PATENT DOCUMENT

Publication Number: US-10720126-B2
Application Number: US-201816119834-A
Country: US
Kind Code: B2

Title: Color ambient light sensor with adjustable neutral density filter

Abstract:
A color ambient light sensor may gather ambient light measurements during operation of an electronic device. The color ambient light sensor may have a color ambient light detector and an adjustable neutral density filter. The electronic device may have components such as a camera and display that are adjusted using ambient light information from the color ambient light sensor. The display may have a display cover layer. Pixels in an active area of the display may display images through the display cover layer. An inactive area of the display may have an opaque masking layer on an interior surface of the display cover layer. An opening in the opaque masking layer may form an ambient light sensor window for the color ambient light sensor. The adjustable neutral density filter may be interposed between the color ambient light detector and the ambient light sensor window.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a housing; 
 a camera in the housing; 
 a display in the housing having a display cover layer, wherein the display has a pixel array that displays images through a portion of the display cover layer in an active area of the display, wherein the display has an opaque masking layer on a surface of the display cover layer in an inactive area of the display, and wherein an ambient light sensor window is formed in the opaque masking layer; 
 a color ambient light sensor having a color ambient light detector aligned with the ambient light sensor window and having an adjustable neutral density filter interposed between the ambient light sensor window and the color ambient light detector; and 
 control circuitry in the housing that:
 gathers a first ambient light measurement with the color ambient light sensor; 
 adjusts the adjustable neutral density filter using the first ambient light sensor measurement; 
 gathers a second ambient light measurement with the color ambient light sensor; and 
 adjusts a component using the second ambient light measurement, wherein the component comprises a component selected from the group consisting of: the display and the camera. 
 
 
     
     
       2. The electronic device defined in  claim 1  wherein the adjustable neutral density filter comprises an electrochromic device. 
     
     
       3. The electronic device defined in  claim 2  wherein the control circuitry compares an ambient light luminance value in the first ambient light measurement to a lower threshold and an upper threshold, wherein the control circuitry adjusts the adjustable neutral density filter to increase ambient light transmission through the adjustable neutral density filter in response to determining that the ambient light luminance value is below the lower threshold, and wherein the control circuitry adjusts the neutral density filter to decrease ambient light transmission through the adjustable neutral density filter in response to determining that the ambient light luminance value is above the upper threshold. 
     
     
       4. The electronic device defined in  claim 3  wherein the adjustable neutral density filter includes first and second transparent electrodes, first and second electrochromic layers between the first and second transparent electrodes, and a solid layer between the first and second electrochromic layers. 
     
     
       5. The electronic device defined in  claim 4  wherein the first electrochromic layer comprises nickel oxide, wherein the second electrochromic layer comprises tungsten oxide, and wherein the solid layer comprises silicon oxide. 
     
     
       6. The electronic device defined in  claim 3  wherein the control circuitry is configured to adjust a brightness level of the display using the second ambient light measurement. 
     
     
       7. The electronic device defined in  claim 3  wherein the display has an associated white point setting and wherein the control circuitry adjusts the white point setting using the second ambient light measurement. 
     
     
       8. The electronic device defined in  claim 3  wherein the camera has a white point setting and wherein the control circuitry is configured to adjust the white point setting using the second ambient light measurement. 
     
     
       9. The electronic device defined in  claim 2  further comprising a layer of ink in the ambient light sensor window that overlaps an opening and that is interposed between the display cover layer and the adjustable neutral density filter. 
     
     
       10. The electronic device defined in  claim 2  wherein the electrochromic device has a visible light transmission spectrum that varies by less than 10% between 400 nm and 700 nm. 
     
     
       11. The electronic device defined in  claim 2  wherein the color ambient light sensor comprises an array of photodetectors on a semiconductor substrate and wherein each photodetector is overlapped by a respective color filter with a different respective color. 
     
