Signal Acquisition And Control System Design Of Self-calibration Spectrum Radiometer

For the precision of traditional radiation calibration can't meet the requirements of quantitative applications and climate change studies,a self-calibration radiometer based-on spontaneous parametric down-conversion is proposed,which has the function of self-calibration and absolute observation.The problems about automatic calibration of the radiometer and the precision verification of the data acquisition software is mainly solved in this paper.According to the measuring needs of the radiometer,the plan about data collection and control system is designed,and the control software based on Lab VIEW is written.In self-calibration mode,the control software can obtain the detection efficiency of multiple channels automatically.Using a continuous wave(355nm)laser to pump BBO crystal,the quantum efficiency of APD at 736nm is measured using the control software of self-calibration mode.The measuring result is 67.3%,and the relative uncertainty and the deviation with the factory data is better than 0.71%and 1%respectively.In observation mode,it can get the photon counts in the microsecond range of multiple channels simultaneously.The output photon count of APD in 0.1s is acquired using control software of observation mode,which is compared with the output value of 994 counter,and the average relative deviation is 0.22%.It shows that the control software can meet the function demands of the self-calibration radiometer system.The experimental verification plan of self-calibration radiometer principle is designed,and the corresponding control software is written.We insert the variable neutral density filter(NDF)into the system,which can be regarded as the system decay,and choose the monochromatic integral sphere as light source.The relative spectral radiance corresponding to different attenuation is measured using the control software,and the relative deviation is 2.39%.It shows that the spectral radiance calculated by the radiometer doesn't vary with the system decay,and the system has the function of self-calibration.The ultimate objective of self-calibration radiometer is to calibrate other optical remote sensor as radiation reference in visible light to near infrared light waveband.We analyze the volume and accuracy limits of the current data acquisition system,and propose a high-precision and miniaturized designing scheme based on time-to-digital converter(TDC).