The image demonstrates how a filter can be used to improve contrast in an optical system.
Low Frequency (Coarse Patterns):
Without filter: The contrast of the coarse pattern is reduced after passing through the lens.
With filter: The filter helps to restore the contrast of the coarse pattern, making it more distinct.
High Frequency (Fine Patterns):
Without filter: The contrast of the fine pattern is significantly reduced due to diffraction and other optical effects.
With filter: The filter further degrades the contrast of the fine pattern, making it appear even more blurred.
