PATENT DOCUMENT

Publication Number: US-10446112-B2
Application Number: US-201715710657-A
Country: US
Kind Code: B2

Title: Electronic devices having light sensors with thin-film filters

Abstract:
An electronic device may be provided with a display mounted in a housing. The display may have an array of pixels that form an active area and may have an inactive area that runs along an edge of the active area. An opaque layer may be formed on an inner surface of a display cover layer in the inactive area of the display or may be formed on another transparent layer in the electronic device. An ambient light sensor window may be formed from the opening and may be aligned with color ambient light sensor. The ambient light sensor may have an integrated circuit with an array of photodetectors and may have a color filter layer forming a corresponding array of thin-film interference color filters with different respective pass bands. The color filter layer may have a shared dielectric stack and multiple color-filter-specific dielectric stacks on the shared dielectric stack.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a display; 
 a color ambient light sensor; and 
 control circuitry configured to adjust the display based on ambient light color and ambient light intensity information from the color ambient light sensor, wherein the color ambient light sensor comprises:
 a light detector integrated circuit having first and second photodetectors; and 
 a color filter layer on the light detector integrated circuit, wherein the color filter layer has a first thin-film interference color filter overlapping the first photodetector and a second thin-film interference color filter overlapping the second photodetector, the first thin-film color filter has a first pass band associated with a first color, the second thin-film color filter has a second pass band associated with a second color, the color filter layer has a common dielectric stack that overlaps the first and second photodetectors and has first and second color-filter-specific dielectric stacks formed on the common dielectric stack, the first thin-film interference color filter includes the first color-specific dielectric stack and a first portion of the common dielectric stack, and the second thin-film interference color filter includes the second color-filter-specific dielectric stack and a second portion of the common dielectric stack that is different from the first portion. 
 
 
     
     
       2. The electronic device defined in  claim 1  wherein the common dielectric stack and the color-filter-specific dielectric stacks are formed from inorganic dielectric layers. 
     
     
       3. The electronic device defined in  claim 2  wherein the display has an active area with an array of pixels, an inactive area without pixels, and a display cover layer overlapping the active area and the inactive area and wherein the color ambient light sensor is overlapped by the inactive area. 
     
     
       4. The electronic device defined in  claim 3  further comprising:
 an opaque masking layer on a surface of the display cover layer in the inactive area; and 
 an ambient light sensor window formed from an opening in the opaque masking layer that is aligned with the color ambient light sensor. 
 
     
     
       5. The electronic device defined in  claim 2  wherein the inorganic dielectric layers comprise silicon oxide. 
     
     
       6. The electronic device defined in  claim 5  wherein the inorganic dielectric layers comprise inorganic dielectric layers selected from the group consisting of: niobium oxide layers, tantalum oxide layers, titanium oxide layers, silicon nitride layers, and aluminum oxide layers. 
     
     
       7. The electronic device defined in  claim 2  wherein the first and second thin-film interference color filters each have 30-120 of the dielectric layers. 
     
     
       8. The electronic device defined in  claim 1  further comprising an encapsulant layer overlapping the first and second photodetectors, wherein the common dielectric stack is interposed between the first and second color-filter-specific dielectric stacks and the encapsulant layer. 
     
     
       9. The electronic device defined in  claim 1  further comprising an opaque polymer patterned to form an array of openings, wherein the array of openings comprises a first opening aligned with the first color-filter-specific dielectric stack and a second opening aligned with the second color-filter-specific dielectric stack. 
     
     
       10. The electronic device defined in  claim 1  wherein the color filter layer has a third thin-film interference color filter with a third pass band associated with a third color. 
     
     
       11. An electronic device, comprising:
 a housing; 
 a display coupled to the housing, wherein the display has an ambient light sensor window; and 
 a color ambient light sensor in alignment with the ambient light sensor window, wherein the color ambient light sensor has an integrated circuit with first and second photodetectors and a color filter layer overlapping the first and second photodetectors, wherein the color filter layer includes first and second thin-film interference color filters, wherein the first thin-film interference color filter overlaps the first photodetector and is configured to pass light in a first band of wavelengths, wherein the second thin-film interference color filter overlaps the second photodetector and is configured to pass light in a second band of wavelengths, wherein the color filter layer has a shared dielectric stack that overlaps the first and second photodetectors and has first and second color-filter-specific dielectric stacks formed on the shared dielectric stack, wherein the first thin-film interference color filter comprises the first color-filter-specific dielectric stack and a first portion of the shared dielectric stack, and wherein the second thin-film interference color filter comprises the second color-filter-specific dielectric stack and a second portion of the shared dielectric stack that is laterally offset from the first portion. 
 
