Improvement of signal-to-noise ratio in digital holography using wavelet transform

Sharma, Akshay; Sheoran, Gyanendra; Jaffery, Zainul Abdin; Moinuddin, Mohammed

doi:10.1016/j.optlaseng.2007.07.004

Cited by 103 publications

(34 citation statements)

References 21 publications

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“…Combining Equations 11, 18, 19, as well as the definition of fringe visibility in Equation 15 and average electric field intensity in Equation 16, results in the following expression for phase error due to the three bucket/step method. …”

Section: Four Bucket/step Methodsmentioning

confidence: 99%

“…Other methods to reduce noise include phase error compensation, spatial light modulation (SLM), and multiple frequency overlapping [9] [10][11][12][13], which improve the contrast of phase measurements. Noise reduction is also accomplished by filtering certain frequencies, both in the spatial and Fourier planes, with Butterworth filters and masks, respectively [14,15] [6]. In addition, efficient encoding methods and correlation based de-noising algorithms have been developed to significantly reduce speckle noise [16,17].…”

Section: Introductionmentioning

confidence: 99%

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Sources and propagation of errors in quantitative phase imaging techniques using optical interferometry

et al. 2017

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Section: Four Bucket/step Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sources and propagation of errors in quantitative phase imaging techniques using optical interferometry

et al. 2017

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“…On the one hand, the digital processing perspective take advantage of the digital part involved in DH to intervene by using different filtering techniques in either the final reconstructed image [23][24][25] or the numerical reconstruction step [18][19][20][21][22]. Amongst these digital techniques exist classical filters like mean or median filtering [25], wavelet transform filtering [24] or nonlocal means filtering [23] that operate when the reconstructed image has been obtained. Other approaches intervene in the numerical process of reconstruction modifying the obtained hologram by discrete Fourier filtering [18], using binary masks [19,20], random resampling masks [22] or using a sparsity denoising technique [21].…”

Section: Introductionmentioning

confidence: 99%

Assessing digital micromirror devices for speckle noise control in digital holography

Gaviria-Mesa¹,

Hincapie²,

Garcı́a-Sucerquia³

et al. 2017

Opt. Pura Apl.

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ABSTRACT:Speckle noise is a common issue in coherent imaging techniques. As one of these techniques, digital holography (DH) is affected by this problem. Although several attempts have been made to overcome speckle noise in the numerical reconstruction of digitally recorded holograms, there still exists the need for fast and effective methods to get rid of speckle and improve image quality. We assess the suitability of a digital micromirror device (DMD) as modulator of the object illumination in a digital holographic setup, where the DMD acts generating speckle-like patterns that are projected onto the object. These patterns change the object beam in a random way. Several holograms, each with a different pattern in the object illumination, are recorded and numerically reconstructed. The image with reduced speckle noise is the result of a superposition in an intensity basis of various such reconstructions. The feasibility of the method is validated by experimental results.Key words: Digital holography; Speckle; Digital Micromirror Device RESUMEN:El ruido speckle es un problema inherente a las técnicas de formación de imágenes con luz coherente. Ya que la holografía digital es una de estas técnicas, también se ve afectada por este problema. Aunque se han hecho varios intentos por eliminar el ruido speckle en la reconstrucción numérica de hologramas registrados digitalmente, todavía existe la necesidad de métodos rápidos y efectivos para eliminar el speckle y mejorar la calidad de las imágenes reconstruidas. Nosotros evaluamos la conveniencia del uso de un dispositivo digital de microespejos (DMD) como modulador de la iluminación del objeto en un montaje holográfico digital. El DMD actúa generando patrones aleatorios tipo speckle que son proyectados sobre el objeto. Estos patrones cambian el haz objeto de una manera aleatoria y después interfiere formando el holograma. Se registran varios hologramas, cada uno con un patrón diferente en la iluminación del objeto, y se reconstruyen numéricamente. La imagen final con el ruido speckle reducido es el resultado de la superposición en intensidades de varias de estas reconstrucciones. La viabilidad del método es validada mediante resultados experimentales. [28] X. Cai and H. Wang, "The influence of hologram aperture on speckle noise in the reconstructed image of digital holography and its reduction", Opt. Commun. 281, 232-237 (2008).

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“…Other methods to reduce noise include phase error compensation, spatial light modulation (SLM), and multiple frequency overlapping [13][14][15][16], which improve the reconstructed phase image of holograms. Noise reduction is also accomplished by filtering certain frequencies, both in the spatial and Fourier planes, with Butterworth filters and masks, respectively [17][18][19]. In addition, efficient encoding methods and correlation based de-noising algorithms have been developed to significantly reduce speckle noise [20,21].…”

Section: Introductionmentioning

confidence: 99%

Holographic microscopy for 3D tracking of bacteria

et al. 2016

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Understanding when, how, and if bacteria swim is key to understanding critical ecological and biological processes, from carbon cycling to infection. Imaging motility by traditional light microscopy is limited by focus depth, requiring cells to be constrained in z. Holographic microscopy offers an instantaneous 3D snapshot of a large sample volume, and is therefore ideal in principle for quantifying unconstrained bacterial motility. However, resolving and tracking individual cells is difficult due to the low amplitude and phase contrast of the cells; the index of refraction of typical bacteria differs from that of water only at the second decimal place. In this work we present a combination of optical and samplehandling approaches to facilitating bacterial tracking by holographic phase imaging. The first is the design of the microscope, which is an off-axis design with the optics along a common path, which minimizes alignment issues while providing all of the advantages of off-axis holography. Second, we use anti-reflective coated etalon glass in the design of sample chambers, which reduce internal reflections. Improvement seen with the antireflective coating is seen primarily in phase imaging, and its quantification is presented here. Finally, dyes may be used to increase phase contrast according to the Kramers-Kronig relations. Results using three test strains are presented, illustrating the different types of bacterial motility characterized by an enteric organism (Escherichia coli), an environmental organism (Bacillus subtilis), and a marine organism (Vibrio alginolyticus). Data processing steps to increase the quality of the phase images and facilitate tracking are also discussed.

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Improvement of signal-to-noise ratio in digital holography using wavelet transform

Cited by 103 publications

References 21 publications

Sources and propagation of errors in quantitative phase imaging techniques using optical interferometry

Sources and propagation of errors in quantitative phase imaging techniques using optical interferometry

Assessing digital micromirror devices for speckle noise control in digital holography

Holographic microscopy for 3D tracking of bacteria

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