WO2019213364A1

WO2019213364A1 - Glass angle limiting filters, methods for making the same, and pulse oximeters including the same

Info

Publication number: WO2019213364A1
Application number: PCT/US2019/030347
Authority: WO
Inventors: Woong-Hee Lee; Georges Roussos
Original assignee: Corning Incorporated
Priority date: 2018-05-03
Filing date: 2019-05-02
Publication date: 2019-11-07
Also published as: TW202002898A

Abstract

Angle limiting filter include a glass substrate including a plurality of non-transparent glass-ceramic regions and a plurality of substantially optically transparent regions in an alternating arrangement. The non-transparent glass-ceramic regions and the substantially optically transparent regions are formed from the same glass composition. A method for forming the angle limiting filter includes irradiating a glass substrate with an ultra-violet radiation source through a patterned photomask to selectively irradiate regions in the glass substrate. The method also includes heating the glass substrate thereby transforming the irradiated regions into non-transparent glass-ceramic regions and forming an alternating arrangement of non-transparent glass-ceramic regions and substantially optically transparent regions in the glass substrate. Electronic devices, including pulse oximeters, including the angle limiting filter are also described.

Description

GLASS ANGLE LIMITING FILTERS. METHODS FOR MAKING THE SAME, AND PULSE OXIMETERS INCLUDING THE SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 62/666,364, filed May 3, 2018, the content of which is incorporated herein by reference in its entirety.

BACKGROUND

1. FIELD

[0002] This disclosure relates to glass angle limiting filters, methods for making the same, and pulse oximeters including the same.

2. TECHNICAL BACKGROUND

[0003] Angle limiting filters can be used in a number of applications, including medical applications, display applications, and sensor applications. Conventional angle limiting filters include machined cavities that are filled with a light blocking material. However, the demand for reduced thicknesses of filters can result in manufacturing difficulties and device brittleness.

[0004] Accordingly, a need exists for alternative glass angle limiting filters.

SUMMARY

[0005] Disclosed herein are angle limiting filters formed from glass substrates and methods for making the same. Such angle limiting filters can be used for pulse oximeter devices, display devices, and sensors.

[0006] Disclosed herein is an angle limiting filter comprising a glass substrate comprising a plurality of non-transparent glass-ceramic regions and a plurality of substantially optically transparent regions in an alternating arrangement. The non-transparent glass-ceramic regions and the substantially optically transparent regions are formed from the same glass composition. [0007] Disclosed herein is a method for forming an angle limiting filter including irradiating a glass substrate with an ultra-violet radiation source through a patterned photomask to selectively excite regions in the glass substrate. The method also includes heating the glass substrate thereby transforming the irradiated regions into non-transparent glass-ceramic regions and forming an alternating arrangement of non-transparent glass-ceramic regions and substantially optically transparent regions in the glass substrate.

[0008] Also disclosed herein is a pulse oximeter comprising an emitter, an angle limiting filter, and a photodetector. The emitter emits light at a first wavelength and a second wavelength. The angle limiting filter includes a glass substrate comprising a plurality of non transparent glass-ceramic regions and a plurality of substantially optically transparent regions in an alternating arrangement. The non-transparent glass-ceramic regions and the substantially optically transparent regions are formed from the same glass composition. The photodetector detects light passing through the angle limiting filter, which has been reflected by tissue of an individual.

[0009] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description, serve to explain principles and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a cross-sectional schematic view of an angle limiting filter including a plurality of louvers defining a plurality of transparent regions in accordance with one or more embodiments shown and described herein;

[0011] FIG. 2 is a cross-sectional schematic view illustrating a method of calculating transmission in accordance with one or more embodiments shown and described herein;

[0012] FIG. 2A is a cross-sectional schematic view illustrating a method of calculating transmission in accordance with one or more embodiments shown and described herein; [0013] FIG. 3 is a graph plotting the transmission (y-axis) as a function of angle of incidence (x-axis) for various ratios of thickness of the glass substrate (T) to width of transparent region (A) in accordance with one or more embodiments shown and described herein;

[0014] FIG. 3A is a graph plotting the transmission (y-axis) as a function of angle of incidence (x-axis) for various ratios of thickness of the glass substrate (T) to width of transparent region (A) in accordance with one or more embodiments shown and described herein;

[0015] FIG. 4 is a cross-sectional schematic view of a glass substrate including a photomask being exposed to UV light in accordance with one or more embodiments shown and described herein; and

[0016] FIG. 5 is a cross-sectional schematic view of an embodiment of a pulse oximeter including an angle limiting filter in accordance with one or more embodiments shown and described herein.

