US Patent 9024530 Synchronized ambient light sensor and display

An electronic device may be provided that has a display. The display may produce light using a backlight unit or using an array of light-emitting display pixels. An ambient light sensor may be mounted under an active area of the display to measure ambient light that is transmitted through the display. The display may be periodically disabled to prevent the display from producing light that interferes with the ambient light sensor. Display pixels may be coupled to a common cathode switch that can be periodically opened or the backlight in a display with a backlight can be periodically turned off. Control circuitry for periodically disabling the display while enabling the ambient light sensor may be implemented using a display driver integrated circuit mounted to a display.