PATENT DOCUMENT

Publication Number: US-10614752-B1
Application Number: US-201816144990-A
Country: US
Kind Code: B1

Title: Electronic device with polarized ambient light sensor

Abstract:
An electronic device may be provided with an ambient light sensor. The ambient light sensor may be a color ambient light sensor or a monochrome ambient light sensor. The electronic device may have a light-emitting component such as a display. During operation of the display, the display emits light. To reduce noise due to the emitted light while measuring ambient light, the ambient light sensor may have optical structures such as wave plates and polarizers. Theses optical structures may overlap light detectors. The optical structures may be configured to prevent ambient light from reaching a first of the light detectors while allowing ambient light to reach a second of the light detectors. The ambient light sensor may be configured to receive ambient light that has passed thorough an inactive area of a display or that has passed through a pixel array in an active area of a display.

Claims:
What is claimed is: 
     
       1. An electronic device configured to operate in an environment with ambient light, comprising:
 a housing; 
 a display in the housing that is configured to emit display light; 
 an ambient light sensor that is exposed to the emitted display light and the ambient light, wherein the ambient light sensor has first and second light detectors, wherein the display light but not the ambient light is measured by the first light detector, and wherein both the ambient light and the display light are measured by the second light detector; and 
 control circuitry configured to use the ambient light sensor to measure the ambient light by processing output from the first and second light detectors to distinguish contributions due to the ambient light from contributions due to the emitted display light. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the display comprises a circular polarizer through which the ambient light passes before reaching the ambient light sensor. 
     
     
       3. The electronic device defined in  claim 2  wherein the display comprises an array of organic light-emitting diode pixels through which the ambient light passes after passing through the circular polarizer and before reaching the ambient light sensor and wherein the array of organic light-emitting diode pixels is configured to emit the display light. 
     
     
       4. The electronic device defined in  claim 3  wherein the ambient light sensor has a polarizer that overlaps the first light detector. 
     
     
       5. The electronic device defined in  claim 4  wherein the ambient light sensor has a wave plate and wherein the polarizer is between the wave plate and the first light detector. 
     
     
       6. The electronic device defined in  claim 4  wherein the ambient light sensor comprises a waveplate that overlaps the polarizer and wherein the wave plate and the polarizer are configured to prevent the ambient light from being measured by the first light detector. 
     
     
       7. The electronic device defined in  claim 3  wherein the ambient light sensor comprises:
 a first wave plate and a first polarizer that overlap the first light detector to prevent the ambient light that has passed through the circular polarizer from being measured by the first light detector; and 
 a second wave plate and a second polarizer that overlap the second light detector to allow the ambient light that has passed through the circular polarizer to be measured by the second light detector. 
 
     
     
       8. The electronic device defined in  claim 1  wherein the display has an array of pixels and wherein the ambient light detector is configured to receive the ambient light through the array of pixels. 
     
     
       9. The electronic device defined in  claim 8  further comprising optical structures that are configured to allow the first and second light detectors to receive different amounts of the ambient light. 
     
     
       10. The electronic device defined in  claim 1  wherein the display has an active area with an array of pixels that is configured to display an image, wherein the display has an inactive area that is free of pixels, and wherein the abient light dectector is configured to receive the ambient light through the inactive area. 
     
     
       11. The electronic device defined in  claim 10  wherein the inactive area contains a linear polarizer through which the ambient light passes. 
     
     
       12. The electronic device defined in  claim 11  further comprising an ambient light sensor polarizer overlapping the first light detector, wherein the linear polarizer has a first pass axis and wherein the ambient light sensor polarizer has a second pass axis that is orthogonal to the first pass axis. 
     
     
       13. The electronic device defined in  claim 9  wherein the control circuitry is configured to adjust the display based on the measured ambient light. 
     
     
       14. The electronic device defined in  claim 13  wherein the control circuitry is configured to adjust a color cast of the display based on the measured ambient light. 
     
