Co-design of an in-line holographic microscope with enhanced axial resolution: selective filtering digital holography

TL;DR

This paper presents a co-designed optical and data processing approach for in-line holography that enhances axial resolution by reducing reference field dominance, achieving a 60% improvement in localization accuracy.

Contribution

The authors introduce a novel in-line holography setup with a 4-f device and inverse problem reconstruction, significantly improving axial resolution over traditional methods.

Findings

Achieved 60% gain in axial localization accuracy.

Theoretical analysis shows advantages of the co-design approach.

Implementation is cost-effective and maintains robustness against environmental variations.

Abstract

Common-path digital in-line holography is considered as a valuable 3D diagnostic techniques for a wide range of applications. This configuration is cost effective and relatively immune to variation in the experimental environment. Nevertheless, due to its common-path geometry, the signal to noise-ratio of the acquired hologram is weak as most of the detector (i.e. CCD/CMOS sensor) dynamics is occupied by the reference field signal, whose energy is orders of magnitude higher than the field scattered by the imaged object. As it is intrinsically impossible to modify the ratio of energy of reference to the object field, we propose a co-design approach (Optics/Data Processing) to tackle this issue. The reference to object field ratio is adjusted by adding a 4-f device to a conventional in-line holographic setup, making it possible to reduce the weight of the reference field while keeping the object field almost constant. Theoretical analysis of the Cr\`amer-Rao lower bounds of the corresponding imaging model illustrate the advantages of this approach. These lower bounds can be asymptotically reached using a parametric inverse problems reconstruction. This implementation results in a 60 % gain in axial localization accuracy (for of 100 $\mu$m diameter spherical objects) compared to a classical in-line holography setup .