     
       12. The electronic device defined in  claim 2  wherein the control circuitry comprises wireless transceiver circuitry. 
     
     
       13. An electronic device, comprising:
 a housing; 
 a camera in the housing; 
 a display in the housing; 
 a color ambient light sensor having an adjustable neutral density filter and having a color ambient light detector that receives ambient light that passes through the adjustable neutral density filter; and 
 control circuitry in the housing that uses luminance information from the color ambient light sensor to adjust the neutral density filter. 
 
     
     
       14. The electronic device defined in  claim 13  wherein the adjustable neutral density filter comprises an electrochromic device. 
     
     
       15. The electronic device defined in  claim 14  wherein the control circuitry comprises wireless transceiver circuitry and wherein the control circuitry uses color measurements from the color ambient light sensor to adjust the display. 
     
     
       16. The electronic device defined in  claim 15  wherein the control circuitry uses luminance information from the color ambient light sensor to adjust the display. 
     
     
       17. The electronic device defined in  claim 16  wherein the display comprises a display cover layer, wherein a portion of the display cover layer is covered with opaque masking material, and wherein an ambient light sensor window in the opaque masking material is aligned with the adjustable neutral density filter. 
     
     
       18. The electronic device defined in  claim 17  wherein the opaque masking material comprises a first layer of ink that has an opening that forms the ambient light sensor window and wherein the ambient light sensor window includes a second layer of ink that has a light transmission that is greater than the first layer of ink. 
     
     
       19. A portable electronic device, comprising:
 a housing; 
 a camera in the housing; 
 a display in the housing having a display cover layer, wherein images are displayed through the display cover layer in an active area of the display and wherein ambient light passes through an ambient light sensor window in an inactive area of the display; 
 a color ambient light sensor having a color ambient light detector with multiple channels and having an adjustable neutral density filter interposed between the ambient light sensor window and the color ambient light detector; and 
 control circuitry in the housing that adjusts the adjustable neutral density filter using an ambient light measurement from the color ambient light sensor. 
 
     
     
       20. The portable electronic device defined in  claim 19  wherein the control circuitry is configured to adjust a selected one of: the camera and the display using information from the color ambient sensor.

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 a color ambient light sensor into an electronic device. If care is not taken, a color ambient light sensor in an electronic device may not perform as accurately as desired or may be unsightly. 
     SUMMARY 
     An electronic device may be provided with a color ambient light sensor. The color ambient light sensor may gather ambient light measurements during operation of the electronic device. The color ambient light sensor may include a color ambient light detector having multiple channels each of which is associated with a photodetector overlapped by a color filter of a different color. 
     The electronic device may have components such as a camera and display that are adjusted using ambient light information from the color ambient light sensor. For example, the white point of a camera may be adjusted based on measured ambient light color. Display color and brightness may also be adjusted using information such as color and/or luminance values measured with the color ambient light sensor. 
     The display may have a display cover layer. Pixels in an active area of the display may display images through the display cover layer. An inactive area of the display may have an opaque masking layer on an interior surface of the display cover layer. An opening in the opaque masking layer may form an ambient light sensor window for the color ambient light sensor. The color ambient light sensor may have an adjustable neutral density filter such as an electrochromic device. The adjustable neutral density filter may be interposed between the color ambient light detector and the ambient light sensor window. 
    
    
     
