PATENT DOCUMENT

Publication Number: US-10222256-B2
Application Number: US-201615384102-A
Country: US
Kind Code: B2

Title: Ambient light sensor system having light-scattering desiccant

Abstract:
An ambient light sensor system may be mounted in alignment with a window in a display cover layer associated with a display in an electronic device. The ambient light sensor system may have a light diffuser layer and an infrared-light-blocking filter. The light diffuser layer may have a polymer layer with embedded light-scattering desiccant particles. An ambient light sensor in the ambient light sensor system may receive ambient light through the light diffuser layer and the infrared-light-blocking filter. The infrared-light-blocking filter may have a polymer substrate and a thin-film interference filter formed from a stack of inorganic thin-film layers on the polymer substrate. Light-scattering desiccant particles may be incorporated into the polymer substrate of the infrared-light-blocking filter. Desiccant may also be incorporated into ambient light sensor support structures.

Claims:
What is claimed is: 
     
       1. An electronic device that is exposed to ambient light, comprising:
 a display that displays images; 
 a housing in which the display is mounted; 
 a light diffuser layer having a substrate formed from a polymer that includes a first set of light-scattering desiccant particles, wherein the substrate is in contact with a polymer coating layer having a second set of light-scattering desiccant particles embedded therein; 
 an ambient light sensor in the housing configured to receive the ambient light through the polymer; 
 control circuitry configured to gather ambient light information with the ambient light sensor and configured to adjust the display based on the ambient light information; and 
 an infrared-light-blocking filter having a polymer filter substrate, wherein the infrared-light-blocking filter comprises an infrared-light-blocking filter selected from the group consisting of: an infrared-light-blocking filter having a thin-film interference filter formed from a stack of inorganic dielectric layers on the polymer filter substrate and an infrared-light-blocking filter formed from a layer of infrared-light-absorbing material on the polymer filter substrate. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the polymer filter substrate includes a third set of embedded light-scattering desiccant particles and wherein the polymer filter substrate is attached to the substrate of the light diffuser layer by the polymer coating layer. 
     
     
       3. The electronic device defined in  claim 1  wherein the infrared-light-blocking filter filters infrared light from the ambient light and allows visible light in the ambient light to pass to the ambient light sensor. 
     
     
       4. The electronic device defined in  claim 3  wherein the light diffuser layer is separate from the polymer filter substrate. 
     
     
       5. The electronic device defined in  claim 4  wherein the third set of light-scattering desiccant particles comprise light-scattering desiccant particles selected from the group consisting of: calcium chloride light-scattering desiccant particles and silicon oxide light-scattering desiccant particles. 
     
     
       6. The electronic device defined in  claim 1  wherein the polymer filter substrate is formed from an additional polymer that includes a third set of light-scattering desiccant particles. 
     
     
       7. The electronic device defined in  claim 6  wherein the third set of light-scattering desiccant particles comprise light-scattering desiccant particles selected from the group consisting of: calcium chloride light-scattering desiccant particles and silicon oxide light-scattering desiccant particles. 
     
     
       8. The electronic device defined in  claim 1  wherein the first set of light-scattering desiccant particles comprise light-scattering desiccant particles selected from the group consisting of: calcium chloride light-scattering desiccant particles and silicon oxide light-scattering desiccant particles. 
     
     
       9. The electronic device defined in  claim 8  wherein the second set of light-scattering desiccant particles are selected from the group consisting of: calcium chloride light-scattering desiccant particles and silicon oxide light-scattering desiccant particles. 
     
     
       10. The electronic device defined in  claim 1  wherein the display comprises a display cover layer having an ambient light sensor window and wherein the ambient light sensor comprises a color ambient light sensor, the electronic device further comprising a support structure that supports the color ambient light sensor in alignment with the ambient light sensor window. 
     
     
       11. The electronic device defined in  claim 10  further comprising desiccant in at least one of: the support structure and a coating on the support structure. 
     
