![]() However, this improvement in the spatial coherence is accompanied by severe optical power attenuation (from several W to a few mW). Thermal light sources (halogen, xenon, and mercury lamps) and light emitting diodes (LEDs) have been widely used as the partially coherent light sources after the spatial filtering through a small-diameter pinhole ( ∼5–50 μm) spatial filtering provides a higher spatial coherence so enables the formation of higher visibility interferograms over a larger FOV. For the best biomedical laser imaging without speckle, diffraction, and edge effects, there have been considerable research works conducted to suppress the speckle noise in interferometric imaging 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24. On the other hand, the spatial coherence, required for the interferometric imaging over a large field-of-view (FOV), causes high-frequency speckle noises, which degrade overall image quality and measurement precision 7, 8. The temporal coherence, which is the prerequisite for the optical interferometry, causes unwanted scattered or diffracted beams from dusts, particles, roughness, or defects on the surface of optical components and makes them to interfere with the measurement beam this usually generates stationary low-frequency noises in the spatial domain. The coherence can be split into two, the temporal and spatial ones. In QPI, optical interference, enabled by the high degree of coherence of the lasers, superimposes unwanted background speckles so significantly hinders the successful phase reconstruction 1, 2, 3, 4, 5, 6. It is because the coherent artifacts, such as speckle, diffraction, and intensity overshoot around the edges, degrade the image quality severely in both tradiational non-coherent imaging and coherenent quantitative phase imaging (QPI). ![]() However, the random scattering in imaging systems caused by coherenet laser field works as the primary obstacle for the optical imaging. These commonly require a high brightness light illumination over a wide field-of-view, which can get benefits by introducing coherent lasers as the light source. biological tissues, plasmonic nanoparticles, and non-ideal optics with surface roughness or contamination, has been highly requested in the field of biological science, material science, medical diagnosis, and precision engineering. High-speed and high-resolution optical imaging through scattering optical media, e.g. 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. 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. 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. QPI utilizes optical interference for high-precision measurement of the optical properties where the speckle can severely distort the information. 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). ![]() High coherence of lasers is desirable in high-speed, high-resolution, and wide-field imaging.
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