Speckle reduction in optical coherence tomography by frequency compounding

Abstract

We are investigating the possibility of a frequency compounding method for speckle reduction in optical coherence tomography. The method is based on incoherent summation of the magnitudes of two independent interferometric signals, which were recorded at two different center wavelengths simultaneously. We derive the corresponding statistics and compare the theoretical results with measurements obtained in a uniformly scattering sample. Finally we demonstrate our method by comparing images of human skin recorded in vivo with and without frequency compounding. The compounding method results in an increased contrast and improved image quality without loss of resolution.

Application of Improved Homogeneity Similarity-Based Denoising in Optical Coherence Tomography Retinal Images

“…It has been shown that speckle noise is the most predominant noise source in OCT imaging [3][4][5][6][7][8][9]. Apart from other systemspecific noise like electric or shot noise, speckle is common to all OCT commercial systems [26].…”

“…In order to quantitatively measure the denoising performance with full reference metrics, synthetic noise OCT images were generated by computationally corrupting virtually noiseless clinical images using a known amount of noise. We obtained images of background noise from a commercial SD-OCT device (i.e., CirrusOCT) in order to characterize the expected noise, which was later employed to computationally alter averaged HD clinical B-scans in a signal-dependent manner (as expected with noise in SD-OCT systems [3][4][5][6][7][8][9]). The effect of corrupting the averaged HD clinical images with a more general simulated speckle noise was also investigated.…”

“…In Schmitt's paper [3], three hardwarebased speckle-reduction techniques (polarization diversity [6], spatial compounding [7,8], and frequency compounding [9]) were described. In the compounding technique, a series of images of one target are sampled at different times, with different frequencies, or in different scan directions.…”

Optical coherence tomography—current technology and applications in clinical and biomedical research

“…Numerous speckle reduction methods have therefore been developed and applied to OCT [54]. Some are based on incoherent addition of several signals from the same location under varying conditions, e. g. angular compounding [57], spatial compounding [58,59], and frequency compounding [60]. Where compounding is not feasible different image processing techniques can be applied to suppress speckle, e. g. various types of smoothing filters, deconvolution [61,62], wavelet analysis [63], rotating kernel transformation [64], and anisotropic diffusion [65].…”

Angular high-speed massively parallel detection spectral-domain optical coherence tomography for speckle reduction

“…However speckles provide information about both the structure of the imaged object as well as image noise. Therefore, several approaches have been developed for speckle reduction using angular compounding, [1][2][3][4] frequency compounding, 5 polarization compounding, 6 and strain compounding. 7,8 Angular compounding is performed by averaging multiple images acquired at different angles.…”