     
     
       12. The electronic device defined in  claim 11  further comprising a light diffuser layer configured to pass ambient light to the color ambient light sensor. 
     
     
       13. The electronic device defined in claim  12  further comprising an infrared-light-blocking filter interposed between the light diffuser layer and the color filter layer. 
     
     
       14. The electronic device defined in  claim 11  wherein the shared dielectric stack has a plurality of inorganic dielectric layers of alternating refractive index. 
     
     
       15. The electronic device defined in  claim 14  wherein each of the first and second color-filter-specific dielectric stacks is formed directly on the shared dielectric stack and has a plurality of inorganic dielectric layers of alternating refractive index. 
     
     
       16. The electronic device defined in  claim 11  wherein the shared dielectric stack has 20-120 inorganic dielectric layers of alternating refractive index. 
     
     
       17. The electronic device defined in  claim 16  wherein each of the first and second color-filter-specific dielectric stacks has 20-120 inorganic dielectric layers of alternating refractive index. 
     
     
       18. An ambient light sensor, comprising:
 a light detector integrated circuit having first and second photodetectors; and 
 a color filter layer overlapping the first and second photodetectors, wherein the color filter layer has:
 a shared dielectric stack that overlaps the first and second photodetectors, 
 a first color-filter-specific dielectric stack formed directly on the shared dielectric stack, wherein the first color-filter-specific dielectric stack and a first portion of the shared dielectric stack that is overlapped by the first color-filter-specific dielectric stack forms a first color filter that passes light in a first wavelength band to the first photodetector, and 
 a second color-filter-specific dielectric stack formed directly on the shared dielectric stack, wherein the second color-filter specific dielectric stack and a second portion of the shared dielectric stack that is laterally separated from the first portion forms a second color filter that passes light in a second wavelength band to the second photodetector. 
 
 
     
     
       19. The ambient light sensor defined in  claim 18  wherein the shared dielectric stack has at least 20 inorganic dielectric layers of alternating refractive index. 
     
     
       20. The ambient light sensor defined in  claim 19  wherein each of the first and second color-filter-specific dielectric stacks has at least 20 inorganic dielectric layers of alternating refractive index. 
     
     
       21. The electronic device defined in  claim 1 , wherein the first color-filter-specific dielectric stack is separated from the second color-filter-specific dielectric stack. 
     
     
       22. The electronic device defined in  claim 1 , wherein the first color-filter-specific dielectric stack has more dielectric layers than the second color-filter-specific dielectric stack.