     
       12. The electronic device defined in  claim 11  wherein the first set of light-scattering desiccant particles are configured to absorb infrared light. 
     
     
       13. An electronic device configured to be exposed to ambient light, comprising:
 a display; 
 a light diffuser layer with a polymer substrate having a first set of embedded light-scattering desiccant particles, wherein the polymer substrate is in contact with a polymer coating having a second set of embedded light-scattering desiccant particles; and 
 a color ambient light sensor configured to receive the ambient light through a portion of the display and through the light diffusing layer. 
 
     
     
       14. The electronic device defined in  claim 13  wherein the first set of embedded light-scattering desiccant particles comprise calcium chloride particles. 
     
     
       15. The electronic device defined in  claim 13  wherein the infrared-light-blocking filter is interposed between the light diffuser layer and the color ambient light sensor. 
     
     
       16. An ambient light sensor system configured to monitor ambient light, comprising:
 a light diffusing layer having a polymer substrate containing a first set of light-scattering desiccant particles, wherein the polymer substrate is in contact with a polymer coating containing a second set of light-scattering desiccant particles; 
 an infrared-light-blocking filter layer; and 
 a semiconductor device containing light detectors configured to measure different colors of the ambient light received through the light diffusing layer and the infrared-light-blocking filter layer. 
 
     
     
       17. The ambient light sensor system defined in  claim 16  wherein the infrared-light-blocking filter layer includes a polymer substrate and includes calcium chloride particles in the polymer substrate and wherein the infrared-light-blocking filter layer comprises an infrared-light-blocking filter layer selected from the group consisting of: an infrared-light-blocking filter layer having a thin-film interference filter formed from a stack of inorganic thin-film layers on the polymer substrate and an infrared-light-blocking filter layer having an infrared-light-blocking layer on the polymer substrate. 
     
     
       18. The ambient light sensor system defined in  claim 16  wherein the first set of light-scattering desiccant particles are at least 10 microns in diameter.

