Metrology is the science of measurement.It's a very broad topic because so much is measured. In manufacturing, the need to verify and validate dimensions of parts is crucial. These dimensional measurements are done at many stages in the manufacturing process with a range of devices, from simple hand gages to coordinate measuring machines (CMMs).

Many times, the choice of measuring device to be used is based on its resolution and range of the desired measurement. One such technology is known as video measurement, performed with video measuring systems. So, what’s video metrology?

A video measurement system is a machine that optically magnifies the image of a part captured by a camera and converted to a video signal that's analyzed by electronics and software to determine edges and features. The relationships among edges and features in one magnified image are monitored and tracked for comparison to other imaged areas to provide dimensions across the measurement range of the system’s translation stages. High-resolution imaging over large areas or volumes without any part contact makes video measurement a popular technology for manufacturers in many industries.

Video technology is also used for inspection. The same benefits of magnifying a part to better resolve detail apply to devices used for visual inspection. Such use isn't metrology, because the user subjectively analyzes the image, and nothing is measured. This use is more qualitative than quantitative. There is no universal definition of "video inspection," and some people refer to "video inspection" when they mean "video measurement."

The capabilities described above can be provided in a number of ways. The simplest devices have fixed magnification optics and require manual adjustment of focus and part positioning. Such systems usually have small measurement ranges and fit on a bench top. Automated systems have motorized zoom optics and stages, automatic focus, closed loop-positioning capability, and can run detailed, multistep measurement routines—measuring sizes, dimensions, and relationships of single parts or of an array of parts—without any user intervention. The operator loads the part, starts the measurement and the machine does the rest. Automated systems are available in bench top and large-capacity, floor-mounted configurations. The latest video measurement systems provide the resolution and accuracy necessary to perform critical dimensional measurements quickly. Detailed numeric and graphical reports show specific results and flag out-of-tolerance conditions. Engineers can compare measured results to computeraided design (CAD) files and drawings for process control and monitoring.