Description:
FIELD 
     This relates generally to electronic devices, and, more particularly, to electronic devices with optical components. 
     BACKGROUND 
     Electronic devices such as laptop computers, cellular telephones, and other equipment are sometimes provided with optical components. For example, an electronic device may have an ambient light sensor, an optical proximity sensor, image sensors, light sources, and other optical components. 
     It may sometimes be desirable to provide optical components with wavelength-dependent optical filters. For example, it may be desired to pass one color of light to a light sensor while blocking other colors of light. Organic color filters such as polymer layers with colored dye can be used in filtering light, but may not exhibit desired wavelength selectivity. 
     SUMMARY 
     A color ambient light sensor may have an integrated circuit with an array of photodetectors and may have a color filter layer forming a corresponding array of thin-film interference color filters with different respective pass bands. One or more diffuser layers may be interposed between the ambient light sensor window and the array of photodetectors. One or more infrared-light-blocking filters may be interposed between the diffuser layers and the array of photodetectors. 
     The color filter layer on the integrated circuit in the color ambient light sensor may have a shared dielectric stack and multiple color-filter-specific dielectric stacks on the shared dielectric stack. The shared dielectric stack may overlap the array of photodetectors. The color-filter-specific dielectric stacks and corresponding portions of the shared dielectric stack that are overlapped by each of the color-filter-specific dielectric stacks form respective color filters with different respective pass bands. This allows the color filters to selectively pass different colors of light to multiple different respective photodetectors in the integrated circuit. 
     An electronic device may be provided with a display mounted in a housing. The display may have an array of pixels that form an active area and may have an inactive area that runs along an edge of the active area. An opaque layer may be formed on an inner surface of a display cover layer in the inactive area of the display or may be formed on another transparent layer in the electronic device. An optical component window such as an ambient light sensor window may be formed from the opening and may be aligned with an optical component such as the color ambient light sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device having optical components in accordance with an embodiment. 
         FIG. 2  is a perspective view of a portion of an electronic device display having an optical component window overlapping an optical component in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative optical component window overlapping an optical component such as a color ambient light sensor in accordance with an embodiment. 
         FIG. 4  is a graph in which light transmittance has been plotted as a function of wavelength for an illustrative set of ambient light sensor color filters in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of patterned dielectric thin-film layers used in forming thin-film interference filter structures for color ambient light sensor color filters in accordance with an embodiment. 
         FIG. 6  is a flow chart of illustrative operations involved in forming thin-film interference color filters using thin-film dielectric layers in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with optical components. The optical components may include optical filters. The optical filters may include, for example, bandpass filters that pass different colors of light to an optical component such as a color ambient light sensor. 
     An illustrative electronic device of the type that may be provided with optical components is shown in  FIG. 1 . Electronic device  10  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     As shown in  FIG. 1 , electronic device  10  may have control circuitry  16 . Control circuitry  16  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  16  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Device  10  may have input-output circuitry such as input-output devices  12 . Input-output devices  12  may include user input devices that gather user input and output components that provide a user with output. Devices  12  may also include communications circuitry that receives data for device  10  and that supplies data from device  10  to external devices and may include sensors that gather information from the environment. 
     Input-output devices  12  may include one or more displays such as display  14 . Display  14  may be a touch screen display that includes a touch sensor for gathering touch input from a user or display  14  may be insensitive to touch. A touch sensor for display  14  may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, a light-based touch sensor, or other suitable touch sensor arrangements. Display  14  may be a liquid crystal display, a light-emitting diode display (e.g., an organic light-emitting diode display), an electrophoretic display, or other display. 
