Patent Publication Number: US-11665310-B2

Title: Ambient light sensor windows for electronic devices comprising an optical sensor within an opening in the locally thinned area of an opaque layer

Description:
This application is a continuation of U.S. patent application Ser. No. 16/428,635, filed May 31, 2019, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices, and, more particularly, to electronic devices with optical components such as light sensors. 
     BACKGROUND 
     Electronic devices may have optical components such as light sensors. For example, electronic devices may have ambient light sensors for measuring ambient light levels. During operation of an electronic device with an ambient light sensor, display characteristics such as display brightness and color cast can be adjusted based on ambient light intensity and color measurements. 
     It can be challenging to incorporate an ambient light sensor into an electronic device. If care is not taken, the presence of an ambient light sensor may adversely affect a device&#39;s appearance or an ambient light sensor may not gather ambient light readings accurately. 
     SUMMARY 
     An electronic device may have a housing with a display. The housing may be supported on a desktop by a stand or may have other configurations. The display may have a display cover layer that overlaps an array of pixels. The array of pixels may form an active area of the display that displays images for a user. 
     A layer of black ink or other opaque material may be formed on an inner surface of the display cover layer in an inactive area of the display that does not overlap pixels. The housing may have walls such as a rear housing wall that faces away from the display. 
     Ambient light sensor windows may be formed in the device to allow ambient light from the exterior region surrounding the device to reach ambient light sensors in the interior of the device. Ambient light sensor windows may be formed on opposing front and rear sides of the device or other suitable locations on the device. 
     Ambient light sensor windows may be formed from tapered holes or other holes. The tapered holes may be formed in the opaque material on the display cover layer, may be formed in a rear housing wall or other housing structure, or may be formed in other portions of the electronic device. Non-tapered holes may also be used in forming ambient light sensor windows. In some configurations, tapered and/or non-tapered holes in opaque structures in a device may be used in forming optical component windows for components other than ambient light sensors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG.  2    is a cross-sectional side view of an illustrative opaque layer with tapered holes for forming an optical component window such as a light sensor window in accordance with an embodiment. 
         FIG.  3    is a cross-sectional side view of illustrative ambient light sensor window formed from tapered holes in an opaque layer on a display cover layer in accordance with an embodiment. 
         FIG.  4    is a cross-sectional side view of an illustrative electronic device with front and rear light sensors in accordance with an embodiment. 
         FIG.  5    is a plan view of illustrative tapered holes for an ambient light sensor window in accordance with an embodiment. 
         FIG.  6    is a cross-sectional side view of the illustrative holes of  FIG.  5    in accordance with an embodiment. 
         FIG.  7    is a plan view of additional illustrative tapered holes for an ambient light sensor window in accordance with an embodiment. 
         FIG.  8    is a cross-sectional side view of the illustrative holes of  FIG.  7    in accordance with an embodiment. 
         FIG.  9    is a cross-sectional side view of an illustrative optical component window such as an ambient light sensor window in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device may have optical components. The optical components may operate through transparent portions of a device that serve as optical component windows and that allow light to pass between the exterior and interior of the device. The optical components may include, for example, light sensors such as ambient light sensors. 
     Ambient light sensors may be used to gather measurements of ambient light intensity and color. During operation of an electronic device, display adjustments may be made and other actions may be taken based on ambient light sensor measurements. For example, display characteristics such as display brightness and/or display color cast may be adjusted based on measurements of ambient light intensity and/or ambient light color. 
     Optical component windows are sufficiently transparent to allow light to pass from the interior of the electronic device to the exterior of the electronic device and to allow light to pass from the exterior of the electronic device to the interior. For example, an ambient light sensor window is sufficiently transparent to allow visible light from the exterior of an electronic device to pass to an ambient light sensor in the interior that is aligned with the ambient light sensor window. 
