• 3D full-wave multi-scattering forward solver for coherent microscopes 

      Qin, Yingying; Butola, Ankit; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-21)
      A rigorous forward model solver for conventional coherent microscope is presented. The forward model is derived from Maxwell’s equations and models the wave behaviour of light matter interaction. Vectorial waves and multiple-scattering effect are considered in this model. Scattered field can be calculated with given distribution of the refractive index of the biological sample. Bright field images ...
    • 3D refractive index reconstruction from phaseless coherent optical microscopy data using multiple scattering-based inverse solvers - a study 

      Qin, Yingying; Butola, Ankit; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-27)
      Reconstructing 3D refractive index profile of scatterers using optical microscopy measurements presents several challenges over the conventional microwave and RF domain measurement scenario. These include phaseless and polarization-insensitive measurements, small numerical aperture, as well as a Green's function where spatial frequencies are integrated in a weighted manner such that far-field angular ...
    • Characterization of color cross-talk of CCD detectors and its influence in multispectral quantitative phase imaging 

      Ahmad, Azeem; Kumar, Anand; Dubey, Vishesh Kumar; Butola, Ankit; Ahluwalia, Balpreet Singh; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-08)
      Multi-spectral quantitative phase imaging (QPI) is an emerging imaging modality for wavelength dependent studies of several biological and industrial specimens. Simultaneous multi-spectral QPI is generally performed with color CCD cameras. Here, we present a new approach for accurately measuring the color crosstalk of 2D area detectors, without needing prior information about camera specifications. ...
    • Deep learning architecture “LightOCT” for diagnostic decision support using optical coherence tomography images of biological samples 

      Butola, Ankit; Prasad, Dilip Kumar; Ahmad, Azeem; Dubey, Vishesh Kumar; Qaiser, Darakhshan; Srivastava, Anurag; Senthilkumaran, Paramasivam; Ahluwalia, Balpreet Singh; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-13)
      Optical coherence tomography (OCT) is being increasingly adopted as a label-free and non-invasive technique for biomedical applications such as cancer and ocular disease diagnosis. Diagnostic information for these tissues is manifest in textural and geometric features of the OCT images, which are used by human expertise to interpret and triage. However, it suffers delays due to the long process of ...
    • Effect on the longitudinal coherence properties of a pseudothermal light source as a function of source size and temporal coherence 

      Ahmad, Azeem; Mahanty, Tanmoy; Dubey, Vishesh; Butola, Ankit; Ahluwalia, Balpreet Singh; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-01)
      In the present Letter, a synthesized pseudothermal light source having high temporal coherence (TC) and low spatial coherence (SC) properties is used. The longitudinal coherence (LC) properties of the spatially extended monochromatic light source are systematically studied. The pseudothermal light source is generated from two different monochromatic laser sources: He–Ne (at 632 nm) and DPSS (at 532 ...
    • High space-bandwidth in quantitative phase imaging using partially spatially coherent digital holographic microscopy and a deep neural network 

      Butola, Ankit; Kanade, Sheetal Raosaheb; Bhatt, Sunil; Dubey, Vishesh Kumar; Kumar, Anand; Ahmad, Azeem; Prasad, Dilip K.; Senthilkumaran, Paramasivam; Ahluwalia, Balpreet Singh; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-16)
      Quantitative phase microscopy (QPM) is a label-free technique that enables monitoring of morphological changes at the subcellular level. The performance of the QPM system in terms of spatial sensitivity and resolution depends on the coherence properties of the light source and the numerical aperture (NA) of objective lenses. Here, we propose high space-bandwidth quantitative phase imaging using ...
    • High spatially sensitive quantitative phase imaging assisted with deep neural network for classification of human spermatozoa under stressed condition 

      Butola, Ankit; Popova, Daria; Prasad, Dilip K.; Ahmad, Azeem; Habib, Anowarul; Tinguely, Jean-Claude; Basnet, Purusotam; Acharya, Ganesh; Paramasivam, Senthilkumaran; Mehta, Dalip Singh; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-04)
      Sperm cell motility and morphology observed under the bright field microscopy are the only criteria for selecting a particular sperm cell during Intracytoplasmic Sperm Injection (ICSI) procedure of Assisted Reproductive Technology (ART). Several factors such as oxidative stress, cryopreservation, heat, smoking and alcohol consumption, are negatively associated with the quality of sperm cell and ...
    • High-throughput spatial sensitive quantitative phase microscopy using low spatial and high temporal coherent illumination 

