Fig. 5: Filters frequency response before and after optimization for both the binary (top box) and ternary (bottom box) segmentation problems.

In the ternary case, the top plot (c) in green illustrates the frequency response of the conduction filter, which shows a distinct amplification of the frequency contents at the lower end of the spectrum and at the frequency corresponding to the pulse repetition rate (250 kHz). In contrast, the center plot (d) in orange and the bottom plot (e) in red show the frequency response of the band-pass filters for stable keyhole and unstable keyhole, respectively. The filter for the unstable keyhole has a lower attenuation at the lower end of the spectrum compared to the stable keyhole filter. However, the key difference between the two is the absence of the 250 kHz peak in the unstable keyhole filter. Similarly, for the binary case (top box), the top plot (a) in green illustrates the frequency response of the conduction filter, which again shows a specific amplification of the frequency contents at the lower end of the spectrum. In contrast, the bottom plot (b) in red shows the keyhole filter compared to the initial filter.