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J. Eur. Opt. Society-Rapid Publ. 22, 6( 2026)
Fig
. 8. Comparing simulated results with scanned profiles of SOL,( a) and( b) are SOL’ s measurements labeled laser beam of 1 and 2 in Figures 6d, 6c and 6d are corresponding simulation results. The color bar represents the number of simulated photoelectrons.
Fig. 9. IOPs of Jerlov II( a), Jerlov 3C( b).
It is widely known that SNR can be improved by integrating several profiles. To improve the SNR of N st �N sw, the horizontal sampling interval should be reduced so that more laser shots are able to encounter the target. We have already discovered that the horizontal detectable length range of target is beyond its actual length [ xe( �0.4 m, 0.4 m)]( Figs. 10 and 11). Therefore, after counting the number of photoelectrons with horizontal distribution at the same depth of target, the definition of extended detection range is made as the x-range when the photoelectron numbers with target reduce to half of that at the center top( x = 0). The statistical results of the extended detection range are displayed in Figure 12c. Assume the SNR does not change within this range, and set SNR = 3 as the standard. Then the relationships between max detectable depth and horizontal scanning resolution of Jerlov II and Jerlov 3C water are shown in Figure 12d by interpolating at the depth resolution of 0.1 m. Only one single profile is needed when the target depth is shallower than 25.0 m in Jerlov II water and 9.2 m in Jerlov 3C water, so the max point resolutions are equal to the extended detection ranges. It should be noted that the phenomenon of photoelectron numbers of the target dropping to half does not mean the target cannot be recognized. Recognition still depends on its true value and SNR( Fig. 10a). As the depths of target add up, more and more profiles have to be integrated, so the point resolutions are equal to the corresponding extended detection range divided by the number of integrated profiles. If the SNR reduces to a very small value, like lower than 1, it will be better to level up the number of integrated four times as calculated by equation( 18).
The preceding analysis reveals that, to achieve a certain target SNR, deeper targets require the integration of more lidar profiles to enhance signal quality. This requires an increase in horizontal sampling density to ensure that more laser beams effectively interact with the target. While this approach improves the detectability of deep targets, it simultaneously reduces the area that can be covered within