Coherent imaging of extended objects

TL;DR

This paper investigates how coherent imaging systems distort the intensity and phase of extended objects, revealing limitations in imaging large or specially shaped objects, supported by theoretical analysis and experiments.

Contribution

It introduces a detailed analysis of non-isoplanatism effects in coherent imaging of extended objects, highlighting distortions not previously well-characterized.

Findings

Intensity distribution can be significantly distorted for large or specially shaped objects.

Theoretical predictions are confirmed by experimental observations.

Non-isoplanatism affects phase and amplitude reproduction in coherent imaging.

Abstract

When used with coherent light, optical imaging systems, even diffraction-limited, are inherently unable to reproduce both the amplitude and the phase of a two-dimensional field distribution because their impulse response function varies slowly from point to point (a property known as non-isoplanatism). For sufficiently small objects, this usually results in a phase distortion and has no impact on the measured intensity. Here, we show that the intensity distribution can also be dramatically distorted when objects of large extension or of special shapes are imaged. We illustrate the problem using two simple examples: the pinhole camera and the aberration-free thin lens. The effects predicted by our theorical analysis are also confirmed by experimental observations.