Experimental validation of a customized phase mask designed to enable efficient computational optical sectioning microscopy through wavefront encoding

Abstract

In this paper, wavefront-encoded (WFE) computational optical sectioning microscopy (COSM) using a fabricated square cubic (SQUBIC) phase mask, designed to render the system less sensitive to depth-induced aberration, is investigated. The WFE-COSM system is characterized by a point spread function (PSF) that does not vary as rapidly with imaging depth compared to the conventional system. Thus, in WFE-COSM, image restoration from large volumes can be achieved using computationally efficient space-invariant (SI) algorithms, thereby avoiding the use of depth-variant algorithms. The fabricated SQUBIC phase mask was first evaluated and found to have a 75% fidelity compared to the theoretical design; it was then integrated in a commercial wide-field microscope to implement a WFE-COSM system. Evaluation of the WFE-COSM system is demonstrated with comparative studies of theoretical and experimental PSFs and simulated and measured images of spherical shells located at different depths in a test sample. These comparisons show that PSF and imaging models capture major trends in experimental data with a 99% correlation between forward image intensity distribution in experimental and simulated images of spherical shells. Our experimental SI restoration results demonstrate that the WFE-COSM system achieves more than a twofold performance improvement over the conventional system of up to a 65 μm depth below the coverslip investigated in this study.

Design and analysis of extended depth of focus metalenses for achromatic computational imaging

“…The axial intensity distribution of the shifted axicon resembles that of a diffractive axicon lens 28 , hence the nomenclature. The SQUBIC metasurface was first demonstrated by Patwary to have EDOF properties 29 . The phase mask directs a collimated light beam into a line of discrete foci, achieving an EDOF, and is given by the equation:…”

“…where 1 = sin (# (L<), given that L< is the nominal numerical aperture of the optics. Here, < is a design parameter that determines the strength of the phase mask 29 . In our design, we set < = 50…”

“…Although several methods exist to restore the image #, given P and O, we chose to use Wiener deconvolution 29 due to its effectiveness and simplicity. The normal metalens exhibits such a high level of chromatic aberration that we were unable to restore the raw images with any reasonably good results.…”

Experimental Demonstration of Genetic Algorithm Based Metalens Design for Generating Side‐Lobe‐Suppressed, Large Depth‐of‐Focus Light Sheet

“…In order to provide an insight into the formation of our light sheet and demonstrate the unique advantage of our proposed 2D light sheet in LSFM, we make a comparative study in Figure 4, of the optical patterns created by 1D metalenses with a respective cylindrical lens, SQUBIC lens and perturbed prism phase profile. [51][52][53] The 2D SQUBIC metalens, as well as other metalenses with analytical phase profiles such as axicon, [14][15][16] shiftedaxicon, [51] and log-aspherical lens, [51,54] can be used to generate 3D optical focusing with extended DOF and weak side lobes. See Figure S3 in Section SIII, Supporting Information, for discussion on the 3D patterns and the optical properties of SQUBIC, shiftedaxicon, and log aspherical metalenses.…”

Optical Aberration Calibration and Correction of Photographic System Based on Wavefront Coding

“…Another way to mitigate optical aberrations operates by adding masks to the optical system to encode the wavefront, including amplitude masks [12,13] and phase masks [14][15][16]. However, amplitude masks can block a portion of the incident light, and very fine printing patterns can cause diffraction artifacts [12].…”