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J. Eur. Opt. Society-Rapid Publ. 21, 13( 2025)
Fig
. 3. Experimental setup and equipment.( a) Structure of the actual measurement optical path;( b) Schematic diagram of the experimental system;( c) HEP-756-S SHS;( d) Potassium lamps and activators.
Table 1. Parameters of the HEP-765-S spectrometer.
Parameter attribute |
Value |
Wavelength range |
756.8 ~ 771.7 nm |
Spectral resolution |
0.029 nm |
Clear aperture |
< 30 mm |
Field of view |
> 4 ° |
Pixel size |
13 lm |
Table 2. Experimental parameters.
Serial number
Distance between potassium lamp and detector / cm
Potassium lamp current / mA
1 |
442 |
0.2 |
2 |
442 |
0.5 |
3 |
442 |
1 |
4 |
442 |
2 |
5 |
442 |
4 |
6 |
442 |
6 |
indicators for assessing the success of signal extraction. This experiment fully confirms the effectiveness of the PCA- NLM algorithm adopted in this paper for potassium lamp spectrum extraction.
Six groups of mixed data were collected in the experiment. Figure 5a shows an interferogram of the potassium lamp under the conditions of a current of 6 mA and a sunny atmosphere as the background. The bright line with a zero optical path difference in the middle of the interferogram was slightly inclined in the vertical direction. This occurred because the grating in the interferometer was shifted from its ideal position, and the component in the y direction was slightly tilted [ 25 ]. In addition, the interferogram also had dark spots and uneven intensity distributions; thus, performing PCA on the interferogram dimension led to erroneous results. Here, the analysis was carried out mainly in the spectral dimension. The size of a single interferogram was 2048 2048 pixels, and each row represented a set of one-dimensional interferometry data. One-dimensional spectral data was obtained from the single-row data of the interferogram after apodization, first-order difference removal of the baseline, and one-dimensional Fourier transform. To reduce the influence of the high-frequency random noise in the single-line spectrum, an averaging process was performed on the spectral data of 2048 lines. Figure 5b shows the average spectrum after the above preprocessing.
To provide a closer view, Figure 6 shows a partially magnified portion of Figure 5b. Under a potassium lamp current of 6 mA, a small peak at 766.49 nm was present; however, this peak was similar to the other small peaks at the trough positions of the adjacent periods, could be an intrinsic signal of the atmospheric background and did not likely reflect the potassium signal. A smooth downward curve was observed at 769.89 nm, with a small valley near