Description:
This application claims the benefit of provisional patent application No. 62/398,178, filed Sep. 22, 2016, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices, and, more particularly, to light sensors for electronic devices. 
     BACKGROUND 
     Electronic devices such as laptop computers, cellular telephones, and other equipment are sometimes provided with light sensors. For example, ambient light sensors may be incorporated into a device to provide the device with information on current lighting, conditions. Ambient light readings may be used in controlling the device. If, for example bright daylight conditions are detected, an electronic device may increase display brightness to compensate. 
     Ambient light conditions sometimes include significant changes in color. For example, an electronic device may be used in a cool color temperature environment such as outdoors shade or warm color temperature environment such as an indoors environment that is lit with incandescent lighting. Content that appears to be correctly displayed on a display in one of these environments may have an unpleasant color cast in the other environment. For example, a display that is properly adjusted in an outdoors environment may appear overly cool under incandescent lighting. To allow adjustments of display color based on ambient light color measurements, electronic devices may be provided with color ambient light sensors. 
     Ambient light sensor systems can be challenging to design. If care is not taken, ambient light sensors will be overly sensitive to the variations in the angle-of-incidence of light, will be affected by noise from infrared light, and will degrade due to environmental effects. 
     SUMMARY 
     An electronic device may be provided with an ambient light sensing system. The ambient light sensing system may have an ambient light sensor such as a color ambient, light sensor that is mounted in alignment with a window in a display cover layer associated with a display in the electronic device. 
     The ambient light sensing system may have a light diffuser layer and an infrared-light-blocking filter. The light diffuser may have a polymer light diffuser layer with embedded light-scattering desiccant particles. The color ambient light sensor may receive ambient light through the light diffuser layer and the infrared-light-blocking filter. The infrared-light-blocking filter may have a polymer substrate and a thin-film interference filter formed from a stack of inorganic thin-film layers on the polymer substrate. Light-scattering desiccant particles may be incorporated into the polymer substrate of the infrared-light-blocking filter. Polymer coating layers and other layers in the light diffuser and filter may also include light-scattering desiccant particles. 
     Desiccant may be incorporated into ambient light sensor support structures that hold the ambient light sensor in alignment with the window in the display cover layer. For example, desiccant particles can be incorporated into a polymer or other material that is used in forming a housing, or other support structure that holds an ambient light sensor in alignment with the window in the display cover layer. 
     If desired, the desiccant particles can absorb infrared light while passing (scattering) visible light. Infrared-light-absorbing desiccant particles may help enhance the amount of infrared light that is blocked and may therefore help reduce dependence on the infrared-light-blocking filter to block infrared light. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device having an ambient light sensor in accordance with an embodiment. 
         FIG. 2  is a perspective view of a portion of an electronic device display within which an ambient light sensor has been mounted in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative light sensor that is being exposed to ambient light in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of an illustrative light diffuser and visible-light-transmitting-and-infrared-light-blocking filter for an ambient light sensor in accordance with an embodiment. 
         FIG. 5  is a graph of illustrative diffuser and infrared-light-blocking filter performance in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative diffuser having light diffusing desiccant particles in a substrate layer in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of an illustrative diffuser having light diffusing polymer coatings with light-scattering desiccant particles on a substrate such as a polymer light diffuser substrate with optional light diffusing desiccant particles in accordance with an embodiment. 
         FIG. 8  is cross-sectional side view of an illustrative infrared-light-blocking thin-film interference filter formed on a filter substrate that includes light diffusing desiccant particles in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of an illustrative light diffuser layer and infrared-light-blocking thin-film filter for an ambient light sensor in accordance with an embodiment. 
         FIG. 10  is a cross-sectional side view of a portion of an electronic device with an illustrative ambient light sensing system in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with one or more light sensors is shown in  FIG. 1 . Electronic device  10  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation, device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     As shown in  FIG. 1 , electronic device  10  may have control circuitry  16 . Control circuitry  16  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  16  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Input-output circuitry in device  10  such as input-output devices  12  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  12  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  12  and may receive status information and other output horn device  10  using the output resources of input-output devices  12 . 