     Ambient light sensor windows may be formed within opaque structures in an electronic device such as within opaque border regions in a display or within opaque housing wall structures. To ensure that the ambient light sensor windows are sufficiently transparent, the opaque structures may be provided with holes. The holes may, as an example, allow light to pass from the exterior of the device through the opaque structures to an ambient light sensor in the interior of the device. 
     A perspective view of an illustrative electronic device with optical component windows such as ambient light sensor windows is shown in  FIG.  1   . Electronic device  10  may have a display such as display  14  mounted in a housing such as housing  12 . Device  10  of  FIG.  1    is a desktop device (e.g., a desktop computer, stand-alone display, or other desktop equipment) that is supported by stand  18  on a support surface such as a desktop. Other types of electronic devices may be provided with ambient light sensor windows if desired. Electronic device  10  may be, for example, a computing device such as a laptop computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wristwatch 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 display, a gaming device, a navigation device, an embedded system such as a system mounted in a kiosk or automobile, or other electronic equipment. 
     Housing  12  may be formed from polymer, metal, glass, crystalline material such as sapphire, ceramic, fabric, fibers, fiber composite material, natural materials such as wood and cotton, other materials, and/or combinations of such materials. Housing  12  may be configured to form housing walls. The housing walls may enclose an interior region within device  10  and may separate the interior region from an exterior region surrounding device  10 . The housing walls may include a rear wall on rear side (surface) R of device  10 , opposing front side (surface) F of device  10 . 
     Display  14  may be a liquid crystal display, an organic light-emitting diode display, or other suitable display. Display  14  may be covered with a transparent display cover layer that covers sensitive display circuitry. The display cover layer may be formed from glass, crystalline material such as sapphire, clear polymer, other transparent materials, and/or combinations of these materials. The display cover layer may be coupled to metal housing walls or other housing structures and may sometimes be referred to as forming transparent housing structures or a transparent housing wall. 
     The display cover layer may overlap active area AA of display  14  on front side F of device  10 . Active area AA may include an array of pixels that display an image for viewing by a user of device  10 . One or more portions of the display cover layer may also overlap inactive display areas such as inactive area IA. Inactive area IA may contain display driver circuitry and other components, but does not include pixels and does not display images. Inactive area IA may, as an example, form a pixel-free border for active area AA that runs along four peripheral edges of device  10 . 
     A layer of opaque material (e.g., black ink formed from black dye and/or black particles in a polymer or other opaque materials in polymer) may be formed as a coating on an inner surface of the display cover layer in inactive area IA. This opaque coating layer, which may sometimes be referred to as an opaque masking layer, black ink layer, opaque ink layer, etc., may be black, white, gray, silver, or other neutral colors or may have a non-neutral color (e.g., red, blue, yellow, etc.). In some configurations, the opaque coating layer may be formed from multiple sublayers. The opaque coating layer may be visible from the exterior of device  10  (e.g., through peripheral portions of the display cover layer). Due to the presence of the opaque coating layer in inactive area IA, display driver circuitry and other components in inactive area IA may be hidden from view from the exterior of device  10 . 
     Ambient light sensor windows for device  10  may be mounted within opaque portions of device  10  such as within an opaque portion of housing  12  on rear side R, within opaque sidewall portions of housing  12 , and/or within the opaque coating on the inner surface of the display cover layer in inactive area  14  on front side F. As an example, ambient light sensor  20  may be mounted along the upper peripheral edge of device  10  in inactive area IA, as shown in  FIG.  1   . 
