Parallel optical coherence tomography in scattering samples using a two-dimensional smart-pixel detector array M. Ducros, M. Laubscher * , B. Karamata, S. Bourquin, T. Lasser, R.P. Salath e Institute of Applied Optics, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland Received 21 September 2001; accepted 5 December 2001 Abstract Parallel optical coherence tomography in scattering samples is demonstrated using a 58  58 smart-pixel detector array. A femtosecond mode-locked Ti:Sapphire laser in combination with a free space Michelson interferometer was employed to achieve 4 lm longitudinal resolution and 9 lm transverse resolution on a 260  260 lm 2 field of view. We imaged a resolution target covered by an intralipid solution with different scattering coefficients as well as onion cells. Ó 2002 Published by Elsevier Science B.V. Keywords: Optical coherence tomography; Parallel detection; Smart pixels; CMOS photodetector; Femtosecond laser 1. Introduction Optical coherence tomography (OCT) allows acquisition of spatially resolved maps of reflectiv- ity in scattering samples. In most common OCT systems, depth scanning is achieved by the longi- tudinal translation of a reference mirror, and lat- eral scanning is obtained by the lateral translation of a focused probe beam using scanning mirrors [1–3]. To increase the acquisition speed and elim- inate the need for lateral scanning, parallel detec- tion schemes have been investigated [4–8]. Parallel OCT systems previously developed consist of a free-space Michelson interferometer illuminated by a short temporal coherence source. The sample under study is placed in one arm of the interfer- ometer, illuminated with a uniform extended beam and imaged on an array of photodetectors. Charge coupled devices (CCD) cameras are the most commonly used imaging devices for parallel de- tection schemes. However, CCD cameras suffer from two drawbacks when used in parallel OCT systems: (1) the high optical DC intensity reflected by the reference mirror reduces the dynamic range available for AC interferometric signal detection, (2) the CCD frame rate (typically 100 Hz for 512  512 pixels) is much lower than the inter- ferometric signal frequency (typically >1 kHz). In this case a lock-in detection or synchronous illu- mination scheme has to be employed [5], which limits the image acquisition speed. A different photodetector array based on CMOS technology was developed for parallel OCT [8,9]. Besides transducing light signals into electrical signals, 1 February 2002 Optics Communications 202 (2002) 29–35 www.elsevier.com/locate/optcom * Corresponding author. Fax: +41-21-693-3701. E-mail address: markus.laubscher@epfl.ch (M. Laubscher). 0030-4018/02/$ - see front matter Ó 2002 Published by Elsevier Science B.V. PII:S0030-4018(02)01073-8