Re: Help: has anyone ever used Olympus DCW Darkfield condenser?
Posted: Tue Nov 21, 2023 5:33 pm
Earlier BH era catalogues describes the BH-DCW condenser as being a cardioid type. The detailed specs are very slightly different (7.8mm fl for BH, vs 7.65mm for BH2), but I think it's fair to assume that they are optically very similar.apochronaut wrote: Your DF condenser should be a mirror/reflectingcondenser of some type. Perhaps Viktor knows which for sure. The degree of ca produced in high N.A. DF condensers is from very low to none. Paraboloids have a small amount, spherical too but cardioids, none.
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I did some checking and the BH2-DCW condenser model # based on it's specs., likely translates as For BH2 model microscope, .dark field condenser, cardioid design, wide field. It's high cost , likely stems from it's wide field design, which can go as low as a 20X objective at an F.N. of 22, which is pretty good. An average oil immersion high N.A. DF condenser would get to an F.N. of about 18 with a 20X. That is one rational for many older microscope systems using 25X objectives, rather than 20X, allowing more conventional DF oil condensers to cover the field at 25X.
The best I have seen are the AO/ Reichert toric DF condensers, which cover an F.N. of 20 at 10X.