     
       15. An electronic device configured to operate in an environment with ambient light, comprising:
 a housing; 
 a display coupled to the housing, wherein the display has an array of pixels through which the ambient light passes; and 
 an ambient light sensor having optical structures including an ambient light sensor polarizer, wherein the ambient light sensor is configured to measure the ambient light that has passed through the array of pixels and wherein the ambient light sensor comprises a first light detector that is overlapped by the ambient light sensor polarizer and that does not receive the ambient light and comprises a second light detector that receives the ambient light. 
 
     
     
       16. The electronic device defined in  claim 15  wherein the display includes a circular polarizer, wherein the ambient light has a polarization state after passing through the circular polarizer and the array of pixels and wherein the ambient light sensor comprises a wave plate that converts the polarization state of the ambient light into a linear polarization before the ambient light reaches the ambient light sensor polarizer. 
     
     
       17. The electronic device defined in  claim 16  wherein the first light detector is overlapped by the wave plate. 
     
     
       18. An electronic device configured to operate in an environment with ambient light, comprising:
 a housing; 
 a display coupled to the housing, wherein the display has an array of pixels with light-emitting diodes; and 
 an ambient light sensor having a first light detector and a second light detector and having a linear polarizer that overlaps the first light detector but not the second light detector, wherein the linear polarizer is configured to receive ambient light that has passed through the array of pixels. 
 
     
     
       19. The electronic device defined in  claim 18  wherein the display comprises a circular polarizer through which the ambient light passes, wherein the ambient light sensor has a waveplate that is configured to convert the ambient light that has passed through the array of pixels to linearly polarized ambient light, and wherein the linear polarizer is between the wave plate and the first light detector and is configured to prevent the linearly polarized ambient light from reaching the first light detector. 
     
     
       20. The electronic device defined in  claim 19  wherein the second light detector is configured to detect the ambient light that has passed through the array of pixels.

