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Journal ArticleDOI

Very efficient speckle contrast reduction realized by moving diffuser device

10 Aug 2010-Applied Optics (Optical Society of America)-Vol. 49, Iss: 23, pp 4385-4391
TL;DR: Very efficient speckle contrast reduction is measured by temporal averaging using a moving diffuser on a tuning fork, which vibrates at 100 Hz over 60 microm in amplitude, a distance that is three times the surface roughness correlation length of the diffuser.
Abstract: Speckle noise reduction is best tested on a precise speckle contrast measurement bench, which should be able to measure 100% contrast in fully developed speckle as well as the smallest contrast (for example, less than 10%) after its reduction. On such a test bench, we have measured very efficient speckle contrast reduction by temporal averaging using a moving diffuser on a tuning fork, which vibrates at 100Hz over 60μm in amplitude, a distance that is three times the surface roughness correlation length of the diffuser.
Citations
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Journal ArticleDOI
TL;DR: A broad discussion about the noise issue in DH is provided, with the aim of covering the best-performing noise reduction approaches that have been proposed so far and quantitative comparisons among these approaches will be presented.
Abstract: Digital holography (DH) has emerged as one of the most effective coherent imaging technologies. The technological developments of digital sensors and optical elements have made DH the primary approach in several research fields, from quantitative phase imaging to optical metrology and 3D display technologies, to name a few. Like many other digital imaging techniques, DH must cope with the issue of speckle artifacts, due to the coherent nature of the required light sources. Despite the complexity of the recently proposed de-speckling methods, many have not yet attained the required level of effectiveness. That is, a universal denoising strategy for completely suppressing holographic noise has not yet been established. Thus the removal of speckle noise from holographic images represents a bottleneck for the entire optics and photonics scientific community. This review article provides a broad discussion about the noise issue in DH, with the aim of covering the best-performing noise reduction approaches that have been proposed so far. Quantitative comparisons among these approaches will be presented.

176 citations

Journal ArticleDOI
TL;DR: A novel framework is proposed that combines the concepts of encoding multiple uncorrelated digital holograms, block grouping and collaborative filtering to achieve quasi noise-free DH reconstructions and is comparable to the quality achievable with non-coherent techniques and far beyond the current state of art in DH.
Abstract: One of the main drawbacks of Digital Holography (DH) is the coherent nature of the light source, which severely corrupts the quality of holographic reconstructions. Although numerous techniques to reduce noise in DH have provided good results, holographic noise suppression remains a challenging task. We propose a novel framework that combines the concepts of encoding multiple uncorrelated digital holograms, block grouping and collaborative filtering to achieve quasi noise-free DH reconstructions. The optimized joint action of these different image-denoising methods permits the removal of up to 98% of the noise while preserving the image contrast. The resulting quality of the hologram reconstructions is comparable to the quality achievable with non-coherent techniques and far beyond the current state of art in DH. Experimental validation is provided for both single-wavelength and multi-wavelength DH, and a comparison with the most used holographic denoising methods is performed.

130 citations

Journal ArticleDOI
TL;DR: In this article, a non-destructive optical imaging technique that combines a conventional microscope with a compact Mach-Zehnder interferometer is used to measure etch rates at each location across the sample with resolution of 0.085 nm s−1 per pixel.
Abstract: Semiconductor etching can now be monitored in real time at nanoscale resolution using a non-destructive optical imaging technique that combines a conventional microscope with a compact Mach–Zehnder interferometer. Developed by Chris Edwards, Amir Arbabi, Gabriel Popescu, and Lynford Goddard at the University of Illinois at Urbana-Champaign in the United States, epi-diffraction phase microscopy makes it possible to collect three-dimensional videos of semiconductor fabrication processes using a CCD camera. The approach is able to measure etch rates at each location across the sample with a resolution of 0.085 nm s−1 per pixel. Such an in situ monitoring capability could be useful for improving the manufacturing quality of a wide variety of semiconductor devices.

122 citations

Journal ArticleDOI
05 Jan 2015
TL;DR: Recent progresses in developing imaging tools based on coherent imaging microscopy that can be very useful when applied into biomicrofluidics are presented.
Abstract: Today, fast and accurate diagnosis through portable and cheap devices is in high demand for the general healthcare. Lab-on-chips (LoCs) have undergone a great growth in this direction, supported by optical imaging techniques more and more refined. Here we present recent progresses in developing imaging tools based on coherent imaging microscopy that can be very useful when applied into biomicrofluidics. In some cases, the optical tweezers (OT) technique is combined with digital holography (DH), thus offering the possibility to manipulate, analyze, and measure fundamental parameters of different kinds of cells. This approach can open the route for rapid and high-throughput analysis in label-free microfluidic devices and for prognostic based on cell examination, thus allowing advancements in biomedical science.

