PATENT DOCUMENT

Publication Number: US-10553179-B2
Application Number: US-201715699941-A
Country: US
Kind Code: B2

Title: Electronic devices with ambient light sensors

Abstract:
An electronic device may be provided with a display mounted in a housing. The display may have an array of pixels that form an active area and may have an inactive area that runs along an edge of the active area. An opaque layer may be formed on an inner surface of a display cover layer in the inactive area of the display or may be formed on another transparent layer in the electronic device. An optical component window may be formed from the opening and may be aligned with an ambient light sensor such as a color ambient light sensor. The color ambient light sensor may have an infrared-blocking filter to block infrared light such as infrared light emitted by an infrared-light-emitting diode in the device. A light diffuser layer, light guide, and other structures may also be included in the ambient light sensor.

Claims:
What is claimed is: 
     
       1. An ambient light sensor configured to provide ambient light measurements to control circuitry in an electronic device, the ambient light sensor comprising:
 a light detector integrated circuit; 
 a light guide configured to guide ambient light to the light detector integrated circuit, wherein the light guide comprises a core and a cladding surrounding the core, wherein the core has a first index of refraction, wherein the cladding has a second index of refraction that is less than the first index of refraction, and wherein at least a portion of the ambient light passes through the core without first passing through the cladding; and 
 an infrared-blocking filter through which the ambient light passes. 
 
     
     
       2. The ambient light sensor defined in  claim 1  further comprising a light diffuser, wherein the light guide is interposed between the light diffuser and the infrared-blocking filter. 
     
     
       3. The ambient light sensor defined in  claim 2  further comprising:
 a support structure surrounding the cladding of the light guide, wherein the cladding is interposed between the support structure and the core. 
 
     
     
       4. The ambient light sensor defined in  claim 3  wherein the cladding comprises polymer, the ambient light sensor further comprising an opaque support structure surrounding the light detector integrated circuit and the light guide. 
     
     
       5. The ambient light sensor defined in  claim 4  wherein the light detector integrated circuit includes a plurality of photodetectors. 
     
     
       6. The ambient light sensor defined in  claim 5  further comprising a plurality of color filters, each color filter passing a different respective range of visible light wavelengths to a respective one of the plurality of photodetectors. 
     
     
       7. The ambient light sensor defined in  claim 6  wherein the light diffuser includes a plurality of light diffuser layers each light diffuser layer having a substrate and a polymer coating on the substrate that has embedded light scattering particles. 
     
     
       8. The ambient light sensor defined in  claim 7  wherein the plurality of light diffuser layers includes first and second light diffuser layers separated by an air gap. 
     
     
       9. The ambient light sensor defined in  claim 6  wherein the infrared-blocking filter includes at least one stack of thin-film dielectric layers of alternating refractive index values. 
     
     
       10. The ambient light sensor defined in  claim 7  wherein the infrared-blocking filter includes a glass substrate on which the thin-film dielectric layers are formed. 
     
     
       11. The ambient light sensor defined in  claim 10  wherein the glass substrate comprises infrared-light-blocking glass. 
     
     
       12. The ambient light sensor defined in  claim 11  wherein the color filters each include a stack of thin-film inorganic dielectric layers that is configured to pass a respective range of visible light wavelengths while blocking infrared light. 
     
     
       13. An electronic device, comprising:
 an array of pixels; 
 a display cover layer that overlaps the pixels; 
 an optical component window in a portion of the display cover layer through which ambient light passes; and 
 a color ambient light sensor aligned with the optical component window, wherein the color ambient light sensor includes:
 an opaque support structure; 
 a light diffuser coupled to the opaque support structure through which the ambient light passes, wherein the light diffuser has a peripheral edge and wherein the opaque support structure extends around the peripheral edge; 
 a light detector integrated circuit that is at least partially surrounded by the opaque support structure, wherein the light detector integrated circuit has a plurality of photodetectors each overlapped by a color filter that is configured to pass a different respective band of visible light wavelengths; 
 an infrared-light-blocking filter that is coupled to the support structure and that is located between the light diffuser and the light detector integrated circuit; and 
 a layer of black ink through which the ambient light passes prior to passing through the light diffuser. 
 
 
     
     
       14. The electronic device defined in  claim 13  wherein the color filters each include organic material and wherein the color ambient light sensor further comprises an infrared-light-blocking thin-film interference filter having thin-film inorganic dielectric layers between the color filters and the light detector integrated circuit. 
     
     
       15. The electronic device defined in  claim 13  wherein the light diffuser comprises multiple light diffuser layers, each of the light diffuser layers including a substrate layer coated with a polymer containing light scattering particles of inorganic dielectric. 
     
     
       16. The electronic device defined in  claim 13  wherein the infrared-light-blocking filter comprises a plurality of infrared-light-blocking layers each infrared-light-blocking layer including a substrate and a thin-film interference filter formed from a stack of dielectric layers of alternating index of refraction on the substrate. 
     
     
       17. The electronic device defined in  claim 13  further comprising:
 an infrared light-emitting diode configured to emit infrared light that is blocked by the infrared-light-blocking filter; and 
 an infrared sensor configured to capture images illuminated by the emitted infrared light. 
 
     
     
       18. The electronic device defined in  claim 13  further comprising control circuitry configured to adjust a white point of images displayed on the array of pixels in response to color ambient light sensor information measured with the color ambient light sensor. 
     
     
       19. An electronic device, comprising:
 a display having a display cover layer; 
 an ambient light sensor window in the display cover layer; and 
 an ambient light sensor configured to receive ambient light through the ambient light sensor window, wherein the ambient light sensor comprises:
 a light detector integrated circuit having a plurality of photodetectors each overlapped by a color filter configured to pass a different respective band of visible light wavelengths; and 
 a visible-light-transmitting-and-infrared-light blocking thin-film interference filter interposed between the color filters and the ambient light sensor window, wherein the visible-light-transmitting-and-infrared-light blocking thin-film interference filter comprises a glass infrared-blocking substrate having opposing first and second surfaces, a first thin-film interference filter directly on the first surface, and a second thin-film interference filter directly on the second surface, wherein the visible-light-transmitting-and-infrared-light blocking thin-film interference filter has a peripheral edge, and wherein an opaque support structure extends around the peripheral edge. 
 
 
     
     
       20. The electronic device defined in  claim 19  further comprising:
 an infrared light-emitting diode configured to emit infrared light that is blocked by the visible-light-transmitting-and-infrared-light blocking thin-film interference filter; and 
 an infrared sensor configured to capture images illuminated by the emitted infrared light. 
 