     Input-output devices  12  may include optical components  18 . Optical components  18  may include ambient light sensors (e.g., color ambient light sensors configured to measure ambient light color and intensity by making light measurements with multiple light detector channels each of which has a corresponding color filter and photodetector to measure light in a different wavelength band), optical proximity sensors (e.g., sensors with a light-emitting device such as an infrared light-emitting diode and a corresponding light detector such as an infrared photodiode for detecting when an external object that is illuminated by infrared light from the light-emitting diode is in the vicinity of device  10 ), a visible light camera, an infrared light camera, light-emitting diodes that emit flash illumination for visible light cameras, infrared light-emitting diodes that emit illumination for infrared cameras, and/or other optical components. 
     In addition to optical components  18 , input-output devices  12  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, light-emitting diodes and other status indicators, non-optical sensors (e.g., temperature sensors, microphones, capacitive touch sensors, force sensors, gas sensors, pressure sensors, sensors that monitor device orientation and motion such as inertial measurement units formed from accelerometers, compasses, and/or gyroscopes), data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  12  and may receive status information and other output from device  10  using the output resources of input-output devices  12 . 
     Device  10  may have a housing. The housing may form a laptop computer enclosure, an enclosure for a wristwatch, a cellular telephone enclosure, a tablet computer enclosure, or other suitable device enclosure. A perspective view of a portion of an illustrative electronic device is shown in  FIG. 2 . In the example of  FIG. 2 , device  10  includes a display such as display  14  mounted in housing  22 . Housing  22 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  22  may be formed using a unibody configuration in which some or all of housing  22  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass, clear plastic, sapphire, or other clear layer (e.g., a transparent planar member that forms some or all of a front face of device  10  or that is mounted in other portions of device  10 ). Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button, a speaker port, or other components. Openings may be formed in housing  22  to form communications ports (e.g., an audio jack port, a digital data port, etc.), to form openings for buttons, etc. In some configurations, housing  22  may have a rear housing wall formed from a planar glass member or other transparent layer (e.g., a planar member formed on a rear face of device  10  opposing a front face of device  10  that includes a display cover layer). The planar member forming the rear housing wall may have an interior surface that is coated with an opaque masking layer. 
     Display  14  may have an array of pixels  28  in active area AA (e.g., liquid crystal display pixels, organic light-emitting diode pixels, electrophoretic display pixels, etc.). Pixels  28  of active area AA may display images for a user of device  10 . Active area AA may be rectangular or may have other suitable shapes. 
     Inactive portions of display  14  such as inactive border area IA may be formed along one or more edges of active area AA. Inactive border area IA may overlap circuits, signal lines, and other structures that do not emit light for forming images. To hide inactive circuitry and other components in border area IA from view by a user of device  10 , the underside of the outermost layer of display  14  (e.g., the display cover layer or other display layer) may be coated with an opaque masking material such as a layer of black ink (e.g., polymer containing black dye and/or black pigment, opaque materials of other colors, etc.) and/or other layers (e.g., metal, dielectric, semiconductor, etc.). Opaque masking materials such as these may also be formed on an inner surface of a planar rear housing wall formed from glass, ceramic, polymer, crystalline transparent materials such as sapphire, or other transparent material. 
     Optical components (e.g., a camera, a light-based proximity sensor, an ambient light sensor, status indicator light-emitting diodes, camera flash light-emitting diodes, etc.) may be mounted under one or more optical component windows such as optical component window  20  of  FIG. 2 . In the example of  FIG. 2 , optical component window  20  is formed in inactive area IA of display  14  (e.g., an inactive border area in a display cover layer). If desired, optical component windows such as window  20  may be formed in other portions of device  10  such as portions of a rear housing wall formed from a transparent member coated with opaque masking material. Arrangements in which optical component windows such as window  20  are formed in portions of a display cover layer for display  14  may sometimes be described herein as examples. 
     In an arrangement of the type shown in  FIG. 2 , one or more openings for one or more respective optical component windows such as optical component window  20  may be formed in the opaque masking layer of inactive area IA to accommodate the optical components. A partially transparent layer (e.g., a layer of polymer containing dye and/or pigment such as a layer of black ink) and other structures may optionally overlap the openings to adjust the appearance of the optical component windows (e.g., to adjust the appearance of the optical component windows so that the optical component windows have appearances that match the surrounding opaque masking layer). 
