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Abstract

Digital holography (DH) which is the technology of acquiring and processing measurement data via a CCD camera is spreading to industrial applications, finds wide employment in engineering problems of testing and investigation. In this paper, a simple digital holographic system, comprising a He-Ne laser source, CCD camera and analyzing software, is used for testing surface flatness and detecting the presence of a propagating crack on the surface plane and the effect of the crack on the neighborhood. Phase variations across the surfaces planes are extracted to represent the surface deviation from a reference plane. The analysis methods differ according to the interference fringes in the recorded holograms. Both fringe tracking and Fourier transform with phase unwrapping methods are used in the interpretation of interferometric fringe patterns.

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Authors and Affiliations

Niveen Maaboud
Mohamed El-Bahrawi
Fedia Abdel-Aziz
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Abstract

In this paper we propose a method which allows to overcome the basic functional problems in holographic displays with naked eye observation caused by delivering too small images visible in narrow viewing angles. The solution is based on combining the spatiotemporal multiplexing method with a 4f optical system. It enables to increase an aperture of a holographic display and extend the angular visual field of view. The applicability of the modified display is evidenced by Wigner distribution analysis of holographic imaging with spatiotemporal multiplexing method and by the experiments performed at the display demonstrator.

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Authors and Affiliations

G. Finke
M. Kujawińska
T. Kozacki
W. Zaperty
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Abstract

Spatial light modulators (SLM) are devices used to modulate amplitude, phase or polarization of a light wave in space and time. Current SLMs are based either on MEMS (micro-electro-mechanical system) or LCD (liquid crystal display) technology. Here we report on the parameters, trends in development and applications of phase SLMs based on liquid crystal on silicon (LCoS) technology. LCoS technology was developed for front and rear projection systems competing with AMLCD (active matrix LCD) and DMD (Digital Mirror Device) SLM. The reflective arrangement due to silicon backplane allows to put a high number of pixels in a small panel, keeping the fill-factor ratio high even for micron-sized pixels. For coherent photonics applications the most important type of LCoS SLM is a phase modulator. In the paper at first we describe the typical parameters of this device and the methods for its calibration. Later we present a review of applications of phase LCoS SLMs in imaging, metrology and beam manipulation, developed by the authors as well as known from the literature. These include active and adaptive interferometers, a smart holographic camera and holographic display, microscopy modified in illuminating and imaging paths and active sensors.

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Authors and Affiliations

Małgorzata Kujawińska
Rosario Porras-Aguilar
Weronika Zaperty

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