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Design and Construction of a Two Degrees of Freedom Laser Linear Encoder in a Littrow Configuration
J-Z. Cui, M. Zhang, Y. Zhu, C. Ni and S-Q. Ding

We propose herein a new optical sensor head designed in Littrow configuration for laser linear encoder which can directly measure X-direction and Z-direction displacement of a linear stage using one-dimensional (1-D) gratings. Given the benefits of Littrow configuration, the measuring range along Z-direction is extremely enlarged compared with traditional encoders. Finally, the optical configuration was successfully constructed and its measurement performance was evaluated and analysed. Under non-environmentally controlled conditions, the maximum positioning error in a movement of 2.0 mm was 0.261 μm with a standard deviation of 0.134 μm in the X-direction and 0.211 μm with a standard deviation of 0.070 μm in the Z-direction.

Keywords: Laser linear encoder, grating interferometer, Littrow configuration, two degrees of freedom, displacement measurement, Doppler effect

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