Effects of aberrations on the point spread function and the two-point resolution with versatile apodization pupils
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Effects of aberrations on the point spread function and the two-point resolution with versatile apodization pupils ANDRA NARESH KUMAR REDDY1 DASARI KARUNA SAGAR3
,∗ ,
MAHDIEH HASHEMI2
and
1 Samara
National Research University, Moskovskoye Shosse, 34, Samara, Russia 443086 of Physics, College of Science, Fasa University, Fasa 74617-81189, Iran 3 Department of Physics, University College of Science, Osmania University, Hyderabad 500 007, India ∗ Corresponding author. E-mail: [email protected] 2 Department
MS received 30 August 2019; revised 31 May 2020; accepted 29 July 2020 Abstract. In this work, efficient amplitude-apodization pupils have been presented for tailoring the point spread function (PSF), which results in a decreased full-width at half-maximum (FWHM) and suppressed sidelobes. Comparison of PSF intensity profiles for both the unapodized and apodized cases have been reported. By analysing the resulting PSFs, the well-known effects induced by monochromatic aberrations such as defocussing effect, and the primary spherical aberration have been controlled for various degrees of apodization parameter β. It is shown that the two-point resolution of the apodized optical system significantly increased in the presence of aberrations. The proposed pupil apodizer is very effective in enhancing the resolution of the optical systems applicable in imaging and focussing applications. Keywords. Apodization; point spread function; defocussing; spherical aberration; full-width at half-maximum; two-point resolution. PACS Nos 42.15.Fr; 42.25.FX; 42.30.Kq
1. Introduction Point spread function (PSF) engineering is the modulation of the light distribution in the focal region of the optical system, exploited for improving the performance of optical systems employed in numerous applications [1–18]. This mechanism, demonstrated by inserting suitable phase or amplitude filter masks in the Fourier plane of the optical system, results in changes of the focal spot size and level of its surrounding sidelobes [1–4]. Presence of optical aberrations generally degrades the performance of the optical system [5,6]. In general, the detrimental effects of aberrations can be reduced by inserting an optical element with a suitable optical transmittance function [7–18]. In our previous work [19], we studied apodization of Hanning complex pupil functions where primary aberrations were only confined to the central region and omitted for the semiannular regions of the pupil. Aberrations considered in the earlier study were confined to the middle region, and therefore the performance is attributed to the pupil mask itself. Therefore, it was not a perfect assumption. However, in this case sidelobes were completely 0123456789().: V,-vol
suppressed on one side of the PSF at the cost of enhanced sidelobes on the counter side, and the resultant PSF, being asymmetric, plays a vital role in confocal imaging [3]. Traditionally, apodization across the exit pupil of the system has focussed on obtaining the quality output
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