An Approach for Megahertz OCT: Streak Mode Fourier Domain Optical Coherence Tomography Rui Wang 1 , Julie X. Yun 1 , Xiaocong Yuan 2 , Richard Goodwin 3 , Roger Markwald 4 and Bruce Gao 1* 1 Department of Bioengineering and COMSET, Clemson University, Clemson, SC 29634, USA 2 Institute of Modern Optics, Nankai University, Tianjin, PR China 3 Department of Cell Biology and Anatomy, University of South Carolina, Columbia, SC 29208, USA 4 Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, 29425, USA *Corresponding author email: zgao@clemson.edu ABSTRACT We report a technique, which uses an area-scan camera to record the interference spectrum of the OCT signals. Traditional point-scanning is remained in this streak-mode FD-OCT so that the small aperture of the single-mode fiber functions as a confocal gate and screens multiply scattered photons very well. While the sample beam is scanning the specimen laterally, the interference spectrum is physically scanned on the area scan camera using a streak scanner. Therefore, pixels of the camera are illuminated by the spectrum of the OCT signal row by row, corresponding to each A- scan at different lateral position. A unidirectional B-scan of 700 lines is obtained in 1 ms; thus, an A-scan time of 1.4 µs is achieved. A Day 4 chick embryo sample is imaged using this method. This technique is highly potent for multi- Megahertz OCT imaging. Keywords: Optical Coherence Tomography, Fourier Domain, Streak Mode, Area-Scan Camera 1. INTRODUCTION Much research has been devoted to increasing the imaging speed and resolution of optical coherence tomography (OCT). Although multi-megahertz OCT A-scan rate has been achieved using a swept light source [1], it, however, has not been achieved for the 800 nm regime [2]. In addition, the wavelength sweep range is narrow for presently available swept sources, resulting in limited axial resolution. Currently, supercontinuum light generated by photonic crystal fibers can cover both 800 nm and 1.3 µm regimes [3, 4], making spectrometer-based Fourier domain OCT (FD-OCT) [5-7] a solution for ultrahigh-resolution OCT imaging. In conventional FD-OCT, the OCT spectrum is recorded by a line-scan camera (either a CCD type [6, 7] or a CMOS type [8]), as shown in Fig. 1(a). A state-of-the-art area-scan camera can achieve a higher data-acquisition rate than a line-scan camera can. For example, an area-scan camera can achieve 7500 Mega pixels per second (Fastcam SA5, Photron), a rate much higher than the line-scan camera (SPL4096-140k, Basler Vision Tech, 560 Mega pixels per second) used by Benjamin and coworkers [8] to achieve the fastest Fourier domain OCT documented thus far. This high speed area-scan camera allows for the development of a megahertz OCT. In a recently reported area-scan camera based parallel OCT [9], an area-scan camera was used to record spectrum of the OCT signal in parallel by illuminating the sample with a line-light source. However, both of the signal to noise ratio (SNR) and the spatial resolution were reduced due to the crosstalk among different spatial image spots since there is no confocal gate to reject the multiply scattered photons in two dimensions. This problem is also found in full field swept- source OCT [10]. Here, we report a technique, called streak-mode Fourier domain optical coherence tomography (SM-FDOCT), in which an area-scan camera is used instead of a line-scan camera to record the OCT spectrum. This SM-FDOCT still includes traditional point-scanning mechanisms so that the small aperture of the single-mode fiber functions as a confocal gate for rejecting multiply scattered photons. While the probe beam is scanning the specimen laterally, the corresponding OCT spectrum is physically scanned on the area-scan camera using a streak scanner, which can be, for example, a galvano Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XV, edited by James G. Fujimoto, Joseph A. Izatt, Valery V. Tuchin, Proc. of SPIE Vol. 7889, 788920 · © 2011 SPIE · CCC code: 1605-7422/11/$18 doi: 10.1117/12.875384 Proc. of SPIE Vol. 7889 788920-1 Downloaded from SPIE Digital Library on 08 May 2011 to 58.251.166.9. Terms of Use: http://spiedl.org/terms