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arxiv: 2605.04297 · v1 · submitted 2026-05-05 · ⚛️ physics.optics

High-Sensitivity, High-Throughput Double Sagnac Lateral Shearing Quantitative Phase Microscopy and Tomography with Pseudo-Thermal Illumination

Pawel Goclowski , Maciej Trusiak , Balpreet S. Ahluwalia , Azeem Ahmad This is my paper

Pith reviewed 2026-05-08 17:11 UTC · model grok-4.3

classification ⚛️ physics.optics
keywords quantitative phase microscopylateral shearing interferometrySagnac interferometerpseudo-thermal illuminationphase tomographyHeLa cellsdiffraction-limited resolution
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The pith

A double Sagnac lateral shearing quantitative phase microscope with pseudo-thermal illumination achieves diffraction-limited resolution over a large field of view.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper presents a quantitative phase microscopy system built on a double Sagnac common-path interferometer paired with pseudo-thermal illumination. This combination is intended to deliver high phase sensitivity and temporal stability while removing the usual resolution-versus-field-of-view trade-off found in standard quadriwave lateral shearing setups. Pseudo-thermal light is used to cut coherent noise and speckle yet still produce dense fringes that support single-shot phase recovery. Experiments on polystyrene beads confirm uniform phase maps across the full imaging area, and demonstrations on HeLa cells show label-free capture of subcellular features in both fixed and live samples, along with basic volumetric tomography.

Core claim

The double Sagnac architecture with pseudo-thermal illumination allows quantitative phase imaging at diffraction-limited resolution across a large field of view, with enhanced stability and noise suppression compared to conventional quadriwave lateral shearing systems.

What carries the argument

The double Sagnac common-path interferometric configuration combined with pseudo-thermal illumination, which supplies stable high-density fringes and reduces speckle for single-shot phase retrieval.

If this is right

  • Accurate and spatially uniform phase values are recovered across the entire field using calibrated polystyrene beads.
  • Label-free imaging reveals subcellular structures and dynamic processes in fixed and live HeLa cells.
  • Three-dimensional phase tomography is demonstrated on embedded bead samples.
  • The lateral shearing geometry increases tolerance to multiple scattering, opening use with thicker specimens.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The noise-reduction property could support continuous label-free tracking of fast cellular events if acquisition speed is maintained.
  • Common-path stability elements might transfer to other interferometric modalities that currently require active locking.
  • Direct tests on scattering biological tissues would show how far the multiple-scattering robustness extends beyond bead phantoms.

Load-bearing premise

The pseudo-thermal illumination reduces coherent noise and speckle while still generating enough high-density interference fringes for reliable phase retrieval.

What would settle it

A side-by-side measurement of achieved spatial resolution and field-of-view size against a conventional QWLSI system, or a quantitative map of residual speckle amplitude in the reconstructed phase images.

read the original abstract

Quantitative phase microscopy (QPM) enables label-free measurement of local optical path length variations, providing critical insight into the structure and dynamics of transparent biological specimens. Here, a highly sensitive lateral shearing QPM (LS-QPM) system is presented, based on a novel double Sagnac common-path interferometric configuration combined with pseudo-thermal illumination. The pseudo-thermal light source plays a central role in enhancing spatial phase sensitivity by suppressing coherent noise and speckle artifacts, while maintaining sufficient temporal coherence to generate high-density interference fringes, thereby enabling robust single-shot phase retrieval. In addition, the double Sagnac architecture introduces an inherently stable common-path geometry, significantly enhancing temporal phase stability. Unlike conventional quadriwave lateral shearing interferometry (QWLSI)-based QPM systems, which typically suffer from a trade-off between spatial resolution and field of view (FOV), the proposed approach enables simultaneous achievement of diffraction-limited resolution and a large FOV. Experimental validation using calibrated polystyrene beads demonstrates accurate and spatially uniform phase reconstruction across the entire imaging area. Further, the system's capability for biological imaging is demonstrated through experiments on fixed and live HeLa cells, where subcellular features and dynamic processes are captured in a label-free manner. Furthermore, volumetric imaging of embedded bead samples highlights the potential of the approach for three-dimensional phase tomography. The lateral shearing mechanism, analogous to differential interference contrast (DIC), improves robustness to multiple scattering, indicating strong potential for future applications in imaging thick and heterogeneous samples.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The manuscript introduces a double Sagnac common-path lateral shearing quantitative phase microscopy (LS-QPM) system employing pseudo-thermal illumination. It claims this architecture simultaneously delivers diffraction-limited spatial resolution and a large field of view, suppresses coherent noise and speckle while retaining sufficient temporal coherence for high-density single-shot fringes, and provides high temporal phase stability. Experimental demonstrations on calibrated polystyrene beads show spatially uniform phase reconstruction, with additional results on fixed/live HeLa cells and volumetric bead tomography.

