Patent Description:
In another example, information regarding the NIR light may be used to recognize an identity of the user, a characteristic of the user (e.g., a height or a weight), a characteristic of another type of target (e.g., a distance to an object, a size of the object, or a shape of the object), or the like. However, during transmission of the NIR light toward the user and/or during reflection from the user toward the optical receiver, ambient light may interfere with the NIR light. Thus, the optical receiver may be optically coupled to an optical filter, such as a bandpass filter, to filter ambient light and to allow NIR light to pass through toward the optical receiver.

<CIT> and <CIT> disclose examples of interference filters known in the art.

According an aspect of the invention, there is provided an optical filter according to claim <NUM>.

The material may include at least one of: a silicon dioxide (SiO<NUM>) material, an aluminum oxide (Al<NUM>O<NUM>) material, a titanium dioxide (TiO<NUM>) material, a niobium pentoxide (Nb<NUM>O<NUM>) material, a tantalum pentoxide (Ta<NUM>O<NUM>) material, a magnesium fluoride (MgF<NUM>) material, a zirconiumoxide (ZrO<NUM>) material, a yttriumoxide Y<NUM>O<NUM>) material, a silicon nitride (S<NUM>N<NUM>), a boron based material, or a phosphorous based material.

The first subset of optical filter layers may be high refractive index material layers (H) and the second subset of optical filter layers may be low refractive index material layers (L); and where the set of optical filter layers may be arranged in at least one of: an (H-L)m order, an (H-L)m-H order, or an L-(H-L)m order, where m is a quantity of alternating H and L layers.

The first refractive index may be greater than <NUM> at a spectral range of approximately <NUM> nanometers (nm) to approximately <NUM>.

The first refractive index may be approximately <NUM> at a wavelength of approximately <NUM> nanometers (nm) to approximately <NUM>.

The first refractive index may be greater than approximately <NUM> at a spectral range of approximately <NUM> nanometers (nm) to approximately <NUM>.

The first subset of optical filter layers may be annealed.

The first subset of optical filter layers may be hydrogenated.

The first subset of optical filter layers may be nitrogenated.

The first subset of optical filter layers may be doped with at least one of: a phosphorous based dopant, a nitrogen based dopant, or a boron based dopant.

The second refractive index may be less than <NUM> at a spectral range of approximately <NUM> nanometers (nm) to approximately <NUM>.

The second refractive index may be less than <NUM> at a spectral range of approximately <NUM> nanometers to approximately <NUM>.

The optical filter may be a band pass filter.

The optical filter may be annealed. Layers of the optical filter may be deposited via a sputtering procedure.

The optical filter may further comprise: an anti-reflective coating.

According to another aspect of the invention, there is provided an optical system according to claim <NUM>.

The optical filter may be associated with greater than <NUM>% transmissivity at approximately <NUM>.

The first subset of layers may be hydrogenated.

An optical receiver may receive light from an optical source, such as an optical transmitter. For example, the optical receiver may receive near infrared (NIR) light from the optical transmitter and reflected off a target, such as a user or an object. In this case, the optical receiver may receive the NIR light as well as ambient light, such as visible spectrum light. The ambient light may include light from one or more light sources separate from the optical transmitter, such as sunlight, light from a light bulb, or the like. The ambient light may reduce an accuracy of a determination relating to the NIR light. For example, in a gesture recognition system, the ambient light may reduce an accuracy of generation of a three-dimensional image of the target based on the NIR light. Thus, the optical receiver may be optically coupled to an optical filter, such as a bandpass filter, to filter ambient light and to pass through NIR light toward the optical receiver.

The optical filter may include a set of dielectric thin film layers. The set of dielectric thin film layers are selected and deposited to block a portion of out-of-band light below a particular threshold, such as <NUM> nanometers (nm), and pass light for a particular range of wavelengths, such as a range of approximately <NUM> to approximately <NUM>, a range of approximately <NUM> to approximately <NUM>, a range of approximately <NUM> to approximately <NUM>, a range of approximately <NUM> to approximately <NUM>, or the like. For example, the set of dielectric thin film layers may be selected to filter out the ambient light. Additionally, or alternatively, the set of dielectric film layers may be selected to block out-of-band light below the particular threshold, and to pass light for another range of wavelengths, such as a range of approximately <NUM> to approximately <NUM>, a range of approximately <NUM> to approximately <NUM>, or at a wavelength of approximately <NUM>.