     Input-output devices  12  may include one or more displays such as display  14 . Display  14  may be a touch screen display that includes a touch sensor for gathering touch input from a user or display  14  may be insensitive to touch. A touch sensor for display  14  may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, a light-based touch sensor, or other suitable touch sensor arrangements. 
     Input-output devices  12  may also include sensors  18 . Sensors  18  may include one or more ambient light sensors and other sensors (e.g., a capacitive proximity sensor, a light-based proximity sensor, a magnetic sensor, an accelerometer, a force sensor, a touch sensor, a temperature sensor, a pressure sensor, a compass, a microphone or other sound sensor, or other sensors). 
     Ambient light sensors for device  10  may be used to gather information on the intensity of ambient light and, if desired, ambient light color. Monochromatic ambient light sensors may be used to make ambient light intensity measurements so that device  10  can automatically adjust display brightness or take other actions based on ambient light levels. Color ambient light sensors can measure intensity and color information (e.g., color temperature, etc.). Device  10  may also include light detectors that measure light associated with a light-based proximity sensor or other incoming light. Illustrative configurations in which device  10  includes a color ambient light sensor may sometimes be described herein as an example. If desired, device  10  may include one or more light detectors such as one or more ambient light sensors and these ambient light sensors may be monochrome ambient light sensors and/or color ambient light sensors. 
     A color ambient light sensor for device  10  may have an a ray of detectors each of which is provided with a different respective color filter or other structures that provide that detector with sensitivity to a particular spectral range (e.g., a particular color in the visible light spectrum). Information from the detectors may be used to measure the total amount of ambient light that is present in the vicinity of device  10 . For example, the ambient light sensor may be used to determine whether device  10  is in a dark or bright environment. Based on this information, control circuitry  16  can adjust display brightness for display  14  or can take other suitable action. The array of colored detectors may also be used to make color measurements (i.e. the ambient light sensor may be a color ambient light sensor). Color measurements may be gathered as color coordinates, color temperature, or correlated color temperature. Processing circuitry may be used to convert these different types of color information to other formats, if desired (e.g., a set of color coordinates may be processed to produce an associated correlated color temperature, etc.). 
     Ambient light color information and ambient light intensity information from a color sensing ambient light sensor can be used to adjust the operation of device  10 . For example, the color cast of display  14  may be adjusted in accordance with the color of ambient lighting conditions. If for example, a user moves device  10  from a cool lighting environment to a warm lighting environment (e.g., an incandescent light environment), the warmth of display  14  may be increased accordingly, so that the user of device  10  does not perceive display  14  as being overly cold. In general, any suitable actions may be taken based on color measurements and/or total light intensity measurements (e.g., adjusting display brightness, adjusting display content, changing audio and/or video settings, adjusting sensor measurements from other sensors, adjusting which on-screen options are presented to a user of device  10 , adjusting wireless circuitry settings, etc.). 
     A perspective view of a portion of an illustrative electronic device is shown in  FIG. 2 . In the example of  FIG. 2 , device  10  includes a display such as display  14  mounted in housing  22 . Housing  22 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  22  may be formed using a unibody configuration in which some or all of housing  22  is machined or molded as a single structure or may be formed using multiple structures (e.g. an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass, clear plastic, sapphire, or other clear layer. Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button, a speaker port, or other components. Openings may be formed in housing  22  to form communications ports (e.g., an audio jack port, a digital data port, etc.), to form openings for buttons, etc. 
     Display  14  may include an array of display pixels formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of plasma pixels, an array of organic light-emitting diode pixels or other light-emitting diodes, an array of electrowetting pixels, or pixels based on other display technologies. The array of pixels of display  14  forms an active area AA. Active area AA is used to display images for a user of device  10 . Active area AA may be rectangular or may have other suitable shapes. 
