PATENT DOCUMENT

Publication Number: US-12189902-B2
Application Number: US-202418411907-A
Country: US
Kind Code: B2

Title: Photo-sensing enabled display for touch detection with customized photodiode and light emitting diode component level angular response

Abstract:
An electronic device may have a touch sensitive display with optical touch sensors that are insensitive to the presence of moisture. The optical touch sensors may include light sources and light detectors. Light illuminator and detector angular filters (e.g., masks, baffles) can be employed to limit the illumination and receive angles of emitted and detected light to minimize false object detection. In some examples, light illuminator and detector masks and baffles can be formed during the photodiode component fabrication process. Interference filters may be included over the light sources and/or the light detectors to improve discrimination between a user&#39;s finger and water, and may have a greater transmission for light at a first incident angle that is greater than the critical angle of the water/cover interface than at a second incident angle that is less than the critical angle.

Claims:
The invention claimed is: 
     
       1. An electronic device configured to gather touch input from a finger, comprising:
 a display having a display cover layer with a surface, wherein the surface has a surface normal; and 
 an optical touch sensor comprising:
 light sources configured to emit light into the display cover layer, wherein the light has a wavelength; 
 light detectors that are configured to detect reflections of the light when the surface is contacted by the finger; and 
 interference filters that are formed over at least one of the light detectors, wherein the interference filters have a first transmission for light at the wavelength and at a first incident angle relative to the surface normal, wherein the interference filters have a second transmission for light at the wavelength and at a second incident angle relative to the surface normal, wherein the second incident angle is greater than the first incident angle, and wherein the second transmission is greater than the first transmission. 
 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the first incident angle is 0 degrees and wherein the second incident angle is greater than 65 degrees. 
     
     
       3. The electronic device defined in  claim 1 , wherein the display cover layer has a first refractive index, wherein water has a second refractive index, wherein an interface between a water droplet and the display cover layer has an associated critical angle based on the first refractive index and the second refractive index, and wherein the first incident angle is less than the critical angle. 
     
     
       4. The electronic device defined in  claim 1 , wherein the wavelength is a near infrared wavelength. 
     
     
       5. The electronic device defined in  claim 1 , further comprising:
 additional interference filters that are formed over at least one of the light sources. 
 
     
     
       6. The electronic device defined in  claim 5 , wherein the additional interference filters have a third transmission for light at the wavelength and at a third incident angle relative to the surface normal, wherein the additional interference filters have a fourth transmission for light at the wavelength and at a fourth incident angle relative to the surface normal, wherein the fourth incident angle is greater than the third incident angle, and wherein the fourth transmission is less than the third transmission. 
     
     
       7. The electronic device defined in  claim 6 , wherein the display cover layer has a first refractive index, wherein air has a second refractive index, wherein an interface between air and the display cover layer has an associated critical angle based on the first refractive index and the second refractive index, and wherein the third incident angle is less than the critical angle. 
     
     
       8. The electronic device defined in  claim 5 , wherein each one of the additional interference filters comprises multiple sublayers with alternating index of refraction values. 
     
     
       9. The electronic device defined in  claim 1 , wherein each one of the interference filters comprises multiple sublayers with alternating index of refraction values. 
     
     
       10. The electronic device defined in  claim 1 , wherein each one of the interference filters comprises alternating layers of glass and silver. 
     
     
       11. The electronic device defined in  claim 10 , wherein each one of the interference filters comprises:
 a first sublayer formed from glass; 
 a second sublayer formed from silver; 
 a third sublayer formed from glass; and 
 a fourth sublayer formed from silver. 
 
     
     
       12. The electronic device defined in  claim 11 , wherein the second sublayer has a thickness of less than 100 nanometers, wherein the third sublayer has a thickness of less than 1,000 nanometers, and wherein the fourth sublayer has a thickness of less than 100 nanometers. 
     
     
       13. The electronic device defined in  claim 1 , further comprising:
 additional filters, wherein each additional filter is adjacent to a respective interference filter and formed over a respective light detector. 
 
     
     
       14. The electronic device defined in  claim 13 , wherein the additional filters block visible light. 
     
     
       15. The electronic device defined in  claim 13 , wherein the additional filters have a same transmission at the first incident angle as at the second incident angle. 
     
     
       16. The electronic device defined in  claim 1 , wherein the optical touch sensor is configured to distinguish between when the surface is contacted by the finger and when the surface is contacted by a water droplet. 
     
     
       17. An electronic device configured to gather touch input from a finger, comprising:
 a display having a display cover layer; and 
 an optical touch sensor comprising:
 light sources configured to emit light into the display cover layer; 
 light detectors that are configured to detect reflections of the light when the cover layer is contacted by the finger; 
 first interference filters, wherein each first interference filter overlaps a respective light source of the light sources; and 
 second interference filters, wherein each second interference filter overlaps a respective light detector of the light detectors. 
 
 
     
     
       18. The electronic device defined in  claim 17 , wherein the display cover layer has a surface normal, wherein the first interference filters are configured to pass more light at an on-axis angle that is parallel to the surface normal than at an off-axis angle that is not parallel to the surface normal, and wherein the second interference filters are configured to pass more light at the off-axis angle than at the on-axis angle. 
     
     
       19. The electronic device defined in  claim 17 , wherein each one of the first and second interference filters comprises multiple sublayers with alternating index of refraction values. 
     
     
       20. An electronic device configured to gather touch input from a finger, comprising:
 a display having a display cover layer; and 
 an optical touch sensor comprising:
 at least one light source configured to emit near-infrared light into the display cover layer; 
 light detectors that are configured to detect reflections of the near-infrared light when the cover layer is contacted by the finger; 
 interference filters, wherein each interference filter is formed over a respective light detector, wherein each one of the interference filters comprises multiple sublayers with alternating index of refraction values, and wherein each interference filter has different transmission of near-infrared light at different incident angles; and 
 visible light blocking filters, wherein each visible light blocking filter is formed over a respective light detector.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 63/480,465, filed Jan. 18, 2023, and U.S. Provisional Application No. 63/583,846, filed Sep. 19, 2023, the contents of which are herein incorporated by reference in their entireties for all purposes. 
    