     Optical component windows may, in general, include any suitable layer(s) of material (e.g., inorganic and/or organic thin-film layers, partially transparent metal films, dielectric coating layers such as thin-film interference filter coatings formed from stacks of dielectric layers, etc.). These layers of material may be formed within an opening in a layer of opaque masking material. 
       FIG. 3  is a cross-sectional side view of display  14  of  FIG. 2  taken along line  24  through optical component window  20  and viewed in direction  26  of  FIG. 2 . As shown in  FIG. 3 , display  14  may have a display cover layer such as display cover layer  14 C. Display cover layer  14 C may be formed from clear glass, transparent polymer, transparent crystalline material such as sapphire, transparent ceramic, and/or other suitable transparent material. Display cover layer  14 C may have a portion that covers active area AA of display  14  and a portion such as the portion shown in  FIG. 3  that covers inactive area IA. Layer  14 C may be formed from glass, plastic, ceramic, sapphire, or other transparent materials and may be a part of display  14  or a separate protective layer that covers active display structures. 
     Window  20  may be formed from an opening in opaque masking layer  30 . Opaque masking layer  30  may be formed from polymer containing dye and/or pigment (e.g., black ink) and/or other opaque material on the inner surface of display cover layer  14 C in inactive area IA. The opening associated with window  20  may be left free of overlapping coatings or may be covered with one or more overlapping layers such as layer  32  to adjust the outward appearance of optical component window  20 . Layer(s)  32  may be, for example, a layer of polymer containing dye and/or ink having a light transmission of about 1-10%, at least 2%, at least 0.5%, at least 1.5%, less than 7%, less than 5%, less than 3%, etc. If desired, optical component windows may be formed in housing walls and/or other structures in device  10 . The example of  FIG. 3  is merely illustrative. 
     Any suitable optical component  18  that emits and/or detects light (e.g., an ambient light sensor, an optical proximity sensor, an image sensor, a light-emitting diode or other light source, etc.) may be aligned with window  20 . As shown in  FIG. 3 , for example, an optical component such as color ambient light sensor  50  may be formed in alignment with optical component window  20  (sometimes referred to as an ambient light sensor window) in display  14 . 
     Display  14  has an array of pixels overlapped by display cover layer  14 C in an active area (AA) of display  14  (not shown in  FIG. 3 ). In inactive area IA, portions of the underside of display cover layer  14 C may be coated with opaque masking layer  30  (e.g., black ink, etc.) and an opening in layer  30  may be covered with optional partially transparent layers such as layer  32  to help visually match the appearance of window  20  to the visual appearance of surrounding portions of display cover layer  14 C (e.g., to match the appearance of opaque masking layer  30 ) while still allowing ambient light sensor  50  to measure ambient light. 
     Color ambient light sensor  50  may include support structures such as support structure  36  (sometimes referred to as a sensor wall, a sensor body structure, a sensor housing structure, etc.). A ring or patch of adhesive such as pressure sensitive adhesive layer  34  may be used to couple support structure  36  to the underside of display cover layer  14 C in alignment with optical component window  20 . Support structure  36  may form walls that surround optical layers  38 . Optical layers  38  may include one or more light diffuser layers that diffuse incoming ambient light and/or may include one or more visible-light-transmitting-and-infrared-light-blocking filters (sometimes referred to as infrared-light-blocking filters or infrared-blocking filters). With one illustrative configuration, the diffuser layer(s) may be mounted between layer  32  and the infrared-blocking filter(s), so that the infrared-blocking filter(s) are between light-detector integrated circuit  40  and the light diffuser layer(s). If desired, other optical layers may be included in layers  38 . Ambient light traveling through window  20  (e.g., through layer  14 C, layer  32 , and layers  38 ) may be detected using photodetectors  42  in light detector integrated circuit  40 . Control circuitry  16  ( FIG. 1 ) can use measurements from integrated circuit  40  to determine the color and intensity of ambient light. 
     Viewed from above through layer  14 C, support structure  36  may extend around the periphery of optical window  20  (e.g., with a footprint that is circular, oval, rectangular, or other suitable shape). Support structure  36  may be formed from an opaque material that blocks visible and infrared light such as black plastic and/or other opaque materials. Support structure  36  may be used to form a one-piece or a multi-piece housing for sensor  50 . In the example of  FIG. 3 , support structure  36  is a single member having an upper region in which optical layers  38  are mounted and a lower region in which light detector integrated circuit  40  is mounted. 
     Light detector integrated circuit  40  may be formed from a silicon die or other semiconductor die. Wire bonds, through-silicon vias and solder joints, or other conductive paths may be used in coupling the circuitry of light detector integrated circuit  40  to contact pads on printed circuit  46 . Solder joints or other electrical connections may be used to couple signal paths formed from metal traces in flexible printed circuit  48  to signal paths in printed circuit  46  (e.g., signal paths formed from metal lines in printed circuit  46  that are coupled to the circuitry of integrated circuit  40 ). In this way, the circuitry of light detector integrated circuit  40  may be coupled to the signal paths in flexible printed circuit  48  so that these signal paths may route signals to and from control circuitry  16 . 
