Why does the PathFindIR II image “freeze” every now and then?

To ensure that the sensor is providing the best possible image, the PathFindIR II incorporates a shutter mechanism that enables the unit to self-calibrate itself. The shutter activates every 2 minutes, or when the temperature of the camera is changing due to ambient conditions. When the shutter activates, the video image freezes for approximately one-half second.