Quantification and elimination of the CCD dark current in weak spectrum measurement by modulation and correlation method

In weak spectrum measurement, the dark current of CCD could be very large and thus affect the proper application. It's essential to suppress the dark current and other noises to get high quality spectral data. In this paper we proposed a modulation and correlation method to eliminate it for weak spectrum measurement. In this design, only a compact camera shutter is to be mounted on the spectrometer, which will facilitate the independent control of CCD integral-time and light passing or blocking status. To measure the weak spectrum, the shutter is modulated by a pseudorandom binary sequence under fixed CCD integral-time, and the correlation processing is performed on the captured spectra to produce high quality spectrum, where dark current will be totally eliminated and random noises be suppressed. The system setup and the brief analysis of this method are introduced. Computer simulation and preliminary weak spectrum measurement results are also provided in this paper.