       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 color ambient light sensor in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative adjustable neutral density filter for an ambient light sensor in accordance with an embodiment. 
         FIG. 6  is a graph in which light transmission as a function of wavelength through an illustrative ink layer has been plotted for two different angles of incidence for the light in accordance with an embodiment. 
         FIG. 7  is a graph in which light transmission has been plotted as a function of wavelength for an illustrative adjustable neutral density filter in accordance with an embodiment. 
         FIG. 8  is a flow chart of illustrative operations associated with gathering and using color ambient light sensor measurements in an electronic device 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 wired and wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry such as cellular telephone transceiver circuitry, wireless local area network transceiver circuitry (e.g., WiFi® (IEEE 802.11) transceiver circuitry), Bluetooth® transceiver circuitry, millimeter wave transceiver circuitry, near field communications (NFC) transceiver circuitry, or other communications circuitry. Wireless communications circuitry may be used to support voice and/or video telephone calls, to transmit and receive data, etc. 
     Input-output circuitry in device  10  such as input-output devices  12  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  12  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, 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 digital image sensor (e.g., a visible light camera having a visible light image sensor and associated lens), infrared image sensors, and other sensors. Sensors  18  may also include one or more color ambient light sensors. 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 (luminance). 
     To make color measurements, a color ambient light sensor in device  10  may have multiple photodetectors each of which receives light through a different color filter. The color filters may have different colors that pass light at different respective wavelengths. In this way, the color ambient light sensor may make light intensity measurements in multiple different channels each of which is associated with a different color of light. The spectrum of ambient light can be determined from the relative intensities of the light measurements made by the photodetectors. 
     During operation, control circuitry  16  may use the color ambient light sensor to make measurements of the color and intensity of ambient light. These measurements may then be used to make adjustments to the operation of device  10 . For example, when bright ambient light conditions are detected, control circuitry  16  may increase the brightness of display  14  and when dim ambient light conditions are detected, control circuitry  16  may decrease the brightness of display  14 . As another example, the color cast of images displayed on display  14  can be adjusted based on ambient light color measurements from the color ambient light sensor. For example, the white point or other color settings associated with display  14  can be adjusted based on color ambient light measurements. Control circuitry  16  may, for example, adjust display  14  to make the images on display  14  more yellow in warm ambient lighting conditions and to make the images on display  14  bluer in cold ambient lighting conditions. Images captured with a digital image sensor (camera) in sensors  18  may also be affected by the color of ambient light. Control circuitry  16  may therefore make adjustments to the white point of a camera based on the measured color of the ambient light. 
     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  30 . Housing  30 , 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  30  may be formed using a unibody configuration in which some or all of housing  30  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass, clear plastic, sapphire, or other clear layer. Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button, a speaker port, or other components. Openings may be formed in housing  30  to form communications ports (e.g., an audio jack port, a digital data port, etc.), to form openings for buttons, etc. 
     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, 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 that extend across some or all of the front face of device  10  and/or other external device surfaces. The pixel array may be rectangular or may have other suitable shapes. 
     Optical components (e.g., a camera, a light-based proximity sensor, an ambient light sensor, status indicator light-emitting diodes, camera flash light-emitting diodes, etc.) may be mounted in an inactive portion of the display (e.g., a portion of the display without pixels), may be mounted along an edge of housing  30 , may be mounted on a rear housing wall, may be mounted in a location that allows light to pass between pixels in display  14 , and/or may be mounted in any other suitable location in device  10 . In one illustrative configuration, one or more openings (sometimes referred to as windows) may be formed in an opaque masking layer that is formed on an interior portion of the display cover layer for display  14 . For example, a light component window such as an ambient light sensor window may be formed in a peripheral portion of the front face of device  10  such as region  22 . Ambient light from the exterior of device  10  may be measured by an ambient light sensor in device  10  after passing through region  22  and the display cover layer in region  22 . If desired, other portions of device  10  may be provided with window regions to receive ambient light (e.g., openings may be formed in housing  30 , etc.). 
