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PFCA Lab Analysis

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To a certain sample, X(n×m) was used to represent the n sets of measured spectral data within time, where m is the number of wavelength , and n = t/τ. Specifically, rth wavelength, the sequence x(n, r), where r = 1,2,3…,m is obtained. The sequence contained the modulated useful signal, together with ambient light noise, the dark current of the instrument, etc. The FT of x(n, r) could be expressed by Eq.(1) and the sequence was decomposed in the frequency domain. (1) Similarly, the original matrix X(n×m) was computed by FT and could be expressed as Eq. (2) in the frequency domain. (2) where is the frequency component, is the loading vector, a matrix with is also called the principal frequency component …show more content…

Then, the demodulation spectrum signals are shown in Fig. 1(c ), obviously, the interference light is filtered, and the spectrum is similar to that shown in Fig. 1(d). In addition, the foundation frequency is 9.18 Hz in the amplitude-frequency curves, same as the chopper frequency, proving that the optical chopper could effectively suppress the ambient light noise, and would be especially applicable to situations such as unable black box . Fig. 1 Curves of validation experiment of optical chopper (a) spectrum curves of the existence of interference light (b) amplitude–frequency curves of a certain wavelength (c) the demodulated spectral signal by FT under different frequency (d) the spectrum curves of inexistence of interference light 4.2 PFCA experiment Based on the results in Section 4.1, the following experiments were designed to prove the proposed PFSA method. The experimental setup and data are already introduced in Sections 2.1 and 2.2. Each sample was measured under two conditions: no-chopper and chopper. The spectral data of a set of 64 samples of no-chopper was processed by overlapping and averaging. The spectral data of the chopper was demodulated by the method mentioned in Section 3.2, and different primary frequency components were selected from 1 to 5, and spectral data for the set of 64 samples were calculated according to Eq.

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