Description:
BACKGROUND 
     This relates generally to electronic devices, and, more particularly, to light sensors for electronic devices. 
     Electronic devices such as laptop computers, cellular telephones, and other equipment are sometimes provided with light sensors. For example, ambient light sensors may be incorporated into a device to provide the device with information on current lighting conditions. Ambient light readings may be used in controlling the device. If, for example bright daylight conditions are detected, an electronic device may increase display brightness to compensate. Color ambient light sensors can detect changes in the color of ambient light so that compensating color cast adjustments can be made to displayed content. 
     It can be challenging to incorporate ambient light sensors into electronic devices. If care is not taken, an ambient light sensor may consume more space in an electronic device than desired. In some arrangements, there may be challenges associated with operating an ambient light sensor accurately due to potential interference from other components. 
     SUMMARY 
     An electronic device may be provided with a light-detecting component such as an ambient light sensor. The ambient light sensor may be a color ambient light sensor or a monochrome ambient light sensor. Control circuitry in the electronic device may use information from the ambient light sensor in adjusting the operation of the electronic device. For example, the electronic device may be provided with a display. The brightness and/or color of the display may be adjusted dynamically based on intensity and/or color measurements from the ambient light sensor. 
     During operation of the electronic device, the display in the electronic device may emit light. To reduce noise from the emitted light and thereby enhance the accuracy of the ambient light sensor, the ambient light sensor may have optical structures such as wave plates and polarizers. These optical structures may overlap light detectors in the ambient light sensor. In an illustrative configuration, the optical structures of the ambient light sensor are configured to prevent ambient light from reaching a first of the light detectors while allowing ambient light to reach a second of the light detectors. The control circuitry can process the output of the first and second light detectors to remove display noise contributions from ambient light measurements. 
     The display of the electronic device may be an organic light-emitting diode display or other display with an array of light-emitting diode display pixels or may be a liquid crystal display or other display. The ambient light sensor may be configured to receive ambient light that has passed thorough an inactive area of a display or may be configured to receive ambient light that has passed through a pixel array in an active area of a display. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device having an ambient light sensor in accordance with an embodiment. 
         FIG. 2  is a perspective view of an electronic device with an ambient light sensor in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative ambient light sensor in an electronic device in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of an illustrative light-emitting diode display and ambient light sensor in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative liquid crystal display and ambient light sensor in accordance with an embodiment. 
         FIG. 6  is a diagram of an illustrative ambient light sensor with an adjustable polarizer layer in accordance with an embodiment. 
         FIG. 7  is flow chart of illustrative operations involved in operating an electronic device with an ambient light sensor in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with one or more light sensors is shown in  FIG. 1 . Electronic device  10  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     As shown in  FIG. 1 , electronic device  10  may have control circuitry  16 . Control circuitry  16  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  16  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. Control circuitry  16  may include communications circuitry for supporting wired and/or wireless communications between device  10  and external equipment. For example, control circuitry  16  may include wireless communications circuitry such as cellular telephone communications circuitry and wireless local area network communications circuitry. 
     Input-output circuitry in device  10  such as input-output devices  12  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  12  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  12  and may receive status information and other output from device  10  using the output resources of input-output devices  12 . 
     Input-output devices  12  may include one or more displays such as display  14 . Display  14  may be a touch screen display that includes a touch sensor for gathering touch input from a user or display  14  may be insensitive to touch. A touch sensor for display  14  may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, a light-based touch sensor, or other suitable touch sensor arrangements. 
     Input-output devices  12  may also include sensors  18 . Sensors  18  may include a capacitive sensor, a light-based proximity sensor, a magnetic sensor, an accelerometer, a force sensor, a touch sensor, a temperature sensor, a pressure sensor, a compass, a microphone, a radio-frequency sensor, a three-dimensional image sensor, a camera, a light-based position sensor (e.g., a lidar sensor), and other sensors. Sensors  18  may also include one or more light detectors that are configured to detect ambient light. Sensors  18  may, for example, include one or more monochrome ambient light sensors and one or more color ambient light sensors that are configured to measure ambient light from the environment in which device  10  is operated. A monochrome ambient light sensor may be used to measure ambient light intensity. A color ambient light sensor may be used to measure the color (color spectrum, color temperature, color coordinates, etc.) of ambient light and may be used to measure ambient light intensity. 
