Monitoring an emission state of light sources

A wearable device comprising:

• a power source;
• one or more infrared (IR) light sources configured to direct light toward an eye for eye tracking, the one or more IR light sources connected to an output of the power source;
• a control circuit comprising a pulsed voltage source and a control transistor configured to regulate a current through the one or more IR light sources based upon an output of the pulsed voltage source;
• a monitor transistor comprising a gate connected to an output of the one or more IR light sources such that a voltage at the output of the one or more IR light sources controls an output of the monitor transistor;
• and
• a monitor transistor detector connected to the output of the monitor transistor, the monitor transistor detector configured to monitor a state of the one or more IR light sources based upon a state of the output of the monitor transistor.

A method enacted on a wearable device comprising one or more infrared (IR) light sources, a monitor transistor comprising a gate connected to an output of the one or more IR light sources, and a monitor transistor detector connected to an output of the monitor transistor, the method comprising:

• controlling a voltage at the output of the one or more IR light sources to emit pulses of light;
• monitoring, via the monitor transistor detector, a response of the output of the monitor transistor;
• and
• when the response corresponds to light from the one or more IR light sources exceeding a threshold duration of emission, disabling the one or more IR light sources.