Long focal depth zone plate for optical coherence tomography

Abstract

Based on the focus principle of the zone plate and the encoding method of the computer-generated hologram, a zone plate applied in OCT to increase the focal depth is proposed. The phase distribution of this kind of zone plate is constructed by superimposing a shifted elliptical phase to the phase function of a common sine zone plate, which will confine the spot size of the focused beam within a particular range along axis and thus extend the focal depth. The numerical simulation shows that the focal segment of the zone plate meet the requirement of the commonly used OCT imaging system in the two aspects of focal depth and transverse resolution. Because the zone plate has many advantages such as flexible focal length and depth design, simple structure for fabrication, low cost and convenient micromation and integration, it is a potential long focal depth component for optical coherence tomography.