Single-exposure 3D label-free microscopy based on color-multiplexed intensity diffraction tomography

Abstract

We present a 3D label-free refractive index (RI) imaging technique based on single-exposure intensity diffraction tomography (sIDT) utilizing a color-multiplexed illumination scheme. In our method, the chromatic LEDs corresponding R/G/B channels in an annular programmable array provide oblique illumination geometry which matches the numerical aperture of the objective precisely to maximize the spectrum coverage. A color intensity image encoding the scattering field of the specimen from different directions is captured, and monochromatic intensity images with respect to three color channels were separated and then used to recover the 3D RI distribution of the object following the process of IDT. In addition, the axial chromatic dispersion of focal lengths at different wavelengths introduced by the chromatic aberration of the objective lens and the spatial position misalignment of the ring LED source in the imaging system’s transfer functions modeling are both corrected to significantly reduce the artifacts in slice-based deconvolution procedure for the reconstruction of 3D RI distribution. Experimental results on MCF-7, Spirulina algae, and live C. elegans samples demonstrate the solid performance of the sIDT method in label-free, high-throughput, and real-time (∼ 24 fps) 3D volumetric biological imaging applications.