    
     FIELD OF THE DISCLOSURE 
     This relates generally to electronic devices, and, more particularly, to electronic devices with optical touch sensors. 
     BACKGROUND OF THE DISCLOSURE 
     Many types of input devices are presently available for performing operations in an electronic device having a computing system, such as buttons or keys, mice, trackballs, and joysticks. In addition, electronic devices such as tablet computers, cellular telephones, and other equipment are often provided with touch sensors. For example, displays in electronic devices are often provided with touch sensors to receive touch input; the combination of a display and touch sensors is referred to herein as a touch screen. Touch screens are popular because of their case and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD), light emitting diode (LED) display, micro-LED display, or organic light emitting diode (OLED) display that can be positioned partially or fully behind the touch sensor panel, or integrated with the touch sensor panel, so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger or other object at a location often dictated by a user interface (UI) being displayed by the display device. 
     In some embodiments, optical touch sensing can be employed in the touch sensor panel to detect the presence of a finger or other object in contact with a detection surface. However, when optical sensing is employed, light impinging on the boundary between the detection surface and a medium (e.g., air, water, or other liquid or moisture) above the detection surface can reflect off the boundary, or refract as it passes through the boundary, and cause false or inaccurate touch detection. It can therefore be challenging to utilize optical sensing for touch detection in the presence of moisture. 
     SUMMARY OF THE DISCLOSURE 
     An electronic device may have a touch sensitive display that is insensitive to the presence of moisture. The display may have a two-dimensional optical touch sensor such as a direct illumination optical touch sensor or a total internal reflection touch sensor. The optical touch sensor may be used to gather touch input not only in benign conditions (e.g., in the absence of water or other moisture), but also while the electronic device is immersed in water or otherwise exposed to moisture. 
     An array of pixels in the display may be used to display images. A display cover layer may overlap the array of pixels. One or more light sources may be included to illuminate an external object such as a finger of a user or a stylus when the object contacts a surface of the display cover layer. This creates scattered light that may be detected by an array of light sensors. The light sources and the light sensors may be mounted on a common substrate with the array of image pixels (which may be formed by crystalline semiconductor light-emitting diode dies). 
     In some embodiments, the light sensors (light detectors) and light sources can include photodiodes and light emitting diodes (LEDs) (e.g., standard LEDs, organic LEDs (OLEDs), micro-LEDs and the like). The LEDs and photodiodes can be configured in a direct illumination optical reflective touch mode to detect the presence of an object such as a finger or stylus by detecting modulated light generated by some of the LEDs and reflected off the object. 
     In some examples, interference filters may be included over the light sources and/or the light detectors to improve discrimination between a user&#39;s finger and water droplets. An interface between air and the display cover layer is characterized by a first critical angle. An interface between water and the display cover layer is characterized by a second critical angle. The interference filters over the light sources may have a greater transmission for light at the wavelength of interest (such as near-infrared light) at a first incident angle that is less than the first critical angle than at a second incident angle that is greater than the first critical angle. The interference filters over the light detectors may have a greater transmission for light at the wavelength of interest (such as near-infrared light) at a first incident angle that is greater than the second critical angle than at a second incident angle that is less than the second critical angle. 
     Direct illumination optical touch sensors and total internal reflection touch sensors both rely on light passing through the detection surface of a cover material located above the integrated touch screen to photodiodes located below the cover material. However, light impinging on the boundary between the detection surface and a medium above the detection surface (e.g., air, water, finger, or stylus), from either above or below the detection surface, can reflect off the boundary or be refracted as it passes through the boundary. In some instances, this reflected or refracted light can be detected and incorrectly identified as a touching object. Accordingly, in some embodiments of the disclosure, light illuminator angular filters can be employed within each LED component configured as an illuminator to limit the illumination angle of those illuminators, and light detector angular filters can be employed within each photodiode component configured as a detector to limit the detection angle of those detectors. Each angular filter acts as mask, including an inner mask baffle and an outer mask, that together effectively block or filter light transmitted, reflected or refracted within the cover material to facilitate a customized angular response that reduces or eliminates the false detection of water droplets on the touch surface. 
     Forming the inner mask baffle and the outer mask at the photodiode component level, during the fabrication of the photodiode component, can provide several advantages. By doing so, the process of forming the inner mask baffle and the outer mask can be isolated from the display assembly process, and the baffle and mask become part of the modularized photodiode component, thereby casing the challenges of forming the baffle and mask at a higher level of integration. Forming the inner mask baffle and outer mask within the photodiode component also miniaturizes the baffle and mask to produce a smaller footprint, and in some instances component-level fabrication processes can enable formation of the baffle and mask with greater accuracy than at the display assembly level. In contrast, forming the inner mask baffle and outer mask at a higher level of integration, such as at the display assembly level, requires that the baffle and mask be formed at a greater height above the photosensitive surface of the photodiode as compared to the photodiode component level, which in turn requires that the baffle and mask be larger and consume more display surface area. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an illustrative electronic device in accordance with some embodiments of the disclosure. 
         FIG.  2    is a perspective view of an illustrative electronic device in accordance with some embodiments of the disclosure. 
         FIG.  3    is a side view of an illustrative electronic device in accordance with some embodiments of the disclosure. 
         FIG.  4    is a top view of an illustrative array of pixels for an electronic device in accordance with some embodiments of the disclosure. 
         FIGS.  5  and  6    are side views of illustrative pixel arrays for electronic devices in accordance with some embodiments of the disclosure. 
         FIGS.  7 ,  8 , and  9    are side views of illustrative display and sensor arrangements with different numbers of pixel layers in accordance with some embodiments of the disclosure. 
         FIG.  10    is a side view of an illustrative optical touch sensor when a display cover layer is contacted by a finger in accordance with some embodiments of the disclosure. 
         FIG.  11    is a side view of an illustrative optical touch sensor when ambient light passes through a display cover layer in accordance with some embodiments of the disclosure. 
         FIG.  12    is a side view of an illustrative optical touch sensor when a display cover layer is contacted by a water droplet in accordance with some embodiments of the disclosure. 
         FIG.  13    is a side view of an illustrative optical touch sensor with a light source in accordance with some embodiments of the disclosure. 
         FIG.  14    is a side view of an illustrative optical touch sensor showing critical angles associated with the optical touch sensor in accordance with some embodiments of the disclosure. 
         FIG.  15    is a graph of intensity as a function of incident angle for light reflected from a finger and light reflected from a water droplet in accordance with some embodiments of the disclosure. 
         FIG.  16    is a side view of an illustrative light detector that is covered by an angular filter with a light blocking mask layer in accordance with some embodiments of the disclosure. 
         FIG.  17    is a side view of an illustrative light detector that is covered by an interference filter in accordance with some embodiments of the disclosure. 
         FIG.  18    is a graph of transmission as a function of wavelength at an incident angle that is greater than the critical angle of the interface between water and the display cover layer in accordance with some embodiments of the disclosure. 
         FIG.  19    is a graph of transmission as a function of wavelength at an incident angle that is less than the critical angle of the interface between water and the display cover layer in accordance with some embodiments of the disclosure. 
         FIG.  20    is a side view of an illustrative light detector that is covered by an interference filter and a visible light blocking filter in accordance with some embodiments of the disclosure. 
         FIG.  21    is a side view of an illustrative optical touch sensor with light sources overlapped by first interference filters and light detectors overlapped by second interference filters in accordance with some embodiments of the disclosure. 
         FIG.  22 A  illustrates a cross-sectional view of a photodiode including a photosensitive surface and a top light blocking layer formed on a first layer in accordance with some embodiments of the disclosure. 
         FIG.  22 B  illustrates a top view of the photodiode of  FIG.  22 A  showing the top light blocking layer in accordance with some embodiments of the disclosure. 
         FIG.  22 C  illustrates a cross-sectional view of a photodiode including a photosensitive surface, a second light blocking layer formed within a first layer, and a top light blocking layer formed on top of the first layer in accordance with some embodiments of the disclosure. 
         FIG.  22 D  illustrates a top view of the photodiode of  FIG.  22 C  showing the top light blocking layer and a portion of the second light blocking layer showing through an aperture in accordance with some embodiments of the disclosure. 
         FIG.  22 E  illustrates a cross-sectional view of a photodiode including a photosensitive surface, a second light blocking layer formed on a second layer having a second refractive index n2, and a top light blocking layer formed on a first layer having a first refractive index n1 in accordance with some embodiments of the disclosure. 
         FIG.  22 F  illustrates a top view of the photodiode of  FIG.  22 E  showing the top light blocking layer and a portion of the second light blocking layer showing through an aperture in accordance with some embodiments of the disclosure. 
         FIG.  22 G  illustrates a cross-sectional view of a photodiode including multiple photosensitive surfaces and a top light blocking layer with multiple merged apertures formed on a first layer in accordance with some embodiments of the disclosure. 
         FIG.  22 H  illustrates a top view of the photodiode of  FIG.  22 G  showing the top light blocking layer and the apertures in accordance with some embodiments of the disclosure. 
         FIG.  22 I  illustrates a cross-sectional view of a photodiode including multiple photosensitive surfaces and a top light blocking layer with multiple separated apertures formed on a first layer in accordance with some embodiments of the disclosure. 
         FIG.  22 J  illustrates a top view of the photodiode of  FIG.  22 I  showing the top light blocking layer and the apertures in accordance with some embodiments of the disclosure. 
         FIG.  22 K  illustrates a cross-sectional view of an LED including a photoemitting surface having a diameter c and a top light blocking layer formed on a first layer having a thickness d in accordance with some embodiments of the disclosure. 
         FIG.  22 L  illustrates a top view of the LED of  FIG.  22 K  showing the top light blocking layer, an aperture, and a photoemitting surface in accordance with some embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the disclosed examples. 
     An electronic device may have a touch sensitive display that is insensitive to the presence of moisture. The electronic device can include a mobile telephone, a tablet computer, a wearable device (e.g., a watch), a personal computer, a digital media player, a smart speaker, and the like. The display may have a two-dimensional optical touch sensor such as a direct illumination optical touch sensor or a total internal reflection touch sensor. The optical touch sensor may be used to gather touch input not only in benign conditions (e.g., in the absence of water or other moisture), but also while the electronic device is immersed in water or otherwise exposed to moisture. 
     An array of pixels in the display may be used to display images. A display cover layer may overlap the array of pixels. One or more light sources may be included to illuminate an external object such as a finger of a user or a stylus when the object contacts a surface of the display cover layer. This creates scattered light that may be detected by an array of light sensors. The light sources and the light sensors may be mounted on a common substrate with the array of image pixels (which may be formed by crystalline semiconductor light-emitting diode dies). 
     In some embodiments, the light sensors (light detectors) and light sources can include photodiodes and light emitting diodes (LEDs) (e.g., standard LEDs, organic LEDs (OLEDs), micro-LEDs and the like). The LEDs and photodiodes can be configured in a direct illumination optical reflective touch mode to detect the presence of an object such as a finger or stylus by detecting modulated light generated by some of the LEDs and reflected off the object. 
     In some examples, interference filters may be included over the light sources and/or the light detectors to improve discrimination between a user&#39;s finger and water droplets. An interface between air and the display cover layer is characterized by a first critical angle. An interface between water and the display cover layer is characterized by a second critical angle. The interference filters over the light sources may have a greater transmission for light at the wavelength of interest (such as near-infrared light) at a first incident angle that is less than the first critical angle than at a second incident angle that is greater than the first critical angle. The interference filters over the light detectors may have a greater transmission for light at the wavelength of interest (such as near-infrared light) at a first incident angle that is greater than the second critical angle than at a second incident angle that is less than the second critical angle. 
     Direct illumination optical touch sensors and total internal reflection touch sensors both rely on light passing through the detection surface of a cover material located above the integrated touch screen to photodiodes located below the cover material. However, light impinging on the boundary between the detection surface and a medium above the detection surface (e.g., air, water, finger, or stylus), from either above or below the detection surface, can reflect off the boundary or be refracted as it passes through the boundary. In some instances, this reflected or refracted light can be detected and incorrectly identified as a touching object. Accordingly, in some embodiments of the disclosure, light illuminator angular filters can be employed within each LED component configured as an illuminator to limit the illumination angle of those illuminators, and light detector angular filters can be employed within each photodiode component configured as a detector to limit the detection angle of those detectors. Each angular filter acts as mask, including an inner mask baffle and an outer mask, that together effectively block or filter light transmitted, reflected or refracted within the cover material to facilitate a customized angular response that reduces or eliminates the false detection of water droplets on the touch surface. 
     Forming the inner mask baffle and the outer mask at the photodiode component level, during the fabrication of the photodiode component, can provide several advantages. By doing so, the process of forming the inner mask baffle and the outer mask can be isolated from the display assembly process, and the baffle and mask become part of the modularized photodiode component, thereby casing the challenges of forming the baffle and mask at a higher level of integration. Forming the inner mask baffle and outer mask within the photodiode component also miniaturizes the baffle and mask to produce a smaller footprint, and in some instances component-level fabrication processes can enable formation of the baffle and mask with greater accuracy than at the display assembly level. In contrast, forming the inner mask baffle and outer mask at a higher level of integration, such as at the display assembly level, requires that the baffle and mask be formed at a greater height above the photosensitive surface of the photodiode as compared to the photodiode component level, which in turn requires that the baffle and mask be larger and consume more display surface area. 
     A schematic diagram of an illustrative electronic device that may include an optical touch sensor is shown in  FIG.  1   . Electronic device  10  of  FIG.  1    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 wristwatch or other device worn on a user&#39;s wrist, a pendant device, a headphone or earpiece device, a head-mounted device such as eyeglasses, goggles, 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. Illustrative configurations in which device  10  is a portable device such as a wristwatch, cellular telephone, or tablet computer and, more particularly, a portable device that is water resistant or waterproof may sometimes be described herein as an example. 
     As shown in  FIG.  1   , electronic device  10  may have control circuitry  16 . Control circuitry  16  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  16  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. Control circuitry  16  may include communications circuitry for supporting wired and/or wireless communications between device  10  and external equipment. For example, control circuitry  16  may include wireless communications circuitry such as cellular telephone communications circuitry and wireless local area network communications circuitry. 
     Input-output circuitry in device  10  such as input-output devices  12  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  12  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, haptic output devices, cameras, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  12  and may receive status information and other output from device  10  using the output resources of input-output devices  12 . 
     Input-output devices  12  may include one or more displays such as display  14 . Display  14  may be an organic light-emitting diode display, a display formed from an array of crystalline semiconductor light-emitting diode dies, a display formed from an array or regular LEDs, a display formed from an array of micro-LEDs, a liquid crystal display, or other display. Display  14  may be a touch screen display that includes an optical touch sensor for gathering touch input from a user. The optical touch sensor may be configured to operate even when device  10  is immersed in water or otherwise exposed to moisture. If desired, the optical touch sensor may also be configured to operate when a user is wearing gloves, which might be difficult or impossible with some capacitive touch sensors. Moreover, because the optical touch sensor operates optically, the touch sensor is not impacted by grounding effects that might impact the operation of capacitive touch sensors. 
     As shown in  FIG.  1   , input-output devices  12  may include sensors  18 . Sensors  18  may include touch sensors. Touch sensors may be provided for display  14  and/or other portions of device  10  and may be formed from an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, light-based touch sensor structures, or other suitable touch sensor arrangements. Illustrative optical touch sensor arrangements for device  10  (e.g., for display  14  of device  10 ) are sometimes described herein as an example. 