     Active area AA may cover the entire front face of device  10  (as an example) or an inactive region such as inactive border area IA may run along one or more edges of active area AA. Inactive border area IA may contain circuits, signal lines, and other structures that do not emit light for forming images. To hide inactive circuitry and other components in border area IA from view by a user of device  10 , the underside of the outermost layer of display  14  (e.g., the display cover layer or other display layer) may be coated with an opaque masking material such as a layer of black ink. Optical components (e.g., a camera, a light-based proximity sensor, an ambient light sensor, status indicator light-emitting diodes, camera flash light-emitting diodes, etc.) may be mounted under inactive border area IA or may be mounted under small windows in display  14  that are located in active area AA. Optical components may also be mounted in ports in housing  12 . Configurations for device  10  in which optical components are mounted under inactive border area IA may sometimes be described herein as an example. 
     If desired, one or more openings (sometimes referred to as windows) may be formed in an opaque masking layer formed on the underside of a display cover layer in inactive area. IA of display  14  to accommodate optical components. For example, alight component window such as an ambient light sensor window may be formed in a peripheral portion of display  14  such as, region  20  in inactive border area IA. Ambient light from the exterior of device  10  may be measured by an ambient light sensor in device  10  after passing through region  20  and the display cover layer. 
       FIG. 3  is a cross-sectional side view of display  14  of  FIG. 2  taken along line  24  and viewed in direction  25  of  FIG. 2 . As shown in  FIG. 3 , light sensor  26  may be mounted in alignment with window  20 . Window  20  may have a circular shape, a square shape, a shape with curved and/or straight edges, a circular ring shape with a central opaque region, or any other suitable shape. The diameters of window  20  may be 0.1 to 1 mm, less than 2 mm, more than 0.05 mm, or other suitable size. Light sensor  26  may be a color sensing ambient light sensor that is used in measuring ambient light in the vicinity of device  10 . As shown in  FIG. 3 , display  14  may have an outermost layer such as display cover layer  30 . Display cover layer  30  has an outer surface such as surface  34 . Surface normal n is perpendicular to surface  34 . Rays of ambient light  52  are characterized by various angles of incidence A measured with respect to surface normal n. 
     Window  20  may be formed from an opening in opaque masking layer  28  on inner surface  32  of display cover layer  30  in inactive area IA. Layer  30  may be formed from glass, plastic, ceramic, sapphire, or other transparent materials and may be a part of a display module for display  14  or may be a separate, protective layer that covers active display structures. The opening associated with window  20  may be filled with optical structures such as ambient light sensor ink  54 , light diffuser  56 , and infrared-light-blocking filter  64  and may be aligned with color ambient light sensor  26 . 
     Ambient light sensor ink  54  may have sufficient transparency at visible wavelengths to allow sensor  26  to operate (e.g., to allow sensor  26  to receive ambient light  52  through ink  54 ), while at the same time enhancing the outward appearance of window  20  (e.g., by partly obscuring the presence of window  20  to a user of device  10  by making window  20  have a visual appearance that is not too dissimilar from the portion of layer  30  that includes layer  28 ). If desired, ambient light sensor ink  54  may be omitted (e.g., sensor  26  may be mounted under a clear window in layer  28 . Configurations in which layer  28  has sufficient transparency to allow visible light to pass through layer  28  to sensor  26  may also be used. Arrangements of the type shown in  FIG. 3  in which incoming ambient light  52  passes through a window having ambient light sensor ink  54  in an opening in layer  28  that is aligned with diffuser  56  and infrared-light-blocking filter  64  may sometimes be described herein as an example. 
     Sensor  26  may have multiple light detectors  60  (e.g., photodiodes, phototransistors, or other semiconductor photodetector structures). Light detectors  60  may be formed in an array on a common semiconductor substrate (die) such as substrate  62  or may be formed using two or more substrates. Each of light detectors  60  may be provided with a corresponding color filter  58 , To provide sensor  26  with the ability to accurately measure colors, sensor  26  may include two or more detectors  60  (e.g., 2-10 detectors, 3-8 detectors, 4-7 detectors, 5-7 detectors, only 4 detectors or more than 4 detectors, only 5 detectors or more than 5 detectors, only 6 detectors or more than 6 detectors, only 7 detectors or more than 7 detectors, only 8 detectors or more than 8 detectors, fewer than 8 detectors, or any other suitable number of detectors). Filters  58  may be thin-film interference filters and/or may be colored layers of polymer or other color filter elements (e.g., colored filters formed from dyes and/or pigments). 
     Light diffuser (light diffuser layer)  56  may be used to gather light  52  from a variety of angles of incidence A and to effectively pass this light to sensor  26 . Light diffuser  56  may include light-scattering particles (and, if desired, protrusions, recesses, and/or other light-scattering features) that help redirect off-axis ambient light rays into sensor  26  at an angle that is close to perpendicular to the surface of substrate  62 , thereby reducing the dependence of ambient light readings on the relative orientation between device  10  and the sources of ambient light. 