     Electrical components  22  may be mounted in the interior of device  10  (e.g., between the cover layer that covers display  14  on front side F and an opposing rear housing wall on rear side R). Components  22  may include integrated circuits, discrete components, light-emitting components, sensors, and/or other circuits. Electrical components  22  may include control circuitry. The control circuitry 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 the control circuitry may be used to control the operation of device  10 . For example, the processing circuitry may use sensors and other input-output circuitry to gather input and to provide output, to transmit signals to external equipment, to adjust display  14 , and/or to perform other tasks. 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. The control circuitry may include wired and/or wireless communications circuitry (e.g., antennas and associated radio-frequency transceiver circuitry such as cellular telephone communications circuitry, wireless local area network communications circuitry, etc.). The communications circuitry of the control circuitry may allow device  10  to communicate with other electronic devices. For example, the control circuitry (e.g., communications circuitry in the control circuitry) may be used to allow wired and/or wireless control commands and other communications to be conveyed between devices such as cellular telephones, tablet computers, laptop computers, desktop computers, head-mounted devices, handheld controllers, wristwatch devices, other wearable devices, keyboards, computer mice, remote controls, speakers, accessory displays, accessory cameras, and/or other electronic devices. Wireless communications circuitry may, for example, wirelessly transmit control signals and other information to external equipment in response to receiving user input or other input from sensors or other devices in components  22 . 
     Input-output circuitry in components  22  of device  10  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. The input-output circuitry may include input devices that gather user input and other input and may include output devices that supply visual output, audible output, or other output. 
     Output may be provided using light-emitting diodes (e.g., crystalline semiconductor light-emitting diodes for status indicators and/or displays, organic light-emitting diodes in displays and other components), lasers, and other light-emitting devices, audio output devices (e.g., tone generators and/or speakers), haptic output devices (e.g., vibrators, electromagnetic actuators, piezoelectric actuators, and/or other equipment that supplies a user with haptic output), and other output devices. 
     The input-output circuitry of device  10  (e.g., the input-output circuitry of components  22 ) may include sensors. Sensors for device  10  may include force sensors (e.g., strain gauges, capacitive force sensors, resistive force sensors, etc.), audio sensors such as microphones, touch and/or proximity sensors such as capacitive sensors (e.g., a two-dimensional capacitive touch sensor integrated into a display, a two-dimensional capacitive touch sensor and/or a two-dimensional force sensor overlapping a display, and/or a touch sensor or force sensor that forms a button, trackpad, or other input device not associated with a display), and other sensors. Touch sensors for a display or for other touch components 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. If desired, a display may have a force sensor for gathering force input (e.g., a two-dimensional force sensor may be used in gathering force input on a display). 
     If desired, the sensors may include optical sensors such as optical sensors that emit and detect light, ultrasonic sensors, optical touch sensors, optical proximity sensors, and/or other touch sensors and/or proximity sensors, monochromatic and color ambient light sensors such as ambient light sensor  20 , image sensors, fingerprint sensors, temperature sensors, sensors for measuring three-dimensional non-contact gestures (“air gestures”), pressure sensors, sensors for detecting position, orientation, and/or motion (e.g., accelerometers, magnetic sensors such as compass sensors, gyroscopes, and/or inertial measurement units that contain some or all of these sensors), health sensors, radio-frequency sensors (e.g., sensors that gather position information, three-dimensional radio-frequency images, and/or other information using radar principals or other radio-frequency sensing), depth sensors (e.g., structured light sensors and/or depth sensors based on stereo imaging devices), optical sensors such as self-mixing sensors and light detection and ranging (lidar) sensors that gather time-of-flight measurements, humidity sensors, moisture sensors, gaze tracking sensors, three-dimensional sensors (e.g., time-of-flight image sensors, pairs of two-dimensional image sensors that gather three-dimensional images using binocular vision, three-dimensional structured light sensors that emit an array of infrared light beams or other structured light using arrays of lasers or other light emitters and associated optical components and that capture images of the spots created as the beams illuminate target objects, and/or other three-dimensional image sensors), facial recognition sensors based on three-dimensional image sensors, and/or other sensors. 
     In some configurations, components  22  may include mechanical devices for gathering input (e.g., buttons, joysticks, scrolling wheels, key pads with movable keys, keyboards with movable keys, and other devices for gathering user input). During operation, device  10  may use sensors and/or other input-output devices in components  22  to gather user input (e.g., buttons may be used to gather button press input, touch and/or force sensors overlapping displays can be used for gathering user touch screen input and/or force input, touch pads and/or force sensors may be used in gathering touch and/or force input, microphones may be used for gathering audio input, etc.). The control circuitry of device  10  can then take action based on this gathered information (e.g., by transmitting the information over a wired or wireless path to external equipment, by supplying a user with output using a haptic output device, visual output device, an audio component, or other input-output device in housing  12 , etc.). 