     Sensors  18  may include capacitive sensors, light-based proximity sensors, magnetic sensors, accelerometers, force sensors, touch sensors, temperature sensors, pressure sensors, inertial measurement units, accelerometers, gyroscopes, compasses, microphones, radio-frequency sensors, three-dimensional image sensors (e.g., structured light sensors with light emitters such as infrared light emitters configured to emit structured light and corresponding infrared image sensors, three-dimensional sensors based on pairs of two-dimensional image sensors, etc.), cameras (e.g., visible light cameras and/or infrared light cameras), light-based position sensors (e.g., lidar sensors), monochrome and/or color ambient light sensors, and other sensors. Sensors  18  such as ambient light sensors, image sensors, optical proximity sensors, lidar sensors, optical touch sensors, and other sensors that use light and/or components that emit light such as status indicator lights and other light-emitting components may sometimes be referred to as optical components. 
     It is to be understood that electronic device  10  is not limited to the components and configuration described with respect to  FIG.  1   , but can include other or additional components in multiple configurations according to various examples. Additionally, the components of electronic device  10  can be included within a single device, or can be distributed between multiple devices. 
     A perspective view of an illustrative electronic device of the type that may include an optical touch sensor is shown in  FIG.  2   . In the example of  FIG.  2   , device  10  includes a display such as display  14  mounted in housing  22 . Display  14  may be a liquid crystal display, a light-emitting diode display such as an organic light-emitting diode display or a display formed from crystalline semiconductor light-emitting diode dies, or other suitable display. Display  14  may have an array of image pixels extending across some or all of front face F of device  10  and/or other external device surfaces. The array of image pixels may be rectangular or may have other suitable shapes. Display  14  may be protected using a display cover layer (e.g., a transparent front housing layer) such as a layer of transparent glass, clear plastic, sapphire, or other clear layer. The display cover layer may overlap the array of image pixels. 
     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. As shown in the side view of device  10  of  FIG.  3   , housing  22  and display  14  may separate an interior region of device  10  such as interior region  30  from an exterior region surrounding device  10  such as exterior region  32 . 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.). If desired, a strap may be coupled to a main portion of housing  22  (e.g., in configurations in which device  10  is a wearable device, such as a wristwatch or head-mounted device). Internal electrical components  36  (e.g., integrated circuits, discrete components, etc.) for forming control circuitry  16  and input-output devices  12  may be mounted in interior  30  of housing  22  (e.g., on one or more substrates such as printed circuit  38 ). In some configurations, components  36  may be attached to display  14  (e.g., circuitry may be mounted to the surface of display  14 ). To obtain touch input from a user&#39;s fingers or other external object (see, e.g., user finger  34  or a stylus), display  14  may include a touch sensor such as an optical touch sensor (e.g., a two-dimensional optical touch sensor that gathers information on the XY location of a user&#39;s finger or other external object when that object touches the surface of display  14 ). 
     Display  14  may include a display panel such as display panel  14 P that contains pixels P covered by display cover layer  14 CG. The pixels of display  14  may cover all of the front face of device  10  or display  14  may have pixel-free areas (e.g., notches, rectangular islands, inactive border regions, or other regions) that do not contain any pixels. Pixel-free areas may be used to accommodate an opening for a speaker and windows for optical components such as image sensors, an ambient light sensor, an optical proximity sensor, a three-dimensional image sensor such as a structured light three-dimensional image sensor, a camera flash, an illuminator for an infrared image sensor, an illuminator for a three-dimensional sensor such as a structured light sensor, a time-of-flight sensor, a lidar sensor, etc. 
       FIG.  4    is a top view of an array of illustrative pixels P in display panel (display)  14 P. As shown in  FIG.  4   , pixels P may include image pixels such as pixel P- 1  that are used in presenting images for a user of device  10 . Image pixels in display  14  may, for example, include a rectangular array of red, green, and blue light-emitting diodes or backlit red, green, and blue liquid crystal display pixels for presenting color images to a user. 
     Pixels P may also contain optical touch sensor pixels such as pixel P- 2 . Optical touch sensor pixels may include pixels that serve as light detectors and/or light emitters. Emitted light that reflects from an object such as a user&#39;s finger on the surface of display  14  may be detected using the light detectors, thereby determining the location of the object. If desired, diodes or other components may be used to form pixels that can be operated both as image pixels and as touch sensor pixels. When used as touch sensor pixels, image pixels can be configured to emit optical touch sensor illumination and/or to detect optical touch sensor light. For example, a display emitter can be used to produce image light for a display while also being used to produce optical touch sensor illumination, and/or while also being used to serve as a photodetector (sometimes referred to as a light detector) for an optical touch sensor. 
     Image pixels such as pixels P- 1  and/or optical touch sensor pixels P- 2  may have any suitable pitch. For example, image pixels may have a density that is sufficient to display high-quality images for a user (e.g., 200-300 pixels per inch or more, as an example), whereas optical touch sensor pixels may, if desired, have a lower density (e.g., less than 200 pixels per inch, less than 50 pixels per inch, less than 20 pixels per inch, etc.). Optical touch sensor pixels P- 2  may include both light sources and light detectors. The light sources may have a density of less than 200 pixels per inch, less than 50 pixels per inch, less than 20 pixels per inch, etc. The light detectors may have a density of less than 200 pixels per inch, less than 50 pixels per inch, less than 20 pixels per inch, etc. 
     Image pixels emit visible light for viewing by a user. For example, in a color display, image pixels may emit light of different colors of image light such as red, green, and blue light, thereby allowing display  14  to present color images. Optical touch sensor pixels may emit and/or detect visible light and/or infrared light such as near infrared light (and/or, if desired, ultraviolet light). 
     In some configurations, optical touch sensor light for illuminating an object such as a user&#39;s fingers or a stylus passes directly through the thickness of display cover layer  14 CG from its interior surface to its exterior surface. Optical touch sensors in which light that illuminates objects such as a user&#39;s fingers or a stylus passes outwardly from light sources such as light-emitting pixels in display panel  14 P directly through the thickness of display cover layer  14 CG before being backscattered in the reverse (inward) direction to the light detectors of the optical touch sensors may sometimes be referred to herein as direct illumination optical touch sensors. 
     In other configurations, light for an optical touch sensor may be guided within layer  14 CG in accordance with the principal of total internal reflection. For example, a light-emitting diode may emit light into the righthand edge of display cover layer  14 CG that is guided from the righthand edge of display cover layer  14 CG to the opposing lefthand edge of display cover layer  14 CG within the light guide formed by display cover layer  14 CG. In this way, light may be guided laterally across layer  14 CG in the absence of contact from an object such as a user&#39;s finger or a stylus. When an object such as a user&#39;s finger or a stylus touches the surface of layer  14 CG, total internal reflection can be locally defeated. This local frustration of total internal reflection scatters light inwardly toward the light detectors of the optical touch sensor. Optical touch sensors that are based on locally defeating total internal reflection may sometimes be referred to herein as total internal reflection optical touch sensors. If desired, objects other than the fingers of users (e.g., a computer stylus, a glove, and/or other external objects with appropriate optical properties) may also locally defeat total internal reflection, thereby allowing the optical touch sensors to function over a wide range of operating environments. 
     Pixels P that emit light and pixels P that detect light in display panel  14 P may be formed using shared structures and/or structures that are separate from each other. These structures may be located in the same plane (e.g., as part of a single layer of pixels on a single substrate) and/or may include components located in multiple planes (e.g., in arrangements in which some components are formed in a given layer and other components are formed in one or more additional layers above and/or below the given layer). 
     Consider, as an example, an optical touch sensor that contains an array of photodetectors formed from reverse-biased diodes. These diodes may be dedicated photodetectors or may be light-emitting diodes that serve as light detectors when reverse biased and that serve as light sources when forward biased. Light sources in the optical touch sensor may include visible light sources (e.g., visible light sources dedicated to use in the optical touch sensor or visible light sources that also serve as image pixels) and/or may include infrared light sources. Light-emitting pixels for the optical touch sensor may be formed from light-emitting diodes (e.g., dedicated light-emitting diodes or diodes that serve as light-emitting diodes when forward biased and that serve as photodetectors when reversed biased). Light-emitting pixels may also be formed from pixels P that are backlit with light from a backlight unit to form backlit pixels (e.g., backlit liquid crystal display pixels). In general, any type of photodetector signal processing circuitry may be used to detect when a photodetector has received light. For example, photodetectors may be configured to operate in a photoresistor mode in which the photodetectors change resistance upon exposure to light and corresponding photodetector signal processing circuitry may be used to measure the changes in photodetector resistance. As another example, the photodetectors may be configured to operate in a photovoltaic mode in which a voltage is produced when light is sensed and corresponding photodetector signal processing circuitry may be used to detect the voltage signals that are output from the photodetectors. Semiconductor photodetectors may be implemented using phototransistors or photodiodes. Other types of photosensitive components may be used, if desired. 
       FIG.  5    is a side view of an illustrative display having an array of pixels P that are not backlit. Pixels P of  FIG.  5    may include light-emitting diodes (e.g., organic light-emitting diodes such as thin-film organic light-emitting diodes and/or light-emitting diodes formed from crystalline semiconductor light-emitting diode dies). During operation, image pixels formed from the light-emitting diodes may present an image on display  14  that is visible to a user such as viewer  40  who is viewing display  14  in direction  42 . 
       FIG.  6    is a side view of an illustrative display having an array of pixels P that are backlit using backlight unit  44 . Backlight unit  44  may include one or more strips of light-emitting diodes that emit light into a backlight unit light guide layer (e.g., a clear optical film with light-scattering structures). As the emitted light propagates through the light guide layer, the scattered light serves as backlight illumination for pixels P (e.g., liquid crystal display pixels). In another illustrative configuration, backlight unit  44  is a direct lit backlight unit that contains an array of backlight light-emitting diodes that provide backlight (e.g., an array-type backlight unit that supports local dimming functionality). 
     In display  14  (e.g., in display panel  14 P), the image pixels that are used in displaying images for a user (e.g., the red, blue, and green pixels in a color display) and/or the optical touch sensor pixels (e.g., light emitters and/or detectors for implementing a direct illumination and/or total internal reflection optical touch sensor) may be implemented using one or more layers of pixels, as shown in the side view of the illustrative displays of  FIGS.  7 ,  8 , and  9   .  FIG.  7    is an illustrative arrangement for display panel  14 P that has a single layer of pixels P. In  FIG.  8   , two layers of pixels P are used in display panel  14 P. The diagram of  FIG.  9    shows how display panel  14 P may, if desired, have three or more layers of pixels P. In general, optical touch sensor pixels may be located in the same layer as image pixels (i.e., coplanar with the image pixels) and/or may be located in a layer that is above or below the image pixels. 
     Pixels P of  FIGS.  7 ,  8 , and  9    may include image pixels and/or optical touch sensor pixels. In some arrangements, pixels P may include backlight pixels that supply backlight illumination in a local dimming backlight unit. The pixels P in different layers may have the same pitch or different pitches. As an example, there may be more image pixels per inch than optical touch sensor pixels. Thin-film structures and/or discrete devices may be used in forming pixels P. 
       FIG.  10    is a side view of an illustrative display with a direct illumination optical touch sensor. In the example of  FIG.  10   , light sources  52  and detectors  102  for the optical touch sensor are coplanar with image pixels P- 1 . As shown in  FIG.  10   , light source  52  may emit illumination  46  that travels directly through display cover layer  14 CG from its inner surface to its outer surface, thereby illuminating an external object contacting the surface of display  14  such as finger  34 . This creates localized backscattered light  48  that propagates in the inward (−Z) direction and that is detected by photodetectors (such as detectors  102 ) associated with display panel  14 P that are below finger  34 . In this way, the optical touch sensor can determine the lateral position (XY location) of finger  34 . 
     Note that the backscattered light  48  that reflects off finger  34  is distributed across a wide range of angles (e.g., approximately −90 degrees to 90 degrees relative to the Z-axis). 
     To improve the performance of the direct illumination optical touch sensor, care may be taken to discriminate between backscattered light from finger  34  and noise light from other sources. One source of noise, shown in  FIG.  11   , is ambient light. As shown in  FIG.  11   , ambient light such as ambient light  62  may pass through display cover layer  14 CG. If care is not taken, the ambient light may be detected by one or more detectors  102 , undesirable decreasing the signal-to-noise ratio within the optical touch sensor. 
     Snell&#39;s law dictates that, at an interface between two materials, there is a critical angle above which substantially all of the incident light will be reflected (via total internal reflection). Consider the angle  66  relative to the Z-axis in  FIG.  11   . When incident light travels through the air in the negative Z-direction and strikes the display cover layer  14 CG, incident light will pass through the interface into the display cover layer. The refracted rays can only transmit at angles less than or equal to the critical angle  66  inside the  14 CG layer. Likewise, rays originating from inside the  14 CG layer can only transmit into air if their angle relative the z-axis is less than or equal to the critical angle. If the rays inside the  14 CG material exceed the critical angle, then they will be totally internally reflected. The cross-hatched region in  FIG.  11    shows the range of angles within which incident light passes through the display cover layer. 
     To summarize, incident light that passes through display cover layer  14 CG from the exterior of the electronic device must, by definition, pass through the display cover layer with an angle A that is less than the critical angle. Consider an example where display cover layer  14 CG is formed from glass with a refractive index of 1.5. In this case, the critical angle of the interface between air and the glass is 42 degrees. Therefore, ambient light that passes from the exterior of electronic device  10  through display cover layer  14 CG has an angle that is greater than −42 degrees and less than 42 degrees inside of the glass, and ranges from −90 to 90 degrees in air. 
     It is desirable for the optical touch sensor herein to discriminate between an object such as a user&#39;s finger or a stylus, and a water droplet. This ensures that water droplets are not improperly interpreted as touch events. 
       FIG.  12    shows a side view of a display with a water droplet  68  on the outer surface of display cover layer  14 CG. Illumination  46  from light source  52  may reflect off of water droplet  68  and be detected by one or more detectors  102 , thus reducing the signal-to-noise ratio. Light that reflects off of water droplet  68  may enter display cover layer  14 CG (from water  68 ) within the critical angle  70  dictated by the interface of the water and the display cover layer. Water has a refractive index of 1.33. Therefore, as one specific example, the critical angle (where the water has a refractive index of 1.33 and the display cover layer has a refractive index of 1.5) may be 62.7 degrees. Reflected light from within the water droplets therefore cannot have an angle inside the display cover layer that is greater than −62.7 degrees and less than 62.7 degrees. The cross-hatched region in  FIG.  12    shows the range of angles within which the reflected light (off of water) passes through the display cover layer. 
     The signal-to-noise ratio of the optical touch sensor may therefore be improved by blocking light that is incident on photodetectors with angles greater than −62.7 degrees and less than 62.7 degrees. Blocking light within these angles will necessarily (as described in connection with  FIG.  12   ) block noise caused by reflections returning from inside of water on the surface of the display cover layer. The angular distribution of ambient light (as described in connection with  FIG.  11   ) is a subset of the angular distribution of light reflected from water (as described in connection with  FIG.  12   ). Therefore, blocking light within these angles will also necessarily block noise caused by ambient light. The remaining signal that is detected by the photodetector (caused by incident light at angles that are less than −62.7 degrees and greater than 62.7 degrees) is a result of the backscattered reflections off of finger  34  (as shown in  FIG.  10   ). An angular filter may be applied to the detectors  102  to block light within the aforementioned angular range and improve the signal-to-noise ratio of the optical touch sensor. 
     Additional signal-to-noise ratio improvements in the optical touch sensor may be achieved by also applying an angular filter to the light sources. As shown in  FIG.  13   , light emitted by light source  52  that is greater than the negative magnitude of the critical angle  66  and less than the positive magnitude of the critical angle  66  will pass through display cover layer  14 CG. The cross-hatched region in  FIG.  13    shows the range of angles within which the transmitted light passes through the display cover layer. However, light that is less than the negative magnitude of the critical angle  66  and greater than the positive magnitude of the critical angle  66  will be reflected. For example, see incident light  72 - 1  with an angle that is greater than the critical angle and is therefore reflected as reflection  72 - 2 . 
     An angular filter may therefore be applied to light source  52  that causes light source  52  to only emit light at angles that are greater than the negative magnitude of the critical angle and less than the positive magnitude of the critical angle. This ensures that light that is not backscattered (e.g., by a user&#39;s finger) will pass through the display cover layer  14 CG (instead of reflecting off of the upper surface of the display cover layer  14 CG as with reflection  72 - 2  and possibly being detected by one or more detectors  102 ). 
     To summarize, as shown in  FIG.  14   , there is a first critical angle A C1  associated with the interface of display cover layer  14 CG and air (as dictated by the refractive index of the display cover layer  14 CG and the refractive index of air). Light travelling from the display cover layer to the air is transmitted when the incident angle A is within the angular range that is not subject to total internal reflection (e.g., |A|&lt;|A C1 |). Incident light travelling from the display cover layer to the air is internally reflected when the incident angle A is larger than the critical angle (e.g., |A|&gt;|A C1 |). Light incident from the air may only propagate inside the display cover layer within the angular range bounded by the critical angle (e.g., |A|&lt;|A C1 |). In some examples, the critical angle A C1  can be determined to be +/−42 degrees from the surface normal. For practical applications, the critical angle A C1  can include some margin, such as +/−42 degrees+/−1 degree from the surface normal, or +/−42 degrees+/−2%. 
