Correction of image distortions in endoscopic optical coherence tomography based on two-axis scanning MEMS mirrors

Abstract

A two-axis scanning microelectromechanical (MEMS) mirror enables an optical coherence tomography (OCT) system to perform threedimensional endoscopic imaging due to its fast scan speed and small size. However, the radial scan from the MEMS mirror causes various distortions in OCT images, namely spherical, fan-shaped and keystone distortions. In this paper, a new method is proposed to correct all of three distortions presented in OCT systems based on two-axis MEMS scanning mirrors. The spherical distortion is corrected first by directly manipulating the original spectral interferograms in the phase domain, followed by Fourier transform and three-dimensional geometrical transformation for correcting the other two types of distortions. OCT imaging experiments on a paper with square ink printed arrays and a glass tube filled with milk have been used to validate the proposed method. Distortions in OCT images of flat or curved surfaces can all be effectively removed.

Microscanners for optical endomicroscopic applications

“…First, the scanning MEMS mirrors are operated by using electrostatic [25][26][27][28][29][30][31], electromagnetic [22,32], or electrothermal [33][34][35][36][37][38][39] actuation. An electrostatic force between suspending and fixed electrodes induces the electrostatic actuation, which allows a high scanning resonant frequency but it often requires high operational voltages.…”

“…The MEMS mirror scans 30° at DC 5.5 V voltage for both xand y-axes. Wang et al have demonstrated a 2D electrothermal MEMS mirror, which has four pairs of unique dual S-shaped bimorph structures [38].…”

“…The catheter was combined with a SD-OCT system to obtain the OCT images of a fingertip. Figure 4c demonstrates an electrothermal MEMS mirror for side-looking and en-face configuration [38]. The endomicroscopic probe consists of a mount base, a GRIN lens, a GRIN lens fiber, and a MEMS mirror with a post-objective arrangement within an outer diameter of 3.5 mm.…”

“…c Electrothermal MEMS mirror probe. OCT image of glass tube filled with milk was obtained [38]. d Circumferential probe with microprism.…”

Progress of MEMS Scanning Micromirrors for Optical Bio-Imaging

“…Conventionally, this type of distortion was corrected using algorithms based on a point-to-point method [47,48], which can consume substantial computing resources. In reference [49], the authors discuss a new method that directly manipulates the original spectral interferograms in the phase domain to correct the spherical distortion. The algorithm continues with a Fourier transform and 3D geometrical transformation to correct fan-shaped and keystone distortions.…”