Time domain OCT measures the interference between sample and reference radiation as a function of the reference arm length. In full-field-OCT (FF-OCT) a camera is used instead of a scanned beam for a parallel detection of the interference pattern and thus acquiring a complete en face image. Because multiple images have to be acquired to resolve the phase ambiguity, this method is prone to motion artifacts.
We present a novel motion-insensitive approach to FF-OCT. Spatially coherent illumination and an off-axis reference beam is used to introduce path-length differences between reference and sample light in neighboring pixels. This spatial carrier frequency replaces the temporal carrier frequency in scanned TD-OCT.
The setup is based on a Mach-Zehnder interferometer with a super-luminescent diode and a CMOS area camera. The Sensitivity of the system was determined to be 75 dB. The field of view was 1.42 x 1.42 mm. Each frame had 237x237 lateral channels at an axial resolution of 9 µm in tissue. By step-wise changing the length of the reference arm between the en face scans, volumetric in vivo FF-OCT measurements of the human retina have been acquired within 1.3 s.
OCT with a spatially coherent off-axis reference beam is suitable for in vivo imaging of human retina. The quality of the images is sufficient to discriminate the different tissue layers.
Helge M. Sudkamp, Peter Koch, Dierck Hillmann, Hendrik Spahr, Gesa L. Franke, Michael Münst, Fabian Mütel, and Gereon M. Hüttmann, "In vivo full-field time-domain optical coherence tomography using a spatially coherent off-axis reference (Conference Presentation)," Proc. SPIE 10053, Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XXI, 100531Q (Presented at SPIE BiOS: February 01, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2254850.5371723166001.
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