     There is a second critical angle A C2  associated with the interface of display cover layer  14 CG and water (as dictated by the refractive index of the display cover layer  14 CG and the refractive index of water). Light travelling from the display cover layer to water is transmitted when the incident angle A is smaller than the critical angle (e.g., |A|&lt;|A C2 |). Incident light travelling from the display cover layer to water is internally reflected when the incident angle A is larger than the critical angle (e.g., |A|&gt;|A C2 |). Light incident from the water only propagates inside the display cover layer within the angular range bounded by the critical angle (e.g., |A|&lt;|A C2 |). In some examples, the critical angle A C2  can be determined to be +/−62.7 degrees from the surface normal. For practical applications, the critical angle A C2  can include some margin, such as +/−62.7 degrees+/−1 degree from the surface normal, or +/−62.7 degrees+/−2%. 
     The refractive index of water is greater than the refractive index of air, which causes A C2  to be greater than A C1 . 
     To mitigate signal contamination from ambient light in the optical touch sensor for device  10 , an angular filter may be applied to detectors for the optical touch sensor. The angular filter may transmit light at incident angles that are outside of the critical angle A C2  associated with the interface of water and the display cover layer. In other words, the angular filter transmits light at incident angle A when |A|&gt;|A C2 | and blocks light at incident angle A when |A|&lt;|A C2 |. This type of angular filter blocks substantially all ambient light and substantially all light that is refracted through the glass-water interface. 
     To mitigate cross talk from the internal illumination sources in the optical touch sensor for device  10 , an angular filter may also be applied to light sources for the optical touch sensor. The angular filter may be tailored to an angular range that would prevent a direct path from the emitters to the position sensing elements in the photodiode array, which would include a path dependent upon a total internal reflection at the cover glass, originating from the source emitter. 
       FIG.  15    is a graph of intensity as a function of incident angle on a detector  102  in the optical touch sensor. Profile  74  shows the intensity of backscattered light from a user&#39;s finger. In other words, profile  74  is the desired signal for optical touch sensing. Profile  76  shows the intensity of reflected light from water. In other words, profile  76  is a noise signal for the optical touch sensing. 
     As shown in  FIG.  15   , profile  76  has a peak intensity I 1  at an incident angle of 0 degrees (e.g., parallel to the Z-axis). The magnitude of the intensity of profile  76  drops with increasing angle and reaches 0 at the critical angle A C2  (because reflections off the water are necessarily at an angle below the critical angle A C2 ). Profile  74  has a peak intensity I 2  at an incident angle of 0 degrees (e.g., parallel to the Z-axis). The magnitude of the intensity of profile  76  drops with increasing angle. However, the magnitude of the intensity of profile  76  is greater than 0 beyond critical angle A C2 . Therefore, a detector that blocks incident light at angles less than A C2  (and transmits light in range  78  above A C2 ) will detect light from a user&#39;s finger but not from a water droplet. 
     In one possible arrangement, a light blocking angular filter  82  is formed over photodetector  102  (sometimes referred to as light detector  102 ) using one or more masking layers. As shown in  FIG.  16   , angular filter  82  may be formed from one or more mask layers  88  on a transparent layer  84 . Mask  88  may be formed from black ink, metal, or other opaque masking materials that are substantially opaque (e.g., with opacity greater than 80%, greater than 90%, greater than 95%, greater than 98%, etc.). Transparent layer  84  may be one of the layers in panel  14 P such as an encapsulation layer or other clear dielectric layer. 
     As shown in  FIG.  16   , mask layer  88  physically blocks incident light at on-axis angles. On-axis angles may refer to angles that are parallel or close to parallel (e.g., within 10 degrees of parallel) to the surface normal (e.g., Z-axis). In contrast, off-axis angles may refer to angles that are not close to parallel (e.g., greater than 10 degrees from parallel) to the surface normal. Light that reaches detector  102  has an angle that is greater than angle  86 . The dimensions of the mask layer and the separation  90  between the mask layer and the detector may be selected to block incident light at a desired angle. The angular filter in  FIG.  16    may, for example, transmit light  92  at incident angle A when A&lt;−A C2  or A&gt;+A C2  and block light at incident angle A when −A C2 &lt;A&lt;+A C2 . 
     The angular filter of  FIG.  16    may require a total thickness (e.g., the separation  90  from the top of the detector to the top of the masking layer) that is greater than desired. The thickness of the angular filter may undesirably increase the thickness of the display. Additionally, due to separation  90  the masking layer may block adjacent pixels P- 1  that are used in presenting images for a user of device  10 . 
     To mitigate the thickness of the display and blocking the operation of pixels P- 1 , an interference filter may be used as the angular filter instead of the light blocking filter of  FIG.  16   . An interference filter (sometimes referred to as a dichroic filter or thin-film interference filter) includes multiple sublayers with alternating index of refraction values. An interference filter selectively transmits incident light based on the interference effects at the interfaces between the layers within the interference filter. 
       FIG.  17    is a cross-sectional side view of an illustrative detector  102  that includes an interference filter  104 . As shown, the interference filter is formed directly on an upper surface of the detector. In other words, the interference filter is in direct contact with the upper surface of the detector. The interference filter may include a plurality of sublayers  106 . In  FIG.  17   , the interference filter includes four sublayers: sublayer  106 - 1 , sublayer  106 - 2 , sublayer  106 - 3 , and sublayer  106 - 4 . The sublayers may alternate between different materials. For example, sublayers  106 - 1  and  106 - 3  may be formed from a first material whereas sublayers  106 - 2  and  106 - 4  may be formed from a second material. 
     The first and second materials may have an index of refraction difference that is greater than 0.1, greater than 0.3, greater than 0.5, greater than 0.8, greater than 1.0, greater than 1.5, greater than 2.0, etc. Each one of the first and second materials may be a dielectric material (e.g., silicon, glass, etc.) or a metal material (e.g., silver, aluminum, niobium, titanium dioxide, etc.). Each sublayer within filter  104  may have a high transparency (e.g., greater than 80%, greater than 90%, greater than 95%, greater than 98%, etc.). 
     As one specific example, sublayers  106 - 1  and  106 - 3  may be formed from an optical glass whereas sublayers  106 - 2  and  106 - 4  may be formed from silver. Continuing this specific example, sublayer  106 - 1  may have a thickness of between 500 and 10,000 nanometers (e.g., 5,000 nanometers), sublayer  106 - 2  may have a thickness of between 10 nanometers and 100 nanometers (e.g., 40 nanometers), sublayer  106 - 3  may have a thickness of between 100 and 1,000 nanometers (e.g., 550 nanometers), and sublayer  106 - 4  may have a thickness of between 10 nanometers and 100 nanometers (e.g., 40 nanometers). 
     The aforementioned example is merely illustrative. In general, the thickness of each sublayer may be greater than 1 nanometer, greater than 20 nanometers, greater than 40 nanometers, greater than 100 nanometers, greater than 1,000 nanometers, greater than 4,000 nanometers, less than 1 nanometer, less than 20 nanometers, less than 40 nanometers, less than 100 nanometers, less than 1,000 nanometers, less than 4,000 nanometers, etc. The total thickness  108  may be greater than 1 nanometer, greater than 20 nanometers, greater than 40 nanometers, greater than 100 nanometers, greater than 1,000 nanometers, greater than 4,000 nanometers, greater than 8,000 nanometers, less than 1 nanometer, less than 20 nanometers, less than 40 nanometers, less than 100 nanometers, less than 1,000 nanometers, less than 4,000 nanometers, less than 8,000 nanometers, etc. The number of sublayers included in filter  104  may be three, four, five, six, more than six, more than eight, more than ten, more than twenty, etc. 
     The interference filter  104  for detector  102  may be configured to, at the wavelength emitted by light sources  52  for the optical touch sensor, block incident light at incident angles less than A C2  and transmit incident light at incident angles that are greater than A C2 .  FIGS.  18  and  19    are graphs showing the transmission of light through interference filter as a function of wavelength. In particular,  FIG.  18    shows the transmission of light through interference filter  104  as a function of wavelength at a first angle (relative to the surface normal which is defined as 0 degrees) that is greater than A C2  (e.g., 67 degrees, greater than 62.7 degrees, greater than 65 degrees, etc.) whereas  FIG.  19    shows the transmission of light through interference filter as a function of wavelength at a second angle that is less than A C2  (e.g., 0 degrees). 
     As shown in  FIG.  18   , the interference filter may transmit light at three peaks at an incident angle of 67 degrees: λ 1 , λ 2 , and λ 3 . The largest peak at λ 3  may be the wavelength of interest (e.g., near infrared light at approximately 950 nanometers that is emitted by the light sources  52 ). There may be smaller peaks at λ 1  and λ 2  within the visible light range (e.g., λ 1 =450 nanometers and λ 2 =630 nanometers). 
     As shown in  FIG.  19   , the interference filter may transmit light at three peaks at an incident angle of 0 degrees: λ 4 , λ 5 , and λ 6 . There may be peaks at λ 4  and λ 5  within the visible light range (e.g., λ 4 =450 nanometers and λ 5 =600 nanometers). There may also be a peak at λ 6  around 890 nanometers. Ideally, all light would be blocked at incident angles of 0 degrees. Additional layers may be added to the interference filter to further tune the response. However, this may add additional complexity to the interference filters. 
     In  FIGS.  18  and  19   , λ 6  (with undesirably transmitted light) is less than λ 3  (with desirably transmitted light). Therefore, an additional filter may be included in series with the interference filter to block the light that is transmitted at the 0 degree incident angle in  FIG.  19   . For example, the additional filter may block all light at wavelengths of 900 nanometers or smaller (regardless of incident angle). The additional filter may be a near-infrared light bandpass filter that transmits light between 900 nanometers and 1000 nanometers (regardless of incident angle). The additional filter may therefore block the light at wavelengths λ 4 , λ 5 , and λ 6  in  FIG.  19   . 
       FIGS.  18  and  19    show how at an angle (e.g., an off-axis angle) greater than A C2  (as in  FIG.  18   ), the angular filter may transmit more light at the wavelength of interest (λ 3  which is the wavelength emitted by light sources  52 ) than at an angle (e.g., an on-axis angle) less than A C2  (as in  FIG.  19   ). 
       FIG.  20    is a side view of a detector that is overlapped by an interference filter and an additional filter. As shown in  FIG.  20   , the additional filter  110  (sometimes referred to as a cut filter, visible light blocking filter, etc.) is formed directly over the detector such that light passes through both the additional filter  110  and the interference filter  104  to reach detector  102 . In  FIG.  20   , interference filter  104  is interposed between filter  110  and detector  102 . This example is merely illustrative. Filter  110  may instead be interposed between interference filter  104  and detector  102  if desired (such that filter  110  is in direct contact with detector  102 ). 
     Filter  110  may have the same filtering performance regardless of the incident angle of light. Filter  110  may block substantially all (e.g., more than 95% of) visible light. Filter  110  may block substantially all (e.g., more than 95% of) light at wavelengths less than 900 nanometers while passing substantially all (e.g., more than 95% of) light at wavelengths greater than 900 nanometers. This transmission profile is consistent regardless of the incident angle. This is in contrast to interference filter  104 , which has a different transmission profile at different incident angles. 
     A specific example has been described above where an interference filter is formed directly over the detectors  102  in electronic device  10 . Interference filters may also be formed over light sources  52 . Using interference filters as the angular filters for light sources  52  may mitigate the thickness of the display and avoid blocking pixels that are neighboring the light sources. These interference filters may be configured to transmit light at incident angle A when −A C1 &lt;A&lt;+A C1  and block light at incident angle A when A&lt;−A C1  or A&gt;+A C1 . 
       FIG.  21    is a side view of an illustrative display with an optical touch sensor that includes first interference filters  104  over detectors  102  and second interference filters  112  over light sources  52 . The arrangement of each first interference filter  104  may be the same as the other filters  104  and the arrangement of each second interference filter  112  may be the same as the other filters  112 . However, the arrangement of filters  104  and  112  may be different to achieve the target transmission profile for the light sources and the detectors. Interference filters  112  may transmit light at incident angle A when −A C1 &lt;A&lt;+A C1  and block light at incident angle A when A&lt;−A C1  or A&gt;+A C1 . More generally, interference filters  112  may transmit more light at the wavelength of interest (e.g., λ 3  as discussed above) at an angle (e.g., an on-axis angle) that is less than A C1  than at an angle (e.g., an off-axis angle) that is greater than A C1 . 
     Although  FIG.  16    illustrates mask layer  88  formed over light detector  102  and separated from the light detector by transparent layer  84 , in some instances it can be advantageous to form the mask layer at the photodiode component level, while the photodiode component is being fabricated. By doing so, the formation of mask layer  88  can be isolated from the display assembly process, and the mask layer can become part of the modularized photodiode component, thereby casing the challenges of forming the mask layer at a higher level of integration. Forming mask layer  88  within the photodiode component also miniaturizes the mask layer to produce a smaller footprint, and in some instances component-level fabrication processes can enable formation of the mask layer with greater accuracy than at the display assembly level. In contrast, forming mask layer  88  at the display assembly level requires that the mask layer be formed at a greater height above the photosensitive surface of the photodiode as compared to the photodiode component level, which in turn requires that the mask layer be larger and consume more display surface area. 
       FIG.  22 A  illustrates a cross-sectional view of photodiode  2264  (e.g., detector  102  of  FIG.  16   ) including photosensitive surface  2204  and top light blocking layer  2212  formed on first layer  2214  in accordance with some embodiments of the disclosure. Note that the term photodiode, as used herein, is a light-sensitive semiconductor diode inclusive of an LED, micro-LED, or other diode configured as a light detector. Photodiode  2264  can have a thickness e, and can include photodiode substrate or body  2216  and photosensitive surface  2204  located in a confined area in the photodiode substrate or body. Although not evident in the example of  FIG.  22 A , photosensitive surface  2204  has a surface area for receiving incoming light rays. Photodiode body  2216  can include a p+ area (photosensitive surface  2204 ), a depletion region, and an n-type substrate that together form a semiconductor p-n junction, and can also include an n material and a metal contact, most of which are not shown in  FIG.  22 A  for purposes of simplifying the figure. Photosensitive surface  2204  can be created by blocking areas of photodiode body  2216  other than the area of the photosensitive surface using an opaque mask layer (not shown in  FIG.  6 E ) formed over the photodiode body. The opaque mask can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. 
     In the example of  FIG.  22 A , during the photodiode fabrication process, first layer  2214  can be formed over photosensitive surface  2204  and photodiode body  2216 . First layer  2214  can be optically transparent, at least at the wavelengths of interest of the received light rays. In various examples, first layer  2214  can be a passivation layer deposited over photosensitive surface  2204  and photodiode body  2216 , or alternatively an epoxy, a filter, or a grown oxide having a thickness of several microns. Because photodiode  2264  will operate within a certain range of wavelengths, in some examples, first layer  2214  can be a wavelength selective filter (e.g., a color filter) that can pass light within the same range of wavelengths that are generated by corresponding LEDs configured as illuminators, so that the photodiodes will not receive much light from sources other than the reflected light from the illuminators. In one example, the LEDs can be configured to generate light in the infrared or near-infrared spectrum. In another example, the LEDs can be configured to generate light in the visible spectrum. In one illustrative example, first layer  2214  can be a thin film filter that is formed from Silicon Nitride (SiN) having a refractive index of about 1.7-2.2. 
     An opaque mask layer such as top light blocking layer  2212  can then be formed over first layer  2214  during the photodiode component fabrication process to permit only certain angles of light to reach photosensitive surface  2204 . Top light blocking layer  2212  can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. In some examples, top light blocking layer  2212  can allow only about 0.01% of received light to pass through. In some examples, top light blocking layer  2212  can also be absorptive, reflecting not more than about 1% of received light. 
     Although the preceding discussion describes received light rays with permitted angles (“receive angles”) of greater than +/−62.7 degrees (indicative of a touching finger or stylus) from a photodiode surface normal (e.g., normal to a top surface of the photodiode, which can be the same as the normal to photosensitive surface  2204 ), allowing all angles between +/−62.7 degrees may permit some undesirable reflections and refractions to be detected by photodiode  2264 . Thus, top light blocking layer  2212  can include not only inner mask baffle  2212 -D (e.g., mask  88  of  FIG.  16   ), but also outer mask portions  2212 -C and  2212 -E to act as an angular filter and limit the receive angles to narrow ranges, such as within a specific number of degrees (e.g., within 10 degrees, 5 degrees, one degree, etc.) or some fixed percentage (e.g., within 20%, 10%, 5%, etc.) of +/−62.7 degrees. In one specific example for purposes of illustration only, inner mask baffle  2212 -D in conjunction with outer mask portions  2212 -C and  2212 -E can pass light between a first receive angle of 65 degrees and a second receive angle of 75 degrees. Inner mask baffle  2212 -D can be formed above photosensitive surface  2204  (e.g., separated from the photosensitive surface by first layer  2214  in a vertical direction) and can extend beyond the photosensitive surface (e.g., extend beyond the edges of the photosensitive surface in a horizontal direction). Note that although outer mask portions  2212 -C and  2212 -E appear to be separate portions in the cross-sectional view of  FIG.  6 E , they are actually continuously connected as one outer mask portion that encircles inner mask baffle  2212 -D. Aperture  2218  can be created in areas of first layer  2214  that are not covered by inner mask baffle  2212 -D or outer mask portions  2212 -C and  2212 -E. 
     Inner mask baffle  2212 -D and outer mask portions  2212 -C and  2212 -E can be formed with diameters a and b to create aperture  2218  that permits only a range of receive angles between a first receive angle Ø 1  and a second receive angle Ø 2  to reach photosensitive surface  2204 , such as within a specific number of degrees (e.g., within 10 degrees, 5 degrees, one degree, etc.) or some fixed percentage (e.g., within 20%, 10%, 5%, etc.) of +/−62.7 degrees. The generalized diameter equation is:
 
