Abstract: An electronic device may be operated in ambient light. The electronic device may have a color ambient light sensor that is configured to produce color ambient light sensor data based on the ambient light. The electronic device may also have a flicker sensor that has a faster response time than the color ambient light sensor and that is used in detecting dynamic changes in the ambient light. Control circuitry in the electronic device may analyze flicker sensor data to identify the number of light sources producing the ambient light. The control circuitry may apply a frequency transform to the flicker sensor data or make measurements with the flicker sensor in multiple directions. Based on this information, the control circuitry may identify the number of light sources and may use this information in retrieving an ambient light spectrum associated with the ambient light using the color ambient light sensor data.

Abstract: An electronic device may include a light sensor system. The light sensor system may have a light source that emits light and a light detector that receives the emitted light after the emitted light has interacted with an external object. The light source may include a ring of light-emitting diodes or other light-emitting devices surrounding the light detector or may have light-emitting devices that are surrounded by a ring-shaped light detector. Polarizer structures may be incorporated into the light sensor system. Control circuitry in the device may control the light source so that different polarizations of light are emitted at different times. The control circuitry may process signals from the light detector that are gathered under different polarizations to discriminate between specular and non-specular reflections from the external object.

Abstract: An electronic device may have a camera that captures images of objects that are illuminated by ambient light. Some ambient light sources may not render the colors of objects faithfully. To detect low quality ambient lighting conditions and to correct for these conditions, control circuitry in the electronic device gathers ambient light measurements from a color ambient light sensor. The measurements are used to produce an ambient light spectral power distribution. The ambient light spectral power distribution can be applied to a series of test color samples to produce responses. Responses can also be produced by applying a reference illuminant to the test color samples. These responses can then be processed to generate a color rendering index or other color rendering metric for the ambient light and can be used to create a color correction matrix to correct the color of the captured images.

Abstract: A device such as a computer stylus may have a color sensor. The color sensor may have a plurality of photodetectors each of which measures light for a different respective color channel. The color sensor may also have one or more light-emitting devices. Control circuitry may use the light-emitting devices to illuminate an external object while using the photodetectors to measure reflected light to determine the color of the external object. The electronic device may have a housing with an elongated shaft. The shaft may have a tip and an opposing end. The tip may be configured to emit electromagnetic signals that are detected by a touch sensor in a touch sensitive display. The color sensor may be located at the end opposite the tip, may be located at the tip, or may be optically coupled to the tip using a light guide.

Abstract: A device such as a computer stylus may have a color sensor. The color sensor may have a plurality of photodetectors each of which measures light for a different respective color channel. The color sensor may also have one or more light-emitting devices. Control circuitry may use the light-emitting devices to illuminate an external object while using the photodetectors to measure reflected light to determine the color of the external object. The electronic device may have a housing with an elongated shaft. The shaft may have a tip and an opposing end. The tip may be configured to emit electromagnetic signals that are detected by a touch sensor in a touch sensitive display. The color sensor may be located at the end opposite the tip, may be located at the tip, or may be optically coupled to the tip using a light guide.

Abstract: An electronic device may have a camera that captures images of objects that are illuminated by ambient light. Some ambient light sources may not render the colors of objects faithfully. To detect low quality ambient lighting conditions and to correct for these conditions, control circuitry in the electronic device gathers ambient light measurements from a color ambient light sensor. The measurements are used to produce an ambient light spectral power distribution. The ambient light spectral power distribution can be applied to a series of test color samples to produce responses. Responses can also be produced by applying a reference illuminant to the test color samples. These responses can then be processed to generate a color rendering index or other color rendering metric for the ambient light and can be used to create a color correction matrix to correct the color of the captured images.

Abstract: A system and method for multi-spectral gas concentration analysis that includes using a library of multiple sets of optimized spectral sensitivities prepared in advance, and a multi-spectral IR gas analyzer tuned to a set of optimized spectral sensitivity. The multi-spectral IR gas analyzer measures spectral absorption of gas using one or more different sets of optimized spectral sensitivities.

Abstract: An electronic device may include a light sensor system. The light sensor system may have a light source that emits light and a light detector that receives the emitted light after the emitted light has interacted with an external object. The light source may include a ring of light-emitting diodes or other light-emitting devices surrounding the light detector or may have light-emitting devices that are surrounded by a ring-shaped light detector. Polarizer structures may be incorporated into the light sensor system. Control circuitry in the device may control the light source so that different polarizations of light are emitted at different times. The control circuitry may process signals from the light detector that are gathered under different polarizations to discriminate between specular and non-specular reflections from the external object.

Abstract: A display calibration system may include a first electronic device that includes an ambient light sensor and a display to be calibrated in a second electronic device. The first electronic device may generate test patterns to be displayed on the display. The ambient light sensor may receive light emitted from the display based on the test patterns to generate display color space data. The first electronic device may generate calibration data for the display based on the display color space data and a target reference color space. The second electronic device may store the calibration data and use the calibration data to generate more accurate images. Because the first electronic device may include other functionalities other display calibration, specialized display calibration equipment may be omitted. Additionally, a third electronic device that acts as an intermediary between the first and second electronic devices.

