A comparison of wavelet analysis techniques in digital holograms

Molony, Karen M.; Maycock, Jonathan; McDonald, John; Hennelly, Bryan M.; Naughton, Thomas J.

doi:10.1117/12.782786

Cited by 5 publications

(3 citation statements)

References 29 publications

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“…Here we present results of a comparison between the best performing filter from this paper, the 2D filter and other standard speckle reduction techniques including the mean and median filters, the discrete Fourier filter (DFF) [41] and the best performing wavelet from a previous paper of ours [42]. Table 5 provides a comprehensive set of results and reveals that 2D filtering has outperformed the other techniques, achieving a similar level of speckle reduction but maintaining a higher resolution.…”

Section: Comparison With Other Techniquesmentioning

confidence: 91%

Speckle reduction of reconstructions of digital holograms using three dimensional filtering

Maycock

McDonald

Hennelly

2013

Optics Communications

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We report on a new digital signal processing technique that reduces speckle in reconstructions of digital holograms. This is achieved by convolving the three dimensional intensity pattern (the intensity of the propagated DH at a series of different distances) with a 3D point spread function in all three dimensions (x,y,z ). It is based on the fact that the addition of different independent speckle images on an intensity basis reduces the speckle content. We provide quantitative results in terms of speckle index and resolution, and show that filtering in the z direction has the added benefit of an increase the depth of focus of the digital hologram reconstruction.

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Section: Comparison With Other Techniquesmentioning

confidence: 91%

Speckle reduction of reconstructions of digital holograms using three dimensional filtering

Maycock

McDonald

Hennelly

2013

Optics Communications

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“…Few studies comparing the performance of speckle filters have been published so far. Wavelet-based techniques were assessed by K. M. Molony et al [4] in a study that addressed the behavior of stationary wavelet transforms and discrete wavelet transforms, with soft and hard thresholding, in terms of speckle suppression effectiveness and edge preservation capability. After testing 51 wavelets on phase-shifting and off-axis digital holograms, they found the best results for the Haar mother wavelet with soft thresholding at decomposition level 5, outperforming more traditional approaches such as mean filtering, median filtering, and Fourier filtering.…”

Section: Introductionmentioning

confidence: 99%

Assessment of speckle denoising filters for digital holography using subjective and objective evaluation models

Fonseca¹,

Fiadeiro²,

Bernardo

et al. 2019

Appl. Opt.

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Digital holography is an emerging imaging technique for displaying and sensing three dimensional objects. The perceived image quality of a hologram is frequently corrupted by speckle noise due to coherent illumination. Although several speckle noise reduction methods have been developed so far, there are scarce quality assessment studies to address their performance and they typically focus solely on objective metrics. However, these metrics do not reflect the visual quality perceived by a human observer. In this work, the performance of four speckle reduction algorithms, namely the nonlocal means, the Lee, the Frost and the block matching 3D filters, with varying parameterizations, were subjectively evaluated. The results were ranked with respect to the perceived image quality to obtain the mean opinion scores using pairwise comparison. The correlation between the subjective results and twenty different no-reference objective quality metrics was evaluated. The experiment indicates that block matching 3D and Lee are the preferred filters, depending on hologram characteristics. The best performing objective metrics were identified for each filter.

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“…In this case the final resolution is only one quarter that of the system. We also investigated wavelet filtering [6] on the reconstructed intensity. This method is the fastest and shows results that are at least as good as the other techniques but again there is a reduction in the resolution of the final image.…”

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confidence: 99%