diameter=2* d *tan(Ø)+ c   (1)
 
where c is the width or diameter of photosensitive surface  2204 , and d is the distance between the photosensitive surface and inner mask baffle  2212 -D.
 
     The generalized diameter equation (1) can be utilized with dimensions c (width of photosensitive surface  2204 ) and d (the distance between the photosensitive surface and top light blocking layer  2212 ) to compute diameters a and b. In various examples, diameter a can be in the range of 10-50 microns, the thickness d of first layer  2214  can be in the range of 1-5 microns, and the width or diameter c of photosensitive surface  2204  can be in the range of 2.55-66 microns. Table I below lists some example dimensions of photodiode  2264 : 
                         TABLE I               Photosensitive Surface 2204 x-y Dimensions   Photodiode thickness e                                            2.5 μm × 2.5 μm   2.5   μm       5 μm × 5 μm   3   μm                     12 μm × 12 μm   2.5 μm or 4.5 μm                         15 μm × 15 μm   3   μm                     22 μm × 22 μm   2.5 μm or 4.5 μm                         25 μm × 25 μm   3   μm       30 μm × 30 μm   4   μm       33 μm × 33 μm   5   μm       33 μm × 66 μm   5   μm                    
In some examples, the maximum area of photosensitive surface  2204  can be limited to 50 μm×100 μm, and the photosensitive surface can be centered in the x dimension with respect to the package. In one example for purposes of illustration only, for a first receive angle Ø 1  of 65 degrees, the diameter b=4.29d+c, and for a second receive angle Ø 2  of 75 degrees, the diameter a=7.46d+c. In another example, the dimensions c and d can be selected to produce a first receive angle Ø 1  of 62.7 degrees, and a second receive angle Ø 2  that is a fixed percentage or a fixed number of degrees greater than the first receive angle Ø 1  (e.g., 10 degrees greater or 72.7 degrees, or 20% greater or 75 degrees, etc.).
 
