Optical coherence tomography and scanning laser ophthalmoscopy: Approaches to dual-channel retinal tissue imaging

We report a Talbot bands-based optical coherence tomography (OCT) system capable of producing longitudinal B-scan OCT images and en-face scanning laser ophthalmoscopy (SLO) images of the human retina in-vivo, with various degrees of simultaneity

Solid Chemical Radiation Dosimeter Semiannual Report

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High-precision, high-accuracy ultralong-range swept-source optical coherence tomography using vertical cavity surface emitting laser light source

We demonstrate ultralong-range swept-source optical coherence tomography (OCT) imaging using vertical cavity surface emitting laser technology. The ability to adjust laser parameters and high-speed acquisition enables imaging ranges from a few centimeters up to meters using the same instrument. We discuss the challenges of long-range OCT imaging. In vivo human-eye imaging and optical component characterization are presented. The precision and accuracy of OCT-based measurements are assessed and are important for ocular biometry and reproducible intraocular distance measurement before cataract surgery. Additionally, meter-range measurement of fiber length and multicentimeter-range imaging are reported. 3D visualization supports a class of industrial imaging applications of OCT.National Institutes of Health (U.S.) (R01-EY011289-26)National Institutes of Health (U.S.) (R01 EY013178-12)National Institutes of Health (U.S.) (R01-EY013516-09)National Institutes of Health (U.S.) (R01-EY019029-03)National Institutes of Health (U.S.) (R01-CA075289-15)National Institutes of Health (U.S.) (R01-NS057476-05)National Institutes of Health (U.S.) (R44-CA101067-05)United States. Air Force Office of Scientific Research (FA9550-10-1-0551)United States. Air Force Office of Scientific Research (FA9550-10-1-0063

Real-time intraoperative 4D full-range FD-OCT based on the dual graphics processing units architecture for microsurgery guidance

Real-time 4D full-range complex-conjugate-free Fourier-domain optical coherence tomography (FD-OCT) is implemented using a dual graphics processing units (dual-GPUs) architecture. One GPU is dedicated to the FD-OCT data processing while the second one is used for the volume rendering and display. GPU accelerated non-uniform fast Fourier transform (NUFFT) is also implemented to suppress the side lobes of the point spread function to improve the image quality. Using a 128,000 A-scan/second OCT spectrometer, we obtained 5 volumes/second real-time full-range 3D OCT imaging. A complete micro-manipulation of a phantom using a microsurgical tool is monitored by multiple volume renderings of the same 3D date set with different view angles. Compared to the conventional surgical microscope, this technology would provide the surgeons a more comprehensive spatial view of the microsurgical site and could serve as an effective intraoperative guidance tool

Imaging limbal and scleral vasculature using Swept Source Optical Coherence Tomography

We demonstrate application of high-speed swept source optical coherence tomography for vessel visualization in the anterior segment of the human eye. The human corneo-scleral junction and sclera was imaged in vivo. Imaging was performed using a swept source OCT system operating at 1050nm wavelength range and 100kHz A-scan rate. The high imaging speed enables generation of 3D depth-resolved vasculature maps. The vessel visualization method revealed the rich vascular system in the conjunctiva and episclera.National Institutes of Health (U.S.) (NIH grant R01-EY011289-25)National Institutes of Health (U.S.) (NIH grant R01-EY013178-11)National Institutes of Health (U.S.) (NIH grant R01-EY01356-06)National Institutes of Health (U.S.) (NIH grant R01 CA075289-15)United States. Air Force Office of Scientific Research (FA9550-10-1-0551)United States. Air Force Office of Scientific Research (FA9550-10-1-0063)Foundation for Polish Science (KOLUMB Programme; KOL/3/2010I

Investigation of the impact of water absorption on retinal OCT imaging in the 1060 nm range

Recently, the wavelength range around 1060 nm has become attractive for retinal imaging with optical coherence tomography (OCT), promising deep penetration into the retina and the choroid. The adjacent water absorption bands limit the useful bandwidth of broadband light sources, but until now, the actual limitation has not been quantified in detail. We have numerically investigated the impact of water absorption on the axial resolution and signal amplitude for a wide range of light source bandwidths and center wavelengths. Furthermore, we have calculated the sensitivity penalty for maintaining the optimal resolution by spectral shaping. As our results show, with currently available semiconductor-based light sources with up to 100–120 nm bandwidth centered close to 1060 nm, the resolution degradation caused by the water absorption spectrum is smaller than 10%, and it can be compensated by spectral shaping with negligible sensitivity penalty. With increasing bandwidth, the resolution degradation and signal attenuation become stronger, and the optimal operating point shifts towards shorter wavelengths. These relationships are important to take into account for the development of new broadband light sources for OCT