     If desired, electronic device  10  may include a battery or other energy storage device, connector ports for supporting wired communications with ancillary equipment and for receiving wired power, and other circuitry. In some configurations, device  10  may serve as an accessory and/or may include a wired and/or wireless accessory (e.g., a keyboard, computer mouse, remote control, trackpad, etc.). 
     Ambient light sensor windows and other optical component windows in device  10  transmit sufficient light to allow aligned optical components to receive or emit light. For example, ambient light sensors that are overlapped by ambient light sensor widows may gather ambient light measurements. The transmission of an ambient light sensor window may be, for example, at least 0.5%, at least 1%, at least 2%, at least 10%, at least 50%, less than 100%, less than 60%, less than 20%, or other suitable value. In an illustrative configuration, the light that passes through an ambient light sensor window passes mostly or entirely through holes that are formed within an opaque material (e.g., a metal housing layer or a housing wall of other opaque material, an opaque layer in an inactive portions of a display, etc.). The holes may be air-filled holes or the holes may be filled with clear material such as clear polymer that does not affect the spectrum of the light passing through the holes. 
     A cross-sectional side view of an illustrative hole for an ambient light sensor window (or other optical component window) is shown in  FIG.  2   . As shown in  FIG.  2   , a through hole such as hole  30  may be formed in opaque structure  36 . Opaque structure  36  may be a coating of opaque masking material (e.g., a layer of black ink or other opaque ink on a display cover layer), a housing wall (e.g., a housing wall formed from a layer of metal or opaque polymer), an opaque layer formed from other materials and/or multiple layers of these material, and/or other opaque structures in device  10 . 
     Hole  30  may separate region  34  from region  38 . Region  38  may be in the interior of device  10  (e.g., in the interior of housing  12 ). An ambient light sensor may be located in region  38  in alignment with an ambient light sensor window formed from an array of multiple holes such as hole  30 . Region  34  may encompass the exterior region surrounding device  10  and may include housing walls, a display cover layer, and/or other device structures that separate the exterior region from the interior of device  10 . One or more ambient light sources such as the sun, interior and/or exterior lighting, and other sources of light (e.g., visible light) may be located in the exterior region and may produce light rays such as illustrative light rays  46 ,  48 , and  50 . 
     Hole  30  may have tapered sidewalls such as sidewalls  42 . Hole  30  may be conical (frustoconical) and may be rotationally symmetric about longitudinal axis  52  and/or may have other shapes. Sidewalls  42  may be tilted away from axis  52  and may therefore be characterized by a surface normal that is not perpendicular to axis  52 . Opaque layer  36  may be characterized by outwardly facing (outer) surface  54  and opposing inwardly facing (inner) surface  56 . When a tapered hole shape is used for hole  30 , hole  30  has a first outwardly facing (outer) opening TP in surface  54  (sometimes referred to as a light entrance opening) and a second larger inwardly facing (inner) opening BT in surface  56  (sometimes referred to as a light exit opening). Openings TP and BT may have circular outlines (footprints when viewed from above) or other suitable shapes. 
     Hole  30  may be filled with clear material  40  (e.g., clear polymer) or may be filled with air. In the absence of the tapered shape of hole  30 , incoming ambient light rays such as illustrative ambient light ray  46  might reflect off of vertical hole sidewall surfaces such as surface  44  as shown by reflected ray  46 ′ and might be spectrally altered by the reflection spectrum associated with layer  36 . This could degrade color accuracy for ambient light measurements. The intensity of light may also be reduced due to reflection off of vertical hole sidewall surfaces, which could degrade brightness accuracy for ambient light measurements. 