     LEDs in close proximity to photodiode  2264  can emit light that is intended to reflect off a touching or hovering object such as a finger or a stylus and back to the photodiode. In some examples, to ensure that light emitted from proximate LEDs does not travel directly to photodiode  2264  and be erroneously detected by photosensitive surface  2204 , the photodiode can include side light blocking layers  2220  to block this stray light. Side light blocking layers  2220  can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. In some examples, side light blocking layers  2220  can allow only about 0.01% of received light to pass through. In some examples, side light blocking layers  2220  can also be absorptive, reflecting not more than about 1% of received light. Note that  FIG.  22 A  and its description herein may omit certain layers and assembly/fabrication processes for purposes of simplifying the disclosure. 
       FIG.  22 B  illustrates a top view of photodiode  2264  of  FIG.  22 A  showing top light blocking layer  2212  in accordance with some embodiments of the disclosure. Note that the cross-sectional view of  FIG.  22 A  is taken along the view A-A of  FIG.  22 B , and that photosensitive surface  2204  of  FIG.  22 A  is shown in  FIG.  22 B  as being hidden beneath inner mask baffle  2212 -D. From the top view of  FIG.  22 B , it can be seen that aperture  2218  can be ring-shaped (e.g., an annulus) that encircles photosensitive surface  2204  from above (e.g., separated from the photosensitive surface by first layer  2214  in a vertical direction). 
       FIG.  22 C  illustrates a cross-sectional view of photodiode  2264  including photosensitive surface  2204 , second light blocking layer  2222  formed within first layer  2214 , and top light blocking layer  2212  formed on top of the first layer in accordance with some embodiments of the disclosure. Photodiode  2264  can have a thickness e, and can include photodiode substrate or body  2216  and photosensitive surface  2204  located in a confined area on the photodiode substrate or body. Although not evident in the example of  FIG.  22 C , photosensitive surface  2204  has a surface area for receiving incoming light rays. Photosensitive surface  2204  can be created by blocking areas of photodiode body  2216  other than the area of the photosensitive surface using an opaque mask (not shown in  FIG.  22 C ) formed over the photodiode body. The opaque mask can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. 
     The addition of second light blocking layer  2222  can provide for better control of the angles of light received at photosensitive surface  2204 , and better control of the detection area on the photosensitive surface. For example, with reference to  FIG.  22 A , light rays entering from the right of photodiode  2264  (with reference to the viewpoint of  FIG.  22 A ) may impinge upon many different areas of photosensitive surface  2204 , including areas along the left side of the photosensitive surface, depending on the angle of incident light. In contrast, with reference to  FIG.  22 C , light rays entering from the right side of photodiode  2264  (with reference to the viewpoint of  FIG.  22 C ) will impinge upon fewer areas of photosensitive surface  2204 , and potentially no areas along the left side of the photosensitive surface, even with varying angles of incident light, due to the further restriction of light angles caused by the presence of second light blocking layer  2222 . In some examples, second light blocking layer  2222  can also advantageously absorb some of the tolerances and misalignments that occur during photodiode processing and allow photosensitive surface  2204  to be manufactured with a smaller than nominal size. 
     During the photodiode fabrication process, a first portion of first layer  2214  can be formed over photosensitive surface  2204  and photodiode body  2216 . In various examples, first layer  2214  can be a passivation layer deposited over photosensitive surface  2204  and photodiode body  2216 , or alternatively an epoxy, a filter, or a grown oxide having a thickness of several microns. Because photodiode  2264  will operate within a certain range of wavelengths, in some examples, first layer  2214  can be a wavelength selective filter (e.g., a color filter) that can receive light within the same range of wavelengths that are generated by corresponding LEDs configured as illuminators, so that the photodiodes will not receive much light from sources other than the reflected light from the illuminators. In one illustrative example, first layer  2214  can be a thin film filter formed from Silicon Nitride (SiN) having a refractive index of about 1.7-2.2. 
     An opaque mask layer such as second light blocking layer  2222  can then be formed over the first portion of first layer  2214  during the photodiode component fabrication process to permit only certain angles of light to reach photosensitive surface  2204 . Second light blocking layer  2222  can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. In some examples, second light blocking layer  2222  can allow only about 0.01% of received light to pass through. In some examples, second light blocking layer  2222  can also be absorptive, reflecting not more than about 1% of received light. Second light blocking layer  2222  can include inner mask baffle  2222 -D and outer mask portions  2222 -C and  2222 -E. Inner mask baffle  2222 -D can be formed above photosensitive surface  2204  (e.g., separated from the photosensitive surface by the first portion of first layer  2214  in a vertical direction) and can extend beyond the photosensitive surface (e.g., extend beyond the edges of the photosensitive surface in a horizontal direction). Note that although outer mask portions  2222 -C and  2222 -E appear to be separate portions in the cross-sectional view of  FIG.  22 C , they are actually continuously connected as one outer mask portion that encircles inner mask baffle  2222 -D. Aperture  2224  can be formed between inner mask baffle  2222 -D and outer mask portions  2222 -C and  2222 -E. 
     As noted above, although received light rays with receive angles of greater than +/−62.7 degrees (with respect to the photodiode surface normal) can be indicative of a finger or stylus touch, allowing all receive angles between +/−62.7 degrees may permit some undesirable reflections and refractions to be detected by photosensitive surface  2204  of photodiode  2264 . Thus, inner mask baffle  2222 -D and outer mask portions  2222 -C and  2222 -E can be formed with diameters a 2  and b 2  to create aperture  2224  that act as an angular filter and permits only a range of receive angles between a first receive angle Ø 1  and a second receive angle Ø 2  to reach photosensitive surface  2204 , such as within a specific number of degrees (e.g., within 10 degrees, 5 degrees, one degree, etc.) or some fixed percentage (e.g., within 20%, 10%, 5%, etc.) of +/−62.7 degrees. The generalized diameter equation (1) shown above can be utilized with dimensions c (width or diameter of photosensitive surface  2204 ) and d 2  (the distance between the photosensitive surface and second light blocking layer  2222 ) to compute diameters a 2  and b 2 . 
     A second portion of first layer  2214  can then be formed over second light blocking layer  2222 . Another opaque mask layer such as top light blocking layer  2212  can then be formed over the second portion of first layer  2214  during the photodiode component fabrication process to permit only certain angles of light to reach photosensitive surface  2204 . Top light blocking layer  2212  can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. In some examples, top light blocking layer  2212  can allow only about 0.01% of received light to pass through. In some examples, top light blocking layer  2212  can also be absorptive, reflecting not more than about 1% of received light. Top light blocking layer  2212  can include inner mask baffle  2212 -D and outer mask portions  2212 -C and  2212 -E. Inner mask baffle  2212 -D can be formed above photosensitive surface  2204  (e.g., separated from the photosensitive surface by both the first and second portions of first layer  2214  in a vertical direction) and can extend beyond photosensitive surface  2204  (e.g., extend beyond the edges of the photosensitive surface in a horizontal direction). Note that although outer mask portions  2212 -C and  2212 -E appear to be separate portions in the cross-sectional view of  FIG.  22 C , they are actually continuously connected as one outer mask portion that encircles inner mask baffle  2212 -D. Aperture  2218  can be created in areas of the second portion of first layer  2214  that are not covered by inner mask baffle  2212 -D or outer mask portions  2212 -C and  2212 -E. 
     Inner mask baffle  2212 -D and outer mask portions  2212 -C and  2212 -E can be formed with diameters a 1  and b 1  to create aperture  2218  that act as an angular filter and permits the same range of receive angles (e.g., between Ø 1  and Ø 2 ) as inner mask baffle  2222 -D and outer mask portions  2222 -C and  2222 -E to reach photosensitive surface  2204 , such as within a specific number of degrees (e.g., within 10 degrees, 5 degrees, one degree, etc.) or some fixed percentage (e.g., within 20%, 10%, 5%, etc.) of +/−62.7 degrees. The generalized diameter equation (1) shown above can be utilized with dimensions c (width of photosensitive surface  2204 ) and d 1  (the distance between the photosensitive surface and top light blocking layer  2212 ) to compute diameters a 1  and b 1 . In one example for purposes of illustration only, for a first receive angle Ø 1  of 65 degrees, the diameter b 1 =4.29d 1 +c, and for an angle Ø 2  of 75 degrees, the diameter a 1 =7.46d 1 +c. In another example, the dimensions c and d 1  can be selected to produce a first receive angle Ø 1  of 62.7 degrees, and a second receive angle Ø 2  that is a fixed percentage or a fixed number of degrees greater than Ø 1  (e.g., 10 degrees greater or 72.7 degrees, or 20% greater or 75 degrees, etc.). 
     As described above, LEDs in close proximity to photodiode  2264  can emit light that is intended to reflect off a touching or hovering object such as a stylus and back to the photodiode. In some examples, to ensure that light emitted from such proximate LEDs does not travel directly to photodiode  2264  and be erroneously detected by photosensitive surface  2204 , the photodiode can include side light blocking layers  2220  to block this stray light. Side light blocking layers  2220  can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. In some examples, side light blocking layers  2220  can allow only about 0.01% of received light to pass through. In some examples, side light blocking layers  2220  can also be absorptive, reflecting not more than about 1% of received light. Note that  FIG.  22 C  and its description herein may omit certain layers and assembly/fabrication processes for purposes of simplifying the disclosure. 
       FIG.  22 D  illustrates a top view of photodiode  2264  of  FIG.  22 C  showing top light blocking layer  2212  and a portion of second light blocking layer  2222  showing through aperture  2218  in accordance with some embodiments of the disclosure. Note that the cross-sectional view of  FIG.  22 C  is taken along the view A-A of  FIG.  22 D , and that photosensitive surface  2204 , inner mask baffle  2222 -D, and aperture  2224  of  FIG.  22 C  are shown as being hidden beneath inner mask baffle  2212 -D. From the top view of  FIG.  22 D , it can be seen that apertures  2218  and  2224  can be ring-shaped (e.g., an annulus) that encircles photosensitive surface  2204  from above (e.g., separated from the photosensitive surface by first layer  2214  in a vertical direction). 
       FIG.  22 E  illustrates a cross-sectional view of photodiode  2264  including photosensitive surface  2204 , second light blocking layer  2222  formed on second layer  2226  having a second refractive index n2, and top light blocking layer  2212  formed on first layer  2214  having a first refractive index n1 in accordance with some embodiments of the disclosure. Second layer  2226  can be optically transparent, at least at the wavelengths of interest of the received light rays. Photodiode  2264  can include photodiode substrate or body  2216  and photosensitive surface  2204  located in a confined area on the photodiode substrate or body. Although not evident in the example of  FIG.  22 E , photosensitive surface  2204  has a surface area for receiving incoming light rays. Photosensitive surface  2204  can be created by blocking areas of photodiode body  2216  other than the area of the photosensitive surface using an opaque mask (not shown in  FIG.  22 E ) formed over the photodiode body. The opaque mask can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. 
     The addition of second layer  2226  with a refractive index n2 that is different from the refractive index n1 of first layer  2214  can provide for better control of the angles of light received at photosensitive surface  2204  by virtue of the “bending” of light rays as they refract across the layer boundary. This increased control of light rays can allow for a photosensitive surface  2204  with a larger surface area and an advantageous increase in light detection sensitivity. For example, with reference to  FIG.  22 E , light rays entering from the right of photodiode  2264  (with reference to the viewpoint of  FIG.  22 E ) at entry angles between Ø b1  and Ø a1  may decrease in angle (with respect to the photodiode surface normal) to between Ø b2  and Ø a2  as they cross the boundary between first layer  2214  and second layer  2226 . This decrease in angle (e.g., increase in steepness) can allow for the diameter c of photosensitive surface  2204  to increase, while still capturing only those light rays with photodiode entry angles between Ø b1  and Ø a1 . 
     During the photodiode fabrication process, second layer  2226  having a refractive index of n2 can be formed over photosensitive surface  2204  and photodiode body  2216 . In various examples, second layer  2226  can be a passivation layer deposited over photosensitive surface  2204  and photodiode body  2216 , or alternatively the second layer can be an epoxy, a filter, or a grown oxide having a thickness of several microns. Because photodiode  2264  will operate within a certain range of wavelengths, in some examples, second layer  2226  can be a wavelength selective filter (e.g., a color filter) that can receive light within the same range of wavelengths that are generated by corresponding LEDs configured as illuminators, so that the photodiodes will not receive much light from sources other than the reflected light from the illuminators. 
     An opaque mask layer such as second light blocking layer  2222  can then be formed over the first portion of second layer  2226  during the photodiode component fabrication process to permit only certain angles of light to reach photosensitive surface  2204 . Second light blocking layer  2222  can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. In some examples, second light blocking layer  2222  can allow only about 0.01% of received light to pass through. In some examples, second light blocking layer  2222  can also be absorptive, reflecting not more than about 1% of received light. Second light blocking layer  2222  can include inner mask baffle  2222 -D and outer mask portions  2222 -C and  2222 -E. Inner mask baffle  2222 -D can be formed over photosensitive surface  2204  (e.g., separated from the photosensitive surface by second layer  2226  in a vertical direction) and can extend beyond the photosensitive surface (e.g., extend beyond the edges of the photosensitive surface in a horizontal direction). Note that although outer mask portions  2222 -C and  622 -E appear to be separate portions in the cross-sectional view of  FIG.  22 E , they are actually continuously connected as one outer mask portion that encircles inner mask baffle  2222 -D. Aperture  2224  can be created in areas of second layer  626  that are not covered by inner mask baffle  2222 -D and or mask portions  2222 -C and  2222 -E. 
     First layer  2214  can then be formed over second layer  2226  and second light blocking layer  2222 . Another opaque mask layer such as top light blocking layer  2212  can then be formed over first layer  2214  during the photodiode component fabrication process to permit only certain angles of light to reach photosensitive surface  2204 . Top light blocking layer  2212  can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. In some examples, top light blocking layer  2212  can allow only about 0.01% of received light to pass through. In some examples, top light blocking layer  2212  can also be absorptive, reflecting not more than about 1% of received light. Top light blocking layer  2212  can include inner mask baffle  2212 -D and outer mask portions  2212 -C and  2212 -E. Inner mask baffle  2212 -D can be formed above photosensitive surface  2204  (e.g., separated from the photosensitive surface by first layer  2214  and second layer  2226  in a vertical direction) and can extend beyond the photosensitive surface  2204  (e.g., extend beyond the edges of the photosensitive surface in a horizontal direction). Note that although outer mask portions  2212 -C and  2212 -E appear to be separate portions in the cross-sectional view of  FIG.  22 E , they are actually continuously connected as one outer mask portion that encircles inner mask baffle  2212 -D. Aperture  2218  can be created in areas of first area  614  that are not covered by inner mask baffle  2212 -D or outer mask portions  2212 -C and  2212 -E. 
     As noted above, although received light rays with receive angles of greater than +/−62.7 degrees (with respect to the photodiode surface normal) can be indicative of a stylus, allowing all receive angles between +/−62.7 degrees may permit some undesirable reflections and refractions to be detected by photosensitive surface  2204  of photodiode  2264 . Thus, inner mask baffle  2212 -D and outer mask portions  2212 -C and  2212 -E of top light blocking layer  2212  can be formed with diameters a 1  and b 1  to create aperture  2218  that act as an angular filter and permits only a range of receive angles between first receive angle Ø b1  and second receive angle Ø a1  to reach photosensitive surface  2204 , such as within a specific number of degrees (e.g., within 10 degrees, 5 degrees, one degree, etc.) or some fixed percentage (e.g., within 20%, 10%, 5%, etc.) of +/−62.7 degrees. Additionally, inner mask baffle  2222 -D and outer mask portions  2222 -C and  2222 -E of second light blocking layer  2222  can be formed with diameters a 2  and b 2  to create aperture  2224  that, in conjunction with the light rays having a range of receive angles between Ø b1  and Ø a1  passing through first layer  2214 , allow a larger diameter photosensitive surface  2204  to be utilized while still only capturing those light rays with entry angles between Ø b1  and Ø a1 . 
     Given a desired range of incoming light ray receive angles between Ø b1  and Ø a1 , the refracted light ray receive angles in second layer  2226  can be computed as: 
                     ∅     a   ⁢   2       =     a   ⁢     sin   (     n   ⁢   1   /   n   ⁢   2   *     sin   ⁡   (     ∅     a   ⁢   1       )                   (   2   )                             ∅     b   ⁢   2       =     a   ⁢     sin   (     n   ⁢   1   /   n   ⁢   2   *     sin   ⁡   (     ∅     b   ⁢   1       )                   (   3   )               
and the average light ray receive angle in second layer  2226  can be computed as:
 
     
       
         
           
             
               
                 
                   
                     
                       ∅ 
                       2 
                     
                     ( 
                     
                       average 
                       ⁢ 
                           
                       angle 
                       ⁢ 
                           
                       in 
                       ⁢ 
                           
                       second 
                       ⁢ 
                           
                       layer 
                       ⁢ 
                           
                       2214 
                     
                     ) 
                   
                   = 
                   
                     
                       ( 
                       
                         
                           ∅ 
                           
                             a 
                             ⁢ 
                             2 
                           
                         
                         + 
                         
                           ∅ 
                           
                             b 
                             ⁢ 
                             2 
                           
                         
                       
                       ) 
                     
                     / 
                     2 
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
     In some examples, the material and refractive index of second layer  2226  can be selected for increased antireflective index matching between first layer  2214  (having a refractive index of n1) and photodiode body  2216  (having a refractive index of np). Ideally, the refractive index n2 of second layer  2226  can be selected such that: 
                     n   ⁢   2     =     sqrt   ⁡   (     n   ⁢   1   *   np     )             (   5   )               
In addition, for light having a wavelength L, the thickness d2 of second layer  2226  can be computed as:
 
                     d   ⁢   2     =     L   ⁢     cos   ⁡   (     ∅   2     )     /   4   /   n   ⁢   2             (   6   )               
More generally, in all display level and photodiode component level embodiments described herein, the materials can be selected to have similar refractive indices to minimize unwanted reflections between material boundaries.
 