       FIG. 3  is a cross-sectional side view of display  14  of  FIG. 2  taken along line  24  and viewed in direction  26  of  FIG. 2 . As shown in  FIG. 3 , ambient light sensor  50  may be mounted in alignment with region (window)  22  (e.g., window  22  may overlap sensor  50 ). During operation, ambient light sensor  50  measures ambient light  42 . Ambient light  42  may be produced by one or more light sources (i.e., the sun, artificial lighting, etc.). Ambient light  42  may reach device  10  directly and/or may be reflected towards device  10  from objects in the environment surrounding device  10 . Incoming ambient light  42  may be characterized by rays of light that make an angle A with respect to surface normal n of display cover layer  44 . In typical lighting conditions, ambient light  42  will be characterized by a range of angles A. Ambient light  42  may be measured by ambient light sensor  50  after passing through window  22   
     As shown in  FIG. 3 , ambient light sensor  50  may include color ambient light detector  40  and adjustable neutral density filter  38 . Color ambient light detector  40  may be formed from a semiconductor substrate and may have multiple photodetectors (e.g., photodiodes, phototransistors, etc.) each of which has an associated color filter configured to pass light of a different respective color (e.g., a different respective band of wavelengths). Color ambient light detector  40  may have any suitable number N of photodetectors and associated color filters. For example, the value of N (which may sometimes be referred to as the number of channels for detector  40 ) may be 3-10, at least 4, at least 5, at least 7, at least 10, less than 25, less than 20, less than 15, less than 10, etc. During operation, color ambient light sensor  50  may measure the color and luminance of ambient light  42 . 
     Display  14  may have an active area in which images are displayed for a user and may have one or more inactive areas such as inactive borders, notches (e.g., elongated notches running along the edge of device  10 ), inactive area islands surrounded by active area pixels, or other pixel-free portions that do not display images. A portion of display cover layer  44  may cover the active area of display  14 . Pixel array  32  (e.g., an organic light-emitting diode display, a liquid crystal display, and/or other display layers that produce images for display  14 ) may be formed under display cover layer  44  in the active area and may display images during operation of device  10 . 
     Display cover layer  44  may also cover inactive display areas such as pixel-free notches in the edge of display  14 , pixel-free openings in the active region of display  14 , pixel-free inactive borders, and/or other inactive regions in display  14 . To hide components such as component  52  in the interior of device  10  from view from the exterior of device  10 , the inactive area of display  14  may include an opaque masking layer. As shown in  FIG. 3 , for example, opaque masking layer  34  may cover the interior surface of display cover layer  44  in the inactive display area (i.e., the portion of display  14  not overlapped by the pixels of pixel array  32 ). Opaque masking layer  34  may have a visible light transmission of less than 3%, less than 1%, more than 0.1%, or other suitable amount. With one illustrative configuration, opaque masking layer  34  is formed from a material that is sufficiently opaque to block 99% or more or 99.5% or more of ambient light  42 . 
     Opaque masking layer  34  may be formed from a layer of black ink (e.g., polymer with black embedded particles such as carbon black particles), may be a layer of ink of other colors (e.g., neutral colors such as white, silver, or gray, non-neutral colors such as red or blue, gold, etc.). Metal layers, thin-film interference filters thin-film mirrors, thin-film light-blocking filters, etc.) and/or one or more layers of other opaque materials may be used in forming opaque masking layer  34 , if desired. 
     Display cover layer  44  may be formed from glass, plastic, ceramic, sapphire, or other transparent materials and may be a part of display  14  (e.g., a display substrate) or a separate protective layer that covers active display structures. A window such as ambient light-sensor window  22  may be formed from a selectively thinned region of opaque masking layer  34  on the inner surface of display cover layer  44  or may be formed from an opening in opaque masking layer  34 . An opening in layer  34  that is associated with window  22  may be filled with optional window layer  36 . Window layer  36  may be formed from ink (e.g., black ink, colored ink, etc.), a thin-film interference filter structure such as a thin-film mirror, a metal layer, or other structure and may have different materials and/or structures than surrounding layer  34 . 
     Window layer  36  may be more transparent than opaque masking layer  34  to help pass sufficient light  42  to ambient light sensor  50  through window  22  to allow accurate ambient light measurements to be made. For example, window layer  36  may be formed from a more transparent type of ink and/or a thinner layer of ink than layer  34  to ensure that layer  36  transmits more of light  42  than layer  34 . The shape of window  22  and layer  36  may be circular, rectangular, oval, and/or may have other suitable shapes (e.g., other outlines when viewed from the front of device  10 ). 
