Key Technology Of Signal Processing In Laser Heterodyne Interferometry With Pico Meter Resolutin

The next generation microelectronics manufacturing, precision measurement and frontiers of physics exploration and other fields will seek for sub nanometer even picometer scale ultra precision displacement measurement technology and equipment as the foundation and key means. The classical heterodyne laser interferometry technology and equipment has been widely used in ultra precision measurement field, but the displacement resolution is generally difficult to make a breakthrough of 0.1 nm, so signal subdivision process technology in nanometer or sub picometer heterodyne interference, especially dynamic segmentation processing technology, has become one of the core contents in a new generation of laser interference measurement technique.The limits of the heterodyne interference measurement signal processing performance mainly concentrate in two aspects: on one hand it is the design of high-speed heterodyne signal acquisition and processing platform which meets both high speed and high precision signal acquisition needs, another is how to design more streamlined, double orthogonal lock-in amplification phase measurement algorithm under conditions where platform resource is limited. In view of the above problems, this paper will study the design and implementation of high speed heterodyne signal acquisition and processing platform and the dual quadrature phase locked loop.The integral error model of the phase measurement with double phase locked loop is established. On expounding the existing error analysis model based, it is supplemented with the effective wordlength effect caused by the analysis of the AD sampling phase measurement error introduced by quantization, digital operation, FIR digital filter and CORDIC algorithm, and discuss upon the wordlength design feature of finite word length effects related to error reduction; Eventually we established the mathematical relationship between the displacement measurement resolution force and the input signal real effective digits and finish the numerical simulation analysis, which provide guidance for the follow-up design.Research on design method of signal acquisition and processing platform of high speed heterodyne signal with high speed and high precision signal acquisition is discussed. For heterodyne signals with high speed and high precision, signal acquisition and processing requirements, detailed analysis and optimization design is completed focusing on the realization of the principle and module function: analog circuit design seems the noise analysis which decides the final performance as the main line, through comprehensive consideration of key nodes in the analog part, with a particular focus on analysis and optimization of the analog circuit of signal function device and board formation / power supply noise; digital circuit consider digital LVDS signal lines and signal chain design with emphasis.Based on the analysis of the process of the phase measurement algorithm, the resource optimization technique is studied. Existing algorithm model in FPGA to achieve the need takes up too much of the multiplier and other resources, resulting in the need to occupy more FPGA logical space and reduce the speed of computing. Therefore, this article will reduce the processing flow structure of "input signal × detection signal ? multiplication results ? digital filter(online multiplication) " in classical digital phase sensitive algorithm to the structure of " input signal × detection signal and digital filter off-line product volume value”, which reduce the demand of key resources of the hardware multiplier in phase measurement method to the lower of 1/3 or even above.Based on the research of the design method of the signal acquisition and processing platform and the resource optimization technique of the phase measurement algorithm, the heterodyne interference signal subdivision measurement system is designed and Standard equivalent tested. Test results show that the design of the static standard deviation is 4.8 pm, the dynamic standard deviation is 18 pm @1.5 m/s, it can meet the 10 pm level of dynamic / static displacement measurement requirements.