# Regulated Power Supply with High Power Factor for Hyperspectral Imaging Applications
## 4 Experimental Results
### Evaluation of Performance for the Hyperspectral Image Application
#### 4.2.4 Light Stability Evaluation
In terms of transmittance measurements, [PERSON]'s test showed significant differences between CPS-1 and CPS-2 (\(p\) < 0.0001) and between PPS and CPS-2 (\(p\) = 0.0169) but found no significant difference between PPS and CPS-1 (\(p\) = 0.1118). In summary, our results indicate a mix of significant and non-significant differences depending on both the power supply and the mode of illumination. This suggests that both the illumination system and the power supply play a crucial role in the performance of hyperspectral imaging systems. The light stability shown in Figure 16 represents the average light intensity across the entire spectral range captured by the HS camera. To study how light stability varies across different wavelengths, we computed the light stability for each spectral band of the instrument (Figure 17). This approach allows for a comprehensive understanding of the light stability performance across the spectrum, highlighting the wavelength-specific variations in light-intensity stability. The observed pattern in the SNR for the average light intensity remained consistent across different power supplies. However, there was a noticeable dependency of light stability on the wavelength for the power supplies light sources under evaluation as well as variations depending on the illumination modes. In reflectance measurements (Figure 17a), PPS displayed a SNR over 50 dB from roughly 450 to 800 nm, peaking at 600 nm (55.5 dB). CPS-2 outperformed with a SNR above 50 dB spanning from 450 to 850 nm and its highest SNR at 600 nm (60 dB). CPS-1 exhibited a unique performance, maintaining an SNR above 50 dB from 620 to 850 nm, with its peak  
Figure 16: Light stability (SNR) for the different types of power supplies (PPS, CPS-1, and CPS-2). (a) Reflectance mode. (b) Transmittance mode. at 780 nm (54 dB). CPS-1 achieved the optimal SNR between 800 and 880 nm. Across all power supplies, the SNR was comparable from 900 to 1000 nm. In the transmittance measurements in Figure 17b, PPS shows a SNR of 50 dB across the 440 to 900 nm wavelength range, peaking at 560 nm (55 dB). CPS-2 surpasses the others by maintaining an SNR above 50 dB from 420 to 920 nm, reaching its highest at 560 nm (62 dB). CPS-1, on the other hand, achieves an SNR greater than 50 dB between 640 and 860 nm, with its peak at 790 nm (54 dB). In this case, CPS-2 offers the best SNR across the entire spectrum, while CPS-1 outperforms PPS in the 730 to 860 nm range. From 920 to 1000 nm, PPS and CPS-2 demonstrate comparable SNR levels, while CPS-1 falls behind. According to our observations, the SNR measurements tend to be higher across the spectral range for transmittance illumination compared to reflectance, indicating that the type of illumination head has an impact on the overall light stability. However, the primary factor influencing light stability within the studied spectral range is attributed to the power supply used. Both the PPS and CPS-2 power supplies exhibit consistently high SNR across the entire spectral range. In contrast, the CPS-1 power supply demonstrates superior performance in the infrared spectral range (from 700 nm) but shows decreased performance in the visible spectral range (from 400 to 700 nm). Since the only differences in the different measurements is the power supply, these findings emphasize the critical importance of selecting an appropriate power supply for HSI systems, as the type of power supply can lead to notable differences in lighting performance.