Abstract: An electronic device such as a watch may include a display and a light sensor located behind the display. The light sensor may be used to measure the color of external objects. During color sampling operations, the display may emit light towards the external object in front of the display while the light sensor gathers color measurements. The display may emit light of different colors and the light sensor may detect an amount of reflected light for each color, which in turn may be used to determine the color of the external object. The control circuitry may use a watch-band-specific algorithm to determine the color of watch bands and may use a clothing-specific algorithm to determine the color of clothing. The control circuitry may display the color on the display so that the face of the watch matches the user's clothing or matches the user's watch band.

Abstract: The disclosure features wireless power devices for receiving power from a wireless power source. The devices include a first plurality of magnetic material pieces of substantially planar shape arranged in a first plane, where the first plurality of magnetic material pieces have a first planar surface and a second planar surface. The devices include a device resonator comprising at least one wound conductor disposed on the first planar surface and a second plurality of magnetic material pieces in a second plane, where at least one of the second plurality of magnetic material pieces overlaps at least one of the first plurality of magnetic material pieces and where a separation between the first and second planes is less than 2 mm.

Abstract: Methods and apparatus for flux cancellation includes first and second inductors. A system cam include first and second inductors and a layer of magnetic material disposed between the first inductor and the second inductor. In embodiments, when the inductors are driven with a respective oscillating current, at least a portion of magnetic flux generated by the first inductor is substantially canceled by at least a portion of magnetic flux generated by the second inductor in the layer of magnetic material.

Abstract: Methods and apparatus for flux cancellation includes first and second inductors. A system cam include first and second inductors and a layer of magnetic material disposed between the first inductor and the second inductor. In embodiments, when the inductors are driven with a respective oscillating current, at least a portion of magnetic flux generated by the first inductor is substantially canceled by at least a portion of magnetic flux generated by the second inductor in the layer of magnetic material.

Abstract: Methods and apparatus for flux cancellation includes first and second inductors, wherein the first inductor is configured for coupling to a first energy source and the second inductor is configured for coupling to a second energy source. A layer of magnetic material is disposed between the first and second inductors, wherein the first and second inductors are configured such that, when driven with an oscillating current, magnetic flux generated by the first inductor is substantially canceled by magnetic flux generated by the second inductor in the layer of magnetic material.

Abstract: Methods and apparatus for flux cancellation includes first and second inductors, wherein the first inductor is configured for coupling to a first energy source and the second inductor is configured for coupling to a second energy source. A layer of magnetic material is disposed between the first and second inductors, wherein the first and second inductors are configured such that, when driven with an oscillating current, magnetic flux generated by the first inductor is substantially canceled by magnetic flux generated by the second inductor in the layer of magnetic material.

Abstract: The disclosure features systems for wireless power transfer that include a resonator featuring a coil with at least two windings and at least one inductor having an inductance value, where the at least one inductor is connected in series to at least one of the windings, and where the inductance value is selected so that when the coil carries a current during operation of the system, the at least one inductor maintains a distribution of current flows among the at least two windings such that for each of the at least two windings, an actual current flow in the winding differs from a target current flow for the winding by 10% or less.

Abstract: The disclosure features wireless power devices for receiving power from a wireless power source. The devices include a first plurality of magnetic material pieces of substantially planar shape arranged in a first plane, where the first plurality of magnetic material pieces have a first planar surface and a second planar surface. The devices include a device resonator comprising at least one wound conductor disposed on the first planar surface and a second plurality of magnetic material pieces in a second plane, where at least one of the second plurality of magnetic material pieces overlaps at least one of the first plurality of magnetic material pieces and where a separation between the first and second planes is less than 2 mm.

Abstract: The disclosure features transmitters for wireless power transfer that include first and second coils each having at least one loop extending in a first plane and a controller configured to drive the first and second coils with electrical currents during operation of the transmitter, where the controller is configured so that during operation of the transmitter: in a first mode of operation, the controller drives the first and second coils to generate a magnetic field having a dipole moment that is parallel to the first plane to wirelessly transmit power to first and second receivers; and in a second mode of operation, the controller drives at least one of the first and second coils to generate a magnetic field having a dipole moment that is orthogonal to the first plane to wirelessly transmit power to a third receiver.

Abstract: The disclosure features systems for wireless power transfer that include a resonator featuring a coil with at least two windings and at least one inductor having an inductance value, where the at least one inductor is connected in series to at least one of the windings, and where the inductance value is selected so that when the coil carries a current during operation of the system, the at least one inductor maintains a distribution of current flows among the at least two windings such that for each of the at least two windings, an actual current flow in the winding differs from a target current flow for the winding by 10% or less.

Abstract: Photodetecting fiber. The fiber detects and localizes an incident optical beam. A semiconducting core is in intimate contact with a material forming a resistive channel that breaks axial symmetry. The resistive channel has a resistivity between that of metals and the semiconducting core, enabling the imposition of non-uniform, convex electric potential distributions along the fiber axis allowing photo-current measurements along the fiber.

Abstract: Photodetecting fiber. The fiber detects and localizes an incident optical beam. A semiconducting core is in intimate contact with a material forming a resistive channel that breaks axial symmetry. The resistive channel has a resistivity between that of metals and the semiconducting core, enabling the imposition of non-uniform, convex electric potential distributions along the fiber axis allowing photo-current measurements along the fiber.