Research On Laser Interferometer System For The Form Standard Measurement Device

There are many problems in the existing measurement technology of complex form,such as the limitation of measurement,the poor consistency of measurement results,and the rationality of form evaluation.Therefore,it is necessary to study the measurement theory and method of complex form,and develop the corresponding form standard measurement device,so as to improve the value unity and traceability system of form.The research on laser interferometer system for the form standard measurement device is the key technology of laser interference measurement system in form standard measurement device.Firstly,the structure of the form standard measurement device which is suitable for non-contact,large caliber and high asphericity is studied.It adopts the main frame structure of the combination of rotary and fixed bridge and the rotary non-contact scanning probe based on the principle of laser interference.The coordinates of the probe are measured by X-axis and Z-axis laser interferometers,and the form standard measurement results trace to the definition of SI unit "meter".Secondly,the optical path structure and layout of the homodyne laser interference measurement system in the measurement device are studied.The measurement system with the standard sphere as the reference mirror is designed.According to the design requirements of miniaturization and integration of the laser interference probe,the module of phase-shifting and photoelectric conversion of the interference light is designed by the combination of beam splitting mirror,wave plate array and four quadrant detector.Finally,based on the hardware design of the interference signal processing,aiming at the nonlinear error in the interference signal,the module which uses the extremum method to detect the DC bias error and the unequal amplitude error in the FPGA and to correct the input interference signal is designed;The interference signal processing system based on CORDIC algorithm is designed.The half wavelength error in the signal processing system is studied and a phase compensation technology based on the correction table is proposed to eliminate the influence of half wavelength gross error on the laser interference measurement system;The design idea of the three-axis synchronous laser interference signal processing system for the measurement device is analyzed.On the basis of the above research,the corresponding experimental system of laser interferometry is built.The experimental results show that the nonlinear error correction module can eliminate the DC bias component of the input interference signal to less than 1m V,the amplitude ratio is better than 99%,the static resolution of the laser interference measurement system is better than 1nm,and the standard deviation is48.58 nm in the measurement range of 2000mm;For the laser interferometry system with the standard sphere as the reference mirror,the measurement deviation is between-2nm and 6.5nm in the range of 30?m,and the resolution is about 1nm;In the range of30?m,the measurement deviation of the system is between ±3nm and the resolution of the system is about 1nm for the laser interference probe system which uses the standard sphere as the reference mirror to measure the aspheric form.