Implementations, described, herein, may utilize a hydrogenated silicon-germanium (SiGe:H) material or the like, as a set of high index layers for an optical filter, such as low angle shift optical filter. In this way, based on having a higher effective refractive index relative to another filter stack that uses another high index layer material, the optical filter may provide a relatively low angle-shift. Moreover, a filter using the SiGe or SiGe:H material may substantially block or effectively screen out ambient light and pass through NIR light. The wavelength shift at a particular angle of incidence may be calculated as: <MAT> where λshift represents a wavelength shift at a particular angle of incidence, Θ represents the particular angle of incidence, neff represents the effective refractive index, and λ<NUM> represents the wavelength of light at Θ=<NUM>°.

<FIG> are diagram of an example <NUM> of a set of geometries for sputter deposition systems for manufacturing example implementations described herein.

As shown in <FIG>, example <NUM> includes a vacuum chamber <NUM>, a substrate <NUM>, a cathode <NUM>, a target <NUM>, a cathode power supply <NUM>, an anode <NUM>, a plasma activation source (PAS) <NUM>, and a PAS power supply <NUM>. Target <NUM> may include a silicon-germanium material in a particular concentration selected based on optical characteristics of the particular concentration, as described herein. In another example, an angle of cathode <NUM> may be configured to cause a particular concentration of silicon-germanium to be sputtered onto substrate <NUM>, as described herein. PAS power supply may be utilized to power PAS <NUM> and may include a radio frequency (RF) power supply. Cathode power supply <NUM> may be utilized to power cathode <NUM> and may include a pulsed direct current (DC) power supply.

With regard to <FIG>, target <NUM> is sputtered in the presence of hydrogen (H<NUM>), as well as an inert gas, such as argon, to deposit a hydrogenated silicon-germanium material as a layer on substrate <NUM>. The inert gas may be provided into the chamber via anode <NUM> and/or PAS <NUM>. Hydrogen is introduced into the vacuum chamber <NUM> through PAS <NUM>, which serves to activate the hydrogen. Additionally, or alternatively, cathode <NUM> (e.g., in this case, hydrogen may be introduced from another part vacuum chamber <NUM>) or anode <NUM> may cause hydrogen activation (e.g., in this case, hydrogen may be introduced into vacuum chamber <NUM> by anode <NUM>). In some implementations, the hydrogen may take the form of hydrogen gas, a mixture of hydrogen gas and a noble gas (e.g., argon gas), or the like. PAS <NUM> may be located within a threshold proximity of cathode <NUM>, allowing plasma from PAS <NUM> and plasma from cathode <NUM> to overlap. The use of the PAS <NUM> allows the hydrogenated silicon layer to be deposited at a relatively high deposition rate. In some implementations, the hydrogenated silicon-germanium layer is deposited at a deposition rate of approximately <NUM>/s to approximately <NUM>/s, at a deposition rate of approximately <NUM>/s to approximately <NUM>/s, at a deposition rate of approximately <NUM>/s, or the like.

Although the sputtering procedure is described, herein, in terms of a particular geometry and a particular implementation, other geometries and other implementations are possible. For example, hydrogen may be injected from another direction, from a gas manifold in a threshold proximity to cathode <NUM>, or the like.

As shown in <FIG>, a similar sputter deposition system includes a vacuum chamber <NUM>, a substrate <NUM>, a first cathode <NUM>, a second cathode <NUM>, a silicon target <NUM>, a germanium target <NUM>, a cathode power supply <NUM>, an anode <NUM>, a plasma activation source (PAS) <NUM>, and a PAS power supply <NUM>. In this case, silicon target <NUM> is a silicon target and germanium target <NUM> is a germanium target.

As shown in <FIG>, silicon target <NUM> is oriented at approximately <NUM> degrees relative to substrate <NUM> (e.g., approximately parallel to substrate <NUM>) and germanium target <NUM> is oriented at approximately <NUM> degrees relative to substrate <NUM>. In this case, silicon and germanium are sputtered by cathode <NUM> and cathode <NUM>, respectively from silicon target <NUM> and germanium target <NUM>, respectively, onto substrate <NUM>.

As shown in <FIG>, in a similar sputter deposition system, silicon target <NUM> and germanium target <NUM> are each oriented at approximately <NUM> degrees relative to substrate <NUM>, and silicon and germanium are sputtered by cathode <NUM> and cathode <NUM>, respectively, from first target <NUM> and second target <NUM>, respectively, onto substrate <NUM>.

