Anton Barty

Quantitative optical phase microscopy.

We present a new method for the extraction of quantitative phase data from microscopic phase samples by use of partially coherent illumination and an ordinary transmission microscope. The technique produces quantitative images of the phase profile of the sample without phase unwrapping. The technique is able to recover phase even in the presence of amplitude modulation, making it significantly more powerful than existing methods of phase microscopy. We demonstrate the technique by providing quantitatively correct phase images of well-characterized test samples and show that the results obtained for more-complex samples correlate with structures observed with Nomarski differential interference contrast techniques.

Quantitative phase-amplitude microscopy I: optical microscopy

In this paper, the application of a new optical microscopy method (quantitative phase‐amplitude microscopy) to biological imaging is explored, and the issue of resolution and image quality is examined. The paper begins by presenting a theoretical analysis of the method using the optical transfer function formalism of Streibl (1985 ). The effect of coherence on the formation of the phase image is explored, and it is shown that the resolution of the method is not compromised over that of a conventional bright‐field image. It is shown that the signal‐to‐noise ratio of the phase recovery, however, does depend on the degree of coherence in the illumination.

Quantitative phase-amplitude microscopy. III. The effects of noise.

We explore the effect of noise on images obtained using quantitative phase‐amplitude microscopy – a new microscopy technique based on the determination of phase from the intensity evolution of propagating radiation. We compare the predictions with experimental results and also propose an approach that allows good‐quality quantitative phase retrieval to be obtained even for very noisy data.

Quantitative phase tomography

We describe the application of a new technique for the simultaneous determination of three-dimensional absorption and refractive index distributions using a combination of quantitative phase-amplitude microscopy and tomographic reconstruction techniques. We briefly review the phase-amplitude microscopy technique and present experimental results in which we have successfully reconstructed the refractive index profile of two different optical fibres.

Refractive-index profiling of optical fibers with axial symmetry by use of quantitative phase microscopy

The application of quantitative phase microscopy to refractive-index profiling of optical fibers is demonstrated. Phase images of axially symmetric optical fibers immersed in index-matching fluid are obtained, and the inverse Abel transform is used to obtain the radial refractive-index profile. This technique is straightforward, nondestructive, repeatable, and accurate. Excellent agreement, to within approximately 0.0005, between this method and the index profile obtained with a commercial profiler is obtained.

Noninterferometric quantitative phase imaging with soft x rays.

We demonstrate quantitative noninterferometric x-ray phase-amplitude measurement. We present results from two experimental geometries. The first geometry uses x rays diverging from a point source to produce high-resolution holograms of submicrometer-sized objects. The measured phase of the projected image agrees with the geometrically determined phase to within +/-7%. The second geometry uses a direct imaging microscope setup that allows the formation of a magnified image with a zone-plate lens. Here a direct measure of the object phase is made and agrees with that of the magnified object to better than +/-10%. In both cases the accuracy of the phase is limited by the pixel resolution.

The holographic twin image problem : a deterministic phase solution

We describe a novel method for solving the twin image problem of in-line holography using a new technique for deterministic phase retrieval combined with numerical back-propagation of the reconstructed complex field. The technique presented here is applicable to any field described by the paraxial scalar wave equation, and is therefore equally applicable to X-ray, electron and neutron optics as well as visible light optics. q 2000 Published by Elsevier Science B.V.

5. Phase retrieval in lorentz microscopy

Publisher Summary This chapter discusses the application of the technique of phase measurement to high energy electrons in an electron microscope. This work is applied to the Lorentz microscopy of magnetic structures at the domain level. The ideas behind phase recovery strategy are reviewed and some practical issues that apply to microscopy are examined in the chapter. Phase structure in microscopic samples is successfully imaged using a transmission electron microscope, and both the direction and magnitude of the magnetization are directly imaged in a microscopic cobalt grain using transport-of-intensity equation (TIE)-based phase retrieval techniques. The TIE technique can be used to measure the phase structure of the electron wave exiting from the sample, once appropriate calibration of the microscope system has been performed, and that the measurements so made agree with the results of electron holography on the same sample. The TIE technique for electron phase imaging is not limited to magnetic samples and can, in principle, be used to image any sample, magnetic or otherwise, that introduces a phase shift into an electron beam.

Sub-wavelength characterisation of optical focal structures

A technique for mapping the focal region of a lens with 100 nm spatial resolution is described. The technique is tested against a well characterised focal structure produced by a glass aspheric lens with a numerical aperture of 0.4. The results are in very good agreement with theory confirming the accuracy of this method.