It is a device that measures the geometric shape of the measured object through the probe and the discrete points on the surface of the object. There are various types of probes in CMM, including mechanical, optical, laser and so on. Depending on the machine, the probe position can be manually controlled by the operator, or it can be controlled by a computer. CMM usually specifies the position of the probe according to its reference position (XYZ axis) in the Cartesian coordinate system. In addition to moving the probe along the X, Y, and Z axes, many machines also allow the angle of the probe to be controlled to allow measurement of hard-to-reach surfaces.