Prior to the advent of focal plane or staring array detectors which may contain hundreds of thousands of pixels, early thermal imagers contained relatively few elements in their detectors. These early thermal imagers relied upon a sophisticated optical system that scanned the target repeatedly in order to produce an image. Because of this, thermal imagers were often referred to as ‘infrared scanners’. This gave rise to the term ‘infrared scan’ when referring to an infrared inspection.

Thermal imagers that relied upon optical scanning mechanisms remained popular until just after the turn of the century when they were largely replaced by microbolometer imagers due to their low cost and image clarity. Although infrared scanners are rarely used today, many people still refer to infrared inspections as infrared scans.

During a thunderstorm, each flash of cloud-to-ground lightning is a potential killer. Whether a particular flash could be deadly depends on a person being in the path of the lightning discharge. In addition to the visible flash that travels through the air, the current associated with the lightning discharge travels along the ground.

Although some victims are struck directly by the main lightning stroke, many victims are struck as the current moves in and along the ground.

Lightning can strike as far as 10 miles away from the rain area in a thunderstorm. That’s about the distance you can hear thunder. When a storm is 10 miles away, it may even be difficult to tell a storm is coming. If you can hear thunder, you are within striking distance and should seek shelter immediately.