     The generalized diameter equation (1) shown above can be utilized with dimensions c (width of photosensitive surface  2204 ), d 2  (the thickness of second layer  2226 ), and d 1  (the thickness of first layer  2214 ) to compute diameters a 2 , b 2 , a 1 , and b 1  as follows: 
     
       
         
           
             
               
                 
                   
                     b 
                     2 
                   
                   = 
                   
                     
                       2 
                       * 
                       
                         d 
                         2 
                       
                       * 
                       
                         tan 
                         ⁡ 
                         ( 
                         
                           ∅ 
                           
                             b 
                             ⁢ 
                             2 
                           
                         
                         ) 
                       
                     
                     + 
                     c 
                   
                 
               
               
                 
                   ( 
                   7 
                   ) 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     a 
                     2 
                   
                   = 
                   
                     
                       2 
                       * 
                       
                         d 
                         2 
                       
                       * 
                       
                         tan 
                         ⁡ 
                         ( 
                         
                           ∅ 
                           
                             a 
                             ⁢ 
                             2 
                           
                         
                         ) 
                       
                     
                     + 
                     c 
                   
                 
               
               
                 
                   ( 
                   8 
                   ) 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     b 
                     1 
                   
                   = 
                   
                     
                       2 
                       * 
                       
                         d 
                         1 
                       
                       * 
                       
                         tan 
                         ⁡ 
                         ( 
                         
                           ∅ 
                           
                             b 
                             ⁢ 
                             1 
                           
                         
                         ) 
                       
                     
                     + 
                     
                       b 
                       2 
                     
                   
                 
               
               
                 
                   ( 
                   9 
                   ) 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     a 
                     1 
                   
                   = 
                   
                     
                       2 
                       * 
                       
                         d 
                         1 
                       
                       * 
                       
                         tan 
                         ⁡ 
                         ( 
                         
                           ∅ 
                           
                             a 
                             ⁢ 
                             1 
                           
                         
                         ) 
                       
                     
                     + 
                     
                       a 
                       2 
                     
                   
                 
               
               
                 
                   ( 
                   10 
                   ) 
                 
               
             
           
         
       
     
     As described above, LEDs in close proximity to photodiode  2264  can emit light that is intended to reflect off a touching or hovering object such as a stylus and back to the photodiode. In some examples, to ensure that light emitted from such proximate LEDs does not travel directly to photodiode  2264  and be erroneously detected by photosensitive surface  2204 , the photodiode can include side light blocking layers  2220  to block this stray light. Side light blocking layers  2220  can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. In some examples, side light blocking layers  2220  can allow only about 0.01% of received light to pass through. In some examples, side light blocking layers  2220  can also be absorptive, reflecting not more than about 1% of received light. Note that  FIG.  22 E  and its description herein may omit certain layers and assembly/fabrication processes for purposes of simplifying the disclosure. 
       FIG.  22 F  illustrates a top view of photodiode  2264  of  FIG.  22 E  showing top light blocking layer  2212  and a portion of second light blocking layer  2222  showing through aperture  2218  in accordance with some embodiments of the disclosure. Note that the cross-sectional view of  FIG.  22 E  is taken along the view A-A of  FIG.  22 F , and that photosensitive surface  2204 , inner mask baffle  2222 -D, and aperture  2224  of  FIG.  22 F  are shown as being hidden beneath inner mask baffle  2212 -D. From the top view of  FIG.  22 F , it can be seen that apertures  2218  and  2224  can be ring-shaped (e.g., an annulus) that encircles photosensitive surface  2204  from above (e.g., separated from the photosensitive surface in a vertical direction). 
     In the examples of  FIGS.  22 A- 22 F  discussed above, an aperture can be formed on one or more layers of photodiode  2264  to permit light rays within a range of angles to impinge upon photosensitive surface  2204 . However, in some instances, light rays within the desired range of angles may only impinge upon a small portion of photosensitive surface  2204 , such as only along the perimeter of the photosensitive surface. As a result, the amount of light detected by that photodiode may be sub-optimal. Therefore, in some instances it can be advantageous to detect more light within the desired range of angles at a single photodiode. To achieve this, some embodiments of the disclosure can employ multiple photosensitive surfaces and multiple apertures within a single photodiode to increase the opportunities to receive light rays at the angles of interest. 
       FIG.  22 G  illustrates a cross-sectional view of photodiode  2264  including multiple photosensitive surfaces  2204  and top light blocking layer  2212  with multiple merged apertures  2218  formed on first layer  2214  in accordance with some embodiments of the disclosure. One inner mask baffle  2212 -D on top light blocking layer  2212  can be formed above and extend beyond each photosensitive surface  2204 . Each inner mask baffle  2212 -D can be at least partially encircled by an outer mask portion of top light blocking layer  2212 , except for where apertures  2218  are partially merged.  FIG.  22 G  is similar to  FIG.  22 A , except that the example of  FIG.  22 G  includes multiple photosensitive surfaces  2204 , multiple inner mask baffles  2212 -D, and multiple merged apertures  2218 . 
       FIG.  22 H  illustrates a top view of photodiode  2264  of  FIG.  22 G  showing top light blocking layer  2212  and partially merged apertures  2218  in accordance with some embodiments of the disclosure. Note that the cross-sectional view of  FIG.  22 G  is taken along the view A-A of  FIG.  22 H , and that photosensitive surfaces  2204  of  FIG.  22 H  are shown as being hidden beneath inner mask baffles  2212 -D. From the top view of  FIG.  22 H , it can be seen that ring-shaped apertures  2218  are merged together due to the close spacing of photosensitive surfaces  2204 . In some instances, it can be advantageous to place multiple photosensitive surfaces  2204  as close together as practical to increase the amount of light detected by photodiode  2264 , resulting in the overlap of apertures  2218  shown in  FIG.  22 H . 
     In some examples, the dimensions of photosensitive surfaces  2204 , inner mask baffles  2212 -D, and apertures  2218  can be the same within a single photodiode  2264 . However, in other examples, the dimensions need not be the same. For example,  FIG.  22 H  shows that due to the arrangement of photosensitive surfaces  2204  across photodiode  2264 , there are some small open areas where no detection activity is taking place. Thus, although not shown in  FIG.  22 H , in some examples one or more smaller photosensitive surfaces and corresponding inner mask baffles and apertures can be formed in the open areas of photodiode  2264  to utilize those small areas for light detection. 
       FIG.  22 I  illustrates a cross-sectional view of photodiode  2264  including multiple photosensitive surfaces  2204  and top light blocking layer  2212  with multiple separated apertures  2218  formed on first layer  2214  in accordance with some embodiments of the disclosure. One inner mask baffle  2212 -D on top light blocking layer  2212  can be formed above and extend beyond each photosensitive surface  2204 . Each inner mask baffle  2212 -D can be encircled by an outer mask portion of top light blocking layer  2212 .  FIG.  22 I  is similar to  FIG.  22 G , except that the example of  FIG.  22 I  includes multiple separated apertures  2218 . 
       FIG.  22 J  illustrates a top view of photodiode  2264  of  FIG.  22 I  showing top light blocking layer  2212  and apertures  2218  in accordance with some embodiments of the disclosure. Note that the cross-sectional view of  FIG.  22 I  is taken along the view A-A of  FIG.  22 J , and that photosensitive surfaces  2204  of  FIG.  22 J  are shown as being hidden beneath inner mask baffles  2212 -D. From the top view of  FIG.  22 J , it can be seen that ring-shaped apertures  2218  are separated due to the wider spacing of photosensitive surfaces  2204 . 
       FIG.  22 K  illustrates a cross-sectional view of LED  2240  including photoemitting surface  2228  having a diameter c and top light blocking layer  2230  formed on first layer  2232  having a thickness d in accordance with some embodiments of the disclosure. First layer  2232  can be optically transparent, at least at the transmit wavelengths of interest. LED  2240  can include LED substrate or body  2234  and photoemitting surface  2228  located in a confined area on the LED substrate or body. LED body  2234  can include a p-type region and an n-type region that together form a semiconductor p-n junction, and can also include metal contacts for anode and cathode connections, most of which are not shown in  FIG.  22 K  for purposes of simplifying the figure. Photoemitting surface  2228  can be created by blocking areas of LED body  2234  other than the area of the photoemitting surface using an opaque mask (not shown in  FIG.  22 K ) formed over the LED body. The opaque mask can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. 
     In the example of  FIG.  22 K , during the LED fabrication process, first layer  2232  can be formed over photoemitting surface  2228  and LED body  2234 . In various examples, first layer  2232  can be a passivation or encapsulation layer deposited over photoemitting surface  2228  and LED body  2234 , or alternatively the first layer can be an epoxy, a filter, or a grown oxide having a thickness of several microns. 
     An opaque mask layer such as top light blocking layer  2230  can then be formed over first layer  2232  during the LED component fabrication process and configured to define aperture  2236  to act as an angular filter and permit only certain angles of light to exit LED  2240 . Top light blocking layer  2230  can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. In some examples, top light blocking layer  2230  can allow only about 0.01% of received light to pass through. In some examples, top light blocking layer  2230  can also be absorptive, reflecting not more than about 1% of received light. Aperture  2236  can be created in areas of first layer  2232  that are not covered by light blocking layer  2230 . Aperture  2236  can be formed above photoemitting surface  2228  (e.g., separated from the photoemitting surface by first layer  2232  in a vertical direction) in areas beyond the photoemitting surface (e.g., the edges of the aperture extend beyond the edges of the photoemitting surface in a horizontal direction). Although not shown in  FIG.  22 K , in some embodiments multiple apertures  2236  can be created in top light blocking layer  2230  to create multiple light emission points from a single photoemitting surface  2228 . Note that  FIG.  22 K  and its description herein may omit certain layers and assembly or fabrication processes for purposes of simplifying the disclosure. 
     As mentioned above, light rays with emission angles of less than +/−42 degrees from an LED surface normal can reduce the likelihood of emitted light rays producing unwanted reflections off the boundary between first layer  2232  and air or water above the first layer. Thus, aperture  2236  can be formed with a diameter a that permits only light with a range of emission angles +/−Ø to be emitted from LED  2240 , such as within a specific number of degrees (e.g., within 10 degrees, 5 degrees, one degree, etc.) or some fixed percentage (e.g., within 20%, 10%, 5%, etc.) of +/−42 degrees. The diameter a of aperture  2236  can be computed as: 
                   a   =       2   *   d   *     tan   ⁡   (   ∅   )       -   c             (   11   )               
where c is the diameter of photoemitting surface  2228 , and d is the thickness of first layer  2232 . For optimal efficiency, a=c. Therefore:
 
     
       
         
           
             
               
                 
                   a 
                   = 
                   
                     d 
                     * 
                     
                       tan 
                       ⁡ 
                       ( 
                       ∅ 
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   12 
                   ) 
                 
               
             
           
         
       
     
     Table II below lists some example dimensions of LED  2240 : 
     
       
         
           
               
               
               
             
               
                   
                 TABLE II 
               
               
                   
                   
               
               
                   
                 Photoemitting Surface 2228 x-y Dimensions 
                 LED thickness e 
               
               
                   
                   
               
             
            
               
                   
                 5 μm × 5 μm 
                 2.5 μm to 5 μm 
               
               
                   
