arXiv subjects

Pranay Mohta

Publications and source records attributed to Pranay Mohta.

4 recordsLinked to original sources

arXiv2026

Spatial coherence enabled sensorless adaptive optical imaging

Optical aberrations degrade imaging performance in label-free microscopy, where the absence of a guide star often necessitates sensorless adaptive optics (AO). Conventional sensorless AO approaches rely on image-quality metrics whose optimal choice depends on both the specimen and the imaging modality. Here, we present a guide-star-free AO framework based on the spatial coherence properties of spatially incoherent light. The proposed method exploits aberration-induced broadening of the measured spatial correlation distribution as the feedback signal for aberration correction. Experiments in a conventional bright-field imaging system using standard LED illumination demonstrate successful correction of phase aberrations. Furthermore, the approach remains effective even in the presence of spatially structured background noise. These results establish spatial coherence measurements as an effective feedback mechanism for sensorless AO and indicate that the correlation-based feedback principle employed in quantum-assisted AO can likewise be realized using the spatial correlations of incoherent light.

physics.optics↗

arXiv2026

Noise-Resilient Imaging through Coherence Filtering

Noise is a significant challenge in imaging. Conventional intensity-based techniques mitigate noise through various filtering methods, but they often require prior knowledge of noise characteristics and struggle, especially under low-light conditions and with spatially structured noise. Quantum distillation provides enhanced noise rejection; however, its applicability is limited as it requires specialised illumination and substantial modifications to existing imaging setups. In this article, we introduce a coherence-based image distillation approach that separates object from noise by leveraging the difference in their temporal coherence properties. We implement this through our interferometric protocol, which enables imaging based on spatial coherence while simultaneously filtering out noise via temporal coherence. This overcomes the limitations of both intensity-based and quantum distillation methods. We experimentally demonstrate noise resilience by successfully recovering feature-rich objects, such as QR codes and grayscale wheels, obscured by spatially uniform and structured noise 20 times as intense as the object. We further show that our method remains effective for fields with substantial spectral overlap, outperforming spectral filtering in regimes where the latter provides little noise suppression. This approach provides a robust framework for noise-resilient imaging with applications in optical communication, fluorescence microscopy, and biological imaging at both high and low light levels.

physics.optics↗

arXiv2024

Eight-shot measurement of spatially non-stationary complex coherence function

Spatial coherence plays an important role in several real-world applications ranging from imaging to communication. As a result, its accurate characterization and measurement are extremely crucial for its optimal application. However, efficient measurement of an arbitrary complex spatial coherence function is still very challenging. In this letter, we propose an efficient, noise-insensitive interferometric technique that combines wavefront shearing and inversion for measuring the complex cross-spectral density function of the class of fields, in which the cross-spectral density function depends either on the difference of the spatial coordinates, or the squares of spatial coordinates, or both. This class of fields are most commonly encountered, and we experimentally demonstrate high-fidelity measurement of many stationary and non-stationary fields.

physics.optics↗

arXiv2022

Quantifying polarization changes induced by rotating Dove prisms and K-mirrors

Dove prisms and K-mirrors are devices extensively used for rotating the wavefront of an optical field. These devices have several applications, including measurement of orbital angular momentum, microscopy, beam steering and pattern recognition. However, the wavefront rotation achieved through these devices is always accompanied by polarization changes in the incident field, which is an undesirable feature in many of these applications. Although the polarization changes induced by a Dove prism have been explored to quite some extent, no such study is available for a K-mirror. In this letter, we theoretically and experimentally investigate polarization changes induced in the transmitted field by a rotating K-mirror. For quantifying such polarization changes, we define a quantity, mean polarization change D, which ranges from 0 to π. We find that K-mirrors can reduce D to about 0.03π, for any incident state of polarization; however, reducing D to the same extent with a Dove prism is practically unviable. Therefore, K-mirrors are better alternatives to Dove prisms in applications in which the polarization changes accompanying wavefront rotation need to be minimum.

physics.optics↗