     The amount of light  42  that reaches detector  40  is determined by the collective light transmission of optional window layer  36  and adjustable neutral density filter  38 . For example, the collective transmission of window material  36  (if present) and adjustable neutral density filter  38  may be 2-20%, may be 2-10%, may be 3-15%, may be at least 1.5%, may be at least 2%, may be at least 3%, may be at least 4%, may be at least 5%, may be less than 18%, may be less than 12%, may be less than 10%, etc.). In arrangements in which window layer  36  is present, window layer  36  may help block neutral density filter  38  from view from the exterior of device  10  and may help provide a matte appearance or other appearance to window  22  that matches surrounding portions of layer  34 . In arrangements in which window layer  36  is not present, neutral density filter  38  may exhibit a relatively low light transmission value (e.g., 2-20%, 2-10%, 3-15%, at least 1.5%, at least 2%, at least 3%, at least 4%, at least 5%, less than 18%, less than 12%, less than 10%, etc.). This may help block internal components  52  of device  10  from view from the exterior of device  10 . 
     The intensity of ambient light  42  may vary between dim (e.g., typical indoor light conditions or outdoor conditions at night) and bright (e.g., daytime outdoor conditions). The transmission of neutral density filter  38  may be adjusted dynamically to help ensure that the amount of light  42  that reaches detector  40  is within a desired operating range for detector  40  regardless of the intensity of light  42 . For example, in dim lighting conditions the transmission of neutral density filter  38  may be increased, thereby enhancing the ability of detector  40  to measure ambient light without excessive noise. In bright lighting conditions, where there is a risk that the photodetectors in detector  40  could be saturated from excessive light exposure, control circuitry  16  may dynamically decrease the light transmission of adjustable neutral density filter  38 , thereby decreasing the intensity of light reaching detector  40  and preventing detector saturation. 
       FIG. 4  is a cross-sectional side view of an illustrative color ambient light sensor. As shown in  FIG. 4 , color ambient light detector  40  may include photodetectors  56  (e.g., photodiodes or phototransistors). Photodetectors  56  may be formed on one or more semiconductor substrates such as substrate  54  (e.g., a silicon substrate). Photodetectors  56  may measure incoming ambient light  42  after light  42  has passed through window  22  (e.g., through layer  44  and, if desired, through optional layer  36 ). Each photodetector  56  is overlapped by an associated color filter  58  that is configured to pass light of a different color (i.e., each color filter  58  has a different color and passes ambient light of a different respective band of wavelengths). Color ambient light sensor control circuitry such as portions of control circuitry  16  may therefore determine the light spectrum (intensity as a function of wavelength) of ambient light  42  by gathering signals from photodetectors  56 . 
     Adjustable neutral density filter  38  may be formed from any suitable light modulator. With one illustrative configuration, which is sometimes described herein as an example, adjustable neutral density filter  38  is formed from an electrically adjustable optical modulator such as an electrochromic device. Other types of light modulator (e.g., a photochromic light modulator that changes optical density in response to ambient light exposure or other light exposure, etc.) may be used, if desired. 
     An illustrative neutral density filter formed from an electrochromic device is shown in  FIG. 5 . As shown in  FIG. 5 , neutral density filter  38  (e.g., an electrochromic device) may have a substrate such as substrate  72 . Substrate  72  may be formed from clear polymer, glass, transparent crystalline material such as sapphire, or other suitable transparent substrate. Filter  38  may have transparent conductive electrodes  62  and  70  coupled respectively to control terminals TM 1  and TM 2 . During operation, control circuitry  16  controls the electrical signal applied to terminals TM 1  and TM 2  to adjust the light transmission of filter  38 . Electrodes  62  and  70  may be formed from layers of transparent conductive material such as indium tin oxide or other transparent conductive oxide (as an example). 
     First electrochromic layer  64  and second electrochromic layer  68  may be formed between conductive electrodes  62  and  70 . The first and second electrochromic layers may be respectively a Li (lithium) doped NiO (nickel oxide) layer and a WO 3  (tungsten oxide) layer or other suitable layers of electrochromic material. Electrolyte layer  68  may be sandwiched between electrochromic layers  64  and  68 . Electrolyte layer  68  may be, for example, a solid electrolyte layer such as a layer of silicon oxide (SiO 2 ). Application of electric signals to terminals TM 1  and TM 2  of filter  38  may cause Li+ migration between the NiO and WO3 layers, thereby adjusting the light transmission of filter  38 . Layers  70 ,  68 ,  66 ,  64 , and  62  may be deposited on substrate  72  during fabrication and may be attached to the inner surface of display cover layer  44  using clear adhesive such as polymer adhesive layer  60 . An optional encapsulation layer (e.g., a layer of aluminum oxide (Al 2 O 3 )) may be formed on surface  61  of layer  62 . Optional window layer  36  may be interposed between adhesive layer  60  and display cover layer  44 , if desired. 