     To make color measurements, a color ambient light sensor in device  10  may have a light detector such as a photodiode that is overlapped by a tunable wavelength filter and/or may have multiple channels each of which has a light detector such as a photodiode that is overlapped by a filter that passes a different color of light (e.g., a different wavelength band) to that light detector. By processing the readings from each of the multiple channels, the relative intensity of each of the different colors of light can be determined. Using data from the different channels in a color ambient light sensor, control circuitry  16  can therefore produce ambient light color temperature measurements and other color measurements (e.g., colors represented in color coordinates, etc.). The ambient light spectrum information may be used in controlling display  14  and/or in taking other actions in device  10 . As an example, the color cast of images displayed on display  14  can be adjusted based on ambient light color measurement (e.g., to make the images on display  14  yellower in warm ambient lighting conditions and to make the images on display  14  bluer in cold ambient lighting conditions). If desired, display brightness may be automatically increased by control circuitry  16  in response to detection of bright ambient light conditions and may be automatically decreased by control circuitry  16  in response to detection of dim ambient light conditions. 
     Electronic device  10  may include one or more ambient light sensors. Illustrative arrangements in which device  10  includes a single ambient light sensor are sometimes described herein as an example. The ambient light sensor may be located behind a window in a housing member, under an inactive portion of a display (e.g., a border portion of a display that does not contain pixels) and/or may be located elsewhere within device  10 . If desired, electronic device  10  may have an ambient light sensor that is overlapped by pixel array in an active area of a display (e.g., a portion of the display that is configured to display images). The display may have transparent portions (e.g., transparent gaps between metal traces and other opaque structures) so that ambient light may pass through the pixel array to the overlapped ambient light sensor. By locating the ambient light sensor behind the active area of the display in this way, the appearance of device  10  may be enhanced and the amount of space consumed by the ambient light sensor may be reduced. Configurations in which the ambient light sensor is located under an inactive display area or is located elsewhere within device  10  may also be used. 
     A perspective view of an illustrative electronic device of the type that may include an ambient light sensor is shown in  FIG. 2 . In the example of  FIG. 2 , device  10  includes a display such as display  14  mounted in housing  22 . Display  14  may be a liquid crystal display, an electrophoretic display, an organic light-emitting diode display or other display with an array of light-emitting diodes (e.g., a display that includes pixels having diodes formed from crystalline semiconductor dies), may be a plasma display, may be an electrowetting display, may be a display based on microelectromechanical systems (MEMS) pixels, or may be any other suitable display. Display  14  may have an array of pixels  26  that extend across some or all of front face F of device  10  and/or other external device surfaces. The pixel array may be rectangular or may have other suitable shapes. Display  14  may be protected using a display cover layer such as a layer of transparent glass, clear plastic, sapphire, or other clear layer. The display cover layer overlaps an array of pixels  26 . 
     Housing  22 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  22  may be formed using a unibody configuration in which some or all of housing  22  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Pixels  26  may cover substantially all of the front face of device  10  or display  14  may have inactive areas (e.g., notches or other regions) that are free of pixels  26 . The inactive areas may be used to accommodate an opening for a speaker and windows for optical components such as image sensors, an ambient light sensor, an optical proximity sensor, a three-dimensional image sensor such as a structured light three-dimensional image sensor, a camera flash, etc. Pixels  26  may, for example, extend over front surface F of device  10  and may overlap ambient light sensor  30 . In this type of arrangement, ambient light may pass to ambient light sensor  30  through the array of pixels  26  in display  14 . 
       FIG. 3  is a cross-sectional side view of device  10  of  FIG. 2  in an illustrative configuration in which pixels  26  overlap ambient light sensor  30 . As shown in  FIG. 3 , housing  22  of device  10  may enclose interior region  23 . Electrical components  38  (see, e.g., control circuitry  16  and input-output devices  12 ) may be mounted within interior region  23  (e.g., on one or more printed circuits such as printed circuit  36 ). 