DETAILED DESCRIPTION

[0017] Reference will now be made in detail to various embodiments of glass angle limiting filters, embodiments of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. The components in the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the exemplary embodiments.

[0018] In various embodiments, an angle limiting filter includes a glass substrate including a plurality of non-transparent glass-ceramic regions and a plurality of substantially optically transparent regions in an alternating arrangement. The non-transparent glass-ceramic regions and the substantially optically transparent regions are formed from the same glass composition.

[0019] In various embodiments, a method for forming an angle limiting filter includes irradiating a glass substrate with an ultra-violet radiation source through a patterned photomask to selectively excite (irradiate) regions in the glass substrate. The method also includes heating the glass substrate thereby transforming the irradiated regions into non-transparent glass- ceramic regions and forming an alternating arrangement of non-transparent glass-ceramic regions and substantially optically transparent regions in the glass substrate. [0020] According to various embodiments, a pulse oximeter includes an emitter, an angle limiting filter, and a photodetector. The emitter emits light at a first wavelength and a second wavelength. The angle limiting filter includes a glass substrate comprising a plurality of non transparent glass-ceramic regions and a plurality of substantially optically transparent regions in an alternating arrangement. The non-transparent glass-ceramic regions and the substantially optically transparent regions are formed from the same glass composition. The photodetector detects light passing through the angle limiting filter, which has been reflected by tissue of an individual.

[0021] Angle limiting filters can be used in a variety of applications, including medical applications, display applications, and sensor applications. For example, angle limiting filters can be used to suppress scattered light in devices that detect light, including heart rate monitors and blood oxygenation monitors (i.e., pulse oximeters).

[0022] The rapid development of wearable devices capable of detecting vital signals has been driven primarily by the development of smartphones, smartwatches, and fitness trackers. Because the transmission properties of oxygenated and de-oxygenated blood vary significantly, many of these types of devices monitor blood oxygenation levels by measuring the transmission of the skin at at least two wavelengths of light, often in the green and red-infrared spectral regions of the electromagnetic spectrum. In particular, a light angle limiting filter can be placed in front of a photodetector to control the angle of incidence of the light reflecting back from the tissue and reaching the photodetector, reducing noise caused by environmental light.

[0023] Conventional techniques for forming angle limiting filters include applying filters directly to the surface of the photodetector using material deposition and photolithography. Such techniques include deposition of various layers, and are process intensive and costly. Other techniques include forming angle limiting filters by etching channels into a substrate and filling the channels with a light absorbing material. However, the demand for reduced thicknesses of filters can result in manufacturing difficulties, including substrate breakage, and device brittleness. Various embodiments herein enable angle limiting filters with reduced thicknesses to be manufactured from a glass substrate. [0024] FIG. 1 is a cross-sectional schematic view of an angle limiting filter 100 formed from a glass substrate 101 and including a plurality of substantially optically transparent regions 102 (also referred to herein as“transparent regions”), and a plurality of non-transparent glass- ceramic regions, referred to herein as louvers 104. In particular, the glass substrate 101, including the transparent regions 102 and louvers 104 is a single layer of solid glass. In various embodiments, the louvers 104 are arranged as parallel straight lines with respect to one another. Accordingly, in some embodiments, the interface between the transparent regions 102 and adjacent louvers 104 are substantially perpendicular to the surface of the glass substrate 101.

[0025] In one or more embodiments, the transparent regions exhibit high transmittance when measured with respect to a thickness of the optically transparent material of 1 mm or 2 mm. For example, the transparent regions exhibit an average transmittance of about 80% or greater over an optical wavelength regime in the range from about 600 nm to about 1000 nm (the “Optical Wavelength Regime”). In one or more embodiments, the transparent regions exhibit an average transmittance of about 82% or greater, about 84% or greater, about 86% or greater, about 88% or greater, about 90% or greater, about 92% or greater, about 94% or greater, about 95% or greater, or about 96% or greater, all over the Optical Wavelength Regime and measured with respect to a thickness of 1 mm to 2 mm.

