Speckle-free common-path quantitative phase imaging with high temporal phase stability using a partially spatially coherent multi-spectral light source

Abstract

Quantitative phase imaging (QPI) has been an important technique for the determination of various biophysical parameters, such as the refractive index and morphology of biological cells and tissues. The technique has been implemented using off-axis and common path digital holographic microscopy (DHM). Off-axis DHM, though being ideal for QPI, offers lower temporal phase stability compared to common path techniques. Common path DHM offers a higher temporal phase stability but, being a coherent imaging technique, suffers from speckle artefacts and spurious interference fringes due to the high coherence of the light source. Both artefacts not only degrade the image quality, but also affect the phase measurement results. In this paper, we report the implementation of common path QPI set-up using a partially spatially coherent multi-spectral light source. The spatial coherence of the red and green color lasers is reduced by using a rotating diffuser. Also, a speckle free QPI was implemented using common path Fresnel biprism interferometer. A Fresnel biprism is used in the self-referencing mode, thus offering the advantage of no optical power loss in addition to high temporal stability and the least speckle artefacts. Furthermore, it is very easy to implement, as the system completely replaces the need for spatial filtering at the source end as well as for the reference beam generation. The experiments have been carried out on industrial and biological samples to prove the effect.

Single-Shot 3D Topography of Transmissive and Reflective Samples with a Dual-Mode Telecentric-Based Digital Holographic Microscope

“…Common-path DHM systems rely on the principle that both interfering waves travel nearly the same optical path, making them the most stable and robust DHM systems. These common-path DHM systems require the use of an optical element such as a diffraction grating [ 26 , 27 ], a Wollaston prism [ 28 ], a lateral shear plate [ 29 , 30 ], a beamsplitter [ 31 , 32 , 33 ], or a Fresnel biprism [ 34 , 35 , 36 , 37 ] to generate a self-interference pattern. The hallmarks of common-path systems are their temporal stability and compactness, making them suitable for implementation as an external module in current commercial microscopes.…”

Single-Element Reflective Digital Holographic Microscopy

“…Among all CPIs described in the literature, there are some of them that employ just one optical element to produce interferences, such as a Lloyd's mirror [28], a thick glass plate [26], a diffraction grating [29], a beam splitter cube [30], or a Fresnel's biprism [31][32][33][34]. Those reduce even more the price and the complexity of CPIs and present a very simple usability.…”

Advantages of Fresnel biprism-based digital holographic microscopy in quantitative phase imaging

“…More recently, a FB-based DHM system has been proposed for a multiwavelength approach. 26 In a close related work, Ebrahimi et al 27 proposed an off-axis lensless DHM system using a FB. Because the system follows an off-axis configuration, meaning that there is no overlay between the different orders composing the Fourier spectrum of the recorded hologram, one can retrieve both amplitude and phase distributions by means of just spatial filtering the object frequencies from the spectrum of the single hologram.…”

“…More recently, a FB-based DHM system has been proposed for a multiwavelength approach. 26 In a close related work, Ebrahimi et al. 27 proposed an off-axis lensless DHM system using a FB.…”