Development of full-field optical coherence tomography system

Deconvolution methods are not feasible in spectral domain optical coherence tomography (SD-OCT) system due to the linear space variant property of its axial point spread function (PSF). In order to improve the axial resolution and enhance the imaging quality of the SD-OCT system, a Lucy-Richardson algorithm based deconvolution method is implemented with the numerically compensated A-scan signals and the effective axial PSF in this paper. The main factors decreasing the value of PSF along the axial direction and blurring the images, as well as the deconvolution process, are theoretical studied. With the developed SD-OCT system, the axial modulation function of the PSF is retrieved by curve fitting of the measured peak values of the PSF at different axial positions. After compensating the A-scan signal with the modulation function, deconvolution is performed with the measured effective axial PSF. In vivo imaging on typical samples is conducted and reconstruction is done based on the deconvolution method. The comparing results demonstrate that the proposed deconvolution method not only enhances the axial resolution but also improves the depth dependent sensitivity fall-off in SD-OCT system.

Imaging quality enhancement by deconvolution in spectral domain optical coherence tomography

Wang¹,

Yan²,

Ding³

et al. 2010

Path length coded coherence combination for three-dimensional superresolution

Zai-Ming¹,

Zhihua²,

Wang³

et al. 2011

Axial resolution and traverse resolution in optical coherence tomography (OCT) imaging are determined by different factors, while axial resolution is determined by both the coherence length of light source and the beam-focusing condition, and traverse resolution is determined by the beam-focusing condition of the sample arm. In the main approaches to axial resolution improvement in OCT, a light source with a broaden bandwidth is used and coherence gating is combined with apodization, which cannot improve the traverse resolution. A method is introduced to increase both the axial resolution and traverse resolution simultaneously in an OCT system by the path length code and coherent compounding method. Different effective functions are formed by adding a path length coding lens in to the proposed OCT system, which are corresponding to different path lengths. Owing to the intrinsic ability to differentiate path lengths, we can obtain several images of the same sample, corresponding to the different effective functions simultaneously. By adding these functions through numerically controlling their relative contributions, we can finally obtain a coherent compounding signal with three-dimensional superresolutions of axial resolution and traverse resolution. Compared with the previous approaches, the path length code and coherent compounding method is very easy to operate and its cost is very low, which can not only avoid the high cost and inconvenience in implantation, but also increase both axial and traverse resolutions simultaneously.

Correlated Doppler optical coherence tomography

Huang¹,

Ding²,

Wang³

et al. 2012

A new method based cross-correlation technique (CD-OCT) is proposed to acquire and analyse the information about flow velocity with low signal-to-noise ratio(SNR) in spectral-domain optical coherence tomography(SD-OCT). We theoretically study the procedure of this method, and analyse the correlation between the noises by computer simulation and experiment. The Doppler flow images reconstructed by CD-OCT are compared with those reconstructed by Joint spectral and time-domain optical coherence tomography (STD-OCT). The results demonstrate that CD-OCT can significantly improve the SNR, thus rendering it suitable for the flow measurement in low SNR.