As shown in <FIG>, in a similar sputter deposition system, silicon target <NUM> is oriented at approximately <NUM> degrees relative to substrate <NUM> and germanium target <NUM> is oriented at approximately <NUM> degrees relative to substrate <NUM>. In this case, silicon and germanium are sputtered by cathode <NUM> and cathode <NUM>, respectively from silicon target <NUM> and germanium target <NUM>, respectively, onto substrate <NUM>.

With regard to <FIG>, each configuration of components in a silicon sputter deposition system may result in a different relative concentration of silicon and germanium. Although, described, herein, in terms of different configurations of components, different relative concentrations of silicon and germanium may also be achieved using different materials, different manufacturing processes, or the like.

As indicated above, <FIG> are provided merely as an example.

<FIG> and <FIG> are diagrams of an example of characteristics relating to using an example implementation described herein.

As shown in <FIG>, and by chart <NUM>, a set of characteristics are determined, for example, for a SiGe layer (e.g., a SiGe:H layer for use in an optical filter). Assume that an increase in cathode angle of a cathode sputtering silicon corresponds to an increased germanium content in the optical filter relative to a silicon content, as described in further detail with regard to <FIG>. For example, for high index layers of an optical filter, deposited at <NUM> degrees, the high index layer may be associated with an approximately <NUM>% germanium content. Similarly, for deposition at <NUM> degrees the optical filter may be associated with an approximately <NUM>% germanium content, and for deposition at <NUM> degrees the optical filter may be associated with an approximately <NUM>% germanium content.

As further shown in <FIG>, and by chart <NUM>, a refractive index n at a wavelength of <NUM> is provided for a set of layers based on a cathode angle (in degrees) at which sputtering was performed to sputter material to form the set of high index material single layers. As shown, for a silicon-germanium (SiGe) and annealed silicon-germanium (SiGe-280C) (e.g., silicon-germanium for which an annealing procedure has been performed at <NUM> degrees Celsius (C)) based high index single layer or SiGe single layers, an increase in cathode angle corresponds to an increase in refractive index. Moreover, the refractive index for silicon layers including germanium is greater than for silicon not including germanium, such as a silicon (Si) based optical filter and an annealed silicon (Si-280C) based optical filter, thereby improving performance of an optical filter that includes SiGe layers.

As shown in <FIG>, and by chart <NUM>, another set of optical characteristics are determined for the SiGe single layers. As shown, an absorption at a wavelength of <NUM> of the set of SiGe single layers is determined in relation to a type of material for the high index layers and a cathode angle used for a sputtering procedure to deposit the high index layers. For example, increased germanium content (e.g., increased cathode angle) is associated with increased absorption loss in the SiGe layer. However, annealed silicon-germanium is associated with a reduced absorption loss for an optical filter associated with a similar cathode angle relative to non-annealed silicon-germanium. For example, annealed silicon-germanium may be associated with a loss value that satisfies an absorption threshold for utilization in optical filters at a cathode angle that corresponds to a refractive index that satisfies a refractive index threshold for utilization in low angle shift for an optical filter. In this way, annealing silicon-germanium (or hydrogenated silicon-germanium) may permit silicon-germanium (or hydrogenated silicon-germanium) to be used as a low-angle shift coating with a relatively high refractive index and without an excessive absorption of NIR light.

As indicated above, <FIG> and <FIG> are provided merely as examples. Other examples are possible and may differ from what was described with regard to <FIG> and <FIG>.

<FIG> and <FIG> are diagrams of another example of characteristics relating to using an example implementation described herein.

As shown in <FIG>, and by chart <NUM>, a set of mechanical characteristics are determined for the set of SiGe single layers. As shown, a stress value (in megapascals (MPa)) of the set of SiGe single layers is determined in relation to a type of material for the high index layers and a cathode angle used for a sputtering procedure to deposit the high index layers. The stress value may be a compressive stress on the SiGe single layer as a result of the sputtering procedure. For example, increased germanium content (e.g., increased cathode angle) is associated with decreased stress for a SiGe single layer. As shown, annealed silicon-germanium is associated with a reduced stress value for a SiGe single layer associated with a similar cathode angle to non-annealed silicon-germanium. For example, annealed silicon-germanium may be associated with a stress value that satisfies a stress threshold for utilization in optical filters at a cathode angle that corresponds to a refractive index that satisfies a refractive index threshold for utilization in optical filters. Reduced stress value may reduce a difficulty in manufacture when the manufacturing procedure includes cutting a wafer into multiple portions for multiple optical filters. Moreover, a reduced stress value may permit a reduced thickness substrate relative to another type of material with a greater stress value. In this way, annealing silicon-germanium (or hydrogenated silicon-germanium) may permit silicon-germanium (or hydrogenated silicon-germanium) to be used as a low-angle shift coating with a relatively high refractive index and without an excessive stress value, thereby improving manufacturability of an optical filter and reducing a thickness of the optical filter relative to a non-annealed optical filter and especially if compared of filters just using silicon or hydrogenated silicon.

