Compensation of the inherent wave front curvature in digital holographic coherent microscopy for quantitative phase-contrast imaging
TL;DR: An approach is proposed for removing the wavefront curvature introduced by the microscope imaging objective in digital holography, which otherwise hinders the phase contrast imaging at reconstruction planes and it is shown that a correction effect can be obtained at all reconstruction planes.
Abstract: An approach is proposed for removing the wave front curvature introduced by the microscope imaging objective in digital holography, which otherwise hinders the phase contrast imaging at reconstruction planes. The unwanted curvature is compensated by evaluating a correcting wave front at the hologram plane with no need for knowledge of the optical parameters, focal length of the imaging lens, or distances in the setup. Most importantly it is shown that a correction effect can be obtained at all reconstruction planes. Three different methods have been applied to evaluate the correction wave front and the methods are discussed in detail. The proposed approach is demonstrated by applying digital holography as a method of coherent microscopy for imaging amplitude and phase contrast of microstructures.
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TL;DR: Four smart computational light microscopes (SCLMs) developed by the SCILab of Nanjing University of Science and Technology, China are presented, empowered by advanced computational microscopy techniques, which not only enables multi-modal contrast-enhanced observations for unstained specimens, but also can recover their three-dimensional profiles quantitatively.
Abstract: Computational microscopy, as a subfield of computational imaging, combines optical manipulation and image algorithmic reconstruction to recover multi-dimensional microscopic images or information of micro-objects. In recent years, the revolution in light-emitting diodes (LEDs), low-cost consumer image sensors, modern digital computers, and smartphones provide fertile opportunities for the rapid development of computational microscopy. Consequently, diverse forms of computational microscopy have been invented, including digital holographic microscopy (DHM), transport of intensity equation (TIE), differential phase contrast (DPC) microscopy, lens-free on-chip holography, and Fourier ptychographic microscopy (FPM). These computational microscopy techniques not only provide high-resolution, label-free, quantitative phase imaging capability but also decipher new and advanced biomedical research and industrial applications. Nevertheless, most computational microscopy techniques are still at an early stage of “proof of concept” or “proof of prototype” (based on commercially available microscope platforms). Translating those concepts to stand-alone optical instruments for practical use is an essential step for the promotion and adoption of computational microscopy by the wider bio-medicine, industry, and education community. In this paper, we present four smart computational light microscopes (SCLMs) developed by our laboratory, i.e., smart computational imaging laboratory (SCILab) of Nanjing University of Science and Technology (NJUST), China. These microscopes are empowered by advanced computational microscopy techniques, including digital holography, TIE, DPC, lensless holography, and FPM, which not only enables multi-modal contrast-enhanced observations for unstained specimens, but also can recover their three-dimensional profiles quantitatively. We introduce their basic principles, hardware configurations, reconstruction algorithms, and software design, quantify their imaging performance, and illustrate their typical applications for cell analysis, medical diagnosis, and microlens characterization.
51 citations
TL;DR: The optical reconstruction in the visible range (0.532 microm) of digital holograms recorded at long IR wavelengths by means of a spatial light modulator is demonstrated and the high NA achievable at a long IR wavelength allows us to image large objects at reasonable distances.
Abstract: We demonstrate the optical reconstruction in the visible range (0.532μm) of digital holograms recorded at long IR wavelengths (10.6μm) by means of a spatial light modulator. By using an integrated recording-reconstruction system, it is, in fact, feasible to achieve direct imaging of holograms acquired outside the visible range, i.e., in the IR spectrum. By choosing a Fourier recording configuration, the reconstructed image, obtained at about a 20 times shorter wavelength than the acquisition image, exhibits minor aberrations, which do not significantly affect the optical reconstruction. The high NA achievable at a long IR wavelength allows us to image large objects at reasonable distances.
49 citations
TL;DR: Digital holography allowed studying the interaction with light of Coscinodiscus wailesii cell wall reconstructing the light confinement inside the cell cytoplasm, condition that is hardly accessible via standard microscopy.
Abstract: Diatoms are among the dominant phytoplankters in the world's oceans, and their external silica investments, resembling artificial photonic crystals, are expected to play an active role in light manipulation. Digital holography allowed studying the interaction with light of Coscinodiscus wailesii cell wall reconstructing the light confinement inside the cell cytoplasm, condition that is hardly accessible via standard microscopy. The full characterization of the propagated beam, in terms of quantitative phase and intensity, removed a long-standing ambiguity about the origin of the light confinement. The data were discussed in the light of living cell behavior in response to their environment.
48 citations
Cites methods from "Compensation of the inherent wave f..."