[0026] In one or more embodiments, the transparent regions exhibit low reflectance when measured on a surface of the material. For example, the transparent regions exhibit an average reflectance of about 15% or less over the Optical Wavelength Regime. In one or more embodiments, the transparent regions exhibit an average reflectance of about 20% or less, about 18% or less, about 16% or less, about 15% or less, about 14% or less, about 12% or less, about 10% or less, about 8% or less, about 6% or less, about 5% or less, about 4% or less, about 3% or less, about 2% or less, about 1% or less, or about 0.5% or less, all over the Optical Wavelength Regime.

[0027] As used herein, the term“transmittance” is defined as the percentage of incident optical power within a given wavelength range transmitted through a material (e.g., the optically transparent material, the article, the substrate or portions thereof). The term “reflectance” is similarly defined as the percentage of incident optical power within a given wavelength range that is reflected from a surface (e.g., the surface of the optically transparent material, article, substrate, or portions thereof). [0028] In one or more embodiments, the non-transparent glass-ceramic regions exhibit low transmittance when measured with respect to a thickness of the optically transparent material of 1 mm or 2 mm. For example, the non-transparent glass-ceramic regions exhibit an average transmittance of about 79% or less over an optical wavelength regime in the range from about 600 nm to about 1000 nm (the“Optical Wavelength Regime”). In one or more embodiments, the non-transparent glass-ceramic regions exhibit an average transmittance of about 75% or less, about 70% or less, about 60% or less, about 50% or less, about 40% or less, about 30% or less, about 25% or less, about 20% or less, about 15% or less, about 10% or less, about 5% or less, or about 2% or less, all over the Optical Wavelength Regime and measured with respect to a thickness of 1 mm to 2 mm.

[0029] Glass substrate 101 can have any suitable composition and be made using any suitable method. Examples of suitable glass compositions can include but not limited to lithium-aluminum-silicate glasses. In general, glass substrate 101 is a photosensitive glass. As used herein, the term“photosensitive glass” refers to a glass that can undergo a transformation in response to exposure to radiation, such as at least a portion of the glass being transformed into glass-ceramic. Examples of photosensitive glass include, but are not limited to, photoreactive glass and photorefractive glass. The transformation can be manifest, for example, by opalization, by a change in refractive index, or by a change in absorption spectrum of electromagnetic radiation (e.g., a change in color). In some embodiments, the radiation comprises ultraviolet (UV) radiation. In some embodiments, the exposure to radiation is followed by a development treatment (e.g., a heat treatment) to aid in bringing about the transformation of the glass, as will be described in greater detail below. In some embodiments, exposure of the photosensitive glass to the radiation followed by the development treatment causes opalization of the exposed portion of the photosensitive glass. Throughout this disclosure, the term“photosensitive glass” is used to refer to the material in either the untransformed state (i.e., prior to exposure to radiation and/or development treatment) or the transformed state (i.e., after exposure to radiation and/or development treatment).

[0030] In various embodiments, the photosensitive glass can comprise a glass composition that is responsive to radiation as described herein. In various embodiments, the glass composition includes one or more photosensitive agents that react to the radiation to cause opalization of the photosensitive glass. Photosensitive agents can include, by way of example and not limitation, silver, gold, copper, cerium, a halogen, an alkali metal, and combinations thereof.

[0031] In some embodiments, the photosensitive glass comprises cerium (e.g., CeC and/or Ce203). For example, the photosensitive glass comprises from about 0.005 wt % to about 0.2 wt % cerium, or from about 0.01 wt % to about 0.15 wt % cerium, calculated as CeCh. In some embodiments, the photosensitive glass comprises the cerium in the +3 oxidation state (e.g., Ce203). The cerium can serve as a sensitizer ion capable of being oxidized and releasing electrons in response to exposure of the glassy article to radiation.

[0032] In some embodiments, the photosensitive glass comprises at least one photosensitive metal selected from the group consisting of silver, gold, copper, and combinations thereof. In some embodiments, the photosensitive glass includes silver. For example, the photosensitive glass comprises from about 0.0005 wt % to about 0.2 wt % silver, or about 0.005 wt % to about 0.05 wt % silver. In some embodiments, the photosensitive glass comprises the at least one photosensitive metal in the +1 oxidation state (e.g., AgNCb). The photosensitive metal can be reduced to form colloidal metal particles in response to exposure of the glassy article to radiation and subjecting the glassy article to the development treatment.

