By default the MLX has a IR (infrared) bandpass filter installed. These help cut out any ambient lighting that may interfere with your vision algorithms. The filter we use range is 850nm +/- 20nm.
As you can see in the chart above we only allow a small range of light to pass into the sensor. The Y axis shows the transmission (how much light is allowed through) in a percentage while the X axis shows the frequency (in nm) of the light.