Optical resolution

Optical resolution is an imaging system’s ability to distinguish nearby details as separate. It is limited by wave diffraction as well as by the system’s design and image quality.

Diffraction limit: The bound on image detail imposed by the wave nature of light and an imaging system’s finite aperture. It sets the fundamental resolution limit for an ideal optical system.
Spatial frequency: The rate at which image intensity varies across space, commonly measured in cycles per unit distance. Resolution can be expressed as the highest spatial frequency an imaging system reproduces.
Microscope: An instrument that produces an enlarged image of small objects. Microscope resolution determines which closely spaced structures appear separately.
Magnification: The ratio between an image’s apparent size and an object’s actual size. Enlargement makes an image bigger but cannot recover details the system did not resolve.
Point spread function: The image formed by an optical system from an ideal point source. Its width and shape determine how neighboring point images overlap.
Modulation transfer function: A function describing how an imaging system transfers contrast at different spatial frequencies. It shows how sharply fine patterns are rendered before they become indistinguishable.
Telescope: An instrument that collects and focuses light from distant objects for observation. Its aperture and atmospheric conditions govern the finest angular details visible.
Image resolution: The amount of spatial detail represented in an image, often described by sampling dimensions or resolved features. Digital image resolution can describe pixel dimensions, which differ from optical resolving ability.
Airy disk: The diffraction pattern produced by a circular aperture, with a bright central spot surrounded by rings. Its central spot gives a characteristic scale for separating point sources.
Contrast: The difference in intensity or color that makes an object distinguishable from its surroundings. Two details may be unresolved at low contrast even when their spacing is unchanged.

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