Fig. 1. The schematic diagram of the proposed optical set-up is shown in (a). The mask geometry is shown in (b). P(α) denotes a linear polarizer with its transmission oriented at an angle α to the reference abscissa. The circular symmetric aperture considered for compensation of on-axis aberration is shown in (i). The quadrant masked aperture used for compensation of astigmatism and coma is shown in (ii).

Fig. 2. Normalised axial irradiance for different values of δ for polarisation masked lens aperture. The polarisation parameters are of the system α = 0°, β = 90°, γ = 45°, and a = b = 1,  = 0.707. The values of δ for the plots are as follows: Plot O – δ = 0°, 360°, Plot A – δ = 45°, Plot B – δ = 90°, Plot C – δ = 135°, Plot D – δ = 180°, Plot E – δ = 225°, Plot F – δ = 270°, Plot G – δ = 315°.

Fig. 3. The comparison of the IPSF of a masked lens with δ = 90°, w₂₀=−0.36λ, with that of the diffraction limited IPSF.

Fig. 4. Focal shift in μm against input beam parameter δ in degree.

Fig. 5. Variation of the Strehl ratio with w₄₀ for different values of δ. The polarization parameters are system α = 0°, β = 90°, γ = 45°, and a = b = 1,  = 0.50. The Strehl ratio for an unmasked normal lens aperture is denoted as NRML.

Fig. 6. The IPSF of the polarization-masked lens, unmasked lens, and ideal lens for (a) δ = 60°, (b) δ = 90° and (c) δ = 120°, other parameters same as in Fig. 5.

Fig. 7. The upper half (i) shows the image of an off-axial point source formed by an unmasked lens in presence of astigmatism and the lower half shows the image of similar point source formed by a masked aperture in presence of varying degrees of astigmatism: (a) w₂₂=3λ, (b) w₂₂=5λ, (c) w₂₂=7λ and (d) w₂₂=9λ, computed at w₂₀=−w₂₂/2 for the system polarization parameters α₁ = 0°, α₂ = 90°, a/b = 1, δ = 90°, γ = 135°.