Why do diffraction effects make optical images slightly fuzzy?

Diffraction causes optical images to appear slightly fuzzy because light does not travel in perfectly straight lines when passing through an aperture; instead, it spreads out as a wave.12

Even in a perfectly corrected lens, this wave nature prevents light from focusing into an infinitely small point. Instead, the image of a point source is transformed into a diffraction pattern known as the Airy disk, which consists of a central bright spot surrounded by concentric rings. Because this disk has a finite size, it imposes an inherent limit on the resolving power of any optical instrument.3

Furthermore, because the aperture of an objective lens is limited, it cannot collect all the diffracted waves originating from an object. The loss of these higher-frequency components means that fine details cannot be perfectly reconstructed, resulting in a loss of sharpness. Consequently, the "fuzziness" is a fundamental physical consequence of the wave nature of light interacting with the finite dimensions of optical systems.412