Based On FPGA Laser Interference Signal Acquisition And Processing

Laser has desirable characteristics of high coherence,narrow spectral output and collimation.Its scope of application as light source of the measurement system has been continuously expanded and improved with development of laser measurement technology.And there are two prominent methods named Dual-beam interferometry and self-mixing interferometry.The dual-beam interferometry can be subdivided into homodyne and heterodyne interferometry.This paper is based on homodyne and self-mixing interferometry,and combines FPGA technology with laser interferometry to make a system with advantages including real-time measurement,portable and low cost.The main work presented by this paper is to design a laser interferometry signal acquisition and processing module which is based on FPGA.The demodulation module includes fringe counting method which is widely used,dual orthogonal signal demodulation which is used to reduce the counting error and the quadrature phase-shift signal demodulation.Concrete realization function includes A/D conversion,waveform conversion,four-times frequency multiplication,counter and display function.In addition,there is a signal generator based on DDS principle yielding adjustable frequency sine wave or triangle wave.Then it can modulate the output light of the laser,adding to the linear modulation self-mixing measurement system.On the basis of the digital tube display results,the serial driver module is added to the signal processing system,in order to realize the communication between the development board and the computer.Through the serial port module,the results can be tested by the serial debugging assistant.And the final results can be shown by the serial communication interface.The communication between the development board and the computer extends the function of development board,and effectively optimizes the allocation of resources.Finally,the signal processing system implemented in this paper optimizes the laser self-mixing interference measurement system by FPGA technology which is high integrated,short-period and low cost.And it has high practicability and reliability.