Linear laser encoders have been widely used for precision positioning control of a linear stage. We develop a five-degrees-of-freedom (5-DOF) laser linear encoder to simultaneously measure the position, straightness, pitch, roll, and yaw errors along one moving axis. This study integrates the circular polarized interferometric technique with the three-dimensional diffracted ray-tracing method to develop a novel laser encoder with 5-DOF. The phases encoded within the and order diffraction lights reflected from the diffraction grating are decoded by the circular polarized interferometric technique to measure the linear displacement when the diffraction grating moves. The three-dimensional diffracted ray tracing of the - and -order diffraction lights induced by the motion errors of the moved grating were analyzed to calculate the other motion errors based on the detection of light spots on two quadrant photodiode detectors. The period of the grating is and the experimental results show that the measurement accuracy was better than for straightness, for angular error components, and for linear displacement.
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