86 citations

Journal ArticleDOI
TL;DR: Speckle contrast close to that of white light was obtained using a vibrating fiber bundle with combined temporal, spatial, and angular diversities of the illumination.
Abstract: We report significant speckle reduction in a laser illumination system using a vibrating multimode optical fiber bundle. The optical fiber bundle was illuminated by two independent lasers simultaneously. The beams from both lasers were first expanded and collimated and were further divided into multiple beams to illuminate the fiber optic bundle with normal and oblique incidence. Static diffusers were also placed at the input and output faces of the fiber bundle, thus introducing the spatial as well as angular diversity of illumination. Experiments were carried out both in free space and in imaging geometry configuration. Standard deviation, speckle contrast and signal-to-noise ratio of the images were computed, and the results were compared with those of white light illumination. Speckle contrast close to that of white light was obtained using a vibrating fiber bundle with combined temporal, spatial, and angular diversities of the illumination.

84 citations

References
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Journal ArticleDOI
TL;DR: The second edition of this respected text considerably expands the original and reflects the tremendous advances made in the discipline since 1968 as discussed by the authors, with a special emphasis on applications to diffraction, imaging, optical data processing, and holography.
Abstract: The second edition of this respected text considerably expands the original and reflects the tremendous advances made in the discipline since 1968. All material has been thoroughly updated and several new sections explore recent progress in important areas, such as wavelength modulation, analog information processing, and holography. Fourier analysis is a ubiquitous tool with applications in diverse areas of physics and engineering. This book explores these applications in the field of optics with a special emphasis on applications to diffraction, imaging, optical data processing, and holography. This book can be used as a textbook to satisfy the needs of several different types of courses, and it is directed toward both engineers ad physicists. By varying the emphasis on different topics and specific applications, the book can be used successfully in a wide range of basic Fourier Optics or Optical Signal Processing courses.

12,159 citations

Book
01 Jan 1968
TL;DR: The second edition of this respected text considerably expands the original and reflects the tremendous advances made in the discipline since 1968 as discussed by the authors, with a special emphasis on applications to diffraction, imaging, optical data processing, and holography.
Abstract: The second edition of this respected text considerably expands the original and reflects the tremendous advances made in the discipline since 1968. All material has been thoroughly updated and several new sections explore recent progress in important areas, such as wavelength modulation, analog information processing, and holography. Fourier analysis is a ubiquitous tool with applications in diverse areas of physics and engineering. This book explores these applications in the field of optics with a special emphasis on applications to diffraction, imaging, optical data processing, and holography. This book can be used as a textbook to satisfy the needs of several different types of courses, and it is directed toward both engineers ad physicists. By varying the emphasis on different topics and specific applications, the book can be used successfully in a wide range of basic Fourier Optics or Optical Signal Processing courses.

9,800 citations

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Additional excerpts

  • ...Because π(2)KxðzÞ with z 1⁄4 ðξ=2Þ2 can be well approximated by p1ðzÞ − p2ðzÞ lnðzÞ in the entire 1⁄20; 1 range of z, where p1ðzÞ 1⁄4 1:38629þ 0:11197zþ 0:07252z2 and p2ðzÞ 1⁄4 0:5þ 0:12134zþ 0:02887z2 [12,13], it has a logarithmic singularity at its origin....

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Journal ArticleDOI
TL;DR: In this paper, a relation from vector scattering theory has been used to predict the angular distribution of scattered light from optical surfaces as a function of the wavelength, optical constants of the material, and spectral density function.
Abstract: A relation from vector scattering theory has been used to predict the angular distribution of scattered light from optical surfaces as a function of the wavelength, optical constants of the material, and spectral density function. For calculations of one-dimensional (two-dimensional) scattering, the spectral density function of the surface roughness is obtained from the Fourier transform (Hankel transform) of the autocovariance function, which in turn is determined from surface-profile data. Measured statistics presented for various types of optical surfaces indicate that there are three basic components of surface structure: long-range waviness, short-range random roughness, and periodicity; one or more of which may be present on a given surface. Averaged and unaveraged surface-profile data for the same surface are shown to be consistent. Experimental data are presented that yield an exponential autocovariance function, and give a reasonably good fit to a Poisson distribution of zero crossings. Finally, angular scattering values calculated using measured surface statistics with vector scattering theory are compared to scattering values measured on the same surface. The shapes of the measured and calculated curves are similar, but the magnitudes are not. However, the rms surface roughnesses calculated from total integrated scattering measurements are in excellent agreement with values measured directly on these same surfaces.

273 citations


"Very efficient speckle contrast red..." refers background in this paper

  • ...A frosted glass diffuser (Sigma Koki, Japan #1000) is a promising candidate for such an FDS generator, because its surface roughness on a roughened side measured Ra 1⁄4 0:34 μm and Sm 1⁄4 40 μm, where Ra approximates root-mean-squared surface roughness σh, while Sm approximates twice the autocorrelation length rc [6]....

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