Holographic Speckle Interferometry Research Articles

Deep sound-field denoiser: optically-measured sound-field denoising using deep neural network.

This paper proposes a deep sound-field denoiser, a deep neural network (DNN) based denoising of optically measured sound-field images. Sound-field imaging using optical methods has gained considerable attention due to its ability to achieve high-spatial-resolution imaging of acoustic phenomena that conventional acoustic sensors cannot accomplish. However, the optically measured sound-field images are often heavily contaminated by noise because of the low sensitivity of optical interferometric measurements to airborne sound. Here, we propose a DNN-based sound-field denoising method. Time-varying sound-field image sequences are decomposed into harmonic complex-amplitude images by using a time-directional Fourier transform. The complex images are converted into two-channel images consisting of real and imaginary parts and denoised by a nonlinear-activation-free network. The network is trained on a sound-field dataset obtained from numerical acoustic simulations with randomized parameters. We compared the method with conventional ones, such as image filters, a spatiotemporal filter, and other DNN architectures, on numerical and experimental data. The experimental data were measured by parallel phase-shifting interferometry and holographic speckle interferometry. The proposed deep sound-field denoiser significantly outperformed the conventional methods on both the numerical and experimental data. Code is available on GitHub (https://github.com/nttcslab/deep-sound-field-denoiser).

IMPROVEMENT OF THE DIFFRACTION EFFICIENCY OF SPECKLE INTERFEROGRAMS BY SELECTING A METHOD OF MANIFESTATION AND DEVELOPER FOR PRACTICAL USE IN EXPERIMENTAL MECHANICS

This article presents a qualitatively new developed technology of out-of-band registration of speckle holograms in the study of deformations in the concentration zone on samples with holes. Summary. One of the most important aspects of speckle-holographic interferometry is the quality of the resulting speckle-hologram, which largely determines its diffraction efficiency. In this case, the improvement of diffraction efficiency in solving practical problems is carried out through the selection of the developer of photographic plates, the installation of a certain exposure time and the choice of methods for processing photographic plates. However, in practice, there are often problems of obtaining the maximum diffraction efficiency of holograms. We made a choice of developer, exposure time, as well as methods of photo processing of speckle holograms in colliding beams in the process of practical experiment. Practical significance. The technology of out-of-band registration of speckle holograms described in the article can be used in the process of research of SSS of full-scale aircraft structures in areas of stress concentration, as well as their detection during industrial full-scale tests.

Crack-Growth on Canvas Paintings during Transport Simulation Monitored with Digital Holographic Speckle Interferometry

Crack-Growth on Canvas Paintings during Transport Simulation Monitored with Digital Holographic Speckle Interferometry

About Holographic (Interferometric) Approach to the Primary Visual Perception

The discussed physical model of the primary visual perception is based on the joint consideration of the structural features of the retina and its functioning, namely, inversion of the retina, the presence of micro-oscillations (tremor), high rate of reaction of photoisomerization and its spatial-time coherence. The above model indicates the existence of significant forward light scattering in the layers of the retina. The existence of micro-oscillations and partial time coherence of the first stage of photoisomerization reaction allows proposing a mechanism of image restoration based on the principles of holographic speckle interferometry.

High Resolution Speckle Methods For Overcoming Image Degradation Caused By The Atmosphere And Telescope Aberrations

We discuss various high resolution speckle methods that can overcome image degradation caused by the atmosphere and telescope aberrations. All methods yield diffraction-limited resolution, for example 0.03" for a 3.6m telescope. We show speckle interferometric observations of asteroids, Pluto/ Charon, double stars, and the gravitational-lens triple quasar. True diffraction-limited images can be reconstructed by speckle interferometry if there is a point, source in the isoplanatic neighborhood of the object (holographic speckle interferometry). Speckle masking is a triple-correlation method that yields diffraction-limited images of general astronomical objects. A point source near the object is not required. We describe an application of speckle masking to the central object in the giant HII region NGC 3603. Speckle spectroscopy is a speckle method that yields diffraction-limited objective prism spectra. It is also possible to apply speckle masking to multiple-mirror interferometers or long-baseline interferometers on the ground or in space. True images of very high angular resolution can be obtained by these techniques. Computer simulations are shown for illustration.

Deformation and fracture of composites by the methods of speckle-holographic interferometry

The holographic method described makes it possible effectively to investigate complex problems of the deformation mechanics of composites, and obtain new precise information on their fracture process. The high sensitivity (to 0.1μm) and the almost unlimitedly small strain measuring bases make it convenient to use the method described to investigate the reliability of the hypotheses and assumptions of theoretical calculation methods, for the direct experimental observation of “fine” deformation effects, and for investigating the laws of deformation and fracture of new composites and the critical elements of structures made of such materials.

Use of speckle-holographic interferometry to study the strain-strain state of a gas-turbine engine disk close to the blade root fixing

Use of speckle-holographic interferometry to study the strain-strain state of a gas-turbine engine disk close to the blade root fixing