An off-axis cylindrical mirror focused line scanning system with high imaging quality for broad spectral band

Abstract

An ultra-broad bandwidth light source is utilized in optical coherence tomography (OCT) for an ultra-high axial resolution. A lens focused scanning system is commonly used in the OCT imaging. The effective focal length of the lens varies as a function of the wavelength and hence it focuses a broadband spectrum in different focal planes. This variation eventually reduces the axial resolution of the OCT imaging. These variations become even more significant at a higher transverse resolution. In the present paper, a cylindrical mirror focused line scanning system for high quality imaging is presented. The imaging quality of the developed system was evaluated using optical design software and tested experimentally with 50.8 and 25.4 mm focal length cylindrical mirrors. A broadband light source with a center wavelength of 843 nm and a spectral bandwidth of 53 nm was used. The scanning system meets the Marechal criterion by providing a high Strehl ratio (SR) within the 2 mm target scan range. Moreover, the developed cylindrical mirror focused scanning is robust and insensitive to minor beam path variations, and this was proved experimentally.