Superresolution imaging system by color-coded tilted-beam illumination in digital in-line holographic microscopy

Abstract

Digital in-line holographic microscopy (DIHM) relates with the capability to achieve microscopic imaging working without lensless in the regime of holography. In essence, DIHM proposes a simple layout where a point source of coherent light illuminates the sample and the diffracted wavefront is recorded by a digital sensor. However, DIHM lacks high numerical aperture (NA) due to both geometrical distortion and the mandatory compromise between the illumination pinhole diameter, the illumination wavelength, and the need to obtain a reasonable light efficiency. One way to improve the resolution in DIHM, is by allowing superresolution imaging by angular multiplexing using tilted beam illumination. This illumination allows the on-axis diffraction of different spatial frequency content of the sample’s spectrum, different in comparison to the case when on-axis illumination is used. And after recover this additional spectral content, a synthetic numerical aperture (SNA) expanding up the cutoff frequency of the system in comparison with the on-axis illumination case can be assembled in a digital post-processing stage. In this contribution, we present a method to achieve one-dimensional (1-D) superresolved imaging in DIHM by a SINGLE SHOT illumination, using color-coded tilted beams. The method has been named as L-SESRIM (Lensless Single-Exposure Super-Resolved Interferometric Microscopy). Although the technique was previously presented showing very preliminary results [34], in this contribution we expand the experimental characterization (USAF resolution test target) as well as derive the theoretical frame for SNA generation using different illumination wavelengths.