Design Of Timing Control System For Time-resolved Spectral Measurement

Time-resolved spectroscopy is an important method for studying fluorescence dynamics.And its experiments require each device keeping the consistency of the instruction sending and signal acquisition,especially high requirements for the generation,duration,and delay time of modulated laser pulses.So it is necessary to perform timing matching on multi-channel pulse signals.Therefore,in this context,this project designed and implemented an four-channel timing pulse control system based on FPGA to match the time-resolved measurement system.Firstly,a scheme combining FPGA and programmable delay chip is proposed for the requirement that the delay,pulse width and frequency of the output four-channel pulse can be adjusted.In the first,a double-loop digital clock source based on phaselocked loop and frequency-locked loop is designed on FPGA to provide 200 MHz clock signal,and then modules such as pulse coarse delay,precise delay and serial port communication are built,and the function is verified by ModelSim.Finally,the thesis completed the serial circuit conversion chip,power supply and download configuration chip and other peripheral circuit design.The system finally has four channels of pulse signal output,and the delay,frequency,and pulse width are all adjustable.The adjustment time of the delay time is 1 ns,the minimum pulse width is 5 ns,and the frequency can reach 999999 Hz.At the same time,according to the demands of the remote operation of scientific research personnel,the software of the pulse timing master computer based on LabVIEW was programmed to realize the functions of parameter configuration,data reading and writing,etc.for pulse signals.Once again for the unavoidable baseline drift in the measurement spectrum,a dynamic moving least-squares polynomial smoothing(DMSG)spectral baseline correction algorithm is proposed and validated in both simulated and actual spectra.The Root Mean Square Error(RMSE)of the baseline correction for the exponential baseline and the anti-curve baseline is 0.6661 and 0.4345,respectively,while the baseline corrections for the LDMA algorithm are respectively 1.2291 and 2.5392.As for baseline correction of the actual spectrum,experiments show that it can effectively avoid baseline correction and baseline correction is not enough,better than the LDMA algorithm to achieve a correction effect.Finally,the whole machine is tested.The experimental results show that the output pulse signal meets the above requirements.The time-resolved spectrum and the steadystate emission spectrum of the doped crystal sample are measured by using the whole machine,and the spectrum of the scattered light and the fluorescence component of the sample spectrum are distinguished through comparative analysis of the spectrum,thereby solving the problem that the quality of the crystal sample is not good and the spectrum has strong problems with scattered light interference that adversely affect spectral analysis.