Project:Digital Holographic Miocroscope

ProjectInfoBox Digital Holographic Microscope
Status:	being built
Initiator:	Patrick, Lennart

Introduction

Holmos

This project is based on project Holmos (https://github.com/holmos-ipm) by Fraunhofer IPM.

Digital Holographic Microscopy

Wikipedia https://en.wikipedia.org/wiki/Digital_holographic_microscopy

This file explains the constraints in optical adjustment https://github.com/holmos-ipm/holmos-hardware/blob/master/instructions/optics_design.md

Assembly

Mounts for the optical components can be printed from files provided in the project repo. These can then be axially moved on metal beams. A Raspberry Pi camera is used for imaging. It is connected to a Raspberry Pi that performs the phase image reconstruction.

Several components can be 3D-printed either from ready-to-use STL files or 3D files generated with Solidpython

Usage

Key steps are

1. Position the components according to https://github.com/holmos-ipm/holmos-hardware/blob/master/reference_assembly.py
2. Adjust slide holder or objective to get a focused image from the objective beam only
3. Direct the reference beam onto the camera sensor

Further practical instructions are given in https://github.com/holmos-ipm/holmos-hardware/blob/master/instructions/adjustment.md

In the Holmos Fourier amplitude view, the first diffraction order is selected as ROI. Then, the captured ("wrapped") phase image is saved on the hard drive. In a separate application, this image is then "unwrapped", e.g. black to white jumps due to the restricted value range of -π to π are removed.

Fourier amplitude view in the Holmos UI. The blue rectangle is moved to encompass the first diffraction order and surrounding frequences stemming from the interference of the reference beam and light passing the sample.

Results

• Quantitative phase image reconstructed from a cheek cell hologram.
• 

  Interference image captured by the camera

• 

  Fourier amplitude in which the information of interest is encoded in the frequencies around the first diffraction order

• 

  Wrapped phase image reconstructed from the ROI in the Fast Fourier Transform

• 

  Unwrapped phase image