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We demonstrate three-dimensional structural and functional retinal imaging with line-field parallel swept source imaging (LPSI) at acquisition speeds of up to 1 MHz equivalent A-scan rate with sensitivity better than 93.5 dB at a central wavelength of 840 nm. The results demonstrate competitive sensitivity, speed, image contrast and penetration depth when compared to conventional point scanning OCT. LPSI allows high-speed retinal imaging of function and morphology with commercially available components. We further demonstrate a method that mitigates the effect of the lateral Gaussian intensity distribution across the line focus and demonstrate and discuss the feasibility of high-speed optical angiography for visualization of the retinal microcirculation.

OCT is a promising tool for performing fast and cheap noninvasive biopsies. High speed imaging helps to reduce motion artifacts that cause decreased sensitivity and resolution. Using a point scanning configuration one is ultimately limited in sensitivity. Therefore parallel configurations are a potentially attractive solution to further enhance the speed capabilities of future OCT systems. Even more, if full field configurations are employed one can exploit the intrinsic phase correlation over the field of view for digital wavefront correction techniques. Full field OCT has nevertheless limitations concerning the missing confocal gating. The sensitivity is decreased in the presence of specular reflexes from optical interfaces, furthermore light scattering cross talk between pixel causes additional signal degradation. A good compromise between parallel detection capabilities and confocal gating seems therefore line field OCT. We built a bench top line field system employing a frequency swept source enabling 2D/3D imaging at up to 200 kA-scans/s with an axial resolution of 8μm and a depth range of 3.53mm in air. To prevent specular reflexes reaching the line scan camera, an off axis configuration of the optical path together with spatial filters placed in conjugate planes of the system was used. Geometrical optics based digital refocusing through the full depth range was shown on a sample target containing FeO particles, on a biological sample and in vivo. Furthermore, we assessed the regime where line field has an advantage over point scanning OCT in terms of sensitivity.

In vascular plexuses perpendicular to the optical axis, traditional Doppler OCT (DOCT) is highly sensitive to the Doppler angle, limiting its reproducibility and accuracy in clinical practice. A more stable approach is the dual-beam bidirectional technique that probes the sample from two distinct illumination directions allowing reconstruction of the true flow velocity and later the blood flow with knowledge of the vessel diameter. However the absolute velocity calculation still requires the evaluation of the flow angle in the en face plane. Based on dual beam bidirectional DOCT we suggest calculating the flow directly from an adequately chosen Doppler cross section and demonstrate that this method is independent of the vessel angle. The principle is implemented with Swept Source OCT at 1060nm with 100,000 A-Scans/s. We confirm, with in vitro measurements of a perfused capillary and with a selected human retinal artery, that this method employing two beams only is completely independent of any vessel orientation.

Bidirectional Doppler optical coherence tomography is a stable and accurate method to extract the absolute velocity of vessels close to perpendicular to the optical axis by illuminating the sample under two different angles. However it requires knowledge of the vessel angle in the en face plane. In this Letter, we demonstrate that a direct calculation of the flow out of bidirectional Doppler cross sections perpendicular to the illumination plane is independent of that angle and of the Doppler angle, thereby improving the accuracy and flexibility of that technique. We validate our approach with an in vitro experiment and in vivo measurements of a human retinal vessel and discuss the practical limitations of this approach. The method yields accurate flow values for most vascular plexuses without precise knowledge of the vessel orientation. The precision gradually decreases for larger en face angles.

Traditional Doppler OCT is highly sensitive to motion artifacts due to the dependence on the Doppler angle. This limits its reproducibility in clinical practice. To overcome this limitation, we use a bidirectional technique with a novel rotating scanning scheme. The volume is probed simultaneously from two distinct illumination directions with variable controlled orientations, allowing reconstruction of the true flow velocity, independently of the vessel orientation. A Dove prism in the sample arm permits a rotation of the illumination directions that can be synchronized with the standard beam steering device. The principle is implemented with Swept Source OCT at 1060nm with 100,000 A-Scans/s. We apply the system to human retinal absolute blood velocity measurement by performing segment and circumpapillary time series scans around the optic nerve head. We also demonstrate microvasculature imaging by calculation of squared intensity differences between successive tomograms.

