What is piston aberration?
In optics, piston is the mean value of a wavefront or phase profile across the pupil of an optical system. Defocus is the lowest order true optical aberration. If piston and tilt are subtracted from an otherwise perfect wavefront, a perfect, aberration-free image is formed.
What is Zernike analysis?
In optometry and ophthalmology, Zernike polynomials are used to describe wavefront aberrations of the cornea or lens from an ideal spherical shape, which result in refraction errors. They are also commonly used in adaptive optics, where they can be used to characterize atmospheric distortion.
What is RMS wavefront?
RMS wavefront error is a way to measure wavefront aberration. Basically, we compare the real wavefront with a perfect spherical wavefront. The RMS value expresses statistical deviation from the perfect reference sphere, averaged over the entire wavefront.
What is piston error?
The piston error is included in the interference factor. The intensity distribution on the image plane is changed with the piston error. According to the interference principle, the interference factor will disappear when the piston error exceeds the coherence length of the light used in the optical imaging system.
What is the advantage of using Zernike polynomials for describing the aberrations of eyes?
Conclusions: Zernike polynomials excel in extracting the low-order optical characteristics of visual optics. Zernikes accurately represent both low- and high-order aberrations in normal eyes where high-order aberrations are clinically insignificant.
How many Zernike polynomials are there?
Image plane of a flat-top beam under the effect of the first 21 Zernike polynomials (as above).
What are third order aberrations?
The aberrations of the third order are: (1) aberration of the axis point; (2) aberration of points whose distance from the axis is very small, less than of the third order — the deviation from the sine condition and coma here fall together in one class; (3) astigmatism; (4) curvature of the field; (5) distortion.