                 10 μm × 10 μm 
                 2.5 μm to 5 μm 
               
               
                   
                 20 μm × 20 μm 
                 2.5 μm to 5 μm 
               
               
                   
                 40 μm × 40 μm 
                 2.5 μm to 5 μm 
               
               
                   
                 40 μm × 80 μm 
                 2.5 μm to 5 μm 
               
               
                   
                   
               
            
           
         
       
     
     In some examples, the maximum area of photoemitting surface  2228  can be limited to 50 μm×100 μm, and the photoemitting surface can be centered in the x dimension with respect to the package. 
     As described above, LEDs in close proximity to a photodiode can emit light that is intended to reflect off a touching or hovering object such as a stylus and back to the photodiode. In some examples, to ensure that light emitted from such proximate LEDs does not travel directly to the photodiode and be erroneously detected by the photodiode, LED  2240  can include side light blocking layers  2238  to block this stray light. Side light blocking layers  2238  can be formed from opaque material (e.g., metal) using masking, ion implantation, etc. In some examples, side light blocking layers  2238  can allow only about 0.01% of received light to pass through. In some examples, side light blocking layers  2238  can also be absorptive, reflecting not more than about 1% of received light. 
       FIG.  22 L  illustrates a top view of LED  2240  of  FIG.  22 K  showing top light blocking layer  2230 , aperture  2236 , and photoemitting surface  2228  in accordance with some embodiments of the disclosure. Note that the cross-sectional view of  FIG.  22 K  is taken along the view A-A of  FIG.  22 L . 
     In some examples, the photodiodes and LEDs having light blocking layers as discussed above can be formed such that there is one photodiode for every LED, but in other examples, different ratios of photodiodes and LEDs are contemplated. In addition, in some examples the photodiodes and LEDS can be arranged in a regular grid with a pitch of 1.25 mm, but in other examples a grid is not required. Also, although the preceding paragraphs describe the formation of light blocking layers either over the light detector (e.g. separate from the light detector component fabrication process;  FIG.  16   ), or alternatively as an integral part of the photodiode or LED component level fabrication process (e.g.,  FIGS.  22 A- 22 L ), in other examples a combination can be employed, where one or more light blocking layers are formed at the photodiode or LED component level, and another light blocking layer is formed at the display assembly level. 
     Therefore, according to the above, some examples of the disclosure are directed to an electronic device configured to gather touch input from a finger, comprising a display having a display cover layer with a surface, wherein the surface has a surface normal, and an optical touch sensor comprising light sources configured to emit light into the display cover layer, wherein the light has a wavelength, light detectors that are configured to detect reflections of the light when the surface is contacted by the finger, and interference filters that are formed over at least one of the light detectors, wherein the interference filters have a first transmission for light at the wavelength and at a first incident angle relative to the surface normal, wherein the interference filters have a second transmission for light at the wavelength and at a second incident angle relative to the surface normal, wherein the second incident angle is greater than the first incident angle, and wherein the second transmission is greater than the first transmission. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first incident angle is 0 degrees and wherein the second incident angle is greater than 65 degrees. Additionally or alternatively to one or more of the examples disclosed above, in some examples the display cover layer has a first refractive index, wherein water has a second refractive index, wherein an interface between a water droplet and the display cover layer has an associated critical angle based on the first refractive index and the second refractive index, and wherein the first incident angle is less than the critical angle. Additionally or alternatively to one or more of the examples disclosed above, in some examples the wavelength is a near infrared wavelength. Additionally or alternatively to one or more of the examples disclosed above, in some examples the electronic device further comprises additional interference filters that are formed over at least one of the light sources. Additionally or alternatively to one or more of the examples disclosed above, in some examples the additional interference filters have a third transmission for light at the wavelength and at a third incident angle relative to the surface normal, wherein the additional interference filters have a fourth transmission for light at the wavelength and at a fourth incident angle relative to the surface normal, wherein the fourth incident angle is greater than the third incident angle, and wherein the fourth transmission is less than the third transmission. Additionally or alternatively to one or more of the examples disclosed above, in some examples the display cover layer has a first refractive index, wherein air has a second refractive index, wherein an interface between air and the display cover layer has an associated critical angle based on the first refractive index and the second refractive index, and wherein the third incident angle is less than the critical angle. Additionally or alternatively to one or more of the examples disclosed above, in some examples each one of the additional interference filters comprises multiple sublayers with alternating index of refraction values. Additionally or alternatively to one or more of the examples disclosed above, in some examples each one of the interference filters comprises multiple sublayers with alternating index of refraction values. Additionally or alternatively to one or more of the examples disclosed above, in some examples each one of the interference filters comprises alternating layers of glass and silver. Additionally or alternatively to one or more of the examples disclosed above, in some examples each one of the interference filters comprises a first sublayer formed from glass, a second sublayer formed from silver, a third sublayer formed from glass, and a fourth sublayer formed from silver. Additionally or alternatively to one or more of the examples disclosed above, in some examples the second sublayer has a thickness of less than 100 nanometers, wherein the third sublayer has a thickness of less than 1,000 nanometers, and wherein the fourth sublayer has a thickness of less than 100 nanometers. Additionally or alternatively to one or more of the examples disclosed above, in some examples the electronic device further comprises additional filters, wherein each additional filter is adjacent to a respective interference filter and formed over a respective light detector. Additionally or alternatively to one or more of the examples disclosed above, in some examples the additional filters block visible light. Additionally or alternatively to one or more of the examples disclosed above, in some examples the additional filters have a same transmission at the first incident angle as at the second incident angle. Additionally or alternatively to one or more of the examples disclosed above, in some examples the optical touch sensor is configured to distinguish between when the surface is contacted by the finger and when the surface is contacted by a water droplet. 
     Some examples of the disclosure are directed to an electronic device configured to gather touch input from a finger, comprising a display having a display cover layer, and an optical touch sensor comprising light sources configured to emit light into the display cover layer, light detectors that are configured to detect reflections of the light when the surface is contacted by the finger, first interference filters, wherein each first interference filter overlaps a respective light source of the light sources, and second interference filters, wherein each second interference filter overlaps a respective light detector of the light detectors. Additionally or alternatively to one or more of the examples disclosed above, in some examples the display cover layer has a surface normal, wherein the first interference filters are configured to pass more light at an on-axis angle that is parallel to the surface normal than at an off-axis angle that is not parallel to the surface normal, and wherein the second interference filters are configured to pass more light at the off-axis angle than at the on-axis angle. Additionally or alternatively to one or more of the examples disclosed above, in some examples each one of the first and second interference filters comprises multiple sublayers with alternating index of refraction values. 
     Some examples of the disclosure are directed to an electronic device configured to gather touch input from a finger, comprising a display having a display cover layer, and an optical touch sensor comprising at least one light source configured to emit near-infrared light into the display cover layer, light detectors that are configured to detect reflections of the near-infrared light when the surface is contacted by the finger, interference filters, wherein each interference filter is formed over a respective light detector, wherein each one of the interference filters comprises multiple sublayers with alternating index of refraction values, and wherein each interference filter has different transmission of near-infrared light at different incident angles, and visible light blocking filters, wherein each visible light blocking filter is formed over a respective light detector. 
     Some examples of the disclosure are directed to a photodiode for performing optical object sensing, comprising a photodiode body including a first photosensitive surface having a first surface area, a first layer formed above the photodiode body, and a first light-blocking layer formed over the first layer, the first light-blocking layer including a first inner mask baffle and a first outer mask portion, the first inner mask baffle formed above and extending beyond the first photosensitive surface, and the first inner mask baffle and the first outer mask portion defining a first aperture therebetween, wherein the first aperture is configured as a first angular filter for allowing incoming light rays to impinge upon the first photosensitive surface at angles between a first receive angle and a second receive angle. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first receive angle is 62.7 degrees from a photodiode surface normal. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first aperture is annulus-shaped and encircles the first photosensitive surface from above. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first layer is a wavelength selective filter configured to pass light within a predetermined range of wavelengths. Additionally or alternatively to one or more of the examples disclosed above, in some examples the photodiode further comprises one or more side light blocking layers formed on one or both sides of the photodiode, the one or more side light blocking layers configured to prevent light rays impinging on the one or both sides of the photodiode from reaching the first photosensitive surface. Additionally or alternatively to one or more of the examples disclosed above, in some examples the photodiode further comprises a second light-blocking layer formed within the first layer and between the first light-blocking layer and the first photosensitive surface, the second light blocking layer including a second inner mask baffle formed above and extending beyond the first photosensitive surface and a second outer mask portion, and the second inner mask baffle and the second outer mask portion defining a second aperture therebetween, wherein the second aperture is configured as a second angular filter for allowing the incoming light rays to impinge upon the first photosensitive surface at angles between the first receive angle and the second receive angle. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first receive angle is 62.7 degrees from a photodiode surface normal. Additionally or alternatively to one or more of the examples disclosed above, in some examples the second aperture is annulus-shaped and encircles the first photosensitive surface from above. Additionally or alternatively to one or more of the examples disclosed above, in some examples the photodiode further comprises a second layer formed between the first layer and the photodiode body, and a second light-blocking layer formed over the second layer, the second light-blocking layer including a second inner mask baffle and a second outer mask portion, the second inner mask baffle formed above and extending beyond the first photosensitive surface, and the second inner mask baffle and the second outer mask portion defining a second aperture therebetween, wherein the second aperture is configured as a second angular filter for allowing the incoming light rays to impinge upon the first photosensitive surface at angles between the first receive angle and the second receive angle. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first layer has a first refractive index and the second layer has a second refractive index different from the first refractive index, and the first and second refractive indices of the first and second layers are selected for allowing the incoming light rays to impinge upon the first photosensitive surface at angles between a third receive angle and a fourth receive angle, the third and fourth receive angles smaller that the first and second receive angles, respectively, with respect to a surface normal of the photodiode. Additionally or alternatively to one or more of the examples disclosed above, in some examples the second aperture is annulus-shaped and encircles the first photosensitive surface from above. Additionally or alternatively to one or more of the examples disclosed above, in some examples the photodiode further comprises one or more second photosensitive surfaces included in the photodiode body, the one or more second photosensitive surfaces having one or more second surface areas, and one or more second inner mask baffles and one or more second outer mask portions included in the first light-blocking layer, with one second inner mask baffle and one second outer mask portion pair associated with each second photosensitive surface, each second inner mask baffle formed above and extending beyond its associated second photosensitive surface, and each second inner mask baffle and second outer mask portion pair defining a second aperture therebetween, wherein each second aperture of a plurality of second apertures is configured as a second angular filter for allowing incoming light rays to impinge upon its associated second photosensitive surface at angles between the first receive angle and the second receive angle. Additionally or alternatively to one or more of the examples disclosed above, in some examples each second aperture is annulus-shaped and at least partially encircles its associated photosensitive surface from above. Additionally or alternatively to one or more of the examples disclosed above, in some examples the plurality of second apertures are partially merged. Additionally or alternatively to one or more of the examples disclosed above, in some examples an integrated touch screen includes the photodiode of one or more of the examples disclosed above. 
     Some examples of the disclosure are directed to a light emitting diode (LED) for performing optical object sensing, comprising an LED body including a first photoemitting surface having a first surface area, a first layer formed above the LED body, and a first light-blocking layer formed over the first layer, the first light-blocking layer defining a first aperture formed above and extending beyond the first photoemitting surface, wherein the first aperture is configured as a first angular filter for allowing light rays to be emitted from the first photoemitting surface and exit the LED at angles between a first light emission angle and a second light emission angle. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first light emission angle is 42 degrees from an LED surface normal. Additionally or alternatively to one or more of the examples disclosed above, in some examples the LED further comprises one or more second apertures formed in the first light-blocking layer to create a plurality of light emission points for the first photoemitting surface. Additionally or alternatively to one or more of the examples disclosed above, in some examples the LED further comprises one or more side light blocking layers formed on one or both sides of the LED, the one or more side light blocking layers configured to prevent light rays emitted from the first photoemitting surface from exiting through the one or both sides of the LED. Additionally or alternatively to one or more of the examples disclosed above, in some examples an integrated touch screen includes the LED of one or more of the examples disclosed above. 
     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. Such modifications and combinations are to be understood as being included within the scope of examples of this disclosure as defined by the appended claims.

Metadata:
Filing Date: 20240112
Publication Date: 20250107
Grant Date: 20250107
Priority Date: 20230118
Inventors: YEKE YAZDANDOOST, MOHAMMAD
GELSINGER, PAUL J.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01L25/167", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04109", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04186", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04186", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L25/167", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04109", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L25/167", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0421", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04186", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 92715227