In the present paper low frequency moiré fringe patterns are used as secure numerical code generator. These moiré
patterns are experimentally obtained by the superposition of two sinusoidal gratings with slightly different pitches. The
Bi12TiO20 photorefractive crystal sample is used as holographic medium An optical numerical base was defined with patterns representing 0,1 and -1 digits like bits. Then, the complete set of these optical bits are combined to form bytes,
where a numerical sequence is represented. The results show that the proposed numerical code could be used as standard
numerical identification in robotic vision or in transmition of security numerical keys.
In the present paper we describe the holographic interferometric beating to produce dynamic photorefractive moiré-like patterns with two or more variation directions. It has been experimentally obtained by the superposition of two sinusoidal gratings with slightly different pitches for each direction of fringe variation obtained. These dynamic moiré-like patterns are induced in the volume of the Bi12TiO20 (BTO) crystal sample used as dynamic holographic medium. The Fourier transform profilometry method is applied using two or more moiré fringe patterns with different direction of variations, simultaneously or not, projected onto an object surface.
In the present work holographic interferometric beating to produce digital moiré like patterns in a well controlled digital Fourier transform holographic experiment are reported. A simple implementation of digital Fourier transform holographic setup is used to produce these patterns. This setup allows us to control some parameters like incident angle of reference beams and spatial frequency of the interferometric beating patterns. The moiré like patterns could be promising to some optical interferometric applications, including profilometry and other opto-mechanical applications.
In the present work digital holographic interferograms obtained by digital Fourier transform holography are used to
analyze fracture propagation. Digital holography is a non-contact optical technique that consists in recording digitally a
hologram with a CCD sensor as holographic media. The image reconstruction of the object is obtained numerically.
Holographic interferograms are obtained by superposition of two holograms of object, being the first one in its initial
state and the second one after some modification produced in this object. Basically, the main purpose is to use
interferograms for investigating mixed-mode I/II fracture. Tests on cracked specimen under combined loading are
performed.
In the present letter low frequency moiré fringe patterns are used as secure numerical code generator. These moiré patterns are experimentally obtained by the superposition of two sinusoidal gratings with slightly different pitches. The Bi12TiO20 photorefractive crystal sample is used as holographic medium An optical numerical base was defined with patterns representing 0,1 and -1 digits like bits. Then, the complete set of these optical bits are combined to form bytes, where a numerical sequence is represented. The results show that the proposed numerical code could be used as standard numerical identification in robotic vision or in transmition of security numerical keys.
In the present work an interferometric approach based on the implementation of a digital holography setup is discussed.
It is used to determine interferograms of materials under small deformations. In order to do this, a fixed-free cantilever
beam subjected to a concentrated force applied at the free end is taken into account. The experimental procedure to
estimate displacements is carried out using digital Fourier transform holography (DFTH) technique. This is obtained
making a very simple modification in the classical setup architecture of the DFTH setup. It is also demonstrated the easy
and practical viability of the setup in an interferometric application for mechanical parameters determination.
In the present work we present a simple comparative analysis of the results in the optical Fourier transform profilometry
which fringe projection is produced by two different methods, dynamic moiré-like patterns and Michelson
interferometer. First, the Fourier transform profilometry technique is applied in the projected moiré fringe pattern onto an
object surface. Then, this result is compared to the Michelson fringe pattern projection in the same method of
profilometry that is applied using the same test object. We have conclude that dynamic moiré-like fringe patterns could
be used with some advantages, comparatively to the results obtained by the classical Michelson fringe patterns.
We propose and physically discuss a kind of holographic Fourier synthesis in the profile of dynamic Moiré-like patterns. The interference patterns are obtained by progressively controlling the superposition of more than two dynamic sinusoidal phase gratings. It represents a new holographic optical nondestructive testing routine in real time for metrological purposes. The sinusoidal phase gratings with slightly different pitches are dynamically generated by photorefraction in the Bi12TiO20 (BTO) crystal sample. The photorefractive holographic medium is used in anisotropic self-diffraction configuration and in a diffusion-only recording mechanism.
Fourier synthesis of dynamic Moire-like patterns generation with square intensity profile obtained by the superposition of more than two dynamic sinusoidal phase gratings is described. The sinusoidal phase gratings of slightly different pitches are involved and occur in the photorefractive crystal Bi12TiO20 (BTO). This holographic dynamic medium has been used in anisotropic two wave mixing architecture in diffusion only recording mechanism.
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