     Light detector integrated circuit  40  may include multiple photodetectors  42  (e.g., photodiodes). Each photodetector  42  may be overlapped by a respective color filter in color filter layer  44 . Each color filter may be formed from a thin-film interference filter (e.g., a stack of thin-film dielectric layers of alternating refractive index) that selectively passes a desired range of wavelengths (e.g., a pass band of a desired color) to an associated overlapped photodetector  42 . For example, a red-pass color filter may overlap a first photodetector  42  to form a red-light-sensing channel in ambient light sensor  50 , a blue-pass color filter may overlap a second photodetector  42  to form a blue-light-sensing channel in ambient light sensor  50 , etc. The thin-film interference color filters of layer  44  may be configured to block infrared light (e.g., stray infrared light that has not been blocked by the infrared-blocking filter(s) in optical layers  38 ). 
     Light transmission curves  52 - 1  and  52 - 2  of  FIG. 4  represent illustrative light transmission characteristics (band-pass characteristics) for first and second respective color filters in color filter layer  44 . Curve  52 - 1  may, as an example, be associated with a pass band for a blue color filter and may cover a range of blue wavelengths, whereas curve  52 - 2  may be a pass band associated with a green color filter and may cover a range of green wavelengths (as an example). Infrared wavelengths may be blocked. 
       FIG. 5  is a cross-sectional side view of a portion of ambient light sensor  50  including light detecting integrated circuit  40 . As shown in  FIG. 5 , photodetectors  42  may be formed in a semiconductor die (e.g., a silicon die) that forms integrated circuit  40 . Photodetectors  42  may be arranged in a rectangular grid (e.g., an array having N rows and M columns, where N and M have values of 1-30, at least 1, at least 2, at least 3, fewer than 25, fewer than 20, or other suitable values), may be arranged in a circular layout (e.g., wedges or rectangles surrounding a central point), and/or may be organized using other patterns. Different photodetectors  42  may be overlapped by thin-film interference color filters of different colors (different pass bands). For example, the photodetector  42  of  FIG. 5  that is on the left side of  FIG. 5  may be overlapped by color filter  44 F- 1  and the photodetector  42  that is on the right side of  FIG. 5  may be overlapped by color filter  44 F- 2 , which has a different pass and than color filter  44 F- 1 . 
     In some configurations, there may be multiple photodetectors associated with each color (e.g., a set of 2-10 red photodetectors, a set of 2-10 blue color filters, etc.) to provide light detector circuitry  40  with redundancy and enhanced immunity to shadowing by external objects. 
     In general, each color filter (or each set of multiple color filters) in color filter layer  44  may be configured to pass light of a different color (e.g., a range of wavelengths in a blue band of wavelengths, green light associated with a band of green wavelengths, red light, etc.). In this way, light readings for multiple color channels (e.g., red, green, blue, etc.) may be gathered by ambient light sensor  50  and used to measure the color and intensity of ambient light. If desired, color filter layer  44  may also include a clear color filter for a clear color channel (e.g., a color filter that passes white visible light and blocks infrared light). 
     Photodetectors for different color channels and, if desired, redundant photodetectors (e.g., photodetectors measuring the same color of ambient light) can be distributed throughout sensor  50  in any suitable pattern. As an example, photodetectors  42  of  FIG. 5  may include an array of photodetectors for 3-10 different color channels (e.g., photodetectors overlapped by 3-10 different color filters with 3-10 respective different pass bands including an optional clear color channel) and each color channel may have 1-5 different individual photodetectors  42  for gathering ambient light color readings for that color channel. Circuitry in integrated circuit  40  (e.g., switching circuitry, amplifier circuitry, analog-to-digital conversion circuitry, communications circuitry for supporting communications with control circuitry elsewhere in device  10 , etc.) may be incorporated into integrated circuit  40  for gathering signals from photodetectors  42  or, if desired, some or all of this supporting circuitry for photodetectors  42  may be formed in one or more integrated circuits that are separate from integrated circuit  40 . 
     Photodetectors  42  may be formed at the top of integrated circuit  40  and may be covered with encapsulation layer  56 . Encapsulation layer  56  may include one or more layers of dielectric (e.g., one or more organic layers such as polymer layers, one or more inorganic dielectric layers such as layers of silicon nitride, etc.) and may be used to help prevent exposure of photodetectors  42  to moisture and oxygen. 