     
     
       21. An electronic device, comprising:
 an ambient light sensor photodetector; 
 an integrating analog-to-digital converter configured to integrate output from the ambient light sensor photodetector; 
 an infrared light-emitting diode; 
 control circuitry configured to pause integration of the output every time the infrared light-emitting diode is turned on; and 
 switching circuitry interposed between the ambient light sensor photodetector and the integrating analog-to-digital converter, wherein the switching circuitry is configured to shunt the output to the ground when the infrared light-emitting diode is turned on. 
 
     
     
       22. The electronic device defined in  claim 21 
 wherein the switching circuitry is coupled to the ambient light sensor photodetector and wherein the control circuitry is configured to adjust the switching circuitry when using the infrared light-emitting diode to emit infrared light. 
 
     
     
       23. The electronic device defined in  claim 22  wherein the switching circuitry comprises:
 a first switch that is coupled between a node and an input of the integrating analog-to-digital converter; and 
 a second switch that is coupled between the node and ground. 
 
     
     
       24. The electronic device defined in  claim 23  wherein the ambient light sensor photodetector has a first terminal coupled to ground and a second terminal coupled to the node. 
     
     
       25. The electronic device defined in  claim 24  wherein the switching circuitry is configured to operate in:
 a first mode in which the first switch is closed to couple the output of the ambient light sensor photodetector to the input of the integrating analog-to-digital converter to allow the integrating analog-to-digital converter to integrate the output from the ambient light sensor photodetector and the second switch is open to isolate the node from ground; and 
 a second mode in which the first switch is open to disconnect the output of the ambient light sensor photodetector from the input of the integrating analog-to-digital converter and the second switch is closed to short the node to ground. 
 
     
     
       26. The electronic device defined in  claim 25  further comprising an infrared image sensor configured to capture an image of an external object illuminated by infrared light emitted by the infrared light-emitting diode while the switching circuitry is operated in the second mode. 
     
     
       27. An electronic device, comprising:
 an ambient light sensor configured to gather an ambient light sensor measurement during an integration period; 
 integration circuitry that produces integrated ambient light sensor data based on the ambient light sensor measurement; 
 an infrared light-emitting diode; and 
 control circuitry configured to discard the integrated ambient light sensor data in response to determining that the infrared light-emitting diode has emitted infrared light during the integration period. 
 
     
     
       28. The electronic device defined in  claim 27  further comprising an infrared image sensor configured to capture an image of an external object illuminated by infrared light emitted by the infrared light-emitting diode. 
     
     
       29. The electronic device defined in  claim 28  wherein the ambient light sensor comprises a light detector integrated circuit having a plurality of photodetectors each overlapped by a color filter configured to pass a different respective band of visible light wavelengths. 
     
     
       30. An electronic device, comprising:
 an ambient light sensor configured to gather an ambient light sensor measurement during an integration period; 
 integration circuitry that produces integrated ambient light sensor data based on the ambient light sensor measurement; 
 an infrared light sensor; and 
 control circuitry configured to discard the integrated ambient light sensor data in response to determining that the infrared light sensor has sensed infrared light during the integration period. 
 
     
     
       31. The electronic device defined in  claim 30  wherein the ambient light sensor comprises a light detector integrated circuit having a plurality of photodetectors each overlapped by a color filter configured to pass a different respective band of visible light wavelengths. 
     
     
       32. The electronic device defined in  claim 31  further comprising a display, wherein the control circuitry is configured to adjust a white point of images displayed on the display based on the ambient light sensor measurement. 
     
     
       33. An electronic device, comprising:
 a rectangular housing having four peripheral edges including an upper peripheral edge; 
 an electrical component; 
 an optical component window; 
 a photodetector; 
 a display cover layer, wherein the electrical component is separated from the display cover layer by a first distance and the photodetector is separated from the display cover layer by a second distance that is less than the first distance; 
 a light guide that is interposed between the electrical component and a sidewall of the rectangular housing and that is configured to guide ambient light from the optical component window past the electrical component to the photodetector, wherein the light guide has opposing first and second ends; 
 a light diffuser attached to the first end of the light guide; and 
 an infrared-light-blocking filter interposed between the second end of the light guide and the photodetectors. 
 
     
     
       34. The electronic device defined in  claim 33  further comprising:
 an array of pixels 
 wherein the display cover layer that overlaps the pixels, wherein the optical component window is formed in a portion of the display cover layer. 
 
     
     
       35. The electronic device defined in  claim 34  wherein the optical component window has an elongated shape that extends parallel to the upper peripheral edge and that is between the electrical component and the sidewall of the rectangular housing. 
     
     
       36. The electronic device defined in  claim 35  wherein the electrical component comprises a speaker aligned with a speaker port formed in the display cover layer and wherein the speaker port has an elongated shape that extends parallel to the optical component window. 
     
     
       37. The electronic device defined in  claim 36  further comprising a light detector integrated circuit on which the photodetector is formed. 
     
     
       38. The electronic device defined in  claim 37  wherein the photodetector is one of multiple photodetectors each of which is configured to measure ambient light of a different color. 
     
     
       39. The electronic device defined in  claim 38  further comprising thin-film interference filters with different respective pass bands each of which overlaps a respective one of the multiple photodetectors. 
     
     
       40. The electronic device defined in  claim 38  further comprising an opaque support structure surrounding the light guide, wherein the light guide has a core with a first index of refraction and a cladding with a second index of refraction that is lower than the first index of refraction. 
     
     
       41. The electronic device defined in  claim 33  further comprising:
 an infrared digital image sensor mounted adjacent to the upper peripheral edge; and 
 an infrared light-emitting diode configured to supply illumination for infrared images captured with the infrared digital image sensor. 
 
     
     
       42. The electronic device defined in  claim 41  wherein the photodetector is one of multiple photodetectors each of which is configured to measure ambient light of a different color and wherein each of the multiple photodetectors is overlapped by a respective thin-film interference filter with a different respective visible-light pass band. 
     
     
       43. The electronic device defined in  claim 42  wherein the thin-film interference filters are configured to block infrared light.

