximately flat surface. Furthermore, as defined above, "substantially similar" is intended to indicate that two values ​​are equal or approximately equal. In some embodiments, "substantially similar" can mean values ​​that are within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0176] Unless otherwise expressly stated, it is not intended that any method described herein be construed as requiring that its steps be performed in a specific order. Therefore, a method claim that does not actually recite that its steps follow a certain order, or that does not specifically indicate in any other way in the claims or specification that the steps are limited to a specific order, is not intended to imply any particular order.

[0177] Although the use of the transitional term "comprising" may disclose various features, elements, or steps of a particular embodiment, it should be understood that this implies alternative embodiments including those that may be described using the transitional term "consisting of" or "consisting essentially of." Thus, for example, implied alternative embodiments of a device comprising A+B+C include embodiments in which the device consists of A+B+C and embodiments in which the device consists essentially of A+B+C. Unless otherwise noted, the terms "comprises" and "comprising," and variations thereof, as used herein, should be interpreted as synonymous and open ended.

[0178] The above embodiments and features of these embodiments are exemplary and may be provided alone or in any combination with any one or more features of other embodiments provided herein without departing from the scope of the present disclosure.

[0179] It will be apparent to those skilled in the art that various modifications and variations may be made to the present disclosure without departing from the scope and spirit of the present disclosure. Therefore, the present disclosure is intended to cover modifications and variations of the embodiments herein as long as these modifications and variations are within the scope of the appended claims and their equivalents.

Claims

1. An apparatus for measuring stress distribution of a sample, comprising: a cavity defined at least in part by a first major surface comprising a first reference block of a first refractive index, the cavity being configured to receive a sample; a first polarization-switching light source configured to emit a first polarization-switched light beam toward the cavity; a second polarization-switching light source configured to emit a second polarization-switched light beam toward the cavity; and a first detector configured to detect a first signal from the first polarization-switched light beam; a second detector configured to detect a second signal from the second polarization-switched light beam, wherein the first reference block is located between the second detector and the cavity, and the first reference block is located between the second detector and the second reference block, The apparatus further includes a sample holder including a first major surface facing the cavity and a second major surface opposite the first major surface, the sample holder being located between the second polarization-switching light source and the cavity, wherein the first polarization-switched beam is configured to travel along a first beam path that strikes an input surface of a first reference block at a substantially normal angle of incidence before striking the cavity, and Wherein, the second polarization-switched light beam is configured to travel along a second light beam path, which, before hitting the cavity, is incident on the second major surface of the sample holder at an angle of about 10° to about 15° relative to the second major surface of the sample holder.

2. The device according to claim 1, wherein The sample holder is capable of translation in a direction perpendicular to the first major surface of the first reference block.

3. The device according to any one of claims 1 to 2, wherein: The cavity is further defined by a second major surface, the first reference block includes a first refractive index, and the second reference block includes a second refractive index.

4. The apparatus of claim 3, wherein: The second refractive index is substantially equal to the first refractive index.

5. The apparatus of any one of claims 1-2, further comprising a liquid in contact with the first reference block, the liquid comprising a third refractive index.

6. The apparatus of claim 5, wherein: The third refractive index is greater than the first refractive index.

7. The apparatus of claim 5, wherein: A magnitude of a difference between the first refractive index and the third refractive index is about 0.05 or greater.

8. The apparatus according to any one of claims 1 to 2, wherein: The second polarization-switched beam is configured to form a focus at an interface between the first major surface of the sample holder and the cavity.

9. A method for determining an estimated stress distribution of a sample, comprising: measuring the delay distribution of the sample; determining the central tension of the sample based on the measured retardation distribution of the sample; Measure the refractive index distribution of the sample; Determining the initial stress distribution of the sample based on the measured refractive index distribution; scaling the initial stress distribution to obtain a scaled stress distribution of the sample based on the initial stress distribution and the central tension; and Adjust the scaled stress distribution to obtain the estimated stress distribution after force balance, wherein the first polarization-switched light beam travels along a first light beam path that impinges on an input surface of a first reference block at a substantially normal angle of incidence before impinging on the sample, and The second polarization-switched beam travels along a second beam path that strikes the second major surface of the sample holder at an angle of about 10° to about 15° relative to perpendicular to the second major surface of the sample holder before striking the sample.

10. The method of claim 9, wherein: The sample included a laminate including a core layer positioned between a first outer layer and a second outer layer, the core layer including a central tension layer.

11. The method of claim 9, wherein: Determining central tension involves: Determine the width of the central area containing the central tension; determining a fitting range including a fitting width that is smaller than a width of a central region excluding one or more end portions of the delay profile; fitting a polynomial to a portion of the delay distribution within a fitting range; and The central tension of the sample is determined based on the fitted polynomial.

12. The method according to any one of claims 9 to 11, wherein Measuring refractive index distribution includes: positioning the sample between a first reference block comprising a first refractive index and a second reference block comprising a second refractive index; emitting a second polarization-switching light beam from a second polarization-switching light source; transmitting a second polarization-switched beam through the first reference block, the sample, and the second reference block; detecting the transmitted second polarization-switched light beam to determine a detection signal; and Based on data in the detection signal corresponding to the first reference block and the second reference block, the detection signal is adjusted to determine a refractive index profile.

13. The method of claim 12, wherein: The minimum difference between the estimated refractive index of the sample and the first refractive index is within a range of about 0.7% to about 10% of the estimated refractive index, and the minimum difference between the estimated refractive index and the second refractive index is within a range of about 0.7% to about 10% of the estimated refractive index.

14. The method according to any one of claims 9 to 12, wherein Measuring the refractive index distribution and determining the initial stress distribution includes: positioning a first reference block comprising a first predetermined refractive index between the sample and the second polarization-switching light source; contacting the first reference block with a liquid comprising a second predetermined refractive index; emitting a second polarization-switching light beam from a second polarization-switching light source; transmitting a second polarization-switched beam through the liquid, the first reference block, and the sample; detecting the transmitted second polarization-switched light beam to determine a detection signal; and determining an estimated stress distribution based on the detected signal and the first predetermined refractive index, wherein the minimum difference between the estimated refractive index of the sample and the first predetermined refractive index is within a range of about 0.7% to about 10% of the estimated refractive index, and the minimum difference between the estimated refractive index and the second predetermined refractive index is within a range of about 0.7% to about 10% of the estimated refractive index.

15. The method of claim 14, wherein: The magnitude of the minimum difference between the first predetermined refractive index and the estimated refractive index of the sample is in the range of about 0.006 to about 0.10, and the magnitude of the minimum difference between the second predetermined refractive index and the estimated refractive index of the sample is in the range of about 0.006 to about 0.

10.

16. The method according to any one of claims 9 to 10, wherein: Measuring the refractive index profile includes simultaneously measuring the refractive index profile using two detectors oriented at an angle of about 85° to about 95° relative to each other.

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