LED-based digital holographic microscopy with slightly off-axis interferometry

Abstract

An LED illuminated Linnik-type digital holographic microscope (DHM) for high-quality phase imaging is presented by the adoption of slightly off-axis two-step blind-phase-shifting interferometry (TB-PSI). Slightly off-axis interferometry lowers the requirement on the angle between the object and the reference waves as well as the requirement on the resolving power of the charge-coupled device (CCD) camera. In addition, the apparatus is cost-effective and offers ease of alignment. The phase-shifting DHM is simply implemented by mechanically moving the reference mirror while disposing of a precise phase modulator such as a piezoelectric transducer (PZT). The phase shift between the two interferograms is extracted by Fourier transformation analysis, and then the phase image is reconstructed. The performance of the TB-PSI used in the scheme is analyzed. The phase imaging for nanostructured specimens is conducted, and the results demonstrate the feasibility of the scheme. The phase noise is reduced by 73% when compared to the result obtained with coherent illumination.

Quantitative phase imaging via Fresnel biprism-based digital holographic microscopy

“…This coherent artefact noise can be overcome using partially coherent source. It is worth mentioning that LED source has been widely used for QPI in DHM [11]. The LED-based DHM not only reduce the coherent noise but also make the system more compact.…”

Microsphere-assisted super-resolved Mirau digital holographic microscopy for cell identification

“…Recently, a self-referencing common-path geometry for DHMicroscopy was demonstrated by the use of a Lloyd's mirror configuration [5], by applying lateral shearing through a glass plate [6], and also by a microscope binocular module [7]. Another possibility to provide common-path DHMicroscopy is to employ interferometric objectives, such as a (modified) Michelson objective [8], Linnik [9], and a Mirau objective [10]. The Michelson objectives provide rather longer working distances, wider fields of view, and larger depths of focus, whereas the Mirau microscope objectives (Mirau-MOs) are used in applications requiring higher magnification and numerical apertures.…”

Single-shot, dual-mode, water-immersion microscopy platform for biological applications

“…Since the first evidences on DHM [17][18][19], a wide range of applications have been reported in the literature enabling DHM as a high-resolution multi-in-focus imaging method for polarization microscopy imaging [20], aberration lens compensation [21], particle tracking [22], extended depth of field imaging [23], microelectromechanical systems inspection [24], 3-D dynamic analysis of cells [25] and refractive index characterization [26][27][28], just to cite a few. Because of its interferometric underlying principle, DHM has been implemented using different classical interferometric configurations [29][30][31][32][33][34] being the most used one the Mach-Zehnder interferometric layout [8,9,11,12,17,19]. Nevertheless and considering illumination by transmission, common-path interferometric (CPI) configuration [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] provides significant advantages over all previous architectures.…”