[0033] In some embodiments, the photosensitive glass comprises at least one halogen selected from the group consisting of fluorine, bromine, chlorine, and combinations thereof. For example, the photosensitive glass comprises from about 2 wt % to about 3 wt % fluorine. Additionally, or alternatively, the photosensitive glass comprises from about 0 wt % to about 2 wt % bromine. In some embodiments, the halogen is present in the photosensitive glass as a halide ion. The halogen can aid in forming microcrystals or crystallites in response to exposure of the glassy article to radiation and subjecting the glassy article to the development treatment.

[0034] In some embodiments, the photosensitive glass comprises an alkali metal selected from the group consisting of lithium, sodium, potassium, and combinations thereof. For example, the photosensitive glass comprises from about 0 wt % to about 20 wt % LriO. Additionally, or alternatively, the photosensitive glass comprises from about 0 wt % to about 30 wt % Na20, or from about 10 wt % to about 20 wt % Na20. Additionally, or alternatively, the photosensitive glass comprises from about 0 wt % to about 10 wt % K2O, or from about 0 wt % to about 1 wt % K2O. The alkali metal can aid in forming microcrystals or crystallites in response to exposure of the glassy article to radiation and subjecting the glassy article to the development treatment.

[0035] In various embodiments, the photosensitive glass can comprise additional components provided that the photosensitive glass retains its photosensitive properties. For example, in some embodiments, the photosensitive glass comprises a glass network former selected from the group consisting of SiC , AhCb, B2O3, and combinations thereof. Additionally, or alternatively, the photosensitive glass comprises one or more of SnCh. ZnO, or Sb₂0₃. For example, the glass substrate 101 may be formed from any one of a number of glass compositions, such as those disclosed in U.S. Patent Application Publication No. 2017/0080688, filed February 19, 2015 and entitled“Layered Glassy Photosensitive Article and Method of Making,” which is hereby incorporated by reference in its entirety.

[0036] Although various embodiments describe formation of the angle limiting filter 100 from a glass substrate, it is contemplated that other transparent substrates may be employed. For example, the transparent substrate can include, but is not limited to, fused silica, synthetic quartz, glass-ceramic, ceramic, or a crystalline material such as sapphire. Other transparent substrates can be employed, provided that they possess the desired optical qualities (e.g., the desired transmission of light over the Optical Wavelength Regime).

[0037] As depicted in FIG. 1, the louvers 104 and transparent regions 102 are in an alternating arrangement, with a pair of louvers 104 defining each transparent region 102. In various embodiments, the louvers 104 and the transparent regions 102 extend through the entire thickness T of the glass substrate 101. The thickness T of the glass substrate 101 can vary depending on the particular embodiment, although in various embodiments, the thickness T is from about 20 pm to about 1000 pm, from about 100 pm to about 500 pm, from about 150 pm to about 250 pm, or from about 175 pm to about 225 pm.

[0038] The dimensions of the louvers 104 and the transparent regions 102 can vary depending on the particular embodiments. In particular, the dimensions of the louvers 104 and the transparent regions 102 can vary depending on the particular optical properties of the angle limiting filter 100. FIG. 2, taken in conjunction with the description below, illustrates a method of calculating the transmission of an angle limiting filter 100 in greater detail. [0039] As shown in FIG. 2, the incident beam of light reaches the surface of the angle limiting filter 100 under an angle Q. The transmission TM through the glass can be calculated according to the following equation:

where T is the thickness of the glass substrate, A is the width of the transparent region 102, and W is the width of the louver 104. The transmission TM is the amount of light passing through the angle limiting filter 100 for a given angle Q of incidence. With the configuration described above, the angle limiting filter 100 limits the transmission of light entering the filter based on the angle Q of incidence of the light.

[0040] In other words, the angle limiting filter 100 allows only light entering the angle limiting filter 100 within a predetermined limited angular range to pass therethrough. In various embodiments, the angle limiting filter 100 filters out light at an angle Q of greater than or equal to about 20° or greater than or equal to about 15°. As used herein,“filters out” means that the transmission of the light through the angle limiting filter 100 is less than about 25%.