Programmable unitary spatial modes manipulation

Free space propagation and conventional optical systems such as lenses and mirrors all perform spatial unitary transforms. However, the subset of transforms available through these conventional systems is limited in scope. We present here a unitary programmable mode converter (UPMC) capable of performing any spatial unitary transform of the light field. It is based on a succession of reflections on programmable deformable mirrors and free space propagation. We first show theoretically that a UPMC without limitations on resources can perform perfectly any transform. We then build an experimental implementation of the UPMC and show that, even when limited to three reflections on an array of 12 pixels, the UPMC is capable of performing single mode tranforms with an efficiency greater than 80% for the first 4 modes of the TEM basis

MEMS tunable VCSEL light source for ultrahigh speed 60kHz - 1MHz axial scan rate and long range centimeter class OCT imaging

This paper demonstrates new wavelength swept light source technology, MEMS tunable VCSELs, for OCT imaging. The VCSEL achieves a combination of ultrahigh sweep speeds, wide spectral tuning range, flexibility in sweep trajectory, and extremely long coherence length, which cannot be simultaneously achieved with other technologies. A second generation prototype VCSEL is optically pumped at 980nm and a low mass electrostatically tunable mirror enables high speed wavelength tuning centered at ~1310nm with ~110nm of tunable bandwidth. Record coherence length >100mm enables extremely long imaging range. By changing the drive waveform, a single 1310nm VCSEL was driven to sweep at speeds from 100kHz to 1.2MHz axial scan rate with unidirectional and bidirectional high duty cycle sweeps. We demonstrate long range and high resolution 1310nm OCT imaging of the human anterior eye at 100kHz axial scan rate and imaging of biological samples at speeds of 60kHz - 1MHz. A first generation 1050nm device is shown to sweep over 100nm. The results of this study suggest that MEMS based VCSEL swept light source technology has unique performance characteristics and will be a critical technology for future ultrahigh speed and long depth range OCT imaging.National Institutes of Health (U.S.) (2R44CA10167-05)National Institutes of Health (U.S.) (R01-EY011289-25)National Institutes of Health (U.S.) (R01-EY01356-06)National Institutes of Health (U.S.) (R01-EY013178-11)National Institutes of Health (U.S.) (R01-CA075289-15)United States. Air Force Office of Scientific Research (FA9550-10-1-0063)United States. Air Force Office of Scientific Research (FA9550-10-1-0551)Thorlabs, Inc

Swept source / Fourier domain polarization sensitive optical coherence tomography with a passive polarization delay unit

Polarization sensitive optical coherence tomography (PS-OCT) is a functional imaging method that provides additional contrast using the light polarizing properties of a sample. This manuscript describes PS-OCT based on ultrahigh speed swept source / Fourier domain OCT operating at 1050nm at 100kHz axial scan rates using single mode fiber optics and a multiplexing approach. Unlike previously reported PS-OCT multiplexing schemes, the method uses a passive polarization delay unit and does not require active polarization modulating devices. This advance decreases system cost and avoids complex synchronization requirements. The polarization delay unit was implemented in the sample beam path in order to simultaneously illuminate the sample with two different polarization states. The orthogonal polarization components for the depth-multiplexed signals from the two input states were detected using dual balanced detection. PS-OCT images were computed using Jones calculus. 3D PS-OCT imaging was performed in the human and rat retina. In addition to standard OCT images, PS-OCT images were generated using contrast form birefringence and depolarization. Enhanced tissue discrimination as well as quantitative measurements of sample properties was demonstrated using the additional contrast and information contained in the PS-OCT images.National Institutes of Health (U.S.) (NIH R01-EY011289-25)National Institutes of Health (U.S.) (R01-EY013178-12)National Institutes of Health (U.S.) (R01-EY013516-09)National Institutes of Health (U.S.) (R01-EY019029-04)National Institutes of Health (U.S.) (R01-EY018184-05)National Institutes of Health (U.S.) (R01-CA075289-14)National Institutes of Health (U.S.) (R01-HL095717-03)National Institutes of Health (U.S.) (R01-NS057476-05)United States. Air Force Office of Scientific Research (AFOSR FA9550-10-1-0063)United States. Dept. of Defense. Medical Free Electron Laser Program (FA9550-07-1-0101