Development of a digital holographic microscope model for the investigate of structures in the optical range

Abstract

One of the modern and relevant methods for investigating the structures of objects is based   on  the  holographic  method  of  recording  signals  (holographic  microscopy).  The  main  advantage  of  this  method  is  the  ability  to  obtain  complete  information  about  the  object.  In  other  words,  this  method makes it possible to record not only the amplitude, but also the phase of the wave. This is achieved thanks to a recording scheme in which the phase of the wave is some modulation of the intensity. This advantage makes holographic microscopy an effective tool for the investigate of particles/microparticles  in gases, liquids and solid materials in the form of thin films or in sufficiently transparent materials for optical  waves  (one  of  the  main  limitations  of  the  holographic  recording  scheme  is  to  investigate  only  objects with high transmissivity, i.e. the reference wave is must be about 70% or more of the total wave). Within the framework of this work, we consider the scheme of in-line holography (Gabor holography). The undoubted advantage of the in-line holographic investigation method is that it is limited only by the wavelength range. In other words, by changing the wavelength of the source, a wide range of objects can be examined. For example, in-line holography is used in low energy electron microscopes, which allows the atomic structure of an object to be studied. In the case when the source is  a laser (optical range),  a holographic microscope provides a wide range of possibilities for investigation the micro-objects, from various  bacteria  to  various  fine–structured  particles.  We  developed  a  model  of  a  digital  holographic microscope  for  the  study  of  structures  in  the  optical  range,  based  on  the  Gabor  in-line  holography  method. This model of the microscope is developed on the Raspberry Pi Zero 2W platform.