Research On Portable Grating Spectrum Measurement System

Spectrometer are important devices for spectroscopy research and analysis of the composition of materials.With the development of modern spectroscopy and electronics technology,the spectrometer has been widely used in military reconnaissance,cosmic exploration,resource exploration,environmental protection,etc.Due to the limited use of space and the need for real-time detection,the traditional bulky,complex structure of the spectrometer in the field of aerospace remote sensing,geological exploration will be difficult or even can not be used,Therefore,the development of small volume,embedded integrated spectrum measuring instrument has become the research focus worldwide.Based on the theory of grating light-split,linear CCD spectral measurement,spectral signal filtering and spectral wavelength calibration,this paper designs a symmetrical Czerny-Turner optical structure with planar grating and concave reflector to form a small volume Optical structure.Based on field programmable gate array(FPGA)technology,the timing of the TCD1304 AP of the linear CCD,the control of the spectral information acquisition,the storage of the spectral data and the read/write timing of the USB transfer are realized on the Quartus-II platform using hardware description language Verilog,and transplanted into the EP4CE15F17C8 FPGA.Spectral data acquisition unit uses a 12-bit high-resolution A/D with a sample-and-hold device to meet the quantitative requirements of CCD measurement signals and simplify the design of the external circuit.Asynchronous FIFO data storage unit is designed to coordinate the data acquisition speed and data transfer speed of USB bus to solve the problem of data stream transmission in two different clock domains.In the aspect of preprocessing of spectral signal,FPGA parallel computing is adopted to realize the filtering algorithm,which improves the real-time performance of the system.Information processing center using ARM-based embedded processor S3C2440,to overcome the shortcomings,which is bulky,difficult to carry,compared with the PC platform,and realize the integrated design of the spectrum instrument.In this paper,a cross-compiling environment is built,the Linux operating system is transplanted,and the human-computer interaction interface of the spectrum measuring instrument is designed by using Qt software.The software modules of wavelength calibration and spectrum curve smoothing software.etc are developed to solve the key technology of the embedded spectrum measuring instrument.To facilitate the test,the paper also designed a high-power adjustable constant current source,drive 75 W tungsten light source as the test sample.It is proved that the grating spectral measurement system can realize small volume and the integration of embedded instrument,and can test the emission spectrum of the light source with wavelength of 400-1100 nm,and can display the spectrum curve of the test sample in the display screen,direct output spectral bandwidth and peak wavelength and other digital information.