      Ahmad, Azeem; Dubey, Vishesh; Jayakumar, Nikhil; Habib, Anowarul; Butola, Ankit; Nystad, Mona; Acharya, Ganesh; Basnet, Purusotam; Mehta, Dalip Singh; Ahluwalia, Balpreet Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-04)
      High space-bandwidth product with high spatial phase sensitivity is indispensable for a single-shot quantitative phase microscopy (QPM) system. It opens avenue for widespread applications of QPM in the field of biomedical imaging. Temporally low coherence light sources are implemented to achieve high spatial phase sensitivity in QPM at the cost of either reduced temporal resolution or smaller field ...
    • Highly temporal stable, wavelength-independent, and scalable field-of-view common-path quantitative phase microscope 

      Ahmad, Azeem; Dubey, Vishesh Kumar; Butola, Ankit; Ahluwalia, Balpreet Singh; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-11)
      <p><i>Significance:</i> High temporal stability, wavelength independency, and scalable field of view (FOV) are the primary requirements of a quantitative phase microscopy (QPM) system. The high temporal stability of the system provides accurate measurement of minute membrane fluctuations of the biological cells that can be an indicator of disease diagnosis. <p><i>Aim:</i> The main aim of this work ...
    • Label-free non-invasive classification of rice seeds using optical coherence tomography assisted with deep neural network 

      Joshi, Deepa; Butola, Ankit; Kanade, Sheetal Raosaheb; Prasad, Dilip K.; Amitha Mithra, Mithra; Singh, N.K.; Bisht, Deepak Singh; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-01)
      Identification of the seed varieties is essential in the quality control and high yield crop growth. The existing methods of varietal identification rely primarily on visual examination and DNA fingerprinting. Although the pattern of DNA fingerprinting allows precise classification of seed varieties but fraught with challenges such as low rate of polymorphism amongst closely related species, destructive ...
    • Multimodal on-chip nanoscopy and quantitative phase imaging reveals the nanoscale morphology of liver sinusoidal endothelial cells 

      Butola, Ankit; Coucheron, David Andre; Szafranska, Karolina; Ahmad, Azeem; Mao, Hong; Tinguely, Jean-Claude; McCourt, Peter Anthony; Paramasivam, Senthilkumaran; Mehta, Dalip Singh; Agarwal, Krishna; Ahluwalia, Balpreet Singh (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 ...
    • Quantitative assessment of morphology and sub-cellular changes in macrophages and trophoblasts during inflammation 

      Singh, Rajwinder; Dubey, Vishesh; Wolfson, Deanna; Ahmad, Azeem; Butola, Ankit; Acharya, Ganesh; Singh Mehta, Dalip; Basnet, Purusotam; Ahluwalia, Balpreet Singh (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 ...
    • Relationship between the source size at the diffuser plane and the longitudinal spatial coherence function of the optical coherence microscopy system 

      Usmani, Kashif; Ahmad, Azeem; Joshi, Rakesh; Dubey, Vishesh Kumar; Butola, Ankit; Mehta, Dalip Singh (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 ...
    • Scalable-resolution structured illumination microscopy 

      Butola, Ankit; Acuna Maldonado, Sebastian Andres; Hansen, Daniel Henry; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-15)
      Structured illumination microscopy suffers from the need of sophisticated instrumentation and precise calibration. This makes structured illumination microscopes costly and skill-dependent. We present a novel approach to realize super-resolution structured illumination microscopy using an alignment non-critical illumination system and a reconstruction algorithm that does not need illumination ...
    • Single-shot multispectral quantitative phase imaging of biological samples using deep learning 

      Bhatt, Sunil; Butola, Ankit; Kumar, Anand; Thapa, Pramila; Joshi, Akshay; Jadhav, Suyog S.; Singh, Neetu; Prasad, Dilip K.; Agarwal, Krishna; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-16)
      Multispectral quantitative phase imaging (MS-QPI) is a high-contrast label-free technique for morphological imaging of the specimens. The aim of the present study is to extract spectral dependent quantitative information in single-shot using a highly spatially sensitive digital holographic microscope assisted by a deep neural network. There are three different wavelengths used in our method: 𝜆=532 , ...
    • Sub-nanometer height sensitivity by phase shifting interference microscopy under environmental fluctuations 

      Ahmad, Azeem; Dubey, Vishesh Kumar; Butola, Ankit; Tinguely, Jean-Claude; Ahluwalia, Balpreet Singh; Mehta, Dalip Singh (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 

      Mann, Priyanka; Dubey, Vishesh Kumar; Ahmad, Azeem; Butola, Ankit; Mehta, Dalip Singh (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 ...