Description:
FIELD 
     This relates generally to electronic devices, and, more particularly, to electronic devices with optical components such as ambient light sensors. 
     BACKGROUND 
     Electronic devices such as laptop computers, cellular telephones, and other equipment are sometimes provided with optical components. For example, an electronic device may have an ambient light sensor, an optical proximity sensor, image sensors, and light sources. 
     The desire to include multiple optical components in an electronic device can pose challenges. It can be difficult to incorporate optical components into an electronic device where space is at a premium. There is also a potential for different optical components to interfere with each other during operation. 
     SUMMARY 
     An electronic device may be provided with a display mounted in a housing. The display may have an active area with an array of pixels for forming images and may have an inactive area along one or more edges of the active area. Optical component windows may be formed in the inactive area and other portions of the electronic device. Optical components such as light-emitting diodes, image sensors, optical proximity sensors, and ambient light sensors may be aligned with the optical component windows. 
     An ambient light sensor may have a light detector integrated circuit with photodetectors. To provide the ambient light sensor with color sensing capabilities, the photodetectors may each be provided with a respective color filter configured to pass a different range of wavelengths. 
     A diffuser may be used to diffuse incoming ambient light. Infrared light-blocking filter layers may be use to block infrared light such as infrared light emitted by an infrared light-emitting diode in the electronic device and other stray infrared light. 
     A light guide may be used to route ambient light to the light detector integrated circuit. The light guide may be interposed between a light diffuser and an infrared-blocking filter. 
     Operation of an ambient light sensor may be coordinated with an infrared light-emitting component such as an infrared light-emitting diode used to provide infrared light illumination for an infrared image sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device having optical components in accordance with an embodiment. 
         FIG. 2  is a perspective view of an illustrative electronic device with a display having optical component windows overlapping optical components in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative electronic device that has optical components such as a light source, image sensor, and ambient light sensor in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of an illustrative diffuser in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative thin-film interference filter in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative ambient light sensor in accordance with an embodiment. 
         FIG. 7  is a graph showing how light transmission may vary as a function of wavelength for illustrative organic ambient light sensor color filters in accordance with an embodiment. 
         FIG. 8  is a graph showing how light transmission may vary as a function of wavelength for a thin-film infrared-light-blocking filter in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of an illustrative electronic device having an ambient light sensor with a light guide in accordance with an embodiment. 
         FIG. 10  is a cross-sectional side view of an illustrative ambient light sensor with a light guide in accordance with an embodiment. 
         FIG. 11  is a cross-sectional side view of an illustrative ambient light sensor integrated circuit having photodetectors overlapped by color filters formed from thin-film interference filters in accordance with an embodiment. 
         FIG. 12  is a graph in which light transmission has been plotted as a function of wavelength for illustrative color filters such as thin-film interference filters with different pass bands in accordance with an embodiment. 
         FIG. 13  is a top view of an illustrative ambient light sensor integrated circuit having a set of photodetectors with a circular outline in accordance with an embodiment. 
         FIG. 14  is top view of an illustrative ambient light sensor having a set of photodetectors with a rectangular outline in accordance with an embodiment. 
         FIG. 15  is a circuit diagram of illustrative circuitry for an electronic device in accordance with an embodiment. 
         FIGS. 16, 17, and 18  are timing diagrams showing illustrative signals involved in using circuitry of the type shown in  FIG. 15  to coordinate the use of an ambient light sensor and a component containing an infrared light-emitting diode in accordance with an embodiment. 
         FIGS. 19 and 20  are timing diagrams showing how a flag signal may be asserted during ambient light sensor data gathering operations in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with optical components such as ambient 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. 
     Device  10  may have input-output circuitry such as input-output devices  12 . Input-output devices  12  may include user input devices that gather user input and output components that provide a user with output. Devices  12  may also include communications circuitry that receives data for device  10  and that supplies data from device  10  to external devices. Devices  12  may also include sensors that gather information from the environment. 
     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. Display  14  may be a liquid crystal display, a light-emitting diode display (e.g., an organic light-emitting diode display), an electrophoretic display, or other display. 
     Input-output devices  12  may include optical components  18 . Optical components  18  may include light-emitting diodes and other light sources. As an example, optical components  18  may include one or more visible light-emitting diodes such as light-emitting diode  20 . Light-emitting diode  20  may provide constant illumination (e.g., to implement a flashlight function for device  10 ) and/or may emit pulses of flash illumination for a visible light camera such as visible light image sensor  26 . Optical components  18  may also include an infrared light source (e.g., a laser, lamp, light-emitting diode, etc.) such as infrared light-emitting diode  22 . Infrared light-emitting diode  22  may provide constant and/or pulsed illumination at an infrared wavelength such as 940 nm, a wavelength in the range of 800-1100 nm, etc. For example, infrared-light-emitting diode  22  may provide constant illumination for an infrared camera such as infrared image sensor  28 . Infrared image sensor  28  may, as an example, be configured to capture iris scan information from the eyes of a user and/or may be used to capture images for a facial recognition process implemented on control circuitry  16 . 
     Optical components  18  may also include optical proximity detector  24  and ambient light sensor  30 . 
     Optical proximity detector  24  may include an infrared light source such as an infrared light-emitting diode and a corresponding light detector such as an infrared photodetector for detecting when an external object that is illuminated by infrared light from the light-emitting diode is in the vicinity of device  10 . 
     Ambient light sensor  30  may be a monochrome ambient light sensor that measures the intensity of ambient light or may be a color ambient light sensor that measures ambient light color and intensity by making light measurements with multiple photodetectors each of which is provided with a corresponding color filter (e.g., a corresponding bandpass filter that passes red light, blue light, yellow light, green light, or light of other colors) and each of which therefore responds to ambient light in a different wavelength band. 
     In addition to optical components  18 , 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, non-optical sensors (e.g., temperature sensors, microphones, capacitive touch sensors, force sensors, gas sensors, pressure sensors, sensors that monitor device orientation and motion such as inertial measurement units formed from accelerometers, compasses, and/or gyroscopes), 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 from device  10  using the output resources of input-output devices  12 . 
