Spatial-domain filter enhanced subtraction microscopy and application to mid-IR imaging

Abstract

Abstract:We have experimentally investigated the enhancement in spatial resolution by image subtraction in mid-infrared central solid-immersion lens (c-SIL) microscopy. The subtraction exploits a first image measured with the c-SIL point-spread function (PSF) realized with a Gaussian beam and a second image measured with the beam optically patterned by a silicon π-step phase plate, to realize a centrally hollow PSF. The intense sides lobes in both PSFs that are intrinsic to the SIL make the conventional weighted subtraction methods inadequate. A spatial-domain filter with a kernel optimized to match both experimental PSFs in their periphery was thus developed to modify the first image prior to subtraction, and this resulted in greatly improved performance, with polystyrene beads 1.4 ± 0.1 µm apart optically resolved with a mid-IR wavelength of 3.4 µm in water. Spatial-domain filtering is applicable to other PSF pairs, and simulations show that it also outperforms conventional subtraction methods for the Gaussian and doughnut beams widely used in visible and near-IR microscopy.

Resolution Enhancement and Background Suppression in Optical Super‐Resolution Imaging for Biological Applications

“…Also, the similar adaptive methodology can be applied to better matching of the two PSFs at their periphery, involved with the identification of a kernel matrix that minimizes the error function. [ 74 ] The approach involves the identification of a suitable linear operation of the Gaussian image pixels that are optimized to achieve a subtracted PSF that is narrowed with little or no side‐lobes.…”

“…[ 67 ] To date, several literatures have specifically investigated the subtraction coefficient based on the evaluation of the differential image in the Fourier domain. [ 73,74 ] The evaluating function C ( α ) can be presented by where u and v denote the corresponding pixel sizes of the image; FFT stands for fast Fourier transform. The weight factor increases linearly with the spatial frequency so as to give a large weight to higher frequency components.…”

“…a2–e2) Optical setups of DA‐2P, differential SHG, CARS‐D, differential IRA imaging, and DTA, respectively. [ 59,63,74,215,227 ] a3) Subtraction of the images with and without aberration will decrease the background noise in 2PE. Reproduced with permission.…”

In Situ, Real‐Time Infrared (IR) Imaging for Metrology in Advanced Manufacturing

“…For example, a diamond SIL was used to demonstrate super‐resolution imaging with STED in diamond with <2 nm resolution with visible light . A silicon SIL has been used for fast imaging with MIR to double the spatial resolution . Such capabilities are currently in their infancy but, when fully developed for on/in line metrology, has the potential to revolutionize metrology in semiconductor industry, polymer industry, additive manufacturing of polymers and ceramics, pharmaceuticals, biopharma, combinatorial medical devices, and products involving hard/soft interfaces.…”

Label‐free superresolution effect of nonlinear reverse saturation absorption thin films through difference method

“…Label‐free imaging techniques can help to study tissue organs or animals without bleaching and optotoxicity of dyes. Subtractive imaging technique has made a great contribution in the field of fluorescence technique, and has been applied to label‐free superresolution techniques, such as spatial‐domain filter enhanced subtraction microscopy (Kumbham et al ., ), transient absorption differential microscopy (Liu et al ., ), second harmonic generation microscopy (Tian et al ., ) and so on. Here we propose label‐free superresolution imaging method, nonfluorescence difference (NFD) based on films with NRSA effect.…”