     In the presence of tapered sidewalls  42 , however, incoming ambient light rays such as illustrative light ray  48  will not strike sidewalls  42  before being detected by the ambient light sensor in region  38 . This enhances color and brightness accuracy. In the presence of clear polymer or other solid materials having an index of refraction greater than that of air (e.g., greater than 1), incoming light rays are refracted. Consider, as an example, incoming ambient light ray  50 , which is refracted towards surface normal n of surface  56  to form refracted light ray  50 R in the presence of clear filler such as polymer  40  having a refractive index greater than 1. Due to the refraction process when polymer  40  is present, the maximum angle of incoming light rays that do not strike sidewall  42  when polymer  40  is present such as illustrative light ray  50  is greater than the maximum angle of incoming light rays that do not strike sidewall  42  when polymer  40  is not present. The inclusion of polymer  40  may therefore help enhance range of angles over which incoming light can be accurately measured. In the example of  FIG.  2   , air is present in region  34  above holes  30 , but the range of angles over which incoming light can be accurately measured will likewise be enhanced in scenarios in which a layer of clear polymer or glass is present between holes  30  and the exterior of device  10 . The behavior of the incoming light rays in  FIG.  2    is illustrative. 
       FIG.  3    is a cross-sectional side view of an illustrative ambient light sensor window and associated ambient light sensor in device  10 . In the example of  FIG.  3   , ambient light sensor  20  has been formed from a semiconductor die  64  (e.g., a silicon die) with multiple photodetectors  66 . Each photodetector  66  may have a corresponding color filter  68  through which light passes before reaching that photodetector. Color filters  68  may be formed from colored polymer layers or other materials that pass particular bands of wavelengths (e.g., different colors of light) and/or may be formed from thin-film interference filters with different pass bands. As an example, color filters  68  may include a first color filter that passes red light, a second color filter that passes blue light, and additional color filters that pass light of different colors. With this type of arrangement, different photodetectors  66  detect light of different colors. A multichannel light sensor such as sensor  20  of  FIG.  3    may therefore measure the relative contribution of each color of light that is present and may therefore serve as a color ambient light sensor that measures both the total light intensity of ambient light and ambient light color. Ambient light color measurements may be gathered as color coordinates, a color temperature, a correlated color temperature, a light spectrum, or as color measurement data represented using other color measurement formats. There may be, for example, at least 3, at least 6, at least 10, fewer than 20, fewer than 9, or other suitable number of photodetectors  66  on die  64 . 
     Ambient light sensor  20  may be mounted within ambient light sensor assembly  62 . Assembly  62  may have housing and support structures such as housing  70  (e.g., structures formed from polymer and/or other materials that support ambient light sensor die  64  in alignment with ambient light sensor window  84 ). A compressible structure such as a spring or other biasing member (e.g., foam layer  82 ) may be interposed between a support structure (e.g., housing  12 ) and the lower surface of housing  70  to bias housing  70  and ambient light sensor  20  against the inwardly facing surface of display cover layer  60 . 
     Assembly  62  may support filter layers, light diffuser layers, and other optical components between ambient light sensor window  84  and ambient light sensor  20 . These layers may include, as an example, one or more infrared-light-blocking filters such as filters  72  and  74 . Filter  72  may be a polymer infrared cut filter, an ultraviolet cut filter, or a filter that blocks ultraviolet and infrared light while passing visible light. Filter  74  may be a thin-film interference filter that blocks infrared light, a thin-film interference filter that blocks ultraviolet light, or a thin-film interference filter that blocks both infrared and ultraviolet light while passing visible light. One or more diffuser layers such as first diffuser  76 , second diffuser  78 , and optional third diffuser  80  (e.g., a film of 300-900 microns in thickness or other suitable thickness) may help diffuse incoming ambient light and thereby prevent hotspots in the ambient light reaching ambient light sensor  20 . Optional diffuser  80  may rest on top of housing  70  or may be omitted. An air gap (e.g., an air gap of tens of microns in size) may separate the diffusers from holes  30  in ambient light sensor window  84 . Optional air gaps may also be formed between respective diffuser layers and/or other layers, if desired. 
     Ambient light sensor window  84  may have a circular outline or other suitable shape. Window  84  may, as an example, have a circular shape with a diameter of 2.8 mm, at least 0.5 mm, at least 1 mm, at least 2 mm, at least 4 mm, less than 10 mm, less than 4 mm, less than 3 mm, less than 1.5 mm, or other suitable size. There may be multiple ambient light sensor windows such as window  84  in device  10 . In the example of  FIG.  3   , a single window  84  has been formed in an opaque coating such as opaque coating layer  36 F. Opaque coating layer  36 F is formed on the inner surface of display cover layer  60  in inactive area IA. In active area AA of display  14 , pixels P of display panel  14 P for display  14  display images for viewing by a user through display cover layer  60 . 
