The microchip laser self-mixing interferometer is different from the Michelson interferometer in principle. The main difference is that the beam of the laser self-mixing interferometer is amplified by the amplifying medium in the laser after it has been irradiated on the object to be measured and reflected back. The laser self-mixing interferometer developed by the author's research group has achieved a measurement speed of more than 1 m/s, and the environmental error was as small as 40 nm for an air path of 10 m. It has all solid state, can measure the displacement of "black" target, and has reached the technical index of the traditional laser interferometer. If the optical interferometer using a spectral lamp as light source is considered as the first-generation interferometer and that using He-Ne laser as the second-generation interferometer, the solid laser self-mixing interferometer can be regarded as the third-generation laser interferometer because of its laser "self mixing" principle.