Fabrication Of Linear Diffraction Grating Interferometer System With High Accuracy

As the development of micro-electronics industry, it is exigent of the position system with micrometer-to-nanometer resolution in large stroke. Laser interferometers are most commonly adopted. Though laser interferometer with high accuracy, high resolution and long measurement range, it's so expensive and the change of the environment should seriously influence the measurement accuracy. Thus, the need to develop compact, high resolution, low cost and easy-to-use displacement sensors is becoming even more indispensable in metrology.A new miniature laser diffraction grating interferometer is developed in this thesis. According to the theory of grating diffraction and polarization optics, associating with the decoding phase theory of quadrature signal, to make the system achieve nanometer resolution. Because of the measurement standard of grating system is the precision grating pitch, compared to usual interferometer, the diffractive grating system reduce the environment influences on measurement accuracy.On the optical frame, the use of polarized optical components can improve the head-to-scale tolerance substantiall,. Furthermore, it can avoid the feedback of the zero-order diffraction beam so as to improve the SNR of the encoder output.A series of signal processing procedure is also developed in this thesis. Errors in quadrature signals caused by misalignment of optical components or the oscillating of the grating can be compensated through the signal processing circuits.After the miniature optical design, measurement principles, signal processing were integrated, the compact laser diffraction encoder system was accomplished through several simple and easy adjustment and fabrication steps in an optical table. Calibration experiment between grating interferometer and HP5529 has implemented, the results show the optical encoder's standard deviation is less than 20nm in the travel of 15mm.