| Photoelectric direct-reading spectrometer,the metal detection equipment,is widely used in iron and steel industry.PMT,as the light receiving device,was used in the traditional direct-reading spectrometer,which not only was big and weight but also need complex operations.The channel is required to be converted at all times if the PMT direct-reading spectrometer was being used.So traditional direct-reading spectrometer was difficult to be extended.Linear Array CCD with small size,high sensitivity,wide spectral range,multichannel sampling,provides a new way for the development of spectral analysis technology.Aiming at the direct reading spectrometer design requirements,combined with linear array CCD image acquisition technology and embedded software and hardware,this thesis carried out a thorough study of spectral signal acquisition and processing.The contents included three aspects which exist in all of the working process of the system,and there are these three questions: a kind of auto-exposure control circuit for output signal,multi-channel data acquisition,noise analysis and processing.This thesis analyzed the relationship between voltage of CCD signal and exposure time,and combined with the electronic shutter features,designed a kind of auto-exposure control circuit.Through adjusting the integral time automatically,this circuit could change the amplitude of CCD output signal,which kept signals from distortion.This thesis analyzed the quantization of CCD output signals and combined with ADC,FGPA and SRAM,designed a kind of multi-channel CCD data acquisition and caching proposal.This thesis analyzed the interference and noise of signal acquisition system in direct reading spectrometer and provided solutions.Shielding technology,large-area grounding and PCB layout in hardware was used in the system to filter electromagnetic interference.And this thesis used mean filter,wavelet threshold as well as a combination of these two algorithms to process the data. |
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