     If desired, device  10  may have multiple ambient light sensors  20 . Consider, as an example, the illustrative arrangement of  FIG.  4   . As shown in  FIG.  4   , display  14  of device  10  may be mounted in housing  12  on front side F. Display cover layer  60  may overlap an array of pixels P in display panel  14 P. The array of pixels forms a display active area that displays images for a user that are visible through display cover layer  60 . In the inactive area of display  14 , opaque coating layer  36 F is formed on the inner surface of display cover layer  60 . An array of openings  30  in layer  36 F forms ambient light sensor window  84 . Front-facing ambient light sensor  20 F may be aligned with a front-facing ambient light sensor window such as ambient light sensor window  84  to receive ambient light from the front of device  10 . 
     Housing  12  may have a metal housing wall or a housing wall formed from other materials on rear side R facing away from the interior of device  10  and away from display  14 . A rear-facing ambient light sensor such as ambient light sensor  20 R may receive ambient light from the rear of device  10  through a rear-facing ambient light sensor window such as rear-facing ambient light sensor window  84 R. Rear ambient light sensor window  84 R may be formed from one or more holes (e.g., tapered holes and/or non-tapered holes) in housing  12  and/or may be formed using other ambient light sensor window configurations. The diameter of this hole (or holes) may be 100-400 microns, at least 50 microns, less than 2 mm, or other suitable size. Electrical components  22  in the interior of device  10  may be interconnected by signal paths such as signal paths on one or more printed circuits such as printed circuit  90 . 
     With an arrangement of the type shown in  FIG.  4   , the control circuitry of device  10  may make display intensity and color adjustments and/or may take other actions based on ambient light sensor measurements taken to the front and rear of device  10 . Weighting functions or other combining operations may be used to produce desired intensity and color adjustments based on ambient light measured in front of device  10  and ambient light measured to the rear of device  10 . For example, the control circuitry of device  10  may be configured to use the brightest reading, to use an average of the front and rear readings, to use a weighted average of the front and rear readings, etc. In an illustrative configuration, the control circuitry may increase the brightness of images displayed on display  14  in bright lighting conditions and can decrease display brightness when ambient lighting is dim. In warm lighting conditions, the color cast of display  14  (e.g., the display&#39;s white point) can be shifted warmer and in cold lighting conditions, the color cast of display  14  can be shifted colder. Display brightness may also be adjusted based on ambient light color measurements and/or display color cast may be adjusted based on ambient light intensity measurements, if desired. 
     Ambient light sensor windows in layer  36 F, housing  12 , and/or other opaque layers  36  can use arrays of holes such as circular tapered holes  30 . A plan view of an illustrative set of ambient light sensor window holes is shown in  FIG.  5   . As shown in the example of  FIG.  5   , outwardly facing openings TP of holes  30  may have smaller diameters than inwardly facing openings BT of holes  30 .  FIG.  6    is a cross-sectional side view of holes  30  of  FIG.  5    taken along line  92  and viewed in direction  94 . As shown in  FIG.  6   , holes  30  of  FIG.  5    are spaced sufficiently far apart that openings BT do not overlap each other. 
     Device  10  may have opaque structures such as opaque Layer  36  may be formed from any suitable opaque material(s). 
     In an illustrative configuration, layer  36  is formed from screen printed opaque ink (e.g., black ink) having a thickness T of 300 microns, 50-100 microns, 100-300 microns, at least 5 microns, 5-10 microns, at least 10 microns, at least 30 microns, at least 50 microns, at least 150 microns, less than 9 mm, less than 3 mm, less than 600 microns, less than 350 microns, less than 100 microns, less than 50 microns, less than 40 microns, or other suitable thickness. The diameters of outwardly facing openings TP may be small enough to be invisible to a user&#39;s naked eye (e.g., less than 30 microns or other suitable diameter), may be 16-26 microns, may be at least 3 microns, at least 16 microns, at least 20 microns, at least 25 microns, less than 30 microns, less than 125 microns, or other suitable size. The surface of sidewall  42  may lie at a non-zero and non-perpendicular angle A with respect to longitudinal axis  52  (and to surface normal n of outer surface  54  and inner surface  56 ). The diameters of inwardly facing openings BT may be 200-600 microns, at least 20 microns, at least 50 microns, at least 300 microns, less than 6 mm, less than 4 mm, less than 3 mm, less than 1000 microns, or other suitable size. 
