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 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 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 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.