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Proceedings Paper

Volumetric retinal fluorescence microscopic imaging with extended depth of field
Author(s): Zengzhuo Li; Andrew Fischer; Wei Li; Guoqiang Li
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Paper Abstract

Wavefront-engineered microscope with greatly extended depth of field (EDoF) is designed and demonstrated for volumetric imaging with near-diffraction limited optical performance. A bright field infinity-corrected transmissive/reflective light microscope is built with Kohler illumination. A home-made phase mask is placed in between the objective lens and the tube lens for ease of use. General polynomial function is adopted in the design of the phase plate for robustness and custom merit function is used in Zemax for optimization. The resulting EDoF system achieves an engineered point spread function (PSF) that is much less sensitive to object depth variation than conventional systems and therefore 3D volumetric information can be acquired in a single frame with expanded tolerance of defocus. In Zemax simulation for a setup using 32X objective (NA = 0.6), the EDoF is 20μm whereas a conventional one has a DoF of 1.5μm, indicating a 13 times increase. In experiment, a 20X objective lens with NA = 0.4 was used and the corresponding phase plate was designed and fabricated. Retinal fluorescence images of the EDoF microscope using passive adaptive optical phase element illustrate a DoF around 100μm and it is able to recover the volumetric fluorescence images that are almost identical to in-focus images after post processing. The image obtained from the EDoF microscope is also better in resolution and contrast, and the retinal structure is better defined. Hence, due to its high tolerance of defocus and fine restored image quality, EDoF optical systems have promising potential in consumer portable medical imaging devices where user’s ability to achieve focus is not optimal, and other medical imaging equipment where achieving best focus is not a necessary.

Paper Details

Date Published: 15 March 2016
PDF: 7 pages
Proc. SPIE 9713, Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing XXIII, 97131C (15 March 2016); doi: 10.1117/12.2213813
Show Author Affiliations
Zengzhuo Li, The Ohio State Univ. (United States)
Andrew Fischer, The Ohio State Univ. (United States)
Wei Li, National Eye Institute (United States)
Guoqiang Li, The Ohio State Univ. (United States)

Published in SPIE Proceedings Vol. 9713:
Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing XXIII
Thomas G. Brown; Carol J. Cogswell; Tony Wilson, Editor(s)

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