Five-degrees-of-freedom diffractive laser encoder

Abstract

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 +1 and -1 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 +1- and -1-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 0.83 microm and the experimental results show that the measurement accuracy was better than +/-0.3 microm/+/-41 microm for straightness, +/-1 arc sec/+/-215 arc sec for angular error components, and +/-160 nm/2 mm for linear displacement.

Compensation for straightness measurement systematic errors in six degree-of-freedom motion error simultaneous measurement system

“…Multi degree-of-freedom (DOF) error simultaneous measurement method and system is urgently needed and preferably adopted in machine tool calibration due to its high efficiency and easy assembly [1][2][3][4][5][6][7][8][9][10]. A simple system for simultaneously measuring six DOF geometric motion errors of a linear guide was developed in our previous work [11].…”

Errors crosstalk analysis and compensation in the simultaneous measuring system for five-degree-of-freedom geometric error

“…However, only one error component can be measured during each adjustment and measurement. So, some simultaneous measuring methods for multi-degree-of-freedom error are studied [8][9][10][11][12][13], including the laser collimation method based on the cube corner prism. However, the crosstalk between each of the error components is a serious problem for this method.…”

Determination of the position and orientation of a flat piezoelectric micro-stage by moving the optical axis

“…11 Liu et al used a onedimensional reflective grating to produce a four-DOF measurement system. [12][13][14][15] In contrast to the previous systems, the optics of this system was modular and this made it quite small. In 2013, Li et al proposed a six-DOF measuring system that used two one-dimensional gratings.…”