Study On Laser Wavelength Measurement Based On Single Frequency Orthogonal Linearly Polarized Light

Length reference is the basis for ensuring the accuracy of the value and achieving interchangeability.The current length reference uses the wavelength of light as the unit of length.Laser wavelength as the ruler of geometric measurement,widely used in geometric measurement of length,angle,flatness,straightness and perpendicularity,is an important measurement parameter in precision measurement,precision machinery and microelectronics industry.Therefore,the precise measurement of wavelength is the key to ensure the accuracy of geometric measurement and traceability.In this thesis,a direct measurement method of laser wavelength based on single-frequency orthogonal linearly polarized light is proposed.Two sets of Michelson interferometers are built in the optical path.The reference mirror of two sets of interferometers is modulated by piezoelectric actuators.The measurement of unknown wavelengths is converted into the measurement of the interference fringe signal full cycle count and the interference signal phase difference.The main research works are as follows: The optical path structure of laser wavelength measuring system based on single-frequency orthogonal linear polarization is designed and the measurement principle is analyzed in detail with the optical path structure;The signal preprocessing circuit is designed to adjust the signal voltage range and improve the circuit output characteristics;The signal is filtered using the CIC digital filtering algorithm,which improves the signal quality;The cause of measurement error is analyzed and a phase compensation algorithm is proposed,which realizes the high precision measurement of phase,the algorithm of phase compensation is validated by experiment;The principle of large number counting and the method of integration of large and small numbers are introduced;The principle of large number counting is used to determine the direction of the reference mirror and the fractional phase is measured in the specific moving direction of the reference mirror;The visual basic language is used to design the software of PC.In order to verify the feasibility and effectiveness of the laser wavelength measurement system based on single-frequency orthogonal linearly polarized light,the following experiments were carried out respectively:(1)Phase difference detection and compensation experiment,with 10 ° step In the phase difference compensation experiment,the average error of phase difference measurement before compensation is 2.38 ° and the average error of phase difference measurement after compensation is 0.22 °.(2)The experiment of integrating full cycle count value and decimal count value was carried out in 5mm steps,the difference between the integration value and the theoretical value was less than 0.5.(3)The experiment of system stability,the successive measurement experiment of phase difference was carried out,the system instability caused by the wavelength measurement error is small,the stability of system is good.(4)The experiment of wavelength measurement accuracy influenced by the different moving distance of the measuring mirror,wavelength measurement experiment was carried out when the distance of the measuring mirror were 100 mm,150mm,200 mm and 250 mm.The uncertainty of wavelength measurement was 1.38×10-6,9.86×10-7,7.80×10-7 and 5.36×10-7.(5)The application experiment of measuring wavelength,The measurement uncertainty of the ZYGO laser is 5.17 × 10-7.