Ambient light sensing system and method for measuring ambient light during pixel on and off periods

A method of measuring ambient light using an optical detector located beneath a display, the method comprising:

• integrating an output from the detector over a first period of time;
• when the first period of time ends, writing an integrator output value into a memory and starting a second period of time;
• when the second period of time ends, writing an integrator output value into the memory and starting a new first period of time;
• and
• continuing integration of the output detector for additional second and first periods of time in the same alternating manner to obtain and provide additional output values into the memory,
• wherein the first periods of time correspond to when pixels above the optical detector are not emitting light,
• wherein the second periods of time correspond to when pixels above the optical detector are emitting light, and
• wherein the first and second periods of time are configured to be controlled by one of:
• first and second counters counting the first and second periods of time respectively, or
• a counter which is programmed to alternate between counting the first and second periods of time.

An ambient light sensing system comprising an optical detector located beneath a display and detector electronics, wherein the detector electronics comprises:

• an integrator configured to integrate an output from the optical detector;
• at least one counter which is connected to the integrator;
• and
• a memory which is connected to the integrator;
• wherein the at least one counter is synchronized to a synchronization signal of the display, and wherein the at least one counter causes values to be periodically written from the integrator into the memory,
• wherein the values periodically written from the integrator into the memory are obtained when pixels above the optical detector are not emitting light,
• wherein additional values are periodically written from the integrator into the memory, the additional values being obtained at least partially when pixels above the optical detector are emitting light,
• wherein the at least one counter causes values to be written into the memory which alternate between values obtained when pixels above the optical detector are not emitting light and values obtained at least partially when pixels above the detector are emitting light, and
• further comprising a delay counter configured to delay, with respect to the synchronization signal, operation of the at least one counter, the delay depending upon a position of the optical detector beneath the display.