arXiv subjects

Moonseok Kim

Publications and source records attributed to Moonseok Kim.

5 recordsLinked to original sources

arXiv2024

Multiphoton super-resolution imaging via virtual structured illumination

Imaging in thick biological tissues is often degraded by sample-induced aberrations, which reduce image quality and resolution, particularly in super-resolution techniques. While hardware-based adaptive optics, which correct aberrations using wavefront shaping devices, provide an effective solution, their complexity and cost limit accessibility. Computational methods offer simpler alternatives but struggle with complex aberrations due to the incoherent nature of fluorescence. Here, we present a deep-tissue super-resolution imaging framework that addresses these challenges with minimal hardware modification. By replacing the photodetector in a standard laser-scanning microscope with a camera, we measure an incoherent response matrix (IRM). A dual deconvolution algorithm is developed to decompose the IRM into excitation and emission optical transfer functions and the object spectrum. The proposed method simultaneously corrects excitation and emission point-spread functions (PSFs), achieving a resolution of λ/4, comparable to structured illumination microscopy. Unlike existing computational methods that rely on vector decomposition of a single convoluted PSF, our matrix-based approach enhances image reconstruction, particularly for high spatial frequency components, enabling super-resolution even in the presence of complex aberrations. We validated this framework with two-photon super-resolution imaging, achieving a lateral resolution of 130 nanometers at a depth of 180 micrometers in thick mouse brain tissue.

physics.optics↗

arXiv2022

Exploiting volumetric wave correlation for enhanced depth imaging in scattering medium

Imaging an object embedded within a scattering medium requires the correction of complex sample-induced wave distortions. Existing approaches have been designed to resolve them by optimizing signal waves recorded in each 2D image. Here, we present a volumetric image reconstruction framework that merges two fundamental degrees of freedom, the wavelength and propagation angles of light waves, based on the object momentum conservation principle. On this basis, we propose methods for exploiting the correlation of signal waves from volumetric images to better cope with multiple scattering. By constructing experimental systems scanning both wavelength and illumination angle of the light source, we demonstrated a 32-fold increase in the use of signal waves compared with that of existing 2D-based approaches and achieved ultrahigh volumetric resolution (lateral resolution: 0.41 um, axial resolution: 0.60 um) even within complex scattering medium owing to the optimal coherent use of the extremely broad spectral bandwidth (225 nm).

physics.optics↗

arXiv2013

Pixelation-free and real-time endoscopic imaging through a fiber bundle

Endoscopy has been an indispensible tool in medical diagnostics, and yet the demands for reduced unit diameter and enhanced spatial resolution have steadily been growing for the accurate investigation of distal sites with minimal side effects. However, the attempts to make use of thin image-guiding media accompany the degradation in spatial resolution as the micro-optics often induces aberrations. Here, we present a microendoscope that performs real-time correction of severe aberrations induced by image-guiding media such as a bundled fiber. Specifically, we developed a method exploiting the full binary control of a digital micro-mirror device (DMD) for characterizing the input-output response of image-guiding media and subsequently compensating the aberrations. As a proof-of-concept study, we completely eliminated the pixelation artifact, a severe form of aberration, in endoscopic imaging through an image fiber bundle and achieved spatial resolution much better than the diameter of an individual fiber. Our study lays a foundation of applying extremely thin, but highly aberrant image-guiding media for high-resolution microendoscopy.

physics.optics↗

arXiv2013

Exploring anti-reflection modes in disordered media

Sensing and manipulating targets hidden under scattering media are universal problems that take place in applications ranging from deep-tissue optical imaging to laser surgery. A major issue in these applications is the shallow light penetration caused by multiple scattering that reflects most of incident light. Although advances have been made to eliminate image distortion by a scattering medium, dealing with the light reflection has remained unchallenged. Here we present a method to minimize reflected intensity by finding and coupling light into the anti-reflection modes of a scattering medium. In doing so, we achieved more than a factor of 3 increase in light penetration. Our method of controlling reflected waves makes it readily applicable to in vivo applications in which detector sensors can only be positioned at the same side of illumination and will therefore lay the foundation of advancing the working depth of many existing optical imaging and treatment technologies.

physics.optics↗

arXiv2013

Enrichment of deeply penetrating waves in disordered media

Waves incident to a highly scattering medium are incapable of penetrating deep into the medium due to the diffusion process induced by multiple scattering. This poses a fundamental limitation to optically imaging, sensing, and manipulating targets embedded in opaque scattering layers such as biological tissues. One strategy for mitigating the shallow wave penetration is to exploit eigenmodes with anomalously high transmittance existing in any disordered medium. When waves are coupled to these eigenmodes, strong constructive wave interference enhances deeply penetrating waves. However, finding such eigenmodes has been a challenging task due to the complexity of disordered media. In this Letter, we present an iterative wavefront control method that selectively enriches the coupling of incident beam to high-transmission eigenmodes. Specifically, we refined the high-transmission eigenmodes from an arbitrary initial wave by either maximizing transmitted wave intensity or minimizing reflected wave intensity. Using the proposed method, we achieved more than a factor of 3 increases in light transmission through a scattering medium exhibiting hundreds of scattering events. Our approach is readily applicable to in vivo applications in which only the detection of reflected waves is available. Enhancing light penetration will lead to improving the working depth of optical imaging and treatment techniques.

physics.optics↗