Compare PRECISION INSPECTION and MEASUREMENT SYSTEMS which permit precision inspection with the aid of precision inspection and measuring instruments for dimensions and visual observations.

Precision inspection and measuring of two dimensions can be performed by the traditional optical comparators, or often called, shadowgraph. Here standard precision optics look at the edges and profiles of a part placed in the path of a light beam. The clarity of the optical lenses plus the accuracy of the device holding the object determine the precision of any dimensional measurement.

A vision inspection system replaces some the optics with a CCD camera. In addition to edge measurements, the camera permits visual inspection of surface characteristics and surface point to point measurements. With the addition of a computer and software, the inspection and measuring capabilities are greatly increased.

With the vision technology, limited three dimensional measurements are prossible.

For precision three dimensional measurement, the Coordinate Measuring Machine, CMM is the ultimate tool. The most common CMM machine is called the Bridge type machine. It has a granite base with a precision ground and polished surface. On two oposing edges are towers that can glide along the edge of the granite block forward and backward. A bridge connects the top of the towers. Riding on this bridge is a head with a very fine pribe pointing downward. This head moves between the towers forming the X direction while the towers moving back and forward give the Y axis. The tip moving up and down on the head forms the Z axis.