Summary

The prototype condenser demonstrates that there is an easy design solution that provides rapid switching among the various illumination modes. The imaging tests with Pleurosigma angulatum of the Abbe condenser versus the aplanatic condenser confirm Dr. McCrone’s requirement that a good polarized light microscope (I believe he would also apply this requirement to the biological microscope) must have an aplanatic condenser. This requirement also avoids the need to adjust condenser height for high NA brightfield or darkfield after Koehler illumination has been properly established for the 10X objective. I was tempted to use the LOMO aplanatic condenser lens for the prototype, but that would have prevented the study of the effects of spherical aberration with the LOMO Abbe condenser. LOMO has a separate single-element aspherical lens that interchanges in the same base as the high NA lens. This design should be as acceptable as having the top lens removable for use with a 4X objective, as I have done with the Abbe condenser. 

Acknowledgement

I could not have done this study without the donation of the phase contrast condenser base by Chris Vander Tuuk of LOMO America. The historical background on Abbe condensers was provided by John Delly. Discussions with John and his reviews of the test results also contributed to this article.

References

1. Clarke, T. M. Building an Affordable Universal Student Microscope. The Microscope, 2000;48:19-39.

2. James, P. “Circular Oblique Lighting” Balsam Post, 2003;61:3-10.

3. Clarke, T. M. (2001). A versatile low power microscopy set-up with a modified Russian Biolam stand. Micscape, September 2001, http://www.microscopy-uk.org.uk/mag/artsep01/tcmacro.html

4. McCrone, W. C. The Microscope, 1985;33:87. 

5. Herlihy, E. P. An Amateur’s Retrospect. The New York Microscopical Society Annual, 1968:14-21.

6. McCrone, W. C. Response to Letter-to-the-Editor from Oppenheimer Goldberg. The Microscope, 1985;33:71.

7. Ellam, B. Diatoms by Dark-ground Illumination- with Some Historical Musings-Part II. The Amateur Diatomist, 2003;1 (4):33-42.

8. Lonert, A. C. Turtox Microscopy Booklet, General Biological Supply House, 1962.