Miniature objective lens with variable focus for confocal endomicroscopy

Minkyu Kim,Dongkyun Kang,Yoshikazu Nakajima,George M Whitesides,Nima Tabatabaei,Guillermo J Tearney,Robert W Carruth,Ramses V Martinez,Tao Wu

doi:10.1364/boe.5.004350

Abstract

Spectrally encoded confocal microscopy (SECM) is a reflectance confocal microscopy technology that can rapidly image large areas of luminal organs at microscopic resolution. One of the main challenges for large-area SECM imaging in vivo is maintaining the same imaging depth within the tissue when patient motion and tissue surface irregularity are present. In this paper, we report the development of a miniature vari-focal objective lens that can be used in an SECM endoscopic probe to conduct adaptive focusing and to maintain the same imaging depth during in vivo imaging. The vari-focal objective lens is composed of an aspheric singlet with an NA of 0.5, a miniature water chamber, and a thin elastic membrane. The water volume within the chamber was changed to control curvature of the elastic membrane, which subsequently altered the position of the SECM focus. The vari-focal objective lens has a diameter of 5 mm and thickness of 4 mm. A vari-focal range of 240 μm was achieved while maintaining lateral resolution better than 2.6 μm and axial resolution better than 26 μm. Volumetric SECM images of swine esophageal tissues were obtained over the vari-focal range of 260 μm. SECM images clearly visualized cellular features of the swine esophagus at all focal depths, including basal cell nuclei, papillae, and lamina propria.

Highlights

Encoded confocal microscopy (SECM) is a high-speed confocal endomicroscopy technology [1] that can achieve significantly faster imaging speeds than those of other confocal endomicroscopy devices [2, 3]
One of the main challenges for large-area Spectrally encoded confocal microscopy (SECM) imaging in vivo is maintaining the same imaging depth within the tissue when patient motion and tissue surface irregularity are present
We report the development of a miniature vari-focal objective lens that can be used in an SECM endoscopic probe to conduct adaptive focusing and to maintain the same imaging depth during in vivo imaging

Summary

Introduction

Encoded confocal microscopy (SECM) is a high-speed confocal endomicroscopy technology [1] that can achieve significantly faster imaging speeds than those of other confocal endomicroscopy devices [2, 3]. This high imaging speed of SECM can be utilized to image large areas of tissue by scanning the SECM optics so that the spectrally-encoded line focus traverses the tissue. Large-area confocal microscopy of luminal tissue has been demonstrated with an SECM bench top probe [4] In this bench top probe, a miniature piezoelectric transducer (PZT) actuator was used to axially translate the objective lens and adaptively change the focus [4].

Methods

Results

Conclusion