We present an extended focus OCT system for dermatologic applications that maintains high lateral resolution over a large depth range by using Bessel beam illumination. More, Bessel beams exhibit a self-reconstruction property that is particularly useful to avoid shadowing from surface structures such as hairs. High lateral resolution and high-speed measurement, thanks to a rapidly tuning swept source, allows not only for imaging of small skin structures in depth but also for comprehensive visualization of the small capillary network within the human skin in-vivo. We use this information for studying temporal vaso-responses to hypothermia. In contrast to other perfusion imaging methods such as laser Doppler imaging (LDI), OCT gives specific access to vascular responses in different vascular beds in depth.

We present a Bessel beam illumination FDOCT setup using a FDML Swept Source at 1300 nm with up to 440 kHz A-scan rate, and discuss its advantages for structural and functional imaging of highly scattering samples. An extended focus is achieved due to the Bessel beam that preserves its lateral extend over a large depth range. Furthermore, Bessel beams exhibit a self-reconstruction property that allows imaging even behind obstacles such as hairs on skin. Decoupling the illumination from the gaussian detection increases the global sensitivity and enables dark field imaging. Dark field imaging is useful to avoid strong reflexes from the sample surface that adversely affect the sensitivity due to the limited dynamic range of high speed 8 bit acquisition cards. In addition the possibility of contrasting capillaries with high sensitivity is shown, using inter-B-scan speckle variance analysis. We demonstrate intrinsic advantages of the extended focus configuration, in particular the reduction of the phase decorrelation effect below vessels leading to improved axial vessel definition.

We present a Bessel beam illumination FDOCT setup with FDML buffered swept source at 1300nm. An extended focus is achieved due to the Bessel beam that preserves its lateral extend over a large depth range. Decoupling the illumination from the Gaussian detection improves the sensitivity as compared to double passing the ring filter and enables dark field imaging. Dark field imaging is useful to avoid strong reflexes from the samples surface that adversely affect the sensitivity due to the limited dynamic range of high-speed 8bit acquisition cards. Furthermore, Bessel beams exhibit a self-reconstruction property that allows imaging even behind obstacles such as hairs on skin. Densely sampled volumes of skin in-vivo with high lateral resolution are acquired at up to 440kHz A-Scan rate. In addition the possibility of contrasting capillaries with high sensitivity is shown, using inter-B-scan speckle variance analysis. High-speed imaging is of crucial importance for imaging small details since sample motion artifacts are reduced and high sampling can be maintained while increasing the B-Scan rate.

We present an extended focus FDOCT setup with FDML swept source centered at 1310nm. The illumination, preserving its lateral extend over a large depth range thanks to the use of a Bessel beam, is decoupled from the Gaussian detection in order to increase the global sensitivity. The efficient spatial separation enables dark-field imaging. In-vivo measurements in the skin were performed to demonstrate the gain in lateral resolution while preserving the imaging depth. More, the calculation of the speckle variance between B-Scans allows a clear visualization of the microvasculature.

We present a spectral domain refractive low coherence interferometry technique (SD-rLCI) using a novel extreme broadband Super Continuum laser source equipped with a dual spectrometer system which is able to measure the dispersion in the visual and near infrared range simultaneously. The setup was verified obtaining the second order dispersion of distilled water. We will use this system for measuring the dispersion sensitivities of important tissue substances in order to determine analyte concentrations within mixtures.

Using refractive low coherence interferometry (rLCI) technique we determined the concentration of aqueous mixtures of glucose and albumin. The method is based on second-order dispersion derived from spectral phase of time-domain interferogram. A series of 9 mixtures with different concentration ratios in the range of 5mg/ml to 50mg/ml was performed. The results show errors between prepared and measured concentration of a few percent up to 38%.

We present a low-coherence technique for the measurement of concentrations in aqueous solutions. It is based on a second-order dispersion measurement using the phase of the Fourier transform of the interferogram term obtained with an unbalanced Michelson interferometer. We demonstrate this approach by concentration measurements of aqueous mixtures of NaCl and glucose solutions. Results show errors between a few percent for high concentrations, up to 31% for low concentrations. The application of such a technique in OCT might require ultrahigh depth resolution and/or other scattered photon rejection techniques.

We present an Optical coherence tomography (OCT) system which records full tomograms of in vivo eye structure in parallel. A full tomogram of 256(x) x 512(z) pixels covering a sample region of 6.7mm x 3,8mm is recorded in only 1ms. A standard Superluminescent diode (SLD) is used which results a depth resolution of 17 mm. Since neither depth nor transverse scanning is necessary, the system allows capturing full tomograms with high acquisition speed and reduced motion artifacts. To the best of our knowledge we present the first in vivo tomogram obtained with full parallel FD OCT system. In order to study cross talk issues for parallel illumination the transversal resolution for a thermal light source is compared to that with an SLD.

