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High Speed Optical Coherence Tomography Based On K-linear Swept-Source And Optical Computing

Posted on:2015-12-08Degree:DoctorType:Dissertation
Country:ChinaCandidate:T C HuoFull Text:PDF
GTID:1108330476955917Subject:Physics
Abstract/Summary:PDF Full Text Request
This thesis originates from the research on the traditional swept-source optical coherence tomography(SS-OCT) itself, and then extends to the investigation on the high speed swept-source, and finally, based on the deep understanding of the core ideas of optical coherence tomography(OCT), to the demonstration of the time-serial optical computing method which surpasses all the high speed imaging techniques of current OCT system and is a distinctive state of the art technique.Firstly, the conventional SS-OCT generally requires converting the original detected spectrum from the wavelength domain to the wavenumber domain by numerical interpolations and resampling, so as to reconstruct a high quality OCT image via the fast Fourier transform. However, this process is time-consuming and becomes a bottleneck to enhance imaging speed. Meanwhile, the traditional swept-sources commonly use optical filters with mechanical movement devices to select the optical frequency; therefore it was di?cult to achieve high-speed wavelength scanning due to the inertia limit. In this thesis,we proposed and developed an acousto-optic deflector based high speed k-linear swept source. Based on the feature of the acousto-optic deflector, it is possible to scan linearly the optical frequency over time. Therefore the complex wavenumber linearization correction and resampling process in typical Fourier-domain OCT can be avoided, leading to great increase of the imaging speed. With the fast response characteristic of sound and light interaction, the k-linear swept source was able to have a scan speed up to 2 MHz.Secondly, the traditional time-stretch swept source uses fiber as the dispersive medium, which cannot achieve linear frequency output with time. Its scan rate is generally below 8 MHz. This thesis proposed and developed, for the first time, a linearly chirped fiber Bragg grating and optical bu?ers stage based 40 MHz swept-source that is able to scan linearly the output frequency with time. With this light source, we demonstrated OCT imaging of biological tissues at an ultra-high scan rate of 40 MHz with high sensitivity and no need of any averaging processes. To our knowledge, this is the highest speed swept-source for OCT at 1550 nm wavelength range.In particular, based on deep understanding of dispersive Fourier transform and swept-source OCT system, we creatively put forward the concept of time serial optical computing and combine it with the principle of spectral-domain OCT and swept-source OCT to develop the totally new techniques of optical computing SD-OCT(S D- OC2T)and optical computing SS-OCT(S S-OC2T), respectively. These two new techniques enable OCT to extract biological structure information directly by using time-serial optical computing with no need of high speed AD sampling, transport and big data processing.We believe that optical computing gives a fundamental solution to the basic di?culties of massive data processing in current high speed OCT system, launching the new era of true real-time 3D imaging.With the development of linear in frequency swept-source and optical computing,the non-invasive OCT real-time imaging with high-speed, high resolution and high sensitivity is coming to the revolutionary progress, and will have a profound influence in other related fields. The development of OCT technology would give people a long-term inspiration, as we believe.
Keywords/Search Tags:Swept-source OCT, Acousto-optic Deflector, time-stretch, Dispersive Fourier transformation, Optical computing
PDF Full Text Request
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