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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21 Apr 2006
TL;DR: In this article, the fabrication and characterization of periodic nanoscale surface structures in congruent 500 μm thick lithium niobate crystal samples have been obtained, with periods from 2 μm down to around 500 nm, lateral feature sizes down to 200 nm and depths compatible with conventional waveguide fabrication.
Abstract: We report on the fabrication and characterization of periodic nanoscale one- and two-dimensional surface structures in congruent 500 μm thick lithium niobate crystal samples. Structures with periods from 2 μm down to around 500 nm, lateral feature sizes down to 200 nm and depths compatible with conventional waveguide fabrication, have been obtained. Such structures are fabricated by applying polarity selective etching to periodically domain reversed samples obtained by electric field poling performed by overpoling regime. Holographic lithography is used to obtain sub-micron periodic insulating gratings to be used for selective ferroelectric domain reversal. The short pitch structures are attractive in a wide range of applications ranging from nonlinear optics, for short-wavelength conversion processes or backward second-harmonic generation, to the field of photonic crystals to fabricate novel tunable photonic crystal devices or electro-optically modulated Bragg gratings. Moreover moire beating effect is used in the photolithographic process to fabricate even more complex structures which could find applications in complicated photonic bandgap devices involving for example micro-ring resonators. In order to investigate the possibility to utilize these structures for photonic crystal applications, accurate topography characterization has been performed by using different techniques. Atomic force microscope provides high-resolution information about the lateral and depth feature size of the structures, while interferometric techniques, based on digital holography, have been used for wide field information about the homogeneity and periodicity of the structures.
1 citations
28 Apr 2006
TL;DR: In this article, the optical phase difference (OPD) between the light beam traveling through the layer and portion of the beam in air is measured exploiting an interferometric technique, which can be used even for inspection of nonplanar or stressed structures.
Abstract: In this paper is reported a method for measuring the thickness of a silicone nitride layers employed for fabricating silicon MEMS bi-morph structures. The method allows the precise evaluation of layer thickness by adopting Digital Holographic Microscope. The measurement is based on the fact that the silicon nitride layer is transparent to the visible light. The optical phase difference (OPD) between the light beam traveling through the layer and portion of the beam in air is measured exploiting an interferometric technique. The approach is very simple and can be utilized even for inspection of non-planar or stressed structures. Experimental values have been compared with ellipsometric measurements.
1 citations
15 Nov 2005
TL;DR: In this paper, it is shown that it is possible to construct an extended focused image (EFI) image by a coherent optical microscope without any mechanical movement but by using the 3D imaging capability of digital holography (DH).
Abstract: In microscopy, high magnifications are achievable for investigating micro-objects but the paradigm is that higher the required magnification, the lower the depth of focus. In this paper we show that it is possible to construct an extended focused image (EFI) image by a coherent optical microscope without any mechanical movement but by using the 3D imaging capability of digital holography (DH). In fact, DH has the unique property of allowing direct calculation and management of an amplitude and phase map along the longitudinal direction in front of the digital camera. That constitutes a fundamental feature of DH to construct an EFI image of an object or systems experiencing dynamic evolution since the recording of only one image is needed instead of performing a mechanical scanning and to record several images at different focus planes. In other words, by means of this approach it is possible to obtain an EFI image for studying dynamic objects, such as biological objects, dynamic MEMS.
1 citations
01 Jan 2010
TL;DR: In this article, the integration of near-field microscopy with digital holography has been investigated and the results conclusively demonstrate the correlation between the physical extent of the Amoeba proteus plasma and the angular spectrum of digital holographic images.
Abstract: Total Internal Reflection Holographic Microscopy (TIRHM) combines near-field microscopy with digital holography to produce a new form of near-field phase microscopy. Using a prism in TIR as a near-field imager, the presence of microscopic organisms, cell-substrate interfaces, and adhesions, causes relative refractive index (RRI) and frustrated TIR (f-TIR) to modulate the object beam’s evanescent wave phase front. Quantitative phase images of test specimens such as Amoeba proteus, Dictyostelium Discoideum and cells such as SKOV-3 ovarian cancer and 3T3 fibroblasts are produced without the need to introduce stains or fluorophores. The angular spectrum method of digital holography to compensate for tilt anamorphism due to the inclined TIR plane is also discussed. The results of this work conclusively demonstrate, for the first time, the integration of near-field microscopy with digital holography. The cellular images presented show a correlation between the physical extent of the Amoeba proteus plasma
1 citations
TL;DR: Experimental results of the indirect synthesis of the interference term corresponding to the lensless Fourier hologram using the Fresnel hologram are presented.
Abstract: We propose a numerical wavefront manipulation method for synthesizing a new interference term from two digital holograms recorded using the same reference wavefront. The interference term of interest is synthesized indirectly, and its reconstructed image is unaffected by the reference wavefront used during hologram recording. We present experimental results of the indirect synthesis of the interference term corresponding to the lensless Fourier hologram using the Fresnel hologram.
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References
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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