     Color filter layer  44  may include a dielectric stack such as dielectric stack  58  that is common to each of the color filters of color ambient light sensor  50 . Dielectric stack  58  is formed from dielectric layers  60 . Layers  60  may have index of refraction values that alternate in successive layers (e.g., layers that alternate between higher refractive index layers and lower refractive index layers). Layers  60  of dielectric stack  58  may overlap all photodetectors  42  in integrated circuit  40 , so dielectric stack  58  may sometimes be referred to as a common dielectric stack or shared dielectric stack. 
     Each thin-film interference color filter also has a color-filter-specific dielectric stack that, in conjunction with the dielectric layers of common stack  58  provides that color filter with a desired bandpass characteristic. For example, color filter  44 F- 1  includes color-filter-specific dielectric stack  66  formed on top of common stack  58  and color filter  44 F- 2  includes color-filter-specific dielectric stack  70  on top of a different portion of common stack  58 . Each color filter in layer  44  may have a corresponding color-filter-specific dielectric stack that operates in conjunction with an overlapped portion of common dielectric stack  58  to provide that color filter with its desired bandpass characteristic (e.g., all of the dielectric layers including both the layers of dielectric stack  58  and the overlapping color-filter-specific dielectric stack participate in forming the desired bandpass characteristic). In arrangements in which each color channel includes multiple redundant photodetectors  42  covered by color filters of the same color, the color-filter-specific dielectric stack  70  in each of these color filters will generally be identical. Because there are multiple different color channels in sensor  50 , there are multiple different color-filter-specific dielectric stacks on common stack  60 . 
     Each color-filter-specific dielectric stack in color filter layer  40  includes dielectric layers. The dielectric layers of the color-filter-specific dielectric stacks may have index of refraction values that alternate in successive layers (e.g., layers that alternate between higher refractive index layers and lower refractive index layers). In the example of  FIG. 5 , color filter  44 F- 1  has a stack  66  of dielectric layers  68  on common stack  58  and color filter  44 F- 2  has a stack  70  of dielectric layers  70  on common stack  58 . To preserve alternation in the refractive index values of the dielectric layers of each color filter, the refractive index of the layers can alternate between the uppermost layer of stack  58  and the immediately adjacent lowermost layer of each color-filter-specific dielectric stack. For example, if the uppermost layer  60  of stack  58  has a higher index of refraction value, the lowermost layer  68  of stack  66  and the lower most layer  72  of stack  70  may have a lower index of refraction value. If the uppermost layer  60  has a high index, the lowermost layer  68  and the lowermost layer  72  may have a low index. This alternation in index value at the interface between common dielectric stack  58  and the overlapping stacks helps ensure that the combined stacks formed by each color-filter-specific dielectric stack and the respective overlapped portion of common dielectric stack  58  each operate effectively as a respective thin-film interference color filter. 
     The dielectric layers of stack  58  and color-filter-specific stacks such as stacks  66  and  70  may be formed from organic dielectric (e.g., polymer) and/or inorganic dielectric. These dielectric layers may, for example, be formed from inorganic dielectric materials such as silicon oxide, silicon nitride, niobium oxide, tantalum oxide, titanium oxide, aluminum oxide, other metal oxides, etc. There may be any suitable number of dielectric layers in each dielectric stack (e.g., at least 5, at least 10, at least 30, at least 40, 20-90, 10-120, 30-120, 20-120, fewer than 100, etc.), so each color filter may have at least 5 layers, at least 10 layers, at least 30 layers, at least 40 layers, at least 70 layers, at least 100 layers, fewer than 200 layers, fewer than 150 layers, 10-120 layers, 30-120 layers, 20-120 layers, 40-200 layers, or other suitable number of layers). 
     Opaque material such as opaque layer  62  may have a mesh shape with an array of openings  64  aligned with respective color filters. Layer  62  may be used to help reduce crosstalk due to light leakage between adjacent channels. Layer  62  may be formed from an organic material (e.g., polymer containing black ink or black dye) and/or inorganic opaque structures. 
       FIG. 6  is a flow chart of illustrative operations involved in forming a color filter layer such as color filter layer  44  of  FIG. 5  for ambient light sensor  50 . In selecting the refractive indices and thicknesses of the layers in each color filter, the thicknesses (and, if desired, the materials and refractive indices) of each color-filter-specific dielectric stack can be chosen individually for that color-filter-specific dielectric stack to configure the color filter associated with that color-filter-specific dielectric stack for bandpass filter performance in a particular color band, whereas the refractive index values and thicknesses of layers  60  in the common portion of the color filters (common stack  58 ) are necessarily shared by all of the color filters. The use of a common dielectric stack such as common dielectric stack  58  can help reduce processing time, because the time associated with depositing the layers in stack  58  is shared between multiple color filters. Moreover, each of the color-filter-specific stacks is shorter (has less height above the surface of common stack  58 ) than would be possible if common stack  58  were omitted, which makes it possible to form smaller gaps between adjacent color filters during fabrication (e.g., during lift-off operations). Smaller gaps between color filters help reduce dead space and allow more photodetectors to be formed for enhanced redundancy (e.g., for enhanced immunity to external object shadowing). 
