Joined: 21 Nov 2009
Location: Stockholm, Sweden
|Posted: Sun Jul 15, 2018 11:55 pm Post subject: Debugging Olympus BX50 DIC performance, take 4
|I now have an Olympus UPlanFl 100x 0.6-1.3 with variable aperture ring, which more or less completes my set of objectives (unless I will eventually go for a 60x WI).
The main problem with this objective and the U-DP100 Nomarski prism is the unevenness of the field brightness, which is still there after re-doing the Köhler and DIC alignments every time. It is pretty much the same with the 40x objective, although perhaps a little less darkening in the two opposite corners with the 40x. I guess I will have to live with it, and either turn the camera 45 degrees to minimize it, or crop the picture (probably the easiest solution), or make a custom mask to equalize the field brightness in Photoshop. It is not as offensive when observing visually, because the field of view through the eyepieces is so wide that I tend to ignore its periphery.
This objective produces a low-contrast but sometimes usable image without oil, but oiling the objective to the cover glass does improve the image immensely. As a whole I would tend to be satisfied with the image quality, given the unavoidable limitation in NA that would require a new condenser and Nomarski prism to oil the slide to the condenser.
The test subject is a streak of bacteria, alive in water and not stained. The effective NA is around 0.9 and limited by the condenser and the air gap between condenser and slide.
Full field of view, oiled objective, direct projection onto Micro 4/3 (through tube lens of course), reduced to 1,000 x 750 pixels:
Slightly cropped, a collection of different bacteria:
Something strange, with trailing tracks and possibly a few very long bacteria hanging onto it in a weak water current, cropped: