Design And Research Of A Weak Spectrum System Based On Photoelectric Inspecting Technology

The weak spectrum signal technology, which is based on the diffraction, interference, polarization of light to acquire the message of the object, has been a new science at the field of engineering, but on the condition of relatively low of SNR(Signal to Noise Ratio), what troubles mostly is extracting the useful one while keeping the detecting results effectively. With the development of this technology, more and more related research appearances, whereas, it is still far from the maturity and needs for deeper research. In this essay, two vital programs, that is the collection of useful signals and its intelligence control for the weak spectrum system has been analyzed. The concrete research and results are as follows:(1) Based on the detection index and functional requests for the weak spectrum system, It is going to select the proper optical devices:at the light option aspect, as for the hardware limits in the lab, a mercury-argon lamp, which has the optical scale ranging from 253nm to 922nm is selected; In the optical splitting field, a grating spectrometer with two different blazed grating (1200g/mm and 600g/mm) is introduced, it has the scanned accuracy of 0.2nm as well as 0.005nm for the miniature stepping distance as the result; In the photoelectric part, a PMT has the parameters of cathode sensitivity (peak value) of 74 mA/W, average dark current of 3nA, and working temperature scale of -80—+50℃; As for the AD acquisition, USB7660 AD card is used, as it bases USB 2.0 port to transform data, it helps to form the high frequency of 250kHz, what is more, relatively high resistant of the analog input helps to reduce the zero drifts.(2) Because of the weakness of the spectrum itself as well as essay to be covered by noise after photoelectric conversion, it needs to eliminate the noise signals at the output port. In this essay, it introduces photoelectric detection technology which contains amplification technology and low-pass filter technology. At the amplification field, isolator AD202JN is used for the I/V circuit as well as co-ratio amplification circuit, meanwhile, operational amplifier OP07 is applied for the low-pass filter circuit, the circuit is assembled and displayed as a product at the end. The circuit has the function of the amplification of 1.5*106 as well as cut-off frequency of 1.59Hz.(3) A software analysis system based on MFC single document is designed in this essay, which helps to automatically control the devices. Its functions are as follows:single frame scanning of multi-wavelength, multiple frames scanning of multi-wavelength, timing collection of single wavelength, parameter settings of spectrometer, parameter settings of AD card, AD output, data save, exit, etc.(4) At the application research, it sets the chlorella as the starting point, based on the spectrum absorption characteristic to scan the chlorella online. Moreover, it has disported the fresh chlorella as well as introduced a parallel and focusing process for incident light. As a result, the liquid absorbing the red-orange light (600nm-700nm) and blue-violet light (400nm-500nm) most is verified, moreover it has the separately maximum absorbed value of 411nm and 665nm. In addition, the analyzed Linear Regression shows that it has relatively high correlation degree compared with the standard result and it is effective for the error compensation.Based on the photoelectric detection technology, the designed weak spectrum system has the application prospect in biomedicine, physical chemistry, and environmentally detection etc.