Beam-shifting technique for speckle reduction and flow rate measurement in optical coherence tomography

Chen, Chaoliang; Shi, Weisong; Deorajh, Ryan; Nguyen, Nhu; Ramjist, Joel; Marques, Andrew J.; Yang, Victor X. D.

doi:10.1364/ol.43.005921

Cited by 10 publications

(5 citation statements)

References 15 publications

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“…To effectively reconstruct OCT images from noisy versions, researchers have proposed many different methods, which are generally grouped into two categories: hardware-based approaches [ [9] , [10] , [11] , [12] , [13] , [14] , [15] ] and software-based approaches [ [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] , [42] , [43] ]. However, the former category of approaches [ [9] , [10] , [11] , [12] , [13] , [14] , [15] ] requires significant modifications to existing imaging system hardware, which makes them less applicable to ordinary commercialized imaging equipment based on OCT technologies. By contrast, software-based post-processing approaches [ [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , …”

Section: Introductionmentioning

confidence: 99%

Optical coherence tomography image despeckling based on tensor singular value decomposition and fractional edge detection

Fang

Shao

Liu

et al. 2023

Heliyon

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Section: Introductionmentioning

confidence: 99%

Optical coherence tomography image despeckling based on tensor singular value decomposition and fractional edge detection

Fang

Shao

Liu

et al. 2023

Heliyon

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“…Different causes for speckle variation have been studied, including using a wavelength-diverse light source (frequency compounding) 18,19 , spatial compounding of adjacent regions 20 , dynamic speckle illumination (speckle modulation) 15,21 , and illumination from multiple incident angles (angular compounding) 22 . However, the number of speckle patterns generated by frequency compounding is limited by the total bandwidth of the light sources; spatial compounding induces loss of resolution; speckle modulation also causes resolution loss since introducing random phase patterns into the light wavefront makes the illumination area larger and unstable; angular compounding can also produce concurrent spatial compounding and mismatch in the defocused regions because the detection area varies with angle 23 .…”

mentioning

confidence: 99%

“…When this takes place, the angle-coded optical pathlength and propagation direction make the mapping between real space and image space change with angle. Although some universal image registration algorithms have been applied for angular compounding 16,23,28,29 , none of them are based on geometrical considerations of the beam path, resulting in errors produced in the registration process. The vertical correction 23 can only guarantee pure angular compounding at the focal plane.…”

mentioning

confidence: 99%

“…Although some universal image registration algorithms have been applied for angular compounding 16,23,28,29 , none of them are based on geometrical considerations of the beam path, resulting in errors produced in the registration process. The vertical correction 23 can only guarantee pure angular compounding at the focal plane. The common 'rotation + translation' method 28 does not correct quadratic deformations and can prevent spatial averaging in the focal region within a relatively small scanning range.…”

mentioning

confidence: 99%

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Angular compounding for speckle reduction in optical coherence tomography using geometric image registration algorithm and digital focusing

Zhao¹,

Winetraub²,

Yuan³

et al. 2020

Sci Rep

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Optical coherence tomography (OCT) suffers from speckle noise due to the high spatial coherence of the utilized light source, leading to significant reductions in image quality and diagnostic capabilities. In the past, angular compounding techniques have been applied to suppress speckle noise. However, existing image registration methods usually guarantee pure angular compounding only within a relatively small field of view in the focal region, but produce spatial averaging in the other regions, resulting in resolution loss and image blur. this work develops an image registration model to correctly localize the real-space location of every pixel in an OCT image, for all depths. The registered images captured at different angles are fused into a speckle-reduced composite image. Digital focusing, based on the convolution of the complex OCT images and the conjugate of the point spread function (PSF), is studied to further enhance lateral resolution and contrast. As demonstrated by experiments, angular compounding with our improved image registration techniques and digital focusing, can effectively suppress speckle noise, enhance resolution and contrast, and reveal fine structures in ex-vivo imaged tissue.

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“…Because the technique relies on coherent detection of scattered light, however, OCT images are confounded by speckle noise: a grainy texture that reduces the signal-to-noise ratio (SNR) and effective spatial resolution. A widely used method to reduce speckle noise is angular compounding, 1,2 which averages results obtained with the imaging beam probing the sample at different angles. Both the imaging system and the sample can remain stationary during the scan, allowing high imaging throughput with high image quality.…”

mentioning

confidence: 99%

Upper limit for angular compounding speckle reduction

Winetraub

Collins

et al. 2019

Applied Physics Letters

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Angular compounding is a technique for reducing speckle noise in optical coherence tomography that is claimed to significantly improve the signal-to-noise ratio (SNR) of images without impairing their spatial resolution. Here, we examine how focal point movements caused by optical aberrations in an angular compounding system may produce unintended spatial averaging and concomitant loss of spatial resolution. Experimentally, we accounted for such aberrations by aligning our system and measuring distortions in images and found that when the distortions were corrected, the speckle reduction by angular compounding was limited. Our theoretical analysis using Monte Carlo simulations indicates that "pure" angular compounding (i.e., with no spatial averaging) over our full numerical aperture (13 in air) can improve the SNR by not more than a factor of 1.3. Illuminating only a partial aperture cannot improve this factor compared to a spatial averaging system with equivalent loss of resolution. We conclude that speckle reduction using angular compounding is equivalent to spatial averaging. Nonetheless, angular compounding may be useful for improving images in applications where the depth of field is important. The distortions tend to be the greatest off the focal plane, and so angular compounding combined with our correction technique can reduce speckle with a minimal loss of resolution across a large depth of field.

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Beam-shifting technique for speckle reduction and flow rate measurement in optical coherence tomography

Cited by 10 publications

References 15 publications

Optical coherence tomography image despeckling based on tensor singular value decomposition and fractional edge detection

Optical coherence tomography image despeckling based on tensor singular value decomposition and fractional edge detection

Angular compounding for speckle reduction in optical coherence tomography using geometric image registration algorithm and digital focusing

Upper limit for angular compounding speckle reduction

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