     With this type of configuration, filter  38  can be darkened (tinted) or lightened (bleached) or placed in a desired intermediate light-transmission state by adjusting the flow of current through layers  64 ,  66 , and  68  using electrodes  62  and  70 . Consider, as an example, a scenario in which layer  64  is a nickel oxide layer and layer  68  is a tungsten oxide layer. The NiO material of layer  64  is brownish in color when undoped, but turns transparent when doped with Li. The WO 3  material of layer  68  is bluish in color when doped by Li, but turns transparent when not doped by Li. When it is desired to darken device  16 , a positive voltage may be applied to electrode  62  relative to electrode  70 . This causes Li+ ions to be injected into electrolyte layer  66  from layer  64  and causes ions to form LiWO 3  complexes at the interface between layers  66  and  68 , thereby coloring both layers  64  and  68  and darkening filter  38 . When it is desired to render filter  38  transparent, a negative voltage may be applied to electrode  62  relative to electrode  70 . This causes Li+ ions to be injected into layer  66  from layer  68 , leaving behind undoped WO 3  in layer  68  and causes LiNiO complexes to form at the interface between layers  64  and  66 , thereby discoloring both layers  64  and  68  and rendering filter  38  transparent. States of intermediate transparency may be obtained by halting the state transition process partway between the tinted (opaque and less transmissive) and bleached (clear and more transmissive) states. The selected state of filter  38  may be relatively stable and may require modest amounts of power to maintain. Periodic refreshes to the state of filter  38  (e.g., periodic application of control signals to terminals TM 1  and TM 2  by control circuitry  16 ) may be used to help maintain a desired transmission state for filter  38 . 
     The transmission spectrum of filter  38  may be relatively flat across visible light wavelengths of interest (e.g., across the visible light spectrum from 400 to 700 nm). This helps reduce angle-of-incidence-induced spectral shifts in the light transmission through filter  38  (changes in the spectrum of ambient light transmitted through filter  38  to detector  40  that vary as a function of ambient light incident angle A of  FIG. 3 ). This may help improve the color accuracy of ambient light sensor  50 . 
     As shown in  FIG. 6 , for example, an illustrative dark ink layer (e.g., ink for covering an optical component window such as window  22 ) may exhibit a non-flat visible light transmission spectrum. As shown by curve  80 , for example, the transmission of an ink layer may be less at 400 nm than at 700 nm. As a result of this non-flat spectrum, there can be significantly unequal amounts of light transmission across the visible light spectrum as ambient light passes through the ink. The angle of incidence of ambient light also affects light transmission. At an angle of incidence A ( FIG. 3 ) of 0°, the light transmission of the ink layer may be represented by curve  80 . At a higher angle of incidence (e.g., A=70°), the path length of a ray of ambient light through the ink layer will be greater than at normal incidence (A=0°) and this will result in an increased tilt in the visible light spectrum as illustrated by curve  82 . In adjustable neutral density filter  38 , in contrast, the visible light transmission spectrum is relatively flat (e.g., varying by less than 10%, less than 5%, less than 2, or other suitably small amount between 400 nm and 700 nm (across the visible light spectrum)), as shown by illustrative transmission spectrum T 1  and illustrative spectrum T 2  of  FIG. 7 . 
     As a result of the flatness of the neutral density filter transmission spectrum, angle-of-incidence-induced spectral tilt effects are significantly reduced (e.g., the light transmission spectrum of filter  38  at A=0° will not differ significantly from the light transmission spectrum of filter  38  at A=70°). The accuracy of color ambient light sensor measurements with ambient light detector  40  can thereby be increased by omitting ink in window  22  and relying exclusively on the opacity of filter  38  for blocking internal components from view through window  22  and/or by including both filter  38  and optional window layer  36  in window  22  while reducing the amount of ink in layer  36  relative to what would otherwise be desired for blocking components from view. 
     If desired, filter  38  can be adjusted dynamically. For example, when ambient lighting conditions are dim, the transmission of filter  38  can be increased (see, e.g., illustrative transmission T 2  of  FIG. 7 ). This enhances the amount of light reaching detector  40  and thereby decreases noise. When ambient lighting conditions are bright, the transmission of filter  38  can be decreased (see, e.g., illustrative transmission T 1  of  FIG. 7 ). This reduces the amount of light reaching detector  40  and helps prevent the photodetectors of detector  40  from becoming saturated. 
     Control circuitry  16  can adjust the light transmission setting of filter  38  based on ambient light luminance (brightness) data gathered by detector  40 . If desired, control circuitry  16  can set the light transmission of filter  38  to one or more intermediate values (see, e.g., intermediate light transmission T 3  of  FIG. 7 ). The values of T 1  and T 2  may each be in the range of 1-20%, at least 0.5%, at least 1%, at least 2% at least 3%, at least 4%, at least 5%, at least 7%, at least 10%, at least 12%, at least 15%, at least 20%, at least 25%, less than 25%, less than 22%, less than 18%, less than 14%, less than 10%, less than 6%, less than 5%, less than 3%, less than 2%, or other suitable values. The ratio R of the maximum transmission (T 2 ) of filter  38  to the minimum transmission (T 1 ) of filter  38  may have a value of 1.5-20, at least 1.5, at least 2, at least 3, at least 4, at least 5, at least 10, at least 20, less than 20, less than 15, less than 7, less than 4, or other suitable value. As an example, T 1  may be 4% and T 2  may be 20%. 