...he reconstructed image allows to remove and/or compensate the unwanted wavefront variations (such as optical aberrations, slide deformations etc.) (24, 25). In this paper, a double exposure technique (26) has been used. The first exposure is made on the object under investigation, whereas the second one is made on a flat reference surface in proximity of the object. This second hologram contains infor...
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TL;DR: In this paper, a phase grating with period 30 lines/mm and height 0.3μm was compared with a pre-magnification DMH and a lens-less DMH.
47 citations
TL;DR: The quantitative phase microscopy by DH is described including some of the special techniques such as optical phase unwrapping and holography of total internal reflection.
Abstract: Digital holography (DH) is a potentially disruptive new technology for many areas of imaging science, especially in microscopy and metrology. DH offers a number of significant advantages such as the ability to acquire holograms rapidly, availability of complete amplitude and phase information of the optical field, and versatility of the interferometric and image processing techniques. This article provides a review of the digital holography, with an emphasis on its applications in biomedical microscopy. The quantitative phase microscopy by DH is described including some of the special techniques such as optical phase unwrapping and holography of total internal reflection. Tomographic imaging by digital interference holography (DIH) and related methods is described, as well as its applications in ophthalmic imaging and in biometry. Holographic manipulation and monitoring of cells and cellular components is another exciting new area of research. We discuss some of the current issues, trends, and potentials.
46 citations
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TL;DR: A new method is proposed in which the distribution of complex amplitude at a plane is measured by phase-shifting interferometry and then Fresnel transformed by a digital computer, which can reconstruct an arbitrary cross section of a three-dimensional object with higher image quality and a wider viewing angle than from conventional digital holography using an off-axis configuration.
Abstract: A new method for three-dimensional image formation is proposed in which the distribution of complex amplitude at a plane is measured by phase-shifting interferometry and then Fresnel transformed by a digital computer. The method can reconstruct an arbitrary cross section of a three-dimensional object with higher image quality and a wider viewing angle than from conventional digital holography using an off-axis configuration. Basic principles and experimental verification are described.
1,813 citations
TL;DR: The principle of recording holograms directly on a CCD target is described and a real image of the object is reconstructed from the digitally sampled hologram by means of numerical methods.
Abstract: The principle of recording holograms directly on a CCD target is described. A real image of the object is reconstructed from the digitally sampled hologram by means of numerical methods.
1,444 citations
TL;DR: A new application of digital holography for phase-contrast imaging and optical metrology and an application to surface profilometry shows excellent agreement with contact-stylus probe measurements.
Abstract: We present a new application of digital holography for phase-contrast imaging and optical metrology. This holographic imaging technique uses a CCD camera for recording of a digital Fresnel off-axis hologram and a numerical method for hologram reconstruction. The method simultaneously provides an amplitude-contrast image and a quantitative phase-contrast image. An application to surface profilometry is presented and shows excellent agreement with contact-stylus probe measurements.
1,202 citations
TL;DR: Off-axis holograms recorded with a magnified image of microscopic objects are numerically reconstructed in amplitude and phase by calculation of scalar diffraction in the Fresnel approximation to show that the transverse resolution is equal to the diffraction limit of the imaging system.
Abstract: We present a digital method for holographic microscopy involving a CCD camera as a recording device. Off-axis holograms recorded with a magnified image of microscopic objects are numerically reconstructed in amplitude and phase by calculation of scalar diffraction in the Fresnel approximation. For phase-contrast imaging the reconstruction method involves the computation of a digital replica of the reference wave. A digital method for the correction of the phase aberrations is presented. We present a detailed description of the reconstruction procedure and show that the transverse resolution is equal to the diffraction limit of the imaging system.
1,174 citations
TL;DR: The principles and major applications of digital recording and numerical reconstruction of holograms (digital holography) are described, which are applied to measure shape and surface deformation of opaque bodies and refractive index fields within transparent media.
Abstract: This article describes the principles and major applications of digital recording and numerical reconstruction of holograms (digital holography). Digital holography became feasible since charged coupled devices (CCDs) with suitable numbers and sizes of pixels and computers with sufficient speed became available. The Fresnel or Fourier holograms are recorded directly by the CCD and stored digitally. No film material involving wet-chemical or other processing is necessary. The reconstruction of the wavefield, which is done optically by illumination of a hologram, is performed by numerical methods. The numerical reconstruction process is based on the Fresnel–Kirchhoff integral, which describes the diffraction of the reconstructing wave at the micro-structure of the hologram. In the numerical reconstruction process not only the intensity, but also the phase distribution of the stored wavefield can be computed from the digital hologram. This offers new possibilities for a variety of applications. Digital holography is applied to measure shape and surface deformation of opaque bodies and refractive index fields within transparent media. Further applications are imaging and microscopy, where it is advantageous to refocus the area under investigation by numerical methods.
1,171 citations