We present a novel medical imaging modality based on optical coherence tomography (OCT) that enables in vivo 3D tomography at acquisition rates up to 1 MHz. Line field parallel swept source interferometric imaging (LPSI) combines line-field swept source OCT with modulation of the interferometric signal in spatial direction for full range imaging. This method enables high speed imaging with cost-effective and commercially available technology. We explain the realization of the LPSI setup, acquisition, and postprocessing and finally demonstrate 3D in vivo imaging of human nail fold. To the best of our knowledge, sensitivity and depth penetration are competitive with respective point scanning OCT methods at a comparable wavelength. Measured maximum sensitivity is 98.5 dB for 100 kHz and 90 dB for 1 MHz. Together with the significantly relaxed technological requirements regarding detection and swept source technology, LPSI might be a promising concept for future diagnostic OCT imaging.

We demonstrate noninvasive structural and microvascular contrast imaging of different human skin diseases in vivo using an intensity difference analysis of OCT tomograms. The high-speed swept source OCT system operates at 1310 nm with 220 kHz A-scan rate. It provides an extended focus by employing a Bessel beam. The studied lesions were two cases of dermatitis and two cases of basal cell carcinoma. The lesions show characteristic vascular patterns that are significantly different from healthy skin. In case of inflammation, vessels are dilated and perfusion is increased. In case of basal cell carcinoma, the angiogram shows a denser network of unorganized vessels with large vessels close to the skin surface. Those results indicate that assessing vascular changes yields complementary information with important insight into the metabolic demand.

Retinal and choroidal vascular imaging is an important diagnostic benefit for ocular diseases such as age-related macular degeneration. The current gold standard for vessel visualization is fluorescence angiography. We present a potential non-invasive alternative to image blood vessels based on functional Fourier domain optical coherence tomography (OCT). For OCT to compete with the field of view and resolution of angiography while maintaining motion artifacts to a minimum, ultrahigh-speed imaging has to be introduced. We employ Fourier domain mode locking swept source technology that offers high quality imaging at an A-scan rate of up to 1.68 MHz. We present retinal angiogram over ∼ 48 deg acquired in a few seconds in a single recording without the need of image stitching. OCT at 1060 nm allows for high penetration in the choroid and efficient separate characterization of the retinal and choroidal vascularization.

In this paper we present a system for intraocular distance measurement of the human eye in vivo with high sensitivity. The instrument is based on Fourier domain low coherence interferometry (FD-LCI). State-of- the-art FD-LCI systems are limited to a depth range of only a few mm, because the depth range is determined by the spectral resolution of the spectrometer. To measure larger distances (e.g. human eye length) we implemented two separate reference arms with different arm lengths into the interferometer. Each reference arm length corresponds to a different depth position within the sample (e.g. cornea and retina). Therefore two different depth sections, each with a depth range of a few mm can be imaged simultaneously. With the new system axial distances could be measured with a precision of 8 microm. We demonstrate the performance of the instrument by measuring the axial eye length of 9 patients with cataract and compare our results with those obtained using the IOL Master (Carl Zeiss Meditec Inc.).

We introduce a method to extract the photoacoustic (PA) signal from the phase time evolution of an optical coherence tomography (OCT) swept source spectral sweep. This all-optical detection is achieved in a noncontact fashion directly on the sample surface by using its specular reflection. High-speed measurement and referencing allow for close to shot noise limited phase-sensitive detection. It offers a simple way to perform OCT and PA imaging by sharing the same system components.

In this paper we present an ultra high speed and highly phase sensitive line-field FD-OCT system for quantitative phase mapping. The system works with a maximum speed of 512 000 A-scan/s (1000 fps) in real time mode. Along the parallel recorded direction excellent phase stability corresponding to a path length variation of only 510 pm was measured. We demonstrate how to exploit this phase accuracy for fast chemical analysis of glucose mixture processes. The system has particular potential for studying micro-fluidic processes.

A parallel Frequency Domain Optical Coherence Tomography (FD-OCT) system and - to the best of our knowledge- first in vivo tomograms obtained with such system are presented. A full tomogram of 256(x) x 512(z) pixels covering a sample region of 8 mm x 3,8 mm is recorded in only 1 ms. Since the transverse as well as the depth information is obtained in parallel, the structure is free of any motion artifacts. In order to study cross talk issues for parallel illumination the transversal resolution for a thermal light source is compared to that with an SLD.