Research On Laser Doppler Interference Displacement Measurement Technology Based On Micron Level

With the rapid development of science and modern industry,high-speed and high-accuracy displacement parameter measurement systems are increasingly required in engineering fields such as precision inspection,precision machining and equipment testing.Laser measurement technology,as a high-precision and non-contact measurement method,has been widely used in various modern projects.Traditional laser ranging technology has poor measurement accuracy and large errors,while laser interferometers have short measurement ranges and complex optical systems.Based on the engineering application background of artillery barrel parameter measurement,the paper proposes a micron-level laser Doppler interference displacement measurement technology with laser Doppler interference technology as the core and optical frequency heterodyne interference system as the basic structure,and designs a set of software and hardware measurement system.The laser Doppler interference displacement measurement system designed in the paper uses FPGA as the core processor and is mainly composed of an optical system part,a weak signal conditioning part and a digital signal processing part.The optical system part refers to the basic structure of Mach-Zehnder interferometer to design the optical system.Based on the laser Doppler interference technology,the heterodyne design of the optical system at 40 MHz is completed.Acquiring the displacement beat frequency signal of the object to be measured through an APD avalanche diode.The weak signal conditioning part completes the preprocessing of the analog signal after laser Doppler photoelectric conversion,including buffer design,pre-amplification of the signal,high-pass filtering,low-pass filtering,follower and analog-to-digital conversion design.The function of the digital signal processing part is to digitally process the signal after analog-to-digital conversion,and perform digital phase discrimination on the laser Doppler interference signal through the improved CIC filter and CORDIC algorithm.The result of phase detection is calculated as the magnitude of the displacement.At the same time,the DDR3 SDRAM data cache unit is designed and the data is transferred to the embedded software for subsequent processing through USB serial communication.The software interface is based on the X86 embedded platform,written using Lab VIEW,and contains a data display unit,which improves the integration of the entire system.The laser Doppler interference displacement measurement system designed and constructed in the paper uses laser Doppler interference technology to perform displacement measurement,which improves the resolution of the measurement.The system chooses the optical structure of the optical frequency heterodyne to reduce the light source requirements of the system and enhance the ability of engineering applications.At the same time,the architecture of FPGA and embedded platform is used to improve the real-time and integration of the measurement system.The simulation and experimental test results show that the measurement accuracy can reach the design requirements of micron-level accuracy in the range of 10 meters.At the same time,the cause of the error is further analyzed,and the suggestions for subsequent system improvements are pointed out.