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Condenser-free contrast methods for transmitted-light microscopy

Webb, Kevin F.



Phase contrast microscopy allows the study of highly transparent yet detail-rich specimens by producing intensity contrast from phase objects within the sample. Presented here is a generalized phase contrast illumination schema in which condenser optics are entirely abrogated, yielding a condenser- free yet highly effective method of obtaining phase contrast in transmitted-light microscopy. A ring of light emitting diodes (LEDs) is positioned within the light-path such that observation of the objective back focal plane places the il- luminating ring in appropriate conjunction with the phase ring. It is demonstrated that true Zernike phase contrast is obtained, whose geometry can be flexibly manipulated to provide an arbitrary working distance between illuminator and sample. Condenser-free phase contrast is demonstrated across a range of magnifications (4–100×), numerical apertures (0.13–1.65NA) and conventional phase positions. Also demonstrated is condenser-free darkfield microscopy as well as combinatorial contrast including Rheinberg illumination and simultaneous, colour-contrasted, brightfield, darkfield and Zernike phase contrast. By providing enhanced and arbitrary working space above the preparation, a range of concurrent imaging and electrophysiological techniques will be technically facilitated. Condenser-free phase contrast is demonstrated in conjunction with scanning ion conductance microscopy (SICM), using a notched ring to admit the scanned probe. The compact, versatile LED illumination schema will further lend itself to novel next-generation transmitted-light microscopy designs. The condenser-free illumination method, using rings of independent or radially-scanned emitters, may be exploited in future in other electromagnetic wavebands, including X-rays or the infrared.


Webb, K. F. (2014). Condenser-free contrast methods for transmitted-light microscopy. Journal of Microscopy, 257(1), 8-22.

Journal Article Type Article
Acceptance Date Aug 14, 2014
Publication Date Sep 16, 2014
Deposit Date Sep 22, 2015
Publicly Available Date Dec 4, 2018
Journal Journal of Microscopy
Print ISSN 0022-2720
Electronic ISSN 0022-2720
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 257
Issue 1
Pages 8-22
Keywords Microscopy, Imaging, LED, Phase contrast
Public URL
Publisher URL
Copyright Statement Copyright information regarding this work can be found at the following address:


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