[0041] In various embodiments, the transparent region 102 has a width A of from about 75 pm to about 150 pm, from about 80 pm to about 125 pm, or from about 95 pm to about 110 pm. According to various embodiments, a ratio of the thickness T of the glass substrate 101 to the width A of the transparent region 102 is from about 1: 1 to about 20: 1. In some embodiments, the ratio of the thickness T of the glass substrate 101 to the width A of the transparent region 102 is from about 2: 1 to about 3:1. In various embodiments, the louver 104 has a width W of from about 1 pm to about 30 pm, from about 5 pm to about 20 pm, from about 7.5 pm to about 15 pm, or from about 9 pm to about 12 pm. According to various embodiments, a ratio of the width W of the louvers 104 to the width A of the transparent regions 102 is smaller than about 1 : 10, smaller than about 1 :5, or smaller than about 1:2. In various embodiments, the combined width of a louver 104 and an adjacent transparent region 102 may be regarded as the pitch P of the angle limiting filter 100. Typically, the pitch P is constant across the angle limiting filter 100, and can be, for example from about 75 pm to about 180 pm, or from about 100 pm to about 120 pm, although other pitches are contemplated. [0042] FIG. 3 is a graph illustrating the transmission (y-axis) as a function of angle of incidence (x-axis) for various ratios of thickness T of the glass substrate 101 shown in FIG. 2 to the width A of the transparent region (T/A). As shown in FIG. 3, as the T/A increases, the transmission for a given angle of incidence decreases. For example, at an angle of 20°, the transmission decreases from nearly 60% for a T/A of 1 to less than 25% for a T/A of 2.

[0043] FIG. 2A, taken in conjunction with the description below, illustrates a method of calculating the transmission of an angle limiting filter 100 in greater detail. The method described in connection to FIG. 2A is similar to the method described in connection to FIG. 2, except that the method described in connection to FIG. 2A accounts for refraction at the surface of the angle limiting filter 100. As shown in FIG. 2A, the incident beam of light reaches the surface of the angle limiting filter 100 under an angle Q and is refracted at the surface such that the beam of light propagates through the angle limiting filter 100 under an angle qi. The transmission TM through the glass can be calculated according to the following equation:

TM =

(l + ¾ (cos Q) where T is the thickness of the glass substrate, A is the width of the transparent region 102, W is the width of the louver 104, and RI is the refractive index of the transparent region 102. The transmission TM is the amount of light passing through the angle limiting filter 100 for a given angle Q of incidence. With the configuration described above, the angle limiting filter 100 limits the transmission of light entering the filter based on the angle Q of incidence of the light.

[0044] FIG. 3A is a graph illustrating the transmission (y-axis) as a function of angle of incidence (x-axis) for various ratios of thickness T of the glass substrate 101 shown in FIG. 2 A to the width A of the transparent region (T/A). As shown in FIG. 3 A, as the A increases, the transmission for a given angle of incidence decreases. For example, at an angle of 20°, the transmission decreases from 61% for a T/A of 1.5 to 28% for a T/A of 3.

[0045] In various embodiments, louvers 104 are formed in the glass substrate 101 to form the glass substrate into the angle limited filter 100 as described herein. The louvers 104 can be formed in the glass substrate 101 using the method schematically depicted in FIG. 4. [0046] In some embodiments, the method includes forming a mask 402 on a surface of a glass substrate 400. For example, the mask 402 can be formed by printing (e.g., inkjet printing, gravure printing, screen printing, or another printing process) or another deposition process. In some embodiments, a conventional contact mask with appropriate UV transparency can also be used.

[0047] In some embodiments, the mask 402 includes one or more open regions at which the glass substrate 400 remains uncovered. The open regions of the mask 402 can have a pattern corresponding to the desired pattern of the louvers 104 to be formed in the glass substrate 400. For example, the pattern of the mask 402 can be an array of regularly repeating rectangular shapes. Other shapes also can be used, and the shapes can have various contours, such as concentric circles, squares, rectangles, or the like. Thus, the mask 402 can be configured as a patterning mask to enable selective exposure of the glass substrate 400 to radiation as described herein.

[0048] In some embodiments, the glass substrate 400 with the mask 402 disposed thereon is exposed to radiation 404 from an ultraviolet radiation source. Although described herein as being an ultraviolet radiation source, any suitable source of radiation can be used, provided that it is capable of altering the properties of the glass substrate 400. For example, the glass substrate 400 can be irradiated with an ultraviolet radiation source, thereby selectively exciting (irradiating) regions in the glass substrate 400 that are uncovered by the mask 402. The irradiation can be carried out by any suitable method. For example, an ultraviolet radiation source can provide collimated ultraviolet light to the glass substrate 400, which is positioned such that the mask 402 is between the glass substrate 400 and the ultraviolet radiation source.

