Aberrations Distortion

Aberration—distortion or defect in an image formed by a lens. 

Spherical Aberration Distortion or blurriness of image caused by the geometrical formation of a spherical lens or mirror. 

Aberrations Distortions (to an image) resulting from incorrect transfer of information (optics)... 

At its simplest, the mirror is a circular disc, of diameter 2a and mean thickness f, simply supported at its periphery (Fig. 7.2). When horizontal, it will deflect under its own weight M when vertical it will not deflect significantly. We want this distortion (which changes the focal length and introduces aberrations into the mirror) to be small... 

Tor the purpose of this brief account we will provide only a notional definition of optical aberrations. In an optical system, the angular coordinates of incident rays are transformed according to sequential applications of Descarte s law from one optical surface to the next. Aberrations are essentially the non-linear terms of the transformation, the angular coordinates of emerging rays not being strictly proportional to those of the incident ones -thereby generating distorted and/or blurred images. 

The distortions in the aberrated image can be better understood if a weak sinusoidal phase grating is considered [93], described by the object wave ... 

The principal problem in estimating potential health effects is one of relating the measured levels of radiation and/or radionuclides in/on a property to the projected cancer deaths if the location of occupants differs from where the measurements were taken. Aberrant high values can also easily distort and invalidate a comparison between properties. For this reason, we have based our estimates on mean or most likely, rather than maximal, values. 

In the preceding Figs, c denotes crown, f flint-glass. Both forms have equal radii of the front and bach surfaces, equal focal lengths, equal curvature of the image, and an equal distortion hut the plan shown in Fig. 409 is the best, because there is rather less spherical aberration. Even this is very bad, and should he superseded by the view-lens, which has recently been invented by Professor Petzyal, and which will be described presently. 

The reflecting stereoscope is not open to any single practical or theoretical objection. As an optical instrument it is absolutely perfect, being subject to no defects of distortion or aberration. For any scientific purpose, therefore, the reflecting stereoscope should always he preferred to the Other. The reflectors may be made of polished speculum metal if objection be raised to glass mirrors, and the pictures may he taken simultaneously in a camera with double lenses two and a half inches from centre to centre. 

Like their glass analogues, magnetic lenses suffer from such defects as coma, distortion, astigmatism, and chromatic and spherical aberration. 

There are three common types of lens aberrations. An aberration is the failure of a lens to produce an exact point-to-point correspondence between an object point and an image point, or in other words, an image distortion. The types of aberrations are spherical, chromatic, and curvature of field as illustrated in Figure 22A-22C. Spherical aberration is the failure of the lens to focus light onto the same focal plane (Fig. 22A). Chromatic aberration is when the different colors focus on different focal planes (Fig. 22B), which makes the image appears blurry. Curvature of field is when the plane of sharpest focus is curved due to this image curvature the whole image cannot be in focus (Fig. 22C). 

F. Perceptual distortions. Common to most ASCs is the presence of perceptual aberrations, including pseudohal1ucinations, increased subjectively felt hyperacuteness of illusions of every variety. The content of these perceptual aberrations may be determined by cultural, group, individual, or neurophysiological factors and represent either wish-fulfillment fantasies, the expression of basic fears or conflicts, or simply phenomena of little dynamic import, such as hallucinations of light. 

---