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A complex, aberrated wavefront profile may be curve-fitted with Zernike polynomials to yield a set of fitting coefficients that individually represent different types of aberrations. These Zernike coefficients are linearly independent , thus individual aberration contributions to an overall wavefront may be isolated and quantified separately.
A wavefront sensor is a device which measures the wavefront aberration in a coherent signal to describe the optical quality or lack thereof in an optical system. There are many applications that include adaptive optics , optical metrology and even the measurement of the aberrations in the eye itself.
If the sensor is placed at the geometric focal plane of the lenslet, [5] and is uniformly illuminated, [6] then, the integrated gradient of the wavefront across the lenslet is proportional to the displacement of the centroid. Consequently, any phase aberration can be approximated by a set of discrete tilts. By sampling the wavefront with an ...
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 .
A pyramid wavefront sensor is a type of a wavefront sensor. It measures the optical aberrations of an optical wavefront. [1] This wavefront sensor uses a pyramidal prism with a large apex angle to split the beam into multiple parts at the geometric focus of a lens. A four-faceted prism, with its tip centered at the peak of the point spread ...
Ocular aberrations are caused by spatial phase nonuniformities in the wavefront exiting the eye. In a Shack-Hartmann wavefront sensor, these are measured by placing a two-dimensional array of small lenses (lenslets) in a pupil plane conjugate to the eye's pupil, and a CCD chip at the back focal plane of the lenslets.
The Gerchberg-Saxton algorithm. FT is Fourier transform. The Gerchberg–Saxton (GS) algorithm is an iterative phase retrieval algorithm for retrieving the phase of a complex-valued wavefront from two intensity measurements acquired in two different planes. [1]
Piston and tilt are not actually true optical aberrations, as they do not represent or model curvature in the wavefront. 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.