     Device  10  may have a housing. The housing may form a laptop computer enclosure, an enclosure for a wristwatch, a cellular telephone enclosure, a tablet computer enclosure, or other suitable device enclosure. 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  32 . Housing  32 , 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  32  may be formed using a unibody configuration in which some or all of housing  32  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.). Housing  32  may have any suitable shape. In the example of  FIG. 2 , housing  32  has a rectangular outline (footprint when viewed from above) and has four peripheral edges (e.g., opposing upper and lower edges and opposing left and right edges). Sidewalls may run along the periphery of housing  32 . 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass, clear plastic, sapphire, or other clear layer (e.g., a transparent planar member that forms some or all of a front face of device  10  or that is mounted in other portions of device  10 ). 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 such as speaker port  34 , or other components. Openings may be formed in housing  32  to form communications ports (e.g., an audio jack port, a digital data port, etc.), to form openings for buttons, etc. In some configurations, housing  32  may have a rear housing wall formed from a planar glass member or other transparent layer (e.g., a planar member formed on a rear face of device  10  opposing a front face of device  10  that includes a display cover layer). 
     Display  14  may have an array of pixels  38  in active area AA (e.g., liquid crystal display pixels, organic light-emitting diode pixels, electrophoretic display pixels, etc.). Pixels  38  of active area AA may display images for a user of device  10 . Active area AA may be rectangular, may have notches along one or more of its edges, may be circular, may be oval, may be rectangular with rounded corners, and/or may have other suitable shapes. 
     Inactive portions of display  14  such as inactive border area IA may be formed along one or more edges of active area AA. Inactive border area IA may overlap 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 (e.g., polymer containing black dye and/or black pigment, opaque materials of other colors, etc.) and/or other layers (e.g., metal, dielectric, semiconductor, etc.). Opaque masking materials such as these may also be formed on an inner surface of a planar rear housing wall formed from glass, ceramic, polymer, crystalline transparent materials such as sapphire, or other transparent material. 
     In the example of  FIG. 2 , speaker port  34  is formed from an elongated opening (e.g., a strip-shaped opening) that extends along a dimension parallel to the upper peripheral edge of housing  32 . A speaker may be mounted within device housing  32  in alignment with the opening for speaker port  34 . During operation of device  10 , speaker port  34  serves as an ear speaker port for a user of device  10  (e.g., a user may place opening  34  adjacent to the user&#39;s ear during telephone calls). 
     Optical components  18  (e.g., a visible digital image sensor, an infrared digital image sensor, a light-based proximity sensor, an ambient light sensor, visible and/or infrared light-emitting diodes that provide constant and/or pulsed illumination, etc.) may be mounted under one or more optical component windows such as optical component windows  40  and  42 . In the example of  FIG. 2 , windows  40  have circular outlines (e.g., circular footprints when viewed from above) and window  42  has an elongated strip-shaped opening (e.g., an elongated strip-shaped footprint when viewed from above). Window  42  is mounted between the sidewall along the upper peripheral edge of device  10  and speaker port  34  and extends parallel to the upper peripheral edge of housing  32 . If desired, windows such as optical windows  40  and  42  may have shapes other than circular and rectangular shapes. The examples of  FIG. 2  are merely illustrative. 
     Optical component windows such as windows  40  and  42  may be formed in inactive area IA of display  14  (e.g., an inactive border area in a display cover layer such as an inactive display region extending along the upper peripheral edge of housing  32 ) or may be formed in other portions of device  10  such as portions of a rear housing wall formed from a transparent member coated with opaque masking material, portions of a metal housing wall, polymer wall structures, etc. In the example of  FIG. 2 , windows  40  and  42  are formed adjacent to the upper peripheral edge of housing  32  between speaker port opening  34  in the display cover layer for display  14  and the sidewall along the upper edge of housing  32 . In some configurations, an opaque masking layer is formed on the underside of the display cover layer in inactive area IA and optical windows  40  and  42  are formed from openings within the opaque masking layer. To help optical windows  40  and  42  visually blend with the opaque masking layer, a dark ink layer, a metal layer, a thin-film interference filter formed from a stack of dielectric layers, and/or other structures may be overlap windows  40  and  42 . 
     In some modes of operation, device  10  may emit infrared light that has the potential to interfere with ambient light sensor operation. Consider, as an example, a scenario in which control circuitry  16  of device  10  is using infrared image sensor  28  to capture eye scan information and/or facial images (e.g., images of a user&#39;s face for use in performing face recognition operations to authenticate the user of device  10 ). As shown in  FIG. 3 , to ensure that the eyes and/or face of a user are sufficiently illuminated, device  10  may use infrared light source  22  (e.g., an infrared light-emitting diode, an infrared laser, etc.) to produce infrared light  48 . Light  48  may illuminate external objects in the vicinity of device  10  such as external object  44  (e.g., a user&#39;s face and/or eyes). Reflected infrared light  50  from external object  44  may be received and imaged using infrared digital image sensor  28  to produce infrared images of the face and/or eyes. 
     While reflected infrared light  50  is being imaged, stray infrared light reflected from object  44  such as stray infrared light  52  may be present at ambient light sensor  30 . To ensure that stray infrared light  52  does not interfere with the ambient light measurements being made with ambient light sensor  30 , ambient light sensor  30  may have an infrared blocking filter such as filter  60 . Filter  60  may be formed from materials that are transparent to visible light and that block infrared light such as blue glass (e.g., blue borosilicate glass or other infrared-light-blocking glass) and/or from thin-film interference filters formed from stacks of dielectric layers configured to block infrared light (e.g., infrared light at the wavelengths associated with stray light  52  and, if desired, additional infrared wavelengths) while passing visible light. 
     Ambient light  54  may be present in the surroundings of device  10  and may include light emitted from a light source such as light source  46  (e.g., the sun, a lamp, etc.). In some situations, ambient light  54  may be directional (e.g., the rays of light  54  from light source  46  may be aligned in a particular direction due to the nature of light source  46 ). To ensure that the response of ambient light detector  30  is even over a range of different orientations relative to light source  46  and ambient light  54 , a light diffuser such as diffuser  62  may be incorporated into ambient light sensor  30 . Ambient light sensor  30  may have one or more photodetectors (e.g., photodiodes) and associated amplifier and digitizing circuitry implemented on light detector integrated circuit  58 . Diffuser  62  may overlap visible-light-transmitting-and-infrared-light-blocking filter layer  60  and integrated circuit  58 . 
