Digital in-line holography in thick optical systems: application to visualization in pipes

TL;DR

This paper demonstrates the use of digital in-line holography with fractional Fourier transform to image opaque objects inside thick pipes, overcoming limitations of classical models and compensating for astigmatism.

Contribution

It introduces a new analytical model for digital in-line holography in thick optical systems, enabling effective imaging through complex pipe geometries.

Findings

Successfully reconstructs holograms through 12 mm thick pipes

The model compensates for astigmatism in thick optical systems

Numerical and experimental validation confirms effectiveness

Abstract

In this paper we apply digital in-line holography to image opaque objects through a thick plano-concave pipe. Opaque fibers and opaque particles are considered}. Analytical expression of the intensity distribution in the CCD sensor plane is derived using generalized Fresnel transform. \textbf{The proposed model has the ability to deal with various pipe shape and thickness and compensates for the lack of versatility of classical DIH models. Holograms obtained with a 12 mm thick plano-concave pipe are then reconstructed using fractional Fourier transform (FRFT).} This method allows us to get rid of astigmatism. Numerical and experimental results are presented.