Topic
Speckle imaging
About: Speckle imaging is a research topic. Over the lifetime, 3730 publications have been published within this topic receiving 62354 citations.
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TL;DR: The Speckle spatial analysis proved to be as accurate as the speckle temporal correlation method reported in previous studies and a noncontact, noninvasive, and low cost method for determining low viscosity values and variations in fluids.
Abstract: The noninvasive detection of a material's viscoelasticity is of great importance in the medical field. In fact, certain diseases cause changes in tissue structure and biological fluid viscosity; tracking those changes allows for detection of these diseases. Rheological measurements are also imperative in the industrial field, where it is necessary to characterize a material's viscoelasticity for manufacturing purposes. In this Letter, we present a noncontact, noninvasive, and low cost method for determining low viscosity values and variations in fluids. Laser speckle and viscometric measurements are performed on test samples having low scattering coefficients and low viscosities. The speckle spatial analysis proved to be as accurate as the speckle temporal correlation method reported in previous studies. Very low viscosities of the order of 1 mPa.s were retrieved for the first time using speckle images with either a frame rate of 1950 fps or a single acquired image.
17 citations
TL;DR: For a wide range of in-plane velocities, up to a maximum of 40% of the Nyquist limit, the random errors in the calculated displacement field are minimized by updating the reference Speckle pattern after a speckle displacement of 1/10 of the pixel spacing.
Abstract: We investigate experimentally the optimal rate at which the reference speckle pattern should be updated when dynamic speckle interferometry is used to measure transient in-plane displacement fields. Images are captured with a high-speed camera and phase shifting and phase unwrapping are done temporally. For a wide range of in-plane velocities, up to a maximum of 40% of the Nyquist limit, the random errors in the calculated displacement field are minimized by updating the reference speckle pattern after a speckle displacement of 1/10 of the pixel spacing. The technique is applied to measurements of microscale deformation fields within an adhesive joint in a carbon-fiber epoxy composite.
17 citations
TL;DR: In this paper, the Fourier transform was used to reduce the noise level of spatially filtered speckle interferograms, and correlation fringes formed by spatial filtering of the developed film were combined numerically.
17 citations
TL;DR: In this article, the authors presented the first diffraction-limited K-band image of the Red Rectangle with 76mm resolution, an H-bands image with 75mm resolution and an RG-715 filter image (∼ 800nm wavelength) with 78mm resolution.
17 citations
TL;DR: A laser microphone system allowing simultaneous detection and regeneration of the audio signal by observing the movement of secondary speckle patterns is proposed, and can restore high quality audio signal in real time under various conditions.
Abstract: Sound detection with optical means is an appealing research topic. In this manuscript, we proposed a laser microphone system allowing simultaneous detection and regeneration of the audio signal by observing the movement of secondary speckle patterns. In the proposed system, optical flow method, along with some denoising algorithms are employed to obtain the motion information of the speckle sequence with high speed. Owing to this, audio signal can be regenerated in real time with simple optical setup even the sound source is moving. Experiments have been conducted and the results show that the proposed system can restore high quality audio signal in real time under various conditions.
17 citations