Patent ID: 8089631

Claim:
A displacement measurement system, comprising: a coherent light source adapted to emit a coherent light beam; a two-dimensional grating disposed on a transmission path of the coherent light beam, the coherent light beam entering the two-dimensional grating to generate a zero-order light beam and a plurality of first-order diffraction beams, wherein the first-order diffraction beams comprise a first first-order diffraction beam and a second first-order diffraction beam, wherein the two-dimensional grating is a periodic two-dimensional substrate, and the periodic two-dimensional substrate is a periodically-arranged hexagonal photonic crystal glass (HPCG); a photo sensor receiving the zero-order light beam and the first-order diffraction beams, wherein the zero-order light beam respectively forms interference fringes arranged in different directions on the photo sensor with the first first-order diffraction beam and the second first-order diffraction beam; and a signal processing apparatus recording each of the interference fringes arranged in different directions, wherein displacements of the two-dimensional grating in the different directions are obtained by calculating phase differences of the interference fringes in corresponding directions when the two-dimensional grating moves.