Open AccessCorrecting spherical aberrations induced by an unknown medium through determination of its refractive index and thickness
Author(s) -
Daniel Iwaniuk,
Pramod K. Rastogi,
Erwin Hack
Publication year - 2011
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.19.019407
Subject(s) - optics , spherical aberration , refractive index , paraxial approximation , point spread function , contrast transfer function , lens (geology) , physics , materials science , optical path length , optical aberration , wavefront , beam (structure)
In imaging and focusing applications, spherical aberration induces axial broadening of the point spread function (PSF). A transparent medium between lens and object of interest induces spherical aberration. We propose a method that first obtains both the physical thickness and the refractive index of the aberration inducing medium in situ by measuring the induced focal shifts for paraxial and large angle rays. Then, the fourth order angle dependence of the optical path difference inside the medium is used to correct the spherical aberration using a phase-only spatial light modulator. The obtained measurement accuracy of 3% is sufficient for a complete compensation as demonstrated in a model microscope with NA 0.3 with glass plate induced axial broadening of the PSF by a factor of 5.