As shown in <FIG>, and by chart <NUM>, a set of optical characteristics are determined for a set of bandpass filters center at <NUM>. As shown, a transmissivity percentage of a first optical filter and a second optical filter is determined in relation to a utilization of annealing and a wavelength of light. Assume that a first optical filter, corresponding to reference number <NUM>, and a second optical filter, corresponding to reference number <NUM>, are each associated with a set of <NUM> cavities, a <NUM> micrometer thickness, a silicon-germanium set of high index layers, a silicon dioxide set of low index layers, no anti-reflective coating on the second side, and a cathode angle of <NUM> degrees (e.g., which may correspond to approximately <NUM>% germanium for the set of high index layers).

With regard to <FIG>, and reference numbers <NUM> and <NUM>, utilization of annealing improves transmissivity at approximately <NUM> by approximately <NUM>% (e.g., to greater than <NUM>% or approximately <NUM>% at approximately <NUM>) relative to not utilizing annealing of an optical filter. In this way, annealing silicon-germanium (or hydrogenated silicon-germanium) may permit silicon-germanium (or hydrogenated silicon-germanium) to be used as a low-angle shift coating with improved transmissivity relative to a non-annealed optical filter. In another example, including an anti-reflective coating (e.g., on a backside surfacce of the optical filter) may improve transmissivity by an additional approximately <NUM>% relative to the first optical filter without an anti-reflective coating.

Although <FIG> shows an example relating to a particular set of characteristics of the first optical filter and the second optical filter, other examples described herein may exhibit similarly improved performance with annealing for other characteristics of an optical filter.

Although <FIG> shows an example relating to optical characteristics of a bandpass filter, similarly improved optical characteristics may be associated with manufacture of a shortwave pass filter, a long wave pass filter, an anti-reflective coating, a non-polarizing beam splitter, a polarizing beam splitter, a dielectric reflector, a multi-bandpass filter, a notch filter, a multi-notch filter, a neutral density filter, or the like.

<FIG> is a diagram of an example optical filter <NUM>. <FIG> shows an example stackup of an optical filter using a silicon-germanium based material as a high index material. As further shown in <FIG>, optical filter <NUM> includes an optical filter coating portion <NUM> and a substrate <NUM>.

Optical filter coating portion <NUM> includes a set of optical filter layers. For example, optical filter coating portion <NUM> includes a first set of layers <NUM>-<NUM> through <NUM>-N+<NUM> (N ≥ <NUM>) and a second set of layers <NUM>-<NUM> through <NUM>-N. Layers <NUM> include a set of layers of a high refractive index material (H layers) comprising silicon-germanium, wherein the layers are hydrogenated and/or nitrogenated. The SiGe layers may include (small quantities of) phosphor, boron, nitride, or the like. Layers <NUM> may include a set of layers of a low refractive index material (L layers), such as silicon dioxide layers or the like. Additionally, or alternatively, the L layers may include silicon nitride layers, Ta2O5 layers, Nb2O5 layers, TiO2 layers, Al2O3 layers, ZrO2 layers, Y2O3 layers, Si3N4 layers, a combination thereof, or the like.

In some implementations, layers <NUM> and <NUM> may be stacked in a particular order, such as an (H-L)m (m ≥ <NUM>) order, an (H-L)m-H order, an L-(H-L)m order, or the like. For example, as shown, layers <NUM> and <NUM> are positioned in an (H-L)n-H order with an H layer disposed at a surface of optical filter <NUM> and an H layer disposed at a surface of substrate <NUM>. In some implementations, optical filter coating portion <NUM> may be associated with a particular quantity of layers, m. For example, a hydrogenated silicon-germanium based optical filter may include a quantity of alternating H layers and L layers, such as a range of <NUM> layers to <NUM> layers.

