2.2.1　Mechanical amplification

The so-called“mechanical amplification”refers to amplifying the small quantity by using the geometric relationship in mechanical components.Spiral micrometer is a typical example of this method,which can accurately measure the tiny displacement along the axial direction by radian length of a larger radius.In general,spiral micrometer can effectively improve the measuring accuracy(more than 100 times).In addition,this method is also used in the high-precision measuring instruments,such as reading microscope and Michelson interferometer.(https://www.daowen.com)