     In another illustrative configuration, layer  36  may be a metal housing wall or a housing wall formed from one or more materials (metal, polymer, and/or other materials). For example, layer  36  may form a rear housing wall and holes  30  may form rear ambient light sensor window  84 R for passing light to rear ambient light sensor  20 R. In this type of arrangement, angle A of tapered openings  30  may be about 30-70°, at least 10°, at least 20°, at least 30° at least 40°, at least 60°, less than 89°, less than 80°, less than 70°, less than 50°, less than 40°, 30-40°, 1-30°, 40-60°, or other suitable value. Openings TP and BT may have diameters of at least 10 microns, at least 100 microns, at least 1 mm, at least 10 mm, less than 5 mm, less than 500 microns, less than 50 microns, less than 25 microns, less than 30 microns, 16-26 microns, or other suitable size. 
     Sidewalls  42  may be tapered and may run between outer surface  54  and inner surface  56 . In some configurations, portions of sidewalls  42  may run vertically (e.g., parallel to surface normal n), as illustrated by surface portions  42 F of  FIG.  6   . The size (height h parallel to surface normal n) of surface portions  42 F may be about 30 microns, at least 3 microns, less than 300 microns, or other suitable size (e.g., about 5-15% of thickness T of layer  36 , at least 1% of thickness T, less than 50% of thickness T, etc.). The use of a straight (non-tapered) upper portion in hole  30  such as the portion formed by non-tapered sidewall portions  42 F may help reduce burs and other undesired features in holes  30  and may help ensure that holes  30  may be formed in a controllable manner. 
     Laser drilling, mechanical drilling, photolithography, printing, and/or other techniques may be used in forming holes  30 . As an example, a straight drill may be used in forming the non-tapered portion of holes  30  and an angled router bit may be used in forming the tapered sidewalls of holes  30  (e.g., the angled router bit may be used in a single vertical application or may be moved in a circular pattern around the perimeter of holes BT). 
     If desired, holes  30  may be placed closer together. As shown in  FIG.  7   , for example, holes  30  may be arranged so that portions of bottom openings BT for holes  30  overlap with portions of bottom openings BT for adjacent holes  30 .  FIG.  8    is a cross-sectional side view of holes  30  of  FIG.  7    taken along line  96  and viewed in direction  98 , showing how bottom openings BT overlap with each other. 
     In addition to forming ambient light sensor windows from an array of tapered openings such as openings  30 , ambient light sensor windows may, if desired, be formed from single openings in opaque structures. Consider, as an example, the illustrative configuration for rear ambient light sensor window  84 R of  FIG.  9   . In this example, opaque layer  36 R is formed from a metal housing wall, other layer(s) of housing  12 , and/or other opaque structures in device  10 . An area of layer  36 R may be locally thinned, as illustrated by thinned area  104 . This thinned area may receive ambient light sensor assembly  106 . Ambient light sensor assembly  106  may include diffusers, infrared cut filters, ultraviolet cut filters, filters that block both ultraviolet and infrared light, and/or other optical components. As an example, ambient light sensor assembly  106  may include a clear structure such as ultraviolet-light-absorbing member  102  which is received in a through-hole opening formed in layer  36 R. Member  102  may be formed from glass, polymer, or other materials and may optionally include one or more layers of optical components (e.g., filters, diffusers, etc.). As shown in  FIG.  9   , an outwardly facing coating such as coating layer  100  may be provided on the outer surface of member  102 . Coating layer  100  may be sufficiently transparent to pass ambient light from the exterior of device  10  to ambient light sensor  20 R while having an appearance that is matched to the appearance of surrounding portions of layer  36 R. For example, if layer  36 R is formed from a rear aluminum housing wall in housing  12 , layer  100  may be formed from gray ink. 
     In addition to or instead of using tapered holes  30  and, if desired, windows of the type shown in  FIG.  9    for forming ambient light sensor windows, these window arrangements may serve as optical component windows for other optical components in device  10  (e.g., light-emitting devices such as light-emitting diodes and/or lasers, light detecting devices such as infrared light sensors, ultraviolet light sensors, and/or visible light sensors, light-emitting devices that are used in forming the sensors of device  10 , cameras, proximity sensors, distance sensors, three-dimensional sensors, and/or other optical components). The use of windows such as windows  84  and  84 R in forming ambient light sensor windows is illustrative. 
     Device  10  may be operated in a system that uses personally identifiable information. It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     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. 
     