In some implementations, each layer of optical filter coating portion <NUM> may be associated with a particular thickness. For example, layers <NUM> and <NUM> may each be associated with a thickness of between <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, or <NUM> and <NUM>, and/or optical filter coating portion <NUM> may be associated with a thickness of between <NUM> and <NUM>, <NUM> and <NUM>, or the like. In some examples, at least one of layers <NUM> and <NUM> may each be associated with a thickness of less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>, and/or optical filter coating portion <NUM> may be associated with a thickness of less than <NUM>, less than <NUM>, and/or less than <NUM>. In some implementations, layers <NUM> and <NUM> may be associated with multiple thicknesses, such as a first thickness for layers <NUM> and a second thickness for layers <NUM>, a first thickness for a first subset of layers <NUM> and a second thickness for a second subset of layers <NUM>, a first thickness for a first subset of layers <NUM> and a second thickness for a second subset of layers <NUM>, or the like. In this case, a layer thickness and/or a quantity of layers may be selected based on an intended set of optical characteristics, such as an intended passband, an intended reflectance, or the like.

In some implementations, a particular silicon-germanium based material may be selected for the layers <NUM>. For example, layers <NUM> may be selected and/or manufactured (e.g., via a sputtering procedure) to include a particular type of silicon-germanium, such as SiGe-<NUM>, SiGe-<NUM>, SiGe-<NUM>, or the like. In some implementations, layers <NUM> may include trace amounts of another material, such as argon, as a result of a sputter deposition procedure, as described herein. The particular silicon-germanium based material may be manufactured using a hydrogenating procedure to hydrogenate the silicon-germanium based material, a nitrogenating procedure to nitrogenate the silicon-germanium based material, one or more optional annealing procedures to anneal the silicon-germanium based material, another type of procedure, a doping procedure (e.g., phosphorous based doping, nitrogen based doping, boron based doping, or the like) to dope the silicon-germanium based material, or a combination of multiple procedures (e.g., a combination of hydrogenation, nitrogenation, annealing, and/or doping), as described herein. For example, layers <NUM> may be selected to include a refractive index greater than that of layers <NUM> over, for example, a spectral range of approximately <NUM> to approximately <NUM>, a spectral range of approximately <NUM> to approximately <NUM>, a particular wavelength of approximately <NUM>, or the like. In another example, layers <NUM> may be selected to include a refractive index greater than that of layers <NUM> over, for example, a spectral range of approximately <NUM> to approximately <NUM>, a spectral range of approximately <NUM> to approximately <NUM>, a particular wavelength of approximately <NUM>, or the like. In this case, layers <NUM> may be associated with a refractive index greater than <NUM>, a refractive index greater than <NUM>, a refractive index greater than <NUM>, or a refractive index greater than <NUM>. For example, layers <NUM> may be associated with a refractive index greater than <NUM> at approximately <NUM>.

In some implementations, a particular material may be selected for layers <NUM>. For example, layers <NUM> may include a set of silicon dioxide (SiO<NUM>) layers, a set of aluminum oxide (Al<NUM>O<NUM>) layers, a set of titanium dioxide (TiO<NUM>) layers, a set of niobium pentoxide (Nb<NUM>O<NUM>) layers, a set of tantalum pentoxide (Ta<NUM>O<NUM>) layers, a set of magnesium fluoride (MgF<NUM>) layers, a set of silicon nitride (S<NUM>N<NUM>) layers, zirconium oxide (ZrOz<NUM>), yttrium oxide (Y<NUM>O<NUM>), or the like. In this case, layers <NUM> may be selected to include a refractive index lower than that of the layers <NUM> over, for example, a spectral range of approximately <NUM> to approximately <NUM>, the spectral range of approximately <NUM> to approximately <NUM>, the wavelength of approximately <NUM>, or the like. For example, layers <NUM> may be selected to be associated with a refractive index of less than <NUM> over the spectral range of approximately <NUM> to approximately <NUM>. In another example, layers <NUM> may be selected to be associated with a refractive index of less than <NUM> over the spectral range of approximately <NUM> to approximately <NUM>, the spectral range of approximately <NUM> to approximately <NUM>, the wavelength of approximately <NUM>, or the like. In another example, layers <NUM> may be selected to be associated with a refractive index of less than <NUM> over the spectral range of approximately <NUM> to approximately <NUM>, the spectral range of approximately <NUM> to approximately <NUM>, the wavelength of approximately <NUM>, or the like. In some implementations, layers <NUM> and/or <NUM> may be associated with a particular extinction coefficient, such as an extinction coefficient of below approximately <NUM>, an extinction coefficient of below approximately <NUM>, an extinction coefficient of below approximately <NUM>, or the like over a particular spectral ranges (e.g., the spectral range of approximately <NUM> to approximately <NUM>, the spectral range of approximately <NUM> to approximately <NUM>, the wavelength of approximately <NUM>, or the like; and/or a spectral range of approximately <NUM> to approximately <NUM>, a spectral range of approximately <NUM> to approximately <NUM>, a particular wavelength of approximately <NUM>, or the like). In some implementations, the particular material may be selected for layers <NUM> based on a desired width of an out-of-band blocking spectral range, a desired center-wavelength shift associated with a change of angle of incidence (AOI), or the like.