Significance. If the performance claims hold, the work would address a longstanding resolution-FOV trade-off in quadriwave lateral shearing interferometry (QWLSI) and offer a stable, label-free platform for dynamic biological imaging with improved robustness to multiple scattering, potentially enabling applications in thicker specimens.

major comments (1)
  1. [Abstract and illumination/results sections] The central claim that pseudo-thermal illumination suppresses speckle/coherent noise while preserving enough temporal coherence for high-density fringes and robust single-shot retrieval (abstract and likely §3–4) is asserted without quantitative metrics. No measured coherence length (e.g., Michelson autocorrelation), fringe visibility versus shear or path difference, or speckle contrast reduction factor relative to a coherent source is reported; this directly undermines assessment of whether the illumination meets the visibility threshold required by the phase-retrieval algorithm at the claimed fringe density and FOV.
minor comments (2)
  1. [Abstract and Results] The abstract states that bead experiments demonstrate 'accurate and spatially uniform phase reconstruction' but supplies no numerical values for phase accuracy, standard deviation, or comparison to ground truth; include these quantitative metrics and error bars in the corresponding results section and figures.
  2. [Figures and Methods] Figures comparing the proposed system to conventional QWLSI should explicitly label resolution, FOV, and stability metrics with scale bars and legends; ensure all experimental parameters (shear amount, illumination power, camera settings) are tabulated for reproducibility.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their detailed and constructive review of our manuscript. The major comment highlights an important point regarding the need for quantitative characterization of the pseudo-thermal illumination. We address this below and will incorporate the requested metrics in the revised version.

read point-by-point responses

  1. Referee: [Abstract and illumination/results sections] The central claim that pseudo-thermal illumination suppresses speckle/coherent noise while preserving enough temporal coherence for high-density fringes and robust single-shot retrieval (abstract and likely §3–4) is asserted without quantitative metrics. No measured coherence length (e.g., Michelson autocorrelation), fringe visibility versus shear or path difference, or speckle contrast reduction factor relative to a coherent source is reported; this directly undermines assessment of whether the illumination meets the visibility threshold required by the phase-retrieval algorithm at the claimed fringe density and FOV.

    Authors: We agree that explicit quantitative metrics were not included in the original submission and that their absence limits independent assessment of the illumination properties. In the revised manuscript we will add: (i) Michelson interferometer autocorrelation measurements to report the temporal coherence length of the pseudo-thermal source; (ii) fringe visibility data as a function of lateral shear and optical path difference, confirming that visibility remains above the threshold required by our single-shot phase-retrieval algorithm at the operating fringe density; and (iii) a direct comparison of speckle contrast obtained with the pseudo-thermal source versus a coherent laser source under identical imaging conditions. These additions will be placed in a new subsection of the methods/results and will be cross-referenced in the abstract and discussion. revision: yes

Circularity Check

0 steps flagged

No circularity; experimental claims rest on direct measurements, not derivations or self-referential fits

full rationale

The paper describes an optical instrument (double Sagnac LS-QPM with pseudo-thermal source) and supports its performance claims exclusively through experimental results on calibrated beads, HeLa cells, and tomographic volumes. No equations, first-principles derivations, parameter fits, or predictions appear in the provided text that could reduce to inputs by construction. The central assertions about resolution-FOV trade-off resolution and coherence balance are presented as outcomes of the physical setup and are validated by imaging data rather than any algebraic or self-citational loop. Self-citations, if present in the full manuscript, are not load-bearing for any claimed derivation.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The work is an experimental demonstration of an optical instrument. No new theoretical entities, free parameters fitted to data, or ad-hoc axioms beyond standard wave optics are introduced in the abstract.

axioms (1)
  • standard math Standard assumptions of wave optics, common-path interferometry, and lateral shearing phase retrieval hold for the described double Sagnac geometry.
    The system relies on established principles of interference and shearing interferometry without stating deviations.

pith-pipeline@v0.9.0 · 5591 in / 1240 out tokens · 58127 ms · 2026-05-08T17:11:52.635990+00:00 · methodology

discussion (0)

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Reference graph

Works this paper leans on

2 extracted references · 2 canonical work pages · 1 internal anchor

  1. [1]

    Conclusion: In this work, a common-path lateral shearing quantitative phase microscopy (LS-QPM) system has been developed and experimentally validated as a stable and versatile platform for quantitative phase imaging. The proposed module can be readily integrated into a conventional bright-field microscope, allowing straightforward implementation without ...

    work page 2022

  2. [2]

    High-Fidelity Single-Shot Quantitative Differential Phase Microscopy Using Pseudothermal Sagnac Interferometer

    Goclowski, P., et al., High-Fidelity Single-Shot Quantitative Differential Phase Microscopy Using Pseudothermal Sagnac Interferometer. arXiv preprint arXiv:2604.20739,

    work page internal anchor Pith review Pith/arXiv arXiv