title: Miniature objective lens with variable focus for confocal endomicroscopy.
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.
authors.affiliation: Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA ; School of Engineering, The University of Tokyo, Yayoi 2-11-16 Bunkyo, Tokyo 113-8656, Japan.
authors.forename: Minkyu
authors.initials: M
authors.lastname: Kim
authors.affiliation: Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
authors.forename: DongKyun
authors.initials: D
authors.lastname: Kang
authors.affiliation: Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
authors.forename: Tao
authors.initials: T
authors.lastname: Wu
authors.affiliation: Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
authors.forename: Nima
authors.initials: N
authors.lastname: Tabatabaei
authors.affiliation: Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Carruth
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA ; Madrid Institute for Advanced Studies, IMDEA Nanoscience, Calle Faraday 9, Ciudad Universitaria de Cantoblanco, 28049 Madrid, Spain.
authors.forename: Ramses V
authors.initials: RV
authors.lastname: Martinez
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA ; Wyss Institute for Biologically Inspired Engineering, Harvard University, 60 Oxford Street, Cambridge, MA 02138, USA.
authors.forename: George M
authors.initials: GM
authors.lastname: Whitesides
authors.affiliation: School of Engineering, The University of Tokyo, Yayoi 2-11-16 Bunkyo, Tokyo 113-8656, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Nakajima
authors.affiliation: Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA ; Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA ; Department of Pathology, Harvard Medical School and Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
authors.forename: Guillermo J
authors.initials: GJ
authors.lastname: Tearney
keywords: (170.1790) Confocal microscopy; (170.2150) Endoscopic imaging; (170.2680) Gastrointestinal; (170.3890) Medical optics instrumentation; (170.4730) Optical pathology; (220.3620) Lens system design