     During the operations of block  80 , a physical vapor deposition tool such as a sputtering tool or other equipment is used to deposit layers  60  of common dielectric stack  58  ( FIG. 5 ). During formation of stack  58  on the surface of integrated circuit  40  (e.g., on encapsulant layer  56  in the example of  FIG. 5 ), the material that is being deposited (e.g., inorganic dielectric material) can be alternated between layers  60 , so that the refractive index of successive layers varies between a higher value (e.g., the refractive index of niobium oxide or other higher index material) and a lower value (e.g., the refractive index of silicon oxide or other lower index material). 
     After forming common stack  58 , multiple different color-filter-specific dielectric stacks may be formed on sensor  50 . In general, any suitable fabrication technique (shadow-mask deposition, etching using photomasks, etc.) may be used in forming patterned dielectric stacks on sensor  50 . With one illustrative configuration, which is described herein as an example, lift-off fabrication techniques are used. 
     With a lift-off process, a photoresist layer may be deposited on the surface of common stack  58  (block  82 ). During the operations of block  82 , this photoresist may be patterned using photolithography to produce a pattern of openings for the desired locations of the color filters of channel N of the ambient light sensor. After forming the patterned photoresist layer on stack  58 , dielectric layers for the color-filter-specific dielectric stack of the Nth channel may, during the operations of block  84 , be deposited in the patterned openings of the photoresist (e.g., directly on the exposed uppermost layer  60  of stack  58 ). Lift-off operations may then be performed to remove the deposited dielectric layers from all areas of integrated circuit  40  other than the areas associated with the openings in the photoresist (e.g., all areas except where the color-specific-dielectric stacks for the Nth channel color filters are located). 
     As indicated by line  88 , the operations of blocks  82 ,  84 , and  86  may be repeated for different channels (e.g., channel N+1, channel N+2, etc.). As each set of color-filter-specific dielectric stacks is deposited, the color filters for a different respective color channel are formed. Once all desired color filters are formed, ambient light sensor  50  may be installed in support structures  36  and mounted within device  10  (e.g., in alignment with optical window  20  of  FIG. 3 ). 
     During operation of device  10 , ambient light sensor measurements from ambient light sensor  50  may be used to control the operation of device  10 . For example, control circuitry  16  may adjust the intensity of images displayed on display  14  in response to measured changes in the intensity of ambient light. If, as an example, a user moves device  10  to a bright outdoors environment from a dark interior environment, control circuitry  16  may increase the brightness of display  14  to overcome glare. Color changes (e.g., white point adjustments) can also be made based on ambient light sensor measurements. If, for example, ambient light color measurements indicate that ambient lighting has become warm (e.g., when a user moves device  10  indoors from a cold outdoor lighting environment), the white point of display  14  can be adjusted by control circuitry  16  so that display  14  displays corresponding warmer content. 
     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: 20170920
Publication Date: 20191015
Grant Date: 20191015
Priority Date: 20170920
Inventors: XU, Tingjun
LYNGNES, OVE
YUEN, AVERY P.
ZHAO, Xianwei
KANG, SUNGGU
ZHONG, JOHN Z.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/13318", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2360/144", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/005", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0018", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0076", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0028", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0053", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G5/024", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/002", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0088", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/285", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0065", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0053", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0065", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0018", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0076", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/005", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/002", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G5/024", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0028", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0088", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/285", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/285", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 65719343