defocus

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defocus

(de-fo'kus) [L. de, away from, + focus, hearth]
The blurring of a visual image caused by spherical aberration, chromatic aberration, or diffraction. Also called optical defocus. Synonym: optical defocus

optical defocus

Defocus.
Medical Dictionary, © 2009 Farlex and Partners

defocus

To put or go out of focus.
hyperopic defocus State of the eye in which the retinal image is focused behind the retina. It may occur when placing a negative lens in front of an emmetropic presbyopic eye; in an uncorrected presbyopic hyperope; in a high hyperope unable to overcome the ametropia by accommodating; or as an accommodative lag in an uncorrected or corrected myope, as well as in an emmetrope viewing a near object. See lag of accommodation; over-correction.
myopic defocus State of the eye in which the retinal image is focused in front of the retina. It may occur when placing a positive lens in front of an emmetropic eye; in an uncorrected or undercorrected myopic eye; or if there is a lead of accommodation, as is the case in some individuals viewing a distant object. See lead of accommodation; under-correction.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
Before performing quantitative texture measurement, different corrections have to be performed on the raw data, namely defocusing, background and absorption correction as shown in Figures 2 and 3.
The defocusing of the single-look SAP by the LLPE and LQPE is examined in Section 3.
For a quadratic phase error, in the smeared image the energy tends to be spread uniformly over the distance of the smear for an unweighted aperture, and the sharpness of target image achieves its maximum value when the moving target is ideally focused [29], which makes it possible to estimate its azimuth velocity component by using symmetric defocusing filters.
The increased qualitative and quantitative awareness offered by the three-dimensional ray tracing assists in explaining certain phenomena not clearly seen or understood by the experiments alone, including focusing and defocusing.
The present investigation is concerned with laser power, welding speed and defocusing distance and their effects on the fusion zone shape and micro- structure of SUS301L stainless steel overlap joints.
In [section]4 a similar study is presented for the focusing and the defocusing NLS equation.
Moreover, the development of the ME sense of futurity when compared with the OE sense of prophecy, is to be viewed as the increase in the level of abstractness via defocusing of the divine conceptual subject.
Designed for factory automation, a locking screw prevents system defocusing, even in areas subject to shock and vibration.
Cameras are protected because the system instantly recognizes the repositioning, covering, or defocusing of a camera.
Ironically, to eliminate autofocusing systems, they devised a defocusing lens.
Bleeding was controlled by increasing the spot size on the micromanipulator and defocusing the laser beam.