Quantitative phase imaging using Transport of Intensity equation

Bhardwaj, Rahul and John, Renu (2019) Quantitative phase imaging using Transport of Intensity equation. Masters thesis, Indian institute of technology Hyderabad.

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Abstract

When light strikes at an object, its details are engraved on wave’s three properties (amplitude, wavelength and phase). Amplitude and wavelength are associated to brightness and color, whereas phase is a prime element of an optical wave field carrying the information of the refractive index, optical thickness, or the geometrical properties of the specimen. Most of the biological samples such as cells are phase objects, resulting in only small variations in the amplitude of transmitted light through the cell. The transport-of-intensity equation (TIE) expresses the internal relationship between the intensity and phase distribution while the wave is propagating in the space. Transport of Intensity Equations Microscopy (TIEM) has a relatively uncomplicated experimental set-up, easily implementable with white light illumination and is cost-effective. The TIE technique benefits from operating with a commercial bright field microscope In general, TIE necessitate one in-focus and two defocused images to be recorded along the optical axis for the reconstruction of phase images and in order to precisely define the focal plane, we have implemented computational algorithm for optimum focal plane determination. We also worked on quantitative phase reconstruction based on TIEM of a phase object and microfluidic channel. We translated the table top experimental setup to a cost-effective setup for TIEM using Raspberry-pi in this thesis. Further, we have also carried out the quantitative phase imaging of live specimen (yeast cell) on the basis of conventional TIEM. Usually multiple recorded focus and defocus images are required for the phase recapturing which impedes the live cell imaging application. Therefore, we have developed an algorithm to reconstruct objects information using a single defocused image.

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