ABSTRACT
The objective of this research includes integration of high-resolution imaging through scattering medium, such as blood, into a disposable micro-endoscope. A fiber laser integrated into the micro-endoscope as part of its illumination channel, allows to project a tunable array of spots of light onto an object, that is located behind the scattering medium. We have a laser fiber as part of the illumination channel of a disposable micro-endoscope. By using proper optics, we convert the temporal modulation of the laser into spatial distribution. Thus, the result is generation of spatial spots when using a pulsed laser. The detection channel is a holographic recording of the collected back scattered light, that allows extraction of the electrical field. By time integrating the field we obtain the realization of the spatial array of illumination spots formed on top of the inspected object and behind the scattering medium. By changing the temporal modulation of the illumination laser (changing its temporal photonic signals), we can tune the positions of the spots in the illumination array. If the distance between the projected spots is larger than the imaging resolution, then by applying localization microscopy algorithms together with scanning of the position of the spots in the array, will yield a high-resolution reconstruction of the inspected object. We theoretically and experimentally demonstrate the discussed operation principle and show the potential of the proposed concept as a modality in medical endoscopic procedures.
ABSTRACT
BACKGROUND: The main objective is related to the capability of integrating into minimally invasive and ultra-thin disposable micro-endoscopic tool, a modality of realizing high-resolution imaging through scattering medium such as blood while performing medical procedure. In this research we aim for the first time to present a time-multiplexing super-resolving approach exhibiting enhanced focus sensitivity, generated by 3D spatial filtering, for significant contrast increase in images collected through scattering medium. METHOD: Our innovative method of imaging through scattering media provides imaging of only one specific object plane in scattering medium's volume while suppressing the noise coming from all other planes. The method should be assisted with axial scanning to perform imaging of the entire 3D object's volume. In our developed optical system noise suppression is achieved by 3D spatial filtering approach while more than an order of magnitude of suppression is experimentally demonstrated. The sensitivity to defocus and noise suppression is dramatically enhanced by placing an array of micro-lenses combined with pinholes raster positioned between two modules of telecentric lenses. RESULTS: We present our novel conceptual designs for the enhanced signal-to-noise ratio (SNR) when imaging through scattering medium and present preliminary experimental results demonstrating both quality imaging performed on resolution bars target as well as SNR quantified results in which SNR enhancement of more than one order of magnitude was obtained. CONCLUSIONS: In this paper, to the best of our knowledge, we present the first ever design of time-multiplexing-based approach for super-resolved imaging through scattering medium. The approach includes a time-multiplexing optical design significantly increasing the depth of focus sensitivity and after performing axial scanning yielding a significant enhancement of the SNR of the 3D object that is being imaged through the scattering medium. Right after the contrast (the SNR) enhancement we scan the object with the projected array of spots (raster) and map it continuously and with high imaging resolution.
