Issue |
J. Eur. Opt. Soc.-Rapid Publ.
Volume 2, 2007
|
|
---|---|---|
Article Number | 07008 | |
Number of page(s) | 9 | |
DOI | https://doi.org/10.2971/jeos.2007.07008 | |
Published online | 23 February 2007 |
Regular papers
Strehl ratio and optimum focus of high-numerical-aperture beams
1
Philips Research Europe, HTC 36, NL-5656 AE Eindhoven, The Netherlands
2
Optics Research Group, Faculty of Applied Sciences, Technical University Delft, Lorentzweg 1, NL-2628 CJ Delft, The Netherlands
3
Philips Research Europe, HTC 4, NL-5656 AE Eindhoven, The Netherlands
Received:
8
January
2007
We analytically calculate the focus setting for a beam with a high numerical aperture (NA) that optimizes its Strehl ratio in the case of small aberrations up to the ’just’ diffraction-limited value (Strehl ratio ≥0.80). The optimum focus setting deviates from the one that follows from a minimization of the wavefront aberration with the aid of the Zernike aberration coefficients. This deviation stems largely from the fact that the common quadratic approximation of the focus term becomes inadequate in the high-NA case. Fundamental high-NA amplitude nonuniformity in the exit pupil of an optical system in the case of a linearly polarized incident beam also influences the optimum focus setting. Results for spherical aberration and astigmatism are presented for an NA-value of 0.95.
Key words: vector diffraction / aberrations / Strehl ratio / high-numerical-aperture beams
© The Author(s) 2007. All rights reserved.
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