     Pixel array  40  includes an array of pixels  26 . Pixels  26  extend over front face F of device  10  and form in an active area for display  14  in which images are displayed. Display cover layer  32  may overlap pixel array  40 . Each pixel  26  may be formed from thin-film transistors and other components (e.g., liquid crystal display pixel components such as pixel electrodes, light-emitting diode pixel components such as light-emitting diodes, etc.). Metal traces and other opaque structures in pixels  26  may block light, however, pixel array  40  may also include transparent regions between the opaque structures. The presence of transparent areas in pixel array  40  allows ambient light  34  to pass through pixel array  40  among pixels  26  to reach ambient light sensor  30 . 
     As the example of  FIG. 3  demonstrates, ambient light sensor  30  may, in some configurations, be mounted under pixel array  40 . In this location within interior  23  of housing  22 , the active area of display  14  that is formed by pixel array  40  overlaps ambient light sensor  30  when viewed from the exterior of device  10 . By mounting ambient light sensor  30  behind pixel array  40  in this way, the overall size of device  10  can be reduced, the appearance of device  10  may be enhanced, and inactive display area may be reduced. 
     During operation of display  14  to display content for a user, display  14  emits light. Some of the emitted light may leak into interior region  23  and may reach ambient light sensor  30 . This emitted light therefore represents a potential source of noise that has the potential to interfere with accurate measurements of ambient light  34 . To ensure that accurate ambient light sensor measurements are made even in the presence of light from display  14 , ambient light sensor  30  may be provided with optical structures that help discriminate between ambient light and emitted display light. The optical structures may include, for example, wave plates and polarizers. By configuring ambient light sensor  30  to discriminate between ambient light and emitted display light, control circuitry  16  can remove emitted noise contributions such as display light contributions from ambient light sensor readings before control circuitry uses these readings in making display adjustments or taking other action. 
       FIG. 4  is a cross-sectional side view of an illustrative pixel array and ambient light sensor. In the example of  FIG. 4 , pixel array  40  is a light-emitting diode pixel array. Each pixel  26  in pixel array  40  includes a light-emitting diode  26 ′ (e.g., an organic light-emitting diode or a light-emitting diode formed from a crystalline semiconductor die). To suppress reflections of ambient light  34  from pixel array  40  as display  14  is viewed by user  33  in direction  35 , display  14  may be provided with circular polarizer  46 . Circular polarizer  46  may include linear polarizer  42  and quarter wave plate  44 . 
     Light that is emitted outwardly by diodes  26 ′ may be viewed as images on display  14 . Some of this emitted light may scatter from the structures of display  14  and other structures in device  10  and may leak into interior region  23 , where this leaked light is detected by ambient light sensor  30  (see, e.g., emitted display light  48 ). To help determine which portion of the light received at ambient light sensor  30  corresponds to ambient light  34  that has passed through pixel array  40  and which portion of the light received at ambient light sensor  30  corresponds to emitted display light  48 , ambient light sensor  30  may be provided with optical structures  57  and multiple light detectors (see, e.g., light detectors  58 - 1  and  58 - 2 , which may be formed from individually controlled photodetectors or other light detecting devices). 
     There may, in general, be any suitable number of photodetectors or other light detectors in ambient light sensor  30  (e.g., two, at least four, at least six, at least 10, fewer than 50, fewer than 30, etc.). In color ambient light sensors, there may be, for example, multiple different color channels (e.g., red, blue, green, etc.) each of which detects light in a different band of wavelengths and each of these color channels may include a pair of photodetectors such as illustrative light detectors  58 - 1  and  58 - 2 . In a monochrome ambient light sensor configuration, light detectors  58 - 1  and  58 - 2  may both be monochrome light detectors. An illustrative monochrome configuration for ambient light sensor  30  is described herein as an example. If desired, ambient light sensor  30  may be configured to make color ambient light sensor measurements by including pairs of detectors such as detectors  58 - 1  and  58 - 2 , each pair corresponding to a different color channel. 
     In the illustrative monochrome ambient light sensor configuration, ambient light sensor  30  includes first detector  58 - 1  and second detector  58 - 2  and each of these light detectors is overlapped by respective optical structures. As shown in  FIG. 4 , for example, first detector  58 - 1  may be overlapped by waveplate (retarder)  52  and polarizer  50  and second detector  58 - 2  may be overlapped by waveplate  56  and polarizer  54 . Waveplate  52  and polarizer  50  are configured to block ambient light  34 . As ambient light  34  passes from exterior region  37  to interior  23  of device  10  through display  14 , this ambient light passes through linear polarizer  42 . Linear polarizer  42  converts the ambient light to linearly polarized ambient light. The linearly polarized ambient light then passes through quarter-wave plate  44  of circular polarizer  46  and becomes circularly polarized. There may be one or more layers (e.g., a polyimide substrate layer, etc.) in pixel array  40  that are birefringent. As the circularly polarized ambient light passes through pixel array  40 , the birefringence that may be present in pixel array  40  may cause the circularly polarized ambient light to become elliptically polarized. 
