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1. Phase-shifting interferometry in fiber-based channeled spectropolarimetry

   https://doi.org/10.1117/12.2529975  

   Altaqui, Ali; Kudenov, Michael W. (September 2019, Polarization Science and Remote Sensing IX)

   Channeled spectropolarimetry measures the spectral dependence of the polarization states of light. This technique is marked by its snapshot feature, in that the complete polarization states can be determined simultaneously from a single intensity spectrum. However, without athermalization, it suffers from high sensitivity to temperature, which in turn, degrades the polarimetric reconstruction accuracy. In this paper, we present a calibration technique for a fiber-based channeled spectropolarimetry that leverages phase-shifting interferometry to accurately demodulate the retarders' phase, thereby improving the accuracy of the acquired Stokes parameters. Additionally, it enables robust spectropolarimetric performance that is insensitive to environmental perturbations. Experimental results demonstrate that calibrations using phase-shifting interferometry improve the Stokes reconstruction results by approximately a factor of 3 when compared to the reference beam calibration method. 

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2. Snapshot phase-shifting diffraction phase microscope

   https://doi.org/10.1364/OL.394033  

   Tian, Xiaobo; Liang, Rongguang (June 2020, Optics Letters)

   We propose a novel and simple snapshot phase-shifting diffraction phase microscope with a polarization grating and spatial phase-shifting technology. Polarization grating separates the incident beam into left and right circular polarization beams, one of which is used as the reference beam after passing through a pinhole. Four phase-shifted interferograms can be captured simultaneously from the polarization camera to reconstruct the high spatial resolution phase map. The principle is presented in this Letter, and the performance of the proposed system is demonstrated experimentally. Due to the near-common-path configuration and snapshot feature, the proposed system provides a feasible way for real-time quantitative phase measurement with minimal sensitivity to vibration and thermal disturbance. 

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3. Comparative analysis of circular and linear fringe projection profilometry: from calibration to 3D reconstruction

   https://doi.org/10.1364/OPTCON.520433  

   Li, Jiaqiong; Li, Beiwen (March 2024, Optics Continuum)

   This study compares the accuracy of circular and linear fringe projection profilometry in the aspects of system calibration and 3D reconstruction. We introduce, what we believe to be, a novel calibration method and 3D reconstruction technique using circular and radial fringe patterns. Our approach is compared with the traditional linear phase-shifting method through several 2 × 2 experimental setups. Results indicate that our 3D reconstruction method surpasses the linear phase-shifting approach in performance, although calibration efficiency does not present a superior performance. Further analysis reveals that sensitivity and estimated phase error contribute to the relative underperformance in calibration. This paper offers insights into the potentials and limitations of circular fringe projection profilometry. 

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4. System design of a single-shot reconfigurable null test using a spatial light modulator for freeform metrology

   https://doi.org/10.1364/OL.44.002000  

   Chaudhuri, R; Papa, J; Rolland, J (April 2019, Optics letters)

   We report the simulation of an adaptive interferometric null test using a high-definition phase-only spatial light modulator (SLM) to measure form and mid spatial frequencies of a freeform mirror with a sag departure of 150 μm from its base sphere. A state-of-the-art commercial SLM is modeled as a reconfigurable phase computer generated hologram (CGH) that generates a nulling phase function with close to an order of magnitude higher amplitude than deformable mirrors. The theoretical uncertainty in form measurement arising from pixelation and phase quantization of the SLM is 50.62 nm RMS. The calibration requirements for hardware implementation are detailed. © 2019 Optical Society of America https://doi.org/10.1364/OL.44.002000 

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5. 2D beam shaping via 1D spatial light modulator using static phase masks

   https://doi.org/10.1364/OL.419419  

   Whitehead, James_E_M; Ryou, Albert; Colburn, Shane; Zhelyeznyakov, Maksym; Majumdar, Arka (May 2021, Optics Letters)

   Many emerging, high-speed, reconfigurable optical systems are limited by routing complexity when producing dynamic, two-dimensional (2D) electric fields. We propose a gradient-based inverse-designed, static phase-mask doublet to generate arbitrary 2D intensity wavefronts using a one-dimensional (1D) intensity spatial light modulator (SLM). We numerically simulate the capability of mapping each point in a 49 element 1D array to a distinct $7\times <\#comment/>7$2D spatial distribution. Our proposed method will significantly relax the routing complexity of electrical control signals, possibly enabling high-speed, sub-wavelength 2D SLMs leveraging new materials and pixel architectures. 

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