[0049] In various embodiments, following irradiation, the glass substrate 400 is heated to a temperature of about 550 °C to 600 °C for a period of several hours, thereby transforming the irradiated regions into non-transparent glass-ceramic regions that form the louvers 104. The heating can be performed according to any suitable method, and can include heating the glass substrate 400 according to a predetermined thermal profile. For example, in some embodiments, the irradiated glass substrate 400 can be placed into a kiln equipped with temperature control to heat the glass substrate 400 to a temperature of up to about 600 °C. The irradiated regions of the glass substrate 400 have heat- developed coloration that results in opacity and absorption of various wavelengths of light. The unexposed areas of the glass substrate 400 that were not irradiated as a result of exposure to the ultraviolet radiation do not have heat-developed coloration and form the transparent regions 102 in the angle limiting filter 100.

[0050] In some embodiments, after thermal development (i.e., heating), the angle limiting filter 100 can be polished to achieve a desired optical quality. For example, the angle limiting filter 100 can be polished such that the glass substrate 100 has a surface roughness (Ra) of at most about 50 nm, at most about 40 nm, at most about 30 nm, at most about 20 nm, at most about 10 nm, at most about 9 nm, at most about 8 nm, at most about 7 nm, at most about 6 nm, or at most about 5 nm. Such low surface roughness can enable light to pass through the transparent regions 102 without substantial distortion.

[0051] In various embodiments, antireflective coatings may be applied to the surface of the angle limiting filter 100. Such coatings can allow for the reduction of light reflections at the surfaces that reduce signal strength and lower angle selectivity. Suitable antireflective coatings can include those known and used in the art.

[0052] Turning now to FIG. 5, in various embodiments, the angle limiting filter 100 is used in a pulse oximeter 500. For example, angle limiting filter 100 can be packaged with an emitter 501 and a photodetector 502 to form a pulse oximeter 500. The pulse oximeter 500 can be, for example, used to measure light reflected by tissue of an individual.

[0053] In the embodiment depicted in FIG. 5, the emitter 501 is configured to emit light at a first wavelength and a second wavelength. It is contemplated that light can be emitted from a single emitter at the first and second wavelengths, or a first emitter can be used to emit light at the first wavelength and a second emitter can be used to emit light at the second wavelength. In various embodiments, the first wavelength is a wavelength of from about 600 nm to about 750 nm, and the second wavelength is a wavelength of from about 850 nm to about 1000 nm. However, it is contemplated that the particular wavelengths may be selected based on the particular application.

[0054] The light beams 504 are emitted from the emitter 501, pass through the skin 505 of the individual, and are reflected by the red blood cells in the blood vessel 506. The reflected light beams 504 are filtered by the angle limiting filter 100, and light passing through the angle limiting filter 100 reaches the photodetector 502. The photodetector 502 receives the signals of each wavelength of light passing through the angle limiting filter 100 and can provide the signal information to a computing device (not shown). In various embodiments, the computing device can calculate a ratio of the signal of the first wavelength to the second wavelength and convert the ratio to a blood oxygen level. For example, ratios and corresponding blood oxygen levels may be stored in a look up table in a database accessible to the computing device.

[0055] Although embodiments have been described in which the angle limiting filter is employed in a pulse oximeter, it is contemplated that the angle limiting filter can be used in other applications, including but not limited to saccharometers, display devices, illuminance sensors, and other types of spectrum sensors. For example, the angle limiting filter can be used as a privacy filter in a display device. As provided hereinabove, the dimensions of the transparent regions and louvers, as well as the glass composition can vary depending on the final application and target optical properties of the angle limiting filter.

[0056] Various embodiments described herein include an angle limiting filter that may be used in electronic devices such as medical devices, display devices, sensors, and the like. The angle limiting filter may include a plurality of non-transparent glass-ceramic regions and a plurality of transparent regions formed in an alternating arrangement the glass substrate without drilling, etching, or other labor intensive processing steps, thereby providing advantages over conventional angle limiting filters. Various embodiments may further advantageously provide thinner angle limiting filters, and/or improve manufacturing efficiencies by reducing machining on thin substrates.

Terminology and Interpretative Norms

[0057] The terms“glass” and“glass composition” encompass both glass materials and glass- ceramic materials, as both classes of materials are commonly understood. Likewise, the term “glass structure” encompasses structures comprising glass.

[0058] Numerical values, including endpoints of ranges, can be expressed herein as approximations preceded by the term“about,”“approximately,” or the like. In such cases, other embodiments include the particular numerical values. Regardless of whether a numerical value is expressed as an approximation, two embodiments are included in this disclosure: one expressed as an approximation, and another not expressed as an approximation. It will be further understood that an endpoint of each range is significant both in relation to another endpoint, and independently of another endpoint.

