The times, they keep on changing. In the 1990s, noncontact level
measurement technology was beginning to be deployed in powder
and bulk applications. It was the heyday of ultrasonic
technology. At that time, lasers were still rare and expensive
measurement devices, used mainly in survey-distance measuring.
Due to continuous advances in technology, laser diode prices
dropped from $150 in the late 1990s to less than $20 today. This
made laser technology an attractive and affordable option for
noncontact measurement. Today, we have three primary noncontact
level and distance measurement technologies in use: ultrasonic,
open-air radar, and laser. Laser measurement systems have two
significant advantages: they can measure any solid surface at
any angle, and they can measure with narrow beams. With
wavelengths of <1 µm, the surface of almost any dry material
appears rough to a laser. The defused reflection emanates from
an exact spot on the reflected beam. This is why lasers measure
distance precisely; the natural