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1. Variable extended depth of field imaging using freeform optics

   https://doi.org/10.1117/12.2568723  

   Moein, Sara; Suleski, Thomas J. (August 2020, SPIE Optical Engineering + Applications, 2020, Online Only)

   Hahlweg, Cornelius F.; Mulley, Joseph R. (Ed.)

   Increasing depth of field in imaging systems can be beneficial, particularly for systems with high numerical apertures and short depth of field, such as microscopy. Extending depth of field has been previously demonstrated, for example, using non-rotationally symmetric (freeform) components such as cubic and logarithmic phase plates. Such fixed phase plates are generally designed for a specific optical system, so a different phase plate is required for each system. Methods that enable variable extended depth of field for multiple optical systems could provide benefits by reducing the number of required components and costs. In this paper, we explore the design of a single pair of transmissive freeform surfaces to enable extended depth of field for multiple lenses with different numerical apertures through relative translation of the freeform components. This work builds on the concept of an Alvarez lens, in which one pair of transmissive XY-polynomial freeform surfaces generates variable optical power through lateral relative shifts between the surfaces. The presented approach is based on the design of multiple fixed phase plates to optimize the through-focus Modulation Transfer Function (MTF) for imaging lenses of given numerical apertures. The freeform surface equation for the desired variable phase plate pair is then derived and the relative shift amounts between the freeform surfaces are calculated to enable extended depth of field for multiple imaging lenses with different numerical aperture values. Design approaches and simulation results will be discussed. © (2020) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only. Citation Download Citation Sara Moein and Thomas J. Suleski "Variable extended depth of field imaging using freeform optics", Proc. SPIE 11483, Novel Optical Systems, Methods, and Applications XXIII, 114830G (21 August 2020); https://doi.org/10.1117/12.2568723 

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2. PSF engineering with variable logarithmic phase plates for the extended depth of field

   https://doi.org/10.1364/OPTCON.465138  

   Moein, Sara; Shadalou, Shohreh; Suleski, Thomas J. (January 2022, Optics Continuum)

   Shallow depth of field in imaging systems with high numerical apertures results in images with in- and out-of-focus regions. Therefore, methods to enhance the depth of field are of special interest. In point spread function engineering, a custom phase plate is designed for each system to reduce sensitivity to defocus and thereby extend depth of field. In this paper, we present a method that enables extended depth of field for a range of numerical apertures using a freeform variable logarithmic phase plate pair. We leverage a numerical design approach for the variable phase plate pair design, and explore phase plate optimization and performance by quantifying and comparing through-focus point spread function variation, and on- and off-axis performance for the designed phase plates. 

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3. Probing Interfacial Nanostructures of Electrochemical Energy Storage Systems by In-Situ Transmission Electron Microscopy

   https://doi.org/10.1007/s40820-025-01720-5  

   Liang, Guisheng; Zhang, Chang; Yang, Liting; Liu, Yihao; Liu, Minmin; Xiong, Xuhui; Yang, Chendi; Lv, Xiaowei; You, Wenbin; Pei, Ke; et al (December 2025, Nano-Micro Letters)

   Abstract The ability to control the electrode interfaces in an electrochemical energy storage system is essential for achieving the desired electrochemical performance. However, achieving this ability requires an in-depth understanding of the detailed interfacial nanostructures of the electrode under electrochemical operating conditions. In-situ transmission electron microscopy (TEM) is one of the most powerful techniques for revealing electrochemical energy storage mechanisms with high spatiotemporal resolution and high sensitivity in complex electrochemical environments. These attributes play a unique role in understanding how ion transport inside electrode nanomaterials and across interfaces under the dynamic conditions within working batteries. This review aims to gain an in-depth insight into the latest developments of in-situ TEM imaging techniques for probing the interfacial nanostructures of electrochemical energy storage systems, including atomic-scale structural imaging, strain field imaging, electron holography, and integrated differential phase contrast imaging. Significant examples will be described to highlight the fundamental understanding of atomic-scale and nanoscale mechanisms from employing state-of-the-art imaging techniques to visualize structural evolution, ionic valence state changes, and strain mapping, ion transport dynamics. The review concludes by providing a perspective discussion of future directions of the development and application of in-situ TEM techniques in the field of electrochemical energy storage systems. 

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4. Fabrication and characterization of freeform phase plates for extended depth of field imaging

   https://doi.org/10.1364/OPTCON.480895  

   Moein, Sara; Gurganus, Dustin; Davies, Matthew_A; Boreman, Glenn_D; Suleski, Thomas_J (March 2023, Optics Continuum)

   Point spread function engineering uses specially designed phase plates placed at the exit pupil of an imaging system to reduce defocusing sensitivity. A custom phase plate is typically required for each system to enable extended depth of field imaging, so methods enabling variable extended depth of field imaging are of particular interest. In this paper, we discuss the fabrication of previously designed fixed cubic phase plates and variable phase plate pairs with quartic surface profiles and present a novel application of a point source microscope for performance characterization. Experimental measurements of through-focus point spread functions are compared with predictions to demonstrate and characterize the extended depth of field for both fixed and variable freeform phase plates. 

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5. Freeform optics for variable extended depth of field imaging

   https://doi.org/10.1364/OE.439980  

   Moein, Sara; Suleski, Thomas_J (November 2021, Optics Express)

   Imaging depth of field is shallow in applications with high magnification and high numerical aperture, such as microscopy, resulting in images with in- and out-of-focus regions. Therefore, methods to extend depth of field are of particular interest. Researchers have previously shown the advantages of using freeform components to extend depth of field, with each optical system requiring a specially designed phase plate. In this paper we present a method to enable extended depth-of-field imaging for a range of numerical apertures using freeform phase plates to create variable cubic wavefronts. The concept is similar to an Alvarez lens which creates variable spherical wavefronts through the relative translation of two transmissive elements with XY polynomial surfaces. We discuss design and optimization methods to enable extended depth of field for lenses with different numerical aperture values by considering through-focus variation of the point spread function and compare on- and off-axis performance through multiple metrics. 

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