     Infrared-light-blocking filter (filter layer)  64 , which may sometimes be referred to as a visible-light-passing-and-infrared-light-blocking filter or infrared cut filter, may allow visible ambient light to pass and may block infrared light (e.g., near-infrared light at wavelengths of 700 nm to 2500 nm or at other near-infrared wavelengths). Filter  64  may include a substrate formed from a polymer film and/or other materials (e.g., glass, etc.) and may include a stack of thin films that form a thin-film interference filter that blocks infrared light (as an example). If desired, filter  64  may be formed from a material with bulk infrared-light-absorption and visible-light-transparency properties (e.g., a thin metal layer such as a thin layer of silver or gold, a semiconductor layer, etc.). This material may be incorporated into filter  64  above or below a thin-film interference filter stack that blocks infrared light while transmitting visible light or may be used in place of the thin-film interference filter structure (e.g., filter  64  may be formed exclusively from a material that absorbs infrared light and transmits visible light without using multiple alternating refractive index layers to form a thin-film interference filter). By filtering out infrared light from light  52 , noise in sensor  26  may be reduced. 
       FIG. 4  illustrates how light  52  may be diffused while passing through diffuser  56  and infrared light-blocking filer  64 . As shown in  FIG. 4 , incoming ambient light rays such as ray  52  may be diffused when passing through diffuser  56  and filter  64  and may produce scattered rays  52 ′ that are measured by sensor  26 . The incorporation of light diffusing structures into the incoming, light path for ambient light  52  helps collect light by redirecting incoming off-axis light back towards sensor  26 . The light diffusing structures of device  10  (e.g., diffuser  56 ) may exhibit a Lambertian scattering profile (e.g., radiance through diffuser  56  may be independent of the angle of incident light) or may exhibit a scattering profile that differs at any, angle of light incidence on the diffuser by less than 20% from a Lambertian scattering profile at that angle of light incidence (as examples). 
       FIG. 5  is a graph showing an illustrative light transmission T that may be associated with diffuser  56  (curve  100 ) and that may be associated with diffuser  56  stacked with infrared-light-blocking filter  66  (curve  102 ). Infrared-light-blocking filter  66  may block light at wavelengths above 650 nm, above 700 nm, or at other suitable wavelengths. If desired, diffuser  56  may exhibit less diffusion (e.g., to enhance transmission T) and/or may exhibit more diffusion (e.g., to enhance light uniformity). In general, transmission T may be 30-70%, more than 40%, more than 60%, less than 70%, less than 50%, or other suitable values for visible light wavelengths. The configuration of  FIG. 5  is merely illustrative. 
       FIG. 6  is a cross-sectional side view of an illustrative light diffuser. In the illustrative configuration of  FIG. 6 , light diffuser  56  includes a substrate layer such as light diffuser substrate  70 . Substrate  70  may, as an example, be a polymer film such as a film of polymethylmethacrylate or other polymer that is transparent to visible light. To help prevent moisture-induced degradation to substrate  70  while providing light-scattering centers that scattering ambient light  52 , light-scattering desiccant particles  72  may be incorporated into substrate  70 . Particles  72  may be, for example, particles of an inorganic material such as calcium chloride (CaCl 2 ) or silicon oxide (SiO 2 ) that have a different index of refraction than substrate  70  and that therefore scatter light  52  and that have water absorbing qualities that allow the material to serve as desiccant that reduces or eliminates moisture in substrate  70 . If desired, desiccant particles  72  may be configured, to absorb infrared light while scattering visible light. In configurations in which infrared-light-absorbing desiccant particles block additional infrared light, dependence on the infrared-light-blocking filter  66  to block infrared light may be reduced. 
     Light-scattering desiccant particles  72  may be incorporated into a polymer such as the polymer of substrate  70  during manufacturing processes such as casting, extrusion, injection molding, rolling, etc. The diameters of particles  72  may be 10-50 microns, more than 5 microns, less than 100 microns, or other suitable size. Substrate  70  may have lateral dimensions of 0.2-2 mm, more than 0.3 mm, less than 1 mm, or other suitable size and may have a thickness of 100 microns, more than 0.05 mm, more than 0.1 mm, less than 1 mm, less than 0.5 mm, less than 0.2 mm, or other suitable size. If desired, non-desiccant light diffusing particles may also be incorporated into substrate  70  to enhance light diffusion (e.g., titanium dioxide particles or other particles that have a refractive index that differs from the refractive index of substrate  70  may be incorporated into substrate  70 ). Configurations in which particles  72  are light-scattering desiccant particles such as calcium chloride particles or silicon oxide particles may sometimes be described herein as an example. 
