Development And Application Of Orthogonal Dispersive Spectral Domain Optical Coherence Tomography

Optical coherence tomography(OCT)uses coherent gating to obtain cross-sectional images of inner sample structures,which is a non-invasive,high-sensitivity and micrometer-scale-resolution imaging modality.Compared with the first generation time domain OCT,the second generation spectral domain OCT offers significant advantages in imaging speed and sensitivity,and it plays an important role in the fields of clinical ophthalmology,functional imaging and industrial examination.The subject of this dissertation is orthogonal dispersive spectral domain OCT and its applications,and detailed works included in the thesis are:An ultralong depth range orthogonal dispersive spectral domain optical coherence tomography system was developed,which was based on an orthogonal dispersive spectrometer consisted by a grating and a virtually-imaged phased array.A complete theory of orthogonal dispersion about grating and virtually-imaged phased array was proposed,and the problems of wavenumber mapping errors and periodic intensity modulations while obtaining desirable one-dimensional spectra from the recorded two-dimensional orthogonal spectra were solved.An innovative method for orthogonal spectra calibration by using actively generated interference pattern was presented,making the orthogonal dispersive spectrometer available in OCT imaging.The developed orthogonal dispersive spectral domain OCT system achieved an ultrahigh spectral resolution of 2 pm,a system sampling rate of 105 and an ultralong imaging depth range over 100 mm.An application for lens dimensional metrology was studied based on orthogonal dispersive spectral domain interferometer.A complex method based on actual spectral phase shift was proposed to achieve ultrahigh suppression of artifacts.Suppression ratios of 80 dB for DC term and 60 dB for mirror images were achieved.Based on the improved method,along with the ultralong depth range orthogonal dispersive spectral domain interferometry and multi-spectral averaged phase measurement algorithm,a high-speed,high-precision and ultralong-range dimensional metrological system was established.Compared with current commercial products,measurement precision and speed of the proposed system were enhanced by an order and two orders of magnitude respectively.An extended-depth-of-focus,high-resolution OCT system was designed and proposed to resolve the trade-off between lateral resolution and depth of focus.A quasi-needle-like focus was synthesized by optical path length coding principle and the ultralong depth range of orthogonal dispersive spectral domain OCT.A custom-built optical path length coder was manufactured for generating multiple beams with different optical path lengths.A well designed optical system was used to focus the multiple beams into different depths in the sample for imaging.To reconstruct the final OCT image with high lateral resolution and extended DOF,multiple in-focus regions from respective sub-images were extracted by windowed functions and stitched together.The synthesized quasi-needle-like focus provided a four-fold extension of conventional depth of focus,while maintaining a high lateral resolution of 2.5 ?m over a depth range of approximately 240 ?m.