     Waveplate  52  may be configured to convert the circularly or elliptically polarized state of the ambient light that has passed through pixel array  40  into linearly polarized light. If, for example, the ambient light passing through pixel array  40  is circularly polarized, waveplate  52  may be a quarter-wave plate. If the ambient light passing through pixel array  40  is elliptically polarized, waveplate  52  may have a different configuration (e.g., waveplate  52  may be a ⅛-wave plate, a ⅜-wave plate, etc.). A satisfactory configuration for waveplate  52  may be selected based on experimental measurements of the polarization state of light after passing through pixel array  40 . 
     Due to the presence of waveplate  52 , the ambient light that has passed through pixel array  40  and waveplate  52  will be linearly polarized. To block this light and thereby prevent ambient light  34  from being detected by detector  58 - 1 , polarizer  50  may be a linear polarizer having a pass axis that is oriented to be perpendicular to the linear polarization orientation of the light that has passed through waveplate  52 . Display light  48  will be unpolarized or will have another polarization state that is different than the linear polarization of the light that has passed through waveplate  52 . As a result, detector  58 - 1  will detect emitted display light  48  that has leaked into interior  23  but will not detect ambient light  34 . 
     The optical structures above detector  58 - 2  may be configured so that detector  58 - 2  detects ambient light  34 . These optical structures may also be configured to help reduce the amount of emitted display light  48  that is detected by detector  58 . As an example, the optical structures above detector  58 - 2  may include waveplate  56  and polarizer  54 . Waveplate  56  may be configured to convert ambient light  34  to linearly polarized light (e.g., waveplate  56  may have the same configuration as waveplate  52 ). Polarizer  54  may be a linear polarizer having a pass axis that is oriented to be parallel to the linear polarization orientation of the light that has passed through waveplate  56 . As a result, waveplate  56  and polarizer  54  will tend to allow all of ambient light  34  that has passed through display  14  pass to detector  58 - 2 . At the same time, waveplate  56  and polarizer  54  may help to reduce the amount of emitted display light  48  that is sensed by detector  58 - 2 . For example, if emitted display light  48  is unpolarized, the presence of polarizer  54  will cut the intensity of emitted display light  48  in half. 
     During ambient light sensor characterization operations (e.g., during design and testing), the output of detectors  58 - 1  and  58 - 2  under different conditions can be characterized. For example, display  14  may be turned off while a known amount of ambient light illuminates device  10 . Detector  58 - 1  will not pick up any ambient light due to the waveplate and polarizer above detector  58 - 1 . The sensitivity of detector  58 - 2  to ambient light can be determined by measuring the output of detector  58 - 2  at different ambient light levels. In a further set of characterization measurements, device  10  may be operated in a dark environment in which ambient light  34  is not present. During these measurements, display  14  may be operated to produce emitted display light  48  and the outputs of detectors  58 - 1  and  58 - 2  may be collected. In an illustrative configuration in which light  48  is not polarized, the output of detectors  58 - 1  and  58 - 2  may be equal when being exposed to light  48  and not being exposed to light  34 . 
     In mixed lighting conditions in which both ambient light  34  and display light  48  illuminate ambient light sensor  30 , the outputs of detectors  58 - 1  and  58 - 2  will have intermediate values that can be processed to determine the relative contributions of ambient light  34  and emitted display light  48 . If desired, weighting factors can be applied to the outputs of each detector in ambient light sensor  30  to produce individual readings of the intensity of ambient light  34  and emitted display light  48 . The equations used for mapping raw readings from detectors  58 - 1  and  58 - 2  to readings of ambient light and emitted display light may be stored in control circuitry  16  during calibration operations (e.g., ambient light sensor  30  can be calibrated based on the results of sensor characterization measurements made during initial design and testing of sensor  30  and device  10 ). 
     As this example demonstrates, control circuitry  16  can be calibrated so that the relative amounts of ambient light  34  and emitted display light  48  that are present can be deter mined using the outputs of detectors  58 - 1  and  58 - 2 . In a color ambient light sensor, the relative contributions of ambient light and emitted display light in each color channel can be determined. After determining intensity and/or color of ambient light that is present by removing the noise associated with emitted display light  48  from the measurements made by sensor  30 , control circuitry  16  can adjust display  14  or take other action. 
     In general, pixel array  40  may include pixels of any suitable type (e.g., light-emitting diode pixels, liquid crystal display pixels, etc.). Ambient light sensor  30  may be overlapped by pixel array  40  as shown in  FIG. 4  or may, if desired, be located in an inactive area of display  14 .  FIG. 5  is a cross-sectional side view of device  10  in an illustrative configuration in which display  14  has an active area AA with an array of pixels to display images and an inactive area IA that is free of pixels. In the  FIG. 5  example, display  14  is a liquid crystal display having a layer of liquid crystal material (liquid crystal layer  64 ) sandwiched between upper layer  62  and lower layer  66 . Upper layer  62  may be, for example, a color filter layer having an array of color filter elements and lower layer  66  may be a thin-film transistor layer having an array of thin-film pixel circuits for the pixels of display  14 . If desired, upper layer  62  may be a thin-film transistor layer and lower layer  66  may be a color filter layer or these layers may be formed on a single substrate. Layers  62  and  66  may have glass substrates or other transparent substrates and may be sandwiched between upper linear polarizer  60  and lower linear polarizer  68 . 
