Three dimensional coordinate measuring machine refers to an instrument capable of measuring geometric shape, length, circumference division, etc. within the space range of a hexahedron. It is also called a three coordinate measuring machine or a three coordinate measuring bed. CMM can be defined as "a kind of detector that can move in three directions and can move on three mutually perpendicular rails. This detector transmits signals in contact or non-contact ways. The three axis displacement measurement system (such as optical ruler) calculates the coordinates (X, Y, Z) of each point of the workpiece and the instrument for measuring various functions through data processor or computer"