     Diffuser  62  may be formed from polymer, glass, or other suitable materials. Diffuser  62  may be formed from one or more diffuser layers such as illustrative diffuser  62 L of  FIG. 4 . If desired, each diffuser layer  62 L may have a substrate such as substrate  64 . Substrate  64  may be formed from clear glass, transparent polymer, or other suitable substrate material. Diffuser coatings such as lower coating layer  66  and upper coating layer  66 ′ may be formed on both sides of substrate  64 , on only the upper side of substrate  64  (see, e.g., coating layer  66 ′), or on only the lower side of substrate  64  (see, e.g., coating layer  66 ). Coating layers  66  and  66 ′ may include polymer (e.g., clear binder such as a transparent polymer resin) such as polymer  70  and may include light-scattering particles  68  embedded in polymer  70 . Light-scattering particles  68  may be titanium oxide particles or other particles with a refractive index that is larger (or smaller) than the refractive index of polymer  70 . If desired, light-scattering particles  68  may be incorporated into substrate  64 . Light-scattering coatings formed from polymer with embedded light-scattering particles may also be formed on a display cover layer, light guide structures, filter layers, and/or other transparent materials in device  10 . If desired, light-scattering features such as protrusions and/or recesses may also be included in one or more of the layers of material forming diffuser  62 . With one illustrative configuration, diffuser  62  may include a pair of diffuser layers  62 L (e.g., first and second diffusers  62  that are stacked above light detector integrated circuit  58  ( FIG. 3 ). In general, any suitable number of diffuser layers  62 L may be included in diffuser  62  (e.g., one, at least two, at least three, etc.). 
     Visible-light-transmitting-and-infrared-light-blocking filter  60  (sometimes referred to as an infrared-light-blocking filter, infrared-blocking filter, etc.) may be formed from one or more layers such as infrared-light-blocking layer  60 L of  FIG. 5 . As shown in  FIG. 5 , layer  60 L may include a substrate such as substrate  76 . Substrate  76  may be a polymer or glass layer that is transparent at visible wavelengths. Substrate  76  may be transparent at infrared wavelengths or may block infrared light. Thin-film interference filters  72  that are configured to transmit visible light and block infrared light may be formed on the upper and/or lower surfaces of substrate  76 . Filters  72  may each include a dielectric stack of thin-film dielectric layers  74  such as inorganic dielectric layers with alternating higher and lower refractive index values. Layers  74  may, for example, be formed from inorganic dielectric materials such as silicon oxide, silicon nitride, niobium oxide, tantalum oxide, titanium oxide, aluminum oxide, etc., and/or may be formed from organic dielectric materials. There may be any suitable number of layers  74  in each dielectric stack (e.g., at least 5, at least 10, at least 30, at least 40, 20-90, fewer than 100, etc.). 
     In general, sensor  30  may include one or more infrared blocking filters such as filter  60  and each filter  60  may include one or more infrared blocking layers  60 L. Each layer  60 L may include one or more dielectric stacks  72  of thin-film layers  74 . If desired, thin-film infrared-light-blocking filters may be implemented from dielectric stacks formed on a display cover layer, a light guide layer, a lens, a diffuser, an integrated circuit, and/or other structures in ambient light sensor  30  through which ambient light passes. 
       FIG. 6  shows an illustrative configuration for a color ambient light sensor in device  10 . In the example of  FIG. 6 , color ambient light sensor  30  is formed in alignment with optical component window  40  (sometimes referred to as an ambient light sensor window) in display  14 . Display  14  has an array of pixels overlapped by display cover layer  78  in an active area (AA) of display  14  (not shown in  FIG. 6 ). In inactive area IA, portions of the underside of display cover layer  78  may be coated with a layer of opaque masking material  80  (e.g., black ink, etc.) to block internal components from view from the exterior of device  10 . Window  40  may be formed from an opening in the opaque masking material  80 . In window  40 , a thin layer of black ink  82  or other material that is at least partially transparent to visible light (e.g., a layer with a light transmission of at least 1%, at least 2%, at least 5%, 1-10%, less than 30%, etc.) may be present to help visually match the appearance of window  40  to the visual appearance of surrounding portions of display cover layer  78  (e.g., to match the appearance of opaque masking material  80 ) while still allowing ambient light sensor  30  to measure ambient light. 
     Color ambient light sensor  30  may include support structures such as support structure  86  (sometimes referred to as a sensor wall, a sensor body structure, a sensor housing structure, etc.). Clear adhesive such as a layer of pressure sensitive adhesive  84  may be used to couple support structure  86  to the underside of display cover layer  78  in alignment with optical component window  40 . Support structure  86  may form walls that surround light diffuser  62 , infrared-light-blocking filter  60 , and light detector integrated circuit  58 . Viewed from above through layer  78 , support structure  86  may extend around the periphery of optical window  40 . Support structure  86  may be formed from an opaque material that blocks visible and infrared light such as black plastic and/or other opaque materials. Support structure  86  may be used to form a one-piece or a multi-piece housing for sensor  30 . In the example of  FIG. 6 , support structure  86  has an upper portion that houses components such as light diffuser  62  and infrared-light-blocking filter  60  and has a lower portion that houses light detector integrated circuit  58 . The upper and lower portions may be joined using pressure sensitive adhesive  111  or other suitable attachment mechanism. 
     Diffuser  62  of  FIG. 6  has an upper diffuser layer  62 L and a lower diffuser layer  62 L. In the upper diffuser layer, substrate  64  ( FIG. 4 ) may be coated with upper diffuser coating  66 ′ and may not have any lower diffuser coating. In the lower diffuser layer, substrate  64  may be coated with lower diffuser coating  66  and coating  66 ′ may be omitted. Air gaps  88  may separate diffuser layers  62 L from each other and from adjacent layers in ambient light sensor  30  (e.g., to enhance the amount of space available for light mixing). 
     Infrared-light-blocking filter  60  may be formed from upper and lower infrared light-blocking layers  60 L. Each layer may include a substrate and a thin-film filter dielectric stack on one or both sides of the substrate configured to block infrared light while passing visible light. 
     Pressure sensitive adhesive rings  90  may separate layers  62 L and  60 L from each other. Pressure sensitive adhesive ring  116  may be used to couple printed circuit  94  to support structures  86 . 
     Light detector integrated circuit  58  may be formed from a silicon die or other semiconductor die. Wire bonds  100  may be used to couple wire bond pads on integrated circuit  58  to wire bond pad on printed circuit  94 . Solder joints  98  may be used to couple signal paths formed from metal traces  112  in flexible printed circuit  96  to signal paths  114  in printed circuit  94  (e.g., signal paths formed from metal lines in printed circuit  94  that are coupled to wire bonds  100 ). In this way, the circuitry of light detector integrated circuit  58  is coupled to the signal paths in flexible printed circuit  96  (e.g., so that these signal paths may route signals to and from control circuitry  16 ). If desired, light detector integrated circuit  58  of  FIG. 6  may be provided with through-silicon vias to electrically couple circuitry in integrated circuit  58  to printed circuit  94  without using bond wires. 
