![]() ![]() Points far apart (top) or meeting the Rayleigh criterion (middle) can be distinguished. In scientific analysis, in general, the term "resolution" is used to describe the precision with which any instrument measures and records (in an image or spectrum) any variable in the specimen or sample under study.Īiry diffraction patterns generated by light from two point sources passing through a circular aperture, such as the pupil of the eye. As explained below, diffraction-limited resolution is defined by the Rayleigh criterion as the angular separation of two point sources when the maximum of each source lies in the first minimum of the diffraction pattern ( Airy disk) of the other. The term resolution or minimum resolvable distance is the minimum distance between distinguishable objects in an image, although the term is loosely used by many users of microscopes and telescopes to describe resolving power. Resolving power is the ability of an imaging device to separate (i.e., to see as distinct) points of an object that are located at a small angular distance or it is the power of an optical instrument to separate far away objects, that are close together, into individual images. For this reason, high resolution imaging systems such as astronomical telescopes, long distance telephoto camera lenses and radio telescopes have large apertures. The Rayleigh criterion shows that the minimum angular spread that can be resolved by an image forming system is limited by diffraction to the ratio of the wavelength of the waves to the aperture width. The closely related term spatial resolution refers to the precision of a measurement with respect to space, which is directly connected to angular resolution in imaging instruments. The value that quantifies this property, θ, which is given by the Rayleigh criterion, is low for a system with a high resolution. The colloquial use of the term "resolution" sometimes causes confusion when an optical system is said to have a high resolution or high angular resolution, it means that the perceived distance, or actual angular distance, between resolved neighboring objects is small. It is used in optics applied to light waves, in antenna theory applied to radio waves, and in acoustics applied to sound waves. A series of images representing the magnification of M87* with an angular size of some microarcseconds, comparable to viewing a tennis ball on the Moon (magnification from top left corner counter−clockwise to the top right corner).Īngular resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution.
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