This paper suggests the possibility of partial compensation of spherical aberration with a polarization-masked lens aperture. The principle is based on the fact that any pre-specified phase step can be introduced between two zones of a lens aperture masked by suitably oriented linear polarizers and employing an elliptically polarized imaging beam. By comparison of the point-spread function of such a polarization-masked imaging system with that of an ideal lens, it has been shown that the effect of spherical aberration can be appreciably compensated by making an appropriate choice of the polarization parameters involved.

KALLOL BHATTACHARYA

Applied Optics and Photonics

D R CHOWDHURY

S SANYAL

A K CHAKRABORTY

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Performance of a polarization-masked lens aperture in the presence of spherical aberration

Journal of Optics A: Pure and Applied Optics

It has been established that the polarization properties of light can be effectively utilized in modifying the characteristic of the imaging system. As a matter of fact, the diffraction properties of the lens get modified when it is masked by polarizing devices. It is therefore well expected that characteristics of an imaging system also be modified by utilizing polarization properties of light. This calls for a systematic study of the effects of variation of polarization on diffraction pattern of different kinds of slit including polarizing devices. In this paper we study the Fraunhofer diffraction pattern of a slit using polarized light having variable state of polarization across it. © Optical Society of India 2011.

Journal of Optics (India)

Modification of diffraction pattern of a slit using polarized light having variable state of polarization

One approach to aberration compensation of an imaging system is to introduce a suitable phase mask at the aperture plane of an imaging system. We utilize this principle for the compensation of astigmatism. A suitable polarization mask used on the aperture plane together with a polarizer-retarder combination at the input of the imaging system provides the compensating polarization-induced phase steps at different quadrants of the apertures masked by different polarizers. The aberrant phase can be considerably compensated by the proper choice of a polarization mask and suitable selection of the polarization parameters involved. The results presented here bear out our theoretical expectation. © 2004 Optical Society of America.

Fulltext

Applied Optics

Polarization-based compensation of astigmatism

This study utilizes the concept of polarization phase to introduce a circularly symmetric phase step in the aperture plane of an imaging system. Since the polarization phase can be controlled by variation of the polarization parameters involved, the effective focal length of the imaging system can be varied within a small range. In the proposed technique, the modification of the focal length is obtained by rotating a retarder at the input of the imaging system. A study of the PSFs at the shifted focal planes shows that the quality of the image in these planes is comparable to that produced by a diffraction-limited system at Gaussian focus. The focal plane displacement achievable is about 300 μm of a f/10 system at 550 nm.

Focal shift in an imaging system with polarization-phase modulated aperture plane

In this work, grating couplers fabricated by sol-gel technique are studied for sensing application. Assuming that the measurand is the refractive index of a film acting as a cover layer, the expression for homogeneous sensitivity, defined as the change of effective refractive index of the guiding mode to the change in cover layer refractive index, is first derived using the basic grating coupler theory. Next the dependence of homogeneous sensitivity and waveguiding condition on grating thickness and period respectively for different grating materials are studied. Thereafter, several characterizations of the fabricated grating couplers are done and the waveguiding characteristics of the fabricated couplers are analyzed based on the developed theory. Finally, the sensing property of the fabricated coupler is also established. © 2017 Elsevier GmbH

Optik

Characterization of sol-gel derived grating couplers for sensing application

The optical transfer function (OTF) of an imaging system using polarization devices depends in general on the state of polarization of the input beam. In fact, the `amplitude point spread function' (APSF) of such a system is different for different linearly polarized components of the input beam. This implies that the APSF of a system using polarizing devices behaves as a vector quantity. The nature of the final image is determined by the relative contribution of the two components of the vector APSF. The specific imaging system considered in the present study consists of a circularly symmetric polarization mask with linear polarizers having different orientations for the central circular and annular regions of an ideal lens aperture. If the light originating from an object point is in general elliptically polarized, the OTF of such a system with an analyser at the output is seen to have three additive components, which are, in fact, the Fourier coefficients of the OTF which varies periodically with the orientation of the analyser. It is also observed that the images produced by each additive component of the OTF can be separated—a fact that seems rewarding in view of potential applications. © 1993 Taylor and Francis Ltd.

Journal of Modern Optics

Vector wave imagery with a lens masked by polarizers

The imaging characteristics of a perfect lens partially masked by a linear polarizer can be varied continuously either by rotating an analyzer placed at the output side or by changing the state of polarization of the input beam. In this paper we study the frequency-response characteristics and the point-spread function of such a system. It is also shown that the proposed system can be adapted either for apodization or for superresolution simply by rotating the analyzer. The fact that the unpredictable phase introduced by the mask has no harmful effect on the performance of the system makes it convenient for several applications. Expressions are obtained for the optical transfer function and the point-spread function of such a system. Some specific cases are illustrated graphically, and some probable applications are discussed. © 1988 Optical Society of America.

Journal of the Optical Society of America A: Optics and Image Science, and Vision

Frequency-response characteristics of a perfect lens masked by polarizing devices

The optical frequency response of a perfect lens partially masked by a retarder has been studied . The optical transfer function (OTF) of such a system depends upon the relative orientation of the analyser, placed at the output, relative to the slow and fast axes of the mask, and also on the relative aportioning of the lens aperture by the mask . The OTF of the system also depends upon the retardation introduced by the mask . In the present paper, we have computed the OTF of the masked lens for different values of the relevent parameters with and without the analyser at the output. © 1987 Journal Of Modern Optics. All rights reserved.

Frequency response characteristics of a perfect lens partially masked by a retarder

The optical transfer function (OTF) of a perfect lens with zonal masking of the lens aperture with polarisation devices has been studied. It is seen that the OTF of such system can be varied continuously by varying state of polarisation of the input beam and also by changing the orientation of the analyser placed at the output side.

Journal	Data powered by TypesetJournal of Optics A: Pure and Applied Optics
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ISSN	1464-4258
Open Access	No