     During operation, light-emitting diodes  74  may emit light  72  into an adjacent edge of light guide layer  70 . This light may be guided within light guide layer  70  in accordance with the principal of total internal reflection. Some of this light may be scattered outwardly through the pixels of active area AA and therefore serves as backlight for display  14  (e.g., light guide layer  70  and diodes  74  and optional additional structures such as reflector layers, diffuser layers, and/or other layers may serve as a backlight unit for display  14 ). While the backlight is being produced for display  14 , some of the light in light guide layer  70  may be scattered out of light guide layer  70  and display  14  to locations in interior region  23  and can then be detected by ambient light sensor  30  as emitted display light  48  (e.g., light  48  may leak out of display  14  and may reach ambient light sensor  30 ). 
     In inactive area IA, lower display layer  66  may be transparent and liquid crystal layer  64  may be absent. Upper polarizer  60  may overlap inactive area IA. Lower polarizer  68  may be absent from inactive area IA. Opaque masking layer  76  (e.g., a black ink layer) may be formed between layers  62  and  66  to help hide internal components from view from the exterior of device  10 . A window such as ambient light sensor window  78  (e.g., a transparent window formed from an opening in layer  76  and/or a transparent material in an opening in layer  76 ) may be formed in inactive area IA in alignment with ambient light sensor  30 , so that ambient light sensor  30  receives ambient light  34 . As described in connection with display  14  of  FIG. 4 , ambient light that passes through display  14  (e.g., through upper polarizer  60  in inactive area IA in the example of  FIG. 5 ) may become linearly polarized. Ambient light sensor  30  of  FIG. 5  may therefore have a first detector such as detector  58 - 1  of  FIG. 4  that is covered with an orthogonal linear polarizer and may have a second detector such as detector  58 - 2  of  FIG. 5  that is covered with a parallel polarizer. In this example, wave plates  52  and  56  may be omitted, because the ambient light that passes through upper polarizer  60  becomes linearly polarized. 
     In general, any configuration for optical structures  57  that allows detectors  58 - 1  and  58 - 2  to produce readings that differentiate between ambient light and emitted display light (or light from other noise sources) may be used in ambient light sensor  30 . For example, waveplate  56  and/or polarizer  54  of  FIG. 4  may be omitted from ambient light sensor  30  of  FIG. 4 , etc. In the illustrative arrangement of  FIG. 6 , ambient light sensor  30  has a single light detector such as detector  58  (e.g., a single photodetector or, in a color ambient light sensor arrangement a single set of photodetectors overlapped by a single corresponding set of respective color filters). Polarizer  80  may be an electrically adjustable polarizer. Optional waveplate  82  may be configured to convert incoming circularly polarized ambient light  34  of  FIG. 4  to linearly polarized light as described in connection with wave plates  52  and  56  of  FIG. 4  or may be omitted (e.g., in an arrangement of the type show in  FIG. 5 ). When it is desired to make ambient light measurements, control circuitry  16  may use control input  84  to adjust the polarization state of adjustable polarizer  80  (e.g., to switch from linearly polarized to block ambient light to unpolarized or to switch between any other suitable set of distinct polarization states). The output from detector  58  in each of the different polarization states may then be processed (e.g., using weighting factors or other suitable processing techniques that remove the noise contribution from the measured data) to determine an accurate ambient light sensor reading. 
       FIG. 7  is a flow chart of illustrative operations involved in using ambient light sensor  30  in device  10 . 
     During the operations of block  90 , control circuitry  16  may make a first measurement with sensor  30  (e.g., a measurement with detector  58 - 1  or a measurement with detector  58  of  FIG. 6  while an adjustable optical component in sensor  30  such as adjustable polarizer  80  is in a first state). During the operations of block  92 , control circuitry  16  may make a second measurement with sensor  30  (e.g., a measurement with detector  58 - 2  or a measurement with detector  58  of  FIG. 6  while the adjustable optical component in sensor  30  such as adjustable polarizer  80  is in a second state). These measurements (and additional measurements from additional detectors in configurations in which ambient light sensor  30  is a color ambient light sensor with multiple color channels of different colors) may be processed during the operations of block  94  to separate out the ambient light contribution to the measurements from the non-ambient-light contribution. The ambient light contribution, which represents an accurate measurement of ambient light  34 , can then be used to take action during the operations of block  96 . For example, control circuitry  16  can adjust the brightness (luminance) of display  14  based on measured ambient light sensor intensity and/or may adjust the color cast of display  14  based on measured ambient light color. 
     