     Light detector integrated circuit  58  may include multiple photodetectors  102  (e.g., photodiodes). Each photodetector  102  may be overlapped by a respective color filter  108 . Each color filter may be formed from colored ink or other material that selectively passes a desired range of wavelengths to an associated overlapped photodetector  102  (e.g., an organic color filter material such as polymer containing dyes and/or pigments). For example, a red-pass color filter may overlap a first photodetector  102  to form a red-light-sensing channel in ambient light sensor  30 , a blue-pass color filter may overlap a second photodetector  102  to form a blue-light-sensing channel in ambient light sensor  30 , etc. Stray infrared light may be blocked using a thin-film interference filter such as filter  104  formed from a stack of dielectric layers (e.g., alternating higher and lower refractive index thin-film inorganic layers). Filter  104  may, for example, have a configuration of the type described in connection with dielectric stack  72  of  FIG. 5 . Filter  104  may be formed from any suitable number of dielectric layers  100  (e.g., at least 5, at least 10, at least 20, 20-80, fewer than 100, etc.). Layers  100  may be formed on the upper surface of light detector integrated circuit  58  overlapping each of photodetectors  102  and interposed between color filters  108  and photodetectors  102 . Encapsulant  92  (e.g., a clear polymer such as epoxy) may be used to protect the silicon integrated circuit die that forms integrated circuit  58  from environmental contamination. 
     Light transmission curves  120  and  122  of  FIG. 7  represent illustrative light transmission characteristics (band-pass characteristics) for color filters  108 . Curve  120  may, as an example, be associated with a blue color filter and may cover a range of blue wavelengths, whereas curve  122  may be associated with a green color filter and may cover green wavelengths (as an example). As shown in  FIG. 7 , dye and/or pigment based color filters formed from organic materials (e.g., polymer colored with dye and/or pigment) may be transparent at infrared wavelengths. To ensure that stray infrared light that passes through color filters  108  does not reach photodetectors  102 , visible-light-transmitting-and-infrared-light blocking layer (filter)  104  may have a light transmission characteristic of the type shown by curve  124  of  FIG. 8  that blocks infrared light. Configurations may also be used for ambient light sensor  30  in which the color filter for each channel in color ambient light sensor  30  of  FIG. 6  is formed from a thin-film interference filter configured to serve as a bandpass filter for a range of wavelengths associated with that channel. 
     If desired, an ambient light sensor may include a light guide. The light guide may help route incoming ambient light to light detector integrated circuit  58  past an electrical component such as a speaker. Consider, as an example, the arrangement shown in  FIG. 9 .  FIG. 9  is a cross-sectional side view of the upper edge portion of device  10  of  FIG. 2 . As shown in  FIG. 9 , display cover layer  78  may overlap an array of pixels  38  for display  14  in active area AA. In inactive area IA, speaker  126  may be mounted in alignment with speaker port  34  in display cover layer  78 . Speaker  126  may be relatively wide and the amount of space between speaker  126  and the adjacent sidewall of housing  32  (e.g., the topmost peripheral edge of housing  32  in  FIG. 2 ) may accordingly be relatively small. This constrains the amount of lateral space available for accommodating color ambient light sensor  30  near display cover layer  78 . 
     Color ambient light sensor  30  may have a lower portion such as portion  30 L that is relatively wide to house light detector integrated circuit  58  and may have a narrower upper portion such as portion  30 T that contains a light guide and that can therefore be accommodated in the relatively narrow space between speaker  126  and sidewall  32 W of housing  32 . The light guide in portion  30 T is interposed between speaker  126  and housing sidewall  32 SW along the upper peripheral edge of housing  32 . To help provide incoming ambient light  54  to the photodetectors in light detector integrated circuit  58  in the limited space available between speaker port  34  and housing sidewall  32 SW of housing  32 , the light guide of ambient light sensor portion  30 T may be configured to guide incoming light  54  from optical component window  34  to photodetectors on light detector integrated circuit  58  past speaker  126 . 
       FIG. 10  is a cross-sectional side view of an illustrative color ambient light sensor with a light guide of the type shown in  FIG. 9 . As shown in  FIG. 10 , color ambient light sensor  30  may include support structure  86  (sometimes referred to as an ambient light sensor housing structure, housing, body, etc.). Support structure  86  may be formed from an opaque material such as black polymer. An upper portion of support structure  86  in portion  30 T of sensor  30  may be coupled to a lower portion of support structure  86  in portion  30 L of sensor  30  using pressure sensitive adhesive  130 . 
     Light guide  132 , which may sometimes be referred to as a light pipe, waveguide, or light guide structure, may have a core such as core  134  and a cladding such as cladding  136  that surrounds core  134 . Core  134  may have a higher index of refraction than cladding  136  to promote total internal reflection and guiding of ambient light  54  within light guide  132 . For example, core  134  may have an index of refraction of 1.5-2.0 and cladding  136  may have an index of refraction of 1.1-1.5 (as examples). Core  134  and cladding  136  may be formed from glass, polymer, sapphire or other transparent crystalline material, or other transparent material. As an example, core  134  may be formed from glass and cladding  136  may be formed from a polymer having a lower index of refraction than the glass of core  134 . Configurations in which cladding  136  is omitted and in which core  134  is surrounded by an air gap to ensure that light is guided within core  134  in accordance with the principal of total internal reflection may also be used, if desired. In arrangements in which cladding  136  is present, dust and other contaminants that might otherwise contact the outer surface of core  134  can be prevented from contacting core  134 . This can improve the reliability of light guide  132 . The presence of cladding  136  may also help support light guide  132  within support structure  86  and may thereby help enhance the ability of light guide  132  to withstand damage during a drop event. 
     Diffuser  62  may diffuse incoming ambient light  54  and may be located between the upper surface of light guide  132  and the lower surface of display cover layer  78  ( FIG. 9 ). After propagating through light guide  132 , ambient light  54  may pass through visible-light-transmitting-and-infrared-light blocking filter  60 . Filter  60  may be mounted in a recessed portion of support structure  86  in lower portion  30 L and may be coupled to support structure  86  using a ring of pressure sensitive adhesive  90 . Rings of pressure sensitive adhesive  90  may also separate diffuser layers  62 L from each other and from light guide  132  to form air gaps  88 . Filter  60  may have a substrate such as substrate  76  of  FIG. 5  (e.g., an infrared-light-blocking glass layer such as a blue borosilicate glass layer or other glass layer that prevents passage of infrared light) and may have upper and lower dielectric stacks  72  on the glass layer that are formed from thin-film inorganic dielectric layers or other dielectric layers  74  with alternating higher and lower refractive index values. Stacks  72  form a thin-film interference filter that passes visible light while blocking infrared light. Because filter  60  is located close to light detector integrated circuit  58  (e.g., because filter  60  is between light guide  132  and integrated circuit  58 ), stray infrared light that enters into the interior of support structure  86  (e.g., at locations near adhesive  130 ) will be blocked and prevented from reaching light detector integrated circuit  58 . If desired, infrared filters such as filter  60  may be placed elsewhere in color ambient light sensor  30  such as between diffuser  62  and light guide  132 . 
