|
In optics, a wavefront is the locus (a line or surface in an electromagnetic wave) of points having the same phase. Since optical frequencies are so high, the temporal component of optical waves is ignored, and it is only the phase of the spatial oscillation that is described. Additionally, most optical systems and detectors are indifferent to polarization, so this property of the wave is also usually ignored. Optical redirects here. ...
A line, or straight line, can be described as an (infinitely) thin, (infinitely) long, perfectly straight curve (the term curve in mathematics includes straight curves). In Euclidean geometry, exactly one line can be found that passes through any two points. ...
An open surface with X-, Y-, and Z-contours shown. ...
A wave is a disturbance that propagates through space, often transferring energy. ...
A spatial point is an entity with a location in space but no extent (volume, area or length). ...
Waves with the same phase Waves with different phases The phase of a wave relates the position of a feature, typically a peak or a trough of the waveform, to that same feature in another part of the waveform (or, which amounts to the same, on a second waveform). ...
In electrodynamics, polarization (also spelled polarisation) is a property of waves, such as light and other electromagnetic radiation. ...
Simple wavefronts and propagation
Strictly speaking, all optical systems can be described with Maxwell's Equations. However, given the above simplifications, Huygens' principle provides a quick method to predict the propagation of a wavefront through, for example, free space. The construction is as follows: Let every point on the wavefront be considered a new point source. By calculating the total effect from every point source, the resulting field at new points can be computed. Sophisticated computational algorithms are often based on this approach. Specific cases for simple wavefronts can be computed directly. For example, a spherical wavefront will remain spherical as the energy of the wave is carried away equally in all directions. Such directions of energy flow, which are always perpendicular to the wavefront, are called rays. Maxwells equations (sometimes called the Maxwell equations) are the set of four equations, attributed to James Clerk Maxwell, that describe the behavior of both the electric and magnetic fields, as well as their interactions with matter. ...
Wave Refraction in the manner of Huygens. ...
In physics, free space is a concept of electromagnetic theory, corresponding roughly to the vacuum, the baseline state of the electromagnetic field, or the replacement for the electromagnetic aether. ...
A point source may be a source of light that is treated as having no physical extension, or a source in fluid flow, or in electrostatics, or a source of pollution coming from a single cause, such as a municipal plant. ...
In Euclidean geometry, a ray, or half-line, given two distinct points A (the origin) and B on the ray, is set of points C on the line containing points A and B such that A is not strictly between C and B. O----O-----*---> A B C In geometric...
The simplest form of a wavefront is the plane wave, which when propagating can be seen to give rise to new plane wavefronts, as the corresponding rays are parallel to each other. Technically, this is referred to as a collimated beam of light. Such a plane wavefront is a good model for a section of a very large spherical wavefront; for instance, sunlight strikes the earth in wavefronts of radius 93 million miles. For all practical purposes, such a wavefront is considered planar. In the physics of wave propagation (especially electromagnetic waves), a plane wave (also spelled planewave) is a constant-frequency wave whose wavefronts (surfaces of constant amplitude and phase) are infinite parallel planes normal to the propagation direction. ...
Parallel is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. ...
Collimated light is light whose rays are parallel. ...
Wavefront aberrations Methods utilizing wavefront measurements or predictions can be considered an advanced approach to lens optics, where a single focal distance may not exist due to lens thickness or imperfections. Note also that for manufacturing reasons, a perfect lens has a spherical (or toroidal) surface shape though, theoretically, the ideal surface would be aspheric. Shortcomings such as these in an optical system cause what are called optical aberrations. The best-known aberrations include spherical aberration and coma. To meet Wikipedias quality standards, this article or section may require cleanup. ...
Focal plane Longitudinal sections In optics, spherical aberration is an image imperfection that occurs due to the increased refraction of light rays that occurs when rays strike a lens or mirror near its edge, in comparison with those that strike nearer the center. ...
In optics (especially telescopes), the coma in an optical system refers to monochromatic aberration inherent to certain optical designs or due to imperfection in the lens or other components which results in off-axis point sources such as stars appearing distorted. ...
However there may be more complex sources of aberrations such as in a large telescope due to spatial variations in the index of refraction of the atmosphere. The deviation of a wavefront in an optical system from a desired perfect planar wavefront is called the wavefront aberration. Wavefront aberrations are usually described as either a sampled image or a collection of two-dimensional polynomial terms. Minimization of these aberrations is obviously very desirable in optical systems.
Wavefront sensor A wavefront sensor is basically a device which measures the wavefront aberration in a coherent signal to describe the optical quality or lack thereof in an optical system. A very common method is to use a Shack-Hartman lenslet array. Probably the most common application of such systems is in measurement of the eye itself. In one approach, a weak laser source is directed into the eye and the reflection off the retina is sampled and processed. This article or section does not cite its references or sources. ...
Human eye cross-sectional view. ...
See also Wave Refraction in the manner of Huygens. ...
A deformable mirror can be used to correct wavefront errors in an astronomical telescope. ...
External links - LightPipes free Unix wavefront propagation software
|
Feeds |
Contact