In some implementations, optical filter coating portion <NUM> may be fabricated using a sputtering procedure. For example, optical filter coating portion <NUM> may be fabricated using a pulsed-magnetron based sputtering procedure to sputter alternating layers <NUM> and <NUM> on a glass substrate or another type of substrate. In some implementations, multiple cathodes may be used for the sputtering procedure, such as a first cathode to sputter silicon and a second cathode to sputter germanium. In this case, the multiple cathodes may be associated with an angle of tilt of the first cathode relative to the second cathode selected to ensure a particular concentration of germanium relative to silicon. In some implementations, hydrogen flow may be added during the sputtering procedure to hydrogenate the silicon-germanium. Similarly, nitrogen flow may be added during the sputtering procedure to nitrogenate the silicon-germanium. In some implementations, optical filter coating portion <NUM> may be annealed using one or more annealing procedures, such as a first annealing procedure at a temperature of approximately <NUM> degrees Celsius or between approximately <NUM> degrees Celsius and approximately <NUM> degrees Celsius, a second annealing procedure at a temperature of approximately <NUM> degrees Celsius or between approximately <NUM> degrees Celsius and approximately <NUM> degrees Celsius, or the like. In some implementations, optical filter coating portion <NUM> may be fabricated using a SiGe:H coated from a target, as described with regard to <FIG>. For example, a SiGe compound target with a selected ratio of silicon to germanium may be sputtered to fabricate optical filter coating portion <NUM> with a particular silicon to germanium ratio.

In some implementations, optical filter coating portion <NUM> may be associated with causing a reduced angle shift relative to an angle shift caused by another type of optical filter. For example, based on a refractive index of the H layers relative to a refractive index of the L layers, optical filter coating portion <NUM> may cause a reduced angle shift relative to another type of optical filter with another type of high index material.

In some implementations, optical filter coating portion <NUM> is attached to a substrate, such as substrate <NUM>. For example, optical filter coating portion <NUM> may be attached to a glass substrate or another type of substrate. Additionally, or alternatively, optical filter coating portion <NUM> may be coated directly onto a detector or onto a set of silicon wafers including an array of detectors (e.g., using photo-lithography, a lift-off process, etc.). In some implementations, optical filter coating portion <NUM> may be associated with an incident medium. For example, optical filter coating portion <NUM> may be associated with an air medium or a glass medium as an incident medium. In some implementations, optical filter <NUM> may be disposed between a set of prisms. In another example, another incident medium may be used, such as a transparent epoxy, and/or another substrate may be used, such as a polymer substrate (e.g., a polycarbonate substrate, a cyclic olefin copolymer (COP) substrate, or the like).

<FIG> are diagrams of another example of characteristics relating to using an example implementation described herein.

As shown in <FIG>, and by chart <NUM>, a set of optical characteristics of a set of optical filters (e.g., a hydrogenated silicon (Si:H) based optical filter and a hydrogenated silicon-germanium (SiGe:H) based optical filter). In this case, the set of optical filters may utilize silicon dioxide as a low index material. As shown, a transmission percentage at a set of wavelengths is determined for the set of optical filters. In this case, the SiGe:H optical filter is associated with a refractive index of <NUM> at <NUM> and the Si:H optical filter is associated with a refractive index of <NUM> at <NUM>. As a result of the SiGe:H optical filter having a higher refractive index than the Si:H optical filter, the SiGe:H optical filter may be associated with a reduced physical thickness. For example, the Si:H optical filter may be associated with a <NUM> micrometer thickness and the SiGe:H optical filter may be associated with a <NUM> micrometer thickness. Additionally, the SiGe:H optical filter may be associated with a greater blocking efficiency (e.g., the SiGe:H optical filter may be more absorbing at approximately <NUM> than the Si:H optical filter resulting in a reduced quarter wave stack coating to block a wavelength range including <NUM>).

