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Abstract: In the present work attention is given to the physical description of phase mismatch produced in sectioned holographic moiré-like patterns. It is obtained by the controlled superposition of two sinusoidal phase gratings made by dynamic holographic process. In the writing stage of the photorefractive hologram, a two wave mixing (2WM) process, half of the transverse section of the reference beam has the optical path increased, producing this way the sectioned moiré-like pattern. The sinusoidal phase gratings, with slightly different pitches, are dynamically generated by photorefraction in a Bi12TiO20 (BTO) crystal sample. This photorefractive holographic medium was used in an anisotropic self-diffraction configuration and in diffusion as the only recording mechanism. [Copyright &y& Elsevier]

Dynamic Moire´-like patterns generation by the superposition of two dynamic sinusoidal phase gratings is described. Two 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. [Copyright &y& Elsevier]

Abstract In lensless digital holography the resolving power is limited by factors such as the finite size of recorded area, pixel dimensions and sampling rate of digital acquisition system. These factors acts as a filter that discards high-frequency components with useful information about the analyzed object. In the present work, we propose a method to overcome these limitations to proving the resolution recovery in digital in-line holography by utilizing adjustable magnification in a compressive sensing framework. Here, we model the sensed field as low-pass filtered and projected on a Fresnel base with adjustable magnification and use sparse regularization in an inverse problem approach to image reconstruction. Our method enhances image reconstruction resolution from a single recorded hologram with magnification independent of parameters such as propagation distance and wavelength of light, which enables to be used in applications like multi-wavelength digital holography. In addition, this technique offers high noise immunity and eliminates typical problems of holographically reconstructed images such as twin image and speckle. Therefore, we demonstrate by simulations and experimentally results that our approach significantly improves the quality of reconstructed images when compared with conventional techniques. Highlights • An approach for holographic magnification using compressive sensing is proposed. • The technique enables holographic reconstruction even from very noisy holograms. • Improves resolution on magnified image reconstructed from a single hologram. • Reduces typical holography problems such as speckle, twin image and aliasing. [ABSTRACT FROM AUTHOR]

Abstract: In the present work dynamic moiré-like fringe patterns, produced by photorefraction with low spatial frequencies, applied for profile determination of small objects is proposed. Basically, a Fourier transform profilometry technique is developed for an automated profile determination. This means, as far as we know, a new experimental procedure that exploits the real time holographic two wave mixing in Bi12TiO20 crystal sample. Besides, the mainly advantages of this procedure are, comparatively to the classical fringe projection method using the Michelson interferometer, best fringe pattern contrast, less speckle noise, absence of noises produced by spurious reflections and, the most significant, a pure sinusoidal shape obtained by dynamic holographic moiré-like process using photorefraction. [Copyright &y& Elsevier]

In the present work, the production of digital holographic moiré-like patterns in a well-controlled digital Fourier transform holographic experiment is reported, and this technique is then applied to profilometry. A simple implementation of the digital Fourier transform holographic setup is used to produce these interference patterns. This setup allows us to control certain parameters, namely the incident angle of the reference beams and the spatial frequency of the moiré-like patterns. These digital moiré-like patterns could have promising applications in relevant optical interferometric fields such as profilometry, as demonstrated here, along with other industrial optomechanical applications. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present a study of metallic surface roughness using the Hurst exponent calculated from speckle pattern. A set of samples was prepared using polishing techniques and the roughness was directly measured by means of an optical profilometer. To study the H exponent, an experiment was performed by illuminating the samples using an expanded laser beam and the surface image was captured by a CCD camera. We applied techniques of the Hurst exponent calculation, traditionally calculated from surface profile, in the digitalized speckle patterns generated by the rough surfaces. We showed a clear dependence of the H exponent on roughness of the samples. We demonstrated that this tool is very sensitive to defects in the surfaces and can be used for roughness control. [ABSTRACT FROM AUTHOR]