Resolution enhancement of spectrum normalization in synthetic aperture digital holographic microscopy

Abstract

This study describes the overlapping of spatial frequency bands for synthetic aperture in digital holography using spectrum normalization to effectively enhance the spatial resolutions of image reconstruction. Synthesized spectrum swelling induced by excessive frequency overlaps can be normalized through the inverse apodization of an adjustable window function, which is similar to the effects of suppressing low-frequency expansion and strengthening high-frequency components of the reconstructed images. The results indicated that using the normalized spectrum synthesis that requires only a few frequency bands effectively enhances the spatial resolution and phase sensitivity of reconstructed images in digital holographic microscopy.

Integrated dual-tomography for refractive index analysis of free-floating single living cell with isotropic superresolution

“…2(f) . Here an enlarged spatial frequency is obtained and its spatial resolution can achieve less than half of the wavelength, such spatial resolution can be referred in different names as, resolution enhancement, super-resolved, sub-diffraction limit or superresolution 11 , 18 , 19 , 37 . And Fig.…”

“…Digital holographic microtomography (DHµT) is one of the promising imaging technique developed for mapping the refractive index (RI) profiles of biological specimens in three dimensions (3D) 4 – 10 . The spatial frequencies imposed by the finite numerical aperture (NA) of the objective lens are collected during image reconstruction by combining the frequency bands corresponding to different angles that is, the synthetic aperture method 11 , 12 , illumination rotation method 14 , one can improve the lateral resolution of imaging 10 – 18 . In beam rotation tomography, the aforementioned spatial frequency collection constraint is commonly referred to as the missing cone problem 17 ; it results in a low axial resolution.…”

A compact synthetic aperture digital holographic microscope with mechanical movement-free beam scanning and optimized active aberration compensation for isotropic resolution enhancement

“…Separately, the spectrum swelling during frequency overlapping process brings in distortion. Our previous works have introduced an inverse apodization for spectrum normalization to suppress the low-frequency expansion and enhance high-frequency components [13][14][15]. This method enables SA-DHM to increase the spatial resolution by recording only a small number of holograms.…”

Sources and propagation of errors in quantitative phase imaging techniques using optical interferometry

“…The interferometric setup may be optimized by reducing the recording distance and using a detector with smaller pixel sizes [8]. Other methods to reduce noise include phase error compensation, spatial light modulation (SLM), and multiple frequency overlapping [9] [10][11][12][13], which improve the contrast of phase measurements. Noise reduction is also accomplished by filtering certain frequencies, both in the spatial and Fourier planes, with Butterworth filters and masks, respectively [14,15] [6].…”