[0059] The term“surface roughness” means Ra surface roughness determined as described in ISO 25178, Geometric Product Specifications (GPS) - Surface texture: areal, filtered at 25 pm unless otherwise indicated. The surface roughness values reported herein were obtained using a Keyence confocal microscope.

[0060] The term“formed from” can mean one or more of comprises, consists essentially of, or consists of. For example, a component that is formed from a particular material can comprise the particular material, consist essentially of the particular material, or consist of the particular material.

[0061] Directional terms as used herein - for example up, down, right, left, front, back, top, bottom, vertical, horizontal - are made only with reference to the figures as drawn and are not intended to imply absolute orientation unless otherwise expressly stated.

[0062] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0063] As used herein, the singular forms“a,”“an” and“the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to“a” component includes aspects having two or more such components, unless the context clearly indicates otherwise. Also, the word“or” when used without a preceding“either” (or other similar language indicating that“or” is unequivocally meant to be exclusive - e.g., only one of x or y, etc.) shall be interpreted to be inclusive (e.g.,“x or y” means one or both x or y).

[0064] The term“and/or” shall also be interpreted to be inclusive (e.g.,“x and/or y” means one or both x or y). In situations where“and/or” or“or” are used as a conjunction for a group of three or more items, the group should be interpreted to include one item alone, all the items together, or any combination or number of the items. Moreover, terms used in the specification and claims such as have, having, include, and including should be construed to be synonymous with the terms comprise and comprising.

[0065] Unless otherwise indicated, all numbers or expressions, such as those expressing dimensions, physical characteristics, and the like, used in the specification (other than the claims) are understood to be modified in all instances by the term“approximately.” At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter recited in the specification or claims which is modified by the term “approximately” should be construed in light of the number of recited significant digits and by applying ordinary rounding techniques.

[0066] All disclosed ranges are to be understood to encompass and provide support for claims that recite any and all subranges or any and all individual values subsumed by each range. For example, a stated range of 1 to 10 should be considered to include and provide support for claims that recite any and all subranges or individual values that are between and/or inclusive of the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 5.5 to 10, 2.34 to 3.56, and so forth) or any values from 1 to 10 (e.g., 3, 5.8, 9.9994, and so forth).

[0067] All disclosed numerical values are to be understood as being variable from 0-100% in either direction and thus provide support for claims that recite such values or any and all ranges or subranges that can be formed by such values. For example, a stated numerical value of 8 should be understood to vary from 0 to 16 (100% in either direction) and provide support for claims that recite the range itself (e.g., 0 to 16), any subrange within the range (e.g., 2 to 12.5) or any individual value within that range (e.g., 15.2). [0068] The drawings shall be interpreted as illustrating one or more embodiments that are drawn to scale and/or one or more embodiments that are not drawn to scale. This means the drawings can be interpreted, for example, as showing: (a) everything drawn to scale, (b) nothing drawn to scale, or (c) one or more features drawn to scale and one or more features not drawn to scale. Accordingly, the drawings can serve to provide support to recite the sizes, proportions, and/or other dimensions of any of the illustrated features either alone or relative to each other. Furthermore, all such sizes, proportions, and/or other dimensions are to be understood as being variable from 0-100% in either direction and thus provide support for claims that recite such values or any and all ranges or subranges that can be formed by such values.

[0069] The terms recited in the claims should be given their ordinary and customary meaning as determined by reference to relevant entries in widely used general dictionaries and/or relevant technical dictionaries, commonly understood meanings by those in the art, etc., with the understanding that the broadest meaning imparted by any one or combination of these sources should be given to the claim terms (e.g., two or more relevant dictionary entries should be combined to provide the broadest meaning of the combination of entries, etc.) subject only to the following exceptions: (a) if a term is used in a manner that is more expansive than its ordinary and customary meaning, the term should be given its ordinary and customary meaning plus the additional expansive meaning, or (b) if a term has been explicitly defined to have a different meaning by reciting the term followed by the phrase“as used in this document shall mean” or similar language (e.g.,“this term means,”“this term is defined as,”“for the purposes of this disclosure this term shall mean,” etc.). References to specific examples, use of“i.e.,” use of the word“invention,” etc., are not meant to invoke exception (b) or otherwise restrict the scope of the recited claim terms. Other than situations where exception (b) applies, nothing contained in this document should be considered a disclaimer or disavowal of claim scope.

