Diffractive laser optical encoder with high tolerance to high-speed mechanical runout

This paper is concerned with the design of a laser linear encoder with high head-to-scale alignment tolerance. It adopts 1-x telescope design that can increase by 6 to 20 times the head-to-scale tolerance of existing encoders of the same class. The optical design of the laser encoder can avoid effec ts from differences in polarization diffraction efficiencies. In other desi gns the non-uniformity of the temperature field within the head-to-scale ra nge yields a nonzero initial phase and thus decreases the measurement accur acy of the system. The misalignment of the polarizers for the circular pola rization interferometer configuration makes for both inclined and elliptica l quadrature signals in the output. For an encoder system which adopts an a rctangent algorithm, this effect may lower the measuring resolution. The re solution of our laser encoder design is verified by experiments.