Here we consider atmospheric blur effects on target acquisition for both contrast-limited and noise-limited imaging. There is an important difference between the two, in addition to the mathematical differences discussed in Chapters 10 and 11. The restoration techniques of the previous chapter involve spatial-frequency filtering. As such, both signal and noise are altered equally at each spatial frequency. Thus, there is no signal-to-noise improvement. This means that image restoration is essentially ineffective in noise-limited imaging. However, it can be quite effective in contrast-limited imaging. As shown in the previous chapter, the image usually still remains contrast-limited despite the increase in noise deriving from high spatial-frequency enhancement. In such situations, blur is reduced significantly by such image restoration and fine, smaller detail can now be resolved. Target acquisition is improved. Target acquisition represents a quantitative measure of image quality.
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