     In bright lighting conditions, transmission T 1  may be low, which helps obscure structures in the interior of device  10  from view from the exterior of device  10  (e.g., detector  40  will be invisible or nearly invisible to the naked eye). In dim lighting conditions, transmission T 2  may be high, which decreases the ability of filter  38  to hide internal structures from view. Nevertheless, when lighting conditions are dim the amount of ambient light available to illuminate internal structures is low, which makes internal structures invisible or nearly invisible to the naked eye. 
     Illustrative operations associated with using ambient light sensor  50  in device  10  are shown in  FIG. 8 . 
     During the operations of block  90 , control circuitry  16  may use ambient light sensor  50  to gather ambient light sensor measurements. Color information (e.g., color coordinates, color temperature information, or other color data) and luminance (brightness) information can be gathered using detector  40 . Control circuitry  16  knows the current light transmission setting of adjustable neutral density filter  38  and can therefore make compensating adjustments to raw color and luminance data gathered from detector  40  accordingly. For example, if the light transmission level of adjustable neutral density filter  38  is low, control circuitry  16  can take this known low light transmission level into account in computing the luminance of ambient light  42  (e.g., the luminance of ambient light  42  may be higher than indicated by the raw reading of detector  40  due to the enhanced light absorption by filter  38  when the raw measurements were gathered). If the light transmission level of adjustable neutral density filter  38  is high, control circuitry  16  can similarly take this high light transmission level into account in computing the luminance of ambient light  42  (e.g., the luminance of ambient light  42  may be lower than indicated by the raw reading of detector  40  due to the enhanced light transmission level of adjustable neutral density filter  38  when the raw measurements were gathered). 
     After gathering ambient light color and luminance data (e.g., an ambient light color measurement represented as a color temperature or color coordinates and an ambient light luminance measurement indicating the brightness of ambient light  42 ), control circuitry  16  may determine whether the ambient light luminance measurement is within a desired operating range for sensor  50 . For example, control circuitry  16  may compare the ambient light luminance reading to a lower (minimum desired) luminance threshold and an upper (maximum desired) luminance threshold. 
     In response to determining that the measured luminance is below the lower luminance threshold, control circuitry  16  may increase the light transmission level of adjustable neutral density filter  38  during the operations of block  94  (e.g., from T 1  to T 2 , from T 1  to an intermediate value such as T 3 , or from an intermediate value such as T 3  to T 2 ). Processing may then loop back to block  90 , so that another ambient light measurement can be made with sensor  50 . The increased light transmission level of filter  38  will help ensure that sufficient ambient light reaches detector  40  to allow an accurate measurement to be made without excessive noise. 
     In response to determining that the measured luminance is above the upper luminance threshold, control circuitry  16  may decrease the light transmission level of adjustable neutral density filter  38  during the operations of block  92  (e.g., from T 2  to T 1 , from T 2  to an intermediate value such as T 3 , or from an intermediate value such as T 3  to T 1 ). Processing may then loop back to block  90  so that another ambient light measurement can be made with sensor  50 . The decreased light transmission level of filter  38  will help ensure that ambient light detector  40  is not saturated due to excessive ambient light. 
     In response to determining during the operations of block  90  that the measured ambient light luminance is within a desired operating range for sensor  50  (e.g., determining that the luminance value that is gathered with sensor  50  is above the lower luminance threshold and below the upper luminance threshold), control circuitry  16  may take suitable action at block  96 . During the operations of block  96 , control circuitry  16  may, for example, use the value of the measured ambient light luminance to adjust the brightness of display  14 . In dim lighting conditions, for example, display brightness may be reduced so that the content on display  14  is not uncomfortably bright for the user. In bright lighting conditions, display brightness may be automatically increased so that the content on display  14  remains visible and is not obscured by glare. As another example, control circuitry  16  may use measured ambient light color information to adjust the color cast (e.g., the white point) of display  14 . If, as an example, ambient lighting conditions are cold, the white point of display  14  may be shifted to a colder value to ensure that there is not an undesirable color mismatch between the content on display  14  and the user&#39;s current ambient lighting environment. If desired, control circuitry  16  may adjust the color settings (e.g., the white point) of one or more cameras in device  10  (e.g., visible light digital image sensors in sensors  18 ) based on the measured ambient light color. If, as an example, warm lighting conditions are detected, a camera white point may be adjusted to a warmer setting. An adjustable aperture, shutter speed, or other camera settings may be adjusted based on measured ambient light luminance. If desired, other adjustments may be made to the operation of input-output devices  12  based on color and luminance measurements from ambient light sensor  50 . The use of ambient light sensor information to make display and camera adjustments is illustrative. 
     