       
         
           
               
             
               
                   
               
               
                 Table of Reference Numerals 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                  10 
                 Electronic Device 
                  12 
                 Housing 
               
               
                  14 
                 Display 
                  14P 
                 Display panel 
               
               
                  18 
                 Stand 
                  20 
                 Ambient Light Sensor 
               
               
                  20F 
                 Front-Facing Ambient 
                  20R 
                 Rear Ambient Light 
               
               
                   
                 Light Sensor 
                   
                 Sensor 
               
               
                  22 
                 Electrical components 
                  30 
                 Hole 
               
               
                  34 
                 Separate Region 
                  36 
                 Opaque Structure 
               
               
                  36F 
                 Opaque coating layer 
                  36R 
                 Opaque layer 
               
               
                  38 
                 Region 
                  40 
                 Polymer 
               
               
                  42 
                 Sidewalls 
                  42F 
                 Surface portions 
               
               
                  44 
                 Surface 
                  46 
                 Light ray 
               
               
                  46′ 
                 Reflected ray 
                  48 
                 Light ray 
               
               
                  50 
                 Light ray 
                  50R 
                 Light ray 
               
               
                  52 
                 Axis 
                  54 
                 Surface 
               
               
                  56 
                 Surface 
                  60 
                 Cover layer 
               
               
                  62 
                 Assembly 
                  64 
                 Die 
               
               
                  66 
                 Photodetectors 
                  68 
                 Color filters 
               
               
                  70 
                 Housing 
                  72 
                 Filter 
               
               
                  74 
                 Filter 
                  76 
                 Diffuser 
               
               
                  78 
                 Diffuser 
                  80 
                 Diffuser 
               
               
                  82 
                 Foam layer 
                  84 
                 Light sensor window 
               
               
                  84R; 84F 
                 Ambient light sensor 
                  90 
                 Printed circuit 
               
               
                   
                 window 
                   
                   
               
               
                  92 
                 Line 
                  94 
                 Direction 
               
               
                  96 
                 Line 
                  98 
                 Direction 
               
               
                 100 
                 Coating layer 
                 104 
                 Thinned area 
               
               
                 106 
                 Ambient light sensor 
                 A 
                 Angle 
               
               
                   
                 assembly 
                   
                   
               
               
                 AA 
                 Active area 
                 BT 
                 Bottom openings 
               
               
                 F 
                 Front side 
                 h 
                 Height 
               
               
                 IA 
                 Inactive area 
                 n 
                 Normal 
               
               
                 P 
                 Pixels 
                 R 
                 Rear surface 
               
               
                 T 
                 Thickness 
                 TP 
                 Opening