[Spectral Calibration of a Solar Spectrometer Based on the Prism-Rotating Method]

In order to calibrate the corresponding center wavelength and bandwidth to the prism’s rotating angle of a scanning prism-dispersive solar spectrometer, a prism-rotating method to measure the spectral response function (SRF) of the solar spectrometer is suggested. The measuring process is as follows. With the wavelength of monochromatic light invariant, the prism is rotated for scanning the monochromatic image at the location of detector. Then the spectral response function is obtained by mapping the coordinate in position to the coordinate in wavelength. At first in this paper, by analyzing the definition of SRF, the conclusion is deduced that the prism-rotating method is equivalent to the wavelength-scanning method in practice. Then the 532 nm solid-state laser and 632.8 nm He-Ne laser are used as light source. The measurement of SRF of the solar spectrometer based on prism-rotating method is performed. A measurement of SRF with wavelength-scanning method is also performed to be used as a comparison. Experimental results indicate that the center wavelength of the scanning prism-dispersive solar spectrometer measured with prism-rotating method is 531.86 and 632.67 nm respectively. On the other hand, the result is 53139 and 631.97 nm with wavelength-scanning method, which is less precise than the result of prism-rotating method. The values of bandwidth measured with prism-rotating method are also more precise than the latter owing to avoiding the performance deficiency of monochromator. At last, using mercury vapor lamp as light source, an experiment for spectral calibration of the solar spectrometer with prism-rotating method is performed. The values of center wavelength and bandwidth are both achieved with the method combining the prism-rotating method and chracteristic spectrum. This method can also be used to calibrate the monochromator and the grating-dispersive spectrometer whose grating is rotatable.