Abstract: An electronic device may have a housing. Input-output devices may be mounted in the housing. The input-output devices may include a display with an array of pixels configured to display images for a user. The electronic device may have an optical component formed under a transparent region in the housing. The transparent region may be associated with an opening in an opaque masking layer in an inactive area of the display or other portion of the electronic device. A diffuser may be formed between the optical component and the transparent region. The diffuser may have a polymer layer with embedded thin-film interference filter flakes configured to scatter light and to exhibit desired reflection and transmission spectral.

Abstract: A method includes imaging, with an optical read head attached to a second mechanical component, a portion of an encoder track disposed on a first mechanical component. The encoder track has a first encoder scale extending along the encoder track and a second encoder scale extending along the encoder track, and the imaged portion of the encoder track includes a first portion of the first encoder scale and a second portion of the second encoder scale. The method further includes transforming an imaged portion of the encoder track to a spatial frequency domain; identifying a pair of frequency bins in the spatial frequency domain; determining a phase difference between a first frequency bin and a second frequency bin in the pair of frequency bins; and mapping the phase difference to a positional relationship between the first mechanical component and the second mechanical component.

Abstract: An imaging system for a portable electronic device includes a variable aperture between a lens group and an image sensor. The variable aperture is defined by an electrochromic stack that defines a switching region and a central non-switching region. The non-switching region can be etched through the same material or set of materials defining the switching region and is backfilled with a dielectric transparent material having an index of refraction substantially equal to an average index of refraction of the layer(s) of the switching region of the electrochromic stack. This construction substantially reduces visible light absorption of the variable aperture.

Abstract: An imaging system for a portable electronic device includes a variable aperture between a lens group and an image sensor. The variable aperture is defined by an electrochromic stack that defines a switching region and a central non-switching region. The electrochromic stack is defined by a layer of electrochromic material in which an electrochromic crystallite dispersion (e.g., nickel oxide) is suspended in a field of a lithiated ion conductor layer (e.g., lithiated tungsten nickel oxide).

Abstract: An electronic device can include a housing that at least partially defines an exterior surface and an internal volume of the electronic device, and a display assembly at least partially disposed in the internal volume. The display assembly can include a transparent cover that at least partially defines the exterior surface of the electronic device, a backlight unit disposed between the cover and the housing, a frame coupling the cover to the backlight unit, a portion of the frame at least partially defining an aperture, and an electronic component disposed in the internal volume and extending through the aperture.

Abstract: A wearable electronic device such as an earbud, wristwatch, or other device may be provided with a skin sensor. The skin sensor may use optical measurements to detect the presence of skin adjacent to the electronic device. The sensor may have first and second light-emitting devices such as infrared devices that emit light at respective first and second infrared light wavelengths. Reflected light is monitored by a photodetector. Control circuitry can initiate or pause audio playback or take other actions in response to determining from the reflected light measurements that skin is present. The sensor may have a thin-film interference filter or other optical structure that overlaps the first and second light-emitting devices to narrow the angular spread of light emitted from the skin sensor. This reduces tilt sensitivity and helps enhance skin sensor accuracy.

Abstract: An electronic device includes a housing and a display. The housing defines an interior cavity and includes an optically-transmissive housing component. The display is disposed in the interior cavity and is viewable through the optically-transmissive housing component. An optoelectronic component is disposed in the interior cavity. An optical fiber extends between a first end positioned adjacent the optoelectronic component and a second end positioned adjacent the optically-transmissive housing component. The optical fiber defines a non-linear optical path between the first end and the second end. At least a portion of the optical fiber is laterally offset from a lateral edge of the display.

Abstract: An electronic device can include a housing that at least partially defines an exterior surface and an internal volume of the electronic device, and a display assembly at least partially disposed in the internal volume. The display assembly can include a transparent cover that at least partially defines the exterior surface of the electronic device, a backlight unit disposed between the cover and the housing, a frame coupling the cover to the backlight unit, a portion of the frame at least partially defining an aperture, and an electronic component disposed in the internal volume and extending through the aperture.

Abstract: An electronic device may have a housing. Input-output devices may be mounted in the housing. The input-output devices may include a display with an array of pixels configured to display images for a user. The electronic device may have an optical component formed under a transparent region in the housing. The transparent region may be associated with an opening in an opaque masking layer in an inactive area of the display or other portion of the electronic device. A diffuser may be formed between the optical component and the transparent region. The diffuser may have a polymer layer with embedded thin-film interference filter flakes configured to scatter light and to exhibit desired reflection and transmission spectral.

