High-factor interpolation method based on space-time modulation and a Kalman filter for optical encoders.

A high-factor interpolation method based on space-time modulation and a Kalman filter for optical encoders is proposed. Space-time modulation employs a reference time signal to modulate the output displacement signal of the optical encoder into a displacement space-time signal. Subsequently, high-frequency pulse signals are used for interpolation, which detect the phase of the reference time signal and the displacement space-time signal to obtain displacement information from the optical encoder output. The interpolation factor of this method depends on the frequencies of the high-frequency pulse signal and the reference time signal, and is independent of the moving speed. A Kalman filter is employed to estimate the velocity, compensating for time lag errors in the displacement information output by space-time modulation to improve the real-time performance of displacement output. The proposed method is simple and effective, which can be implemented on an FPGA. The effectiveness of the proposed method is verified through simulation and experimentation.

Study on the influence of surface roughness on the diffraction efficiency of two-dimensional gratings.

This study investigates the effect of surface roughness on the diffraction efficiency of two-dimensional gratings. Firstly, a roughness model was constructed using FDTD, followed by a significant analysis of the ridge roughness, groove roughness, and sidewall roughness on diffraction efficiency. Then, the impact of each roughness type on diffraction efficiency was studied separately. Results indicate that ridge roughness has a negative impact on diffraction efficiency, whereas groove roughness and sidewall roughness have a positive impact on the diffraction efficiency of two-dimensional gratings. When ridge, groove, and sidewall roughness coexist, diffraction efficiency decreases with an increase in roughness, consistent with previous research. However, under conditions of minimal roughness, diffraction efficiency actually increases. Finally, an experiment was conducted to verify the conclusions. The results of this study have significant reference value for the application and development of precision measurement techniques for gratings.

Distance and depth modulation of Talbot imaging via specified design of the grating structure.

For positioning Talbot encoder and Talbot lithography, etc., properties manipulation of Talbot imaging is highly expected. In this work, an investigation on the distance and depth modulation of Talbot imaging, which employs a specially designed grating structure, is presented. Compared with the current grating structure, the proposed grating structure is characterized by having the phase layers with uneven thicknesses. Such a specific structural design can cause the offset of Talbot image from its nominal position, which in turn generates the spatial distance modulation of self-imaging and imaging depth expansion. Theoretical analysis is performed to explain its operating principle, and simulations and experiments are carried out to demonstrate its effectiveness.