Funding support: CIHR (Canadian Institutes of Health Research)

Students: Marshall Overcast

Collaborators: Alex Vitkin, University of Toronto


Optical coherence tomography (OCT) is a near infrared medical imaging technology allowing microscopic examination of body tissues for diagnosis of  disease, especially retinal disease with imaging performed through the front of the eye, but also useful for imaging the skin and other epithelial tissues.  Agile focus control for OCT instruments will allow an increase in numerical aperture for these instruments, with attendant improvement of image resolution and signal to noise ratio. We are exploring the use of membrane mirrors to accomplish focus control in OCT instruments.

oct image

By adjusting the focus synchronously with the axially-scanned coherence gate during time-domain OCT imaging, much higher NA optics may be used, leading to a significant improvement in resolution and signal strength in the image. Panel (a) shows asynchronous focus sweep; panel (b) shows focus and OCT gate adjusted synchronously; panels (c) and (d) show the effect of fixed focus (focused at the bottom of panel (c)) vs. dynamic focus (synchronous focus in panel (d)). Figure from Qi et. al., 2004.


David L. Dickensheets, Marshall Overcast, Phillip Himmer, Victor X.D. Yang, I. Alex Vitkin, “Focus Tracking in Time Domain Optical Coherence Tomography Using Membrane Mirrors Operated Near Snap-Down,” 2006 IEEE/LEOS International Conference on Optical MEMS, Big Sky, Montana, August 21-24, 2006.

Victor X. D. Yang, Youxin Mao, Beau A. Standish, Nigel R. Munce, Stephanie Chiu, Daina Burnes, Brian C. Wilson, and I. Alex Vitkin, Phillip A. Himmer and David L. Dickensheets, “Doppler optical coherence tomography with a micro-electro-mechanical membrane mirror for high-speed dynamic focus tracking,” Optics Letters, Vol. 31, No. 9, pp 1262-1264, May 2006. 

Bing Qi, Phillip A. Himmer, Maggie L. Gordon, Victor X.D. Yang, David L. Dickensheets, I. Alex Vitkin, “Dynamic focus control in high-speed optical coherence tomography based on a microelectromechanical mirror,” Optics Communications, Vol 232/1-6 pp 123-128, 2004.