This definition of microscope resolution is also often referred to as the Rayleigh Criterion. Light transmission through an individual ap- erture, such as a hole in an opaque screen, has been studied for centuries. Angular width refers to the angle, measured in radians, that is defined by the two intensity minima on either side of the central maximum. As a result of the diffraction limit, two emitting points cannot be optically resolved if the distance between them is smaller than the diffraction limit, which is illustrated in figure 1 (b). The lens, considered as a circular aperture with diameter D, produces a two-dimensional diffraction pattern with a central intensity maximum of angular width about / D. In the first part, the diffraction of light waves by a circular aperture is studied, while the choice of the observation point satisfies condition (1). But this same result is extrapolated to lenses, to calculate its limit of resolution. In a perfect optical system without any aberrations, the PSF is well-described by the so called Airy function. The fraunhoffer treatment of circular apertures yields a diffraction pattern of circles, with the first minimum (dark ring) at an angular radius of where sin() 1.22/b sin ( ) 1.22 / b, where b b is the diameter of the circular aperture. Diffraction refers to the spreading of light around an obstacle. The PSF is the response of an optical system to a point emitter due to the diffraction limit and imperfections in the optical system. Rachel and I briefly looked into the various diffraction patterns that arise from shining light through different shaped apertures: circular, square, and triangular, however our measurements and calculations focus on the square aperture. In more mathematical sense it can also be said that the resulting image is a convolution of the actual object with the so-called point spread function (PSF) of the optical system. This results in a blurry appearance of the captured image. The high frequency components that give an image its sharpness are lost by the finite numerical aperture of the lens that collects the light. The plane wave is released from the back of the slit which is barely visible as the dark blue. What You see here is the electric field intensity plot. First thing I want to show is the light wave diffraction, given in the image below. The limit is basically a result of diffraction processes and the wave nature of light. Although, if they reach an obstacle or an aperture, they will bend around the edges. And the waves that pass through the aperture follow its path normally as shown in the image on the right. The numerical aperture (NA) and the resolution limit is schematically illustrated in figure 1. The Fraunhofer diffraction equation is a simplified version of Kirchhoff's diffraction formula and it can be used to model light diffraction when both a light source and a viewing plane (a plane of observation where the diffracted wave is observed) are effectively infinitely distant from a diffracting aperture.
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