We studied quantitative phase imaging (QPI) using coherent laser illumination coupled with static and moving optical diffusers. The spatial coherence of a continuous-wave laser was controlled by tuning the particle size and the diffusion angle of optical diffusers for speckle-reduced 3D phase imaging of transparent objects. We used a common-path QPI configuration to investigate the coherent phase mapping of polystyrene micro-beads and breast cancer cells (MCF-7) under different degrees of coherent speckles. The proposed speckle reduction method could provide an avenue for enhancing lateral resolution and suppressing coherent artifacts of the phase images from QPI.

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High coherence of lasers is desirable in high-speed, high-resolution, and wide-field imaging. However, it also causes unavoidable background speckle noise thus degrades the image quality in traditional microscopy and more significantly in interferometric quantitative phase imaging (QPI). QPI utilizes optical interference for high-precision measurement of the optical properties where the speckle can severely distort the information. To overcome this, we demonstrated a light source system having a wide tunability in the spatial coherence over 43% by controlling the illumination angle, scatterer’s size, and the rotational speed of an electroactive-polymer rotational micro-optic diffuser. Spatially random phase modulation was implemented for the lower speckle imaging with over a 50% speckle reduction without a significant degradation in the temporal coherence. Our coherence control technique will provide a unique solution for a low-speckle, full-field, and coherent imaging in optically scattering media in the fields of healthcare sciences, material sciences and high-precision engineering.

Hybrid optical elements, which combine refractive and diffractive optical components to enhance the optical performances by taking advantage of the optical characteristics of the individual components, have enormous potential for next-generation optical devices. However, there have not been many reports on the simulation methodology to characterize such hybrid optical systems. Here, we present a method for simulating a hybrid optical element realized by attaching an ultra-thin, flexible diffractive optics array onto a refractive optical element. The ultra-thin diffractive optical element is fabricated by direct-laser-writing technique using a femtosecond pulsed laser as the light source. A systematic investigation of the proposed simulation method, which does not require extensive hardware resources or computational time without sacrificing resolution and accuracy, is presented. The proposed scheme is validated by comparing simulation and experimental results. Simulation and experimental results on the spot size and focal length for the diffractive Fresnel zone plate (FZP) match well with typical errors of less than 6%. The aspect ratio of the focal spot sizes at the compound and FZP focal planes of the hybrid optical system from the simulation and experiment also match quite well with typical errors below 7%. This simulation scheme will expedite the designs for novel hybrid optical systems with optimal optical performances for specific applications, such as microfluidics and aberration-controlled optics.

Coherent imaging enables noninvasive, label‐free, and quantitative monitoring of the dynamic motions of transparent microobjects requested in life sciences, biochemistry, material sciences, and fluid mechanics. Quantitative phase imaging (QPI), a coherent imaging technique, provides full‐field optical phase information through light interference. The use of coherence, however, inevitably accompanies phase ambiguity and coherent artifacts, such as speckle, diffraction, and parasitic interference, which severely deteriorate the interferograms to hinder successful phase reconstruction. Herein, it is demonstrated that a frequency comb can newly provide a wide coherence tunability for higher visibility interferograms, phase‐coherent multiple wavelengths for extracting physical height information from refractive index, and higher phase stability (2.39 × 10−3 at 10 s averaging time) at a higher speed up to 16.9 kHz. These superior characteristics of frequency‐comb‐referenced QPI will enable in‐depth understanding of dynamic motions in cellular, biomolecular, and microphysical samples.