       
         
           
               
             
               
                   
               
               
                 Table of Reference Numerals 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 10 
                 Electronic Device 
                 12 
                 Input-Output Devices 
               
               
                   
                 14 
                 Display 
                 16 
                 Control Circuitry 
               
               
                   
                 18 
                 Sensors 
                 22 
                 Window 
               
               
                   
                 24 
                 Line 
                 26 
                 Direction 
               
               
                   
                 30 
                 Housing 
                 32 
                 Pixel Array 
               
               
                   
                 34 
                 Layer 
                 36 
                 Window Layer 
               
               
                   
                 38 
                 Filter 
                 40 
                 Light Detector 
               
               
                   
                 42 
                 Light 
                 44 
                 Cover Layer 
               
               
                   
                 50 
                 Light Sensor 
                 52 
                 Component 
               
               
                   
                 54 
                 Substrate 
                 56 
                 Photodetectors 
               
               
                   
                 58 
                 Color Filter 
                 60 
                 Adhesive Layer 
               
               
                   
                 61 
                 Surface 
                 62 
                 Electrode 
               
               
                   
                 64, 66, 68 
                 Layers 
                 70 
                 Electrode 
               
               
                   
                 72 
                 Substrate 
               
               
                   
                   
               
            
           
         
       
     
     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: 20180831
Publication Date: 20200721
Grant Date: 20200721
Priority Date: 20180831
Inventors: BHAT, AKSHAY
PETERSON, RUI L.
XU, Tingjun
GUAN, YAN
Assignee: APPLE INC
CPC Classifications: [{"code": "H04N23/63", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N23/71", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N23/88", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04N23/72", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/1523", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0666", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/1523", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/163", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04N5/58", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0228", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J2001/0257", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0666", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0492", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0492", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J2001/4406", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04N9/735", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0492", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G5/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/163", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0666", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1523", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 69640073