     Color filters  108  (e.g., band pass filters having pass bands in different wavelength ranges) may be formed over respective photodetectors  102  in integrated circuit  58  to provide ambient light sensor  30  with color light sensitivity. Encapsulant  92  (e.g., one or more layers of clear polymer such as epoxy, etc.) may be used to cover integrated circuit  58 . Wire bonds  100 , traces  114  in printed circuit  94 , solder joints  98 , and traces  112  in flexible printed circuit  96  may be used to route signals between control circuitry  16  and integrated circuit  58 . If desired, light detector integrated circuit  58  of  FIG. 10  may be provided with through-silicon vias to electrically couple circuitry in integrated circuit  58  to printed circuit  94  without using bond wires. 
     As shown in  FIG. 11 , color filters  108  of  FIG. 10  may be thin-film interference filters. Each color filter  108  for color ambient light sensor  30  of  FIG. 10  may, for example, have a stack of 5-100 dielectric layers  170  (e.g., inorganic dielectric layers such as silicon oxide, niobium oxide, aluminum oxide, tantalum oxide, titanium oxide, silicon nitride, etc. and/or organic dielectric layers) with alternating refractive index values to form desired bandpass color filters for respective photodetectors  102  in integrated circuit  58 . Transmission versus wavelength characteristics for illustrative color filters  108  of the type shown in  FIG. 11  are shown by curves  172  and  174  in  FIG. 12 . As shown in  FIG. 12 , the thin-film interference filter structures that are used in forming filters  108  may be configured to block infrared light. 
     An illustrative circular photodetector layout for photodetectors  102  of integrated circuit  58  of  FIG. 6  is shown in  FIG. 13 . An illustrative elongated rectangular layout for photodiodes  102  of integrated circuit  58  of  FIG. 10  is shown in  FIG. 14 . Other configurations may be used, if desired. In arrangements of the type shown in  FIGS. 13 and 14 , photodetectors for different color channels can be distributed throughout sensor  30  and, if desired, redundant photodetectors (e.g., photodetectors measuring the same color of ambient light) may be included in ambient light sensor  30 . As an example, photodetectors  102  of  FIG. 13  and/or  FIG. 14  may include photodetectors for 3-10 different color channels (including an optional clear color channel) and each color channel may have 1-5 different individual photodetectors  102  for gathering ambient light color readings for that color channel. Circuitry in integrated circuit  58  (e.g., switching circuitry, amplifier circuitry, analog-to-digital conversion circuitry, communications circuitry for supporting communications with control circuitry elsewhere in device  10 , etc.) may be incorporated into integrated circuit  58  with photodetectors  102  or, if desired, some or all of this supporting circuitry for photodetectors  102  may be formed in one or more integrated circuits that are separate from integrated circuit  58 . 
     Ambient light sensor measurements from ambient light sensor  30  may be used to control the operation of device  10 . For example, control circuitry  16  may adjust the intensity of images displayed on display  14  in response to measured changes in the intensity of ambient light. If, as an example, a user moves device  10  to a bright outdoors environment, control circuitry  16  may increase the brightness of display  14  to overcome glare. Color changes (e.g., white point adjustments) can also be made based on ambient light sensor measurements. If, for example, ambient light color measurements indicate that ambient lighting has become warm (e.g., when a user moves device  10  indoors), the white point of display  14  can be adjusted by control circuitry  16  so that display  14  displays corresponding warmer content. 
     If desired, the gathering of ambient light sensor measurements and the illumination of external objects using light sources such as infrared light-emitting diode  22  may be coordinated. With one illustrative arrangement, ambient light sensor measurements may momentarily be paused whenever light-emitting diode  22  emits a pulse of light. With another illustrative arrangement, a flag may be set whenever light-emitting diode  22  is activated during the gathering of ambient light sensor measurements (e.g., so that these measurements, which may be contaminated by noise from the light from diode  22 , may be discarded). In yet another embodiment, potential light contamination from adjacent electronic devices may be detected using a light sensor (e.g., an infrared light sensor). If light from nearby devices is detected, ambient light sensor measurements can be discarded. 
       FIG. 15  is a circuit diagram of illustrative circuitry for device  10  that may be used in coordinating the operation of ambient light sensing circuitry and light-emitting circuitry in accordance with an embodiment. As shown in  FIG. 15 , ambient light sensor  30  may be formed from a photodetector such as a photodiode. The output of photodetector (ambient light sensor)  30  may be provided to integrating analog-to-digital converter  190 . During operation, integrating analog-to-digital converter  190  may integrate the photodiode current associated with the photodetector of ambient light sensor  30  and may supply corresponding digital ambient light sensor measurement data to control circuitry  16 . The time periods during which ambient light sensor  30  gathers ambient light data can be controlled by control circuitry  16 . For example, control circuitry  16  can supply control signals (sometimes referred to as a HOLD signal) to switching circuitry such as switches  192  and  194 . When the hold signal is asserted, switch  192  is closed and shorts node N to ground, thereby shunting the photodiode current from the photodiode of ambient light sensor  30  to ground. At the same time, assertion of the hold signal opens switch  194 , so that node N is disconnected from the input to integrating analog-to-digital converter  190 . When the HOLD signal is deasserted, switch  192  is opened and switch  194  is closed, so that integrating analog-to-digital converter  190  can gather ambient light data. 
     Control circuitry  16  can also control the operation of circuitry  196  such as infrared light-emitting diode  22  and infrared image sensor  28  (e.g., using enable signals). For example, control circuitry  16  can direct light-emitting diode  22  to emit a pulse of light while directing image sensor  28  to capture an image frame (e.g., an image frame containing facial information or other user biometric information). In some configurations, control circuitry  16  may gather light measurements from a light sensor such as infrared light sensor  198  (e.g., an infrared photodetector such as a photodiode). 
     In one illustrative arrangement, control circuitry  16  uses switches  192  and  194  to momentarily pause the integration of ambient light sensor signals whenever infrared-light-emitting diode  22  is being used to emit a pulse of infrared illumination. This helps prevent infrared-induced noise in the visible ambient light measurements being made with ambient light sensor  30 . Consider, as an example, the scenario of  FIGS. 16 and 17 . In this arrangement, control circuitry  16  is using ambient light sensor  30  to measure ambient light over a time period that extends from time t 0  to time t 5 . The duration of this period (e.g., t 5 -t 0 ) may be, for example, 100-700 ms, at least 25 ms, at least 40 ms, at least 75 ms, at least 150 ms, at least 300 ms, less than 150 ms, less than 500 ms, less than 700 ms, less than 900 ms, or other suitable time period. 