[0070] The subject matter recited in the claims is not coextensive with and should not be interpreted to be coextensive with any embodiment, feature, or combination of features described or illustrated in this document. This is true even if only a single embodiment of the feature or combination of features is illustrated and described in this document.

[0071] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claimed subject matter. Accordingly, the claimed subject matter is not to be restricted except in light of the attached claims and their equivalents.

Claims

What is claimed is:

1. An angle limiting filter comprising:

a glass substrate comprising a plurality of non-transparent glass-ceramic regions and a plurality of substantially optically transparent regions in an alternating arrangement; wherein the non-transparent glass-ceramic regions and the substantially optically transparent regions are formed from the same glass composition.

2. The angle limiting filter of claim 1, wherein: each of the plurality of non-transparent glass-ceramic regions has a width W each of the plurality of substantially optically transparent regions has a width A; and a ratio of W:A is smaller than about 1 :5.

3. The angle limiting filter of claim 1, wherein: the glass substrate has a thickness T; each of the plurality of substantially optically transparent regions has a width A; and a ratio of T:A is from about 1 : 1 to about 20: 1.

4. The angle limiting filter of claim 1, wherein the plurality of substantially optically transparent regions have a transmission of greater than about 90% at a wavelength of from about 600 nm to about 1000 nm.

5. The angle limiting filter of claim 1, wherein the plurality of non-transparent glass- ceramic regions have a transmission of less than about 75% at a wavelength of from about 600 nm to about 1000 nm.

6. The angle limiting filter of claim 1, wherein the glass composition comprises a photosensitive agent.

7. The angle limiting filter of claim 6, wherein the photosensitive agent comprises silver.

8. A method for forming an angle limiting filter, the method comprising: irradiating a glass substrate with an ultra-violet radiation source through a patterned photomask to selectively irradiate regions in the glass substrate; and

heating the glass substrate thereby transforming the irradiated regions into

non-transparent glass-ceramic regions and forming an alternating arrangement of

non-transparent glass-ceramic regions and substantially optically transparent regions in the glass substrate.

9. The method of claim 8, wherein the glass substrate comprises a glass composition comprising a photosensitive agent.

10. The method of claim 9, wherein the photosensitive agent comprises silver.

11. The method of claim 8, wherein the regions of non-transparent glass-ceramic material are in an alternating arrangement with the substantially optically transparent regions of the glass substrate.

12. The method of claim 8, wherein heating the glass substrate comprises heating the glass substrate to a temperature up to about 600 °C.

13. The method of claim 8, further comprising polishing the glass substrate after heating.

14. The method of claim 8, further comprising applying the patterned photomask to a surface of the glass substrate between the ultra-violet radiation source and the glass substrate.

15. The method of claim 8, wherein:

the regions of non-transparent glass-ceramic material have a width W

substantially optically transparent regions of the glass substrate have a widths; and a ratio of W:A is smaller than about 1 :5.

16. A pulse oximeter comprising:

an emitter emitting light at a first wavelength and a second wavelength;

an angle limiting filter comprising a glass substrate comprising a plurality of non-transparent glass-ceramic regions and a plurality of substantially optically transparent regions in an alternating arrangement, and wherein the non-transparent glass-ceramic regions and the substantially optically transparent regions are formed from the same glass composition; and a photodetector for detecting light passing through the angle limiting filter, wherein the light passing through the angle limiting filter comprises the light at the first wavelength and the second wavelength emitted by the emitter and reflected by tissue of an individual.

17. The pulse oximeter of claim 16, wherein: each of the plurality of non-transparent glass-ceramic regions has a width W each of the plurality of substantially optically transparent regions has a widths; and a ratio of W:A is smaller than about 1 :5.

18. The pulse oximeter of claim 16, wherein: the glass substrate has a thickness T; each of the plurality of substantially optically transparent regions has a widths; and a ratio of T:A is from about 1 : 1 to about 20: 1.

19. The pulse oximeter of claim 16, wherein the plurality of substantially optically transparent regions have a transmission of greater than about 90% at a wavelength of from about 600 nm to about 1000 nm.

20. The pulse oximeter of claim 16, wherein the plurality of non-transparent glass-ceramic regions have a transmission of less than about 75% at a wavelength of from about 600 nm to about 1000 nm.