A comparative study of lens-less and lens-based optical imaging using full electric field analysis

Abstract

The focus of this thesis is to investigate the feasibility of a lens-less label-free microscope system, and compare this with a conventional lens-based microscope. The imaging performance of conventional microscopes are greatly dependent on the objective lens, due to their inherent physical space constraint and spherical aberrations. We, therefore, will investigate the conceptual feasibility of a lens-less label-free microscope, by analyzing the electromagnetic scattering directly.

Here, a lens-less design is considered. Imaging is achieved through the reconstruction of refractive index of specimens using full-electric-field analysis. The imaging performances are compared with results from lens-based microscopes. We will also briefly discuss intensity-only reconstruction, and discuss the benefits and weaknesses of such a technique.

While lens-based systems are limited by physical space limitations, the limitations of the lens-less system is similar and harder to overcome. Additionally, the lens-based system shows a non-linear proportionality with wavelengths, that the lens-less system is incapable of. The difference in setup and reconstruction results makes a preferred method dependent on the use case.

The possibility of intensity-only imaging is considered. The methods explored are phase reconstruction and a modified MUSIC algorithm.