     If desired, particles  72  may be provided in coating layers on one or both surfaces of substrate  70 . Consider, as an example, the arrangement of light diffuser  56  of  FIG. 7 . In the example of  FIG. 7 , light diffuser  56  includes central layer  56 - 1  (e.g., a substrate layer) and one or more additional layers  56 - 2  (e.g., coating layers). 
     Layer  56 - 1  may be formed from polymer or other substrate material (e.g., material  70 ) and may include optional embedded light-scattering desiccant particles  72 . Coatings  56 - 2  may be formed from binder material  74  (e.g., polymer) into which light-scattering desiccant particles  72  have been embedded. Binder material  74  may be glass or polymethylmethacrylate or other polymer and may, if desired, serve as an adhesive layer to help attach light diffuser  56  to other structures in device  10 . 
     If desired, light-scattering desiccant particles  72  may be embedded within substrate  76  of infrared-light-blocking filter  64 , as shown in  FIG. 8 . Filter  64  may include a stack of thin-film layers  78  on substrate  76 . Thin-film layers  78  may include, for example organic dielectric layers or inorganic dielectric layers with alternating refractive index values (e.g., higher refractive index layers and lower refractive index layers). Thin-film layers  78  may form a stack containing 3-15 layers, 4-10 layers, more than 4 layers, fewer than 25 layers, or other suitable number of thin-film layers. Thin-film layers  78  may be configured to form a visible-light-transmitting-and-infrared-light blocking thin-film interference filter. If desired, a layer of bulk material that absorbs infrared light and transmits visible light may be incorporated into layers  78 . Substrate  76  may include a substrate material such as substrate material  80  (e.g., glass or polymethylmethacrylate or other polymer) and optional embedded light-scattering desiccant particles  72 . The incorporation of light-scattering particles in substrate  76  helps diffuse light  52 . The incorporation of desiccant material in substrate  76  and filter  64  helps, reduce the vulnerability of filter  64  to degradation from moisture. 
       FIG. 9  is a cross-sectional side view of illustrative light diffusing and infrared-light-blocking structures of the type that may be included in device  10 . In the illustrative configuration of  FIG. 9 , light diffuser  56  has a substrate formed from polymer layer  70 . Layer  70  may include light-scattering desiccant particles  72 . Layer  74  (e.g., an adhesive layer formed from polymer material) may contain optional light-scattering particles  72  and may be used to attach light diffuser  56  to infrared-light-blocking filter  64 . Infrared-light-blocking filter  64  may include substrate  76  (e.g., polymer  80  with optional embedded light-scattering desiccant particles  72 ) and may include a stack of thin-film interference filter layers  78  for forming a visible-light-passing-and-infrared-light-blocking thin-film interference filter on substrate layer  76 . Layers  78  may, if desired, be interposed between layer  70  and layer  76 . The configuration in which layer  76  is interposed between layer  74  and layers  78  is illustrative. 
       FIG. 10  is a cross-sectional side view of an illustrative ambient light sensing system for device  10 . In the example of  FIG. 10 , ambient light sensor  26  has been mounted in support structure  90  (sometimes referred to as an ambient light sensor boot). Support structure  90  may be used to mount sensor  26  under window  20  in display  14 . Support structure  90  may be formed from black polymer or other suitable materials and may have the shape of a five-sided box (e.g., a box with an open top facing window  20 ) or other suitable shape. To help reduce the effects of moisture, desiccant (e.g., calcium chloride desiccant, silicon oxide desiccant, etc.) such as desiccant  92  may be embedded in support structure  90 . Desiccant  92  may also be formed on the inner surface of support structure  90 , as shown by illustrative polymer coating layer  94 , which includes desiccant particles  92 . 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20161219
Publication Date: 20190305
Grant Date: 20190305
Priority Date: 20160922
Inventors: NAYAK, Aditya B.
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G5/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0488", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/0242", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/02", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0474", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J1/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0488", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0474", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/208", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/4228", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0233", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/208", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/223", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/0242", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/02", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/223", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/0242", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0474", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/02", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0488", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/208", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/223", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/4228", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0233", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 61620204