Holographic Microscopy Techniques for Multifocus Phase Imaging of Living Cells - Biomedical Optical Phase Microscopy and Nanoscopy - page 94

6.2.1 Fiber Optic Modular DHM

Figure 6.1 shows a fiber optic Mach Zehnder interferometer concept for DHM, designed
for the integration into common commercial research microscopes and for the investigations
on transparent specimens such as living cells [27] . The light of a laser (e.g., a frequency-
doubled Nd:YAG laser, λ 5 532 nm with a large coherence length . 1 m) is divided into

object illumination wave (object wave) and reference wave. For variable light guidance
polarization maintaining, single-mode optical fibers are used. The illumination of the
sample with coherent laser light is performed in transmission by coupling the object wave
into the microscope's condenser. Thus, an optimized illumination similar to the Koehler
concept [28] is achieved.

For imaging, common microscope objectives are utilized. The reference wave is guided
directly to an interferometric unit that is adapted to one of the microscope's camera ports.
Off-axis holography is achieved by a beam splitter that tilts the reference wave front against

White light
source

Polarization
maintaining
optical fiber

Object
wave

Polarizing
beam splitter

Condenser
lens

Cell culture

z

Medium

Stage

Fiber
coupler

y x

Microscope
lens

λ /2

Fiber
coupler

λ /2

Tube lens

Reference
wave

Polarizing
beam splitter

λ /2

Beam
splitter

Polarization
maintaining
optical fiber

Polarizer
Shutter

Z H
Z IP

Δ z CCD

Figure 6.1
Schematic of the fiber optic modular integration of digital holography into an iMIC for live cell
imaging. Source: Modified from Ref. [27] .