23 research outputs found
Investigation of smooth wave fronts using SLM-based phase retrieval and a phase diffuser
A phase retrieval technique using a spatial light modulator (SLM) and a phase
diffuser for a fast reconstruction of smooth wave fronts is demonstrated
experimentally. Diffuse illumination of a smooth test object with the aid of a
phase diffuser (maximum phase shift, Df = 0.85p) results in a significant
diversity in the intensity measurements which, in turn, is beneficial for a
non-stagnating iterative phase reconstruction. The use of the SLM enables
accurate and fast speckle intensity recording and active correction of
misalignments in the setup. The effectiveness of the technique is demonstrated
in the optical testing of lenses.Comment: The paper has been presented in 1st EOS Topical Meeting on Micro-and
Nano-Optoelectronic Systems, Bremen, Germany, 7 - 9 December 201
Non-destructive testing of carbon reinforced plastics by means of phase retrieval
In this work, the SLM-based phase retrieval system will be used to inspect
carbon reinforced plastics samples (CFRP) under applying a thermal load. For
this purpose, the system is used to capture a sequence of 8 spatially separated
recording planes, where the distance between subsequent planes equals 2 mm. For
detecting the hidden failures two sets of intensity observations are recorded.
The first set for the initial state and the second set is captured after
applying the load. To recover the phase information associated with the two
states, the captured intensities have been subjected to an iterative algorithm
based on the method of generalized projection.Comment: Conf. Speckle 201
3D capture, processing, display, and perception with digital holography: results from a European-funded project
“Digital holography for 3D and 4D real-world objects’ capture, processing,
and display” (acronym “Real 3D”) is a research project funded under the Information
and Communication Technologies theme of the European Commission’s Seventh Framework Programme, and brings together nine participants from academia and industry (see
www.digitalholography.eu). This three-year project contributes to a long-term effort to
facilitate the greater presence of digital holography in the three-dimensional capture and
display markets. At the end of its third year, the aims and results of the project are summarized
Roadmap on holography
From its inception holography has proven an extremely productive and attractive area of research. While specific technical applications give rise to 'hot topics', and three-dimensional (3D) visualisation comes in and out of fashion, the core principals involved continue to lead to exciting innovations in a wide range of areas. We humbly submit that it is impossible, in any journal document of this type, to fully reflect current and potential activity; however, our valiant contributors have produced a series of documents that go no small way to neatly capture progress across a wide range of core activities. As editors we have attempted to spread our net wide in order to illustrate the breadth of international activity. In relation to this we believe we have been at least partially successful.This work was supported by Ministerio de EconomĂa, Industria y Competitividad (Spain) under projects FIS2017-82919-R (MINECO/AEI/FEDER, UE) and FIS2015-66570-P (MINECO/FEDER), and by Generalitat Valenciana (Spain) under project PROMETEO II/2015/015
Optical In-Process Measurement: Concepts for Precise, Fast and Robust Optical Metrology for Complex Measurement Situations
Optical metrology is a key element for many areas of modern production. Preferably, measurements should take place within the production line (in-process) and keep pace with production speed, even if the parts have a complex geometry or are difficult to access. The challenge for modern optical in-process measurements is, therefore, how to simultaneously make optical metrology precise, fast, robust and capable of handling geometrical complexity. The potential of individual techniques to achieve these demands can be visualized by the tetrahedron of optical metrology. Depending on the application, techniques based on interferometry or geometrical optics may have to be preferred. The paper emphasizes complexity and robustness as prime areas of improvement. Concerning interferometric techniques, we report on fast acquisition as used in holography, tailoring of coherence properties and use of Multiple simultaneous Viewing direction holography (MultiView), self reference used in Computational Shear Interferometry (CoSI) and the simultaneous use of several light sources in Multiple Aperture Shear Interferometry (MArS) based on CoSI as these techniques have proven to be particularly effective. The use of advanced approaches based on CoSI requires a transition of the description of light from the use of the well-known wave field to the coherence function of light. Techniques based on geometric optics are generally comparatively robust against environmental disturbances, and Fringe Projection (FP) is shown to be especially useful in very demanding measurement conditions
Digital holography and wavefront sensing: principles, techniques and applications
This book presents a self-contained treatment of the principles and major applications of digital hologram recording and numerical reconstruction (Digital Holography). This second edition has been significantly revised and enlarged. The authors have extended the chapter on Digital Holographic Microscopy to incorporate new sections on particle sizing, particle image velocimetry and underwater holography. A new chapter now deals comprehensively and extensively with computational wave field sensing. These techniques represent a fascinating alternative to standard interferometry and Digital Holography. They enable wave field sensing without the requirement of a particular reference wave, thus allowing the use of low brilliance light sources and even liquid-crystal displays (LCD) for interferometric applications.            Â
3D Display System Based on Spherical Wave Field Synthesis
We present a novel concept and first experimental results of a new type of 3D display, which is based on the synthesis of spherical waves. The setup comprises a lens array (LA) with apertures in the millimeter range and a liquid crystal display (LCD) panel. Each pixel of the LCD creates a spherical wave cutout that propagates towards the observer. During the displaying process, the curvature of the spherical waves is dynamically changed by either changing the distance between LA and LCD or by adapting the focal lengths of the lenses. Since the system, similar to holography, seeks to approximate the wavefront of a natural scene, it provides true depth information to the observer and therefore avoids any vergence–accommodation conflict (VAC)