The Development Of Detection System Based On FPGA For Miniature Spectrometer

A spectrometer is an optical instrument used in spectroscopic analysis to identify materials, which is applied in almost all fields of science, such as medicine, chemistry, geology, physics and astronomy, etc. With the development of the modem techniques, miniature spectrometer has become a research focus worldwide and is the trend of the spectrometer. As an important part of spectrometer, data acquisition and transmission system is one of the key techniques to realize miniaturized request.In this thesis, a detection system with spectral data acquisition, processing and transmission for miniature spectrometer is developed. To get a high resolution with wider wavelength range, a 7500 pixels linear CCD is choosed as the detector. CCD output signal converted to digital signal with correlated double sampling and programmable gain amplifier by analog front end AD9822. The converted data which stored in FPGA transmits to PC through USB after processed. Application software completes further processing, analysis and display. FPGA is the core of all system, which generates the timing of CCD, AD9822 and its serial interface. FPGA is also the controller of USB interface chip CH375 and memory unit for 12 bits sample data. To adjust the signal amplitude to appropriate range, adaptive adjustment of CCD integration time and gain of PGA with dark-level voltage correction is realized in FPGA, this also improves the dynamic range of system. To improve the signal to noise ratio, cumulative average and Savitzky-Golay filter suiting for smooth of spectral data is also realized. The average also reduces the number of data communication. The dectection system can get instrunction from application software, which increased flexibility of the system.The schematic and PCB is designed with Protel DXP, and the design, simultation and realization of each logic module is compoleted using EDA tools such as Quartus, Modelsim and Synplify. The actual circuit is debugged using oscilloscope and embedded logic analyzer, each module is normal working. Test with optical platform and application software shows than the dectection system can be successfully completed spectral data acquisition, processing and transmission.