     Control circuitry  16  may capture images with infrared image sensor  28  during ambient light sensor data acquisition. For example, a user may awaken device  10  from a sleep state to use device  10 . Immediately upon awakening device  10  (e.g., at a time such as time t 0 ), control circuitry  16  may begin capturing image data with circuitry  196  (e.g., to allow a user to biometrically authenticate as an authorized user of device  10 ) while beginning to gather ambient light sensor measurements with ambient light sensor  30  (e.g., so that screen brightness of display  14  can be adjusted based on the ambient light sensor data as device  10  exits sleep mode). Because the infrared illumination produced by light-emitting diode  22  has the potential to create noise in the signal measurements gathered with ambient light sensor  30 , control circuitry  16  can synchronize the operation of circuitry  196  and ambient light sensor  30 . In particular, each time control circuitry  16  directs light-emitting diode  22  to output infrared light (for illuminating external objects being imaged by image sensor  28 ), control circuitry  16  may also direct ambient light sensor  30  to temporarily pause the gathering (integrating) of ambient light sensor data. 
     As shown in  FIG. 18 , the infrared light output (IR) of light-emitting diode  22  may be supplied in one or more sets of pulses  200 . Each set of pulses  200  may include one or more pulses of light (e.g., at least 1, at least 2, at least 4, at least 8, at least 15, at least 20, fewer than 100, fewer than 25, fewer than 10, etc.). The pulses may each have a duration of 3 ms, at least 1 ms, less than 5 ms, or other suitable duration. During each pulse (or multiple pulses), a corresponding image frame may be acquired by image sensor  28 . The use of pulsed light may allow light-emitting diode  22  to produce a higher peak light output than would be possible if using continuous illumination, thereby reducing signal-to-noise during image capture operations with infrared image sensor  28 . Pulsed light may also help reduced thermal loads and enhance battery life. The light intensity produced by light-emitting diode  22  may be relatively high, so control circuitry  16  can pause ambient light sensor data gathering (e.g., integration by integrating analog-to-digital converter  190 ) each time light-emitting diode  22  is producing output, as shown by the complementary shapes of the pulses in  FIGS. 16 and 17 . 
     To ensure that ambient light sensor integration operations have been successfully paused before any infrared light is emitted by light-emitting diode  22 , control circuitry  16  can assert the HOLD signal before turning light-emitting diode  22  on. As shown in  FIG. 18 , for example, HOLD can be asserted at time ta. After a short delay (e.g., a delay of about 5 microseconds), switch  192  will close, switch  194  will open, and converter  190  will pause integration (e.g., at time tb). Light-emitting diode  22  may then generate output at time tc without risk of creating interference for the ambient light sensor. Similarly, light-emitting diode  22  may be turned off (time te) before ambient light sensor integration resumes (time tf). There may be a short delay between the release of signal HOLD and the resumption of ambient light sensing (switch  192  open, switch  194  closed, and converter  190  integrating). As a result, hold signal HOLD may, if desired, be deasserted at a time td that is slightly before light-emitting diode  22  is turned on to produce infrared output IR at time te, provided that ambient light sensor  30  becomes active (pausing ceases) at a time tf that is later than time te. 
     If desired, control circuitry  16  may use ambient light sensor  30  without pausing ambient light sensor  30  during light emission from light-emitting diode  22 . In the event that infrared light-emitting diode  22  is activated during the operation of ambient light sensor  30  (e.g., in the event that control circuitry  16  uses light-emitting diode  22  and image sensor  28  to capture images while ambient light sensor  30  is providing output that is being integrated by integrating analog-to-digital converter  190 ), control circuitry  16  can indicate that potential contamination of the ambient light sensor reading by emitted light from diode  22  has occurred (e.g., by setting a flag). Control circuitry  16  can then discard the ambient light sensor reading that has potentially been contaminated by light from diode  22  or can assert a bit to indicate that ambient light sensor data may be contaminated by infrared light.  FIG. 19  shows how ambient light data may be gathered by integrating an ambient light sensor photodiode current over period  210  (shown by the period that ALS is on in  FIG. 19 ).  FIG. 20  shows how a flag (FLAG) can be asserted during the ambient light sensor integration period (e.g., at time tflag) to indicate that light-emitting diode  22  has emitted infrared light during the use of ambient light sensor  30  to gather an ambient light sensor measurement. In response to determining that FLAG has been asserted during an ambient light sensor integration period (e.g., period  210  of  FIG. 19 ), control circuitry can discard the potentially contaminated ambient light sensor data from sensor  30  and can gather a new ambient light sensor measurement. 
     Another way in which to avoid potential contamination from infrared light involves the use of an infrared light sensor such as sensor  198  to determine when infrared light is being emitted. Sensor  198  may, for example, be used by control circuitry  16  to monitor for the presence of infrared light pulses from external light-emitting circuitry. As an example, sensor  198  may detect that infrared light has been emitted by circuitry  196  (e.g., an infrared light-emitting diode  22  that is providing illumination of external objects being imaged by a corresponding infrared light sensor  28 ) in a device other than device  10 . These potentially contaminating infrared light pulses may be emitted from nearby electronic devices (e.g., one or more electronic devices other than device  10 ) such as devices operated by other users. When infrared light pulses or other potentially contaminating infrared light is detected in the vicinity of device  10  using sensor  198 , a flag such as signal FLAG of  FIG. 20  may be asserted. Ambient light sensor data integrated over a period of time that overlaps the asserted flag may then be discarded. 
     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: 20170908
Publication Date: 20200204
Grant Date: 20200204
Priority Date: 20170908
Inventors: HOLENARSIPUR, PRASHANTH S.
ZHENG, DONG
ISIKMAN, SERHAN O.
Assignee: APPLE INC
CPC Classifications: [{"code": "G01J2003/2806", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0474", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0425", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0492", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0437", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0264", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0474", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J2001/448", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1684", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04N5/33", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1686", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J2003/2806", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0259", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0492", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N23/54", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N23/57", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2310/0259", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0437", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N5/33", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J1/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J2001/448", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0259", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G5/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J2003/2806", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J2001/448", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J1/0492", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0474", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0437", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0425", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0425", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K59/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N23/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N23/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N23/20", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 63452757