The function of the workpiece is highly influenced by its surface roughness.With the rapid development of the mechanical

electronic and optical industries

the quality of surface and minimized-structure of precision mechanism are highly demanded

which makes surface roughness measurement take on more and more important position.Optical methods of measuring surface roughness have many advantages such as non-contact

non-damage and high precision etc.The principles and advances of scattering method

speckle method

interferometric method

optical stylus method widely used for roughness measurement are reviewed

the merits and shortcomings of them are discussed

their developing trends are forecasted.