Abstract: A submersible electronic device such as a waterproof cellular telephone may be provided with an image sensor. The image sensor may capture images of underwater objects. Control circuitry in the submersible electronic device may adjust image contrast and color balance based on information from sensors and other information. The electronic device may have an ambient light sensor. The ambient light sensor may be a color ambient light sensor and may be used in measuring ambient lighting conditions above water and underwater. A depth sensor may be used in measuring the depth of the image sensor and other components of the electronic device underwater. Information on the depth of the image sensor, information on the distance of an underwater object to the image sensor, and angular orientation information for the electronic device and image sensor may be used in color balancing an image.

Abstract: An electronic device may have a display with an array of pixels configured to display images for a user. The electronic device may have an ambient light sensor for gathering ambient light information. Control circuitry in the electronic device may control the array of pixels while gathering measurements with the ambient light sensor. This allows the control circuitry to determine which portion of each ambient light sensor measurement is due to ambient light exposure and which portion of each ambient light sensor measurement is due to stray light from the array of pixels. The control circuitry can then remove the stray light contribution to the ambient light sensor measurements to produce corrected readings of ambient light levels. Display adjustments such as display brightness changes and color changes can be made using ambient light readings.

Abstract: A device such as a computer stylus may have a color sensor. The color sensor may have a plurality of photodetectors each of which measures light for a different respective color channel. The color sensor may also have one or more light-emitting devices. Control circuitry may use the light-emitting devices to illuminate an external object while using the photodetectors to measure reflected light to determine the color of the external object. The electronic device may have a housing with an elongated shaft. The shaft may have a tip and an opposing end. The tip may be configured to emit electromagnetic signals that are detected by a touch sensor in a touch sensitive display. The color sensor may be located at the end opposite the tip, may be located at the tip, or may be optically coupled to the tip using a light guide.

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 optical component window may be formed from the opening and may be aligned with an optical component such as a proximity sensor, ambient light sensor, image sensor, or light source. The optical component window may have a quarter wave plate, a linear polarizer interposed between the transparent layer and the quarter wave plate, and a partially reflective mirror interposed between the optical component and the quarter wave plate.

Abstract: An electronic device may be operated in ambient light. The electronic device may have a color ambient light sensor that is configured to produce color ambient light sensor data based on the ambient light. The electronic device may also have a flicker sensor that has a faster response time than the color ambient light sensor and that is used in detecting dynamic changes in the ambient light. Control circuitry in the electronic device may analyze flicker sensor data to identify the number of light sources producing the ambient light. The control circuitry may apply a frequency transform to the flicker sensor data or make measurements with the flicker sensor in multiple directions. Based on this information, the control circuitry may identify the number of light sources and may use this information in retrieving an ambient light spectrum associated with the ambient light using the color ambient light sensor data.

Abstract: A method and system of calibrating multispectral images from a camera on an aerial vehicle, the method including: capturing multispectral images of an area at a plurality of intervals with a multispectral imaging camera; simultaneously or at an arbitrary time capturing sunlight radiance data for each of the captured images; correlating the images with the sunlight radiance data; and calibrating the multispectral images based on the sunlight radiance data to normalize the multispectral images to one or more previous images of the area.

Abstract: A submersible electronic device such as a waterproof cellular telephone may be provided with an image sensor. The image sensor may capture images of underwater objects. Control circuitry in the submersible electronic device may adjust image contrast and color balance based on information from sensors and other information. The electronic device may have an ambient light sensor. The ambient light sensor may be a color ambient light sensor and may be used in measuring ambient lighting conditions above water and underwater. A depth sensor may be used in measuring the depth of the image sensor and other components of the electronic device underwater. Information on the depth of the image sensor, information on the distance of an underwater object to the image sensor, and angular orientation information for the electronic device and image sensor may be used in color balancing an image.

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 optical component window may be formed from the opening and may be aligned with an optical component such as a proximity sensor, ambient light sensor, image sensor, or light source. The optical component window may have a quarter wave plate, a linear polarizer interposed between the transparent layer and the quarter wave plate, and a partially reflective mirror interposed between the optical component and the quarter wave plate.

Abstract: A method for determining a custom power spectral distribution (PSD) for use in a specialized light source and a lighting system. The method includes obtaining a PSD corresponding to light that is output by the lighting system, obtaining a constraint, and determining the custom PSD by optimizing (minimizing or maximizing), subject to the constraint, an evaluation function comprising the PSD, an unwanted light function, a wanted light function, or another characteristic function.

Abstract: A method, a computer program product, and a system are disclosed for stitching aerial data using information from at least one previous image. The method includes capturing a plurality of images of the landscape; obtaining, image metadata for each of the captured images; generating, for each of the captured images, a set of transformed images based on the image metadata, comprises: setting a variable for each of the parameters; preparing a plurality of sets of transformed image metadata by applying the variables to the parameters; and preparing the set of transformed images from the captured image based on the plurality of sets of transformed image metadata, respectively; identifying, for each set of transformed images, one of the transformed images by calculating quality of fit to the top level image for each of the transformed images; and assembling a new aerial image based on the plurality of the identified transformed images.

Abstract: A method for encoding a monochrome or color image. The method includes receiving an image and adjusting the image based on a global uniform macro-type color space. The image is modified spatially based on a local uniform micro-type edge characteristic that includes a just-noticeable difference (JND), and the image is outputted.