As shown in <FIG>, chart <NUM> shows a portion of chart <NUM> at a wavelength range of <NUM> nanometers to <NUM> nanometers. As shown in chart <NUM>, the angleshift is shown to be <NUM> for the Si:H optical filter at an angle of incidence (AOI) from <NUM> degrees to <NUM> degrees and <NUM> for the SiGe:H optical filter at an angle of incidence from <NUM> degrees to <NUM> degrees. In this case, the SiGe:H optical filter is shown to have a reduced angle shift relative to the Si:H optical filter resulting in improved optical performance.

As shown in <FIG>, and by chart <NUM>, a design of Si:H optical filters and SiGe:H optical filters, such as the optical filters of <FIG> and <FIG> and a set of optical characteristics are shown. As shown the set of optical filters are associated with a substrate size of <NUM> to <NUM> and a substrate thickness of <NUM> to <NUM>. For each wafer size and wafer thickness, the SiGe:H optical filter is associated with a reduced substrate deflection relative to the Si:H optical filter. In this way, durability and manufacturability of an optical filter is improved. Moreover, based on reducing a stress value, a substrate size may be increased for a similar substrate thickness relative to other substrate designs, based on reducing a likelihood of braking during a singulation procedure relative to other substrate designs with higher stress values.

As indicated above, <FIG> are provided merely as examples.

<FIG> and <FIG> are a diagrams of an example implementation <NUM> described herein. As shown in <FIG>, example implementation <NUM> includes a sensor system <NUM>. Sensor system <NUM> may be a portion of an optical system, and may provide an electrical output corresponding to a sensor determination. Sensor system <NUM> includes an optical filter structure <NUM>, which includes an optical filter <NUM>, and an optical sensor <NUM>. For example, optical filter structure <NUM> may include an optical filter <NUM> that performs a passband filtering functionality or another type of optical filter. Sensor system <NUM> includes an optical transmitter <NUM> that transmits an optical signal toward a target <NUM> (e.g., a person, an object, etc.).

Although implementations, described herein, may be described in terms of an optical filter in a sensor system, implementations described herein may be used in another type of system, may be used external to the sensor system, or the like. In some implementations, optical filter <NUM> may perform a polarization beam splitting functionality for the light. For example, optical filter <NUM> may reflect a first portion of the light with a first polarization and may pass through a second portion of the light with a second polarization when the second polarization is desired to be received by the optical sensor <NUM>, as described herein. Additionally, or alternatively, optical filter <NUM> may perform a reverse polarization beam splitting functionality (e.g., beam combining) for the light.

As further shown in <FIG>, and by reference number <NUM>, an input optical signal is directed toward optical filter structure <NUM>. The input optical signal may include NIR light emitted by optical transmitter <NUM> and ambient light from the environment in which sensor system <NUM> is being utilized. For example, when optical filter <NUM> is a bandpass filter, optical transmitter <NUM> may direct near infrared (NIR) light toward a user for a gesture recognition system (e.g., of a gesture performed by target <NUM>), and the NIR light may be reflected off target <NUM> (e.g., a user) toward optical sensor <NUM> to permit optical sensor <NUM> to perform a measurement of the NIR light. In this case, ambient light may be directed toward optical sensor <NUM> from one or more ambient light sources (e.g., a light bulb or the sun). In another example, multiple light beams may be directed toward target <NUM> and a subset of the multiple light beams may be reflected toward optical filter structure <NUM>, which may be disposed at a tilt angle relative to optical sensor <NUM>, as shown. In some implementations, another tilt angle may be used (e.g., a <NUM> degree tilt angle for a bandpass filter). In some implementations, optical filter structure <NUM> may be disposed and/or formed directly onto optical sensor <NUM>, rather than being disposed a distance from optical sensor <NUM>. For example, optical filter structure <NUM> may be coated and patterned onto optical sensor <NUM> using, for example, photolithography. In another example, optical transmitter <NUM> may direct NIR light toward another type of target <NUM>, such as for detecting objects in proximity to a vehicle, detecting objects in proximity to a blind person, detecting a proximity to an object (e.g., using a LIDAR technique), or the like, and the NIR light and ambient light may be directed toward optical sensor <NUM> as a result.

As further shown in <FIG>, and by reference number <NUM>, a portion of the optical signal is passed by optical filter <NUM> and optical filter structure <NUM>. Alternating silicon-germanium layers (e.g., a high index material) and another type of material layers (e.g., a low index material, such as silicon dioxide (SiO<NUM>)) of optical filter <NUM> may cause the first polarization of light to be reflected in a first direction. In an example of the claimed invention, the high index material includes a silicon-germanium based material, such as hydrogenated silicon-germanium, or the like as described herein. In this case, optical filter <NUM> blocks visible light of the input optical signal without excessively blocking NIR light and without introducing an excessive angle-shift with an increase in an angle of incidence of the input optical signal.

