English
norskBlar i forfatter "Ahmad, Azeem"
Viser treff 21-34 av 34
-
Multi-moded high-index contrast optical waveguide for super-contrast high-resolution label-free microscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-20)The article elucidates the physical mechanism behind the generation of superior-contrast and highresolution label-free images using an optical waveguide. Imaging is realized by employing a high index contrast multi-moded waveguide as a partially coherent light source. The modes provide near-field illumination of unlabeled samples, thereby repositioning the higher spatial frequencies of the ... -
Multimodal on-chip nanoscopy and quantitative phase imaging reveals the nanoscale morphology of liver sinusoidal endothelial cells
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-23)Visualization of three-dimensional (3D) morphological changes in the subcellular structures of a biological specimen is a major challenge in life science. Here, we present an integrated chip-based optical nanoscopy combined with quantitative phase microscopy (QPM) to obtain 3D morphology of liver sinusoidal endothelial cells (LSEC). LSEC have unique morphology with small nanopores (50-300 nm in ... -
Multiple Damage Detection in PZT Sensor Using Dual Point Contact Method
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-25)Lead Zirconate Titanate (PZT) is used to make ultrasound transducers, sensors, and actuators due to its large piezoelectric coefficient. Several micro-defects develop in the PZT sensor due to delamination, corrosion, huge temperature fluctuation, etc., causing a decline in its performance. It is thus necessary to identify, locate, and quantify the defects. Non-Destructive Structural Health Monitoring ... -
Partially spatially coherent digital holographic microscopy and machine learning for quantitative analysis of human spermatozoa under oxidative stress condition
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-05)Semen quality assessed by sperm count and sperm cell characteristics such as morphology and motility, is considered to be the main determinant of men’s reproductive health. Therefore, sperm cell selection is vital in assisted reproductive technology (ART) used for the treatment of infertility. Conventional bright field optical microscopy is widely utilized for the imaging and selection of sperm cells ... -
Quantitative assessment of morphology and sub-cellular changes in macrophages and trophoblasts during inflammation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-12)In pregnancy during an inflammatory condition, macrophages present at the feto-maternal junction release an increased amount of nitric oxide (NO) and pro-inflammatory cytokines such as TNF-α and INF-γ, which can disturb the trophoblast functions and pregnancy outcome. Measurement of the cellular and sub-cellular morphological modifications associated with inflammatory responses are important in order ... -
Quantitative phase microscopy of red blood cells during planar trapping and propulsion
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-22)Red blood cells (RBCs) have the ability to undergo morphological deformations during microcirculation, such as changes in surface area, volume and sphericity. Optical waveguide trapping is suitable for trapping, propelling and deforming large cell populations along the length of the waveguide. Bright field microscopy employed with waveguide trapping does not provide quantitative information about ... -
Relationship between the source size at the diffuser plane and the longitudinal spatial coherence function of the optical coherence microscopy system
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-25)Coherence properties of light sources are indispensable for optical coherence microscopy/tomography as they greatly influence the signal-to-noise ratio, axial resolution, and penetration depth of the system. In the present paper, we report the investigation of longitudinal spatial coherence properties of a pseudothermal light source (PTS) as a function of the laser spot size at the rotating diffuser ... -
Sampling moiré method: a tool for sensing quadratic phase distortion and its correction for accurate quantitative phase microscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-24)The advantages of quantitative phase microscopy (QPM) such as label-free imaging with high spatial sensitivity, live cell compatibility and high-speed imaging makes it viable for various biological applications. The measurement accuracy of QPM strongly relies on the shape of the recorded interferograms, whether straight or curved fringes are recorded during the data acquisition. Moreover, for a ... -
Single-shot fringe pattern phase retrieval using improved period-guided bidimensional empirical mode decomposition and Hilbert transform
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-17)Fringe pattern analysis is the central aspect of numerous optical measurement methods, e.g., interferometry, fringe projection, digital holography, quantitative phase microscopy. Experimental fringe patterns always contain significant features originating from fluctuating environment, optical system and illumination quality, and the sample itself that severely affect analysis outcome. Before the ... -
Sub-nanometer height sensitivity by phase shifting interference microscopy under environmental fluctuations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-18)Phase shifting interferometric (PSI) techniques are among the most sensitive phase measurement methods. Owing to its high sensitivity, any minute phase change caused due to environmental instability results into, inaccurate phase measurement. Consequently, a well calibrated piezo electric transducer (PZT) and highly-stable environment is mandatory for measuring accurate phase map using PSI implementation. ... -
Synthetic wavelength scanning interferometry for 3D surface profilometry with extended range of height measurement using multi-colour LED light sources
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-05)We report three-dimensional surface profilometry with extended range of height measurements using synthetic wavelength scanning interferometry without tunable filters, wavelength-tuning lasers, grating elements. We have used inexpensive multiple colour light emitting diodes (LEDs) and operate them sequentially one by one or combination of two or more colours simultaneously to visualize synthetic ... -
Transmission structured illumination microscopy with tunable frequency illumination using tilt mirror assembly
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-26)We present experimental demonstration of tilt-mirror assisted transmission structured illumination microscopy (tSIM) that offers a large field of view super resolution imaging. An assembly of custom-designed tilt-mirrors are employed as the illumination module where the sample is excited with the interference of two beams reflected from the opposite pair of mirror facets. Tunable frequency structured ... -
A transparent waveguide chip for versatile total internal reflection fluorescence-based microscopy and nanoscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-20)Total internal reflection fluorescence (TIRF) microscopy is an imaging technique that, in comparison to confocal microscopy, does not require a trade-off between resolution, speed, and photodamage. Here, we introduce a waveguide platform for chip-based TIRF imaging based on a transparent substrate, which is fully compatible with sample handling and imaging procedures commonly used with a standard ... -
Unbalanced low coherence interference microscopy
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-03)Low coherence interference microscopy (LCIM) provides high spatial phase sensitivity, i.e., speckle free and coherent noise free quantitative phase images of the test specimens. Due to low temporal coherence (TC) length of the light source, LCIM requires precise adjustment of the optical path difference (OPD) between the object and the reference arm, which is only a few micrometers. Consequently, ...