Abstract: An electronic device includes a housing and a display. The housing defines an interior cavity and includes an optically-transmissive housing component. The display is disposed in the interior cavity and is viewable through the optically-transmissive housing component. An optoelectronic component is disposed in the interior cavity. An optical fiber extends between a first end positioned adjacent the optoelectronic component and a second end positioned adjacent the optically-transmissive housing component. The optical fiber defines a non-linear optical path between the first end and the second end. At least a portion of the optical fiber is laterally offset from a lateral edge of the display.

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

Abstract: An electronic device may have a housing with a display. A transparent portion of the housing may serve as a display cover layer and may overlap an array of pixels in the display. The array of pixels may form an active area of the display for displaying images for a user. An ambient light sensor window may be formed in an inactive area of the display that does not overlap pixels. An ambient light sensor may be mounted in an interior region of the housing. A metal-coated light guide may have a first end aligned with the ambient light sensor window to receive ambient light from an exterior region surrounding the device and may have a second end at which the ambient light is provided to the ambient light sensor.

Abstract: An electronic device may be provided with a color ambient light sensor. The color ambient light sensor may be used to measure an ambient light spectrum over a wavelength range of interest. Control circuitry in the electronic device can take actions based on the measured ambient light spectrum such as adjusting the brightness and color cast of content on a display. A display may have a display cover layer. The color ambient light sensor can be mounted under the display cover layer and may receive ambient light through the display cover layer. The color ambient light sensor may have a tunable wavelength filter such as an electrically adjustable Fabry-Perot resonator. A light collimator may be interposed between the display cover layer and the Fabry-Perot resonator to collimate ambient light that is passed to the Fabry-Perot resonator. A light detector measures the light passing through the Fabry-Perot resonator.

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

Abstract: An electronic device may be provided with a color ambient light sensor. The color ambient light sensor may be used to measure an ambient light spectrum over a wavelength range of interest. Control circuitry in the electronic device can take actions based on the measured ambient light spectrum such as adjusting the brightness and color cast of content on a display. A display may have a display cover layer. The color ambient light sensor can be mounted under the display cover layer and may receive ambient light through the display cover layer. The color ambient light sensor may have a tunable wavelength filter such as an electrically adjustable Fabry-Perot resonator. A light collimator may be interposed between the display cover layer and the Fabry-Perot resonator to collimate ambient light that is passed to the Fabry-Perot resonator. A light detector measures the light passing through the Fabry-Perot resonator.

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

Abstract: An electronic device may be provided with a display. The display may have an array of pixels that form an active area and may have an inactive area that runs along an edge of the active area. An opaque layer may be formed on an inner surface of a display cover layer in the inactive area of the display or may be formed on another transparent layer in the electronic device. An ambient light sensor window may be formed from the opening and may be aligned with color ambient light sensor. The ambient light sensor may have an integrated circuit with photodetectors. Ambient light passing through the ambient light sensor window may be diffused by a light diffuser having one or more light-diffusing layers. Diffused ambient light may be collimated using a light collimator having one or more light-collimating layers such as layers with inwardly facing protrusions.

Abstract: An electronic device may be provided with a display. The display may have an array of pixels that form an active area and may have an inactive area that runs along an edge of the active area. An opaque layer may be formed on an inner surface of a display cover layer in the inactive area of the display or may be formed on another transparent layer in the electronic device. An ambient light sensor window may be formed from the opening and may be aligned with color ambient light sensor. The ambient light sensor may have an integrated circuit with photodetectors. Ambient light passing through the ambient light sensor window may be diffused by a light diffuser having one or more light-diffusing layers. Diffused ambient light may be collimated using a light collimator having one or more light-collimating layers such as layers with inwardly facing protrusions.

Abstract: An electronic device may be provided with a display. An opaque layer may be formed on an inner surface of a display cover layer in an inactive area of the display. An optical component window may be formed from the opening. A light guide may be aligned with the optical component window and may be used to guide light from the optical component window to an optical component such as an ambient light sensor. The light guide may have a core surrounded by a cladding. The core may be formed from a material such as blue glass that absorbs infrared light and that transmits visible light. Particles of titanium dioxide or other high-refractive-index material may be incorporated into the core to enhance the refractive index of the core. Thin-film interference filters may be formed on the light guide to enhance infrared light blocking.

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