| Usually the wavelength of visible light spectrum is from 400 to 780nm (0.4μm -0.78μm), and the wavelength of near-infrared spectrum is from 780nm to 2500nm (0.78μm-2.5μm). Hydrogen-containing groups, including the ones containing C-H (methyl group, methene, methoxyl group, carboxyl, aryl), O-H (hydroxy), S-H (mercapto) and N-H (amino), are the functional groups that display absorption in visible-near infrared light spectrum. Their frequency synthesis and first frequency frequency multiplication lies in 400-1300nm wave band. Minerals display absorption in some region of near-infrared spectrum because of flex and bend of interatomic chemical bonds or electron transition. Different alteral minerals can be differentiated according to characteristic absorption spectrum of their functional group in visible-near infrared light spectrum. And map of alteral mineral can be plotted after data processing.Classical mineral analytical apparatus is spectrum analyzer. The analyzer is divided into two ranges according to wave band, 0.4μm -2.5μm and 7μm -14μm. The former is used to measure low-temperature alteral mineral, while the latter is used to measure both low-temperature and high-temperature alteral mineral. The analyzer can also be divided into ground, airborne and space-borne mineral spectrum analyzer according to boarding system. Ground analyzer is used to perform cross-section and drill mineral analysis. Airborne mineral spectrum analyzer is used to get high-resolution remotely-sensed image. And space-borne mineral spectrum analyzer is used to get large-area remotely-sensed image.In this paper, ground spectrum analyzer is described, which is used to measure low-temperature alteral mineral. At present there are two kinds of prevalent instruments in the market. One is raster scanning mineral analyzer whose band is at 1300-2500nm. It performs high signal-to-noise ratio, portability and stability. However, it flaws in the narrow wavelength range, disable to measure the iron oxides (the absorption peaks of iron oxides are at 400-1100nm), long measuring time and inability in situ measurement. The other is LabSpec? made by ASD Inc. whose band is at 400-2500nm. Its advantages are fast measurement speed and broad spectral bandwidth. However, it shows low signal-to-noise ratio at 2000-2500nm which includes important mineral information. And it is heavy, huge and not portable because it includes three spectrum analyzers in itself. Also, it lacks special mineral analysis software.In order to solve the problems above, developping a high-speed fibre spectral analyzer which is apt to analyzing mineral by new technology and new method in visible-near infrared light spectrum is proposed. The design idea which makes optics, mechanics and electronics integrated is described based on latest CCD sensor. The unique and innovative idea of making three CCD spliced together for achieving 400-2500nm wavelength coverage visible-near infrared light spectrum is explained. Optics, electronics, communication and corresponding software are further researched. Mineral identification, quantitative analysis, building mineral database and extracting parameter from spectrum are discussed. The apparatus and its software design are displayed. Finally, the application of the analyzer in geological exploration is illustrated. |
PDF Full Text Request