Axicon lens for high-resolution optical coherence tomography over a long focus depth

Zhihua Ding,Zhongping Chen,Yonghua Zhao,J Stuart Nelson,Hongwu Ren

doi:10.1117/12.470468

Abstract

In optical coherence tomography (OCT), axial and lateral resolutions are determined by the source coherence length and numerical aperture of the sampling lens, respectively. While axial resolution can be improved using a broadband light source, there is a trade-off between lateral resolution and focus depth when conventional optical elements are used. In this paper, we report on the incorporation of an axicon lens into the sample arm of the interferometer to overcome this limitation. Using an axicon lens with a top angle of 160 degrees, 10 micrometers or better lateral resolution is maintained over a focus depth of at least 6 mm. In addition to high lateral resolution, the focusing spot intensity is approximately constant over the whole focus depth.

Highlights

Optical coherence tomography (OCT) is a new modality that provides high resolution subsurface microstructural images in a noninvasive manner [1, 2]
Axial and lateral resolutions are determined by the source coherence length and numerical aperture of the sampling lens, respectively
While axial resolution can be improved using a broadband light source [3, 4], there is a trade-off between lateral resolution and focus depth when conventional optical elements are used, because a beam with a long focus depth and narrow lateral width cannot be produced simultaneously

Summary

INTRODUCTION

Optical coherence tomography (OCT) is a new modality that provides high resolution subsurface microstructural images in a noninvasive manner [1, 2]. Axial and lateral resolutions are determined by the source coherence length and numerical aperture of the sampling lens, respectively. While high lateral resolution imaging requires a large numerical aperture, a long focus depth requires a small numerical aperture. In high speed OCT imaging, where an axial scanning mode (A-mode) is used, a tightly-focused lens produces a micrometer sized spot at only one particular depth. An axicon lens 8 is incorporated into the sample arm of the interferometer to achieve both high lateral resolution and long focus depth simultaneously. In addition to high lateral resolution, the focusing spot intensity is approximately constant over the whole focus depth

METHODOLOGY

EXPERIMENTS

CONCLUSION