       
         
           
               
             
               
                   
               
               
                 Table of Reference Numerals 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 10 
                 Electronic Device 
                 12 
                 Input-Output Devices 
               
               
                   
                 14 
                 Display 
                 16 
                 Control Circuitry 
               
               
                   
                 18 
                 Sensors 
                 23 
                 Interior Region 
               
               
                   
                 22 
                 Housing 
                 26 
                 Pixels 
               
               
                   
                 30 
                 Light Sensor 
                 32 
                 Cover Layer 
               
               
                   
                 33 
                 User 
                 34 
                 Ambient Light 
               
               
                   
                 36 
                 Printed Circuit 
                 37 
                 Exterior Region 
               
               
                   
                 38 
                 Electrical 
                 40 
                 Pixel Array 
               
               
                   
                   
                 Components 
                   
                   
               
               
                   
                 42 
                 Linear Polarizer 
                 44 
                 Quarter Wave Plate 
               
               
                   
                 46 
                 Circular Polarizer 
                 48 
                 Display Light 
               
               
                   
                 50 
                 Polarizer 
                 52 
                 Wave Plate 
               
               
                   
                 54 
                 Polarizer 
                 56 
                 Wave Plate 
               
               
                   
                 57 
                 Optical Structures 
                 58-1 
                 Light Detector 
               
               
                   
                 58-2 
                 Light Detector 
                 60 
                 Upper Polarizer 
               
               
                   
                 62 
                 Upper Layer 
                 64 
                 Liquid Crystal Layer 
               
               
                   
                 66 
                 Lower Layer 
                 68 
                 Lower Linear 
               
               
                   
                   
                   
                   
                 Polarizer 
               
               
                   
                 70 
                 Light Guide Layer 
                 72 
                 Light 
               
               
                   
                 74 
                 Light-Emitting 
                 76 
                 Layer 
               
               
                   
                   
                 Diodes 
                   
                   
               
               
                   
                 78 
                 Light Sensor Window 
                 80 
                 Polarizer 
               
               
                   
                 82 
                 Optional Wave Plate 
                 84 
                 Control Input 
               
               
                   
                   
               
            
           
         
       
     
     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: 20180927
Publication Date: 20200407
Grant Date: 20200407
Priority Date: 20180927
Inventors: DODSON, CHRISTOPHER M.
POLYAKOV, ALEKSANDR N.
SHAO, Guocheng
HO, MENG-HUAN
Ran, Niva A.
ISIKMAN, SERHAN O.
BORSHCH, VOLODYMYR
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/2092", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B47/11", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B47/11", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B45/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/32", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B5/3025", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05B47/11", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/32", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B5/3025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B45/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02B20/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/281", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05B45/22", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 69946060