As further shown in <FIG>, and by reference number <NUM>, based on the portion of the optical signal being passed to optical sensor <NUM>, optical sensor <NUM> may provide an output electrical signal for sensor system <NUM>, such as for use in recognizing a gesture of the user or detecting the presence of an object. In some implementations, another arrangement of optical filter <NUM> and optical sensor <NUM> may be utilized. For example, rather than passing the second portion of the optical signal collinearly with the input optical signal, optical filter <NUM> may direct the second portion of the optical signal in another direction toward a differently located optical sensor <NUM>. In another example, optical sensor <NUM> may be an avalanche photodiode, an Indium-Gallium-Arsenide (InGaAs) detector, an infrared detector, or the like.

As shown in <FIG>, a similar example implementation <NUM> may include sensor system <NUM>, optical filter structure <NUM>, optical filter <NUM>, optical sensor <NUM>, optical transmitter <NUM>, and target <NUM>. <FIG> shows a particular example implementation <NUM> that includes an optical filter <NUM> as described herein.

Optical transmitter <NUM> emits light at an emission wavelength in a wavelength range of <NUM> to <NUM>. Optical transmitter <NUM> emits modulated light (e.g., light pulses). Optical transmitter <NUM> may be a light-emitting diode (LED), an LED array, a laser diode, or a laser diode array. Optical transmitter <NUM> emits light towards target <NUM>, which reflects the emitted light back towards sensor system <NUM>. When sensor system <NUM> is a gesture-recognition system, target <NUM> is a user of the gesture-recognition system.

Optical filter <NUM> is disposed to receive the emitted light after reflection by target <NUM>. Optical filter <NUM> has a passband including the emission wavelength and at least partially overlapping with the wavelength range of <NUM> to <NUM>. Optical filter <NUM> is a bandpass filter, such as a narrow bandpass filter. Optical filter <NUM> transmits the emitted light from the optical transmitter <NUM>, while substantially blocking ambient light.

Optical sensor <NUM> is disposed to receive the emitted light after transmission by optical filter <NUM>. In some implementations, optical filter <NUM> is formed directly on optical sensor <NUM>. For example, optical filter <NUM> may be coated and patterned (e.g., by photolithography) on sensors (e.g., proximity sensors) in wafer level processing (WLP).

When sensor system <NUM> is a proximity sensor system, optical sensor <NUM> is a proximity sensor, which detects the emitted light to sense a proximity of target <NUM>. When sensor system <NUM> is a 3D-imaging system or a gesture-recognition system, optical sensor <NUM> is a 3D image sensor (e.g., a charge-coupled device (CCD) chip or a complementary metal oxide semiconductor (CMOS) chip), which detects the emitted light to provide a 3D image of target <NUM>, which, for example, is the user. The 3D image sensor converts the optical information into an electrical signal for processing by a processing system (e.g., an application-specific integrated circuit (ASIC) chip or a digital signal processor (DSP) chip). For example, when sensor system <NUM> is a gesture-recognition system, the processing system processes the 3D image of the user to recognize a gesture of the user.

As indicated above, <FIG> and <FIG> are provided merely as an example. Other examples are possible and may differ from what was described with regard to <FIG> and <FIG>.

In this way, a set of silicon-germanium based layers may be used as a high index material for an optical filter coating of an optical filter to provide out-of-band blocking of visible light, transmission of NIR light, and/or filtering of light with a reduced angle shift relative to another type of material used for a set of high index layers. Moreover, based on using hydrogenated silicon-germanium with an optional annealing procedure, out-of-band blocking and in-band transmission are improved relative to another type of material.

Claim 1:
An optical filter (<NUM>, <NUM>), comprising:
a substrate (<NUM>);
a set of optical filter layers disposed onto the substrate (<NUM>),
the set of optical filter layers including:
a first subset of optical filter layers (<NUM>),
the first subset of optical filter layers (<NUM>) comprising silicon-germanium, SiGe, with a first refractive index, and
a second subset of optical filter layers (<NUM>),
the second subset of optical filter layers (<NUM>) comprising a material with a second refractive index,
the second refractive index being less than the first refractive index
characterised in that the first subset of layers (<NUM>) is hydrogenated and/or nitrogenated.