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: In this article, the effects of spherical aberration on the structure of single-particle holograms and on the accuracy of particle characterization were investigated, and it was shown that fitting with a model that accounts for spherical aberrations decreases this aberration-dependent error by a factor of two or more.
Abstract: Holographic microscopy combined with forward modeling and inference allows colloidal particles to be characterized and tracked in three dimensions with high precision. However, current models ignore the effects of optical aberrations on hologram formation. We investigate the effects of spherical aberration on the structure of single-particle holograms and on the accuracy of particle characterization. We find that in a typical experimental setup, spherical aberration can result in systematic shifts of about 2% in the inferred refractive index and radius. We show that fitting with a model that accounts for spherical aberration decreases this aberration-dependent error by a factor of two or more, even when the level of spherical aberration in the optical train is unknown. With the new generative model, the inferred parameters are consistent across different levels of aberration, making particle characterization more robust.
29 Nov 2007
TL;DR: In this article, the phase mask was used to compensate automatically the phase aberration in the phase reconstruction, which was done by an automatic focusing procedure based on image-gray-entropy method.
Abstract: Based on the point spread function of the off-axis Fresnel digital holographic system with pre-magnification, the phase
aberration introduced by microscope objective is obtained. Using a collimated light as reconstructing wave, the phase
aberration introduced by the difference between the reconstructing wave and the reference recording wave is analyzed.
This method is very simple, and it is very different from the one proposed by T. Colomb et al . The phase mask that can
be used to compensate automatically the phase aberration in the phase reconstruction is obtained. According to the
principle of digital holography, it must be pointed out that for Fresnel digital holography, the recording distance must be
determined accurately before compensating automatically the phase aberration. This is done by an automatic focusing
procedure, which is based on image-gray-entropy-method. The simulation result for a special three-dimensional micro
object, which is polluted by a random noise, is presented. The percentage error of the reconstructing distance obtained by
the focusing procedure is below 0.6 for SNR = 25. Then an automatic aberration compensation procedure, which is the
same as that one proposed by T. Colomb et al ., is applied to reconstruct the phase image. The results show that for a
weak noise the above method is very effective; for a stronger noise the procedure described here is applied iteratively,
starting from the initial values provided by the first evaluation; while for a very strong noise the procedure fails at all.
Moreover, after applying a median filter to the primary reconstructed phase image, the aberration of the phase image
obtained by further iteration decreases, at the same time the noise is strengthen.
Proceedings Article•
29 Jul 2010
TL;DR: Based on the concept of the digital lateral shearing interferometry (LSI) and the idea of the automatic aberration compensation (AAC), a method to eliminate the linear term of the sheared phase map in digital holographic reconstruction is proposed in this article.
Abstract: Based on the concept of the digital lateral shearing interferometry (LSI) and the idea of the automatic aberration compensation (AAC), a method to eliminate the linear term of the sheared phase map in digital holographic reconstruction is proposed. The procedures for reconstruction phase image using the LSI-DH method have been analyzed in detail, which indicates that one-dimensional phase unwrapping must be applied to the original phase map before lateral shearing. Moreover, the zeros pad must be applied to the hologram if the phase difference between the two adjacent pixels of the shearogram map is more than 2π. The computer simulations, which are based on the Fresnel digital holography with pre-magnification, demonstrate the validity of the proposed method.
TL;DR: In this paper, the relationship between the illuminating wave and the reconstructed phase is studied based on the wave optics and the analysis is confirmed by the simulations in a super-resolution digital holographic microscope.
Abstract: Digital holography (DH) has a big advantage to retrieve the
three-dimensional (3D) information of the object from only
one interference recording. Especially, the digital holographic microscope (DHM) using a microscope objective (MO)
has been researched for 3D microscopy. The researches have progressed for compensation of aberrations and
improvement of the resolution in the optical system in recent years. Most of small aberrations caused by a MO are
compensated through various researches. However, the measured phase is distorted in the optical system, which has the
significant wavefront deformation in illuminating wave larger than number of wavelengths. In this paper, the relation
between illuminating wave and the reconstructed phase is studied based on the wave optics and the analysis is confirmed
by the simulations. The analysis of the wavefront compensation is applied to a super-resolution DHM in theory and the
technique for retrieving the distribution of the intensity and phase is demonstrated in simulation.
21 Apr 2006
TL;DR: In this paper, the authors examined the scattering problem from first principles beginning from the Helmholtz equation that governs scalar diffraction and wave propagation, and demonstrated the use of the Born approximation and show typical errors when it is applied in practice.
Abstract: In Optical Diffraction Tomography (ODT) the refractive index is reconstructed from images with different illuminating
wavefronts. In most cases the Born approximation is assumed, although this limits the applicability of the technique to
weak-scattering problems. In this work we examine the scattering problem from first principles beginning from the
Helmholtz equation that governs scalar diffraction and wave propagation. We demonstrate the use of the Born
approximation and show typical errors when it is applied in practice. Solution of the Helmholtz equation using a Finite
Element Method (FEM) with an appropriate Absorbing Boundary Condition (ABC) is described, and a non-linear
optimization technique, the Conjugate Gradient Method (CGM), previously proposed for microwave imaging, is applied
to the inverse problem.
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